US2903938A

US2903938A - Anchor bolt having elastically connected wedge members

Info

Publication number: US2903938A
Application number: US632036A
Authority: US
Inventors: Strand Sven Hugo
Original assignee: Individual
Current assignee: Individual
Priority date: 1956-01-18
Filing date: 1957-01-02
Publication date: 1959-09-15
Anticipated expiration: 1976-09-15

Description

Sept. 15, 1959 s. H. STRAND 2,903,933

ANCHOR BOLT HAVING ELASTICALLY CONNECTED WEDGE MEMBERS Filed Jan. 2 1957 2 Sheets-Sheet 1 FIG.1 FIG? n, a l; i: 8 i 7 l' ":Hi

1| {I I: 1} TI :l :1 L 44 INV TOR. Ann/Z 7

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12,4, z/AWJ Sept; 15, 1959 s. H. STRAND 2,903,938

' ANCHOR BOLT HAVING ELASTICALLY CONNECTED WEDGE MEMBERS Filed Jan; 2, 1957 2 Sheets-Sheet 2 'FIG.4

IN V EN TOR.

ANCHOR BOLT HAVING ELASTICALLY CON- NECTED WEDGE MEMBERS Sven Hugo Strand, Stockholm, Sweden Application January 2, 1957, Serial No. 632,036

Claims priority, application Sweden January 18, 1956 4 Claims. (Cl. 85 -2.4)

The present invention relates to a bolt to be anchored to the rock in the ceiling and walls of galleries and rock chambers, which bolt is to be inserted in a bored hole and secured there, so that for example a cracky rock portion is held together, the free end of the bolt being provided with a nut and a washer or the like, and the invention is substantially characterized in that two cooperpating wedges axially displaceable in relation to each other rest against the end to be secured of the bolt and, coaxially in relation to the said bolt, one of the said wedges being fixed on the bolt, the second wedge being so arranged that one side thereof, by the action of an elastic member, is caused to rest against the wall of the bore hole, while the other side is caused to rest against the fixed wedge.

Different kinds of bolts to be anchored to the rock are already known, which are firmly anchored, whereby the ceiling and the walls of galleries and rock chambers will form the essential constituents of the bearing structure so that softer or cracked rock portions are prevented from falling down. For this purpose there is a substantial number of different embodiments of bolts, for example cotter bolts, expansion bolts, et cetera, which for the attachment to the rock are threaded. Such bolts are also known the upper part of which has cut-out cones.

instead of threads. When dimensioning cotter bolts the slotting in the bolt must be greatly considered, as the said slot weakens the bolt more than a thread. What is common to most of the earlier known bolts is that they are complicated and expensive to produce.

An advantage of a bolt according to the invention is that it can be cut to a suitable length on the working site due to the fact that it is threaded in one end only.

The object of the invention is to provide a rock bolt which is eflicient and at the same time simple and cheap to manufacture.

The rock bolt according to the invention will now be described in detail with reference to the accompanying drawings in which different embodiments are shown. Fig. 1 shows a rock bolt just inserted in a bored hole and Fig. 2 shows the same rock bolt seen from the left in Fig. 1. Fig. 3 shows the rock bolt seen from above. Fig. 4 shows another embodiment of the invention and Fig. 5 shows the same embodiment seen from above. Fig. 6 shows a detail of the embodiment of Fig. 4 on a larger scale.

The rock bolt according to the invention consists of a cylindrical bolt 1, which at its lower free end is provided with threads 3 for a nut 2. An arcuate wedge 4 is pressed to the upper end of the bolt 1 or applied in some other manner. The concaveside of the wedge 4 that faces the bolt is formed in such a manner that it rests against the bolt 1 along the whole of its length and it is attached to the said bolt thereby that the

limit surfaces

5 and 6 pass beyond the central line of the bolt, so that the Wedge 4, when applied on the bolt 1, is clamped to the latter. The concave side of the wedge 4 that faces the bolt is provided with barb-like teeth 7,

ited States Patent 9 a longitudinally towards each other.

