AU776282B2 - Air switch operator - Google Patents

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

Applicant(s): KIPLEY ROYDON MARKS Actual Inventor(s): KIPLEY ROYDON MARKS Address for Service: PATENT ATTORNEY SERVICES 26 Ellingworth Parade Box Hill Victoria 3128 Australia Title: AIR SWITCH OPERATOR The following statement is a full description of this invention, including the best method of performing it known to me/us:- IP Australia 9 Documents received on: 1 0 19 JAN 2000 (DBath Batch No: AIR SWITCH OPERATOR This invention relates to apparatus for operating pneumatic switches, commonly referred to as air switches.

"Air switch" is the name generally used to refer to devices that are actuated by delivery of a pulse of relatively high pressure air. Air switch assemblies usually comprise an electric switch, usually a diaphragm type switch. In use, the pulse of high pressure air, when incident upon a diaphragm, causes movement of the diaphragm which in turn causes the engagement or disengagement of electrical contacts to open or close an electric circuit.

Air switches are commonly used in installations such as spa baths or spa pools to operate pumps. They may also be used in a variety of other applications, for example for the operation of waste disposers in or adjacent to household kitchen areas. The main reason for use of air switches is to provide electrical safety. The delivery of a pulse of air to a remote location where electric contacts are located, minimises the risk of inadvertent electrocution of a user.

Known air switch operators work on a bellows system. Therefore, they typically include a 20 push button mounted in a housing, with the flexible bellows provided between the button and an end of the housing. An air inlet/outlet port is usually provided at the end of the Shousing. When a user presses on the push button, the bellows usually compress in a concertina-like fashion to expel air out of the inlet/outlet port under pressure. Some form of biasing means, for example a spring, is provided to return the button to the initial 25 position once a user has removed a finger from the button. In this way, air is returned from the inlet/outlet port into the bellows. A disadvantage with the bellows system is that the bellows themselves need to be constructed from a flexible material which will inevitably wear as a result of flexing in use. For example, the material which is most commonly used is a rubber or plastics material and such materials ultimately fatigue and perish so that air escapes from the bellows.

Another disadvantage with existing operators is that the air used to operate the apparatus is sealed within the system. Thus air is returned to the bellows from the inlet/outlet port and no substantial quantity of air enters the system. Due to small leaks through which the high pressure air escapes during use of the operator, the push button eventually fails to return to its proper operative position after repeated operations since a vacuum tends to form within the system. One attempt to overcome this problem has been the use of a hole in the push button which is manually opened as disclosed in United States patent 4,647,738. However, this has the further disadvantage of allowing foreign matter to enter the apparatus which can block the pneumatic passageways.

It is an object of the present invention to provide a pneumatic switch operator which will at least go some way toward overcoming the foregoing disadvantages, or which will at least provide the public with a useful choice.

In one aspect the invention consists of a pneumatic operator comprising: an inner body; a plunger retained relative to the inner body and moveable relative to the inner body from a first position to a second position, said plunger having a surface for application of force by a user to displace said plunger between said first and second positions, walls of said plunger and said inner body together defining a space; a seal between said plunger and said inner body; an air inlet/outlet port in said inner body or said plunger and in communication with said space, wherein movement of said plunger from said first position to said second position expels air from said space through said inlet/outlet port; and a vent that opens to allow air to enter said space when said plunger is moved from 20 said second position to said first position.

In a further aspect the invention consists of a pneumatic operator comprising: an inner body; a plunger retained relative to the inner body and moveable relative to the inner 25 body from a first position to a second position, said plunger having a button •.surface for application of force by a user to displace said plunger between said first and second positions, walls of said plunger and said inner body together defining a space therebetween; sealing means between said plunger and said inner body for sealing said space; an air inlet/outlet port in said inner body or said plunger; and venting means for venting said space, wherein movement of said plunger from said first position to said second position expels air from said space through said air inlet/outlet port; and wherein movement of said plunger from said second position to said first position opens said venting means to allow air to enter said space through said venting means.

To those skilled in the art to which the invention relates, many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the scope of the invention as defined in the appended claims. The disclosures and the descriptions herein are purely illustrative and are not intended to be in any sense limiting.

The invention consists in the foregoing and also envisages constructions of which the following gives examples only.

One preferred form of the invention and modifications thereof will now be described with reference to the accompanying drawings in which; Figure 1 is a front elevation in cross-section of apparatus in accordance with the present invention.

Figures 2 and 3 are enlarged front elevations in cross-section showing the sealing means of figure 3 when displaced in two different positions.

o.o.

oo o •go•* ooo Figure 4 is a further elevation of a part of the apparatus of figure 1 including a clearer view of an air supply line retention means in accordance with the present invention, and Figure 5 is a diagrammatic sketch of a part of the apparatus of figure I including an air supply 15 line.

