US3234876A - Self-retaining blasting cartridge - Google Patents

Description

Feb. 15, 1966 F. TEATHER ETAL SELF-RETAINING BLASTING CARTRIDGE 2 Sheets-Sheet 1 Filed July 27, 1962 INVENTORSI FRANK TEATHER JOHN R. KING ALFRED C. WHELAN BY Feb. 15, 1966 F. TEATHER ETAL SELF-RETAINING BLASTING CARTRIDGE 2 Sheets-Sheet 2 Filed July 27, 1962 mmean:

JOHN R. KING ALFRED? WHELAN INVENTORSI FRANK TEATHER BY W ATTORNEY a hole in the mine face. to one end of the tube when the shell is in position for moves under the action of air entering the inlet.

The present invention concerns shell-heads for use in mine-blasting 'by means of compressed air.

A shell used in compressed air mine blasting generally comprises a length of rigid tube suitable for insert-ion in High pressure air is supplied United States Patent blasting and is allowed to escape through a shell head screwed to the inner end of the shell. A frangible plate or disc is normally provided inside the shell so that the air pressure builds up behind it and is suddenly released when such plate or disc ruptures. A difliculty which has been found with such shells is that under certain conditions, the sudden release of air on rupture of the plate or disc tends to force the shell out of the hole in the mine I face rather than blast the coal or ore in which the hole is made.

. According to one aspect of the present invention there is provided a shell head for use in mine-blasting comprising a tube adapted to be inserted in a hole in the mine face and having a high pressure air inlet and at least one aperture through which air may be discharged for blasting, a piston slid-ably mounted within the tube and a holding member mounted on the tube for movement between a retracted position and a protracted'position the construction and arrangement being such that said holding member moves outwardly of the tube to its protracted position to hold the tube in the hole in the mine face in response to movement of the piston under the pressure of air entering the air inlet.

According to another aspect the invention also provides a shell head for use in mine blasting by high pressure air, which comprises a tube adapted to be inserted in a hole in the mine face and a holding member mounted on the tube for movement between a retracted position and a protracted position, which holding member is arranged to move to its protracted position when blasting occurs to hold the tube in the hole in the mine face but is spring-biased towards its retracted position.

The aperture or apertures through which the air is discharged from the shell head may be so arranged that they I are partially or wholly blocked by the piston in its initial position but are progressively uncovered as the piston 7 With this construction, it will be seen that initially a large pro- 7 portion of-the air pressure released on rupture of the frangible disc in the shell is applied to the piston and accordingly the holding member is forced well into the material forming the walls of the hole before a substantial proportion of the air pressure is released from the head for blasting.

Normally, two or three holding members are provided on the shell head and they are in the form of fiat metal flaps which are mounted on the tube for rotation about an axis at right angles to their planes so that a cam surface behind and movable with the piston can swing them outwards into their protracted positions. Such rotational axes may be parallel to or at right angles to the axis of the head.

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The invention will be more fully described by way of example with reference to the accompanying drawing in which:

FIGURE 1 is a longitudinal section through a shell head according to the invention which is screwed into a shell part of which is shown in dotted lines;

FIGURE 2 is a section IIII of FIGURE 1;

FIGURE 3 is a section similar to FIGURE 2 wherein the holding members are shown in their protracted positions;

FIGURE 4 is a longitudinal section through a modified shell-head; Y

FIGURE 5 is a section VV of FIGURE 4.

Referring particularly to FIGURES 1-3, the shellhead shown therein comprises a cylindrical tube I having an air inlet 2 and air discharge apertures or ports 3 and in which the-re is slidably mounted a circular piston 4 (shown partly in section). The piston 4 may have discs 5 secured to its front face by a bolt 6 to effectively adjust the position of the front face with respect to the position of the apertures 3. A rod 7 integral with the piston extends backwardly therefrom through a hole 8 in the end of the tube 1 and abuts against a disc 9 held by a helical compression spring 12 against the tube 1. The spring 12 is housed in a spring casing 13 which is attached to the tube 1 by screwthread-s 14 and which is provided with vents 15 communicating with the atmosphere. To limit the movement of the piston 4 the rod 7 may be attached to the disc 9 by a recessed set screw (not shown).

