US3163143A - Hydraulic cushions for die pads of ram type presses - Google Patents

Description

Dec. 29, 1964 F. M. WILLIAMSON HYDRAULIC CUSHIONS FOR DIE PADS OF RAM TYPE. PRESSES Filed April 27, 1962 2 Sheets-Sheet 1 INV EN TOR.

)Vay/ M 144752711501. BY

Dec- 29, 19 F. M. WILLIAMSON HYDRAULIC CUSHIONS FOR DIE PADS OF RAM TYPE PRESSES Filed April 27, 1962 2 Sheets-Sheet 2 INVENTOR. f/ay /y Ma 47214022 BY 661% M 16 2 7 United States Patent 3,163,143 HYDRAULIC lUSHlGNS FGR DE PADS @F RAM TYPE PREES Floyd M. Williamson, Detroit, Mich, assignor, by niesne assignments, to National Bank of Detroit, Detroit, Mich, a national banking association Filed Apr. 27, 1962, Ser. No. 1%,542 15 Claims. (Cl. 113-45) This invention relates to presses having hydraulic cushions for controlling movement of the die pads and has particular relation to a new and improved hydraulic control system for controlling the hydraulic cushion.

The hydraulic control system of the present invention is designed to offer a predetermined resistance to movement of the die pad upon closing of the press ram and is provided with an air pressure device actuated during the opening of the press ram for returning the die pad to its extended position for stripping the work from the die.

A principal object of the invention is to provide a new and improved hydraulic control circuit for the hydraulic cushion in a press having a movable die pad.

Another object of the invention is to provide a control system of the type described having a means for delaying return movement of the die pad until after the press begins to open and including a booster unit to increase the pressure in the hydraulic cushion for stripping the work from the die.

Other and further objects of the invention will be apparent from the following description and claims and may be understood by reference to the accompanying drawings, of which there are two sheets, which by way of illustration show preferred embodiments of the invention and what I now consider to be the best mode of applying the principles thereof. Other embodiments of the invention may be used without departing from the scope of the present invention as set forth in the appended claims.

In the drawings:

FIG. 1 is a schematic sectional view illustrating a hydraulic cushion for a movable die pad and the control system for the hydraulic cushion;

FIG. 2 is an elevational view illustrating one form of actuating means for the controls;

FIGS. 3 and 4 show modified actuating means for the controls; and

FIG. 5 is a schematic view of a modified form of the invention.

In PEG. 1 of the drawing there is illustrated a portion of a ram type press which includes a reciprocating ram carrying an upper die 12 and a lower die'id mounted on a fixed bolster 1d. The die 14 is provided with a vertically reciprocable die pad 18 which is engaged by the work Zii during the working stroke of the press. A piston 22 is reciprocable within a cylinder 24 and the piston 22 and cylinder 24 provide a hydraulic cushion engaging the underside of the die pad 13 to control its movement both during the working stroke of the press and upon opening of the press to strip the work from the die 14.

The control system includes a tank 36 containing hydraulic fluid under pressure. The tank is supplied with air under pressure through an air pressure line 32 to maintain the hydraulic fluid at a predetermined relatively low pressure in the tank, say, for example, 100 lbs. per square inch. The hydraulic cushion cylinder 24 is provided with an inlet and exhaust port 34 to which a line 36 is connected, with the other end of the line 36 communicating with a bore 38 in a valve block 49. Valve block til is provided with a chamber 42 containing a pressure relief valve 44 which is reciprocable therein andnorrnally engages a valve seat 46 under the influence of a spring 43 which is confined between the valve member 44 and a washer 5i and an adjustingscrew 52 engages the washer 5i so that f ice the strength of the spring 48 may be adjusted to permit the valve 44 to open when a predetermined pressure in the line 36 is reached.

