EP0277551A2

EP0277551A2 - Armoured resistance element with thermostat

Info

Publication number: EP0277551A2
Application number: EP88100837A
Authority: EP
Inventors: Sandro Marcer
Original assignee: IRCA SpA Industria Resistenze Corazzate e Affini
Current assignee: IRCA SpA Industria Resistenze Corazzate e Affini
Priority date: 1987-01-27
Filing date: 1988-01-21
Publication date: 1988-08-10
Also published as: IT211701Z2; IT8761904V0; EP0277551A3

Abstract

An armoured resistance element with safety thermostat, provided with a fixing base (7) comprising a block (4) of elastic material interposed between a flange (3) and a backing flange (5), which can be tightened together during installation, characterised by being provided with at least one thermostat (13,21) housed in a corresponding seat (12,20) provided in said block (4).

Description

This invention relates to an armoured resistance element with thermostat.
Those known household electrical appliances which comprise a heating stage during their operating cycle are generally provided with one or more armoured resistance elements. An armoured resistance element consists of an electrical resistor housed within a metal sheath and kept electrically insulated from the walls of this latter, which is connected to earth. Generally, the armoured resistance element is mounted on a rubber base bounded by a flange and backing flange, which when suitably tightened together during installation of the resistance element compress said base and cause it to expand laterally with the result that its side surface presses against the edge of the aperture which has previously been formed in the water holding tank of the household electrical appliance, so that it both secures the element to the tank and forms a water seal at the same time.
Suitable electrical connections are then used to connect the resistance element to the electricity mains and to possible members for implementing and controlling the operating cycle.
Normally a household electrical appliance comprises a control thermostat which controls the fixed or variable temperature to which the water is to be heated an such as to cut in or cut out the electrical resistance element whenever the water temperature strays from the predetermined value. In addition to this control thermostat, a household electrical appliance normally also comprises a safety thermostat the purpose of which is to act whenever the electrical resistance element accidentally operates under abnormal conditions which differ from and are more arduous than the scheduled conditions, for example because of lack of operation of the control thermostat.
Generally the known control and safety thermostats are fitted to the base of the tank which holds the water to be heated, this base having been previously drilled for the fitting of the thermostat, this resulting in certain drawbacks, in particular:
- space requirement problems,
- the need for a gasket to form a seal between the thermostat and tank base,
- the need for electrical connections and all the necessary expedients to ensure proper insulation,
- a certain laboriousness in assembly, which inevitably affects the final cost of the household appliance.
All these drawbacks are obviated according to the invention by an armoured resistance element provided with a fixing base comprising a block of elastic material interposed between a flange and a backing flange, which can be tightened together during installation, characterised by being provided with at least one thermostat housed in a corresponding seat provided in said block.
The present invention is further clarified hereinafter with reference to the accompanying drawings, in which:

Figure 1 is a partial longitudinal section through an electrical resistance element according to the invention with a thermostat incorporated in its fixing base, and
Figure 2 is the same view as Figure 1 showing an embodiment with two thermostats.

