Abstract:
A method for assembling a blast initiation device is provided. The method comprises providing a length of signal transmission line having first and second ends, mounting a tag to the line and mounting a first detonator to the first end of the line wherein all of the steps are each performed at a single operator station by a single operator. Also provided is an apparatus for utilizing the method. The apparatus comprises a tagger device for mounting a tag to a length of signal transmission line having first and second ends. A crimp device is adjacent the tagger device for mounting a first detonator to the first end of the line. A blocker device is adjacent the detonator crimp device for locking a connecting block to the first detonator. The tagger, crimp and blocker devices are spatially arranged adjacent an access position for ease of operation by a single operator. Further provided is a kaizen cell comprising a plurality of workstations.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of United States Provisional Application No. 60/113,708, filed Dec. 24, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates generally to assembly of explosive devices. More particularly, the present invention relates to an apparatus and method for the assembly of blast initiation devices. 
     It is common practice in blasting operations to initiate the detonation of one or more main explosive charges by transmitting an initiation signal to the charges through initiation signal transmission lines. There are various conventional forms of signal transmission lines, e.g., detonating cord, shock tube, low velocity signal tube, etc. It is often necessary to transfer an initiation signal from a first transmission line to a second transmission line or a plurality of second transmission lines, such as when long distances are involved or when multiple main charges must be initiated. It may also be necessary to amplify the initiation signal from the first line to accomplish the initiation signal transfer to a second line or a plurality of second lines. This may be accomplished by using the initiation signal to initiate a detonator mounted to the first line and disposed in signal transfer relation to the second transmission line or lines. Typically, this is accomplished with a connector device. The connector device includes a body portion having a channel holding the detonator cap and an engaging member for holding one or more signal receiving transmission lines in signal transfer relationship to the detonator cap. The end of the signal transmission line opposing the connector block may be connected to an initiator for initiating a signal in the transmission line or, alternatively, may be connected to another detonator. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to provide an improved method and apparatus for the assembly of blast initiation devices. 
     Another object of the invention is to provide an improved method and apparatus for the assembly of blast initiation devices which may be efficiently utilized by a single operator. 
     Other objects and advantages of the invention will become apparent from the drawings and the specification. 
     Briefly stated, the invention in a preferred form is a new and improved method for assembly of a blast initiation device. The invention also encompasses an apparatus for use with the method. The apparatus in preferred form is an inventive single operator workstation. 
     The workstation comprises a tagger device for fixing an identification tag to a predetermined length of a transmission line. A crimp device is located on the workstation. The workstation operator loads a detonator within an aperture in the crimp device, inserts a bushing within the detonator and places the end of the transmission line within the bushing. Actuation of the crimp device crimps the outside of the detonator at a predetermined location and to a predetermined depth to securely fasten the transmission line and bushing to the detonator. In a preferred embodiment, the crimp device comprises a dual crimp head with two apertures. The workstation operator loads a desired detonator in each aperture of the dual crimp head. A bushing is inserted within each detonator and both ends of the transmission line are inserted within a respective bushing and held adjacent an explosive charge within the detonator. Actuation of the dual crimp head crimps each of the detonators at a predetermined location and to a predetermined depth substantially simultaneously. The detonator crimping operation creates a cannelure at least partially around the circumference of the detonator. 
     The operator places a connector block over one crimped detonator. The workstation includes a blocker device adjacent the cap crimp device. The connector/detonator/transmission line subassembly is placed in the blocker device. The blocker device drives a locking member into the connector block. The locking member includes spaced legs, each of which is driven into an opposing side of the detonator cannelure. The blocker device fixes the position of the detonator/transmission line within the connector block. It should be realized that the inventive workstation is arranged so that a single operator can safely and expediently operate all of the above devices and handle the high explosive components to create an assembled blast initiation device. 
     Preferably, the workstation is adjacent a feeder to provide a supply of predetermined lengths of coiled transmission line to the operator and includes feeders or holders to provide the operator with a ready supply of detonator, bushings and connector blocks. Naturally, the component feeders are designed and located so that explosive components, such as detonators while available for quick access by the operator are also safely contained. The workstation is preferably located adjacent a bundler. The bundler receives a predetermined number of blast initiator assemblies; bands the predetermined number of assemblies together; and transfers the banded assemblies to a pack-out station. 
