US2025907A - Instantaneous circuit-closing device for electric shot firing machines - Google Patents

Description

GLC'JSSL 2,025,907

NG DEVICE FOR ELECTRIC SHOT FIRING MACHINES Dec. 31, .1935.

KISCHAFFLER INSTANTANEOUS CIRCUIT CLOSI Filed Aug. 27, 1932 [72002 fan Patented Dec. 31, 1935 UNITED STATES INSTANTANEOUS CIRCUIT- CLOSING DEVICE FOR. ELECTRIC SHOT FIRING MACHINES Konrad Schafller-Gltissl, Vienna, Austria Application August 2'1, 1932, Serial No. 630,674 In Austria May 30, 1932 7 Claims.

This invention relates to instantaneous circuitclosing devices for electric shot firing machines of the type comprising a direct current dynamo housed in a casing and provided with an armature adapted to be set temporarily in rapid rotation by a restricted movement of a handle acting through the medium of a driving element and a suitable train of gears.

The invention consists essentially in the pro- 1 vision of means adapted to cooperate with the driving element for effecting a momentary closing of the normally open firing circuit after a given motion has been imparted to the driving element.

Instantaneous closing of the circuit has the 15' advantage, more particularly in coal mines in which fire-damp is apt to occur, that no dangerous sparking under the influence of the firing machine can take place in the conductors on partial destruction of the latter by the explosion. The de- 20 vice according to the invention also has the advantage, as compared with shot firing machines of known types, that the duration of the circuit closing is not dependent upon the speed with which the machine is operated.

25 A form of construction embodying the invention is shown by way of example in the accompanying drawing, in which:-

Fig. 1 is a vertical section of the upper part of a shot firing machine showing the essential parts 30 of the instantaneous circuit-closing device according to the present invention, taken on the line II of Fig. 2.

Fig. 2 is a cross-section taken on the line 11-11 of Fig. 1, certain parts of the instantaneous cir- 35 cuit-closing device being indicated in their respective positions of rest by means of dotted lines.

Referring to the drawing, there is mountedin the upper parts of the casing I8 of the shot firing machine the main driving shaft 3 to the lower end 40 of which there is attached a driving element in the form of a toothed sector 2 from which the drive can be taken through a suitable train of gears to a dynamo contained in the lower part of the casing. These gears, the dynamo, and the 45 lower part of the casing are omitted from the drawing since they do not form part of the prese ent invention. The upper end of the shaft 3 is adapted for the application thereto of a handle I for the hand operation of the machine. The

50 operative movement of the drivingelement 2 is to be considered in the present instance as taking place in a clockwise direction. Automatic restoring means, such as the spring 4, are interposed between the driving element and the machine 551 casing for returning the driving element into its initial or rest position after operation, on the releasing of the handle I. An abutment surface I3 on the casing I8 limits the movement of the sector 2. In the example shown, the terminals of the machine are connected to two contacts consisting of leaf springs II, and the firing circuit is closed by the momentaryengagement of a contact pin I0 between these spring contacts II. For this purpose the pin III is loaded by the spring I2, and is momentarily thrown forward, against 10 the action of this spring, by the impact of a sliding thrust member 9 which is guided in the casing I8, and to which a momentary thrust is imparted, in dependence on the operation of the machine, by the following means. A bell-crank lever 6 mounted eccentrically with regard to the axis of the shaft 3 on a pivot I5 carries on one arm a lug 36 whichis engaged by a powerful blade spring I. The other arm of this lever carries a curved cam ledge I1 adapted for cooperationwith a tripping member 5 mounted in a fork 35 on the sector 2. At the outer end of the cam arm of the bell-crank lever 6 there is mounted a spring loaded catch 8 which is free to move inwards only, against the action 2 of its spring, while being prevented from outward movement by means of suitable abutting surfaces. In the position of rest the described parts occupy the respective positions indicated by dotted outlines in Fig. 2 in which the spring I is in the tensionless state and the cam arm of the bell-crank lever 6 rocked inwards with the catch 8 resting against the inner side of the slide 9. On the sector 2 being rotated for driving the firing machine, the tripping member 5 engages the cam ledge I1 and rocks the lever 6 against the action of the spring 'I,the catch 8 being thereby caused to'yield to pass the end of the slide 9 and then to return to the extended position under the action of its spring after 40 clearing the end of this slide. At a given displacement of the sector 2, that is to say when the armature of the dynamo is ready to supply the firing current, the tripping member 5 slips clear of the end of the cam ledge I1 and allows the lever 6 to be restored by the spring I, with the result, since the catch 8 does not yield outwards, that the contact member I0 is thrown forward against the action of the spring I2 into and out of engagement between the contacts II,

and the firing'circuit thereby closed for a fraction of a second. The actual duration of the closing depends on the strength of A the spring I and on the width of the face of the slide .9

swept by the catch 8, and. is whollyindependent til of the manner in which the firing machine is operated. The timing of the operation of the circuit-closing device, that is to say of the moment at which the bell-crank lever 6 is released to strike against the end of the slide 9 under the action of the tension spring 1, is determined by the relative position of the forked holder 35 and tripping member 5 on the sector 2, andby the length of the 'cam ledge H.

