Abstract:
A sheathed heater assembly includes a sheathed heating element and a cold pin electrically coupled to the sheathed heating element. The cold pin includes a free end including an electrical connector. The electrical connector is configured to mate with a mating connector to electrically connect the sheathed heating element to a wiring harness. The electrical connector has a circumferential groove and a longitudinal axis. The longitudinal axis of the electrical connector is coextensive with a longitudinal axis of the cold pin.

Description:
BACKGROUND OF THE INVENTION 
   This invention relates generally to a sheathed heating element for an appliance, and more particularly, to a connector for coupling a sheathed heating element to a power harness. 
   Sheathed heating elements are commonly used as heating elements in electrical appliances, particularly electric ranges. In addition, sheathed heating elements also find application in such appliances as dishwashers and electric clothes dryers. 
   Sheathed heating elements typically include a tab welded to the sheathed heater for connecting the sheathed heater to a wiring harness. The wiring harness includes a female connector configured to mate with the tab to couple the sheathed heater to the wiring harness. The weld area between the tab and the sheathed heater has a small cross section and is an area of increased resistance to electrical current flow and also to conduction heat transfer. Consequently, the weld area may generally reduce the life of the sheathed heater-to-wiring harness couple. In addition, the tab is a high-volume component that increases the part count of the appliance containing the sheathed heater. With the use of the traditional tab connectors, the ability to control the surface area of the couple or to optimize the interference between the mating surfaces in the connection are substantially precluded. 
   BRIEF DESCRIPTION OF THE INVENTION 
   In one aspect, a sheathed heater assembly for an appliance is provided. The sheathed heater assembly includes a sheathed heating element and a cold pin electrically coupled to the sheathed heating element. The cold pin includes a free end including an electrical connector. The electrical connector is configured to mate with a mating connector to electrically connect the sheathed heating element to a wiring harness. The electrical connector has a circumferential groove and a longitudinal axis. The longitudinal axis of the electrical connector is coextensive with a longitudinal axis of the cold pin. 
   In another aspect, a connector assembly for electrically coupling a sheathed heater assembly to a wiring harness is provided. The connector assembly includes a pin connector formed on an end of the sheathed heater assembly such that the pin connector and the end of the sheathed heater assembly have a common centerline. The pin connector includes a circumferential groove. A receptacle connector has a mating end and a wire receiving end. The wire receiving end is configured to be joined to a wiring harness conductor. The pin connector is configured to mate with the receptacle connector. 
   In yet another aspect, a method for coupling a sheathed heater assembly to a wiring harness is provided. The method includes providing a sheathed heating element, joining a cold pin to the sheathed heating element such that the cold pin has a free end, forming a pin connector on the free end of the cold pin, forming a receptacle connector having a substantially cylindrical mating end sized to receive the pin connector, attaching the receptacle connector to a wiring harness, and mating the pin connector with the receptacle connector. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a front view of an electric range. 
       FIG. 2  is a perspective view of the range shown in  FIG. 1 . 
       FIG. 3  is a perspective view of an exemplary sheathed heater. 
       FIG. 4  is a cross sectional view of a portion of the sheathed heater shown in  FIG. 3 . 
       FIG. 5  is a perspective view of a male electrical connector for a sheathed heater. 
       FIG. 6  is a perspective view of a female electrical connector for a wiring harness. 
       FIG. 7  is a perspective view of a prior art sheathed heater. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  is a front view of an electric range  50  speedcook oven including a cooktop  52  and an oven  54 .  FIG. 2  is a perspective view of electric range  50 . Cooktop  52  includes a plurality of heating elements  58  for cooking food on cooktop  52 . Oven  54  includes an oven cooking cavity  60 . An oven door  62  is provided that has a handle  64  secured thereto. Oven door  62  includes a window  66  provided for viewing food in oven cooking cavity  60 . Range  50  also includes a control panel  70 . A dial  72  for each heating element  58  is provided on control panel  70  to regulate a heat output of a respective heating element  58 . Control panel  70  also includes at least one display  74 , and a plurality of other controls and dials that may include tactile control buttons  76 . 
   Although the invention will be described with reference to an electric oven, it is to be understood that no limitation is intended thereby, and the benefit hereinafter described may be applicable to other types of electric appliances, including, but not limited to, dishwashers, clothes dryers, toaster ovens, and other appliances having heating elements. Further, the invention may be used in combination with ranges and ovens other than the particular range described above. 
     FIG. 3  is a perspective view of an exemplary sheathed heater assembly  100  that is suitable for use in oven  54  of range  50 .  FIG. 4  is a cross sectional view of a portion of the sheathed heater assembly  100 . Sheathed heater assembly  100  is a resistance heater that includes a sheathed heating element  102  formed with multiple bends or loops  104  which facilitates fitting the sheathed heater assembly  100  in oven cooking cavity  60 . In the illustrated embodiment, two major loops  104  are formed. A brace  106  is attached to sheathed heating element  102  in such a manner that brace  106  spans loops  104 . Brace  106  also acts as a standoff to support sheathed heating element  102  off of a floor (not shown) of oven cooking cavity  60 . 
