Abstract:
An improved housing for a thermostatic valve has a nonconducting cover that features a projection into the interior of the valve housing. Mounted on the projection is a thermostatic operating element, which operates to control the valve when wax inside the thermostatic operating element is heated. A pair of electrical leads, connectable to an exterior power source, are embedded within the cover, extending through the projection and connecting to a heating element within the thermostatic operating element. When electrical current is applied to the heating element through the embedded electrical leads, the wax is heated, thereby expanding, driving a work piston of the thermostatic operating element, and opening the valve.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application claims the benefit of German patent application no. 10056076.8, filed Nov. 7, 2000, herein incorporated by reference. 
     1. Field of the Invention 
     The invention relates to an improved housing for a thermostatic valve for a coolant circuit of an internal combustion engine, which housing is formed at least partially of a plastic material, and in which housing electrical connecting leads are embedded. 
     2. Background of the Invention 
     In a thermostatic valve for a coolant circuit of an internal combustion engine, it is advantageous to be able to control the operation of the valve other than through the temperature of the coolant flowing through the valve. One means by which the operation of a thermostatic operating element for such a valve may be controlled is by the inclusion of a heating element within the thermostatic operating element, which heating element is controlled electrically from the exterior of the valve. 
     The desire to maintain electrical control over the heating element presents a substantial conflict between the need to have electrical leads enter into the valve housing and the need to prevent coolant from leaking through the point of entry of the electrical leads. For instance, German Patent Appl. No. DE 42 33 913 A1 teaches a housing for a thermostatic valve for a coolant circuit of an internal combustion engine in which the electrical leads supplying a heating element of a thermostatic operating element within the valve housing run from the heating element to a point outside the valve housing. Specifically, the housing of the thermostatic operating element is mounted on the valve housing and the electrical leads are embedded in a plastic casing of the housing of the thermostatic operating element. The electrical leads are directed through a conduit within a crosspiece of the valve housing, upon which crosspiece the thermostatic operating element is supported, and to the exterior of the valve housing. Because coolant flows within the valve housing, around the thermostatic operating element and the crosspiece on which it is supported, this configuration necessitates a substantially perfect seal between the interior of the valve housing and the conduit, lest coolant leak from the system through the conduit. 
     Moreover, in order to facilitate the connection of the electrical leads to a plug socket to be mounted on the outer wall of the valve housing, the electrical leads must be longer than the conduit within the crosspiece. When the plug socket is mounted to the outer wall, the excess length of the electrical leads must be pressed into the conduit, thereby resulting in slack in the electrical leads. This slack causes the electrical leads to be susceptible to vibrations, which can result in movement of the supply leads, unwanted noise, or damage to the supply leads-in any event, sub-optimal performance of the system. 
     OBJECT AND SUMMARY OF THE PRESENT INVENTION 
     It is accordingly an object of the present invention to improve upon prior-art thermostatic valves, in order to ensure a greater level of manufacturing and operational reliability. 
     In order to meet this object, the present invention includes a housing of a thermostatic valve for a coolant circuit of an internal combustion engine, which housing is formed at least partially of a plastic material. During the manufacturing process of the housing, electrical leads for supplying electricity to a thermostatic operating element are injected or cast into the housing. Because the electrical leads are embedded in the plastic material, they remain in a fixed position, which eliminates the rubbing or flapping associated with movement of slack electrical leads in a conduit and the resulting noise or damage. Moreover, embedding the electrical leads in the plastic material eliminates the need for an additional seal, since there is no conduit for coolant to leak through. An additional benefit of the present invention is that the plastic material insulates the electrical leads; no additional insulation of the electrical leads, as would be needed in a conduit system, is required. Consequently, the thermostatic valve of the present invention is both operationally reliable and economical to manufacture. 
     An additional feature of the present invention is the ability to form electrical connectors, such as contact tags or sockets, in the plastic portion of the valve housing. By selecting electrical leads of a shape appropriate for placement within an electrical connector and forming the insulating/connecting portion of the electrical connector as part of the valve housing, a mechanically loadable electrical connector may be formed and placed without any additional work steps, thereby reducing the cost of manufacture. 
     In accordance with this feature of the present invention, part of the portion of the value housing projects into the interior of the valve and into the coolant flow path to form a support. The electrical leads are embedded within this projection, at the end of which is formed a receptacle that includes an electrical connector and a support upon which is mounted, depending on the particular configuration of the valve, the housing of the thermostatic operating element or the work piston of the thermostatic operating element. Because the electrical leads are sealed within the projection, no further sealing mechanism is necessary despite the placement of the projection within the coolant flow path. Moreover, the embedding of the electrical leads and the forming of the electrical connector and support for the thermostatic operating element may be accomplished simultaneously with and as part of the manufacturing process for the valve housing. In one embodiment of the present invention, the receptacle is formed with a circumferential wall that defines a recess, on the bottom of which the electrical connectors are arranged. The contact pins of the work piston or of the heating element are inserted into the electrical connectors, and the thermostatic operating element is thereby seated on the projection. 
