US3608491A

US3608491A - Tamping plug

Info

Publication number: US3608491A
Application number: US787161A
Authority: US
Inventors: Vernon Jan Botes
Original assignee: Dunaplug Pty Ltd
Current assignee: Dunaplug Pty Ltd
Priority date: 1967-12-27
Filing date: 1968-12-26
Publication date: 1971-09-28
Anticipated expiration: 1988-09-28
Also published as: GB1253218A; DE1816758A1; FR1598761A; ZM18768A1

Abstract

The invention provides for a plug for use in blasting holes, the plug consisting of substantially rectangular section striplike material formed into a cone-shaped spiral member in which the convolutions overlap one another and having their larger faces diverging in the direction of the small end of the member.

Description

United States Patent Inventor Vernon Jan Botes Johannesburg, South Africa Appl. No. 787,161 Filed Dec. 26, 1968 Patented Sept. 28, 1971 Assignee Dunaplug (Proprietary) Limited Pietersburg Transvaak Province, South Africa Priority Dec. 27, 1967 South Africa 671-7731 TAMPING PLUG 7 10 Claims, 10 Drawing Figs.

US. Cl 102/30 Int. Cl F42d 1/08 Field of Search 102/26, 30;

[56] References Cited UNITED STATES PATENTS 2,403,386 7/1946 Lubelsky et al 102/30 2,553,757 5/1951 Evans 156/195 X 3,081,705 3/1963 Warnken 156/195 X Primary Examiner-Verlin R. Pendegrass Attorney- Karl W. Flocks ABSTRACT: *The invention provides for a plug for use in blasting holes, the plug consisting of substantially rectangular section striplike material formed into a cone-shaped spiral member in which the eonvolutions overlap one another and having their larger faces diverging in the direction of the small end of the member.

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TAMPING PLUG BACKGROUND OF THE INVENTION This invention relates to an improved plug and more par ticularly a tamping plug for bored blast holes.

According to the invention a tamping tubular plug member is provided having a wide end and a small end and comprising a helically wound strip of material presenting a pair of opposed wide faces, the helically wound strip material providing overlapping convolutions of progressively smaller size and which convolutions are arranged with both the wider faces of the strip material convergent toward the wide end of the member and with smaller convolutions extending from the larger convolutions, within which they are disposed, in the direction of the small end of the member whereby, on application of a force in a substantially axial direction on the small end of the member and toward the wide end of the member, the wide faces of the helically wound strip slide and engage wedgingly on one another and cause radial expansion of the convolutions for the convolution at the wide end of the member to be tightly engaged onto walls of a hole in which the member is located.

When the strip material has been wound or shaped and formed to present the tapering tubular plug member the outer face of the outermost convolution is preferably of substantially constant radius on the axis of the member to form a substantially true cylinder which is surmounted by a generally conical surface of substantially helically ribbed appearance presented by exposed portions of the overlapped convolutions of the helically wound strip material. The outwardly directed surface of the outer appearance. The The outwardly directed surface of the outermost convolution may be provided with ribs or other roughening formations to increase frictional engagement on the walls of the hole in which the plug member is inserted.

To insert the plug member according to the invention, the wide end is held and the small end forced into the hole with the aid of a rod or bar to the required depth and whereby the tapering tubular member is extended in length and reduced in respect of its width. The held wide end or outer end of the strip material is then slowly allowed to be moved inwardly when the length is reduced and the width increased. Said wide end may be subsequently forced further into the hole and, due

becomes firmly held in the hole. When subjected to pressure on the small end, the lateral expanding action is increased due to the wcdging action of the overlapping convolutions and as a result of which the plug member becomes firmly held in the hole. Such wcdging action may be increased by providing the strip material with the substantially wedge-shaped cross section.

If required the transverse end portion at the narrow end of the strip material wound spirally and outwardly overlappingly to truncated cone-shape, may be twisted through an angle of approximately 90 to present a larger face disposed across the narrow end of the member.

