GB2201752A - Gas tap - Google Patents

Abstract

A gas tap has a low flow rate control provided by a passage 16, 18 parallel to the inlet passage 10. Both passages open to the space 30 which accommodates the rotatable plug of the tap. The two passages are connected by an angled drilling made along an axis 50 from the same end face 20 to which the two parallel passages open. Alternatively, the passage 16, 18 and inlet 10 are connected by a peripheral groove in the inlet 10 which breaks into the passage 16, 18 (Fig. 5), or by a screw-threaded portion of the passage 16, 18 breaking into the inlet 10 (Fig. 1) An adjuster screw 22 controls the flow rate along the passage 16, 18 by its position relative to the shoulder or seat 26. <IMAGE>

Description

GAS TAP This invention relates to gas taps for domestic appliances such as cookers.

When the flame at a gas burner is turned down by restricting the flow of gas, there is a minimum flow rate necessary to maintain that flame. Below such rate the flame will fail, although gas continues to flow. The actual minimum safe rate depends upon the design of burner for example.

It is known to provide a gas tap with a flow path via a preset adjustable control, so that the minimum safe flow rate can be provided. Hitherto, so far as we are aware, the actual construction of tap for this purpose has been relatively complex and expensive to manufacture, involving many extra machining operations.

In a previous proposal it was suggested to make a plug tap for a gas appliance with an inlet opening radially of the plug.. a minimum flow passage extending parallel to said inlet and also opening to the plug, and a connection between the two parallel passages formed by a portion of a third passage of which the axis lies in a plane substantially normal to the axes of the said parallel passages, the third passage breaking into both of the parallel passages to establish the said connection and being internally screwthreaded over at least a portion of its length to receive and locate a screw, the free end of the screw projecting or being projectable into the said connection to form an adjustable flow restriction.This had the advantage that, in manufacture of the tap, the body is required to be held in one position whilst it is being drilled to provide the (main) inlet, and because the second passage is adjacent and parallel, that second passage can be drilled either at the same time, or at least without needing substantial repositioning of the body. As mentioned no closure plug is needed, and hence all of the required operations on the body from that particular face can be carried out at one and the same time.

The object of the present invention is to provide alternative or improved means for achieving the same effect, possibly advantageously in manufacture.

According to the invention a plug tap for a gas appliance has an inlet opening radially of the plug, a minimum flow passage extending parallel to said inlet and also opening into the plug, and a connection between the two parallel passages, said parallel passage being screwthreaded over at least a portion of its length so as to receive and locate a screw, and said screw being adjustable axially relative to a shoulder in the passage to form an adjustable flow restriction.

The invention is now more particularly described with reference to the accompanying drawings which illustrate three embodiments: Figure 1, 4 and 5 are similar sectional views of the three embodiments; and Figures 2 and 3 are sections on the line 2-2 and 3-3 of Figure 1.

Referring first to Figure 1, the main inlet flow passage 10 may be radial to the plug axis 12 and form the main flow passage. The second of the passages may be parallel, generally tangential to the plug, and have a smaller diameter portion 16 opening into the plug bore and a larger diameter portion 18 opening into an external face of the tap, herein called a side face 20. The larger diameter portion 16 is internally screwthreaded to receive the adjusting screw 22 which has a conical or frusto-conical end portion 24 to cooperate with the shoulder 26 between the smaller and larger diameter portions and provide control at that point.

The connection between the two passages is essentially between the larger diameter of the parallel passage 18 and the inlet passage 10, so as to open on the opposite side of the shoulder 26, ,which forms the control point, to the plug (not shown, but occupying space 30).

In Figure 1, the two passages overlap. That is to say the axes 32.34 are sufficiently close so that the larger diameter portion of the parallel passage breaks into the inlet port. The overlap may be such that the screw is supported around say 270 degrees of arc, or more (Figure 2).

In the second embodiment, Figure 4, the two passages are spaced but a port 40 opens between the two, for example at an axial point between the screwthreaded larger diameter portion and the smaller portion and this port may be provided by an angled drilling from the inlet into the parallel passage. The angled drilling along axis 50 like the two passages themselves, can be made by a machining operation via the said side face.

In the third embodiment, see Figure 5, the inlet port has an encircling groove or channel 52 part way along its length and that groove breaks through into the parallel passage, again at the point adjacent the shoulder in that passage and effectively between the large diameter portion of the screw and the tip of the screw.

Conveniently, and as shown, the screw in all cases has a larger diameter portion formed with male screwthreads to cooperate with the female screwthreads in the passage, and a smaller diameter portion terminating in the conical or frusto-conical tip, but the smaller diameter portion of the screw is itself of larger diameter than the smaller diameter portion of the passage.

In any of these situations it is necessary to seal the parallel passage against backflow or leakage of gas.

and this may be done for example by sealant applied to the screwthreads, possibly using a sealant of a nature which will lock the screw in position after adjustment has been effected empirically.

Usually the inlet passage will be sealed to a supply manifold or the like and that sealing may extend across the end of the parallel passage so as to provide a further means of preventing leakage.

In all of these cases, the machining can be done from the said side face. It is the same side face which is sealed to said manifold or the like.

As will be appreciated by those skilled in the art, gas can flow from the inlet passage via the shoulderwhen the plug (not shown) is in a position to close off the main inlet but leave the parallel passage open to the space 30.

Claims (6)

1. A plug tap for a gas appliance having an inlet opening radially of the plug, a minimum flow passage extending parallel to said inlet and also opening into the plug, and a connection between the two parallel passages, said parallel passage being screwthreaded over at least a portion of its length so as to receive and locate a screw, and said screw being adjustable axially relative to a shoulder in the passage to form an adjustable flow restriction.

2. A plug tap as in claim 1 wherein the said parallel portion is of larger diameter over the screwthreaded portion and smaller diameter beyond said shoulder, and the screw has a smaller diameter portion extending from the screwthreaded portion, the smaller diameter portion of the screw being of larger diameter than the smaller diameter portion of the passage.

3. A plug tap as claimed in claim 1 or claim 2 wherein the connection between the passages is provided by the screwthreaded portion of the parallel passage breaking into the inlet.

4. A plug tap as claimed in claim 1 wherein the connection between the passages is provided by a peripheral groove opening from the inlet and breaking into the parallel passage.

5. A plug tap as claimed in claim 1 or claim 2 wherein the connection between the passages is provided by an angled port extending from the inlet and opening into the parallel passage.

6. A plug tap for a gas appliance substantially as described with reference to Figures 1 to 3 or 4 or 5 of the accompanying drawings.