METHOD OF FIXING A TEMPERATURE SENSITIVE ELEMENT OF A HEAT CONSUMPTION METERING SYSTEM TO A SPOT WELDED SHEET IRON RADIATOR

Abstract: A method serves for fixing a temperature sensitive element (22) to a spot welded sheet iron radiator (1). A hole is drilled through the sheets (4, 5) of the radiator (1) in one of the areas where the sheets (4, 5) are in contact with each other. A pop-rivet (9) is mounted in the hole and the pop-rivet is used for the securing of the temperature sensitive element (22). It is achieved that the temperature element may be mounted while the radiator is in its mounted condition and in operation.

Description: Method of fixing a temperature sensitive element of a heat consumption metering system to a spot welded sheet iron radiator. The present invention relates to a method of fixing a temperature sensitive element of a heat consumption metering system to a spot welded sheet iron radiator. Temperature sensitive elements of the kind referred to above are used in order to be able to distribute the heating costs between the radiators connected to a central heating plant and accordingly, to distribute the heating costs between e.g. different tenants. In this connection it is important that the temperature sensitive element registers a temperature which is representative as regards the heat emitted from the radiator in question. In order to achieve this it is necessary that the temperature sensitive element is arranged upon the radiator in a definite way because the temperature sensitive element must not be positioned too near the side edges of the radiator and also not too near the top or bottom of the radiator. It is well known that the surface temperature of a radiator decreases from the top toward the bottom when the radiator is in use, and along the outer edges of the radiator the heat emission varies considerably and acordingly, temperatures measured along the outer edges will not be representative. In cases where the temperature sensitive element is a temperature sensor of a circuitry it is, aestetically, and also due to practical reasons, preferred that the electric wire for the temperature sensitive element is positioned at the rear side of the radiator because the wire then will be well protected. It is well-known to mount temperature sensitive elements of the kind here in question by positioning the elements in blocks consisting of material having high heat conductivity and to clamp such blocks against the rear side of the radiator e.g. by means of a U-shaped clamp. However, due to the fact that such clamp must grip about the edge of the radiator, temperature sensitive elements mounted in this way will be positioned relatively near one of the edges of the radiator which is inappropriate as it appears from the above. Moreover, it has been proposed to position a temperature sensitive element in a block of a material having high heat conductivity and to glue the block to the rear side of the radiator. However, such gluing also causes difficulties in particular if the mounting is to be made after the radiator has been arranged at its intended location and furthermore, a gluing does not secure a reliable heat transfer. It is the aim of the present invention to provide a method according to which it becomes possible to mount the temperature sensitive element upon a radiator which is not only mounted along a wall but also is filled with heating medium and even may be in operation for heating. Accordingly, methods which require welding or the use of a holding tool, e.g. a wrench, at the reverse side of the radiator are, in advance, excluded. The problem constituting the basis of the present invention is in connection with a method of the kind referred to above according to the invention solved by the following steps: drilling a hole through the sheets of the radiator in one of the areas where the sheets are in contact with each other and are welded together at distributed spots, mounting a pop-rivet (blind tubular rivet) in the hole and using the pop-rivet for fixing the temperature sensitive element. The invention is based upon the realization that it is possible by the shortening of the shaft of the pop-rivet caused during the mounting of the pop-rivet to achieve a complete and permanent sealing between the pop-rivet and the hole edges of the contacting sheet parts and that the drilling of the hole and the mounting of the pop-rivet take such a short time that only a neglectible leakage of heating medium out between the contacting sheet parts will occur before the complete and permanent sealing is obtained. In case the temperature sensitive element is constituted by a temperature sensor for a circuitry it is, according to the invention, preferred to use a sensor having a size and a shape such that the sensor may be accommodated in the interior of the pop-rivet. Thereby it is achieved that the sensor may be mounted by drawing the sensor into the rivet by means of an electric wire at the end of which the sensor is arranged and until the sensor is in heat transferring contact with the rivet. Hereby an effective fixing of the sensor in good heat transferring connection with the radiator is achieved in a simple way and the mounting location may be freely chosen. Moreover, if the wire is drawn in from the front surface of the radiator through the hole, the wire will be positioned along the rear side of the radiator and accordingly, will not interfere with cleaning of the radiator and moreover, will not ruin the appearance of the radiator. Moreover, the rivet will be slightly visible only and a displacement of the mounting location of the sensor will in practise be impossible and accordingly, it is secured that the result of the measuring will not be distorted