US2177828A - Hydraulic cycle control - Google Patents

Description

Oct. 3l, 1939. L Q HUCK 2,177,828

HYDRAULIC CYCLE CONTROL Filed July 24,V 193e l 65 I NVENTOR l alea f Huck,

M Zinesrwq, l

ORNEYS- Patented oci. 31, 1939 2,177,828 HYDRAULIC CYCLE CoN'raoL Louis C. Huck, Buchanan, Mich., asslgnor to Huxon Holding Corporation, a corporation of Michigan Application .my 24, '1988, serial No. 92,342

Claims. 'I'his invention relates to reciprocating iluid pressure motors of the type utilizdto operate l means ,resides in a reversing'l valve actuator i5 which is responsive'to the 'drop in exhaust pressure at one side of the operating piston incident to the completion of the,exhaust movement of that piston when it strikes the end walloi the cylinder. lI headvant'age of'such a means re= sides in the fact that it reverses the operating cylinder at exactly the same point in its path of movement during each cycle, namely, after it has struck the end wall of the cylinder. This results in a very accurate limitation ofthe travel o! the operating system and associated'machine" tool or work holder.

It has beeniound that -while the structure disclosed by Miller and Morris is operative for its int'ended purpose, there is a` slight lag be- '30 tween the completion of the voperating piston movement and the reversal of the fluid pressure connection to theoperating cylinder, which has the eiect of slowing the cycle of operation of the machine. 'I'his time lag is due to the iact that the valve actuating cylinder exhausts through that end of themain operating cylinder which exhausts during the working stroke, which end in turn exhausts through a relatively restricted outlet. Thus, the exhaust or back pres- 40 sure in the actuating cylinder has a tendency to retard its movement in the direction in which it shifts the reversing valve to reverse the operating cylinder. The present invention is broadly directed to the provision of means for quickly venting that'side of the actuating cynnder which exhaustsduring the workingstroke as soon as lthe working strokeis completed.

A morev specific object of the invention is to provide a one way conduit between one end` of the operating cylinderand one end of the actuatingcylinder, which conduit has provided therein means for automatically venting the actuating cylinder to the storage reservoir when the exhaust pressure drops in that end of the `operating cylinder which exhausts during the working stroke.

Other objects and advantages of the invention will become apparent from the accompanying drawing and attached specification and 6 claims.

The drawing fillus'trates, partly ldiagrammati- `cally,' a preferred form of the invention, the essential elements thereof being illustrated in section.

In the drawing there is shown at I the cylinder of a hydraulic motor which includes a piston V2 and piston rod 2. The piston rod 3 may be adjustably-connected to a reciprocating work or tool holder, not shown, of a machine tool. Such l5 a machine may, for example, be a drill press having a `reciprocating drill head which is adjustably connected tothe piston rod. 'Ihe cylinder I has a removable head 4 secured in placeby suitable studs 5. The opposite 20 end of the cylinder is formed at 6 to receive a conventional packing gland 1 .having a packing. 8 for preventing leakage around the pistonv rod.v The interior end wall 9 is :dat and is adapted to engage abutment IIJ on the piston when the 25 latter reaches the limit of its movement ink the working direction. A similar abutment II is provided at the opposite face of the piston, and piston rings I2 are fitted into conventional-ring grooves about the periphery of the piston. The 30 walls of the cylinder adjacent its lower end are provided with a pair of ports I3 and I4, while similarports I5 and I6 are provided adjacent the opposite end of the cylinder. These ports l are threaded or otherwise adapted to receive 35 4suitable fluid conduits .I'I, I8, I9 and 20, respectively. Each of the conduits I1 and I9 is adapted to operate either as a pressure or exhaust conduit for the end of the cylinder to which it is connect- 40 ed and these functions are controlled by a reversing valve, indicated generally at 2i, which is interposed in lines I1 and I9. The reversing valve comprises a casing 22 closed at one end and having at the opposite end thereof a removable 45 closure plate 23 secured in place by studs 24. Plate 23 is provided with an opening forthe reception of `a packing gland 25 and a valve rod 26 extends through the opening and has a valve head 2T on its inner end. The valve housing 50 22 is provided with five ports-28, 29, 30, 3| and 32 spacedl respectively along the axis of the housing and the conduits I'I and I9 are threaded or otherwise secured into the ports 28 and 29, respectively. Port 30 communicates with a con- 55 duit 63 which is connected to the discharge side of a pump 34, while ports 3| and 32 communicate through conduits and 36 with a low pressure storage reservoir 31. The intake of pump 36 is connected to reservoir 61 byl a conduit 38.