The part of the piston 4 between the front face and the rod 7 is tapered to frusto-conical form and provides a cam surface 16 which is arranged to abut against surfaces 18 of two holding members 19 (see FIG. 2) when the piston 4 moves to the right as shown in FIGURE 1. The holding members 19 are formed of fiat metal flaps which are rotatably mounted on the shafts of respective bolts 22 screwed into the tube and are biased towards their retracted positions shown in FIGURE 2 by helical springs 23. I

The part of the shell 24 to which the shell head is screwed includes particularly a frangible plate 25 behind which the air pressure can build up. An example of such a shell is described in the Filstrup Patent No. 2,778,309.

The shell head operates as follows. In the position illustrated in FIGURE 1, the holding members 19 are in their retracted positions and are held in such positions by the springs 23 so that the head may be screwed into the shell 24 and the shell pushed well into a hole in the mine face without difiiculty. High pressure air is then supplied to the outer end of the shell 24 until a sufficient pressure (of the order of 12,000 p.s.i.) is reached to rupture the plate 25. The air then strikes the effective front face of the piston formed by the discs 5 and forces the piston to the right as shown in FIGURE 1, the rod 7 at the same time moving the disc 9 along the casing 13 and compressing the spring 12. The air in the casing 13 is expelled through the vents 15.

As a result of this movement the cam surface 16'on the piston 4 abuts against the surface 13 of the holding members 19 which are swung outwards from the tube 1 against the bias of the springs 23 to their protracted positions (FIG. 3). The mechanical advantages produced between the force applied to the piston 4 and the force applied to the members 19 is considerable and the members 19 will dig Well into the material forming the walls of the hole. The mechanical advantage can of course be easily adjusted by altering the shapes and dimensions of the components of the head. As the piston 4 moves to the right it exposes the apertures 3 and the air may pass from the inlet 2 out of the head through these apertures 3 for blasting. The apertures 3 are so shaped that the air is directed slightly backwardly from the shell head so that the consequent reaction tends to force the shell into the hole. It will thus be seen that effective blasting does no take place until the members 19 are in their protracted positions and are holding the shell head in its hole.

When blasting is complete and the air supply is cut off, the spring 12 returns the piston 4 toits FIG. 1 position and this allows the members 19 to return to their retracted positions under the action of the springs 23. In the great majority of cases, the material in which the members 19 were embedded will have been blasted away but if this is not the case and the members 19 remain embedded, they can normally be released merely by twisting the shell anticlockwise about its axis.

The shell shown in FIGURES 4 and 5 is basically similar in construction and function to that shown in FIG- URES 1-3 and accordingly like reference numerals are used to indicate like parts.

One main difference between the shell illustrated in FIGURES 4-5 and that just described is that the disc Q, the spring 12 and the casing 13 are omitted. These parts are not normally essential since as mentioned above the material forming the walls of the hole is normally blasted away and the shell may be easily withdrawn so that the rod 7 may be forced back manually or by a sharp blow. In the FIGURE 4 shell head, a bolt 25 is screwed into the end of the rod '7' to protect it and to prevent the piston 4 sliding out of the inlet end of the tube ii. A similar disc 9, spring 12 and casing 13 may, of course, be fitted to the FIGURE 4- shell if desired.

The other main diiference between the illustrated constructions is that three holding members 19' are provided in FIGURES 4 and 5 and these are mounted on pins 27 which are disposed at right angles to the axis of the shell head. The springs 23' in this construction may conveniently be in the form of V-springs as shown.

The operation of the shell head is essentially similar to that just described with reference to FIGURES l3 but the construction is such as to have the advantage that once the members 19' have started to move outwards any tendency of the shell head to move to the left will tend to wedge the members 19' even more deeply and firmly into the material surrounding the shell head.