A passage 54 in the valve 2 i intersects the valve cham ber 42 and is connected by means of the line 56 to the lower end of the supply tank '30. When the ram of the press descends, the movable die pad 18 which is engaged by the work is forced downwardly, thereby moving the piston 22 downwardly in the cylinder 24 to force the hydraulic fiuid therein out through the line 36. The pressure relief valve 44 provides a predetermined resistance to such movement of the die pad and, as soon as the pressure in the hydraulic cylinder 24 exceeds a predetermined pressure, the valve 44 will open thereby allowing the hydraulic fiuid to flow through line 56 back to the supply tank 36. As soon as the ram completes its working stroke, the pressure relief valve id will close thereby blocking the return of hydraulic fluid from the tank 36 back to the hydraulic cushion cylinder 24.

iieans comprising a booster unit 66 are provided for effecting the flow of hydraulic fluid back into the cylinder 2 under increased pressure to efiect return movement of the die pad 13 and strip the work from the die 14. The

booster unit includes a booster cylinder having a piston 64 therein and a larger diameter cylinder 66 having a piston 63 therein, with the pistons 64 and 68 interconnected by a stem '76}. The booster cylinder 62 is filled with hydraulic fluid from the. tank 3% through a line 72 leading from the lower end of the tank fill to a passage 74- in a valve body '76. A passage 78 intersects the passage 74 and is normally closed by a check valve 83 in the form of a ball located in a chamber 82 which is intersected by a passage 84 leading to a bore 86 in the valve body 76. The lower end of the bore Sr: communicates with the booster cylinder 62 above the piston as therein. The booster cylinder is filled with the hydraulic fluid from the tank 39 through the passages described. The upper end of the bore 36 is closed by a normally closed, balanced, positive shut-oil valve of the sleeve or spool type indicated at 38, which comprises a sleeve 99 located in a recess in the valve body 76 and surrounded by an annular chamber 92 intersected by a passage 4 which leads to a line 96. A valve member 98 is reciprocable within the sleeve 9% and is biased by a spring me against a shoulder W2 which determines the normallyclosed position of the valve 83. The sleeve 9i) is provided with annularly spaced radial ports 104 which provide communication between the bore 86 and the line 'sd when the valve 83 is opened. The passage 74 communicates with the upper end of the sleeve 9%) so that both sides of the valve member 9%- are subjected to the pressure existing in the supply tank 36.

The line as is connected to a passage 1% in the valve block 4% which communicates with a passage 1% leading to the bore 33 and the line 36. The passage 1% is normally closed by a check valve lib, although this check valve maybe omitted if desired.

The lower end of the air cylinder 66 below piston 68 is provided with a port 112 leading to a control or pilot valve lid which includes a supply line port 116, an exhaust line port 113, and a control lever 12% by means of which the cylinder port 112 may be connected either to the exhaust port 11% or the supply port 11d which is connected to a source of air under pressure, such as the upper end of pressure tank 34 or the air pressure suppiy line 32 -therefor. The control lever 12b is actuated by a solenoid,

I to the cylinder ea.

movement. The electrical circuit into which the solenoid 122 is connected may include a fixed contact 13%} and a normally open movable contact 13?; carried by a pivoted arm 134 which is adapted to be engaged by a cam 135 carried by a shaft 138 which rotates with the crank of the press. The cam 13s is adjusted on the shaft 138 so as to close the contacts 139 and 132 at a predetermined time after the press ram begins to open during each cycle of the press. When the contacts close, the solenoid 122 is energized to shift the control valve 114 to connect the cylinder p0rt112 with the supply line 116, thereby to force the piston 68 upwardly within the cylinder as thereby forcing the piston 64 upwardly to force the hydraulic fluid therein through the bore 86 to shift the valve member 5% upwardly to open the radial ports 1%. As soon as valve member 98 moves sufiiciently to expose ports ids, by

