GB2041478A - A device for making a tightened screw inaccessible - Google Patents

Abstract

This invention relates to a device for making a tightened screw inaccessible. The screw (17) is located in a deformable housing (18) which has a portion (19) that extends beyond the screw when tightened, so that after the screw has been tightened the housing (19) can be deformed to close access to the screw. Such a device is particularly useful for preventing tampering with the position of a screw secured abutment (13) having a passageway (14) therethrough accommodating an elongate member (15) slidable in the passageway. <IMAGE>

Description

SPECIFICATION A device for making a tightened screw inaccessible This invention relates to a device for making a tightened screw inaccessible.

In motor vehicle hydraulic braking systems having an axle controlled pressure reducing valve incorporated in the braking system to the rear brakes, the hydraulic pressure at which the reducing valve begins to operate is usually controlled by the load in a spring extending between the vehicle axle and a lever operating on the valve piston. It is usual for the operating length of the spring to be pre-set before the valve is fitted on the vehicle. This is accomplished by securing an abutment, through which the spring operates against the lever, to a determined position along the tang of the spring.

The fine adjustment for achieving the correct load on the valve is made after the valve is fitted to the vehicle. This is usually accomplished by having a screw adjuster through which the lever acts on the valve piston, the adjuster is utilised to vary the angle of the lever relative to the valve to vary the length of the control spring. Thus it is possible to obtain the correct load in the spring, when for example, the vehicle is unlaiden.

During servicing of the vehicle it may be necessary to re-adjust the setting at which the pressure reducing valve operates. This is accomplished by altering the screw adjuster and not by altering the position of the abutment on the spring tang, such alterations can have dangerous consequences.

The abutment on the spring tang is normally secured in position by a grub screw which bites into the tang; altering the position of this abutment can be discouraged by making it difficult to loosen the screw.

Accordingly there is provided a device for making a tightened screw inaccessible, wherein the screw is located in a deformable housing which extends beyond the screw when tightened, so that after the screw has been tightened the housing can be deformed to close access to the screw.

The invention will be described by way of example and with reference to the accompanying drawing which is a section through a device for making a tightened screw inaccessible.

With reference to the drawing, a 'U' section lever 11 has a hemi-spherical seat 1 2 for receiving a hemi-spherical surface on an abutment 1 3. The abutment 1 3 has an axial passageway 1 4 therethrough which accommodates a tang 1 5 of a tension spring (not shown) which passes through an aperture 1 6 in the seat 1 2. The spring pulls the abutment 13 into its seat 12.

The abutment 1 3 is slidable on the tang 1 5 and is secured in position, in use, by a grub screw 1 7 arranged radially of the axial passageway 14. The grub screw 17 is located in a deformable cylindrical housing 1 8 integral with the abutment and which extends beyond the screw 1 7 (as shown in dotted lines), when it is tightened so as to grip the abutment onto the spring tang 1 5.

That portion 1 9 of the housing 18 that projects beyond the screw is then deformed, by for example squashing with a pair of pliers, to close access for a tool such as a screw driver or Allen key, to the screw.

The deformed portion 1 9 of the housing 1 8 will also grip the head of the screw 1 7 helping to lock the screw in its tightened position. Thus, it is now quite impossible to alter the position of the abutment 1 3 on the spring tang 1 5 without deliberately opening up the housing 1 8.

1. A device for making a tightened screw inaccessible, wherein the screw is located in a deformable housing which extends beyond the screw when tightened so that after the screw has been tightened the housing can be deformed to close access to the screw.

2. A device as claimed in Claim 1, wherein the deformed housing also locks the screw in position.

3. An abutment having a passageway therethrough suitable for an elongate member to slide therein, and a screw for securing in use the abutment onto said member, wherein the screw is made inaccessible by a device as claimed in any proceeding claim.

4. A device substantially as described herein with reference to the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION A device for making a tightened screw inaccessible This invention relates to a device for making a tightened screw inaccessible. In motor vehicle hydraulic braking systems having an axle controlled pressure reducing valve incorporated in the braking system to the rear brakes, the hydraulic pressure at which the reducing valve begins to operate is usually controlled by the load in a spring extending between the vehicle axle and a lever operating on the valve piston. It is usual for the operating length of the spring to be pre-set before the valve is fitted on the vehicle. This is accomplished by securing an abutment, through which the spring operates against the lever, to a determined position along the tang of the spring. The fine adjustment for achieving the correct load on the valve is made after the valve is fitted to the vehicle. This is usually accomplished by having a screw adjuster through which the lever acts on the valve piston, the adjuster is utilised to vary the angle of the lever relative to the valve to vary the length of the control spring. Thus it is possible to obtain the correct load in the spring, when for example, the vehicle is unlaiden. During servicing of the vehicle it may be necessary to re-adjust the setting at which the pressure reducing valve operates. This is accomplished by altering the screw adjuster and not by altering the position of the abutment on the spring tang, such alterations can have dangerous consequences. The abutment on the spring tang is normally secured in position by a grub screw which bites into the tang; altering the position of this abutment can be discouraged by making it difficult to loosen the screw. Accordingly there is provided a device for making a tightened screw inaccessible, wherein the screw is located in a deformable housing which extends beyond the screw when tightened, so that after the screw has been tightened the housing can be deformed to close access to the screw. The invention will be described by way of example and with reference to the accompanying drawing which is a section through a device for making a tightened screw inaccessible. With reference to the drawing, a 'U' section lever 11 has a hemi-spherical seat 1 2 for receiving a hemi-spherical surface on an abutment 1 3. The abutment 1 3 has an axial passageway 1 4 therethrough which accommodates a tang 1 5 of a tension spring (not shown) which passes through an aperture 1 6 in the seat 1 2. The spring pulls the abutment 13 into its seat 12. The abutment 1 3 is slidable on the tang 1 5 and is secured in position, in use, by a grub screw 1 7 arranged radially of the axial passageway 14. The grub screw 17 is located in a deformable cylindrical housing 1 8 integral with the abutment and which extends beyond the screw 1 7 (as shown in dotted lines), when it is tightened so as to grip the abutment onto the spring tang 1 5. That portion 1 9 of the housing 18 that projects beyond the screw is then deformed, by for example squashing with a pair of pliers, to close access for a tool such as a screw driver or Allen key, to the screw. The deformed portion 1 9 of the housing 1 8 will also grip the head of the screw 1 7 helping to lock the screw in its tightened position. Thus, it is now quite impossible to alter the position of the abutment 1 3 on the spring tang 1 5 without deliberately opening up the housing 1 8. CLAIMS

1. A device for making a tightened screw inaccessible, wherein the screw is located in a deformable housing which extends beyond the screw when tightened so that after the screw has been tightened the housing can be deformed to close access to the screw.

2. A device as claimed in Claim 1, wherein the deformed housing also locks the screw in position.

3. An abutment having a passageway therethrough suitable for an elongate member to slide therein, and a screw for securing in use the abutment onto said member, wherein the screw is made inaccessible by a device as claimed in any proceeding claim.

4. A device substantially as described herein with reference to the accompanying drawing.