US2702577A

US2702577A - Button die for dimpling

Info

Publication number: US2702577A
Application number: US223804A
Authority: US
Inventors: Charles C Harrison; Bert B Mead; George D Rechton; Orville A Wheelon
Original assignee: Douglas Aircraft Co Inc
Current assignee: Douglas Aircraft Co Inc
Priority date: 1951-04-30
Filing date: 1951-04-30
Publication date: 1955-02-22
Anticipated expiration: 1972-02-22

Description

Feb- 22, 1955 c. c. HARRISON ET AL 2,702,577

BUTTON DIE FOR DIMPLING Filed April 30, 1951 W 2 nu n United States Patent O BUTTON DIE FOR DIMPLING Charles C. Harrison, Long Beach, Bert B. Mead, Garden Grove, George D. Rechton, San Pedro, and Orville A. Wheelon, Pacific Palisades, Calif., assignors to Douglas Aircraft Company, Inc., Santa Monica, Calif.

Application April 30, 1951, Serial No. 223,804

7 Claims. (Cl. 153-21) This invention relates to hot dimpling of relatively hardalloy metallic sheets and particularly to means for dimpling such sheets while they are in place in their final assembly position on the basal framework of an airplane.

The airframe of most modern aircraft is constructed from prefabricated panels consisting of a metal frame covered-by a metal skin, usually of an alloy of aluminum or magnesium. These panels are united to each other and to the basal framework of the airplane by flush-riveting together and to the sub-adjacent framing overlappingly arranged marginal skin portions of adjacent panels, which operation usually completes the airframe. In effecting this union, the overlapping sheets are first provided with rivet holes in their marginal portions; thereafter the top or overlapping sheet has its edges raised and the rivet holes in the overlapped sheet are dimpled with a male die while resting on the basal frame. Theoverlapping upper sheet is thereafter dimpled while raised.

Heretofore, dimpling this marginal edge of the overlapping sheet required the insertion of bre wedges between the sheets to space them far enough apart to enable the insertion therebetween and around the pilot pin of the male die of a makeshift spacer in the form of a hard metallic ring provided with a wire handle for positioning it. This ring, as conventionally used, has planeal upper and lower surfaces with sharp, hard peripheral edges.

During dimpling, a considerable amount of temporary upward overbending of the upper, overlapping sheet in the region around the rivet hole is necessary, the overbend absorbing dimplingstresses which would otherwise distort the dimple and oilcan the sheet around the dimple. Since the upper surface of the conventional spacer ring is usually planeal, the sheet-contacting surface of the male die cannot be provided with a back angle to assist in overbending. Accordingly, this die has to be stroked hard in order to overbend the metal sufficiently around the rivet hole. The resultant high pressure forces the sharp upper and lower peripheral edges of the spacer ring into the pure metal cladding of the alloy sheets and these edges often entirely abrade away the cladding. This cladding removal locally thins and weakens the sheets in the vital jointures-regions of the air plane and also makes them quite subject to corrosion. The unsightly appearance of such jointures adversely affects the opinion of inspectors as to the reliability of the workmanship of the fabricator. l

Again in dimpling the overlapping sheet heretofore, it was necessary to employ a separate female die having an upper surface adapted to cooperate with the convexly conical part of the lower surface of the male die, the female die also having a lower surface adapted to fit in the countersink drilled or teamed in the heavier overlapped sheet resting on the massive sub-structure. This separate die was interposed between the sheets concentrically inwardly of the spacer ring and surrounding the pilot pin of the male die.

The present invention, in overcoming these and other defects, provides a single piece, multi-function hand tool which is, in effect, a combined female button type die for forming a dimple in the upraised sheet and a form block that enables the optimum temporary overbending of this sheet around the holes therein without requiring high male die pressures. It hence precludes the necessity for using separate spacer rings and female dies and obviates exposure of the core of the sheets to corrosion.

In one of its now-preferred embodiments, the tool essentially consists of an elongate, rectangular strip of metal of 2,702,577 Patented F eb. 22, 1955 ICC low thermal conductivity. The one end of the strip is formed into a handle and the opposite end is formed into a female button die. The handle and the head are connected by a exible neck portion thinned in planform and in section or otherwise conformed to clear the overlapping sheets and minimize heat transfer. The flexibility of the neck also facilitates placement of an aperture in the head between the sheets and around the pilot pin passing through both the aligned rivet holes therein. The peripheral lip of this aperture is downwardly angularly deflected in such manner as to form a central conical concavity opening on the upper surface of the head and adapted to cooperate with the male die in dimpling and a central conical convexity on the lower surface of the head is concurrently thereby formed which is adapted to seat in the dimple preformed in the lower sheet or in the substructure. The upper surface of the head of the tool slopes downwardly and outwardly away from the concavity therein at an angle equal to the back angle which the present invention makes it possible to employ on the working face of the male die. The optimum overbending is therefore achieved in the upper sheet with a comparatively low male die pressure. Consequently, even if the peripheral edges of the head, contacting the upper and lower sheets, were sharp and hard, little cladding would be removed thereby from either sheet. However, the broad sloping upper face terminates peripherally in round edges and the lower dat face of the head is equally broad. Use of this tool therefore effects no removal of the cladding from either sheet.

