US3382801A

US3382801A - Shielded explosive cutting device

Info

Publication number: US3382801A
Application number: US481009A
Authority: US
Inventors: Francis B Burkdoll; George B Huber
Original assignee: Explosive Technology Inc
Current assignee: Explosive Technology Inc
Priority date: 1965-08-19
Filing date: 1965-08-19
Publication date: 1968-05-14
Anticipated expiration: 1985-05-14

Description

y 14, 1968 F. B. BURKDOLL ETAL 3,382,801

SHIELDED EXPLOSIVE CUTTING DEVICE Filed Aug. 19, 1965 3 Sheets-Sheet 1.

/N l E N TOPS 24 FRANC/S B. BUR/(DOLL GEORGE B. HUBER ATTO PIJEVS y 1968 F. B. BURKDOLL ETAL 3,382,801

SHIELDED EXPLOSIVE CUTTING DEVICE 3 Sheets-Sheet 2 Filed Aug. 19, 1965 lNVENTO/PS FRANC/S B. BUR/(DOLL GEORGE B. HUBER A7 TOPNEVS yxx mwm los L99 M02 y 1968 F. s. BURKDOLL ETAL 3,382,801

SHIELDED EXPLOSIVE CUTTING DEVICE 3 Sheets-Sheet 3 Filed Aug. 19, 1965 F/G /O R MM 5 M m Tm was M V 0 6R 60 NE WJ m B F m m M h mm \m United States Patent 3,382,801 SHIELDED EXPLOSIVE 'CUTTmG DEVICE Francis B. Burkdoll and George B. Huber, Sunnyvale,

Calif., assiguors to Explosive Technology, Inc., Fairfield, Calif., a corporation of California Filed Aug. 19, 1965, Ser. No. 481,009 29 Claims. (Cl. 102-24) ABSTRACT OF THE DISCLOSURE This invention relates to a shielded explosive cutting device and more particularly to a shielded explosive cutting device in which explosives can be utilized for cutting relatively large objects.

In the installation of cast iron pipe, it frequently becomes necessary to cut the cast iron pipe to a desired length. In the past, when this has been done in the field, standard type pipe cutters on wheels are utilized. However, in order to utilize such a pipe cutter, it is necessary that there be sufiicient room around the pipe to rotate the cutter around the pipe. Thus, for example, if the pipe is in a trench, a wide spot must be dug in the trench where the cut is to be made. Thus, it can be seen that a cut in the field can be very expensive and time consuming depending upon the conditions which are encountered. When the cast iron pipe is lined with cement, an additional operation is required to peel back the cement from the portion of the pipe in which the cut is to be made. Field cutting of the cement is also disadvantageous in that it requires the use of at least two men. Similar roblems are encountered in cuttin concrete pipe or in cutting large holes in roofs, side walls and other objects. There is, therefore, a need for a new and improved cutting device.

In general, it is an object of the present invention to provide an explosive cutting device which overcomes the above named disadvantages.

Another object of the invention is to provide an expiosive cutting device of the above character which is safe to use.

Another object of the invention is to provide an explosive cutting device of the above character which can be uti'ized by one man.

Another object of the invention is to provide an explosive cutting device of the above character which can be utiized repeatedly.

Another object of the invention is to provide an explosive cutting device of the above character in which all of the parts of the explosive cutting device must be in position before the initiating device for the explosion can be applied.

Another object of the invention is to provide an explosive cutting device of the above character in which the initiating mechanism can be applied only in the unarmed or safe condition.

Another object of the invention is to provide an explosive cutting device of the above character which can be readily applied to the object.

Another object of the invention is to provide an eX- posive cutting device of the above character which can be utilized for making cuts in the field at relatively low cost.

Another object of the invention is to provide an explosive cutting device of the above character which will provide relatively clean cuts.

Another object of the invention is to provide an ex- Patented May 14, 1968 plosive cutting device of the above character which can be readily and economically manufactured.

Additional objects and features of the invention will appear from the following description in which the preferred embodiments are set forth in detail in conjunction With the accompanying drawings.

Referring to the drawings:

FIGURE 1 is a side elevational view with certain parts broken away of an explosive cutting device incorporating the present invention.

FIGURE 2 is a top plan view of the explosive cutting device shown in FIGURE 1.

FIGURE 3 is a cross-sectional view taken along the line 33 of FIGURE 1.

FIGURE 4 is a cross-sectional view taken along the line 4-4- of FIGURE 3.

FIGURE 5 is a cross-sectional view taken along the line 5-5 of FIGURE 3.

FIGURE 6 is a cross-sectional view taken along the line 66 of FIGURE 2.

FIGURE 7 is a detail view of means utilized for interconnecting the ends of the band carrying the explosive.

FIGURES 8 and 9 are cross-sectional views of the breech and breech block, respectively.