     In use of a preferred embodiment of the inventive workstation, an operator loads a desired detonator in each of the two crimp head apertures. A bushing is placed within each of the detonators. The operator receives a predetermined length of coiled transmission line and attaches a tag with the tagger device adjacent one end of the line. The operator inserts each end of the transmission line into a respective bushing/detonator subassembly so that the end of the transmission line is adjacent the explosive charge in the detonator. Actuation of the crimp head causes a crimp to be formed in the metal housing of the detonator, securing the detonator through the bushing to the transmission line. The operator removes from the crimp head aperture one end of the transmission line with the now attached detonator and places the attached detonator within the bore of a connector block. The connector block/detonator/transmission line subassembly is placed in a blocker device. The blocker device drives a locking member through the connector block so that the locking member legs are driven into the cannelure formed during the detonator crimp operation. This operation locks the detonator to the connector block. The operator removes the locked connector block/detonator/transmission line subassembly from the blocker and the opposing crimped detonator/transmission line end from the crimp head aperture. The operator places the assembled blast initiator device in a bundler. When a predetermined number of initiator devices have been placed in a bundler, the operator actuates the bundler to band the predetermined number of devices together into a bundle and to transfer the bundled devices to a pack-out station for subsequent packaging. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects and advantages of the invention will be evident to one of ordinary skill in the art from the following detailed description may with reference to the accompanying drawings, in which: 
     FIG. 1 is an overhead plan view of the inventive workstation; 
     FIG. 2 is an overhead plan view of a pair of inventive workstations arranged in a kaizen cell; 
     FIG. 3 is a perspective view schematically showing an inventive workstation; 
     FIG. 4 is an enlarged view showing a portion of FIG. 3; 
     FIG. 5 is a perspective view schematically showing a pair of inventive workstations arranged in a kaizen cell; 
     FIG. 6 is a perspective view of two conventional blast initiation devices; 
     FIG. 7 is a side view, partly in section, of a connector with a detonator and signal transmission line inserted therein; and 
     FIG. 8 is a perspective, cut away and partly in section side view of a connector with a detonator and signal transmission line inserted therein. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to the drawings, wherein like numerals designate like components throughout the Figures, a blast initiation device as shown in FIG. 6 is generally designated  10 . The blast initiation device comprises a length of signal transmission line or tube  12  which is attached at each end to a detonator  14 . A connector block  16  is mounted to a detonator (not visible) at one end of the blast initiation device. An identification tag  18  is affixed to the signal transmission line  12  adjacent one end. The transmission line  12  of the blast initiation device is coiled and held by a tape or band  20  to allow packing, transportation, and handling. 
     The signal transmission line or tube  12  typically comprises hollow plastic tubing. The inside surfaces of the transmission tube are coated with reactive material, such as, a mixture of a high brisance explosive and aluminum powder in the case of shock tube or a deflagrating material in the case of low velocity signal transmission tube. The inventive method and apparatus may be used with any suitable signal transmission line, such as, for instance, shock tube, low velocity signal transmission tube or low energy detonating cord. 
     A detonator  14  is firmly attached to at least one end of the signal transmission line  12  by a method such as crimping. The detonator may be an instant acting detonator or a delayed detonator, both types being of course well known in the art. If a detonator  14  is attached at each end of the signal transmission line  12 , each detonator may be of a different delay or explosive force. Alternatively, an initiator device (not shown) may be attached to one end of the signal transmission line  12  to initiate a signal within the tube. With reference also to FIGS. 7 and 8, the detonator  14  comprises a generally tubular shaped housing  22 , having an axially extending channel formed therein, with a closed end  24  and an open end  26  opposite the closed end. An explosive charge  28  is placed within the channel at the closed end  24  of the housing  22 . The explosive charge  28  is typically comprised of a base charge of a secondary explosive, such as, pentaerythritol tetranitrate (PETN) adjacent the housing-closed end. An initiating charge comprising a primary explosive such as lead azide overlays the base charge. 
     The normal functioning of the detonator  14  requires that a signal transmission line  12  transmit an initiating signal to be applied to the initiating charge to cause it to detonate and thereby activate the base charge. The activated base charge amplifies the initiating signal to initiate further signals in receiving or receptor signal transmission lines  30  or to activate a main explosive charge. The initiating signal can take the form of a detonation shock wave from a shock tube, a deflagrating flame front from a deflagrating type tube, or a detonation from a detonating cord. 