A valve operating lever 69 is slotted at its end 40 to receive the end of valve rod 26 and the end of the valve rod is threaded to receive a pair of nuts 9| and 92 which are adapted to engage opposite sides of the end of the lever. The lever 39 is pivoted at 99 to a xed portion of the machine M, and carries an extension d5 to which is secured a roller 96. A cam 61 adjustably secured to the piston rod 6 of the hydraulic motor by any suitable means, such as set screws 68, has a bevel i9 adapted to cooperate with the roller. it will be apparent that as piston 2 approaches the upper end of cylinder l, as viewed in the drawing, thebeveled 'portion 49 of cam t1 can engage roller i6 and will shift lever 39 to the position it assumes in the drawing. However, upon return movement of the piston, downward as viewed in the drawing, cam 41 will pass beyond roller d6 without changing the position of lever 89. V 1

The lever 39 is apertured at 50 to receive a piston rod 5| of an actuating motor comprising a cylinder 52 and a piston 53 having abutments similar to those on piston 2. This cylinder has a removable closure plate 54 at one `end thereof,

end is provided with a packing gland 56 for the reception of piston rod 5|. The upper end of cylinder 52 is in constant communication with Y the upper end of the operating cylinder through conduit 20. At its upper end, the rod 5I has a reduced portion 51, and a compressible abutment member is mounted on the latter and includes a pair of telescopic housings 58 and 59 and a coiled compression spring 66 within the housings. A nut 6| threaded on the end of Arod 51 is provided for retaining this assembly in place. It will be observedthat when piston 53 moves downwardly as shown in the drawing, housing member 59 will engage one side of leverv 39 and will resiliently force itin a clockwise direction about pivot 48.

'I'he motor 52, 59, etc., it will be observed, is of the double acting expansible chamber type inasmuch as movement of the piston is accompanied by an increase in the volume of the space at one end oi the cylinder and a reduction of the volume at the opposite end.

The opposite, or lower, end of cylinder 52 is in communication with the lower end of cylinder through conduit 62, a one-way dump valve mechanism indicated generally at 63, and a conduit I6. The one-way' dump valve mechanism 69 comprises a housing 64 containing a pair of parallel longitudinal bores and 66 extending throughout its length. Longitudinal bores 65 and 66 are connected adjacent their ends by a pair oi'transverse bores 61 and 68, each of which is drilled from one side of housing 64 .through both longitudinal bores. The open ends oi bores 61`and 66 are closed by plugs 69 and 10, respectively. A third' transverse bore 1| extends from the exterior of housing 64 into communication with the longitudinal bore 65 and is connected by means of an adapter 12 to a conduit 13 extending V/to the reservoir 31.

A valve houslng14 is fitted into bore 65 and is held in place against an abutment 15 by a plug member 16 which is threaded into one end of longitudinal bore 65. Housing 14 is provided with a cylindrical recess 11 for the reception of a sliding valve member 16. A longitudinal passageway 19, which connects recess 11 with the right hand end of the housing, is adapted to be closed bya projection on valve member 19 when the latter assumes the position `shown in the drawing. The valve housing 14 contains a plurality of radially extending transverse bores 8 i, communicating with an annular groove which in turn communicates with the transverse bore 1| in housing 64. When valve member 19 is shifted to the left from the position shown in the drawing, a communication is provided from transverse bore 1| through recess 11 to passageway 19 and thence into bore 65. Valve -member 16 is provided with a small longitudinal groove |68 and a communicating circumferential groove ill?. through winch any uid that may leak past the seal of projection 66 may ow to the exhaust passages 6i. This prevents the pressure from building up over the entire area oi the right hand end of member 16 and perhaps prematurely opening the valve.

