GB2107830A - Valve plate for an alternating compressor - Google Patents

Abstract

Valve plate 5 for an alternating compressor is constructed in press- cast metal alloy and has the sealing seats 8 of the valves (on which the valves are directly assembled) formed directly upon it. The valve plate 5 requires mechanical working only at the sealing seats, and an effective cooling of the seats 8 of the valves results due to the material continuity of these with the mass of the plate 5 through which the heat is removed. Cooling is further enhanced if plate 5 is provided with a cooling fin 6 as illustrated. Furthermore, the plate is preferably shaped so as to reduce to a minimum the dead spaces at the top of the cylinders of the compressor. <IMAGE>

Description

SPECIFICATION Valve plate for an alternating compressor This invention concerns a valve plate for an alternating (or reciprocating) compressor, namely a plate intended to be applied at the top of a compressor cylinder or group of cylinders and carrying, for each cylinder, one or more suction valves and one or more delivery valves. In particular, the valve plate to which the invention applies is of the type having disc valves urged elastically against sealing seats.

In known constructions, such a valve plate is equipped with valve seats which are separately assembled and fitted to the plate. Each such valve set comprises a sealing seat, a closure disc cooperating with the seat, elastic means for urging the disc against the seat and means generally in the form of an axial bolt-for assembling the said parts. Each valve set is fitted to the plate by fixing the respective valve seat in a suitable cavity formed in the plate. The plate is mounted, with interpolation of packing, between the cylinder or block of cylinders of the compressor and an overhanging suction and delivery collector, both the cylinder and the collector having fins for the purpose of cooling.

Cooling of the plate and of the valves occurs principally by conduction towards the cylinder and the collector.

In such known constructions of valve plates, the cavities destined to receive the seats of the valve sets must be formed with great accuracy and this has a considerable effect on their production cost. Moreover, the cooling of the valve seats (which constitute the parts of the compressor which tend to be under highest thermal stress) is not efficient because the discontinuity of material hinders transmission of heat from the valve seats to the plate, through which the cooling takes place. Furthermore, the transmission of heat from the plate to the cylinder and the collector, (which are cooled because they are finned) is inevitably hindered by the interposed sealing packing. Finally, in the known plates, the conformation necessary for fitment of the detachable valve seats introduce dead spaces which have a detrimental effect on the efficiency of the compressor.

An object of the present invention is to provide an improved valve plate of the kind alluded to wherein its production is simpler and more economical than hitherto, wherein dead spaces are reduced to a minimum and wherein cooling of the seats of the valves is more effective than with previous valve plates.

With this object in view, the present invention provides a valve plate, of the type having disc valves urged elastically against sealing seats, for an alternating compressor, characterised in that the plate is made of press-cast metal alloy and has cavities, the bases of which form the sealing seats for the valve sets which are assembled directly above said seats.

As a result of the aforesaid feature, production of the plate is considerably simplified because only a brief machining or grinding of the sealing surfaces of the valve seats is required, all the remaining surfaces being readily obtained in their required final form by an accurate press-casting operation.

The fact that the seats of the valves cease to exist as separate components also has a favourable influence on the economy of production.

Furthermore, as the seats of the valves are formed by the plate itself, these ceases to be discontinuity of material between the zone to which thermal stress is applied and the plate through which the heat is removed. Thus, a reduction of local high temperature points and therefore a longer life of the valves is ensured.

Finally, the fact that couplings between the plate and the valve seats are not required in a valve plate according to the invention makes it possible to simplify the entire conformation by providing the valve plate with a perfectly flat surface with which to face the cylinder or the block of the cylinders of the compressor, thereby avoiding any unnecessary dead space.

The valve plate preferably extends peripherally to form a cooling fin which, when mounted in the compressor will be interposed between the fins of the cylinders and the fins of the collector.

The aforesaid feature ensures direct cooling of the valve plate by way of the fin which is in metallic continuity with the plate and therefore ensures unimpeded transmission of heat therefrom. This results in a considerable increase in the dissipation of heat from the valve plate, with consequent further reduction of the high temperature points which stress the valves.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a side elevation illustrating a compressor equipped with a preferred embodiment of the valve plate of the invention; Fig. 2 is a view to a larger scale of the underside of the same embodiments of the valve plate in accordance with the invention; Fig. 3 is a side elevation of the same valve plate; Fig. 4 is a plan view of the same valve plate; Fig. 5 is a cross-section on an even larger scale taken along the line V-V of Fig. 4; Fig. 6 is an exploded side view of the components of a delivery valve set in the previously illustrated valve plate; Fig. 7 is a plan view of a retaining member of the valve; Fig. 8 is a plan view of a resilient disc of a valve; and Fig. 9 is a plan view of a closure disc of a valve.

The compressor shown in Fig. 1 comprises a block 1, the lower part of which, accommodates a driving shaft 3, and which extends upwardly to form cylinders provided with cooling fins 2. A valve plate 5 in accordance with the invention is mounted above the block of the cylinders and above said plate 5 is mounted a suction and delivery collector 4 which also has fins. Sealing packings are interposed between the cylinders, the valve plate and the collector. As shown in Fig.

1, the valve plate 5 in accordance with the invention extends peripherally to form a cooling fin 6, which continues the external line of the fins 2 of the cylinders and the fins of the collector 4.

