US 3334504 A
Description (OCR text may contain errors)
Aug. 8, 1967 H, MQLLER 3,334,504
CUP-SHAPED DIAPHRAGM FOR HYDRAULIC FORMING PRESS Filed May 25, 1965 United States Patent 3,334,504 CUP-SHAPED DIAPHRAGM FOR HYDRAULIC FORMING PRESS Hugo 'Miiller, Trollhattan, Sweden, assignor to Saab Aktiebolag, Linkoping, Sweden, a corporation of Sweden Filed May 25, 1965, Ser. No. 458,673 2 Claims. (Cl. 72-63) This invention relates to improvement in resilient diaphragms for hydraulic forming presses, and, more specifically, the invention concerns the type of cup-shaped diaphragm which has a circumferential upwardly projecting side wall that closely fits in the lower portion of a bore in a pressure chamber member of a hydraulic forming press, and which has a bottom wall that closes the bottom of the bore and transmits force from pressure fluid in the bore to a sheet metal blank therebeneath, to cooperate with a forming tool in shaping the blank.
The side wall of a cup-shaped diaphragm of the type with which this invention is concerned mainly serves to provide a seal around the bottom portion of the bore in the pressure chamber member of the press, and is subjected to relatively little strain and wear when the diaphragm is in use. But the bottom wall of such a diaphragm is subjected to very large strains because of the flexing which it must undergo to accommodate the shape of the forming tool as the blank is formed over it.
Heretofore such cup-shaped diaphragms have been made in one piece, from rubber or the like, and hence when the bottom wall of the diaphragm was damaged, the entire diaphragm had to be replaced. Because of the relatively complicated shape of a cup-shaped diaphragm, its replacement was costly, and the comparatively short useful life of the diaphragm had to be amortized over the number of parts that could be produced by it, with the result that production cost was high for each part.
It is the general object of the present invention to provide an improved cup-shaped diaphragm for a hydraulic forming press that will bring about a substantial reduction in the cost of forming each part produced on the press.
In the attainment of this objective the pattern of strains imposed upon a cup-shaped diaphragm has been given careful attention. Particularly with forming tools used for deep drawing, the central portion of the bottom wall of the diaphragm is subjected to substantial axial stretchiug during each forming operation as it is displaced upwardly into the bore in the pressure chamber member of the press by the blank and forming tool. However, the peripheral portions of the bottom wall, which cooperate with a fiat blank holding ring beneath the marginal edge portion of the blank, are subjected to a substantial degree of radial stretching. Thus the bottom wall of the diaphragm is subjected to severe and nonuniform streching forces, particularly in zones thereof that produce abrupt changes in curvature of the blank being formed in the press. It is as a result of these stretching forces It lat such diaphragms heretofore had a limited useful With the foregoing in mind, it is an object of the present invention to provide a cup-shaped diaphragm of the character described which has great durability, and more particularly to provide such a diaphragm which comprises a cup-shaped main diaphragm member having a bottom wall portion with a configuration that best accommodates the stretching forces to which it is subjected, and certain relatively simple and inexpensive bottom wall members which are detachably secured to the bottom wall portion of the main cup-shaped member to complement the same and which are adapted to receive the major portion of the normal wear to which the dia- 3,334,504 Patented Aug. 8, 1967 phragm as a whole is subjected in use: and to be readily replaced when they are damaged or worn out.
More particularly it is an object of this invention to provide a cup-shaped resilient diaphragm of the character described which is in three parts, one of said parts including the side wall and a bottom wall element and being relatively complicated and expensive but having an indefinitely long useful life, and another of said parts being intended to receive the major portion of wear and to be relatively frequently replaced, but being extremely simple and inexpensive.
In general, the above stated objects are attained by the provision of a cup-shaped diaphragm comprising three parts that are readily detachably adhered to one another, namely a main member having a circumferential side wall and an inner bottom wall portion which is integral with the side wall and which has a substantially flat upper surface and a spherically concave lower surface, an intermediate member which is detachably adhered to the undersurface of the inner bottom wall portion of the main member and which has a flat undersurface and a spherically convex upper surface complementing the undersurface of the inner bottom wall portion, and a lower bottom wall member having substantially flat parallel top and bottom surfaces and which is flatwise detachably adhered to the underside of the intermediate member.