In both constructions described it is desirable to provide a cutting edge on the parts of the members 19' which first enter the material forming the walls of the hole in the mine face in order to give optimum penetration. This cutting action also serves to weaken such material and thus to some extent prepare it for blasting. A further important feature is that the piston 4 need not be a tight fit in the tube 1 and indeed it is advanageous to allow some air to pass around the outside of the piston to keep the holding members 39' and their bearings and springs clear of loose dirt and other material which may hamper efficient working.

While the preferred embodiments of the invention have been described in detail, it will be understood that changes in the construction may be made within the scope of the appended claims without departing rorn the spirit of the invention.

What is claimed is:

1. A head member for a blasting shell comprising, a generally cylindrical tube having an air inlet at one end and lateral discharge ports intermediate the ends of the tube, means at said one end for connecting said tube to a blasting shell adapted to release a charge of compressed air into said tube at a predetermined discharge pressure, a pressure actuated piston having a front face directed toward said one end slidably mounted in said tube and normally positioned to span and seal said discharge ports, said piston being adapted to slide within said tube and open said discharge ports upon the sudden release of discharge pressure into the tube at said one end, said tube having a plurality of apertures in the side wall thereof between said discharge ports and the other end thereof, holding members pivotally mounted in said apertures by pivot means and adapted to be moved from first position flush with the side wall of said tube to a second position extending outwardly from said side wall, spring means biasing said holding members toward said first position, and cam means formed integral with said piston operative to engage said holding members and move members to said second position as the piston is moved longitudinally by the sudden release of discharge pressure into the tube, and means for adjusting the proportion of the air pressure released through said discharge ports in relation to the engagement of said cam means with said holding members comprising removable disc members secured to the front face of said piston to adjust the position of said front face of the piston relative to said discharge ports.

2. A head member for a blasting shell comprising a generally cylindrical tube having an air inlet at one end and lateral discharge ports intermediate the ends of the tube, means at said one end for connecting said tube to a blasting shell adapted to release a charge of compressed air into said tube at a predetermined discharge pressure, a pressure actuated piston having a front face directed toward said one end slidably mounted in said tube and normally positioned to span and seal said discharge ports, said piston being adapted to slide within said tube and open said discharge ports upon the sudden release of discharge pressure into the tube at said one end, said tube having a plurality of apertures in the side wall thereof between said discharge ports and the other end thereof, holding members pivotally mounted in said apertures by pivot means and adapted to be moved from a first position flush with the side wall of said tube to a second position extending outwardly from said side wall, spring means biasing said holding members toward said first position, and cam means formed integral with said piston operative to engage said holding members and begin movement of said holding members toward the second position thereof before said discharge ports are opened by movement of said piston and to move said holding members to said second position as the piston is moved longitudinally by the sudden release of discharge pressure into the tube.

3. The head member of claim 2 in which spring means is provided between the piston and an end wall of said tube to return said piston to a position spanning said discharge ports upon the complete discharge of said shell.

4. The head member of claim 2 wherein said holding members have a cutting edge on the part thereof extending outwardly from the sidewall of said tube.

5. The head member of claim 2 in which said piston is provided with means for adjusting the proportion of the air pressure released through said discharge parts in relation to the engagement of said cam means with said holding members comprising removable disc members secured to the front face of said piston to adjust the position of said front face of the piston relative to said discharge ports.

