GB2289608A - A process for producing a panel heater - Google Patents

Abstract

A process for producing a panel heater (1) of the type comprising a body member (2) in the form of a slab comprises securing a plurality of bollards 10 on a base (6) of an open mouthed rectangular box (4) and placing an electrical heating element 8 having end connectors (22, 34) around the bollards 10. The end connectors engage within an internal connector housing 12. A matrix of fire retardant material (9) is cast in the box (4) about the electrical heating element 8 and the bollards 10 and allowed to set before being covered with an insulating panel 26. A closing lid 5 is attached to the open mouthed rectangular box 4 to form the base of the panel heater 1. The bollards 10 may be secured to the base 6 of the open mouthed rectangular box 4 by a jig (33) having bollard engaging prongs (32) removable after casting of the matrix 9. The process allows slab-like panel heaters (1) to be produced simply and cheaply. <IMAGE>

Description

"A Process for Producing a Pane Heater" IntroductioR This invention relates to a process for producing a panel heater and in particular to a process for producing a panel heater in the form of a slab.

Panel heaters of this type are well known. Generally, they comprise a body member of slab like shape the body member comprising an external shell or frame and a heating means embedded within a matrix of fire retardant material, the matrix of fire retardant material being mounted within the shell or frame. Usually, the heating means is an electrical heating element which is mounted on an internal frame or a series of bollards before the matrix is cast.

All known panel heaters of this type are made in a mould and removed from the mould when manufacture is complete.

For example, DE 423,825 describes a panel heater comprising a zigzag flexible electrical conductor mounted on a grid-like frame, both the conductor and the frame being sandwiched between two layers of fire resistant material, namely, an artificial stone layer and a natural stone slab. This heater is produced in a number of separate moulding stagers, thus making it time consuming and relatively expensive to produce. The use of both the grid-like frame upon which the conductor is mounted and the natural stone slab add to the expense of the heater.

SU 1,814,505 describes an electric heating panel for young livestock comprising a concrete slab with an outer metal frame and containing an electric heating element mounted within a matrix of fire resistant concrete. The slab also contains a rectangular tubular frame around which the heating element is spirally wound, the heating element being surrounded by a metal braiding which is connected to earth. Although this panel is relatively easy to produce, the inclusion of the frame upon which to mount the element and the metal braiding around the element add to the expense of production. Another problem associated with this type of heater is the loss of heat to ground through the base of the panel resulting in both higher energy consumption and operating costs. The outer metal frame is also prone to corrosion.

A further example of this type of panel heater is described in IES 59643. This specification describes a panel heater comprising a body member of slab-like shape, the body member comprising a shell having an outer major surface forming a heat exchange surface, an electrical heating element mounted within the shell and supported by a number of spaced-apart bollards, a matrix of fire retardant material moulded within the shell around both the heating element and the bollards and an insulating panel positioned between the matrix and the base of the shell. However, as this panel is completely produced in a mould and involves a number of moulding steps, the process is very complicated. For example, the shell of the heater described in IES 59643 is moulded in at least four separate stages, each stage involving a curing step.

This is very time consuming and therefore makes such panel heaters very expensive to produce. A further problem with the panel heater described in lES 59643 is that it is extremely difficulty to inspect both surfaces of the shell before proceeding with the further moulding stages.

GB 1,164,285 describes an electric space heating panel of layered construction comprising an external shell which envelopes an electric element embedded in a concrete mix.

A block of concrete and a layer of insulation lies between a base of the panel and the fire resistant concrete.

Although this heater is relatively efficient in operation, the complexity of its construction makes it expensive to produce.

GB 2,278,188-A describes an electric panel heater comprising front and rear panels which together define an enclosed space. A pair of electrical resistive elements are mounted within the enclosed space between two sheets of high electrical resistance insulation material.

This invention seeks to provide a process for producing a panel heater which overcomes at least some of these disadvantages, Statelents of Invention According to the invention there is provided a process for producing a panel heater of the type comprising a body member in the form of a slab, the process comprising the steps of:: securing a plurality of bollards on a base of an open mouthed rectangular box; placing an internal connector housing against one wall of the box to form an enclosed space within the box; leading an electrical heating element having end connectors around the bollards and terminating with the end connectors within the internal connector housing; casting a matrix of fire retardant material in the box about t the electrical heating element and the bollards covering the matrix of fire retardant material with an insulating panel; and attaching a closing lid to the open mouthed rectangular box to form the base of the panel.

