US2555115A - Hydraulic decompression circuit with automatic reverse - Google Patents

Description

. CIZEK HYDRAULIC DECOMPRESSION CIRCUIT WITH AUTOMATIC REVERSE 3 Sheets-Sheet 1 Filed June 14. 1946 m QOH Wm Qm Q0 new ow Q 3 NM INVENTOR.

May 29, 1951 F. G. CIZEK HYDRAULIC DECOMPRESSION CIRCUIT WITH AUTOMATIC REVERSE 3 Sheets-Sheet 2 Filed June 14, 1946 MM @Q N% Nu WM i I! fiw Y I. i QQ fin OOH *3 N% F V 00 NQN mow IN V EN TOR.

Patented May 29, 1951 HYDRAULIC DECOMPRESSION CIRCUIT WITH AUTOMATIC REVERSE Frank G. Cizek, Chicago, Ill., assignor to American Steel Foundries, Chicago, 111., a corporation of New Jersey Application June 14, 1946, Serial No. 676,837

11 Claims.

This invention relates to hydraulic equipment and more particularly to a novel hydraulic circuit adapted to actuate a hydraulic machine such as. a press. In many hydraulic presses, after the ram has accomplished its working stroke, the work tends to spring back against the ram and this condition is often aggravated by the presence of a such as presses, having a surge or prefill valve,

the liftin forces on the ram tend to build up pressure in the main cylinder and thus often tend to. prevent the prefill valve from moving to the open position thereof. As a result of this con-- dition, the main ram is lifted from the work very slowly and when the pressure fluid is directed to, the return side of the ram, the lifting force thereag-ainst aggravates the condition by increasing the pressure in the main cylinder with the result that the press locks up with its prefill valve closed so that the ram creeps upwardly forcing the fluid in the main cylinder outwardly therefrom through whatever valves may be open, generally the main operating valve. ,Various decompression circuits have been proposed to solve this problem and have been used with some success; however, decompression circuits known in the art frequently involveextra valves, known as decompression valves. Furthermore, in known systems of this type comprising reversing pumps and a closed circuit, the pump has been used to decompress the main cylinder, such an arrangement being necessarily limited to a system including a reversible pump.

The present invention relates to a decompression circuit for use with a system comprising a vunidirectional pump and is so designed as to eliminate the necessity of so-called decompression valves- A general object of the invention is to design a. circuit which will accommodate back pressure in hydraulic machines, such as valve controlled presses, without the use of extra valving, usually associated with decompression circuits.

Another object of the invention is to provide a system which will decompress the main cylinder in the shortest possible time consistent with shockless operation and which will be self-regulating in this respect.

A more specific object of the invention is to provide, in a system such as above described, means for causing the main operating valve to pause in its neutral position for a short period of time during the reversal phase of the cycle, thus permitting the main cylinder to decompress before pressure fluid is admitted to the return side of the ram. Attempts have been made in the prior art to produce such a delay by the use of timers and restrictions in pilot lines controlling thev operating valve; however, mechanism of this type must be set to accommodate maximum conditions plus a little additional time to accommodate viscosity changes, so that the delay is always longer than absolutely required and is often objectionably long. The present invention comprises a circuit which is self-regulating in that the delay period is automatically adjusted long enough to accommodate decompression under the particular conditions obtained momentarily and no longer.

The foregoing and other objects and advantages of the invention will be more fully understood by reference to the following specification and the accompanying drawings, wherein:

Figure l is a flow diagram of a novel hydraulic circuit embodying the invention, portions of the hydraulic press and associated valving being shown in section to clarify the illustration;

Figure 2 is a sectional view through the prefill or surge valve shown in Figure 1, a portion of the valve and associated piping being shown in elevation;

Figure 3 is a sectional view showing a modified prefill valve; and

Figure 4 is a fragmentary diagrammatic view, partially in section, illustrating the invention as applied to another type of hydraulic press.

Describing the invention in detail and referring first to Figure 1, the hydraulic device comprises a working member such as a platen 2 supported by a ram 4 which is reciprocable within a cylinder 6 in a cylinder casting 8, said ram having a head In defining advance and return chambers l2 and I4 Within the cylinder. The device preferably comprises a rapid advance motor, here shown in the form of a rapid advance cylinder or chamber l6 within the ram 4 receiving a tube or pipe l8 supported by the casting 8.

