US2346254A - Pump stroke varying structure - Google Patents

Description

Aprl 11, 1944.

W. .ERNST PUMP STROKE VARYING STRUCTURE original Filed Dec. 15,' 1939 2 Sheets-Sheet l N INVENTOR WALTER ERNST BY@ l W 2 ATTORNEYS April 1l, 1944. w, ERNST 2,346,254

PUMP STROKE VARYING STRUCTURE Original Filed Dec. 15, 1939 2 Sheets-Sheet 2 INVENTOR. WALTER ERNST ATTORNEYS Patented Apr. 11, 1944.

. UNiTED s'rA'rss PATENT orrlcsv 2,346,254 PUMP sraoxs vanmc s'rnuc'runs Walter Ernst, Mount Gilead,

The Hydraulic Development Ohio, assitnor to Corporation. Inc.,

Wilmington, Del., a corporation of Delaware 1o anims. (ci. 12p-ss) December 15, i939.

This invention relates to control mechanisms and, in particular, to mechanisms for controlling the movement of a reciprocable member, such as the ow control member of hydraulic pumps or motors.

Control mechanisms, as heretofore known, for controlling the iiow control member of hydraulic pumps or motors required quite a number of packings around the movable members, which packings on one hand, due to friction caused thereby, impaired the efciency of the device, while, on the other hand, the replacement of said packings causes additional work and cost, aside from the necessary interruption of the operation of said device. A

Accordingly, it is an object of the invention to provide an improved control mechanism which will overcome the above mentioned drawbacks.

Another object is to provide a control mechanism for controlling the iiow control member of hydraulic pumps or motors, in which the packings heretofore required around reciprocable members are reduced to a minimum or substantially eliminated, thereby eliminating to a great extent the friction arising from the presence of said packings and correspondingly increasing the sensitivity of the control mechanism.

It is a further object of the invention to provide a control mechanism of the above type, which constitutes a material simplication in structure, while simultaneously aording a sim- A plilled adjustment thereof.

It is still another object of the invention to provide a control mechanism for controlling the movement of a reciprocable member, which comprises a main control piston and an auxiliary conthe invention will appear more clearly from the following specication in connection with the accompanying drawings, in which:

Figure l. shows a control mechanism according' to the present invention, in connection with a variable delivery pump serving as pressure fluid source for a hydraulic circuit.

Figure 2 is an enlarged longitudinal section through the control mechanism according to the invention, showing the moving pistons disengaged to render the unit temporarily inoperative.

Figure 3 is a View similar to Figure 2, but with f the pistons of the control mechanism engaging each other and shifted into their right hand positions.

Referring now to the drawings in detail, the

control mechanism according to the invention is shown in connection with a variable delivery pump lli, merely by way of example, but is by no means limited thereto. The variable delivery pump I0 shown in the drawings is provided with a flow control element or shift ring 20 which is mounted upon the control rods 2l and 22 slidably supported in the pump casing 23 and passing cutwardly therethrough. The shift ring 20 ordinarilyencircles the secondary rotor of theI pump and by varying the eccentricity of the latter relatively to the axis of rotation of the primary rotor or cylinder barrel alters the delivery or output of trol piston operatively connected with said reciprocable member, and in which the main control piston is placed at the end of said control member Where it is accessible for adjustment and also serves to transmit the thrust from said auxiliary piston to said reciprocable member.`

A still further object of the invention consists in the provision of a control mechanism for a rotary pump or motor, which control mechanism is adapted to shift the flow control element of said pump or motor independently of the shifting accomplished by an additional pressure responsive piston. This invention is a continuation application of my copending application, Serial No. 309,435. flied December l5, 1939'. and which has since become abandoned.

The above and other objects and advantages of the pump. When the axis of the secondary rotor coincides with that of the primary rotor or cylinder barrel, and the eccentricity is zero, the shift ring 20 is then said to be in its neutral or zero delivery position. Under these circumstances, as is well known to those skilled in the hydraulic art, the pistons of the pump i0 will not reciprocate and hence the pump delivers substantially no fluid.

