US3224243A

US3224243A - Method of thickening the wall of a tube

Info

Publication number: US3224243A
Application number: US121216A
Authority: US
Inventors: Walter H Van Deberg
Original assignee: EARL A THOMPSON Manufacturing CO
Current assignee: EARL A THOMPSON Manufacturing CO
Priority date: 1961-06-30
Filing date: 1961-06-30
Publication date: 1965-12-21
Anticipated expiration: 1982-12-21

Description

1965 w. H. VAN DEBERG 3,224,243

METHOD OF THICKENING THE WALL OF A TUBE Filed June 50, 1961 IND MEMBER? IN VEN TOR.

WAL QEQ H l ANDEBERG ATTORNL'Y Dec. 21, 1965 w. H. VAN DEBERG METHOD OF THICKENING THE WALL OF A TUBE Filed June 30, 1961 5 Sheets-Sheet 2 INVENTOR.

WALTERH WA/DEBERG BY QZ KM ATTORNEY Dec. 21, 1965 w. H. VAN DEBERG 3,224,243

METHOD OF THICKENING THE WALL OF A TUBE Filed June so, 1961 5 Sheets-Sheet 5 INVENTOR.

WALLER H l/A/V DEBERG ATTORNEY United States Patent 3,224,243 METHOD OF THICKENING THE WALL OF A TUBE Walter H. Van Deberg, Ferndale, Mich, assignor to Ear! A. Thompson Manufacturing Company, a corporation of Michigan Filed June 30, 1961, Ser. No. 121,216

12 Claims. (Cl. 72-354) This invention relates to cold working metal, and more particularly to an improved method of thickening the wall of a tube throughout a given axial Zone to obtain a desired configuration of the tube by means of axially applied pressure.

Certain problems have been encountered prior to this invention in attempts to obtain tubular work pieces having adjacent lengths of varying wall thickness desirable for particular products. These problems and the manner in which this invention has overcome them are aptly illustrated by the example of valve tappets for internal combustion engines. Tappet bodies currently in demand utilize as a basic component a tubular length of metal having an inwardly thickened portion at one end, and having the other end closed by hardenable cam following means.

One method currently in use for obtaining such a configuration of the tubular portion starts with a tube having a wall thickness desired at the thick end of the finished product, and then machines away the metal of part of the piece to provide the thinner portion and the desired internally shouldered shape. Aside from the time involved in such a tedious process, the immense amount of turning scrap out from inside each work piece constitutes a substantial percentage of waste material. Also such a tappet body has an undesirable grain structure.

Other processes which start with tubing of the smallest of the desired finished wall thicknesses have not heretofore been applicable to the production of tappet bodies. One such process is the well known hot upsetting in which an axial force applied to the heated end of a length of tubing produces an inward thickening of the wall in the heated zone if the outer diameter is prevented from excess bulging by external dies or other means. This process, however, does not lend itself to the formation of tappet bodies because of the diificulty and expense of providing heating apparatus with sufficiently accurate controls so that the thickening will occur only in the desired zone. Furthermore, the inner diameters of both portions of the tube have to be machined after the com pressing operation by an internal grinding or other expensive step to re-establish size, roundness, and concentricity. This plurality of steps is, in the end, comparable in cost to the previously mentioned machining operation.

Accordingly, it is an object of the present invention to provide an improved method of forming a tubular product for use in a tappet body from an inexpensive grade of metal tubing which forms the product with adjacent portions of varying wall thickness without any waste in the form of machining scrap and without heating, yet which inherently establishes size, roundness and concentricity well within desired tolerances.

Another object of this invention is to provide in the art of tube wall expanding an improved method whereby a short length of tubing is subjected to an axially compressive force suflicient to upset the metal wall into contact with inner and outer dies to form a product having a generally cylindrical exterior wall and a shouldered interior configuration without any buckling, folding and creasing of the metal.

A further object is to provide an improved method of cold forming a blank for a tappet body from a piece 3,224,243 Patented Dec. 21, 1965 of metal tubing which may be of an inexpensive variety and somewhat out of round which prevents outward and inward folding of the tube wall in areas of minimum outer diameter and forms a true round tube and thickens the wall without interrupting the generally longitudinal grain structure of the metal.

Further objects and advantages of the present invention will be apparent from the following detailed description, with reference to the accompanying drawings in which like reference characters refer to the same parts throughout the several views, and in which:

FIGURE 1 is a longitudinal sectional view showing a length of tubing in transfer member preparatory to its insertion in the die;

FIGURE 2 is a view corresponding to FIGURE 1 showing the length of tubing inserted in the die by the ram member;

FIGURE 3 is a view corresponding to FIGURE 1 showing the end portion of the piece of tubing beginning to thicken under the axially compressive force of the ram member;

FIGURE 4 is a view corresponding to FIGURE 1 showing the tube wall fully formed into intimate contact with the inner annular die under the intense force or the ram member;

FIGURE 5 is a view corresponding to FIGURE 1 showing the shouldered internal die stripping the finished part from the external die and replacing it in the transfer member;

FIGURE 6 is a view corresponding to FIGURE 1 showing the finished part retained by a stripper fork in the transfer member while the internal die is extracted therefrom and returned to its rest position;

FIGURE 7 is a fragmentary longitudinal sectional view on an enlarged scale of the tube in the dies prior to compression and indicating the longitudinal grain structure of the metal;

FIGURE 8 is a view corresponding to FIGURE 7 showing the tube wall beginning to upset and thicken;

FIGURE 9 is a view corresponding to FIGURE 7 showing the tube wall in a further state of thickening;

FIGURE 10 is a view corresponding to FIGURE 7 showing the tube wall fully formed into contact with the internal die and showing how the original grain structure still constitutes the common grain of the thicker and thinner portions of the wall;

FIGURE 11 is a longitudinal section view of a finished part preparatory to other forming operaions which render it suitable for use as a blank for a valve tappet body.

