US2868418A - Control valve for adhesive dispensing apparatus - Google Patents

Description

CONTROL VALVE FOR ADHESIVE DISPENSING APPARATUS Jan. 13, 1959 F. J. KASZYNSKI Filed April 8. 2 Sheets-Sheetl F [nae/1 ,507

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Jan. 13, 1959 F. J. KASZYNSKI 2,868,418

CONTROL VALVE FOR ADHESIVE DISPENSING APPARATUS Filed April 8. 1954 2 Sheets-Sheet 2 J7 71 E m I q 1; fizz/970501" I 1 /s/ W Fraud 1/. 1i as ynslw 65 a/, a2 a3 1%? Wok/Qt,

United States Patent CONTROL VALVE FOR ADHESIVE DISPENSING APPARATUS Frank J. Kaszynski, Wilmington, Mass., assignor, by

mesne assignments, to Jacob S. Kamborian, West Newton, Mass.

Application April 8,1954, Serial No. 421,727

8 Claims. (Cl. 222-373) This invention relates to an improvement in adhesive dispensing apparatus for machines of a kind in which a thermoplastic or thermosetting adhesive is used.

In Patent No. 2,667,908, which discloses a machine designed especially to stretch sheet material about a rigid core for making panels there is a nozzle arranged close to the lasting instrumentalities for delivering liquid adhesive to the lasting margin between the place of applying the drafting stress to the margin of the sheet material and the place at which it is wiped inwardly over the bottom of. the core. This nozzle is supplied with adhesive from a pressure chamber which in turn receives liquid adhesive through an orifice from a reservoir. The adhesive in the pressure chamber is forced therefrom to the nozzle by air under pressure admitted to the pressure chamber at such times as the lasting instrnmentalities are brought into operative position and is cut off when the latter are returned to their inoperative position. Movement of the lasting instrumentalities into and out of operative position is elfected by a treadle and as there shown the treadle actuates a valve for controlling admission of air to the pressure chamber. During application of pressure to the adhesive in the pressure chamber it is necessary to seal it, hence av valve is located between it and the reservoir and is simultaneously operated to close the orifice between the pressure chamber and the reservoir when air is admitted to the latter and to open it when the air is cut off. At the moment when the air valve is closed there is a considerable amount of residual pressure in the pressure chamber, hence when the valve between the pressure chamber and the reservoir opens this air blows out through the orifice with considerable force. The release of this air into the hot liquid adhesive in the receptacle results in an explosive expansion of the. air which will blow the adhesive out of the receptacle if the receptacle is not closed at its top or through carelessness the cover is left Off.

The principal object of this invention is to provide means for insuring escape of the residual air pressure within the pressure chamber. in such fashion as to avoid blowing into the reservoir. Another object is to provide means, operable by the treadle mechanism for moving the lasting instrumentalities into and out of operative position, to control the flow of air to the pressure chamber and to effect exhaust of the residual air pressure in the pressure chamber. Another object is to provide means, operating in conjunction with the air admission valve and the valve for closing the orifice between the pressure chamber and the reservoir, to exhaust air from the pressure chamber simultaneously with the closing of the air valve and the opening of the valve between the pressure chamber and the reservoir.

In accordance with the foregoing objects, the aforesaid means comprises a block having an air operated piston therein, which is adapted to be moved by air admitted to the block to close the valve' against the 2,868,418 Patented Jan. 13,. 1959 orifice between the pressure chamber and the reservoir and a valve for simultaneously by-passing part of the air to the pressure chamber above the adhesive therein. The piston operates in a cylinder within the block and is. normally held in an inoperative position by a spring. As the piston is displaced in opposition to the spring it uncovers ports to a by-pass in which there is a slide valve normally held in a blocking position by a spring. Displacement of the valve by the .by-pass air operates to uncover another port in the block which in turn is connected to the pressure chamber and at the same time to cover a portinthe block opening to the atmosphere. Restoration of this valve to its: initial position interconnects the port to the atmosphere with the port to the pressure chamber.