     In another embodiment of the present invention, the outer wall of the valve housing is formed with a receptacle, in which electrical connectors of the connecting leads are embedded, and which is adapted to receive an external power source. In accordance with this embodiment, a plug receptacle for connecting an external electrical supply to the valve is integrated within the valve housing, thereby eliminating the need for a separate manufacturing step or separate structural components in order to provide a suitable receptacle. 
     In still another embodiment of the present invention, the electrical leads are formed from substantially planar conducting strips instead of conventional wires. Conducting strips, also known as current bars, provide a number of substantial advantages over conventional wires when used in the system of the present invention. For instance, conducting strips, by virtue of their planar design, are inherently more stable than are conventional round wires when injected into plastic material during the manufacturing process of the housing. The conducting strips are easily bent into a particular configuration in order to achieve a desired shape. Moreover, rotating the strips about their longitudinal axes serves to anchor them firmly within the plastic material. 
     Further features and advantages of the invention result from the claims and the following description of preferred embodiments of the invention in conjunction with the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view of a valve housing of a thermostatic valve. 
     FIG. 2 is a detail view showing electrical leads and connectors in accordance with a preferred embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIG. 1, thermostatic valve  10 , shown in cross-section, includes a two-part valve housing with cover  12  and base  14 . Cover  12  is formed of a plastic material and is connected to bottom part  14  by screws  15 . Thermostatic valve  10  is disposed in the coolant circuit of an internal combustion engine and coolant flows through interior  16  of thermostatic valve  10 . The flow of coolant through interior  16  is controlled by valve plate  18 . A portion of valve plate  18  is disposed adjacent to, and within the drive path of, work piston  20  of thermostatic operating element  22 , and the movement of valve plate  18  is therefore controllable by means of work piston  20 . Valve plate  18  is pre-tensioned by a spring (not shown) so as to bias it against the drive motion of work piston  20 . 
     Thermostatic operating element  22  includes a housing, preferably made of a metal, such as brass, defining an inner space  26  filled with an expandable material, such as wax. Work piston  20  extends into inner space  26 , and membrane  28  is disposed in surrounding relation to work piston  20 . When the expandable material is heated, as by coolant flowing through interior  16  or by means of heating element  30  (as discussed below), the expandable material expands, driving work piston  20  downward. Valve plate  18  is likewise driven downward, opening a coolant flow path through thermostatic valve  10 . When the expandable material cools and work piston  20  is retracted, the biasing action of the spring restores valve plate  18  upward as allowed by the retraction of work piston  20 . 
     The operation of thermostatic operating element  22  is further controllable by means of heating element  30 , which is disposed in inner space  26  (and thereby in contact with the expandable material). The expandable material can be controllably heated, and therefore the movement of work piston  20  can be controlled, by means of heating element  30 . Heating element  30  is a resistor disposed in inner space  26  of thermostatic operating element  22  with contact pins  24  running therefrom to the outside of thermostatic operating element  22 . The portion of the housing of thermostatic operating element  22  where contact pins  24  exit is preferably sealed by pouring plastic on contact pins  24  after contact pins  24  and heating element  30  have been placed within the housing of thermostatic operating element  22 . In this manner, contact pins  24  are mechanically fixed and electrically insulated from the housing of thermostatic operating element  22 . 
     Cover  12  is formed with a projection  34  extending into interior  16  thereof. Projection  34  is formed as a unitary part of cover  12  (and therefore is made of the same material as cover  12 ). In a preferred embodiment, projection  34  is formed within interior  16  to extend from the wall of cover  12  first transversely to the coolant flow path, then arching toward a central axis of interior  16  so as to form a support on its distal end for thermostatic operating element  22 . A pair of conducting strips  32 , the placement of which is discussed below, extend from the exterior of cover  12  to the distal end of projection  34  to provide electrical current from the exterior of thermostatic valve  10  to thermostatic operating element  22 . Projection  34  is formed on its distal end with a mounting receptacle for thermostatic operating element  22 . The mounting receptacle includes circumferential wall  36  defining a recess in which are embedded a pair of electrical connectors  38 , which are disposed to receive contact pins  24  of heating element  30  of thermostatic operating element  22 . 
