US2990687A

US2990687A - Hydro-pneumatic press

Info

Publication number: US2990687A
Application number: US861580A
Authority: US
Inventors: Charles H Mccrea
Original assignee: Individual
Current assignee: Individual
Priority date: 1959-12-23
Filing date: 1959-12-23
Publication date: 1961-07-04
Anticipated expiration: 1978-07-04

Description

July 4, 1961 C. H. M CREA HYDRO-PNEUMATIC PRESS Filed Dec. 23, 1959 Fig. 2. 70 ea l E A w: Z

a if &//

Fig. 4.

INVENTOR Charles H. McCrea BY ZWIW new and unique press which is controlled directly bylinput of pneumatic pressure and which is actuated by hydraulic forces in such a way as to have a first stage of operation having an inherently low force to movement ratioand a second phase of operation which has a high force to movement ratio due to the action of an integral intensifier. v

Anotherobject of this invention is to provide a novel press having a housing and a press ram which is reciprocally mounted within the housing. The bottom portion of the ram opens to the housing and the top portion. of

the housing forms a fluid seal where the housing and the ram areslidably engaged. The spacing within the hous- United States Patent Q ing between the housing and the ram walls and a portion 1 of the interior of the ram are filled with a hydraulic fluid. A pneumatically actuated piston is mounted 'withinthe ram on an air cushion over the hydraulic fluid to. force the hydraulic fluid down through the bottom of thev ram and into the housing. The force thus generated is translated into physical movement of the ram upwardly to form a press function.

As a further object of the invention the bottom of: the piston is formed with a stem formed to mate a restricted aperture on the bottom of the ram. When the piston is moved down to the point where the stem engages the aperture fluid communication between the ram andoil: reservoir is blocked to cause a hydraulic intensifying action for the generation of extremely high hydraulic pressures.

A feature and advantage of this invention is that the press requires only three basic parts which are relatively movable to each other, a housing, a ram and a piston.

An other feature and advantage of this invention is that the intensifier comprises only the integral structure of the piston and the ram in such a way as to completely eliminate the need of external hydraulic valving and other intensifying arrangements previously employed to create fluid intensifiers. An other important object of this invention is the provision of a buffer air chamber between the piston and the hydraulic fluid which can be adjusted as to pressure to provide means for adjusting the home or lower position of the ram.

A still further object of this invention is to provide a press in which a stemmed piston mounted within the ram itself'establishes both the function of main ram movement and an intensifying action.

A further feature and advantage of this invention is that the press may work in an upright vertical, inverted vertical or horizontal position. 7

Other objects of the present invention will become apparent upon reading the following specification,- and referring'to the accompanying drawings in which similar characters of reference represent corresponding parts in each of the several views.

In the drawings:

FIG. 1 is -a schematic side elevational view of the invention showing the ram in the home or lowermost position.

FIG. 2 is a view similar to FIG. 1 but showing the ram in an intermediate position with the piston in a position to create the intensifying action.

FIG. 3 is a view similar to FIGS. 1 and 2 showing the ram in its most extended position.

2,990,687 Fatented July 4, 1961 .FIG. 4 is an enlarged cross-sectional view showing the needle opening for allowing air to pass into the ram. The principal embodiment of the press comprises a main frame A, a press ram B reciprocally mounted for movement within the housing or frame A and a piston C mounted within ram B for slidable movement therein.

Press ram B is arranged to move upwardly relative to the housing by virtue of the downward movement of piston C within the ram. This action is facilitated by pneumatic pressure which causes the piston to move down to cause transference of oil from the bottom portion of the ram into the oil reservoir area 15 between the ram and the housing.

Ram B is formed with a round outer cylindrical wall 18- and with an inner cylindrical wall surface 19.

Piston C is slidably mounted within cylindrical wall 19 and is provided with an O-ring 21 so that a good fluid tight seal exists. The piston divides the inner part of the ram into a compression chamber 25 between the top 26 of the piston and the top 28 of the ram and an air buffer chamber 30 formed under the piston between the bottom face 31 of the piston and the top 34 of the oil within the ram.

A stem 38 depends downwardly from the bottom 31 of piston C to a point below top surface 34 of the oil level in the ram.

