ELECTRICAL RADIANT HEATING DEVICE
The present invention generally relates to the area of electric heating elements, intended for radiant heating of premises, baseboards, heating of walls etc. These heating devices may be used in domestic, industrial and agricultural installations.
BACKGROUND OF THE INVENTION
Previously known heating device, based on metal foil heating element, is disclosed in US Patent 4,659,906. The described heater is intended for infrared radiation and operates at the temperature range 800 - 1000°C, which determines choice of special materials for the heater substrate. Thus, this heater relates to other class of heaters. Its heating element is made by etching and therefore it has limited small dimensions.
US Patent 5,624,750 proposes a low temperature heating element etched from metal alloy and embedded or sandwiched between two layers of thermoplastic adhesive, which encapsulate the heating element. Patent proposes also the original method of object assembly.
US Patent 4,797,537 and European patent 0175662 also propose foil heating elements made by etching or punching technologies.
All elements, made by above-mentioned technologies, have limited sizes and small surface area.
US Patent 4,574,186 proposed "a heating sheet, in which protective covers are laminated to both surfaces of a heating element". In this design the protective covers, comprising thermoplastic resin, such as PVC or the like, are hot-pressed from both outer surfaces for air-tight insulation.
In US Patent 3603764 a heating panel for rooms heating is described. The panel contains an electric heating element embedded in the heating panel, wherein one side is formed from heat conducting material, and other side is formed from heat insulating material.
US Patent 5138134 proposes a wall hanging heating panel, comprising a front
decorative panel, a layer of electro-insulating heat conductive material, a heating element, including a layer of graphite fabric, and a backing panel.
All above described heating devices are manufactured or by hot-press technology or by mechanical mounting. Both the hot-press technology and mechanical mounting foresee manufacturing of single plates in non-continuous process. Manufacturing process of described heating devices is characterized by low productiveness.
Besides, such heaters have a limited scope of practical application and a limited size and shape.
The present invention, therefore, aims to obtain universal heating device with unlimited dimensions and multitude forms and also to create production of heating panels and profiles with very high productiveness, with the added benefit of an increased life-span and the highest reliability.
All these goals can be attained using the proposed new electric heating devices.
SAMMARY OF THE INVENTIONS
The present invention describes a new electric heating device, construction of which is formed in a result of pultrusion process. Fiberglass reinforced plastics profile, received during pultrusion process, serves as a watertight shell for a heating element. The properties, such as high mechanical strength, high electrical strength and heat resistance, do this group of plastics by excellent materials for heating devices, used for radiant heating. Besides, using of pultrusion process allows to create continuous process for manufacturing of radiant heating panels and profiles and to provide high productivity.
Described heating devices comprise a flexible heating element, which consists of a thin resistance ribbon, arranged between layers of fiberglass mat or mesh. Resistance ribbon has electrical terminals on its ends. This sandwich forms the heating insert, which is used as one of reinforced materials for fiberglass reinforced plastics profile, which serves as a plastics shell.
The heating insert is disposed between other reinforcing fiberglass materials and is incorporated into said plastics profile during the pultrusion process. Using of
pultrusion technology provides high quality of impregnation of our heating insert by polymer resins and firm cohesion of whole composite material. Such material has high steadiness to temperature deformations, high reliability and life span.
Obtained in result of pultrusion process continuous plastics profile or panel contains multitude inserts. Length of the inserts and profiles is limited by length of a workshop and may reach ten and more meters. The profile is cut in places between inserts, such that terminals of the inserts are disposed about cut edges of said profile. The cut edges of the profile must be sealed. Simultaneously electrical terminals must be extracted from profile composite and brought out for connection with power supply or other profile. Therefore, flanges are disposed on the edges of pultruded rigid plastic profile. The flanges realize also mechanical fastening to walls.
Material, used for the heating insert, incorporated into a plastic shell, must provide even distribution of temperature on plastic surface. Absence of temperature concentration prevents plastics destroying in result of overheat, essentially increases reliability and life span of heating devices. For these insert may be used thin metal foil with high electrical resistance, high mechanical strength and plasticity.