The invention will now be described in greater detail with reference to the accompanying drawings wherein:

Fig. 1 is an elevation of. the head of a lasting machine with the adhesive reservoir in vertical section and with certain other parts broken away and omitted;

Fig. 2 is a vertical section to larger scale through the valve which controls the flow of adhesive from the reservoir to the pressure chamber;

Fig. 3 is a vertical section of the motor control valve to larger scale, showing. the valve in its operative position;

Fig. 4 is a corresponding view showing the valve in its inoperative position;

Fig. 5 is an elevation of the head of the machine and part of the supporting frame as seen from the rear side of Fig. l;

Fig. 6 is a fragmentary elevation. of the lasting instrumentalities to larger scale as seen from the left-hand side of Fig. 1;

Fig. 7 is a fragmentary elevation of the lasting instrumentalities to larger scale as seen from the rear side of Fig. 1;

Fig. 8 is a fragmentary elevation of a conical wiper carrying a helical rib; and

Fig. 9 is a section of an air control valve.

The invention is illustrated in combination with a machine of the kind disclosed in Patent No. 2,667,908, granted February 2, 1954, although it is to be understood that it is not restricted to such use but maybe employed with other machines of similar character which have heretofore been patented, both for covering panels and lasting shoes .and/ or with any machine where it is desirable to supply liquid adhesive from a pressure chamber to a nozzle for application to work without danger of blow-back when the pressure is cut ofi.

Since the illustrated machine is described in detail in the aforesaid patent, to which reference may be had, it will sufiice merely to describe the operating. instrumentalities in a general way as a background! for illustrating the construction and. operation of the adhesive supplying mea'nsand control therefor.

Fig. 1 shows the head 6' of the aforementionedmachine as supporting the pulling over instrumentalities (Fig. 6) for stressing the margin of the sheet material F, applying an adhesive to the stressed margin and then wiping it into contact with the bottom of arigid core C. These lasting instrnmentalities (Figs. 1, 6 and 7) specifically comprise .frusto-conical feed-rolls 3 and 4, fast 'to the lower end of a pair of shafts 1 and2 for rotation about inclined axes, a nozzle 54 located below the feed rolls, a rotary wiper 17 (Fig, 6),.having a conically tapered body (Fig. 8) carrying a helical rib 1'17forwardly thereof in the. direction of movement of the work as advanced by the feed rolls for folding the stressed marginand pressing it firmly against the botcordingly, the shaft 2 is journaled in bearings carried by a horizontally movable slide 5, Fig. 1, mounted in guides carried by the head 6. The slide 5 is urged rearwardly by a spring 19 and may be moved forwardly to separate the rolls 3 and 4 by means of a bell crank lever comprising the arms 20 and 120, the former of which is connected by appropriate means 23 to a treadle not shown.

Adhesive is delivered to the nozzle 54 from a reservoir 27, Fig. 1, secured to the right-hand side of the slide 5. This reservoir has walls defining a chamber 28 of substantial capacity having a forwardly and downwardly sloping floor 128, located above the level of the rolls 3 and 4, and which is designed to hold a reserve supply of adhesive. Preferably the adhesive employed is a synthetic thermoplastic resin. As received, resin of this type is usually in solid form, varying from fine powder to granules or large lumps. It is placed in this reservoir 27 and reduced to liquid form therein by the application of heat, as hereinafter more fully described. As illustrated, the reservoir 27 is a large, box-like container, supported by the slide 5, with provision for adjustment relative to the slide. Thus as illustrated, the reservoir has a rearwardlyextending rigid arm 29 having an opening which receives a pin 30, by means of which motion is transmitted from the arm 20 of the bell crank to the slide 5. As shown, the outer end of the pin 30, which passes through the opening in the arm 29, is eccentric with reference to the inner end of the pin which has screw-threaded engagement with the slide 5. The pin has a fixed collar 130 provided with radial holes to accommodate a spanner wrench, by means of which the pin may be turned. Turning the pin adjusts the position of the arm 29 by reason of the eccentric form of the pin. The reservoir has another bracket arm 31 provided with an opening for the reception of a pin 32, similar to the pin 30, and turning in a threaded hole in the slide 5.

