DE3448570C2 - Temp. sensor for cooking equipment - Google Patents

Abstract

The metal rod is clamped to the quartz tube at the free end via a compression fitting with a metal sleeve (8) with a high expansion coefficient and a packing ring (6) with an expansion coefficient between that of the metal rod and that of the quartz tube. The control end has the metal rod moving relative to the clamped sleeve. The control end has the quartz tube clamped to the housing by the intermediate expansion coefficient spacer (5). The spacers bridge the gap between the very low expansion coefficient of the tube and the high coefficient of the metal components. The spacers are made from alumina type compounds, or nickel-iron-cobalt alloys.

Description

The invention relates to a device for regulating and / or limiting the temperature for two heating zones with radiant or contact radiators of electrical Cooking appliances in which to regulate and / or limit the temperature at least one a switch housing attached temperature sensor is arranged, the rod with high thermal expansion, which rod in a tube with low thermal Expansion is arranged, the tube being adjacent to the end of the tube Has rod surrounding support body and each held between holding parts are.

The regulation or limitation of the temperature takes place in a device of the above Kind especially in that the temperature-related axial movement of the rod-shaped Temperature sensor is used to actuate the contact system, in such a way that the heating circuit is switched on at a certain temperature and at a certain one higher temperature is switched off again.

Previously known devices can only be used for electric cooking appliances that have only one heating zone have, are used. Would be the temperature sensor in such devices over two zones with different temperatures, both zones would The extent of the rod influence, the exact measurement of the temperature of a zone independent depending on the temperature of the other zone would not be feasible.

From DE 28 39 161 A1 a temperature limiter for a glass ceramic cooker was known unit of a substantially rod-shaped temperature sensor, which consists of a tube and there is a rod in it with different coefficients of expansion, having. The tube is encased in metal sleeves at the lower and upper ends. That tempera door sensor actuates one arranged in a base Power snap switch for off switching the power of the heating of the glass ceramic cooktop and one in the Soc kel arranged signal switch, the circuit of a signaling device for warning touching the hot cooking surface can switch on or off.

A similar temperature sensor was known from DE 78 26 549 U1, its rod is made of two sections, one of these two sections being the same Expansion coefficient like the pipe, the second one has a different one. The Pipe sections described are arranged directly adjacent to one another in the rod.  

GB-A-2 069 300 has one heating plate with several concentrically arranged Heating zones known. To record the temperature of the individual heating zones, pro Heating zone a separate, each from a tube with an internal one-piece rod formed temperature sensor used, which extends over all heating zones. So its thermal expansion depends only on the temperature of a single heating zone is influenced, his pipe is thermal in the area of the remaining heating zones surrounding insulating material.

The object of the present invention is now to provide a device for Regulation or limitation of the temperature for radiation zones having several heating zones or contact radiators of electrical cooking appliances of the type described in the introduction which is the temperature of one heating zone regardless of the temperatures of the other zones can be regulated or limited.

According to the invention this is achieved in that the tube consists of two axially one behind the other, directly assigned to the two heating zones sections with different expansion coefficients α ₃₁ and α ₃₂ and that the individual sections in a - seen in cross section - H-shaped intermediate support body with are supported by a coefficient of thermal expansion α ₁₁ , where: α ₃₂ <α ₁₁ <α ₃₁ .

With such a design, the advantages of a reduced relative movement between pipe end and intermediate support body for itself through several heating zones stretching rods can be used, with an additional advantageous centering of the tube and an extension of the spark discharge path between the heating coil and rod can be achieved.

In a further development of the invention it can be provided that between each end of the tube and the holding part a supporting body is arranged enclosing the rod, the thermal expansion coefficient α _{1 is} smaller than the thermal expansion coefficient α _{2 from} the subsequent holding part, but greater than the thermal expansion coefficient α ₃₁ , α32 of the respective end of the respective pipe section.