FIGURE 10 is a top plan view of another embodiment of an explosive cutting device incorporating the present invention.

FIGURE 11 is a crosssectional view taken along the line 1111 of FIGURE 10.

FIGURE 12 is still another embodiment of an explosive cutting device incorporating the present invention which is utilized for cutting holes in flat plates.

In general, the explosive cutting device is utilized for cutting an object and consists of a cover member which has an open side. The cover member is adapted to be positioned adjacent the object to be cut. A resilient lining is disposed within the cover member and faces the open side of the cover member. A linear explosive charge is disposed within the cover member. Means is provided for mounting the explosive charge on the cover member so that it lies adjacent the object to be cut. Means is also provided on the cover member for detonating the explosive charge.

More particularly, as shown in the drawings, the explosive cutting device consists of a holder 11 which is formed of two

half sections

12 and 13. The

half sections

12 and 13 are substantially U-shaped in cross-section as can be seen in FIGURE 4 and have top wall portions identified as 12a and 13a, respectively, and

side Wall portions

12b and 120, and 13b and 13c, respectively, to provide a holder having an open side. Hinge means 16 is provided for connecting two ends of the two

half sections

12 and 13 and consists of

hinge members

17 and 18 which are secured to the

half sections

12 and 13 by suitable means such as welding. The hinge member 17 is provided with a pair of spaced ears "17a and the hinge member 18 is provided with a single ear 18a which fits between the two cars 17a of the hinge member 17. A pin 19 passes through the ears 17a and through the ear 18a to pivotally interconnect the

hinge members

17 and 18 and the

half sections

12 and 13 so.-that the

half sections

12 and 13 can be moved between open and closed positions.

As can be seen from FIGURE 1, the holder 11 is adapted to be positioned adjacent the object to be out which, in the case shown in FIGURE 1, is a cast iron pipe 21. From FIGURE 4, it can be seen that the open side of the holder is adapted to face the object to be cut when the holder is positioned adjacent the object. When the holder 11 is in position adjacent the object to be cut, a chamber 22 is formed which, in the embodiment shown in FIGURES 1-9, is an annular chamber 22 which encircles the pipe 21.

Shielding means is provided for protecting the holder 11 and consists of a protective liner 24 formed of a suitable material such as rubber. The liner 24 as shown in FIGURE 4 is removable but is also substantially U- shaped so that it fits rather snugly within the inner confines of the holder 11 adjacent the

top wall portions

12a and 13a and the

side wall portions

12b, 13b, 12c and 13c. The protective liner 24- is also formed in half sections in the same manner that the holder 11 is formed in half sections.

A linear shaped explosive charge 26 is disposed within the chamber 22 adjacent to the object to be cut. The linear shaped explosive charge can be of any suitable type; for example, it can be of the type marketed under the trademark Jetcord by Explosive Technology, Inc., of Fairfield, Calif. As is well known to those skilled in the art, such a linear shaped explosive charge consists of a shaped metal member 27 of a suitable material such as lead which is substantially V-shaped or chevron-shaped in cross-section to concentrate the exposive effects. The open side of the V or chevron is positioned so that it faces in the direction in which the cut is to be made in the object to be cut. The explosive charge 28 is embedded within the metal member 27 and extends longitudinally of the metal member. The explosive charge can be of any suitable material such as RDX, PETN, TNT or any powdered explosive.

Means is provided is provided for positioning the linear shaped explosive charge 26 with respect to the holder 11 and to the pipe 21. As shown particularly in FIGURE 4, this means consists of a band 31 of a suitable flexible material such as plastic. The band 31 is provided with large beads 32 on opposite side margins thereof extending longitudinally of the band. The beads 32 are spaced apart so that side wall portions of the holder 11 generally abut the same when both are in place so that a relatively tightly sealed chamber 22 is formed between the holder 11 and the object to be cut. The beads 32 also serve to align the band 31 with respect to the holder and to align the linear shaped explosive charge so that it will be initiated as hereinafter described.

The inner surface of the band 31 is substantially fiat so that it can be positioned immediately adjacent the surface of the object to be cut. The linear shaped explosive charge 26 is disposed in an annular recess 33 formed in the band which runs down the middle of the band and, in other words, is positioned intermediate the side edges of the band so that the linear shaped charge 26 is positioned in the center between the side walls of the holder 11.

In the embodiment of the invention shown in FIGURES 19, the band 31 is held in place by a serrated tongue 36 provided on one end of the band 31 and removably locked in a T-shaped slot 37 provided in the other end of the band. This connection makes it possible to fit the band 31 relatively snugly about the pipe 21. The serrations provided on the tongue 36 make it possible to accommodate different pipe diameters. It should be noted that when the band 31 is properly positioned adjacent the pipe, the V-shaped opening provided in the linear shaped explosive charge faces the pipe 21 at the point where the cut is to be made in the pipe.

