US3563167A

US3563167A - Frames for presses

Info

Publication number: US3563167A
Application number: US747857A
Authority: US
Inventors: John Antony Pennell; Alan Saunders
Original assignee: Vickers Ltd
Current assignee: Vickers Ltd
Priority date: 1967-07-26
Filing date: 1968-07-26
Publication date: 1971-02-16
Anticipated expiration: 1988-02-16
Also published as: FR1573749A; SE353031B; DE1752851A1; GB1240823A; NL6810605A

Abstract

A press frame made up from a number of platelike subframes, each defining a frame opening, disposed with the frame openings in registry, and interconnected by two platens or part platens secured, in facing-spaced relationship in the registering frame openings, across facing inner edges of opposing members of each subframe. Slide surfaces are also provided in the press frame openings substantially perpendicular to the platens, by or on plates each secured across corresponding inner edges of the members of at least two adjoining subframes.

Description

United States Patent [72] Inventors John Antony Pennell [56] References Cited fi g C D h E I UNITED STATES PATENTS [21] A I No and 2,286,721 6/1942 Ernst 100/214x 2,416,058 2/1941 1916 1611.... 100/214x [22] F1led July 26, 1968 1 2,932,245 4/1960 Hausman.... 100/214x [45] Patented 3 064 55s 11/1962 v P1 100 214 [731 Assign vickersumied 3 278 993 l0/l966 s men 1oo/2 14x London'England rayman eta [32] Priority July 26, 1967 Primary Examiner Billy J. Wjlhite [33] Great Britain Artomey- Pennie, Edmonds, Morton, Taylor and Adams [31] 34475/67 ABSTRACT: A press frame made up from a number of [541 51131122212233.2:32:15 zsi'szszz'xzss'zsiiifl 9Claims,6Drawing Figs.

platens or part platens secured, 1n facmg-spaced relatlonshlp [52] U.S. Cl 100/214 in the registering frame openings, across facing inner edges of 100/269 opposing members of each subframe. Slide surfaces are also [51] Int. Cl B30b l/00, provided in the press frame openings substantially perpen- B30b l/32 dicular to the platens, by or on plates each secured across cor- [50] Field ofSearch l00/2l4 (Cursory), 269; 29/155 (Cursory); 72/455; 83/701 responding inner edges of the members of at least two adjoining subframes.

tachments or stress concentrations of any BACKGROUND OF THE INVENTION The whole press frame of the invention has very low-stress concentration factors, and very efficient utilization of the constructional material. This allows high nominal stresses without any danger of fatigue failure, and enables the construction of very light high-capacity presses. For a given size and weight, the press frame of the invention is more rigid than most other types due to the absence of clamped joints and regions of highstress concentration. 1

Further weight reductions and increased stress levels (at the expense of rigidity) can be achieved without sacrifice of strength by virtue of the small safety factor that can profitably be used with the press frame of the invention. Applying a proof" load between the platens of about 150 percent of the press capacity causes localized yielding in the regions of highest stress concentration in the press frame, and sets up beneficial residual compressive stresses at these points. This raises the fatigue strength of the metal in those regions where high fatigue strength is most necessary. There is no change in regions of low stress where there is already an adequate margin of safety. This prestressing technique is far more efficient than those normally used on press-frames, such as for example pretensioned tie rods or wire winding, since the residual stresses set up are exactly those required to partially neutralize the applied stresses. This is not the case with other prestressing techniques in which the residual stress system often bears little resemblance to the applied stresses, especially in the complex end platens where the benefits are most necessary. The proposed technique is also far more cheaply applied.

A number of other advantages result in the press frame of the invention. In particular, for a press frame of given overall dimensions, it is a simple matter to alter the press capacity by varying only the number or thickness of the platelike subframes. This enables a whole range of presses to be manufactured from common templates and patterns. Furthermore, unlike most conventional presses in which a hydraulic intensifier cylinder is incorporated into oneof the end platen castings or fabrications, in this press frame an intensifier cylinder can be attached to the platen so that the cylinder is free from indeterminate axial stresses, and, if single acting, is entirely free of atkind. It is thus possible to raise the working stresses in the cylinder as well, with further reductions in weight and cost. Very high hydraulic pressures are also more easily accommodated allowing the design of extremely compact high-capacity presses.