,draulic fluid flows through line and passage 1%, past check valve 116, and through passage 138 and line back to the hydraulic cushion cylinder 24 to force the piston 22 therein upwardly against the die pad 18 to return the die pad to its extended position, thereby stripping the work from the die 14. The relative size of the pistons 68 and 64 greatly increases the pressure in he hydraulic cushion cylinder 24 above the pressure at which the hydraulic fluid is normally maintained within the supply tank 3%, thereby insuring return of the die pad 13 and efiicient stripping of the work from the die. The time interval during which the unit 6% remains energized is determined by the length of the cam 13s. As soon as the contacts 136 and 132 are opened, the solenoid is de-energized and the control lever 124i is then shifted by the spring 124 to connect the cylinder port 112 with the exhaust line 118 thereby allowing the booster piston 63 to return to its lower position as the cylinder olis again filled with hydraulic fluid from the tank 3% in the manner described. The valve member 3 will also close at this time since it is subjected to equal hydraulic pressures on its opposite sides and is urged to itsclosed position by the spring tea.

The connection between the supply tanlr 351 and the hydraulic cushion cylinder 2% is normally closed by the valve 88 and, since this valve is a balanced valve, the spring 166) may be very light to maintain such valve in its normally closed position. Since the valve $8 is in the fluid connection between the tank Elli and the cylinder 24, the return of the die pad 18 will be controlled by the opening of the valve 88 and this in turn depends upon the setting of the cam 13s.

Instead of using the solenoid actuated pilot valve 114, a spool type normally closed pilot valve 28%, as shown in FIG. 3, actuated directly by the earn 135 may be used for controlling the return of the die pad. in this case the valve Zilll, when closed, ports the line 112 communicating with cylinder as with line 113 leading to atmosphere, while the movable valve element 2&2. is normally positioned by the spring 2% so as to shut oil the flow of air under pressure from the air supply line 1% to the passage 112. When the earn 13% engages the roller on the follower arm 2% carried by the sliding valve member 2 32, the valve member ZilZ will be shifted to a position to shut oft the atmospheric port and to establish communication between the air pressure line 112 and the line ltd leading The spring 2&4 causes the roller on the arm 2&8 to follow the earn 136. This type of valve control is like that shown in my prior copending application Serial;No. 768,889, filed ()ctober 22., 1958, for. By-

' draulic Press, Ram Cushion.

FIG. 4 sh ws a normally closed rotary pilot valve V as shown in FIG. 1 arranged so as to be actuated directly by cam 13%. p

In the arrangement of FlG. 1, the pressure which can be developed upon the encrgization of the booster unit so is limited by the pressure setting of the pressure relief valve 4% In some cases it is necessary or desirable to provide a higher pressure in the hydraulic cushion on the 12* roke than on the downstrolre, and this may be achieved with the i system illustrated in F1 5 where the pressure relief valve is separated from the discharge side of the booster unit 166.

in the system as disclosed in FlG. 5 hydraulic fluid under the pressure prevailing in the tank 39 is supplied through the hydraulic fluid pressure line 1.72 to the valve unit indicated generally at 171. The valve unit 171 is quite similar to the corresponding valve of the system in FIG. 1 and includes a passage 178 communicating with the line 172, a check valve 188 in the passage 1'78, and a passage 186 w rich at one end communicates with the discharge cylinder 162 of the booster 1%. The other end of the passage 186 communicates with a valve chamber in the unit 171, the valve chamber having disposed therein a valve sleeve 15?; and a valve piston 19% biased to seat on the port around the upper end of passage res under the influence of spring 1%. Thus under the pressure prevailing in the tank 3%, hydraulic fluid is supplied through the line 172 past the check valve 1% to the passage 136 and to the booster cylinder 162.