Excellent reinforcing material, used for fiber reinforced plastics, is carbon fibers (rovings). Therefore, the present invention proposes the heating device with a heating element, which comprises carbon roving, which is simultaneously one of reinforced plastics material. All rovings are disposed along the heating element and are divided one from other. In zone of ends of the heating element all rovings are covered by film. The film has no adhesion with resin (matrix) in pultrusion process and has a melting temperature more than 200°C. After pultrusion process, zone of rovings, which was covered by the film, are easily extracted from profile and are connected between them in electrical scheme, forming the terminals of heating element.
The present invention proposes also the heating device with a heating element, which comprises carbon fabric and also serves as excellent reinforcing material. In this case, zones of the fabric about ends of the heating element are covered by film. This film has no adhesion with resin (matrix) in pultrusion process and has a melting temperature more than 200°C. Zone of the fabric under the film is easily extracted from profile.
These zones of the fabric contain woven or stitched electro-conductive filament- threads, which are used as terminals of the heating elements. The terminals may be made also by other methods, for example, by electro-conductive metal bus-bars, connected with carbon materials by electro-conductive glue.
The present invention proposes some patterns of the inserts. The simplest insert consists of some separate heating elements, and each such element is finished by terminals. In other case the insert contains bus-bars, made of electro-conductive flexible metal ribbons, and flexible resistor ribbon. These bus-bars are disposed along of the insert. The resistor ribbon forms multitude of heating sections. Each of the heating sections is connected with said bus-bars in parallel, forming continuous flexible heating strip, which may be cut after each section in dependence on required electrical power and length. In such structures the bus-bars can form two pairs of terminals from two sides of the heating panel or profile for connections of several heating devices one to other and with power supply. For wide heating panels the insert may contain at least two groups of the heating elements, located by rows. Each row contains pair of busbars and the heating sections, connected to bus-bars in parallel. The bus-bars of the rows form at least three terminals from each end of the heating panel or profile for connections of the groups in parallel or serially.
In accordance with the present invention the heating profile have flanges on every side. The main destination of these flanges is sealing of cut edges of the plastics profile in order to prevent water absorption through cut surface and to except influence of water absorption on dielectric strength of the heating device. The present invention proposes example of design of the heating device, wherein the flange have slots, and the slots have size and form, coinciding with transversal cross section of the heating profile. The cut edges of the profile are fit into the slots and sealed by polymer, providing water-proofhess of the device. The flanges are intended also for mechanical fastening to walls and electrical connections between inserts and power source.
The pultruded profile may have a complicated form. In accordance with present invention, complicated profile may contain two and more inserts, which are incorporated into different sides of the profile. In this case the following condition must be fulfilled during pultrusion process: all inserts pass pultrusion die synchronously, i.e.
beginning position and ending position of each of incorporated inserts coincide on a length of said profile. Terminals of inserts are connected between them in parallel or serially.
The heating devices may be constructed in different forms, sizes and electrical power. Such structures consist of several profiles, united by the flanges, disposed on every side of the heating device. The flange contains several slots, one by one for each profile. The slots have dimensions and form, coinciding with transversal cross section of the profiles. Every profile is introduced into its slot. The profiles are arranged with space, providing improved air circulation. The terminals of inserts are connected between them in parallel or serially.
Forming of optimum disposition of profiles in assembly, favorable for economical heat distribution, allow to optimize heat flow, to influence on temperature distribution in a heated premise, to increase effectiveness of heating device and to reach energy saving.
In accordance with the present invention the assemblies can be joined in a block. The block design allows to obtain multitude heaters with various forms and sizes on base one - two type of the profile. Assemblies may be joined longitudinally, forming block - baseboard. Assemblies may be joined also in a radiant heating panel. Special pins and sockets, disposed on assembly blank-flanges, provide above-mentioned mechanical joining. The flanges have holes inside said mechanical connectors (pins and sockets) for passing of electrical cables.
The present invention proposes also yet one solution of the heating device, based on pultrusion technology. In accordance with this solution, the heating device contains a single-line heating ribbon, disposed between two stripes of fiberglass mat or mesh. The single-line heating ribbon and fiberglass substrate together form the heating insert in a shape of flexible stripe, which is incorporated in plastics profile during pultrusion process. Ends of the heating ribbon are joined with electro-conductive terminals. Manufacturing of such insert is greatly simpler.