A floating'spacer disk 39 is mounted on top surface 34 of oil reservoir 15 to prevent fluid communication between the air and buffer chamber in oil reservoir 15. Disk 39 is slidably mounted relative to both ram wall 19 and stem 38.

The bottom of ram B is provided with a bottom plate 41 having a restricted aperture 42 which is formed in cross-sectional dimension substantially equal to the crosssectional dimension of stem 38.

An O-ring 44 is provided within aperture 42 to provide a fluid tight seal between stem 38 and the aperture when the stem engages the aperture as will hereinafter be explained.

The top portion of housing A is provided with an annular inner top face 45 which is provided on its inner edge 46 with O-rings to form a guide and fluid tight seal between top face 45 and outer wall .18 of press ram B.

A port 55 is provided in the side wall of housing A which is provided with fittings 56 and a hose 57 so that hydraulic fluid or oil may be inserted within oil reservoir 15. The side wall of piston C is provided with an ex tremely restricted aperture on its inside face indicated at 58 which is connected to a fitting 59 and a hose 60 to allow air to be fed into air buffer chamber 30.

A pump 61 and a regulator 62 are provided in the circuit connected to hose 60 to provide means for establishing substantially equal pressure at all times within the buffer chamber.

The control of the press is eflected by injecting air in or bleeding air out of compression chamber 25. This is done through a port 68 which is fed through a fitting 69 and a hose 70. Hose 70 is connected to a valve '71 which in turn is fed by a pump 73. Valve 71 is a three-way valve allowing either air to pass into compression chamber 25 or to bleed air from the compression chamber; The end of stem 38 is tapered at to allow easier en'- gagement with aperture 42.

In operation hydraulic fluid is placed within oil reservoir 15 so that the entire area between ram B and housing A is filled with oil and so that the oil reaches a level approximately half way between the upper and lower ends of ram B. It is important that the usual precautions be employed to completely bleed off any air that might be'in the oil or hydraulic fluid.

Air is then forced into air buffer chamber 30. The

- air pressure in chamber 30 will determine the home or Ln. Ln...

lower position of the ram. This is due to the fact that greater intensity of air pressure within bufier chamber 30 causes the ram to seat at a higher position relative to the reservoir. Consequently the starting position for the ram can be adjusted by adjusting regulator 62 to maintain the pressure at a predetermined level. Lower bufier air pressure will cause the ram to return to its lowest possible position and a higher pressure will allow the mm to return to selected intermediate positions after each operation.

Once the pressure has been regulated within buffer chamber 30 valve 71 is actuated to cause air to enter compression chamber 25. The pressure of air within compression chamber 25 causes piston C to move downwardly to cause the air bulfer chamber 30 to force the oil within the ram down and out through aperture 42 intooil reservoir 15. The transfer of oil from the ram housing into main chamber A forces ram B to move upwardly. The

force generated is directly proportional to the pressure within compression chamber 25 until stem 38 engages aperture 42 as seen in FIGS. '2 and 3. Under these conditions there can be no transfer of oil from the ram to the housing. Therefore the only further oil displacement which is caused by further lowering of piston C is that of the stem protruding into the lower reservoir. This creates a tremendous intensifying action and relatively small ram movement.

To drop the press, valve 71 is simply moved to a bleeding position wherein the inherent weight of the ram will cause the ram to drop to a point equilibrium. This point is established by maintaining pressure within buffer area 30 at the determined pressure.

Floating spacer disk 39 need not be utilized if the press is to be operated in a vertical upright position. However, with the provision of disk 39 the press can be operated upside down or horizontally in that there can be no transference or fluid communication past the disk.

Aperture 58 for supplying air to the butter chamber is of pinhole size so that O-ring 21 on piston C will be able to pass the aperture without causing undue wear on the O-ring 21 or the cylindrical wall. It is also to be noted that the aperture 58 is located on the upper portion of the ram so that as the piston is lowered the butter chamber is completely sealed and it is only after the piston raises to its upward home position that the bufller chamber is in fluid communication to be equalized by air pressure from regulator 62.

Although the foregoing invention has been described in some detail by way of illustration and example for purposes of clarity of understanding, it is understood that certain changes and modifications may be practiced within the spirit of the invention as limited only by the scope of the appended claims.

