Heating element arrangement for an electric blanket or the like

[0002] This invention relates to a pliable member incorporating an electrically operated heating element, such as an electric blanket, mattress pad, heating pad or the like, and more particularly to an arrangement for positioning a heating element within the pliable member so as to prevent the adverse consequences that can result from exposure of the heating element to tensile forces or other conditions that can cause strain on the heating element.

[0003] A pliable electric heating member, such as an electric blanket, mattress pad, heating pad, throw or the like, typically includes a soft pliable outer member or shell formed of two layers between which one or more heating elements, such as resistive heating wires, are located. In a typical construction, the heating wires are generally parallel and spaced apart from each other, and are maintained in place via a stitching arrangement or a web-type material secured to one of the layers about each heating wire. Each heating wire is supplied with electrical power from a power supply, and the resistance of the heating wires functions to generate heat to provide a warm environment for the user of the electric blanket, heating pad or throw.

[0004] In a conventional construction, the heating wires are arranged in a linear orientation parallel to each other. While this type of heating wire configuration provides satisfactory operation, it involves certain disadvantages in that the heating wires have little or no “give”. This can result in the heating wires becoming broken or disconnected from the power input of the pliable heating member, such as when a concentrated load (e.g. a user's elbow or knee) is applied to a portion of the pliable member within which the heating wire is located, which results in application of tensile forces to the heating wires. Such breaking of the heating wires or disconnection of the heating wires from the power input can occur in any condition that causes stretching of the blanket material, and thereby the heating elements, beyond the capability of the heating wires to accommodate the tensile forces applied to the heating wires.

[0005] It is an object of the present invention to provide a heating element arrangement for a pliable heating member such as an electric blanket, mattress pad, heating pad, throw or the like which eliminates the adverse consequences associated with the heating element being subjected to tensile forces, which can result from application of concentrated loads to the pliable heating member. It is a further object of the invention to provide such a heating element arrangement which provides even distribution of heat throughout the area of the pliable heating member within which the heating element is contained. It is a further object of the invention to provide such a heating element arrangement which provides little or no additional cost of materials or in labor associated with manufacture of the pliable heating member. It is a further object of the invention to provide such a heating element arrangement which can be incorporated into the pliable heating member in various ways.

[0006] In accordance with the present invention, a heating device such as an electric blanket, mattress pad, heating pad or throw, includes a pliable member having first and second oppositely facing surfaces, and at least one elongated heating element located between the first and second oppositely facing surfaces. The pliable member defines a series of passages, and an elongated heating element is located within each passage. The elongated heating element in each passage has a non-linear configuration, such that the overall length of the elongated heating element contained within the passage exceeds the length of the passage. In this manner, application of a concentrated load to the pliable member, which normally results in the elongated heating elements experiencing a tensile force, enables the heating elements to flex and stretch within the passages to prevent the adverse effect on the heating elements caused by application of tensile forces to the heating elements, such as breakage or disconnection from the power input.

[0007] The pliable member preferably defines an interior within which the one or more passages are formed. The passages open onto open end areas that establish communication between adjacent passages. The heating elements in each pair of adjacent passages define a connector portion located in one of the open areas, such that the heating elements are preferably formed of a single length of heating wire that extends back and forth within the passages throughout the area of the pliable member. The heating wire defines a pair of ends, which are secured to a heating wire connector mounted to a circuit board, which in turn has a connector for receiving power from a power supply. In a preferred form, the heating wire in each passage has a wave-type or sinusoidal configuration throughout the extent of the passage.

[0008] The invention contemplates a heating device having a heating element arrangement as set forth above, as well as an improvement in a heating device having a pliable member and a method of positioning heating elements within an interior defined by a pliable member, substantially in accordance with the foregoing summary.

[0009] Various other features, objects and advantages of the invention will be made apparent from the following description taken together with the drawings.

[0010] The drawings illustrate the best mode presently contemplated of carrying out the invention.

[0011] In the drawings:

[0012] FIG. 1 is an isometric view illustrating an electrically operated heating device, such as an electric blanket, mattress pad, heating pad or throw, incorporating the heating element arrangement of the present invention;

[0013] FIG. 2 is a partial section view taken along line 2—2 of FIG. 1, showing a first embodiment for positioning the heating elements into the interior of a pliable member forming a part of the electrically operated device;

[0014] FIG. 3 is a view similar to FIG. 2, showing another embodiment for incorporating the heating element arrangement of the present invention into the pliable member forming a part of the electrically operated heating device; and

[0015] FIG. 4 is a plan view showing the arrangement of the heating elements incorporated in the pliable member forming a part of the electrically operated heating device of FIG. 1.

[0016] Referring to FIG. 1, an electrically operated heating device, which may be an electric blanket, heating pad, mattress pad, or throw shown generally at 20, consists of a pliable member generically designated as a blanket portion 22, a power supply 24 and a controller 26. Power supply 24 includes a housing 28 within which the components of power supply 24 are contained. A connection cable 30 has a connector 32aat one end and a connector 32bat the opposite end. Connector 32ais adapted for engagement with a power input associated with blanket portion 22, which may representatively include a pair of power input connection prongs 34. Power supply 24 includes a power output receptacle with which connector 32bis adapted to be engaged, such that cable 30 communicates power from power supply 24 to blanket portion 22. Similarly, controller 26 includes a connection cable 36 having a connector 38 at its opposite end adapted for selective engagement with a control receptacle incorporated in power supply 24. A power input cord 40 extends from power supply 24, and includes a plug 42 at its end for engagement with a wall outlet or the like, to supply conventional 110 VAC 60 Hz power to power supply 24.

