GB2275966A - Security device for blocking ducts - Google Patents

Abstract

The security device intended for preventing unauthorised access to a duct is described. It is particularly suitable for preventing unauthorised access to water meters or stopcocks. Rather than providing a clamp or cover attached to the control device itself, a device is placed in the duct including members 8, 13 expanding radially to engage walls of the duct by a drive, and a coupling for input to the drive via a mechanical security key. Suitably the expandable members are toggle-action arms 8 of which joints move laterally outwardly upon longitudinal drawing together of the arms by a screw shaft 11 of a rotatable drive. The security key is a shaped socket or spigot 7 adapted to be engaged for transmission of rotation by a complimentary shaped drive spigot or socket of a drive member 20. To prevent manual rotation of the shaped socket, it can be protected by a shield element 21 rotatable independently thereof. Suitably, this shield element is a cup with its skirt extending longitudinally around the coupling. <IMAGE>

Description

SECURITY DEVICE This invention relates to security devices and in particular to a device which is intended for preventing unauthorised access to a duct.

Control devices associated with the supply or metering of mains services are frequently housed in ducts and in particular it is common for the main stopcock for water or gas supplies to premises to be housed underground at or near the bottom of a vertical duct sunk into the ground. Pressure control valves and meters may be similarly positioned.

There is a problem of unauthorised access to such control devices. It is not unknown for example for water meters to be fraudulently reversed so as to cut down on metered consumption, or for stopcocks which have been shut off by the supplying company because of payment default, to be turned on again by the consumer.

It is therefore desired to prevent this unauthorised operation.

So far the means used have been clamps or covers securely attached to the control device itself - for example a padlocked clamp on the key of a stopcock.

These devices though efficient in some cases are not always easy to fit or remove since the control device to be secured may be at a range of distances from the mouth of the duct - sometimes as much as one metre.

US4101154 describes a well cover with which a

locking devicet comprises at least one pivotal lever which falls under gravity to a locking position and which is pushed into an unlocked position by a rod inserted through well cover. The lever may be biased towards the locking position by (eg) a spring. Since the locking device is an integral part of the well cover, this arrangement suffers from corresponding difficulties.

The approach proposed by the present invention is to block the duct itself, in front of the control device, in a secure manner. The position of blockage then becomes largely independent of the actual position of the control device.

The invention therefore proposes a device for preventing unauthorised access to a duct (the duct housing a control device such as a stopcock or meter) which includes members expandable laterally to engage walls of the duct by a drive so that the device is firmly retained in the duct, the drive being achieved with a coupling for its input to the device being through a mechanical security key.

Example of such keys are well-known and include square or hexagonal spigots and sockets with combinations of splinings and cylindrical spigots and sockets with individual facetings.

The expandable members are preferably jointed toggle arms of which the joints are driven outwardly by drawing longitudinally together of the ends of the arms, this drawing together being achieved by a rotatable screw shaft. The coupling will be at one end of the screw shaft and will normally draw the far end of the arms towards that one end by a single screw action.

To help prevent attempts to rotate such a coupling by a crude grappling action, a shield for the coupling may be present and preferably will be in the form of a cup-like element mounted rotatably on the shaft, extending longitudinally around and beyond the coupling, and being separately rotatable from the coupling. The longitudinal extension of the shield prevents any powerful access to the coupling and any attempt to grapple with the shield will rotate merely the shield and not the coupling.

Preferably the coupling on the device is a socket, to be engaged by a spigot on a driving member such as a Tspanner.

It is advantageous for the coupling to be springloadedly urged longitudinally away from the adjacent ends of the toggle arms and a preferable spring is one or more Belleville washers.

Embodiments of the invention will now be described with reference to the accompanying drawings, wherein: Fig 1 is a side elevation of a device in a duct, the duct being shown in diammetrical section; and Fig 2 is a top plan view of the device (with parts omitted).

In Fig 1 we see a stopcock 1 for mains water as an example of a ducted control device. It is housed in a vertical duct 2 lined with plastics material ducting 3 below ground level 4.

To prevent unauthorised access to the stopcock 1 which may have been turned off for a default of payment or other reasons, a device 5 is provided.

This is a device which is expandable laterally so as to engage the walls of the duct 2 by means of rotational drive of which the prime mover is a T-spanner 6 with a spigot end 7.

The laterally expandable parts of the device 5 are jointed toggle arms 8. At their ends these arms are pivotted in end plates 9,10, being equally angularly spaced about a central axis at which there is a screw shaft 11.

This screw shaft passes freely through end plate 9 but is screw-threadedly engaged with end plate 10. It can be seen therefore that as the shaft 11 is rotated the end plates 9 and 10 are moved longitudinally towards or away fom each other according to the direction of rotation causing a corresponding lateral change in the position of the joints 13 of the jointed arms 8.

On the shaft 11 there is positioned a sleeve 12 which has two main functions. By virtue of its axial length the sleeve 12 prevents any too-close approach together of the plates 9 and 10, which could cause strain or bending in the arms 8 due to exceeding the capacity of the joints 13. A diameter 14 of the sleeve 12 is such as to prevent the joints 13 of the arms 8 going over centre, that is to say bending inwardly of the longitudinal axial direction.