FIGURE 12 is a view of the rolling step utilized on the blank to produce an inwardly deformed zone around the mid-portion of the blank;

FIGURE 13 is a view of the next step of the manufacturing method which involves the fusion bonding of a cast iron end piece to the tube to complete the blank for a tappet body in accordance with the principles of this invention;

FIGURE 14 is a fragmentary sectional view corresponding to FIGURE 8 showing the result obtained when the piece of tubing does not fit within the outer annular die in accordance with the principles of this invention;

FIGURE 15 is a view corresponding to FIGURE 14 showing the undesirable final results of such an operation;

FIGURE 16 is a fragmentary longitudinal sectional view of the thick end of a piece of tubing showing the interrupted grain structure resulting from machining away part of the internal wall of a thick piece of tubing to obtain the desired shouldered internal configuration as in the prior art practice; and

FIGURE 17 is a schematic view of the preferred form of apparatus for practicing this invention including the mechanico-hydraulic motivator and its flexible powering and controlling connections with the apparatus of this invention.

In its broader aspects, this invention contemplates completely sizing a finished tubular part from a comparatively short length of inexpensive thus ordinarily rough tubing made by processes having large tolerances as to volume, roundness, straightness, and concentricity. According to this invention, such a piece of rough tubing is forced axially into a cylindrical external die which may have a flaring taper at one end to facilitate the compression of the tubing therein. The external die is slightly smaller in diameter than the minimum external diameter of the tubing, so that all parts of the tubing, even low points on the outer surface are compressed slightly beyond the elastic limit. This causes the tubing to take a permanent set so that the tubes outer surface completely and permanently shapes itself to the die configuration. An inner sizing mandrel or die is placed within the piece of tubing, and it may have a comparatively loose fit to accommodate irregularities in the tubing wall thickness. At one end, the internal mandrel is stepped down to a smaller diameter in the zone where it is desired that the tube wall be inwardly thickened. With the length of tubing thus located around the internal form and compressed within the external form, an axially compressive forming force is exerted against the ends of the tube without prior artificial heating to thicken the tube and force the inner surface of the tube into intimate contact with the internal form. This produces a tubular workpiece having a thickened wall portion at one end which is accurately sized in accordance with the configurations of the internal and external dies, and which maintains the parallelism of the original grain structure of the metal in a somewhat expanded form.

Referring now with more particularity to the drawings, FIGURE 1 shows a piece of rough tubing 10 located in a cylindrical work piece carrying cavity 12 located in a transfer member 16, described in more detail below. The transfer member can be indexed about an axis 14 (FIG. 17). Axially aligned with the socket 12 is a die cavity in the press frame or bed 18. The die cavity arrangement may comprise a generally cylindrical bore serving as an external form 20 having a flared or outwardly tapered opening 22 defining its one end and an internal shoulder 24 defining its other extremity. The internal form means may comprise a cylindrical mandrel 26 of a radius less than the radius of the outer form 21], a stepped down cylindrical portion 28 of a somewhat smaller radius, and a conical shoulder section 36 joining the two mandrel sections in a concentric relationship. On the end opposite the stepped down portion 28, the internal form 26 has an enlarged rod portion 32 joined thereto by an external shoulder 34 which may have a lateral dimension of about half the wall thickness of a piece of tubing. The rod portion 32 is slidably received within a bore 36 in the frame 18, and serves as a support to maintain the larger and smaller diameter portions of the internal form concentrically located within the external form 20.

Axially aligned with the work carrying socket 12 on the other side of the shiftable member 16 is a ram 49 having an annular end pressing surface 42 formed by an aperture 44 in its end. The outer diameter of the plunger ram 41) is smaller than the diameter of the workpiece socket 12 in the transfer member, and very closely conforms to the diameter of the external form 20. The diameter of the aperture 44- in the end of the ram is such as to receive the stepped down portion 28 of the internal form.

The shiftable index member 16, the ram or press plunger 40, and the internal form 26 mounted on the shaft 32 are all connected to be shifted relative to the press frame 18 by suitable hydraulic motors. Referring to FIGURE 17, the index member 16 may comprise a unit containing at least two of the work piece carrying means 12 which is pivotally mounted about a fixed axis 14. While a to-and-fro oscillating index member could readily be employed for transferring work pieces to and from the pressing station, the preferred embodiment of this invention employs a turret type index member mounted for rotation in a vertical plane, as indicated by the dash dot continuation lines 46. This member may be intermittently indexed through a predetermined interval by a pair of shiftable piston type fluid motors 43 and 50. A gear 52 connected as at 54 with the index member 16 is adapted to be periodically rotated by a pinion 56 rotated by a reciprocating rack 58 formed on the rod 60 of the piston 62 of the motor 48. The pinion 56 is also adapted to be shifted axially by the fluid motor 50 to disengage from the rack teeth 58 so that the rack may be returned to its rest position while the index member 16 remains idle during a pressing operation.

A loading station comprising a gravity fed chute 61 containing a supply of properly cut lengths of rough tubing may be provided to load single work pieces to successively presented sockets 12. A fluid motor 63 positioned to shift the bottom work piece from the stack to a socket may receive pressurized fluid at either end through suitable connections from a source described below. Similarly, an unloading station comprising an ejector plunger 65 operated by a fluid motor 67 may be provided to remove finished work pieces from the sockets 12 and discharge them into a suitable carryaway chute, not shown.

