United States patent specification 4,730, 468 describes an anti-theft device: An anti-theft device for semi-truck trailer landing gear of the type of telescoping concentric inner and outer cylinders which inhabits the landing gear from being raised by preventing the retraction of the inner cylinder into the outer cylinder, the anti-theft device defining an elongated pin adapted to reside in an opening situated transversely through the inner cylinder and located proximate the outer cylinder, the elongated pin having a head at one end, an extending and retractable cog emerging from the shank of the elongated pin proximate the head, and a locking means interiorly to the hollow bore of he elongated pin with the lock located at the at the elongated pin opposite the head and connected with the cod in order to extend and retract it.

With the landing gear extended supporting one end of the semi-truck trailer, the anti-theft device with the cog retracted is inserted into an opening in the inner cylinder proximate the end of the outer cylinder and the lock operated to extended the cog, thereby preventing removal of the elongated pin and thus inhibiting the raising of the gear which then prevents easy removal of the semi-truck trailer by a semi-truck tractor.

A disadvantage of this solution is that the locking pin is inserted into a hole in the inner cylinder, extending through the cylinder, and out through a hole opposite the entrance hole, this method is vulnerable to attack as both ends of the locking pin are exposed, by applying force by way of hammering the locking pin back through the cylinder the same direction as it was inserted, by way of the locking cog 14 Fig 1 shearing. Another disadvantage of this locking pin it that it is detached from the trailer leg when not in use and could be lost.

Accordingly, the present invention only extends through one side of the leg section and there no access to the locking mechanism, therefore is not vulnerable to attack by applying force to retract the locking device. An advantage of the present invention is that it can be permanently attached to the semi-truck trailer leg making it less likely to loose the locking device.

RELATED APPLICATION A similar invention to the present invention relates to a method for immobilizing vehicles comprising of locking a vehicle-weight-loaded, ground-engaged member in an immobilising condition.

GB2262076 This invention describes a key operated cam and a second key to deadlock the cam or key and release plunger.

A disadvantage or the first solution is that the device requires two keys.

A disadvantage of the second solution is that the release plunger and grip can protrude from the vehicle leg when the vehicle is in operation making the device plunger and grip vulnerable to damage or attack.

Accordingly the present invention only relies on one key to operate the locking device and has no vulnerable plunger grips protruding.

It has become known that locking devices of similar invention can be compromised in a short period of time by means of cutting the outer casing and removing the key system to release the plunger.

Accordingly the present invention has a secondary locking device built in to the inner body that automatically activates when the outer casing is cut or compromised and the key system removed, the re-locker will lock the inner lock body into the vehicles landing or stabiliser leg, inhibiting the retraction of the leg.

This invention is a locking device intended for the prevention of the theft or the unauthorised moving of semi-truck trailers and of the theft or the unauthorised moving of backhoe diggers that are fitted with wheels and tyres.

This invention is intended to inhibit easy moving of such semi-truck trailers and backhoe digger machines by way of locking the telescoping landing legs, or stabiliser legs into the extended position.

The stabiliser legs of such backhoe digger machines are designed to lift the backhoe digger machine to a height that, the rear drive wheels are suspended off the ground, so that when the backhoe is in operation the digger machine is stable.

By way of locking the landing legs of the semi-truck trailer in the extended position, inhibits the forward or reverse movement of the trailer when the tractor unit is attached. Unauthorised attempts to drive the tractor unit and trailer away will be inhibited because the legs cannot be retracted and will foul the ground.

By way of locking the stabiliser legs of the backhoe digger machine in the raised position, inhibits the traction from the rear drive wheels, therefore disabling the digger machine from a forward or reverse movement.

The landing legs of semi-truck trailers are of the same construction as the backhoe digger legs, but the semi-truck trailer legs are intended to support the trailer at a height that the tractor unit can be attached or detached to or from the trailer.

The semi-truck trailer legs and the backhoe digger machines legs are constructed from two vertical hollow box sections, which are of a diameter that allow one section to slide inside the other forming a telescoping effect.

With the anti-theft locking device fitted in a pre-drilled hole, in a pre- determined position, on the upper or lower leg section, the locking device will prevent the telescoping effect of the upper and the lower leg sections.

Accordingly, this invention provides a anti-theft locking device, comprising a inner lock body, an associated key operated locking system where by the inner lock body is mounted in to a outer body, the inner body part with its associated key system is the locking device, the outer body provides a holding place for the inner lock body, keeping the inner lock body permanently attached to the telescoping leg section, when the inner lock bodies associated key system is in the unlocked position, allows the inner lock body to travel through a pre-drilled hole in a pre-determined position, with the key system in its locked position, holds the inner lock body in place through the pre-drilled hole, inhibiting the lower leg section to retract in to the upper leg section, with the key system in the unlocked position allowing the inner lock body to retract from the pre-drilled hole, allowing the inner leg section to retracted into the outer leg section, with the inner lock body fully retracted in its outer body, allows the key system to go to its locked position, holding the inner lock body to the outer lock body in its retracted position.

The anti-theft device is fitted with a key system that is attached to a cam; the cam in turn pushes out the two ball bearings when the key is turned to the locked position.