Length and a width of the heating ribbon depend on different factors: power of the heating device, surface specific electrical resistance of heating material, specific power of the heating device, accepted for all surface of plastics profile, and relationship
of area of the heating ribbon and all heating profile.
As it is proposed in the present invention, a length and a width of the heating ribbon for one heating device are defined in accordance with equations:
L >= U / (Psp * Rsurface) / (k3 * k4), (1)
W = P * k3 * k4 /(Psp * L), (2) where: L - length of the heating ribbon, m W - width of the heating ribbon, m; P - power of said heating device, W; U - voltage, V
Rsurface - surface specific electrical resistance of heating material, equal to electrical resistance of heating foil with the length lo=lm and the width Wo = lm; R surface = p*lo / δ* Wo ; p - specific resistance of heating material, Ohm*m; δ - thickness of heating material, m Psp - specific power of the heating device, W/sq.m; k3 - ratio of length of said heating ribbon and length of said profile; in calculation it is possible to receive k3 = 1; k4 - ratio of width of said heating ribbon and width of said profile; the volume of k4 is usually in limits 0.4 - 0.8. After pultrusion process the heating profile has a shape of a long continuous toolbar. This toolbar is cut such that each part has length, determined by the length of the heating element in accordance with relation (1).
Extrusion technology may be used also for manufacturing of such heaters. In this case the heating ribbon is incorporated in extruded plastics rigid or flexible strip during extrusion process, and said strip is cut such that each part has length, determined by the length of the heating element in accordance with relation (1).
Described heating device is very long profile, which may be used, for example, as a baseboard. It is possible to use this heating toolbar in other design. The present invention proposes a heating device, which consists of some parts, and a sum of lengths of these parts is equal to length of the whole heating plastics profile in accordance with relation (1). Each of these parts has electrical terminals on two ends. These parts are
joined between them by one flange on each side. The flange contains slots for each part of the profile and box for electrical connections between inserts of every part. Such heating device is simple in manufacturing and provides improved temperature distribution in a heated premise.
The present invention discloses the methods of manufacturing of described heating profiles and panels. These methods use known pultrusion technological process for manufacturing of usual plastics profiles. However, process of making of described heating profiles has some peculiarities. Heating insert must be incorporated into a die of pultrusion machine between of reinforced fiberglass and glass mat. Quantity and distribution of the reinforcing materials on every side of insert is defined by conditions of mechanical and dielectric strength of the heating plastic profile. Such conditions are: sufficient wetting of the heating insert together with rovings and glass mat, impregnating of heating insert and glass mat layers by liquid resin and uniform distribution of reinforcing materials on the heating insert surface. It is desirably also that distribution of reinforcing materials on every side of insert is the same.
Method of manufacturing of heaters comprises the following steps: a) Coiling of a continuous flexible heating insert, consisting of plurality heating elements, on bobbins; b) Impregnating of the flexible heating insert by liquid resin in bath together with other reinforcing materials; c) Feeding of the flexible heating insert in a slot of additional infeed plate before pultrusion machine; d) Pre-positioning of the impregnated insert between layers of reinforcing glass mat and roving such, that the glass materials are disposed uniformly on two sides of the heating insert; e) Feeding of the flexible heating insert together with reinforcing materials in a die of pultrusion machine, forming the shape of a profile, and forming a heating rigid plastics profile during continuous pultrusion process in this die; f) Cutting of the heating rigid continuous plastic profile in places between heating elements of the heating insert; h) Mounting of one or more cut heating profiles in a heating device.