Preferably the reservoir 27 has a hinged cover 33, which is normally closed but which may be raised to permit the reservoir to be filled. The forward wall 34 of the reservoir 27 is provided with a normally open delivery port or orifice 35, which at times may be closed by a flap valve 36. This flap valve 36, Fig. 2, is fixed to an end of an arm 37 pivoted at 38 on the wall 34 of the reservoir and carries a ball 136 for seating engagement with the port 35. The flap valve is normally held away from the delivery port 35 by a spring 39 so that it occupies the position shown in Fig. 1. Above the flap valve is a vertically slidable piston rod 40, the lower end of which is adapted to engage a shoulder 137 of the flap valve and by downward movement to swing the flap valve downwardly and inwardly against opposition of the spring 39 to cover the delivery port 35.

The port 35 opens into a pressure chamber 41, defined by parts carried by or integral with the forward wall of the reservoir 27, this pressure chamber having a removable, normally air tight top 42, on which is mounted a motor valve housing 43, in which operates a piston valve 44, Figs. 3 and 4, connected to the inner end of the rod 40. A spring 45 tends to lift the piston so as to hold the rod aloft and hence to permit the valve 36 to be held open by the spring 39.

A block 46 is fixed to the front wall 280 of the pressure chamber, said wall having an outlet-port 49 which communicates with a slot 50 in the inner face of the block 46. A downwardly-inclined, rigid, tubular arm 51 is mounted in the block 46. An axial bore in the tubular arm 51 communicates at all times with the slot in the block. A cap member 52 is secured to the lower end of the'rigid tubular arm 51 and the tubular shank 53 of the delivery foot or nozzle 54 is secured in a downwardly inclined bore in the cap 52. A passage in the cap 52, provides communication between the bore in the arm 51 and a passage in the shank 53. The foot or nozzle 54 has a substantially flat undersurface (Fig. 7) for contact with that surface of the form or core to which the margin of the cover is to be secured. The shape and position of the foot or nozzle may be like that described in the aforementioned patent or varied therefrom depending upon the type of work being operated upon without departing from the spirit of the inventron.

If desired as pointed out in the above-mentioned patent an air jet pipe 62 (Fig. 6) may be provided to discharge air into the angle between the margin and the surface of the form or core just after the adhesive has been delivered to hasten setting.

A valve device 63 (Fig. 5) is mounted upon the rear portion of the machine head. This valve device as herein shown (Fig. 9) is operated by swinging a lever 64 downwardly. Swinging the lever 64 displaces a hollow stem 63a within the valve casing which has three ports in it, a a and a The casing has ports b and b with which the inlet and outlet pipes 66 and 71 are connected. When the valve is open to admit air pressure from the source to the cement pot the ports a and a are in registration with the inlet and outlet openings b and b of the casing,

the port a at this time being blocked by the wall of the casing. When the lever 64 is released a coiled spring r moves the stem 63a to the right, so as to move the port al out of registration with the port b and hence to close it. Simultaneously the port a is opened to an exhaust position by movement out of the end of the casing. The port a is elongate and hence still registers with the port 12 so that the pressure within the pot exhausts through the ports [2 and b The casing of the valve 63 is supplied with compressed air from any suitable source, for example, by an air pump (not shown) housed in the base 10 and driven by the same motor which drives the shaft 7. Alternatively, the air may be supplied from a replaceable tank of compressed air obtained from any suitable source. Preferably when a pump forms a part'of the machine structure, the air is delivered from the pump into a storage tank 65, mounted on or in the base 10, thereby to insure a supply of air at substantially constant pressure. From this tank the air is delivered by a pipe 66 to the casing of the valve 63.