Since a double cylinder of bi-cylinder compressor has been chosen as an example the valve plate 5 comprises four valves, i.e. two suction valves and two delivery valves. It will be appreciated, however, that the invention may also be applied to a single-cylinder compressor, to individual cylinders of compressors having separate cylinders or to blocks of any number of cylinders of compressors having more than two cylinders.

The plate 5 is press-cast in metal alloy, and, as indicated in Figs. 2 and 5, its lower surface, destined to be turned towards the cylinders, is substantially flat to reduce to a minimum the dead spaces. On the other hand, the upper face, shown in Fig. 4, has ribs and hollows suitably arranged to allow accurate press- asting, and to obtain with minimum weight a suitable rigidity.

As shown in Fig. 5, the sealing seats 8 of the valves are formed directly by the bases of cavities in the plate 5, which cavities correspond with traversing passages 7, for respective suction or delivery according to the function of the various valves. In the suction valves the sealing seat faces towards the lower surface of the plate, whereas in the delivery valves the sealing seats face towards the upper surface of the plate 5.

A closure disc 9 in the form of an annular washer cooperates with each sealing seat 8. Each disc 9 is restrained and guided by a retaining member 10 fixed above the seat 8 by means of a screw 12 with a conical head 13 and of a nut 14.

The conical head 1 3 of the screw 12 is inserted into a corresponding recess in the plate 5 for the delivery valves, or into a corresponding recess in the retaining member 10 for the suction valves, so that all the heads 1 3 are disposed on the lower surface of the plate 5 and all the nuts 14 are disposed on the upper surface. Thus, the desired planarity of the lower surface of the plate 5 is maintained.

Between each closure disc 9 and the corresponding retaining member 10 is located elastic means urging the disc 9 against the corresponding seat 8. In the illustrated embodiment, the elastic means is constituted by a pair of resilient discs 1 5 each having an interruption or split 1 6 and being deformed helically. These discs 1 5 are arranged with their interruptions or splits 1 6 diametrically opposed, as shown in Fig. 6. The discs 1 5 are made of spring steel and together, arranged in this way, form a spring operative to urge the closure disc 9 uniformly against the seat 8, and which can be repeatedly flattened (as will occur during operation of the compressor) without losing its elasticity.To ensure that the required relative positions of the discs 1 5 are maintained, i.e. that they have their splits 1 6 diametrically opposed, each disc 15, has a central non-circular aperture 1 7, for example a hexagonal aperture, and the hub 11 of the retaining member 10 is correspondingly hexagonal with bevelled vertices, so as to constitute an effective guide both for the resilient discs 1 5 and for the closure disc 9.

It will be readily understood, that the valves made up of the components 9 to 16 are assembled directly on the respective sealing seats 8 formed by the plate 5. When, after long use, the valves have undergone a great deal of wear and tear or are spoiled, their substitution is simple.

Either the entire valve plate is replaced or the valves or individual worn or spoiled parts thereof are replaced, or both, as appropriate.

It will be understood, particularly from Fig. 5, that the heat which especially stresses the seats 8 of the delivery valves flows directly into the mass of the plate 5. Part of the heat is conducted towards the upper and lower surfaces of the plate 5 and from here is transmitted to the other cooled parts of the compressor. However, a considerable proportion of the heat is also conducted towards the directly cooled fin 6, so that the seats 8 are effectively protected against overheating, thereby increasing the life of the valves.

It will be understood that the particular shape of the plate 5 and the arrangement in it of the valves may vary depending on the design of the compressor. Also other particular dispositions may be modified, and all the parts indicated may be replaced by their technical equivalents, without thereby departing from the limits of the invention.

Claims (8)

Claims

1. A valve plate, of the type having disc valves urged elastically against sealing seats, for an alternating compressor, characterised in that the plate is made of press-cast metal alloy and has cavities, the bases of which form the sealing seats for the valve sets, which are assembled directly above said seats.

2. A valve seat as claimed in claim 1, characterised in that mechanical working in its production is limited to machining or grinding of the sealing surfaces of the seats.

3. A valve plate as claimed in claim 1 or 2, characterised in that it extends peripherally to form a cooling fin which is intended to be disposed between and in line with the respective cooling fins of the cylinders and of the collector of the compressor.

4. A valve plate as claimed in claim 1, 2 or 3, characterised in that each valve set comprises an annular closure disc, at least one spring member, and a retaining and guiding member for the aforesaid components, assembled directly on the seat of the valve by means of a screw having a head which is set in the surface of the plate destined to be turned towards the cylinders of the compressor, and by a nut situated on the opposite side of the plate.

5. A valve plate as claimed in Claim 4, characterised in that the heads of the said assembly screws are conical and are set in corresponding recesses provided, for delivery valves, in the valve plate, and, for suction valves, in the retaining members.

6. A valve plate as claimed in claim 4 or 5, characterised in that each spring member is formed of a pair of resilient discs which are each interrupted or split and helically deformed, which are arranged with their interruptions or splits diametrically opposed and which are held in position by a non-circular hub of the retaining member cooperating with a correspondingly noncircular central aperture of the resilient discs.

7. A valve plate as claimed in any preceding claim, characterised in that its surface opposed to the one destined to be turned towards the cylinders of the compressor has a plurality of ribs and hollows.

8. A valve plate for an alternating compressor substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.