GB2268004A

GB2268004A - A detonator harness unit

Info

Publication number: GB2268004A
Application number: GB9312061A
Authority: GB
Inventors: Robert William Baker
Original assignee: Whitaker LLC
Current assignee: Whitaker LLC
Priority date: 1992-06-15
Filing date: 1993-06-11
Publication date: 1993-12-22
Anticipated expiration: 2013-06-11
Also published as: AU4005593A; ES2085825B1; ZA934142B; AU670280B2; CN1037631C; ES2085825A2; GB2268004B; GB9212654D0; GB9312061D0; ES2085825R; CN1083920A

Abstract

A detonator harness unit (2) comprises first and second electrical connectors (6, 8) and a detonator (12) from which extends a length of cable (10). An end of the cable (10) is sealingly received in the first connector (8) and an intermediate portion of the cable (10) is sealingly received in the second connector (6). The connectors (6, 8) can be mated sealingly to connect respective conductors of the end of the cable (20) with respective conductors of the intermediate portion of the cable (10). To protect the harness unit (2) from damp so that it can be stored in a mine, the connectors (6, 8) are mated. In use, in order to provide a daisy chain connection between a row of detonators (12), the first connector (8) of one harness unit (2) is unmated from the second connector (6) and is mated with the second connector (6) of the next adjacent detonator harness unit (2), and so on. A grease seal (48, 76) is used throughout. <IMAGE>

Description

A DETONATOR HARNESS UNIT AND A METHOD OF MAKING THE SAME This invention relates to a detonator harness unit for use in providing a detonator harness in combination with other such units, and to a method of making a detonator harness unit. Harnesses for supplying activating voltage to an array of detonators received in respective bores in a working face of a mine, for example, a gold mine, the bores receiving explosive charges, are, when stored in the mine, for subsequent use, subject to damage by the ingress of moisture. The present invention is intended to provide a detonator harness unit which can be stored with impunity in a damp environment.

According to one aspect of the invention, a detonator harness unit comprises first and second mating electrical connectors and a detonator from which extends a length of a cable having conductors for the supply of activating voltage to the detonator, an end portion of the cable being received in the first connector in sealing tight fashion and a portion of the cable intermediate the detonator and the first connector being received in the second connector in sealing tight fashion, the connectors being matable in sealing tight fashion electrically to connect respective conductors of the end portion of the cable with respective conductors of the intermediate portion of the cable.

For the storage, in a mine, of such a detonator harness unit, the two connectors thereof are mated in sealing relationship, so that the unit is sealed against the ingress of moisture. In use, with the detonators in situ in their respective bores, the first connector of each detonator harness unit, is unmated from the second connector thereof and is mated with a respective second connector of the next adjacent unit, whereby a complete harness for all of the detonators is provided.

According to a preferred embodiment of the invention, each connector comprises a lid and a housing, the cable being sandwiched between the lid and the housing of each of the two connectors, the lid and the housing of each connector defining an annular channel, through which the cable passes, and a grease seal being provided in the channel. The electrical connections between the conductors of the two portions of the cable may be effected by means of electrical terminals provided either in one of the housings or in both of the housings. The terminals may be double ended insulation displacement terminals.

According to another aspect of the invention, a method of making a detonator harness unit comprises the steps of, supporting a length of detonator supply cable having conductors for supplying a detonator with activating voltage, applying a first electrical connector to one end portion of the cable, applying a second electrical connector to an intermediate portion of the cable, stuffing the other end portion of the cable into a detonator, sealing each connector to the cable, and mating the connectors in sealing tight relationship, electrically to connect the respective conductors of the end, and the intermediate, portions of the cable.

The step of sealing each connector to the cable, is carried out, according to a preferred embodiment of the invention, by injecting a grease sealing material into a cavity in the connector, through which cavity cable passes.