The sleeve need not be of two or more diameters as shown but could be all of the one diameter which is needed to achieve that effect.

The articulation of each joint 13 is by means of a channel section element 15 of which the solid walls are penetrated by a pivot pin 16 and of which an outer face 17 is provided with serrations or other roughenings so that it grips securely the wall of the duct 2 as it is pressed into it.

The pivot pins 16 and also the pins 18 which pivot the arms to the end plates are preferably of the spring pin type, that is to say broken cylinders or spirals which are forced into the pivot hole and expand outwardly under their own resilience so as to give a particularly secure fitment.

Drive to input to the shaft 11 is assured by a coupling 20 secured to one end of it. The coupling 20 has a central socket which corresponds in shape to the spigot 7.

The shape may be basically hexagonal or square or cylindrical, but in each case with-some irregularity-so that each part forms a mechanical security key interengageable only with the other part. In the case of many of these basic shapes there may be irregularly positioned splinings/recesses or in the case of the cylindrical shape, one or more flattened facets. Thus the spigot 7 of a Tspanner 6 will engage only in a socket of a coupling 20 which it is authorised to engage in, and thus only a person in possession of an appropriate spanner (or spigot head which may be fitted removably on the end of a spanner) can fit or remove the device 5.

As a further obstacle to unauthorised removal, the coupling 20 is placed within a cup-like shield element 21, the base of which fits freely around the shaft 11 outside the end plate 9 and the skirt of which extends longitudinally beyond the coupling 20. The shield 21 is rotatable about the shaft; that is, if it is rotated it does not transmit its rotation to the shaft. The shield therefore prevents any crude attempts to grapple with the outside of the coupling 20 by means of wrenches, pincers or the like and if it itself is grappled with will rotate freely without affecting the fitting of the device.

Between the base of the coupling 20 and the inner surface of the base 22 of the shield 21 spring means 23 are fitted to urge the coupling 20, on the shaft 11, upwardly in the drawing. Preferably these spring means are Belleville washers. The provision of these springs gives the operator of the T-spanner a "feel" that the device is approaching its maximum lateral expansion in the duct. As the surfaces 17 become progressively more firmly engaged with the walls of the duct 2, further rotation of the shaft 11, not being able to press the joints 13 further outwardly will instead cause a shift longitudinally of the end plate 9 against the spring 23. Thus the operator is given a warning of impending full expansion and the danger of distorting or damaging the device by excessive application of force is lessened.

The end plate 9 (Fig 2) has at one diameter a screw-threaded aperture 24.

This is for the temporary positioning of the device in the duct while the coupling 20 and spigot 7 are initially engaged and the arms 8 are not in contact with the duct wall. Before the device in its unexpanded condition is offered up to the duct, the screw-threaded end of a shaft or second T-spanner is engaged in the aperture 24 and this is then used to insert the device into the duct, up to a standard distance. It is also used to hold the device in position during rotation of the T-spanner 6 and hence of the shaft, while the arms 8 are expanded.

The embodiments shown are made from metals selected for rust resistance e.g. aluminium (or aluminion alloy) or plated steel.

In the device shown there are three jointed arms and this is an especially suitable configuration for a cylindrical duct. For a square duct four arms may be preferable.

As yet a further security precaution the cup-like shield 21 may be provided with a diametrically opposed pair of ports intended for the reception of the hasp of a padlock or a securable pin, thus further preventing unauthorised access to the coupling 20.

Claims (9)

CLAIMS:

1. A device for preventing unauthorised access to a duct which includes members expandable laterally to engage walls of the duct by a drive, and a coupling for input to the drive being through a mechanical security key.

2. A device according to claim 1 wherein the expandable members are toggle-action arms of which joints move laterally outwardly upon longitudinal drawing together of the arms by a screw shaft of a rotatable drive.

3. A device according to claim 2 wherein the screw shaft is surrounded for part of its length by a sleeve, the sleeve defining a distance of minimum longitudinal spacing of the arms and a distance of minimum lateral spacing of the joints of the arms.

4. A device according to claim 2 or claim 3 wherein the arms are pivoted at their mutually longitudinally outermost ends on end plates borne on the shaft, and the coupling is spring-loadedly urged away from one of the end plates in a direction away from the other of the end plates.

5. A device according to claim 4 wherein one of the end plates nearer the coupling has auxiliary retention means temporarily engageable with means for positioning the device in the duct while unexpanded.

6. A device according to any one of the preceding claims wherein the security key is a shaped socket or spigot adapted to be engaged for transmission of rotation by a complementary shaped drive spigot or socket of a drive member.

7. A device according to claim 6 wherein the coupling is protected by a shield element which is rotatable independently of the coupling.

8. A device according to claim 7 wherein the shield element is a cup with its skirt extending longitudinally around the coupling.

9. A device substantially as herein described with reference to and as illustrated in the accompanying drawings.