FI57509B - TEMPERATURBEGRAENSARE - Google Patents

Description

R2C ^ 1 ΓβΙ ^ ANNOUNCEMENT PUBLIC.SU en en o Μα lbj (11 'utläggningsskrift 5/5 0 9 ^ (51) Kv.ik.3 / Int.ci.3 H 05 B 1/02 // H 01 H 37A8 ENGLISH —FINLAND (21) P »t * nttlh» k * inu $ - Ptt «ntant <Mcnlnt 731371 (22) Hikamltpilvft - Antttknlng * di | 09.05-75 ^ (23) AlkupUvt — Giltlgh« ttdag 09.05.75 (41) Tullut To the public - Bllrlt affentllg 11.11.75

National Board of Patents and Registration (44) Date of issue of NihUviluipeno

Patent · och registerstyrelsen 7 Aratkin utiagd ech uti. * Krift «n publictnd 30.0U.80

(32) (33) (31) Pyy «>« ty «uolk« u * —Btgird prlorlt «10.05.7U

Federal Republic of Germany Förbundsrepubliken Tyskland (DE) P 2U2262U.2 (71) (72) Karl Fischer, Am Gaensberg, 7519 Oberderdingen, Federal Republic of Germany Förbundsrepubliken Tyskland (DE) (7U) Oy Kolster Ab (5U) Temperature limiter - Temperature limiter

The invention relates to a temperature limiter having a temperature sensor, the switch housing of which, which includes a switch fixedly adjusted with respect to its switch temperature, is arranged on the lower surface of the unheated central area of the electric hob.

One such temperature limiter is disclosed in German Patent No. 1,123,059. It has a crescent-shaped insulating housing in which a bimetallic and a quick-release switch are placed for switching off the heating element. Normally, only one of the three heating elements of the hob is switched off, so that barely half of the total power is switched off. Since the bimetals are already very unstable in the relatively high temperature ranges in which the temperature limiter operates and provide only small driving forces, the switching temperature difference (switching hysteresis) between the switch-off and the switch-on is very large. It is in the order of about 80 ° C. Although the device can be used to keep the temperature slightly lower in the unheated central area, the use of thermal connection for the heating line temperature is also very low.

The object of the invention is to develop a temperature limiter which, due to its structure and arrangement, makes it possible to cut off the temperature of the heating line as narrowly as possible with only a small switching hysteresis.

2 57509 According to the invention, this object is achieved in that the temperature sensor mounted on the switch rack consists of an expansion sleeve known per se with a higher coefficient of thermal expansion than a transfer rod inserted therein and extending from the unheated central region of the plate substantially radially over heater and in good heat transfer connection to it. The temperature sensor, which is not sensitive to high thermal loads and includes an expansion sleeve and a transfer rod, is thus tightly connected to the temperature of the heating line, but transfers only relatively little heat to a switch head with a quick switch and can therefore be made a precision switch. the size is only 1/100 rtm. When using a transfer structure, a temperature limiter with the highest possible reaction sensitivity is thus obtained. It is also relatively easy to make connections in an unheated central area.

Other advantages and features of the invention will be apparent from the subclaims and the description taken in conjunction with the drawings. Embodiments of the invention are shown in the drawings and will be described in more detail below with reference to the drawings, in which: Figure 1 shows a bottom view of an electric hob with a temperature limiter according to the invention; Fig. 2 shows a cross-sectional view along the line II-II in Fig. 1; Fig. 3 is a cross-sectional view of a portion of the transformation with the section line running transverse to the section line of Fig. 2; Fig. b shows a longitudinal sectional view of the temperature limiter; Fig. 5 shows an enlarged view of the expansion sleeve as seen from its free end; Fig. 6 shows a schematic circuit view of a temperature limiter in cooperation with an energy regulator; Fig. 7 shows a schematic diagram in which the temperature is plotted as a function of time and the upper part of which shows the relationships at the temperature sensor and the lower part of which shows the relationships at the energy controller; Fig. 8 shows a diagram corresponding to Fig. 7 of the second operating mode; Fig. 9 shows a cross-section of another embodiment of an electric hob; and Figure 10 is a view of the arrow X of Figure 9.