The control rod 2l is urged to the right to shift the shift ring or flow control element 20 into aQ full delivery position by the spring-urged device il, consisting of a stationary tubular casing 24 within which is telescopically mounted a movable tubular casing 25. The stationary casing. is secured to the pump casing 23 and both casings 26 and 25 enclose a coll spring 26, one end oi which rests against the inner left end wall of the stationary casing 2d, whereas the other end engages the right-hand end wall of the movable casing 25. which has a ,ball thrust bearing 2l associated therewith and encased on its opposite side by the hub of a hand wheel 28 internally threaded upon the threaded portion 29 of the controlrod 2|. A lock nut 30 beyond the hand wheel -22 enables the locking of the hand.

wheel 28 in any desired position of adjustment. The control unit I2, in general, urges the control rod 22 and pump shift ring 23 to the left when it receives pressure fluid, thereby tending to overcome the thrust of the coil spring 26 and move the shift ring 20 back toward its zero delivery or neutral position.

The control unit I2 (Figure 2) consists of a housing 3| attachable by its flanged portion 32 to the pump casing 23. This housing 3| contains a cylinder bore 33 having a threaded entrance' port 34, giving access to the end thereof nearest the pump casing 23. Reciprocable within the cylinder bore 33 is an auxiliary piston 35 having sleevelike extensions or hubs 36 and 31 extending in opposite directions along the control rod 22 but separated therefrom by a substantial clearance space 38 therebetween. Fluid leaking past the auxiliary piston 35 to the lofthand end of the cylinder bore 331 escapes by way of the transverse passageway 39 into the clearance space 38, and thence along the control rod 22, back into the pump casing 23, the clearance space 38 forming the annular passageway along the control rod 22. An accuratev sliding ilt is maintained in the bore 40 between the hub 36 and the casing 3| so that no packing is required at this location. The hub 31, however, is separated by a clearance space 4| from the cylinder head 42, which is bolted-to the housing 3| by means of the screws 43 and with the gasket 44 therebetween to prevent leakage.

Bolted to the cylinder head 42, as by the screws 45, is a housing 46 containing a cylinder bore. generally designated 41, and receiving a stepped piston, generally designated 48. The stepped piston 48 consists of three portions 49, 50 and 5|, of different diameters, respectively reciprocable in the bore portions 52, 53 and 54 of the cylinder bore 41. This construction provides annular pis-- ton areas 55 and 56 opening into bore enlargements 51 and 58, servedby the threaded ports 59 and 60; and also provides an annular end wall 6| which is adapted to be engaged by the annular end wall 62 of the piston hub 31 when the piston 48 is moved to the right to close up the space (Figure 2) between the annular end walls 6I and 62, in the manner shown in Figure 3. For this purpose, the stepped piston 48 is separated from the control rod 22 by a clearance space 63, similar to the clearance space 38 between the auxiliary piston 35 and the control rod 22.

The outer end of the control rod 22 is threaded, as at 64 (Figure 2), and provided with a lock nut 65 engaging a collar 66, which,in turn, engages the conical bore 61 in the end of the stepped piston 48. A longitudinal passageway68, communicating with a transverse passageway 69 in the control rod 22, provides for the drainage of iiuid which escapes past the stepped piston 48. Such iiuid passes through the passageways 68 and 69, and through the clearance spaces 63 and 38, along the control rod 22 to the pump casing 23.