The linear shaped explosive charge 26 is disposed in the recess '33 in the band 31 to protect the linear shaped explosive charge. If the V-shaped recess 29 of the chevron should become filled with water or some other foreign material, this would seriously affect the concentration of the explosive effects and the desired cutting effect would not take place. For this reason, it is desirable that the ends of the recess 33 in the band 31 be completely sealed so that the band 31 which serves as a holder for the linear shaped explosive charge can even be submerged in water to thereby permit the explosive cutting device to be utilized under adverse conditions.

With the construction of the holder 11 as shown, the two

half sections

12 and 13 can be readily split apart so that the holder can be positioned around a pipe or other similar object. Means is provided for securely retaining the holder 11 on the pipe during its use and consists of a latching mechanism 41. The latching mechanism 41 consists of an elongate lever 42 which is pivotally mounted upon a pin 43 mounted in a U-shaped support member :4- provided on the section 13. A bolt 46 is mounted in the lever 42. The bolt 46 is provided with a shoulder 4-7 which engages one side of the lever 42. A nut 48 is threaded onto the bolt 46 and engages the other side of the lever 42 and serves to retain the bolt 46 on the lever. The bolt 46 is provided with holes 4-9 at opposite ends thereof in which are slidably mounted very long bolts 51. Collars 52. are slidably mounted on the bolts 51 and are yieldably urged toward the head of the bolt by springs 53 mounted on the bolts. The springs 53 are retained on the bolts by washers 54 and nuts 56. The bolts 51 are adapted to be positioned in slots 57 formed in a curved portion 55a of a retaining member 58 secured to the half section 12. As can be seen particularly from FIGURE 1, the curved portion 58a faces away from the lever 42 provided on the half section 13 and is adapted to receive the collars 52 provided on the bolts 51.

A blast shield 61 is secured to the half section 12 and, as shown in FIGURE 1, when the holder '1 is in a closed position, extends over the slot which may be present between the

half sections

12 and 13 to prevent the blast from escaping through the slot.

Thus, the latching mechanism 41 actually consists of an over-center toggle mechanism which serves to firmly secure the holder 11 to the object to be cut. As soon as the center line of the bolt 46 drops below the center line of the pin 43, the latching mechanism will be latched in a closed position. When the lever 42 is lifted, it will move to an open position as soon as the center of the bolt 46 moves about the center for the pin 43. The amount of force required for opening and closing the latching mechanism can readily be adjusted by increasing the compression or decreasing the compression on the springs 53 by adjustment of the nuts 56. To completely open the holder, it is merely necessary to raise the lever 42 and then to move the bolts 51 out of the slots 57.

Means is provided on the holder for initiating the linear shaped charge 26 after the holder 11 has been secured to the object to be cut and consists of a breech mechanism 64 mounted on one of the

half sections

12 and 13 of the holder 11. As shown in the drawings, the breech mechanism 64 consists of a breech 66 which is mounted in half section 12 in the top wall 12a thereof so that it extends downwardly into the chamber 22 and generally overlies the band 31 and the linear shaped explosive charge 26 carried by the band 31. The breech 66 is provided with side lugs 66:: as shown in FIGURE 8. It is also provided with a centrally disposed bore 67 which extends therethrough. A detonator assembly 69 is adapted to be positioned in the bore 67 of the breech which consists of a cartridge 71 of a conventional 12 gauge shotgun shell. As is well known to those skilled in the art, such a cartridge contains a primer '72. A metal cylinder 73 of a suitable material such as copper is mounted within the cartridge 71 in an axially aligned position by a resilient sleeve 74 of a suitable material such as rubber. A safety type blasting cap 76 is mounted within the cylinder 73 at the lower end thereof as shown in FIGURE 4 so that it is immediately adjacent the linear shaped explosive charge 26. The space 77 above the cap is empty. Thus, it can be seen that the breech 64 positions the detonator assembly 69 so that it is accurately positioned over the linear shaped explosive charge 26.

The breech mechanism 64 also includes a breech block 81 which is provided with a hole 82 having generally the same configuration as the breech 66 so that it can be positioned over the breech and threaded onto the breech, as shown in FIGURE 4. The firing pin 83 is slidably mounted in the breech block and is adapted to pass through a hole 84 provided in the breech block to actuate the primer 72. A cocking knob 85 is mounted on the firing pin 83.

Means is provided for yieldably urging the firing pin 82 into a actuating position and consists of a spring 86 mounted on the firing pin 83 and disposed in a well 87 provided in the breech block 81. One end of the spring 86 engages a plug 88 provided in the breech block and the other end engages enlarged portion 89 of the firing pin 83.

The breech block 81 is armed by pulling the firing pin 83 upwardly against the force of the spring 86 and a safety pin 91 is inserted in a hole 92 in the firing pin 83 to retain the firing pin in the safety position as shown particularly in FIGURE 4.