[0017] Power supply 24 may representatively have a construction and operation as shown and described in co-pending application Ser. No. 10/269,189, filed Oct. 11, 2002, the disclosure of which is hereby incorporated by reference. Power supply 24 converts the 110 VAC input power from power supply cord 40 into low voltage output power that is supplied to blanket portion 22 through cable 30, as well as to controller 26 through cable 36, for controlling the operation of power supply 24 to control the output of power to blanket portion 22.

[0018] Referring to FIG. 2, blanket portion 22 may have a construction including a top layer 44 and a bottom layer 46. A series of heating elements 48a,48b,48c,48d,etc. are located between top layer 44 and bottom layer 46. Heating elements 48a,48b,48c,48d,etc. are contained within respective longitudinal passages 50a,50b,50c,50d,etc., which are formed by spaced apart linear connections 52 between top layer 44 and bottom layer 46. Passages 50a,50b,50c,50d,etc. are all parallel to each other, and may either run in a lengthwise or crosswise direction throughout the area of blanket portion 22.

[0019] In an alternative construction as shown in FIG. 3, heating elements 48a,48b,48c,48d,etc. are contained within a carrier member 54, which includes a top layer 56 and a bottom layer 58 that are connected at spaced apart linear connections 60 to form separate parallel passages 62a,62b,62c,62d,etc. within which heating elements 48a,48b,48c,48d,etc. are contained. Carrier 54 is located between a top layer 64 and a bottom layer 66 of blanket portion 22, which define edges that are connected together to enclose carrier 54. In this manner, carrier 54 is prefabricated and heating elements 48a,48b,48c,48d,etc. are assembled into blanket portion 22 simply by assembling carrier 54 between blanket portion layers 64 and 66.

[0020] In either the embodiment of FIG. 2 or the embodiment of FIG. 3, the connections such as 52, 60 between the layers within which the passages are defined, may be made in any satisfactory manner, such as by stitching, ultrasonic bonding, etc.

[0021] FIG. 4 illustrates the arrangement of heating elements 48a,48b,48c,48d,etc. within blanket portion 22 in accordance with the present invention. FIG. 4 illustrates carrier 54 with top layer 64 removed. The areas of bottom layer 66 that are destined to be connected to top layer 64 are shown at C, to illustrate passages 62a,62b,62c,62d,etc.

[0022] Heating elements 48a,48b,48c,48d,etc. extend throughout the length of respective passages 62a,62b,62c,62d,etc. Each heating element has a non-linear configuration as positioned within its respective passage, such that the overall length of the heating element exceeds that of the passage within which the heating element is located. In the illustrated embodiment, the heating elements have an undulating or sinusoidal wave-type configuration. It is understood, however, that any other satisfactory non-linear configuration may be employed, e.g. a zigzag configuration, a loop configuration, etc.

[0023] The heating elements 48a,46b,48c,48d,etc. are all formed of a single length of heating wire, which representatively may be a _ gauge wire formed of a material such as _, which has been found to provide a satisfactory resistive load to generate heat throughout the area of blanket portion 22 when supplied with low voltage electrical power from power supply 24. It is understood, however, that any type of electric blanket heating wire of any gauge may be used, in a manner as is known.

[0024] Each part of adjacent heating elements are connected together at one end, such that a single length of wire is used throughout the area of blanket portion 22. For example, heating element 48ais interconnected with heating element 48bby means of a connector 68alocated outwardly of the ends of passages 48a,48band connection area C therebetween. Connector portion 68adefines a loop which is located in an open area 70 into which the passages 48a,48b,48c,48d,etc. open, which establishes communication between the adjacent passages. In a similar manner, the opposite end of heating element 48bis connected to the adjacent heating element 48cvia a connector portion 68bwhich extends between and interconnects the ends of heating elements 48band 48c.Connector portion 68bdefines a loop that is located outwardly of the end of the connection area C between passages 62band 62c,and is located in an open area 72 into which the opposite ends of passages 62a,62b,62c,62d,etc. open, which establishes communication between the adjacent passages.

[0025] The end heating elements, shown at 48aand 48x,have lead sections 74 that are connected to a heating wire connector 76 mounted to a PCB junction box 78. A supply power connector 80 is also mounted to junction box 78, and includes power input prongs 34 that extend outwardly of blanket portion 22 for engagement with connector 32aof cable 30. Junction box 78 also includes a pair of stitch slots 82, which are adapted to receive stitch lines that connect top and bottom layers 64, 66, respectively, to maintain junction box 78 in position within the interior of blanket portion 22.

[0026] In operation, power that is supplied to the heating elements 48a,48b. . . 48xthrough junction box 78 and heating wire connector 76 functions to generate heat within blanket portion 22. The arrangement of heating elements 48a,48b,. . . 48xprovides a uniform distribution of heat throughout the surface area of blanket portion 22, to prevent the presence of cool spots in blanket portion 22. In the event blanket portion 22 is subjected to a concentrated load, e.g. from the knee or elbow area of a user, the undulating or wave-type configuration of heating elements 48a,48b,. . . 48xallow the heating element that is subjected to the load to stretch, so as to prevent the heating element from being exposed to tensile forces which otherwise could result in breaking of the heating element or disconnection from the power input. The presence of the loop connector portions such as 68a,68b,which are located outwardly of the end edge of the wall that separates the passages within which the heating elements are received, accommodates such stretching of the heating element so as to prevent the connector portion from coming into contact with the end edge of the passage wall. In this manner, blanket portion 22 is capable of withstanding significant concentrated loads without any adverse effects on the heating elements, to prolong the life of blanket portion 22 and to maintain its continuous operation.

[0027] Various alternatives and embodiments are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter regarded as the invention.