A tank or reservoir 20 is supported by the casting 8 and is adapted to contain a supply of hydraulic fluid such as oil. The tank is connected to the advance chamber I2 by means of a prefill valve 22, hereinafter described in detail, said valve being adapted to open and close communication between the chamber 12 and the tank 20 under the conditions hereinafter described.

Mounted on the tank is a motor 24 operatively connected to a pair of pumps 26 having their suction sides connected to the tank 20 and their discharge sides connected to a main supply line 28 comprising conventional relief valves 29 adapted to discharge into the tank 20 when the pressure in the line 28 reaches a predetermined maximum Value. The main supply line 28 is connected to an operating valve, generally designated 38, comprising a body 32 with an in'-' ternal cylindrical bore and a valve stem with spaced cylindrical spools 34 and 36 slidably fitted in said bore in substantially fluid-tight engagement therewith. The spools are notched as at 38 so that when the valve stem is in its neutral position, shown in Figure 1, fluid from the line 28 is delivered through annular distribution chambers i0 and 42 into discharge chambers 43, and from the discharge chambers to a discharge line 44 connected to the tank 20.

The distribution chambers and 42 are connected respectively to advance and return lines 46 and 48, the line it being connected to the chambers i2 and I6, as hereinafter described in detail, and the line 48 being connected to the return chamber I4. The advance line 46 is connected through the tube I8 to the rapid advance chamber I6 and is connected by a branch line 58. to a conventional sequence valve 52 including a casing 54 with an internal cylindrical bore affording a slidable substantially fluid-tight fit for three spaced spools 56 of a valve stem which is spring-pressed to its closed position by a spring 58, thus restricting passage of fiuid from the line into the prefill valve 22 but accommodating flow of fluid from the prefill valve to the tank 26 through the ports 60 and 62 for the purpose hereinafter described.

The port 62 is connected to the port 64 (Figure 2) of the prefill valve 22. The prefill valve is described in detail in a copending Sedgwick application, Serial No. 516,207, filed December 30, 1943, now Patent No. 2,423,120, issued July 1, 1947, and comprises a body 66 with the beforementioned port 64 and a low pressure chamber with an opening or port 68 communicating with the tank 20. The prefill valve also comprises a stem I0 with a larger-diameter portion I2 slidably fitted within a high pressure chamber I3 in the body 66 and adapted to seat at 14 to close the port 68 from communication with an outlet passage or a chamber I6 which is connected to the advance chamber I2 of the hydraulic press.

The larger-diameter portion I2 of the prefill valve stem comprises a cylindrical chamber I8 with a ring valve 80 slidably fitted therewithin and adapted to close ports 82 communicating with the chamber I6. The ring valve is connected to a spindle or piston 84 reciprocable within a cylinder 86 associated with the body 66. The prefill valve stem also comprises a smallerdiameter portion slidably fitted within a cylinder 87 of the body 66.

The hydraulic circuit above described is operated by a pilot circuit which is hereinafter described in connection with the operation of the device. This pilot circuit comprises a pilot pump 88 (Figure 1) having its suction side connected to the tank 20, the discharge side of said pump being connected to a pilot line 99 having two conventional three-way pilot valves 92 and 94 therein. In the advance phase of the cycle, the valve92 is opened by any conventional means such as a solenoid (not shown) and the valve 94 is closed. Under these conditions, fluid is delivered from the pilot line 90 to the pilot chamber 96 of the valve 30, moving the stem thereof to the left causing the hydraulic fluid in the supply line 28 to flow into the advance line 66, thus actuating the rapid advance motor of the device to move the ram 4 rapidly downward, thereby moving the platen 2 to work-engaging position. As the ram moves downwardly, fluid in the return chamber I4 is urged through the line 48 and the valve 30 into the discharge line 44.

