US3175491A

US3175491A - J-shaped detonating fuse connector

Info

Publication number: US3175491A
Application number: US349425A
Authority: US
Inventors: Robertson Thomas Russell
Original assignee: Canadian Industries Ltd
Current assignee: PPG Architectural Coatings Canada Inc
Priority date: 1963-06-08
Filing date: 1964-03-04
Publication date: 1965-03-30
Anticipated expiration: 1982-03-30

Description

7 March 30, 1965 T. R. ROBERTSON J-SHAPED DETONATING FUSE CONNECTOR Filed March 4, 1964 INVENTOR Thomas Russell ROBERTSON AGENT United States Patent Ofiice E-SHAPED DETGNATING FUSE CONNECTGR Thomas Russell Robertson, Lachnte, Quebec, Canada,

assignor to Canadian Industries Limited, Montreal,

Quebec, Canada, a corporation of Canada Filed Mar. 4-, 1964, Ser. No. 349,425 Claims priority, application Canada, June 8, 1963, 877,526 3 Claims. (Cl. 102--27) This invention relates to the art of blasting with explosives and, more particularly, to a novel device for connecting a main or trunk line of detonating fuse to branch lines of detonating fuse. I Detonating fuse has been used for many years in commercial blasting operations for the purpose of carrying a detonation wave or detonation impulse to an explosive charge. By detonating fuse is meant a fuse consisting of a core of high explosive, such as pentaerythritol tetranitrate (P.E.T.N.), confined within a sheath which normally consists of textile material, the said sheath being surrounded by a protective and reinforcing covering. The high explosive core of detonating fuse may consist of from 0.1 to even more than 50 grains of high explosive per foot of length of fuse and the fuse may be made in diameters ranging from about .050 to .250 inch or possibly even larger. The fuse is particularly adaptable to carrying a detonation impulse to two or more charges of explosive material simultaneously when such charges are arranged in a pattern to achieve maximum removal or loosening of earth or rock.

It is a known and common practice to place in close physical contact with explosive charges in, for example, boreholes, lengths of detonating fuse. Such length of detonating fuse from each of several charged boreholes are selected so that they extend outward beyond the loading or collar end of each borehole. The extended free ends of detonating fuse, which are known in the trade as branch lines, can then be attached to another length of detonating fuse known as a main or trunk line. The pattern of detonating fuses so arranged thus describes a single trunk line with two or more branch lines attached at intervals along its length, each branch line extending to a separate explosive charge. When detonation is supplied to one free end of the trunk line detonating fuse by means of, for example, a blasting cap, the detonating impulse is carried along the trunk line and initiates in turn each attached length of branch line detonating fuse. The detonation impulse is thus transmitted nearly simultaneously along each branch fuse to the explosive charge in each borehole.

Due to the high velocity of the detonation wave propagated along a length of detonating fuse, it is difficult to attach together two lengths of such fuse so that a detonation impulse can be transmitted between the two with certainty under all conditions in the field. Experience has shown that in order to accomplish successful transmission of detonation energy between two connected lengths of detonating fuse, specific procedures must be followed. As detonating fuse is reasonably flexible and cord-like in construction, it is logical to attach together two adjacent fuse lengths by means of hand-tied knots. However, it has been found that only certain configurations of hand-tied knots can be employed successfully. Alternatively, connections can be made by various methods of coiling together, splicing, etc., lengths of fuse in combination with a securing means, usually by the use of a waterproof tape; otherwise detonation may not propagate between or across the points of attachment. In addition, connections between two lengths of detonating fuse in trunk and branch lines must be made so that the fuse lines lie as nearly as possible at right-angles to one another. It has been found that the lengths of 3,175,491 Patented Mar. 30, 1965 detonating fuse beyond the point of attachment must be kept separate to ensure propagation of the detonating impulse and guard against the possibility of the exploding trunk line cutting but not detonating an adjacent branch line.

It can be seen, therefore, that to ensure against the failure of a detonating fuse-initiated system of explosive charges, great reliance must be placed on the skill and care exercised by the blasting technician in preparing the detonating fuse network. Furthermore, the proper preparation of such a network is time-consuming and is often carried out in locations and under conditions which, by virtue of inadequate lighting, imperfect ventilation, high moisture and extremes of temperature, do not contribute to careful preparation.

