US3310943A

US3310943A - Hydraulic transformer

Info

Publication number: US3310943A
Application number: US463993A
Authority: US
Inventors: John R Horetzke
Original assignee: GRAND STEEL AND Manufacturing CO
Current assignee: GRAND STEEL AND Manufacturing CO
Priority date: 1965-06-15
Filing date: 1965-06-15
Publication date: 1967-03-28
Anticipated expiration: 1984-03-28

Description

EBEQWE 2 sheets Sheet 1 o w mm m 9 M4 0 w m H W0 2; 1H.

fli N 8 nummmw lui j u du MW d Mamgl 197 J. R. HORETZKE HYDRAULIC TRANSFORMER Flled June 15, 1965 2 4 i \\\\\S\ \.4 mm a H Q8 6 2 ATTORNEYS United States Patent 3,310,943 HYDRAULIC TRANSFORMER John R. Horetzke, Royal Oak, Mich., assignor to Grand Steel & Manufacturing Co., Clawson, Mich, a corporation of Michigan Filed June 15, 1965, Ser. No. 463,993 16 Claims. (Cl. 6054.5)

The invention relates to hydraulic presses and refers more specifically to hydraulic press actuating apparatus including a single pump and a hydraulic transformer capable of moving a press toward a workpiece at a high velocity under low pressure during a portion of a ram stroke while a die carried by the ram approaches the workpiece and automatically adjusting to move the ram at a lower velocity under higher pressure for the remainder of the ram stroke while the workpiece is engaged and work is performed on the workpiece.

In the operation of a hydraulic ram press it is desirable to move the press ram toward a workpiece at a more rapid rate before engagement of a die carried by the ram with the workpiece than thereafter and to provide high pressure during performance of Work on the workpiece. Such operation shortens the cycle of operation for the press so that the press is able to satisfactorily complete more workpieces in a predetermined time.

-In the past the high speed advancing of a ram toward a workpiece and subsequent low speed, high pressure engagement of a die carried by the ram with the workpiece has required relatively complicated hydraulic press actuating apparatus including two separate pumps for efiicient circulation of hydraulic fluid for the apparatus. Such hydraulic press actuating apparatus has been relatively expensive and therefore limited in use.

It is one of the objects of the present invention to provide improved hydraulic press actuating apparatus.

Another object is to provide a hydraulic actuating apparatus for initially moving a ram toward a workpiece at a high rate of travel under a low pressure and subsequently moving the ram into engagement with the workpiece at a lower rate of travel and working the work piece under a high pressure which apparatus includes a single hydraulic fluid pump.

Another object is to provide hydraulic actuating apparatus for moving a press ram toward a workpiece at a high rate of travel under low pressure and subsequently engaging the workpiece with the ram moving at a lower rate of travel under a high pressure including a hydraulic t-rans former, means for pumping hydraulic fluid into the trans former at a low rate under a high pressure to force hydraulic fluid out of the transformer to the press ram at a high rate and low pressure while the ram is approaching the workpiece and means for bypassing the hydraulic transformer to pump the hydraulic fluid at the low rate under a high pressure directly to the press ram immediately before engagement of the workpiece and during work on the workpiece.

Another object is to provide hydraulic press actuating apparatus as set forth above and further including means for returning the ram to the raised position and for selecting a predetermined limiting raised position for the ram.

Another object is to provide hydraulic press actuating apparatus as set forth above wherein the apparatus is provided with means for recharging the hydraulic transformer on raising of the ram.

Another object is to provide hydraulic press actuating apparatus as set forth above wherein the apparatus is provided with an alternative overflow path from the hydraulic transformer to the hydraulic fluid reservoir for presses having stripper or knock-out structure operable on the return stroke of the press.

3,31%,943 Patented Mar. 28, 1967 Another object is to provide an improved hydraulic transformer.

Another object is to provide hydraulic press actuating apparatus which is simple in construction, economical to manufacture and eflicient in use.