This one of the presently preferred embodiments is illustrated in the accompanying drawing and described hereinafter in conjunction therewith merely in order Vto further clarify and sharply delineate the nature and some of the advantages and practical aspects of the above and other inventive concepts.

In the drawings:

Figure l is a top plan view of the tool;

Figure 2 is a perspective view thereof partly in section;

Figure 3 is a side elevational view of the tool; and

l Figure 4 is a longitudinal section of the tool in use in s1tu.

The drawing shows the tool as a generally rectangular elongate strip of tempered stainless steel 1l) terminating at the one end in a handle 11 and at the opposite end in a head 12. The handle may be shaped to lit comfortably in the hand of the operator and the head is preferably circular and includes formations adapting it to act as a combined sheet spacer and overbender, and as a female, button-type dimpling die.

The head and the handle are joined by a neck portion 13 which is constricted in plan-form and thinned in the direction at right angles thereto, or thicknesswise, thereby to render the tool somewhat flexible longitudinally. By means of the handle and the flexible neck, an aperture 1.4 in the head can be readily inserted between the wedgespaced sheets 15 and 16 and flexibly fitted around the pilot pin 17 of the heated male dimpling die 18, which pin passes through the aligned rivet holes 19 and 20 of the overlapped sheets 15 and 16. Thereafter, the wedges are withdrawn and this tool acts as the sole sheet spacing means. The periphery of the rivet hole 20 has already been countersunk as at 21 in conformity with an aperture 22 in the relatively massive sub-structure 23, and the peripheral lip of the aperture 19 is to be dimpled in conformity with the countersink 21.

The neck portion 13 extends from the outermostperiphery of the head to the innermost portion of the handle, and since it clears both sheets and may have any desired linear extent, on occasion occupying most of the length of the tool, it can be so made as to reduce that area of the tool that makes heat transferring contact with the sheets, to the minimum. Thereby, loss of dimpling heat from the male die and the lip of the rivet hole 19 is minimized so that there is little danger of the lip cooling to such an extent as to crack when the male die is stroked.

The head of the tool is preferably swaged or otherwise thickened to a thicknesswise dimension greater than that of the handle, in order to facilitate sheet-overbending and, being composed of a metal having a relatively low thermal conductivity such as stainless steel, minimizes heat loss fromthe lip of the upper dimple to the sub-structure. This fact, combined with the structure of the neck, effectively prevents the lip in the upper sheet from cooling off to an extent sufficient to induce radial or circumferential cracks in the dimple when the male die is stroked.

The flexible neck enables the head to absorb the heaviest type of die stroke without damage to the head, since this neck permits the head to bodily yield downwardly .and inwardly to an extent that prevents fracture of the head.

The invention contemplates that the specific shape of the die in the head, and of the head itself, can be readily altered to suit varying conditions without departing from the scope of the present concepts.

The upper peripheral edge of the aperture 14- in the head of the tool is surrounded by a concavity 24 which is downwardly angularly deflected to a degree conforming to the downward angular formation of the countersink 21 in the heavier lower sheet, in order to enable nesting of the two formations in the sheets when they are riveted. This downward deflection forms, in the central region of the lower face of the head of the tool a conically convex formation 25 which centers and seats the head in the countersink in the sheet 16. The lower circular surface of the head, lying radially outwardly of the convexity 25, is flat and planeal and is adapted to fayingly contact the upper surface of the sheet 16 over a relatively large area as compared to the previously employed bushing-type spacer rings. Consequently, the pressure of the male die is distributed over an enlarged area and the die loading of the sheets per unit of area thereof is reduced considerably.

The central portion of the upper face of the head, rendered concave as at 24, as a consequence of the downward deflection of the lips of the aperture 14, is angled to the degree properly to dimple the lip of the rivet hole in the upper sheet. This degree may vary with the type of dimple desired. The upper face 26 of the head, beginning at the periphery of the concavity, is outwardly and downwardly angled, in its entire circumferential extent, at a predetermined angle to the planeal lower face. This angle is usually of the order of 3 and corresponds to the back angle or upwardly reentrant angle, on the working face 29 of rthe male die. The peripheral edge of the head, on both the upper and the lower faces thereof, may be rounded to further diminish the chances of marring the sheets.

