AU687587B2 - A float arm interconnection mechanism - Google Patents

Description

S F Ref: 303205

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

Name and Address of Applicant: Invention Title: Actual Inventor(s): 00* ASSOCIATED PROVISIONAL 31] Application No(s) PM8030 Caroma Industries Limited 10 Market Street Brisbane Queensland 4000

AUSTRALIA

Timothy De Pieri Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Wales, 2000, Australia A Float Arm Interconnection Mechanism APPLICATION DETAILS [33] Country

AU

[32) Application Date 7 September 1994 The following statement is a full description of this invention, including the best method of performing it known to me/us:- 5815 L c -1 f- A Float Arm Interconnection Mechanism The present invention relates to cisterns (or flush tanks as they are known in the USA) and, in particular, to the float arm mechanism utilised to activate the cistern inlet valve.

The cistern inlet valve supplies the cistern with water and is provided with a float and float arm which enables the level of water in the cistern to control the inlet valve. When the cistern is being emptied during flushing of the toilet above which the cistern is mounted, the float arm drops, thereby opening the inlet valve. Conversely, as the level of water within the cistern rises, the float and float arm also rise and ultimately close off the inlet valve. In such a conventional arrangement, the upwards buoyant force of the float, or the downward force due to the weight of the float, are magnified by the ratio of the length of the float arm between pivot and float to the length of the float arm between the pivot and the inlet valve actuator.

With conventional cisterns having flush volumes of the order of 9 to 11 litres, the left to r.ght dimension of the cistern has been sufficient to enable a float arm of adequate length to be utilised. However, in recent times there has been a trend towards the use of cisterns with a maximum flush of the order of 6 litres. Such cisterns have a relatively short left td right dimension, and, as a consequence, the length of the float arm must be reduced.

In addition, as the interior volume within a cistern has been reduced, so the complexity of the cistern internals has increased, particularly in relation to dual flush cisterns and the like. The net result is that space within the cistern is becoming increasingly limited. Therefore it is desirable that the float arm be as short as possible.

It is also desirable that the float itself be movable along the stem of the inlet valve so that the inlet valve, float arm and float together form a relatively compact unit which can be located inside the cistern and adjacent one side of the cistern.

Since the priority date, the applicant has become aware of New Zealand Patent No. 157548 to American Standard Inc (to which US Patent No. 3,533,437 corresponds). This patent discloses a conventional long float arm but uses two part 30 spur gears in the pivoting of the float arm. The gear ratio is thought to be about 1:1 since the long float arm provides plenty of torque. Furthermore, the gear mechanism converts rotary pivoting motion into an equivalent rotary motion so the net mechanical effect is equivalent to a conventional float arm.

In view of the foregoing it is the object of the present invention to provide a float arm mechanism for a cistern inlet valve in' wich the length of the float arm can be reduced relative to the length of conventional float arms and in which the rotary motion of the float arm is converted to a linear motion for the inlet valve.

-2- In accordance with a first aspect of the present invention there is disclosed a float arm mechanism for a cistern inlet valve, said float arm mechanism comprising a float arm pivoted at one end thereof on said inlet valve, a float carried on the other end of the float arm, and an inlet valve actuator movable between valve open and valve closed positions by the pivotal motion of said float arm, wherein said actuator and float arm are interconnected via a gear mechanism which converts rotary motion to linear motion. Preferably the gear mechanism is a rack and pinion arrangement.

In accordance with a second aspect of the present invention there is disclosed a method of actuating a cistern inlet valve having an actuator, said method comprising the step of magnifying the buoyant or gravitational force applied to a float arm by a float, by interposing between the actuator and the float arm a gear mechanism which converts rotary motion to linear motion.

An embodiment of the present invention will now be described with reference to the drawings in which: Fig. 1 is a schematic side elevation of a cistern inlet valve and float arm of a prior art arrangement, ~Fig. 2 is a similar view but of the preferred embodiment of the present invention, Fig. 3 is a view similar to Fig. 2 but illustrating on an enlarged scale and in vertical cross section the details of the inlet valve of Fig. 2, and Fig. 4 is an exploded perspective view illustrating the interconnections between the valve actuator, rack and pinion.