A number of safety devices have been incorporated in the explosive cutting device to make it substantially foolproof. For example, means has been provided for preventing the breech block from being screwed onto the breech unless the holder 11 is in a closed position. This safety feature is made possible because when the latching mechanism 41 is in an open position, the bolts 51 will be in a raised position so they will be engaged by the flange 81a of the breech block 81 to thereby prevent the breech block 81 from being threaded down onto the breech 66. Thus, it is only when the latching mechanism 41 is in a closed position that the breech block 81 can be threaded into the position shown in FIGURES 1 and 4.

Additional safety means is provided for preventing the breech block from being screwed onto the breech when the holder 11 is in an open position. This additional safety means consists of a bar 96 which is secured by suitable means such as welding to the breech 66. The bar 96 is provided with a large bore 97 which extends from one end of the bar 96 and a smaller bore 98 extending from the other side of the bar 96 and communicating with the bore 97. A safety cam rod 99 is mounted in the bore 97 and is provided with a stem 101 which extends through the bore 98. The safety cam rod 99 is also provided with a tapered portion 162 and a head 183. Means is provided for yieldably urging the safety cam rod 99 to the right as viewed in FIGURE 6 or, in other words, to urge the stern 1411 through the bore 98 and consists of a spring 196 mounted in the bore 97 and having one end engaging the safety cam rod 99 and having the other end engaging a nut 1G4 threaded into one end of the bore 97. A safety pin 111 is slidably mounted in a bore 112 provided in the breech 66. As can be seen from FIGURE 6, the bore 112 extends in a direction which is substantially at right angles to the bore 97. The safety pin 111 is provided with a stem 114 which is slidably mounted in a bore 116 provided in the breech 66 and which is normally urged downwardly by the force of gravity. The stem portion 101 of the safety cam rod 99 is received by a countersunk hole 117 provided in the retaining member 58. Unless the holder 11 is in a closed position in which the member 58 is in engagement with the bar 96 and the stem portion 181 to ur e the stem portion 101 to the left against the force of the spring 106 to permit the safety pin 111 to drop down to the position shown in FIGURE 6, it is impossible to place the breech block 81 into a position so that it can be used for detonating the detonator assembly 69. This is true because when the stern portion 101 is out of engagement with the retaining member 58, the spring 106 will urge the safety cam rod 99 to the right as viewed in FIGURE 6 so that the safety pin 111 is urged upwardly by the safety cam rod 99 so that the stem 114 prevents the breech block 81 from being threaded into a position in which it can be utilized for operating the detonator assembly 69.

Means is also provided for arming the breech mechanism 64 which must be left in place to fire and which cannot be inserted unless the breech block is in position on the breech. This means consists of an arming key 121 which is adapted to be removed from and inserted in the breech block 81. The arming key is provided with a knob 122 and eccentrics 123 and 124. An arming spring 126 is provided in the breech block 81 and has one end fixed at 126:: as shown in FIGURE 3. Thus, the spring 126 extends through an annular groove 127 provided in the firing pin 83. The groove 127 has a width which is at least twice the width of the spring 126. Means is provided for yieldably retaining the arming spring 126 in the groove 127 and consists of a helical spring 128 provided in a bore 129 (see FIGURE 3) in the breech block 81. The arming spring 126 is engaged by the eccentric 124 and is adapted to be moved out of the groove 127 by the eccentric 124. The eccentric 123 of the arming key 121 is adapted to ass under the knob of the firing pin 83. The knob 85 is provided with a slot 131 to permit vertical movement of the firing pin knob 85 during detonation of the detonator assembly 69.

A spring 132 (see FIGURE 5) is provided in the breech block 81 and is secured thereto by rivet 133. When the breech block is not threaded into a position on the breech 66, the spring 132 is in alignment with the hole 134 provided for the arming key 121 to prevent insertion of the arming key unless the breech block 81 is threaded to the home position on the breech 66. The firing pin 83 is retracted and the safety pin 91 is inserted in the hole 92 to hold the firing pin in a retracted position. When it is desired to arm the breech mechanism 64, the key 121 is inserted in the breech block 81. The key 121 is rotated so that it is in a position in which the eccentric or cam 124 has moved the arming spring 126 out of the groove 127 and the eccentric 123 is in alignment with the recess 131 provided in the knob 85 of the firing pin 83.

Operation and use of the explosive cutting device may now be briefly described as follows. Let it be assumed that it is desired to cut a cast iron pipe as, for example, a 12- inch cast iron pipe which has an outside diameter of 13.2- .06 inches. After the place at which the cut is to be made has been determined, a band 31 which also may be called the explosive charge holder with the linear shaped explosive charge 26 mounted therein is wrapped about the pipe and secured snugly thereto by the connecting means consisting of the tongue 36 and the T-shaped slot 37. After this has been accomplished, the holder 11 is placed over the band 31 so that the holder is positioned in the manner shown in FIGURE 4 between the beads 32 provided on the band 31. The

half sections

12 and 13 are then clamped about the band 31 by the latching mechanism 41. Suitable adjustments can be made such as by adjusting the position of the nuts 56 to ensure that the holder is securely clamped to the pipe.

