GB2348691A

GB2348691A - Motor driven control valve assembly

Info

Publication number: GB2348691A
Application number: GB9908237A
Authority: GB
Inventors: John Woodman; David William Southern
Original assignee: Horstmann Timers and Controls Ltd
Current assignee: Horstmann Timers and Controls Ltd
Priority date: 1999-04-09
Filing date: 1999-04-09
Publication date: 2000-10-11
Also published as: GB9908237D0

Abstract

A motor driven valve comprises a clutch arrangement which prevents reverse rotation of the motor and so prevents damage to the motor during valve bounce. Preferably, a motor driven shaft 3 has mounted on it a toothed driven sleeve 5 and driving sleeve 7. Sleeves 5 and 7 have adjacent portions of the same external diameters which are surrounded by a close fitting coil spring 17. In use rotation of shaft 3 is transmitted to sleeve 7 by a connection, preferably comprising a slotted collar 9 of sleeve 7 and drive pin, which causes the spring 17 to wrap tightly onto the adjacent portions of sleeves 5, 7. Reverse motion of sleeve 5 (e.g. due to valve bounce) causes unwinding of spring 17 and decoupling of sleeves 5, 7. Alternatively a ratchet may be provided between the drive shaft and driven sleeve.

Description

MOTOR DRIVEN CONTROL VALVE ASSEMBLY This invention relates to a motor driven control valve assembly.

Motor driven control valve assemblies are used in various applications including those in which a three way valve controls the supply of hot water to either a hot water system or to a central heating system. Typically, such a motor driven control valve assembly will comprise a motor acting on a valve spindle via appropriate gearing in order to adjust the position of a valve member attached to the valve spindle.

When the valve member is turned to a fully closed position and engages the aperture which it is intended to close, it can suffer a reaction force which counter-rotates it and transmits a reaction to the motor via the valve spindle and the gearing, which can damage the motor and gearing and reduce its working life.

According to one aspect, the present invention consists in a motor driven control valve assembly comprising a motor, a valve, a valve operating mechanism and transmission means for connecting the motor to the valve operating mechanism when the motion of the latter corresponds to the direction of motion of the motor and for disconnecting the motor from the valve operating mechanism when the direction of motion of the latter does not correspond to that of the motor.

In one embodiment, the transmission means comprises a one-way clutch, preferably a wrap spring clutch. Alternatively, the transmission means comprises a ratchet.

The valve operating mechanismcan simply be a spindle attached to the valve which is driven by the motor, or it could be more complex and may comprise gearing intermediate the motor and a valve spindle.

Embodiments of the invention will now be described by way of example only and with reference to the accompanying figures, in which: Figure 1 shows a first view of a motor driven control valve transmission assembly comprising a wrap spring clutch; Figure 2 is a section through the assembly of Figure 1 in a direction parallel to the longitudinal axis of the drive shaft and perpendicular to the engaging protrusions; Figure3is a side view of the assembly of Figure 1 with the engaging protrusions lying in the plane of the paper; Figure 4 is a side view of the assembly of Figure 1 with the engaging protrusions perpendicular to the plane of the paper; Figure 5 is a view of the assembly of Figure 1 from the end of the drive shaft bearing the engaging protrusions; Figure 6 is a view of the transmission assembly within a motor driven control valve arrangement; and Figure 7 is a view of the valve member within the valve arrangement.

As best seen in Figure 2, the motor driven control valve transmission assembly 1 comprises a motor drive shaft 3 on which are rotatably mounted a toothed driven sleeve 5 and a slotted driving sleeve 7. The sleeves 5 and 7 are mounted on the drive shaft 3 alongside one another with adjacent inner portions of the same external diameter. The driving sleeve 7 terminates, at its outer end in a slotted collar 9 of enlarged external diameter, and the driven sleeve 5 is formed at its outer end with radially extending teeth 11 so that the driven sleeve 5 serves as a cog to drive a valve spindle, preferably via gearing.

