US3362207A - Hydraulic control system - Google Patents

Description

2 Sheets-Sheet l Jan. 9, 1968 J. v. PERRONE A HYDRAULIC CONTROL SYSTEM Filed Aug. 25. 1966 Jan. 9, 1968 J. v. PERRONE HYDRAULIC CONTROL SYSTEM 2 Sheets-Sheet 2 Filed Aug. 23, 1966 INVENTOR. JAMES Y Pawn/v5 Ma-0N, 557725, 54mm-205 United States Patent Glice 3,362,207 HYDRAULIC CONTROL SYSTEM .lames V. Perrone, 41 Shady Hollow,

Dearborn, Mich. 48124 Filed Aug. 23, 1966, Ser. No. 574,463 9 Claims. (Cl. 72--351) ABSTRACT F THE DISCLSURE A hydraulic control system for presses and the like which provides cushioning of a die pad on the work stroke of the press and a delayed return of the die pad to its working position on the return stroke of the press. The cushioning of the die pad is accomplished by a continuously open, variable discharge relief valve disposed in a rst fluid ow path between an accumulator and a cylinder while the delayed return of the die pad is accomplished by =a normally closed valve that is disposed in a second fluid ow path between the accumulator and the cylinder and is opened at a predetermined stage of the return stroke of the ra-m to allow substantially unrestricted hydraulic low from the accumulator to the cylinder.

This application is a continuation-in-part of a copending application of the same inventor, Ser. No. 418,925, led Dec. 16, 1964. The copending application is directed to a valve assembly having a flow control valve mechanism which cushions the initial con-tact of the die elements to alleviate shock loads at the beginning of each press work stroke, and further having a variable volume reservoir with means for delaying return of a piston for the die pad to its extended position. Despite the advantages of this valve assembly, there are some situations and applications where an even simpler hydraulic control system is advantageous.

This invention relates `to control systems for presses and the like, and more particularly to a hydraulic control system employing a minimum number of valve components to provide cushioning of a die pad on the work stroke of the press 'and delayed return of the die pad to its working position on the return stroke of the press.

The present invention is directed to a simplified control system which provides the desired cushioning action and also delays the return of the piston to its initial extended working position. The valve assembly includes the same basic flow controlling valve mechanism as that utilized in the Iassembly of the copending application; i.e., a continuously open variable discharge relief valve through which controlled flow of fluid from a cylinder to an accumulator is accommodated during the initial stage of the press Work stroke. This flow cushions initial contact of the die elements and alleviates shock loads in the desired manner. Combined with this variable discharge relief valve -there is a normally closed valve in a parallel or by-pass ow path which is opened automatically 'at a predetermined stage of the press return stroke to allow full flow of hydraulic fluid from accumulator to cylinder on the remainder of the return stroke of the press ram. Until this Valve is opened, there is no ilow of hydraulic fluid from accumulator to cylinder so the return of the piston and die pad to their initial positions is delayed. The combination valve assembly, then, cushions initial shock loads by means of a controlled llow of hydraulic iiuid and subsequently provides delayed return of the piston and the die pad to their initial extended positions.

3,362,297 Patented Jan. 9, 1968 Accordingly, it is an object of this invention to provide a novel and simplied control valve .assembly to control the movement of a die pad in a press.

Another object of the invention is to provide a ram actuated valve in a valve assembly which also includes a variable discharge relief valve such that the relief valve provides cushioning action and the ram actuated valve opens up the valve passages for full flow a-t a certain stage of the return stroke of the ram.

A further object of the invention is to provide a normally closed valve with a pneumatic actuator operated by the ram of a press to open a normally closed flow path through a valve body in parallel with a flow path having a variable -discharge relief valve therein after the latter Valve has cushioned shock loads occurring at the beginning of a work cycle and after the return stroke of the press ram has reached a predetermined stage.

Among the other objects of the invention are to provide a hydraulic control system for presses which is operable automatically, is easy to construct, install and service, and is reliable in operation.

Other objects of this invention will appear in the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

On the drawings:

FIGURE 1 is a section-al view, partly in schematic form, of a hydraulic control system for a press showing in particular a valve assembly in accordance with the invention positioned in a neutral condition;

FIGURE la shows a fragmentary schem-atic control system including a modified valve actuator;

FIGURE 2 is a fragmentary sectional view of the hydraulic control system of FIGURE 1 with the valve assembly positioned for flow from cylinder to accumulator;

FIGURE 3 is a fragmentary sectional view of the hydraulic control system of FIGURE 1 with the valve assembly positioned for flow from accumulator to cylinder.

