US3886842A

US3886842A - Self-cocking explosively actuated cable cutter with shock absorber

Info

Publication number: US3886842A
Authority: US
Inventors: Joseph L Giebel; Ernest E Temple
Original assignee: Mine Safety Appliances Co
Current assignee: MSA Safety Inc
Priority date: 1971-07-19
Filing date: 1973-09-10
Publication date: 1975-06-03
Anticipated expiration: 1992-06-03

Abstract

A cable cutter frame has a laterally opening recess near its front end for receiving a cable that can be cut against an anvil by a chisel slidably mounted in the frame behind the recess when it is driven forward by an explosive charge. A plunger for actuating a firing pin is carried by the frame beside the recess and chisel and is slidable lengthwise of the frame. The plunger is provided adjacent the recess with a lateral notch that receives one end of a trigger extending transversely of the frame near the front of the recess in a position to be moved forward by a cable entering the recess, whereby to move the plunger forward against spring pressure. As the trigger is moved forward it withdraws from the notch, whereupon the plunger is driven rearwardly to actuate the firing pin. The anvil is slidably mounted in the frame and provided with a shock absorber. The firing pin preferably is in the inner end of a transverse passage through the frame, in which a hollow breech block that contains a cartridge is screwed.

Description

United States Patent [1 1 Giebel et a1.

1 1 June 3, 1975 1 SELF-COCKING EXPLOSlVELY ACTUATED CABLE CUTTER WITH SHOCK ABSORBER {75] Inventors: Joseph L. Giebel, Pittsburgh; Ernest E. Temple, Murrysville. both of Pa.

[73] Assignee: Mine Safety Appliances Company,

Pittsburgh. Pa.

[22] Filed: Sept. 10. 1973 [21] App]. No.: 395578 Related U.S. Application Data [62] Division of Ser. No. 163949. July 19. 1971, Pat. No.

Primary E.\'aminerBenjamin A. Borchelt Assistant Examiner(. T. Jordan Armrney, Agent, or Firm-Brown, Murray, Flick & Pcckham [57] ABSTRACT A cable cutter frame has a laterally opening recess near its front end for receiving a cable that can be cut against an anvil by a chisel slidably mounted in the frame behind the recess when it is driven forward by an explosive charge. A plunger for actuating a firing pin is carried by the frame beside the recess and chisel and is slidable lengthwise of the frame. The plunger is provided adjacent the recess with a lateral notch that receives one end of a trigger extending transversely of the frame near the front of the recess in a position to be moved forward by a cable entering the recess, whereby to move the plunger forward against spring pressure. As the trigger is moved forward it withdraws from the notch. whereupon the plunger is driven rearwardly to actuate the firing pin. The anvil is slidably mounted in the frame and provided with a shock absorber. The firing pin preferably is in the inner end of a transverse passage through the frame. in which a hollow breech block that contains a cartridge is screwed.

1 SELF-COCKING EXPLOSIVELY ACTUATED CABLE CUTTER WITH SHOCK ABSORBER This application is a division of our copending patent application, Ser. No. 163,949, filed July 19, 1971, now US. Pat. No. 3,780,689.

Explosively actuated cable cutters and the like are operated by tapping a firing pin against the detonator of an explosive charge, or by manually withdrawing a firing pin against spring pressure and then releasing it to set off the charge, or by cocking the tool and holding it in that condition by means of a flexible pin that releases the firing mechanism when the cable to be cut engages and separates the pin from the firing mechanism. Only this last system of operating a cable cutting tool can be operated at a distance from the operator, but it has the disadvantage that the tool may be fired accidentally or prematurely by something engaging the pin that holds the tool in its cocked condition.

It is among the objects of this invention to provide an explosively actuated cable cutter which is not cocked until a cable that is to be cut is in correct position in the cutter, which is cocked by the cable, which is safe to use, which has a long life and which can easily be disarmed.

The invention is illustrated in the accompanying drawings, in which FIG. 1 is a longitudinal section of a cable cutter; and

FIG. 2 is a view, similar to FIG. 1, of a modification.

Referring to FIG. 1 of the drawings, the metal frame 45 of the cutter or tool is long in comparison with its width and thickness and is provided with a passage extending through it from end to end. The rear end of this passage may be threaded to permit the tool to be mounted on one end of a long pole. The central portion of the passage forms a barrel for a chisel-like cutting member 55 with a cutting edge at its front end. The front end of the passage is closed by a screw plug 65 that forms an end wall for the frame passage. Spaced from the inner end of this plug is an anvil 64, behind which the opposite sides of the frame are cut away and the front side of the frame is provided with a slot 62 that opens into the cable-receiving recess thus formed.