   Sheathed heater assembly  100  includes a mating end  110  that is configured to be mated to a wiring harness (not shown) that provides power to sheathed heater assembly  100 . Sheathed heating element  102  is a continuous member having first and second ends  112  that are both coupled to a bracket  114  proximate mating end  110 . A cold pin  116  is coupled to each end  112  of sheathed heating element  102 . Each cold pin  116  has an end  120  that is formed as a connector  122 . 
   Sheathed heating element  102  includes a tubular outer sheath  130  that houses a helical resistance wire  132 . In an exemplary embodiment, outer sheath  130  is fabricated from a metal such as inconel or stainless steel. The interior of outer sheath  130  is filled with a packing material  134  such as magnesium oxide to isolate helical resistance wire  132  from outer sheath  130 . Cold pin  116  extends into outer sheath  130  and is joined to helical resistance wire  132 . Cold pin  116  is joined to helical resistance wire  132  by known methods such as spot welding or tig welding. In some embodiments, cold pin  116  is formed with a lead-in portion  138  for ease of assembly. A stopper or plug  140  is provided to close ends  112  of outer sheath  130  to inhibit the entry of moisture into the interior of outer sheath  130 . 
     FIG. 5  is a perspective view of connector  122  which is formed on the end of cold pin  116 . Connector  122  is in the form of a male pin type connector. Connector  122  is generally bullet shaped and may be formed using a stamping or pressing process such that connector  122  and cold pin  116  have a common centerline C. In an exemplary embodiment, connector  122  is unitarily formed with cold pin  116 . Connector  122  includes a tip  150  that may exhibit a spherical or conical profile or a combination thereof. Connector  122  has a generally circular cross section and has a tip diameter D 1 . Connector  122  tapers from tip  150  to a generally cylindrical rearward portion  152  having a diameter D 2  that is greater than tip diameter D 1 . A groove  156  is formed rearward of and adjacent to rearward portion  152 . Connector  122  has an engagement length L that extends from tip  150  to groove  156 . 
     FIG. 6  is a perspective view of a female electrical connector  200 . Connector  200  may be electrically connected to a wiring harness (not shown). Female connector  200  is configured to be mated with connector  122  to provide power to sheathed heater assembly  100 . Connector  200  includes a generally cylindrical body  202  that has an internal diameter D 3 . Body  202  is formed with a longitudinally extending seam or slit  204  that allows body  202  to expand while being mated and unmated with connector  122 . Body  202  also includes a dimple  206  formed at seam  204 . A portion of dimple  206  extends into an interior  208  of body  202 . Body  202  defines a first distance S 1  extending from a forward end  210  to dimple  206  and a second distance S 2  from dimple  206  to a rearward end  212 . Connector  200  includes a wire barrel  220 , wire crimp tabs  222 , an insulation barrel  224  and insulation crimp tabs  226 . 
   Connector  200  includes a wire receiving end  230  that receives an insulated cable  240  from a wiring harness (not shown). A portion of the insulation is removed to expose a length of bare wire or conductor  242  which is placed in wire barrel  220  and crimped to connector  200  using wire crimp tabs  222 . An insulated portion  244  of cable  240  is place in insulation barrel  224  and is crimped to connector  200  using insulation crimp tabs  226 . In this manner, cable  240  is secured to connector  200  to provide an electrical connection. 
   Dimple  206  is configured to be received in groove  156  on connector  122  when connector  122  is mated with connector  200  to retain connector  122  within connector  200 . Additionally, the extension of dimple  206  into interior  208  may be established so as to provide a desired separation force to separate connector  122  from connector  200 . Connectors  122  and  200  are formed such that distance S 2  on connector  200  at least slightly exceeds engagement length L on connector  122  so that dimple  206  may be received in groove  156 . Further, diameter D 2  of connector  122  and inner diameter D 3  of connector  200  are sized to provide a desired push force to join connectors  122  and  200 . 
   When connectors  122  and  200  are joined, an interface is formed that has an interface area defined by the total area of mutual contact between the surfaces on conductors  122  and  200 . The engaged lengths together with respective diameters of connectors  122  and  200  may be established to yield an interface area that facilitates reducing electrical at the interface and minimizing hot spots at the interface. 
     FIG. 7  is a perspective view of a known sheathed heater  300 . Sheathed heater  300  includes an electrical interface  302  including tabs  304  that are welded to cold pins  308 . Weld areas  310  define an interface between tabs  304  and cold pins  308  that presents a relatively small interface area that may be susceptible to failures and that present a discontinuity to conduction heat transfer. The interface area thus formed is an area of relatively high electrical resistance and an obstruction to heat flow that results in the formation of hot spots. Cost reduction opportunities may be realized from the elimination of tabs  304  and the welding operation to attach tabs  304  to cold pins  308 . 
   The embodiments thus described provide a coupling method for sheathed heater assemblies that reduce manufacturing costs by eliminating the connector tabs and the welding operation to attach the tabs to the cold pins of the sheathed heater assembly. Additionally, the design of the male pin or bullet type connector and the female socket connector provide an opportunity to control connector engagement and disengagement forces and contact surface areas to reduce resistance and hot spots. Though described with respect to a sheathed heater assembly for an oven, the benefits of the invention are also applicable to broiler elements as well as cooktop heating elements. 
   While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.