6. A shell head comprising a generally cylindrical tube, an air inlet at one end of said tube, means at said one end for connecting said head to a blasting shell adapted to release a charge of compressed gas into said tube air inlet at a predetermined discharge pressure, said tube having ports positioned in the side wall intermediate the ends of said tube, a piston having a front face directed toward said one end slidably mounted in said tube and normally positioned to span and seal said discharge ports, a rod formed integral with said piston and extending through an opening in the other end of said tube, spring means acting against said rod to normally bias said piston to seal said discharge ports, said piston being adapted to slide within said tube against the bias of said spring means and open said discharge ports upon the sudden release of discharge pressure into the tube at said one end, a plurality of holding members pivotally mounted in the side wall of said tube between said discharge ports and said other end, said members being movable from a first position flush with the side wall of said tube to a second position extending outwardly from the side wall of said tube, a cam surface formed integral with said piston and adapted to engage said holding members and begin movement of said holding Inembers toward the second position thereof before said discharge ports are opened by movement of said piston and to move said holding members from said first position to said second position as the piston is moved longitudinally in said tube by the discharge pressure of the shell directed against said piston.

References Cited by the Examiner UNITED STATES PATENTS 1,873,858 8/1932 Armstrong 10 225 1,921,229 8/1933 Hodge 10 225 2,222,405 11/1940 COX et a1 10=221.8 X 2,253,115 8/1941 Ferrel et a1 10226 2,729,388 1/1956 Ringharn 92258 2,750,886 6/1956 Filstrup 10225 FOREIGN PATENTS 810,528 3/1959 Great Britain.

BENJAMIN A. BORCHELT, Primary Examiner.

SAMUEL FEINBERG, ARTHUR M. HORTON,

Examiners.

Claims (1)

1. A HEAD MEMBER FOR A BLASTING SHELL COMPRISING A GENERALLY CYLINDRICAL TUBE HAVING AN AIR INLET AT ONE END AND LATERAL DISCHARGE PORTS INTERMEDIATE THE ENDS OF THE TUBE, MEANS AT SAID ONE END FOR CONNECTING SAID TUBE TO A BLASTING SHELL ADAPTED TO RELEASE A CHARGE OF COMPRESSED AIR INTO SAID TUBE AT A PREDETERMINED DISCHARGE PRESSURE, A PRESSURE ACTUATED PISTON HAVING A FRONT FACE DIRECTED TOWARD SAID ONE END SLIDABLE MOUNTED IN SAID TUBE AND NORMALLY POSITIONED TO SPAN AND SEAL SAID DISCHARGE PORTS, SAID PISTON BEING ADAPTED TO SLIDE WITHIN SAID TUBE AND OPEN SAID DISCHARGE PORTS UPON THE SUDDEN RELEASE OF DISCHARGE PRESSURE INTO THE TUBE AT SAID ONE END, SAID TUBE HAVING A PLURALITY OF APERTURES IN THE SAID WALL THEREOF BETWEEN SAID DISCHARGE PORTS AND THE OTHER END THEREOF, HOLDING MEMBERS PIVOTALLY MOUNTED IN SAID APERTURES BY PIVOT MEANS AND ADAPTED TO BE MOVED FROM FIRST POSITION FLUSH WITH THE SIDE WALL OF SAID TUBE TO A SECOND POSITION EXTENDING OUTWARDLY FROM SAID SIDE WALL, SPRING MEANS BIASING SAID HOLDING MEMBERS TOWARD SAID FIRST POSITION AND CAM MEANS FORMED INTEGRAL WITH SAID PISTON OPERATIVE TO ENGAGE SAID HOLDING MEMBERS AND MOVE MEMBERS TO SAID SECOND POSITION AS THE PISTON IS MOVED LONGITUDINALLY BY THE SUDDEN RELEASE OF DISCHARGE PRESSURE INTO THE TUBE, AND MEANS FOR ADJUSTING THE PROPORTION OF THE AIR PRESSURE RELEASED THROUGH SAID DISCHARGE PORTS IN RELATION TO THE ENGAGEMENT OF SAID CAM MEANS WITH SAID HOLDING MEMBERS COMPRISING REMOVABLE DISC MEMBERS SECURED TO THE FRONT FACE OF THE PISTON TO ADJUST THE POSITION OF SAID FRONT FACE OF THE PISTON RELATIVE TO SAID DISCHARGE PORTS.

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