As can be seen from the figures, the armoured resistance element 1 according to the invention is of conventional type, and its ends pass through a fixing base indicated overall by 2 and comprising a flange 3, a rubber block 4 and a backing flange 5.
The flange 3 is formed by a pressing process, and its width is slightly greater than the aperture in the tank into which the resistance element is to be inserted. It has a raised edge and is provided with holes 6 and 7, through which the ends of the resistance element 1 and a fixing screw 8 secured to the backing flange 5 can pass.
The rubber block 4 is of conventional type and comprises a portion 9, which has dimension slightly greater than those of the aperture in the tank to be heated, but which is exactly contained within the raised edge of the flange 3, and a portion 10 of dimensions equal to those of the tank aperture. In this manner, the portion 9 forms with the portion 10 a perimetral step which acts as an abutment against the wall of the tank to be heated, when the resistance element 1 is fitted thereto.
The rubber block 4 also comprises holes 11 for passage of the ends of the resistance element 1 and screw 8. In addition, in that surface facing the backing flange 5, the block 4 comprises a seat 12 housing a thermostat 13 which has its heat-sensitive surface facing said backing flange 5 and is arranged to make contact with the water contained in the tank by way of an aperture 14 provided in the backing flange. The rim 15 of the seat 12 projects internally and is slightly thickened, so that when the resistance element 1 is mounted in the water tank and the backing flange 5 is drawn towards the flange 3 by tightening, it compresses the rim 15 against the heat-sensitive surface of the thermostat 13, to ensure complete water-sealing of the seat 12.
That rubber block portion which divides the base of the seat 12 from the surface in contact with the flange 3 comprises two through apertures for the two terminals 16,16ʹ of the thermostat 13. These apertures extend beyond the flange 3 as two appendices 17,17ʹ which also pass through said flange.
As in the case of the flange 3, the backing flange 5 is also formed by pressing, its dimensions corresponding to the portion 10 of the rubber block 4 and its edge being raised. It is also provided with holes 18,19 for passage of the ends of the resistance element 1 and the screw 8 respectively.
From the aforegoing it is apparent that the armoured resistance element according to the invention, which is mounted in the manner of a conventional armoured resistance element offers numerous advantages compared with this latter, and in particular:
-it obviates the need to drill the tank, with all the consequent sealing problems which arise,
- it reduces the numer of electrical connections in that one end of the resistance element 1 and one terminal 16 of the thermostat 13 can be connected together during the actual construction of the element, it then being necessary on installation to make only two connections (to the other end of the resistance element 1 and to the other terminal 16ʹ of the thermostat 13), ie the two connections normally made for the armoured resistance element alone,
- it reduces assembly costs.
The thermostat 13 is preferably a safety thermostat if the control thermostat is directly installed in the water tank, or if this latter thermostat is replaced by a normal timer which powers the electrical resistance element 1 for a predetermined time.
In the embodiment shown in Figure 2, the rubber block 4 comprises not only the seat 12 but a further seat 20 for a second thermostat 21, the terminals 22,22ʹ of which emerge to the outside beyond the flange 3 in the same manner as the terminals 16,16ʹ of the thermostat 13.
In the preceding embodiment the single thermostat 13 is preferably a safety thermostat, although it could be a control thermostat, whereas in this second embodiment one thermostat 13 is definitely a control thermostat and the other thermostat 21 can be either a safety or a control thermostat. In the first case, the resistance element 1 also incorporates all the regulating and control members and the relative electrical connections, so making the operations involved in assembly and connection to the mains extremely rapid and simple. In the second case the two thermostats 13 and 21 are set to different operating values for use in household electrical appliances which have two different operating temperatures, for example for different wash cycles.

Claims

1. An armoured resistance element with safety thermostat, provided with a fixing base (7) comprising a block (4) of elastic material interposed between a flange (3) and a backing flange (5), which can be tightened together during installation, characterised by being provided with at least one thermostat (13,21) housed in a corresponding seat (12,20) provided in said block (4).

2. An armoured resistance element as claimed in claim 1, characterised in that the backing flange (5) comprises an aperture (14) facing the seat (12,20) for the thermostat (13,21) in order to put the heat-sensitive surface of this latter into contact with the water to be controlled.

3. A resistance element as claimed in claim 1, characterised in that the aperture forming the seat (12,20) is provided with a rim (15) which projects towards the interior of said seat to become interposed between the thermostat (13,21) and the backing flange (5) when the resistance element (1) is installed.

4. A resistance element as claimed in claim 3, characterised in that the rim (15) of the aperture forming the seat (12,20) is thickened in that portion which is to be interposed between the thermostat (13,21) and backing flange (5).

5. An armoured resistance element as claimed in claim 1, characterised in that the two terminals (16,16ʹ) of the thermostat (13,21) emerge to the outside through corresponding insulating bosses (17,17ʹ) forming the extension of the block (4) beyond the flange (3).

6. An armoured resistance element as claimed in claim 1, characterised by comprising a pair of thermostats (13,21) having different operating temperatures.