One end of a spring 67 is attached to the machine head and its other end is connected to the upper end of a rod 68 which extends down and is secured at its lower end to a treadle not shown. A Spring 171 connects the upper end of the rod 68 to the lever 64. By depressing the treadle the valve is opened, thus permitting air from the valve casing to escape into a pipe 71, which leads to a manifold 72 mounted on the side wall of the machine head. From this manifold extends a conduit 73 which leads to the motor valve housing 43 and a conduit 73]: which leads to the air jet pipe 62. A branch 73a from conduit 73 enters the chamber 41 above the surface of the adhesive therein so that the pressure is applied to the surface of the adhesive at the same time that the valve 36 is closed.

The reservoir 27 is heated sufficiently to melt the plastic which has been placed therein. For this purpose an electric heating unit 77 may be disposed beneath the floor 128 of the reservoir. Likewise, the pressure chamber 41 is supplied with heat for keeping its contents liquid by an electric unit or units 78 arranged externally of and below the bottom of the chamber.

In the apparatus disclosed in the aforesaid patent, when the treadle was depressed, the valve 63 was opened to admit air to suitable means for closing a valve similar to the valve 36 shown herein and simultaneously to admit air to the pressure chamber so that the liquid adhesive therein was forced. through the tubular 53 to the nozzle 54 and hence delivered to the work. In the aforesaid apparatus, when the treadle was released to close the valve 63 delivery of air to the pressure chamber 41 was cut olf and simultaneously the valve corresponding to the valve 36 herein was opened to permit resumption of flow of adhesive from the chamber 28 to the pressure chamber 41. During the application of adhesive, pressure built up in the pressure chamber and since there was no provision for backflow of the pressure from the chamber, except through the orifice therein, when the pressure was cut off and the valve opened this pressure blew out through the orifice with considerable violence, into the liquid adhesive in the chamber 28. While the chamber 28 was supposed to be kept closed with the cover 33, through carelessness on the part of the operators, the cover 33 was very seldom fixed in place and often was misplaced so that the chamber was constantly opened. Under such conditions, a surge of pressure from the pressure chamber into the melting chamber 28 often results in blowing a considerable quantity of hot adhesive from the chamber which was highly undesirable because it could cause serious burns; because it was wasteful of adhesive; and because it was undesirable to have adhesive spattered about on adjacent machinery and on work located in the vicinity of the machine so as to dirty it or spoil it.

It is, accordingly, the primary object of the present invention to provide means for releasing the residual pressure in the pressure chamber so that there is no chance of it blowing through the opening 35 into the chamber 28 regardless of how quickly the valve 36 is opened, and this has been conveniently accomplished by use of the motor control valve device 43 which includes as a part of it the piston 44 for operating the rod 40.

