US1990279A - Casing for electric shot-firing machines - Google Patents

Description

1935. K. SCHAFFLER-GLCSSL 1,990,279

CASING FOR ELECTRIC SHOT FIRING MACHINES Filed Nov. 18, 1933 FIG. 1. 12

Patented Feb. 5, 1935 PATENT OFFICE casino roa ELECTRIC SHOT-FIRING moms Konrad Schafller-Gliissl, Vienna, Austria Application November 18 3 Claims.

This invention relates to an improved protective casing for electric shot-firing machines for use in connection with blasting work in mines, and has for its object to provide a light weight casing 01 this nature having a reliably'tight joint between 'the cover and the main body portion thereof. Further objects of the invention will become clear in the course of the ensuing description. The essential feature of the invention consists in the fact that the lid of the casing consists of two sheets of metal disposed one above the other and at a distance from each other, so that they form between them the groove for the groove joint between the cover and the body of the casing.

It is already known to manufacture a protective casing consisting of a body portion and a cover, for portable electric shot-firing machines for use in mines where there is danger of firedamp explosion, of metal castings, and to effect a tight joint between the casing proper and the edge of the cover by a groove-joint.

If it is desired to avoid the obvious disadvantage of castings, which consists in their heavy weight conditioned by relatively great wall-thickness, and to make both casing and cover of sheet metal it is no easy matter to obtain a groove-joint which is comparable in effectiveness to that obtainable when the parts are cast. It is in fact possible, with a sheet metal cover having a downwardly extending flange adapted to fit over the upper edge of the main body of the casing, to provide a jointing groove by the arrangement of a second flange which is disposed parallel to the said first flange and distanced therefrom to the extent of the thickness of the upper rim of the main body 01 the casing, and which is attached to the cover for example by rivets or soldering. Such an attachment, however, apart from the fact that it is complicated and expensive in manufacture, would not provide with reliability the degree of tightness required as a precaution against the danger from firedamp, and would also not satisfy the requirements of the more recent mine regulations.

The difliculty here involved is overcome, in accordance with the invention, by making the cover of two similarly shaped parts which are arranged in spaced relation one above the other, and which are preferably made of drawn sheet metal. The edges of these parts are flanged or turned over, so that they together form the groove for the reception 01' the rim of the main body of the casing. These turned-over flanges fit tightly against both sides of the edge of the casing over their entire length, when the cover is placed in position on 1933, Serial No. 698,733 Germany November 18, 1932 the main body of the casing, with the result that long leakage paths are formed which check the intrusion of explosive gases, and prevent by cooling the blowing past of the flame of any gas happening to become ignited.

A constructional example embodying the invention is shown, by way of example, in the accompanying drawing, in which:

Fig. 1 is a longitudinal section of a shot-firing machine provided with a protective casing accordl0 ing to the invention.

Fig. 2 is a plan view of the casing, showing the cover, and the apertures therein.

Referring to the drawing, in Fig. 1 the casing and cover which enclose the shot-firing machine proper, and which are the subject of the present invention are rendered prominent by being drawn in heavier lines. In the drawing 1 denotes the main body of the casing, 2 and 3 the two parts, respectively, of the cover, 4 and 5 the flanged edges of the latter and 6 the upper edge of the main body of the casing.

A tight joint is formed between the body 1 of the casing and the two-part cover by the insertion of a packing in the groove, against which the upper edge 6 of the body is pressed by tensioning or stressing means of a known type, such as for example the screw 9 and the lugs 7 and 8. The mode of construction of the lid or cover in accordance with the invention makes it possible to provide this packing in a particularly convenient and suitable manner in a continuous piece filling out the narrow space between the two parts 2 and 3 of the cover and extending up to the head of the jointing groove. This packing is denoted by the reference number 10. This arrangement has the particular advantage that the packing can not fall out of the groove as is otherwise the case with packings inserted in grooves.

Packing can also be provided in a similar manner for the parts of the firing machine projecting through the cover, such as the boss 11 of the winding-up pin 12, the insulation body for the lead-in terminals 13, and the like, the arrangement being that one or both of the parts of the cover are flanged up at these points, and made to fit closely with their flanged edges 14 and 15 about the parts concerned. In this manner long leakage paths are formed which effectually prevent the intrusion of explosive gases into the casing at these points.

An additional packing of these joints can also be provided by the provision of inserted packing material. For this purpose the flanged rim 16 of the outer sheet of the cover can for example be inwardly bent over at right angles, and a packing 18 provided between the ring 17 thus formed and the edge of the flanged rim 14. The pressure required for forcing this packing into close fitting contact both with the boss 11 of the winding-up pin and with the edges 14 and 17, and also the pressure required for holding together the two sheets forming the cover, is supplied by known means, in the present instance for example by means of the nut 19 pertaining to the firing machine, so that no special means need be provided for this purpose.

What I claim is: V

1. A casing for an electric shot-firing machine comprising a main body portion, and a cover consisting of two superposed substantially similar sheet metal parts having bent-over outer edges in parallel spaced relation and adapted to contact closely throughout their entire width with the inside and outside surfaces of the top of the said body portion throughout the entire peripheral length thereof, for the purpose of ensuring that the said cover be explosion-proof, readily removable, of great rigidity, and of light weight.

2. A casing for an electric shot-firing machine comprising a main body portion, a cover consistlength thereof.

3. A casing for an electric shot-firing machine comprising a main body portion, a cover consisting of twosuperposed substantially similar sheet metal parts having bent-over outer edges, apertures in the said cover for projecting elements pertaining to the said machine, the edges of the said cover parts adjacent the said apertures being upwardly flanged in contiguity with each other and I with the said elements, an inwardly turned rim on the upwardly flanged edge of the outer of the said cover parts, and a packing element between the said rim and the upper edge of the upwardly flanged edge of the inner of the said cover parts,

KONRAD scHAFFLER-Gwssn

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