GB2115107A - Pressure control valve for pressure cookers - Google Patents

Abstract

A pressure control valve assembly attachable to a pressure cooker 2 providing adjustable loading of a displaceable valve member 10. The loading is provided by two weights 15, 20 arranged in a nested stack. The inner weight 15 is secured to the valve member 10 so as to load the latter, while the second weight 20 is rotatable between a first position in which its weight is supported by a cam member 6, a second position in which the second weight loads the valve member, and a third position in which the second weight lifts the valve member 10 by flange 14 to a venting position. <IMAGE>

Description

SPECIFICATION Improvements in or relating to pressure control valves for pressure cookers The invention relates to a pressure control valve suitable for use in a pressure cooker, particularly a domestic pressure cooker.

It is known to control the operating pressure of a domestic pressure cooker by means of a needle valve loaded by a weight. Since it is desirable to provide adjustment of the operating pressure, several weights are usually provided, the user removing or adding weights as required to change the load on the needle valve.

Known systems, requiring the removal and addition of weights suffer various disadvantages including, for example, the tendency for weights to be misplaced and the need to disassemble and assemble the weights when the operating pressure has to be changed.

It is an object of the present invention to alleviate the problem just mentioned.

According to the present invention, a pressure control valve assembly for a pressure cooker comprises a vent pipe for venting to atmosphere the interior of the pressure cooker, a control valve for closing the vent pipe, a plurality of weights for loading the control valve to determine the pressure at which the interior of the pressure cooker is vented, a surface for supporting some at least of the weights in a position in which they do not load the control valve, each of said some weights being transferable from the surface to the control valve to load the latter and from the valve to the surface to unload the valve, the means for preventing the removal of the weights from the assembly.

Preferably, one of the weights is operatively linked to the control valve and the surface provides a further support position for the said one weight in which further position the control valve is moved by the one weight to a location in which it opens the vent pipe to atmosphere.

Another of the weights may be connected to the control valve in such manner as to load the latter, the said other weight not being transferable to the supporting surface.

The surface may be a cam surface, each of said some of the weights being movable relatively to the cam surface between a first position in which the weight is supported by the cam surface and a second position in which the weight loads the control valve.

The weights may be nested one within the other, the cam surface being concentric with the axis of the vent pipe, each of said some weights being rotatable about said axis relatively to the cam surface to move the weight between the first and second positions.

The assembly may comprise a first weight secured to the control valve and a single second weight movable between the first and second positions.

The second weight may have three equi-spaced legs for supporting it on the cam surface, the latter having three identical parts each of which provides a first position in which the second weight is supported by the surface, a second position in which the second weight loads the control valve, and a third position in which the control valve is lifted clear of the vent pipe by the second weight.

By way of example only, a domestic pressure cooker with a valve assembly embodying the invention will now be described in greater detail with reference to the accompanying drawings of which Figure 1 is a sectional elevation through a centre line of the pressure control valve assembly and part of a pressure cooker, Figure 2 is a view, in the direction of arrow A in Figure 1, of the valve assembly only with a part cut away, Figure 3 is a plan view of the assembly only with certain components removed, and, Figures 4 and 5 are scrap views taken in the direction of arrows B and C in Figure 3.

Shown in Figure 1 is a pressure control valve assembly including a tubular vent pipe 1 secured in a central aperture in the lid 2 of a domestic pressure cooker. Only part of the lid is shown in the Figure 1, the remainder of the lid and the pressure cooker itself are of conventional design and will not be described further. The bore of the vent pipe communicates with the interior of the pressure cooker.

The vent pipe 1 is screw threaded over its lower (as seen in Figure 1) part as at 3 and has an outwardly-extending flange 4 seated in a central recess in the floor 5 of a shallow cup-shaped cam member 6 to be described in more detail below.

The upper part of the vent pipe 1 is formed as an enlarged head 7 of rectangular transverse cross section, the upper end of the head being contoured as at 8 to form a seating for an inverted, frustoconical surface 9 of the displaceable valve member 10.