As illustrated in Figs. 3 and 4, the motor control valve block has in it chambers 55 and 56, which have axially extending portions 57 and 58 respectively, of smaller diameter. The piston 44 is located in the chamber 55 and as heretofore pointed out, actuates the rod 40 which extends from the piston through the axial extension 57, a hole 59 in the block, and a hole 60 in the cover 42, vertically downward to a point above and in operative relation with the valve 36, Fig. 1. The rod comprises in addition to the part 40 a sleeve 61 which is made fast to the piston 44, in which the part 40 is slidably inserted and held by engagment of a notch 162, Fig. 4, therein, with a pin 163 set in the sleeve. The notch is wide enough to permit limited axial play and a spring 164 located in the sleeve yieldably backs the inner end of the rod. Thus the shock of impact of the rod 40 with the valve 36 is cushioned by the yieldable play in the rod. The extension 57 through which the piston rod passes is of larger diameter than the sleeve 61 and the coiled spring 45 is mounted therein so that it bears against the lower end of the piston 44 and normally holds it with its upper end engaged with the top of the chamber. The piston 44 itself, is in the form of a hollow cylinder open at its upper end and near its lower end has one or more ports 167. The other chamber 56 has in it a hollow open end sleeve-valve 156 that is normally held with its open end engaged with the top of its chamber by a coiled spring 168 located below it in the extension 58. The sleeve-valve has in it ports 69. Thus, the piston and sleeve-valve are normally held with their open ends engaged with the upper ends of the chambers within which they move. An inlet port 70, Figs. 3 and 4, is provided in the block near the top of the chamber 55, the mouth of which is threaded for reception of an end of the air pipe 73 and provides for access of air to the open end of the piston 44. Admission of high pressure air thereto will force the piston 44 downwardly against the opposition of the spring 45, thus pushing the rod 40 downwardly to close the valve 36. As the piston 44 moves toward the lower end of the chamber the ports 167 are brought into registration with a lateral opening 271 in the block which is in communication with a vertical passage 172 located between the chambers, the upper end of which has a lateral port 173 in communication with the upper open end of the sleeve-valve 156. Hence, part of the air delivered to the piston 44 flows through the un covered port 271, passage 172 and port 173, to the second chamber forcing the sleeve-valve 156 the-rein downwardly against the compression spring 168 below it. As sleevevalve 156 is displaced downwardly its ports 69 are brought into registration with a lateral port 74 which is connected to the upper end of a vertical passage 75 forming an outlet passage from the block. The mouth of the outlet passage 75 is in registration with an opening 76 through the cover 42 of the pressure chamber. Thus, it will be apparent that the part of the air supplied to the block which is hy-passed through the ports 271, 173 and the passage 172 is admitted by the sleeve valve 156 to the passage 75 and hence to the top of the pressure chamber at the same time that the valve 36 is closed. In the extension 58 below the sleeve-valve 156 is an exhaust port 177 which is in direct communication with the atmosphere at. all times and in communication with the port 74 when the sleeve-valve is in its upper position but is cut off therefrom or blocked when the sleeve-valve is in its lower position. Consequently, when the treadle is released to cut off the delivery of pressure to the Piston 44 the springs 45 and 168 will force the piston 44 and sleevevalve 156 upwardly, opening the valve 36 and simultaneously interconnecting the exhaust port 177 with the passage 75 so that the residual air in the high pressure chamber 41 will flow back through the passage 75, port 74 and out through the exhaust port 1.77 to the atmosphere without any danger of forcing its way through the opening 35 into the chamber 28.

In operation the treadle rod 23 is drawn down to actuate the valve lever 64 which in turn is actuated thereby to admit air by way of the manifold 72 to the motor valve housing 43 which it enters at the port 70. Admission of air to the port displaces the piston 44 downwardly and in like manner the rod 40 downwardly so as to close the valve 36. Substantially, simultaneously with the closing of the valve 36, the ports 167 register with the port 271 so that part of the air is delivered through the passage 172 and port 173 to the upper end of the sleeve valve 156. Admission of air to the sleeve valve 156 displaces it downwardly until its ports 69' register with the port 74 whereupon air passes through the port 74 and passage to the top of the pressure chamber 41. The air pressure may be admitted to the pressure chamber either before the feed rolls 3 and 4 are engaged with the work, simultaneously therewith or after engagement, depending upon the skill of the operator and whether adhesive is to be applied to the entire margin or only to a part thereof. When the treadle is released after the lasting operation has been completed or at least a part thereof, the valve 63 promptly closes, cutting off air to the piston 44. As a result, the spring 45 promptly lifts the piston 44 which in turn raises the piston rod so that the valve 36 flies, open and substantially, simultaneously the spring 168 lifts the valve sleeve 156 thereby interconnecting the exhaust port 177 with the port 74 and passage 75 so that the residual air pressure in the pressure chamber is allowed to flow from the chamber through the passage 75 and port 74 to the outlet or exhaust port 177.