When the platen 2 reaches work-engaging position, pressure builds up in branch line 50 and in the chamber 98 of the sequence valve, moving the stem thereof upwardly to its open position at which pressure fluid may pass from the branch line 50 through the port 62 of the valve 52 to the port 64 of the prefill valve 22. This pressure moves the prefill valve stem T6 to the closed'position shown in Figure 2, cutting off the advance chamber I2 of the press from communication with the tank 20 through the prefill valve port 68. It may be noted at this point that the opening of the prefill valve stem I0 will be described later in connection with the return or retraction phase of the cycle. After the valve stem 10 has closed and a predetermined pressure is built up against the spindle 84, the latter is moved to open position, forcing fluid in line I00 through a one-way check valve I02 adapted to open at said pressure value permitting fluid in the line I90 to flow through pilot line I06 (Figures 1 and 2) to the three-way pilot valve 94 and thence through line I06 to the tank 20. It will be understood that in the closed position of the conventional pilot valve 94, flow of fluid from the line I04 to the line I06 is accommodated.

When the ring valve 30 moves to its open position, pressure from the port 64 enters the chamber I6 through the ports 82 and passes to the advance chamber I2 of the hydraulic press, thus affording pressure against the full cross-sectional area of the ram 4 to urge the platen against the associated work.

In the return or retraction phase of the cycle, the pilot valve 92 is closed to prevent flow of fluid from line 90 to the chamber 96 of the valve 30, and the pilot valve 94 is opened by any conventional actuating means, such as a solenoid (not shown), whereupon pressure fluid from the pilot pump 88 is forced through the line I64 which, under these conditions, is closed from communication with the line I536. The pressure fluid is transmitted through the line I04 to the before-mentioned cylinder 8? inasmuch as the check valve I02 is incapable of opening in response to pressure in the line I64. Under these conditions, the stem of the operating valve 30 is moved by a spring I01 to the neutral position shown in Figure 1 forcing fluid from chamber 96 into the tank 20 through a line I09 which communicates with chamber 96, When valve 92 is closed. It may be noted that the spring IE1 is operable to resist movement of the operating valve stem in either direction from its neutral position. When the stem of the operating valve 36 has assumed its neutral position, the pressure in line 46 and branch line 50 is relieved, thus permitting the st'in of the sequence valve 52 to move-to its closed position shown in Figure l, whereupon, as heretofore mentioned, pressure fluid may pass from the port 64 of the prefill valve tothe port 62 of the sequence valve 52 and outwardly from the port 60 thereof into the tank 20, thus relieving pressure within the chamberl3 of the prefill valve, said pressuretending to maintain the prefill valve stem 19 in the closed position inasmuch as the larger diameter portion thereof affords a relatively great cross-sectional area. upon which the pressure within the chamber it may act. As soon as the pressure on the larger-diameter portion of the preflll valve stemifi has been bled off, as above described, the stem moves to the right to its open position 1111- covering port Hi8, whereupon pressure fluid from the pilot line HM is conveyed through the cylinder 81- and port I88 to pilot line I90, and thence to the pilot cylinder or chamber H39 of the operating valve 39, thereby moving the stem thereof to the right to its return position whereat pressure fluid is delivered fromthe line 28 to the return line 8 and thence to the return chamber H3 moving the ram 4 and the platen 2 upwardly to the return or retracted position thereof illustrated in Figure 1. As the ram 4 moves upwardly, fluid within the chamber I2 is urged. back into the tank 20 through the prefill valve port 68 and the fluid in the rapid advance chamber I is urged through the line 46 and the operating valve 39 into the discharge line 44 and thence into the tank it.

At this time the pressure in pilot line I00 moves the piston 84 and ring valve 80 to the closed position illustrated in Figure 2, whereupon as the valve stem l0 moves to theclosed position in the advance phase of the next cycle of the press, the ring valve 80 is effective to close the ports 82 as heretofore described.

It will be understood that if desired the rapid advance motor of the hydraulic press may be eliminated and the line 46 may be connected to the preflll valve port 64 directly, under which conditionsthe ram 4 may be moved to workengaging position by a force of gravity or manually, or by any other suitable actuating means. After the ram has been moved to work-engaging position pressure fluid may be directed to the line 46 by means of the valve 30 as above described.

Figure 3 shows a modification of the prefill valve which is identical with the embodiment disclosed in Figure 2 except that the ring valve 80 and spindle 84 are moved to their closed positions by means of a spring I I0 rather than the hydraulic means described in connection with Figure 2.

