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GB2278262A - Thermally insulated heating device - Google Patents

Thermally insulated heating device Download PDF

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Publication number
GB2278262A
GB2278262A GB9319050A GB9319050A GB2278262A GB 2278262 A GB2278262 A GB 2278262A GB 9319050 A GB9319050 A GB 9319050A GB 9319050 A GB9319050 A GB 9319050A GB 2278262 A GB2278262 A GB 2278262A
Authority
GB
United Kingdom
Prior art keywords
electrical heating
heating device
heating element
thermally
electrical
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB9319050A
Other versions
GB9319050D0 (en
Inventor
David Johannes Scheeres
John Ray Pendergraft
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
EXOTHERM PROD Ltd
Original Assignee
EXOTHERM PROD Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by EXOTHERM PROD Ltd filed Critical EXOTHERM PROD Ltd
Publication of GB9319050D0 publication Critical patent/GB9319050D0/en
Publication of GB2278262A publication Critical patent/GB2278262A/en
Withdrawn legal-status Critical Current

Links

Classifications

    • HELECTRICITY
    • H05ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05BELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B3/00Ohmic-resistance heating
    • H05B3/40Heating elements having the shape of rods or tubes
    • H05B3/54Heating elements having the shape of rods or tubes flexible
    • H05B3/58Heating hoses; Heating collars
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25Component parts, details or accessories; Auxiliary operations
    • B29C48/78Thermal treatment of the extrusion moulding material or of preformed parts or layers, e.g. by heating or cooling
    • B29C48/80Thermal treatment of the extrusion moulding material or of preformed parts or layers, e.g. by heating or cooling at the plasticising zone, e.g. by heating cylinders
    • B29C48/83Heating or cooling the cylinders
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25Component parts, details or accessories; Auxiliary operations
    • B29C48/78Thermal treatment of the extrusion moulding material or of preformed parts or layers, e.g. by heating or cooling
    • B29C48/80Thermal treatment of the extrusion moulding material or of preformed parts or layers, e.g. by heating or cooling at the plasticising zone, e.g. by heating cylinders
    • B29C48/83Heating or cooling the cylinders
    • B29C48/832Heating
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/03Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion

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  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Injection Moulding Of Plastics Or The Like (AREA)
  • Resistance Heating (AREA)

Abstract

An electrical heating device, which may be flat (see Fig.5) or a wraparound device for the feed barrel of a plastics injection molding machine, comprises an electrical heating element 10, a layer of thermally insulating material 14 disposed against one side of the electrical heating element 10, and a cover 12, 16 enclosing the electrical heating element and the thermally insulating layer 14, the cover including a sheet of heat-resistant material 12 disposed over the opposite side of the electrical heating element 10. The device may also include a current sensor 52 and a light emitter 54. <IMAGE>