'Ihe plug member 16 is provided with a longitudinal bore 62, to the outer end of which the conduit I8 is connected bymeans of an adapter This bore at its inner end communicates with a transverse bore 84 which is align'ed with the bore 61 in the housing V64, and at the inner end of the plug,16, a recess 85 is in communication with the transverse bore 64' by means of passages 66. At its right end the bore 65 is conn ected to thev conduit 62 by means of a threaded adapter 81.

One end of longitudinal bore 66 is closed by plug 86 while the other is threaded for the reception of the ball and spring supporting member 89 of a one-way valve assembly. This one- Way valve comprises a seat member 9 0 having an axial bore 9|, which is seated against a shoulderv 92 formed `by an enlargement of bore 66. The ball and spring supporting member 89 is axially bored for the reception of a spring 93, which operates tol hold a ball valve 94 against the seat 99, and prevent flow of fluid from the transverse bore 66 into bore 66 beyond the seat 90. Flow in the opposite direction is permitted by reason oi the compressibility of the spring, and a slot 95 in the side of member 69 adjacent the seat. A cap 96 is threaded on the end of the member 89 and engages the face of the housing 64 to lock the member 69 in position. Suitable packing, as indicated at 91, is provided be- -tween the cap 96 and housing 64.

. 62, but flow in the opposite direction is prevented by ball 94. Moreover, if at any time the pressure in conduit 62 exceeds that in I8 by a predetermined amount, valve member 18 will be moved off its seat, opening communication between bores 19 and 1| and thus permitting the ow of uid from conduit 62 through the valve housing 14, transverse bore 1| and conduit 13 to the reservoir 31. This arises by reason of the fact that the pressure in conduit AI8 iscommunicated to the recess 65 at the end of plug 16 and thus is effective against one end of valve 18, while the pressure in conduit 62 is communicated through bores 65 and 19 to the extension 80 on valve member 18. It is apparent that inasmuch as the effective areas at the opposite sides of valve 16 when the latter is closed are dierent, that no motion of 7b d, Vi

' this member will occur until the pressure in con- -duit 62 exceeds that in conduit I8 by a predetermined amountywhereupon the valvemember will be initially cracked. Immediately thereafter the pressure from conduit 52 will be effective over the entire area of the lower end of valve member 18,

through this bore. In order to permit a free ilow and the valve will open rapidly and remainopen to vent conduit 62 to the reservoir 31.

Anjimportant feature of this valve\mechanism resides in the fact that valve 18 will open automatically as soon as the exhaust pressure'at the lower end of cylinder I drops a predetermined amount. This arises by reason of the fact that the pressure trapped in the lower end of the actuator cylinder by ball valve 94 is effective on the reduced end. 80 of valve member 18. Thus, as soon as the exhaust pressure, and therefore the pressure on the opposite end of valve 18, drops below normal, the 'valve member'will be opened to vent cylinder 52. A

Between the cylinder I and the reversing valve 2| and interposed in conduit I1, a one-way throttle valve 98 is provided which comprises a block 99 having a longitudinal bore |00 passing entirely therethrough. The opposite ends of 4bore |00 are connected respectively to the adjacent ends of conduit I1, and an adjustable metering screw IIII is provided for restricting the flow of fluid to the cylinder I through conduit I1', a one-way by-pass is provided around the vscrew I0| and comprises connected passages |02, |03 vand |04, and a one-way ball valve. 'I'he latter comprises a ball |05 at the end of passage |03 and a spring |06 engaging the ball and which is mounted in a housing I01'secured` to block 99.'

The'outer .end of hores |02 and |04 may be closed by any suitable means, such as plugs.