The ram plunger 40 is formed as the rod of a piston 64 shiftable through a long stroke within a cylinder 66. Hydraulic fluid admitted to the cylinder 66 through a connection 68 serves to retract the plunger 40 from the vicinity of the work piece carrying socket 12 at the pressing station. An opening 70 admits pressure fluid to the cylinder 66 on the other side of the piston 64 to shift the plunger 40 forward during the pressing operation. Closing the other end of the opening 70 is the cylindrical rod 72 of a large area intensifier piston 74 shiftable to and fro through a short stroke in a large diameter cylinder 76. A connection 78 at the rear end of the opening 70 admits hydraulic medium thereto to shift the piston 64 forwardly. A connection 80 admits pressurized fluid against one side of the intensifier piston '74 in the cylinder 76, and a connection 82 admits pressurized fluid to the other side of the piston 74. As can be seen, when the piston 74 is shifted to the left, its rod 72 will cover the connection 78 and then exert an extremely high pressure upon the fluid medium in the opening 70 and the cylinder 66 behind the piston 64 to enable the plunger 40 to exert an intense forming force at the terminal portion of its leftward travel.

The internal form 26 on the other side of the shiftable work carrying member is connected with a fluid motor 84 to be shifted to the right to eject a finished work piece from the external form. The support bar 32 of the internal form is mounted on the outward end of the rod 86 of a piston 88 shiftable to and fro in the motor 84. A connection 98 admits pressurized fluid to the rear end of the motor 84 to shift the piston 88 away from its rest position for stripping and transferring work pieces, and a connection 92 admits fluid to the other side of the piston 88 to return it to its rest position.

Another fluid motor 94 located at the pressing station contains a shiftable piston 96 on the outward end of the rod of which is a bifurcated spacing member 93. When the piston 96 is shifted away from its rest position by pressurized fluid admitted to the motor 94 through a connection 160, the bifurcated member 98 is shifted to a position against the press frame 18 and within a milled slot 102 in the transfer member 16 adjacent a workpiece carrying socket 12. This member 98 serves to retain a finished work piece in the socket 12 and support the transfer member 16 against axial deflections while the internal mandrel is extracted therefrom by rearward motion of the piston 88, as will be explained below.

For the purpose of giving coordinated motivation to the various fluid motors described above, there is provided a mechanico-hydraulic programming system for producing a cycle of coordinated movement, illustrated diagrammatically in FIGURE 17. This system may be constructed as a self-contained unit having its own housing, not illustrated, which may be positioned at any convenient location on or adjacent the machine and connected to the various hydraulic cylinders by suitable flexible piping. The mechanico-hydraulic drive unit comprises a master camshaft 104 carrying a plurality of cams 106, the followers of which operate the transmitter pistons 108, each of which forms part of a liquid column type motion transfer device of which there are nine units shown in the diagram of FIGURE 17. Each piston reciprocates in a cylinder 110 having a head B which contains a suitable inlet replenishing check valve 112 and a high pressure adjustable relief valve 114, both of which communicate with a low pressure oil reservoir 116 preferably formed in a housing enclosing the drive unit.

For turning the camshaft 184, a motor 118 drives an input shaft 120 of a two-speed transmission through a belt drive 122. The input shaft 120 drives a pinion 124 and also the input member of a hydraulically engaged, spring-released clutch 126. Pinion 124 drives a gear 128 secured to a countershaft 130 which carries a pinion 132 at its opposite end. Pinion 132.drives a gear 134 and therewith constitutes a set of change speed gears. Gear 134 drives the input member of a second hydraulically engaged, spring-released clutch 136. The driven members of

clutches

126 and 136 are secured to the opposite end of a shaft 138, having a worm 140 thereon and a brake drum 142. The latter has a spring-biased hydraulic motor 144 for engaging the brake. Worm 140 drives a worm wheel 146 secured to the master camshaft 104.

For the purpose of automatically controlling the starting, stopping, and speed of the transmission, there is provided a hydraulic control pump 148 driven from the gear 134, which may circulate a body of oil contained in the housing surrounding the transmission. The pump 148 may deliver to a combined accumulator and relief valve comprising a spring-loaded piston 150 and also supplies oil to a bank of

control valves

152, 154 and 156. In the diagrams, each valve is shown as a two-position valve, spring-biased to the position illustrated in which the connections shown in the cross-hatched rectangles are established. Single headed arrows are used to indicate flow at reservoir pressure. and double headed arrows to indicate flow at pump delivery pressure. Each of the valves, when shifted, establishes the connection shown in the unhatched retangles immediately below the hatched rectangles.

Valve 152 is arranged to be shifted by a solenoid 158. The

valves

154 and 156 are arranged to be shifted by the

adjustable cams

168 and 162 respectively, which are positioned on the camshaft 184. In addition, the valve 154 has a hydraulic holding cylinder 164 which holds the valve 154 in its shifted position until it is released by the shifting of valve 156. Valve 152, in the position shown, delivers pressure fluid to engage the brake 144 and also exhaust fluid to release the low speed clutch 136, subject, however, to a conjoint control by the valve 154.

The latter valve, in the position illustrated, exhausts fluid to release the high speed clutch 126 and places the low speed clutch under the control of the valve 152. In its shifted position, valve 154, provided valve 152 has been shifted, delivers pressure fluid to engage high speed clutch 126 and exhaust fluid to release low speed clutch 136. As previously explained, the valve 156 is merely a rest valve for by-passing the holding cylinder 164 to permit valve 154 to return to its spring-biased position shown in the drawings.

Thus, energization of solenoid 158 will start the camshaft rotating at slow speed. Thereafter, the cam 160 will shift the transmission to drive the camshaft 104 at high speed, and still later the. cam 162 will again shift the transmission to slow speed. So long as the solenoid 158 remains energized, the camshaft 104 will continue to rotate, first at a low speed and then at a high speed during each revolution, controlling its own speed changes by operation of the

cams

160 and 162.

