Ball valve assembly

Abstract

A dielectric insulating insert arranged to be positioned between a drive shaft and a ball shaft of a motorised ball valve assembly. The insert includes a body of dielectric material to form an insulating layer and having opposing sides from each of which extends an engagement portion having a non-circular cross-section and configured to engage, respectively, with the drive shaft and the ball shaft in torque transfer engagement.

Claims

1. A dielectric insulating insert arranged to be positioned between a drive shaft and a ball shaft of a motorised ball valve assembly, the insert comprising: a substrate having opposing sides from each of which extends an engagement portion having a non-circular cross-section and configured to engage, respectively, with the drive shaft and the ball shaft in torque transfer engagement, wherein the engagement portions define a series of lobes; a dielectric layer formed on the substrate; and an outer adhesive layer formed on over the dielectric layer on the engagement portions.

2. The insert of claim 1, wherein the outer adhesive layer is formed of an elastic adhesive.

3. The insert of claim 1, wherein the substrate comprises aluminium.

4. The insert of claim 3, wherein the dielectric material comprises a plasma electrolytic oxidation (PEO) aluminium layer on the substrate.

5. A ball shaft assembly comprising: a ball shaft; and an insert as claimed in claim 1 fitted to the ball shaft.

6. The assembly of claim 5, further comprising: a motor arranged to drive the ball shaft via the drive shaft, the insert located between and in torque transfer engagement with the ball shaft and the drive shaft.

7. The assembly of claim 6, further comprising: a handle to manually rotate the ball shaft.

8. The assembly of claim 6, wherein the motor is an electric motor.

9. A water supply system comprising: a ball shaft assembly comprising: a ball shaft; and an insert as claimed in claim 1 fitted to the ball shaft.

10. The water supply system of claim 9, being an aircraft water supply system.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Preferred embodiments will now be described by way of example only, with reference to the drawings in which:

(2) FIG. 1 is a perspective view of a motor driven ball valve assembly according to this disclosure;

(3) FIG. 2 is an exploded view of the assembly of FIG. 1;

(4) FIG. 3 is a perspective view of a dielectric insulator insert for an assembly in accordance with the disclosure;

(5) FIG. 4 shows individual components assembled to form the insert of FIG. 3; and

(6) FIG. 5 is a sectional view of an assembly incorporating a dielectric insulator insert according to the disclosure.

DETAILED DESCRIPTION

(7) FIG. 1 is a perspective view of a motorised ball valve assembly including a dielectric insulation component according to the present disclosure.

(8) The operational part of the valve comprises a ball shaft 10 having a hole 12 therethrough defining a flow passage. In use, the valve is arranged in a water or fluid pipe system such that in a first rotational position of the ball shaft 10, the hole is aligned with a fluid pipe to form a flow passage from the pipe and through the hole 12. To switch off the flow, the ball shaft is rotated e.g. by one quarter turn, so that the hole is no longer aligned with the pipe and, instead, flow from the pipe is blocked by the body 13 of the ball shaft.

(9) In a motorised ball valve, the ball shaft is rotated by means of an electric motor 1. The electric motor 1 drives a cam shaft 4 which engages with the ball shaft 10. In the example shown (see FIG. 2) the cam shaft 4 is provided with a key feature 3 that engages with a D-shaft 2—i.e. a D-shaped shaft component extending from the motor. Rotation of the motor 1 causes rotation of the D-shaft 2 which, in turn, rotates the cam shaft 4 which rotates the ball shaft 10. Seals e.g. O-rings 11 are provided around the ball shaft 10 to prevent water passing into the electric part of the assembly. The cam shaft may be provided with indicators such as microswitches which can be mounted in recesses or races 14 on the cam shaft 4 to provide an indication of the angular position of the shaft. These components are standard for a motorised ball valve such as described in U.S. Pat. No. 8,172,198.

(10) As mentioned above, to provide the required strength and to satisfy other standards such as safety, life and hygiene standards, the various shafts and the key feature will often be made of metal e.g. steel. If there is a problem with the electrics at the motor end of the assembly, these would be transmitted directly to the ball shaft and can cause problems such as electric shocks or arcing. To avoid this problem, the assembly of the present disclosure includes a dielectric insulator insert 20 to be fitted between the ball shaft 10 and the electric motor 1.