Other objects and features of the invention will become apparent as the description proceeds, especially when taken in conjunction with the accompanying drawings, illustrating a preferred embodiment of the invention, wherein:

FIGURE 1 is a partially broken away diagrammatic perspective view of press structure including hydraulic actuating apparatus having a hydraulic transformer constructed in accordance with the invention installed thereon.

FIGURE 2 is a schematic hydraulic diagram of the hydraulic actuating apparatus of the press structure illustrated in FIGURE 1.

With particular reference to the figures of the drawings, one embodiment of the present invention will now be considered in detail.

As shown in FIGURE 1, hydraulic press actuating apparatus 10 is positioned on the press 12 to lower and raise the ram 14 of the press 12. The hydraulic apparatus includes the hydraulic transformer 16 connected between the pump 18 and the cylinder 20 in which the ram 14 is reciprocated.

In operation the hydraulic transformer 16 functions to pump hydraulic fluid into the top of the cylinder 20 at a hi h rate and low pressure to cause the ram 14 to descend rapidly to a predetermined position. At the predetermined position the hydraulic apparatus 10 functions to automatically bypass the hydraulic transformer 16 and feed the hydraulic fluid pumped by the pump 18 at a relatively low rate and high pressure directly into the cylinder 20 to cause the ram 14 to continue to descend at a slower speed under the higher pressure for forming a workpiece (not shown) positioned on the press 12.

More specifically the press 12 includes a base 22 supporting the horizontal bed 24 on which a lower die or workpiece (not shown) may be positioned beneath the ram 14. Press 12 further includes superstructure 26 for supporting the ram 14, ram cylinder 20 and hydraulic apparatus 10. The ram 14 and ram cylinder 20 are part of the press structure 12.

The hydraulic apparatu 10 includes the hydraulic fluid tank 28 positioned in the base 22 of the press 12, pump 18, 'motor 30, hydraulic transformer 16, manually operated four-way valve 34, piloted four-way valve 38, switching four-way valve 40 and cam actuating structure 42 therefor, upper ram limit four-way valve 44 and cam actuating structure 46 therefor, foot valve 48, check valve 50, pressure relief valve 52 and pump bypass valve 54 connected as shown best in FIGURE 2. The upper ram limit four-way valve 44 and cam operating structure 46 therefor, the pump bypass valve 54, foot valve 48 and sequencing valve 36 may be eliminated along with their corresponding function as will be seen subsequently.

The pump 18 is capable of pumping approximately fifteen gallons per minute of hydraulic fluid at a pressure of one thousand pounds per square inch. As shown best in FIGURE 2, the pump is connected to the tank 28 through hydraulic conduit 56 and to the manually actuated four-way valve through the hydraulic conduit 58. The output of the pump 18 is addition-ally connected to the down-stream side of the check valve 50 through conduit 60 and is connected to the input side of the pump return valve 54 through the conduit 62. Pump 18 may be a Vickers Incorporated No. 104-D pump and is driven by motor 30 through output shaft 64 and the dog clutch structure 66.

The four-way valve 34 may be manually actuated by handle 32. Besides being connected to the output of the pump 18 through the conduit 58 valve 34 is connected through conduit 68 to the input side of the sequencing valve 36. The manually actuated four-way valve 34 is further connected to the input side of the foot valve 48 through conduit 70 and to the return side of the piloted four-way valve 38 by the pilot conduit 72. The valve 34 may be a Vickers Incorporated No. C-430A valve which in its actuated condition, as illustrated in FIGURE 2. vents the hydraulic conduit 78 from foot valve 48 and the pilot conduit 72 from the piloted four-way valve 38 to the tank 28 through the conduit 74 and connects the output of the pump 18 to the input side of the sequencing valve 36. In its reverse actuated condition the valve 34 vents the conduit 68 from the sequencing valve 36 to the tank 28 and applies hydraulic fluid at pump pressure through the foot valve 48 to the bottom of ram cylinder through

hydraulic conduits

70 and 146 to raise the ram 14 and applies hydraulic fluid under pressure in pilot conduit 72 to reset the piloted four-way valve 38. Valve 34 is also provided with a neutral unactuated position in which all conduits connected thereto are blocked.