The rear end of the barrel forms the breech of the tool. A short distance behind the chisel 55 and the frame 45 is provided with a transverse cylindrical passage 56 that extends entirely through it, although the inner or back end of this passage is reduced in diameter. A hollow cylindrical breech block 54 containing a cartridge 53 is screwed into the passage, and a firing pin 57 is slidably mounted in the reduced inner end of the passage. The pin projects out into the path ofa rodlike plunger 51 slidably mounted in aligned bores extending lengthwise of the frame. One end of the plunger is notched to accommodate the firing pin and provide a sloping forward wall 58. At the inner end of the cartridge the breech block is provided with a radial port 59 that communicates with an opening 60 behind the chisel.

The plunger is urged toward the firing pin end of the frame by means of a coil spring 63 encircling the plunger between its enlarged front end portion and a shoulder in the frame. To normally hold the plunger in inoperative position and to make the tool self-cocking, a U-shape trigger straddles part of the frame 45. That is, the trigger is formed from two arms 46, one at each side of the frame, with their inner ends rigidly connected by a cross pin 47. The front or outer ends of the arms are mounted on a pivot pin 48 projecting from opposite sides of the frame. The cross pin of the trigger extends through an arcuate slot 49 in the back side of the frame, located in such a position that when the trigger is at the rear end of the slot the pin will lit in a notch 50 in the spring-pressed firing plunger 51 and hold the plunger retracted. A removable safety pin 52 can also be used.

After this tool has been loaded with a cartridge, it is prepared for use by removing the safety pin 52. The tool then is hooked over a cable by moving the tool laterally to cause the cable to enter the frame recess 62, where it will engage the trigger. Then, by pulling backward on the tool, the cable will swing the trigger forward in the frame, which will cause the trigger cross pin 47 to slide the firing plunger'forward in the frame and compress the coil spring 63. As the cross pin swings forward in an arcuate path, it is withdrawn from the notch 50 in the plunger. The moment this occurs the plunger is released and is propelled rearwardly in the frame by its spring to cause the sloping wall 58 of the plunger to drive the firing pin against the cartridge. The resulting explosion drives the chisel forward in the barrel and severs the cable against an anvil 64.

It is a feature of this invention that the anvil is slidably mounted in the frame and normally is spaced from the plug 65 in the front end of the frame passage by means of a shock absorber, preferably in the form of a short metal tube 66 engaging both the anvil and the plug. When the anvil receives the impact of the chisel, it moves forward and crushes the tube, which thereby absorbs the shock to prolong the life of the tool. The crushed shock absorber can easily be removed and replaced by a new one.

If, after the tool has been fired, someone removes the breech block and the spent cartridge, reloads the breech block and then screws it back into the frame without first moving the plunger back to receive the inner end of the trigger in its notch 50, the act of screwing the breech block into the frame could press the firing pin against the side of the plunger and fire the cartridge. To prevent this from occurring, a safety device can be used which is in the form of a piston 68 pressed against the rear end of the plunger by a small coil spring 69 encircling the piston rod 70 between the piston and a ring nut 71 screwed into the rear end of the frame. The spring exerts just enough pressure against the plunger to move it back to the position it occupies while the trigger is in its notch. In this position the side of the plunger is spaced slightly from the firing pin, so there is no danger of a cartridge being detonated when the breech block is screwed into the frame.

In the further modification illustrated in FIG. 2, the tool is equipped with a sliding trigger instead of a pivoted trigger. Thus, an anvil 75 is slidably mounted in the frame barrel 76 and normally is spaced from the screw plug 77 at the front end. A tubular shock absorber like the one previously described may be placed between them, or a cup-like shock absorber 78 can be screwed into the front end of the anvil with the open side of the cup facing the plug. In either case there must be a space between the shock absorber and either the plug or the anvil. The anvil is provided with a straight passage 79 extending through it from the front side of the frame to the back side. slidably mounted in this passsage is a trigger pin 81 that extends out of the back side of the anvil and into a slot 82 in the back side of the frame. The side of the pin normally engages the back wall of this slot and projects into a lateral notch 83 in a spring-pressed plunger 84. The forward wall of this notch slopes toward the front end of the pin. Also, the inner surface 85 of the frame at the outer end of the pin slopes forward and away from the anvil. The plunger causes the trigger pin to normally hold the anvil in its rearmost position as shown.

When a cable enters the frame recess 86 and the tool is pulled backward, the cable moves the anvil and trigger pin forward together in the tool frame. The pin, in turn, moves the plunger forward against the pressure of coil spring 87, but since the inner end of the pin is pressed against the sloping wall of the plunger notch the pin is urged away from the plunger and along the sloping surface85 of the frame. The latter surface is sloped enough to allow the pin to leave the plunger notch after the plunger has been compressed sufficiently. Then the plunger is driven forward to fire the cartridge. This causes the chisel to be driven through the cable and against the anvil. The anvil now being free to slide in the frame. it is driven forward and the hollow front end of shock absorber 78 is crushed against plug 77 to absorb shock. The trigger pin is protected and concealed within the tool at all times.