With the above and other objects in view which will appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise embodiment of the hereindisclosed invention may be made as come within the scope of the claims.
The accompanying drawing, which illustrates one complete example of the physical embodiment of the invention constructed according to the best mode so far devised for the practical application of the principles thereof, is a fragmentary vertical sectional view through a portion of a hydraulic forming press incorporating a diaphagm that embodies the tion:
In the drawing the numeral 5 designates generally a pressure chamber body in a hydraulic forming press, only the lower portion of that chamber being shown. Through the chamber body there extends a vertical bore 6 which is closed near its bottom by the cup-shaped resilient diaphragm of this invention, which is designated generally by 7.
Beneath the pressure chamber 5 the press has, as is conventional, a blank holding ring 8 with a fiat upper surface, and a punch 9 which is encircled by the blank holding ring and which cooperates therewith to provide a forming tool. During a forming operation, the marginal edge portion of a sheet metal blank 10 is flatwise clampingly confined between the blank holding ring 8 and the peripheral portion of the diaphragm, while the central portions of the blank and diaphragm are displaced upwardly into the bore 6 by the punch 9. Suitable mechanism (not shown) is provided in the press structure to produce the necessary axial motions of the pressure chamber 5 and blank holding ring 8 relative to one another and the punch 9, and fluid is maintained under pressure in the bore 6 above the diaphragm to force the blank into conformity with the shape of the forming tool.
In general, the diaphragm 7 comprises three resilient elements, namely a cup-shaped main member 11 having a circumferential upwardly projecting side wall 12 and an integral inner bottom wall portion 13, an intermediate principles of the present invenof the main member and is adhered thereto, and a lower bottom wall member which underlies the intermediate wall member and is adhered to the latter.
The assembly constituting the cup-shaped diaphragm 7 is secured in the lower portion of the bore 6 by means of a circumferential radially outwardly projecting ridge or land 16 on the side wall 12, spaced a short distance below the rim thereof, which is received in a closely fitting circumferential groove 17 in the bore 6. An internal clamping ring 18, confined within the side wall portion of the diaphragm, in radial alignment with the land 1.6, maintains radially outward force upon the side wall to hold the land 16 seated in the groove 17 and thus prevent axial displacement of the diaphragm.
The lower portion of the diaphragm assembly 7 has a reduced outside diameter and is surrounded by a resilient sealing ring 19 which is displaceable both radially and axially to some extent by reason of its resilience. The lower portion of this sealing ring has a smaller outside diameter than its upper portion to define on the sealing ring an external downwardly facing circumferential shoulder 20. A small radially inwardly projecting circumferential land or ridge 21 in the bore 6, near the lower end thereof, defines an upwardly facing shoulder against which is seated the shoulder on the sealing ring, and by which the sealing ring is thus held in place The purpose of the sealing ring is to obviate the need for an extremely close fit between the forming tool and the bore 6 which the forming tool is adapted to enter, all as more particularly explained in the copending application of Hugo Moller, Ser. No. 458,672, filed May 25, 1965, to which reference may also be made for additional details concerning the press herein referred to.
The bottom wall portion 13 of the cup-shaped main diaphragm member 11, which comprises the inner wall portion of the diaphragm assembly, has, when in its unflexed condition, a substantially flat upper surface 22 and a spherically concave bottom surface 23; and hence it is thinnest at its center and has increasing thickness toward its periphery. The intermediate wall member 14 has a spherically convex upper surface 24 which complements the concave underside of the inner wall portion, and has a flat undersurface 25; hence the intermediate member is thickest at its center and tapers in thickness toward its periphery. The lower bottom wall member 15 has flat, parallel upper and lower surfaces 26 and 27, respectively, and is thus of uniform thickness across its diameter. It will be noted that the three wall elements 13, 14 and 15, when adhesively joined to one another, cooperate in defining a bottom wall for the diaphragm which is of uniform thickness across its diameter and which, in unfiexed condition, has flat, parallel top and bottom surfaces.
