US2683966A

US2683966A - Hydraulic press

Info

Publication number: US2683966A
Authority: US
Inventors: Tyler Ransom
Original assignee: Oilgear Co
Current assignee: Oilgear Co
Priority date: 1953-06-08
Filing date: 1953-06-08
Publication date: 1954-07-20
Anticipated expiration: 1971-07-20

Description

July 20, 1954 R, TYLER 2,683,966

HYDRAULIC PRESS Filed June 8, 1953 46-1L| 4o 43 4H 42 39 FIG. 1

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f \\k\\ RANSOM TYLER 8 9/ n3 l2J BY 6 Mygzugg Patented `uly 20, 1954 UNITED STATES PATENT OFFICE HYDRAULIC PRESS tion of Wisconsin Application June 8, 1953, Serial No. 360,274

(Cl. (S- 51) 8 Claims. 1

This invention relates to machines for performing pressing operations. The machine to which the invention relates in particular has a reciprocating hydraulic motor for exerting forces upon work pieces, a pump for supplying motive liquid to the motor to energize it, and means for controlling the ow of liquid to and from the motor.

An object of the invention is to provide a hydraulic system whereby a reciprocating hydraulic motor powered by a pump having a relatively small volumetric capacity may be operated at very high speeds.

Another object is to provide a hydraulic press which is simple in construction and relatively economical to manufacture.

These and other objects and advantages will appear from the following description of the hydraulic press shown schematically in the accompanying drawing in which the views are as follows:

Fig. 1 is a diagram of the hydraulic circuit oi a press in which the invention is embodied.

Figs. 2 and 3 are views showing a control valve with its valve member o1' plunger in positions different from the that shown in Fig. 1.

Fig. 4 is a View showing a foot valve and a pilot valve with the plungers thereoic in positions diiferent from those shown in Fig. 1.

A system embodying the invention has been shown in Fig. 1 as being applied to a hydraulic press of which only the reciprocating hydraulic motor has been shown because the remainder of the press forms no part of the invention. The motor is of the dierential type and includes a cylinder I, which has been shown arranged in a vertical position, and a ram 2 having a piston 3 xed upon its upper end and closely tted in cylinder I. Ram 2 is closely tted in the lower end of cylinder I and extends therethrough for connection to a plate or other means (not shown) through which ram 2 may exert pressing forces upon the work to be operated upon.

Ram 2 is so proportioned that the pressure area on the upper end of piston 3 is several times, such as four or five times, the pressure area on the lower end of piston 3 so that motive liquid supplied to the lower end of cylinder I at a given rate will move ram 2 upward at several times the speed at which it will be moved downward by liquid supplied to the upper end of cylinder I at the same rate.

While motor I-3 has been shown arranged in a position to act downward, it may be arranged in other positions and it is to be understood that directional terms used herein refer to the drawing and not to the physical structure. Also, cylinder I may be stationary and ram 2 be reciprocable, in which case motive liquid is supplied to opposite ends of piston 3 alternately through channels connected to opposite ends of cylinder I as shown, or ram 2 may be stationary and cylinder I be reciprocable in which case motive liquid is supplied to opposite ends of piston 3 alternately through channels which extend through ram 2 and terminate at opposite sides of piston 3 as is well known.

Liquid for energizing motor is supplied by a pump i which draws liquid from a reservoir 5 and discharges it into a channel 6. Pump 4 may be a constant displacement pump having a volumetric capacity only sufficient to move ram 2 downward at the correct speed to perform a given pressing operation or it may be a Variable displacement pump which may be adjusted to vary the pressing speed of ram 2.

The ow of liquid from pump 4l to motor I-3 is controlled by a control valve 1 shown as including a valve body 8 having an axial bore 9 formed therein and a valve plunger Iii arranged within bore 9 to control communication between ve annular grooves or ports II, i2, i3, I6 and i5 which are formed in the wall of bore 9. Port II communicates with channel G. Port I2 is connected to the upper end of cylinder I by channel It. Port I3 is connected to the lower end of cylinder i by a channel Il having a restriction such as a choke i8 connected therein. Ports M- and I5 communicate with an exhaust channel i9 which discharges into reservoir 5. Channel i9 has been shown as discharging freely into reservoir 5 but sometimes the system is so arranged that there is danger of liquid seeping out of certain valves when the press is idle in which case channel I9 discharges into reservoir 5 through a relief valve (not shown) which will open at a very low pressure such as l0 p. s. i.

