This invention relates to an adaptor facilitating the coupling of a manual adjustment knob to an enclosed thermostat for controlling the temperature of water stored in the tank of an electrically heated water heater.

Prior art in the field, Australian patent 549569 (AU-B 82463/82) discloses an electrically heated, insulated storage tank type water heater embodying an adjustable thermostat operatively connected electrically to the heating element and mechanically attached to the outer surface of the side wall of the storage tank. There, an adjustment stub screw protruding a very short distance from the face of the thermostat is adapted by a tubular extension to enable the thermostat to be adjusted by rotating a knob outside of a protective jacket enclosing the thermostat and heat ^: -ulation around the tank. Previously it had been necessary to remove a screw retained blank cover plate to obtain access to the adjustment stub screw inside the jacket.

However, it has not been disclosed, to the applicant's knowledge, to adapt an inaccessible thermostat adjustment of the above-described type with an arrangement providing:

(i) Protection against ingress of water as would be required to enable outdoor installation of water heaters, which is a frequent requirement in more recent times;

(ii) Resistance to undesired tampering with the temperature setting by young children and;

(iii) Cost saving assembly tolerance in view of variable tolerance in the relative locations of a pre-formed hole in a cover plate through which the adaptor protrudes and the position of the thermostat.

Furthermore, in a preferred embodiment, the present invention provides facilitated assembly of the thermostat adaptor after the cover plate or cover enclosure is attached to the jacket. Otherwise, assembly line procedures would be made unacceptably more complicated.

Statement of the Invention.

The invention consists of an adaptor for adjusting a thermostat of a water heater, the water heater including a hot water tank having an outer wall, a heat insulating layer surrounding the tank and having a recess formed therein to accommodate the thermostat affixed in direct contact to the outer wall of the tank, a protective jacket surrounding the heat insulating layer having an opening in alignment with the recess, the thermostat being of the type provided with a rotatable temperature adjustment means, the thermostat being located in the recess provided in the insulating layer, an enclosure housing attached to the jacket to deter casual access to the recess,

the enclosure being aligned with the opening in the jacket and the recess in the heat insulating layer, said adaptor means comprising;

a slotted thermostat coupling member connected to the rotatable temperature adjustment means of the thermostat;

a connector shaft adapted to be connectable at a first end to the thermostat coupling member in a manner effective to enable transmission of rotation between the coupling member and the connector shaft;

a child-resistant adjustment knob connected to a hole provided in the cover and inter-engagable with a rotation transmission means at a second end of the connector shaft which is adapted to be connected in a slotted collar forming an inward facing rotation transmission coupling portion of the knob; and wherein

the enclosure is provided with a hole in a front face to receive the second end of the connector shaft and is provided with a flat emboss surrounding the hole to enable a tight sliding fit against a rear face of the adjustment knob to provide protection against ingress into the enclosure of sprayed or splashed water.

Preferably the child resistant knob comprises a resilient, finger-engagable housing partly enclosing an inner mating boss, said housing and boss being adapted to require greater finger compression than possible by young children before rotation of the housing will transmit rotation to the boss and thereby to the rotation transmission coupling portion of the knob.

Preferably the knob is retained against the emboss by plural snap action fingers with barbed tips, the fingers depending axially inwardly from the rear face of the knob to engage said hole in the centre of the emboss with radially outwardly directed resilience.

Preferably the thermostat coupling member is in the form of a cup shaped member having a circular base and a generally cylindrical peripheral wall wherein the wall is provided with aligned opposed slots adapted to receive an end shaft transverse to the longitudinal axis of the connector shaft. To facilitate assembly, the slots and the transverse end shaft are a tight fit.

These and other preferred features of the invention will be described in more detail in relation to a preferred embodiment.

Brief Description of the Drawings.

