US2129835A - Electric shot-firing machine - Google Patents

Description

Sept. 13, 1938. K. S-CHAFFLER-GLC3SSL 2,129,835

ELECTRIC SHOT-FIRING MACHINE Filed May '5, 1957 Ratented Sept. 13, 1938 UNITED STATES PATENT OFFICE Application May 5, 1937, Serial No. 140,870 InAustria April 15, 193':

6 Claims.

This invention relates to electric shot-firing machines equipped with means for ensuring the delivery of current of suflicient strength to effect ignition with certainty.

It is already known to provide handor springdriven shot-firing machines with an instantaneous contacting device which only closes the current circuit through the generator and the shotfiring line at the end of the driving impulse, that is to say when the armature of the generator has attained its maximum speed of rotation. In the case of hand-driven shot-firing machines, however, this maximum speed of rotation depends upon the manual force and skill used in carrying out the driving operation, and it may easily happen, if this operation is performed with insufiicient energy or skill, that the voltage of the current generated in the machine is not high enough to ensure faultless firing of all the fuses connected to the machine.

Attempts have been made to overcome this drawback by arranging for the circuit to be closed by a relay responsive to the voltage of the current generated in the machine. It is impossible, however, with an arrangement of this nature, to preclude with certainty the possibility of the relay effecting closing of the circuit with some delay, that is to say at a moment of time at which the drop in the voltage of the current generated by the machine, which occurs immediately after the driving impulse ceases, owing to the immediate falling off of the speed of rotation of the armature, has already taken effect. Now since with electric shot-firing machines the maximum duration of the firing current may not exceed @30 of a second it will be clear that a very slight error in timing will suflice, under unfavorable circumstances, to render the short current impulse supplied to the shot-firing line too weak to ignite all the fuses connected thereto.

With the shot-firing machine according to the present invention the danger of the current impulse generated being insuflicient to fire all the fuses connected thereto, or rather of too weak an impulse being allowed to flow through the shotfiring line, is avoided with certainty by the provision of a blocking device for the firing current switch contact, which only liberates this contact for operation providedthe magnetic field of the firing machine has attained the strength corresponding to the requisite voltage of the firing current. If then in the case of a hand-driven shot-firing machine the voltage of the current generated is not quite high enough, for instance owing to an insufliciently powerful driving impulse, to ensure faultless firing of all the fuses the magnetic field in the magnet frame or yoke of the machine does not attain the strength appropriate to the required output voltage, and the switch contact consequently remains blocked by the means provided for this purpose. The shotfiring circuit including the fuses thus remains open, and no current impulse that would be inadequate for firing all the fuses connected up to the machine can pass into the shot-firing line. The operator of the machine is thus compelled to start again and to impart a more powerful driving impulse to the machine, and if this be successfully achieved the blocking device is 'put out of action, and a current impulse of sufiicient voltage flows into the shot-firing line.

In the accompanying drawing there is shown, diagrammatically, an electric shot-firing machine according to the invention equipped with means for blocking and releasing the switch contact in dependence on the strength of the magnetic field of the current generator. In the shotfiring machine, which consists in a known manner of the armature i, magnet core 3, magnet field coil 2, and toothed sector 4 adapted to be driven by means of a handle in the direction indicated by the arrow and to effect rotation of the armature through the instrumentality of intermediate gearing not shown in the drawing, the switch contact for the firing current, which may consist for instance of the switch pin 5, the slide 6, and the leaf springs I, is operated by means of the pawl 8 mounted on the toothed sector 4. This pawl bears slidingly against the end of the slide 6 during the movement of the sector amounting to about one-third of a complete revolution, thereby moving this slide and causing the switch pin 5 to pass between the springs l, with the result that the current circuit through the machine and the fuses 9 ,is closed. After the pawl 8 comes clear of the slide 6 this latter and the pin 5 are restored to the circuit-breaking position by the previously compressed spring Ill. The length of time elapsing between circuitclosing and circuit-interruption amounts at the most to 7 sec.

In order to ensure that the contacting device 5, '6 shall not be able to effect circuit closing when the speed of rotation of the armature l is less than is necessary to generate a current of suflicient voltage the slide 6 is blocked by means of a latch II the end of which engages in a notch l5 in the slide. The blocking thus effected is only cancelled when the magnetic field of the machine, after having increased in strength until the voltage of the current generated in the machine has attained a predetermined figure, attracts an armature l3 mounted on the blocking latch l I, through the intermediary of a pole piece I! connected with the magnet core 3 and magnetized thereby. Provided the switch contact be liberated immediately before the moment at which the current impulse generated by the armature reaches its maximum value, the circuitclosing will be effected when the voltage is at its maximum. Ii. however, in consequence of too weak a driving impulse being imparted to the Sector 4 in operating the machine, only a current of somewhat too low a voltage is generated, the magnetic field set up will be correspondingly too weak, with the result that the armature l3 on the latch II is not attracted and the current circuit remains open. A current impulse that is not sufficient to ensure ignition of all the fuses connected up to the machine can not, therefore, pass into the shot-firing line.