In actual practice, valve I ordinarily is operated hydraulically and is controlled by a pilot valve which is operated electro-magnetically under the control of suitable switches. But since such control or a valve is well known and does not per se form any part of the present invention, valve I has been shown as being manually operable by means of a lever 2G which has its lower end suitably connected to the stem of plunger I and which is pivoted intermediate its ends to a bracket 2l carried by valve body 8.

Ram 2 is adapted to be moved downward at high speed by a large volume of liquid supplied to the upper end of cylinder l from an accumulator in addition to the liquid supplied thereto by pump il. Communication between accumulator 25 and the upper end of cylinder l is contrclled by a pilot controlled foot valve 26 which has a body 2l having an axial bore 28 and an axial port 2S formed therein concentric with each other and an annular port 3l) formed therein between port 2S and the end of bore 2B. Port 3e is connected to channel i6 by a channel 3i. Port 29 is connected by channel 32 to accurnulator 25 which is also connected to reservoir 5 by a channel 33 having low pressure relief valve 34 connected therein.

The peripheral edge of port 2S constitutes an annular valve seat for a valve plunger 35 which normally engages the valve seat and is formed integral with a piston 3S tted in bore 2S. Plunger 35 is smaller in diameter than piston 36 to provide an annular lifting area 3l' on the lower end of piston 35. Plunger 3S is urged against the valve seat around port 29 by a spring 38 arranged within piston 36 and reacting against a pilot valve body 39 which is fastened to body 2'! and closes the upper end of bore 28.

Pilot valve body 3Q has an axial bore ll formed therein and three annular grooves or ports 4l, l2 and cl3 formed in the wall of bore 4U. Communication between those ports is controlled by a valve plunger d4 which is tted in bore 4U. Port 4l communicates with the bore 28 in body 2l. Port 2 and the right end of bore il are connected by a branched channel to channel 32. Port i3 is connected to channel I by a. channel 156. The

left end of bore it is connected to channel Il by f a channel c7.

OPERATION Assuming that the parts are in the positions shown in Fig. l, that pump 4 is running and that accumulator 25 has been charged with liquid at a relatively low pressure such as 100 p. s. i., the press will operate as follows:

Idle

With the plunger le of control valve 'l in its central or neutral position as shown in Fig. l, pump Il is bypassed through valve body 8 and port i3 is blocked from any other port which causes ram 2 to be held up by the liquid trapped in the lower end of cylinder l.

The weight of rain 2 and the parts iixed thereto creates pressure in the lower part of cylinder l and that pressure extends through channels Il and il to the left end of bore 4b and holds pilot valve plunger is in its right hand position. Pressure extends from accumulator 25 through channel 32 into port 29 and tends to raise plunger 25 but it cannot do so because accumulator pressure extends from channel 32 through channel l5 and pilot valve body 39 into the upper end of bore 28 and acts upon piston 36 which has a pressure area much larger than that of plunger 35. Accumulator pressure also extends from channel 45 into the right end of bore lil and tends to move plunger @il toward the left but it cannot do so because the pressure in the left end of bore 4d is higher than the accumulator pressure.

Downstoke When plunger IE of control valve 1 is shifted into the position shown in Fig. 2, it connects channel S to channel E6, which causes the liquid discharged by pump il to flow through channel i6 to the upper end oi' cylinder l, and it connects channel il to channel i9 which permits ram 2 to descend by gravity and cause piston 3 to eject liquid from the lower part of cylinder i through channel Il, valve body 8 and channel l into reservoir E. Choke IS prevents ram 2 from dropping freely but permits it to descend rapidly.

Connecting channel Il to channel I9 also drops the pressure in the left end of pilot valve bore lil substantially to zero and permits liquid to flow from accumulator 25 through channel 45 into the right end of bore 4G and move pilot valve plunger 54 into the position shown in Fig. 4, thereby connecting the upper end of bore 28 to channel d and reducing the pressure on piston 3G to a low value because ram 2 is at that instant moving downward so fast that pump l cannot create much if any pressure in channels I6 and 46.

