WO1989009116A1

WO1989009116A1 - Self-locking tongs and a method of producing self-locking tongs intended for round and hexagonal material

Info

Publication number: WO1989009116A1
Application number: PCT/DK1988/000058
Authority: WO
Inventors: Axel Grønlund NIELSEN
Original assignee: Nielsen Axel Groenlund
Priority date: 1986-10-03
Filing date: 1988-03-30
Publication date: 1989-10-05
Also published as: DK473686D0; DK473686A

Abstract

A method of producing a self-locking tong adapted to clutch preferably round and hexagonal bodies, the jaws of the tong interacting with the body at three places, essentially separated 120° from each other. Moreover, the tong comprises a revolving jaw section (2) having two jaw surfaces forming an angle with each other of mainly 60°, the jaw section being pivotally fixed to a handle jaw section (1) carrying a third jaw surface adapted to perform the third interacting point with the body. As blank material a steel plate capable of being hardened is used, e.g. a boron alloy steel plate analyzing: C 0.2 to 0.25, Cr 0.5 to 1.5, Mn 0.8 to 1.5, B 0.002 to 0.003. The handle section (1) or the jaw section (2) or both are produced by laser cutting, and the jaw surfaces are casehardened in a depth of mainly 0.1 to 0.15 mm followed by hardening and tempering to achieve a resulting hardness of the size of 60 to 62 Rc.

Description

Self-locking tongs and a method of producing self-locking tongs intended for round and hexagonal material.

The invention relates to a method of producing self-locking tongs 5 intended for round and hexagonal material.

The self-locking tongs consist in the main of a handle part with a spiral-shaped and, as a rule, serrated jaw, a pivot located at the polar centre of the latter, as well as a jaw part capable of rotating about a 0 pivot, with two locking faces forming a V-shaped opening with a top angle of 60° .

Self-locking tongs of this kind have been kncwn for many years. They are used frequently in Eastern Europe and in the East, whereas they have 5 not become very widespread either in Western Europe or the U.S.A.

This is surely due to the fact that the known tongs are produced ty hot forging or casting or a combination of these processes, and are therefore relatively strong, heavy and difficult to handle, owing to the C geometry of their configuration and usual design. If their appearance is to be confidence-inspiring, they become too costly, since this necessitates rather extensive finishing. Their appearance is therefore frequently rough and unfinished, and is not improved by cast-metal agglomerations and residual burrs due to drop-forging. In many cases 5 their teeth are forged or cast and remain unfinished, and as a rule they are made from the cheapest types of steel, with a final hardening and tempering resulting in a product with a semi-soft and rough surface.

Since the operation of these tongs depends on the friction which can be brought about between the tong jaws and the material to be gripped, and since the low hardness ana the roughness of the teeth, the edges of which are as a rule not sharp, are not particularly apt to produce high friction, they are designed in accordance with a geometry which entails extensive boosting of forces, in consequence wherecf tubular objects are readily deformed, in spite of the fact that the tongs are so wide. The large width and the high notch-impact strength, respectively, naturally result in a relatively large surface area and hence s rather low load per unit of area, as well as in high resistance to fractures caused by impacts. The wear resistance, on the other hand, is very low. In case of tongs with sharp edges when new the latter are rounded very quickly, and If the tongs are subject to high point loads, e.g. by being used on relatively small objects, or if they are used with objects harder than themselves, this immediately causes deformation of the teeth. As a result, the low wear resistance and the very low capacity of resisting deformation quickly entail a very considerable reduction of their capacity to produce high overall friction and an effective grip.

Even if this type of tongs has as such many good qualities, and even if they are colourfully lacquered, their image is poor. The visual impression is always that this type cf tongs has not changed in a hundred years and they evoke a picture cf obsolete processes and a poor production environment with much noise, smells, dust and the effects of - heat and cold.

