US2568687A - Hydraulic press having differential area prefill valve responsive to pullback line restriction - Google Patents

Description

p 1951 R. K. SEDGWICK 2,568,687

HYDRAULIC PRESS HAVING DIFFERENTIAL AREA PREFILL VALVE RESPONSIVE TO PULLBACK LINE RESTRICTION Filed March 25, 1948 2 SheetsSheet 1 MANUAL OR RESPONSIVE TO RAM TRAVEL I 2,568,687 HYDRAULIC PRESS HAVING DIFFERENTIAL AREA PREFILL VALVE RESPONSIVE TO PULLBACK LINE RESTRICTION Filed March 25. 1948 I R. K. SEDGWICK Sept. 18, 1951 2 Sheets-Sheet 2 I N V EN TOR. .Zoer Z Fa 05714161 B Y hm Sept- 18. rear HYDRAULIC PRESS HAVING DIFFERENTIAL AREA PREFILL VALVE RESPONSIVE TO PULLBACK LINE RESTRICTION Robert K. Sedgwick, Oak Park, 111., assignor American Steel Foundries, Chicago, 11]., a corporation of New Jersey Application March 25, 1948, Serial No. 17,001

15 Claims. (CI. 60-52) This invention relates to hydraulic presses and more particularly to a' novel actuating circuit for a pipeless hydraulic press of the type disclosed In my co-pending application, Serial No. 545,058, Died in the United States Patent Ofllce on July i8, 1944, now abandoned.

A general object of the invention is to provide I novel circuit for a press, such as above delcribed. wherein means are provided for initiating the relatively slow pressing speed of the device before the ram encounters resistance of the work. The circuit disclosed in the abovementioned application is oi the controlled gravity drop type in'which the ram is allowed to drop at I rate dictated by the pump capacity until the work is contacted whereupon the work resistance automatically effects the change to pressing speed at which the full tonnage is available. Such a circuit while suitable for a large range of work is not suitable for operations requiring the change to pressing speed before contact of the ram or ram mounted tool with the work. A principal reason for this requirement is the well-known phenomena of rapid tool wear occurring under certain conditions when the tool enters the work at the rapid advance speed. In such applications tool life has been increased many fold by slowing the press just before contact between the work and the tool.

The primary object of the invention, therefore, is to design a pipeless circuit having the characteristics of great simplicity and compactness, being of economical construction, and capable of sflecting the change from rapid advance to pressing speed prior to slowing of the ram in response to resistance of the work.

A more speciflc object of the invention is to provide a novel circuit wherein the change from rapid advance speed to pressing speed is effected by valve means responsive to restriction of the flow of hydraulic fluid from the pullback chamber of the press as the ram moves on its advance stroke.

Another object of the invention is to devise a circuit wherein the preflll valve means which connect the advance chamber or the press and the associated hydraulic reservoir are maintained in open position by pressure in the pullback line of the circuit-the preflll valve means being closed by restricting flow or fluid from the pullback chamber to the preflll valve means.

Still another object of the invention is to aitord, in combination with the above-mentioned ieatures, preflll valve means which close immediately upon restriction oi. fluid flow from the pullback chamber and other valve means responsive to pressure in the main chamber for connecting the pullback chamber to the hydraulic reservoir until the operating pressure within the main chamber hasbeen drawn oil through the fluid supply system thereby'preventing noise and shock to the reservoir resulting from opening oi the preflll valve means while high pressures exist in the main chamber.

The foregoing and other objects and advantages oi the invention will become apparent from a consideration of the following specification and the accompanying drawings, wherein:

Figure 1 is a side view of the hydraulic press embodying the invention, portions of the press being shown in elevation and other portions being shown in vertical section;

Figure 2 is a sectional view on the line 2-2 of Figure 1; and

Figure 3 is a view comparable to Figure 1 but illustrating a modification of the invention.

Describing the invention in detail and referring first to the embodiment shown in Figures 1 and 2, the press comprises a main cylinder casting, generally designated 2, containing a ram 4. with a head 6 defining an advance chamber 8 and a return or pullback chamber l0 within the cylinder casting 2. The ram 5 is provided with a central bore or passage i2 connected to the pull- .back chamber I0 as by radial ports II and containing a pullback tube is slidablyfltted in'a restricted portion I8 of the passage l2 in fluidtight engagement with said portion at the upper end of the passage.