Reducing the pressure on piston 38 permits the accumulator pressure in port 29 to raise plunger and piston 3S and then liquid will flow from accumulator 35 through channel 32, ports 29 and 3Q and channels .al and i5 to the upper end of cylinder' i and create pressure therein and in the upper end of bore 2S but that pressure will be less than the accumulator pressure due to the force exerted upon piston 35 by a spring The liquid delivered to the upper end of cylinder l from pump 4 and from accumulator will move ram 2 downward at a very high speed which is proportional to the rate at which liquid can flow through choke I8.

Ram 2 will continue downward at high speed until the work is engaged and then the ilow through foot valve 265 will cease because the pressure prevailing at that instant in the upper end of cylinder I is insuilicient to move ram 2 against the resistance of the work. The instant that flow through foot valve 2G ceases, the pressure in the upper end of bore 28 will rise suiciently to enable spring 35 to cause plunger 35 to close port E9.

After port 2S is closed, ram 2 will continue to move downward but at a slow speed proportional to the rate at which pump 4 delivers liquid to the upper end of cylinder l. Pump Ll will create in channel i6 and in cylinder i a pressure sufcient to enable ram 2 to perform the pressing operation and that pressure will extend from pressure channel E5 through channel 413 and ports Il@ and i into the upper end of bore 2G and positively hold foot valve 26 closed.

Upstroke When the pressing operation is completed, plunger IS of control valve 'I is shifted into the position shown in Fig. 3. As plunger lil passes through neutral, channel l@ is connected zncinentarily to exhaust channel I9 which causes the pressure in the upper end of cylinder i to be reduced substantially to Zero. With plunger l; in the position shown in 3, pump Il will discharge liquid into channel il and the lower end of channel It is blocked so that no liquid can escape therefrom into reservoir 5.

Some of the liquid discharged into channel Il will flow therefrom through channel il into bore lil and move pilot valve plunger into the position shown in Fi l and the remainder of the liquid will flow through channel Il into the lower end ci cylinder i and cause ram 2 to move upward and eject liquid from the upper end of cylinder l into channel i6. Since the lower end of channel l is blocked and foot valve 26 is closed. at this time, the liquid ejected into channel i6 will create a pressure which will act upon annular lifting area 31 of valve and will raise piston 36 and valve plunger 35, thereby permitting liquid to flow from the upper end of cylinder l through channels l and 3|, foot valve 26 and channel 32 into accumulator 25 and recharge it.

Since liquid was delivered to the upper end of cylinder I by pump i during the downstroke, the volume of liquid to be ejected from the upper end of cylinder l is in excess of the volume required to recharge accumulator 25. After accumulator 25 is fully charged, the excess liquid is ejected through channel 33 and relief valve 34 into reservoir 5, the pressure required to open relief valve 34 being the same as the accumulator pressure.

When ram 2 reaches the end of its upstroke or has been raised to a desired height, control valve 'l is ordinarily adjusted to its neutral position, thereby completing a cycle of operations, but if the work can be changed quickly enough, valve l' may be adjusted to start a second cycle of operations.

It has been found in actual practice that the press can perform more cycles of operation per minute than is ordinarily possible with other types of hydraulic speed presses and that reversal takes place without the shocks which are inherent in the prior presses.

The hydraulic system described herein may be modiied in various ways without departing from the scope of the invention which is hereby claimed as follows:

l. A hydraulic system comprising a hydraulic motor which includes a cylinder and a ram having a piston nxed thereon and iitted in said cylinder, said ram dividing said cylinder into a large capacity chamber and a small capacity chamber, a pump connected to said motor for supplying motive liquid thereto to energize the same, a control valve connected between said pump and said motor and adapted to direct liquid from said pump to said chambers alternatively or to cut 01T flow of liquid from said pump to said motor, an accumulator containing liquid under pressure, means for connecting said accumulator to said large chamber including a hydraulically operated foot valve which normally is closed and blocks communication between said accumulator and said large chamber, and means responsive either to the accumulator pressure exceedingthe pressure in said small chamber or to the pressure in said small chamber exceeding the accumulator pressure for causing said foot valve to open.

