US2359848A

US2359848A - Magnetic bucking bar

Info

Publication number: US2359848A
Application number: US346911A
Authority: US
Inventors: Holcomb William Ray
Original assignee: Lockheed Aircraft Corp
Current assignee: Lockheed Corp
Priority date: 1940-07-23
Filing date: 1940-07-23
Publication date: 1944-10-10
Anticipated expiration: 1961-10-10

Description

- Oct. 10, 1944.

w. R. HOLCOMB MAGNETIC BUCKING BAR Fild July 25, 1940 IN VENTOQ Patented Oct. 10, 1944 MAGNETIC BUCKING BAR William Ray Holcomb, Burbank, Calif., assignor to Lockheed'Aircraft Corporatiom Burbank,

Calif.

Application July 23,1940, Serial No. 346,911 J Claims. -.(Cl. 78-48) This invention relates to an improved apparatus and method for heading rivets in confined places inaccessible to manually held bucking bars or rivet squeezing machines.

With the development of skin stressed metal aircraft, riveting of the skin to structural or other members, especially at the nose and trailing edge of the wing, has become a difiicult process. With the advent of integral fuel tanks utilizing the skin structure as part thereof it becomes-increasingly difiicult to reach both ends of the rivets, as is necessary to properly set up a rivetby means of a riveting hammer and a manually held bucking bar. There is a practical limit as to how far an offset bucking bar can be held firmly enough to produce a ound rivet head; the modern use of relatively large skin sheets backed by closely spaced or continuous corrugated longitudinals, and the addition of an inner skin for various purposes, has added to the difficulties in producing acceptacle riveting on a pro-.

duction basis.

It is accordingly an object of this invention to'provide a novel form of bucking bar that can'be inserted in cramped quarter andv maneuvered into position from an opening some distance away, the bar being brought into and held in operative position against the end of the rivet by a magnet applied to the external surface of the object being riveted.

'It is also an object of this invention to provide a magnetically held bucking bar in combination with a magnet associated with a riveting hammer. so arranged that the magnet will draw up and hold the bucking bar in position on the back or inner side of the work, while the riveting hammer sets and forms the rivet inthe usual manner.

It is a further object of thi invention to provide a combined riveting hammer and magnet for the purpose described, the magnet having a polev or shoe formed as an annular surface coaxial with and embracing the hammer-to hold the latter accurately at right angles to the surface of the work to assure truly positionedrivet heads in the ease of both flush and round headed.

rivets.

Other and further important objects of this the line I-I of Figure II, of an airplane wing structure, for illustrative purposes.

Figure II is a view at right angles to the showing of Figure I, comprising a traverse section of the wing structure.

Figure III embodiesa modified form of bucking bar suitable for use in riveting wing reinforcingmembers of continuous corrugated form.

Asshown:

In-orderto illustrate a form of this invention adapted for a particular type of work, an airplane wing structure has been chosen-for descriptive purposes. Anouter skin Ill is to be riveted to the flanges H of a series .of channel members 12, which in turn may have an inner skin or lining l3 riveted to the inner flanges .14 thereof; As shown in Figure III, the channel members l2 may be replaced by'a corrugated reinforcing sheet l5. The details of such airplane structures form-no part of the present invention, and it is contemplated that-the bucking bar will be so formed as to be readily inserted and. moved 1 throughout the length of the spaces available behind the surfacawhich spaces may extend for a number of feet, limited only by the size of commercially available sheet material. It will be evident that the usualtype of hand held bucking bar or rivet squeezing machine cannot reach several feet-into such small spaces. Other examples of inaccessible riveting locations in airplane construction will -'readily occur to those skilled in the art; such as the nose and trailing edges of the wings, for example.

As disclosed herein, the skin I0 and channel flange it are perforated and dimpled for the'insertion of countersunk head rivets Hi. This invention is not limited to that type of rivet however as other types of rivets can be set equally well, if necessary by theprovisionof suitable shaped recesses in the hammer and bucking bar as is common'p-ractice with hand held tools.-

The bucking bar of this invention comprises a holder l7 shaped'in general to fit the space available,- and a magnetically responsive movable member guided by the holder l1. As shown in Figures I-and II the holder I1 is centrally recessed to-receive the bucking bar member 18, which latter carries guiding tongues 19 slida-ble in slots in the side pieces 20 of the holder, pins 2| serving to limit the outward movement of the member I8, to leave space for the desired thickness of rivet head. The upper ends of the side pieces 20 are grooved at 22 to-pass over already formed rivet heads. The holder, may be conveniently shifted along ,the .channel member 12 by means 011a long flexible shaft23,"which can be operated om o n end f t c an e or thro hand. .hole .or inspectionopening at, some distance from the desired rivet location. While the flexible shaft can be marked to closely approximate the location of the bucking bar, which can also be seen through the rivet holes, it is also possible to feel for the bucking bar by means of a small permanent horseshoe magnet, the two poles of which will accurately locate or define the edges of the bucking bar by variations in the attraction on the magnet when the materials being Worked on lack magnetic response; as in the case of aluminum alloys, and non-magnetic type of stainless steel for example.