An embodiment of the present invention will now be described by way of example with reference to the accompanying drawings in which; Figure 1 is a schematic isometric view illustrating a method of making a detonator harness unit for use in mining operations; Figure 2 is a diagrammatic cross-sectional view of a completed detonator harness unit; Figure 3 is an enlarged cross-sectional view of the completed harness unit taken on a first plane; Figure 4 is an enlarged cross-sectional view of the harness unit taken on a second plane which is orthoganal with respect to said first plane; Figure 5 is an isometric view illustrating electrical connections between terminals of a connector of the harness unit and a flat flexible cable thereof; Figure 6 is a diagrammatic plan view of Figure 5; Figure 7 is a fragmentary front view shown partly in section and illustrating a working face of a mine and showing a complete detonator harness, in situ and comprising a plurality of detonator harness units; and Figure 8 is an enlarged fragmentary view, taken from above, shown partly in section, and illustrating details of Figure 7.

As shown in Figures 2 to 4, a detonator harness unit 2 for a detonator harness 4 (Figures 7 and 8) comprises a male electrical connector 6 for mating with a female electrical connector 8, a length of ribbon cable 10, and an electrically activateable detonator 12 connected to the cable 10.

The connector 6 comprises a one-piece, moulded, insulating housing 14, a one-piece, moulded insulating lid 16 for the housing 14, four double ended, uniplanar stamped-out, insulation displacement electrical terminals 18, 20, 22 and 24, respectively, and one double ended, stamped and formed, right angle insulation displacement electrical terminal 26. The housing 14 has a substantially square, as seen plan view, body 28, having an upper face 30 formed with an annular groove 32 extending around the body 28 proximate to its outer periphery. An annular sealing skirt 34 depends from the lower face 35 of the body 28 and defines therewithin a receptacle 36. The terminals 18, 20 and 22 are force fitted, or otherwise secured, in respective vertical, coplanar, through slots in the body 28. Each of the slots opens into both of the faces 30 and 35. The terminal 26 is force fitted, are otherwise secured in, a right angle shaped slot in the body 28, which is coplanar with the slots in which the terminals 18, 20 and 22 are received. The terminal 24 is force fitted into, or is otherwise secured in, a vertical slot in the body 28, which slot is offset from the plane of the other slots in said body, which are mentioned above. Each terminal has a first conductor receiving portion 37 formed with a conductor receiving slot 38 opening away from, and extending above, the face 30, and a second conductor receiving portion 39 having a conductor receiving slot 40. Each conductor receiving portion 39 projects beyond the face 35 and thus into the receptacle 36, each slot 40 opening in a direction away from the face 35.

The lid 16 of the connector 6 has an outer face 42, and an inner face 44 formed with an annular groove 46 proximate to the periphery of the lid 16. The groove 46 is aligned with the groove 32 of the body 28, to define, in co-operation therewith, a closed, annular, grease channel into which has been injected a grease seal 48. The seal 48 provides, in effect, a sealing O-ring. The face 44 of the lid 16 is formed with slots bounded by conductor stuffer surfaces 50. Each of the slots receives the conductor receiving portion 37 of a respective one of the terminals.

An intermediate portion of the cable 10 is sandwiched between the faces 30 and 44 and extends in sealing-tight fashion through the annular grease seal 48. During production of the harness unit 2, the lid 16 was force fitted to the housing 14, to sandwich an intermediate portion of the cable 10 between the lid 16 and the housing 14, thereby causing the stuffer surfaces 50 to stuff first voltage conductor V1 of the cable 10 into the slot 38 of the terminal 13, a ground conductor G of the cable 10 into the slot 38 of the terminal 20, a second voltage conductor V2 of the cable 10 into the slot 38 of the terminal 22, a return conductor R into the slot 38 of the terminal 24 and a first signal conductor S1 into the slot 38 of the terminal 36, as best seen in Figures 5 and 6. In each case, the edges of the slot 38 are in firm and permanent electrical contact with the respective cable conductor.

A second signal wire SO of the cable 10 is not required to be connected into the harness unit 2.

