US2588205A - Control mechanism for screw machines - Google Patents

Description

March 4, 1952 x. F. CASTELLI 2,538,205

CONTROL MECHANISM FOR SCREW MACHINES Filed Jan. 8, 1946 5 Sheets-Sheet l March 4, 1952 x. F. CASTELLI -CONTROL MECHANISM FOR SCREW MACHINES 5 Sheets-Sheet )2 Filed Jan. 8, 1946 March 4, 1952 x. F. CASTELLI 2,538,205

CONTROL MECHANISM FOR SCREW MACHINES Filed Jan. 8, 1946 5 She'ets-Sheet 5 Fig-6 m I is.

5 Fig 7 [i if 5 Sheets-Sheet 4 March 4, 1952 x. F. CASTELLI CONTROL MECHANISM FOR SCREW MACHINES Filed Jan. 8. 1946 & ulllllln u Hum March 4, 1952 x. F. CASTELLI CONTROL MECHANISM FOR SCREW MACHINES 5 Sheets-Sheet 5 Filed Jan. 8. 1946 I I .a i I Patented Mar. 4, 1952 CONTROL MECHANISM FOR SCREW MACHINES Xavier Francois Castelli, Paris, France, assignor to society called Societe Cri-Dan, Paris, France Application January 8, 1946, Serial No. 639,774 In France January 10, 1945 3 Claims.

The present invention relates to screw-cutting machines of the kind which performs a succession of operations similar to that of a semiautomatic lathe, i. e.: first cut, retraction of the tool, quick return, depth stroke for the next cut, second cut, and so on, until the work is performed but in which the longitudinal displacement of the toolholder is controlled by a rotating cam which is rotated from the driving spindle for the piece to be threaded while the prcgressive transverse advance of the tool, after each cut, is controlled by another cam intermittently rotated, also from the spindle, through a ratchet-wheel and a ratchet-mechanism, the various mechanisms being automatically stopped when the number of cuts selected to perform the thread has been reached.

Attempts have been heretofore made to perform, with machines of that kind, screw-cutt ng with multiple threads, but the app ratus proposed to that end, being generally of an irrational conception, were not adapted, in the majority of the works they were intended to perform, to efiect a uniform spacing of the cuts between the different threads and to achieve strictly identical depths of each of the latter.

The invention has for its object to produce a machine for cutting multiple threads in a remarkably simple manner, whatever may be the number of threads to be formed.

The process according to the invention substantially consists in angularly moving th cam which. controls the transverse advance of the tool, in order to secure the drive of the tool to the depth corresponding to the cut to be made, only once before each series of c' ts corres onding to the number of threads to be formed, and to maintain said cam stationary while the tool is performing said series of cuts, and correlatively realizing, between the driving spindle for the piece to be threaded and the cam controlling the longitudinal displacements of the tool, a speed ratio such that the complete revolution of the last cam corresponds to an integer number of complete turns of the spindle plus a fraction of a turn of said spindle equal to the inverse of the number of threads to be out.

In other words, if a threading of n threads is to be eifected, the cam for the transverse advance is angularly displaced, to give the advance depth for each successive cut, only once before each series of n cuts and is maintained stationary during the time said n cuts are performed, while the speed ratio between the spindle and the cam for the longitudinal displacements (pitch cam) is 2 selected such that the complete revolution of said pitch cam corresponds to an integer number of complete turns of the spindle plus a fraction equal to l/n of a turn of said spindle.

In such conditions, the threading tool, after each cut, is efiectively longitudinally displaced with respect to the previous thread cut; this displacement is equal to l/n times the lead given by the pitch cam, i. e. to the width of one of the n threads to be formed; the tool returns to its normal starting position, corresponding to the beginning of the first thread, when it cuts have been performed. The cam for the transverse advance remaining stationary during said 11. cuts,

' the tool is maintained at the same depth, so

that said cuts are successively performed on each of said 17. threads, at the rate of one cut for one thread, exactly at the same depth, a new advance of the tool being only realized for a successive series of n cuts, when the previous series of 12 cuts have been performed.

I have shown in the appended drawing an em-v bodiment of the invention as applied to a control mechanism for the transverse advance of the tool in a screw-cutting machine of the type described in my copending patent ap lication Serial No. 639,773, filed January 8, 1946, now Patent No. 2,576,570, granted November 27, 1951, for Screw Machine, but it is to be understood that such a mechanism is adapted to be combined with any screw machine which comprises a control for the advance cam by means of a ratchet-wheel.

