Technical Fi ld of the Invention In a first aspect, this invention relates to a grab tool of the shear-type, comprising two pivotably movable legs which are interconnected via a joint and whose lower parts are arranged to clamp an object to be lifted, and whose upper parts are connected to a coupling part which may be coupled to a lif- ting means, e.g., a chain, a cord or similar, the legs having the shape of plates in upper parts of which are formed slots accomodating the coupling part, which slots are obliquely posi¬ tioned in order to bring the upper parts - and, thereby, also the lower parts - of the leg plates to approach each other when a pulling force is applied to the coupling part .

Background. Objects and Characteristics of the Invention

Previously known grab tools of the type referred to above are composed of a comparatively large amount of compo- nents, each one of which on one hand requiring special working operations during the manufacturing, and on the other hand requiring special working moments in connection with the final assembly of the tool. The diversity of components leads to the result that the grab tools in their entirety become compara- tively costly to manufacture.

The present invention aims at eliminating the above mentioned disadvantages and creating an improved grab tool of the shear-type. Thus, a primary object of the invention is to provide a grab tool that is composed of a minimal number of separate components and, therefore, is possible to manufacture to a minimal total cost. A simultaneous object is to provide a tool which in spite of its constructive simplicity gives a simple and efficient function. In a particular aspect, the invention aims at providing a grab tool that is particularly suitable for the lifting of rails.

According to the invention, at least the primary object is achieved by the features that are defined in the characte-

rizing clause of claim 1. Preferred embodiments of the grab tool according to the invention are further defined in the dependent claims 2 to 5.

Besides the grab tool per se, the invention also rela- tes to a method of manufacturing grab tools of the shear-type. The features of the method according to the invention are de¬ fined in claim 6.

Brief Elucidation of the Prior Art A grab tool of the shear-type has been previously dis¬ closed in SU 887 415. However, this grab tool comprises two closed, V-shaped slots with which a closed ring cannot at all be brought into engagement. Moreover, the lower parts of the grab tool are not free, but articulatedly connected with special grab means.

Brief Description of the Appended Drawings

In the drawings Fig 1 is a frontal view illustrating a first embodiment of the grab tool according to the invention, in connection with an application upon an object to be lifted in the form of a rail, Fig 2 is a frontal view showing the same tool after having grabbed the rail, Fig 3 is a side view of the grab tool according to fig 1 and

2, Fig 4 is an enlarged frontal view showing an individual leg comprised by the tool according to fig 1 to 3, Fig 5 is a side view of the leg according to fig 4, Fig 6 is a frontal view corresponding to fig 2, showing a second, alternative embodiment of the tool according to the invention, Fig 7 is a side view of the tool according to fig 6, Fig 8 is an enlarged view showing solely a support element comprised by the tool according to fig 6 and 7, and

Fig 9 is a view illustrating a joint pivot comprised by the tool.

Detailed Description of Preferred Embodiments of the Invention

The grab tool shown in fig 1 to 5 comprises two legs 1, l ¹ which are held together by a common joint generally desig- nated 2. The tool also comprises a coupling member in the form of a ring 3 which may be coupled with an arbitrary, not shown lifting means, e.g., a hook, a chain, a cord or similar. The exemplified tool is specially shaped for the lifting of rails 4, which in a conventional way, in addition to a rail web, com- prises a foot 4' and a head 4". In a manner being characteristic for grab shears, the two legs 1, 1' are pivotable around the joint 2 in such a way that the lower parts 5, 5' of the legs approach each other when the upper parts 6, 6' approach each other and vice versa. The two legs have the shape of plates in whose upper parts are provided open slots 7, 7' which are obliquely posi¬ tioned in a direction outwards/upwards from their opening. As may be clearly seen in fig 1 and 2, the ring 3 is accomodated in these slots 7, 7' . Reference is now made to fig 4 and 5, which illustrate the features of an individual leg plate. In practice, the plate is most suitably made of sheet-metal with a thickness within the range of 10 to 20 mm, for instance about 15 mm. In an intro¬ ductory step, the sheet-metal is punched or cut to the prede- termined contour shape and formed with a hole 8 so as to form the previously mentioned joint. In a subsequent step, the sheet- metal is bent, more specifically in a region 9 between the upper part 6 and the lower part 5. As may be clearly seen in fig 5, the lower part 5 will be located in a plane that is parallel with, although staggered relative to, the plane in which the upper part 6 is situated. In practice, the lower part 5 is stag¬ gered in relation with the upper part 6 by a distance that cor¬ responds to half of the sheet-metal thickness. Thus, if the sheet-metal is 15 mm thick, the upper and lower parts are stag- gered by 7,5 mm relative to each other via the bent portion 9.