The invention is further described by way of a particularly preferred example and variations thereof, with reference to the accompanying drawings in which;

Fig. 1 is a schematic upright cross-sectional elevation of a portion of a water heater showing a thermostat adaptor according to the invention;

5 Figs. 2A to 2F are an exploded perspective view of component parts of a thermostat adaptor according to the invention;

Figs. 3A to 3D are a further series of views of the principal component parts of the adaptor and the cover plate; and

10

Figs. 4A to 4D shows the sequence of assembly operations of the thermostat adaptor of the invention to the thermostat affixed to the water heater.

In the illustrations, the following table of reference numbers describe the terminology used for the 15 illustrated component parts mentioned in the following detailed description:

10 water heater tank wall

12 thermostat

14 flange to receive heating element

20 16 heat insulation for tank

17 protective jacket

18 cover

19 cover emboss

20 electrical shield

25 21 flat face on emboss

22 thermostat stub shaft/rotatable adjustment means

24 yoke member

25 transverse opposed slots

26 connector shaft 30 27 tee-shaped head

28 connector shaft centraliser

29 knob

30 knob body 32 knob cap

35 34 knob-to-connector shaft locating ring

35 transverse opposed slots

36 lock tabs

38 hole in emboss

40 Detailed Description.

In Fig. 1 , the thermostat 12 is illustrated, for clarity, slightly removed from but close to the outer surface of the water heater tank wall 10 where it will be attached. When the thermostat is

assembled (in known manner) it is in heat conducting contact with the tank wall, inside a cavity formed in known manner in the heat insulating layer 16 surrounding the tank. A protective jacket 17 surrounds substantially all the heat insulation but has a cut-out opening to provide access to the cavity housing the thermostat and the electrical heating element (not shown) which would be attached to the flange 14 which is located likewise in the cavity.

A cover 18 in the form of a pressed metal housing (but which could alternatively be moulded of a rigid plastics material) is provided and is attached by a flanged edge to the jacket using screws (not shown) or other equivalent fixing means of a nature to discourage casual or inquisitive removal of the cover, at least to the extent that a deliberate action using a screw-driver or other tool would be required. In the use of the water heater, live electrical connections would be exposed upon removal of the cover at both the thermostat and heating element. In the present invention, as an added precaution to minimuse the possibility of a person touching the live electrical connections, a dielectric shield 20 is preferably incorporated. However, for normal adjustment of the thermostat, the adaptor of the invention avoids the need to remove the cover. The adaptor comprises several discrete parts and a modification to the cover 18 as will be described below. In prior art water heaters, the cover would be blank, having no openings provided in its face external to the visible surface when assembled.

In the invention, an emboss 19 is formed in the outward face of the cover, having a central hole through which the inter-engagement between a knob 29 and connector shaft 26 is made. For clarity, in Fig. 1 the knob 29 is shown away from its assembled position; upon assembly, the face 29 of the knob body 30 closely contacts the flat face 21 of the cover emboss 19. This close contact assists in providing the required protection against ingress of water into the cover. This enables the assembly to meet appropriate outdoor environmental requirements by conformance for example with Australian Standard 1939-1990, Degrees of protection provided by enclosures for electrical equipment, designation IP34. This designation provides for protection against sprayed water at an angle up to 60° on either side of the vertical or water splashed against the enclosure or cover plate from any direction, to the extent that no water entry results.

The thermostat stub shaft 22 or other rotatable adjustment means is fitted with a yoke member 24 in such manner that the yoke member engages tightly the stub shaft so that no relative rotation is possible between the two parts. In one form of commonly used thermostat, the stub shaft 22 is splined and protrudes from the face of the thermostat, in which case the yoke member has a mating splined hole to suit. Another form of commonly used water heater thermostat (not illustrated) in fact does not have a protruding shaft adjustment but rather has a rotatable part with a countersunk recess; to suit this the yoke member has a complementary member insertable into the recess.The yoke member has at least one pair of transverse opposed slots 25 extending radially from an inside diameter and axially inwardly from a front edge. The connector shaft 26

