Powder actuated tool and method for forcing locks

The powder actuated door lock-forcing tool has a modular construction which comprises: a pistol grip module; and a barrel assembly module. The barrel assembly module is readily detachable from the pistol grip module to allow interchangeability of different barrel assemblies which are specifically adapted to disrupt different types of door locks. The barrel assembly module includes a piston carried in a barrel, which piston is configured to be driven beyond the muzzleward end of the tool sufficiently to disable or disrupt a lock at which the tool is fired. The piston may have a cylindrical configuration or a flattened oval configuration at its muzzleward end.

TECHNICAL FIELD 
This invention relates to an improved piston-type powder-actuated tool. 
More particularly, this invention relates to a tool of the character 
described having an improved piston structure which is adapted to 
neutralize door locks when the piston is driven into a door or lock by 
firing the tool. Certain aspects of the preferred embodiment of the tool 
of this invention are disclosed and claimed in copending U.S. patent 
application No. 687,069, filed Apr. 18, 1991, now U.S. Pat. No. 5,119,634. 
BACKGROUND ART 
Law enforcement personnel, firemen, rescue personnel, and others frequently 
must force open locked doors in order to gain entrance to premises so that 
they can perform their duties therein. There are a number of different 
procedures for breaking through such locked doors, ranging from firing 
bullets into the locks; to axes for breaking the doors down; to lock picks 
for picking the locks; to crow bars; and so on. There are various 
drawbacks to such procedures, as for example, fired bullets can strike 
people inside or outside of the premises; an axe is difficult to use, time 
consuming, and can cause personal injury; crowbars are time consuming and 
sometimes ineffective; and lock picking requires special training, skills 
and knowledge. 
It would be very desirable from a safety standpoint, and from an efficiency 
standpoint, to have a specialized tool which could be used to quickly 
neutralize a variety of door locks, wherein the force used to neutralize 
the locks is a captive force; and wherein no special skill is required to 
use the tool. A specialized powder-actuated tool would be very amenable to 
the aforesaid use. 
Powder actuated tools are well known in the construction field for driving 
fasteners, such as nails, studs, or anchors, into a relatively hard 
supporting surface, such as concrete. Such tools utilize a piston for 
driving the fastener. The piston is typically driven by an explosive blank 
cartridge. Combustion gases generated from the cartridge drive the piston 
from a breechward position to a muzzleward position to drive the fastener 
into the supporting surface. 
The explosive charge will occasionally overdrive the fastener driving 
piston, a condition which occurs when the piston is driven past the piston 
return pawl and into the buffer. This always occurs when the operator 
forgets to insert a fastener into the muzzle of the tool, and can also 
occur occasionally at other times. Such an occurrance is undesirable in a 
fastener driving tool. 
DISCLOSURE OF THE INVENTION 
According to this invention, a powder actuated tool is provided which has a 
specialized piston/barrel module that is adapted for use in breaking door 
bolts, or dislodging door lock cylinders from locked doors. The 
piston/barrel module is readily detachable from a pistol grip module so 
that the tool can be used with several different piston/barrel modules. 
There are a plurality of different piston/barrel module configurations, 
each of which is particularly adapted for use on a different type of door 
lock. 
The piston/barrel module includes a barrel which has a breechward end with 
an integral firing chamber formed therein. The muzzleward end of the 
barrel is threaded to receive a muzzle bushing/piston guide for 
controlling movement of the piston toward the lock. The piston is disposed 
in a bore in the barrel, which bore communicates with the firing chamber 
to receive combustion gases from cartridges fired therein. A releasable 
locking pawl is mounted in a muzzleward end of the pistol grip module, the 
pawl extending into an elongated recess in the barrel to engage the 
piston/barrel module and releasably hold the latter in the pistol grip 
module. The barrel is closed except for a set of gas vent ports which 
moderate recoil when the tool is used. The gas vent ports are spaced 
muzzlewardly along the barrel so as to ensure that combustion gases will 
leave the barrel breechwardly of the piston head only after the piston has 
moved muzzlewardly past the vent ports. This ensures that the combustion 
gases cannot escape from the tool barrel bore until the piston has 
generated the necessary amount of energy needed to perform its lock 
neutralizing function. 
One embodiment of the piston/barrel module used in the tool of this 
invention is particularly suitable for shooting the lock cylinders out of 
a door, or out of a door knob. In the lock cylinder destruction embodiment 
of the tool, the piston, barrel and muzzle bushing are similar in 
appearance to a conventional fastener driving tool, except that the barrel 
and piston are both longer than a conventional tool, and the piston is 
heavier. In addition, as in all of the tools of this invention, piston 
overdrive is intentional. The piston of this tool will be driven 2.5 
inches to 3 inches beyond the muzzle end of the tool when the tool is 
fired. This ensures that the piston will penetrate the lock cylinder 
sufficiently to destroy the lock cylinder, and/or to dislodge it from a 
door or door knob. 