As may be seen in fig 4, the lower part of the leg plate has a wedge-shaped protrusion 10 arranged to delimit a

seat 11. More specifically, the seat 11 is delimited by three edge surfaces 12, 13 and 14, of which the first mentioned edge surface 12 constitutes a part of the protrusion 10. The edge surfaces 12, 13, 14 have jointly a contour shape which sub- stantially corresponds to the contour shape of the one half of the previously mentioned rail head 4". Underneath the tip of the protrusion 10, the protrusion is delimited by an edge surface 15 that extends obliquely relative to the main longitudinal exten¬ sion of the leg plate. As may be seen in fig 3, the joint that is designated 2 in its entirety is formed by a shaft pivot 16 onto which two flange-forming rings 17, 17' have been welded.

The assembling of the tool according to the invention is made in the following way. In a first step, the two leg plates 1, 1' are brought together with the ring, more specifi¬ cally by hooking the nose-like portions 18 outside the indivi¬ dual slot 7 on the ring. In a final step, the holes 8 of the two plates are brought into alignment with each other and the shaft pivot 16 is introduced into the holes and finally mounted by welding the flange rings 17, 17' onto the pivot. It should be noted that the two leg plates being designated 1 and 1', res¬ pectively, in fig 1, are identically the same, i.e., each one is manufactured with the shape that is illustrated in fig 4 and 5. By the fact that the lower part 5 of each leg plate has been laterally dislocated (by half the sheet-metal thickness) in relation with the upper part 6, the lower parts of the two leg plates will be positioned in a common plane on both sides of a vertical central plane through the joint 2. After the ring 3 has been accomodated into the slots 7, 7', and the shaft pivot 16 finally mounted in the described manner, the ring cannot be re¬ moved from the leg plates.

As to the geometry of the two leg plates, and with reference to fig 4, it should be pointed out that the outer, straight edge surface 19 of the upper part 6 extends substan- tially parallel to the main longitudinal extension of the leg. In the concrete example, the angle between this edge surface 19

and the slot 7 amounts to about 35°. In practice, this angle may vary within the range of 30 to 40°.

The grab tool according to the invention functions in the following way. Independently of whether the tool grabs a load or not, the two legs 1, 1' always strive to place them¬ selves in the mutual position that is shown in fig 2, as soon as the tool hangs from the appurtenant lifting means .

In this state, both the lower parts and the upper parts of the legs are approached to each other, and the lower portion of the ring 3 is located at the bottom-like ends of each slot 7, 7' . When the tool in an empty state is lowered over a rail, the obliquely positioned edge surfaces 15 on the lower parts of the leg plates will force the lower parts apart, so that the clamp that is formed by the two seats 11 will open. In the entirely lowered state of the tool, the protrusions 10 will grab into the underside of the rail head and when the tool is anew lifted by the application of a pulling force in the lifting means, the clamp shuts, more specifically by the fact that the lower por¬ tion of the ring transfers to the noses 18 component forces which, by the oblique positions of the slots, strive to move the upper parts 6, 6' of the leg plates in a direction towards each other. This has the result that also the lower parts 5, 5' app¬ roach each other, while clamping the rail head 4" in the clamp formed by the seats 11. Of course, the lifting of rails with a pronounced length requires at least two grab tools which are axially sepa¬ rate from each other. Therefore, in practice, for the lifting of specifically rails, two separate grab tools are arranged on a common yoke which in turn is lifted by a suitable lifting ar- rangement.