For the purpose of controlling the drive motor 118 and solenoid 158, there is provided an electric control circuit connected between a pair of electric supply lines L1 and L2. The circuit may include a master relay 166 of the holding type having a manual master start switch 168 and a manual master stop switch 170. Relay 166 controls the motor 118 and also a cycle control relay 172 of the holding type having a manual cycle start switch 174 and a manual cycle stop switch 176. The normally open contacts of relay 172, which are of the make-beforebreak type, control energization of cycle solenoid 158 directly. The normally closed contacts of relay 172 also control solenoid 158, but are in series with a cam switch 178 on the end of the camshaft 104 and arranged to be opened once during each revolution thereof. The arrangement is such that when the cycle stop switch 176 is operated at any point in the rotation of camshaft 104, relay 172 will be de-energized, but solenoid 158 will remain energized until cam switch 178 opens at the predetermined stopping point. Operation of the master stop switch 170, however, will de-energize solenoid 158 immediately, regardless of the point in the cycle, and will also de-energize motor 118.

The camshaft 104, as previously mentioned, drives a number of cam operated hydraulic pulsator sections designated a through i inclusive. Each section may comprise units duplicating the single acting pulsating cylinder 110 the head B of which contains the replenishing check valve 112 and the spring-closed relief valve 114. All the replenishing and relief valves are connected to a common oil reservoir 116 formed in the housing of the unit. The reservoir 116 is preferably subjected to a low, superatmospheric pressure by a body of compressed air or other pressure maintaining arrangements. Check valves 112 allow flow from the reservoir 116 to each cylinder 110 while relief valves 114 allow flow oppositely when the cylinder pressure exceeds a certain value. Thus, each of the pairs of valves 112 and 114 may be referred to as a balancing valve which serves to balance the volume of fluid in each of the liquid column sections, as will be later described.

The pulsator sections a through i are connected by closed liquid column lines with the work performing fluid motors. Pulsator section a is connected by its closed liquid column line 180a with the connection 180 of the fluid motor 94. The pulsator section b is connected by its closed liquid column line 18% with the fluid motor 48 for reciprocating the rack 58 to shift the transfer member 16. The pulsator section 0 is connected by its closed liquid column line 1800 with the connection 80 at the rear of the fluid motor 84 for extending the internal form 26 to strip the finished workpiece from the external form 20. The pulsator section d is connected by its closed liquid column line 18011 with the fluid motor 50 for shifting the piston 56 out of engagement with the rack 58 so that the rack may be reset during the pressing portion of the machine cycle. The pulsator section e is connected by its closed liquid line 180e with the connection 78 for admitting hydraulic medium to the opening 70 at the rear of the cylinder 66 of the ram actuating motor; likewise, the liquid column line 180g from pulsator section g may be connected in tandem therewith to provide an additional volume of fluid on the piston 64 of the ram 40 to accommodate the unusually long transfer stroke of the ram. The pulsator section 1 is connected by its closed liquid column line 180f with the connection 82 at the rear of the intensifier cylinder 76. Finally, the pulsator sections it and i are connected by their closed liquid column lines 180/1 and 180i with the fluid motors 63 and 67, resoectively, for operating the loading and unloading stations associated with the transfer member 16.

In order to insure proper synchronization of the driving and driven eleemnts of each pulsator section, it is desirable to provide slightly more fluid displacement in the driving or transmitting elements 108, 110 than is present in their respective fluid motors at the opposite end of the liquid column line. Thus, at the end of each advancing stroke of the transmitter piston 103, a small amount of fluid will be discharged to the reservoir 116 through the relief valve 114. This amount, plus any amount lost by leakage, will be returned to the liquid column at the end of the return stroke by the operation of the replenishing valve 112.

In FIGURE 17, there are shown several circles marked RO connected to the end of the motive cylinders opposite the liquid column connections. These symbols designate the return oil connections by means of which a pulsator system may be hydraulically biased so as to maintain the follower in close contact with the cam as the falling portion of the cam contour recedes from the follower. This bias is maintained by a high pressure accumulator or oil reservoir, not shown, which may be provided with a manifold whereby all of the RO connections are joined together and to the high pressure reservoir. The showing of separate return oil connections FIGURE 17 is indicative of any suitable type of biasing pressure source, whether it be a single accumulator or multiplicity thereof. The contours of the individual cams 106 are likewise not illustrated in specific detail since they may be formed in accordance with the usual practice to cause motivation of each of the respective hydraulic motors in accordance with the particular operating cycle desired for the machine. Likewise, the speed ratio between the high and low speeds of the camshaft 104, and the duration of the high speed portion of the cycle, may be selected as desired through use of the appropriate change gears and through the adjustment of the

cams

160 and 162, if desired. Of course, the two speed feature of the transmission may be omitted and the high speed clutch 126, the

cams

160 and 162 and the

valve

154 and 156 eliminated.

In operation, the above described apparatus may be utilized to accomplish the improved method of tube wall expanding of the invention. The index member 16 under control of the motivator section b and d shifts a workpiece socket 12 to the pressing station with a short length 10 of rough tubing having been positioned in the socket 12 by the motor 63 at the loading station under control of the motivator section h, shown in FIGURE 1. With the shiftable member 16 stationary and the pinion 56 disconnected from the rack 58 so that the rack may be reset, the cams 106 at motivator sections 2 and g transfer liquid through their respective liquid column lines to the connection 78 in the opening 70 to shift the ram forwardly into the workpiece carrying socket 12 at the pressing station. As can be seen in FIGURE 2, the ram 40 will push the piece of tubing from the socket 12 and into the axially adjacent tapered or flared end of the external form 20 in the press frame 18. The diameter of the external form 20 is slightly smaller than the smallest anticipated diameter of the piece of rough tubing so that the tubing will be compressed in the flared portion 22 of the form as it enters. Aside from sizing the outer diameter of the tube, this press fit accomplishes an anti-buckling or anti-folding feature discussed below in connection with FIGURES 14 and 15.

The piece of tubing is pushed all the way into the outer die 20 until it abuts the

shoulders

24 and 34 by the long stroke of the piston 64. At this point, the cam 106 at motivator station 1'' pulses fluid through the connection 82 to the rear side of the intensifier piston 74 which in turn creates high pressure in the liquid behind the piston 64 to create an intense forming force transmitted by the ram 40 to the tubular workpiece. As can be seen in FIGURE 3, the end 42 of the ram, which fits closely to the outer form, acts to thicken the wall of the tube in the zone of the stepped down portion 28 of the internal form.