When the piston valve member 1% is moved upwardly in response to the discharge of hydraulic fluid from the booster cydnder 162, it uncovers ports 2% in the sleeve 138 which communicate with the space externally of the sleeve res, which in turn communicates with a passage 292. in the unit r71. At its upper end the passage 292 communicates with a hydraulic fluid pressure conduit 2&4 which leads to the hydraulic cylinder 24 of the hydraulic cushion. Thus, when the ports 2 38' are uncovered, hydraulic rluid under the pressure prevailing in the tank 33* or under the discharge pressure of the booster 166 will be supp ed to the cylinder 24 of the hydraulic cushion for biasing the piston 22 against the pad 1". When the piston valve 1% moves upwardly in the sleeve 188, it closes ports 2% in the sleeve 83 which normally provide open communication between the passage 204 and a hy draulic pressure line 2.62% which leads to the pressure relief valve indicated generally at 249.

Thus the energization of the booster res according to any of the arrangements disclosed in FIGS. l4 inclusive will not on I establish communication between the tank and the hydraulic cylinder 24 of the hydraulic cushion, but it will also shut off the communication between the hydraulic cylinder 24 and the pressure relief valve 24%. The pressure relief valve 24% is like the pressure relief valve ill oi PlG. 1. Thus with the arrangement illustrated in Flt 5, it is possible to develop substantially higher pressures on the upstroke of the press ram than on the downstrolie since the pressure relief valve is separated from the discharge side of the booster 16%. After the de-energization of the booster tea, the piston valve 19% will return to its seat as shown in FIG. 5. The system as illustrated in FIG. 5 other respects will operate as described in connection with the systems illustrated in F165. l4.

This application is a continuation-in-part oi my prior copending application Serial No. 84,900, filed January 25,

961, now abandoned for Hydraulic Cushions for Die i ads of Ram Type Presses, which is a continuation-inpart of my prior cop-ending application Serial No. 832,720, lied August lb, 1959, issued as Patent No. 3,089,375, for lydraulically Actuated Piercing Unit, which is a continuation-.n-part of my now abandoned application Serial No. 788,544, filed January 23, 1959, for l-lydraulically Actuated Piercing Unit.

While l have illustrated and described preferred embodiments of my invention, it is understood that these are capable of modification, and I therefore do not wish to be limited to the precise details set forth but desire to avail myself for such changes and alterations as fall within the purview of the following claims.

I claim:

1. In a press having a movable pressure pad arranged so as to be moved in one direction upon closing of the press and a hydraulic cushion reacting against said pad to resist such movement of said pad and to eflfect return movement of the pad upon opening of the press, said hydraulic cushion including a cylinder and a piston therein arranged to react against said pad, a control system for controlling return movement of said pad comprising a tank separate from said cylinder and containing hydraulic fluid under regulated pressure, a hydraulic fluid connection between said tank and one end of said cylinder through which hydraulic fluid from said tank is supplied to said cylinder, said connection including a valve having a spring biasing said valve to its closed position so as to prevent fluid flow from said tank to said cylinder when said valve is closed, means connecting the opposite sides of said valve to said tank so that both sides of said valve are exposed to the pressure of the hydraulic fluid in said tank, control means connected to said valve and ac tuated by the press after the press begins to open for opening said valve to allow hydraulic fluid to flow through said connection to said cylinder to effect return movement of said pad, a fluid return line through which hydraulic fluid displaced from said one end of said cylinder upon closing of the press is returned to said tank, and a pressure relief valve in said return line providing resistance substantially higher than tank pressure to the return flow of such displaced fluid so as to resist movement of said die pad in said one direction and adapted to open when the pressure in said cylinder exceeds a predetermined pressure.