The anti-theft device is fitted with an anti-tamper re-locking device as part of the locking cam assembly, when the anti-theft device is cut away from the stabiliser or landing leg a spring loaded pushrod forces the locking cam outward misaligning the locking cam ball relief recess from its unlocking position, the distance of the outward travel of the locking cam, is restricted by the outside diameter of one end of the locking cam being larger in diameter, than inside diameter of the inner lock body, once the spring loaded push rod has forced the locking cam outward, the locking cam can not be returned to its original position, as the re-locking ball falls between the locking cam and the cam follower, thereby not allowing the locking cam ball relief recess to re-align to its lock opening position, A preferred embodiment of the invention will now be described with reference to the accompanying drawings in which: FIGURE 1 shows the leg with a preferred locking device 15,16, in its engaged and locked position, 1 shows the top section of the leg, 2 shows the lower section of the leg in its extended position, 3 shows the foot plate of the leg, 4 shows the lid of the leg, 5 shows a cross-section cut out view of the upper leg section, 6 shows the pre-drilled hole, in its pre-determined position, 15 show a cross-section of the outer body permanently attached to the upper leg section 1,16 shows a cross-section of the inner lock body, 14 shows the locking key.

FIGURE 2 shows a three-dimensional view of the inner lock body 16,9 show the locking balls in there locked position.

FIGURE 3,15 shows a cross-sectional, three-dimensional view of the outer lock body, 17 show the ball-retaining groove.

FIGURE 4,16 shows a cross-sectional view of the inner lock body in its retracted position, 9 shows the locking balls in there locked position, 15 shows the outer lock body, 14 shows the locking key, 11 shows the key cylinder, 12 shows the locking cam, 13 shows the can retaining circlip.

FIGURE 5, 16 shows a cross-sectional view of the inner lock body in its engaged position, 9 shows the locking balls in there locked position, 14 shows the locking key, 15 shows the outer lock body attached to the upper leg section 1.

FIGURE 6,2 shows lower leg section in its retracted, raised position, 16 shows the inner lock body held in its retracted position to the outer body 15, by way of the key system 11, being its locked position.

FIGURE 7, shows an alternative fitting of the inner lock body 16, without the use of the outer lock body. 1 shows the upper section of the leg, 2 shows the lower section of the leg in its extended position, 3 shows the leg footplate, 4 shows the lid of the leg, 5 shows a cross-section cut out to give a view of the inside lower section of the leg, 16 inner lock body in its locked position, 6 shows the pre-drilled hole with the Inner lock body 16, in its locked position.

FIGURE 8,1 shows the upper section of the leg, 2 shows the lower section of the leg in its extended position, 3 shows the leg foot plate, 4 shows the lid of the leg, 5 shows a cross-section cut out to give a view of the inside upper section of the leg, 16 shows the inner lock body fitted to the lower leg section 2, its locked position, 6 shows the pre-drilled hole in a alternative position.

FIGURE 9,16 shows a three dimensional view of the inner lock body lock, 9 shows the two locking balls in their locked position 10 shows the key entry for the lock.

FIGURE 10, 16 shows a cross-section of the lock body exposing the key cylinder, 11,12 shows the locking cam, 9 shows the locking balls in there unlocked position, 13 shows the cam retaining circlip, 14 shows the locking key, 10 shows the key entry.

FIGURE 11, shows a backhoe digger with the stabiliser legs 1 and 2 in the extended position section, 1 shows the upper section of the leg, 2 shows the lower section of the leg, 6 showing the preferred position of the preferred locking device, 18 showing the digger drive wheels and tyres in there raised position off the ground, 19 shows the ground.

FIGURE 12, shows an exploded view of the inner-lock body 16 and the outer- lock body 15.

FIGURE 13, shows a backhoe digger with the stabiliser legs 1 and 2 in the extended position, showing an alternative lock position 6,18 showing the rear drive wheels and tyres in there raised position from the ground, 19 showing the ground.

FIGURE 14,16 shows an exploded view of the lock body.

FIGURE 15,21 shows a semi-truck trailer, 1 shows the upper section of the landing leg, 2 shows the lower section of the landing leg in there extended position, 3 shows the leg footplate 4 shows the preferred position of the lock body, Fig 12 shows an exploded view of the preferred inner and outer lock body, 15 and 16,19 shows the ground.

FIGURE 16,21 shows an semi-truck trailer, 1 shows the upper section of the landing leg, 2 shows the lower section of the landing leg in there extended position, 3 shows the leg footplate 5 shows the alternative position of the alternative locking system lock body, 19 shows the ground.

FIGURE 17 shows an exploded view of the preferred inner-lock body 16 in its locked position and the outer-lock body 15, 1 shows the upper section of the landing leg, 2 shows the lower section of the landing leg in its extended position, 15 shows the outer lock body permanently attached, 27 to the upper leg section 1, 22 shows the lock cover, 11 shows the key cylinder, 9 shows the locking balls in there locked position, 13 shows the retaining circlip, 25 shows the cam follower, 23 shows the lock cut off and parted in an attack, 12 shows the cam in its attack relocked position, 26 shows the spring loaded re- locker pushrod in its released position, 24 shows the re-locker ball in its locked position, 28 shows the locking cam ball relief recess in its re- locked position.