METHOD OF MANUFACTURING A THREAD INSERT AND A THREAD INSERT MANUFACTURED ACCORDING TO THE METHOD

Abstract: Method of manufacturing a thread insert of a metallic plate, which has been treated by means of etching so that it gets projecting details on both sides, whereafter the plate is formed in a suitable way. The invention also relates to a thread insert manufactured according to the method.

Description: Method of manu acturing a threa -insert and a thread insert manufactured according to the method This invention relates to a new type of thread insert. When screws are to be threaded into holes in soft mate¬ rials, for instance plastics materials, wood, chipboard, aluminium alloys, lead etc. several difficulties can appear. One reason can be that due to the strength or the grain size of the material it .is difficult to design a thread in the " hole. In other cases the reason is that the resistance to wear of the material is so low that the thread is destroyed by screwing on and off a few times. A third reason can be that due to corrosion the material adheres so hard against the screw that when screwing off fracture occurs in the thread of the hole. In order to eliminate these problems thread inserts of wear-resisting material, for instance steel or brass are used. These thread inserts are often designed as a pro¬ file-wire rolled to a screw thread these thread inserts being able to strengthen a thread, which is made in a soft material or a material with a low wear-resistance. The thread inserts can also be designed as solid bushings with a threaded hole and with the outside formed to grip a soft material by grooves, ridges, strips or teeth, and are then fastened to the soft material by pressing, casting or ultra-sonic welding. The former type of thread inserts implies that the mate¬ rial can be threaded, while the latter type often requires that the material stands to be deformed during the faste¬ ning procedure. This invention relates to a thread insert, which compared with previously known types has low cost, does not require previous thread cutting in the material, gives small de- formations of the wall of the hole, does not require special equipment for the application, allows coarse sur¬ faces and tolerances in the hole, gives a vibration se¬ cure holding of the screw and allows unlimited number of on-and- offscrewings. The invention shall be more closely described with refe¬ rence to the accompanying drawing, which discloses a number of preferred embodiments, and in which Pigs. 1 and 2 disclose a thread insert before bending but after the plate's being etched and cut, Pig. 3 discloses a thread insert being put into a hole and Pigs. 4-6 disclose different embodiments of the thread in¬ serts put into the hole. The thread insert'is manufactured of sheet metal of hard, wear-resisting and elastic material, for instance spring steel. By etching so much material is removed from one side of the plate that the remaining parts of the origi¬ nal surface form a pattern of narrow ridges, dots or other figures, which form a small part of the total surface and are adapted to grip a material, which is softer than that of the plate. From the other side of the plate so much ma¬ terial is removed by etching that the remaining projecting parts form parallel ridges with a distance and a width that correspond to those of the threads of the screw to which the thread insert is intended to fit. The plate is thereafter divided into rectangular pieces which are bent to almost closed gutter-form with such a section that when put into a circular hole they touch the hole with at least one of the free ends and with at least a further area along the periphery. The ^bending is made in such a way that the parallel ridges on the inside of the plate get the same angle towards the axis of the hole as the thread of the screw. Instead of turning the plate in connection with the bending in order to get the right angle between the parallel ridges and the axis of the hole the etching of the parallel ridges can be made in such a way that the intended angle is directly attained. The embodiment according to Fig. has a somewhat flatten¬ ed horseshoe-formed section, which touches the hole with the two cut edges and an area diametrically opposite to these edges. This form allows an easy on-and offscrewing, allows specially large variations in the form of the hole and gives the screw an elastic attachment with a possibi¬ lity of angular motion. The embodiment according to Fig. 5 has a more triangular section, which touches the hole with the two cut edges and two areas along the periphery. This form requires a greater accuracy in the form of the hole but gives a firmer ' grip round the screw with less possibilities of motion. The embodiment according to Pig. 6 has an unsymmetrical, triangular section, that touches the hole with a cut edge and two areas along the periphery. The other cut edge touches the screw. This form gives a strong resistance against offscrewing and is intended for such cases where the highest security against the screw's getting loose due to vibrations is wanted. The invention is, of course, not limited to the mentioned embodiments but can be varied within the scope of the following claims. Thus, the thread inserts, for instance, can have another form than what has been disclosed. Further, instead of etching a big plate which is divided into " smal- ler plates, small plates can be etched, w h ic h are t h en bent to a suitable form, eventually after cuttin g . O PI

Claims: Claims 1. Method of manufacturing a thread insert, which shall be a holder for a threaded screw in a hole in a material, c h a r a c t e r i z e d in that a metallic plate is treated by means of etching, whereby material is removed from the original surface of the plate so that projecting details appear on the two sides of the plate, whereafter the plate is formed in a suitable way. 2. Method according to claim 1, -c h a r a c t e r i z e d in that the plate is so formed that it touches the wall of the hole with at least one edge and at least one area of the periphery. J. Method according to claim 2, c h a r a c t e r i ¬ z e d in that the plate touches the wall of the hole with a cut edge and- two areas of the periphery, while the other cut edge is so positioned that it rests against the screw when screwing on the same. 4. Method according to claim 2, c h a r a c t e r i z e d in that the plate touches the wall of the hole with its two cut edges and an area of the periphery approximately dia¬ metrically opposite these edges. 5. Method according to claim 2, c h a r a c t e r i z e d in that the plate touches the wall of the hole with both cut edges and two areas along the periphery. 6. Method according to anyone of the preceding claims, c h a r a c t e ri z e d in that the projecting details on the inside of the plate comprise parallel ridges. 7. Method according to claim 6, c h a r a c t e r i ¬ z e d in that all ridges are positioned in the same mu¬ tual distance and that the plate is so formed that the parallel ridges form the same angle with the axis of the hole as do the threads of the screw. 8. Method according to anyone of the preceding claims, c h a r a c t e r i z e d in that the projecting details on the outside of the plate comprise dots, ridges or a combination of these. 9. Method according to anyone of the preceding claims, c ha r a c t e r i z e d in that the plate Is so formed that before bending it has rectangular or square form. 10. Method according to anyone of the preceding claims, c h a r a c t e r i z e d in that the plate is made of spring steel. 11. Thread insert manufactured by the method according to anyone of the claims 1 - 10. JSLEA OMH IPO «&*»

Inventors: SUNDSTROEM E
Applicants: SANDVIK AB, SUNDSTROEM E
Application year: 1980
Main classification: C23F1
IPC codes: F16B13