Referring to figure 1, a pneumatic operator for switch apparatus commonly referred to as an air switch is shown generally referenced 1. The apparatus has a housing 2 within which a plunger 4 is provided. The plunger has an upper external surface 6 which provides a push button surface for a user to depress in use, using a finger for example.

It will be seen by one skilled in the art that other embodiments of the invention may require the "button" to be pulled in use. The plunger also has one or more walls 8 enclosing a space 10 which as will be seen further below forms a working chamber for displacement of air when relative movement occurs between the plunger and an inner body 12. The walls 8 also enclose a part of the inner body 12 which may be i provided separately from, or as a part of, the housing 2. Sealing means comprising an 0-ring 14 are provided in a locating groove 16 of the inner body. As will be described in further detail below, the locating groove 16 allows for a predetermined displacement of the 0-ring 14 in use, and a number of apertures 18 comprising venting means are provided in the locating groove 16. It will be seen, to one skilled in the art, that at least one edge of locating groove 16 could simply be formed by a circlip.

The inner body 12 has an inlet/outlet port 20 which in use is attached to an air line 34 shown in figures 1-4) so that a pulse of relatively high pressure air may be 00oo delivered to a remotely located electrical diaphragm switch or the like. It will be seen S- to one skilled in the art that the inlet/outlet port 20 could alternatively be provided in the plunger. A biasing means comprising a spring, for example a coil spring 22 is provided in order to keep the plunger 4 in a position where it is disposed away from the inner body 12. The plunger 4 is prevented from escaping the body under the influence of the spring 22 by use of a collar 22a which makes a snap-fit connection, for example, with the body. As can be seen from figure 1, the edges 24 of the collar engage with the periphery of the button surface 6 to prevent the plunger fom escaping from the body.

It will also be seen that the body includes a shoulder 26 which in use abuts a surface of a bench or a spa pool surround, for example. The housing can then be secured to the spa pool wall or bench surface by use of a threaded collar 28.

A part of a retention loop 30 is shown in figure 1. The loop is shown more clearly in direct front elevation in figure 4. The loop assists in retaining the air supply line in connection with the inlet/outlet port 20, as will be described further below with reference to figure 5. One or more projections or barbs 32 may also be provided on an external surface of the inlet/outlet port 20 to assist with retention of the air supply line.

In use, depression of the plunger by a user pressing button surface 6 moves the plunger 4 relative to the inner body 12 in a direction toward the inner body so that walls 8 of the plunger slide relative to the sealing means comprising 0-ring 14. This reduces the size of space 10 and forces some of the air out inlet/outlet port 20 to provide a pulse of S 15 relatively high pressure air to the air line to activate the electrical diaphragm switch.

Referring to figure 2, the action of 0-ring 14 in the locating groove 16 can be seen in more detail When the plunger is pressed downwardly by a user, the 0-ring 14 slides downwardly within the groove 16 as a result of the friction between the 0-ring and the wall 8 with which it is in sealing contact. As can be seen from figure 2, the position of the 0-ring prevents any egress of air from space 10 while the plunger 4 is being depressed.

*Once the plunger has reached the base of its movement, or once the electric switch has been activated and this has been noticed by a user, the user removes his or her finger 25 from the push button, and the force exerted by spring 22 returns the plunger to the [position shown in figure I. As the plunger begins to return to the starting position, the walls 8 of the plunger move the 0-ring upwardly a slight distance as shown in figure 3 until the 0-ring is captured by an upper shoulder of the groove 16. As can be shown in figure 3, there is sufficient distance now in this position for air from the external environment to enter the space 10 through aperture 18. Therefore, air from the supply line is not required to enter inlet/outlet port 20 in order to supply space 10 with the air required to allow the plunger to return to the position as shown in figure 1.

Turning to figure 5, a possible configuration of the air supply line 34 being supported by the retention loop 30 is shown. The loop 30 is used to bear some or most of the force acting on the air supply line. Such force usually results front the weight of the supply line 34 itself but may also exist from the line being placed under tension during installation, or from interference with the line in use. Therefore, loop 30 assists in preventing the air supply line being inadvertently disconnected from the inlet/outlet port It will be seen that the loop 30 could also be provided in the form of a projection such as a hook or support arm The operation of the apparatus described above provides considerable advantages.

Firstly, the use of an 0-ring as the sealing means overcomes the problem of fatigue suffered by air switches which rely on a bellows system. An 0-ring will stand many switching operations without any measurable signs of fatigue or wear.

