GB2251675A

GB2251675A - Screw-down non-return valve

Info

Publication number: GB2251675A
Application number: GB9200202A
Authority: GB
Inventors: James Kevin Fretwell
Original assignee: Meggitt France SAS
Current assignee: Meggitt France SAS
Priority date: 1991-01-10
Filing date: 1992-01-07
Publication date: 1992-07-15
Also published as: GB9100565D0; GB9200202D0

Abstract

A screw-down non-return valve having a lockable abutment element 13 which, when locked in one position, limits axial movement of a spindle 2 and prevents the valve from being positively opened. When the abutment element 13 is released and withdrawn from its operative position, the spindle 2 can move more freely in a axial direction and hence a valve closure element 9 can be positively lifted from its valve seat 10. <IMAGE>

Description

A SCREW DOWN NON RETURN VALVE The present invention relates to a screw down non return valve.

Screw down non return valves are known in which a valve closure element is not lifted from its seat by a rising spindle, but is left to slide up and down the spindle owing to differential pressure. One use for a valve of this sort is as a "fill" valve on a static cryogenic storage vessel, whereby a road tanker delivering liquid can pump liquid through the valve, but anyone opening the valve when the filling hose of the road tanker is disconnected from the connection will not get liquid back flow through the valve as the pressure difference works to close the valve.

It is desirable for an authorised operator to be able to obtain liquid back flow at certain times, however, with the known type of screw down non return valve, this is not possible.

According to the present invention a screw down, non return valve comprises a body containing two chambers interconnected through a valve seat; a spindle which engages the body via complementary screw threads such that rotation of the spindle causes axial movement of the spindle relatively to the body; a valve closure element captive but axially slidable on an end of the spindle adjacent to the valve seat; and an abutment element which is displaceable between a first position, in which it does not impede axial movement of the spindle, and a second position, in which it is arranged to be locked and in which it limits axial movement of the spindle away from the valve seat; and the arrangement being such that, with the abutment element in its first position, the spindle is axially movable between one end position, in which the closure element is positively held on the seat to close the valve, a second end position, in which the closure element is positively held off the seat to hold the valve open, and an intermediate position, in which the closure element is movable on the spindle under differential pressure in the two chambers to open and close the valve in a non return mode; and with the abutment element in its second position, the spindle is impeded from moving from the one end position beyond the intermediate position.

A screw down non return valve according to the present invention therefore provides a locking mechanism, release of which allows the non return mechanism to be overridden.

Only an operator with a key to the locking mechanism is capable of activating the override and hence obtaining liquid backf low.

The abutment element may be a lever having a projection, which is lockable in a position in which the projection projects into the body to obstruct a projection on the spindle.

An example of a valve constructed in accordance with the invention is illustrated in the accompanying drawings, in which: Figure 1 is an axial section; Figure 2 is a plan of a locking lever; and, Figure 3 is a side elevation of the locking lever.

The illustrated valve comprises a body 1 containing a spindle 2 with a screw threaded portion 3 adjacent to one end engaging with a complementary screw thread 4 in the body. A handle 5 is connected to the top of the spindle 2 and is capable of being rotated manually to rotate the spindle 2 and hence raise or lower it in the body 1.

A part 6 at the lower end of body 1 is divided into an inlet chamber 7 and an outlet chamber 8 which are interconnectable through a valve seat 10. A valve closure element 9, which is captive, but axially slidable, on the lower end of the spindle, cooperates with, to open and close, the seat.

In use, rotation of the handle 5 in one sense lowers the spindle which holds the valve closure element 9 down on the seat 10, as shown in Figure 1, to keep the valve closed. Partial raising of the spindle allows the valve closure element to float up and down on the spindle in response to differential pressure in the chambers 7 and 8, to open and close the seat, in a non-return mode, thus allowing flow only from the chamber 7 to the chamber 8, but not vice versa. This corresponds to the open position in a conventional valve.

A part 11 of the body 1 containing the spindle 2 is enlarged in the form of an open sided yoke, and a collar 12 is fixed to the spindle 2 within the yoke portion 11. A lever 13, pivoted at one end 14 to the body and having projections 15 is disposed adjacent to the enlarged portion 11 of the body 1 and above the collar 12. A padlock 16 is provided to lock the lever 13 in a position in which the projections 15 project into the yoke 11. An annular ring 17 is fixed, to and projects radially outwardly from the end of the spindle 2 An annular shoulder 18 is provided on the valve closure element 9.

In use, when the lever 13 is locked in the engaged position shown in figure 1, upward axial movement of the spindle 2 is obstructed by engagement of the collar 12 with the projections 15, before the ring 17 engages the shoulder 18 so that the valve remains in the non-return mode.

If the padlock 16 is unlocked and the lever 13 is swung away from the body 1, this removes the projections 15 from the yoke 11 and frees the spindle to move further in an upward direction. Such further movement of the spindle 2 causes the annular ring 17 to abut the shoulder 18 and hence to pick up the valve closure element and hold it away from the valve seat 10 thereby opening communication between the two chambers 7, 8 and allowing fluid to flow freely in either direction through the chamber 6.

Claims

1. A screw down, non return valve comprising a body containing two chambers interconnected through a valve seat; a spindle which engages the body via complimentary screw threads such that rotation of the spindle causes axial movement of the spindle relatively to the body; a valve closure element captive but axially slidable on an end of the spindle adjacent to the valve seat; and an abutment element which is displaceable between a first position, in which it does not impede axial movement of the spindle, and a second position, in which it is arranged to be locked and in which it limits axial movement of the spindle away from the valve seat; and the arrangement being such that, with the abutment element in its first position, the spindle is axially movable between one end position, in which the closure element is positively held on the seat to close the valve, a second end position, in which the closure element is positively held off the seat to hold the valve open, and an intermediate position, in which the closure element is movable on the spindle under differential pressure in the two chambers to open and close the valve in a non return mode; and with the abutment element in it second position, the spindle is impeded from moving from the one end position beyond the intermediate position.

2. A valve according to claim 1 wherein the abutment element is a lever having a projection which is lockable in a position in which the projection projects into the body and acts against a projection on the spindle.

3. A valve according to claim 1 or claim 2, wherein an annular ring is fixed to the end of the spindle and projects radially outwardly thereof which cooperates with an annular shoulder on the valve closure element to positively lift the valve closure element when the spindle is in the second end position.

4. A screw down, non return valve substantially as described with reference to the accompanying drawings.