US2413876A - Hydraulic press - Google Patents

Description

1947. J. 1.. LEFLER 2,413,876

HYDRAULIC PRESS I Filed July 12, 1945 a l N N INVENTOR. JAMES L. LEFLER BY i u D ATTORNEY Patented Jan. 7 1947 HYDRAULIC v v Jarn es L. Lefler, North Hollywood, Calif; ass gnor to Bendix Aviation Corporation, South Bend,

1nd,, acorporation ofQDelawar-e Application July 12, 1945, Serial No. 604,629

, v 1 This invention relates is particularly useful in hand-operated presses;

An object of the invention is to provide an in expensive, economical press for use in operations requiring the development of large forces applied through relatively short distances.

Another object is to provide aipress that utilizes" an ordinary source of compressed air forefiecting large movements of the press where small forces are involved while utilizing high pressure by draulic fluid for the developmentof large forces acting through only short distances; i Ordinary hydraulic presses require 'a power pump of substantial capacity for moving the press at a reasonable speed while at the same time developing the desired high forces. Because of the expense of-power-pumping equipment; the use of hydraulic presses had been limited to situations .where there was a substantial amount of press work to be done. For manypur'poses, it is only to hydraulic' 'pressesand 1 m c v There is shown in the diagram a conventional press I consisting of frame vertical members 2 supporting a table 3 on which a work-piece may be placed;- and supportin above the table 3 a hydraulic ram cylinder bcontaining a piston 5 having a stem 6 which'extends through the bottom of the cylinder and can be moved toward the table 3 to bear against a works-piece thereon.

The upper end of theycylinder 4 above the piston 5 is connected to a fluidline 1,, and the lower end of the cylinder below the ,piston 5 is connected to an air line 8. The upperend of the piston is at all times filled with hydraulic fluid,

hereinafter referred to-as oil;

The oil line 1 connects to a control valve I I and also to the discharge port I2 of a hand pump I3.

. This hand pump comprises a relatively small -\necessary to develop high fluid pressures in a s hydraulic press during final movement of the press, and a fluid pressure as large as may be required can be developed with a relatively small and economical hand pump by making the pump piston relatively small; However, when the pump piston is made small to develop the desired high pressure, its volumetric capacity is correspond- ,lngly reduced so that it may require a great deal of time to move the press platen into position where it bears against the work-piece.

I ,1 accordance with the present inv 'ntion, I pro ide a press that is capable of develoriing high forces and, at the same time, is capableof rapid movement up to the point where the gh force must be generated, by providing a sma 1 capacity high pressure hand pump, in combination with means utilizing an ordinary source of compressed air for moving the press rapidly so long as only low forces are involved. The arrangement-is such that only a single ram is employed on the press and only hydraulic fluid is introduced 'i nto the working chamber of} the press ram, the fluid being circulated to and from the ram by {air pressure during rapid movement of the-press to engage and disengage a work-piece.

The manner in w ich the foregoing objects are attained, together, ith other more specific ob- I jects and features" of the invention, will be apparent from the following detailed description of a preferred embodiment of the invention which refers to the drawing.

The single figure of the drawing is a schematic diagram of a system in accordance withrthp invention. I.

diameter. working cylinder I4 containing a piston I5 adapted to be reciprocated by a handle IS. The cylinder I4 is connected to the discharge port I2 past a check valve I6 and to an inlet port I8 past a check valve ll; the latter port being. connected by a line 20 to the upperend of a cylinder 2| and to the valve II. The lower end of cylinder2I is connected by an air line 22 to the valve II. 1 Any ordinary source of compressed air 23 :is connected. by a line to the valve I I.

The cylinder 2| contains a floating piston 25 which servesto maintain oil in the upper end of the cylinder separated from air'in the lower part.

