GB2153593A

GB2153593A - Temperature sensitive safety switch

Info

Publication number: GB2153593A
Application number: GB08502544A
Authority: GB
Inventors: Kurt Wohlfart
Original assignee: Rowenta Werke GmbH
Current assignee: Rowenta Werke GmbH
Priority date: 1984-02-01
Filing date: 1985-02-01
Publication date: 1985-08-21
Also published as: IT8520609V0; GB8502544D0; GB2153593B; FR2558985B3; DE8402834U1; FR2558985A3

Abstract

A temperature sensitive safety switch for electrical appliances comprises a temperature-resistant solid body 1 having switch contacts 9,9' secured thereto, a switch pin 10 cooperating with said switch contacts and movably guided in the solid body 1, a fusible member 7 connectable in heat conducting manner to a heated part (not shown) of a said appliance by means of a plate 3, said fusible member 7 normally holding said switch pin 10 and hence said switch contacts 9,9' in the closed position. The plate 3 has resilient arms extending substantially at right angles thereto and having, at their free ends, flanges (6) (Figure 1) provided with rising slopes (5) which are engagable behind retaining cams (2) of the solid body 1. <IMAGE>

Description

SPECIFICATION Temperature sensitive safety switch The invention relates to a temperature sensitive safety switch for electrical appliances. Such a switch is particularly suitable for heated small appliances such as irons, coffee machines, electric kettles, etc. and includes a temperature-resistant solid body with switch contacts attached to it, a switch pin which is movably guided in the solid body and a fusible member or fuse which is connected via a plate to the heating part of the appliance in heat-conducting manner and holds the switch contacts in the closed position by means of the switching pin.

Temperature sensitive safety switches are incorporated in such appliances in order to protect them from overheating should the temperature regulator fail. These switches are provided with a fusible member or fuse which fuses at a certain temperature, as a result of which switching contacts held under spring tension open and interrupt the supply of current. This protective measure is intended to prevent the heated electrical appliance from overheating.

With the known switches, the manufacturing costs are very high and the heat-transmission resistance in the region of the fusible member is disproportionately great. As a result of the great heattransmission resistance, there is a dangerous delay in switching off, i.e. energy continues to be supplied to the appliance for some time before the safety switch responds. As a result of this energy supply, burns may be caused and/or the appliance may be destroyed as a result of overheating and this should be prevented at all costs for safety reasons. A temperature sensitive safety switch in which securing flaps are formed on a metal plate is already known.

The ends of these securing flaps are bent round after the switch has been assembled and engage with their bent ends in recesses formed in the solid body. In this way the parts of the switch are held together. It is not possible to dismantle the switch without destroying it. Moreover, this type of securing results in considerable additional costs since an additional operation is required in order to bend the ends of mass-produced switches.

Switches with defects caused by assembly cannot be made good. Once the safety switches have responded to a case of overheating and their fusible members have had to be replaced, the switches can only be put back into operation by a considerable amount of labour and resultant costs.

Having regard to this prior art, the aim of this invention is to provide a temperature sensitive safety switch which is simple in construction, can be manufactured fully automatically, does not cause any delay in switching off and can readily be put back into operation at any time.

According to the invention, there is provided a temperature sensitive safety switch for electrical appliances, comprising a temperature-resistant solid body having switch contacts secured thereto, a switch pin cooperating with said switch contacts and movably guided in the solid body, a fusible member connectible in heat-conducting manner to a heated part of a said appliance by means of a plate, said fusible member being effective via said switch pin to hold the switch contacts in the closed position, wherein retaining cams are formed on said solid body, and said plate has resilient arms connected thereto, said resilient arms extending substantially at right angles to the plate and having, at their free ends, flanges provided with rising slopes which are engagable behind said retaining cams.

In accordance with the invention the plate can be securely connected to the solid body in the easiest possible manner. Owing to the said resilient arms, the free ends of which comprise flanges having rising slopes, the plate can readily be connected to the solid body during automatic production of the switches. When the switches are manufactured, the two parts may be automatically connected, the flanges of the resilient arms engaging behind the retaining cams on the solid body and being securely retained in this position in the finished switches, whilst the rising slopes enable the plate and solid body to be joined together fully automatically. Since the connection between the plate and the solid body can easily be released again, the switch can be dismantled without being destroyed.

Thus, defective parts and the fuse can be changed at any time, which is exceptionally advantageous in a mass-produced item.

Preferably, the plate comprises, in the region of the fusible member, an opening the diameter of which is smaller than the diameter of the fusible member. A projection of the fusible member can then pass through said opening in the plate. In such an arrangement, the fusible member is directly thermally connected to the surface of the electrical appliance which is to be monitored. In this way, high heat-transmission resistance and hence the risk of a delay in switching off are avoided.

An embodiment of the invention will now be described, by way of example only, with references to the accompanying drawings, in which: Figure 1 shows a schematic side view of an assembled temperature sensitive safety switch in accordance with the invention; Figure 2 shows a view transverse to Figure 1; Figure 3 shows an enlarged view of the temperature sensitive safety switch in longitudinal section.

Referring to Figure 3, switch contacts 9, 9' are attached to the solid body 1 by means of rivets 11. A switch pin 10 is movably mounted in a bore 12 in the solid body 1. The switch pin 10 is operatively connected at one end to the switch contacts 9, 9' and at the other end to a fusible member 7 which is clamped between the switch pin 10 and a plate 3. An opening 8 in the plate 3 serves to receive a projection 7' of the fusible member 7, thereby mounting the fusible member 7 in the region of the switch pin 10 during production of the switch and, in the position of installation, thermally connecting the fusible member 7 in heat conducting manner to the surface which is to be monitored.

The temperature sensitive safety switch is assembled by means of the following simple steps.

The switch contacts 9, 9' are riveted to the solid body 1. The switch pin 10 and fusible member 7 are inserted in the bore 12. The plate 3 having resilient or spring arms 4 is then pushed onto the solid body 1 until the flanges 6 at the free ends of the spring arms 4 which have rising slopes 5 engage behind retaining cams 2 on the solid body 1.

In this way the individual parts of the switch are securely held to the solid body. The projection 7' of the fusible member 7 passes through the opening 8 and holds the switch contacts 9, 9' over the switch pin 10 in the closed position.

In order to change the fusible member 7, the spring arms 4 are opened and the plate 3 is pulled away from the solid body 1. A new fusible member 7 is inserted and the plate is easily reconnected to the solid body 1 by pushing it on.

Claims

1. A temperature sensitive safety switch for electrical appliances, comprising a temperature-resistant solid body having switch contacts secured thereto, a switch pin cooperating with said switch contacts and movably guided in the solid body, a fusible member connectible in heat-conducting manner to a heated part of a said appliance by means of a plate, said fusible member being effective via said switch pin to hold the switch contacts in the closed position, wherein retaining cams are formed on said solid body, and said plate has resilient arms connected thereto, said resilient arms extending substantially at right angles to the plate and having, at their free ends, flanges provided with rising slopes which are engagable behind said retaining cams.

2. A switch as claimed in claim 1, wherein the plate comprises, in the region of the fusible member, an opening the diameter of which is smaller than the diameter of the fusible member.

3. A switch as claimed in claims 1 and 2, wherein a projection of the fusible member passes through said opening in the plate.

4. A temperature sensitive safety switch for electrical appliances substantially as hereinbefore described with reference to the accompanying