The self-locking tongs according to the invention are special in that they are manufactured from an entirely new type of steel sheet produced in accordance with entirely new technology, which after coding, hardening and tempering has excellent characteristics including high core resistance, yield point and surface hardness, and w^rhich, further- more, after surface finishing has an attractive appearance with clean contours free from burrs and visible traces of the manufacturing processes, with especially sharp teeth and a very markedly different type of curvature. They are simple and, in spite of the fact that their weight is low, they are strong, their strength being so high that they can be supplemented by a shaft extender. They do noτ take up much room, are available in a very comprehensive choice ranging from extremely narrow to extremely wide even within the same clamping range, both with teeth for combined use on tubular and rod materials, bolts and nuts, fittings, union nuts e.g. for cuttering fittings for heating, water and sanitation applications, pneumatics and hydraulics, and without teeth substituting adjustable wrenches, open-ended spanners and similar devices, as well as a large selection in sizes from extremely small to extremely large, in addition to which there are models with loose, exchangeable or attached jaws for special purposes, and lastly they are produced with the aid of modern and rapid production methods, in certain cases by stamping, in which case 50,000 pieces can be produced per day and machine, and in other cases with the aid of computer-controlled laser cutting in accordance with the entirely new superpulse system, which, inter alia, makes it possible that entirely different types with special characteristics can be made, without the use the special tools, merely by producing one drawing.

The sharp teeth, which after a prolonged period of use will continue to remain sharp owing to the high breaking and wear resistance of the material and the very high surface hardness of Re 60-62 enter - if the tongs grip e.g. a tubular object - immediately into powerful contact with the surface of the object, as soon as a slightly backward pull is applied to the handle, thus inducing a starting friction, which, through the boosting of forces, directly increases in proportion with the torque applied to the tongs. The new type of curvature, the subject of a special patent application, will ensure that the progressive grip corresponds at all times to the handle moment applied to the tongs and that said "grip" will at all times have such a value that the deformation forces remain at a minimum.

As regards tongs made without teeth and which are therefore intended for use on hexagonal objects, the effect is the same. A virtually unnoticeable backward pull on the handle, followed by a torque, will lock the tongs and cause them to build up an entirely secure grip about the hexagon. This grip will in such a case increase in direct proportion to the handle moment, so that the tongs can never slip ever and one will never come across destroyed or damaged hexagons if tongs of this type are used.

Always mindful of the fact that tongs provided with teeth operate mainly by friction together with large point loads, one will, as a rule, see tooth marks, the size of which depends on the moment applied and the hardness of the object. When gripping smooth, hard objects also small marks are produced - small but still in evidence. In order to counter¬ act this phenomenon, certain tongs can be provided with loose jaws. These jaws are to consist of at least two basic constituents, i.e. a strong and tough basic material mixed with a large number of fine-grained and sharp particles of another material, the hardness of which must always be greater than the hardness of the object on which the tongs are to develop their grip. If this object consists of brass with or without chromium, nylon will be the right basic material, and the latter can then be filled with particles consisting in the main of silicon, which are therefore capable of ensuring that the tongs can develop their grip, these particles being, on the other hand, so small that they produce virtually no disfiguring traces. If the tongs are to be used for many hours on materials with a hardness Re 6C-62 use must be made of jaws produced of compound steel with analogous characteristics. This must be regarded in the same way as a winter tyre, which is based on the advantageous interplay between rubber and hardmetal, where the rubber is replaced by a tough steel. The loose jaws are produced according to a special process as precision-cast objects, ready for mounting in the plate parts of the tongs. If required, these jaws can be produced with separateparticles in a smooth surface and in quite the other extreme form, i.e. with pronounced teeth filled with the hard particles. In case of need, jaws can also be produced so as to make tongs capable of gripping objects with special profiles. Conventional two-bar-type tongs, with one bar constituting the arm and handle of the tongs themselves and another smaller bar serving as the operating or activating bar are generally not described as self-locking, even though in fact they are after all self-locking once they have been activated. If, after having applied a moment to these two-bar-tongs, one takes the fingers from the activating bar, while at the same time maintaining the moment, tongs of this type are also self-locking in all the cases in which the jaw teeth get a proper grip on the surface of the object. If such two-grip- type tongs are provided with jaws of the type described, they therefore become self-locking, which explains and justifies claim 6.