It is an object of this invention to provide a novel device suitable for connecting branch lines of detonating fuse to trunk lines of detonating fuse.

Another object is to provide a detonating fuse congector which can be affixed quickly and securely in the eld. fAdditional objects of the invention will appear hereina ter.

The novel detonating fuse connector of this invention consists essentially of a J-shaped body of thermoplastic material, the longer arm of the J having two longitudinal perforations adapted to receive in slidable U-type relationship a continuous length of branch line detonating fuse, the shorter arm of the J being narrower than said longer arm and flexibly abutting said longer arm and being indented in its lower portion so as to receive and securely hold in looped relationship the said continuous length of branch line detonating fuse, and the arm-connecting part of the J being also indented so as to receive a continuous length of main or trunk line detonating fuse transversely of and within said looped continuous length of branch line detonating fuse.

The connector will be more fully understood by reference to the accompanying drawing wherein:

FIG. 1 is a perspective view of one form of connector showing two connected lengths of detonating fuse in operative relationship;

FIG. 2 is a top view of the connector of FIG. 1 devoid of connected lengths of detonating fuse; and

FIG. 3 is a plan view of a plurality of branch lines of detonating fuse connected to a single trunk line of detonating fuse by the connector of this invention.

Referring now to FIGS. 1 and 2 of the drawings, there is shown a J-shaped body of, for example, polyethylene having its longer arm 1 provided with two

longitudinal perforations

2 and 3 through which is slidably threaded a continuous length of branch line detonating fuse 4. The shorter arm 5 of the J-shaped body which is narrower than longer arm 1 flexibly abuts the latter at 6 and is indented at 7 for receiving and securely holding detonating fuse 4- in looped relationship. The armconnecting part of the J-shaped body is indented at 8 for receiving a continuous length of trunk line detonating fuse 9 which passes through looped detonating fuse 4.

If desired, a flexible thermoplastic strip it! having a small opening 11 near its end remote from its point of attachment to longer arm 1 can be internally molded with longer arm 1 at the side of the back face thereof, in which case longer arm 1 has internally molded therewith a securing button 12 at its side edge opposite the point of attachment of strip It The leading face of button 12 has a size slightly larger in cross-section than opening 11 of strip It) so that the latter can be attached to longer arm 1 by forcing or squeezing button 12 through opening 11. The loop thus formed by the attachment of strip it) to longer arm 1 serves as retaining means for precut loose ends of detonating fuse 4 threading through the connector and thus allows for the marketing of connector and fuse as a package assembly.

In typical operation in the field where it is desired to connect a length of branch line detonating fuse 4 to a main or trunk line of detonating fuse 9 by means of the novel device of this invention, one end of branch line detonating fuse 4 is passed through perforation 2 in the direction indicated and then in return direction through perforation 3 but only sufficiently far that a free loop is left at the bottom of longer arm ll. The connector is then placed against detonating fuse g so that the latter rests within indentation 8 and the free loop of fuse 4 is then drawn over shorter arm 5 and squeezed into indentation 7. The two ends of fuse 4 protruding from

perforations

2 and 3 above longer arm l are then grasped and pulled firmly so as to eliminate any slackness in the loop going through indentation '7 and thus hold fuse 9 tightly in indentation 8, thus allowing for two firm points of contact between fuses 4 and 9.

FIG. 3 of the drawing illustrates a number of connectors, the longer and shorter arms of which are designated as 1a, 1b, 1c and 2a, 2b and 2c, respectively, with

branch line fuses

4a, 4b and 4c threaded therethrough, all providing tight right-angled connections to common trunk line fuse 9a. In operation, trunk linefuse 9a would be detonated by means of, for example, a blasting cap (not shown), the detonation impulse passing along fuse 9a and initiating nearly simultaneously the detonation of connected

branch line fuses

4a, 4b and 4c. The detonation impulses carried by the latter fuses would then be carried nearly simultaneously to explosive charges (not shown) in contact with said fuses.

The connector may be made from any suitable thermoplastic material, including rubber. Polyethylene of a density of about .92 has been found very suitable but it will be apparent to one skilled in the art that other kinds of materials may be successfully employed. It should be appreciated, however, that a material subject to undue hardening in cold temperatures or subject to undue softening in warm temperatures would not be preferred. Furthermore, a material which readily lends itself to fabrication into the desired shape, such as by moulding or casting by modern methods, is to be preferred in the interest of economy.