2,903,938 Patented Sept. 15, 1959 "ice the edges 8 of which are at right angles to the bolt and obliquely upwards. Due to the fact that the radius of the wedge 4 is somewhat smaller than half the diameter of the bolt 1, and due to the fact that the material from which the wedge 4 is made is somewhat harder than the material of the bolt, the teeth 7 will come into mesh with the bolt 1 when the wedge 4 is clamped thereto, and due to the fact that the edges 3 are directed obliquely upward, the bolt cannot be displaced, when pulled downward. The outer convex side of the wedge 4 that is the side remote from the bolt 1 is rounded in accordance with the bolt and is tapered longitudinally and against the outer convex tapered side of said wedge 4 another arcuate wedge 9 cooperating therewith tests,

the inner concave side of which is shaped complementary to the tapered convex portion of the outwardly directed side of the wedge 4. The loose wedge 9 has at that side that is remote from the fixed Wedge 4 barb-like teeth 10 disposed at right angles to the bolt 1, the edges 11 of the said teeth being directed obliquely downward, so that they engage the wall of a bore hole 12, when the bolt 1 is pulled downwards.

The two

Wedges

4 and 9 are axially displaceable between themselves, an elastic member 13, comprising an endless rubber band or like readily rupturable member encircling and drawing the two wedges together and The circumference of the endless rubber band 13 is so dimensioned that, when the bolt 1 is not inserted in a bore hole, the 'two wedges are located opposite each other. The rubber band 13 is fixed to the rock bolt in the following way: Before the wedge 4 is fixed to the bolt 1, the rubber band 13 is threaded thereon along its longitudinal direction, whereby that part of the rubber band 13 that is at that side of the wedge 4 that faces the bolt 1 is received in a slot 14 in the wedge 4. Thereafter the wedge 4 is pressed into its position on the bolt 1, and the loose wedge 9 is inserted between the rubber band 13 and the wedge 4, the said rubber band 13 being received in a recess 15 provided in the lower end of the wedge 9 and adapted to fix the wedges mutually.

Then the rock bolt is ready for use and it is inserted in a bore hole by moving the wedge 9 somewhat downward so that it does not prevent the insertion. The rock bolt is moved to the bottom of the bore hole 12, and when the bolt 1 is pulled, the edges 11 of the teeth 10 of the loose wedge will engage the wall of the bore hole, whereby the two

wedges

4 and 9 more and more will be placed opposite each other to an extent which is dependent on the size of the bore hole 12. The rubber band 13 which then has no function to fulfill, will then be pressed to pieces between the Wedge 9 and the wall of the bore hole 12.

An essential advantage of the device according to the invention is that the forces acting upon the wedges will be substantially radially directed due to the fact that the surfaces facing each other of the

wedges

4 and 9 are shaped in accordance with the bolt 1.

Another advantage is that, if the bolt is to be removed from the bore hole after having been used for some time, this is very simple, and is carried out in such a manner that, after the nut 2 has been loosened from or removed from the bolt, the latter is moved longitudinally by strokes from below, whereby the

wedges

4 and 9 are loosened from each other. When the bore hole is vertical, the wedge 9 will fall down and the rod can be drawn out.

In the embodiment according to Figs. 4-6 the two

wedges

4 and 9 are also displaceable between themselves and are held together by a rubber strip 16. One end of the said strip is fixed to a projection 19 on the upper edge of the fixed wedge 4, the other end being fixed to a projection 20 on the lower edge of the loose wedge 9. Between the

projections

19 and 20 the rubber strip runs in a groove 17 provided in the outwardly facing side of the wedge 4. The loose wedge 9 has at the side facing the fixed wedge 4 a list '18 which engages the groove 17 in such a manner that, when the loose wedge 9 is displaced relatively to the fixed wedge 4 when the bolt 1 is fastened in the bore hole 12, the rubber strip will be pressed to pieces by the list 18.

Through cooperation between the list 18 in the loose wedge 9 and the groove 17 in the fixed wedge 4, the wedges areprevented from being moved relatively to each other, when the bolt is inserted in the bore hole.

The free end of the projection 20 of the loose wedge 9 is wider than the end fixed to the wedge 9, whereby the said projection can be attached to a thread for drawing out the wedge when the bolt is inserted horizontally or slopingly.

As to bolts made in accordance with the embodiment shown in Figs. 4-6 and which are inserted in horizontal or slightly sloping bore holes a thread is attached to the projection 20 of the loose wedge 9 before the bolt is inserted, this being the reason why the free end of the projection is wider. This thread which is to be so long that, when the bolt has been inserted, it protrudes out of the bore hole, can be of nylon, iron or the like. When taking out a bolt applied in this manner the wedges are taken apart as per the above, whereafter the outer loose wedge 9 is drawn out by means of the thread.