The present invention discloses also the methods of heaters manufacturing for intricate multi-sided profiles with several heating sides. In this case several heating inserts are incorporated into the profile, one on the chosen profile side. This method comprises the following additional steps: a) Feeding additional flexible heating inserts to additional slots of said infeed plate before pultrusion machine; b ) Pre-positioning of each of said impregnated inserts between layers of reinforcing glass mat and roving such, that said glass materials are disposed on two sides of said heating inserts; c) Synchronous feeding of all flexible heating inserts together with reinforcing materials to a die of pultrusion machine, such that beginnings and ends of each inserts coincide, and each flexible heating insert is introduced into one of sides of said profile; d) Forming a heating multi-sided rigid plastics profile during continuous pultrusion process in said die; e) Cutting of said heating rigid continuous plastic profile into profiled heating units and said cutting is made in places between heating elements of said heating inserts; f) Mounting of said profiled heating units in a heating device by introducing of said unit into slots in said boxes and gluing together of profiled heating unit and the boxes on its ends.
The present invention provides technical solutions, which are innovative and capable of meeting the requirements for their application. The technical solutions are fit for industrial production, and as formulated in the present patent application, constitute a coherent invention.
BRIEF DESCRIPTION OF THE DRAWINGS
Other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:
Fig.l is schematic top plan view of pultruded plastics profile with incorporated
heating insert on base of metal ribbon in accordance with the present invention;
Fig.2 is schematic top plan view of pultruded plastics profile with incorporated heating insert and with a cap on its end in accordance with the present invention;
Fig.3 is schematic top plan view of a heating element on base of carbon roving in accordance with the present invention;
Fig.4 is schematic top plan view of a heating element on base of carbon fabric in accordance with the present invention;
Fig. 5 is scheme of a heating element with multitude parallel heating sections for heating profiles;
Fig. 6 is scheme of a heating element with multitude parallel heating sections for radiant heating panels;
Fig. 7 is scheme of a heating element, consisting of two groups of the heating sections with three bus-bars for parallel or serial connections;
Fig. 8 is schematic view of pultruded plastics radiant heating panel;
Fig.9 is schematic view of pultruded plastics radiant heating panel with two groups of the heating sections for parallel or serial connections;
Fig.10 is schematic view of pultruded plastics profile with two incorporated heating inserts;
Fig.11 is schematic view of a flange for one pultruded plastics profile with two incorporated heating inserts;
Fig.12 is schematic view of a flange for assembly of rectangular shape, consisting of two pultruded plastics profiles;
Fig.13 is schematic view of an assembly of triangular shape, consisting of two pultruded plastics profiles;
Fig.14 is schematic view of a flange for assembly of triangular shape, consisting of two pultruded plastics profiles;
Fig.15 is schematic view of a flange for assembly, consisting of several pultruded plastics profiles;
Fig.16 is schematic view of a flange for assembly, consisting of several otherwise directional pultruded plastics profiles;
Fig.17 is schematic view of a block, containing two joined longitudinally
assemblies, consisting of two pultruded plastics profiles;
Fig.18 is schematic view of an angle block, consisting of two assemblies, consisting of two pultruded plastics profiles;
Fig.19 is schematic view of a block, consisting of two assemblies, one on other;
Fig.20 is schematic view of an assembly, consisting of multitude single-line pultruded plastics profiles.
Fig.21 is schematic view of a machine for manufacturing of heating plastics profiles.
DETAILED DESCRIPTION OF THE INVENTION
Fig.l illustrates a pultruded plastics profile 1 with incorporated heating insert. Conditionally upper part of the profile is not shown. The insert consists of the substrate 2 made of fiberglass mesh or mat. A heating ribbon 3 from metal foil is disposed on the substrate. The heating ribbon is joined with bus-bars 4 in places 5. End of the heating element may be made from wires 6, which have high temperature insulation with operating temperature not less than 200°C. Such insulation does not destroy in the pultrusion die. Besides, this insulation has no adhesion with matrix of profile. For example, polytetrafluoroethylene insulation may be used. These wires connect with bus-bars in places 7. The profile is cut in place 8 about ends of heating insert. The wires turn up such, that they may be easily extracted from profile after cutting. Straighten wires 6 is shown on Fig. 2.
In other design the ends of the heating elements are made as bus-bars. In this case the bus-bars may be extracted from profile by milling tools. Wires are connected after cutting.