The systemdescribed operates as follows:

When it is desired to elevate the piston 5 of the rain, the valve II is rocked clockwise into the dotteddine position labeled Up. This connects the line 24 from the pressure air supply to the line 8 leading to the lower end of the ram cylinder so that pressure of the compressed air is applied to raise the ram piston. At the same time, oil in the upper end of. the ram cylinder flows out through the line I and through the valve I I to the line 20 and into the upper end of the displacement cylinder 2|. This moves the piston 25 downwardly, and the air in the lower end of cylinder 2| is exhausted to atmosphere through line 22, valve II and an exhaust port 21 in the valve.

When it is desired to lower the piston 5 of I the ram, the control valve II is rocked counterclockwise into'the dotted line positionmarked "Down.? In this position, it admits pressure air from line 24 through line 22 to the lower end of the displacement cylinder 2|, forcing the piston 25 upwardly to displace oil from the upper end of the cylinder through the line 20, and a check valve 28 and the line I into the upper end of the ram cylinder. At the same time, the lower end of the ram cylinder is connected through line,

has contacted a work-piece positioned in'the f press. However, the operator can thereafter build up the pressure in the upper end of the ram cylinder to any desired value by reciprocating the handle l6 of the hand pump. On each outward stroke of the piston I5, it draws in oil from the upper end of cylinder 2| through the pipe 20 past the inlet check valve H, and on each inward" stroke forces such oil past the outlet check valve l6 and directly through the line 1 into the upper end of the ram cylinder.

The operator can leave the valve II in the -Down position or return it to Neutral position, and the hand pump will be equallyefiective. 7

After the pressing operation has been completed, the operator can again raise the rampisconnected to the bottom of cylinder 2|, and the air line 22 should beconnected to the top of the cylinder. It is usually desirable to provide a barrier between the air and the oil within the displacement cylinder to prevent mixing of the air in the oil under pressure.

It is common practice in accumulators for hydraulic systems to emtioned can'be made while still utilizing the invention, which is to be limited only to the extent set forth in the appended claim.

A hydraulic press comprising: a ram cylinder containing a piston adapted to be reciprocated in one direction to press a work-piece. and in the opposite direction to releasethework-piece, said ram cylinder having a liquid opening in one end for receiving liquid to move the piston in said one direction and an air opening in the other end, a source of compressed air under medium pressure, aclosed reservoir for hydraulic liquid and air and having aliquid opening and an air opening, ahigh-pressure, low volumetric capacity pump having an inlet opening and an outlet opening, said pump being adapted to develop pressures much greater than the pressure of said air source, check valve means interconnecting said liquid openings of said ram cylinder and reservoir for permitting flow from said reservoir to'the ram cylinder, while preventing reverse flow,.a control valve having first, second, and third position'sand connections extending from said ram cylinder, said air source, said reservoir,v ands'aid pump to said valve; said valve when in said first position connecting the liquid opening of said reservoir to theliquidopening of said .ram, connecting said air source to the air opening of the ram cylinder,

andconnecting the air opening ofsaid reservoir to atmosphere, whereby said ram piston is moved in said other direction and liquid in the ram cylinder is returned to said reservoir; said valve when in said second positionconnecting said air source to the air opening, ofsaid reservoir, and connecting the airopening of said ram cylinder to exhaust, whereby-liquid is displaced from said reservoir, through said check valve means into ploy either a solid piston or a flexible diaphragm or a flexible bladder to prevent mixing of the oil and the air, and a flexible diaphragm or bladder may be employed in place of the floating piston 25 if desired. In such instances, it is not necessary that the displacement reservoir be in a form of a cylinder, and it may conveniently be in theform of a sphere, similar to conventional hydraulic accumulators.

Although for the purpose of explaining the invention, a specific embodiment has been described, various departures other than those men- ,theram cylinder to move the ram piston in said one direction with low force; said valve, when in said third position, connecting. the air openings of said ram cylinder and reservoir to exhaust;

, and means connecting the liquid opening of the JAMES L.

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