The cylinder casting 2 supports a tank or reservoir 20 adapted to contain a suitable supply of hydraulic fluid such as, for example, oil. The cylinder also supports a bracket 22 carrying a conventional pump 24 preferably of the well.- known variable discharge, reversible delivery type. The bracket is connected in any suitable manner, as by cap screws (not shown), to the cylinder casting and is provided with advance and return ports 26 and 28- respectively, connected with advance and return lines 30 and 32 extending through the cylinder casting, the line 30 being connected to the main or advance chamber 8 and the line 32 being connected to the pullback tube IS. The bracket 22 supports a motor 34 operably connected to the pump 24 and a housing 36 for the motor.

It will be understood that in operation or the device, as hereinafter discussed in detail, the pump 24 alternately delivers pressure fluid to and exhausts pressure fluid irom the respective lines ll and O2 in such manner that the line ll de-' livers pressure fluid when the line 32 is exhausted and vice versa. If desired, this may be accomplished by means of suitable valving rather than a reversible delivery pump such as that disclosed in the present case. However, an object of the present invention is to eliminate such valving and the necessary piping therefor.

The cylinder casting 2 also supports a preflll valve body It containing a cylindrical preflll valve chamber 4| having a smaller diameter portion 42 adapted to communicate through a passage 44 with a port or passage 4! connected to the advance chamber I. A hollow preflli valve stem 4. reciprocates within the chamber 4| and comprises a smaller diameter portion ll adapted to closetheport4lintheclosedpositionofthe stem. The stem portion It comprises ports 82 connected to the passage 44 and other ports 54 connected to the larger diameter portion of the chamber a beneath the larger diameter portion of the stem 44 which deflnes an annular chamber ltconnectedtoapassagellwhichisintumconnectedbyapassagetltotheupperendofthe pullback tube It.

The preflll valve stem 4| comprises a cylindrical chamber '2 having a smaller diameter portion 04 receiving a smaller diameter portion It of a hollow valve stem s1 having a larger diameter portion 68 fltted into the larger diameter portion of the bore 62. The valve stem II is springpressed by a spring II to its closed position whereat the ports I! are closed from communication with the ports '4 and the annular chamber It. Sleeved over the portion I of the preflll valve stem 40 is an annular valve plate 12 adapted to close ports 14 connecting the chamber It with the passage 44.

It may be noted that each stem 4s and 61 is formed with a larger diameter portion and a smaller diameter portion whereby, as hereinafter described in connection with the operation of the press, the development of pressing tonnage in the advance chamber s acting against the relatively great pressure area of the stem 40 thrusts the same downwardly to closed position and also thrusts the valve stem 61 downwardly to open position against the resistance of spring Ill.

The top of valve chamber 40 is connected to a conventional relief valve 16 adapted to discharge into the reservoir III to maintain a predetermined maximum pressure value within the advance chamber I, and the passage It is connected by a e is to a similar relief valve ss adapted to prevent excessive pressure in the pullback chamber and associated conduits in the pullback phase of the operating cycle.

The body 8| supports an air chamber or cylinder 42 containing an air piston 04 and adapted for connection by a nozzle so to a conventional shop air line vll preferably containing valve means 81 responsive to position of the ram for delivering compressed air at a value. for example, of about eighty pounds per square inch to the chamber 82 at the end of the desired rapid advance stroke of the ram 4. The piston 04 is connected to a stem or plunger as having a fluted lower end II which reciprocates within the pullback tube is in snug engagement therewith for a purpou hereinafter described in connection with the operation of the press.

