GB2048419A

GB2048419A - Expansion unit for screw socket for anchor bolt

Info

Publication number: GB2048419A
Application number: GB8013417A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-04-24
Filing date: 1980-04-23
Publication date: 1980-12-10
Also published as: GB2048419B; ES8104863A1; CA1136910A; AU531284B2; AU5765780A; ZA796218B; ES490870A0

Abstract

An expansion unit for a screw socket in which an an anchor bolt may be inserted, comprises a plug 14 which has a polar axis that defines a longitudinal direction, which tapers longitudinally, which has a screw-threaded longitudinal bore 16 therethrough and which has at least two longitudinally extending sides 19 that are transversely outwardly convex with major portions thereof having radii of curvature that are larger than their radial distances from the polar axis, retained within a shell having a plurality of leaves 12 which provide an internal profile corresponding to the external profile of the plug. The plug may preferably be oblong with the shell having two leaves or 3- sided, with the shell having three leaves. <IMAGE>

Description

SPECIFICATION An expansion bolt This invention relates to an expansion unit for an anchor bolt assembly and an anchor bolt which includes the expansion unit.

According to the invention there is provided an expansion unit for an anchor bolt assembly comprising an expansion member which has a polar axis that defines a longitudinal direction, which tapers longitudinally, which has a longitudinal bore therethrough and which has at least two longitudinally extending sides that are transversely convex with major portions thereof having radii of curvature that are larger than their radial distances from the polar axis, retained within; a shell having a plurality of externally serrated wall engaging members providing an internal profile corresponding to the external profile of the expansion member.

It is to be noted that the wall engaging members are also referred to in the art as leaves and the expansion member as a plug.

As those skilled in the art will appreciate, the leaves will preferably increase in thickness longitudinally, in the opposite direction of the plug.

In a first particular embodiment the plug may have an oblong transverse cross-sectional profile, which may particularly be elliptical, oval or oblate. The plug may then have at least one longitudinally directed fin receivable in a slot between the leaves.

With this oblong embodiment, the shell may have two leaves.

In an alternative particular embodiment, the plug may have three sides. These three sides may intersect, in transverse cross-sections, at the vertices of equilateral triangles, the sides of the triangles varying in length from one end of the plug to the other. The sides may further be arcuate in transverse cross-section, having as centres the opposite vertices. It is further preferred that the plug is truncated at its thicker end, such that at its thicker end it has six longitudinally extending surfaces only three of which engage the leaves. The three surfaces that do not engage the leaves may form part of a circular cylinder having the polar axis as its axis. With this plug, it will be appreciated that the shell has three leaves.

A clip may be provided to hold the shell together and/or the expansion unit may have a bail. Such a bail may have a skirt at its end in which the plug is received.

The bore of the plug may be screwthreaded, a complementary screw-threaded rod or stud being engageable therewith.

The invention extends further to an expansion bolt which includes an expansion unit in accordance with the invention in combination with a rod that is engageable with the expansion member either screw-threadedly or in some other manner to displace the expansion member longitudinally.

The invention is now described, by way of examples, with reference to the accompanying drawings, in which: Figure 1 shows a three-dimensional view of a first embodiment of an expansion unit in accordance with the invention; Figure 2 shows a longitudinal sectional view of the expansion unit of Fig. 1, along line A-A in Fig. 1 and line Il-Il in Fig. 3; Figure 3 shows a transverse sectional view of the expansion unit of Figs. 1 and 2, along line A-A in Fig. 1 and line Ill-Ill in Fig. 2; Figure 4 shows a three-dimensional view of a second embodiment of an expansion unit in accordance with the invention; Figure 5 shows a longitudinal sectional view of the expansion unit of Fig. 4, along line B-B in Fig. 4 and line V-V in Fig. 6;; Figure 6 shows a transverse sectional view of the expansion unit of Figs. 4 and 5, along line B-B in Fig. 4 and line VI-VI in Fig. 5; Figure 7 shows schematically the transverse profile of a plug of the expansion unit of Figs.

4, 5 and 6, at its thicker end; and Figure 8 shows schematically the transverse profile of the plug of the expansion unit of Figs. 4, 5 and 6, at its thinner end.

Referring to Figs. 1, 2 and 3 a first embodiment of an expansion unit is designated generally by reference numeral 1 0. It comprises a shell formed from two leaves 1 2 which are externally serrated. The leaves 1 2 co-operate to form a cavity in which is located a plug 1 4.

The plug 1 4 has an axial screw-threaded bore 16. As shown in Figs. 1 and 2, the plug 14 tapers longitudinally. Further, as is seen in Fig. 3, in planes transverse to its polar axis 1 8 the plug 1 4 has an oblong profile. Thus, transversely with respect to the axis 1 8 the plug 1 4 is thicker in one direction than in the other. Two longitudinally directed fins 20 are provided on the outer surface of the plug 1 4 on its thicker sides.These fins 20 are received in slots 22 defined between the leaves 1 2. On its thinner sides, the plug 14 has surfaces 1 9 which engage the inside surfaces of the leaves 1 2. These surfaces 1 9 are transversely convex and at any point along major central portions they have radii of curvature that are greater than the radial distance from that point to the polar axis 1 8 of the plug 14. Further as seen in Fig. 3, the leaves 1 2 have an internal profile corresponding to the external profile of the plug 14. The two leaves widen from a narrow end 24 to a thicker end 26. A bail 28 is secured to the leaves 1 2 at their narrow ends 24. The bail 28 has a body portion 30 from which depends two legs 32.The free ends of these legs 32 are welded to the thinner ends 24 of the leaves 1 2. Further, the bail 28 has a crown portion 34 which is inwardly dimpled at 36, the crown portion 34 being attached to the body portion 30 by means of three bridge portions 38. Finally, the leaves 12 are held together by means of a clip (not shown).