Before explaining the present invention in detail, it is to `be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also, it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

As shown on the drawings:

The valve assembly 10 provides controlled flow of hydraulic fiuid between a cylinder 12 and an accumulator 14 which are connected to the valve assembly 10 respectively by lines 16 and 18. During the work stroke of the press ram 20, the piston 22 moves with the press die pad, and the hydraulic fluid in the cylinder 12 beneath the piston 22 serves as a cushion to protect the die pad as the press ram closes or descends. During the work stroke of the press ram, hydraulic fluid is supplied from cylinder 12 through line 16 to the valve body 1t), and this fluid is passed through valve lbody at a controlled rate and through line 18 to the accumulator 14. On the return stroke of the press rarn, hydraulic fluid is transferred from the accumulator 14 via line 1S, valve body 10 and line 16 back to the cylinder 12 to return the piston 22 t0 its extended position ready for the next work cycle.

On the descending stroke of the ram 2G, a variable discharge pressure release valve 24 within the valve assembly initially provides a limited ow of hydraulic iiuid through the valve assembly 10 and then a full ow such that the shock loads arising from contact of the die elements are alleviated. On the return or ascending of the ram 20, a normally closed valve 26 in a flow path which parallels that through valve 24 is initially closed to provide a time delay in returning the piston 22 to its extended position. The valve 26 is then opened at a predetermined stage of the return stroke of the ram by means of a ram-operated actuator 28.

Referring specifically to the valve assembly 10, one flow path through the valve assembly is provided by a passage 27, variable discharge valve 24, check valve 30 and another passage 32. Hydraulic fiuid flows from line 16 through the iiow path just referred to and through line 18 to the accumulator during the work stroke of the press ram. Another flow path paralleling the first ow path is provided by a passage 34, normally closed valve 26, passage 36 and passage 40. So long as the valve 26 is closed, the latter flow path is blocked, and in fact no flow occurs through this flow path on the work stroke of the press ram. However, on the return stroke of the press ram, valve 26 is opened at a delayed stage of the press ram stroke such that thereafter full ow occurs through the parallel fiow path from the accumulator to the cylinder 12. Thus, there is a predetermined delay in returning the piston 22 to its extended position, and this delay provides an opportunity -for workpieces to be stripped from the die elements -before the return stroke is completed.

At the inlet end of passage 27 there is a side passage 42 which leads to a pressure gauge 44. The pressure within the valve body may be read at any time on the pressure gauge 44, and since the pressure gauge is a standard commercially available type it is not shown in detail.

Positioned within passage 27 there is a valve sleeve 46 which is apertured radially at 4S to provide communication between the inside of sleeve 46 and an annular passage 50 leading to the check valve 30. Within the sleeve 46 there is a movable valve body 52 which has a lip 54 urged against a shoulder 56 of sleeve 46 by a compression spring S8 so as to leave radial apertures 48 at least partly open at all times. Thus, a limited ow of hydraulic iiuid can occur from passage 27 through the radial apertures 48 to passage 50 and from there through check valve 30 which is opened by the pressure above it.

Fluid is vented through an orifice 70 in valve body 52 and through another orifice 72 in body 74 to a ball check valve 76 which is normally urged to a closed position by a compression spring 78. As the fluid pressure in the valve body passage 27 increases, ball valve 76 moves to the left to the position shown in FIGURE 2, thus permitting valve body 52 to move to the left to thereby open radial apertures 48 to their fully opened condition. From this stage on through the work stroke of the press ram, there is full flow of hydraulic fluid through the radial apertures 48 and through check valve 30 to passage 32. The pressure at which ball valve 76 opens is determined by the compression of spring 78, and this compression is in turn set by means of a handle 80 which sets the position of spring stop 82.

The components of the ball valve 76 and the slidable valve 52 with its sleeve 46 are mounted within a support sleeve 84 which can be detached from the valve body 86. The valve assemblies within sleeve 84 may thus be removed from the valve 4body 86 as a unit for replacement or repair of the valve. Thus, the components are so related as to provide a cartridge which may be removed and either repaired or replaced as conditions require. This operation may be done quickly and easily, thus avoiding undesirable down-time of the press for which the hydraulic control system 10 is provided.

The check valve 30 is disposed in a passage 88 leading from annular passage 50 to passage 32. Check valve 30 is urged against a seat by a spring 92. The check valve 30 thus accommodates iiow from passage 28 and chamber 50 through passage 88 to passage 32, but blocks reverse flow from passage 32 to passages 50 and 28.

As previously mentioned, normally closed valve 26 is located in a flow path including passages 34, 36 and 40 which is parallel to the flow path in which valves 24 and 30 are provided. A ltransverse bore 96 is provided in the main valve block, and a valve body 98 is slidable horizontally in this valve bore 96. In the neutral position in which the valve 26 is shown in FIGURE 1, the valve body 98 blocks the ow path between passages 34 and 36, and is urged to this blocking position by compression spring 100.

