WO2005036931A1

WO2005036931A1 - Manufacture of electric blankets

Info

Publication number: WO2005036931A1
Application number: PCT/GB2004/004323
Authority: WO
Inventors: Charles Borril; Barry Ward
Original assignee: BURCO DEAN APPLIANCES Ltd
Current assignee: BURCO DEAN APPLIANCES Ltd
Priority date: 2003-10-10
Filing date: 2004-10-11
Publication date: 2005-04-21
Anticipated expiration: 2006-04-10
Also published as: GB0323771D0

Abstract

A method of manufacture of a flexible heating panel comprising the steps of: bringing a plurality of fabric layers into overlying relation, needle punching to form a first bonded region between the two layers, forming a channel between the layers, inserting a resistive element into the channel, bringing a second region of the layers into contact to enclose the element, and needle punching to bond the second region of the layers.

Description

MANUFACTURE OF ELECTRIC BLANKETS

This invention relates to a method of manufacture of flexible heating panels such as are used in electric blankets and electrically heated clothing. The invention also relates to apparatus for use in such a method. Existing processes for manufacture of electric blankets have involved locating electrical heating wires between two layers of fabric and bonding the layers together with an adhesive. Solvent based adhesives have been used, but the solvents, for example methylene chloride are environmentally undesirable and require use of ventilation equipment in the workplace. Subsequent methods have involved needle punching of the fabric layers to produce channels through which the heating wires may be inserted. Although use of adhesives is avoided, such a process is inefficient as insertion of the heating elements is difficult and requires a separate manufacturing step. Also the configuration of the heating wires is limited as the heating element can only be inserted in a crosswise direction of the fabric web. In conventional needling apparatus the fabric layers are moved reciprocally or have their linear movement through the apparatus interrupted to enable the needles to move laterally in respect of the fabric during needling.

According to a first aspect of the present invention a method of manufacture of a flexible heating panel comprises the steps of: bringing a plurality of fabric layers into overlying relation, needle punching to form a first bonded region between the two layers, forming a channel between the layers, inserting a resistive element into the channel, bringing a second region of the layers into contact to enclose the element, and needle punching to bond the second region of the layers.

Preferred panels comprise two layers. The heating panel may comprise an electric blanket or electrically heated clothing panel. Over and under blankets which may be single or double electric blankets may be manufactured in accordance with this invention.

The fabric layers maybe composed of needle loom cloth, needle felt, knitted cloth or woven cloth. Preferred materials include acrylic polyester and polypropylene blends and wool and polyester blends. a first embodiment of the invention, the method includes the step of bringing the layers together at a location between the needle punching region and the location of insertion of the element, to retain the element in a controlled gap. this way the element is retained between the layers during needling. Alternatively, the layers may be clamped together.

Preferred methods include the further steps of: moving the layers and element to a second position, after insertion of the element and retaining or clamping the layers together between the location of the element and the needle punching region.

A preferred embodiment of the invention comprises repeating a cycle consisting of the steps of: passing upper and lower endless fabric layers from respective supplies to a first station, retaining or clamping the layers together at forward and rearward locations, needle punching with needle punching apparatus between the forward and rearward locations to form a bonded region, inserting a resistive element between the layers upstream of the rearward location, moving the layers and element to a second location wherein the element is located downstream of the needle punching apparatus, and retaining or clamping between the location of the element and the needling apparatus. In particularly preferred embodiments of the invention the steps of needle punching and inserting the element are carried out simultaneously.

In particularly preferred embodiments the needles are caused to reciprocate radially or laterally during insertion and withdrawal. This enables the fibres to become entangled in the web without the need for movement of the fabric sheets or interruption of the continuous movement of them during needling. Radial or lateral reciprocation means maybe provided to cause the needle support to reciprocate radially or laterally as it is raised and lower during the insertion or withdrawal of the needles. In preferred embodiments the means for raising and lowering the needles is independent from the means for radial or lateral movement.

In preferred embodiments the fabric layers are composed of partially needled fabrics, the extent of needling being selected so that the subsequent needling used to bond the layers produces a fully needled but not excessively needled product. Layers with about 70% needling may be conveniently employed. Use of fully needled initial layers results in an excessively needled product with a consequent risk of breakage of the fibres during manufacture. Also the total energy used during the final bonded two needling stages is reduced.