It is accordingly an object of this invention to provide a new and improved press frame of lightweight having good rigidity and high fatigue resistance under high loads.

SUMMARY OF THE INVENTION BRIEF DESCRIPTION OF THE DRAWINGS Other objects, features and advantages of the invention will become more apparent when taken in conjunction with the accompanying drawings in which:

FIG. 1 shows a press frame of the invention in front elevation;

FIG. 2 is a section taken along line A-A of FIG. 1;

FIG. 3 is an isometric view to an enlarged scale of a detail of FIGS. 1 and 2 showing the attachment of a slide surface to subframe member edges, the slide surface having reduced thickness and width near its end;

FIG. 4 is a view similar to that of FIG. 3 but showing use of stress-relieving slots in the slide surface together with reduced width;

FIG. 5 is a section through part of a press frame showing the attachment of an intensifier cylinder to a platen; and

FIG. 6 is a section through part of a press frame showing alternative constructions of subframes for very large presses.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring now to the drawings, a press frame of the invention suitable for a vertical hydraulic press is shown in FIGS. 1 and 2. The press frame of the invention is made up of a plurality of platelike subframes 3, in this case four in number, each defining a frame opening and being arranged in substantially parallel relationship with the frame openings in register, and two platens 1 and 2 which extend through the registering frame openings in facing spaced parallel relationship. The backs of the platens 1 and 2 are secured, as at 15, respectively along facing inner edges of opposing members 4 and S of each subframe 3. I

To this end each subframe 3'consists of upper and lower

transverse members

4 and 5 together with vertical side members 6. Parallel facing slide surfaces 7 to guide the moving parts of the press are provided by plates or plate means, as shown, disposed substantially perpendicular to the platens I and 2 and are secured within the registering frame openings by welding to inner edges, as at 14, of the subframe vertical side members 6 which edges and members 6 extend at right angles to the edges of the

members

4 and 5 carrying the platens l and 2 Edges of the subframe members 6 to which the plates having the slide surfaces 7 are attached, are each profiled to provide a rebate at point 13 at each end of the associated surfaces 7 so that the plates having these surfaces 7 are attached to inward projecting extensions 8 of the side members 6. This has the effect of offsetting inwardly the respective neutral axes 9 of the cross section of the rebated side members 6 in the vicinity of the surfaces 7. Because of the axial tensions in these members 6 under the working load, this eccentrically loaded center section of the side members tends to deflect outwards. This deflection is arranged exactly to counteract the tendency of the members 6 of the subframes 3 to deflect inwards due to bending of the upper and lower

transverse members

4 and 5 in conjunction with the platens l and 2. Thus by suitable selection of the profile of the side members 6 of the frame, and the thickness and position of the plates having the machine slide surfaces 7, in conjunction with the elastic properties of the platens I, 2, and

transverse members

4 and 5, it is possible to minimize the tendency of the side members and slide surface plates of the press frame to bow inwards under load. This gives the press frame of the present invention a considerable advantage over most other press frames, particularly in coldmetal forming applications in which accurate guidance of moving press components is essential.

FIG. 2 shows a section through the press frame on a vertical plane perpendicular to the subframes 3. Due to the distributed load over the upper and lower platens-1 and 2, these will tend to bend in the plane of FIG. 2, as beams supported at the points of attachment to the

transverse members

4 and 5 of the subframes. These deflections will, in turn, tend to cause bending of the side members 6 in this plane, with consequent deflections of the slide surfaces 7 in the same plane. This effeet can also be eliminated if the transverse spacing between adjoining subframes 3 in the section shown in FIG. 2 is selected in conjunction with the relative thickness of the pairs of frame members 5', 5", etc., to eliminate bending moments in the subframes 3 other than those in the plane of FIG. I.

