US2258886A - Mechanism for varying the speed of hydraulic press rams - Google Patents

Description

Oct. 14, 1941. w, gfi s 2,258,886

I MECHANISM FOR VARYING THE SPEED OF HYDRAULIC PRESS RAMS Filed July 21, 1.938 3 Sheets-Sheet l Oct. 14, 1941.

w. ERNST MECHANISM FOR VARYING THE SPEED OF HYDRAULIC PRESS RAMS s Sh eets-Sheet 2 Filed. July 21, 1938 Wm an 6 mm A mm mm m& .i. 3 I g 8 w U8 E w mm Patented Get. 14, 194i MECHANISM FOR VARYING THE SPEED OF HYDRAULIG PRESS RAMS Walter ma, Mount Gilead, om, assignor to The Hydraulic Development Corp. Ina, Wilmington, Deh, a corporation of Delaware Application July 21, 1938, Serial No. 220,554 9, (llaims. (Cl. 60-52) This invention relates to hydraulic machine.

control systems, and in particular, to systems in cluding a hydraulic pump andhaving provision for altering the delivery of the pump to vary the speed of the machine at different points in its operation One object of this invention is to provide means responsive to the motion of a hydraulic machine for varying the delivery of a hydraulic pumpso as to cause the machine to slow down at a predetermined point in its operation. I 1

Another object is toprovide means, as described above, wherein the machine is thereafter caused to gain speed-again following the slowing down thereof. v

Another objectis to provide a hydraulic press control system operated by a hydraulic pump, and including means responsive to the arrival of the press platen at a predetermined point to cause the platen to slow down immediately prior to its engaging the workpiece, and thereafter to gain speed so as to apply an increased pressing force control system, as described in the preceding paragraph, wherein the press is operated by a variable delivery pump having a flow-control of the pump, and preferably also to cause the link to resume its original-position afterthe platen has passed the above-mentioned predetermined point.

Another object is to provide a hydraulic press control system, as above described, wherein a time delay device in the system Operates to .cause an increase of flow of pressurefluid from the pump to the press a predetermined time afterthe reduction of flow from the pump to the press.

This application is a continuation in part of my copending application, Ser. No. 128,827, filed March 3, 1937.

In the drawings: a

Figure 1 is a diagrammatic view, partly broken away. of the essential portions of a hydraulic press circuit with a pneumatic collapsible link interposed between the press control rod and th servomotor control of the pump.

Figure 2 is an enlarged central longitudinal section through the pneumatic collapsible link of Figure l, with the link parts in one position.

Figure 3 is a view similar to Figure 2, but with the link parts in a reversed position relatively to Figure 2.

Figure 4 is a diagrammatic view of a hydraulic press control system having an electrically oper- General arrangement In general, the hydraulic press control system of this invention consists of a hydraulic press to which pressure fluid is supplied by a variable de-' livery pump having a. flow-control element for varying its delivery. Interposed between the manually controlled lever or control rod of the press and-the servomotor valve rod forvcontrolling the delivery' of the pump, is a collapsible or expansible link operated either pneumatically or electrically when the press platen reaches a predetermined position upon its stroke. When this position is reached the link is operated to permit the shifting of the servomotor valve rod so as to shift the pump flow-control member and reduce the. nelivery of the pump. A time delay device,

suchas a dash-pot; is optionally provided for establishing atime delay period for the operation under reduced flow so that the pump resumes its normal or increased flow at the end of a predetermined time interval following its reduction of flow. The link device may beeither pneumatically or electrically operated, and both such systems are illustrated herein. The link may also be expansible or collapsible, according to the. me-

' chanical requirements of its particular position in advisable to increase the speeds of hydraulic the pump operating mechanism, as hereinafter presses far beyond the speeds previously thought necessary. When such presses are used'in connection with dies, however, it has been found that the life of the dies is greatly shortened and damage frequently caused thereto because of the considerable shock which is set up when the press platen engages the dies while moving 'at this high speed. The purpose of the present invention, therefore, is to enable the press platen to close the dies at a high speed so as to shorten the working cycle, yet to slow down the platen just before the dies are engaged, whereupon the dies are engaged smoothly and without serious shock,

Pneumatic collapsible link system Referring to the drawings in detail, Figure 1 shows a reversible variable'delivery pump I having fluid connections II and I2, connected to conduits i3 and I4, respectively.- Depending upon whether the pump is in a forward or reverse position, one of the conduits II or H serves as a pressure conduit while the other serves as a suctionconduit. The conduit ljserves as a pressure conduit for supplying pressure fluid to the main cylinder of the press during the pressing stroke, while the conduit l4 serves as a suction conduit to withdraw fluid from the return side. of the press-operating circuit, in a manner well known to those skilled in the art.