The application is described in detail below with reference to the enclosed five drawings showing different embodiments in accordance with the invention, wherein figs. 1, 2, 3 ^an- 4 show the four basic models in perspective while figs. 5_> 6 and 7 show the models with loose jaws attached respectively. Fig. 1 shows the so-called "standard" model

Fig. 2 " " " "half" " (right hand) Fig. 3 " " " "half" " (left hand) Fig. 4 " " " "double" "

Figs. 1 - 4 show that the tongs consist mainly of handle part (l), jaw part (2), pivot (3) and handle (4), as well as in case of the double model additionally jaw part (7) and jaw part (8).

The handle parts (1) and jaw parts (2) are stamped and cut by laser from steel sheet alloyed with boron with the composition C. 0.2, Mn 1 , Cr 0.5_S B 0.002 and are, in the plane state, entirely identical with all four models of the same size, and they are stamped or cut, respectively, complete with teeth and holes, and they new only require to be bent and embossed, which is done in such a way that so-called "left-hand" and "right-hand" blanks are produced. The handle jaw parts are provided with a longitudinal recess at either side of the handle. These recesses are used in fig. 1 and in fig. 4 for mounting and locking the plastic handle, as is shown in sectional form at the side of fig. 4- The same figures show that a "double" model, fig. 4 , can be produced by combining "right-hand" and "left-hand" blanks with the additional jaw parts (7) and (8).

The plastic handle (4) is easy to grip and covers the sharp edges of the steel plates, while at the same time the plastic handle is well protected by the steel plates against overloading, if the tongs are supplemented with a tubular extender, which must be taken all the way past the outer end of the plastic part.

Fig. 2 and fig. 3 show the "half" models, which, at the same size, consist of the same steel sheet blanks. The same plastic handle is not suitable for these models, but use must be made of a corresponding two- part handle, or as shov.n of a rubber handle (4) or alternatively one consisting of shrink plastic, unless one prefers to supply a model without handle by omitting the recesses in the steel parts. If that is the case, the side edges must be "edge-ground" or "edge-dressed", and the same applies to all other sharp edges which must not be sharp. The idea underlying "half" tongs is that they are as cheap as tongs can ever be - even if, owing to the characteristics of the steel, their quality is very high - that they can be produced from e.g. 2 mm plate and therefore take up very little space, and lastly the tongs in fig. 2 are flat on the underside when locking "in clockwise direction" (right hand) and the tongs in fig. 3 are flat on the underside when locking "in counter¬ clockwise direction" (left hand), while at the same time there Is a clearance between the handle and the base.

Owing to the characteristics of the steel, these "half" tongs can transmit a relatively very high moment and have e.g. proved particularly suitable for loosening hardened sheet metal screws, which - even with still very weak corrosion - can virtually not be removed, also if they are provided with ordinary slits or cross-slits, even when using the correct screwdriver, so that instead use must be made of small chisels, which e.g. quickly produce major, costly damage to latter.

It must also be pointed out that the same tongs, which after all are made from e.g. 1. and 2 mm sheet, are extremely suitable for counternuts, irrespective cf whether these are round, hardened and smoothed or hexagonal. If tooth marks on soft bolts and nuts are not permissible, use is made only of the model "without teeth".

Fig. shows tongs, where handle jaw part (1) is provided with an attached loose jaw (9) and assembled with two jaw parts (2), between which there is a loose jaw (10).

Fig. 6 shows tongs consisting of two handle jaw parts (1 ) with a recess with oblique corner cut-outs, which, without rivets, can hold fast the loose jaw, as well as two jaw parts (2) with a space at the bottom between them for mounting a loose jaw part. The upper part of jaw parts (2) is extended upward by comparison with conventional ones and are, In addition, bent towards one another so that they can be placed in the space between handle jaw parts (2) on pivot (3).