In Figure 2 the stepped piston 48 is shown as separated by a quarter of an inch from the auxiliary piston 35, yet the latter is at the extreme end of its stroke in the left-hand direction. This separationvbetween the end walls 6| and 62 of the piston portions and 31, respectively, is provided to render the lunit I2 temporarily inoperative at the will of the operator. When it is desired to render the unit operative (Figures 1 and 3), the operator rotates the lock nut 65, thereby moving the stepped piston 48 to thev right, along the control rod 22, until the end 5B and lock nut 65.

wall 6| engages the end wall 62. Thus, when pressure is admitted through the port 34 to the end wall 6| of the stepped piston 48, moving itI to the left and with it the control rod 22 by reason of the connection provided by the collar The lock nut 65 may be locked at any desired position along the threaded portion 64 by turning the set screw 10. The lefthand end of the cylinder bore 41 is closed by the end plate 1|, secured to the housing 46 by the screws 12, leakage being prevented by the gasket 13.

The stepped piston 48 is provided for the purpose of creating a multiplicity of piston areas of differentsizes so that the pump iiow control element or shift ring 2|) may be shifted to its neutral position at one of a plurality of selected pressures. The particular pressure selected is determined by whether the control conduit is connected to the port 63 or to the port 69. In the example shown in Figure 2, the port 59 is illustrated as closed by the threaded plug 14 so that the port 60. cylinder bore 53 and annular piston area 56 are in use. The same arrangement is shown in Figure 1. It will also be obvious that a third piston area will be available ii' both of the ports 59 and 60 are connected to the pressure circuit, thereby subjecting the combined piston areas 56 and 55 to the action of the pressure fluid. 'I'he stepped piston construction shown at the left-hand end of Figure 2 forms no part of the present invention, and is described and claimed in the U. S. Patent No. 2,229,965 to Ernst.

It will be observed that the motion oi' the auxiliary piston 35 to the left is limited by the shoulder 15 at the end of the portion 16 containing the transverse passageway 39. In Figure 2 the auxiliary piston 351s shown in its extreme left-- hand position, which position it will occupy only when there is sufficient pressure in the cylinder bore 33 to overcome the force of the coil spring 26. By turning the lock nut 65 the amount of movement o1' the control rod 22, which may be brought about by the auxiliary piston 35, is increased or decreased, depending' upon the direction in which the nut 65 is turned.

It will be observed that there is no packing engaging the moving parts excepting the oil seal 11 (Figure 1) surrounding the control rod 2| at the point where it passes out of the spring casing II into the pump casing 23. As the oil seal 11 is not under pressure, however, it causes no appreciable friction by its engagement with the control rod 2|. The piston rings 18 in the auxiliary piston 35 assist in preventing leakage thereby, but where such leakage occurs it is rapidly taken care-of vby the leakage system previously described and consisting of the passages 39, 63 and 69 and the clearance spaces 63 and 33 surrounding the control rod 22.- 'I'he thrust of the spring 26 and, therefore, the force opposing the action oi' the pistons 35 and 48 is regulated by turning the hand wheel 23.

' The variable delivery pump with the control unit described above is capable of a variety of uses, Figure 1 showing the press having an upwardly moving platen ,and a booster ram. In Figure 1 the press I1 is provided with a head 83, a bed 8| interconnected by the strain rods '82 having the nuts 83 threaded upon the ends thereof. The press I1 is provided with an upwardly moving platen 84, to which is attached the main plunger 35 having a piston head 36 reciprocable in the main cylinder bore Il, the entrance to which is closed by the packing I8 and gland 89. The main plunger 85 is hollowV the aperture s? at the lower end of the main,

cylinder 93, and having a bore extending longitudinally therethrough. The booster cylinder 90 is provided to move the platen 8d more rapidly toward its closing position than would be pocslble by using the piston area 95 oi the main plunger it alone.