Fig.l and Fig.2 show the heating element, created on base of metal foil. The foil is made of the alloy with high strength, high plasticity and high electrical resistance. Thickness of the foil is chosen starting with 10 microns. This thickness provides high surface resistance of the heating material and allows to create heaters in large range of dimensions: from 0.02 m2 for voltage 230V to tens square meters. Specific power of heaters also may be chosen in large range: from 20 W/m2 to 1200 W/ m2. Upper limit is
determined by operating temperature of used polymer for matrix.
Fig.3 shows a heating element, made on base of carbon rovings 12. Carbon roving is excellent reinforcing material, used equally with fiberglass material. Carbon roving is characterized by high impregnation ability, which provides high quality of composite material. This fact provides absence of air cavities inside plastics profile and prevents its exfoliation. But above-mentioned high impregnation ability embarrasses to extract these rovings from ready profile for electrical connection. Therefore, part of rovings about cutting zones 8 must be covered by polymer film 13, which have operating temperature not less than 200°C. Such film does not destroy in the pultrusion die. Besides, this film has no adhesion with matrix of profile. For example, polytetrafluoroethylene film may be used. After cutting of the profile, rovings are easily extracted from profile composite and connected in electrical scheme. For relief of roving incorporation in plastics profile during pultrusion process, the rovings may be interlaced with an additional net with large holes (this net does not shown in the drawings).
Fig.4 illustrates the heating device, where the heating element is made from carbon fabric 14. Carbon fabric also is reinforcing material, which is characterized by high impregnation ability. In zone of ends of the heating element the fabric is covered by film 13, which have no adhesion with resin (matrix) in pultrusion process and which has a melting temperature not less than 200°C. The carbon fabric contains also woven or stitched electro-conductive filament-threads 15 on ends of the heating element, which serve as electrical terminals.
Ready heating device comprises, besides the heating profile, flanges on ends of the profiles. These flanges are intended for sealing of profile cut edges, mechanical fastening to walls and electrical connections between inserts and power source. Fig. 2 illustrates one of possible designs of the heating device. In accordance with this design, the flange 9 has slot 10, which has size and form, coinciding with transversal cross section of the heating profile 1. Ends of the profile are fit into the slot 10. The wires 6 pass the flange 9 through openings for the wires. The profile and wires, fitted in slot, are sealed by polymer, providing waterproofness of the device. Wires 6 are electrical terminals of the heating element. They are connected with a connector 11, disposed on
other side of the flange 9.
Fig. 5 and Fig. 6 illustrate different patterns of the inserts. The insert, which consists of some separate heating elements, is shown in Fig. 1. In Fig. 5 continuous insert 16 with great number of heating elements contains bus-bars 17, and heating ribbon 18. The bus-bars are disposed along of the insert. The heating ribbon is also disposed along of the insert. Such disposition is convenient for narrow profiles. The resistor ribbon forms multitude of heating sections 19. Each of the heating sections is connected with said bus-bars in parallel, forming continuous flexible heating strip, which may be cut after each section in dependence on required electrical power and length, h Fig. 6 the heating ribbon 18 is disposed perpendicularly to bus-bars 17. Such disposition is convenient for wide profiles and panels. In such structures the bus-bars 17 can form two pairs of terminals 20 from two sides of the heating panel or profile for connections of several heating devices one to other and with power supply.
Fig. 7 shows wide heating panel. The insert 16 may contain two rows of the heating elements. Each row contains pair of bus-bars 17 and the heating sections 19, connected to bus-bars in parallel. The bus-bars of the rows form three terminals 20 of the heating panel for connections of the groups in parallel or serially.
Fig. 8 illustrates the heating panel 21 with heating insert 22, made in accordance with Fig. 6. The insert has two pairs of terminals 20 for connection with other panels and with power supply. Fig. 9 shows the heating panel 24 with insert 22, made in accordance with Fig. 7. The panel 24 contains three terminals 20 for parallel and serial connection of above mentioned groups.
Fig. 10 shows the heating pultruded profile 30, which has a compound form. In this structure two inserts 31 are incorporated into different sides of the profile. Inserts 31 are incorporated into profile 30 such, that beginning position and ending position of each of incorporated inserts coincide on a length of said profile. Fig. 11 illustrates design of the flange 32 for described profile 30. The profile is fitted in a slot 33. Form of the slot 33 corresponds to the form of the profile 30. The openings 34 serve for passing of insert terminals. The flange 32 has opening 35 to fasten to walls.