Referring now to Figure 4, a modification of the invention is disclosed, wherein the novel hydraulic circuit described in connection with Figures 1 and 2- is applied to a different type of hydraulic motor wherein the platen I52 is moved to work-engaging position by rapid advance pistons or rams I54 reciprocable within rapid ad Vance cylinders I56 connected to the advance line 4 5 of the hydraulic circuit. The main ram I58 of the device is reciprocable within a main cylinder 160 which is connected to the advance line 66 through the prefill valve 22, the sequence valve 52 and the branch line 50 of the advance line 46, as in the embodiment of Figures 1 and '2. The platen IE2 is urged to its return or retracted position by push-back rams I82 received within pushbaclr cylinders I64 which are connected to the return line 48 of the hydraulic circuit.

It will be understood that in the embodiment of Figure 4 the hydraulic circuit associated with the press is identical with that described in connection with Figures 1 and 2, the sole difference being the above-described modification of the hydraulic actuating motors associated with the platen I52. The portions of the hydraulic circuit which. correspond with those shown in Fig- 6; ures l and 2 are identified by the corresponding numerals It is to be understood that I do not wish to be limited by the exact embodiments of the device shown which are merely by way of illustration and not limitation as various and other forms of the device will, of course, be apparent to those" skilled in the art without departing from the spirit of the invention or the scope of the claims.

I claim:

1. In combination, a platen, a booster motor associated with said platen for actuating the same to work-engaging position, hydraulic motor means associated with said platen comprising advance and return chambers and ram means reciprocable therein, a reservoir having a con,- nection to said advance chamber, prefill valve means adapted in the open and closed positions thereof to open and close said connection, an advance line connected to said advance chamber and to said valve means, said valve means being adapted to move to its closed posiiton in response to fluid pressure from said line, a return line connected to said return chamber, operating valve means having passage means in the advance position thereof for directing pressure fluid to said advance line and for opening said return line to discharge, said operating valve means having passage means in the return position thereof for directing pressure fluid to said return line and for opening said advance line to discharge, and said operating valve means having passage means in its neutral position for relieving pressure in said advance line, means for yieldingly urging said operating valve means to the neutral position thereof, means for moving said operating valve means to its advance position against the resistance of said yielding means, and means responsive to opening of said prefill valve means for automatically moving said operating valve means to the return position thereof against the resistance of said yielding means, and operating means independent of hydraulic pressure in the return line for opening said prefill valve means when said up crating valve means is in the neutral position thereof.

2. In an hydraulic device comprising a working member, a rapid advance motor operatively associated therewith for moving said member to work-engaging position, and hydraulic motor means operatively associated with said member comprisin advance and return chambers and ram means reciprocable therein, the combination of a source of low pressure fluid having connection to the advance chamber, prefill valve means for opening and closing said connection, a source of high pressure fluid, operating valve means adapted in the advance position thereof to direct fluid from said high pressure source to said prefill valve means to close the same and thereby admit fluid from said source to said advance chamber, said operating valve means being adapted in the neutral position thereof to relieve the pressure in said prefill valve means, spring means for biasin said operating valve means to the neutral position thereof, said operating valve means being adapted in the return position thereof to direct pressure fluid from said high pressure source to said return chamber, power means independent of hydraulic pressure from said source for opening said prefill valve means when the pressure in said advance chamber has been relieved, and means responsive to the position of said prefill valve 7 means for automatically actuating said operating valve means to the return position thereof against the resistance of said spring means when said prefill valve means has opened.

3. In an hydraulic device comprising a working member, a rapid advance motor operatively associated therewith for moving said member to work-engaging position, and hydraulic motor means operatively associated with said member comprising advance and return chambers and ram means reciprocable therein, the combination of a source of low pressure hydraulic fluid connected to the advance chamber, prefill valve means for opening and closing said connection, a source of high pressure fluid, operating valve meansfor directing fluid from said high pres sure source to said prefill valve means to close the same, said prefill valve means being adapted when closed to deliver fluid from said operating valve means to said advance chamber, said operating valve means being adapted in the neutral position thereof to relieve the pressure in said prefill valve means and being adapted in the return position thereof to direct pressure fluid from said source to said return chamber, operating means independent of hydraulic pressure fluid delivered by said operating valve means to said'return chamber for opening said prefill valve means when the pressure therein has been relieved, and means responsive to the opening of said prefill valve means for automatically actuating said operating valve means to the return position thereof after said prefill valve means has opened.

