US2387190A - Hydraulic press - Google Patents

Description

@ct. 1, 1945. M. D. STONE ET AL 2,337,390

HYDRAULIC PRESS Filed April s, 1943 2 sheet -s eet 1 INVENIORS ATTORNEY! L 0 2 A Q Q f I- w HQ Io i. 1 w 9 g 5 1 Wm I l I I I l I ll G I lllllllllllll ll 2 m lll 4 1 z planes of their juncture Patented Oct. 16, 1945.

Morris tion of Pennsylvania Application April 3, 1943, Serial No. 481,764

Claims.

, v This invention relates to hydraulic presses of the heavy duty type used for forging, bending and other working and shaping of metals and other materials, and has to do particularly with presses of this type which are eccentrically loaded in either their normal or abnormal operation.

Presses of the type here contemplated comprise spaced columns whose ends are engaged by upper and lower-entablatures that are supported by the columns, and a crosshead borne by the upper entablature for vertical reciprocatory strokes.

Conventional forms of such presses have been so constructed that when their crossheads are loaded eccentrically, that is to say when the load is so applied that the downward resultant of the pressure applied by cylinders does not coincide with the upward reaction from the work piece, the resulting lateral reaction of the crosshead is taken up by some or all of the'columns in variable positions in relation to the entablature. In such presses heavy eccentric load produce high bending stresses in the'columns which have resulted in breaking them, and they also cause the upper end of presses to sway laterally several inches with the result that the pipes for supplying hydraulic pressure fluid to the presses have broken. The critical stresses that cause such' breakages and sway are those. arising from the bending moments on the columns in the 'general with the lower side of the upper entablature.

The object of this invention is to provide a heavy duty press of the type explained which is so constructed that when an eccentricload is applied to its crosshead the load is balanced substantially wholly by normal tension forces in the columns, instead of resulting in the application of lateral pressure to them, the columns being substantially free from such bending moments and lateral forces as would caus -lateral sway of the press and breakage of the columns as well as of pipes connected to the top of the press.

"Normal tension forces. as used above and throughout the specification and claims means forces that produce uniform tension stresses throughout a body by direct pull on it, as distinguished from tension stresses that are produced by bending. I

Heavy duty presseshave four columns which may be considered as being arranged in pairs, as they usually are, one pair being to the right and the other to the left end of the work-feeding and manipulating side of the press, However, one pair of columns may be considered as the two front and the other pair as the two rear coln. Stone and Frank J. Gleve, Pittsburgh, asslgnors to United Foundry Company, Pittsburgh, Pa.,

Engineering and a corpora- (Cl. loo-u) umns. It is in the space between the columns that loads are applied eccentrically to the crosshead of a press. The press provided according to our invention has spaced pairs of columns, and an entablature ,Which engages and is supported by'their upper ends. The entablature is provided centrally with a vertical opening in which the guide stock of a vertically reciprocable crosshead is mounted, the crosshead being integrally formed with or otherwise rigidly connected' to the guide stock. The crosshead is positioned between the columns and is incapable of applying lateral pressure directly to them when it is eccentrically loaded.

' -The guide stock of the crosshead and the wall j of the vertical central opening of the entablature are so formed at vertically-spaced opposite portions thereof that when the crosshead is eccentrically loaded the eccentric load couple so formed is taken substantially wholly by laterally directed forces which form an intemal' couple within'the entablature. To this end the wall of the opening is' preferably provided with vertically-- spaced localized bearings which engage opposite sides of the guide stock. When the crosshead is eccentrically loaded as explained the eccentric load couple so formed is, except for negligible slidin friction forces, taken entirely by laterally directed forces which form aninternal couple within the entablature. By providing, as is preferably done, an upper entablature of such massiveness and rigidity that the load strains to which it is subjected are negligible, an eccentric load applied to the crosshead as explained is balanced substantially wholly by normal tension force in the columns. As a result of this the columns are Substantially free from such bending moments and lateral-forces as have resulted in their breakage, and in lateral sway of presses.

The invention will be further explained with reference to the accompanying drawings, which diagrammatically illustrate an embodiment of itin the form of an armor plate bending press which has been built and placed in operation, and in the use of which the correctness of the fundamental principles of our invention have been dem- 'onstrated.

In the drawings, Fig. 1 is a front elevation of a press, the upper right-hand portion being shown in vertical central section; Fig. 2 a right-hand elevation and Fig. 3 a plan view of the press shown in Fig. 1; and Fig. 4 a small scale stress elevation of the press.

The press comprises two pairs of columns I, la

and 2, 2a, the lower ends of which are provided with a lower entablature I and theupper ends' with an upper entabiature 4. Positioned between the columns there is a crosshead {which is elongate in the direction of the spacing of the pairs thereof, and is provided integrally with a guide stock that is mounted for vertical recip rocation in a'vertioal central.opening 'l formed .bearings being vertically spaced and on opposite sides of guide stock 0. In other words, the eccentric load couple is taken up by laterally directed forces which form an internal couple within the entablature.

