Locking device

A locking device suitable for use in a gun to prevent unauthorized use of the gun includes a key operated lock (3) operable to expand a ring (8) into locking engagement with the gun chamber. In order to prevent removal of the device by applying force to the muzzle end of the device locking pins (14) are mounted in radial bores (11) to be driven radially outwardly by a tapered piston (18) if the piston is driven away from the muzzle end. An explosvie cartridge (23) is detonated by a firing pin (25) if force is applied to an end plate (26) thereby driving the piston in the desired manner.

This invention relates to a locking device which, upon actuation, is locked 
to a hollow body within which the device is situated. Although of general 
applicability the preferred embodiment of locking device is particularly 
suitable for forming part of a safety device for firearms, the safety 
device being adapted to be secured by a key within the chamber of a 
firearm and to be locked permanently to the chamber of the firearm upon 
actuation of the locking device of the invention. 
According to one aspect of the present invention there is provided a 
locking device which, upon actuation, is locked to a hollow body within 
which the device is situated, the locking device comprising: a body having 
a central longitudinal bore and a plurality of radial passages extending 
from the bore radially outwardly to the surface of the body; a locking pin 
located in each passage with the radially inner end of each pin located 
extending into the bore; an actuating member located in the bore, the 
actuating member having a cylindrical region and a tapering region which 
tapers inwardly from the cylindrical region and being positioned such that 
upon axial movement of the actuating member the locking pins will be 
cammed radially outwardly by the tapering region and thereafter locked in 
a radial outward position by the cylindrical region; a piston mounted in 
the cylinder and coupled to the actuating member for axially moving the 
actuating member; an explosive charge for driving the piston; and means 
for detonating the explosive charge in response to application of axial 
force to one end of the device. 
A security device, particularly suitable for shot guns, has been proposed 
which has the overall size and configuration of a shot gun cartridge, but 
which incorporates a lock which enables the device to be locked into the 
chamber of a shot gun. One such device of this type incorporates a ring 
which is cammed radially outwardly by a taper to lock the security device 
into engagement with the wall of the chamber. Such devices suffer, 
however, from the disadvantage that they can often be forced from the 
chamber by inserting a suitable drift through the barrel from the muzzle 
end to apply an axial force to the security device. 
If a locking device in accordance with the present invention is 
incorporated within the security device any attempt to remove the security 
device in this manner will result in detonation of the explosive charge 
with the result that the locking pins will be driven radially outwardly 
into locking engagement with the walls of the chamber. Once this has 
occurred extreme force will be necessary to drive the security device from 
the chamber, and the application of such force will result in substantial 
damage to the chambers of the gun. 
Whilst the invention is particularly suited to use in a security device for 
a firearm it will be appreciated that it is of more general applicability 
and may be used to provide a plug which may be installed extremely rapidly 
within a hollow body to provide a permanent closure to the hole in which 
the device is located. 
The invention will be better understood from the following description of a 
preferred embodiment thereof, given by way of example only, reference 
being had to the accompanying drawing wherein the single Figure 
illustrates schematically in partial axial cross-section a preferred 
embodiment of the invention.

The locking device 1 prevents any attempt to drive the security device 2 
from the chamber of the gun by applying a force to the end 9 of the 
security device using a drift which is inserted through the muzzle end of 
the barrel of the gun. 
The locking device 1 comprises the body 6 which is machined from a suitable 
material, for example mild steel. The body 6 includes an axial bore 10 and 
a plurality of radially extending passages 11 which extend from the bore 
10 to the radially outer surface 12 of the body 6. In a typical embodiment 
of the invention six radially extending passages 11 are provided 
equi-angularly spaced about the axis 13 of the locking device. In each 
passage 11 a locking pin 14 is provided. Only one such locking pin 14 is 
illustrated in the drawing in the interests of clarity. The locking pins 
14 may be of any suitable material, for example hardened steel, and each 
has a pointed radially outer end 15 and a rounded radially inner end 16. 
The radially inner ends 16 project into the bore 10 and the radially outer 
ends 15 are substantially flush with the radially outer surface 12 of the 
body 6. If desired, means in the form of a hoop extending about the body 
12 may be provided to prevent accidental dislodgement of the pins 14. The 
hoop may be of any suitable material, for example a thin copper alloy or 
of plastics. 
The radially inner ends 16 of the pins 14 rest on a first cylindrical 
region 17 of an actuating member 18. The actuating member 18 includes a 
second cylindrical region 19 and a third cylindrical region 20 both of 
which are a snug fit within the cylindrical bore 10. The cylindrical 
region 17 is connected to the cylindrical region 19 by a tapering region 
21. Upon movement of the actuating member 18 to the right as viewed in the 
drawing the pins 14 will be cammed radially outwardly by contact of the 
radially inner ends 16 with the tapering region 21 with the result that 
the radially outer ends 15 of the pins will be driven into locking 
engagement with the wall of the chamber of the gun. The amount of axial 
movement available to the actuating member is sufficient for the actuating 
member to be driven to a position in which the radially inner ends 16 of 
the locking pins rest against the cylindrical region 19 of the actuating 
member. Accordingly, once the actuating member has arrived at this 
position it cannot be cammed in the reverse direction by the radially 
inward force which is applied to the pins 14 by virtue of their engagement 
with the chamber wall. 
A piston 22 is formed integrally with the actuating member 18 and operates 
in the cylindrical bore 20. In order to drive the piston, and with it the 
actuating member, an explosive charge is provided by means of a blank 
cartridge 23 which is positioned within an end region of the bore 10 and 
is held in position by means of a cap 24 which screw threadingly engages 
the exterior surface of the body 6. The piston 22 is sized to be tight fit 
within the bore 10 so that upon detonation of the cartridge 23 there is 
minimum passage of gasses past the piston. The entire explosive force of 
the cartridge is accordingly contained between the piston 22 and the 
cartridge case and the piston is driven to the right as viewed in the 
drawing with sufficient force to move the actuating member to the right to 
set the locking device as described above. 
Detonation of the cartridge 23 is achieved by means of a firing pin 25 
which abuts an end plate 26. A pair of Belleville washers 27 are located 
between the plate 26 and the cap 24 so that upon application of a steadily 
increased force to the exposed end of the plate 26 there will be little 
movement of the plate 26 until the force of the Belleville washers 27 is 
overcome, whereupon the plate 26 will snap to the right as viewed in the 
drawing applying a percussive force to the firing pin 25 to detonate the 
cartridge. 
Preferably, a plastics protective sleeve is positioned over the cap 24 and 
the plate 26 in order to ensure that if the security device is dropped on 
the floor or otherwise accidentally knocked the cartridge will not be 
detonated. It will be noted, however, that in the event of accidental 
detonation of the cartridge there is no risk that the pins 15 will be 
propelled out of their associated bores because there is minimal flow of 
gas past the piston 22 and accordingly after the pins have reached the top 
of the tapered region 21 there will be no further force available to drive 
them from the body. The retaining hoop over the pins will absorb any 
kinetic energy posed by the pins at this point. 
Whilst the invention has been described with particular reference to a 
security device for a gun it will be appreciated that the locking device 
of the present invention if of general applicability and may be used for 
any purpose where a rapid, reliable, and permanent closure of a hole is 
required.