At a point adjacent the end of the slotted collar 9 of the sleeve 7, the drive shaft 3 carries a radially extending cross pin with protruding ends 13, best seen in Figures 3 to 5. The outer end of the slotted collar 9 bears two slots 15, each adapted to accommodate one of the ends 13 of the cross-pin. It will be appreciated that when drive shaft 3 rotates, the sleeve 7 will be caused to rotate with the drive shaft 3 by engagement of the ends of the cross pin with the sides of the respective slots 15 in the collar 9. Alternatively, instead of a cross pin with two protruding ends, there may be just one protrusion and a corresponding slot, but symmetrical arrangements are preferred since they confer greater stability.

A coil spring 17 surrounds, and is a close fit with, the inner portions of the drive sleeve 7 and the driven sleeve 5 between the collar 9 and the teeth 11. This spring is coiled in the opposite sense as that in which the drive shaft 3 rotates so that rotation of the shaft 3 and sleeve 7 will cause the spring to wrap more tightly onto the sleeve 7 by virtue of the frictional grip therebetween. In the same way, the spring wraps move tightly onto the driven sleeve 5.

Thus, when the drive shaft 3 rotates, the sleeve 7 and sleeve 5 are effectively coupled together to the drive shaft 3, and the driven sleeve 5 then drives a valve spindle, optionally by way of intermediate gearing cogs.

When the valve member 60 (see Figure 7) driven indirectly by toothed sleeve 5 reaches its end position, in the body 62, any reaction force with cause transient rotation of the toothed sleeve 5 in a direction opposite to the drive shaft 3. However, this counter rotation is not transmitted through the driving sleeve 7 to the drive shaft 3. When the valve member 60 reaches its end position, there is rotation of the driven sleeve 5 relative to the driving sleeve 7 in a direction opposite to the direction in which the drive shaft 3 is being driven by the motor. This relative counter rotation arises because the counter rotation of the toothed sleeve 5 causes the spring 17 to loosen such that it no longer grips or couples the driving sleeve 7 to the driven sleeve 5. It will therefore be appreciated that any counter motion of the valve member when reaching its end position will not be transmitted to the motor or driving gear.

Figure 6 shows the arrangement of the motor driven control valve transmission assembly 1 within the motor driven control valve arrangement. The motor 50 rotates the drive shaft (3, Fig. 2, etc) of the transmission assembly which causes the toothed driven sleeve (5, Fig. 2, etc) to rotate gearing member 52 by acting on the toothed region 54 on the circumference of gearing member 52. The gearing member 52 has a hole 56, in which valve spindle 58 is engaged for rotation with gearing member 52.

Figure 7 illustrates the valve member 60 attached to the valve spindle 58 for cammed rotation therewith to control the opening and closing of the passages within the junction body 62. In an alternative embodiment of the motor driven control valve transmission assembly, not illustrated, a ratchet arrangement is arranged between a drive shaft and a driven sleeve such that the driven sleeve can be driven by the drive shaft in one direction but counter motion of the driven sleeve arising from the valve reacting at its end position is not transmitted back to the drive shaft.

Claims

Claims 1. A motor driven control valve assembly comprising a motor, a valve, a valve operating mechanism and transmission means for connecting the motor to the valve operating mechanism when the motor of the valve operating mechanism corresponds to the direction of the motor and for disconnecting the motor from the valve operating mechanism when the direction of motion of the valve operating mechanism does not correspond to that of the motor.
2. A valve assembly according to claim 1, wherein the transmission mean comprises a clutch.
3. A valve assembly according to claim 2, wherein the clutch is a wrap-spring clutch.
4. A valve assembly according to claim 1, wherein the transmission means comprises a ratchet.
5. A valve assembly according to any preceding claim, wherein the valve operating mechanism comprises a spindle extending from the valve to the transmission means.
6. A valve assembly substantially as hereinbefore described with reference to the accompanying drawings.