The vent pipe 1 is secured to the lid 2 by means of a nut 11 screwed over the threaded part 3 of the pipe, the flange 4 clamping the cam member 6 in position against the lid 2.

The valve member 10 has a threaded portion 12 that separates the valve member 9 from a part 13 of greater diameter than the portion 12. That part 13 terminates in a head 14.

Encircling the upper part of the vent pipe lisa first weight 15 of inverted cup-shaped form.

The wall 16 of the weight 15 has a central, threaded aperture, whilst the interior dimension of the cup just exceeds that of the head 7 which acts as a guide for weight 15 as will be described later. The weight 15 is secured to the valve member 10 by screwing the portion 12 of the latter into the threaded aperture in the wall 16.

The interior wall 17 of weight 15 has a circum ferential groove 18 in which a circlip 19 is seated, the latter preventing separation of the vent pipe 1 and weight 15 during operation, whilst allowing removal for cleaning purposes by exerting a force which will overcome the resistance of circlip 19.

A second weight 20 also of generally inverted, cup-shaped form is nested externally of the weight 15asshown in Figure 1.Thetop21 ofthe weight 20 is recessed as at 22 and centrally of the recess 22 is an aperture 23 through which extends the portion 13 of the valve member 10.

The lower edge 24 of the side wall 25 of the weight 20 has three equi-spaced, downwardly extending legs of which one, referenced 26, is seen in Figure 2.

Each leg 26 has a bottom face with a portion 27 with a slight downward inclination and a portion 28 with a much sharper upward inclination.

A portion of the cam member 6 is also shown in Figure 2. Member 6 has a cam surface formed on the upper edge 29 of its curved wall which wall is concentric with the axis of the vent pipe 1. The portion of the cam surface is shown in Figure 2 and this portion is repeated over three parts of the edge 29 as is shown in Figure 3.

Each cam surface comprises a horizontal part 30 bounded on one side by a vertical edge 31 that merges with the part 30 via a curved edge 32, and on the other side by an upwardly-inclined part 33 that leads into a part 34 having a slight downwards inclination. Part 34 is followed by part 35 that is upwardly inclined rather sharply and by part 36 having a downwardly inclination similar to that of part 34. Finally, the part 37 that succeeds part 36 is upwardly inclined at an angle similar to that of part 35 and leads into a horizontal portion 38 that separates the portion of the cam surface just described from the next, similar cam surface portion.

As can be seen from Figure 2, the upper part of wall 31 is bevelled as at 39.

Fitting closely over the outerweight20 is cover 40 of a plastics material. The cover may be removably secured to the weight 20 and it extends downwardly to an extent sufficient to encompass the upper part of the curved wall of the cam member 6 and the edge 29 thereof.

Adjacent its lower edge, the cover has a ring of small apertures through its wall, one of the apertures being indicated at 40a.

It will be understood that the vertical position of the weight 20 depends upon which parts of the cam surface the legs 26 rest on. The arrangement is such that the following conditions are met: (1) With the legs 26 seated as shown in Figure 2 on the parts 34 and 35, whose inclinations match those of the portions 27 and 28 respectively, the vertical position of the weight 20 is as shown in Figure 1. In that position, the weight 20 is entirely supported by the parts 34 and 35 of the cam surface, the matching contours providing a stable, well defined position.

(2) With the legs 26 located directly above the parts 30 of the cam surface, the vertical position of the weight 20 is such that it is supported entirely by weight 15. That is to say, weight has been lowered bringing surfaces 41 and 42 of the weights 15 and 20 into contact. This position is identified by anticlockwise rotation of the weight 20 so bringing the legs 26 into contact with the vertical wall 31.

(3) With the legs 26 seated upon the parts 36 and 37, whose inclinations match those of the portions 27 and 28 of the legs, the weight 20 is lifted to an extent which brings the bottom of the recess in the upper face 21 of weight 20 into contact with head 14 and lifts the latter sufficiently to raise the surface 9 well clear of seat 8. Again, the matching contours provide a stable, well-defined position.

