GB2272180A - Tool for removing valve spindle - Google Patents

Abstract

A tool has a force-transmitting elongate stock 11 with a yoke 12 at one end to fit behind the stem of a false spindle and an impulse-receiving surface 16 at the other end of stock 11. Preferably, a heavy cylindrical member 17, captivated on stock 11, and including handles 21, 22, is grasped and urged towards the top end of stock 11, in order to deliver an impulse to stock 11 and thereby shock the false spindle off the valve stem. The impulse has to be delivered on the axis of stock 11. Off-axis upward blows with an ordinary hammer, delivered to a transverse plate on the top of the valve stock, are ineffective, whereas blows from the cylindrical member 17, delivered to an annular impulse receiving surface 16 at the top end of the stock 11, have been found to be very effective. For added security, the yoke 12 at the foot of the stock can be provided with a restraining means across its open jaws, such as a bolt. <IMAGE>

Description

VALVE SPINDLE TOOL This invention relates to a tool for freeing the false spindle of a projecting valve stem, where lateral access to the stem is restricted.

In the water industry, each water distribution pipe network includes a multitude of gate valves located within a subterranean chamber. Projecting from the top of the valve housing is a stem, rotation of which moves the gate of the valve between open and closed dispositions. A false spindle is attached to the stem, usually by means of a grub screw, and to turn the valve on and off a tool is used which engages with a square shaft of the false spindle. In this way, repeated use of the tool damages only the shaft of the false spindle, which is easily replaced, and not the more permanent stem of the valve.

Over the long period of time in which the false spindle remains bound fast to the valve stem, in damp conditions, binding of the false spindle to the stem can occur, which can persist even when the grub screw is loosened.

When, for whatever reason, the false spindle needs to be replaced, it is often difficult, within the narrow confines of the chambers in which the valves are typically located, to extract the spindle from the stem. This is a long-standing problem in the water industry. It is extremely expensive to excavate and widen the chamber, but this is still necessary in order to extract the spindle without damaging the valve, whenever the false spindle is bound fast to the valve stem.

It is an object of the present invention to overcome, or at least ameliorate, the above identified problems.

A tool according to the present invention comprises i) a force-transmitting elongate stock, having a distal end and a proximal end ii) at the distal end, a yoke to fit around the stem, behind the false spindle iii) at the proximal end, an impulse-receiving surface adapted to receive an impulse, and iv) means to deliver to the surface an impulse in a direction along the axis of the stock and with the resultant impulse on the axis of the stock, from the distal end towards the proximal end, for generating an endwise tension in the stock, thereby to urge the spindle off the end of the stem.

Normally, the yoke is no more than a bifurcated plate-like member welded to the distal end of the stock, perpendicular to its length. If desired, as a safety device, a bolt or some other restraining means can be extended across the jaw of the yoke, on the other side of the valve stem from the stock, in order to retain the yoke on the stem when the impulse is delivered to the stock.

In one preferred embodiment, the impulse-receiving surface is nothing more than a flat plate welded to the proximal end of the stock, on the axis of the stock, so that it extends transversely outwardly of the circumference of the stock. Captivated on the stock, in this preferred embodiment, is the means to deliver the impulse, namely a cylindrical member, of large inertial mass and conveniently including a pair of handles arranged on the diameter of the cylinder.

In use, the cylindrical member is grasped by its handles and urged towards the plate at the proximal end of the stock. On impact with the plate, a large impulse is delivered to the plate and thereby transmitted, as a tension force, along the length of the stock, from its proximal end to its distal end, thereby delivering the same tension impulse to the yoke. With the upper surface of the yoke flush with the undersurface of the false spindle, the impulse is fully transmitted across from the yoke to the false spindle. Usually one blow with the cylindrical member against the end plate of the stock is sufficient to drive the false spindle off the end of the valve stem. In particularly difficult cases, however, several blows may be necessary.

Of course, other means of generating the tension impulse at the proximal end of the stock will be apparent to those skilled in the relevant art.