In fig. 7 the standard jaw part (2) has been replaced by a complete precision-cast jaw part (11 ).

Claims

1. Method for producing self-locking tongs designed to grip relatively round and hexagonal objects, irrespective cf whether these are unhardened or hardened, inasmuch as the tong jaws engage the object at 5 three points substantially 120° separate from one another, said tongs having a rotatable jaw part (2) with two jaw faces forming in respect of one another an angle of 6C° and engaging the object at two points, whereby said jaw part is rotatably ixed to a handle jaw part ( ) bearing a third jaw face which is so designed as to produce the third 0 engagement with the object, inasmuch as this jaw face is curved in such a way that the tongs can grip objects of different diameters and hexagonal objects with different widths across flats, c h a r a c t e r¬ i s e d in that handle jaw part (|) or jaw part (2) or both of them are produced of hardenable steel sheet. 5 2^ Self-locking tongs according to claim 1, c h a r a c t e r i s e d in that handle part ( ) or jaw part

(2) or both of them are produced by stamping or laser cutting.

3. Self-locking tongs according to claims 1 and 2, c h a r a c t e r¬ i s e d in that handle jaw part (l) and jaw part (2) are bent and 0 embossed so that two and two they constitute, each by itself, "right- hand" and "left-hand" pieces.

4- Self-locking tongs according to claims 1, 2 and 3_J c h a r a c t e r i s e d in that handle jaw part (l) or jaw part (2) or both of them are produced from steel sheet alloyed with boron with 5 a composition C. 0.2 - 0.25 Or 0.5 - 1-5 M 0.8 - 1.5 E 0.002 -

0.003, which after cooling is hardened and tempered to a depth of 0.1 - 0.15 nun, so that their resultant hardness amounts to Re βθ-62.

5. Self-locking tongs according to claims 1 , 2, 3 ^an(i 4_? c h a r a c t e r i s e d in that tongs can be constructed by assembling 0 a handle jaw part ( ), a jaw part (2) and a pivot (3), and made from sheets of different thickness from 1 mm upward.

6. Self-locking tongs according to claims 1 , 2, 5 ^ar-£ 4, c h a r a c t e r i s e d In that the tongs can be assembled from one or two laterally reversed handle jaw parts (1), two laterally reversed R jav, parts (2), a pivot and a plastic handle (4) or not, consisting either of one or several pieces fitted between c-r entirely encompassing handle jaw parts (|), and with or without recesses for fitting loose jaws of composite materials, nylon etc. with silicon compounds or carbides or compound steel.

7. Self-locking tongs according to claims 1, 2 and 3_> c h a r a c t e r i s e d in that they can be composed of a handle part (1) or two handle parts (1) made of steel sheet, with an inter¬ mediate layer (7) produced by powder pressing or casting, from compound steel or steel sheet, a pivot (3) and two laterally reversed jaw parts (2) made of steel sheet with an intermediate layer (6) produced by powder pressing or casting, from compound steel or steel sheet, and with or without recesses for inserted jaw parts.

8. Method for improving the friction-based gripping a.ction of twc-bar- pipe tongs by achieving an, in fact, self-locking function by producing such a fixed and/or loose pipe tong jaw part from compound steel, vrhich in this context is understood to be Cr and W-carbide grain within a tough steel material and which can be produced by powder pressing cr casting, or by as such known methods providing it with detached segments or details of compound steel.

9. Self-locking tongs according to one of the preceding claims, c h a r a c t e r i s e d in that both the curved part and the jaw part can be provided with loose "jaw parts" made from materials consisting of a tough matrix with fine-grained, hard fillers, e.g. glass-filled nylon, composite materials etc. or compound steel, which can ensure high friction and do not cause pressure marks and can, in addition, be used e.g. in ccn unction with chromium-piated and similar objects.