2. In a press having a movable pressure pad arranged so as to be moved in one direction upon closing of the press ram and a hydraulic cushion reacting against said pad to resist such movement of said pad and to effect return movement of the pad upon opening of the press ram, said hydraulic cushion including a cylinder and a piston therein arranged to react against said pad, a control system for controlling movement of said pad comprising a tank separate from said cylinder and containing hydraulic fluid under regulated pressure, a booster cylinder, a unidirectional hydraulic fluid connection between said tank and booster cylinder through which hydraulic fluid flows under tank pressure from said tank to said booster cylinder when said booster is inactive, a unidirectional fluid flow passage connecting said booster cylinder and tank with one end of said hydraulic cushion cylinder, a piston in said booster cylinder, a control valve connecting said booster cylinder to a source of pressure fluid and adapted when open to actuate said booster piston in a direction to increase the pressure in said hydraulic cushion cylinder to effect return movement of said pad, control means connected to said valve and actuated by the press for opening said valve to actuate said booster piston at a predetermined time during the opening portion of each cycle of the press, a normally closed valve in said passage etween said tank and said hydraulic cushion cylinder and having its opposite sides subjected to the pressure of the hydraulic fluid in said tank, said normally closed valve being opened by fluid discharged from said booster cylinder upon actuation of said booster piston, a liuid'return line con ected into said passage and to said tank through which hydraulic fluid displaced from said hydraulic cushion cylinder flows to said tank upon closing of the press, and a pressure relief valvein said return line providing for resistance to the flow of such displaced fluid so as to resist movement of said die pad in said one direction and adapted to open when the pressure in said hydraulic t cushion cylinder exceeds a predetermined pressure.-

3. In a press having a movable pressure pad arranged so as to be moved in one direction upon closing of the press, a hydraulic cushion reacting against said pad to resist such movement of said padand to effect return 'movement of the pad upon opening of the press said hydraulic cushion including a cylinder and a piston therean arranged to react against said pad, a control system for controlling movement of said pad comprising a tank through said passage to said one end of said hydraulic cushion cylinder to etlect return movement of said pad, control means connected to said valve and actuated by the press for opening said valve to actuate said booster piston at a predetermined time during the opening portion of each cycle of the press, a normally closed valve insaid passage between said tank and said hydraulic cushion cylinder and comprising means defining a valve chamber communicating at one end with said booster cylinder, said passage intersecting said valve chamber, a valve member reciprocable in said valve chamber and a spring biasing said valve member to a position closing said passage, means connecting the other end of said valve chamber with said tank so that both sides of said valve member are exposed to the pressure of the hydnaulic fluid in said tank, said valve member being rnoV- able against said spring to open said passage upon actuation of said booster piston, a return line through which hydraulic fluid displaced from said one end of said hydraulic cushion cylinder flows to said tank upon closing of the press, and a pressure relief valve in said return line press and a hydraulic cushion reacting against said pad to resist such movement of said pad and to eifect return movement of the pad upon opening of the press, said hydraulic cushion including a cylinder and a piston therein arranged to react against said pad, a control system for controlling return movement of said pad comprising a tank separate from said cylinder. and containing hydraulic fluid under pressure, a booster cylinder, at hydraulic fluid connection between said tank and booster cylinder, a passage connecting said booster cylinder and tank with one end of said hydraulic cushion cylinder, a piston in said booster cylinder, a control valve connecting said booster cylinder to a source of pressure fluid and adapted when open to actuate said booster piston in a direction to force the hydraulic fluid in said booster cylinder through said passage to said one end of said hydraulic cushion cylinder to effect return movement of said pad, control means connected to saidvalve and actuated by the press for opening said valve to actuate said booster piston a predetermined time'interval after the press begins to open during each cycle of the press, a normally closed valve in said passage between said tank and said hydraulic cushion cylinder and comprising a sleeve communicating at one end with said-booster cylinder and having radical ports therein providing a part of said passage,a valve member reciprocable in said sleeve and a spring biasing said valve member to a position closing said posts, and means connecting-the other end of said sleeve with said tank .so that both sides of said valve member are exposedto the pressure'of the hyduaulic fluid'in said. tank, said valve member being movable against said spring to open said ports upon actuation of said booster piston, and a pressure relief controlled fluid return line leading. "from said one end of said hydraulic cushion cylinder to said "tank providing resistance to movement of said die pad upon closing of the press'ram and adapted to open Whenthe pressure in said hydraulic cushion cylinder exceedsa predetermined pressure. 7 5. In a press having a'movable pressurepad arranged so as to' be moved in one direction upon closing of the i H press and a hydraulic cushion reacting against said pad to resist such movement of said pad and to eifect return movement of the pad upon opening of the press, said hydraulic cushion including a cylinder and a piston therein arranged to react against said pad, a control system for controlling return movement of said pad comprising a tank separate from said cylinder and containing hydraulic fluid under regulated pres-sure, a hydraulic fluid connection between said tank and one end of said cylinder through which hydraulic fluid is supplied from said tank to said cylinder, a normally closed valve in said connection, mean connecting the opposite sides of said valve to said tank so that both sides of said valve are exposed to the pressure of the hydraulic fluid in said tank, control means for said valve actuated by the press for opening said valve to allow hydraulic fluid to flow through said connection to said one end of said cylinder at a predetermined time during the opening portion of each cycle f the press, and a pressure relief controlled fluid return line leading from said one end of said hydraulic cushion cylinder to said tank providing resistance to movement of said die pad upon closing of the press ram and adapted to open when the pressure in said hydraulic cushion cylinder exceeds a predetermined pressure.