Description

THERMALLY INSULATED HEATING DEVICE BACKGROUND OF THE INVENTION 1) Field of the Invention The present invention relates to a thermally insulated heating device, particularly but not solely in wrap-around form for application around a feed barrel of a plastics injection molding machine, for example.
2) Description of the Prior Art Plastics injection moulding machines typically include a feed barrel housing a rotating auger, for feeding pellets of plastics material into the machine: a plurality of electrical heater devices are wrapped around the barrel, and apply heat to melt the plastics pellets as they are fed towards the machine. Typically wrap-around heaters of this type have a metal outer casing and no thermal insulation: accordingly, a substantial amount of heat escapes radially outwards and is wasted; furthermore, the outer surface of the wrap around heater becomes very hot (sometimes 2500C) and therefore represents a danger to operating personnel.
SUMMARY OF THE PRESENT INVENTION In accordance with the present invention, there is provided an electrical heating device comprising an electrical heating element having first and second opposite surfaces, a layer of thermally insulating material disposed over said first surface of the electrical heating element, and a cover enclosing said electrical heating element and thermally insulating layer, said cover including a sheet of heatresistant material disposed over said second surface of the electrical heating element.
Preferably the heating device is of wrap-around form exhibiting a degree of flexibility so that it can be opened sufficiently to slip over e.g. the feed barrel of a plastics injection molding machine, then closed up to embrace the feed barrel. The heating device may similarly be used on a plastics extrusion machine or on pipes.
Preferably the cover of the heating device includes a sheet of plastics-impregnated fabric disposed over the layer of thermally insulating material. This forms an exterior surface of the heating device, in use thereof: the surface is therefore impervious to moisture and resistant to the adherence of molten plastics. Preferably this sheet comprises a woven fibreglass fabric having its outer surface impregnated with PTFE. Preferably the heat-resistant sheet material is capable of withstanding a continuous temperature of 2500C or more.
Preferably the heat-resistant sheet material comprises a fabric woven from mineral or ceramic fibres.
Preferably the thermally-insulating material is arranged that the exterior surface of the heating device does not exceed a temperature of 800C whilst the opposite surface of the device runs at 2500C. Preferably the thermally insulating material comprises compressed mineral, ceramic or glass fibres. Preferably the thermally insulating layer has a thickness of between 20 and 30 mm, most preferably 25 mm.
Preferably the heating element comprises a planar array of electrically insulating bricks through which electrical resistance heating wires run. Preferably these bricks inters it with each other in a manner enabling relative flexing, so that the heating element exhibits a degree of flexibility.
The heating device of this invention provides substantial environmental benefits, firstly in substantial energy saving and secondly in avoiding the workroom becoming overheated. Furthermore, the processing temperature of the apparatus, to which the heating device is applied, is relatively immune to changes in ambient temperature.
Moreover, preferably the heating device of this invention includes a current sensor having a light emitter, arranged to illuminate in response to current passing through the electrical heating element. Thus, operating personnel can easily see if the heating device is working correctly or not, from whether the light emitter is illuminated or not: if the heating device is switched off or if there is a fault with its electrical heating element, then the light emitter will be off.
The current sensor is positioned where it is thermally insulated by the layer of insulating material of the heating device: it has not been possible to incorporate such a sensor in the prior art heating devices mentioned above, because those heating devices have lacked any thermal insulation and the plastics housing of the current sensor would have melted.
BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the present invention will now be described by way of examples only and with reference to the accompanying drawings, in which: FIGURE 1 is a schematic elevation, partly in section, showing the feed barrel of a plastics injection molding machine fitted with a number of wrap-around heating devices in accordance with the present invention; FIGURE 2 is an end view, partly in section, of a wraparound heating device in accordance with the present invention; FIGURE 3 is a perspective view of the wrap-around heating device of Figure 2; FIGURE 4 is a view of a heating element of the heating device of Figures 2 and 3; and FIGURE 5 is a perspective view, partly in section, of a heating device in accordance with this invention, of a flat form.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Referring to Figure 1, there is shown, in diagrammatic form, a feed barrel 1 of a plastics injection molding machine 2. The feed barrel 1 has a hopper 3 at its outer end, into which plastics pellets are introduced. A rotating auger 4 is housed within the feed barrel 1, to feed the plastics pellets along the barrel 1 and into the machine 2. A plurality of heating devices 5 are wrapped around the feed barrel 1, to apply heat and melt the plastics pellets as they are fed along the barrel.
Figures 2 and 3 show the construction of the heating devices 5. Thus, each heating device 5 comprises a number of successive layers of different materials, together formed into a generally tubular shape but longitudinally split and sufficiently flexible that it can be opened up, slipped around the feed barrel 1 and then closed up again. More particularly, the heating device comprises a heating element 10, an inner covering 12 of flexible, heat-resistant material, a layer 14 of thermally insulating material outwardly of the heating element 10, and an outer covering 16 of flexible material. The inner and outer coverings 12,16 are stitched together along the longitudinal free edges of the heating device: the device further comprises two end coverings 18 (one shown) of the same material as the inner covering 12 and stitched to the inner and outer coverings 12,16 respectively. It will accordingly be noted that the heating element 10 and thermally insulating layer 14 are enclosed within a cover consisting of the inner and outer coverings 12,16 and the two end coverings e.g. 18.