With a support body designed in this way, the transition with respect to the thermi expansion coefficients significantly weakened, so that the radial Relativbe movement between the pipe end and the subsequent support body on a ver negligible minimum is reduced. So there is every possibility of damage tion, especially chipping, of the pipe end reliably excluded.

The invention is described below with reference to three embodiment shown in the drawing Examples described in more detail:

In the drawings Fig. 1 is a side view of an enlarged device for regulating and / or limiting the temperature of radiant or contact heating elements of electrical cooking appliances, Fig. 2 shows an embodiment of the pipe end the device according to Fig. 1 and Fig 3 shows an embodiment of the invention. The invention according to Fig. 1.

In Fig. 1 consisting of a temperature sensor 1 and a switching head 2 Vorrich device for regulating or limiting the temperature is shown. The temperature sensor 1 has a rod 3 made of a high-temperature-resistant material with a high coefficient of thermal expansion, for example a nickel-chromium alloy or an iron-chromium alloy, which is arranged in a tube 4 . This consists of a high temperature-resistant material with a low coefficient of thermal expansion, for example quartz glass or ceramic, which forms a shell for the rod 3 . The ends of the tube 4 are each delimited by a support body 5 , 6 . Holding parts 7 , 8 in the form of a base plate or a washer or screw nut made of metal adjoin these. While the thermal expansion coefficient α _{3 of} the quartz tube 4 is approximately 5 × 10 ^-7 / ° C, the thermal expansion coefficient α _{2 of} the metallic holding parts 7 , 8 is approximately 180 × 10 ^-7 / ° C. If Al ₂ O _{3 is used} as the material for the support bodies 5 , 6 in between , the coefficient of thermal expansion α _{1 is} approximately 70 × 10 ^-7 / ° C. The rod 3 is through holes in the support body 5 , the base plate 7 , the support body 6 and the washer 8 and a nut 16 leads. The other end of the rod 3 has a cambered collar 9 . Between this collar 9 and the base plate 7 and thus between the collar 9 and one end of the tube 3 containing the tube 4 , a compression spring 10 is arranged which holds the rod 3 under tensile stress, and thus the nut 16 against the outside of the washer 8 presses.

The rod 3 with the parts arranged thereon and the compression spring 10 form the temperature sensor which is screwed to the switching head 2 with the screws 11 , this having a recess 12 into which the end of the rod 3 having the compression spring 10 is inserted .

The switch head 2 forms a housing 13 which is open on the upper side, the open side being coverable by a cover plate. The interior of the housing 13 is in communication with the recess 12 via an at least approximately coaxial with the rod 3 bore in which there is an axially displaceable transmission member 14 in the bore. One end of the transmission member 14 lies on the cambered surface of the collar 9 .

The transmission member 14 has an actuating surface 15 for actuating the control or limitation of the temperature serving contact system, which has a movable contact 16 carrying contact spring 17 and a fixed contact 18 having the connection flag 19 . The contact spring 17 is fixedly connected to a spring carrier 20 which also carries the contact spring 17 .

In the state shown, the contacts 16 , 18 are open and the heating circuit is thus interrupted. If the heating circuit is connected to the supply voltage, a heating coil of the radiator is heated, consequently the temperature in the space between a cooking surface and the heating coil rises. The rod 3 expands so that the transmission member 14 is moved to the actuation point of the contact spring 17 . Reaches the temperature in the space between the cooking surface and the heating coil, for example, the value of 700 ° C, the actuating surface 15 of the transmission member 14 abuts against the contact spring 17 , the contacts 16 , 18 being separated suddenly, so that the heating is switched off. If the rod 3 is shortened in the course of the following cooling, the contact spring 25 snaps back into the position in which the contacts 16 , 18 are closed.

As a result of the arrangement of a support body 5 or 6 in each case at one end of the quartz tube 4 with a coefficient of thermal expansion α ₁ which is smaller than the thermal expansion coefficient α _{2 of} the subsequent holding part, in FIG. 1 the washer 8 or metal each consisting of the base plate 7 , and greater than the thermal expansion coefficient α _{3 of} the tube, in Fig. 1 of the quartz glass tube 4 , an excessive radial movement between the tube end and the support body and thus damage to the tube ends is reliably excluded.