According to a second aspect of the invention apparatus for manufacture of flexible heating panel comprises: a needle punch, a guide to guide a plurality of overlying fabric layers to pass adjacent the needle punch, a plurality of retaining means or clamps upstream and downstream of the needle punch, adapted in use to secure the layers to the guide, the rearward retaining means or clamp forming a channel between the layers, and means for inserting a resistive element into the channel.

The guide may comprise a fixed bed plate and a movable stripper. The stripper may comprise an array of transversely extending members or a perforated plate defining apertures to receive the needles. In a preferred embodiment the transversely extending members comprise plates extending parallel to the direction of insertion of the needles to form needle receiving channels. The transversely extending members provide corresponding transversely extending apertures. This has the advantage that the needles can be arranged to move radially or transversely during their insertion into the felts.

Movement of the needles from side to side increases the area that each needle covers, so that fresh fibre is collected during each insertion.

Use of transversely extending channels allow the pattern of needles to be changed without need to replace the stripper plate. h preferred embodiments the spacing between the bed plate and stripper is controlled, for example by use of adjustable screws. The spacing is adjusted to be sufficiently small so that the elements inserted between the fabric layers are retained between the layers or gripped so that they are pulled through the apparatus as the layers move. In preferred embodiments the spacing is not excessively close so that the layers are compressed, to such an extent that the efficiency of the needling process is impaired.

Alternatively or in addition clamping means may be used to urge the layers together retaining the element as the needling is carried out.

In preferred embodiments of the invention 4 to 10. preferably 5 or 6 plates maybe employed. hi preferred embodiments of the invention apparatus the bed plate and stripper are arranged so that the direction of passage of the layers through the apparatus is inclined to the horizontal, preferably inclined downwardly, h such an embodiment the needles do not reciprocate in a vertical direction but instead reciprocate at an angle, for example 45° to the horizontal, so that the energy expended in raising and lowering the needles during needling is reduced. This arrangement has the further advantage that the channel formed between the layers as they are brought together opens upwardly so that the element is retained in the channel by gravity. The stripper plate may be movable towards and away from the bed plate to secure the layers to the fixed bed plate during needling and to release the layers for movement through the apparatus.

A preferred embodiment further comprises a nozzle or shuttle movable transversely relative to the plate to insert the resistive element in the channel between the layers.

A brush may be positioned upstream of the needling station to bear downwardly or apply a restraining force to the element preventing movement of the element. The nozzle may be arranged to pass through the bristles of the brush during laying of the element.

Use of the apparatus in accordance with the invention confers a number of advantages. A versatile method of manufacture of electric blankets or other heating panels is provided. The need for the separate step of insertion of the elements into pre-formed passageways in the fabric is avoided. The pitch or separation between the heating elements can be varied to provide additional heating, for example, a smaller pitch was to be provided at the foot of an electric blanket. Double blankets can be provided with separate heated portions for each user. The needle punched layers can be arranged to provide a patterned appearance.

The invention is further described by means of example but not in any limitative sense with reference to the accompanying drawings of which:

Figure 1 is a schematic side elevation of apparatus in accordance with the invention, Figure 2 is a schematic plan view of the apparatus. Figure 3 is a schematic side elevation of alternative apparatus in accordance with the invention and Figure 4 is a schematic plan view of the apparatus shown in figure 3. Figure 5 is a sectional view of alternative apparatus in accordance with the invention Figure 6 is a perspective view of the apparatus as shown in Figure 5. Figure 7 shows the movement of the apparatus shown in Figures 6; and Figure 8 shows the drive belt of the apparatus shown in Figure 6; The apparatus shown schematically in the Figures comprises a fixed upper bed plate 4 and a lower movable stripper plate 6, defining between them a horizontal guide channel through which upper 6 and lower 7 fabric webs or sheets may pass. The direction of movement of the sheets is right to left in the drawings. The sheets may be composed of the same or different thicknesses of needle loom cloth or needle felt, knitted cloth, woven cloth or combinations thereof. Preferred materials include acrylic polyester, polypropylene blends and wool and polyester blends.

The upper and lower sheets may be composed of the same fabric or may be different and additional layers may be incorporated in either of the upper or lower sheets. A needling station comprising an array of barbed needles 2 located below apertures in the fixed bed plate 4 is adapted to reciprocate upwardly and downwardly in a conventional manner by drive means 8. The density of needling may be 5-10, preferably 6 needles per square centimetre. 60 to 100 insertions per square centimetre may be used.