The platen @t may operate in any manner upon the work. piece or upon the other mecha nism to be operated. 'In Figure 1 the platen 835, for purposes of example, is shown as carrying a die half 'et cooperating with the stationary die haii t? mounted upon the press head 88. The platen @d is also provided with a platen arm 9@ adapted to engage a collar e@ upon the valve rod itt of the two-way auxiliaryyalve i6, previously described. An additional collar lili is provided beneath the platen arm S8 so that the latter will shift the valve rod itt, and change the setting of the two-way valve ld at the ollposite ends of its stroke.

reached the upper mold hal! Il. or at any desired point in the operation of the press I1, the platen arm 8B engages the collar 99 and lifts the valve rod m of lthe auxiliary valve It, opening the latter by shifting its heads to the positions shownl y in Figure 1. Since the pressure fluid can now pass from the conduit W9 through the vauxiliary The variable delivery pump is connected to the tank i3 :by the suction conduit N2 from the suction connection 93. The fluid received along the suction conduit |02 is pumped through the pressure head ltd, along the conduit it to the four-way main control valve l5 having thevalve rod |06. From the valve l5 the discharge conduit lill leadsback to the tank B3, and the conduits Hi8 and llt lead respectively to the upper end of the main cylinder bore 81 and to the twoway auxiliary valve It. A branch conduit Il@ leads from the conduit it@ to the bore te within the stationary booster ram tl. A conduit lli leads from the two-way Valve it to the port it `in the lower end of the main cylinder bore t?,

and in this conduit a choke it is optionally inserted. A branch conduit I l runs from the oona duit lll to the check valve it within the tank i3.' A control conduit lill also runs from the conduit ill to the port 3S of the cylinder bore 33, whereas the control conduit llt runs from the pressure conduit IBS to either or |both of the ports 59 and Eid, adapted 'to admit pressure i'iuid to the stepped piston dd.

In the operation of the circuit shown ure l, the variable delivery pump It is started in operation, it being` assumed that the main plunger 85 isin its lower position opposite tc that shown in Figure 1. AIt is also assumed that the two-way auxiliary valve I8 is in the opposite position from that shown in Figure 1, namely, with its valve heads in their lowered positions. Fluid is then pumped bythe variable delivery pump from the tank lll, through the suction con'- duit It?, along the pressure conduit B05, through the four-way main control valve I5, thence valve it, and the conduit lli and port H2, into the main cylinder bore 81,' it encounters less resistance therein than in the booster cylinder il. Most of the discharge from the variable delivery pump H Lcnthis account, will now be'diverted to the main cylinder bore IB, where it acts against the large piston area 95 thereof, withlthe result that e. sufficient pressure will be produced to continue the lffing of the main-plunger 85 but at a reduced speed and with a much greater potential pressing force. Pressure fluid now backs up in the conduit il@ and passes through the port St (Figure 2), into the cylinder bore 33, where it lacts against the piston head and moves it to the left.

Assuming that the stepped piston d@ has been brought into operative engagement by rotating the nut d5 in a clockwise direction (Figure 3) and the gap between the end walls di and 52 is closed up from the position shown in Figure 2 to that shown in Figure 3, the motion of the piston 35 will be transmitted tothe control rod 22,1shifting the latter to the left by overcoming the thrust l of the coil spring 25. This movement shifts the now control element or shift ring 2d of the pump it toward its neutral Aor zero delivery position, thereby reducing the delivery ofthe pump it and placing the latter upon part stroke. The amount of reduction in pressure depends upon the ad- .lustment of the nut 65. This reduction in the discharge of the pump Il! thus slows up the movement of the main plunger dal, the speed of which can be adjusted by adjusting the nut t6. The area of the piston head it is preferably made sufficiently large so thatthe pressure, due to the `in Figthrough the conduits W9 and H6 and the bore 81 is illled with iluid through the port H2, the l conduit l I3 and the check valve il from the tank When the lower mold 'half DI` hasalmost weight of the moving parts td and (35,' will be sulcient to cause the shifting or the piston head Bto the left as soon as the two-way valve it is opened bythe engagement of the platen arm 98 with the collar @t on the control rod iw.