The drawing is a perspective view of the parts of a preferred embodiment of the tool according to the invention.

In the drawing, the device 10 comprises a steel stock 11 with a diameter of 2.5 cm and a length of around 120 cm. At its lower end is a yoke 12 made from a piece of steel plate with thickness 2.5 cm. A U-shaped recess 13 is flanked by a first jaw 14 and a second jaw 15, the mouth of the recess having a width of around 4.5 cm and the depth of the recess being around 5.5 cm. Overall, the plate has a length, that is, a lateral extent relative to the stock 10, of about 10 cm and a transverse width of about 7 cm.

The impulse-receiving plate 16 at the proximal end of the stock 11 has a length of about 7 cm and a width of about 4.5 cm. It is also made of steel plate with thickness 2.5 cm (1 inch).

Welding the plate 16 to the stock 11 captivates on the stock 11 the impulse-delivering cylindrical structure 17. This has a core 18 which is a heavy steel tube which slides with some spacing on the stock 11. Welded to the length of the tube 18, at opposite sides of a diameter to the tube, are first and second impulsive masses 19 and 20 which are of steel plate with thickness 1.25 cm. Each plate is 5 cm wide and about 18 cm in length. Handles 21 and 22 project laterally from the impulsive masses 19 and 20, being welded to them such that the two handles share the same longitudinal axis. The handles are of steel bar with diameter 2.2 cm and are provided with rubber hand grips.

In use, to break the bond of a false spindle to the stem of a gate valve which is part of an underground water distribution network, all that is necessary is to introduce the distal end of the tool into the valve chamber and install the yoke behind the false spindle, around the stem of the valve. While one person holds the stock, another can grasp the handles 21 and 22 and thrust the cylindrical tube 18 upwardly into impact with the plate 16, for delivery of a tension force through the stock 11 to the yoke 12. A single blow is usually sufficient to release the spindle from the stem, but several blows can be delivered in cases of difficulty. Alternatively, each of two people can grasp the stock 11 with one hand and one of the handles 21 and 22 with the other hand, working co-operatively to deliver a particularly powerful impulse to the plate 16.

Experiments by the Applicant have shown that success is dependent on the impulse being delivered on the axis of the stock. Merely striking the underside of a shoulder at the proximal end of the stock with an ordinary hammer has proved ineffective, perhaps because the energy of the hammer blow is absorbed in bending stresses in the stock rather than tensile stress delivered to the false spindle.

The device solves rather economically an expensive problem which the water industry has endured for a very considerable period of time.

Claims (7)

1. A tool for freeing the false spindle of a projecting valve stem, where lateral access to the stem is restricted, the tool comprising: i) a force-transmitting elongate stock, having a distal end and a proximal end ii) at.the distal end, a yoke to fit around the stem behind the false spindle iii) at the proximal end, an impulse-receiving surface adapted to receive an impulse, delivered in a direction along the axis of the stock from the distal end towards the proximal end, and transmit the impulse to the stock as an endwise tension in the stock, thereby to urge the spindle off the end of the stem.

2. A tool as claimed in claim 1 wherein the yoke is a bifurcated plate-like member perpendicular to the length of the stock.

3. A tool as claimed in claim 2 including a restraining means across the jaw of the yoke, for retention of the yoke on a valve stem.

4. A tool as claimed in any one of the preceding claims wherein the impulse-receiving surface is a flat plate at the proximal end of the stock which extends transversely outwardly of the circumference of the stock.

5. A tool as claimed in any one of the preceding claims in which the means to deliver the impulse is a cylindrical member captivated on the stock.

6. A tool as claimed in claim 5 wherein the cylindrical member is provided with a pair of handles by which the cylindrical member can be grasped and urged towards the impulse-receiving surface for impact therewith.

7. A tool for freeing the false spindle of a projecting valve stem, substantially as hereinbefore described and shown in the accompanying drawing.