Fig. 1 shows a bottom view of an electric hob 11 consisting of a hob body 12 according to Fig. 2, below which (above in the figure) 5 57509 there is a heating ring region 13. In this groove 14 the heating lines 13 in the form of coils. They are enclosed in their insulating mass 16 which fills a helical groove. The heating ring area is delimited outwards by a ring rib 17 and inwards by a ring rib 18. Inside the ring rib 16 there is an unheated central area 19 »in the middle of which a central eye 20» is cast, by means of which the hob or covers are attached. Until now, therefore, it is a question of an ordinary electric hob.

Housed in the unheated central region 19 is a housing 22 containing a switch 21 of the temperature limiter 23 (see Fig. 4). The housing consists of an insulating material »e.g. steatite and has a substantially flat, rectangular shape towards the ring rib 18 at beveled angles 24 · Figure 2 shows that the height dimensions of the housing 22 are very small and also the radial dimensions are so small that the housing 22 can be easily placed in the middle of the unheated central area between the central eye 20 and the ring rib. This is also aided by the beveled corners 24, which make it possible to fit the shape of the central region.

Slightly eccentrically, the temperature sensor 23 extends from the outwardly directed side of the housing with beveled corners 24 »which sensor consists of an expansion sleeve 26» having relatively high coefficients of thermal expansion »and a transfer rod 27» housed in a housing having low coefficients of thermal expansion, e.g. Figure 4) ·

Figure 1 shows that the rod-like temperature sensor 23 extends out of the unheated central region substantially radially (relative to the radius slightly offset) over the heating ring region 13. In this case, it passes through the notch; 28 of the annular rib. The housing of the flat structure allows the temperature sensor 23 passes directly adjacent to kuumennusjohtoja a surrounding insulation of mass lower side (in the drawings the upper side preferably with a certain heat touch-evaporation, which, however, should not be too large laajennushylsyn 26 because of box-jennusliikkeiden. Outermost circle must ensure that the pole expansion is enough space for the temperature sensor , .iolla.ou between the adjusting sleeve 29 »connecting the expansion sleeve and the transfer rod and the outer ring rib 17.

From the rear of the housing 22, which is opposite the temperature sensor 23, conductive connections 30 are connected via lines 31. The wires 31 lead out of the unheated central region through the insulating grommet 32. As shown in Figure 2, this is closed by a flat, box-shaped jacket 33 placed inside the inner annular rib 18, which, together with a conventional lower plate cover (not shown), is fastened to the central air by means of a screw twisted. The jacket 33 protects the part containing the switch from the temperature limiter from dust and other disturbing effects of the environment. Cables 31 can easily pass past their hubs 20 on both sides because the connections 30 are close to the two narrow sides of the housing 22 *

Fig. 3 shows a flushed embodiment in which the unheated central region and the temperature limiter 23 have the same shape, but the heating ring region of the electric hob 11 is covered with a damper 34 having an annular shape of the heating ring region 13 but slightly larger so that it can be pressed between the ribs 17 and 18. it remains self-stick * this plate is closely eristyemassan 16 on the bottom side and closes this difference completely sealed from external influences (e.g., * the forming rid of dust). This damper, which is in thermal contact with the insulating compound or with the extending ribs separating the grooves 14, at the same time forms an ideal heat transfer surface for connecting the temperature sensor 23 to a narrow thermal connection to the heating ring area temperature * The temperature sensor 23 then extends In the embodiment shown, it is surrounded by a 3/4 part cover 35 »having a large Omega cross-sectional shape and bent from a sheet metal. The cover 33 is elongate corresponding to the transverse expansion of the temperature sensor 23 and rests on its flanges 36 on a damper 34, to which it can be attached e.g. by spot welding * It is also possible to connect the cover 35 directly to the jacket 33 so that the entire temperature limiter is closed and thermally tightened. Nevertheless, only the temperature sensor is then exposed to the high temperature of the heating ring region, so that it can react very quickly to changes in the heating line temperature, while the housing 22 containing the temperature sensitive switch is located in the unheated central region. Both the cover 33 and the damper 34 thus act * to protect both the electric hob and the temperature limiter against dirt or other environmental influences, as well as to provide a narrow thermal connection of the temperature sensor with the lowest possible thermal inertia to the heating line temperature.

