Abstract:
The invention relates to a heating element with an electrical resistance heating element, at least one electrical connector line for supplying power to the heating element, a metal body with a connector, through which the at least one connector line and a duct seal, by means of which the connector opening is sealed. The duct seal is embodied with a glass body as a compression glass duct. The invention further relates to a heated expanding material working element for the operation of a thermostatic valve that includes a housing and a moving working rod extending from the housing.

Description:
[0001]    This invention relates to a heater insert with an electric resistance heating element and at least one electric connector lead through which the heating element can be supplied with power. The invention furthermore relates to an expansion material element with a housing and a movable actuation pin passed out of the housing, with the expansion material and such a heater insert being provided in the housing. 
         [0002]    Such a heater insert and a heatable expansion material working element are known from WO 02/086646, for example. 
         [0003]    Expansion material working elements are used in particular for actuating thermostat valves. In the housing of the expansion material working element, the heater insert heats up the expansion material so that the expansion material expands and pushes the actuation pin out of the housing. A thermostat valve can thus be controlled by supplying electric power to the heater insert. 
         [0004]    When heating the expansion material, paraffin for example, a pressure of up to 300 bar arises in the housing of the expansion material working element. Requirements on the tight seal of the expansion material working element are high due to this pressure, in combination with the expansion material&#39;s reduced viscosity at elevated temperatures. 
         [0005]    One weak point through which expansion material can escape is, in particular, the heater insert with its opening for the at least one connector lead (as a rule, two connector leads are provided). 
         [0006]    In the heater insert known from U.S. Pat. No. 7,172,133, the connector leads are embedded in a solid plastic base which is sealed off by an O-ring towards the housing of the expansion material working element. 
         [0007]    It has been shown that, during operation, small amounts of expansion material escape through the seal formed by such a plastic base. In the course of time, this results in a reduction of the working stroke and the reaction times of the expansion material working element since a smaller amount of expansion material must be heated up to correspondingly higher temperatures until sufficient pressure is built up to push the actuation pin by the desired length from the housing. 
         [0008]    Furthermore, utmost care must be taken in the assembly of the expansion material working element so that no leakage points result through which expansion material can escape between the heater insert and the housing since the plastic base may not be subjected to any major mechanical load. 
         [0009]    Accordingly, it is an object of the invention to show a way of how an improved seal can be economically provided for a heater insert of the above-mentioned type and of how such a heater insert can be more easily mounted with a housing. 
         [0010]    This object is solved according to the invention by a heater insert with an electric resistance heating element, at least one electric connector lead through which the heating element can be supplied with power, a metal body with a connecting opening through which the at least one connector lead is passed, and a duct seal by means of which the connecting opening is closed, the duct seal being formed with a glass body as a compressed glass-to-metal seal. 
         [0011]    A compressed glass-to-metal seal takes advantage of the fact that the metal body has a considerably higher coefficient of thermal expansion than the glass body it surrounds. To produce a compressed glass-to-metal seal, the metal body is heated and glass introduced into the connecting opening with the connector lead passing through it. Upon cooling down to room temperature, the glass body solidifies and contracts. Due to its higher coefficient of thermal expansion, the metal body contracts more than the glass body so that the glass body is pressed with considerable pressure against the embedded connector lead. Thus, a compressed glass-to-metal seal provides an excellent seal not only between the glass body and the penetrating connector lead(s), but also between the glass body and the surrounding metal body. 
         [0012]    Aside from the improved tightness, a heater insert according to the invention moreover has the essential advantage that the metal body surrounding the glass body can be combined much more easily with a housing—for example, the metal housing of an expansion material element—than the plastic bases common in prior art with embedded connector leads. This is due to the fact that the metal body can be exposed to considerably greater mechanical loads in the assembly process, due to its much greater hardness compared with plastic materials—without any resulting damages. Moreover, a metal body, a lathe-cut part for example, can be manufactured with smaller tolerances than a plastic part and for that reason can be more easily inserted into the housing of an expansion material working element with the precision required for a tight connection. 
         [0013]    While heater inserts with their plastic bases, commonly used in prior art, had to be inserted into an upper, larger opening of a cylindrical housing and be pushed through the housing until the connector lead exits from a smaller opening at the bottom end of the cylindrical housing, a heater insert according to the invention can be inserted, for example, into a lower housing opening, and the edge of this housing opening can be rolled in or flanged to close the opening tightly. In addition, the metal body can be connected with a substance-to-substance bond or a material connection to the housing—it can be welded, in particular—so that an excellent seal can also be reliably provided between housing and metal body. No an additional seal like an O-ring is necessary. It is favorable in this respect to manufacture the housing and the metal body of steel, preferably of stainless steel. 