The drawing shows the parts in the positionthey occupy during downward movement of the operating piston 2, towards its piston rod, andi before the completion of such movement. Under this condition the reversing valve 21.wi1l connect the pump 434 yto the upper end of cylinder I through conduit 33, the housing of the reversing valve, and conduit I9, thus supplying pressure' to effect movement of the piston. At the same time the lower end of cylinder I will be exhausting through conduit I1, the throttle Vvalve 98, the lower end of housing 22 of the reversing valve,

' conduit 35 and conduit3|i to the reservoir 31.

' seI 'Ihe metering screw IOI will be adjusted to provide an appreciable back pressure at the exhaust sideof'piston 2 for a purpose to be described,

The high pressure at the upper yside of piston 2 will be communicated through conduit 20 to the piston rod end, of cylinder 52 of the reversing valve actuator. vAt the same time the pressure in the lower end of cylinder 52 ycannot be much less thanv the exhaust pressure in the lower end of cylinder I because any appreciable difference in pressure will lift ball valve 94 and permit the fluid in the lower end of cylinder I to ilow -through conduit I8, bores or passageways 82, 84

parts and the operating and exhaust-pressures are so selected, however, that the lowV pressure -at the lower end of piston 53,will overcome the high pressure at the opposite end and maintain the piston 53 at the rod end of the cylinder, as shown in the drawing. This overbalancing of a high pressure by a lower pressure is effected by reason of the fact that the piston rod 5I reduces the effective area at the upper end of piston 53 sufiiciently to compensate for the excess pressure at that end. The relative diameters of the piston and the piston rod of the actuator may be so proportioned as to insure that the piston 53 will *remain at its uppermost position until the resistance to movement of piston 2 exceeds the maxi. mum resistance that will beofered by the tool during normal use.

Other features which contribute to effect this balance between unequal pressures should be noted. In the first place the working pressure in the cylinder I is applied at the upper or 'rodless side of the piston 2 Vwith the result that for a given resistance to movement of piston 2, the diff ference between the working and exhaust pressures will be less, due to the decreased area at areas were the same. This means either that the working pressure and therefore the pressurein the upper end of actuator cylinder may be less or that the exhaust pressure in the lower end of cylinder I may be greater than would otherwise be possible. In either case, this reduction in the the exhaust side, than would be possible if the pressure differential makes it easier to hold the piston in actuator cylinder 52 in its upper position. 4

'I'he piston 53 will be held in its uppermost ment toward the Ilower end of cylinder I. However, when piston 2 reaches and abuts the end of its cylinder, no further movement is possible regardless of the pressure at the upper end of the cylinder. Therefore, the iluid at the exhaust side will be relieved of the normal exhaust Apressure caused by movement of the piston. As soon as the pressure at the lower end of cylinder I drops below the normal exhaust pressure, the pressure in conduit I8 and chamber 85 will likewise drop, and .the normal exhaust pressure which is trapped' at the lower end of cylinder 52 by ball valve 94, and which acts .on the reduced end of vent valve`18, `will shift valve member 78 and vent the lower end of cylinder 52to reservoir 31 through conduit 13.- As previously described, this permits a rapid exhaust of the fluid at the lower end-of the actuator cylinder 53 through conduit 62, the right hand end of bore 65, bores 19, 8|, 1| and conduit 13 to the reservoir 31. In this way the actuator piston 53 will rapidly move downwardlyunder the influence of full operating pressure from the upper end of cylinder I through conduit 20, bringing the resilient abutment member 59 into contact with the lever 39 and swinging the latter clockwise to shift reversing valve 21 downwardly.

Shifting of the reversing valve from the position illustrated, places conduit I1 in communication with the pump through conduit 33 vand. the

lvalve housing, and it places conduit I9 in communication with the discharge reservoir 31 through conduit 38 and the valve housing. The pressure in conduit I1 passes through .the bypass passages and one-way valve of the metering device 98 tothe lower end of cylinder thus initiating and effecting movement of the operating piston 2 in a reverse direction, or upwardly position so long as piston 2 continues its moveas viewed in the drawing. During such movement the uid at the upper end'of piston 2 disn charges freely through conduit I9.