The process provides a simple and efficient way of producing a panel heater. The efficiency of production is due in part to the box being pre-produced in two parts, the open mouthed rectangular box acting as a mould for the matrix. Thus, the panel heater will not be damaged by premature removal from the mould. As the bollards and the heating element are secured in the box before the matrix is cast, the casting can be carried out in one step, thus saving a substantial amount of time and expense compared to the multi-moulding processes described in the prior art. As the box is pre-produced, all of its surfaces can be inspected for flaws prior to assembly of the panel heater. The provision of the void forming container allows for easy replacement of both the power cable and/or the end connectors if either are damaged in use.

In one embodiment of the invention the bollards are secured to the base of the open mouthed rectangular box by means of an adhesive. The use of an adhesive allows the bollards to be sealed to the box quickly, securely and efficiently.

In another embodiment of the invention, the bollards are secured to the base of the open mouthed rectangular box using a jig having bollard engaging prongs removable after casting of the matrix. This is a simple and efficient method of securing the bollards to the base of the box without using an adhesive.

In a preferred embodiment of the invention, the open mouthed rectangular box is not completely filled with the matrix of fire retardant material, thereby leaving a recess for the insulating panel.

The invention also provides a panel heater whenever formed by the above process.

Preferably, the end connectors of the electrical heating element includes a pair of male bullet connectors for connection to corresponding female bullet connectors on a power cable.

This arrangement allows the power cable to be quickly and efficiently connected to the electrical heating element, thus further simplifying the manufacture of the panel.

Most preferably, the male and female bullet connectors are covered with a heat shrinking sleeve containing a glue.

This arrangement allows the power cable and electrical element to be securely connected. Upon heat shrinking, a glue is released from the sleeve which further secures the connection.

Ideally, the power cable projects through a strain relief cable gland mounted in the open mouthed rectangular box.

The provision of the strain relief cable gland prevents the power cable being easily removed from the panel heater. This is important as removal of the power cable could result in damage to the cable and consequent safety risks.

In one embodiment of the invention, the matrix comprises a heat retentive polymer. The provision of a heat retentive polymer in the matrix improves the thermodynamic efficiency of the panel.

Typically, the bollards, the open mouthed rectangular box and the closing lid are manufactured from Acrylonitrile Butadiene Styrene. The manufacture of the box and the bollards from Acrylonitrile Butadiene Styrene (ABS) provides a considerable advance in the art. ABS has good toughness, stiffness and formability while providing an attractive high gloss finish. it also has excellent resistance to chemical attack from aqueous solutions of inorganic acids, alkalis and salts. Due to the higher rigidity of ABS, the box has superior moulding properties, offering improved shape formation in the mould. In addition, ABS offers a higher thermodynamic output compared to polypropylene and fibreglass based boxes, thus increasing the overall thermodynamic and operational efficiency of the panel heater of the invention.Indeed, the combined use of ABS and the heat retentive polymer has resulted in an energy usage of 0.8 KW/hr.

Ideally, the panel heater includes a conduit for insertion of a sensor such as a thermometer formed in the matrix by a hollow tube, open at one end, said open end projecting through a side wall of the box.

Detailed Description of the Invention The invention will be more clearly understood from the following description of some embodiments thereof, given by way of example only with reference to the accompanying drawings in which: Fig, 1 is a perspective view of a panel heater manufactured by the process of the invention in an in-use position; Fig. 2 is an exploded perspective view of a final assembly step of the process for producing the panel heater; Fig. 3 is a perspective view with a section cut-away of a first stage in the process used in forming the panel heater with a plurality of bollards and an internal connector container secured in place; Fig. 4 is a perspective view of a further step in the process of the invention with an electrical heating element in place; Fig. 5 is a plan view of the partly assembled panel heater of Fig. 4;; Fig. 6 is a sectional elevational view taken along the line X-X of Fig. 5; Fig. 7 is a perspective view of the void forming internal connector housing used in the process of the invention; Fig. 8 is a perspective view of a jig with a plurality of hollow bollard-forming posts attached, used in an alternative process of the invention; and Fig. 9 is a perspective view of a bo3.lard-forming hollow post of Fig. 8.