After interruption of the current and disappearance of the efiective magnet field between the parts l2 and IS, the latch H returns into its locking position under the influence of its spring H.

I claim:

1. In a dynamo-electric shot-firing machine the combination with an igniting circuit including a charge igniting device, of an electric current generator in said igniting circuit, spaced contacts in said circuit, means for momentarily bridging said contacts and thereby closing said circuit, means for operating said generator having associated therewith means for imparting an operating impulse of predetermined extremely short duration to said circuit-closing means, a detaining contrivance normally arrestingly engaging in said impelling means and operatively responsive to the strength of the magnetic field of said generator to release said impelling means only when the strength of said magnetic field reaches a predetermined value. 2. In a dynamo-electric shot-firing machine the combination with an igniting circuit including a charge igniting device, of an electric current generator having a field magnet yoke and disposed in said igniting circuit, spaced contacts in said circuit, means including a sliding thrust member for momentarily bridging said contacts 'and thereby closing said circuit, means for operating said generator having associated therewith means for imparting an operating impulse of predetermined and extremely short duration to said circuit-closing means, -a movable latch normally arrestingly engaging in said thrust member, and a magnet armature mounted on said latch within the range of the lines of force proceeding from the said magnet yoke, said latch and armature being so disposed that said latch is moved out of engagement with said thrust member when the strength of the magnetic field of said generator reaches a predetermined value.

3. In a dynamo-electric shot-firing machine the combination with an igniting circuit including a charge igniting device, of an electric current generator having a field magnet yoke and disposed in said igniting circuit, a pole piece made of magnetizable material and conductively connected with the said magnet yoke, spaced contacts in said circuit, means including a sliding thrust member for momentarily bridging said contacts and thereby closing said circuit, means for operating said generator having associated therewith means for imparting an operative impulse of predetermined and extremely short duration to said circuit-closing means, a movable latch normally arrestingly engaging in said thrust member, and a magnet armature mounted on said latch for attraction to said pole piece to move said latch out of engagement with said thrust member when the strength of the magnetic field of said generator reaches a predetermined value.

4. In a dynamo-electric shot-firing machine the combination with an igniting circuit including a charge igniting device, of an electric current generator having a field magnet yoke and disposed in said igniting circuit, a pole piece made of magnetizable material and conductively connected with the said magnet yoke, spaced contacts in said circuit, means including a sliding thrust member for momentarily bridging said contacts and thereby closing said circuit, said thrust member having an abutment surface accessible from the direction towards which said member is adapted to move in the circuit-closing operation, means for operating said generator having associated therewith means for imparting an operative impulse of predetermined and extremely short duration to said circuit closing means, a movable latch normally engaging against said abutment surface to detain said thrust member, and a magnet armature mounted on said latch for attraction to said pole piece to move said latch out of engagement with said abutment surface and thereby to liberate said thrust member for operation in response to said impelling means when the strength of the magnetic field of said generator reaches a predetermined value.

5. In a dynamo-electric shot-firing machine the combination with an igniting circuit including a charge igniting device, of an electric current generator having a field magnet yoke and disposed in said igniting circuit, a pole piece made of magnetizable material and conductively connected with the said magnet yoke, spaced contacts in said circuit, means including a sliding thrust member for momentarily bridging said contacts and thereby closing said circuit, said thrust member having a recess presenting an abutment surface accessible from the direction towards which said member is adapted to move in the circuit-closing operation, means for operating said generator having associated therewith means for imparting an operative impulse of predetermined and extremely short duration to said circuit-closing means, a movable latch normally engaging against said abutment surface to detain said thrust member, and a magnet armature mounted on said latch for attraction to said pole piece to move said latch out of engagement with said abutment surface and thereby to release said thrust member for operation in response to said impelling means when the strength of the magnetic field of said generator reaches a pre determined value.

6. In a dynamo-electric shot-firing machine the combination with an igniting circuit including a charge igniting device, of an electric current generator having a field magnet yoke and disposed in said igniting circuit, a pole piece made of magnetizable material and conductively connected with the said magnet yoke, spaced contacts interposed in said circuit, means including a sliding thrust member for momentarily bridging said contacts and thereby closing said circuit, said thrust member having a recess presenting an abutment surface accessible from the direction towards which the said thrust member is adapted to move in the circuit-closing operation, means for operating said generator having associated therewith means for imparting an operative impulse of predetermined and extremely short duration to said circuit closing means, a movable latch spring stressed into engagement against said abutment surface to detain said thrust member, and a magnet armature mounted on said latch for attraction to said pole piece to move said latch clear of said abutment surface against the action 10 of said spring and thereby to release said thrust member for operation in response to said impelling means when the strength of the magnetic field of said generator overcomes the strength of said spring, said spring being also adapted to restore said latch to its initial position in engagement in front of said abutment surface after discontinuance of the magnetic field in said yoke and pole piece and after the said thrust member has returned into its inoperative position.

KONRAD SCHAFFLER-GLCSSL.

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