However, the weight ci these moving parte may not be suiliciently large to provide enough pressure to shift the piston head 3d, asmay occur in the case oi' a downwardly acting press plunger with a booster cylinder in which no pressurev would build up because the ram travels downwardly under the influence of gravity. In that event, thechoke IB may be inserted in the conduit iii, las shown by the dotted lines in Figure l. This choke i8 articially increases the pressure in the conduit ill and therefore causesv the piston head 35 to move. l

The piston head 35 is intended to reduce the stroke of the pump but not to reduce it to zero. Thus, after the two-way valve I6 is opened at a predetermined point in the motion of the platen 84, the pump i6 is on part stroke and is still delivering pressure iluid. When the main plunger t5 meets a sumcient positive resistance so that the pressure duid backing up in thecondult I is of sumclent force to shift the stepped piston Il to the leit.1 and overcome the thrust oi the coll .spring 28 the control'rod 22 and shift ring 2l in the circuit, if such leakage is present. To reverse themotion 4of tbeplaten 84, the valve. rod

|06 of the main control valve I5 is shifted to its opposite position, whereby pressure iiuid is delivered to the conduit |08, into the space at the upper end of the main cylinder bore 81.

Since the two-way valve I6 remains open until the platen arm 98 encounters the lower collar IOI on the valve rod |00, uid escapes from the lowerv end of the main cylinder bore 81, through the port |I2, the conduit ||I, the two-way valve I6, the conduit |09, the main control valve I and the conduit I01, into the tank I3. At the same time, fluid escapes from the booster cylinder 90, through the bore 94, the conduit |I0, the conduit |09, the main control valve I5 and the conduit |01, into the tank I3. The platen 84, therefore,

descends until the platen arm 9a engages the collar |0| and closes the two-way valve I6. Pressure then builds up in the circuit and backs up in the conduit IIE to shift the stepped piston `08, the control rod 22 and shift ring 20 to the left to reduce the discharge of the pump I0 substantially toy zero. Y

While the control system according to the invention has been illustrated and described in connection with a variable delivery pump for an upwardly acting press, it will be evident that the arrangement may be used with any hydraulic pump, regardless of whether the press plunger isdownwardly acting, upwardly acting, or moving horizontally.

It will be understood that I desire to comprehend within my invention such modifications as come within the scope of the claims.

Having thusfully described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. In combination in a control mechanism for controlling the movement of a reciprocable element, yeldingmeans urging said element in one direction, a pair of cylinders, a fluid operable control piston reciprocable in one of said cylinders, a fluidoperable auxiliary piston reciprocable in the other one of said cylinders, said auxiliary piston being provided with means adapted to be engaged by said control piston, a reciprocable control member operatively connected to said Areciprocable element and passing through bores in both of said pistons, said control member forming with said bores a passageway connected with a chamber for returning leakage thereto, and

means for transmitting iiuid pressure acting upon said pistons to said control member against the thrust of said yielding means.

2. In combination in a control mechanism, a reciprocable element, yielding means for urging said clement in one direction, a pair of cylinders, a fluid operable control piston in one cylinder, a fluid operable auxiliary piston reciprocally mounted in the other cylinder and provided with a portion adapted to be engaged by said control piston, a control member connected to said reciprocable element, said control member passing and being movable relative to both of said pistons,`said control member also being provided with a threaded portion, a threaded element for engagement with said control piston, said threaded element being adjustably mounted on said threaded portion for selectively changing the effectiveness of said auxiliary piston, and means operable to admit iiuicl pressure to said pistons for moving the same against the thrust of said yielding means.

3. In combination in a control mechanism, a reciprocable element, yielding means for urging said element in one direction, a pair of cylinders,

a fluid operable control piston in one cylinder, a iiuid operable auxiliary piston reciprocable in the other cylinder and provided with a portion for engagement with said control piston to selectively actuate the latter or to be actuated thereby, a control member connected to said reciprocable element and passing through and movable relative to both of said pistons, said control member having a threaded portion thereon and being operable against the thrust of said yielding means, and a threaded element on said threaded portion-for engagement with said control piston, said threaded element being movable to vary the space between said pistons from the other piston, to thereby vary the actuation of said control piston by said auxiliarypiston.