.I'or applying power to crosshead i, the upper entablature is preferably provided with hydraulic cylinders is positioned one on each side of the guide stock and each equipped with a piston II, the upper end'of each cylinder being formed for attachment to a pipe i4 extending to a source of supply of hydraulic pressure. Between the lower side of each piston and the top of crosshead I there is a thrust rod I! having spherical ends,

the upper of which bears against a spherical socket formed 'on the bottom of the piston and the lower of which bears against a like socket formed on the\top of the crosshead. The opposite ends of each thrust rod thus have hinged engagement with a piston and the crosshead.

To counterbalance the crosshead and to move it upwardly at the end of eachworking stroke,

s,ssv,1oo I g just explained. The enormous forces required to do this are indicated by the fact that the press has a capacity of 14,000 tons of pressure. While our invention is not limited to any Particular capacity or size of press, it is noted that, properly to carry the high stresses to which the press disclosed herein is subjected, each column is thirtyfour inches in diameter, the pairs of columns 1, la and 2, is being spaced twenty-three feet center to center and the columns is and tabe ns spaced rearwardly of columns i and 2 elevenand one-half feet center to center. The upper entablature 4 issixteen feet in depth from the top to bottom. and is massive in structure throughout'gxcept for its central guide stock opening I and the openings in it for receiving hydraulic cylinders Ill. The main-body of the crosshead is about twentyfeet in length between the spaced columns I, la and 2, 2a, about eight feet in width and about five feet in depth. From the base of their footings to their upper ends, the columns are approximately seventy feet in height.

when the crosshead of a press embodying our 1 invention is eccentrlcally loaded, as for exameach of itsends is connected to the lower e'nd of a piston rod ll whose upper end is attached to a piston ll positioned in a pressure fluid cylinder l'l' whose lower end is connected to a pipe I! leading to a source of pressure fluid supply. The upper end of each cylinder" is provided with an opening I! so that air may be admitted to and discharged from the cylinder upon the reciprocation of piston l0.

The press shown in the drawings is equipped to bend heavy armor plates to their desired curved forms, there being a platen 20 supported by the lower entablature l and a platen 2| attached to the lower face of crosshead i. To bend properly a heavy armor plate it is necessary to apply bending forces to it incrementally from one end to the other end. As shown in Fig. 1 a heavy armor plate II is supported near its right end by a pair of spaced blocks 20 which rest on platen II, and

- at its left end by a third block 21. Attached toplaten 2| and positioned midway between blocks. 20 there is a block 28 which bends the portion pie, for bending armor plate in the, manner shown in Fig. 1. the forces acting upon the upper structure of the press are, for all vertical positions of the crosshead 5, as indicated in Fig. 4 in which 1? represents a load applied eccentrically to the crosshead a distance e from the vertical axis of the crosshead in the direction of the spacing of the columns I, in and 2, 2a, whose center to center spacing is indicated as 20. Neglecting relatively insignificant friction between guide stock 8 and bearings 8, 0 and to, so as the crosshead is moved downwardly, the eccentric moment If equals Rh, in which h is the vertical distance between the centers of pressure onguide stock 0 on bearings 0 and is which are on-vertically-spaced opposite sides of the guide stock.- In the operationof the press the same hydraulic pressure is applied to the upper end of each of pistons ll so that the forces applied to the upper faces of the crosshead by thrust rods I! are alike, eachbein Asifstated above,'thecritical stresses on presses such as here contemplated are those arising from the bending moments on the columns in the generalplane of their juncture with the loweriside of the upper entablature. In the stress diagram of Fig. 4 these moments are indicated at these loaded eccentricaiiy, it is these bending moment of plate 25 between blocks 20 when crosshead 2| is moved downwardly. Between strokes .of the crosshead the several blocks are r'epositioned to the end that the plate may be bent step-by-step times heavily loadedeccentrically on oneside of its vertical axis in the direction of one of the pairs of spaced columns i, in or 2, 2a.

'. -"to the desired curvature-from one to the other of its ends, and in doing so the crosshead is at stresses added to the normal stresses upon the column that result in column breakage and press sway. 1 when the crosshead of our improved press is eccentrically loaded as shown, the load is balanced substantially wholly by normal tension fo'rces in the column, the critical stress moments Mr and M: then being very small as compared tothose that prevail when the lateral reaction resulting from an eccentrically loaded crosshead is taken up by columns on which the crosshead bears. The correctness of this appears from'a consideration of the following formulae, that we have evolved by a theoretical mechanics analysis of the press as an indeterminate structure, inwhich formulae, A is the cross sectional area oi each column, I the moment of inertia of each column, and N1 and N2 the normal tension forces for an eccentric load.

in columns 2, 2a and I, la, respectively, as a sequence oi. the eccentricity of the load:

1 M=Rh=Pe the eccentric moment Pe.

As appears from formulae (3) and (4), the

normal tension force in the columns increases from for a load applied centrally to the crosshead to For an eccentric loading in which whichis very large in practice, the normal tension stresses added to columns I and la by the eccentricity of the load are only fifty per cent above the stresses for central loading.