2. A hydraulic system comprising a hydraulic motor which includes a cylinder and a ram having a piston fixed thereon and iitted in said cylinder, said ram dividing said cylinder into a large capacity chamber and a small capacity chamber, a pump connected to said motor for supplying motive liquid thereto to energize the same, a control valve connected between said pump and said motor and adapted to direct liquid from said pump to said chambers alternatively or to cut off flow of liquid from said pump to said motor, an accumulator containing liquid under pressure, means for connecting said accumulator to said chamber including a normally closed foot valve having a holding area to which pressure may be applied to hold said foot valve closed and two lifting areas which are connected to said accumulator and to said large chamber and upon which pressure may act to open said foot valve, and means for applying pressure to said holding area including a pilot valve responsive to the pressure in said small chamber exceeding the pressure in said accumulator for connecting said holding area to said accumulator and responsive to the 6 pressure in said accumulator exceeding the pressure in said small chamber for connecting said holding area to said large chamber.

3. A hydraulic system comprising a hydraulic motor which includes a cylinder and a ram having a piston iixed thereon and fitted in said cylinder, said ram dividing said cylinder into a large capacity chamber and a small capacity chamber, a pump connected to said motor for supplying motive liquid thereto to energize the same, a control valve connected between said pump and said motor and adapted to direct liquid from said pump to said chambers alternatively or to out oil flow of liquid from said pump to said motor, an accumulator containing liquid under pressure, means for connecting said accumulator to said large chamber including a foot valve body having two ports formed therein and connected to said accumulator and to said large chamber respectively, a valve plunger normally closing one o1' said ports and exposed to the pressure therein, a spring for urging said plunger toward closed position, a piston fitted in said valve body and having one of its ends fixed to said plunger and exposed to the pressure in the other of said ports and having a holding area to which pressure may be applied to hold said plunger in closed position, and means for applying pressure to said holding area including a pilot valve responsive 'to the pressure in said small chamber exceeding the pressure in said accumulator for connecting said holding area to said accumulator and responsive to the pressure in said accumulator exceeding the pressure in said small chamber for connecting said holding areato said large chamber.

4. A hydraulic system comprising a hydraulic motor which includes a cylinder and a ram having a piston fixed thereon and tted in said cylinder, said ram dividing said cylinder into a large capacity chamber and a small capacity chamber, a pump connected to said motor for supplying motive liquid thereto to energize the same, a control valve connected between said pump and said motor and adapted to direct liquid from said pump to said chambers alternatively or to cut off flow of liquid from said pump to said motor, an accumulator containing liquid under pressure, means for connecting said accumulator to said large chamber including a foot valve body having two ports formed therein and connected to said accumulator and to said large chamber respectively, a valve plunger normally closing one of said ports and exposed to the pressure therein, a spring for urging said plunger toward closed position, a piston tted in said valve body and having one of its ends nxed to said plunger and exposed to the pressure in the other of said ports and having a holding area to which pressure may be applied to hold said plunger in closed position, means for applying pressure to said holding area including a pilot valve body having a bore communicating with said holding area, two iluid channels connecting said bore to said accumulator and to said large chamber respectively, a pilot valve plunger arranged in said bore for connecting said holding area either t0 one or the other of said channels, and channel means connecting opposite ends of said bore to said accumulator and to said small chamber respectively.

5. A hydraulic system comprising a hydraulic motor which includes a cylinder and a ram having a piston nxed thereon and fitted in said cylinder, said ram dividing said cylinder into a large capacity chamber and a small capacity chamber, a pump for supplying motive liquid to said motor to energize the same, an accumulator containing liquid under pressure, means for connecting said accumulator to said large chamber including a hydraulically operated foot valve which normally is closed and blocks communication between said accumulator and said large chamber, means responsive either to the accumulator pressure exceeding the pressure in said small chamber or to the pressure in said small chamber exceeding the accumulator pressure for causing said foot valve to open, a control Valve body, a rst fluid channel connecting said pump to said control valve body, a second and a third fluid channel connecting said control valve body to said large chamber and to said small chamber respectively, and a plunger fitted in said control valve body and adjustable to three positions in the first oi which it connects said iirst and second channels to exhaust and blocks the end ci said third channel, in the second of which it connects said first channel to said second channel and connects said third channel to exhaust and in the third of which it connects said first channel to said third channel and blocks the end of said second channel.