6. In a press having a movable pressure pad arranged so as to be moved in one direction upon closing of the press and a hydraulic cushion reacting against said pad to resist such movement of said pad and to eflect return movement of the pad upon opening of the press, said hydraulic cushion including a cylinder and a piston therein arranged to react against said pad, a control system for controlling return movement of said pad comprising a tank separate from said cylinder and containing hydraulic fluid under pressure, a hydraulic fluid connection between said tank and one end of said cylinder whereby hydraulic fluid is supplied from said tank to said cylinder, a normally closed valve in said connection and a spring biasing said valve to its closed position, meansconnecting the opposite sides of said valve to said tank so that both sides of said valve are exposed to the pressure of the hydraulic fluid in said tank, control means for said valve actuated by the press for opening said valve to allow hydraulic fluid to flow through said connection to said cylinder to increase the pressure in said cylinder to effect return movement of said pad; said control -means being operable to open said valve a predetermined time interval after the press begins to open during each cycle of the press, and a pressure relief fluid controlled return line leading from said 'one end of said hydraulic cushion cylinder to said tank providing resistance to movement of said die pad upon closing of the press ram and adapted to open when the pressure in said hydraulic cushion cylinder exceeds a predetermined pressure.

7. In a press having amovable pressure pad arranged so'as to be moved in one direction upon closing of the press ram and a hydraulic cushion reacting against said pad to resist such movement of said pad and to eltect return movement of the pad upon opening of the press ram, said hydraulic cushion including a cylinder. and a piston therein arranged to react against said pad, a tank separate from said cylinder and containing hydraulic fluid under regulated pressure, a hydraulic fluid connection between said tank and one end of said cylinder through which hydraulic fluid is supplied to said cylinider, a normally closed shut-off valve in said connection which in'its closed position prevents fluid flow in both directions, a pressure relief by-pass around said shut-oft valve providingresistance to movement of said die pad upon closing of the-press ram and adapted to open when thepressure in said hydraulic cushion cylinder exceeds a. predetermined pressure, and control means for said shut-off valve, said control means being, actuated by the press for-opening said shu -off valve to allow hydraulic came fluid to flow through said fluid connection to said one end of said cylinder to eiifect return movement of said pad, said control means being operable to open said shutoff valve a predetermined time interval after the press ram begins to open dur ng each cycle of the press.