The detonator assembly 69 is then placed in the breech 67. Thereafter, the breech block is positioned over the breech and threaded into place. This can be accomplished because the stem 114 will be in a retracted position because the latching mechanism 41 is in a closed position. The breech block 81 is then armed by pulling the firing pin 83 outwardly and inserting the safety pin 91. Before the firing pin 83 can be fired, the arming key 121 must be inserted in the breech block 81.

As soon as it is desired to fire the explosive cutting device, the pin 91 is removed by suitable means such as a lanyard (not shown) which causes the firing pin 83 to strike the detonator assembly 6-9 which sets off the primer 72. The primer 72 sets off the cap 76 which, in turn, initiates the linear shaped explosive charge 26.

As the linear shaped explosive charge 26 explodes, the metal jacket or sheath 27 is propelled outwardly in the area that is away from the pipe being cut or, in other words, in the chamber 22. The explosion in the area which is facing the pipe is propelled inwardly in a concentrated jet to partially penetrate the pipe. In effect, it is believed that the linear shaped explosive charge actually causes a scoring of the pipe which causes a stress concentration in the area. The shock waves generated by the linear shaped explosive charge and the overpressure from the expanding gases within the holder 11 then serve to break the pipe at the point at which it has been scored.

The metal sheath of the linear shaped explosive charge must be contained within the holder 11 in order to prevent injury to any nearby workmen. Thus, one of the principal purposes of the holder ill is to serve as a metal shield to collect and retain the metal particles. The metal particles become embedded within the liner Z4 and after a sufficient number of firings, the liner 24- can be readily changed. The chamber 22 provided within the holder 11 serves to attenuate any shock waves which may be generated so that their intensity with respect to the holder is greatly reduced. The shock waves which are generated within the chamber 22 are rapidly attenuated by the air in the chamber. This rapid attenuation of the shock waves makes it possible to utilize lighter material than otherwise would be possibe. A compromise must be made between excessive Weight and excessive size.

By way of example, it has been found that such a pipe cutter can readily cut eightinch cast iron pipe. The wall of such pipe was approximately /2 inch in thickness and was lined with a concrete liner ha ing a thickness of approximately /s inch. The cut made with the explosive cutting device was uniform and encircle the pipe and had the characteristic appearance of penetration of approximately inch from the o side of the pipe, with the remainder of the wall of the pipe having the appearance of being fractured a normal brittle fracture. Thus, it can be seen that, in addition to cutting the pipe, the explosive cutting device has the additional advantage in that the shock wave generated by the linear shaped charge spalls the concrete lining from the inside of the pipe quite uniformly in an annular area completely around the pipe extending from approximately /4 to one inch back from the cut surface.

In making the cut in the pipe, two effects are being utilized. One is the blast eltect, and the other is the shock Wave effect. The shock wave is propagated at a supersonic velocity in the medium for a very short duration. The pressure at the front of the shock wave rises very rapidly in a continuous ma er to a very high value and drops very rapidly immediately behind the shock wave. The blast effect, on the other hand, does not occur at supersonic velocities and, therefore, the pressure rise is relatively slow in comparison to the shock wave. The blast efiects follow the shock wave effects and it is these two sequential elfects which make it possible to cut the pipe rather easily.

After the explosive cutting device has been fired, the explosive cutting device can be removed by first removing the breech block 81 and then opening the latch mechanism by raising the lever 42 and separating the two

sections

12 and 13. The explosive cutting device can then be placed on another section of pipe in which it is desired to make a cut, and the same sequence of operations followed.

it shoul be pointed out that after the explosive cutting device has been fired, the explosive cutting device cannot be armed again until the firing pin 253 has been retracted and the safety pin 91 inserted. This is because the eccentric or cam 123 will contact the knob 85 of the firing pin 83 to prevent further movement of the arming key 121. Thus, it is necessary to raise the firing pin 33 and to place the pin 91 into position to hold the firing pin 83 in a raised position shown in FIGURE 4. As soon as this has been accomplished, the arming key 121 can be rotated to again cause the cam 124- to move the safety spring 126 into a position to permit the firing pin 83 to be fired when the safety pin 91 is removed.

in addition to cutting pipes and other tubular objects, the explosive cutting device can also be utilized for cutting holes in tubular objects. Thus, as shown in FIGURES l0 and 11, there is shown an explosive cutting device which is particularly adapted for cutting an oval-shaped hole into pipe. This explosive cutting device consists of a holder 141 which has the general ovoid conformation of the portion of the pipe it engages as shown in FIGURE 7 and which is substantially U-shaped in cross-section much the same as the holder 11. The holder 141 is provided with a liner 8 142 of a suitable material such as rubber. A linear shaped explosive charge 143 is held in place by a holder 144 similar to the band 31.