As has been explained, conventional forms of presses have been so constructed that when their crossheads are loaded eccentrically the resulting reaction of ,the crossheads is taken up by the columns. By theoretical mechanics analysis of such conventionaipresses as indeterminate structures, the analysis being the same as that used in deriving the above formulae, we have found that bending moments M1 and M2 vary from about to of M, instead of being sway of the top of the press herein disclosed when heavily loaded eccentrically, which sway was found to be only small fraction of an inch as compared to a sway of several inches which attends a like loading of conventional presses.

v assmoo con- They can be quantitatively corroborated by strain measurements of the press.

According to the provisions of the patent statutes, we have explained the principle and mode of operation 01' our invention, and have described and diagrammatically illustrated what we now consider to be its best embodiment. However, we

desire to have it understood that, within the scope v of the appended claims, our invention may practiced by forms of presses other thanth We claim as our invention:

1. An hydraulic press, comprising spaced pairs of columns, an 'entablature engaging and sup-1;; ported by the upper ends of the columns and-,7. provided centrally with a vertical guide-stock; opening, and a vertically reciprocable crosshead positioned between the columns and incapable of. applying lateral pressure directly to them when it is eccentrically loaded, the crosshead having'a' guide stock rigidly connected to it extending up+..,-w; .wardly through said entablature opening for vertical reeiprocatory movements therein, said guide stock and the wall of said opening being so formed at vertically-spaced opposite side portions thereof that when'the crosshead is eccentrically loaded the eccentric load couple so formed is taken substantially wholly by laterally directed forces which form an internal couple within the entablature, whereby a load so applied to the crosshead is balanced substantially wholly by normal tension forces in the columns which asa result thereof are substantially free from such bending moments and lateral forces as would cause lateral sway of the press.

2; An hydraulic press, comprising spaced pairs of columns, a massive substantially rigid entablature engaging and supported by the upper ends of the columns and provided centrally with a vertical guide-stock opening, and a vertically reciprocable crosshead positioned between the columns and incapable of applying lateral pressure directly to them when it is eccentricallyloaded,

the crosshead having a guide stock rigidly connected to it extending upwardly through said entablature opening for vertical reciprocatory movements therein, the wall of said opening being provided on its opposite sides with verticallyspaced bearings engaging opposite sides of said guide stock whereby when the crosshead is eccentrically loaded the eccentric load couple so formed is taken substantially wholly by laterally directed forces which form an internal couple within the entablature, whereby a load so applied to the crosshead is balanced substantially wholly by normal tension forces in the columns whichas a result thereof are substantially free from such bending moments and lateral forces as would cause lateral sway of the press.

3. An hydraulic press, comprising spaced pairs of columns,an entablature engaging and supported by the upper ends of the colum a d P ovided centrally with a vertical guide-stock opening, a vertically reciprocable cross-head positioned between the columns and incapable of applying lateral pressure directly to them when it is eccentrically loaded, the crosshead having a guide stockrigidly connected to it extending upwardly through said entablature opening for vertical reciprocatory movements therein, an hydraulic cylinder borne by said entablature at each side of said guide stock, a piston within each cyland said eros'she ad. we guide stock and the wall 01' said opening being 80 formed at verticallyspaced opposite side portions thereof that when l the crosshead is eccentrlcally loaded the sheentric load couple so formed is taken substantially wholly by laterally directediorces which form an internal couple within the entablature, whereby a load so applied to the crosshead is balanced substantially wholly by normal tension forces in the columns which as a resultthereol are substantially free from such bending moments and lateral forces as would cause lateral sway of the press. I

4, An hydraulic press, comprising spaced pairs of columns, on entablature engaging and sup ported by the upper ends orthe columns and provided centrally with a vertical guide-stock opening, a vertically reciprocable crosshead positioned assmeo taken substantially wholly by laterally directed iorces which form an internal couple within the entablature, whereby a load so applied to the crosshead is balanced substantially wholly by normal tension forces in the columns which as a result thereof are substantially free from such bending moments and lateral forces as would cause lateral sway or 5. An hydraulic press, comprising spaced columns, an entablature ensasina and supported by the upper ends of the columns and provided centrally with a vertical guide-stock opening, and a,

vertically reciprocable crosshead positioned between the columns and incapable oi applying lateral pressure directly to them when it is eccentrically loaded. the crosshead having a guide stock rigidly connected to it extending upwardlythrough said entablature opening for vertical between the columns and incapable of applying I loaded, the eccentric loadcouple. so iormed is reciprocatory movements therein, said guide stock and the wall of said opening being so i'ormed at vertically-spaced opposite side portions thereof that when the crosshead is eccentrically loaded the eccentric load couple so formed is taken substantially wholly by laterally directed forces which form an internal couple within the entablature, whereby a load so applied to the crouhead is balanced substantially wholly by normal tension forces in the columns which as a result thereot'are substantially free from such bending moments and lateral forces as would cause lateral 'swayof the press.

moans D. s'r'oss. mssx a. cum:

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