     One detonator  14  is fixedly mounted in an axial channel  34  defined within a connector block  16 . The detonator closed end  24  is adjacent a receiving line retaining end  36  of the connector block  16  to be in signal transmission relationship with receptor signal transmission lines engaged therein. The detonator  14  is retained within the axial channel  34  by engagement at a locking member  38  with a crimp  40  formed in the detonator housing  22 . U.S. Pat. No. 5,792,975, issued Aug. 11, 1998, which is incorporated by reference herein, discloses a blast initiation device  10  suitable for assembly by the inventive method and apparatus. 
     With reference to FIGS. 1 and 3, the inventive apparatus for assembly of the above described blast initiation device comprises a workstation  44  designed for efficient utilization by a single operator  46  (shown in FIG.  2 ). The workstation  44  includes a support frame  48 , which may comprise four vertically extending legs  50  and a generally rectangular table  52  mounted to the legs. One edge of the table defines an access position  54  for an operator with the opposing edge defining a table back edge  56 . 
     A tagger device  60  is mounted for support to the frame  48 . The tagger device  60  stores a quantity of identification tags  18  similar to those shown in FIG.  6 . When a length of signal transmission line  12  is held adjacent the tagger head  62  and the tagger device is actuated, one tag  18  is wrapped around the signal transmission line  12  and affixed thereto. 
     A crimp device  66  is mounted to the frame  48  adjacent the middle of the access position  54 . The crimp device  66  includes a crimp head  68  containing a crimp head aperture  70 . A blocking device  74  is mounted to the frame  48  between the crimp device  66  and the table back edge  56 . 
     Preferably, the workstation includes a hopper-type feeder  76  located above the blocking device  74 . The hopper feeder  76  holds a plurality of connector blocks  16  for easy access by the operator  46 . The workstation  44  also preferably includes safe storage devices for detonators, both bulk storage devices  78  and in lesser working quantity storage devices  80 . Naturally, the workstation  44  would include electrical, hydraulic and pneumatic supply systems (only hydraulic supply system  82  shown for clarity) as well as safety devices such as guards (a portion shown as  84  in FIG. 3) attached to a guard frame  86  required by regulatory agencies such as OSHA. The workstation may also include ergonomic devices such as arm rests  90 . 
     As shown in FIG. 2, the workstation  44  is ergonomically arranged so that all devices  60 ,  66 ,  74 ,  78 ,  80  and components  12 ,  14 ,  16 ,  18  are readily accessible for operation by a single operator  46 . The arrangement of the devices and components allows a single operator to quickly, efficiently, and safely assemble a blast initiator device  10 . Typically, the devices and components would be arranged at an ergonomic distance from the operator, defined by the operator&#39;s reach which will generally be about two feet. This will tend to place the devices and components in an arc around the operator position. 
     With reference again to FIGS. 1-3, an operator  46  at the access position  54  loads a first detonator  14  within the crimp head aperture  70  and a first nonmetallic bushing  88  (shown best in FIG. 8) in the axially extending channel  34  of the detonator  14 . The nonmetallic bushing  88  is a tubular member with an external diameter smaller than the internal channel diameter of the detonator housing  22 . Bushings  88  may be stored in any position at the workstation  44  convenient to the operator  46 , such as adjacent the small quantity detonator storage  80 . The operator  46  reaches for a coiled length of signal transmission line  12 , preferably provided at a conveyor  92 . The conveyor is arranged with relation to the workstation  44  so that minimal operator  46  movement from the access position  54  is required. The operator  46  grasps the coiled length of transmission line  12  and holds a length of transmission line adjacent the first end to the tagger head  62 . Actuation of the tagger device  60  causes an identification tag  18  to be affixed to the transmission line  12 . The operator  46  inserts the first end of the transmission line  12  into the tubular bore of the bushing  88  within the crimp device aperture  70  so that the end of the transmission line  12  is adjacent the detonator explosive charge  28 . While maintaining the transmission line end adjacent the detonator explosive charge, the operator  46  actuates the crimp device  66 . The crimp device  66  functions to apply force to the exterior of the detonator housing  22  adjacent the open end  26 . The applied force plastically deforms the metallic detonator housing  22  to create a crimp or cannelure  40 , thereby fixing the detonator housing  22  to both the bushing  88  and transmission line  12 . The crimp device  66  is adjustable as is well known to vary crimp  40  position and depth. The transmission line first end with the now fastened detonator  14  may be removed from the crimp device  66  and a second detonator  14  and bushing  88  inserted into the crimp head aperture  70 . The free second end of the transmission line  12  may be inserted into the bushing  88  and the process repeated to crimp the second detonator  14  to the second end of the transmission line  12 . 