     In order to permit the mounting of thermostatic operating element  22  in interior  16  of thermostatic valve  10  on the distal end of projection  34 , the housing of thermostatic operating element  22  is formed so as to engage with circumferential wall  36  and seat in the recess thereof, such that contact pins  24  are received in connectors  38 . Proper seating of thermostatic operating element  22  is aided if thermostatic operating element  22  is formed with a circumferential shoulder and circumferential wall  36  is further formed with a matching offset, as seen in FIG.  1 . The circumferential shoulder of thermostatic working element  22  is further provided with a cylindrical groove for carrying seal  40 , which sealingly engages with an inner surface of circumferential wall  36  so as to protect electrical connectors  38  and contact pins  24  from contact with coolant flowing through interior  16 . 
     Conducting strips  32  are injected into the plastic material of projection  34  during the manufacture of cover  12 . Conducting strips  32  are substantially parallel to each other and extend from electrical connectors  38 , which are situated on the bottom of the recess of the distal end of projection  34 , along the course of and within projection  34 . In their further course in the direction of the wall of cover  12 , conducting strips  32  are rotated about their longitudinal axis by 90°. Conducting strips  32  are each formed on the end extending through cover  12  with a contact tag  42 , which extends to the exterior of cover  12 . Cover  12  is further formed, at the point at which contact tags  42  pass through cover  12 , with a connector receptacle  44 , and contact tags  42  are arranged within connector receptacle  44  on the outside of cover  12 . A plug that includes electrical leads to an external power source (not shown) may be inserted into connector receptacle  44 . In a preferred embodiment, connector receptacle  44  includes a pair of engagement flanges  46  on its outer circumferential surface. Connector receptacle  44  and projection  34  are formed at the same time as the manufacture of cover  12  by a plastic injection process or other suitable method, and conducting strips  32  with contact tags  42  and electrical connectors  38  are embedded in the plastic material of cover  12  simultaneously with the manufacture of cover  12 . As a result, conducting strips  32 , contact tags  42 , and electrical connectors  38  are fixed within cover  12  and electrically insulated. 
     Referring now to FIG. 2, an embodiment of the present invention is shown in detail. Electrical leads  50  are formed of conducting strips as in the embodiment shown in FIG.  1 . Electrical leads  50  are embedded in plastic material  52  that forms, as seen in FIG. 1, a cover  12  of a valve housing for a thermostatic valve  10 . In order to show in precise detail the particular configuration of electrical leads  50 , only a parallelepipedic section of plastic material  52  is shown, though in this embodiment of the present invention plastic material would extend from the parallelepipedic section through broken lines  60 , 62 . Electrical leads  50  each include a section  54  that is rotated about its longitudinal axis by 90°, which serves to anchor electrical leads  50  in plastic material  52 . Electrical leads  50  are bendable about their transverse axes to produce bends  56 . The ability of electrical leads  50  to be bent or twisted enable a wide variety of configurations of the thermostatic valve in accordance with the present invention. 
     Electrical leads  50  are each provided on one end with a contact tag  56  for connecting the thermostatic valve to an external power supply, and on the opposite end with a socket  58  for receiving a contact pin of a heating element for a thermostatic working element (as seen in FIG.  1 ). In order to embed contact tags  56  and sockets  58  more reliably in plastic material  52 , contact tags  56  are provided with tabs  64 , and sockets  58  are each provided with a circumferential flange  66 . Tabs  64  and circumferential flanges  66  are embedded within plastic material  52 , which extends to broken lines  60 , 62 . 
     Those skilled in the art to which the present invention pertains will note that the thermostatic operating element of the preferred embodiment could very easily be replaced with any of a variety of means for opening and closing the valve, without departing from the scope of the present invention. For instance, the thermostatic operating element could be replaced with a proportional magnet, a DC motor, a linear motor, or a step motor. 
     It will therefore be readily understood by those persons skilled in the art that the present invention is susceptible of broad utility and application. Many embodiments and adaptations of the present invention other than those herein described, as well as many variations, modifications and equivalent arrangements, will be apparent from or reasonably suggested by the present invention and the foregoing description thereof, without departing from the substance or scope of the present invention. Accordingly, while the present invention has been described herein in detail in relation to its preferred embodiment, it is to be understood that this disclosure is only illustrative and exemplary of the present invention and is made merely for purposes of providing a full and enabling disclosure of the invention. The foregoing disclosure is not intended or to be construed to limit the present invention or otherwise to exclude any such other embodiments, adaptations, variations, modifications and equivalent arrangements, the present invention being limited only by the claims appended hereto and the equivalents thereof.