A powerful electromagnet 24 is combined with an air operated riveting hammer 25, the magnet having an annular pole piece 26 which is pressed against the outside skin l and serves, when the magnet is energized, to draw the member l8 to its limit of travel in the holder, also causing the side members 26 of the holder to press the channel flange l2 against the skin ID.

A tappet 21 for the air hammer 25 has an enlarged head 28 countersunk in the annular magnet pole piece 26,'the surface of the head 28 being flush with the end of the pole piece, in this case of flush rivets, and of considerably greater diameter to produce a truly flush surface. The magnet pole piece 26 also holds the air hammer and tappet 2'! vertical relative to the skin Ill, assuring a smooth riveted joint.

It is to be understood that this invention has been described as used with an air hammer merely for illustrative purposes, as other types of riveting processes and spot welding can be combined with the magnetic bucking bar. For example, a powerful magnet of the type described would be capable of squeeze riveting the small aluminum rivets commonly used in airplane construction. The tappet 2! could be arranged as one electrode of a spot welding machine, the bucking bar forming the other electrode, while the magnet applied the necessary pressure for spot welding. V

The bucking bar l8 and its holder I! may be tailored to fit the space available, as indicated in Figures II and III. In Figure II the holder I1 is slidable in the channel member l2 and is of a width sufiicient to center the line of rivets when the holder rests against the web of the channel. A spring 29 may conveniently be used to hold the bucking bar against the web.

In Figure III the holder 30 is formed as a flat plate slidable in the base of the channels 3! formed by the corrugated reinforcing material IS. the plate having upstanding guide pins 32 for a bucking bar 33 which can be drawn up against the rivet by the magnet 24.

In the operation of the magnetic bucking bar of this invention the material to be riveted is assembled and drilled for a series of rivets. In the case of flush riveting relatively thin sheets, the sheets may be dimpled to provide the desired countersink for the rivet heads, or the rivet may be allowed to form its own countersink at the time it is driven. In either case, the holder l1 and its bucking bar I8 is inserted through some available opening and pushed along the passage until it is in a position to back up the rivet, after which a rivet is inserted in the hole provided therefor and the combined magnet and riveting hammer approximately centered over the head of the rivet. Upon closing the electric circuit energizing the magnet, the magnet pole piece 26 will attract the bucking bar I8. A subsequent operationof the air hammer will act to both seat the preformed countersunk head of the rivet, and form a flat head on the inner end thereof,

the magnetic force acting on the bucking bar l8 pulling it towards the material as the head forms, until the pins 2| limit further forward motion. In effect, the air hammer taps a series of blows on the tappet 21, which is held against the surface of the skin in by the magnet pole piece 26, the effect of the blows being transmitted through the rivet shank to the bucking bar, which bounces slightly to perform the heading operation.

It will be evident from the foregoing that the magnetic bucking bar of this invention can be utilized in confined places inaccessible to manually held bucking bars and that one man can both position the bucking bar and perform the riveting heading operation.

Having thus described my invention and the present preferred embodiment thereof, I desire to emphasize the fact that many modifications may be resorted to in a manner limited only by a just interpretation of the following claims.

I claim:

1. A riveting tool of the class described comprising a bucking bar, holding means for said bucking bar adapted to allow freedom of movement thereof towards the rivet to be bucked, electro-magnetic means for attracting and holding said bucking bar against the material being riveted, said electro-magnetic means having an annular pole adapted to contact the material ?being riveted about the rivet location therein, and rivet driving means concentrically seated within said annular pole flush with the surface thereof.

2. A riveting tool of the class described comprising a bucking bar, a guide for said bar adapted to allow freedom of movement thereof towards the rivet to be bucked, an electromagnet for attracting and holding said bar against the rivet, said electromagnet having a polepiece adapted to contact the material being riveted about the rivet location therein, a riveting mandrel extending axially through said electromagnet and. having a head of increased diameter on one end thereof, a recessed seat formed in said polepiece, said head being positioned within said seat when the head and the polepiece are in operative position in contact with the material being riveted.

3. A riveting tool of the class described comprising a bucking bar having a heading surface thereon and being adapted for progressive movement towards the rivet being bucked as the heading thereof proceeds, a guide for said bar, said bar being guided for lateral movement in said guide towards said rivet, means associated with said guide and bar for limiting the extent of said movement, an electromagnet for holding said bar against said rivet, said electromagnet having a polepiece adapted to contact the material being riveted, a riveting mandrel extending (0; through said electromagnet and having a rivet driving head thereon concentrically seated within said polepiece flush with the surface thereof.

4. In a device as set forth in claim 3 wherein the rivet driving head on the mandrel is frustoconical in form, the polepiece having a conical seat formed therein to provide a seat for said driving head.

5. In a device as set forth in claim 3, wherein 4 the limiting means associated with the guide and bar comprises an extension on the bar and means on the guide adapted to engage said extension to limit movement of the bar towards the rivet.

WILLIAM RAY HOLCOMB.