The device further comprises a flap 22 formed of the same material as, and stitched to, the outer covering 16. The flap 22 is positioned so that it projects at 23 beyond one end of the device and also projects at 24 beyond one of the longitudinal edges of the device. In use when the device is wrapped around e.g. the feed barrel 1 of the plastics injection molding machine, the projecting portion at 24 of the flap 22 overlies the other longitudinal edge of the device and a velcro
fastener 25,26 (preferably of stainless steel) is engaged to fasten the device in position: furthermore, the projecting portion at 23 of the flap 22 overlies the adjacent heating device 5 on the feed barrel, as shown in Figure 1.
As shown in Figure 4, the heating element 10 comprises a plurality of electrically insulating ceramic bricks 30 fitted together, and having electrical resistance heating wires, e.g.
40 running through them. Each ceramic brick 30 is of elongate shape, having opposite edges 31,32 which are respectively convex and concave curved, and holes 33 for the wires 40 extend through the brick between its curved surfaces. The ceramic bricks are arranged in successive rows, the bricks of one row having their convex-curved edges engaged with the concavecurved edges of the bricks of the adjacent row: accordingly, the adjacent rows of ceramic bricks are able to flex to a limited degree relative to each other, imparting a degree of flexibility to the heating element to enable the heating device to be opened up, slipped over the feed barrel 1 and then closed up again, as described previously. It will also be noted that the ceramic bricks of each row are staggered relative to the bricks of the adjacent rows, lengthwise of those rows. At a central portion of the heating element 10, the heating wires extend outwardly to a terminal box 50 (Figure 2) mounted to the outer surface of the heating device 5.
In use, when electrical current is passed through the wires 40 via terminals 51 of the terminal box 50, the heating element generates substantial heat which passes directly to the feed barrel 1, around which the heating device 5 is wrapped, via the inner covering 12. The material of the inner covering 12 is heat resistant, able to withstand a continuous temperature of 5000C or more although typically it will be run at about 2500C. One suitable material comprises a fabric woven from mineral or ceramic fibres, the fabric being marketed by
JM under tne trade name NextelA Tne thermally insulating layer 14 prevents substantial amounts of heat passing to the outer surface of the device 5, such that the latter surface remains at less than 800C and is therefore not excessively dangerous to touch, whilst the inner surface of the device is at 2500C.
Preferably the material of the thermally insulating layer 14 comprises compressed mineral, ceramic or glass fibres, for example a material marketed by Carborundum Ltd. under the trade name Durablanket: the thermally insulating layer 14 has a thickness of typically 25mm. The material of the outer covering comprises a woven fibreglass fabric having its outer surface impregnated with PTFE: accordingly, if any plastics from the molding machine should spill on this surface, it will not adhere permanently but can be wiped off.
Although the heating device of Figures 2 to 4 has been described for use on the feed barrel of a plastics injection molding machine, it may be used on other apparatus requiring heating or maintaining hot, e.g. plastics extrusion machines or pipes.
As shown in Figure 5, the heating device may be in a flat shape. In this example, the device comprises a heating element 60 of the same construction as shown in Figure 4, but laid flat, and a flat layer 64 of thermally insulating material laid over the heating element. The heating element 60 and thermally insulating layer 64 are enclosed in a cover comprising a sheet of heat resistant material 62 adjacent the heating element and a sheet of PTFE impregnated material 66 adjacent the thermally insulating layer 64. The heat resistant sheet 62 extends over two opposite edges of the heating element 60 and thermally insulating layer 64 and its corresponding edges are stitched to the outer sheet 66. End pieces e.g. 68, also of the heat resistant material, cover the other opposite edges of the heating element and thermally insulating layer.
The electrical resistance heating wires of the heating element are brought out to a terminal box 70.
An additional feature of the heating devices of Figures 2 to 4 and 5 is the provision of a current sensor having a light emitter, to indicate whether the electrical heating element is functioning. This current sensor is shown at 52 in Figure 2 and its light emitter (a light emitting diode) at 54.
The current sensor may be a CR-45 sensor from CR Magnetics Inc of Fenton MO, USA. The current sensor comprises a ring-shaped plastics housing as shown, and one of the electrical wires from the heating element passes through the centre of this ring to a respective terminal 51 of the terminal box 50: the electrical wire is inductively coupled to the current sensor and so long as current is passing through this wire, the light emitter 54 of the sensor is illuminated. The current sensor may be positioned within the terminal box 50, as shown in Figure 2, with the light emitter projecting from or visible at a wall of the terminal box. Alternatively, as shown in Figure 5, the current sensor may be mounted under the outer covering of the heating device, with the light emitter 54 projecting therefrom. In any event, the current sensor is on the lowertemperature side of the thermally insulating layer 14 or 64 of the heating device, and therefore not subjected to excessive heat.
The current sensor enables operating personnel to see readily whether the heating device is functioning correctly or not, depending whether the light emitter is illuminated or not.
The current sensor therefore provides a very quick indication if any heating device is faulty.