The female connector 8 comprises a one-piece, moulded, insulating housing 52, and a lid 54 for the housing 52. The housing 52 comprises a body 56 from which upstands a hollow plug portion 58 which is received in the receptacle 36 of the housing 14 in sealing tight relationship therewith. The hollow plug portion 58 defines a socket 60 having an end wall 62 formed with through slots 64 each receiving the conductor receiving portion 39 of a respective one of the terminals. The body 56 has an outer face 61 formed with an annular groove 63 proximate to its periphery. The lid 54 has a body 66 from which upstands a plug portion 68, the body 66 having an outer face 70 and an inner face 72 surrounding the plug portion 68 and being formed with an annular groove 74 cooperating with the groove 63 to provide an annular closed channel into which has been injected a grease seal 76, effectively providing a sealing 0-ring as in the case of the grease seal 48. Since the material of each seal 48 and 76 is viscous, being to some extent fluent, it serves to block adjacent interstices between the lid and the housing, in each case. The plug portion 68 has an end surface 78 formed with slots 80 each aligned with a respective slot 64 the end wall 62. During production of the unit 2, an end portion of the cable 10 remote from the detonator 12 was sandwiched between the lid 54 and the housing 52 by mating the lid 54 therewith. The said end portion of the cable 10 extends from one side of the plug portion 68 between the faces 61 and 72, passing through the seal 76 in sealing tight relationship therewith, over the plug portion 68 and across its end surface 78, terminating proximate to the face 61 on the other side of the plug portion 68. As the lid 54 was mated with the housing 52, the conductors of the cable 10 were forced into respective slots 40 of the terminals, as the conductor receiving portions 39 thereof were received in the respective slots 80. Between its intermediate portion and its end portion, the cable 10 extends in a loop projecting from the harness unit 2 as shown in Figure 2. The cable 10, is, for example of 1.5 meters in length, having a pitch of 0.254 cm or 0.127 cm.

By virtue of the grease seals 46 and 76 and the sealing tight engagement of the plug portion 58 in the receptacle 36, the harness 2 is fully sealed against the ingress of moisture. Harness units 2 can accordingly be stored in a mine, for future use, without impairment by the damp environment usually to be encountered in mines.

The use of a set of units 2 to provide a complete detonator harness 4 will now be described with particular reference to Figures 7 and 8. As shown in Figure 7, a working face of a mine, for example a gold mine, consists of a rock face of stope RF, which extends between a standing wall or floor SW and a hanging wall or ceiling HW. In order to prepare the face RF for a mining operation, rows of bores H1, H2, H3 and so on, are drilled in the face RF, the detonator 12 of a respective unit 2 is inserted into each of the bores so that the mated connectors 6 and 8 hang down on the cable 10 across the face RF and an explosive charge is inserted into each bore. The units 2 must then be connected in daisy chain fashion to an electrical supply source in order to prime the detonators 12, that is to say to charge firing capacitors therein and to activate timers in the detonators, which are arranged to ensure that they fire in a predetermined sequence.

In order to provide the harness 4 to make the daisy chain connection between the detonators, the connector 8 of each unit 2 is unmated from the connector 6 thereof and is mated with the connector 6 of the next adjacent unit 2.

Thus, the connector 8 of the unit 2 hanging from the bore H1 is mated with the connector 6 the unit 2 hanging from the bore H2 and the connector 8 of that unit is mated with the connector 6 of the unit 2 hanging from the bore H3, and so on. A separate connector 8', identical with a connector 8 and which is connected to a supply cable 10' is then mated with the connector 6 hanging from the bore H1. The detonators 12 are then activated by way of the supply cable 10' and the harness 4.

A method of making detonator harness units 2 will now be described with reference to Figure 1. First the cable 10 is supported so as to extend rectilinearly. A connector 6 having its lid 16 formed integrally with its housing 14 and projecting from an edge thereof is advanced in the direction of the arrow A so that the lid 16 lies over the intermediate portion of the cable 10, and a connector 8 having its lid 54 formed integrally with its housing 2 and projecting therefrom, is advanced in the direction of the arrow B so that the lid 54 lies over the end portion of the cable 10. The lids 16 and 54 are then cropped from the housings 14 and 52 and are maintained in their positions over the cable 10. The housings 6 and 8 are then lowered in the respective directions of the arrows C and D, preferably after advancing them further in the directions of the arrows A and B respectively. The housings 6 and 8 are then retracted in the directions of the arrows E and F, respectively, so as to lie beneath the cable 10 with their faces 30 and 72, respectively, facing the underside of the cable 10. The lids 16 and 54 are then driven down on to the housings 14 and 52, respectively, as indicated by the arrows G and H,so that the intermediate portion of the cable 10 is sandwiched between the lid 16 and the housing 14 and the end portion of the cable 10 is sandwiched between the lid 54 and the housing 52. The lids may be force fitted to the housings or may be secured thereto by any convenient detent means. The lids having been applied to the housings, grease seals 48 and 76 are injected into said annular closed channels of the connectors 6 and 8 thus provided, by way of perforations (not shown) in the housings or the lids. The connectors 6 and 8 are then mated after doubling over the cable 10 as shown in Figure 2. The end portion of the cable 10 opposite to the end portion to which the connector 8 was applied, may be stuffed into the detonator 12, as indicated by the arrow J, either before, or after, the application of the connectors 6 and 8 to the cable 10.