     Preferably, the crimp device  66  comprises a dual crimp head  96  as shown in FIG.  3 . In this configuration, the crimp head  96  includes two apertures  70 , each receiving a detonator  14  and a bushing  88  therein. It should be appreciated that the dual crimp head  96  may accommodate different detonators having different sizes, different forces or different delays in each aperture. The operator  46  inserts each end of a tagged transmission line into the appropriate detonator/bushing subunit within a crimp head aperture  70  and actuates the crimp device  66 . In this embodiment, a detonator housing  22  is crimped to a bushing  88  and each end of the transmission line  12  substantially simultaneously. 
     In either embodiment, after crimping the operator  46  removes one end of the transmission line  12  including the now affixed detonator  14 , and inserts the affixed detonator  14  into a connector block  16  obtained from the connector block feeder  76 . Typically, the detonator  14  affixed to the first or tagged end of the transmission line  12  is mounted within the connector block  16 . The interior bore of the connector block  16  preferably includes stop members  98  as shown in FIG. 8 which seat the detonator  14  within the connector block  16 . The operator  46  loads the connector block  16  containing a seated detonator  14  with signal transmission line  12  extending therefrom into the blocking device  74 . While maintaining the detonator  14  against the stop members  98 , the operator  46  actuates the blocking device  74 . The blocking device  74  drives a locking member  38  into the channel  34  of the connector block wherein it engages the detonator  14  and locks the detonator in place with respect to the connector block  1 , 6  as previously described. After the blocking operation, the operator  46  removes the first end of the transmission line  12  containing the connector block  16  locked to the detonator  14 . The operator  46  takes the now assembled blast initiation device  10 , comprising a transmission line  12  including a tag  18  with a detonator  14  affixed to each end by crimping and a connector block  16  mounted at one end by engagement of the locking member  38  with the detonator  14 , and places the assembled device  10  in a bundler  100 . 
     As shown in FIG. 2, the bundler  100  is preferably located separately from the workstation  44 , although, within easy reach of the operator access position  54 . The bundler  100  functions to wrap a tape or band  20  around the coiled blast initiation device  10  to create a bundled device as shown in FIG.  6 . The completed blast initiation device  10  may include many meters of coiled transmission line and the tape  20  functions to prevent the transmission line  12  from becoming tangled during handling. While not shown in FIG. 6, the operator  46  preferably places the ends of the blast initiation device  10  within the center of the coiled transmission line  12  so that the tape  20  serves to hold the ends as well as the transmission line  12 . Naturally, a plurality of blast initiation devices could be wrapped with a single tape  20  at the bundler  100 , if desired. Once bundled, the completed blast initiation device  10  is ready for packing into appropriate containers or storage or shipping. 
     As shown in FIG. 2, a first and second workstation,  102  and  104  respectively, may be incorporated into a kaizen cell  106  which shares under utilized facilities such as the transmission line conveyor  92 , bundler  100 , bulk detonator storage  78  and a packing station  108 . Since the cycle times of the conveyor  92  and bundler  100  are shorter than the cycle time for assembly of a blast initiation device  10  by an operator  46  at the inventive workstation,  102 ,  104 , the sharing of,such facilities decreases total cell cost while maintaining optimum output from each workstation. Additionally, only one operator  46  is required to intermittently bundle and package the bundled blast initiation devices into containers, allowing the other operator to continue assembly of blast initiation devices. This further increases efficiency of the cell when compared to two separate workstations. As each workstation may be designed generally in an arc or circle around the operator, the kaizen cell will be arranged around some point at which the workstation arcs or circles meet. 
     While preferred embodiments of the foregoing invention have been set forth for purposes of illustration, the foregoing description should not be deemed a limitation of the invention herein. Accordingly, various modifications, adaptations and alternatives may occur to one skilled in the art without departing from the spirit and scope of the present invention.