At a purely vertical lifting of, e.g., rails, sub¬ stantially only vertical forces are applied upon the two leg plates of the tool. However, it also occurs that rails are lifted at one of their ends and dragged with their other end against the ground. In such cases, also horizontal component forces are applied upon the tool. More specifically, both ver¬ tical and horizontal component forces are applied upon the upper

parts of the leg plates via the ring, at the same time as the lower parts of the leg plates are held against the rail head. Where the horizontal forces are sufficiently large, e.g. when the rail is long and heavy, there is a risk that the upper parts of the leg plates are deformed at their transitions to the lower parts. Such deformation tendencies result in that the legs jam when pivoting and in worst case the deformation may become so pronounced that the tool becomes unusable.

In order to avoid such a deformation - according to the embodiment shown in fig 6 to 9 - on at least one of the leg plates, in this case the leg plate 1, a protruding support element 20 is arranged at an angle to the plate. In the example, this support element consists of a plate or a sheet-metal of a substantially triangular basic shape. As may be seen in fig 8, the support plate 20 is delimited by on one hand two small side- like edges 21,22 which extend in a right angle to each other , and on the other hand by an obliquely positioned edge 23 which has the character of a hypotenuse. In the plate is a recess 24 which opens in the edge portion 21. The support plate 20 is welded or fastened in any other way on the outside of the leg plate 1 in such a way that the support plate extends in a right angle to the plane of the leg plate. More specifically, the support plate 20 is placed so that it takes a substantially ver¬ tical position when the legs 1,1' take their active, grabbing position according to fig 6. Further, it may be noted that the lower edge 22 extends perpendicularly outwards from the plane of the leg plate 1 and that the rectangular recess 24 extends pa¬ rallel with this lower edge 22.

^' A shaft pivot 25 with a head or end flange 26, as shown in fig 9, serves as a joint. The diameter of the pivot 25 is substantially equally large as the width of the recess 24.

When the tool is assembled, in a first step the ring 3 is passed into the slots 7,7', whereafter the shaft pivot 16 is passed through the holes in question in the leg plates 1,1', to an end position in which the inner end portion of the pivot is accomodated in the recess 24, at the same time as the head 26 is located on the outside of the leg plate 1' . In this condition,

the pivot 25 is welded to the edge portions on the support plate 20 that delimits the recess 24. In this way, the joint pivot is fixed relative to the support plate 20 as well as the leg plate 1, at the same time as the other leg plate 1' is freely rota- table relative to the pivot and is kept together with the leg plate 1 by means of the head 26.

The function of the support plate 20 may be clearly seen in fig 6 and 7. When the grab tool is applied to the rail 4 and submitted to the influence of both vertical and horizontal component forces in connection with the rail being simulta¬ neously lifted and pulled, the lower edge 22 of the support plate will be laid against the upper side of the rail head and prevent that the upper parts 6,6' of the leg plates are bent or otherwise deformed relative to the lower parts 5,5' that are clamped against the rail head.

Feasible Modifications of the Invention

The invention is not restricted solely to the embo¬ diments as described and shown in the drawings. Hence, it is feasible to form the grab tool for lifting entirely different objects than just rails. The only essential is that the shape of the lower parts of the leg plates are adjusted to the shape of the object in question to be lifted. In connection therewith, it may become necessary to complete the lower parts of the leg plates with special additional means, e.g., clamping plates that are placed crosswise relative to the sheet-metal, or similar. In this context, it may be noted that the slot does not necessarily have to be linear as shown in the drawings. Thus, the slot may also be slightly arched. It is also feasible to provide support plates 20 not only on one of the leg plates, but also on the other one.