Regarding FIGURES 7 through 10, it can be seen that the thickness of the tube Wall is increased with a plasticlike flow under the intense axial pressure of the ram. This type of flow maintains the grain structure lines 182, which extend generally longitudinally of the tubing, in a generally straight or linear pattern. There is no buckling or folding of the metal, but a gradual, flowing increase in the thickness of the wall. This proceeds initially in the midportion of the zone to be thickened, being restrained at one end by the large diameter portion 26 of the internal form and at the other end by the pressure between the metal and the face 42 of the ram. The tube is thickened into intimate contact around the full surface of the

portions

26, 28 and 30 of the internal form, the grain structure lines flowing smoothly into the thickened zone. Trapped air and parting agent or other fluid may escape at one end through a narrow vent 31 and at the other end it may squeeze between the ram and the inner die and be collected in the cavity 44. When this point of full thickening is reached, as in FIGURES 4 and 10, the lateral dimensions of the tubular part are accurately established, the length of individual workpieces varying slightly as a result of the volume variations between original rough pieces. When the die is thus filled, further rise on the cam 106 at motivator section f causes excess liquid to be diverted through the pressure relief valve to the reservoir 116. At this point in the description, an advantage additional to the sizing advantages above noted of the close press fit between the outer diameter of the tubular workpiece and the external form 20 is apparent. Regarding FIGURE 14, if there is space between the outer surface of the tube wall and the surface of the external form, the following will occur. A completely unsupported length of tube subjected to axial pressure has an inherent tendency to move in the direction of least resistanceoutwardly. If the length of tube is short enough, this tendency will result in a single outward bulge surrounding the tube; if the tube is considerably longer than its outer diameter, this will result in a plurality of axially spaced annular bulges separated by portions which will eventually tend to buckle inwardly as axial compression continues. This, in cross section, takes the form of waves which are soon squeezed into folds resulting in creases upon the application of suflicient pressure. Even though the outer bulging tendency is belatedly constricted by means of an external form, after it has once started on unheated metal tubing the buckling phenomena continues once the longitudinal relationship of the grain structure has been disturbed. As seen in FIGURES 14 and 15, even a slight space between the original outer surface of the wall and the external form will thus result in a creased and folded tube end which, while thicker in appearance, is merely bent or folded into that configuration, and the wall itself is not actually thickened at all. This is a very undesirable feature for work components such as valve lifter bodies. It results in a weak structure having fissures and cracks running circumferentially of the workpiece both on the inner and outer walls, as well as occasional voids around the center of the wall.

After the wall has been thickened as shown in FIG- URES 4 and 10, the ram 40 may be retracted from the press frame and workpiece carrying socket 12 by hydraulic pressure from the source RO as the cams at the motivator sections e, f and g recede by continued rotation of the camshaft 104. The cam 106 at motivator section 0 may then shift the piston 88 forward whereupon the shoulder 34, at the end of the annular die cavity, strips the finished workpiece from the external die 20, as in FIGURE 5. The

shoulder 34 continues to push the workpiece until it is again located in the workpiece carrying socket 12 of the transfer member 16.

At this point, the cam at motivator section a transfers motion via its liquid column 180a to the upper face of piston 96 to move the fork 98 between the pressing frame 18 and the transfer member 16 (FIGURE 6) in abutting relationship with the finished workpiece. This maintains the workpiece in its socket and also steadies the transfer member while the internal form is retracted therefrom by rearward shifting of the piston 88. During the pressing operation, a previously thickened tube is removed from the transfer member 16 at the unloading station by operation of the fluid motor 67 under control of the motivator section i. As the fluid motors all return to their rest positions, one machine cycle is complete.

The product formed by this method as performed by the preferred exemplary apparatus described above is best seen in FIGURE 11. In longitudinal central sectional elevation, the tubular workpiece has a cylindrical body portion 184 of a predetermined wall thickness, an axially adjacent portion 186 which forms an internal shoulder, and a thickened end portion 188. The radial dimensions of this part are accurately sized, and the three axially adjacent portions have a continuous common, longitudinally extending grain structure which expands gradually from the thinner to the thicker wall portion.

FIGURE 16 shows, by way of comparison, the appearance of the tube Wall grain structure of a part formed from an initially thick piece of tubing which has had one portion machined out. It will be observed that the grain structure of the thick portion of the wall comes to an abrupt end at the internal shoulder, as compared with the gradually expanding, completely intact grain structure preserved in the article of this invention.

FIGURE 12 represents the next tube Working operation in the method of forming bodies for valve tappets. Internal arbors 200, 202 having

external shoulders

204, 206, respectively, are inserted in opposite ends of a work piece with each shoulder abutting an end thereof. A plurality of rollers 2G8 of the forming variety are then moved radially into the rotating workpiece intermediate its ends while the

shoulders

204 and 206 exert an axially compressive force on the work piece to produce an annular deformed wall portion having both the inner and outer diameters reduced. The inner diameter of this deformed portion may be reduced to a diameter corresponding to the inner diameter of the thickened wall portion 188 formed by the previous wall upsetting step of the method. This also may be a cold forming step, and it produces an internal diameter sized to the mandrel 202 and an external cannelure or annular groove which may serve as an oil pickup groove in the finished product.