During the reverse movement of piston 2, the high pressure at the lower end of cylinder I is communicated through port I4, conduit I8, the one-way dump valve mechanism 63, and conduit 62 to the lower end of the actuator piston 53. Since free exhaust pressure is effective upon the upper end of piston 53, this piston will move upwardly until it assumes the position shown in the drawing. Such motion, however, will not affect the position of lever 39, which will remain in the position to which it was previously moved by the reverse movement of the actuator piston 53, until roller 46 is engaged by the beveled surface49 of cam 41 on piston rod 3. During the upward movement of piston 2, valve member 18 in the one-way dump valve mechanism will be restored to the position shown in the drawing by reason of the excess pressure in conduit I8 over that in conduit 62. This excess in pressure exists by reason of the pressure drop between these two conduits due to the flow of fluid from conduit I8 through the bores 61, 66, 92 and 68, and also by reason of the resistance of spring pressed ball 94.

Near the end of the upward movement of piston 2 the beveled surface 49 of cam 41 engages roller 46 on lever 39 and thereafter shifts the lever and reversing valve to the position shown in the drawing. From this point the above described cycle of movement will be repeated.

It will be apparent from the description and the accompanying drawing that the invention constitutes an improved means for reversing a reciprocating fluid pressure motor at a fixed point in its stroke, and only after its movable element has engaged and been stopped by a fixed abutment. The invention not only positively insures that the movable carriage or other device operated by themotor will always change its direction of motion at exactly the same point in each cycle, but provides a quick reversal of the carriage at that point. This feature is of great value Where very accurate cuts must be made by production machine tools.

While there is illustrated and described the preferred form of the invention, it is apparent that considerable variations may be made in the details and arrangement of parts without departing from the spiritthereof, or the scope of the appended claims.

What is claimed is:

1-. Means for reversing a fluid pressure motor having intake and 'exhaust passages comprising a reversing valve for controlling said passages, a pressure responsive means for operating said reversing valve, means for conducting fluid from one side of said motor to said pressure responsive means, an exhaust passage for said pressure responsive means independent of said motor intake and exhaust passages, means operable upon a predetermined decrease in the pressure in said side of the motor for exhausting the pressure from said pressure responsive means through said independent exhaust passage, and means for operating said pressure responsive means upon exhaust of fluid therefrom through said independent exhaust passage.

2. Means forreversing a reciprocatory fluid pressure motor comprising a reversing valve, a pressure responsive means for operating said reversing valve, an exhaust valve for said pressure responsive means, means including `a one-way pressure motor comprising a reversing valve, a

pressure' responsive means for operating said reversing valve, an exhaust valve for said pressure responsive means, means including a one-Way value for conducting fluid from one side of said motor to said pressure responsive means, means associated with said exhaust valve operable upon a flow of fluid from the motor to said pressure responsive means to close said valve and operable when the pressure in said side of the motor is less than that in said pressure responsive means by a predetermined amount to open the valve, and means for operating said pressure responsive means upon exhaust of uid therefrom through said exhaust valve.

4. In combination, a fluid pressure motor including a piston and cylinder, means including a reversing valve for reversing pressure and exhaust connections to the opposite ends of said cylinder, an expansible chamber actuator for operating said reversing valve, conduit means connecting one end of said cylinder to said expansible chamber, mea'ns `tending to operate said expansible chamber actuator to collapse the chamber and thereby shift the reversing valve, said means being ineffective to overcome the normal pressure in said chamber but effective when said pressure is reduced below normal, and a dump valve for venting said chamber when the exhaust pressure in said one end of the cylinder drops below normal.

5. In combination, a fluid pressure motor comprising a piston and cylinder, means including a reversing valve for reversing pressure and exhaust connections to the opposite ends of said cylinder, an expansible chamber actuator for operating said reversing valve, conduit means connecting one end of said cylinder to said expansible chamber whereby the pressure is substantially equalized in said end of the cylinder and said chamber, adjustable means for restricting the exhaust outlet for said end of the cylinder, means tending to operate said expansible chamber actuator to collapse the chamber and thereby shift the reversing valve, said means being ineffective to overcome normal exhaust pressure in said chamber but effective when said exhaust pressure is reduced below normal, and a dump valve for venting said chamber when the pressure in said chamber exceeds that in said end of the motor cylinder.