Other characteristics of t is invention will appear from the following description of an embodiment thereof taken in connection with the annexed drawings in which:

Fig. 1 is an elevation view of the control mechanism of the .cam for the transverse advance;

Fig. 2 is a partial section through II-II of Fig. 1 looking upwardly from the section line;

Fig. 3 is a partial view of the mechanism shown in Fig. 1, in another position for working;

Figs. 4 and 5 are views of the same mechanism in two other positions of working;

Figs. 6 to 8 show different rotating members corresponding to the execution of different numbers of threads,

Figure :9 is a perspective view of the opfirating parts of a screw machine of the type described in my co-pending patent application, the frame. casings and supports being omitted.

Figure 9A is .a perspective view on a larger scale of that portion appearing on the left-hand part of Figure 9. 7

First, the exact location of the device according to the present invention in the entire machine will be positioned according to Figure 9, and the part played by each member connected mechanically to this device will be briefly described. In the example shown in Figure 9, the machine comprises a work bed IOI on which are mounted, on the one hand, a driving spindle I02 for the work piece and, on the other hand, a carrier I03, stationary during working but the longitudinal position of which may be varied. The rotation of the spindle I02 is controlled by means of a pulley I04 coaxial of the spindle and connected by belts I05 with a motor (not shown). The carrier I03 supports a longitudinal carriage I06, which is mounted so as to freely slide on the carrier. On the longitudinal carriage I06 is mounted a transversely movable carriage I 01 on which is mounted in a selected position a second transversely movable carriage I08 carrying a tool-holder turret I09. Moreover, the carrier I03 supports, on the side opposite the apron of the machine, the mechanisms adapted to automatically control the movement of the carriages I06 and I01. These mechanisms, which are arranged at the front of Figure 9, shall be further described hereinafter.

At its rear end, the spindle I02 carries a pinion IIO, through which it transmits its rotation to the mechanisms of the carrier. To this end, the pinion I I meshes with a toothed Wheel I I I keyed to a shaft H2. The shaft II2 carries a pinion II3, which drives a removable set of gears H4, H and H6, the shafts H1 and H8 of which are mounted on a support I I9 adapted to be locked in the correct meshing position by means of bolts I20. These gears, together with the pinion II 3 which is also removable, determine the step down ratio between the speed of rotation of the spindle I02 and the speed of the mechanisms carried by the carrier I 03. The shaft II 8 of the last gear I'I6 carries a pinion I2I adapted to mesh, at will, with one or the other of two pinions I22 and I23 mounted on a movable support I24 acting as motion-reversing means in order to produce left or right handed threads. The pinion I 2| is maintained in the desired position of rotation by means of locking bolts I25. The two inverting pinions I22 and I23 cooperate with a last pinion I26 keyed to a longitudinal shaft I21, which terminates inside the carrier I'03 where it carries a pinion I28 which is fixed to it for rotation by a key I29. The key I29 enters a longitudinal groove I 21a cut in the shaft I21, in which it can freely slide, thereby enabling the pinion I28 to be moved along the shaft I21 together with the carrier I03 when the longitudinal position of the latter is adjusted. The pinion I28 meshes with a toothed wheel I30 keyed to a shaft I3I, which carries at its end near the toothed wheel I30 a cam I32. The cam I32 engages a roller I33 fixed under the corresponding end of the longitudinal carriage I06. The roller I33 is urged into engagement with the cam I32 by two springs I34 disposed under the carriage I06, thereby urging the carriage in a direction away from the spindle I02. The cam I32, which is referred to as-pitch cam, controls the longitudinal movements of the carriage I06 and consequently of the tool (not shown) carried by the tool holder I09. The cam I32 determines the maximum length and the pitch of the screw to be cut, account being taken of the rotational speed given by the set of gears interposed between the spindle I02 and the shaft I21.