The next step in forming the metal blank for use with valve tappets (FIG. 13) involves the joining of a closure member 300 to the unthickened end of the tubular work piece. This closure member may comprise a cast iron button having an outer diameter corresponding to the outer diameter of the tube, and a concentric upstanding central section 302. which may fit telescopically within the end of the tube to provide a larger joining area. A pair of electrodes 304, 306, one engaging the tube and the other engaging the button 390, produce a fusing heat above the melting temperature of the cast iron end piece but below that of the steel tube. Compressive members 310, 312 then exert an axially compressive force to upsetthe steel of the tube into intimate contact with the raised portion 302 of the button 30% as a fusion bond is formed by the electric heating current at the outer extremity of the joint. This final step in the production method produces a cup-shaped tappet body having an inwardly thickened rim 188, an annular inwardly deformed groove around the mid-section ll) of the wall, and a wear resistant bottom 300 adapted to follow a rotary cam in an automotive internal combustion engine.

Thus, in three steps, all of which lend themselves admirably to mass production techniques, a blank for a valve lifter body is formed having a tubular skirt portion with two portions of reduced inner diameter, and one portion of reduce-d outer diameter for an oil pickup groove; the cast iron end piece fusion bonded to the unthickened end of the skirt portion completes the unitary structure to provide a part of complex shape without any waste.

The first of these operations, the expanding of the tube Wall to provide a thickened wall portion, maintains substantially the original inherent parallelism of the grain structure of the original tube wall, and produces the desired radial dimensions without the necessity of a heating operation. The mechanico-hydraulic power and control apparatus of this invention performs the tube wall expanding method in a manner which lends itself admirably to mass production techniques, the total cycle time of such a machine being in the neighborhood of one second.

While the above described embodiment constitutes a preferred mode of carrying out this invention, many other forms might be adopted within the scope of the actual invention, which is variously claimed as:

1. The method of cold thickening an axial zone of a tubular metal workpiece which includes taking a nominally circular tube having a longitudinally extending grain, which tube may vary slightly from precise circular shape and has a nominally uniform outside diameter, which diameter may vary slightly along the length of the tube, pressing the tube axially into a cylindrical die having in said zone a uniform internal diameter slightly less than the minimum outside diameter of the tube to form the portion of tube in the zone into a precisely circular shape of uniform outside diameter, which portion in the zone is uniformly rigidly supported radially by intimate contact with the die as a result of the forming operation, using an internal form in said zone of the tube, and applying to the tube at opposite ends of said zone axially compressive force to shorten the tube and cause the cold metal to flow and conform accurately to the internal form without folding or bending to make a workpiece having a thick walled annular portion and an axially adjacent thin walled annular portion in which workpiece the grain of the metal remains generally straight and parallel to the axis throughout the length of the workpiece and expands smoothly and continuously, from the thin walled portion into the thick walled portion.

2. The method of cold thickening an axial zone of a tubular metal workpiece which includes taking a nominally circular tube having a longitudinally extending grain, which tube may vary slightly from precise circular shape and has a nominally uniform outside diameter, which diameter may vary slightly along the length of the tube, radially supporting the tube against outward deformation rigidly and uniformly along the length of the zone, using an internal form in said zone of the tube, and applying to the tube at op osite ends of said zone axially compressive force to shorten the tube and cause the cold metal to flow and conform accurately to the internal form without folding or bending to make a workpiece having a thick walled annular portion and an axially adjacent thin walled annular portion in which workpiece the grain of the metal remains generally straight and parallel to the axis throughout the length of the workpiece and expands smoothly and continuously from the thin walled portion into the thick walled portion.

3. The method of cold thickening an axial zone of a tubular metal workpiece which includes taking a nominally circular tube having a longitudinally extending grain, which tube may vary slightly from precise circular shape and has a nominally uniform outside diameter, which diameter may vary slightly along the length of the tube, pressing the tube axially into a cylindrical die having in said zone a uniform internal diameter sufficiently less than the minimum outside diameter of the tube to deform the tube beyond its elastic limit and permanently to form the portion of tube in the zone into a precisely circular shape of uniform outside diameter, which portion in the zone is uniformly rigidly supported radially by intimate contact with the die as a result of the forming operation, using an internal form in said zone of the tube, and applying to the tube at opposite ends of said zone axially compressive force to shorten the tube and cause the cold metal to flow and conform accurately to the internal form without folding or bending to make a workpiece having a thick walled annular portion and an axially adjacent thin walled annular portion in which workpiece the grain of the metal remains generally straight and parallel to the axis throughout the length of the workpiece and expands smoothly and continuously from the thin walled portion into the thick walled portion.

4. The method of cold thickening an axial zone of a tubular metal workpiece which includes taking a nominally circular tube having a longitudinally extending grain, which tube may vary slightly from precise circular shape and has a nominally uniform outside diameter, which diameter may vary slightly along the length of the tube, placing the tube in a carrier, placing the carrier to hold the tube in axial alignment with a cylindrical die having in said zone a uniform internal diameter slightly less 'than the minimum outside diameter of the tube, pressing the tube axially into the die by means exerting a first force in one direction on one end of the tube to form the portion of tube in the zone into a precisely circular shape of uniform outside diameter, which portion in the zone is uniformly rigidly supported radially by intimate contact with the die as a result of the forming operation, using a shouldered internal form in said zone of the tube, applying to the opposite end of the tube a force which is derived from the shoulder and opposes said first force while said first force is maintained so that the two forces shorten the tube and cause the cold metal to flow accurately against the internal form without folding or bending to make a workpiece having a thick walled annular portion and an axially adjacent thin walled annular portion in which workpiece the grain of the metal remains generally straight and parallel to the axis throughout the length of the workpiece and expands smoothly and continuously from the thin walled portion into the thick walled portion, ejecting the workpiece from the die into the carrier by said shoulder while withdrawing the means exerting the first force, holding the workpiece in the carrier and withdrawing the form from the interior of the workpiece.