6. A hydraulic system comprising a hydraulic motor which includes a cylinder and a ram having a piston xed thereon and tted in said cylinder, said ram dividing said cylinder into a large capacity chamber and a small capacity chamber, a pump for supplying motive liquid to said motor to energize the same, an accumulator containing liquid under pressure, means for connecting said accumulator to said chamber including a normally closed foot valve having a holding area to which pressure may be applied to hold said foot valve closed and two lifting areas which are connected to said accumulator and to said large chamber and upon which pressure may act to open said foot valve, means for applying pressure to said holding area including a pilot valve responsive to the pressure in said small chamber exceeding the pressure in said accumulator for connecting said holding area to said accumulator and responsive to the pressure in said accumulator exceeding the pressure in said small chamber for connecting said holding area to said large chamber, a control valve body, a rst fluid channel connecting said pump to said control valve body, a second and a third fluid channel connecting said control valve body to said large chamber and to said small chamber respectively, and a plunger fitted in said control valve body and adjustable to three positions in the first of which it connects said first and second channels to exhaust and blocks the end of said third channel, in the second of which it connects said rst channel to said second channel and connects said third channel to exhaust and in the third of which it connects said first channel to said third channel and blocks the end of said second channel.

7. A hydraulic system comprising a hydraulic motor which includes a cylinder and a ram having a piston fixed thereon and tted in said cylinder, said ram dividing said cylinder into a large capacity chamber and a small capacity chamber, a pump for supplying motive liquid to said motor to energize the same, an accumulator containing liquid under pressure, means for connecting said accumulator to said large chamber including a foot valve body having two ports formed therein and connected to said accumulator and to said large chamber respectively, a valve plunger' normally closing one of said ports and exposed to the pressure therein, a spring for urging said plunger toward closed position, a piston fitted in said valve body and having one of its ends xed to said plunger and exposed to the pressure in the other of said ports and having a holding area to which pressure may be applied to hold said plunger in closed position, means for applying pressure to said holding area including a pilot valve responsive to the pressure in said small chamber exceeding the pressure in said accumulator for connecting said holding area to said ccumuiator and responsive to the pressure in said accumulator exceeding the pressure in said small chamber for connecting said holding area to said large chamber, a control valve body, a first fiuid channel connecting said pump to said control valve body, a second and a third uid channel connecting said control valve body to said large chamber and to said small chamber respectively, and a plunger fitted in said control valve body and adjustable to three positions in the first of which it connects said rst and second channels to exhaust and blocks the end of said third channel, in the second of which it connects said first channel to said second channel connects said third channel to exhaust and in the third of which it connects said iirst channel to said third channel and blocks the end of said second channel.

8. A hydraulic system comprising a hydraulic motor which includes a cylinder and a ram having a piston lixed thereon and tted in said cylinder, said ram dividing said cylinder into a large capacity chamber and a small capacity chamber, a pump for supplying motive liquid to said motor to energize the same, an accumulator containing liquid under pressure, means for connecting said accumulator to said large chamber including a foot valve body having two ports formed therein and connected to said accumulator and to said large chamber respectively, a valve plunger normally closing one ci Said ports and exposed to the pressure therein, a spring for urging said plunger toward closed position, a piston fitted in said valve body and having one of its ends ixed to said plunger and exposed to the pressure in the other of said ports and having a holding area to which pressure may be applied to hold said plunger in closed position, means for applying pressure to said holding area including a pilot valve body having a bore communicating with said holding area, two fluid channels connecting said bore to said accumulator and to said large chamber respectively, a pilot valve plunger arranged in said bore for connecting said holding area either to one or the other of said channels, cannel means connecting opposite ends of said bo-re to said accumulator and to said small chamber respectively, a control valve body, a iirst fluid channel connecting said pump to said control valve body, a second and a third iiuid channel connecting said control valve body to said large chamber and to said small chamber respectively, and a plunger fitted in said control valve body and adjustable to three positions in the rst or which it connects said iirst and second channels to exhaust and blocks the end of said third channel, in the second of which it connects said first channel to said second channel and connects said third channel to exhaust and in the third of which it connects said first channel to said third channel and blocks the end of said second channel.

No references cited.