A METHOD OF MAKING SHELL SEGMENTS FOR EXPANSION BOLTS, APPARATUS FOR CARRYING OUT THE METHOD AND EXPANSION BOLT COMPRISING SHELL SEGMENTS MADE BY THE METHOD

Abstract: A system for manufacturing expansion bolts, in par­ ticular their shells, which comprise a plurality of gener­ ally channel-shaped segments. A continuous trip of metal having substantially the width and the channel shape of the shell segments to be produced, is sub­ jected to cold deformation following manufacture of an intermediate product with at least locally a smaller size than the finished product, this size difference being judicially selected so as to necessitate a certain amount of cold deformation resulting in a local increase of ma­ terial strength.

Description: Title: A method of making an expansion bolt, apparatus for carrying out the method, and expansion bolt made by the method. This invention relates to a method of making an expansion bolt, in particular the shell segments thereof, which have a generally channel-shaped cross-sectional configuration with an interior ramp adjacent one end thereof for the wedge-shaped expansion element of the device. Expansion bolts generally consist of a central bolt with an expansion element in the form of a widened head or a screwed-on nut at one end, and an operating member at the other end, referred to herein as the head end, by means of which bperating member, by rotation of the bolt, the head or the nut can be drawn towards the operating end. The bolt is surrounded by a plurality of segments of a shell which, in the non-expanded condition form a substantially closed cylinder around the bolt. The assembly can be placed in a pre-drilled hole, and by rotation of the bolt the expansion element can be moved, whereby the shell segments are expanded swivelling about an end located in the vicinity of the operating member of the bolt, and the expansion bolt becomes wedged in the hole. The expansion element may have a wedge-shaped configuration, and during the initial expansion of the shell segments cooperate with an inclined surface formed on the inside of these segments. The shell segments of most of the prior expansion bolts have hitherto been made by casting in lost sand moulds, whereafter they are made malleable by annealing for a long time, that is to say, the segments, which after casting are still brittle, are given the required tenacity to avoid breakage from local loads exerted during the expansion. Nevertheless, especially if the expansion element is made of a hard material, fracture regularly occurs in the segments. On account of the coarse tolerances, and the fact that the known expansion bolt shell segments are often not straight; the use of expansion bolts equipped with such segments not infrequently entails difficulties in that they do not properly fit pre-drilled holes, and in the case of crooked segments, the range of expansion is limited, and the ratio of plug diameter/hole diameter is relatively small. Furthermore, the result of major dimensional differences of the shell segments is that prior expansion bolts cannot be assembled automatically. In addition to the casting process, shell segments for expansion bolts can be made by pressing from wire or rod-shaped material. A disadvantage of this is a very high power consumption, and relatively large amounts of waste material. Both prior techniques have the drawback of being relatively expensive. All of the drawbacks mentioned hereinbefore are avoided when, in accordance with the present invention, for the manufacture of case segments for expansion bolts, as defined in the opening paragraph of this specification, a continuous metal strip having substantially the width and channel-shaped cross-sectional configuration of -the shell segments to be made is subjected to shaping operations, comprising first removing material to produce an intermediate product having at least locally smaller transverse dimensions than that of the contemplated end product, taking account, as regards both the place thereof and the amount of material removed, of the degree of cold deformation required for the at least local increase in material strength, bringing the resulting intermediate product into the final form by cold deformation, and separating thus completed shell segments from the strip. The method according to the invention ensures accurate dimensioning, minimal waste and lends itself to fabricating the segments of stainless steel, while, as compared with prior methods of manufacture for such segments, a saving in cost of 50% has proved possible in practice. Moreover, in the method according to the invention, use is made of the circumstance that the cold deforma tion of metal results in an increase in strength. Indeed, within the framework of the present invention, the cold deformation not only serves for shaping purposes, but also for strengthening the locations of the shell segments where, in use of the expansion bolt, the expected load is greatest. In particular, in this manner, material reinforcements can be realized at the friction-increasing mouldings provided on the outside of the segments, and at the ramp for the expansion element. For the manufacture of a shell segment having annular grooves in its outer circumference, designed to receive annular members for keeping