On the end of the shaft I3I opposed to that carrying the cam I26 are mounted two coupled cams I35 and I36 encased one in the other. and

acting on a roller I31 carried by a lever I38, the lower end of which is mounted on a fixed pin I39. A compressed spring I40 acts on the lever I38 to permanently maintain the roller I31 in contact with the cams I35 and I36. At its upper end, the lever I38 is connected by means of a cardan joint I4I to a. bar I42, which operates in a longitudinal slide (not shown) provided in the carrier I03. The free end of the bar I42 is fitted with a slope I42a, which terminates in a part I42b of less thickness, such part contacting one of the arms of a rocking lever I43 pivotally mounted on the carrier I03 by means of an axle I44. The other arm of the lever I43 bears on a pushing rod I45,

which is in contact with a control element I46 fixed on the transverse carriage I01, said pushing rod transmitting to the carriage I01, and thus to the tool, the transverse feeding motions against the action of a compressed spring I41 interposed between the longitudinal carriage I06 and the transverse carriage I01 and which tends to drive the latter toward the operator. The transverse feeding motions are controlled by a double eccentric cam I48 mounted on a rotatable shaft I48a and which acts on a pushing rod I49 connected by a ball and socket joint to a sliding bushing I50. The sliding bushing is adjustable in height and is fixed on one arm of a pivotally mounted lever I5I, the other arm of which contacts the bar I42 in front of the rocking lever I43. Thus, the cam I48, which is referred to as the feeding cam,"-

controls through the parts I49, I50, I5I, I42, I43, I45, I46 and the carriage I01, the progressive advance in depth of the tool. 7

The rotation of the feeding cam I48 is controlled by the mechanism hereinafter described (see also Figures 1 and 2). This mechanism comprises a ratchet-Wheel I keyed to a shaft 2 carrying a pinion I52, which meshes with a curved rack I53 fixed on the shaft I48a. The rotation of the ratchet wheel I is controlled by means of a driving pawl 3 pivotally mounted through an axle 4 on a lever 5, which itself is pivotally mounted on a stationary axle 6; the lever 5 receives, after each cut, a rocking movement upon the axle 6, in the direction of the arrow f1, through the action of a connecting rod 1 connected to the lever I38. The amplitude of said movement is such that the angular movement transmitted each time by the pawl 3 to the ratchet-wheel I corresponds to one tooth of the latter. The reverse rotation of the ratchet-wheel is prevented by a stop-pawl 8. The two pawls 3 and 8 are normally maintained in engagement with said wheel through springs 9 and I0.

To allow determining, according to the conditions of the threading, the number of cuts in which the total advance of the tool is to be effected, one face of the ratchet-wheel I (Fig. 2) is made fast to a plate II carrying a lug or pin I2 which can be engaged, at will, in one of the holes I3a provided on the same circumference in a coaxial idle plate I3 mounted on the shaft 2, each of said holes corresponding to a determined number of cuts. The plate I3 carries a finger I4, on the trajectory of which is disposed a lever I5 keyed on a shaft I6 mounted in parallel relation to the shaft 2 of the ratchet-wheel. On the shaft I6 is keyed a second lever I1 with two arms, whose lower arm I'la is located opposite a lug I8 provided on the stopping pawl 8. The lever I1 in turn drives, through a convenient key connection, a third lever I9 mounted on the shaft I6, whose lower arm I9a is located opposite a lug 20 provided on the driving-pawl 3. The disposition of said members is such that, when the finger Id of the plate I3 bears upon the lever I5, i. e. when the selected number of cuts is achieved, the levers I1 and I9 bear respectively, through their lower arms I'Ia and Ilia, upon the lugs I8 and 26 of the pawls 8 and 5, raise said two ratchets and clear the ratchet-wheel I and the plate I3. The feeding cam I 38 is then returned to its first position through a spring I54 connected to the shaft Mile. Simultaneously, the rotation of the shaft I5 determines, through the medium of the following mechanism, the freeing and the braking of the driving spindle for the piece to be threaded, and, consequently, the automatic stopping of the machine. To this end, the shaft I6 carries an helicoidal pinion I (see Figure 9) meshing with a pinion I56 keyed to a shaft I51, which terminates near the spindle I92. At its end located near the spindle, the shaft I57 carries a lever I58 urged by a spring I59 and which controls through a bolt I a lever I6I urged by a spring I62. When the shaft I6 is angularly moved by the thrust of the finger I4 of the perforated plate I3 acting on the lever I5, the shaft I5? is itself rotated through the pinions I55 and I56 and provides through the lever I58 for the lowering of the bolt i 60, thereby clearing the lever I6 I. The lever I6I actuates the clutch cone I63 away from the cone H54 of the pulley I05 and engages the braking cone I with the stationary cone I56, thus automatically stopping the rotation of the spindle I02 and, consequently, the working of the Whole of the mechanisms carried by the carrier I63.