in view of the fact that the explosive cutting device shown in FEGURES 10 and 11 does not completely surround the pipe, additional means must be provided for securing the same to the pipe so that it will be retained on the pipe during the explosion. This means can take any suitable form such as a strap which has one end secured to the holder Ml. A hook 147 is mounted on the other side of the holder 143i and is adapted to be engaged by link 148 pivotally mounted on pins 149 eccentrically mounted on a bearing member 151 and rotatably mounted on ears 152 provided at the other end of the band lid-i5. A lever 153 is mounted on the bearing member 151 and is provided for rotating the bearing member to firmly secure the holder 141 to the pipe Zll and is movable to an overcenter position as shown in FIGURE 8 so that it will be retained in the latched position. A breech mechanism 156 substantially identical to the breech mechanism ea hereinbefore described is provided.

Operation of the embodiment shown in FIGURES l0 and 11 is substantially identical to that for the embodiment hereinbefore described. The principal difference is that when the cut is made, an opening is cut into the pipe as determined by the positioning of the linear shaped charge 14-3 within the holder 141. Such holders are particularly desirable when it is necessary to make a T connection to a pipe.

Still another embodiment of the invention is shown in FIGURE 12 which is particularly useful for cutting holes in flat surfaces as, for example, a flat plate 7.61. The explosive cutting device consists of a circular holder 162 having a U-shaped cross-section substantially identical to the holders hereinbefore descrited. A liner of a suitable resilient material is provided. A linear shaped charge 164 is carried by a holder 166 in much the same manner as the linear shaped explosive charges hereinbefore described were carried. A breech mechanism 167 similar to that described is mounted in the holder 162 and is provided for initiating the linear shaped explosive charge 164.

in order to prevent the holder 164- from becoming a dangerous projectile and being projected upwardly by the gas pressure during firing, additional hold down means is provided. The hold down consists of a flat plate 171 which is mounted across the top of the holder 162. A combustion chamber 172 is moun ed upon the plate 1'71 and is adapted to contain a suitable explosive such as black powder. Ignition means (not shown) is provided for initiating the charge within the chamber 172. so that it begins to burn and build up pressure in the combustion chamber 172 to cause propellant to be eiected through the nozzle 173 to provide a resulting downward force against the plate 171 which would serve to hold the holder 162 in place when the breech mechanism 16'? is fired to cause initiation of the linear shaped charge 164. Thus, the force generated within the chamber 1'73 counterbalances the upward force caused by firing of the linear shaped charge so that the device remains stationary.

The explosive cutting device shown in FIGURE 12 is particularly desirable for cutting openings in flat plates or flat structures such as tank tops, ship decks, and the like. It would be particularly useful for cutting holes in such structures where it is desired to do so very rapidly.

It is apparent from the foregoing that we have provided a new and improved explosive cutting device which is particularly useful for rapid cutting of pipes and other tubular objects or for cutting holes in tubular objects or fiat surfaces. The device is particularly advantageous in that it can be utilized by one man and is reusable. The device is also one which can be readily and economically manufactured. The device also makes it possible to greatly reduce the cost of cutting pipes and forming openings. in addition, the explosive cutting device is provided with 9 many safety features to provide practically foolproof operation.

We claim:

1. In a shielded explosive cutting device for cutting an object, shielding means having an open side, said shielding means being adapted to be positioned adjacent the object to be cut, a linear explosive charge disposed within the shielding means, means for mounting said linear explosive charge in said shielding means so that it lies adjacent the object to be cut, said shielding means being formed so that there is a substantial space between the shielding means and the explosive charge so there is no direct contact between the shielding means and the explosive charge, and means carried by the shielding means for detonating the :linear explosive charge, said shielding means being constructed so that it arrests the travel of substantially all of any solid particles within a limited distance in at least one direction which are propelled by the detonation of the linear explosive charge.

2. A cutting device as in claim 1 wherein said shielding means is substantially in the form of an annulus and is adapted to encompass a cylindrical object.

3. A cutting device as in claim 2 wherein said shielding means is split into at least two parts and includes means for securing the shielding means to said cylindrical object.

4. A cutting device as in claim 1 wherein the open side lies in substantially one plane.

5. A cutting device as in claim 1 wherein the open side is substantially ovoid in plan.

6. A cutting device as in claim 1 wherein said means for detonating the linear explosive charge consists of a breech mounted in the shielding means, a removable detonating assembly mounted in the breech and disposed adjacent the linear explosive charge, a breech block mounted on said breech, said breech block having a firing pin, and means for urging the firing pin into engagement with the detonating assembly.