5. The method of cold thickening an axial zone of a tubular metal workpiece which includes taking a nominally circular tube having a longitudinally extending grain, which tube may vary slightly from precise circular shape and has a nominally uniform outside diameter, which diameter may vary slightly along the length of the tube, placing the tube in a carrier, placing the carrier to hold the tube in axial alignment with a cylindrical die having in said zone a uniform internal diameter slightly less than the minimum outside diameter of the tube, pressing the tube axially into the die by means exerting a first force in one direction on one end of the tube to form the portion of tube in the zone into a precisely circular shape of uniform outside diameter, which portion in the zone is uniformly rigidly supported radially by intimate contact with the die as a result of the forming operation, using a shouldered internal form in said zone of the tube, applying to the opposite end of the tube a force which is derived from the shoulder and opposes said first force while said first force is maintained so that the two forces shorten the tube and cause the cold metal to flow accurately against the internal form without folding or bending to c make a workpiece having a thick walled annular portion and an axially adjacent thin walled annular portion in which workpiece the grain of the metal remains generally straight and parallel to the axis throughout the length of the workpiece and expands smoothly and continuously from the thin walled portion into the thick walled portion, ejecting the workpiece from the die into the carrier by said shoulder while withdrawing the means exerting the first force, holding the workpiece in the carrier while withdrawing the form from the interior of the workpiece, moving the workpiece in the carrier away from the die, and ejecting the workpiece from the carrier with said force-exerting means.

6. The method of forming a tubular tappet blank from a nominally circular tube having a longitudinally extending grain, which tube may vary slightly from precise circular shape and has a nominally uniform outside diameter, which diameter may vary silghtly along the length of the tube, which method includes radially supporting the tube against outward deformation rigidly and uniformly along the length of a zone to be thickened, using an internal form in the tube, the form having a first cylindrical portion fitting the inside diameter of the tube and a concentric portion of materially smaller diameter disposed in the zone, applying to the tube at opposite ends of the axially compressive force to shorten the tube and cause the cold metal to flow and conform accurately to the internal form without folding or bending to make a workpiece having a thick walled annular portion and an axially adjacent thin walled annular portion in which workpiece the grain of the metal remains generally straight and parallel to the axis throughout the length of the workpiece and expands smoothly and continuously from the thin Walled portion into the thick walled portion, holding in the open end of the thin walled portion a mandrel which fits the diameter of the thin walled portion, holding in the remainer of the thin walled portion a second mandrel whose diameter fits the inside diameter of the thick walled portion, and rolling an inside annular head into the thin walled portion to fit the second mandrel, thereby to form a tappet blank having two portions of reduced inside diameter and one portion of reduced outside diameter.

7. The method of forming a tubular tappet blank from a nominally circular tube having a longitudinally extending grain, which tube may vary slightly from precise circular shape and has a nominally uniform outside diameter, which diameter may vary slightly along the length of the tube, which method includes radially supporting the tube against outward deformation rigidly and uniformly along the length of a zone to be thickened, using an internal form in the tube, the form having a first cylindrical portion fitting the inside diameter of the tube and a concentric portion of materially smaller diameter disposed in the zone, applyng to the tube at opposite ends of the zone axially compressive force to shorten the tube and cause the cold metal to flow and conform accurately to the internal form without folding or bending to make a workpiece having a thick walled annular portion and an axially adjacent thin walled annular portion in which workpiece the grain of the metal remains generally straight and parallel to the axis throughout the length of he workpiece and expands smoothly and continuously from the thin walled portion into the thick walled portion, holding in part of the thin walled portion a mandrel whose diameter fits the inside diameter of the thick walled por tion, and rolling an axial length of the thin walled portion to fit the mandrel to form a tappet blank having two portions of reduced inner diameter and one portion of reduced outer diameter.

8. The method of forming a tubular tappet blank from a nominally circular tube having a longitudinally extending grain, which tube may vary slightly from precise circular shape and has a nominally uniform outside diameter, which diameter may vary slightly along the length of the tube, which method includes uadially supporting the tube against outward deformation rigidly and uniformly along the length of a zone to be thickened, using an internal form in the tube, the form having a first cylindrical portion fitting the inside diameter of the tube and a concentric portion of material of smaller diameter disposed in the zone, applying to the tube at opposite ends of the zone axially compressive force to shorten the tube and cause the cold metal to flow and conform accurately to the internal form without folding or bending to make a workpiece having a thick walled annular portion and an axially adjacent thin walled annular portion in which workpiece the grain of the metal remains generally straight and parallel to the axis throughout the length of the workpiece and expands smoothly and continu-oulsy from the thin walled portion into the thick walled portion, holding in part of the thin walled portion a mandrel whose diameter fits the inside diameter of the thick Walled portion, and rolling an axial zone of the thin walled portion to fit the mandrel While maintaining the shape and size of the open end of the thin walled portion to form a tappet blank having two portions of reduced inner diameter and one portion of reduced outer diameter.

9. The method of forming a tubular tappet blank from a nominally circular tube having a longitudinally extending grain, which tube may vary slightly from precise circular shape and has a nominally uniform outside diameter, which diameter may vary slightly along the length of the tube, which method includes radially supporting the tube against outward deformation rigidly and uniformly along the length of a zone to be thickened, using an internal form in the tube, the form having a first cylindrical portion fitting the inside diameter of the tube and a concentric portion of materially smaller diameter disposed in the zone, applying to the tube at opposite ends of the zone axially compressive force to shorten the tube and cause the cold metal to flow and conform accurately to the internal form without folding or bending to make a workpiece having a thick walled annular portion and an axially adjacent thin walled annular portion in which workpiece the grain of the metal remains generally straight and parallel to the axis throughout the length of the workpiece and expands smoothly and continuously from the thin walled portion into the thick walled portion, holding in part of the thin walled portion a mandrel whose diameter fits the inside diameter of the thick walled portion, and rolling an axial zone of the thin walled portion to fit the mandrel while maintaining the shape and size of both ends of the thin walled portion to form a tappet blank having two portions of reduced inner diameter and one portion of reduce outer diameter.