As seen in Fig. 1, the prior art arrangement 1 takes the form of an inlet valve 2, a float arm 3 and a float 4. The float arm 3 is pivoted about a pivot 5 and includes a projection 6 having a length X which operates on the inlet valve 2 in order to open or close same.

In accordance with simple mechanics, the magnification of the force of gravity, or the buoyant force, applied by the float 4 to the float arm 3 is magnified by the ratio of the length of the float arm 3 to the distance X. With conventionally sized cisterns 30 this magnification is generally of the order of 30:1-50:1. However, as the length of the float arm 3 becomes shorter, so this magnification decreases until the point is mached where the force being applied by the float armnn 3 to the inlet valve actuator is insufficient. For conventional valves this can be a particular problem in closing the valve in areas of high water pressure. For some types of hydraulic valve, the force required to open the valve is larger than the force required to close the valve. Agair, under these circumstances the length of the float arm 3 can be insufficient to provide the necessary force. Additionally, with a conventional lever float arm arrangement the point ofaction is necessarily close to the pivot point when a high mechanical advantage -3is required (and especially so when the float arm is shorter than normal). Thus as the length of the float arm decreases, the distance X between the pivot point and the point of application of force to the valve reduces. Thus the whole arrangement becomes very cluttered and increasingly impractical since the force application arrangement interferes with the float arm pivot point.

The float arm arrangement 10 of the preferred embodiment is illustrated in Figs. 2 to 4 and takes the form of an inlet valve 12 of the type described in detail in the applicant's co-pending Australian Patent Application No. 72899/94 (previously Application No. PM1316) (Attorney Reference 281002), the contents of which are hereby incorporated into the present specification by cross-reference. A much shortened float arm 13 is provided which is connected to a float 14 by means of a linkage 15. This enables the float 14 to slide up and down the stem 16 of the inlet valve 12.

As best seen in Fig. 4, the cap 18 of the valve 12 is provided with a pair of journals 19 which each receive a corresponding stub axle 20 on the float arm 13. By means of lead-in openings 21 and the flexible plastics material from which the journals 19 are fabricated, the stub axles 20 can be snap-engaged with the journals 19.

Also provided on the cap 18 is an upstanding post 23 provided with a webbed S flange 24. The post 23 and flange 24 are received in a T-shaped slot 25 in a block 26 which is slidably received on the post 23 and flange 24. The block 26 carries a rack 27 which is engagable with a part pinion 28 located between the stub axles The gearing preferably uses twenty degree involute spur gear teeth with only five teeth on the part pinion 28.

2 3 As seen in Fig. 3, the inlet valve 12 is provided with an inlet 31 and an outlet 32 and has a valve chamber 33 which is able to be occluded by means of an egg-shaped valve body 34 retained at the lower end of a valve actuator stem 35. The valve actuator stem 35 passes through a hole 36 in the base of the block 26 and is retained in engagemient with the block 26 by means of a U-shaped peg 27 which engages a reduced diameter portion 38 of the stem 35 below a formed head 39.

30 As will apparent from Figs. 2 to 4, as the float 14 rises and falls, so the float arm 13 pivots by means of rotation of the stub axles 20 in the journals 19. The interengagement of the part pinion 28 and rack 27 raises the block 26 when the float arm 13 pivots in a clockwise direction as seen in Fig. 3, and vice versa.

Clearly, as the block 26 rises and falls, because of the entrapment of the head 39 of the stem 35 by ineans of the peg 37, so tdo does the valve actuator stem 35 move.

In this way, the inlet valve 12 is operated in the manner described in the above referenced patent application.

The above described arrangement makes possible a force magnification of approximately 20:1 which is effectively half that of the prior art arrangement. Thus for a conventional inlet valve a larger float would be required. For the preferred inlet valve 5, 0 small force is more than adequate. Most importantly, however, a very substantial shortening of the length of the float arm 13 is able to be achieved.