         [0014]    Despite the relatively high expenditure of manufacturing a compressed glass-to-metal seal, a heater insert according to the invention can be produced at a rather reasonable price in comparison with heater inserts known from prior art with plastic bases in which the connector leads are embedded. This is due to the fact that a relatively expensive plastic injection mold is required for embedding the connector leads into plastic bases since the individual connector leads are difficult to handle here. For a heater insert according to the invention, the metal body can be manufactured inexpensively as a stamped part or, preferably, as a lathe-cut part into whose connecting opening a drop of glass can be introduced by relatively simple means to enclose the at least one connector lead. 
         [0015]    An additional cost reduction can be achieved with a heater insert according to the invention which uses a nickel/iron alloy for the connector leads. This has the advantage that the at least one connector lead can be inexpensively connected to the heating element by means of welding. Furthermore, nickel/iron alloys have a coefficient of thermal expansion which is excellently suitable for a compressed glass-to-metal seal. 
         [0016]    With little expenditure, a plastic body can be injection-molded onto the metal body of a heater insert according to the invention—for example, as a carrier for the heating element or on the other side of the compressed glass-to-metal seal, for example, as the body of a plug-in connector. 
         [0017]    Instead of a plastic body, a ceramic body can also be used—especially of polymer ceramics. 
         [0018]    Compressed glass-to-metal seals are known in other areas of technology, for example for the housings of electronic semiconductor components with integrated circuitry. For producing compressed glass-to-metal seals and for the selection of materials for the glass body and the metal body enclosing it, reference is made to EP 0574797 B1 which is incorporated by reference into the present application. 
         [0019]    A heater insert according to the invention is particularly suitable for a heatable expansion material working element with a housing and a movable actuation pin passed out of the housing, with the expansion material and a heater insert according to the invention being provided in the housing. However, a heater insert according to the invention is also suitable per se for other devices. Accordingly, the subject matter of the invention is also the use of a compressed glass-to-metal seal a connector lead of a heater insert. 
         [0020]    Depending on the application of a heater insert according to the invention, the metal body with the compressed glass-to-metal seal can be part of a base or/and part of a housing. In cases in which the heater insert is provided with its own housing, good thermal coupling of the heater insert to the housing is generally desired. 
         [0021]    The invention relates furthermore to a thermostat valve with a heatable expansion material element in which a heater insert according to the invention is provided. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    Additional advantages and features of the invention are explained on the basis of exemplary embodiments with reference to the enclosed drawings. In the Figures: 
           [0023]      FIG. 1  shows an exemplary embodiment of an expansion material working element with a heater insert according to the invention, in cross-section; 
           [0024]      FIG. 2  shows the compressed glass-to-metal seal of the heater insert in cross-section; 
           [0025]      FIG. 3  shows the heater insert without heating element and carrier body in a side view; 
           [0026]      FIG. 4  shows the compressed glass-to-metal seal in a top view; 
           [0027]      FIG. 5  shows the heater insert without heating element in a side view; 
           [0028]      FIG. 6  shows another exemplary embodiment of a heater insert according to the invention in a side view; 
           [0029]      FIG. 7  shows the exemplary embodiment shown in  FIG. 6  in a cross-sectional view along the intersecting line AA; and 
           [0030]      FIG. 8  shows another exemplary embodiment of a heater insert according to the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0031]    The expansion material working element  1  shown in  FIG. 1  comprises an essentially cylindrical housing  14  with a cup-shaped bottom part  14   a  and a top part  14   b  which, by flanging of the free front face of the housing part  14   a , is firmly connected with it to form the housing  14 . A heating device  1   a  is provided in the area of the bottom part of the housing  14   a  facing away from housing  14   b . Through the top part of the housing  14   b , an actuation pin  1   b  is leading out which is surrounded by a diaphragm  1   c  within the housing. The other inside space of the housing  14  is filled out with expansion material  1   d , for example, paraffin with suitable additives. 
         [0032]    The expansion material  1   d  can be heated with the heater insert  1   a  so that pressure builds up in the housing  14  by means of which the actuation pin  1   b , for example for controlling a thermostat valve, can be pushed out of the housing  14  in relation to the heat applied. Further details on the mode of functioning of heatable expansion material elements are disclosed in U.S. Pat. No. 7,172,133 and therefore need not be explained in more detail. 
         [0033]    The heater insert  1   a  comprises an electric resistance heating element  3  in the form of a PTC heating wire of a nickel/iron alloy, a plastic carrier  2  around which the heating wire  3  is wound, and connector leads  5 ,  6  which are passed through a base  4 . The connector leads  5 ,  6  are embedded over a part of their length in the plastic carrier  2 . It is especially favorable when the resistance heating element  3  as well as the connector leads  5 ,  6  consist of nickel/iron alloys so that particularly good weldability is provided. 