The strip material should be a suitable nonferrous material but advantageously comprises a synthetic resinous or plastic material.

For the invention to be readily understood, reference will now be made to the accompanying drawings in which:

FIG. l is a pictorial view ofa tamping plug member according to the invention;

FIG. 2 is a cross section of a tamping plug member according to the invention, drawn to a larger scale;

FIG. 3 is a cross section of a tamping plug member shown in position within a hole;

FIG. 4 is a view similar to FIG. 3 shown in a larger diameter hole; and

FIG. 5 to are cross sections of modified forms of plug members constructed according to the invention.

Referring to the drawings reference numeral 10 denotes a truncated cone-shaped plug member formed by helical conto the recoiling action of the coils, expands transversely and volutions of strip material 12. The convolutions are outwardly overlapping. The top end 14 of the strip is twisted through an angle of approximately as at 16, to be disposed radially and substantially diametrically across the small end 18 of the truncated cone 10. The tip end 14 is provided with a hole 20 which is disposed coaxially with the axis of the truncated cone 10. However, said tip end 14 is not essential and need not be provided.

The strip material [2 is preferably of tapering cross-sectional shape as is clearly shown in FIG. 2.

The strip material 12 is preferably of a suitable synthetic resinous or themo plastic material.

The small end convolution according to the modification shown in FIG. 5 provides a thicker portion 22 of which the outer surface forms a truncated cone converging towards the wide end of the truncated conically shaped plug member. Said portion 22 may be provided on its smaller end with a lip adapted to form a tubular region 24 and forms an axial passage 26 through which a fuse may be passed.

The small end convolution 22.1 according to the form of plug member shown in FIG. 6 may be provided with an outwardly flared lip 28 to present an increased projected area on the small end of the plug member. Said lip 28 may be in the form of wings moulded integrally with the top convolution forming portion of the strip material. Said lip 28 may be provided with radial slits if required.

The aforesaid small end convolution of the plug member in the forms of the invention shown in FIGS. 5 and 6 may be formed as a solid annulus to which one end of the strip material is attached.

As it may be necessary in certain instances to remove a plug member from a hole in which it has been placed, a ridge 30 or a groove or recess 32 may be provided on or in the inside face of one of the larger convolutions as is shown in FIGS. 7 and 8. Preferably the large end convolution is provided with such ridge 30 or groove 32 for engagement by tool means in order to facilitate the removal by extraction.

In the form of the plug shown in FIG. 9 the cross-sectional shape of the strip material is modified and provides a step forming rib 34 on the wider edge portion of the strip material and the edge adapted to be directed towards the wide end of the plug member 10.

In the modification shown in FIG. 10 a outwardly protruding lip 36 is provided at the narrow edge of the tapering section strip material directed towards the small end of the plug member.

Plug members according to the invention may be manufactured by injection moulding between coacting complementary male and female moulds. In one form an open radially widening pitched spiral strip is moulded on a plane with major faces of the strip slopingly relative to the plane. The spiral strip is subsequently drawn to form the truncated cone-shaped member with the major faces of the convolutions of the thus formed helix converging toward the wide end of the member. In another form of moulding coacting moulds present continuous rebatelike spiral recesses. After moulding of the strip material and removal from the moulds the small end of the thus formed helical spiral is displaced in an axial direction through the larger end and whereby the convolutions become placed in their required overlapping positions with the major faces converging toward the wide end of the truncated cone member thus formed.

Alternatively the strip material may be formed in a plane and according to a substantially rapidly widening s iral. Such spiral, of which the cross section of the strip material is also of tapering shape, can be manufactured by injection moulding. Such widening spiral may be subsequently wound to the required frustoconically shaped helically coiled plug member.

The outwardly directed face of the large end convolution is preferably roughened or provided with protrusions for increased nonslipping engagement with the surface of the hole in which it is placed.