A second embodiment of the piston/barrel module used in the tool of this 
invention is particularly suitable for use to breaking lock bolts or in 
driving lock bolts, such as dead bolts out of a door and door frame, when 
the tool is fired at the door or door frame. The bolt-breaking tool has a 
longer barrel assembly than a conventional fastener driving tool, and has 
a piston with a conventional breechward cylindrical piston head and piston 
stem, to which is affixed a muzzleward chisel blade and stem. The chisel 
blade has a flattened configuration with a sharpened or pointed muzzleward 
end. The chisel stem is rectangular in cross-sectional configuration. This 
embodiment of the tool has a muzzle guide member mounted on the muzzleward 
end of the barrel. The guide member has a flattened configuration (similar 
to a crevice tool accessory for a vacuum cleaner), and it guides movement 
of the chisel blade and chisel stem when the tool is fired. When the tool 
is fired, the chisel blade and stem will be driven about 3 inches past the 
muzzleward end of the guide so as to drive the chisel blade well into, 
and/or through a door or door jamb. A fraction of the chisel stem will 
remain in the guide after the tool is fired so as to maintain the proper 
orientation of the chisel blade relative to the guide. 
Still another embodiment of the tool of this invention is particularly 
adapted to break padlocks. The padlock embodiment of the tool is provided 
with a shield mounted on the muzzleward end of the piston guide, which 
shield catches the several parts of the padlock after the tool is fired on 
the lock. This prevents parts of the broken lock from striking the person 
using the tool, and others near the person using the tool. 
It is therefore an object of the invention to provide a powder actuated 
tool which is particularly adapted for forcing locks in doors, or the 
like, and which is composed of separate and individually replaceable 
modules. 
It is a further object of the invention to provide a tool of the character 
described which is simple, and can be used on a variety of different lock 
types due to the modular construction thereof. 
It is an additional object of this invention to provide a tool of the 
character described in which piston overdrive is intentionally effected. 
These and other objects and advantages of the invention will become more 
readily apparent from the following detailed description of several 
preferred embodiments of a tool formed in accordance with this invention 
when taken in conjunction with the accompanying drawings in which:

DETAILED DESCRIPTION OF THE BEST MODE 
Referring now to FIG. 1, one embodiment of the powder actuated tool of the 
invention is shown, the tool being shown is a ready-to-fire state. The 
powder actuated tool 2 comprises a pistol grip module 4, and a 
piston/barrel module 6. The tool 2 is designed to utilize a strip of 
explosive charges which are automatically fed through the tool after each 
time the tool is fired and reset. 
The piston/barrel module 6 includes a cylindrical barrel member 10, a 
piston/chisel member 20 disposed within the barrel 10, and a muzzle 
bushing/guide member 14 which is secured to the muzzleward end of the 
barrel 10 by a threaded collar 8 which is screwed onto an external thread 
18 on the guide 14. The barrel 10 is formed with a muzzleward flange 12 
against which the end surface 16 of the guide 14 is pressed. The collar 8 
serves to hold the guide surface 16 against the barrel flange 12. The 
barrel 10 is mounted slideably within the muzzleward end 3 of the pistol 
grip module 4. The piston/chisel member 20 has a cylindrical piston head 
portion 22 and a cylindrical piston stem portion 24 extending along the 
bore 11 of the barrel 10 toward the guide 14. A piston ring 26 is disposed 
about the head portion 22 to provide a gas tight fit within the barrel 
bore 11. The piston/chisel member 20 also has a chisel stem portion 24 
disposed in the barrel bore 11, and a chisel blade portion 36 with a 
sharpened end 38, the blade 36 being positioned in the interior 13 of the 
guide 14. The piston and chisel portions of the member 20 are preferably 
welded together, end-to-end. 
As seen in FIG. 2, the configuration of the guide interior 13 closely 
conforms to the cross-sectional shape of the chisel blade 36. The basal 
part 40 of the guide 14 on which the threads 18 are formed is provided 
with a tapped through passage 42 in which a set screw 44 is disposed. The 
set screw 44 projects beyond the end surface 16 of the guide 14 into an 
opening (not shown) in the barrel flange 12. The set screw 44 and the 
flange opening serve to ensure that the guide interior 13, and thus the 
chisel blade 36 are properly oriented for the bolt-breaking operation to 
be performed by the tool. 
As seen in FIG. 3, the detent pawl assembly 46 comprises a pawl housing 48, 
a spring 50 disposed within a bore in the housing 48, and a pawl 52 which 
is disposed in the pawl housing bore atop the spring 50. The pawl 52 
extends into a barrel slot 54 to releasably connect the barrel 10 to the 
pistol grip module 4. A pull ring 56 is mounted on a stem 58 secured to 
the pawl 52. To release the barrel 10 from the grip module 4, the ring 56 
is pulled to compress the spring 50 and withdraw the pawl 52 from the slot 
54. The piston/barrel module 6 can then be pulled out of the pistol grip 
module 4. 
Referring back to FIG. 1, the barrel 10 includes a breechward boss 60 which 
contains the cartridge firing chamber. A firing pin assembly 62 is 
slidably mounted in the tool breech, and a trigger 64 is mounted in the 
pistol grip 66 to actuate the firing pin assembly 62. A breech spring 68 
biases the piston/barrel module 6 muzzlewardly by means of a biased push 
rod 70 which projects through the breech block 72 and engages the 
breechward end of the barrel 10. 