Valve body 98 includes a reduced diameter portion 102 which has piston members 104 and 106 attached thereto on the right hand side of the valve, the piston member 106 being provided in a cylinder 108 so as to be movable to the left therein. An air line communicates with the cylinder 108 at the right hand side of piston 106, and air is introduced into this cylinder space upon operation `of an air valve or actuator 28 provided in the air line 110.

The air valve 28 is operated on the ascending or return stroke of the press ram 20 after a predetermined delay from the beginning of the return stroke. Thus, the valve 98 remains closed through the entire descending stroke of the press ram and does not open at the beginning of the return stroke of the press ram. It is only after a predetermined delay that the press ram operates lair valve 28 which in turn builds up air pressure on the right side of piston 106 and cylinder 108, thus forcing the piston and the valve member 98 with it to the left. This leftward movement of valve body 98 aligns reduced diameter portion 102 with the passages 34 and 36 to allow return iiow of hydraulic iiuid from the accumulator 14 through line 18, passages 40, 36, 34, 27 and line 16 to the cylinder 12.

Operation The starting condition is that wherein the valves 24, 30 and 26 are in the positions shown in FIGURE 1. The valve body 52 of relief valve 24 is in its partially open position such that ow can take place through radial apertures 48. The valve body 98 of normally closed valve 26 is in its rightward position blocking the iiow path through passages 34 and 36. At the making of initial contact between the die elements, the hydraulic fluid in cylinder 12 and line 16 is subjected to a relatively high pressure which is exerted on the relief valve assembly 24 through passage 27. The shock of this initial hydraulic pressure is initially alleviated by immediate flow of the pressurized Huid through the continuously open radial apertures 48 of relief valve 24. This initial iiow of hydraulic fluid cushions the initial shock of the dies and aids in prolonging the useful life of the press assembly.

At and immediately following initial contact of the die elements, the press ram forces the piston 22 downwardly, further increasing the pressure in line 16 and passage 27. This pressurized iluid flows through orifice 70 to lift ball 76 from its seat, allowing relief valve body 52 to move to the left against the force of spring 58 to increase discharge of uid through the radial ports 48 and passage 50 into passages 88 and 32. At this point, the radially extending ports 48 are fully open, so there is a full ow of hydraulic iluid from line 16 through the valve assembly 10 to line 18 and the accumulator 14. This fiow continues until the piston 22 reaches the bottom of its stroke as determined by the work stroke of the ram 20. Maximum flow accommodates steady downward movement of the piston 22 within cylinder 12 as the press work stroke continues. When the press work stroke has been completed, pressure within line 16 drops substantially to zero, and the relief valve 24 returns to its initial at rest, partially open position and valve 30 closes. At this time, the press work stroke is completed.

It is now necessary to elevate the piston 22 for the next press stroke. Check valve 30 has closed against its seat 90to prevent accumulator to cylinder flow via passages 32 and 27. The valve body 98 of valve 26 remains in its blocking position such that the flow path via passages 36 and 34 is closed. Thus, at the beginning of the return stroke of the ram 20 and piston 22, there is no open ilow path for ow of uid from the accumulator 14 to the cylinder 12. After a delay which is desired in order to allow time for workpieces to be removed from the die elements, the actuator air valve 28 is operated at a predetermined stage of the return stroke of ram 20.

The actuator valve 28 may be operated for example by a cam 28a (FIGURE la) which is engaged by the ram 20 on its return stroke, the cam in turn opening valve 28 to release air pressure via line 110 to the cylinder space at the right of piston 106. Alternatively, a limit switch can be provided for the ram, the limit switch being engaged after a predetermined portion of the return stroke of the ram so as to actuate a solenoid 29 which operates the air pressure valve 28. The increased pressure in line 110 in turn moves piston 106 and valve body 98 to the left, thus opening the parallel flow path via passages 34 and 36. From this point on, then, there is full flow of hydraulic uid from the accumulator 14 through line 18, passages 40, 36, 34 and 27, and line 16 to cylinder 12. The position of the valve body 98 during this return iiow of uid is as shown in FIGURE 3.

The valve body 98 remains in this open condition while l the piston 22 is elevated to its initial position to make the control system rea-dy for the next work stroke of ram 20. The actuator 28 is returned to its initial position at the end of the return stroke of the ram 20, and the spring 100 then moves the valve body 9'8 to the right back to its initial position as shown in FIGURES l and 2.