Referring to the drawings and initially to Figs. 1 to 7 thereof, there is illustrated a panel heater 1 particularly a floor panel for a livestock unit, especially a pig farrowing unit. The panel heater 1 comprises a slab-like body member 2 having a two-part housing which extends completely around the body member.

The two-part housing is formed by an open mouthed rectangular box 4 and a closing lid 5. The box 4 has a base 6 which forms a heat exchange surface from which heat is dissipated from the body member 2. In use, as illustrated in Fig. 1 the base 6 forms an upper surface of the panel heater 1. Panel heating means is provided by an electrical heating element 7 formed by an elongated electrical resistance wire 8 arranged longitudinally in a matrix of fire resistant material 9 in the open mouthed rectangular box 4. The resistance wire 8 is arranged longitudinally in the open mouthed rectangular box 4 and terminates in male bullet connections 34. The wire 8 is led around a plurality of bollards 10 which are glued to the base 6 by means of methyl ethyl ketone solvent. The bollards 10, box 4 and lid 5 are of Acrylonitrile Butadiene Styrene (ABS).The matrix of fire resistant material 9 comprises a mixture of cement and a polymer.

A suitable matrix forming material is a cement sand/ polymer material sold under the trade name LARCEM 200 which is manufactured and sold by the LARCEM GROUP of Belfast, Northern Ireland. This particular polymer used offers particularly good heat retention.

An internal connector housing 12 is located in the body member 2 adjacent an upstanding wall 13 of the open mouthed rectangular box 4. As illustrated particularly in Fig. 7 the internal connector housing 12 has two holes 14 in one wall 15 thereof communicating with the interior of the open mouthed rectangular box 4. Another hole 16 in an opposite wall of the housing 12 is aligned with a hole 18 in the upstanding wall 13 to form a through passageway 19.

A strain relief cable gland 20 is mounted in the passageway 19 and a two core power cable 21 is led through the gland 20 into the internal connector housing 12. The two core power cable 21 terminates in a pair of female bullet connectors 22 which connect to the corresponding male bullet connectors 34 at the ends of the resistance wire 8.

A conduit for the protection of a sensor lead is provided in the matrix 9 by a hollow tube 23, approximately 20mm in length, open at one end 24, which projects through the upstanding wall 13.

An insulating panel 26 of heat insulating material, namely, a sheet of compressed polystyrene insulation material is interposed between the matrix 9 and the lid 6.

The use of polystyrene is a considerable improvement over fibreglass-based insulations which are considered to be flammable.

In the method of the invention, the panel heater 1 is formed by gluing a plurality of the ABS bollards 10 onto the base 6 of the open mouthed rectangular box 4 in the appropriate positions. The internal connector housing 12 is then secured in position as is the hollow tube 23.

This assembly is illustrated in Fig. 3. The elongated electrical resistance wire 8 is then led around the bollards 10 and through the holes 14 in the wall 15 of the internal connector housing 12 leaving the bullet connectors 34 at the ends of the elongated electrical resistance wire 8 exposed within the housing 12.

The strain relief cable gland 20 is then placed in the passageway 19. The two core power cable 21 is led through the gland 20 and the pair of female bullet connectors 22 are connected to the corresponding male bullet connectors 34 on the ends of the elongated electrical resistance wire 8. Each of the bullet connectors 22, 34 are covered with a glue releasing heat shrinking sleeve which is crimped and heat-shrunk. Upon heat-shrinking a glue is released from the connectors sleeves which bonds to both connectors 22, 34. The strain relief cable gland 20 is then tightened until the desired tension on the elongated electrical resistance wire 8 is reached. This stage of the assembly is illustrated in Fig. 4.

Cement and a polymer is then poured in one step into the open mouthed rectangular box 4 filling it to within approximately 20 nm of the top to provide the matrix 9.

When the cast matrix 9 has completely set the compressed polystyrene insulating panel 26 is placed on top of the matrix 9 within the box 4. The lid 5 is then placed on the open mouthed rectangular box 4 as illustrated in Fig.

2. The lid 5 is glued to the base 4 by a methyl ethyl ketone solvent, A sufficient length of electrical resistance wire 8 may be led into the internal connector housing 12 so that, if necessary the wire 8 and bullet connectors 34 may be withdrawn through the through hole 19. This may be required if either the bullet connectors 22, 34 or the power cable 21 are damaged during use and require replacement.