The plug member according to the invention is particularly intended for use as a tamping plug to contain the gasses of combustion and explosion in a blast hole. The plug member may also be used for other purposes such as for instance, as a socket plug for placement in sockets left in rock which have previously being drilled and blasted. The plug member according to the invention may also be used as a wedging device to secure a bolt placed in drilled holes for the anchoring of roof bolts or the like.

The cross-sectional shape of the strip material may vary in respect of at least portions of its length.

lclaim:

l. A tapering tubular plug member having a wide end and a small end and comprising a helically wound strip of material presenting a pair of opposed wide faces, the helically wound strip material providing overlapping convolutions of progressively smaller size and which convolutions are arranged with both the wide faces of the strip material convergent toward the wide end of the member and with smaller convolutions extending from the larger convolutions, within which they are disposed, in the direction of the small end of the member whereby, on application of a force in a substantially axial direction on the small end of the member and toward the wide end of the member, the wide faces of the helically wound strip slide and engage wedgingly on one another and cause radial expansion of the convolutions for the convolution at the wide end of the member to tightly engage onto walls of a hole in which the member is located.

2. A tapering tubular plug member as claimed in claim 1 wherein the strip material is of narrow rectangular cross-sectional shape.

3. A plug member as claimed in claim 1 wherein the strip material is of tapering and substantially truncated narrow triangular cross-sectional shape, the wide and relatively sloping faces of the helically wound strip material being arranged to converge in the direction of the wide end of the member and diverge in the direction of the small end of the member.

4. A tapering tubular plug member as claimed in claim 1 wherein the strip material provides a transverse end portion disposed across the small end of the member.

5. A tapering tubular plug member as claimed in claim 1 wherein the portion of the strip material adapted to form the convolution at the wide end of the member is of progressively decreased thickness and adapted to form a substantially true cylindrical circumferential face for engaging the walls of the hole, said true cylindrical surface beingsurmounted by a generally conical surface of substantially helically ribbed appearance presented by exposed portions of the overlapping convolutions of the helically wound strip material.

6. A tapering tubular plug member as claimed in claim 1 wherein a substantially conical part is provided on the end of the strip at the small end of the member, said conical part being provided with an axial passage and is arranged with its small end directed toward the wide end of the member.

7. A tapering tubular plug member as claimed in claim 1 wherein an outwardly flared formation is provided on an outwardly directed edge portion of the convolution at the small end of the member.

8. A tapering tubular plug member as claimed in claim 1 wherein a formation for engagement by tool means, for extraction of the member, is provided on a portion of the inwardly directed wide face of the convolution at the wide end of the member.

9. A tapering tubular plug member as claimed in claim 1 wherein the strip material is provided at an edge portion, to be directed toward the wide end of the member, with a lip which is directed inwardly of the member.

10. A tapering tubular plug member as claimed in claim 1 wherein the strip material is provided at an edge portion, to be directed toward the small end of the member, with a lip directed outwardly of the member.

Claims

1. A tapering tubular plug member having a wide end and a small end and comprising a helically wound strip of material presenting a pair of opposed wide faces, the helically wound strip material providing overlapping convolutions of progressively smaller size and which convolutions are arranged with both the wide faces of the strip material convergent toward the wide end of the member and with smaller convolutions extending from the larger convolutions, within which they are disposed, in the direction of the small end of the member whereby, on application of a force in a substantially axial direction on the small end of the member and toward the wide end of the member, the wide faces of the helically wound strip slide and engage wedgingly on one another and cause radial expansion of the convolutions for the convolution at the wide end of the member to tightly engage onto walls of a hole in which the member is located.

5. A tapering tubular plug member as claimed in claim 1 wherein the portion of the strip material adapted to form the convolution at the wide end of the member is of progressively decreased thickness and adapted to form a substantially true cylindrical circumferential face for engaging the walls of the hole, said true cylindrical surface being surmounted by a generally conical surface of substantially helically ribbed appearance presented by exposed portions of the overlapping convolutions of the helically wound strip material.