4. In an hydraulic device comprising a workengaging member and an hydraulic motor operatively associated therewith comprising advance and return chambers and ram means reciprocable therein, the combination of a reservoir containing low pressure hydraulic fluid, prefill valve means connecting said reservoir to said advance chamber, said member being movable to and from the work-engaging position thereof when said valve means is open to accommodate flow of fluid between said reservoir and said advance chamber, a high pressure line connected, to said valve means, said valve means being'adapted to move to the closed position thereof in response to the pressure of fluid in said line and having passage means in said closed position for accommodating flow of fluid from said line to said advance chamber, operating means entirely independent of hydraulic pressure in the return chamber for moving said valve means to the open position thereof when the pressure. in said line is relieved, and means responsive to the position of said prefill valve means for automatically directing pressure fluid to said return chamber after said valve means has been moved to the open position thereof.

5. In a system of the class described comprising a working member, and a hydraulic motor for actuating said member including advance and return chambers and ram means reciprocable therein; the combination of a reservoir containing low pressure hydraulic fluid, prefill valve means for connecting and disconnecting said advance chamber with respect to said tank, advance and return lines connected to said advance and return chambers respectively, means for alternately connecting said lines to a source of pressure fluid and to a discharge line so that one of said advance and return lines is connected to said source when the other is connected to said discharge line, a hydraulic piston and 8 cylinder device for opening said prefill valve means, a pilot line closed by said piston when the prefill valve means are closed, said pilot line being open to flow of fluid from said cylinder when the prefill valve means are opened, and another piston and cylinder device connected to said pilot line for operation by fluid pressure therein to actuate said connecting means so as to connect said source to said return line when said prefill valve means has opened to connect said advance chamber to said reservoir.

6. In an hydraulic device including a workengaging member and actuating means therefor comprising an hydraulic motor with advance and return chambers and ram means reciprocable therein, the combination of a reservoir of low pressure hydraulic fluid connected to said advance chamber, prefill valve means in said connection for opening and closing the same, said member being movable to and from the workengaging position thereof when said valve means is open, a source of high pressure hydraulic fluid, means for closing said valve means thereby directing fluid from said source to said advance chamber, means entirely independent of hydraulic pressure in said return chamber for opening said valve means when said advance chamber has been disconnected from said source, and means responsive to opening of said prefill valve means for automatically directing pressure fluid to said return chamber.

'7. In an hydraulic device comprising advance and return chambers and ram means reciprocable therein, the combination of a source of low pressure fluid, valve means associated with said source and said advance chamber for opening and closing communication therebetween, means for delivering fluid under relatively high pressure to said advance chamber when said valve means is closed, means entirely independent of pressure fluid from said delivering means for opening said valve means when the pressure in said advance chamber has been relieved, and condition responsive means effective upon opening of said valve means to automatically direct relatively high pressure fluid to said return chamber.