Referring to Figs. 8 and 9 an alternative process for manufacturing a panel heater is illustrated. The bollards 10 of the previous embodiment are provided by hollow bollard-forming posts 29 which are secured in the open mouthed rectangular box during assembly by means of a jig 33 having prongs 32. The hollow bollard-forming posts 29 are secured to the prongs 32 as illustrated in Fig. B.

The jig 33 is then set into the open mouthed rectangular box 4 so that the prongs 32 supporting the hollow bollardforming posts 29 sit on the base 6 of the open mouthed rectangular box 4. The matrix 9 is then poured until it reaches a top of the bollards 29 without covering them and allowed to set. The jig 33 is then removed. The other steps in the process are as previously described.

The panel heater 1 is suitable as a floor panel or tile for space heating, and is particularly suitable for forming part or indeed most of a floor of a pig farrowing unit or other livestock housing.

In use in a pig farrowing unit or other livestock housing, the panel heater 1 is mounted on a floor of the unit or housing with the base 6 abutting the floor. The panel heater 1 may be secured to the floor by adhesive, by mounting brackets or it may be free standing. Indeed, the panel heater 1 may be recessed into depressions in the floor with an upper surface of the panel 1 being aligned with an upper surface of the floor. The two-core power cable 21 is connected to a standard 220V AC mains electricity supply. Preferably, in the case where the panel heater 1 is being used on a slatted floor, the power cable 21 will be depressed into one of the slats. This will help prevent damage to the cable from animals hooves.

In an event of a power cable needing to be replaced, the strain relief cable gland 20 is removed from the box and the resistance wire B and bullet connections 34 are withdrawn from the void forming housing 12. Thus, the power cable 21 may be easily replaced.

It will be appreciated that the panel heater of the invention may be covered in a resilient sleeve or covering which, in use, would make the panel heater more comfortable to lie on. Indeed, the resilient covering may be attached to an exterior of the base of the open mouthed rectangular box.

While the heating element has been described as being powered by a 220v AC mains supply, it is understood that the heating element may be suitable for powering by a low voltage AC or DC power supply for safety purposes.

The invention is not limited to the embodiments hereinbefore described but may be varied in both construction and detail.

Claims (14)

CWLIMS

1. A process for producing a panel heater of the type comprising a body member in the form of a slab, the process comprising the steps of: securing a plurality of bollards on a base of an open mouthed rectangular box; placing an internal connector housing against one wall of the box to form an enclosed space within the box; leading an electrical heating element having end connectors around the bollards and texminating with the end connectors within the internal connector housing; casting a matrix of fire retardant material in the box about the electrical heating element and the bollards; covering the matrix of fire retardant material with an insulating panel; and attaching a closing lid to the open mouthed rectangular box to form the base of the panel.

2. A process as claimed in claim 1 in which the bollards are secured to the base of the open mouthed rectangular box by means of an adhesive.

3. A process as claimed in claim 1 in which the bollards are secured to the base of the open mouthed rectangular box by a jig having bollard engaging prongs removable after casting of the matrix.

4. A process as claimed in claims 2 or 3 in which the open mouthed rectangular box is not completely filled with the matrix of fire retardant material, thereby leaving a recess for the insulating panel.

5. A process for producing a panel substantially as hereinbefore described with reference to the accompanying drawings.

6. A panel heater whenever formed by a process as claimed in any preceding claim.

7. A panel heater as claimed in claim 6 in which the end connectors of the electrical heating element includes a pair of male bullet connectors for connection to corresponding female bullet connectors on a power cable.

8. A panel heater as claimed in claim 7 in which the male and female bullet connectors are covered with a glue-releasing heat shrinking sleeve.

9. A panel heater as claimed in claims 7 or 8 in which the power cable projects through a strain relief cable gland mounted in the open mouthed rectangular box.

10. A panel heater as claimed in any of claims 6 to 9 in which the matrix comprises a heat retentive polymer.

11. A panel heater as claimed in any of claims 6 to 10 in which the bollards, the open mouthed rectangular box and the closing lid are of Acrylonitrile Butadiene Styrene (ABS).

12. A panel heater as claimed in any of claims 6 to 11 including a conduit for insertion of a sensor formed in the matrix by a hollow tube, open at one end, said open end projecting through a side wall of the box.

13. A panel heater as claimed in any of claims 6 to 12 in which a base of the open mouthed rectangular box includes an exterior surface of resilient material.

14. A panel heater substantially as hereinbefore described with reference to the accompanying drawings.