Radial combustion gas vents 74 are disposed in the barrel 10 and are 
operable to vent combustion gases from the barrel bore 11 after the piston 
head 22 has passed the vents 74 during its work stroke. The vents 74 
minimize tool recoil, while providing the piston/chisel member 20 to 
generate sufficient energy to perform its bolt or lock-breaking function. 
It will be noted that the barrel bore 11 is closed except for the vents 
74, thereby providing the piston/chisel member 20 with the necessary 
lock-breaking energy. 
Referring to FIGS. 4-6, in FIG. 4, the piston/chisel member 20 is shown in 
its fired overdrive position wherein the chisel 36 extends well beyond the 
open end of the guide 14. In this position, the chisel 36 will have 
penetrated a door jamb into which the tool is fired, and will have cut or 
dislodged the door bolt or door lock from their door-locking positions. 
The surface 16 of the guide 14 acts as a stop surface for the piston head 
22 to ensure that the lock-breaking force-producing member 20 remains 
captive in the tool. 
The rectangular cross sectional shape of the chisel stem 34 and chisel 
blade 36, combine with the flattened shape of the guide interior 13 are 
important factors in properly aligning the piston/chisel member 20 so that 
it can perform its lock-disrupting function. When the piston/chisel member 
20 is in its fired overdrive position, a fraction of the chisel stem 34 
remains inside of the guide interior 13 thereby preventing the 
piston/chisel member 20 from becoming rotationally misaligned after the 
tool has been fired. This assures that the tool can be quickly reset and 
used on other locked doors that may be encountered. Reset of the 
piston/chisel member 20 is accomplished by pushing the member 20 back to 
its retired position shown in FIG. 1 with a tool similar to a screw driver 
or the like. 
The tool is operated in the following manner. The tool 2, as shown in FIG. 
1, is in its ready-to-fire condition. When the tool 2 is pressed against a 
door jamb, or a lock, either in the door or door knob, the barrel 10 moves 
breechwardly to compress the spring 68 and move the firing chamber to a 
firing position wherein a chambered cartridge can be fired by pulling the 
trigger 64. When the cartridge is fired, the piston/chisel member 20 will 
be propelled muzzlewardly, and the chisel point 38 will clear the guide 14 
about when the piston head 22 clears the vents 74. Thus, substantially the 
only recoil encountered by the user of the tool will be the resistance of 
the lock or door jamb to the chisel blade 36, which is not a significant 
factor. Tool recoil is thus minimal. As the chisel penetrates the door 
jamb, or encounters the door knob or lock cylinder, the piston/chisel 
mass, and the velocity thereof, provide sufficient energy to dislodge or 
break any lock components which the chisel point 38 hits. 
Referring now to FIG. 7, a second embodiment of the tool of this invention 
is shown, which is particularly suited for disabling lock cylinders, 
either in doors or in door knobs. The tool of FIG. 7 is shown in its 
ready-to-fire condition. The tool 102 comprises a pistol grip module 104, 
and a piston/barrel module 106. 
Like the first above-described embodiment, the piston/barrel module 106 
includes a cylindrical barrel member 110, a piston 120 disposed within the 
barrel 110, and a muzzle bushing member 114 which is secured to the 
muzzleward end 106 of the barrel 110. The barrel 110 is mounted slideably 
within the muzzleward end of the pistol grip module 104. The piston 120 
has a cylindrical piston head portion 122 and a cylindrical piston stem 
portion 124. It will be noted that the tool of FIG. 7 is very similar to a 
conventional fastener driving tool, except that the piston/barrel module 
106 is longer than the barrel of a conventional fastener driving tool, and 
the piston 120 is also longer and heavier than the piston of a 
conventional fastener driving tool. Finally, the muzzle bushing 114 is 
sufficiently shorter than a muzzle bushing on a fastener driving tool to 
ensure that the piston 120 will be fired to an overdrive position wherein 
the piston stem 124 extends well beyond the muzzleward end of the muzzle 
bushing 114 each time the tool 102 is fired, as will be set forth 
hereinafter in greater detail. 
In FIG. 8 the piston 120 is shown in the overdrive position wherein the 
piston stem 124 has been driven muzzlewardly beyond the end of the muzzle 
bushing 114 to the extent necessary to penetrate the lock cylinder found 
in the center of a door-lock door knob K. The tool is used by simply being 
pressed against the door knob K, with the muzzle bushing 114 being aligned 
with the door knob lock cylinder to set the tool for firing, and the tool 
is then fired by pulling the trigger 164. The piston stem 124 will enter 
the lock cylinder portion of the door knob K and push the lock cylinder 
out of the opposite end of the door knob. The lock will thus be disabled 
and the door can be opened. This embodiment of the tool can also be used 
against locks which have their cylinders positioned in the door proper. In 
the latter case, the piston stem 124 will easily penetrate the door and 
knock the lock cylinder out of the opposite side of the door. 
Since many changes and variations of the disclosed embodiments of the 
invention may be made without departing from the inventive concept, it is 
not intended to limit the invention other wise than is required by the 
appended claims.