In operation of the press, with the prefill valve stem 48 in open position due to pressure in chamber II caused by the weight of the ram 4, the operator initiates the rapid advance phase of the cyelsbyactuatingthemunpfltctheadv'ancs position thereof whereat fluid is drawn to the suction side of the pump from the pullback passage 32 and is delivered from the discharge side of the pump to the advance passage 3.. Under thus conditions the ram descends toward the work. forcing fluid from the pullback chamber I. through the pullback tube It into the passage 8! and into the annular pamage I! holding the preflll valve stem 4' in the open position, inasmuch as the suction rate of the pump is less than the rate at which fluid is forced into the passage is and chamber is by the weight of the advancing ram 4. Thus. the stem 48 is held in open position accommodating flow of fluid from the hydraulic reservoir 20 to the advance chamber 4. since the pressureinchamberllismuchgreaterthanthe ahnospheric pressure of the fluid in reservoir 2. acting on the top and bottom areas of the valve stem 4., and in this connection it may be noted that the discharge of the pump 24 into the chamber I on rapid advance phase of the cycle h open to the reservoir ll through passages 44 and 4| sothatprusureintheadvancechamberissubstantially the same as the atmospheric prc'ure of the fluid in the reservoir II.

at a predetermined point in the advance stroke of the ram, air pressure is admitted to the cylinder '2, either by manually operated or automatically operated valve means l'l responsive to position of the ram. to urge the piston l4 and plunger ss downwardly cutting oil or restricting the supply of fluid from the pullback tube It to the pullback e It. This cames a rapid drop in the pressure within the annular chamber It causing the preflll valve stem 4| to be sucked to the closed position shown in Figure l and sucking the annular valve plate I! to its open position to accommodate supply of hydraulic fluid to the pullback passage 12 which is, under these conditions, delivering fluid to the suction side of the pump. With the valve stem 4| closed. pressure rapidly builds up in the advance chamber 0 acting on the larger diameter portion of the stem 48 to maintain it in tightly closed position and acting on the larger diameter portion I of the valve stem 01 to force the latter downwardly to the open position shown in Figure l whereat fluid is supplied from the reservoir 20 through the passage 44, the ports I! and B4 to the annular chamber It which is in communication with the pullback line I: thus insuring an adequate supply of fluid for the pump 24 while the latter is on the advance troke thereof.

The great pressure of the ram 4 against the fluid in the pullback chamber ill forces the plunger es and piston 84 upwardly to accommodate further escape of fluid from the pullback chamber In as the ram moves on its prssing stroke under full tonnage.

The pullback phase of the cycle is initiated by reversing the pump 24 and exhausting the cylinder e: to maintain the plunger ll in its open position. Under these conditions the pump directs pressure fluid to the pullback passage 8! and draws fluid from the advance passage II. The fluid in the pullback passage 32 is exhausted through the passages I and it and the annular chamber It into the ports 54 and thence through ports 52 into the reservoir 20 inasmuch as the stem 61 is still in its open position accommodating flow of fluid through ports l2 and '4. When pressure within the advance chamber 0 is relieved sufllciently to accommodate closing of the stem 61, the pressure of the fluid trapped witha cylindrical pistonlike portion 48 of a valve stem 48 which is connected to a valve member 41. All of these parts are sleeved over the plunger 88 and are adapted to perform the function of the corresponding valve means 81 aand 12 of the previously described embodiment. Referring again to Figure 3, the body 38 is provided with a port 8! adapted to be closed against communication a 6 against the valve member 48 tingflow, of fluid from the pullback line 82 and the a port 88 into the reservoir 28 until the pressure within the chamber 8 has beenbled off sufliciently to accommodate raising of the preflll valve stesn48bythepressureinthepas'sage "and to to closing of the valve 4| whereupon the ram 4 moves on its pullbat stroke urging fluid from the advance chamber 8 through the port 48 and passage 44 into the reservoir :8.

ltwillbeunderstoodthatldonotwishtobe 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 with the pullback line 32 and opened to com- I munication therewith by means of the valve member 41, which is held in open position on the full pressure stroke by pressure fluid admitted to chamber 4i by means of a port 82 communicating with the top of the preflll valve chamber 48.

Thus on the rapid advance phase of vthe cycle, the ram 4 moves downwardly as fluid is pumped into the advance line 38 and is sucked from the pullback line 82. Under these conditions, the preflll valve stem 48 is held in its open position by pressure conveyed through the passage 88 to the annular chamber 58. This pressure is maintained by the fluid forced from the pullback tube It as the ram moves downwardly and this pressure is also effective to hold the valve member 41 in its upper or closed position.