Figure 4 shows the details of the temperature limiter. The temperature sensor 23 already described extends through the opening in the housing 22. The expansion sleeve 26 has a flange 37 on which a plate 70 is placed to enlarge the flange. The housing is made as one part of a ceramic insulating lumen, e.g. steatite, and has a notch 40 which is open towards the other side, i. transverse to the expansion portion, and which, after installation of the switch, is closed by an insulating cover 71 (Fig. 2). The flange 37 with its plates 70 is inserted laterally into the slot 38 of the housing in the region of the opening of the temperature sensor and thus secures this.

5 57509

The switch 21 is located in the notch 40 as a quick switch. The quick coupling spring 21 is a suction spring 41 »from which a spring tongue 42» is bent, which is supported on a support bearing 43. The operating point 44 * to which the transfer rod 27 engages is relatively close to the support bearing 43, so that due to the small lever arm the switch engages very sensitively, i. its switching difference between disconnection and reconnection at the operating point 44 is about 1/100 nuns.

At its free end, the snap spring 41 carries a contact 43 which cooperates with the joint 30 with a counter-contact part 46 of the same piece, which is inserted into the slot of the housing from the side and thus fastened. The counter-support 47 »which is also fixed by insertion and which is bent from the damper, supports the contact of the key spring in the open position and is designed so that the key spring moves only the distance absolutely necessary to open the contact. This also improves the sensitivity of the switch. The second connection 30 is made as a bracket 73 »inserted into the slot 72 leading out of the notch 40 and bent in the form of a sheet metal strip, the end of which in the notch 40 is fixed laterally into the slot 74 · A bottom part 73 of the quick coupling 21 is placed on the sheet metal strip 73. 43 and a key spring located here at the other end. The bracket 73 is supported on the housing in the area of the access point 44.

The housing is substantially rectangular with those already mentioned, chamfered at an angle 24.

Thus, a temperature limiter with a very simple structure and a very sensitive structure with the smallest possible dimensions is obtained. For example, the expansion distance of the temperature limiter shown in Figure 4 may be about 33/100 mm when the effective length of the expansion sleeve is only about 43 am and the temperature difference is 360 ° with respect to room temperature. Thus, when the switching distance between switching on and off is l / 100 mm, the hysteresis of the temperature limiter is about 10 °. This is very small compared to about 00 °, which bimetallic switches usually require * Nevertheless, no lever transmission is required, but the transfer rod can directly affect the operating point of the compression spring. The expansion sleeve 26 is preferably circular in cross section for manufacturing reasons, but can also be flattened or square on one side. shape, especially to fit the surface of the heating ring region.

Due to the shape of the housing, which is indivisible in the transverse direction of the temperature sensor and thus transverse to the main carriage, it is ensured that no electricity is present in the force direction which could lead to inaccurate coupling · This is also influenced by the fact that the key spring 41 normally holds the switch and temperature coupling voimakytkennässä *

It should be noted that a heat transfer member 76 in the form of a sheet metal plate is applied to the expansion sleeve 26. This, on the other hand, provides a large heat transfer surface for radiation and convection transfer and can also transfer heat by contacting parts of the hob or damper 34 by conducting to the expansion sleeve. It may also be advantageous to displace the hob in a plane parallel to the hob.

In addition, it is preferred to reduce the heat transfer resistance of the temperature sensor, possibly with a heat transfer element, by means of a corresponding surface treatment. A coating with a high heat-resistant, coarse varnish 77 is suitable for this, which substantially improves the heat transfer properties of the relatively smooth and clear surface of the expansion sleeve, which is mostly made of stainless steel.