Fluid for operating the circuit is'contained in the surge tank IS. The pump it is provided on -tor I1 is, in turn, controlled by the servomotor valve rod 18. The details of the pump I and its associated elements form no part of the present invention, and a disclosure thereof "is found in my copending application, Ser. No. 170,250, filed October 21, 1937.

The pump I4 is mounted upon a bracket i4 secured to the press head 20, which in turn, is connected to the press bed 2| by the strain rods 22 having the nuts 23 threaded upon the ends thereof. The press head contains a main cylinder (not shown) within which a main plunger 24 reciprocates. Secured to the main plunger 24 is a platen 26 having an arm 26 extending laterally aasasso upon the opposite end or the link device 49 is a yoke 52 ivotally connected, as at 53, to the lever 54. The latter is pivotally connected, as at 55,

to the servomotor valve rod i8 oi. the pump II and is pivotally mounted, as at 56, upon the floating link 51, which in turn, is pivotally mounted, as at 54, upon the casing of the servomotor l1.

Connected to the link device 48 is a flexible compressed air conduit l0, connected in turn, to a conduit 40 which leads to a two-way. air release valve having a valve rod 42 operated by an arm 43 carrying a roller 84. The valve rod 42 is urged by an internal spring into a normally closed position. The valve rod 2 is adapted to be moved to the left into an open position to release air from the valve II by the engagement of the roller 4 with the cam '8 upon the cam arm 44, secured as at 41 to the platen 2|. The cam 44 is provided with oppositely beveled portions 44 and 40 for engaging the valve-operating .roller 64. Mountedeat an hater-mediate point along the conduit 84 is a T-connection I0 having a conduit 'll leading thereto, and containing a choke valve 12. On the opposite side of the choke valve 12 the conduit. ll leads to a source of compressed air. such asa tank served by a compressed air pump.

The link device 44, shown in Figures 2 and 3, consists ofia cylinder 14 terminating at one end in the yoke 42, as previously explained. Within the cylinder 14 is a cylinder bore ll, having ports 16 and 11 communicatingtherewith at opposite ends thereof. Only one o! the ports 14 or 11 is utilized at a given time, the other being opened to the atmosphere, depending upon whether the link device 4! is to be used for a collapsible or expansible link. The cylinder 14 is provided with pipe connections 14 and 14 leading to the ports I6 and I1, and serving as connections for the flexible conduit 49.

Reciprocably mounted within the cylinder bore I! is a piston head 40, mounted as at Ii upon therefrom to encircle the press control rod 21, l

and to engage an adjustable collar 28 thereon collar 32 arranged to operate a limit switch 34 in the electrical circuit for controlling the reversal of the press circuit in full automatic operation.

The control rod 21 also is provided with a 'collar 34 engagable .by the yoked end 45 of a rocker arm 46, pivotally -moimted upon the rocker shaft 31 which, in turn, is mounted upon the press head 24. Pivotally connected, as at 34, to the opposite end of the rocker arm' 38 is-a connecting rod 3! having its lower end pivotally connected, as at 44, to the armature 4i of the operating solenoid 42. Also pivotally connected to the rocker arm 34, as at 43, is alink 44 pivotally connected at 7 45 to abellcrank 46, the other end of which is pivotally connected at 41 to the clevis 48 of a linkdevice, generally designated 49, hereinafter. described in more detail. The bellcrank 4B is pivotally mounted, as at 50, upon the bracket the threaded end 82 of the piston rod 04. The latter is connected, as at 84, to the clevis 48 and locked,in position by the .locknut-lfi. The piston rod 83 passes through the cylinder head 85, secured as at 81, to the cylinder 14. The cylinder head 46 contains a bore 84 with a packing 4!, which is held in place by a gland 9| threaded therein as at II. The cylinder 14 and cylinder head 4' are provided, respectively, with annular abutments 92 and 92, adapted to engage and limit the stroke of the piston head at the opposite ends of its stroke.