The sequence valve 36 includes a check valve portion 76 through which hydraulic fluid is'passed by means of

conduits

78, 80 and 82 to the hydraulic transformer 16 or through

conduits

78 and 84 to the piloted four-way valve 38. Sequence valve 36 further includes a piloted relief valve portion 86 through which hydraulic fluid from the hydraulic transformer 16 may be returned to the tank 28 by way of

conduits

82, 80, and 78, sequence valve 36, conduit 68, four-Way valve 34 and conduit 74 should the check valve 50 fail to open due, for example, to a stripper or knock-out used with the press 12 on the return stroke of the ram 14. The sequence valve 36 may be a Vickers Incorporated No. RCT06-Al-l0.

The hydraulic transformer 16, as best shown in FIG- URE 1, includes top and

bottom end plates

88 and 90 and a cylinder 92 positioned between the top and

bottom end plates

88 and 90. The hydraulic transformer further includes a rod 94 secured to the bottom end plate 90 and having an opening 96 extending axially therethrough connected through the bottom end plate 90 to the conduit 82 and a piston 98 reciprocally mounted in the cylinder 92 and having a recess 100 therein receiving the upper end of the rod 94, as shown best in FIGURE 1. Suitable sealing structure may be provided between the upper end of the rod 94 and the recess 100 of the piston 98, between the outer surface of the piston 98 and the cylinder 92 and between the ends of the cylinder 92 and the top and

bottom end plates

88 and 90. The top and

bottom end plates

88 and 90 are held in assembly with the cylinder 92 by means of the longitudinally extending rods 104 which extend through the

end plates

88 and 98 at the corners of the end plates which may be held in position by bolts or the like.

The diameter of the piston 98 is chosen to have four times the area of the rod 94. Thus hydraulic fluid entering the recess 100 at, for example, a rate of fifteen gallons per minute under a pressure of one thousand pounds per square inch will cause movement of hydraulic fluid out of the top chamber 106 of the hydraulic transformer 16 to the top of cylinder 20 through conduit 108, four-way valve 38 and conduit 110 at sixty gallons per minute at a pressure of two hundred fifty pounds per square inch to move the ram 14 downward at a relatively fast speed, as for example six hundred inches per minute.

Conversely, on the return stroke of the ram 14, hydraulic fluid is forced out of the upper chamber 112 of cylinder 20, back through conduit 110, piloted four-way valve 38, conduit 108 and into chamber 106 of the hydraulic transformer 16. If the fluid returns to the hydraulic transformer in chamber 106 at a rate of fifteen gallons per minute, at a pressure of one thousand pounds per square inch, the hydraulic fluid will be forced out of the chamber 100 at a possible pressure of up to four thousand pounds per square inch at the rate of three and one-fourth gallons per minute.

The piloted four-way valve 38, as indicated, is connected to the sequencing valve 36 through

conduits

84 and 78 to the hydraulic transformer 16 through conduit 108 and to the ram cylinder 20 through the conduit 110. Four-way valve 38 has also been indicated as connected to the pilot conduit 72. Valve 38 is additionally connected to the pilot conduit 114 through the switching four-way valve 40 and to tank 28 through conduit 118. The piloted four-way valve 38 in its rightward or initial position, as shown in FIGURE 2, connects the chamber 106 of hydraulic transformer 16 to the chamber 112 of the ram cylinder 20. At this time the conduit 84 is blocked.

When the valve 38 is moved to the left on receipt of a piloting signal from pilot conduit 114, the chamber 112 of cylinder 20 is connected directly to the sequencing valve 36 through the

conduits

78 and 84 and the conduit 108 is blocked. On receipt of a pilot signal from pilot conduit 72, the valve 38 will return to the position shown in FIGURE 2.

Thus, in accordance with the position of the piloted four-way valve 38, hydraulic fluid through valve 38 for the actuation of the ram 14 may either come from the hydraulic transformer 16 actuated by hydraulic fluid from the sequence valve 36 or may be fed directly from the sequence valve 36 through valve 38 to the cylinder 20. The piloted four-way valve may be a Vickers Incorporated No. DG354060-20.