It can be seen from Figures 4 and 5 that the adjusting screw 80 is screwed into the lower end of the expansion sleeve 26 of very thin, stainless steel tube. To this end, the thread 81 in the expansion sleeve 26 is made by pressing. Although this tube becomes almost cut at the tip of the thread when pressed. Therefore, the thread is made by pressing it against the tension core with a longitudinally spaced cylindrical slider (Pinole) which presses the three portions 82 of the tube inwards and leaves between them the longest extensions or partitions extending in the longitudinal direction 83 * Few or no threads are pressed in, so that they form a longitudinally oriented whole in the region of the threaded parts, and in particular the full thickness of the material for the thread is available on both sides of the triangular partition. This feature also contributes to the achievement of a fast and accurate temperature limiter, where it is possible to make the expansion sleeve very thin and therefore with low thermal inertia.

It is preferred to make the transfer rod 27 from a ceramic material. This has almost no thermal expansion over the entire temperature range, which is the case for other substances with low thermal expansion only over a certain temperature range. The advantage of the ceramic rod is also a very low heat capacity, so that the sensitivity of the temperature limiter increases here as well.

Figure 6 shows the connection of the temperature limiter 23 in cooperation with the energy regulator 30. The energy regulator 30 is a so-called a quantizable energy regulator that supplies energy, in particular always full energy, to the heating lines of the electric hob 15 in power pulses, the Interval and Duration of which determine the average, input power. It may have a conventional structure and in the schematic circuit diagram shown it has a switch 51 »which is normally closed and can be opened by a thermally expandable bimetallic 52. The heating of the x-metal takes place by a control heat resistor 53. The effect of the bimetal 52 on the switch 51 can be adjusted with the operating knob 5 power. In the example shown, switch 51, control heating resistor 53, hob heating line 15 and temperature limiter switch 21 are connected in series to the hob circuit. This means that the circuit, and thus the hob and energy regulator heating, is cut off when either switch 21 or switch 51 (or both) opens . It is essential that the temperature limiter 23, due to its structure and arrangement on the hob, has such a characteristic that, when it starts operating, the switching period between its switching on and off is of the same order of magnitude as the switching period of the energy controller. This means that compared to conventional temperature limiters, the temperature limiter 23 must have a very short switching period. This is achieved, on the one hand, because the temperature sensor is very narrowly connected to the region of the heating ring and thus to the temperature of the heating line, and on the other hand due to the very small temperature difference between switching on and off. The temperature limiter of Figure U in the arrangement of Figures 1-3 is best suited for this. However, it is also possible to use other temperature limiters that perform this function. Modifications can also be made to the energy regulator and connection. In this way, for example, the control heating resistor 53 can also be placed in a parallel circuit, which, however, also depends on the switch 51, and the temperature limiter does not have to switch on all power, but can also switch on partial power, although it is very advantageous to use it on full power.

Referring to Figures 7 and 8, the operation of the control device according to Figure 5 will be described. Figure 7 shows the normal operation of the hob and here a lower temperature is used than the cut-out temperature of the temperature limiter, which is e.g. U05 ° C. When the energy regulator switch 51 is connected, the thermal resistors 15 and 53 operate and the bimetallic temperature of the energy regulator rises (lines 55) until the cut-off point 56 of the energy regulator, which can be adjusted with the operation knob 5 ^, is reached. Switch 51 opens and thermal resistors 15 and 53 are turned off so that the bimetallic temperature drops (line 57), 8 57509 untilB is overridden by switching hysteresis (temperature difference between set cut-off temperature 58 and reconnection temperature 59), and reconnect switch and thus a new quantization cycle begins. This is the normal operation of the energy controller. The switching period between the two cut-off points 56 or the reconnection point 60 is then usually less than one minute, so that uniform heating is possible as a result of the thermal inertia of the hob. However, the switching periods depend on the The use of the situation. In particular, the different heat dissipation from the hob, which is caused by the differences in the cooking and frying pans and their filling (the temperature limiter probably works with the roasts at the earliest), has a large effect on the switching cycles.