Referring to Figs. 4, 5 and 6, a further embodiment of an expansion unit is shown, designated generally by reference numeral 10.1. This unit 10.1 is similar to the unit 10 of Figs. 1, 2 and 3 and similar parts are referenced with the same number, being distinguished by meals of a suffix '.1'. It will, however, immediately be noticed that the unit 10.1 has a plug 14.1 that has three surfaces 19.1 that engage the leaves 12.1 and that there are correspondingly three leaves 1 2.1.

If regard is had to Fig. 8, it will be seen that at the thinner end of the plug 14.1 the surfaces 1 9.1 intersect at the vertices of an equilateral triangle and that they are arcuate, having centres at the vertices. Accordingly, at any point on the surfaces 19.1 at this end, the radius of curvature R, is greater than the radial distance R2 from that point to the polar axis 18.1.

It will be appreciated that if the surfaces 19.1 were to extend their full width, as the plug 14.1 widens; that the edges defined by their intersections would project from the shell defined by the leaves 1 2.1. As this is not desirable, the surfaces 1 9.1 are truncated, progessively towards the thicker end of the plug 14.1, by surfaces 23.1 that lie on a circular cylinder having R3 as radius, as shown in Figs. 4, 5, 6 and 7. Further as will be seen in Fig. 7, the surfaces 19.1 have radii of curvature R1' at the thicker end of the plug 1 4. 1 that are greater than the radial distance R2' of the surfaces 19.1 from the axis 21.1. It will also be appreciated that this is also the case at all axial positions between the ends of the plug 14.1.

In use the expansion units have their plugs screwed onto screw-threaded rods (not shown) to form anchor bolt assemblies. The expansion units are then inserted into holes in a wall, usually in mining operations, so that the outer surfaces of the shells engages the walls of the holes.

When the rods are rotated rotation of the plugs is resisted causing the plugs to move longitudinally within their shells thereby spreading their leaves apart. The leaves are thus forced to engage and grip the walls firmly thereby securely anchoring the rods in the holes.

Claims

1. An expansion unit for an anchor bolt assembly comprising an expansion member which has a polar axis that defines a longitudinal direction, which tapers longitudinally, which has a longitudinal bore therethrough and which has at least two longitudinally extending sides that are transversely convex with major portions thereof having radii of curvature that are larger than their radial distances from the polar axis retained within; a shell having a plurality of externally serrated wall engaging members providing an internal profile corresponding to the external profile of the expansion member.

2. An expansion unit as claimed in Claim 1, in which the wall engaging members increase in thickness in a longitudinal direction, oppositely to that of the expansion member.

3. An expansion unit as claimed in Claim 1 or 2, in which the expansion member has an oblong transverse cross-sectional profile.

4. An expansion unit as claimed in Claim 3, in which the expansion member has at least one longitudinally directed fin receivable in a slot between the wall engaging members.

5. An expansion unit as claimed in Claim 3 or 4, in which the expansion member has an elliptical transverse cross-sectional profile.

6. An expansion unit as claimed in Claim 3 or 4, in which the expansion member has an oval transverse cross-sectional profile.

7. An expansion unit as claimed in Claim 3 or 4, in which the expansion member has a oblate transverse cross-sectional profile.

8. An expansion unit as claimed in Claim 1 or 2, in which the expansion member has three sides.

9. An expansion unit as claimed in Claim 8, in which the three sides intersect, in transverse cross-sections, at the vertices of equilateral triangles.

10. An expansion unit as claimed in Claim 9, in which the sides are arcuate in transverse cross-section, having as centres the opposite vertices.

11. An expansion unit as claimed in any one of Claims 8 to 10, in which the expansion member is truncated at its thicker end, such that at its thicker end it has six longitudinally extending surfaces only three of which engage the wall engaging members.

12. An expansion unit as claimed in Claim 11, in which the three surfaces that do not engage the wall engaging members form part of a circular cylinder having the polar axis as its axis.

1 3. An expansion unit as claimed in any one of the preceding claims, in which the bore of the expansion member is screwthreaded.

14. An expansion unit as claimed in any one of Claims 3 to 7, which has two wall engaging members.

1 5. An expansion unit as claimed in any one of Claims 8 to 12, which has three wall engaging members.

1 6. An expansion unit as claimed in any one of the preceding claims, which includes a clip which holds the shell together.

1 7. An expansion unit as claimed in any one of the preceding claims, which includes a bail.

18. An expansion unit as claimed in Claim 17, in which the bail has a skirt in which the expansion member is received.

1 9. An expansion unit substantially as described in the specification with reference to the accompanying drawings.

20. An expansion bolt which includes an expansion unit as claimed in any one of the preceding claims in combination with a rod that is engageable with the expansion member to displace the expansion member longitudinally.