Claims (12)

What is claimed is:
1) An electrical heating device, comprising an electrical heating element having first and second opposite surfaces, a layer of thermally insulating material disposed over said first surface of the electrical heating element, and a cover enclosing said electrical heating element and thermally insulating layer, said cover including a sheet of heatresistant material disposed over said second surface of the electrical heating element.
2) An electrical heating device as claimed in claim 1, comprising a wrap-around heating device of generally tubular shape with a longitudinal split.
3) An electrical heating device as claimed in claim 1, in which said cover comprises a sheet of plastics-impregnated fabric disposed over said layer of thermally insulating material.
4) An electrical heating device as claimed in claim 3, in which said plastics-impregnated fabric comprises a woven fibreglass fabric impregnated with PTFE.
5) An electrical heating device as claimed in claim 1, in which said heat-resistant sheet material is capable of withstanding a continuous temperature of at least 5000C.
6) An electrical heating device as claimed in claim 1, in which said heat-resistant sheet material comprises a fabric woven from mineral or ceramic fibres.
7) An electrical heating device as claimed in claim 1, in which the thermally-insulating material is such that in use the exterior surface of the device does not exceed a temperature of 800C whilst the opposite surface of the device runs at 2500C.
8) An electrical heating device as claimed in claim 1, in which the thermally-insulating material comprises compressed mineral, ceramic or glass fibres.
9) An electrical heating device as claimed in claim 1, in which the thermally-insulating layer has a thickness in the range of 20 to 30 mm.
10) An electrical heating device as claimed in claim 1, in which the heating element comprises a planar array of electrically insulating bricks and a plurality of electrical resistance heating wires running through said bricks.
11) An electrical heating device as claimed in claim 10, in which said bricks inters it with each other in a manner enabling relative flexing.
12) An electrical device as claimed in claim 1, further comprising a current sensor means having a light emitter, coupled to said electrical heating element and arranged to illuminate in response to current passing through said electrical heating element, said current sensor being thermally insulated from said electrical heating element by said thermally insulating layer.
GB9319050A 1993-05-17 1993-09-15 Thermally insulated heating device Withdrawn GB2278262A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US6245393A 1993-05-17 1993-05-17

Publications (2)

Publication Number Publication Date
GB9319050D0 GB9319050D0 (en) 1993-11-03
GB2278262A true GB2278262A (en) 1994-11-23

Family

ID=22042589

Family Applications (1)

Application Number Title Priority Date Filing Date
GB9319050A Withdrawn GB2278262A (en) 1993-05-17 1993-09-15 Thermally insulated heating device

Country Status (1)

Country Link
GB (1) GB2278262A (en)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0824299A3 (en) * 1996-08-12 1998-07-08 Nichias Corporation Heating mantle and method for fabricating the same
GB2302490B (en) * 1995-06-21 2000-01-19 Exotherm Prod Ltd Thermally insulated heating device
EP0781805B1 (en) * 1995-12-29 2002-05-29 General Electric Company Stabilized thermoplastic polymer composition
US6486445B1 (en) * 1999-11-04 2002-11-26 Gordon M. Pendergraft Vacuum cast ceramic fiber insulated band having heating and cooling elements
US6903308B2 (en) 2000-11-01 2005-06-07 Gordon M. Pendergraft Vacuum cast ceramic fiber insulated band having heating and cooling elements
WO2010056281A1 (en) * 2008-10-30 2010-05-20 Xaloy, Inc. Plasticating barrel with integrated exterior heater layer
ITTO20090521A1 (en) * 2009-07-13 2011-01-14 Roberto Domenico Ravaglia HEATING AND COOLING DEVICE FOR AN EXTRUDER CYLINDER
WO2015031720A1 (en) * 2013-08-29 2015-03-05 Sabic Global Technologies B.V. Thermally insulated melt processor and process for melt processing with same
WO2017100937A1 (en) * 2015-12-17 2017-06-22 Sasipa Inc. Heat-insulating shroud for facilitating temperature control of a heated device or product