It can be seen from Figure 7 that the temperature limiter does not respond to the operation example shown here. However, the energy regulator 50 is set so high that the hob heats up very close to the allowable limit. However, the switch 21 of the temperature limiter 23 remains continuously connected because the cut-off temperature limit 61 of the temperature limiter is not reached. However, it is obvious that due to the very narrow connection of the sensor 25 of the temperature limiter 23, temperature fluctuations due to energy supply rate are shifted slightly attenuated. This would not be the case for a temperature limiter whose connection is less narrow. Here, the upper line of Fig. 7, i. the temperature of the hotplate detected by the temperature limiter would run substantially horizontally ti. The line between the two sawtooth curves indicates the switching duration 62 and the switching period 63. The quotient of both gives the relative switching duration and thus the adjusted partial power.

In Fig. 8, it was not shown as an example that when the setting of the energy regulator is constant, the temperature of the hob can rise when, for example, the cookware is removed from the hob or a larger, more heat-consuming soup is replaced by a smaller one. In the connected circuit, therefore, the temperature detected by the temperature limiter (line 64) rises more strongly and reaches the fixed cut-off temperature limit 61 earlier than in Fig. 7. In this case, the temperature limiter cut-off point 65 is reached before the energy regulator heating resistor 53 heats the bimetallic cut-off point (this would occur as the dashed line in Figure 8 continues).

It is thus clear that at cut-off point 65, the temperature limiter disconnects the 57509 energy regulator and the hob circuit by opening the switch 21. The switch 51 of the snerger regulator 50 remains continuously closed, but nevertheless the temperatures drop at both the hotplate 15 and 53 when the hotplate 15 and 53 are reached. the temperature limiter reconnection temperature limit 66, this again switches the switch 21 and the power is again supplied to the hob and the energy saver, because the energy · regulator has not switched off at all. It can be seen from the formation of power pulses that, despite the constant position of the energy controller, the switching duration time and, above all, the relative switching duration time have decreased. It is thus obvious that the temperature limiter takes over the quantification operation of the energy controller when the specified temperature limit is reached, and then steadily and steplessly reduces the power so much that the maximum permissible temperature limit is not exceeded. Thus, a combination of two, preferably space-independent, quantizable switching elements is created, one of which is adjustable and below the specified limiting temperature operates alone and is not subject to this effect, while at a certain limiting temperature the second switching element takes over the first quantizing operation. In this case, it is important that the predetermined switching periods of the temperature limiter and the energy regulator are of the same order of magnitude within the specified limits. Ideally, both predetermined switching periods are the same. However, they can deviate from each other in part or even many times, as long as the disturbing temperature fluctuations are not thus introduced into the cooking vessel. In any case, due to the extremely long switching periods of the temperature limiter, the hob and thus also the energy regulator must not be switched off for a long time, so that when the cookware cools the host thinks it has set too low a power and therefore turns the power control to a higher value. This would not be of any use at first, and the next cut-out of the temperature limiter would have even longer cut-off periods. When we speak here of a predetermined switching period, this means the switching period of the coupling member while it is in operation. Thus, for example, it can be seen from Fig. 7 that the actual switching period of the energy controller is short and of limited length, but that the actual switching period of the temperature limiter is theoretically infinitely long because it does not start operating at all. Nevertheless, its predetermined switching period, which can be seen, for example, in Fig. 8, is of the same order of magnitude as that of the energy controller.

The invention provides a control device, the operation of which can be easily understood by the host, but which still has an excellent effect. The host adjusts the power level set by the energy controller and this becomes steplessly reduced if the maximum temperature is exceeded. It is known that many hostesses prefer to adjust the power levels because temperature level adjustment, as with automatic controllers, requires the hostess to get used to and a certain amount of abstract thinking. The control device is also very simple in construction, because a temperature limiter that meets the requirements, as shown in Fig. 4, is very easy to manufacture, and the energy regulator also does not require high manufacturing costs. However, only two purely power supply wires are required between the energy regulator and the hob, which represents a structural advantage over the automatic regulator.