The pressing or full pressure advance stroke of the ram 4 is initiated, as in the previously described embodiment, by actuation of the fluted plunger 88 to cut oil the supply of fluid to the pump from the pullback tube l8 whereupon pressure in the passage 68 of the body 88 drops, accommodating movement of the prefill valve stem 48 to its closed. position and at the same time sucking the valve member 41 to its open position whereupon thereservoir 28 is opened to communication through the port 8| and the passage 68 with the pullback line 32. As pressure builds up in the advance chamber 8, it is transmitted upwardly through the hollow preflll valve stem 48 which is provided with a central passage, indicated at 94. Under these conditions the pressure in the top of the preflll valve chamber 48 is effective to hold the valve stem 48 in its closed position inasmuch as the top pressure area thereof is substantially greater than the bottom pressure area. The pressure in the top of the chamber 48 is conveyed through the port 82 to the chamber 4| thereby acting against the top of the valve member 43 holding the valve member 41 in its open position to insure steady flow of fluid through the port 8 i.

The pullback phase of the cycle is initiated by exhausting the cylinder 82 to maintain the plunger 88 in its open position assumed, as in the previously described embodiment, under the great pressure developed on the full pressure stroke of the ram 4. At the same time the fluid supply is reversed so that the pressure fluid is admitted to the pullback line 32 and the advance line 38 is exhausted, the valve member 41 beins claims. a I

I claim:

1. In a system for actuation of an hydraulic motorhaving advance and return chambers, and ram means reciprocal therein; the combination o1 fluid supply means adapted in the advance position thereof to direct pressure fluid to the advance chamber and exhaust fluid from the return chamber and adapted in the return position thereof to deliver pressure fluid to the return chamber and exhaust fluid from the advance chamber, a reservoir of low pressure fluid, preflll valve means connecting said reservoir to said advance chamber. said valve means comprising a casing having a passage connecting said reservoir to said advance chamber, a valve steal slidably fltted in said chamber and having a passage extending longitudinally therethrough, the pressure area at the end of said stem remote from said advance chamber being greater than that adjacent said advance chamber whereby fluid pressure within the latter tends to hold I said stem in the closed position thereof, said casing having a passage connected to the return chamber and to a portion of the casing con- -taining an area of said stem opposed to the firstmentioned area thereof whereby fluid pressure delivered to the last-mentioned passage from the return chamber is effective under certain conditions to hold said stem in the open position thereof, valve means having opposed pressure areas acted upon by the fluid in the respective chambers, said last-mentioned valve means being adapted to open accommodating flow of fluid between the return chamber and the reservoir whenever the pressure in the advance chamber exceeds that within the return chamber by a predetermined value and adapted at other times to restrict flow of fluid between the reservoir and the return chamber, and means for restricting flow of fluid from the return chamber to the second-mentioned area and to the second-mentioned valve means during the advance position of the fluid supply means thereby terminating the rapid advance stroke of said ram means and initiating the full pressure advance stroke thereof. a

2. In a system of the class described for actuation of an hydraulic motor having a cylinder carrying a pullback tube, and a ram having a head slidably fltted in said cylinder to define ad-- vance and return chambers therein, the ram being hollow and having the tube slidably fitted therein, and passage means connecting the interior of the ram with the return chamber; the combination of fluid supply means for delivering maintained in its open position by the pressure (5 pressure fluid to the advance chamber while exbausting the tube and for delivering pressure fluid to the tube while exhausting the advance chamber, a reservoir oi low pressure fluid, pre-, flll valve means comprising a casing with a passage connecting the advance chamber to the reservoir, a valve chamber in the casing, and a preflll valve stem in the valve chamber adapted to open and close the passage with respect to said advance chamber, said stem having a passage extending from end to end thereof and having a greater pressure area adapted to close the stem than that adapted to open the stem, a passage in said casing connecting the tube to a portion of said valve chamber containing an area of said stem adapted to open the same, valve means adapted to connect said last-mentioned passage to the reservoir when the pressure in the advance chamber exceeds that within the return chamber by a predetermined value and adapted at other times to cut oil communication between the reservoir and the last-mentioned passage, and control means ior cutting of! communication between the tube and the last-mentioned passage when said pressure delivering means is on the advance stroke thereof.