' and as soon as pressure is removed from the pipe connection II by the opening of the valve 6|, the device will expand intothe position shown in Figure 2, the expansion being accomplished by a spring IIa engaging the servomotor valve rod l8 within the servomotor II. On the other hand, if the compressed air conduit 54 is connected. to the pipe connection It, the link device 4! will be held in the expanded condition shown in Figure 2. and will becollapsed as soon as pressure is removed from the pipe connection 18 and conduit I by the opening of the valve 4 I.

In Figure 1 the link device 419 is in tension when the solenoid 42 is enersized'because the latter,

through the linkage, tends to pull the piston rod 83 and clevis 4b to the left while the'spring IIa Si mounted upon the press head Ill. Mounted servomotor valve rod I8 to the left, thereby urging the opposite end of the lever 54 and the yoke 52 to the right. This arrangement provides a contracted link which is permitted to expand by the release of the compressedair from the port I6 and conduit 59. If, however, the link device 49 were connected directly to the servomotor valve rod I8, the conduit 59 would be connected to the pipe connection I9 in order to accomplish the same result. The link device 49, under these conditions, would be in compression rather than in tension under the same circumstances. It is, therefore, an advantage to have the link device 49 adapted to be arranged either as a collapsible or expansible link so as to operate either in tension or in compression, as desired, depending upon the manner in which it is installed.

Operation In the operation of the system shown in Figure 1, let it be assumed that the press platen 25 and main plunger 24 are in their retracted positions so that the platen is up instead of being down, as shown in Figure l. The compressed air reaching the link device 49, through the conduits 13, II,

the now contracted link device 49, to the servomotor valve rod I8, shifting the servomotor I'I into a position to cause the pump III to .deliver pressure fluid through the line I3, into the upper end of the main cylinder. This causes the main plunger 24 and platen 25-to descend rapidly, aided by gravity and a surge valve (not shown), which for a time permits fluid to enter the main cylinstrikes the roller 84 and shifts the arm 63 to move the valve rod 8|. from the conduits 59 and 69 and from the port 15 in the cylinder I4 of the link device 49, so that the deviceis now free to expand. The spring IIa that is within the servomotor II is then free to shift the servomotor valve rod I8, thereby causing the shiftring or flow-control member of the pump to be shifted nearly to its neutral position. The stroke of the piston 80 is such that the servomotor valve rod I8 cannot cause the shiftring' or pump flow-control member to be pulled quite to its neutral position. However, because the pump The air then escapes its full stroke position for full delivery, the

workpiece or dies have been engaged. The operby the pump I8 from the retraction area of the press, which is relatively small in comparison with the advancing area upon the main plunger 24. 1

After the workpiece or dies are engaged, the platen 25 will-no longer descend by gravity, but is urged in a forward direction to continue its working stroke by pressure fluid delivered by the pump I8 through the conduit i3 to the main cylinder against the platen-advancing side of the main plunger 24. As'this area is considerably greater than the retraction area, the platen 25 moves more slowly than it did during the idle advance stroke, even though the pump capacity is the same as it was before the brief period during which its delivery was reduced by the action of the link device 49, as explained above.

Electrically operated link device and circuit In the modified arrangement shown in Figures 4 and 5, the pneumatic link device 49 is replaced by an electrically operated device 5. Thelatter consists of a solenoid II6 having a winding II'I connected to the lines H8 and H9, running to the power lines I28 and I2I, respectively. Inserted in the line I I9 is a normally closed switch I22 having a switch arm I23, adapted to be operated by a bellcrank I24 pivoted, as at I25, and

having an operating roller I26 adapted to be engaged by the cam5 operated by the platen 25.

The switch I22 contains a spring constantly urging the lever 123 into the position shown in Figure 4. The bellcrank I24 also engages the operating rod I21 of a time delay device I28, having an adjustment screw I29. Th time delay device I28 may consist of a dash-pot and the adjustment screw I29 a needle valve. Reciproca- 'ble within the solenoid bore I3I is a solenoid exception that a time delay device, such as a' dash-pot I32, is interposed between the solenoid flow-control 'member has been pulled nearly to its neutral position, the pump I 8 is capable only of removing oil slowly from the retraction chamber of the press. This causes the platen 25 to slow down materially for a time.

As soon as the cam 85 passes the roller 54, however, the lever 63 is returned by springs to its normal position, thereby permitting the valve rod 82 of the air release valve BI to return to its normally closed position. The valve 8! then closes. but the choke I2 prevents the rapid refilling of the'cylinder I4 of the link device 49 with compressed air. The duration of this time delay can be adjusted by adjusting the choke 12. As"

the slowing up of the platen 25 is timed to occur just before the platen 25 engages the workpiece I or dies, by the time the link device 49 is restored to its original position and the servomotor valve rod I8 isshifted to cause the pump III to resume plunger I38, and the solenoid winding III. This dash-pot is provided with an adjusting screw I33 so that the relative motion between the parts is delayed when the solenoid is energized. An ordinary switch I22 is employed without the time .delay device or dash-pot I28 in this arrangement.