Figures 9 and 10 show an electric hob 11 'corresponding to Figures 1 and 2, the same parts having the same reference numerals. It has a lower, annular cover plate 90 which closes the heating ring region 13 and the temperature sensor 23 »from below but leaves the central region 19 free. It rests on the inside over the inner annular rib 18 and forms a barrier which prevents convection heat from penetrating the central region. It is secured to the sheet metal by a stamped cover portion 92 so that its star-like arms 94 extending from the center portion press the cover portion onto the annular rib 18. A nut threaded into the central eye 20 on the riveted central tube 99 »pushes the cover portion 92 upward. Large air passages 91 »are created between the arms 94, by means of which the temperature limiter housing containing the switch is cooled and by which the cut-out temperature of the temperature limiter can be set high without damage to the switch, so that a lot of power can be transferred to poor boilers.

It is also possible to make the cover plate integral with the cover part. In this case, the cover would rest on the ring rib 18 according to the figures and have an opening in the middle area.

Claims (17)

A temperature limiter having a temperature sensor and a switch housing comprising a switch fixedly adjusted for its switch temperature arranged on the lower surface of the unheated central region of the electric hob, characterized in that the temperature sensor (25) mounted on the switch housing (22) consists of an expansion sleeve (26) having a higher heat transfer coefficient than the transfer rod (27) fitted therein and extending from the unheated central region (19) of the plate substantially radially over the lower surface of the heating ring region (13) containing the heater (15) near the heater (15) and in good condition blast transfer connection to it. Temperature limiter according to Claim 1, characterized in that the housing (22) containing the switch (21) is arranged at the edge of the unheated central region (19) and leaves the central region of the electric hob (11) free. Temperature limiter according to Claims 1 and 2, characterized in that the temperature sensor (25) extends through a notch (28) in an annular rib (18) which delimits the heating ring region (13) of the electric hob (11) relative to the unheated central region (19). ). Temperature limiter according to one of Claims 1 to 3, characterized in that the temperature sensor (25) is located immediately below the cover (16) of the heating line (15). Temperature limiter according to one of Claims 1 to 3, characterized in that the temperature sensor (25) is located immediately below the damper (34) which covers the underside of the heating ring region (13). Temperature limiter according to one of Claims 1 to 5, characterized in that the temperature sensor (25) is surrounded by a partially closed cover (35). Temperature limiter according to Claim 6, characterized in that the cover is a JTL-shaped damper, the flanges (36) of which are on the side of the electric hob (11). Temperature limiter according to one of Claims 4 to 7, characterized in that the cover (35) is arranged on the damper (34). Temperature limiter according to one of Claims 1 to 8, characterized in that the temperature sensor (25) or its cover (35) is in contact with the electric hob (11) for transferring heat by contact. Temperature limiter according to one of Claims 1 to 9, characterized in that the transfer rod (27) acts directly on the actuating spring (41) of the quick coupling (21) without transmission. Temperature limiter according to Claim 10, characterized in that the operating point (44) to which the transfer rod (27) is connected at the compression spring (41) 12 57509 is located close to the quick-release (21) support tongue (43) of the spring tongue (42). 11 57509 Temperature limiter according to Claim 10 or 11, characterized in that the coupling-side end of the expansion sleeve (26) has a flange (37) which is arranged in a one-piece, side-open coupling housing (22) covered by a cover (71). Temperature limiter according to one of Claims 1 to 12, characterized in that the temperature sensor (25) is adapted to be force-coupled under the pressure of the key spring (41) of the quick-release switch (21). Temperature limiter according to one of Claims 1 to 13, characterized in that the switch housing (22) has beveled or rounded corners (24) on the side from which the temperature sensor (25) protrudes therefrom, which are arranged in the unheated central region (11) of the hob (11). 19) according to the round shape. Temperature limiter according to one of Claims 1 to 14, characterized in that noise transfer elements (76) are arranged on the east temperature sensor (25). Temperature limiter according to Claim 15, characterized in that the heat transfer elements (76) are plates inserted into the temperature sensor element (25). Temperature limiter according to one of Claims 1 to 16, characterized in that the temperature sensor (25) has a cover layer (77) which increases the heat uptake. 13 57509