Fig. 12 illustrates a flange for a structure of a rectangular shape, which contains two pultruded profiles with heating inserts. Such structure forms an assembly, in which
the profiles are introduced into one flange 36 on every side. The flange contains two slots 37, 38, having dimensions and form, coinciding with transversal cross section of the profiles. Every profile is introduced into its slot. Disposition of profiles in the assembly anticipates two spaces 39 between profiles for improved air circulation.
Fig. 13 shows an example of an assembly 40 of triangular shape, containing two plastics profiles 41, jointed by the flanges 42. Air space 43 is disposed between the profiles 41. Fig. 14 shows one of variants of the flanges 42 for a triangular heating device. These flanges 42 have slots 44. Openings 45 in the slots 44 are intended for passing of wires-terminals of heating insert. This heating device is intended for standing on floor.
Fig.15 and Fig.16 show other variants of profiles disposition in assemblies, which includes several profiles. In these cases every flange 46 has slots 47, disposed in different directions. Quantity of slots is equal to the quantity of profiles.
Described assemblies may be joined in a block by mechanical joints, disposed on the flanges. Fig.l 7 illustrates a block 50, consisting of two joined longitudinally assemblies 51, which in one's turn consists of two profiles 52. Mechanical joints 53, disposed on the flanges 54, connect the assemblies. For electrical connection mechanical joints 53 contain holes for electrical cables (the ho2121 are not shown on the drawings).
Fig.18 shows an angle block 55 for installation in a corner of a room. The block consists of two assemblies 51, which in one's turn consists of two profiles 52. The assemblies 51 are connected in the block 55 by a joint 56.
The block 57, shown in Fig.19, consists of two assemblies 58, mechanically connected by flanges 59.
Fig. 20 shows an example of the heating device 60 on base of cut single-line profiles 61. The parts 61 are joined between them by one flange 62 on each side. Each of these parts has electrical terminals on two its sides.
Fig. 21 illustrates the pultrusion process for manufacturing of heating plastics profiles. The heating insert 70 is incorporated into a die 71 of pultrusion machine between of reinforced fiberglass 72 and glass mat 73. Fiberglass 72 and glass mat 73 are arranged on every side of insert evenly.
The continuous flexible heating insert, consisting of plurality heating elements, coils on one of bobbin 74. During the pultrusion process the heating insert is pulled through a bath 75 with liquid resin for impregnating together with other reinforcing materials. The insert, impregnated by liquid resin, feeds in a slot 76 of additional infeed plate 77 before pultrusion machine. An infeed 78 is designed for pre-positioning of the impregnated insert between layers of reinforcing glass mat and roving. The infeed 78 has, besides usual slots for reinforcing materials 79, the additional slot 80 for the heating insert 70. The flexible heating insert together with reinforcing materials arrive at a die of pultrusion machine, forming the shape of a profile.
After pultrusion process the rigid continuous profile 81 is cut in places between heating elements of the heating insert. These cut heating profiles are mounted in finished heating devices.
Multi- sided profiles with several heating sides are formed in accordance with the same method, but in this case each heating side is provided by one heating insert. Each of the inserts is impregnated by liquid resin in bath together with other reinforcing materials and is pulled through its slot on the additional infeed plates. Flexible heating inserts synchronously feed together with reinforcing materials to a die of pultrusion machine, such that beginnings and ends of each inserts coincide, and each flexible heating insert is incorporated into one of sides of said profile.
Continuous rigid profile, received after pultrusion process, is cut, forming profiled heating units. This unit is mounted in a heating device by introducing of the unit into slots in the boxes. The unit and the box are glued together on its ends.
The invention has been described in an illustrative manner, and it is to be understood that the terminology, which has been used, is intended to be in the nature of words of description rather than of limitation. Clearly, many modifications and variations of the present invention are possible in light of the above teachings. For example, length and width of the flexible resistor ribbon in single- line heating devices are chosen in accordance with equation (1), and this fact provides high reliability and life span of the heating device. Accordingly, it is to be understood that the invention can practiced otherwise than specifically described.