GB2207402A

GB2207402A - Vehicle gearbox selector lock

Info

Publication number: GB2207402A
Application number: GB08816231A
Authority: GB
Inventors: Reginald Knowles
Original assignee: Robert John Knowles
Current assignee: Robert John Knowles
Priority date: 1987-07-13
Filing date: 1988-07-07
Publication date: 1989-02-01
Also published as: GB8816231D0; GB8716460D0

Abstract

So that the vehicle may be immobilised, the gear selector rods (10, 12, 14) can be locked in position by means of a locking bar (22) in combination with steel balls, which can be moved only by the use of a key operated lock (32). <IMAGE>

Description

Gearbox selector lock.

The invention relates to a gearbox selector lock.

It is a particular problem that the theft of vehicles, including buses, lorries, tractors and earth moving equipment for example, is on the increase. Various means have been employed to prevent such thefts but none have been entirely successful basically because a really determined thief can usually by brute force either break or overcome the preventive means employed. For example, steering locks of various kinds can usually be broken by the use of a sledge hammer.

The use of preventive means which merely immobilise the engine of a vehicle is no deterrent to a really determined thief because such a vehicle can simply be towed away to a place of safety where the thief can either break the vehicle and sell its component parts as spare parts or remove its load, or both.

The invention has for its object to at least alleviate this problem.

According to the invention, the gear selector rods of a gearbox can be locked in position by means of a locking bar which can be moved only by the use of a key operated lock. The arrangement will preferably be such that the locking bar acts also to trap hydraulic or air pressure in conduits connected to hydraulic or pneumatic brakes of the vehicle. A part of the gearbox immediately behind the key operated lock will preferably be weaker than surrounding structure so that any attempt to break the lock will merely cause the locking bar to become Jammed in position with the result that the gear selector rods remain locked in position and the vehicle brakes remain applied.

In order that the invention may be fully understood and readily carried into effect, the same will now be described, by way of example only, with reference to the accompanying drawings, of which: - Figure 1 is a scrap plan view showing a part of the selector mechanism of a gearbox with the top cover of the gearbox removed, Figure 2 is a sectional view on the line 2-2 in Figure 1, and Figures 3, 4 and 5 are sectional views on the lines 3-3, 4-4 and 5-5 respectively.

Referring now in particular to Figures 1 and 2 of the drawings, the gearbox selector mechanism there illustrated has three selector rods 10, 12 and 14 which are movable axially to obtain required gear ratios. However, in the positions in which the selector rods are illustrated in Figure 1, the gearbox is in neutral and notches in the rods are located immediately beneath respective steel balls 16 which are slidable in vertical bores in a housing part 18. The steel balls having dropped into the notches, as shown, so that they are located wholly below a surface 20, a locking bar 22 has been able to be moved to the position in which it is shown in Figure 2. In this position of the locking bar, the steel balls are prevented from moving upwards and the selector rods are therefore prevented from moving axially to engage any gear ratio.

The lower surface of the locking bar is provided with three notches 24 at the same spacing as the selector levers, the arrangement being such that, when the locking bar is moved to a position in which said notches overlie the respective steel balls 16, the latter are able to be displaced upwardly into said notches and the selector rods are thus freed for movement to enable any required gear ratio to be selected. However, as previously stated, in the position in which the locking bar is shown in Figure 2, the selector rods are locked in position against movement giving any gear ratio.

Also in this position of the locking bar, a notch 26 in the top surface of the bar coincides with the position of a ball member 28 which is acted on by a spring loaded plunger of a hydraulic valve 30, the latter being located in a hydraulic circuit for applying pressure to the vehicle brakes. The arrangement is such that with the ball member 28 in the outermost position relative to the valve, hydraulic pressure is locked in the braking circuit so that the vehicle brakes are applied. The locking bar itself is locked in position by means of a key operated lock 32.

As shown, the key operated lock is located in a thickened portion of the gearbox casing in which substantially the full length of the lock barrel is located. However, immediately behind the key operated lock the housing part 18 is weaker than surrounding structure, that is to say weaker than the main body of said- housing part in which the selector rods are mounted. As illustrated diagrammatically in chain-dotted lines therefore, any attempt to break the lock by hitting it with a hammer or chisel will merely break off a portion of the housing part with the result that the locking bar will become bent and be jammed in position.

The gear selector rods will remain locked in position and the vehicle brakes will remain applied.

A gear selector lock embodying the invention has a number of advantages. Firstly, it does not interfere in any way with the starting of the vehicle engine. A potential thief may be able to start the engine but will still not be able to drive the vehicle away. The noise of the engine being started or being turned over in an attempt to start it may well rouse people within earshot that an attempt is being made to steal the vehicle.

Secondly, as previously mentioned, any attempt to smash the key operated lock will be likely to lock the locking bar more firmly in position. Thirdly, any attempt to tow the vehicle away without starting the engine will be foiled by the fact that the vehicle brakes are applied. Any attempt to release the brakes can only be by cutting the brake pipes in which case the thief will be faced with driving a vehicle without brakes (that is unless the vehicle is the kind having brakes applied by spring pressure, the air pressure being required to release the brakes. The cutting of the brake pipes in this case will have no effect because the brakes will still be fully applied by spring pressure).

Various modifications may be made. For example, different gearboxes may have different numbers and arrangements of selector rods. The locking bar may need to be designed accordingly to ensure that no transmission ratio can be selected.

Claims

CLAIMS:

1. A change speed gearbox having gear selector rods capable of being locked in position by means of a locking bar which can be moved only by the use of a key operated lock.

2. A change speed gearbox according to claim 1, in which the locking bar acts also to trap hydraulic or air pressure in conduits connected to hydraulic or pneumatic brakes of the vehicle.

3. A change speed gearbox according to either one of the preceding claims, in which a part of the gearbox immediately behind the key operated lock is weaker than surrounding structure so that any attempt to break the lock will merely cause the locking bar to become jammed in position with the result that the gear selector rods remain locked in position and the vehicle brakes remain applied.

4. A change speed gearbox constructed, arranged and adapted to be rendered inoperative substantially as hereinbefore described with reference to and as illustrated by the accompanying drawings.