the shell segments together around the bolt, according to a preferred feature of the presen#t invention, notches are punched from the edges in the annular groove zones, said notches being of such depth that the width of the remaining web portion between the notches is less than the relevant dimension of the end product, and during the cold de-formation of the annular grooves, the width of the web portion can be adjusted to the required size. In the case of expansion bolts equipped with an expansion element formed as a nut screwed on the bolt, rather than an expansion head fixedly secured to the bolt, the shell segmentstmay¯be provide* with a x-est-rietfd neck portion which adjacent to the ramp connects the web of the shell segments with an inwardly projecting terminal edge to retain and surround the expansion element. According to the invention for the manufacture of such shell segments, so much material can be removed laterally from said neck zone that during the subsequent cold deformation by displacement of material both from the neck zone proper and from the ramp zone, the transverse end dimension is reached in both zones. The ramp zone, which forms a heavily loaded location of the shell segments, is thus additionally reinforced. For the performance of the method the present invention provides a follow die device comprising feeding means for feeding strip-shaped material, die means and cutting means for severing end products from the strip, said die means comprising dies for locally removing material from the strip and a die for forming a shoulder in the strip by partial shearing action, there being provided a stop surface facing in the downstream direction for the shoulder formed, said stop surface being situated downstream of said shearing die and upstream of a forming die and said cutting means. Preferably the various follow die members are controlled in such a manner that after the strip has been placed in position with a shoulder in contact with the stop surface, first a shell segment previously brought into its final form is severed from the strip, and only then a next intermediate product is brought into its final form by cold deformation In case during the final forming operation an elongation of the intermediate product is brought about, the shoulder prevents such elongation from being transmitted in the upstream direction, which would interferewith the uniformity of the material supply, and the shoulder also serves as a reference for the function of the cutting means. There are a number of advantages in first cutting off the strip of material and only then carrying out the cold-deformation step. During the cutting-off operation the stop surface can be used as a reference, and any elongation from the cold deformation can take place in the downstream direction without interference from the cutters. Furthermore, as regards the control of the various parts of the follow die, the cutters have the longest cycle, and with the sequence of operation accor dingto the invention the non-effective part of this cycle can be utilized for the cold deformation operation. The invention also relates to shell segments made in accordance with the invention, and an expansion bolt provided with such shell segments. One embodiment of the follow die will now be described, by way of example, for clarifying the invention, with reference to the accompanying drawings, in which Fig. 1 is a perspective view of one embodiment of an expansion bolt; Fig. 2 diagrammatically shows an apparatus for the manufacture of shell segments for the expansion bolt shown in Fig. 1; Fig. 3 is side-elevational view and Fig. 4 a top plan view of a strip which has been operated upon in successive stages; and Fig. 5 is a bottom view of a shell segment according to the arrow V in Fig. 3. As shown in Fig. 1, an expansion bolt is composed of a bolt 1 having a head 2 with which bolt 1 can be rotated. Bolt 1 carries an expansion element 3, which in the embodiment shown is a nut, which by rotation of bolt 1 can be moved axially on bolt 1. Bolt 1 and nut 3 are embraced by a shell composed of a plurality of segments 4 which in the non-expanded condition are held together by a spring ring 5 and by a beaded edge 6 formed on a metal cap 7. After being positioned in a pre-drilled hole, bolt 1 can be rotated to move nut 3 into the direction of head 2, whereby segments 4 are expanded, tilting about the end under cap 7, and clamp down against the hole wall. Shell segments 4 for the bolt of the type shown in Fig. 1 have a channel-shaped cross-sectional configuration, which is shown on the left in Fig. 4. Each segment has on its web portion on the outside annular groove segments 8 and 9 for receiving beaded edge 6 and spring ring 5, respectively, and further an inwardly-projecting terminal edge 10 connected to the web portion by a restricted neck portion 11. The convex outer surface of segments 4 is provided with a moulding 12 for increasing the friction on the wall of a drilled hole, and with a ramp 13 on the inside for nut 3. As shown in Fig. 4, in the nonexpanded condition, shell segments 4 are capable of retaining and enclosing nut 3 with the terminal edges 10 and the restricted neck portions 11. For the manufacture of such shell segments, use can be made of an apparatus broadly