The switching four-way valve 40 is connected to the manual four-way valve 34 through conduit 68 and pilot conduit 116. Valve 40 is connected to the hydraulic fluid tank 28 through conduit 118. In the actuated position valve 40 connects pilot conduit 116 with pilot conduit 114 to shift the piloted four-way valve 38 to the left. In the unactuated condition the valve 40 closes the pilot conduit 116 and vents the pilot conduit 114 to the hydraulic fluid supply tank 28 through conduit 118. Valve 40 may be a Vickers Incorporated No. C572E valve.

The valve 40 is mechanically actuated by the cam actuating structure 42. operating in conjunction with a cam follower 120 connected to the valve 40. The cam actuating structure, as shown best in FIGURE 1, is carried on one end of a yoke 122 connected to the ram 14 and includes the vertically extending rod 124 and the cam 126 adjustably mounted on the rod 124. Thus, the switching four-way valve 40 is actuated in accordance with the vertical position of the ram 14.

The ram upper limit four-way valve 44 is connected by pilot conduit 128 to the conduit 68 from four-way valve 34 and is connected by pilot conduit 130 to the bypass valve 54. Valve 44 is further connected by a conduit 132 to the hydraulic fluid tank 28. In the unactuated condition shown, the valve 44 connects the pilot conduit 130 from bypass valve 54 to the tank 28 and closes the pilot conduit 128. On actuation by the cam actuating structure 46, the four-way valve 44 will provide a direct connection between the

pilot conduits

128 and 130 to actuate the bypass valve 54 and close the conduit 132.

The cam actuating structure 46 for the four-way valve 44 is secured to the other end of the yoke 122 on the ram 14 and includes the adjustable rod 134 and actuating cam 136. Thus, the actuation of the ram upper limit four-way valve 44 depends on the vertical position of the ram 14.

The bypass valve 54 is, as previously indicated, internally connected to the pump 18 through conduit 62 and is connected to the pilot conduit 128 through upper limit four-way valve 44 and pilot conduit 130. The bypass valve 54 is further connected to the hydraulic fluid tank 28 through the conduit 138. On receipt of a signal from the pilot conduit 130, the bypass valve 10 is actuated to bypass the hydraulic fluid from the pump 18 through the conduit 6-2 back to the tank 28 through conduit 138.

Thus, the return stroke of the ram 14 may be limited by the setting of the cam 136 since the valve 54 will open the bypass around the pump 18 when the upper limit valve 44 is actuated by the cam 136 to connect the

pilot conduits

128 and 130. The bypass valve 54 may be a Vickers Incorporated No. CT06B.

The pressure relief valve 52, as shown is connected to the chamber 106 of hydraulic transformer 16 by conduit 140 and is connected to the hydraulic conduit 68 through the conduit 142. The pressure relief valve 52 operates to return excess fluid pumped into the hydraulic transformer 16 from the chamber 112 of cylinder 20 to the tank 22 through

conduits

140, 142, 68 and 74 during the return stroke of the ram 14. The pressure relief valve 52 may be a Vickers Incorporated No. C-175-B valve.

The foot valve 48 is connected to the four-way valve 34 through the conduit 70, as previously indicated, and is connected to the bottom chamber 144 of cylinder 20 by the conduit 146. The foot valve 48 includes a check valve portion 148 through which hydraulic fluid is pumped into chamber 144 of cylinder 20 to provide the return stroke of the ram 14. The check valve part 150 of the foot valve 48 is spring loaded by spring 152 and opens on downward movement of the piston 154 in cylinder 20 on the downward stroke of the ram 14 sufficient to build a pressure in chamber 144 overcoming spring 152. The spring 152 is provided to prevent lowering of the ram 14 due to leakage of hydraulic fluid from cylinder 20 as the result of the weight of the ram 14 when the press 12 is left in an idle condition with the ram 14 up.