In the formation of a sheet metal part by means of any cup-shaped diaphragm, the greatest strains on the diaphragm occur, as explained above, in the peripheral portion of the bottom wall, in the neighborhood of its junction with the side walls; and it will be observed that the bottom wall portion 13 of the main body member 11 in the diaphragm of this invention has its greatest thickness in this region of greatest strain. The intermediate wall member 14 is subjected to strains which increase the value toward its center Where it has its greatest thickness. The lower bottom wall member 15, which is in direct contact with the sheet metal blank being formed, and which therefore receives the most wear, is the least expensive of the three members comprising the diaphragm, by reason of its flat parallel upper and lower surfaces, which enable it to be cut from suitable sheet material.
Of course the lower bottom wall member 15 needs the most frequent replacement of the three elements comprising the diaphragm of this invention, but since it receives all of the normal wear imposed upon the diaphragm, and is very inexpensive, diaphragm costs per part produced is relatively very low. The intermediate bottom wall member 14 normally does not need replacement, but it sometimes happens, in the formation of parts having complicated shapes, that a sheet metal blank is split during the forming operation, and the sharp edges thus produced on the blank damage not only the lower bottom wall element 15 but also the intermediate member 14. Even in such cases, the cost of the two damaged members is substantially less than the cost of an entire cup-shaped diaphragm of prior unitary construction.
From the foregoing description taken together with the accompanying drawing it will be apparent that this invention provides a cup-shaped diaphragm for hydraulic forming presses which achieves a comparatively low diaphragm cost per formed part by reason of its comprising three members, the most expensive of which is of pratically indefinite useful life, while the member which receives almost all of the normal wear, and thus needs most frequent replacement, is very simple in shape and therefore low in cost.
What is claimed as my invention is:
1. A resilient substantially cup-shaped diaphragm for a hydraulic forming press, of the type having a circumferential upwardly projecting side wall which closely fits in the bottom portion of a downwardly opening bore in a pressure chamber member of a press, and a bottom wall for closing the bottom of said bore and for transmitting to a sheet metal blank therebeneath force exerted by pressure fluid in the bore, wherein said bottom Wall of the diaphragm is characterized by:
(A) an inner resilient wall portion integral with said circumferential side wall, said inner wall portion being thinnest at its center and increasing in thickness toward its periphery;
(B) an intermediate resilient wall member having an upper surface which is complementary in shape to the undersurface of the inner wall portion and which is detachably adhered thereto, said intermediate wall member being thickest at its center and tapering in thickness toward its periphery; and
(C) a lower most wall member which is of uniform thickness at all points thereacross and which has its upper surface complementary in shape to the undersurface of the intermediate wall member and detachably adhered thereto.
2. A resilient substantially cup-shaped diaphragm for a hydraulic press, of the type having a circumferential upwardly projecting side wall which closely fits in the bottom portion of a downwardly opening bore in a pressure chamber member of a press, and a bottom wall for closing the bottom of said bore and for transmitting to a sheet metal blank therebeneath force exerted by:
(A) an inner resilient wall portion which is integral with said circumferential side wall and which, when unflexed, has a substantially flat upper surface and a substantially spherically concave undersurface, said inner wall portion having its least thickness at the axis of the diaphragm;
(B) an intermediate resilient wall member having a substantially fiat undersurface and a spherically convex upper surface which is complementary to the under surface of the inner wall portion and detachably adhered thereto; and
(C) a lowermost resilient wall member having substantially flat, parallel top and bottom surfaces and having its top surface detachably adhered to the undersurface of the intermediate wall member.
References Cited UNITED STATES PATENTS 2,878,767 3/1959 Paulton 7263 3,033,143 5/1962 Grankowski 7263 FOREIGN PATENTS 875,364 6/1942 France.
CHARLES W. LANHAM, Primary Examiner.
K. C. DECKER, Assistant Examiner.