8. in a press having a movable pressure pad arranged so as to be moved in one direction upon closing of the press ram and a hydraulic cushion reacting against said pad to resist such movement of said pad and to effect return movement of the pad upon opening of the press, said hydraulic cushion including a cylinder and a piston therein arranged to react against said pad, a control system for controlling return movement of said pad comprising a tank separate from said cylinder and containing hydraulic fluid under. pressure, a hydraulic fluid connection between said tank and one end of said cylinder whereby hydraulic fluid is supplied to said cylinder, a normally closed shut-oil valve in said connection, the opposite sides of said valve being connected to said tank so that both sides of said valve are normally subjected to the pressure of the hydraulic fluid in said tank, means for opening said shut-oil valve whereby hydraulic fluid is supplied through said connection to said cylinder at a predetermined time during the opening portion of each cycle of the press, a pilot valve operated by a cam driven with the press for controlling said last-mentioned means, and a pressure relief controlled return line leading from said one end of said hydraulic cushion cylinder to said tank providing resistance to movement of said die pad upon closing of the press ram and adapted to open when the pressure in said hydraulic cushion cylinder exceeds a predetermined pressure.

9. in a press having a movable pressure pad arranged so as to be moved in one direction upon closing of the press and a hydraulic cushion reacting against said pad to resist such movement of said pad and to eflect return movement of the pad upon opening of the press, said hydraulic cushion including a cylinder and a piston therein, a control system for controlling return movement of said pad comprising a tank separate from said cylinder and containing hydraulic fluid under pressure, a hydraulic fluid connection between said tank and one end or said cylinder whereby hydraulic fluid is supplied to said cylinder, a normally closed shut-off valve in said connection, means for opening said valve whereby hydraulic fluid is supplied to said one end of said cylinder at a predetermined time during the opening portion of each cycle of the press, a cam driven with the press, a pilot valve operated by said cam for controlling the supply of fluid pressure to said valve opening means, and a pressure relief controlled return line leading from said one end of said hydraulic cushion cylinder to said tank providing resistance to movement of said die pad upon closing of the press ram and adapted to open when the pressure in said hydraulic cushion cylinder exceeds a predetermined pressure.

10. In a press having a movable pressure pad arranged so as to be moved in one direction upon closing of the press and a hydraulic cushion reacting against said pad to resist such movement of said pad and to eilect return movement of the pad upon opening of the press, said hydraulic cushion including a cylinder and a piston therein, a control, system for controlling return movement of said pad comprising a tank separate from said cylinder and containing hydraulic fluid under pressure, a hydraulic fluid connection between said tank and one end of said cylindn' through which hydraulic fluid is supplied to said cylinder, a normally closed positive shut-oi? valve in said connection, means independent of the pressure in said tank for opening said valve whereby hydraulic fluid is supplied to said cylinder at a predetermined time during the opening portionof each cycle of the press, and a pressure relief controlled return line leading from said one end of said hydraulic cushion cylinder to said tank providing resistance to movement of said die pad upon closing of the press ram and adapted to open when the pressure in said hydraulic cushion cylinder exceeds a predetermined pressure.

11. Apparatus according to claim wherein said means includes a pressure booster associated with said hydraulic fluid connection and operable for increasing the pressure of the hydraulic fluid supplied to said cylinder.

12. Apparatus according to claim 11 wherein said normally closed valve is operatively disposed between said booster and said pressure relief valve.

13. In a press having a movable pressure pad arranged so as to be moved in one direction upon closing of the press ram and a hydraulic cushion reacting against said pad to resist such movement of said pad and to effect return movement of the pad upon opening of the press, said hydraulic cushion including a cylinder and a piston therein, a control system for controlling return movement of said pad comprising a tank separate from said cylinder and containing hydraulic fluid under pressure, a hydraulic fluid connection between said tank and one end of said cylinder through which hydraulic fluid is supplied to said cylinder, a normally closed positive shut-01f valve in said connection, pressure booster means for opening said shutoff valve whereby hydraulic fluid is supplied at increased pressure through said connection to said one end of said cylinder at a predetermined time during the opening portion of each cycle of the press, and a pressure relief controlled return line leading from said one end of said hydraulic cushion cylinder to said tank providing resistance to movement of said die pad upon closing of the press ram and adapted to open when the pressure in said hydraulic cushion cylinder exceeds a predetermined pressure.