Of particular importance in reducing the maximum stresses in the press frame are the fillet contours at

points

11, 12, 13, and 16, and the

joints

14 and 15 between respectively the side members 6 of the subframe and the plates providing the machine slide surfaces 7, and the side members 6 and the transverse members and

platens

4 and 1, and 5 and 2. It is particularly beneficial if the internal contours at the points 16 between the transverse and side members of the subframes are smoothly notched with an arc of relatively large radius as shown in FIG. 1. That is, the rebated edges on the side members 6 of a subframe 3 merge at the four corners of the frame opening into the edges of the

transverse members

4 and 5, through smooth notches formed with relatively large radii. This prevents superposition of the stress concentrations due to the fillet at point 11 and the joint 15 which conveniently is a welded joint. Similarly, at the fillet or rebated point 13, a smooth blend of the two profiles is essential to avoid superposition of the stress concentrations due to the attachment at 14 of the plate having the slide surface 7. In order to reduce the stress effect of this attachment it is preferable to reduce the thickness 7a or width of the plate providing the slide surface 7 near its ends, as shown in FIG. 3 or to reduce the width 7b of the plate having the surface 7 as shown in FIG. 4. Alternatively or additionally slots can be machined in the slide surface 7, as shown at 17in FIG. 4.

A way of detachably securing a press cylinder such as a hydraulic intensifier cylinder'l8 to the press frame is shown in FIG. 5. The cylinder 18 is of plaincylindrical construction made of high-grade steel if necessary and having a very high working stress level to minimize its weight and overall diameter. Pressure fluid to actuate a moving part of the press (not shown in the FIG.) is supplied to the cylinder via a bore 19 in the press end platen 1. An upper open end of the cylinder 18 is closed by a disc or annulus 20 which is provided with a hydraulic seal 21 around the lower end of its outer edge which engages the bore of the cylinder 18. The disc 20 also provides reinforcement for the platen 1 to which it is secured relatively lightly, such as by bolts 22, or by any other convenient means, and it may also incorporate a supply nozzle to engage the pressure fluid supply bore 19, or a guide bush for the rear of the moving press part.

Because the upper region of the cylinder 18, above the seal 21 is not subject to internal fluid pressure, the hoop stresses in it are much lower than in the lower pressurized region, and it is possible to secure the cylinder'directly to the upper platen 1, using short bolts, as shown at 23 in FIG. 5. Alternatively a taper 24 or a recess 24a is formed on either the inside or outside diameter of the cylinder 18 to engage a suitable projecting rim on either the disc 20 or an annular clamp ring 24b surrounding the cylinder and also bolted to the upper platen 1. These techniques result in a very small stress concentration in the cylinder 18 which allows high nominal working stresses to be achieved without risk of fatigue failure. On small presses this can also be achieved by screwing the cylinder onto threads formed around the periphery of the disc 20 above the seal 21.

The method of manufacturing a press frame of the invention as hereinbefore described and as shown in FIGS. 1 to 5 of the drawings comprises the steps of aligning a plurality of subframes 3 substantially parallel to one another with their frame openings in register, fixedly securing the platens l and 2 and the plates having the slide surfaces 7 to the inner edges of

respective subframe members

4, 5 and 6 within the frame openings to interconnect the subframes 3 and then prestressing the interconnected subframes 3.

This prestressing of the press frame is accomplished after completing the fabrication, heat treatment, and rough machining of the interconnected subframes, the latter including the boring of all essential holes in the structure. This prestressing is achieved by applying a proof load between the platens of about I50 percent of the normal press frame working load. This load causes localized yielding to take place in the regions of the press frame of highest stress concentration and sets up beneficial residual compressive stresses at these regions. The press cylinder itself can be used to supply the required prestressing load, in conjunction with a suitable hydraulic supply, at a pressure greater than the normal working pressure, and a rigid loading frame. In this way the press cylinder itself may also be slightly autofrettaged, together with its attachment to the frame. For very large presses, in which the design of a suitable loading frame to withstand for example percent of the press capacity would present many difficulties, the numerous subframes 3 incorporated in the press frame are conveniently fabricated, rough machined, and prestressed as separate units, each requiring a much lower preloading capacity. These subframes 3 can furthermore be transported separately, making installation a much more simple operation. A technique of construction which permits this method of manufacture is shown in FIG. 6.