10. The method of forming a tubular tappet blank from a nominally circular tube having a longtitudinally extending grain, which tube may vary slightly from precise circular shape and has a nominally uniform outside diameter, which diameter may vary slightly along the length of the tube, which method includes radially supporting the tube against outward deformation rigidly and uniformly along the length of a zone to be thickened, using an internal form in the tube, the form having a first cylindrical portion fitting the inside diameter of the tube and a concentric portion of materially smaller diameter disposed in the zone, applying to the tube at opposite ends of the zone axially compressive force to shorten the tube and cause the cold metal to flow and conform accurately to the internal form without folding or bendng to make a workpiece having a thick walled annular portion and an axially adjacent thin Walled annular portion in which workpiece the grain of the metal remains generally straightand parallel to the axis throughout the length of the workpiece and expands smoothly and continuously from the thin walled portion into the thick walled portion, holding in the open end of the thin walled portion a mandrel which fits the diameter of the thin Walled portion, holding in the remainder of the thin Walled portion and in the thick walled portion mandrel means whose diameter fits the inside diameter of the thick walled portion, and rolling an inside annular bead into the thin walled portion to fit the mandrel means thereby to form a tappet blank having two portions of reduced inside diameter and one portion of reduced outside diameter.

11. The method of cold thickening an axial zone of a tubular metal workpiece which includes taking a nominally circular tube having a longitudinally extending grain, which tube may vary slightly from precise circular shape and has a nominally uniform outside diameter, which diameter may vary slightly along the length of the tube, pressing the tube axially into a cylindrical die having in said zone a uniform internal diameter slightly less than the minimum outside diameter of the tube to form the portion of tube in the zone into a precisely circular shape of uniform outside diameter, which portion in the zone is uniformly rigidly supported radially by intimate contact with the die as a result of the forming operation, having the wall of the tube initially spaced from any inner sup-porting means in said zone of the tube, and applying to the tube at opposite ends of the zone axially compressive force to shorten the tube and case the cold metal to flow and thicken into the space within the tube without folding or bending to make a workpiece having a thick walled annular portion and an axially adjacent thin walled annular portion in which workpiece the grain of the metal remains generally straight and parallel to the axis throughout the length of the workpiece and expands smoothly and continuously from the thin walled portion into the thick walled portion.

12. The method of cold thickening an axial zone of a tubular metal workpiece which includes taking a nominally circular tube having a longitudinally extending grain, which tube may vary slightly from precise circular shape and has a nominally uniform outside diameter, which diameter may vary slightly along the length of the tube, radially supporting the tube against outward deformation rigidly and uniformly along the length of the zone, having the wall of the tube initially spaced from any inner supporting means in said zone of the tube, and applying to the tube at opposite ends of the zone axially compressive force to shorten the tube and cause the cold metal to flow and thicken radially into the space within the zone without folding or bending to make a workpiece having a thick walled annular portion and an axially adjacent thin walled annular portion in which workpiece the grain of the metal remains generally straight and parallel to the axis throughout the length of the workpiece and expands smoothly and continuously from the thin walled portion into the thick walled potrion.

References Cited by the Examiner UNITED STATES PATENTS 1,735,695 11/1929 Rich 123-90 2,027,406 1/1936 Spatta 78-63 2,319,546 5/1943 Insley et al. 29156.7 2,344,285 3/1944 Cormode 78-63 2,408,325 9/1946 Luce et al. 29543 2,494,128 1/1950 Holquist et a1 29543 X 2,859,510 11/1958 Baxa 29545 X 2,887,098 5/1959 Thompson 123-90 2,935,059 5/1960 Thompson.

2,983,991 5/1961 Carlson 29-156.7 2,988,805 6/1961 Thompson 29156.7

WHETMORE A. WILTZ, Primary Examiner.

Claims

1. THE METHOD OF COLD THICKENING AN AXIAL ZONE OF A TUBULAR METAL WORKPIECE WHICH INCLUDES TAKING A NOMINALLY CIRCULAR TUBE HAVING A LONGITUDINALLY EXTENDING GRAIN, WHICH TUBE MAY VARY SLIGHTLY FROM PRECISE CIRCULAR SHAPE AND HAS A NOMINALLY UNIFORM OUTSIDE DIAMETER, WHICH DIAMETER MAY VARY SLIGHTLY ALONG THE LENGTH OF THE TUBE, PRESSING THE TUBE AXIALLY INGO A CYLINDRICAL DIE HAVING IN SAID ZONE A UNIFORM INTERNAL DIAMETER SLIGHTLY LESS THAN THE MINIMUM OUTSIDE DIAMETER OF THE TUBE TO FORM THE PORTION OF TUBE IN THE ZONE IN TO A PRECISELY CIRCULAR SHAPE OF UNIFORM OUTSIDE DIAMETER, WHICH PORTION IN THE ZONE IS UNIFORMALY RIGIDLY SUPPORTED RADIALLY BY INTIMATE CONTACT WITH THE DIE AS A RESULT OF THE FORMING OPERATION, USING AN INTERNAL FORM IN SAID ZONE OF THE TUBE, AND APPLYING TO THE TUBE AT OPPOSITE ENDS OF SAID ZONE AXIALLY COMPRESSIVE FORCE TO SHORTEN THE TUBE AND CAUSE THE COLD METAL TO FLOW AN CONFORM ACCURATELY TO THE INTERNAL FORM WITHOUT FOLDNG OR BENDING TO MAKE A WORKPIECE HAVING A THICK WALLED ANNULAR PORTION AND AN AXIALLY ADJACENT THIN WALLED ANNULAR PORTION IN WHICH WORKPIECE THE GRAIN OF THE METAL REMAINS GENERALLY STRAIGH AND PARALLEL TO THE AXIS THROUGHOUT THE LENGTH OF THE WORKPIECE AND EXPANDS SMOOTHLY AND CONTINUOUSLY FROM THE THIN WALLED PORTION INTO THE THICK WALLED PORTION.