By Virtue of the back angle surface 26 on the upper face of the head enabling the employment of an equal back angled surface 29 on the working face of the male die,

.a lower pressure in stroking the male die is required to overbend the sheets around the rivet holes than when the bushing type spacer rings of the prior art are employed. Consequently, the pressural reaction of the head on the sheets contacting it is considerably reduced without reducing the overbend. Marring of the cladding o n the sheets is thereby reduced to the minimum.

It will be understood that the same dimpling operation can be performed on a sheet immediately overlying a framing structure in which a countersink has been preformed.

Although one of the now-preferred embodiments of the invention has been described in most of its speciiic details, it is to be understood that the description has been given only by way of example of the many forms which the invention may take. The invention itself is not in any wise limited to these or other specific structural details except as necessitated by the scope of the annexed claims.

We claim:

l. A hand-held, spoon-type button die adapted to cooperate in situ on a framed and plated structure with a male die having a pilot pin so as to dimple a rivet hole in the one of a pair of overlapping sheets which are separable transversely of the overlapping portions to provide a limited space transversely of the overlapping portions, said sheets being tixed to a perforate substructure, the other sheet having a countersunk rivet hole therein registerable with the iirst said rivet hole, comprising: an elongate strip of material having a button-type head at the one end portion thereof, substantially all of the strip except said head portion constituting a handle, said button-type head being no thicker than the limited distance renderable available between the two overlapping sheets to be dimpled; a bore extending transversely fully through said head, said bore being arranged and adapted to receive therethrough the pilot pin on a cooperative male dimpling die; a concavity arranged on the one surface of said head and lying concentrically with said bore for dening a .female die; .a convexity arranged on the opposite surface of said head and lying concentrically with said bore so as to dually define substantially a male die and an anchor for anchoring said head in said countersink between said sheets; a planeal, smooth surface annularly concentrically surrounding said concavity and sloping downwardly and outwardly therefrom at an angle sufficient to enable the stressabsorbing over-bending of the first said sheet thereon by said male die, said planeal smooth surface having an area suicient to prevent ringing of the portions of said sheet contacted by said male die and by said planeal smooth surface and having chamfered peripheries; and a planeal, smooth annular surface extending radially outwardly on said opposite face from said convexity in substantial parallelism to the handle of said tool and having an area adapted to congruently lit the adjacent surface of the second-said sheet so as to prevent ringing of said sheet under the male die-stroke.

2. A tool adapted for use in situ on a plated structure with a male die having a pilot pin so as to enable dimpling a hole in the one of a pair of overlapping perforate sheets which form part of the plating and overlie a perforation in a substructure the other of said sheets including a countersunk rivet hole therein arranged in coaxial alignment with the lirst-said hole and adapted to receive the dimple, .the overlapping sheet-portions being temporarily separable in the direction extending transversely thereof to provide a space extending transversely of the overlapping portions, comprising: an elongate strip of material having a head at the one end portion of the strip, the dimension of said head thicknesswise of the strip being no greater than the transversely extending space render-able available between said overlapping portions; substantially all the strip, excepting said head, constituting a handle; a bore lying thicknesswise of said head and extending entirely through said head; said bore defining means for receiving entirely through said head the pilot pin of a male dimpling die so as to enable the pilot pin on the male die to enter the perforation in the substructure and anchor the perforations in said sheets, head and substructure in mutual coaxial registry with each other and with the male die during stroking of the male die, thereby to preclude cooking of the dimple relatively to the axis of the hole in the firstsaid sheet; and a concave surface arranged on the one face of said head transversely of and coaxially with the one end of the aforesaid receiving bore and adapted to constrain the peripheral margin of the hole in the first-said sheet to conform to a predetermined dimple shape.

3. A tool adapted for use in situ on a plated structure with a male die having a pilot pin so as to enable dimpling a hole in the one of'a pair of overlapping perforate sheets which form part of the plating and overlie a perforation 1n a substructure, the overlapping sheet-portions being temporarily separable in the direction extending transversely thereof to provide a space extending transversely of the overlapping portions, comprising: an elongate strip of material having a head at the one end portion of the strip, the dimension of said head thicknesswise of the strip being no greater than the transversely extending space renderable available between said overlapping portions; substantially all the strip, excepting said head, constituting a handle; a bore lying thicknesswise of said head and extending entirely through said head; said bore delining means for receiving entirely through said head the pilot pin of a male dimpling die so as to enable the pilot pin on the male die to enter the perforation in the substructure and anchor the perforations in said sheets, head and substructure in mutual coaxial registry with each other and with the male die during stroking of the male die, thereby to preclude cooking of the dimple relatively to the axis of the hole in the first-said sheet; a concave surface arranged on the one face of said head transversely of and coaxially with the one end of the aforesaid receiving bore and adapted to constrain the peripheral margin of the hole in the first-said sheet to conform to a predetermined shape; and a convex surface arranged on the opposite face of said head transversely of and coaxially with the opposite end of the above said receiving bore, said convex surface seating in a countersink disposed coaxially on the adacent end of the perforation in the second-said sheet and adapted to anchor said head and said concave surface in coaxiality with all the aforesaid holes in the absence of said pilot pin therein and before the male die descends.

