DRIVE MECHANISM

DRIVE MECHANISM

This invention relates to a drive mechanism for transmitting programmed bidirectional drive to two or more rotary actuators, and in particular to such a mechanism which is suitable for controlling a plurality of fluid flow control valves in sequence.

Various requirements exist for controlling a plurality of rotary valves in a predetermined sequence, for example in backwashing a filter, or regenerating a water softener or an ion exchange system. Hitherto in conventional automatically operated systems a complex valve structure has been required which is difficult and expensive to make, or alternatively several solenoid- operated valves have been necessary. A need, therefore, exists for an inexpensive but effective system for driving several fluid flow control valves in a desired sequence. Other examples exist of a more general problem where it is required to operate several rotary elements in a predetermined sequence.

The present invention is defined in the appended claims to which reference should now be made. The invention will be described in more detail, by way of example, with reference to the drawings, in which:-

Figure 1 is a side sectional view through one drive mechanism embodying the invention and employing a tooth drive; Figure 2 is a plan view taken on the line II-II in Figure 1;

Figure 3 is a schematically shown detail in plan of a modified embodiment using a cam follower and cam track;

Figure 4 is a schematically shown side sectional plan view of a further modification using a cam follower and cam track taken on the line IV-IV in Figure 5;

Figure 5 is a schematic sectional plan view through the mechanism of Figure 4 taken on the line V-V;

Figure 6 diagrammatically illustrates the motor drive to the drive wheel of the modification of Figure 4; and Figure 7 is a schematically shown detail in plan of another modified embodiment using a lever and pegs.

The drive mechanism 10 shown in Figures 1 and 2 is designed to transmit drive from an input shaft 12 which rotates in one direction only to a plurality of rotary actuators, which are in this ins nce the spindles 14 of conventional and readily available liquid flow control valves 16, such as might be found on the water inlet to a conventional domestic washing machine or similar appliance. The valves 16 are required to be opened and closed in a predetermined sequence. In the example illustrated there are six such valves and they are used to control the operation of a water softener or water conditioner which requires periodically a sequence of operations involving backwashing, brining, rinsing, and refilling etc. The input shaft 12 rotates a spur gear 18 which engages teeth on the peripheral lip 20 of a rotatable disc 22, mounted for rotation by any suitable central support 24. The disc 22 and the spindles 14 all rotate about parallel axes. The disc 22 is moulded from a suitable plastics material. On the underside of the disc 22, as seen in Figure 1, are two circular channels 30 of different radii. The spindles 14 of three of the valves 16 lie on the centre line of the inner channel and the spindles of the other three valves lie on the centre line of the outer channel, as seen in Figure 2. Each channel 30 is stepped as seen in section (Figure 1) so that the lowermost one-third of the channel forms a relatively wide track 32, the uppermost third forms a relatively narrow track 34, and the middle third forms a track 36 of intermediate width. Each spindle 14 carries a spur gear, and the spur gears associated with each channel are of differing diameters so as to fit in the respective one of the tracks. Thus, in the inner channel, spur gear 38 fits in track 32, spur gear 40 fits in track 36, and spur gear 42 fits in track 34. It is thus seen that more than one output member can be associated with a given channel by providing a plurality of tracks on different radial planes within the channel. At the same time two output members are associated with a given radial plane by the provision of two channels at different radii. Each track has tooth sections on its inner and outer faces at selected positions around the disc. The outer tooth sections thus face inwardly and the inner tooth sections face outwardly, and the inner and outer tooth sections are on different radii. The inner and outer tooth sections associated with each track occupy different radial sectors so that the associated spur gear engages selectively with one or other of the tooth sections as the disc rotates. The gear cannot be simultaneously engaged by both, but there may be large sectors where it is engaged by neither. It will be appreciated that engagement of the spur gear by the inner and outer tooth sections will cause the spur gear to rotate in opposite directions, that is to say engagement by the outer tooth section will cause the spur gear to rotate in the same direction as the disc while engagement by the inner tooth section will cause the spur gear to rotate in the opposite direction to the disc. Thus by providing alternately around the track inner and then outer tooth sections, the spur gear, and hence the spindle 14, can be pivoted alternately in one direction and then the other, thus opening and then closing the valve 16. Each valve can be controlled independently by the provision of appropriate tooth sections in its associated track.

Referring to Figure 2, the uppermost track 44 of the outer channel is seen to have an outer tooth section 50 and an inner tooth section 52. These should have the same number of teeth so that the associated spur gear 46 undergoes no nett rotation after one complete revolution of the disc 22. To achieve the same degree of rotation, tracks of greater width will require a greater number of teeth, in proportion to the number of teeth on the spur gear.

The mechanism shown in Figures 1 and 2 has the advantages of being relatively cheap to manufacture while allowing the complex sequencing of a number of valves. The disc can readily be moulded to provide the desired valve operation sequence. By using such a mechanism it becomes possible to use standard valves to control the flow without the need to make an expensive valve unit of complicated construction. Modifications of the mechanism are shown in Figures 3, 4 to 6 and 7. In respects other than those indicated, these mechanisms are similar to that of Figures 1 and 2. Figure 3 shows an arrangement in which the spur gear and tooth sections are replaced by a disc-shaped cam follower 60 and track 62. The cam follower is mounted on the spindle 14 by a bell crank 66, so that the centre 60a of the cam follower is offset from the axis 14a of the spindle. The track moves radially inwardly and outwardly as the disc rotates, so that side edges 64 of the track engage the cam follower 60 to rotate the valve spindle 14.

In the modification of Figures 4 to 6, disc-shaped cam followers 80 are eccentrically mounted directly on the spindles 14. (The centre of the cam follower is shown at 80a and that of the spindle at 14a in Figure 5). Each cam follower bears on the sides 82 of a respective cam track 84 in the drive wheel 86, and the cam tracks are nested, as with the embodiments of Figures 1 and 2, as shown in Figure 4. That is to say, three tracks of successively decreasing width are arranged at deeper heights into the thickness of the drive wheel on the same pitch circle diameter. Two channels are formed at different radii, each comprising three tracks, as in the embodiment of Figure 1. Where the spindle 14 is to be rotated, the track 84 steps from one radius to another on the drive wheel 86, as shown at 88 on Figure 5. When this occurs with the drive wheel 86 rotating clockwise as seen in Figure 5, the cam follower 80 swings as indicated by the arrow A in Figure 5. Some 90 degrees of rotation of the spindle can be obtained with this arrangement. At at least one point or sector around the track 84 the cam follower 80 will be engaged by the outer edge of the track to swing the spindle 14 in one pivotal direction, and at at least one other point or sector around the track the cam follower will be engaged by the inner edge of the track to swing the spindle in the other direction. It is only these engaged portions of the track that are essential to cause the pivoting function. Figure 4 diagrammatically shows a rotary valve 90 capable of shutting off water flow in a passage 92, in response to rotation of spindle 14 caused by cam follower 80. As shown diagrammatically in Figure 6, the drive wheel 86 may be driven by a motor 94 through a reduction gear train 96. In Figure 7, the spur gear is replaced by a triangular lever 70 which is engaged by pegs 72 on the disc 22. In all these modifications the engageable members mounted on the spindles 14 are engaged on both sides by engagement means (64;72;88) at different radii to produce a predetermined reciprocatory piv al movement. One advantage of the independence of the oper ion of the valves by the individual tracks is that they can be arranged so that the force required from the motor is not excessive at any point, this being achieved by slightly staggering the valve operations so that they do not all occur at precisely the same rotary position ofthe drive wheel 86.