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB311682A (en) * 1928-02-14 1929-05-14 Sterne Morse Improvements in or relating to electric heating units
GB371536A (en) * 1930-03-10 1932-04-28 Etienne Challet Resistance elements for electric heating bodies and processes of manufacture thereof
GB421270A (en) * 1933-08-02 1934-12-18 Eustace Macarthur Young Improvements in or relating to electrical heat-radiating panels
GB996908A (en) * 1964-04-15 1965-06-30 Chemcell 1963 Ltd Improvements relating to heat stretching thermo-plastic yarns and filaments
US4310745A (en) * 1979-04-20 1982-01-12 Huebner Bros. Of Canada Ltd. Heating assemblies

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB311682A (en) * 1928-02-14 1929-05-14 Sterne Morse Improvements in or relating to electric heating units
GB371536A (en) * 1930-03-10 1932-04-28 Etienne Challet Resistance elements for electric heating bodies and processes of manufacture thereof
GB421270A (en) * 1933-08-02 1934-12-18 Eustace Macarthur Young Improvements in or relating to electrical heat-radiating panels
GB996908A (en) * 1964-04-15 1965-06-30 Chemcell 1963 Ltd Improvements relating to heat stretching thermo-plastic yarns and filaments
US4310745A (en) * 1979-04-20 1982-01-12 Huebner Bros. Of Canada Ltd. Heating assemblies

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2302490B (en) * 1995-06-21 2000-01-19 Exotherm Prod Ltd Thermally insulated heating device
EP0781805B1 (en) * 1995-12-29 2002-05-29 General Electric Company Stabilized thermoplastic polymer composition
EP0824299A3 (en) * 1996-08-12 1998-07-08 Nichias Corporation Heating mantle and method for fabricating the same
US5883363A (en) * 1996-08-12 1999-03-16 Nichias Corporation Heating mantle and method for fabricating the same
US6486445B1 (en) * 1999-11-04 2002-11-26 Gordon M. Pendergraft Vacuum cast ceramic fiber insulated band having heating and cooling elements
US6903308B2 (en) 2000-11-01 2005-06-07 Gordon M. Pendergraft Vacuum cast ceramic fiber insulated band having heating and cooling elements
WO2010056281A1 (en) * 2008-10-30 2010-05-20 Xaloy, Inc. Plasticating barrel with integrated exterior heater layer
US8247747B2 (en) 2008-10-30 2012-08-21 Xaloy, Inc. Plasticating barrel with integrated exterior heater layer
ITTO20090521A1 (en) * 2009-07-13 2011-01-14 Roberto Domenico Ravaglia HEATING AND COOLING DEVICE FOR AN EXTRUDER CYLINDER
WO2015031720A1 (en) * 2013-08-29 2015-03-05 Sabic Global Technologies B.V. Thermally insulated melt processor and process for melt processing with same
KR20160051755A (en) * 2013-08-29 2016-05-11 사빅 글로벌 테크놀러지스 비.브이. Thermally insulated melt processor and process for melt processing with same
KR102128512B1 (en) 2013-08-29 2020-07-01 사빅 글로벌 테크놀러지스 비.브이. Thermally insulated melt processor and process for melt processing with same
WO2017100937A1 (en) * 2015-12-17 2017-06-22 Sasipa Inc. Heat-insulating shroud for facilitating temperature control of a heated device or product
US10786938B2 (en) 2015-12-17 2020-09-29 Sasipa Inc. Heat-insulating shroud for facilitating temperature control of a heated device or product

Also Published As

Publication number Publication date
GB9319050D0 (en) 1993-11-03

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