14. Apparatus according to claim 13 wherein said normally closed valve pressure isolates said pressure relief valve from said pressure booster means.

15. In a press having a movable pressure pad arranged so as to be moved in one direction upon closing of the press ram and a hydraulic cushion arranged to react against said pad to effect return movement thereof upon opening of the press ram, said hydraulic cushion including a cylinder and a piston therein, a tank containing hydraulic fluid under pressure, a hydraulic fluid connection between said tank and said cylinder through which hydraulic fluid is supplied to said cylinder, a normally closed shut-off valve in said connection which in its closed position prevents fluid flow from said tank to said cylinder and from said cylinder to said tank, a pressure relief by-pass around said shut-01f valve providing resistance to return of hydraulic fluid to said tank so as to resist movement of said die pad upon closing of the press ram and adapted to open when the pressure in said hydraulic cushion cylinder exceeds a predetermined amount, and control means actuated by the press for opening said shut-ofl? valve to allow hydraulic fluid to flow through said fluid connection to said cylinder to efiect return movement of said pad after the press ram begins to open during each cycle of the press.

References Cited by the Examiner UNITED STATES PATENTS 1,745,549 2/ 30 Marghitan 113-46 2,172,853 9/39 Rode 267-1 2,394,636 2/46 Rode 113-45 2,403,912 7/46 Doll 267-1 2,584,339 2/52 Georgetf 267-1 2,890,669 6/59 Williamson 267-1 2,918,272 12/59 Williamson 267-1 CHARLES W. LANHAM, Primary Examiner.

NEDWIN BERGER, Examiner.

Claims (1)

1. IN A PRESS HAVING A MOVABLE PRESSURE PAD ARRANGED SO AS TO BE MOVED IN ONE DIRECTION UPON CLOSING OF THE PRESS AND A HYDRAULIC CUSHION REACTING AGAINST SAID PAD TO RESIST SUCH MOVEMENT OF SAID PAD AND TO EFFECT RETURN MOVEMENT OF THE PAD UPON OPENING OF THE PRESS, SAID HYDRAULIC CUSHION INCLUDING A CYLINDER AND A PISTON THEREIN ARRANGED TO REACT AGAINST SAID PAD, A CONTROL SYSTEM FOR CONTROLLING RETURN MOVEMENT OF SAID PAD COMPRISING A TANK SEPARATE FROM SAID CYLINDER AND CONTAINING HYDRAULIC FLUID UNDER REGULATED PRESSURE, A HYDRAULIC FLUID CONNECTION BETWEEN SAID TANK AND ONE END OF SAID CYLINDER THROUGH WHICH HYDRAULIC FLUID FROM SAID TANK IS SUPPLIED TO SAID CYLINDER, SAID CONNECTION INCLUDING A VALVE HAVING A SPRING BIASING SAID VALVE TO ITS CLOSED POSITION SO AS TO PREVENT FLUID FLOW FROM SAID TANK TO SAID CYLINDER WHEN SAID VALVE IS CLOSED, MEANS CONNECTING THE OPPOSITE SIDES OF SAID VALVE TO SAID TANK SO THAT BOTH SIDES OF SAID VALVE ARE EXPOSED TO THE PRESSURE OF THE HYDRAULIC FLUID IN SAID TANK, CONTROL MEANS CONNECTED TO SAID VALVE AND ACTUATED BY THE PRESS AFTER THE PRESS BEGINS TO OPEN FOR OPENING SAID VALVE TO ALLOW HYDRAULIC FLUID TO FLOW THROUGH SAID CONNECTION TO SAID CYLINDER TO EFFECT RETURN MOVEMENT OF SAID PAD, A FLUID RETURN LINE THROUGH WHICH HYDRAULIC FLUID DISPLACED FROM SAID ONE END OF SAID CYLINDER

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