The over-all operation of the press 12 and hydraulic apparatus 10 includes a complete downward stroke of the ram 14 for forming a workpiece and a return stroke of the ram 14 into its upper position, as shown in FIG- URE 1, ready for a subsequent downward stroke. Thus, the cycle of the press 12 and hydraulic apparatus 10 starts with the ram 14 in an upper position, as shown in FIGURE 1.

With the ram 14 in the upper position and the manual four-way valve 34 unactuated the piston 98 of the hydraulic transformer 16 will be in its fully down position so that the chamber 106 will be filled with hydraulic fluid and the recess 100 will be empty. The. piloted four-way valve 38 will be positioned, as shown in FIG- URE 2, to provide a fluid path between

conduits

108 and 110 for communication between the chamber 106 of hydraulic transformer 16 and chamber 112 of cylinder 20.

The manual four-way valve 34 is moved to the left in FIGURE 2 to connect the pump 18 through

conduits

58, 68, 78, 80 and 82 to the hydraulic transformer 16 through the check valve portion 76 of the sequencing valve 36. Hydraulic fluid under pump pressure of, for example, one thousand pounds per square inch will therefor flow into the chamber 100 of the hydraulic transformer 16 at a rate of, for example, fifteen gallons per minute. The piston 98 of the hydraulic transformer 16 is moved upward so that hydraulic fluid is forced out of chamber 106 of hydraulic transformer 16 at a pressure of two hundred fifty pounds per square inch at a rate of sixty gallons per minute through

conduits

108 and 110 into the chamber 112 of cylinder 20. The piston 154 and thus the ram 14 of the press 12 connected thereto is therefore moved down rapidly to approach a workpiece (not shown) which may be on the bed 24 of the press 12.

On the downward movement of the ram 14 the piston 154 forces the hydraulic fluid from the chamber 144 through conduit 146, the spring loaded check valve part 150 of foot valve 48, conduit 70, four-way valve 34 and conduit 74 to tank 28.

As the ram 14 approaches the workpiece the cam 126 carried by the ram 14 will actuate the four-way switching valve 40 to connect the pilot lines 116 and 114, whereby the piloted four-way valve 38 is moved to the left in FIG- URE 2 to block the conduit 108 and connect the

conduits

84 and 110. The hydraulic fluid passed from the sump 18 through conduit 68 and sequencing valve 36 will now pass directly through

conduits

78, 84 and 110 into the chamber 112 of cylinder 20 at a pressure of one thousand pounds per square inch at a pump rate of fifteen gallons per minute. The remainder of the stroke of the ram 14 during which a workpiece is engaged and work such as trimming performed thereon is carried out at a lower speed under higher pressure.

On subsequent actuation of the four-way valve 34 to the right in FIGURE 2 the hydraulic fluid from pump 18 is pumped .into the chamber 144 of cylinder 20 to raise the ram 14 through conduit 70, the check valve portion 148 of foot valve 48 and conduit 146. Raising of the piston 154 in cylinder 20 causes the hydraulic fluid in the upper part 112 of cylinder 20 to be discharged therefrom through conduit 110 back through conduit 108, back into chamber 106 of the hydraulic transformer 16 through the piloted four-way valve 38 which has been returned to the right due to a pilot signal from the pilot conduit 72 which is connected to the conduit 70.

The hydraulic fluid in the chamber 106 will bottom the piston 98 on the rod 94 since the cylinder 20 has a greater capacity in the upper chamber 112 than the capacity of chamber 106. The capacity of chamber 106 is slightly greater than the capacity of chamber 112 with the ram in position to actuate valve 40. The excess hydraulic fluid pumped into chamber 106 will cause actuation of the pressure relief valve 52 and the excess hydraulic fluid will be passed from the chamber 106 back to the hydraulic fluid tank 28 through conduit 140, pressure relief valve 52, conduit 142, conduit 68, four-way valve 34 and conduit 74.

The hydraulic fluid will be returned to the chamber 106 at approximately pump pressure of one thousand pounds per square inch and at a rate of fifteen gallons per minute. The fluid will however be forced out of recess at approximately four thousand pounds per square inch and at a rate of three and one-fourth gallons per minute. The hydraulic fluid forced out of the recess 100 will be returned to the pump side of the four-way valve 34 through check valve 50.