Another advantage results from the 0-ring being located within the walls of the plunger. In this orientation, it is almost impossible for dirt to build up between the walls of the plunger and the 0-ring which could he a problem if the 0-ring was located externally of the plunger in which case dirt from the external environment could mount around the 0-ring and cause the button to "stick". In the present arrangement, o*o.

any dirt which finds its way into the housing is likely to fall away by the influence of ,gravity without building up on the 0-ring.

Allowing the sealing means to act as a valve so that air may return to the working chamber 10 also provides considerable advantages. A common problem with air switches in hot environments is that the air in the system expands with heat and in doing so can operate the air switch unintentionally. By having the air flow open in the rest position as with the present invention, the air can vent to atmosphere as it expands, so the air switch is not operated. Furthermore, in some cases with known air switches, when the plunger is pushed fully down, the high pressure created operates the electrical switch but is also sufficient to force air out of joints in the line. This does not hinder the operation of the electric switch, but does cause problems when the operator removes his or her finger from the plunger. In these instances, the spring can often not return the plunger to the rest position because of the vacuum created in the line. The vacuum prevents the plunger moving, so the plunger stays down which is irritating and may be dangerous if a user needs to activate the button again immediately to switch a pump off, for example. With the present invention, this problem is overcome as air is returned to the working chamber from the external environment directly past the sealing means rather than relying on air within the air line to feed the working chamber.

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Claims (15)

1. A pneumatic operator comprising: an inner body; a plunger retained relative to the inner body and moveable relative to the inner body from a first position to a second position, said plunger having a surface for application of force by a user to displace said plunger between said first and second positions, walls of said plunger and said inner body together defining a space; a seal between said plunger and said inner body; an air inlet/outlet port in said inner body or said plunger and in communication with said space, wherein movement of said plunger from said first position to said second position expels air from said space through said inlet/outlet port; and a vent that opens to allow air to enter said space when said plunger is moved from said second position to said first position.

2. The pneumatic operator as claimed in claim 1, wherein said seal comprises an O- ring. 20

3. The pneumatic operator as claimed in claim 1 or claim 2, wherein said seal is on S said inner body.

4. The pneumatic operator as claimed in any one of claims 1 to 3, wherein said inner body includes a first shoulder against which said seal is retained. Sgo.

5. The pneumatic operator as claimed in claim 4, wherein said inner body includes a second shoulder that is opposite said first shoulder and wherein said seal is retained between said first and second shoulders.

6. The pneumatic operator as claimed in claim 5, wherein said vent is adjacent to one of said first and second shoulders, wherein movement of said plunger from said first position to said second position displaces said seal toward one of said first and second shoulders to close said vent and movement of said plunger from said second position to said first position displaces said seal toward the other of said first and second shoulders to open said vent.

7. The pneumatic operator as claimed in any one of claims 1 to 6 wherein the inner body is dependent from a housing assembly. 8

8. A pneumatic operator comprising: an inner body; a plunger retained relative to the inner body and moveable relative to the inner body from a first position to a second position, said plunger having a button surface for application of force by a user to displace said plunger between said first and second positions, walls of said plunger and said inner body together defining a space therebetween; sealing means between said plunger and said inner body for sealing said space; an air inlet/outlet port in said inner body or said plunger; and venting means for venting said space, wherein movement of said plunger from said first position to said second position expels air from said space through said air inlet/outlet port; and wherein movement of said plunger from said second position to said first position opens said venting means to allow air to enter said space through said venting means.

9. The pneumatic operator as claimed in claim 8 wherein said sealing means comprises an O-ring.

10. The pneumatic operator as claimed in claim 8 or 9 wherein said sealing means is on said inner body.

11. The pneumatic operator as claimed in any one of claims 8 to 10 wherein said inner S 25 body includes a first shoulder against which said sealing means is retained.

12. The pneumatic operator as claimed in claim 11 wherein said inner body includes a second shoulder opposite said first shoulder and said sealing means is retained between said first and second shoulder.

13. The pneumatic operator as claimed in claim 12 wherein said venting means comprises an aperture in said inner body adjacent to one of said first and second shoulders, whereby movement of said plunger from said first position to said second position displaces said sealing means toward one of said first and second shoulders to obstruct said aperture to prevent egress of air through said venting means and movement of said plunger from said second position to said first position displaces said sealing means toward the other of said first and second shoulders to allow ingress of air into said space through said aperture.

14. The pneumatic operator as claimed in any one of claims 8 to 13 wherein the inner body is dependent from a housing assembly.

15. A pneumatic operator substantially as herein described with reference to figures I to 3 of the accompanying drawings.