4. In combination inA a control mechanism, a reciprocable element, yielding means for urging said element in one direction, a pair of cylinders. a fluid operable control piston in one cylinder` a uid operable auxiliary piston reciprocably mounted in the other cylinder, a control member connected to s'aid reciprocable element and passing through said pistons, and means for transmitting the thrust of said pistons to said control member against the thrust of said yielding means,

said pistons having enlarged bores therethrough surrounding said control member and providing an annular passageway therebetween for the escape of vleakage fluid.

5. In combination in a control mechanism, a reciprocable element, yielding means for urging said element in one direction, a pair of cylinders,

Va fluid operable control piston in one cylinder,

a uid operable auxiliary piston reciprocable in the other cylinder, a control member connected to said reciprocable element and passing through said pistons, and means for transmitting the thrust of said pistons to said control member against the thrust of said yielding means, said control piston having an enlarged bore larger than said control member and surrounding said 'control member, while providing an annular passageway therebetween for the escape of leakage uid, said auxiliary piston having a passageway leading from vone side thereof to said enlarged bore.

6. In combination in a control mechanism, a reciprocable element, yielding means for urging said element in one direction, a pair of cylinders, a fluid operable control piston reciprocable in one cylinder, a fluid operable auxiliary piston reciprocable in the other cylinder, a control memberconnected Vto said reciprocable element and passing through said pistons, means for admitting pressure uid to said pistons for actuating said control member -against the thrust of said yielding means, said control piston having a plurality of portions of different diameters thereon for providing piston portions of different areas, and means for selectively making one or more of said areas effective.

'1.4 In combination in a control mechanism, a reciprocable element, yielding means for urging said reciprocable element in one direction, a pairl .said rst mentioned bore and being reciprocable in the other cylinder, a control member connected to said reciprocable element and passing through the bores in lsaid pistons, said control member having an outer diameter less than the diameter of said bores so as to form an annular lable auxiliary piston in said auxiliary cylinder,

passageway between said bores and said control member for the escape of leakage iiuid from said cylinders, means for hydraulically connecting one side of said pistons with said annular chamber, and means for transmitting uid pressure acting upon said pistons to said' control member to move the same against the thrust of said yielding means.

8. In combination in a control mechanism, a reciprocable element, yielding means -for urging said element in one di! ection, a pair of cylinders, a uid operable control piston reciprocably rections. of which one extension passes into the mounted in one cylinder, a fluid operable auxiliary piston reciprocabiy mountedin the other cylinder, a control member connected to said reciprocable element and passing through said pistons, meansfor transmitting iluid pressure acting upon said pistons to said control member, said auxiliary piston having an axial extension passing into the other cylinder for engagement with said control piston, and means for selectively eiecting I relative movement betweensaid control member a control member connected to said reciprocable element and passing through said pistons.' and means for transmitting uid pressure acting upon said pistons` to said control member against the thrust oi' said .yielding means, said auxiliary cylinder having axial extensions in opposite dicontrol cylinder for engagement with said con- -trol piston, while the other extension snugly engages said auxiliary cylinder.

10. In a control device, a pressure fluid casing, a control casing connected to said pressure fluid casing and having a pair of cylinders therein,` a movable iiow control element, yielding means for urging said flow control element in one direction, a first uid operable piston movably mounted in one of said cylinders, a second fluid operable piston movablv mounted in the other cylinder and adapted to be engaged by said first piston, a control member connected to said now control element and passing through both of said pistons, and means for transmitting iiuid pressure acting upon said pistons to said control member to move the same against the thrust of said yielding means, said first piston having an axial extension snugly engaging said control casing for minimizing leakage between said control casing and said y

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