4 3. A system, according to claim 2, wherein the control means comprises a plunger adapted to reciprocate within the tube, a piston and cylinder device operatively connected to the plunger, and a source 0! pneumatic fluid connected to said device.

s. A system, according to claim 2, wherein reliei valve means are connected to the reservoir and to the preflll valve chamber and to the second-mentioned valve passage for maintaining the pressure in the advance and return chambers at predetermined values.

5. In an hydraulic circuit for actuation of an hydraulic device comprising advance and pullback chambers, and ram means reciprocal therein; the combination of means for alternately delivering fluid to and exhausting fluid from the advance and return chambers, a reservoir of low pressure fluid connected to the advance chamber, valve means having opposed pressure areas acted upon by the fluid in the advance and return chambers respectively, and adapted when the pressure in the advance chamber exceeds that in the pullback chamber by aipredetermined value to accommodate flow oi fluid between said reservoir and the pullback chamber and adapted at other times to restrict flow oi fluid between said reservoir and the pullback chamber, preflll valve means in the connection between said reservoir and said advance chamber comprising a relatively great closing pressure area and a relatively small opening pressure area acted upon by the fluid in said advance chamber in the closed position of the preflll valve, said preflll valve having another opening pressure area connected to the pullback chamber, and means for cutting of! communication between the last-mentioned area and the pullback chamber to terminate the rapid advance stroke of the device thereby enabling pressure fluid in the advance chamber to close the preflll valve means and to open the first-mentioned valve means to initiate the full pressure advance stroke oi the device.

6. In a system for actuation of an hydraulic motor having advance and return chambers, and ram means reciprocal therein; the combination oi means for alternately directing pressure fluid to and exhausting pressure fluid from the advance and return chambers, a reservoir of low pressure fluid having a connection to the advance chamber, preflll valve means for opening and closing said connection, said valve means comprising a hollow stem having a greater pressure area acted upon by pressure in the advance chamber tending to close the stem than the area tending to open the stem, said stem having another pressure area spaced from the flrst and second-mentioned areas and acted upon by the pressure in the return chamber during the rapid advance stroke and the return stroke of said ram means to hold said stem open, valve means adapted to automatically accommodate unrestricted flow of fluid between the return chamber and the reservoir when the pressure in the advance chamber exceeds that in the return chamber by a predetermined value, said valve mean being adapted at other times to automatically restrict flow oi fluid between the reservoir and the return chamber whereby the pressure in the latter chamber acts upon the second-mentioned area to hold said stem open, and yielding means for restricting flow or fluid from the retum chamber to terminate the rapid advance stroke oi said ram means and initiate the full pressure advance stroke thereoi.

7. A system for actuation oi an hydraulic motor having a cylinder, a pullback tube carried thereby, a ram having a head reciprocal in the cylinder and deflning advance and return chambers therein. said tube being aflorded a substantially fluid-tight flt within a passage in said ram, and pass ge means connecting said passage at all times to the return chamber; the combination of a reversible delivery pump having oppositesides thereof connected to the advance chamber and the tube respectively, a reservoir 0! low pressure fluid, preflll valve means adapted to open and close communication between the advance chamber and the reservoir, a passage connecting the tube to the preflll valve means for delivering pressure fluid thereto to open the latter on the return and the rapid advance strokes of the ram, a plunger adapted to restrict flow oi fluid from the tube to the preflll valve means. compressible actuating means for the plunger, and valve means having opposed areas acted upon respectively by the pressure in the advance chamber and the tube, the last-mentioned valve means being adapted to open communication between the reservoir and the tube when the pressure in the advance chamber exceeds that within the tube by a predetermined value and adapted at other times to close communication between the tube and the reservoir.

8. A system, according to claim 7, wherein the second-mentioned valve means comprises a unit sleeved over the plunger and having a pressure area connected to the advance chamber and another pressure area connected to the tube.