In this way, the valve member 10 is loaded either by weight 15 alone (condition (1) above), or by weights 15 and 20 (condition (2) above) or the valve member is lifted clear of its seating (condition (3) above). Thus, the interior of the pressure cooker is pressurised to an extent determined by weight 15 or by weight 15 + weight 20; or the interior is at atmospheric pressure.

By rotating the outer weight 20, the user can preselect the pressure inside the cooker to one of the values just indicated. The lid 2 of the cooker may have a scale indicating the rotational positions of the outer weight 20 required to give the pressure conditions inside the cooker required for a particular cooking operation.

Once the required pressure has been selected, the contents of the cooker are heated and thereby the pressure inside the cooker starts to increase. When the selected pressure is reached, valve member 10 is lifted off the seat 8 and steam vents up the vent pipe 1, down between the flat faces of the valve head 7 and the inside surface of the inner weight 15, across the recess 5 over the top of the wall 6 and to atmosphere via the holes 40a. Once venting has occurred, the user reduces the heat input to the cooker to maintain the selected pressure.

The embodiment just described has the advantage that it is a unitary assembly which makes it difficult for a user to misplace either of the weights. Moreover, it is much easier for a user to effect the changeover from steaming to pressure cooking than with many conventional arrangements.

Although the embodiment described above has provision for only three different weight loadings of the valve member 10, it will be appreciated that more and less than three different loadings are possible. For example by eliminating the weight 20 and providing the weight 15 with a cam surface, the assembly will allow either pressure cooking at one predetermined pressure or steaming at atmospheric pressure.

Similarly, by adding a further weight in nested relationship with weight 20, and another cam surface and by making provision for independent rotation of weight 20 and the further weight, another different weight loading of the valve member 10 is provided.

Claims (11)

1. A unitary pressure control valve assembly for mounting upon a pressure cooker comprising a vent pipe for venting to atmosphere the interior of the pressure cooker, a control valve for closing the vent pipe, a plurality of weights for loading the control valve to determine the pressure at which the interior of the pressure cooker is vented, a surface for supporting some at least of the weights in a position in which they do not load the control valve, each of said some weights being transferable from the surface to the control valve to load the latter and from the valve to the surface to unload the valve, and means for preventing the removal of the weights from the assembly.

2. An assembly as claimed in claim 1 in which one of the weights is operatively linked to the control valve and in which the surface provides a support position for the said one weight in which position the valve member is moved to a location in which it opens the vent pipe to atmosphere.

3. An assembly as claimed in claim 1 or 2 in which another of the weights is connected to the valve member in such manner as to load the latter, the said other weight not being transferable to the supporting surface.

4. An assembly as claimed in any one of the preceding claims in which the surface is a cam surface, each of said some of the weights being movable relatively to the cam surface between a first position in which the weight is supported by the cam surface and a second position in which the weight loads the control valve.

5. An assembly as claimed in claim 4 in which the weights are nested one within the other, in which the cam surface is concentric with the axis of the vent pipe, and in which each of said some weights if rotatable about said axis relatively to the cam surface to move the weight between the first and second positions.

6. An assembly as claimed in claim 5 in which there is provided a first weight secured to the control valve and a single second weight movable between the first and second positions.

7. An assembly as claimed in claim 6 in which the second weight has three equi-spaced supporting legs for supporting it on the cam surface and in which the cam surface has three identical parts each of which provides a first position in which the second weight is supported by the surface, a second position in which the second weight loads the control valve, and a third position in which the control valve is lifted clear of the vent pipe by the second weight.

8. An assembly as claimed in claim 7 in which the weights are of inverted cup-shaped form the innermost weight being secured to the valve member, and in which the valve member extends through the second weight and has a head by which the valve member is lifted by the second weight.

9. An assembly as claimed in claim 8 in which the vent pipe has a portion whose surface comprises a guide surface for guiding movement of the first weight.

10. A control valve assembly substantially as described with reference to and as illustrated by the accompanying drawings.

11. A pressure cooker including a pressure control valve assembly as claimed in any one of the preceding claims.