         [0034]    Instead of a heating wire, a thick-layer element can also be used, for example, as a resistance heating element which is held by a carrier, for example, of plastic or ceramic. 
         [0035]    In the presented exemplary embodiment, the base is formed by a metal body  4  which is a lathe-cut part of stainless steel. It has a groove  13  in which an O-ring  15  is provided by means of which the metal body  4  is sealed off towards the housing  14 . Alternatively, the metal body  4  can also be connected by a positive material connection with the housing  14 , preferably by welding or brazing. 
         [0036]    In a cross-sectional view,  FIG. 2  presents the base of the heater insert  1   a  formed by a metal body  4 . In the metal body  4 , a connecting opening  7  is provided in the form of a passage channel through which the two connector leads  5 ,  6  are passed. Basically, one single connector lead is sufficient if an mass lead is done without. In the passage channel, a glass body  11  of a compressed glass-to-metal seal is provided in which the two connector leads  5 ,  6  are embedded which consist of a nickel/iron alloy. The metal body  4  is made of stainless steel V2A and therefore has a much higher coefficient of thermal expansion than the glass body  11 . 
         [0037]    To produce the compressed glass-to-metal seal, the metal body  4  was heated and the glass body  11  was introduced in liquid form in the passage channel. Upon cooling down to room temperature, the glass body  11  solidifies, with the metal body  4 —due to its higher coefficient of thermal expansion—contracting more than the glass body  11 . Thus, the metal body  4  is pressing with high pressure against the glass body  11  and it, in turn, against the connector leads  5 ,  6  so that an excellent seal results. 
         [0038]    As seen in  FIG. 2 , the passage channel is only partly filled by the glass body  11 . Another part of the passage channel is taken up by a plastic carrier  2  in which the connector leads  5 ,  6  are embedded over a part of their length. The connector leads  5 ,  6  are thus additionally stabilized, and a compact heater insert  1   a  is created which can be easily handled during assembly. The plastic carrier  2  is an injection-molded part formed on the metal body  4 . 
         [0039]    On the side of the glass body  11  facing away from the plastic carrier  2 , a plastic body  8  is injection-molded onto the metal body  4  in which the connector leads  5 ,  6  are embedded. Thus short circuiting by any unintentional contact between the connector leads  5 ,  6  or the metal body  4  is prevented. The connector leads  5 ,  6  feature a bend in their section which is embedded in the plastic body  8  so that the connector leads  5 ,  6  leave the plastic body  8  with greater spacing between each other. 
         [0040]    Thus, despite the small inside diameter of the connecting opening  7  and a diameter of the connector leads  5 ,  6  of preferably 0.8 mm to 1.2 mm, a space between the two connector leads  5 ,  6  is achieved by means of which short-circuiting due to any unintentional contact between the connector leads  5 ,  6  or the metal body  4  can be excluded. 
         [0041]    For many applications, the outside diameter of the metal body  4  may not exceed a value of 12 mm, preferably 10 mm in the area of the glass body  11 . So that the metal body  4  is not deformed—under the pressure developing during cooling due to the different coefficients of thermal expansion—which might result in an undesirable decrease of the pressure and thus to possible leaks, thickness of its walls in the area of the glass body  11  should amount to at least 0.8 mm, preferably to 1.0 mm, better to at least 1.5 mm. Due to the increasing miniaturization of thermostat valves, the inside diameter of the connecting opening of the passage channel is thus preferably approximately 4 mm to 6 mm. These data apply in case that only one connecting opening is provided. The inside diameters and wall gauges can be reduced in case of a metal body  4  with two connecting openings through which one connector lead each is passed through. 
         [0042]      FIG. 4  shows the compression glass-to-metal seal in a top view. At their end facing the heating element  3 , the connector leads  5 ,  6  are bent in different directions, preferably in opposite directions to be able to protrude from the plastic carrier  2  not shown here. 
         [0043]      FIG. 5  shows the heater insert  1   a  without the heating element in a side view. The plastic carrier  2  is molded to the metal body  4  as an injection-molded part. The connector leads  5 ,  6  are embedded in the plastic carrier  2  and provided on their ends with bifurcated connection elements  17 ,  18  to which the heating wire  3  is fastened, preferably by welding. The plastic carrier  2  has a base  20  projecting into the metal body  4  and a coil form  21  around which the heating wire is wound. The coil form  21  is followed by a ring  22  which centers the heater insert  1   a  in the housing  14  of the expansion material working element  1 . The coil form  21  is formed by longitudinal ribs  23  and transverse ribs  24  between which openings are provided. 