This press frame comprises a number of subframes 3 each having transverse and vertical members as before, but each incorporating only a platen support 25 at each end. These platen supports are fillet welded to the transverse members 4, as shown at 26, using a simple plate for the platen support, or alternatively a number of T-sectioned elements 27 are buttwelded to the transverse members as shown at 28 to constitute the part platen supports. This latter form of construction allows more control over the profile of the fillet, and is tobe preferred. The part platen supports 25 or 27 at each end of the press frame only extend to about the midpoint of the space between each pair of subframes 3. The subframes can thus be stacked side by side with the part platen supports in contact, or slightly separated as shown in FIG. 6 at 29, to form the complete press frame. This press frame is held together by clamping the subframes transversely, or by attaching the outer or all of the part platen supports 25 or 27 to a single platen member 30, either by bolts 31, spigots. (not shown) or by some other suitable means. The bolts etc., are located in the region of relatively low-stress level to avoid weakening the frame,

and the platen member 30 is conveniently a replaceable hardwearing plate. A similar technique of construction can also be used at the joint 14 (FIG. 1) between the side members 6 and the plates carrying the machine slide surfaces 7. Narrow slide supports, similar to the part platen supports 25 or 27 are welded to the side members of each subframe 3, with the whole assembly of subframes being held together as required by a relatively thin hard-wearing slide surface plate similar to the platen member 30, which is bolted to the various narrow slide supports. The plates slide surfaces 7 are thus easily replaceable.

The method of manufacturing a press frame as shown in and described with reference to FIG. 6comprises first prestressing each subframe 3 individually by applying between the part platen supports 25 or 27 thereof, a load sufficient to cause localized yielding in regions in the subframe 3 of highest stress concentration. A plurality of prestressed subframes 3 are then aligned substantially parallel to one another with their frame openings, part platen supports 25 or 27 and supports (not shown) in registry with one another and the aligned subframes are then secured together by means of platen members 30 and slide surface plates as hereinbefore described.

It must be emphasized that since each subframe in the press is designed to carry a definite proportion of the total press force, independently of the others, the various connecting parts such as the platen member 30, do not transmit appreciable forces between the subframes 3, and can therefore be made relatively light. They can thus be attached (to the outer subframes 3 only, if required) to any point where the stress concentration due to bolting is acceptable that is particularly in regions of low stress.

Furthermore the spacing between adjacent platelike subframes 3 of the frame is determined primarily by the bending characteristics of the platens in the plane perpendicular to the press frame, and by the requirement for uniform loading of the subframes 3. Some latitude is possible, however, especially if the subframes 3 are not all of the same thickness, and the space between them can then be utilized to accommodate pipe or cable runs, limit switches, or auxiliary worksaving rams. The latter are conveniently mounted on extensions of themain press platens 1, 2, or on auxiliary platens attached to the press frame in regions of relatively low-stress level.

While there have been shown and described preferred embodiments, it is to be understood that various adaptations and arrangements can be made without departing from the spirit and scope of the invention.

We claim:

1. A press frame comprising:

a. a plurality of platelike subframes each with a frame opening defined by a first pair of opposing subframe members and a second pair of opposing subframe members extending substantially transversely to said first pair, said subframes being disposed in substantially parallel relationship with said frame openings in register;

b. two platens which extend through said registering frame openings in facing spaced parallel relationship, said platens being secured respectively to said first pair of subframe members of each said subframe; and

c. plate means providing slide surfaces along inner edges of each said second pair of subframe members, said slide surface plate means being located substantially at right angles to said platens and each said plate means being secured across corresponding subframe member edges of at least two adjoining subframes so as to span said corresponding subframe member edges.

2. A press frame comprising:

b. two platens which extend through said registering frame openings in facing spaced parallel relationship, said platens being secured respectively to said first pair of subframe members of each said subframe;

c. plate means providing a slide surface along an inner edge of each said second pair of subframe members, said slide surfaces being located substantially at right angles to said platens; and

d. wherein each subframe member provided with a slide surface plate means has a rebated inner edge at each end of said slide surface, thereby to offset inwardly of said frame openings neutral axes of said! rebated members in the vicinity of said slide surfaces to minimize transverse deflection of said slide surfaces and the press frame under load.