(11) The dielectric insulation insert is structured to have dielectric properties and is shaped to provide torque transmission from the electric motor 1 to the ball shaft 10. The shape of the insert should be such as to be able to withstand a short torque peak if the ball shaft end is fixed or blocked. To achieve the torque transfer property, the insert is shaped to define lobes or lugs or ribs or the like that engage into corresponding features provided at the ball shaft and the electric motor. In the example shown, the insert 20 is in the form of a plate 21 from each surface of which extends an engagement portion 22, 23 having a non-circular outer profile. In the example shown, the profile forms rounded lobes 24 but other shapes may also be used. The important thing is that the engagement portion has a shape that can engage with the shafts between which it is located in a manner that torque applied to one of the shafts is transferred to the other shaft via the insert.

(12) In a one embodiment, the shape of the insert will be such that the insert remains centered in position relative to the shafts i.e., so that co-axiality between the shafts and the insert is ensured.

(13) It may also be desired that the insert is designed to minimise or avoid backlash between the shafts. Backlash can result in inaccurate calculations due to small errors introduced at each change of direction. At large power outputs, backlash sends shocks through the whole system and can damage components. To address the problem of backlash, in a preferred embodiment, the dielectric insulation insert is provided with adhesive around the engagement portions. An elastic adhesive layer allows the assembly to accommodate larger manufacturing tolerances, which results in lower production costs since the components do not need to be so precisely manufactured—rather, the adhesive can fill in any small gaps. The adhesive provides a bond between the insert and the shafts which prevents or minimises backlash.

(14) The insert may have dielectric properties. Various dielectric materials are known and can be used. A dielectric that has been found to work particularly well with the insert is formed by a plasma electrolytic oxidation aluminium coating (PEO-aluminium) coating on an aluminium substrate, but this is an example only and other dielectric materials or substances could also be used.

(15) One design of the insert will be described in more detail below.

(16) In the event that the motor fails, there is not only the risk of an electrical fault being transmitted to the wet end of the assembly, but there is also the problem that a motor failure will mean that the ball shaft cannot be rotated. In the event of failure of the motor, it may be necessary to change the position of the ball shaft to switch flow on or off. To address this, a manual handle 8 may be provided in close fitting arrangement around the ball shaft so that manual operation of the handle 8 can rotate the ball shaft 10. The handle 8 can be fitted to the ball shaft such that there is a form fitting or frictional engagement between them. Alternatively, a fixing element e.g. a locking pin 9 may be provided to secure the handle to the shaft.

(17) The dielectric insulation insert of the disclosure, in use, will have one side mounted inside or otherwise fitted to the ball shaft in a manner to transfer torque to the ball shaft 10. The other side of the insert will be fitted into or engaged with the cam shaft 4 for engagement with the motor 1. This can best be seen in FIG. 5.

(18) The one embodiment structure of the insert, as will be described in more detail below, can be seen in situ in the enlarged detail of FIG. 5. The inner part of the insert is a substrate, preferably an aluminium substrate 5 for greater strength, over which is formed the dielectric PEO-aluminium layer 6 (or other dielectric coating). The adhesive bond layer 7 is then formed over the insert as an outer layer to provide an adhesive bond with the cam and ball shafts. While aluminium and PEO-aluminium have particular advantages, other substrate and dielectric materials can be used.

(19) FIG. 4 shows the component parts of the insert in the preferred embodiment. As described above in relation to FIG. 5, a substrate is first formed having the shape required for the torque transfer fitting as described above. A plasma electrolytic oxidation coating 6 is then formed on the substrate 5. A glue or adhesive bond layer 7 is then formed as the outer layer. This results in an integral unit forming the insert 20 that can then be fitted into place between the shafts. The thickness of the PEO coating should be such as to provide sufficient electrical insulation. PEO-aluminium coating has a dielectric strength ranging from 14.6-16.7 kV/mm. A thickness of around 300 micrometers was found to provide good insulation against voltage of 4.4 kV to 5 kV. The use of a PEO coating was found to provide high electrical resistivity and high dielectric strength.

(20) The dielectric insulation insert provides electrical insulation between the dry and wet parts of the motorised ball valve assembly whilst ensuring torque transfer between the shafts of the respective parts. An adhesive layer as the outer layer of the insert ensures secure coaxial location of the insert and prevents or minimises backlash and damps vibrations. The coaxial location and the adhesive help in reducing component wear. The use of an elastic adhesive can also accommodate greater manufacturing tolerances. The use of an aluminium substrate provide superior strength properties.