As previously mentioned, the connector may be marketed already attached or threaded to pre-cut lengths of detonating fuse destined for use for branch line purposes. ln such a case the measurement of the length of fuse to which the connector is attached may be marked on the connector, for example, by printing or embossing on one face of the longer arm of the .J-shaped body or on the flexible thermoplastic strip if desired.

In some instances, it is the practice of manufacturers of blasting accessories to supply pre-cut lengths of branch line detonating fuse already attached to delay devices or relays of various time-delay factors. With the connector of the present invention, information specifying the time-delay factor of such attached relays may also be marked by printing or embossing on one face of the longer ill arm of the J-shaped connector or on the flexible tnermoplastic strip if desired.

It will be apparent from the above that the novel detonating fuse connector of this invention can fulfil a multifold purpose when used in the field. The blasting technician needs only select the lengths and type of branch line fuse required, referring for his selection to the labeling means incorporated with the connector attached to fuse bundle or coil by the manufacturers. Such lengths of branch line fuse may then be quickly and easily attached to a main or trunk line of detonating fuse in any position whatever and by so doing a complete detonating fuse network may be simply prepared. An advantage of the detonating fuse connector of this invention may be found in the fact that no difficult hand-tied knots, taped splices or other such means are required to effect attachments between fuses nor are any special tools or other devices required for the purpose. in addition, the use of the connector assures tight-fitting right-angled junction points between fuse lines at the points of attachment such that branch line fuses will not be dislodged from the trunk line either in handling or from the blast elfects from neighbouring explosive charges. Furthermore, almost any configuration of branch line away from the connector may be tolerated because the connector holds the branch line at right angles to the trunk line at the crucial point of attachment, thereby ensuring transmission of detonation impulse between the lines. Because of the moisture and temperature resistant nature of the material forming the connector, it may be used under all conditions normally encountered at blasting sites.

What I claim is:

l. A device suitable for connecting a main line of detonating fuse to branch lines of detonating fuse which consists essentially of a J-shaped body of thermoplastic material, the longer arm of the J having two longitudinal perforations adapted to receive in slidable U-type relationship a continuous length of branch line detonating fuse, the shorter arm of the J being narrower than said longer arm and flexibly abutting said longer arm and sing recessed in its portion facing said longer arm so as to receive and securely hold in looped relationshi the said continuous length of branch line detonating fuse, said J-shaped body also having its bottom part recessed so as to receive a continuous length of main or trunk line detonating fuse transversely of and within said looped continuous length of branch line detonating fuse.

2. A device as claimed in claim 1 wherein the longer arm of the J has attached to one side of its back face one end of a thermoplastic strip having a small opening near its end remote from its point of attachment to said arm, and the said arm is provided at its side edge opposite the point of attachment of said strip with a button adapted to securely hold said strip by insertion through said opening.

3. A device as claimed in claim 1 made of polyethylone.

No references cited.

BENlAMlN A. BORCHELT, Primary Examiner.

Claims

1. A DEVICE SUITABLE FOR CONNECTING A MAIN LINE OF DETONATING FUSE TO BRANCH LINES OF DETONATING FUSE WHICH CONSISTS ESSENTIALLY OF A J-SHAPED BODY OF THERMOPLASTIC MATERIAL, THE LONGER ARM OF THE J HAVING TWO LONGITUDINAL PERFORATIONS ADAPTED TO RECEIVE IN SLIDABLE U-TYPE RELATIONSHIP A CONTINUOUS LENGTH OF BRACH LINE DETONATING FUSE, THE SHORTER ARM OF THE J BEING NARROWER THAN SAID LONGER ARM AND FLEXIBLY ABUTTING SAID LONGER ARM AND BEING RECESSED IN ITS PORTION FACING SAID LONGER ARM SO AS TO RECEIVE AND SECURELY HOLD IN LOOPED RELATIONSHIP THE SAID CONTINUOUS LENGTH OF BRANCH LINE DETONATING FUSE, SAID J-SHAPED BODY ALSO HAVING ITS BOTTOM PART RECESSED SO AS TO RECEIVE A CONTINUOUS LENGTH OF MAIN OR TRUNK LINE DETONATING FUSE TRANSVERSELY OF AND WITHIN SAID LOOPED CONTINUOUS LENGTH OF BRANCH LINE DETONATING FUSE.