Patent Application
20230099819
This invention relates to a tool for applying torque, a system comprising the tool, and a method of applying torque using the tool or system of the invention.
A known device for applying torque is the “Rocket Wrench”, commercially available from Richmond Defence Systems Ltd. This tool is intended for unscrewing the tail or nose fuse of an unexploded bomb. The rocket wrench comprises a frame provided with a pair of adjustable jaws, which can be clamped to the tail or nose fuse, with a rocket tube and associated venturi disposed on opposite sides of the frame and pointing in opposite directions. The thrust delivered by each of the rocket tubes and venturi is generated by a blank power cartridge, which can be remotely electrically initiated from a safe distance. When actuated, the device creates a “Catherine wheel” effect, rotating (anticlockwise) so as to unscrew the tail or nose fuse of the bomb.
The torque generated by the Rocket Wrench is sufficient to unscrew the fuse of an unexploded bomb which is relatively new or in good condition. However, it is often necessary to remove the fuses from bombs which are old or in poor condition. For example, unexploded bombs dating from the Second World War are often found when excavating land, or in canals, especially in Germany and the Netherlands. These have been buried for decades in damp ground or lying underwater. The resulting corrosion can make the fuses rusty and very difficult to unscrew, and the inventor has found that the known rocket wrench is unable to provide sufficient torque to unscrew the fuses in such circumstances.
The present invention aims to overcome or ameliorate this problem.
In a first aspect the invention provides a tool for applying torque to an object, the tool comprising: a frame for clamping to the object to which torque is to be applied, the frame comprising a pair of jaws with an adjustable separation therebetween, and an adjuster mechanism to adjust the separation between the jaws; at least one thruster disposed on opposite sides of an intended axis of rotation of the frame, respective thrusters providing thrust in opposite directions, so as to cooperate and generate torque on the frame; characterised in that a displaceable mass is provided within a barrel extending from at least one of said thrusters, which mass is displaced by the thruster upon actuation, so as to increase the recoil, and hence the torque, experienced by the frame upon actuation of the thruster.
In a typical embodiment, the frame is provided with two thrusters, said thrusters being disposed on opposite sides of the intended axis of rotation of the frame. In another embodiment, the frame is provided with four thrusters, with one pair of thrusters being disposed on opposite sides of the intended axis of rotation of the frame. This latter embodiment provides even further increased torque. In theory, three or more thrusters may be provided on each side of the frame, although increasing numbers of thrusters increases the overall dimensions of the device and increases the amount of ground clearance required to be able to use the device and often this is not feasible because of the location/situation of the bomb or other munition.
Conveniently each thruster comprises a charge of propellant, explosive or the like. Typically the charge is initiated electrically, (generally by means of an electrically-initiated primer charge, ignition of which detonates the propellant charge) and desirably remotely initiated from a safe distance. In a simple embodiment, the thruster comprises a blank cartridge, with an electrically initiated primer, the propellant in the cartridge serving as a suitable charge to provide thrust. Typically a .50 cal blank cartridge is suitable for this purpose.
It will be apparent that the displaceable mass is advantageously ejected from the barrel by the actuation of the charge, the movement of the mass rearwardly from the barrel providing recoil in the forward direction, enhancing the torque experienced by the frame and hence on the object (such as a bomb fuse) to which the frame is clamped. The displaceable mass conveniently comprises a piston within the bore of the barrel. In a preferred embodiment the piston is formed from a material which is selected and shaped so as to have a substantially gas-tight seal with the interior surface of the barrel once the propellant charge has been initiated. Specifically, the piston advantageously undergoes a deformation when the charge is initiated, the force on the piston exerted by the initiation of the charge tending to cause the piston to deform in such a way as to cause the piston to create a gas-tight seal with the interior surface of the barrel. Preferably the piston substantially comprises or consists of a synthetic plastics material, especially a moulded plastics material. The inventor has found that high-density polyethylene (HDPE) is especially preferred for the piston material. Prior to detonation of the propellant charge, the piston may conveniently be of a size and shape that it may be relatively freely slidably movable within the barrel.
The displaceable mass will preferably have a mass of at least 1 gm, more preferably at least 2 gms, and desirably will have a total mass in the range 2 to 20 gms. Not all of the displaceable mass will necessarily be attributable to the piston, as explained below.
In a preferred embodiment, the tool further comprises a resistance which tends to resist the displacement of the displaceable mass. More specifically, it is preferred that the tool comprises a resistance which tends to resist the displacement of a displaceable piston. Conveniently the resistance is provided in the barrel “downstream” of the piston. The resistance may be provided by a gas but, more preferably, is provided by a liquid, since liquids are far less compressible than gases, and are denser and thus contribute more towards the displaceable mass. The liquid may conveniently be water or an aqueous mixture. For use on land, in order to retain a liquid within the barrel, prior to initiation of the charge, it is advantageous to provide a closure or stopper at the downstream end of the barrel. This may conveniently be, for example, a simple screw cap, which is screwed onto the end of the barrel. The cap may desirably comprise or substantially consist of a synthetic plastics material such as polycarbonate, PTFE or similar plastics polymer. The closure or stopper may be ruptured or forcibly ejected from the end of the barrel in consequence of the force generated by the detonation of the propellant charge. In other circumstances (e.g. removing the fuse from a bomb underwater), there may be no need for a cap, and the barrel can simply be allowed to flood with water from the external environment.