The support body 5 are preferably made of an oxide ceramic material such. B. the aforementioned Al ₂ O ₃ or steatite or beryllium oxide. Materials of this material group combine the advantages of high mechanical strength and scaling resistance up to 800 ° C with an expansion coefficient α _{1 that is} conveniently on the order of magnitude between the expansion coefficients α ₂ and α ₃ .

In those applications where there are no extremely high demands on the mechanical fes activity of the support body can be made while maintaining the favorable ratio nisse of the three expansion coefficients to each other and the scaling resistance also tech porcelain are used, which in turn has the advantage of a lighter bear has processability.

Very good results have also been obtained with Ni-Fe-Co alloys or Ni-Fe alloys aims. A disadvantage of these alloys, however, is that their scale resistance is only  up to approx. 300 ° C, so that the supports come to rest outside the heating zone have to.

The detail shown in FIG. 2 shows the switch housing 30 adjacent the end of a tube 32 surrounding a rod 31 , which has a funnel-shaped end 34 .

A support body 36 having a spherical surface is provided between the metallic holding part 35 of the switch housing 30 and the tube end 34 .

The approximately middle part of a rod 40 shown in FIG. 3 of a device for regulating or limiting a temperature value or a temperature range of radiation or contact heaters of electric cooking appliances with two heating zones has two pipe sections 41 , 42 arranged axially one behind the other . These pipe sections 41 , 42 have different coefficients of expansion α ₃₁ and α ₃₂ .

The individual sections 41 , 42 are in - seen in cross section - supports H-shaped intermediate support body 43 with a thermal expansion coefficient α ₁₁ abge. Between each end of the tube 4 and the holding part 7 , 8 , a support body 5 , 6 enclosing the rod 3 is arranged (see FIG. 1), the coefficient of thermal expansion α _{1 of which is} smaller than the coefficient of thermal expansion α _{2 of} the subsequent holding part 7 , 8 , but is greater than the thermal expansion coefficient α ₃₁ , α _{32 of} the respective end of the tube 4 .

The section 42 , which is located in the zone of the temperature to be measured, is formed with a low thermal expansion coefficient α ₃₁ , the section 41 , which is located in the zone, the temperature of which should not influence the expansion of the rod, will be formed with a coefficient of thermal expansion α ₃₂ , which is essentially the same as the coefficient of expansion of the rod 3 . As a result, the pipe section 41 and the rod section surrounded by this pipe section 41 expand to the same extent, so there is no relative movement between the pipe section 41 and the rod 3 in this area. The temperature in the region of the pipe section 41 cannot influence the shutdown process.

Claims (2)

1. Device for regulating and / or limiting the temperature for two heating zones having radiation or contact heating body of electric cooking appliances, in which at least one temperature sensor attached to a switch housing is arranged for regulating and / or limiting the temperature, which has a rod with high thermal Expansion, which rod is arranged in a tube with low thermal expansion, the tube having the rod enclosing support body adjacent to the end of the tube and the se are each held between holding parts, characterized in that the tube consists of two axially consecutively arranged th, directly assigned to the two heating zones sections ( 41 , 42 ) with different coefficients of expansion α ₃₁ and α ₃₂ and that the individual sections ( 41 , 42 ) in a - seen in cross section - H-shaped intermediate support body ( 43 ) with a thermal expansion g coefficients α _{11 are} supported, where α ₃₂ <α ₁₁ <α ₃₁ . 2. Device according to claim 1, characterized in that each Weil between each end of the tube ( 4 ) and the holding part ( 7 , 8 ) is arranged a rod ( 3 ) surrounding support body ( 5 , 6 ), the thermal expansion coefficient α _{1 is} smaller than the thermal expansion coefficient α _{2 of} the subsequent holding part ( 7 , 8 ) but larger than the thermal expansion coefficient α ₃₁ , α _{32 of} the pipe sections ( 41 , 42 ).