If due to knock-out or stripper structure connected to the press ram 14 operable on the return stroke of the press ram the pressure in the conduit 58 exceeds that in the conduit 82 so that return of hydraulic fluid from the hydraulic transformer through check valve 50- is not possible, the additional pressure in conduit 78 will actuate the pressure relief valve portion 86 of the sequencing valve 36 to return the hydraulic fluid from the hydraulic transformer 16 through the conduit 68 to the hydraulic fluid tank 22 through four-way valve 34 and conduit 74.

As the ram 14 proceeds upwardly, the cam 136 will actuate the four-way ram upper limit valve 44 to connect the

pilot lines

128 and 130, whereby the bypass valve 54 is actuated to cause bypassing of the hydraulic fluid from the pump 18 back to the hydraulic fluid supply tank 28 through

conduits

62 and 138. The effective height of the return stroke of the ram 14 is thus limited by the height of the cam 136.

Thus, it is seen that there is provided hydraulic actuating apparatus for a press capable of moving the ram toward a workpiece at a fast speed, as, for example, six hundred inches per minute at a relatively low pressure 'and subsequently moving the ram toward the workpiece at a slower speed at 'a much higher pressure which hydraulic apparatus includes a single pump operating at a single speed in contrast to the prior more complicated hydraulic apparatus for performing a similar function including 'a plurality of pumps or motors and/ or variable pumps and motors and complicated connections therefor which have been more expensive and less eflicient than the hydraulic apparatus disclosed including a single motor and a hydraulic transformer.

While one embodiment of the present invention has been considered in detail, it will be understood that other embodiments and modifications thereof are contemplated. It is the intention to include all embodiments and modifications as are defined by the appended claims within the scope of the invention.

What I claim as my invention is:

1. Hydraulic actuating apparatus for a hydraulic press including a press ram and a ram piston and ram cylinder for moving the press ram, said actuating apparatus comprising a source of hydraulic fluid, a pump connected to the source of hydraulic fluid, a motor connected to drive the pump to provide hydraulic fluid at the output thereof at a high pressure and low rate, a hydraulic transformer connected between the pump and ram cylinder operable to receive hydraulic fluid from the pump at the high pressure and low rate and to supply hydraulic fluid to the ram cylinder at a high rate and low pressure in response thereto, means responsive to the position of the ram for bypassing hydraulic fluid from the pump around the hydraulic transformer and directly to the ram cylinder and hydraulic means for returning the ram to a predetermined position including a piloted pump bypass valve and pilot valve means operable in response to the position of the press ram for actuating the piloted pump bypass valve to limit the return movement of the ram.

2. Apparatus as set forth in claim 1 wherein the means for bypassing the hydraulic fluid around the hydraulic transformer comprises a piloted valve for effecting the hydraulic fluid bypass on actuation thereof, a switching valve operable on actuation to provide a pilot signal to the pilot valve for actuation thereof and cam and cam follower mechanism operable between the press ram and switching valve for actuation of the switching valve in response to a predetermined position of the ram.

3. Apparatus as set forth in claim 1 wherein the hydraulic transformer is recharged on the return stroke of the press ram and wherein the ram cylinder has a larger capacity than the hydraulic transformer and means connected to the hydraulic transformer for bypassing excess hydraulic fluid back to the hydraulic fluid source on the return stroke of the ram after the hydraulic transformer is recharged.

4. Apparatus as set forth in claim 1 and further including a foot valve in series between the ram cylinder and pump for permitting substantially unrestricted pumping of high pressure fluid into the ram cylinder during the return stroke of the ram and for permitting biased return of hydraulic fluid in the ram cylinder to the source of hydraulic fluid during the work forming stroke of the ram to prevent movement of the ram in a work forming direction due to the weight thereof.