The barrel is typically substantially circular in cross-section and conveniently wholly or predominantly formed from metal, such as steel or alloys comprising steel. In a typical embodiment the barrel has a length in the range of about 40-100 mm, and has a bore in the range of about 20-40 mm diameter. An end of the thruster is desirably provided with a screw thread on its external surface, such that the proximal end of the barrel, provided with a co-operating thread, can be engaged with the thruster.
The frame, adjustable jaws, and the adjuster mechanism for adjusting the separation between the jaws, may all be largely conventional and essentially as already known from the existing rocket wrench device. These components will typically be formed wholly or substantially from metal, such as steel or alloys comprising steel. The adjuster mechanism may conveniently utilise a screw threaded engagement, such that rotation of a wheel, cog or the like causes relative movement of the jaws towards or away from one another, depending on the direction of rotation of the wheel, cog or the like.
The inventor has identified that the invention confers a number of advantages over the existing known rocket wrench device. These include: in the known rocket wrench device a high proportion of the propellant charge is vented, unburnt, through the venturi at the end of the thruster. This is inefficient and means that substantially less torque is created than is theoretically possible for a given size of charge. In contrast, in the device of the present invention, the barrel extending from the thruster, with the piston situated within the bore of the barrel, creates a larger chamber (at least momentarily, immediately following initiation of the charge) beyond the venturi of the thruster, permitting more complete combustion of the propellant charge, increasing efficiency and thrust. Also: displacement of the displaceable mass (e.g. piston and liquid within the barrel) creates increased recoil and therefore increased torque. Once the displaceable mass has been displaced from the barrel, the residual burning propellant/gaseous products of combustion exit the barrel to preserve a “rocket” effect.
In a second aspect the invention provides a system for applying torque to an object, the system comprising a tool in accordance with the first aspect defined above, together with one or more of the following: a plurality of single-use caps for capping the distal end of the barrel; and a plurality of single-use deformable pistons. By way of explanation, it will be apparent from the foregoing that, in at least some embodiments, the piston is deformable and is deformed by detonation of the propellant charge, such that the piston may be a consumable item, which is discarded after a single-use. Equally, the end caps covering the barrel may be ruptured or destroyed after the charge is detonated, and are consumable items which are unusable after a single use. Accordingly, it is convenient to provide the tool of the first aspect of the invention as a system, in combination with one or more of one, or both, of these consumable items.
In a third aspect the invention provides a method for applying torque to an object, the method comprising the steps of:
a) adjusting the separation between the jaws of a device in accordance with the first aspect of the invention defined above, by means of the adjuster mechanism, so as to clamp the device to the object;
b) placing a cap over the distal end of the barrel; and
c) causing the initiation of the thrusters.
The method may additionally comprise the step of introducing a piston into the bore of the barrel. If the method is performed on land, the method may also comprise the step of introducing a fluid, preferably a liquid, typically water, into the barrel downstream of the piston. It will be apparent to those skilled in the art that the steps of introducing a piston, and introducing a fluid into the barrel, are conveniently performed before performing step (b). If the method of the invention is performed under water, then it is preferred that the piston is introduced into the barrel before the barrel is submerged under the water, and there is no necessity for step (b).
In a preferred embodiment, the piston fits snugly (but not in a gas-tight manner) upon insertion into the barrel—this facilitates the piston being introduced reasonably readily without requiring exertion of undue force. However, once the propellant charge has been detonated, the expanding gases created by the detonation distort the thin proximal edges of the piston and force them outwards into a gas-tight seal with the interior surface of the barrel, preventing dissipation of the thrust.
As will be apparent from the foregoing, the object to which torque is to be applied will normally be the tail or nose fuse of an unexploded bomb, and in preferred embodiments, the method of the invention forms a step in a method of de-fusing an unexploded bomb, but in principle the device and method of the invention can be used to apply torque to other objects.
The invention will now be further described by way of illustrative embodiments and with reference to the accompanying drawing figures in which:
Referring to
As with the prior art device, a pair of thrusters is also provided on the frame, located at the outer edge thereof (so as to maximise turning moment on the frame). One such thruster, 10, is shown in
In the illustrated embodiment, the displaceable mass takes the form of a piston 22 seated within the bore of the barrel. The piston is formed from a material which is selected and shaped so as to have a substantially gas-tight seal with the interior surface of the barrel once the charge has been initiated. Specifically, the piston advantageously undergoes a deformation when the charge is initiated, the force on the piston exerted by the charge tending to cause the piston to deform in such a way as to cause the piston to create a gas-tight seal with the interior surface of the barrel. In the illustrated embodiment, the piston is formed from moulded HDPE and has a concave surface facing the propellant charge. When the propellant charge is fired, the expanding gases generated tend to force the thin edges of the piston outwards, into contact with the interior surface of the barrel 20, so as to form a gas-tight seal therewith. At the distal, “downstream” end of the barrel 20 is a plastics cap 24, which is in screw -threaded engagement with, and seals the end of, of the barrel. Further, between the piston 22 and the cap 24, the interior of the barrel 20, the tool comprises a resistance 26 which tends to resist the displacement of the piston. The resistance may be provided by a gas but, more preferably, is provided by a liquid, since liquids are far less compressible than gases. Thus, in the illustrated embodiment, the interior of the barrel 20, “downstream” of the piston 22, is filled completely with water, kept in place in the barrel 20 by the piston 22 and the cap 24.
Referring to
Similarly,
| Number | Date | Country | Kind |
|---|---|---|---|
| 2109026.1 | Jun 2021 | GB | national |