4. A tool adapted for use in situ on a framed and plated structure, in association with a male die of the type having a pilot pin, so as to dimple a perforation in the one of a pair of overlapping sheets forming part of the plating, the overlapping portions of said sheets being temporarily separable transversely thereof to provide a space extending transversely of, and between, said overlapping portions, the other sheet of said pair including a countersunk perforation therein deviating from a predetermined, standard shape and adapted to be reformed to said predetermined shape, comprising: an elongate strip of material having a head at the one end portion thereof, substantially all the strip, except the head-portion, constituting a handle; said head having a thicknesswise dimension no greater than the limited space renderable available transversely between the overlapping portions of said sheet by urging said portions relatively oppositely; a bore extending thicknesswise of said head and penetrating entirely through said head, said bore being arranged and adapted to receive therethrough the pilot pin on a male dimpling die so as to enable the pin to pass through said sheets and said head and center a perforation in a substructure; a concave, frustoconical surface arranged on the one face of said head and lying transversely of, and coaxially with, the one end of said receiving bore; and a convex frustoconical portion of said head arranged on the opposite face of said head and lying transversely of, and coaxially with, the opposite end of the receiving bore, said convex portion having a predetermined shape corresponding to the aforesaid desired predetermined shape of said countersink, and being adapted to formingly t in said countersink so as to reform said countersink to said desired shape upon application of a coaxial stroking force to said head substantially concurrently With the dimpling of the perforation in the rst-said sheet.

5. A spoon-type dimpling tool for use in dimpling a rivet hole in the one of a pair of overlapping sheets, the other of said sheets having a countersunk rivet hole therein for receiving the protruding portion of the dimple, comprising: a strip of material having a thin head portion forming a button-die; a bore extending transversely through said button-die for receiving therethrough the pilot-pin on a cooperating male die; a concavity arranged on the one surface of said die concentrically with said bore so as to dene female dimpling means; a convexity arranged on the opposite surface of said die concentrically with said bore so as to dene male dimpling means; and a frusto-conical overbending surface arranged concentrically with said concavity and lying on the same surface of said die therewith and extending laterally outwardly from said concavity; said frusto-conical surface being smooth and having a total area suiciently large to minimize the unit overbending stress on the first-said sheet during dimpling so as to inhibit ringing of the iirst-said sheet by the spoon-type tool.

6. A spoon type dimpling tool for use in dimpling a rivet hole in the one of a pair of overlapping sheets, the other of said sheets including a countersunk rivet hole therein arranged in coaxial alignment with the first-said hole and adapted to receive the dimple, comprising: a strip of material having a thin head portion forming a button-die; a bore extending transversely through said head portion for receiving a pilot pin; a dimple-forming concavity arranged on the lirst face of said head-portion concentrically with said bore; a convexity arranged on the second of said head-portion concentrically with said bore; and a planeal surface disposed concentrically of said bore around said convexity at right angles to said bore and extending laterally outwardly from the base of said convexity; said planeal surface being adapted to contact the subadjacent face of said second sheet, and said planeal surface being smooth and having an area suciently large to minimize the unit-load on said sub-adjacent surface; thereby to prevent ringing of said sub-adjacent surface.

7. A spoon type dimpling tool for dimpling a rivet hole in the one of a pair of overlapping sheets, the other of said sheets including a deformed or out-of-round countersunk rivet hole arranged in coaxial alignment with the first-said hole and adapted to receive the dimple, comprising: a strip of material having a thin head portion forming a button-die; a bore extending transversely through said head portion for receiving a pilot pin; a dirnple-forming concavity arranged on the first face of said head-portion concentrically with said bore; a convexity arranged on the second of said head-portion concentrically with said bore; said convexity having an exterior surface preshaped to the desired form for the countersunk portion of said rivet hole, said exterior surface being adapted to be forcefully urged formingly into said countersunk portion so as to reform the latter to said desired shape.

References Cited in the le of this patent UNITED STATES PATENTS 556,060 Pierre Mar. 10, 1896 2,288,378 Veit lune 30, 1942 2,292,446 Huck Aug. l1, 1942 2,491,717 Creighton Dec. 20, 1949 2,508,373 Cavallin May 23, 1950