Of course different embodiments Within the scope of the claims may occur. For example if one wishes that the bolt shall be more centered in the bore hole, two fixed wedges may be applied on the bolt, one wedge being provided with ears, which engage corresponding indentations in the other wedge, so that the axially extending limit surfaces of the two wedges can pass the centre line of the bolt.

The bolt according to the present invention has been described in connection with rock anchoring, but can of course be used in a plurality of other fields, for example in concrete constructions, stone slabs and the like, and also in wood constructions.

What I claim is:

1. In a bolt structure adapted to be anchored in a bore hole established in rock forming the ceiling or walls of galleries and rock chambers to hold a cracked rock portion together the combination comprising, a round bolt shank adapted to be inserted in the bore hole, said shank being of uniform diameter along at least a portion of its length and having a threaded end portion adapted to extend out of the bore hole for receiving a washer and tightening nut, a first arcuate wedge member extending longitudinally of and secured to the uniformly diametered portion of said bolt shank at one side thereof, said wedge member including a concave inner surface having a configuration complementary to and resting throughout its length against the surface of said uniformly diametered portion of said bolt shank and an outer convex surface tapering longitudinally, a second arcuate Wedge member disposed at the same side of said bolt shank as is said first wedge member, said second Wedge member having a concave and longitudinally tapered inner surface complementary to and engaging the outer convex tapered surface of said first wedge member and an outer convex surface extending generally parallel with the axis of the bolt shank, said second wedge member being slidable longitudinally of said first wedge member thereby to cause the outer surface of said second wedge member to bear against the adjacent side of the bore hole and the side of said bolt shank opposite said wedge members to bear against the other side of the bore hole, and a readily rupturable endless elastic band extending longitudinally of and around the ends of said wedge members and under tension for drawing said wedge members toward each other, said elastic band being ruptured upon tightening of said bolt in the bore hole.

2. A bolt as defined in claim 1 wherein one flight of said endless elastic band is located in a groove extending longitudinally in the concave inner surface of said first wedge member, the other flight of said elastic band extending longitudinally along the convex outer surface of said second wedge member and adapted to be crushed and ruptured upon tightening of said bolt in the bore hole.

3. In a bolt structure adapted to be anchored in a bore hole established in rock forming the ceiling or walls of galleries and rock chambers to hold a cracked rock portion together the combination comprising, a round bolt shank adapted to be inserted in the bore hole, said shank being of uniform diameter along at least a portion of its length and having a threaded end portion adapted to extend out of the bore hole for receiving a washer and tightening nut, a first arcuate wedge member extending longitudinally of and secured to the uniformly diametered portion of said bolt shank at one side thereof, said wedge member including a concave inner surface having a configuration complementary to and resting throughout its length against the surface of said uniformly diametered portion of said bolt shank and an outer convex surface tapering longitudinally, a second arcuate wedge member disposed at the same side of said bolt shank as is said first wedge member, said second wedge member having a concave and longitudinally tapered inner surface complementary to and engaging the outer convex tapered surface of said first wedge member and an outer convex surface extending generally parallel with the axis of the bolt shank, said second wedge member being slidable longitudinally of said first wedge member, thereby to cause the outer surface of said second wedge member to bear against the adjacent side of the bore hole and the side of said bolt shank opposite said wedge members to bear against the other side of the bore hole, and a readily rupturable elastic strip having one end thereof secured to one end of said first wedge member and the other end secured to the opposite end of said second wedge member, said elastic strip extending longitudinally of said wedge member in a groove provided in the convex outer surface of said first wedge member, and said second wedge member being provided with a complementary list at the concave inner surface thereof and between which groove and list said elastic strip will be crushed and ruptured upon tightening of said bolt in the bore [hole 4. A bolt as defined in claim 3 wherein the end of said second wedge member to which the end of said elastic strip is secured includes means for attaching a thread enabling said second wedge member to be withdrawn from a horizontal or slightly inclined bore hole upon loosening of said bolt.

References Cited in the file of this patent UNITED STATES PATENTS 741,563 Stevens Oct. 13, 1903 798,440 McNulty Aug. 29, 1905 1,041,953 Bennett Oct. 22, 1912 1,521,025 Hubener Dec. 30, 1924 1,585,532 Cole May 18, 1926 1,964,427 Chandler June 26, 1934 2,004,264 Wyrick June 11, 1935 2,666,966 Lockett Jan. 26, 1954 2,878,668 Starling Mar. 24, 1959