It will be seen that the operator does not cock these tools before they are put into use. The cocking is done by the cables that are to be cut, and that cannot occur until after a cable has entered a frame recess and engaged the trigger. When the operator pulls back on the tool the cable first cocks and then fires the tool. Consequently, there is no danger of the tool being fired accidentally or before the cable is in correct position for cutting. The tools also have a longer life than heretofore, because the anvils can move when struck, and the impacts of the chisels are absorbed to some extent by the shock absorbers.

According to the provisions of the patent statutes, we have explained the principle of our invention and have illustrated and described what we now consider to represent its best embodiment. However, we desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

We claim:

1. In an explosively actuated cable cutter having a frame provided with a barrel containing a cutting chisel, and means for detonating an explosive charge to drive the chisel forward, an anvil slidably mounted in the frame in front of the chisel and spaced therefrom, a crushable shock absorber in front of the anvil, and a rigid end wall in said frame in front of the shock absorber and against which the shock absorber is crushed when the anvil is moved forward by the impact of the chisel against the anvil.

2. In an explosively actuated cable cutter according to claim 1, said shock absorber being a crushable short length of a tube extending lengthwise of said barrel.

3. In an explosively actuated cable cutter according to claim 1, said shock absorber being a cup-like member detachably connected to the anvil, with the open end of said member facing away from the anvil.

4. In an explosively actuated cable cutter according to claim 1, said shock absorber always engaging said wall and the anvil.

5. In an explosively actuated cable cutter according to claim 1, said shock absorber being mounted on the anvil and normally spaced from said wall.

6. In an explosively actuated cabie cutter having a frame provided with a barrel containing a cutting chisel, an anvil slidably mounted in the frame in front of the chisel, a firing pin in the frame behind said chisel for detonating an explosive charge to drive the chisel forward in order to sever a cable against said anvil and move the anvil forward, a crushable shock absorber in front of the anvil for absorbing the impact of the chisel against the anvil, a plunger for actuating the firing pin carried by the frame beside said anvil and chisel and slidable lengthwise of the frame, the plunger normally being in an uncocked position and being provided with a lateral notch, a trigger extending transversely of the frame in a position to be moved forward by a cable that is to be cut, one end of the trigger normally projecting into said plunger notch for moving the plunger forward with the trigger from said uncocked position to cock the cutter, the trigger being supported by the frame for retraction from said notch as the trigger is moved forward, and a spring between the frame and plunger adapted to be compressed by the forwardly moving plunger until the trigger leaves said notch and releases the plunger, whereupon the spring will drive the plunger rearwardly to actuate the firing pin.

7. In an explosively actuated cable cutter according to claim 6, said trigger including parallel arms straddling said frame, a cross member normally disposed in said plunger notch and secured to the adjacent ends of said arms, and means pivotally connecting the opposite end of the arms to the frame on a transverse axis, the frame being provided with an arcuate slot therethrough receiving said cross member to permit it to swing forward in the frame and out of said plunger notch.

8. In an explosively actuated cable cutter according to claim 6, said frame being provided behind the chisel with a transverse passage and with an opening connecting the side of that passage with the back of the chisel, and said cutter including a hollow breech block screwed into said passage and having a lateral opening connecting the inside of the block with said frame opening, the outer end of the breech block being closed, said firing pin being slidably disposed in the inner end of said passage, and the end of said plunger adjacent the firing pin having a sloping surface for engaging and forcing the firing pin toward the breech block when the plunger is driven rearwardly.

Claims

6. In an explosively actuated cable cutter having a frame provided with a barrel containing a cutting chisel, an anvil slidably mounted in the frame in front of the chisel, a firing pin in the frame behind said chisel for detonating an explosive charge to drive the chisel forward in order to sever a cable against said anvil and move the anvil forward, a crushable shock absorber in front of the anvil for absorbing the impact of the chisel against the anvil, a plunger for actuating the firing pin carried by the frame beside said anvil and chisel and slidable lengthwise of the frame, the plunger normally being in an uncocked position and being provided with a lateral notch, a trigger extending transversely of the frame in a position to be moved forward by a cable that is to be cut, one end of the trigger normally projecting into said plunger notch for moving the plunger forward with the trigger from said uncocked position to cock the cutter, the trigger being supported by the frame for retraction from said notch as the trigger is moved forward, and a spring between the frame and plunger adapted to be compressed by the forwardly moving plunger until the trigger leaves said notch and releases the plunger, whereupon the spring will drive the plunger rearwardly to actuate the firing pin.