by non-authorized displacement of the measuring location. In this connection it should be mentioned that the method in question also offers a good security against leakage at the mounting location. Even though the front sheet and the rear sheet of modern radiators may be spot welded at the locations where the sheets abut each other, such spot weldings are with modern technique so small that it is not possible by drilling through the center of such spot welding to secure that the hole provided by the drilling does not extend into an area where the sheets are not welded together. In order to achieve a good heat transfer between the sensor and the radiator an electric wire may according to an embodiment of the invention be used at the end of which a tube is secured having a collar and wherein the tube contains the sensor. In order to achieve a further securing against leakage a sealing ring may according to the invention be arranged around the shaft of the rivet and below the head of the rivet before the introduction of the pop-rivet into the hole and also a sealing material may be arranged upon the shaft of the rivet. A further embodiment of the method according to the present invention is characterized in that a holder for carrying a temperature sensitive element may be secured to the pop-rivet by threaded connecting means. Such embodiment of the invention is used in cases where the temperature sensitive element e.g. consists of a glass tube with closed bottom and containing a filling of an evaporable fluid where the evaporation of the fluid is used as a measure for the heat emitted by the radiator. The invention will hereinafter be further explained with reference to the drawing wherein fig. 1 shows a front view of an embodiment of a sheet iron radiator, fig. 2 shows a section along section line II-II on fig. 1, fig. 3 shows on an increased scale horizontal section of a part of the radiator shown on fig. 1, fig. 4 shows a pop-rivet partly in section, figs. 5 and 6 show pictures for illustrating the mounting of a temperature sensitive element in the form of an electric measuring sensor in the radiator shown, fig. 7 shows a front view of a radiator having two mounting locations for mounting a housing for a temperature sensitive element, fig. 8 shows an exploded picture in section for illustrating an embodiment for mounting a holder for a temperature sensitive element, and fig. 9 shows a picture corresponding to fig. 8 but with the parts in the mounted condition and wherein another embodiment of a pop-rivet is used. On fig. 1, 1 is a sheet iron radiator, 2 is a temperature sensitive element mounted upon the radiator and in the form of a measuring sensor and 3 is a connecting box constituting a part of an electric plant or a circuitry for registering the temperature measured by the measuring sensor 2 or a quantity proportional with such temperature. Such plant or circuitry usually also comprises means for summing up the heat emitted from each radiator connected to such plant or circuitry. As it appears from fig. 2, the radiator comprises a front sheet 4 and a rear sheet 5 which abut each other and are spot welded together along longitudinally extending areas 6 indicated on fig. 1. The sheets are sealingly welded to each other along their circumferences. The radiator comprises known and, accordingly, not further illustrated studs for circulating a heating medium through the radiator. The present invention may also be used in connection with radiators having planar front sheets and profiled rear sheets. Fig. 3 shows a part of the radiator shown on fig. 1 on an increased scale and on fig. 3, 7 designates a hole provided by drilling from the front side of the radiator (represented by the front sheet 4). The hole is arranged in one of the longitudinally extending areas 6. The hole provided by such drilling has a size such that the hole can accommodate the shaft 8 of a pop-rivet (blind tubular rivet) which on fig. 4 generally is designated 9. The shaft comprises a head 10 in the form of a circumferentially extending collar and consists of a material which is comparatively easy to deform e.g. aluminium. The pop-rivet is provided with a draw pin 11 which in a way known per se extends out through the front end of the rivet and which at its rear end is provided with a head 12. The head 12 is connected with the draw pin 11 by means of a breakable neck 16. Around the shaft 8 sealing material 17 is arranged e.g. in the form of a piece of teflon tape wound around the shaft 8 and against the rear side of the collar shaped head 10 a sealing ring 18 also consisting e.g. of teflon is arranged. The draw pin 11 consists of a strong material e.g. steel. The pop-rivet is mounted by moving the rivet from the position shown on fig. 4 into the hole 7 until the sealing ring 18 rests against the front sheet 4 of the radiator around the hole 7. Then a strong pulling force is applied to the pin 11 and simultaneously the head 10 is kept in its position. By such pull a deformation of the shaft of the rivet will occur as it clearly appears from fig. 5 because the head 12, which has a greater outer diameter than the internal diameter of the shaft of the rivet, will expand the end of the rivet which has been pushed through the hole 7, and a collar 20 as indicated on fig. 5 will be formed. The expansion of the end of the rivet in order to form the collar 20 requires relatively high forces, however, not greater than the breakable neck 16 will be able to resist such forces. When the formation of the collar has occured and the head 12 accordingly is positioned at the bottom of the collar 20, the head 12 will start to draw material of the shaft into the hole 7 whereby the shaft is shortened and expanded whereby