Above the shaft I6 is disposed another shaft 21 carrying, at one of its free ends, a controlling lever 22. On said shaft is keyed a lever comprising two arms 23- 24 lying in different planes. The arm 23 is located opposite the upper arm Ieb of the lever I9, so that, when the controlling lever 22 is rotated in the direction of the arrow f2 (Fig. 4), said arm 23 rocks the lever I9 which, acting upon the lug 26 of the driving pawl 3, disconnects the latter from the ratchet-wheel i; the rotation of said wheel is thus prevented and the machine runs idle, the tool remaining at the same cutting-depth, which allows completing the adjustment of the tool or testing the operations after each cut. The arm 24 is disposed opposite a double lever 25 which, when the controlling lever 22 is rotated in the direction of the arrow f3 (Fig. 5) acts upon the upper hand Iib of the lever IL with the result, through the intermediary of the latter and of the lever I9, of disengaging the pawls 8 and 5, and, thus, of stopping the machine in conditions similar to that accompanying the automatic disengagement at the end of the work.

According to the present invention, in order to allow performing multiple threads by means of a mechanism of the kind above described, an interchangeable rotating member or disc 26 is iii-:1

mounted on the face of the rocking lever 5 carrying the driving pawl 3, near the tail of the latter. Said rotating member is keyed on an axle 2? which is free to rotate in the lever 5, but on which is fixed a ratchet-wheel 28 with which are in enn gagement, on the one hand, a driving pawl 29 mounted on a fixed axle 36 disposed outside the lever 5 and, on the other hand, a movable stopping pawl 3I carried by the lever 5. The arrangement is such that, when the lever 5 rocks in a direction opposed to that of the arrow ii, at each new cut, the fixed pawl 29 induces an angular movement, in the direction of the arrow ft. of the ratchet-wheel 28 and, consequently, of the rotating member 26, movement which corresponds to a tooth of said wheel, while the ratchet 3I holds the rotating member from retrograde movement. In the example shown in Figs. 1, 3, 4 and 5, which corresponds to the operation of a threading with four threads, the ratchet wheel 28 is fitted with twelve teeth and the rotating member 26 is of a circular outline on which are provided, at one from the other, three notches 26a whose amplitude is equal to that of a tooth of the ratchetwheel 28, each of the plain circular parts 261) corresponding thus to three teeth of the same ratchet-wheel. The rotating member 26 is disposed, with respect to the tail of the pawl 3, so that, when the parts 26b contact the tail of said pawl as in Figure 1, they push back the latter against its spring 9 and clear the same from the ratchet-wheel i which controls the cam I48 for the transverse advance of the tool, while, when the notches 26a are opposite the tail of the pawl 3, as in Figure 3, the latter remains in engagement with the ratchet-wheel I.

The operation of the mechanism so constructed clearly results from the preceding explanation.

For example, to accomplish a threading comprising four threads, as contemplated above, the gears connecting the driving spindle I62 for the work piece with the shaft I21 controlling the pitch-cam I32 are chosen so that the complete revolution of said cam corresponds to an integral number of complete turns of the spindle plus a quarter of a turn of the spindle. Under such conditions the transverse position of the cutting tool remains the same for four threading passes; i. B. there is no change in depth of out after each of the first, second and third threading passes.

However, after each of the first, second, and third threading passes, the tool is longitudinally displaced relative to the work piece and the thread just previously cut by an amount equal to onefourth the lead given by the pitch cam !32.

After the fourth thread is cut, a similar longitudinal displacement of the tool relative to the Work efiectively returns the tool to its normal starting position corresponding to the position of the first thread.

ratchet-wheel 25, and the plain part 26b, adjacent to the aforesaid notch 26a, pushes back the pawl 3 and disengages it from the ratchet-wheel I. The latter, and consequently the cam I43 controlling the transverse advance of the tool, remain thus stationary for the next cut and the tool re mains at the same depth, so that said out is performed on the second thread exactly at the same depth as on the first. It is identically operated for each of the two next cuts related to the third and fourth threads. At the end of the fourth cut, the rotating member 26 is brought in a position where the next notch 26a is in turn opposite the tail of the pawl 5, and the latter determines, through the rocking of the lever 5, a rotation of the ratchet-wheel I of one tooth, from which it results, by means of the cam I48 connected to said wheel, a transverse advance of the tool for the next four cuts.

The same operation is reproduced until the desired number of cuts has been performed on each of the four threads. At this time, the finger H of the plate [3 raises the lever l5, and, by means of the levers Hl9, successively disengages the pawls 8 and 3 and stops the mechanism through the above described process.