3. A press frame according to claim 2, wherein each said plate means is secured across corresponding subframe member edges of at least two adjoining subframes, and in which end portions of each said plate means have reduced dimensions to minimize the effect on stress concentrations in the press frame due to the attachment of said plate means to the respective subframes.

4. A press frame according to claim 2 in which the thickness of individual subframes and spacing between adjoining subframes is selected to minimize bending moments in the press frame at right angles to said subframes, when the press frame is loaded.

5. A press frame according to claim 4 in which said rebated edges on said members of a subframe provided with slide surface plate means merge at the four corners of the frame opening into the edges of the subframe to which the platens are secured, through smooth notches formed with relatively large radii and designed to minimize maximum operative stresses in the press frame.

6. A press frame according to claim 2, in which platen supports are formed on each said subframe, said platen supports cooperating to support said platens in said press frame.

7. A press frame according to claim 2 further comprising a press cylinder with at least one ogen end detachably secured at said one open end to one of san platens, and a disc sealably fitted inside said one open end of said cylinder and secured to said one platen.

8. A press frame according to claim 2, wherein each subframe is prestressed to cause localized yielding in regions of the sub-frame of highest stress concentration.

9. A press frame according to claim 2, wherein the interconnected subframes are prestressed between the platens to an extent which is in excess of normal press frame working load, thereby providing a press frame subject to localized yielding in regions of the highest stress concentration.

line 24, after in" mg 2 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION i atent No. 3 553 1 7 Dated February 16, 1971 In nt John Antony Pennell and Alan Saunders It is certified that error appears in the above-identified paten' and that said Letters Patent are hereby corrected as shown below:

Column *3 insert -the plate having--.

Column 4-,

lines

23, 25, 28, 32, 40, 49 and 54, cancel "part" Column 4, line 45, after "plates" insert --providing-;

a line 54, after "and" insert '--slide-.

(The foregoing refers to lines whereas the line numbers are offset.)

(SEAL) Attest:

ROBERT GOTTSCHALK EDWARD M.FLETCHER,JR.

Commissioner of Patents Attesting Officer

Claims

1. A press frame comprising: a. a plurality of platelike subframes each with a frame opening defined by a first pair of opposing subframe members and a second pair of opposing subframe members extending substantially transversely to said first pair, said subframes being disposed in substantially parallel relationship with said frame openings in register; b. two platens which extend through said registering frame openings in facing spaced parallel relationship, said platens being secured respectively to said first pair of subframe members of each said subframe; and c. plate means providing slide surfaces along inner edges of each said second pair of subframe members, said slide surface plate means being located substantially at right angles to said platens and each said plate means being secured across corresponding subframe member edges of at least two adjoining subframes so as to span said corresponding subframe member edges.

2. A press frame comprising: a. a plurality of platelike subframes each with a frame opening defined by a first pair of opposing subframe members and a second pair of opposing subframe members extending substantially transversely to said first pair, said subframes being disposed in substantially parallel relationship with said frame openings in register; b. two Platens which extend through said registering frame openings in facing spaced parallel relationship, said platens being secured respectively to said first pair of subframe members of each said subframe; c. plate means providing a slide surface along an inner edge of each said second pair of subframe members, said slide surfaces being located substantially at right angles to said platens; and d. wherein each subframe member provided with a slide surface plate means has a rebated inner edge at each end of said slide surface, thereby to offset inwardly of said frame openings neutral axes of said rebated members in the vicinity of said slide surfaces to minimize transverse deflection of said slide surfaces and the press frame under load.

7. A press frame according to claim 2 further comprising a press cylinder with at least one open end detachably secured at said one open end to one of said platens, and a disc sealably fitted inside said one open end of said cylinder and secured to said one platen.

8. A press frame according to claim 2, wherein each sub-frame is prestressed to cause localized yielding in regions of the sub-frame of highest stress concentration.