The solenoid winding I I1 is connected atone end to the yoke I34, which in turn. is connected to" .-the servomotor valve lever 54, in the manner (Figure 4) at I35 to a hand lever I36, adjustable relatively to'a sector plate I31, and pivotally mounted at its lower end upon-a bracket I38, asatl39.-v

The operation of the lectrical circuit shown in Figures 4 and 5 is similar to that already described for the pneumatic link device 49, shown in Figure l. The solenoid H5 is'normally enerto be attracted by the solenoid plunger I30, so that the solenoid bore I3I is drawn over the plunger I30. In this normally energized position, therefore, the solenoid winding Ill and the plunger I30 are. drawn together in a manner analogous to the position of the pneumatically operated parts in Figure 3. Under these conditions, the solenoid lit when energized acts as a rigid contracted link between the hand lever I36 or bellcrank IB- and the servomotor valve rod I8. When, therefore, the hand lever' I36 or the bellcrank 46 is moved to the left to place the pump I upon its full delivery forward stroke, the servomotor valve rod I8 is shifted so that the pump I0 withdraws fluid from the retraction side of the press circuit at a rapid rate, so that the platen 25 moves downward at full speed.

When the cam 65 engages the roller I25, however, the bellcrank I24 is moved, shifting the switch a'rm I23 so as to open the normally closed switch I22. The solenoid winding II! is thereby deenergized, whereupon the spring I'Ia within the servomotor II shifts the servomotor valve rod I8 so as to correspondingly shift the flowcontrol element of the variable delivery pump III almost to its neutral delivery position. The flow is thereby' so greatly reduced, in a manner similar to that already described for the pneumatic control system of Figure 1, as to cause the platen 25to move downwardly at a reduced speed.

Meanwhile, the dash-pot I28 has come into action, and after the cam 65 has passed the roller I28 the bellcrank I24 is prevented from releasing the switch arm 'I23 by;this dash-pot I28. The latter delays ciosingoftlie switch I22 for a sufflcient period to maintain the solenoid IIS deenergized, and the pumpgl'lil is kept on reduced stroke for-a predetermined period. At the end of this period, and when the dash-pot I2l has operated to a suiflcient extent, the bellcrank I24 releases the switch arm I23, and the consequent 0105 8 0! the switch I22 reenergizes the solenoid II. Accordingly, the parts thereof again come together, shifting the servomotor valve rod I8 and the shiitring or flow-control member of the pump 10' again to their full delivery positions. This places the pump III again upon its full forward stroke position. The press platen 2I then picks up its speed and-resumes its normal speed for the completion of the'stroke.

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

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

1. In a hydraulic machine control circuit, a

- pump, a hydraulic ram, means for causing said pump to move said ram, saidmeans comprising" a fluid flow-controlling member'ior controlling the fluid flow from said pump and an operated devicefor initiating a movement of said flow- ,aasasse i 'a fluid flow-controlling member for controlling the fluid flow from said pump and a regulating device for regulating the setting oi! said flowcontrolling member, electrically operable means associated with said. regulating device and said flow-controlling member and adapted to cause movement of said flow-controlling member in one direction, spring means associated with said regulating device andurging said flow-controlling member in the opposite direction, means responsive to a predetermined travel of said ram for causing a. shifting of said flow-controlling member to alter the speed of travel of said ram beyond said predetermined travel, and means responsive to a further predetermined travel of said ram in the same direction for causing said electrically operable means to move in a direction adapted to restore said fluid flow-controlling member to its original position. a

3. In a hydraulic machine control circuit, a pump, a hydraulic ram, means for causing said pump to move said ram comprising a fluid flowcontrolling device for controlling the ,fluid flow from said pump and a regulating device for shifting said flow-controlling device, electrically operable means interposed between said regulating device and said flow-controlling device and adapted whenenergized to move said flow-controlling device so as to increase the fluid flow from said pump, means urging said flow controlling member into the opposite direction to deactuated means for restoringthe original condition of energization to said electrically operable means.