8. In an hydraulic circuit for an hydraulic motor comprising advance and return chambers and ram means therein; the combination of a reservoir of low pressure fluid, a prefill valve comprising a body with a low pressure inlet chamber connected to said reservoir, said valve comprisin a high pressure inlet chamber and an outlet passage connected to said inlet chambers and to said advance chamber, an advance line connected to said high pressure chamber, a return line connected to said return chamber, a stem slidably seated in the high pressure chamber and comprising a pistonlike portion of less diameter than the low pressure chamber, a cylinder associated with the body and receiving said portion, said stem bein adapted in the closed position thereof to cut off communication between the high and low pressure chambers, a chamber in the stem connected to the high pressure chamber, a port through the stem adapted to connect the stem chamber to the outlet passage in the closed position of said stem, said port being disposed within the high pressure chamber in the open position of the stem, a valve member in the stem chamber adapted to open and close said port, said valve member having passage means accommodating flow of fluid between the stem chamber and the high pressure chamber, said valve member having a pistonlike element slidably fitted within a complementary openin in the body, operating valve means connected to said lines and adapted in the advance position thereof to di rect pressure fluid to the advance line and to exhaust fluid from the return line, said operating valve means being adapted in the return position thereof to direct pressure fluid to the return line and to exhaust fluid from the advance line, and said operating valve means being adapted in the neutral position thereof to exhaust fluid from the advance line, means for actuatin said operating valve mean to the advance position thereof, means effective upon release of the first-mentioned actuating means for actuating said operating valve means to the neutral position thereof, and means for actuat ing the operating valve means to the reverse position thereof comprising a pilot line adapted to convey pressure fluid to said cylinder, a port in said cylinder closed by said portion in the closed position of said stem and open to communication with said pilot line in the open position of said stem, another pilot line connected to the last-mentioned port, a piston and cylinder device connected to the last-mentioned pilot line and operatively connected to the operating valve means for actuating the same to the reverse position thereof in response to pressure fluid conveyed to said device through said pilot lines, and check valve means connecting said pilot lines and accommodating flow of fluid from said device to the first-mentioned pilot line, and actuating means associated with said element for moving said valve member to the closed position thereof upon release of pressure in said high pressure chamber.

9. An hydraulic circuit, according to claim 8,

wherein the last-mentioned actuating means comprises a cylinder associated with the prefill valve body and receiving the valve member element, and a connection between said cylinder and the second-mentioned pilot line.

10. An hydraulic circuit, according to claim 8, wherein the last-mentioned actuating means comprises a spring disposed externally of the high pressure chamber and operatively connected to the valve member element.

11. In an hydraulic circuit for an hydraulic apparatus comprising a Working member and actuating means therefor including hydraulic motor means having advance and return chambers and ram means reciprocal therein, and a booster motor for efiecting rapid advance of said motor; the combination of a reservoir of low pressure fluid, a prefill valve comprising a, body with a low pressure inlet chamber connected to said reservoir, said body comprising high pressure inlet chamber and an outlet passage connected to both of said inlet chambers and to said advance passage, an advance line connected to said booster motor and having a connection to said high pressure chamber, said connection comprising valve means adapted to open in response to pressure fluid within the advance line thereby accommodating flow of fluid therefrom to the high pressure chamber and adapted to close when said advance line is exhausted thereby accommodating flow of fluid from the high pressure chamber to said reservoir, a return line connected to said return chamber, a stem slidably seated in communication between the high and low pres sure chambers, a chamber in the stem connected to the high pressure chamber, a port through the stem adapted to connect the stem chamber to the outlet passage in the closed position of said stem, said port being disposed within the high pressure chamber in the open position of the stem, a valve member in the stem chamber adapted to open and close said port, said valve member having passage means accommodating flow of fluid between the stem chamber and the, high pressure chamber, said valve memberhaving a pistonlike element slidably fitted within a complementary opening in the body, operating valve means connected to said lines and adapted in the advance position thereof to direct ..pres sure fluid to the advance line and to exhaust fluid from the return line, said operating valve means being adapted in the return position thereof to direct pressure fluid to the return line and to ex haust fluid from the advance line, and said operating valve means being adapted in the neutral position thereof to exhaust fluid from the advance line, means for actuating said operating valve means to the advance position thereof, means effective upon release of the first-mentioned actuating means for actuating said operating valve means to the neutral position thereof, and means for actuating the operating valve means to the reverse position thereof comprising 'a, pilot line adapted to convey pressure fluid to said cylinder, a port in said cylinder closed by said portion in the closed position of said stem and open to communication with said pilot line in the open position of said stem, another pilot line connected to the last-mentioned port, a piston and cylinder device connected to the last-mentioned pilot line and operatively connected to the operating valve means for actuating the same to the reverse position thereof in response to pressure fluid conveyed to said device through said pilot lines, and check valve means connecting said pilot lines and accommodating flow of fluid from said device to theflrst-mentioned pilot line, and actuating means associated with said element for moving said valve member to the closed position thereof upon release of pressure in said high pressure chamber.

FRANK G. CI ZEK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,200,998 Schmuck May 14, 1940 2,307,585 Harrington Jan. 5, 1943 2,324,697 Harrington July 20, 1943 2,343,177 Flowers Feb. 29, 1944

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