has a mating tee-shaped head 27 which is a tight fit inside the opposed slots 25 of the yoke member 22 as better seen in Figs. 2C and 2E or 3C and 3D. The tee-shaped head may be cross- shaped, as shown in Fig 3D, but in either case the transverse arms have a circular cross-section. This permits the connector shaft to be rotatable if angularly misaligned with the stub shaft 22 while still permitting rotation of the connector shaft 26 to be transmitted as rotation of the stub shaft. The tightness of fit is enabled by moulded terminations of the radially inward edge of the slots with thin, flexible lips that are resiliently deformed upon insertion of the tee-head cross bar into the slots. The tee-head on the outer end of the connector shaft extends just through a hole 38 formed in the cover emboss 19 of the cover 18 upon assembly.

The knob 29 comprises two inter-fitting co-operating parts, the knob body 30 and knob cap 32. When assembled together the knob body is only rotatable so long as the knob cap is firstly squeezed strongly inwardly so that the two parts then interlock to permit relative rotation of the knob cap to be transmitted via the knob body, thence tee-head at the outer end of the connector shaft to the tee-head at the opposite end of the connector shaft thence the stub shaft of the thermostat. As best seen in Fig. 3B the knob body 30 has a connector location ring 34 on its inside face, containing two pairs of opposed slots 35 to receive the outer tee or cross-head 27 of the connector shaft. If the shaft has a tee-head (Fig 2E) one pair of opposed slots 35 suffices. Also the inside face of the knob body has four lock tabs 36 that have radially outwardly directed barbs to engage upon assembly the inside edge of the hole 38 formed in the emboss in the cover. The lock tabs have a lead-in angle to cause them to resiliently deform radially inwardly during assembly of the knob to the cover until upon the correct assembly position being reached the tabs snap radially outwardly to tightly engage against the periphery of the hole 38. The tee or cross head-to-slot connection at both ends of the connector shaft enables considerable angular misalignment of the connector shaft upon assembly without affecting the ability of knob rotation to transmit an equal angular rotation of the connector shaft, yoke member and hence the stub shaft. This enables substantial assembly tolerance between the relative position of the thermostat when fixed to the tank and the final position of the heat insulation jacket when assembled over the storage tank and the space between the tank wall and jacket filled with insulation. Thus the addition of the thermostat adaptor will not lead to increased assembly cost because of any new requirement for tighter tolerance between the jacket and the tank. .

An optional feature that may facilitate assembly is the provision of a connector shaft centraliser 28 (Fig 2F) assembled to the connector shaft to engage inside the hole in the emboss on the cover until the knob body is assembled to engage with the outer tee-head of the connector shaft. The function of the shaft centraliser becomes subsequently redundant when the knob is snapped into position although for convenience it merely remains as part of the assembly. More preferably, the tight fit between the tee-shaped head of the connector shaft and the yoke member facilitates assembly without the need of the shaft centraliser 28. Upon engagement, the yoke mfimber grips

the tee-shaped head so that the connector shaft remains in any desired orientation during assembly.

With reference to Figs. 4A to 4D, the assembly steps are as follows; the thermostat 12 is set at its minimum set point; the yoke member 24 is engaged with the (or one of the pair of ) opposed slots 25 set horizontal; the cover 18 is fitted (Fig 4B) and locked to the jacket 10 with screws (not shown); the shaft centraliser 28 if used is clipped to the connector shaft 26 (Fig 4C) and the shaft and centraliser inserted through the hole 38 to engage tee-shaped head 27 in slots 25 (now hidden); or, alternatively, the connector shaft 26 is alone inserted through the hole 38 and moved to a frictionally held orientation in slots 25 to align its outward end to the hole 38 (Fig 4D); and the knob 29 is inserted in the hole 38, aligning the (or one of the pair of) opposed slots 35 (see Fig

3B) with the tee-shaped or cross-shaped head 27 of the connector shaft 26, and pushed firmly inward until it locks, with the indicated setting "cool" or minimum.