7. A cutting device as in claim 6 together with key means for preventing the firing pin from being armed until the key means has been moved to a predetermined position.

8. A cutting device as in claim 1 together with means for counteracting the forces created when the linear explosive charge is initiated to keep the shielding means in engagement with the body.

9. In an explosive cutting device for cutting a tubular object, a holder having an open side, said holder being comprised of at least two sections, hinge means interconnecting the sections, latching means for securing the sections to the tubular object so that the open side faces and encircles the tubular object, shielding means disposed within the holder, a flexible band adapted to encircle the tubular object, a linear shaped explosive charge disposed within the holder and carried by the band, the band serving to carry said linear shaped explosive charge in a position adjacent to the object, and means carried by the holder for detonating the linear shaped explosive charge, said means for detonating the linear shaped explosive charge includes a breech mounted in the holder and having its lower extremity in close proximity to the linear shaped explosive charge, a detonating assembly mounted in the breech and disposed adjacent the linear shaped explosive charge, a breech block removably mounted on the breech, a firing pin mounted in the breech block, means yieldably urging the firing pin in a direction towards the detonating assembly so that when the firing pin is released, the firing pin causes detonation of the detonating assembly, a safety pin removably mounted in the firing pin and serving to retain the firing pin out of engagement with the detonating assembly, and removable key means mounted in the breech block and including means for preventing movement of the firing pin into engagement with the detonating assembly until the key has been moved to a predetermined position.

10. A cutting device as in claim 9 wherein said means for preventing the firing pin from engaging the detonating assembly until the key means has been moved to a predetermined position consists of a leaf spring mounted in said breech block, the firing pin having a slot through which said spring extends, and wherein said key means includes a cam for moving said spring out of said slot.

11. A cutting device as in claim 9 together with means for preventing the key means from being inserted in the breech block until the breech block has been mounted on the breech.

12. A cutting device as in claim 10 wherein said key means includes an additional cam movable into a position so that it underlies a portion of the firing pin and wherein said portion of the firing pin is provided with a slot to permit said firing pin to clear said second cam when said second cam is in a predetermined angular position.

13. A cutting device as in claim 9 wherein said detonating assembly consists of a cartridge having a primer therein, a resilient sleeve mounted within the cartridge and a detonating cap disposed within the resilient sleeve adjacent the outer end of the sleeve.

14. A cutting device as in claim 9 together with means for preventing the breech block from being placed on the breech unless the holder has been moved to a closed position, said means including a safety cam rod mounted in the holder, spring means mounted in the holder for yieldably urging the safety cam rod in one direction, said holder including means urging said safety cam rod in a direction opposing the force of said spring means when said holder is in a closed position, and additional means engaging the safety cam holder and movable to a position when said holder is open to prevent said breech block from being mounted on said breech.

15. In an explosive cutting device for cutting a hole in the side wall of a tubular object, the holder having an open side adapted to be placed on the side Wall of the tubular object, said holder being substantially U-shaped in cross-section, a flexible band mounted in the open side of said holder, a linear explosive charge disposed within the holder and carried by the flexible band so that it is adjacent the tubular object, said holder being formed so that there is a substantial space between the holder and the linear charge and this portion of band carrying the linear charge so that there is no direct contact between the holder and the linear charge and the holder and the portion of the band carrying the linear charge, means carried by the holder for detonating the linear explosive charge, and means for securing the holder to the tubular object so that it is not separated from the tubular object during detonation of the linear shaped explosive charge.

16. In an explosive cutting device for cutting a hole in a relatively fia-t surface of an object, a substantially continuous holder having an open side lying in substantially one plane, said holder being substantially U-shaped in cross-section, shielding means carried by the holder, at flexible band disposed at the open side of the holder, a linear explosive charge carried within the holder by the band, means carried by the holder for detonating the linear shaped explosive charge, and explosive means mounted on the holder and adapted to be detonated at substantially the same time that the linear explosive charge is detonated to supply a counteracting force to the force of the linear explosive charge to retain the cutting device in contact with the object in which the hole is to be cut.

17. In an explosive cutting device for cutting an object, a holder having an open side, said holder being movable between open and closed positions and being adapted to be positioned adjacent the object to be cut, shielding means disposed in the holder and facing the open side of the holder, a linear explosive charge disposed within the holder, means for mounting said linear explosive charge in said holder so that it lies adjacent the object to be cut, and means carried by the holder for detonating the linear explosive charge, said means for detonating the linear explosive charge consisting of a breech mounted in the holder, a detonating assembly nounted in the breech and disposed adjacent the linear explosive charge, a breech block mounted on said breech, said breech block having a firing pin, means for urging the firing pin into engagement with the detonating assembly and means for preventing the breech block from being placed on a breech unless the holder has been moved to a closed position.