9. A system, according to claim 7, wherein the preflll valve means comprises a stem with a passage exiending longitudinally therethrough, the stem having a greater closing area acted upon by the pressure in the advance chamber than the opening area 0! said stem acted upon by the fluid in the advance chamber, the stem having another opening area connected to the tube, and the other valve means comprises a valve member slidably fltted within the stem passage and having opposed opening and closing areas connected to the advance chamber, the opening area being greater than the closing area.

10. In a system 01 the class described for actuation of an hydraulic device comprising advance and return chambers, and ram means reciprocal therein; the combination of a reservoir of low pressure fluid, preflll valve means connecting said reservoir to the advance chamber and adapted to be maintained in a closed position by the pressure therein, said preflll valve means having an opening pressure area acted upon by the pressure in the return chamber, advance and return lines connected respectively to the advance and return chambers for alternately delivering pressure fluid to and exhausting pressure fluid from the advance and return chambers, and yielding means for restricting flow offluid from the return chamber to the return line thereby diminishing the pressure against said area to accommodate closing of said preflll valve means and resultant initiation of the full pressure advance stroke of said ram means.

11. In a system of the class described for actuation of an hydraulic motor having advance and return chambers, and ram means reciprocal therein; the combination of a reservoir of low pressure fluid, a preflll valvev means adapted to connect the reservoir to the advance chamber on the rapid advance stroke of the ram means and on the return stroke thereof and adapted on the full pressure stroke of said ram means to cut oil communication between the reservoir and the advance chamber, said valve means comprising a pressure area acted upon by fluid pressure in the return chamber for maintaining the valve means in the open position thereof, and means for restricting flow of fluid from the return chamber to said area on the rapid advance stroke of said ram means to initiate the full pressure stroke thereof, the restricting means being adapted to yield under the pressure of fluid forced from the return chamber when the preflll valve means are closed and high pressure fluid is admitted to the advance chamber.

12. In a system of the class described for actuation of an hydraulic devicecomprising advance and return chambers, and ram means reciprocal therein; the combination oi advance and return lines connected respectively to the advance and return chambers, means for alternately delivering high pressure fluid to one line and exhausting the other line, a reservoir of low pressure hydraulic fluid, preflll valve means for alternately opening and closing said reservoir with respect to said advance chamber, means for restricting flow oi! fluid from the return chamber to the return line on the advance stroke of said ram means, and means responsive to said restriction or flow for automatically closing said preflll valve means.

13. In an hydraulic circuit for an hydraulic device comprising advance and pullback chambers, and ram means reciprocal therein; the combination or a reservoir oi low pressure fluid connected to the advance chamber, preflll valve means for opening and closing the connection between the advance chamber and said reservoir. and means responsive to restriction of flow from means, and means for restricting flow of fluid from the return chamber.

15. In a system for actuation of an hydraulic motor having a cylinder, and a ram reciprocal therein dividing the cylinder into advance and pullback chambers; the combination of a pullback tube slidably fltted within the ram and connected to the pullback chamber, a reservoir of low pressure fluid, preflll valve means for opening and closing communication between the reservoir and the advance chamber, said prefill valve means having a relatively great closing area and a relatively small closing area, both communicating with the advance chamber, and having another opening area communicatin with the tube, means for alternately delivering high pressure to and exhausting fluid from the advance chamber and the tube, normally closed valve means adapted to open when the pressure in the advance chamber exceeds that in the tube by a predetermined value, said last-mentioned valve means being adapted when open to connect the pullback tube to the reservoir, and means for closing said preflll valve means comprising a plunger reciprocal to a position relative to the tube whereat flow of fluid therefrom is restricted to reduce pressure against said other opening area to a value whereat pressure on said relatively great closing area is effective to close said preflll valve means, and means for urging the plunger to said position after said ram has advanced any predetermined distance on its advance stroke, said last-mentioned means comprising means compressible by the pressure fluid in said tube when said preflll valve means are closed and pressure fluid is delivered to the advance chamber by said delivering means.

ROBERT K. SE'DGWICK.

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

UNITED STATES PATENTS Number Name Date 1,892,568 Ernst Dec. 27, 1932 2,204,270 Dinzl June 11, 1940 2,324,149 Gray July 13, 1943 2,358,650 Maude Sept. 19, 1944 2,444,339 Dinzl June 29, 1948

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