While the description of the aforesaidmotor valve for controlling the opening of the port 36 between the melting chamber 28, the pressure chamber 41 and the exhaust thereof in such fashionrthat there is no danger of blow back, has been illustrated in connection with the upholstering machine of the-aforesaid patent, it is to be understood as heretofore stated that it is equally applicable to any pulling over or lasting machines employed for the manufacture ofupholstery panels, shoes or the like, whether the adhesive is to be used as the only attaching means or in combination with other attaching means, and it is to be further understood that it is equally useful and within the scope of this invention to employ the aforesaid motor valve control wherever it is desirable to use compressed air as a motive agent without danger of blow back from the pressure chamber when the supply pressure is cut off and the chamber opened.

It should be understood that the present disclosure is for the purpose of illustration only and that this invention includes all modifications and equivalents which fall within the scope of the appended claims.

I claim:

,1. In combination a closed chamber for receiving liquid adhesive, a source of liquid adhesive, a normally open valve connecting said source to said chamber, means operable to close the valve, means for supplying air under pressure to the chamber to apply pressure to the surface of the adhesive therein, and simultaneously to effect operation of said valve closing means, said means comprising a motor valve block having a piston chamber therein, a piston movable in the piston chamber, said piston having a rod fast thereto, operable to actuate the valve to effect movement of it, means normally operating on the piston to hold the rod in an inoperative position so that the valve is open, an inlet port in the block for admitting air under pressure to the other side of the piston to displace it in a direction to cause the rod to close the valve, a by-pass in the block located in a position to be uncovered by the piston as the rod is moved toward operative position, a pair of interconnected ports, one of which is connected to the chamber above the level of the adhesive therein, the other of which is open to the atmosphere, and means in the by-pass movable between two a to the chamber and simultaneously blocks the interconnection between the two ports, and the other of which blocks the by-pass and interconnects the two ports, said means in the by-pass being movable to the one position by the air admitted to the by-pass and means for returning said last-named means to the other position when the supply of air pressure is cut 01f.

2. For use with a pressure chamber adapted to be supplied with liquid adhesive and to deliver it to an applicator nozzle connected therewith, a source of liquid adhesive, a flap valve for controlling the flow of adhesive from said source to the pressure chamber, means normally holding the flap valve open to permit adhesive to flow into the pressure chamber, means for closing the flap valve, means for supplying air under pressure to the pressure chamber, to force the adhesive from the chamber to and through the applicator nozzle and for simultaneously actuating said means for closing the flap valve, said means comprising a motor valve block having a piston chamber therein, a piston movable in the piston chamber, said piston having a rod fast thereto, operably associated with the valve to effect movement of it to a closed position, means normally opposing movement of the piston to hold the rod in an inoperative position, an inlet port in the block for admitting air under pressure to the opposite side of the piston to displace it in a direction to cause the rod to close the flap valve, a bypass in the block located in a position to be uncovered by the piston as the latter moves the rod into operative position, a pair of ports, one of which is connected to the pressure chamber above the level of the adhesive therein, and the other of which is open to the atmosphere and means in the by-pass movable between two positions, one of which connects the by-pass with the port to the pressure chamber and simultaneously blocks the other port, and the other of which blocks the by-pass and interconnects the two ports, said meansin the by-pass being movable to the one position by the air admitted to the bypass. and means for returning said last-named means to the other position when the supply of air pressure is cut off.

3. In a cement lasting machine, an adhesive container having independent chambers connected by a port and so located that cement melted in one chamber will flow through the port to the other chamber by gravity, and a valve operable to close the port so that pressure may be applied to the adhesive in one chamber exclusively of the other to effect delivery of cement from said chamber to an applicator nozzle, control means operable to supply air under pressure to, the pressure chamber to apply pressure to the surface of the adhesive therein to force it from the chamber through the nozzle, and substantially, simultaneously to actuate said valve to close the same during application of pressure to the surface of the adhesive, said control means comprising a motor valve block having a piston chamber therein, a piston slidable in said piston chamber operable to close the valve, means operating on one end of the piston to hold it at one end of the chamber in an inoperative position, an inlet port in the block for admitting air under pressure to the other end of the piston to displace it toward the opposite end of the chamber to actuate the valve, means for by-passing part of the air admitted to the piston as it approaches its operative position, two ports in the block, one of which is open to the atmosphere and the other to the interior of the pressure chamber above the adhesive therein, and means in the by-pass movable in one position to block the port to the atmosphere and to connect the bypass to the pressure chamber, and in another position to block the by-pass' and to interconnect the two ports, and means normally holding the last-named means in its other position in the absence of air delivered to the by-pass. v