shown in Fig. 2, which comprises guide means 14 for channel-section strip material 16 fed -from a supply 15. Disposed downstream of guide means 14 are transport means 17 for incrementally feeding strip 16 to a follow die device 18, in which the successive operating stations are designated by A, B, C, E and D. By the same characters, the operations on strip 16 are designated in Figs. 3 and 4. These operations are: A. forming intermediate products by removing material from the side edges of the strip 16 in the zones where later the annular groove segments 8 and 9 and neck 11 are formed; B. partially shearing strip 16 for forming a shoulder 19 therein; C. positioning strip 16 with shoulder l9 behind a stop 2Q; D. separating a completed shell segment 4 from the end of the strip by means of cutters 21; E. making an end product by cold deformation in a press 22 of the intermediate product present right behind the stop (end of cycle). Phase D (separation) should preferably be carried out before the performance of the cold-deformation step, so that the path of movement of the strip in the vicinity of the cutters is cleared, and any elongation of material which may occur during the cold-deformation step can take place unimpeded, and the overall length of the follow die device 18 can be minimized. In phase A, more material can be removed than would be strictly necessary for final dimensioning. Thus, for example, in phase A, measurements m, n and p may be less than the corresponding final measurements ml, n and pl in phas-e E. Final measurements ml, nl and pl are then realized during the cold-deformation phase by displacement of material, which results in a local increase in strength. In particular, measurement p of neck portion 11 can be realized by displacing material both from neck portion 11 proper, and from the zone of ramp 13, whereby this is additionally reinforced, which is beneficial by reason of the fact that during the initial phases of the expansion this zone is very heavily loaded.

Claims: CLAIMS: 1. A method of making an expansion bolt, in particular the shell segments thereof, which have a generally channelshaped cross-sectional configuration with an interior ramp adjacent one end thereof for the wedge-shaped expansion element of the device, characterized in that a continuous metal strip having substantially the width and channel-shaped cross-sectional configuration of the shell segments to be made is subjected to shaping operations, comprising first removing material to produce an intermediate product having at least locally smaller transverse dimensions that that of the contemplated end product, taking account, as regards both the place thereof and the amount of material removed, of the degree of cold deformation required for the at least local increase in material strength, bringing the resulting intermediate product into the final form by cold deformation, and separating thus completed shell segments from the strip. 2. A method according to claim 1, for the manufacture of a shell segment having annular grooves in its outer circumference, characterized in that notches are punched from the edges in the annular groove zones, said notches being of such depth that the width of the remaining web portion between the notches is less than the relevant dimension of the end product, and during the cold deformation of the annular grooves, the width of the web portion is adjusted to the required size. 3. A method according to claim 2 for making a shell segment with a restricted neck portion which adjacent tothe ramp connects the web of the shell segment with an inwardly projecting terminal edge to surround and retain the expansion element, characterized in that so much material is removed laterally from said neck zone that during the subsequent cold deformation by displacement of material both from the neck zone proper and from the ramp zone, the transverse end dimension is reached in both zones. 4. A follow die device for carrying out the method according to any one of the preceding claims, comprising feeding means for feeding strip-shaped material, forming die means and cutting means for severing end products from the strip, said die means comprising dies for locally removing material from the strip and a die for forming a shoulder in the strip by partial shearing action, there being provided a stop surface facing in the downstream direction for the shoulder formed, said stop surface being situated downstream of said shearing die and upstream of a forming die and said cutting means. 5. A device according to claim 4, characterized in that the various follow -die members are controlled in such a manner that after the strip has been placed in position with a shoulder in contact with the stop surface, first a shell segment previously brought into its final form is severed from the strip, and only then a next intermediate segment-product is brought into its final form by cold deformation. 6. An expansion bolt shell segment made by the method according to any one of claims 1-3. 7. An expansion bolt comprising shell segments according to claim 6.

Inventors: VERMEULEN, JOHANNES WILHELMUS IGNATIUS
Applicants: VERENIGDE BEDRIJVEN VAN THIEL  (VAN THIEL UNITED) B.V.
Application year: 1981
Main classification: B23P15
IPC codes: B23P15, B21D53