Prior to needling the stripper plate 5 is raised by pistons 11, trapping the layers 6 and 7 between the plates 4 and 5.

The array of needles may be configured to provide an aesthetically pleasing pattern. The array may be rectangulai- in plan view and may extend continuously across the width of the fabric layers. Alternatively, the array may be intermittent as shown in Figure 2, to provide one or more unbonded regions extending longitudinally of the web. The forward and rear clamping means la and lb extend across the width of the web and are movable between upper, disengaged positions wherein the web can move between the plates 4 and 5 and lower engaged positions in which the layers of fabric are clamped together against the stripper plate 5 preventing movement of the layers. In the clamped position the convergent sheets of fabric form a Y shaped channel upstream of the clamping means la into which channel the resistive element wire can be inserted as described below.

The clamping means la and lb may comprise an array of pins for a plate or bar extending transversely of the apparatus. A nozzle 9 is mounted for reciprocating movement within the channel between the upper and lower layers 6 and 7. The resistive heating element wire 3 prepared from a spool or other supply (not shown) to the nozzle 9 is deployed across the channel as the nozzle moves transversely of the apparatus. Clamps (not shown) may be provided to secure the element at each side of the web. Alternatively or in addition an adhesive applicator (not shown) may apply a quantity of adhesive to the element at each side of the layer, in order to bond the ends of the element to the fabric in order to prevent creep or movement of the element during prolonged use.

When the run of the element 3 has been laid the clamps la and lb are released and the webs and element wrapped between the webs move longitudinally, from right to left as shown in the Figures, extra fabric being deployed from the supply spools.

The assembly is advanced so that the element wire is moved to a location 10 downstream of the second clamp lb. The clamps la and lb are then lowered to re-engage and secure the webs. The needling and element laying steps are then repeated, the shuttle returning across the bed to the initial position. In this way, a continuous length of element is laid in a castellated or zigzag manner, so that passageways are formed between successive needle punch regions. The pitch between successive element runs may be varied to provide higher or lower densities along the length of the heating panel. For example, an electric blanket may have a higher density at a lower portion to provide greater heating to a user's feet.

In an alternative embodiment two of the apparatus as described above may be located side by side to form individual heating panels in a double electric blanket. Such a double blanket allows each user to individually control the I-heating.

Figures 3 and 4 shows an alternative embodiment to the invention. A lower layer 23 passes over a plate mounted on a spring support 28 and passes over an array of needles 21, movable in channels 22 located below the layer and driven by a reciprocating drive 27. An upper layer 24 is brought into parallel relation with the lower layer 23 to form a channel

30.

An array for example of six laterally extending plates or other members 20 defines apertures to receive the needles 21 after passage through the layers 23 and 24. The reciprocating drive 27 is arranged to move the needles transversely or from side to side during each insertion so that different fibres are engaged on each stroke. A shuttle 25 reciprocates transversely of the channel 30 formed between the upper 24 and lower 23 layers and dispenses a length of element wire 26 across the channel during each stroke.

The separation between the upper 29 and lower guides 28 is adjusted so that the layers 23 and 24 engage the element wire 26 and pull the wire through the apparatus but without compressing the layers excessively to impede the needling process.

In a further alternative embodiment of the invention, (not shown) the apparatus is tilted so that the direction of passage of the layers is inclined to the horizontal, preferably downwardly so that the energy expended by the needling drive mechanism is reduced and also so that the channel between the upper and lower layers faces upwardly so that the inserted element is retained by gravity. Figures 5 to 8 illustrate an alternative embodiment of the invention, particularly the needling mechanism. Figure 5 is a sectional view showing a fixed upper plate (30) and moveable lower stripper plate (31) defining a horizontal guide channel through which upper (32) and lower (33) fabric webs or sheets pass. An array of barbed needles (34) mounted on a needle bar (35) is arranged to reciprocate upwardly and downwardly through the webs (32) and (33). The drive means comprises a connecting rod (36) driven by a crank (37) having an eccentric throw the crank being mounted on axle (38). The axle (38) is driven by belts acting on pulleys (39) as described below. Rotation of the axle (38) causes the eccentric crank (37) to raise and lower the rod (36) and in turn to raise and lower the needle bar (35).