Thus, the invention provides a Valve assembly including both a variable discharge relief valve for controlling flow of fluid on the wor-k stroke of the ram and a ram actuated valve for controlling flow of fluid on the return stroke of the ram so as to obtain both a cushioning action on the work stroke and a delay action on the return stroke of the ram. The variable discharge relief valve is continuously open for cylinder to accumulator How and thus alleviates shock loads which arise immediately at the beginning of the work stroke of the ram. The ram actuated valve is normally closed and remains closed throughout the work stroke of the ram and also throughout an initial portion of the return stroke of the ram. At a predetermined stage of the return stroke the ram actuates the normally closed valve to open it for full flow of hydraulic fluid from accumulator to cylinder. Thus, the desired delay action is provided on the return stroke with a minimum of components and a simplified reliable operation.

I claim:

1. In a ram-type press wherein a die pad engages the work and is retracted upon the closing of the press ram, a hydraulic cylinder and piston reacting upon said die pad to resist retraction thereof and to return the die pad to its extended position after opening of the press ram, an accumulator tank of hydraulic fluid under relatively low pressure, hydraulic connections between said tank and cylinder including rst and second fluid flow paths in parallel with each other, normally closed valve means in said first uid ow path to initially prevent now of fluid therethrough in either direction, continuously open valve means in said second uid ow path accommodating ow of fluid from said cylinder to cushion shock loads initiated at the beginning of the press work Stroke, means in said second flow path closing the same to prevent flow therein from accumulator to cylinder but allowing flow from cylinder to accumulator, and means for opening said normally closed valve at a predetermined stage of the press return stroke after initiation thereof to provide ow of hydraulic fluid from said accumulator to said cylinder during the remainder of said press return stroke,

thereby providing a delay in the return of the die pad to the initial position thereof, said last means comprising a pneumatic device providing air pressure on said normally closed valve means to shift the same to an open position, said pneumatic device being responsive to opening of said press ram at a predetermined stage of the return stroke thereof to provide a delay in flow of fluid from accumulator to cylinder.

2. The device defined in claim 1 in which said pneumatic device is controlled by cam means operated by said ram.

3. The device defined in claim 1 in which said pneumatic device is controlled by solenoid means operated by said ram 4. A hydraulic control system for a ram-type press wherein a die pad is retracted on the work stroke of the ram, said hydraulic control system including in combination a hydraulic piston and cylinder resisting retrac tion of said die pad, an accumulator for receiving uid from said cylinder on the closing of said ram and for returning such uid to said cylinder on opening of said ram, a hydraulic flow path between said cylinder and said accumulator having two branch paths in hydraulically parallel relation with each other, normally closed valve means in one of said branch paths blocking the same to Huid flow in either direction, means in the other of said branch paths accommodating cylinder to accumulator flow but blocking accumulator to cylinder ow, and control means operatively connected to said normally closed valve means for opening the same in response to opening of said press ram at a predetermined stage of the return stroke thereof thereby providing a delay in the return of said die pad to the initial position thereof.

5. The hydraulic control system of claim 4 in which said control means comprises a pneumatic device acting on said normally closed valve by air pressure to open the same.

6. The hydraulic control system of claim 5 in which said control means includes a solenoid for operating said pneumatic device responsive to opening of said press ram.

7. The hydraulic control system of claim 5 in which said control means includes cam means actuated by said press ram to operate said pneumatic device.

8. In a hydraulic system for a ram type press having a die pad carried by a piston and cylinder and an accumulator for receiving fluid from said cylinder on the work stroke of said ram and for returning fluid to said cylinder on the return stroke of said ram, the combination therewith of hydraulic connections between said cylinder and said accumulator including a valve block having first and second ow paths therein in hydraulically parallel relation with each other, a normally closed valve in said tirst flow path blocking all flow therein, a pressure relief valve in said second flow path accommodating cylinder to accumulator flow :at the beginning of the work stroke of said press ram to relieve the shock loads developed then, a check valve in said second flow path blocking accumulator to cylinder ow but allowing said cylinder to accumulator flow, and a pneumatic device operatively connected to said normally closed valve and operable by said press ram at a predetermined stage of the return stroke thereof to open said last named valve by air pressure to thereby accommodate flowpof hydraulic Huid through said first flow path until said cylinder and piston are returned to the starting condition thereof.

9, The device claimed in claim 8 in which said normally closed valve comprises a bore in said valve block communicating with said first flow path, a spring biased valve body slidable in said bore and urged by a spring to a position wherein said valve body blocks a passage forming a part of said one flow path, said valve body having a reduced portion for opening said passage and being movable in said bore against the resistance of said spring References Cited UNITED STATES PATENTS 8/1961 Williamson 267-1 6/1959 Williamson 267-1 8 Williamson 267--1 Williamson 267-1 Williamson 72-351 Williamson 72351 Williamson 267-1 Williamson 267-1 CHARLES W. LANHAM, Primary Examiner.

A. RUDERMAN, A ssstant Examiner.

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