5. Hydraulic actuating apparatus for a hydraulic press including a ram and a hydraulic cylinder and piston for actuating the ram in work forming and return str'okes comprising a source of hydraulic fluid, a pump connected to the source of hydraulic fluid, a motor connected to the pump for driving the pump to provide a hydraulic output therefrom at a predetermined pressure and a predetermined rate, a four-way actuating valve in the pump output line and a sequencing valve in series, a hydraulic transformer for receiving hydraulic fluid at the predetermined pressure and rate from the sequencing valve and providing hydraulic fluid at a lower pressure and higher rate in response thereto to the ram cylinder connected to receive the output of the sequencing valve, a piloted valve connected to the sequencing valve, hydraulic transformer and ram cylinder for bypassing the hydraulic signal at the predetermined pressure and rate from the pump around the hydraulic transformer and directly to the ram actuating cylinder on actuation there- .up-stroke of the ram.

of, a four-wayswitching valve operable on actuation to actuate the piloted four-way valve and-means resp'onsive to the ram position for actuating the switching valve to bypass the hydraulic fluid from the pump directly to the ram actuating valve through the sequencing valve and piloted valve whereby initial movement of the press ram during a work forming stroke is at a high speed under a low pressure and subsequent movement of the ram in the work forming stroke is at a low speed under a high pressure.

6. Apparatus as set forth in claim 5 and further including a connection between the manual four-way valve and the ram cylinder for providing hydraulic fluid to the ram cylinder during the return stroke of theram and further including a foot valve connected. between the manual four-way valve and ram cylinder for preventing Work forming movement of the ram due to the weight of the ram.

7. Apparatus as set forth in claim 5 wherein the ram cylinder is of greater capacity than the hydraulic transformer whereby the hydraulic transformer is fully charged on the return stroke of the ram and a pressure relief valve connected between the hydraulic transformer and the source of hydraulic fluid during the return stroke of the ram.

8. Apparatus as set forth in claim 5 and further including a piloted pump bypass valve for bypassing hydraulic fluid around the pump on actuation thereof, a pilot valve for actuating the piloted pump bypass valve in response to actuation thereof and means operably associated with the ram for actuating the pilot valve on the ram reaching an upper limit in its return stroke.

9. Apparatus as set forth in claim 5 and further including a sequence valve between the pump and hydraulic transformer including a piloted pressure relief portion for returning the hydraulic fluid from the high pressure side of the hydraulic transformer during the up-stroke of a ram in response to knock-out structure operable on the 10. Apparatus as set forth in claim 5 wherein the hydraulic transformer comprises a pair of end plates, a cylinder extending between the pair of end plates and means within the cylinder for providing a high volume, low pressure output from one end of the cylinder in response to a high pressure, low volume input to the other end of the cylinder.

11. Apparatus as set forth in claim 10 wherein the means within the cylinder comprises a rod having an opening extending therethrough connected to one of the end plates at one end of the cylinder for receiving the high pressure, low volume signal therethrough and a piston within the cylinder having a recess in one end thereof into which the rod is inserted.

12. Apparatus as set forth in claim 5 and further including a connection between the manual four-way valve and the ram cylinder for providing hydraulic fluid to the ram cylinder during the return stroke of the ram.

13. Apparatus as set forth in claim 5 and further including a foot valve connected between the manual four-Way valve and ram cylinder for preventing work forming movement of the ram clue to the weight of the ram.

14. Hydraulic actuating apparatus for a hydraulic press including a press ram and a ram piston and ram cylinder for moving the press ram, said actuating apparatus comprising a source of hydraulic fluid, a pump connected to the source of hydraulic fluid, a motor con nected to drive the pump to provide hydraulic fluid at the output thereof at a high pressure and low rate, a hydraulic transformer connected between the pump and ram cylinder operable to receive hydraulic fluid from the pump at the high pressure and low rate and to supply hydraulic fluid to the ram cylinder at a high rate and low pressure in response thereto, means responsive to the position of the ram for bypassing hydraulic fluid from the pump around the hydraulic transformer and directly to the ram cylinder and a check valve between the hydraulic transformer and the pump for returning hydraulic fluid to the pump on the return stroke of the press ram and a piloted pressure relief valve between the hydraulic transformer and the source of hydraulic fluid for providing an alternate discharge path for the fluid in the hydraulic transformer during the return stroke of the press ram.