4. A motor control valve comprising a block having a chamber therein, a piston slidable in the chamber, first means exerting a thrust at one end of the piston operating to hold the piston in a predetermined position, an inlet port in-the block for admitting air under pressure to the other end of the piston to displace it in opposition to said first means, a passage for by-passing part of the air admitted to the piston when the latter reaches a predetermined displacement in the chamber, a pair of ports, and second means movable in the bypass to block one of the two ports from the other and simultaneously to connect the by-pass with the other of said ports, and in another position to block the by-pass from both ports and to connect the ports, movement of said second means in one direction being eifected by said by-passed air, and in the other direction by yieldable means which opposes movement of said second means.

5. A motor control valve comprising a block having a chamber therein, a piston slidable in the chamber, said piston having a rod fast to it, a portion of which extends through one end of the chamber and the wall of the block to a point exteriorly thereof, said piston being movable in one direction to push the rod out of the chamber and in the other direction to retract the rod a coiled spring operating on one side of the piston to hold it in a predetermined position against displacement with the rod retracted, an inlet port in the block for admitting air under pressure to the other side of the piston to displace it in opposition to the spring to extend the rod, a pair of ports in the block, one of which is open to the atmosphere, a by-pass in the block uncovered by displacement of the piston in a direction to extend the rod, to permit part of the air delivered to the chamber to flow through the by-pass, and a valve in the by-pass movable between two positions, in one of which it blocks the by-pass from the two ports, and in another position blocks the by-pass from the atmospheric port and the latter from the other port while interconnecting the by-pass with said other port, and a spring operating on the valve to hold it in said one position.

6. A motor valve comprising a block having a pair of chambers therein, a piston slidable in one chamber, said piston having a rod fast to it, a portion of which extends through the end of the chamber to a place exteriorly of the block, said piston being movable in one direction to push the rod out of the chamber and in the other direction to retract the rod a coiled spring located between one end of the piston and the adjacent end of the chamber, operating on the piston to hold it against the opposite end of the chamber with the rod retracted, an inlet port in the block at said opposite end of the chamber for admitting air under pressure to the opposite'end of the piston to displace it toward the said adjacent end of the chamber in opposition to said spring to increase the length of the rod extending from the chamber, a port connecting the said adjacent end of the one chamber to one end of the other chamber, a pair of ports in the block connected to said other chamber, one of which is also connected to the atmosphere and the other of which is adapted to be connected to a closed chamber, a slide valve in said other chamber movable between two positions, said slide valve in one position connecting the by-pass to the port adapted to be connected to the closed chamber, and simultaneously blocking the by-pass from the port connected to the atmosphere, and in the other position blocking the by-pass from both ports and simultaneously interconnecting said pair of ports, said valve being actuated by air pressure delivered thereto through the by-pass when the piston reaches its displaced position, and a spring opposing movement of the valve by the air pressure.

7. A motor valve according to claim 5, wherein the piston rod has a yieldable part associated therewith to cushion the contact thereof with the valve.

8. A motor valve according to claim 1, wherein the piston rod has two parts, one fast to the piston and the other telescopically engaged with the one part and a coiled spring holding the parts distended.

References Cited in the file of this patent UNITED STATES PATENTS 661,574 Corbett Nov. 13, 1900 2,667,908 Kamborian Feb. 2, 1954 2,670,751 Wilson Mar. 2, 1954

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