         [0044]    In the exemplary embodiment described, the metal body  4  of the heater insert  1   a  comprises a connecting opening  7  through which two connector leads  5 ,  6  are passed. It is also possible, however, to provide a separate connecting opening in the metal body  4  for each connector lead. Then, according to  FIG. 8 , the metal body  4  preferably comprises a blind hole  32  into which the plastic carrier  2  protrudes. It is advantageous when the metal body forms blind holes on both sides of the connecting openings. 
         [0045]    The exemplary embodiment shown in  FIG. 6  differs from the exemplary embodiment explained on the basis of  FIGS. 2 to 5  essentially by the fact that the plastic carrier  2  was not injection-molded to the metal body  4  around the connector leads  5 ,  6 , but was provided to the metal body  4  by means of a pressure fit or a clip connection. Alternatively or additionally, the plastic carrier  2  can furthermore be fastened by adhesive bonding to the metal body and/or the glass body  11 . It is advantageous to use the connector leads  5 ,  6  additionally to fasten the plastic carrier  2  on the metal body  4 , by bending the connector leads  5 ,  6  and thus forming a positive fit with the plastic carrier  2 . 
         [0046]      FIG. 7  shows the exemplary embodiment shown in  FIG. 6  along the intersecting line AA. The connector leads  5 ,  6  are passed through a slot  29  in the plastic carrier  2  and bent in circumferential direction of the plastic carrier  2  so that they form a positive fit with an annular surface  30  of the plastic body. Of course, several separate slits can also be used instead of one single slot  29 . It is particularly advantageous if the connector leads  5 ,  6  contact the annular surface  30  of the plastic carrier  2 . It is principally sufficient, however, if the connector leads  5 ,  6  are provided along the annular surface  30  so that, upon the plastic carrier pulling from the metal body  4 , they will press against the annular surface  30  and thus prevent a removal of the plastic carrier  2 . 
         [0047]    A particularly strong and heavy-duty connection of the plastic carrier  2  with the metal body  4  can be achieved, in particular, by the connecting opening  7  of the metal body  4  being undercut so that the plastic carrier has a positive fit connection with the metal body  4 . An undercut  31  of the metal body  4  is advantageous not only with the preferred injection molding of the plastic carrier  2  to the metal body  4  but also for the adhesive bonding and/or clipping of the plastic carrier  2  into the metal body  4 . 
         [0048]      FIG. 8  shows another exemplary embodiment of a heater insert  1   a  according to the invention in a sectional view which essentially differs from the exemplary embodiment described on the basis of  FIGS. 2 to 5  by the metal body  4  comprising two connecting openings  7  which each enclose a glass body  11  and through which one of the connector leads  5 ,  6  each is passed. In this embodiment, the passage channel forming the connecting openings  7  comprises the two blind holes  32  in whose bottom the connecting openings  7  are provided. 
         [0049]    In the presented exemplary embodiment, the connecting openings  7  are formed as bore holes in the metal body  4  between the cylindrical blind holes  32  and are accordingly circular. The use of two connecting openings for the two connector leads  5 ,  6  has the advantage that, for sealing the connecting openings  7 , smaller glass bodies  11  are sufficient and consequently, the wall thickness of the metal body  4  in the area of the glass bodies  11  can be reduced. The heater insert  1   a  can thus be produced smaller overall and more compact. Furthermore, straight guiding of the connector leads  5 ,  6  is facilitated by thinner outside walls of the metal body  4 . The outside wall thickness for a metal body  4  with two connecting openings  7  through which one connector lead each is passed preferably lies between 0.5 mm and 1 mm, especially preferably between 0.6 mm and 0.8 mm. The diameter of the connecting openings preferably lies between 1.5 mm and 2.5 mm, especially preferably between 1.8 mm and 2.2 mm. 
       LIST OF REFERENCE NUMBERS 
       [0000]    
       
           1 . Expansion material element 
           1   a  Heater insert 
           1   b  Actuation pin 
           1   c  Diaphragm 
           1   d  Expansion material 
           2 . Plastic carrier 
           3 . Heating element 
           4 . Metal body 
           5 . Connector lead 
           6 . Connector lead 
           7 . Connecting opening 
           8 . Plastic body 
           10 . duct seal 
           11 . Glass body 
           13 . Annular groove 
           14 . Housing 
           14   a  Bottom part of housing 
           14   b  Top part of housing 
           15 . O-ring 
           17 . bifurcated connection element 
           18 . bifurcated connection element 
           20 . Base 
           21 . Coil form 
           22 . Ring 
           23 . Longitudinal ribs 
           24 . Transverse ribs 
           29 . Slot 
           30 . Annular surface 
           31 . Undercut 
           32 . Blind hole