4. In a hydraulic machine control circuit, a

' pump, a hydraulic ram, means for causing said controlling member to a predetermined position and for holding said member in that position.

electric means associated with said device and adapted when energized to cause movement ;oi

. said flow-controlling member in one direction in response to the operation of said device, means "responsive toa predetermined travel oi said ram for effecting deenergiaation of said electric Q means, and means responsive to the de-energiza- .ti'on of said electric means to cause movement of said flow-controlling member in another. direcpumpto'move said ram comprising a fluid flow controlling device for controlling the fluid flow from said pump and a regulating device for shiit- .ing said flow-controlling device, an electrical solenoidinterposed between said regulating device and said flow-controlling device and adapted to effect movement of said flow-controlling device inone direction; the armature of said solenoid being connected to one of said devicesand the coil thereofto the other device, spring means associated with said fluid flow-controlling device and adapted to cause movement or said flowcontrolling device in another direction and means responsive to the motion of said rm to a predetermined position for altering the energization oi said solenoid-so that movement of said flow-controlling device relatively to said regulating device occurs.

5. In a hydraulic machine control circuit, "I.

- pump, a hydraulic ram, means for causing said tionto temporarily sl w down the speed of travel :6

pump to move said ram comprising a fluid flowcontrolling device [or controlling the fluid flow from said pump and a regulating device for shirting said flow-controlling device, an electrical solenoid interposed between said regulating device and saidflow-controlling device-and adapted to effect movement of said flow-controlling device in one direction, the armature of said solenoid being connected to one of saiddevices and the coil thereof to the other device, spring means associated with said fluid flow-controlling device and adapted to cause movement of said flow-controlling-devicein another direction, means responsive to the motion of said ram to a predetermined position for altering'the energization of said solenoid so that movement of said flow-controlling device relatively to said regulating device occurs, and time delay means responsive to the expiration of a predetermined period of time after said alteration of the energization of said solenoid for restoring the original condition of energization to said solenoid.

6. Ina hydraulic machine control circuit, a variable delivery pump having a delivery-varying device associated therewith for varying the delivery thereof, a hydraulic ram, means for causing said pump to move said ram, said means comprising a regulating device for shifting said delivery-varying device, an expansible and col-' lapsible link interposedbetween said device, electric means operatively connected with said link and adapted when energized to effect collapse of said link for moving said delivery-varying device into one direction, spring means continuously urging said delivery-varying device into the opposite direction, and means responsive to a predetermined position of said ram for temporarily de-energizing said electric means to allow said spring means to eifect movement of said deliveryvarying device 'while the ram is continuing its movement in the same direction.

'7. In a hydraulic machine control circuit, a variable delivery pump having a delivery-varying device associated therewith for varying the delivery thereof, a hydraulic ram, means for causing said pump to move said ram comprising a regulating device for shifting said delivery-varying device, an electrically actuated expansible and collapsible link interposed between said devices, electric means associated with said link and adapted when energized to efiect collapse thereof, spring means adapted to bring about an expansion of said link when said electric means isdeenergized, means responsive to the motion of said ram to a predetermined position for deenergizing said electric means, and time delay means responsive to the expiration of a predetermined period of time after said de-energization of said electric means for restoring the original condition of energization' thereto.

' 8. In a hydraulic machine control circuit, a pump, a hydraulic ram, means for causing said pump to-move said ram, said means comprising a flow-controlling member for controlling the fluid flow from said pump and a regulating device forregulating the setting of said flow controlling member, electric means, said electric means including two relatively movable parts,

one connected to said flow-controlling member.

and the other connected to said regulating device, said electric means adapted when energized to cause movement of said flow-controlling member'in one direction, biasing means responsive to the deenergization of said electric meansto cause movement of said flow-controlling member in the opposite direction, and means responsive to the movementof said ram to a predetermined position on its working stroke to de-energize' said electric means whereby the biasing means moves the flow control member to temporarily slow down the speed of travel of said ram beyond said predetermined travel without changing. the direction of travel.

9. In a. hydraulic machine control circuit, a

pump, a hydraulic ram, means for causing said pump to move said ram, said means comprising a ber in the opposite direction, and means responsive to. the movement of said ram to a predetermined position on its working stroke to dc-energize said electric means whereby the biasing means moves the flow control member to temporarily slow down'the speed of travel of said ram beyond said predetermined travel without changing the direction of travel, and 'timedelay means responsive to the expiration of a predetermined period of time after the operation of said biasing means, for restoring the original condition of energization of said electric means.

WALTER ERNST.

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