sealing is obtained between the outer surface of the shaft and the sheet edges around the hole. Such deformation continues until the deformation force becomes so high as to exceed the strength of the breakable neck 16 which accordingly breaks and the head 12 falls off whereafter the pin 11 is withdrawn. After the mounting of the rivet a measuring sensor 22 is mounted in the hole provided by means of the pop-rivet as indicated on fig. 5, wherein 21 designates an electric wire at the end of which the sensor 22 is arranged. The sensor 22 may in a way known per se be constituded by a thermo element or by a thermistor i.e. a restistor, the resistance of which depends upon the temperature, or another means which may deliver a signal proportional with the temperature. As it appears from the arrow on fig. 5, the wire is drawn through the rivet from the front surface of the radiator and this drawing continues until the position shown on fig. 6 is obtained, from which it will be seen that the sensor is now positioned within the shaft of the pop-rivet. According to the embodiment shown on fig. 5 the sensor 22 is arranged within a small tube 23 having a circumferentially entending collar 24 which in the mounted position as it appears from fig. 6 rests against the front surface of the head of the pop-rivet. In order to increase the heat transfer between the sensor and the radiator, the tube 23 may be filled with a good heat conducting material, e.g. heat conducting silicone rubber and, moreover, the outer surface of the tube may before the mounting be provided with a layer of the same material. Hereby it is achieved that the sensor will be in good heat conducting connection with the tube and the tube will be in good heat transferring connection with the rivet which as explained above is in good heat transferring connection with the radiator. Simultaneously the material mentioned, e.g. heat conducting silicone, will act as an adhesive whereby the sensor is secured in the pop-rivet. Such securing may be further improved by connecting the wire 21 with the box 3 in a tight condition. In the radiator shown on fig. 7 two pop-rivets 9 are arranged in one of the longitudinally extending areas 6 for mounting the holder e.g. the rear part 25, fig. 8, of a housing for a heat co sumption meter comprising a temperature sensitive element, not shown, e.g. a tube which is closed at one end and which serves for accommodating an evaporable fluid, the evaporation of which gives a measurement of the amount of heat emitted from the radiator. As it appears from fig. 8 each of the pop-rivets 9 are adapted and arranged in the same way as shown on fig. 5 and explained above. The distance between the two pop-rivets on fig. 7 corresponds to the distance between two mounting holes (one of which is shown on fig. 8 and designated 26) in the rear part of the housing and this part is mounted upon the radiator 1 by means of two self-cutting screws 27 which are screwed into the hollow pop-rivets which consist of a comparatively soft material. According to the embodiment shown on fig. 9 pop-rivets are used of the kind comprising a shaft 28 in the form of an inversed cup to the bottom of which a draw pin 29 provided with threads is secured. According to this embodiment the cup 28 of the pop-rivet is inserted with the bottom facing forward into the hole which has been drilled in advance and then a pulling force is applied to the pin 29 while a collar 30 on the cup is maintained in abutment against a seal 21 which is maintained pressed toward the front side of the front sheet 4. By this operation the cup will be deformed and a circumferentially extending bead 32 will be formed. Now sealing has been obtained along the hole and the pin 29 may now be used directly for the mounting of a rear housing part 25. As it appears from figs. 8 and 9 the heat transfer from the radiator to the temperature sensitive element (the tube with the evaporable fluid) is mainly established by the contact between the rear side of the rear part 25 and the front side of the front sheet 4 of the radiator whereas a minor heat transfer occurs via the mounting screws 27 and the pins 29 respectively. Also according to the embodiment according to fig. 9 a tape of sealing material may be wound about the cup and also according to this embodiment the cup will be expanded due to the shortening of the cup within the hole when the drawing force is applied to the pin 29.

Claims: Claims. 1. A method of fixing a temperature sensitive element of a heat comsumption metering system to a spot welded sheet iron radiator comprising the steps of drilling a hole through the sheets of the radiator in one of the areas where the sheets are in contact with each other and welded together at distributed spots, mounting af pop-rivet in said hole and using said pop-rivet for the fixation of the temperature sensitive element. 2. A method as in claim 1, c h a r a c t e r i z e d by using a temperature sensitive element in the form of a circuitry temperature sensor of a size and shape to be receivable in the interior of the pop-rivet. 3. A method as in claim 1, c h a r a c t e r i z e d in that a wire is used at one end of which a tube (23) is secured comprising a collar (24) and wherein the tube (23) contains the temperature sensitive element, said wire being threaded through the pop-rivet from the front side of the radiator. 4. A method as in claim 1, c h a r a c t e r i z e d in that a holder for supporting a temperature sensitive element is attached to the pop-rivet by threaded connecting means.

Inventors: HANSEN JENS PETER FISCHER, HANSEN, JENS, PETER, FISCHER
Applicants: KOSAN BRUNATA AS, KOSAN BRUNATA A/S
Application year: 1990
Main classification: G01K1
IPC codes: G01K1, G01K17