When the sector '2 returns, under the influence of the spring 4, the tripping member 5 is deflected by the cam ledge ll as it travels along the back of the latter. A spring l4 restores the member 5 to its normal position after it has passed the rear end of the cam ledge H. The member 5 is provided with a lug 39 which bears against an abutment which determines its normal position.

As already stated, it is essential according to the invention that the duration of circuit closing should be as short as possible and independent of the strength of the current. The sparking set up between the contact elements on the breaking of the circuit has a tendency to prolong the duration of circuit' closing, and will do so if the external resistance of the circuit be sufficiently small. In order to enable the device to meet such conditions the pin Iii is arranged to be thicker than the space between the spring contacts so as to wedge these latter apart, the forward end of the pin being rounded or abruptly tapered to enable it to enter this space. Thus the spring contacts tend to repel the contact pin and thereby cooperate with the spring l2 in effecting a rapid separation of the pin from the contacts. The pin leaves the two contacts simultaneously, and since the circuit will thus be broken at two different points between which the sparking will be divided, the intensity of the sparking will be halved, and no material prolongation of the duration of eireuit closing will take place. The rapidity with which the circuit is broken can be regulated to some extent by adjustment of the tension of the spring l2. For this purpose the spring [2 bears against an adjustable abutment such as a collar ii! on the pm. 1 The circuit may be broken in this manner at more than two points, in which case the intensity of the sparking will be still further reduced.

The practical effect of the invention is that the circuit is broken before firing actually takes place.

I claim:

1. In an electric shot firing machine a casing, a hand operable driving element pivotally supported in the said casing, at. least one pair of spaced contactsmounted in the saidcasing and interposed in the firing current circuit of the machine; a thrust slide guided in the said casing, a housing located between said slide and contacts, a pin slidably mounted in'said housing and normally bearing against the forward end of said slide, an abutment on said pin, a compressed spring tensioned between said abutment and housing and tending to force the pin away from the contacts, and striking means associated with the said driving element for delivering an impact of predetermined strength and of predetermined momentary duration against the rear end of the said thrust slide, for the purpose of impelling the said pin into momentary engagement between the said contacts against the action of the said compressed spring.

2. In an electric shot firing machine a casing,

a hand operable driving element pivotally supported in the said casing, at least one pair of spaced contacts mounted in the said casing and interposed in the firing current circuit of the 5 machine, a thrust slide guided in the said casing,

a housing located between said slide and contacts, a pin slidably mounted in said casing and normally bearing against the forward end of the said slide, an abutment on said pin, a com- 10 pressed spring tensioned between said abutment and housing and tending to force the pin away from the contacts, a bifurcated holder depending from the under side of the said driving element,

a rocking member having arms pivoted at a 15 point remote from the axis of rotation of said driving element and to one side of the axial plane of symmetry of the said driving element when in its mid-way position, a blade spring mounted by one end in the said casing and bear- 20 ing with its free end against the one arm of the said rocking member, acurved cam ledge on the other arm of the said rocking member and substantially raised above the main upper surface thereof, an inwardly yielding and outwardly rig- 25 id spring-loaded catch pivotally mounted at the outer end of the said second arm, and a springloaded outwardly yielding but inwardly rigid tripping member pivotally mounted in the said blfurcated holder and extending with its lower end go beyond the plane of the upper surface of the said cam ledge but stopping short of the plane of the main upper surface of the said second arm, the radius of the arc of movement of the said end of said catch being greater, and that of the end 5 of said second arm less than the distance between the pivot point of said rocking member and the rear end of said slide, said blade spring, rocking member, and cam ledge being so relatively dimensioned, and said holder and tripping member so positioned on said driving element, that in the position of rest of these parts the said tripping member is inwardly rocked with said catch located on the inner side of the rear end of said slide while the said cam ledge bears with the initial portion of its concave inner side against the front face of said tripping member, whereas towards the end of the operative movement of said driving element the said catch has come clear of and is located in front of the rear end of the said slide, the said blade spring tensioned, and the said cam ledge bearing with the terminal portion of its concave inner side against the front face of the said tripping member.

3. A structure as claimed in claim 1 in which the said driving element is a toothed sector adapted to be rotated by a handle, and is equipped with means for automatically restoring the said driving element into its position ofrest when the said handle is released after operation.

4. A structure as claimed in claim 1 in which the said pin is thicker than the width of the space between the said contacts and roundedoff at its forward end, and in which the said contacts are resilient, for the purpose of aiding the action of the said compressed spring in repelling the pin from engagement between the contacts and thereby reducing the length of time for which the firing circuit is closed.

5. A structure as claimed in claim 1 in which actionof thesaid compressed spring in repellin 1,51

the pin from engagement between the contacts. rounded off and tapered in towards the terminal 6. A structure as claimed in claim 1 in which portion of the front concave operative side therethe said abutment is adjustable longitudinally of, for the purpose of engaging and outwardly of the said pin for the purpose of varying the deflecting the said tripping member during the 5 tension of the said compressed spring. return movement of the said driving element into 5 7. A structure as claimed in claim 2 in which its position of rest after operation. the dorsal convex side of the said cam ledge is KONRAD SCHAFFLER-GLGSSL.

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