As it can be understood, it is possible to accomplish, in similar conditions, threadings which comprise any number of threads by substituting appropriate rotating members for the member 26 and by selecting appropriate gear ratio between the driving spindle l02 and the shaft 13! of the pitch-cam I32. E. g., to accomplish a threading composed of six threadsthe ratchetwheel 28 having twelve teeth as above-one can use a rotating member such as the one shown in Fig. 6, which comprises two notches 26a having an amplitude equal to that of one tooth of the ratchet-wheel 28 and two plain circular parts 26b, each corresponding to five teeth of said wheel, and realize, between the pitch cam and the spindle, a speed ratio such that the rotation of the cam corresponds to a number of complete revolutions of the spindle plus /6 of a turn of said spin- (118, Fig. 7 'shows a rotating member adapted to accomplish a threading comprising three threads;

said member comprises four notches 26a corresponding to one tooth of the ratchet-wheel Z8 and four plain circular parts 261) respectively corresponding to two teeth of said wheel. Fig, 8 shows a rotating member for a threading comprising two threads, with six notches 28a and six plain parts 26b each corresponding to one tooth of the ratchet-wheel 28.

What I claim is:

1. A device for forming multiple screw threads by using a screw machine of the type in which the longitudinal movement of the tool-holder is controlled by a rotative cam which is actuated by the driving spindle of the machine while the progressive transverse advance of the tool, after each cut, is controlled by another cam intermittently actuated by the same spindle, through the intermediary of a ratchet-wheel driven by a pawl, said device comprising, in combination, a removable and interchangeable rotating part mounted near the driving pawl of the ratchet-wheel which controls the cam for the transverse advance, means for intermittently actuating said part in synchronism with said driving ratchet, and means to establish, between the speed of the driving spindle for the work piece and the speed of the cam which controls the longitudinal movements of the tool, such a ratio that the rotation of said last cam corresponds to an integer number of complete revolutions of the spindle plus a fraction of the last turn equal to the inverse of the number of threads to be out, said rotating part being given such an outline that, for a portion of an amplitude corresponding to an angular movement of one tooth of the ratchet-wheel, said part is without action on the driving pawl of said wheel which is left in engagement with the latter, whilst on the next portion, whose amplitude is equal to as many times that of the preceding portion as the threading comprises threads minus one, it maintains the pawl out of engagement with said ratchet-wheel.

2. A screw machine comprising a frame, a driving spindle rotatively mounted on said frame for the work piece, a. tool-holder mounted on said frame, a controlling mechanism actuated by said driving spindle for imparting to said tool-holder to and fro movement parallel to the axis of said spindle, and means including a rotative cam intermittently actuated by said spindle through the intermediar of a ratchet Wheel for imparting to said tool-holder in timed relation to said to and fro movement a progressive advancing movement at right angle to the axis of said spindle, said advancing means comprising a lever mounted on said frame for rocking movement, a driving pawl mounted on a face of said lever to actuate said ratchet-wheel, means in relation with said controlling mechanism for imparting to said lever a rocking movement in timed relation to said to and fro movement, a removable and interchangeable rotating part mounted on the face of said lever carrying said driving pawl, a fixed axle disposed on said frame outside said lever, a second pawl mounted on said axle, and a second ratchet wheel made fast 00- axially to said rotating part and engaging, at eachrocking movement of said lever, with said second pawl to induce an angular movement of said part, corresponding to a tooth of said second ratchet wheel, said rotating part being given such an outline that, for a portion of said outline of an amplitude corresponding to an angular movement of one tooth of said first ratchet wheel, said part is without action on the first driving pawl which is left in engagement with said first ratchet-wheel, whilst on the next portion, which amplitude is equal to as many times of the preceding portion as the threading comprises threads minus one, it maintains said first pawl out of engagement with said first ratchet-wheel.

3. A device according to claim 2, in which said rotating part comprises a circular member having at the periphery thereof regularly spaced notches, full circular parts between said notches, the amplitude of each notch corresponding to an angular movement of one tooth of said second ratchetwheel, the amplitude of each of said full circular parts corresponding to an angular movement of said second ratchet-wheel of as many teeth as the threading has threads minus one, and said circular member being so disposed with respect to said first driving pawl that when one of said notches is facing said first driving pawl, the latter is maintained in engagement with said first ratchet wheel, but when one of said full circular parts is facing said first driving pawl, the latter is maintained out of engagement with said first ratchet wheel.

XAVIER FRANCOIS CASTELLI.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Ardoin Apr. 26, 1949

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