In a preferred embodiment a plurality of cam arrangements (36), (37), (38), (39) are disposed along the length of the needle bar (35) as shown in Figure 6.

Guide rods (40) disposed in journals (41) at intervals along the needle bar (35) permit uniform horizontal raising and lowering of the needle bar in use. The journals (41) are mounted on sliding blocks (50) on a rail (42). Reciprocation of the lever (43) through the crank (44) causes the needle bar (35) to reciprocate along the rail (42). Thus as the needle bar is raised and lower by cranks (37), the needle bar also reciprocates lengthwise causing the needles to move in a loop as they penetrate the web. In this way sufficient needling is achieved without the need for movement of the web or interaction of the continuous movement of the web through the rollers (45),(46). Thus the elements may be laid continuously and the needling carried out continuously without interruption.

Figure 7 shows the movement of the components in greater detail. The link (43) is driven by a reciprocal drive, such as an eccentric crank (not shown) and causes the crank (44) to move horizontally in turn causing the sliding block and bearing support (41) to move along the rail (42). Figure 8 shows a connection of the pulleys (39) to a drive unit (47) by means of belts (48). The pulleys are arranged to rotate in opposite directions on each side of the drive unit to reduce lateral imbalance and to allow the apparatus to run at higher speed.

Claims

1. A method of manufacture of a flexible heating panel comprising the steps of: bringing a plurality of fabric layers into overlying relation, needle punching to form a first bonded region between the two layers, forming a channel between the layers, inserting a resistive element into the channel, bringing a second region of the layers into contact to enclose the element, and needle punching to bond the second region of the layers.

2. A method as claimed in claim lwhere the hearing panel comprises an electric blanket or an electrically heated clothing panel.

3. A method as claimed in claim 1 or 2 wherein the fabric layers comprise needle cloth, needle felt, knitted cloth, or woven cloth.

4. A method as claimed in any preceding claim wherein, the fabric is composed of a material selected from: acrylic polyester and polypropylene blends, wool and polyester blends.

5. A method as claimed in any preceding claim, including the step of retaining or clamping the layers together at a location between the needle punching region and location of insertion of the element.

6. A method as claimed in any preceding claim, including the steps of: moving the layers and element to a second position after insertion of the element, and; retaining or clamping the layers together between the location of the element and needle punching region.

7. A method as claimed in any preceding claim, including repeating a cycle consisting of the steps of: passing upper and lower endless fabric layers from respective supplies to a first station, retaining or clamping the layers together at forward and rearward locations, needle punching with needle punching apparatus between the forward and rearward locations to form a bonded region, inserting a resistive element between the layers upstream of the rearward location, moving the layers and element to a second location wherein the element is located downstream of the needle punching apparatus, and retaining or clamping between the location of the element and the needling apparatus.

8. A method as claimed in any preceding claim, wherein the steps of needle punching and inserting the element are carried out simultaneously.

9. A method as claimed in any preceding claim wherein the needles are caused to reciprocate radially during insertion and withdrawal.

10. A method as claimed in any preceding claim, wherein the fabric layers are composed of partially needled fabric.

11. Apparatus for manufacture of a flexible heating panel, comprising: a needle punch, a guide to guide a plurality of overlying fabric layers to pass adjacent the needle punch, a plurality of retaining means or clamps upstream and downstream of the needle punch, adapted in use to secure the layers to the guide, the rearward retaining means or clamp forming a channel between the layers, and means for inserting a resistive element into the channel.

12. Apparatus as claimed in claim 9 or 10, wherein the stripper comprises an array of transversely extending members, defining apertures between the plates to receive the needles during needling.

13. Apparatus as claimed in claim 12 wherein the stripper comprises an array of transversely extending plates.

14. Apparatus as claimed in any of claims 11 to 13, wherein the needles move radially or transversely during each insertion.

15. Apparatus as claimed in any of claims 9 to 14, wherein the separation between the bed plate and stripper is selected to grip or retain the inserted element but not to compress the layers.

16. Apparatus as claimed in any claims 9 to 15, wherein the direction of passage of the layers between the bed plate and stripper is inclined to the horizontal.

17. Apparatus as claimed in claim 16, wherein the direction of passage is inclined downwardly.

18. Apparatus as claimed in any of claims 6 to 8 further comprising a nozzle movable transversely relative to the plates to insert a resistive element in the channel between the layers.