6. In combination with a double acting uid pressure motor including a piston, a cylinder and a reversing valve for reversing the pressure and exhaust connections at opposite ends of said cylinder, of means operatively connected to said reversing valve including a second fluid pressure motor having a piston and cylinder, a piston rod on said second piston, an open conduit connecting one end of said first cylinder with the piston rod end of said second cylinder, means connecting the opposite ends of s aid cylinders and adapted to permit passage of fluid in one direction only from .said first to said second cylinders, the crosssectional areas of the second piston and its rod being so proportioned that the normal operative 2,177,828 pressure at said piston rod end of the second a reversing valve for reversing the pressure and exhaustconnections at opposite ends of said cylinder, means operatively connected to said reversing valve including a second fluid pressure motor having a piston and cylinder, a piston rod in said second cylinder, an open conduit connecting one end of said first cylinder with the piston rod end of said second cylinder, means connecting the oppositeends of said cylinders and adapted to permit passage of uid in one direction only from said first to said second cylinder, the cross-sectional areas of the'second piston and its rod being so proportioned that the normal operative pressure at said piston rod end of the second cylinder is insufficient to overcomethe normal exhaust pressure at the opposite end of said second cylinder, means for venting the said opposite end of the second cylinder when the exhaust pressure at said opposite end of the iirst cylinder drops below normal, a lost motion device in the connection between said second motor vand said reversing valve for preventing operation of the valve by said second .motor when said second vpiston moves toward the` piston rod end of said second motor but permitting operation in the opposite direction, and means associated with-the rst motor for shifting the reversing valve in the direction in which it cannot 4be moved by said second motor when the piston of said iirst motor approaches the end of its travel in the direction toward said open conduit.

'8. The combination-with a reciprocatory double acting fluid pressure motor comprising a cylinder, a piston, a piston rod extending through one'end of the cylinder, and a reversing valve, of a second cylinder, a piston in said second cylinder, a piston rod` connected to said second piston, extending through one end of said cylinder and connected to said reversing valve, fluid conduit means connecting the rodls end of the iirst cylinder with the rod end of the second cylinder, iiuid conduit means connecting the rod end of the flrstcylinder with the rodless end of the second cylinder, a' one-way valve in said last named, uid conduit means adapted to prevent flow of uid from the second cylinder to'the first. and means automatically operablewhen the pressure in the rodend oi the iirst cylinder isdecreased to a predetermined ratio with respect to the pressure in the rodless end of the' second cylinder to open an exhaust passage for the fluid in the rodless end ofthe second cylinder, said means being operable to close the exhaust passage when the pressure in the rod end ofthe rst cylinder exceeds that in the rodless end of the second cylinder.

9. Means for reversing areciprocatory fluid pressure motor having intake and exhaust passages comprising a reversing valve for controlling said passages, means for operating said reversing valve including a second iiuidgpressure motor having an expansible chamber, and means for exerting a force-on said second uid pressure motor tending to collapse said chamber and thereby shift -said reversing valve, means for conducting exhaust iiuid from one end of said first motor to said chamber to oppose 'the action of said means tending to collapse the chamber, and means operable upon a drop in the exhaust pressure at said one end of said first motor'for venting said chamber.

10. Means for reversing a reciprocatory uid pressure motor having intake and lexhaust passages comprising a reversing valve forv controlling said passages, an expansible chamber fluid pressure motor for operating said reversing valve, means for exerting a force on said second motor tending to collapse the chamber thereof and thereby operate said reversing valve, means for conducting iiuid from one end of said first motor to the expansible chamber on said second motor, means for maintaining suflicient exhaust back pressure on said one end of said first motor when said motor is exhausting at said one end to maintain sumcient pressure in said chamber to overcome the collapsing force of said iirst means and valve.

LOUIS C. HUCK.

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