In the interest of economy, the housings 14 with their lids 16 may be moulded and presented, either chained together or in loose piece form by a vibratory bowl feeder, to a machine for stitching the terminals, fed in strip form from a reel, into the housings 14. The machine may also be arranged to prepare the cable 10, apply the connectors to the cable, inject the grease seals 48 and 76, stuff the cable into the detonator 12 and finally test each unit for electrical continuity.

The housings 6 and 8 may be fed in rows along the directions of the arrows A and B, respectively, and the lid cropped from one housing of a row may be applied to another housing of that row.

Claims

1. A detonator harness unit, comprising first and second mating electrical connectors, and a detonator from which extends a length of cable having conductors for the supply of activating voltage to the detonator, an end portion of the cable being received in the first connector in sealing tight fashion and a portion of the cable intermediate the detonator and the first connector being received in the second connector in sealing tight fashion, the connectors being matable in sealing tight fashion electrically to connect respective conductors of the said end portion of the cable with respective conductors of said intermediate portion thereof.

2. A harness unit as claimed in Claim 1, wherein the end portion of the cable is sandwiched between a lid and a housing of the first connector, the intermediate portion of the cable being sandwiched between a lid and a housing of the second connector, each lid co-operating with its respective housing to define closed annular chamber filled with a grease seal through which the cable passes.

3. A harness unit as claimed in Claim 2, wherein the housing of one connector defines a receptacle for receiving a plug portion of the housing of the other connector in sealing tight relationship, the housing of the one connector containing electrical terminals each connected to respective conductors of the cable, the terminals projecting into the receptacle for engaging respective conductors of that portion of the cable which is sandwiched between the lid and the housing of the other connector.

4. A harness unit as claimed in Claim 3, wherein each terminal has a first slot receiving a respective conductor of the portion of the cable sandwiched between the lid and the housing of the one connector and a second slot for receiving a respective conductor of the portion of the cable sandwiched between the lid and the housing of the other connector.

5. A harness unit as claimed in Claim 4, wherein the plug portion of the housing of the other connector defines a socket receiving a plug portion of the lid of the other connector, the cable extending over the plug portion of the lid.

6. A method of making a detonator harness unit, comprising the steps of supporting a length of detonator supply cable having conductors for supplying a detonator with activating voltage, applying a first electrical connector to one end portion of the cable, applying a second electrical connector to an intermediate portion of the cable, stuffing the other end portion of the electrical cable into a detonator, sealing each connector to the cable and mating the connectors in a sealing tight relationship, electrically to connect the respective conductors of said one end portion of the cable to respective conductors of said intermediate portion of the cable.

7. A method as claimed in Claim 6, wherein each connector comprises a housing and a lid therefor and each connector is applied to its respective portion of the cable by locating the housing of the connector on one side of the cable and the lid for the housing on the opposite side of the cable and force driving each lid on to its housing to sandwich the respective portion of the cable between the lid and the housing.

8. A method as claimed in Claim 7, wherein the housing of each connector co-operates with the lid thereof to define an annular chamber across which the cable extends, and wherein the connector is sealed to the cable by injecting a grease sealant into the annular chamber defined by the lid and the housing of the connector.

9. A method as claimed in Claim 8, wherein before applying each connector to the cable, the lid of the connector which is then formed integrally with housing of the connector is cropped therefrom.

10. A method as claimed in Claim 9, wherein each housing is passed across said one side of the cable with the lid positioned opposite said one side, and when the lid has been cropped from the housing, the housing is moved along first rectilinear path and a second linear path at right angles to said first path to locate the housing opposite said other side of the cable.

11. A detonator harness unit substantially as hereinbefore described with reference to the accompanying drawings.

12. A method of making a detonator harness unit, substantially as hereinbefore described with reference to the accompanying drawings.