What is claimed:

1. A press for obtaining large ratios of displacement to force in a first stage and low ratios in a successive stage comprising, in combination, a housing having a bearing aperture formed through one surface, a hollow bore ram slidably supported in the bearing aperture for movement between extended and retracted positions and cooperating with the housing to form a fluid tight chamberbetween the housing and the ram, said ram having a fluid communicating aperture formed through its interior end and forming a fluid communicating passageway that extends between the interior of said housing and the interior of said ram, hydraulic fluid in said chamber and in a portion of the interior of said ram, a piston with a rod aifixed thereto slidably supported in the bore of said ram, said rod being of a selected length to be spaced from the fluid communicating aperture during the first stage and to enter the fluid communicating aperture to prevent the passage of fluid through the aperture during the successive stage, a gas cushion intermittent the rod side of the piston and the hydraulic fluid in the interior of said ram, and

means to move the ram from a retracted position to an extended position through the first and successive stages by the movement of the piston toward the interior end of said ram.

2. A press comprising a housing containing hydraulic fluid, a hollow ram slidably mounted with a fluid tight seal in said housing for movement between extended and retracted positions relative to said housing, said ram having an aperture formed in its lower end affording a fluid communication passageway between the interior of the ram and the interior of the housing to allow hydraulic fluid in the housing to pass into the interior of said ram, a piston slidably mounted within the interior of the ram,

sa compressible gas cushion formed between said piston 'and the surface of the fluid extending into the interior of said ram, means for supplying preselected quantities of gas to the space between the piston and the outer end of the ram to displace the piston toward said lower end, and a stem depending from said piston toward the apertured end of the ram having a cross-sectional dimension substantially equal to the cross-sectional dimension of the fluid communicating aperture and axially aligned therewith, said stem being formed of a length sufficient to engage the surfaces defining the aperture to block the passage of fluid between the interior of the ram and the exterior of the housing as long as the piston is less than a predetermined distance from the inner end of said ram.

3. 'A press for obtaining large ratios of displacement to force in a first stage and low ratios in a successive stage comprising, in combination, a housing having a bearing aperture formed in one surface, a hollow ram slidably supported in the bearing aperture for movement between extended and retracted positions and to form a liquid tight seal between the housing and the ram, said ram having an aperture formed in the inner end that opens into said housing, a suflicient quantity of hydraulic liquid in the interior of the housing and in the interior of said ram to maintain the interior of said housing completely filled with liquid and a liquid column in a portion of the interior of said ram at all times, a piston and rod combination slidably supported in the interior of the ram 'so that the rod enters the aperture formed in the inner end of said ram at a preselected point in its travel toward said inner end to close the communicating passage between the interior of said ram and said chamber, means for establishing a preselected gas cushion intermediate the rod side of the piston and the hydraulic fluid column in the interior of said ram, and means including a variable pneumatic source to displace the piston toward the inner end of said ram to move the ram toward its extended position whereby during the first stage, with the passage between the interior of the housing and the ram interior open, the ram is moved partially towards its extended position by transferring fluid from the interior of the ram to the interior of the housing and during the second stage, with the passage between the interior of the ram and the chamber blocked by the entrance of the rod into the aperture formed in the inner end of said ram, the ram is moved to its fully extended position by projecting said rod into the interior of said housing.

4. A press according to claim 3 and wherein a disk is slidably supported between the gas cushion and the column of hydraulic fluid in the interior of the ram formed to provide a gas tight seal therebetween.

5. A press according to claim 4 having gas injection means to inject gas. into the gas cushion between the hydraulic fluid in the interior of the ram and said piston.

6. A press comprising a housing containing hydraulic fluid, a hollow ram slidably mounted in a fluid tight seal for movement into and out of said housing, an aperture on the bottom portion of said ram and in communication ram, a body of gas between said piston and the aperture, means for adjustably controlling gas pressure against said piston in the bore of said ram in the area between said piston and the top portion of said ram to force said ll piston to move toward said aperture, and a stem depending from said piston having a cross-sectional dimension substantially equal to the cross-sectional dimension of said aperture and axially aligned therewith, said stem being formed of a length suflicient to mate with said aperture to close fluid communication between the bore of the ram and the interior of the housing when said piston is less than a predetermined distance from the apertured end of said ram.

References Cited in the file of this patent UNITED STATES PATENTS