15. Hydraulic actuating apparatus for a hydraulic press including a press ram and a ram piston and ram cylinder for moving the press ram, said actuating apparatus comprising a source of hydraulic fluid, a pump connected to the source of hydraulic fluid, means for driving the pump to provide hydraulic fluid at the output thereof at a high pressure and low rate, means operable between the output of the pump and the press ram for feeding hydraulic fluid into the ram cylinder at -a high rate and low pressure in response to operation of said pump during an initial portion of the work forming stroke of the ram and for feeding hydraulic fluid at the pump pressure and rate into the ram cylinder during the remainder of the ram work forming stroke and a check valve between the last mentioned means and the pump for returning hydraulic fluid to the pump on the return stroke of the press ram and a piloted pressure relief valve between the last mentioned means and the source of hydraulic fluid for providing an alternate discharge path for the fluid in the last mentioned means during the return stroke of the press ram.

16. Hydraulic actuating apparatus for a hydraulic press including a press ram and a ram piston and ram cylinder for moving the press ram, said actuating apparatus comprising a source of hydraulic fluid, a pump connected to the source of hydraulic fluid, means for driving the pump to provide hydraulic fluid at the output thereof at a high pressure and low rate, means operable between the output of the pump and the press ram for feeding hydraulic fluid into the ram cylinder at a high rate and low pressure in response to operation of said pump during an initial portion of the work [forming stroke of the ram and for feeding hydraulic fluid at the pump pressure and rate into the ram cylinder during the remainder of the ram work forming stroke, and hydraulic means for returning the ram to a predetermined position including a piloted pump bypass'valve and pilot valve means operable in response to the position of the press ram Er actuating the piloted pump bypass valve to limit the return movement of the ram.

References Cited by the Examiner UNITED STATES PATENTS 1,256,451 2/ 1918 Ensign et al 6054.5 2,183,983 12/1939 Bostwick 6052 2,253,617 8/1941 Griflith 60-52 2,408,513 10/ 1946 Gunderson 6054.6

EDGAR W. GEOGHEGAN, Primary Examiner.

Claims

1. HYDRAULIC ACTUATING APPARATUS FOR A HYDRAULIC PRESS INCLUDING A PRESS RAM AND A RAM PISTON AND RAM CYLINDER FOR MOVING THE PRESS RAM, SAID ACTUATING APPARATUS COMPRISING A SOURCE OF HYDRAULIC FLUID, A PUMP CONNECTED TO THE SOURCE OF HYDRAULIC FLUID, A MOTOR CONNECTED TO DRIVE THE PUMP TO PROVIDE HYDRAULIC FLUID AT THE OUTPUT THEREOF AT A HIGH PRESSURE AND LOW RATE, A HYDRAULIC TRANSFORMER CONNECTED BETWEEN THE PUMP AND RAM CYLINDER OPERABLE TO RECEIVE HYDRAULIC FLUID FROM THE PUMP AT THE HIGH PRESSURE AND LOWER RATE AND TO SUPPLY HYDRAULIC FLUID TO THE RAM CYLINDER AT A HIGH RATE AND LOW PRESSURE IN RESPONSE THERETO, MEANS RESPONSIVE TO THE POSITION OF THE RAM FOR BYPASSING HYDRAULIC FLUID FROM THE PUMP AROUND FOR BYPASSING TRANSFORMER AND DIRECTLY TO THE RAM CYLINDER AND HYDRAULIC MEANS FOR RETURNING THE RAM TO A PREDETERMINED POSITION INCLUDING A PILOTED PUMP BYPASS VALVE AND PILOT VALVE MEANS OPERABLE IN RESPONSE TO THE POSITION OF THE PRESS RAM FOR ACTUATING THE PILOTED PUMP BYPASS TO LIMIT THE RETURN MOVEMENT OF THE RAM.