18. In a shielded explosive cutting device for cutting an object, rigid wall-like shielding means having an open side adapted to be positioned adjacent the object to be cut with the open side facing the object to be cut, a linear explosive charge, means mounting said linear explosive charge in said shielding means so that it lies adjacent the object to be cut, said shielding means being dimensioned so that there is a space between the shielding means and the linear explosive charge and at least the portion of the means mounting the explosive charge, and means carried by the shielding means for detonating the linear explosive charge, said shielding means being substantially nonfragmentable and being constructed so that it arrests the travel within a limited distance in at least one direction of substantially all of any solid particles which are propolled by detonation of the linear explosive charge.

119. A device as in claim 18 wherein said means carried by the shielding means for detonating the linear shaped explosive charge includes a removable detonating assembly.

2%. A device as in claim 18 wherein said shielding means is constructed so that all portions of the same are spaced a substantial distance from the linear explosive charge.

21. A device as in claim 18 wherein said shielding means has walls which are formed so that there is a void between the walls of the shielding means and the linear shaped charge.

22. A device as in claim 18 wherein said shielding means is substantially U-shaped in cross section.

23. A device as in claim 18 wherein said shielding means is in the form of an annulus, said shielding means also being formed in at least two parts and means connecting the parts to permit relative movement between the parts.

24-. A device as in claim 18 together with means for retaining the device on the object to be cut when the linear explosive charge is detonated.

25. A device as in claim 24 wherein the means for r retaining the device on the object during the detonation of the linear charge includes explosive means mounted on the shielding means and adapted to be detonated at the same time that the linear explosive charge is detonated to supply a counteracting force to the force which is supplied by the linear explosive charge.

26. In a shielded explosive cutting device for cutting a tubular object, shielding means mounted on the tubular object, said shielding means having an open side facing the tubular object, said shielding means being comprised of at least two sections, means interconnecting the two sections to permit movement of the same between open and closed positions with respect to the tubular object, latching means for securing the sections to the tubular object, a linear explosive charge, means for holding the linear explosive charge in the shielding means in a predetermined position within the shielding means adjacent to the tubular object to encircle the tubular object and spaced from the shielding means, and means carried by the shielding means for detonating the linear explosive 12 charge, said shielding means including means for arresting the travel within a limited distance in at least one direction any solid particles which are propelled by the detonation of the explosive charge.

27. A device as in claim 26 wherein said means for detonating the linear explosive charge consists of a breech mounted in the shielding means, a detonating assembly mounted in the breech and disposed adjacent the linear explosive charge, a breech block mounted on the breech, said breech block having a firing pin and means for urging the firing pin into engagement with the detonating assembly.

28. In a shielding explosive cutting device for cutting an object, shielding means being substantially U-shaped in cross-section with substantially parallel sides and with an open side, said shielding means being adapted to be positioned adjacent the object to be cut, a linear explosive charge disposed within the shielding means, means for mounting said linear explosive charge in said shielding means so that it lies adjacent the object to be cut, said means for holding the linear explosive charge consisting of a relatively fiat elongate member having side beads disposed adjacent the sides of the shielding means, and means carried by the shielding means for detonating the linear explosive charge, said shielding means being constructed so that it arrests the travel of substantially all of any solid particles Within a limited distance in at least one direction which are propelled by the detonation of the linear explosive charge.

29. In a shielded explosive cutting device for cutting a tubular object, shielding means mounted on the tubular object, said shielding means having an open side facing the tubular object, said shielding means being comprised of at least two sections, means interconnecting the two sections to permit movement of the same between open and closed positions with respect to said tubular object, latching means for securing the sections to the tubular object, a linear explosive charge, means for holding the linear explosive charge in the shielding means in a predetermined position within the shielding means adjacent the tubular object to encircle the tubular object, and means carried by the shielding means for detonating the linear explosive charge, said shielding means including means for arresting the travel within a limited distance in at least one direction of any solid particles which are propelled by the detonation of the explosive charge, said means for detonating the linear explosive charge consisting of a breech mounted in the shielding means, a detonating assembly mounted in the breech and disposed adjacent the linear explosive charge, a breech block mounted on the breech, said breech block having a firing pin and means for urging the firing pin into engagement with the detonating assembly, and means for preventing the breech block from being closed on the breech unless the shielding means is in a closed position.

Reterences fitted UNlTED STATES PATENTS 1,745,759 2/1930 Gruber l0270 3,846,968 8/1958 Tipton 269201 3,089,417 5/1963 Beyer et al. 102-24 3,135,163 6/1964 Mechlin et al 10224 3,169,479 2/1965 Byran 102-24 2,638,323 5/1953 Bannon 10224 3,336,868 8/1967 Rush et al 10224 BENlAMlN A. BORCHELT, Primary Examiner.

SAMUEL FEINBERG, Examiner.

V. R. PENDEGRASS, Assistant Examiner.