In addition, if the linkage 15 (Fig. 2) is uncoupled, then the float arm 13 can be pivoted fully clockwise with reference to Figs. 2 to 4 of the drawings. A lug 29 is provided on the float arm 13 to limit the maximum clockwise movement of the float arm by engagement of the lug 29 with the cap 18. In this position of the float arm 13, the teeth of the part pinion 28 are able to be disengaged from the teeth of the rack 27.

In this way, the block 26 can be either slid onto, or removed from the post 23, so as to achieve the assembled condition as shown in Fig. 3, or disassemble the arrangement.

The above described arrangement. offers a number of advantages. Firstly, conventional lever mechanisms convert one large arc of movement to another smaller arc. Since the resultant output is itself an arc there must exist both horizontal and vertical components of the movement. Any horizontal movement must result in either increased friction or "slop" in the mechanism.

Further the valve actuator stem 35 ideally moves in an exactly linear motion.

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The rack and pinion arrangement has the advantage that it converts arcuate rotational motion into perfectly linear motion, via the constant pitch circle diameter of the gearing ratio. In addition, the distance from the pivot point of the float arm 13 to the point at which the stem 35 is connected to the float arm is very small. For the rack and pinion mechanism, this can be accommodated by the diameter of the stub axle 20 and the S distance between the longitudinal axis of the stem 35 and the rack 27.

The foregoing describes only one embodiment of the present invention and modifications, obvious to those skilled in the art, can be made thereto without departing from the scope of the present invention.

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Claims (11)

1. A float arm mechanism for a cistern inlet valve, said float arm mechanism comprising a float arm pivoted at one end thereof on said inlet valve, a float carried on the other end of the float arm, and an inlet valve actuator movable between valve open and valve closed positions by the pivotal motion of said float arm, wherein said actuator and float arm are interconnected via a gear mechanism which converts rotary motion to linear motion.

2. A float arm mechanism as claimed in claim 1 wherein said gear mechanism comprises a rack and pinion arrangement.

3. A float arm mechanism as claimed in claim 2 wherein the inlet valve actuator is connected to the rack and the float arm is connected to the pinion.

4. A float arm mechanism as claimed in claim 3 wherein the pinion is a part pinion.

A float arm mechanism as claimed in claim 1 wherein the gear ratio of the gear mechanism is approximately 20:1.

6. A method of actuating a cistern inlet valve having an actuator, said method comprising the step of magnifying the buoyant or gravitational force applied to a float arm by a float, by interposing between the actuator and the float arm a gear mechanism which converts rotary motion to linear motion.

7. A method as claimed in claim 6 wherein said gear mechanism 20 interposition is removable to permit said gear mechanism to be disassembled. f

8. A method as claimed in claim 7 including the step of using said gear mechanism to convert arcuate movement of said float arm into linear movement of said actuator.

9. A method as claimed in claim 8 including the step of connecting said actuator to the rack of a rack and pinion gear mechanism and connection said float arm to the pinion of said rack and pinion mechanism.

10. A float arm mechanism substantially as herein described with reference to Figures 2-4 of the accompanying drawings.

11. A method of actuating a cistern inlet valve, said method being 30 substantially as herein described with reference to Figures 2-4 of the accompanying drawings. DATED this TWENTY-FOURTH day of AUGUST 1995 Caroma Industries Limited Patdnt Attorneys for the Applicant SPRUSON FERGUSON 4 r A Float Arm Interconnection Mechanism Abstract A method and apparatus are disclosed for actuating an inlet valve (12) of a cistern or flush tank. The cistern has a float arm (13) connected to a valve actuator (35) by a gear mechanism which preferably takes the form of a rack (27) and pinion A substantial increase in effective gear/force ratio is achieved together with conversion of arcuate motion of the float arm (13) into linear motion of the actuator Figure 4 *e 04 S ea 4* ee 9 4 I