AU1357500A - Ribbon/strip heater and method of manufacture - Google Patents

Description

Regulation 3.2

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

V..

A 4 9 Name of Applicant: Actual Inventors: Address for Service: Thermofloor Products Ltd David Ashton David Reid Wilkie Kenneth Michael Richards MADDERNS, 1st Floor, 64 Hindmarsh Square, Adelaide, South Australia, Australia Invention title: "RIBBON/STRIP HEATER AND METHOD OF MANUFACTURE" Details of Associated Convention Application No(s): Based on New Zealand Trade Mark Appln No NZ333952 filed on 28 th January 1999 The following statement is a full description of this invention, including the best method of performing it known to us.

2 This invention relates to a ribbon/strip heater of the type suitable for use in under-floor heating, heater pads or similar applications.

Under-floor heating is a well-known method of heating an air space in a room. This type of heating has many advantages in that the heat source can be felt but not seen and it provides a gentle, even, low intensity heat over the whole floor area. In addition, this type of heating does not create any disruption to the use of the total living space. Conventional methods of providing under-floor heating include electric resistance wiring of concrete floor slabs and hot Swater or air ducts in concrete floor slabs.

Known floor heating methods usually involve the heating system being installed at the time of *o construction of the floor. This is especially so when the floor is constructed from concrete.

Accordingly, known under-floor heating systems usually cannot be fitted after a floor has been constructed without major and costly alterations to the flooring. Problems can arise with electrical under-floor heating of concrete slabs, especially if it is not properly installed, as "incorrect installation can result in burnt or broken wiring. Since the installation is permanent, fault finding and fixing is a major, if not impossible, task.

Electric ribbon/strip heaters may also be utilised for applications such as under-floor heating.

The advantage of this system is that the strip heater(s) are placed onto the floor after construction is completed and the system is thus equally useful for both new and retrofitted applications.

The strip heaters are laid onto a floor according to a predetermined pattern that matches the requisite length of the strip to the room size. (The length of the strip determines the heat output.) Accordingly, once the size of the room or area to be heated is known, a laying pattern is determined so that the strip heater may start and finish at a position convenient for connection to a power supply.

The strip heater element is manufactured in a continuous length and does not include terminals at each end of the length. It is necessary to join "cold" non-heat generating) terminal strips to each end of the heater element before it can be connected to the power supply. To date, it has been found that factory made joints, either by soldering or crimping, have been too bulky to permit a completed heater, including "cold" terminal strips to be wound onto a carrier for supply to an installation site. Accordingly, it has been necessary to Smake these joins in situ which is very unsatisfactory because it is a cumbersome process that oooo• must be performed by a registered electrician or skilled site technician to comply with current electrical regulations.

The aim of this invention is to provide an improved ribbon/strip heater that may be S• completely fabricated at a factory location and dispatched to an installation site on a carrier in a form that complies with current electrical regulations, for installation by an installer with o.oo a. standard electrical knowledge, e.g. a registered electrician using standard non-specialised techniques. This avoids the need for the factory to provide a skilled on-site technician and, further, the registered electricians need only concern themselves with connecting the "cold" terminals to the electrical supply in accordance with standard techniques used in the industry.

According to a first aspect of the invention, there is provided a method of manufacturing a ribbon/strip heater comprising the steps of taking a length of ribbon/strip resistance element; taking a length of "cold" (as herein defined) strip terminal; longitudinally overlapping the first corresponding end portions of the ribbon/strip resistance element and "cold" strip terminal; soldering said overlapping end portions of the ribbon/strip resistance and "cold" strip terminal elements together for at least a portion of their overlapped end portions to form a permanent connection; and repeating steps and for the second corresponding end portions of the ribbon/strip resistance and "cold" strip terminal elements.

In a preferred embodiment, the following additional steps are performed:adhesively bonding together the remainder of the overlapped portions of the ribbon/strip resistance element and "cold" strip terminal; and ooooo sandwiching the ribbon/strip resistance element, overlap connections and a portion S of the "cold" strip terminals between a first heat radiator/electrical discharge earthing strip and a second adhesive-backed insulating strip and bonding these together to form a composite heater strip; and electrically connecting a conducting earthing strip terminal to one end portion of said heat radiator/electrical discharge earthing strip.

In a preferred embodiment, the ribbon/strip resistance element and the "cold" terminal element are the same width. The ribbon/strip resistance element is soldered to the "cold" terminal element at its terminal end portion.

According to a second aspect of the invention, there is provided a composite strip heater comprising a length of ribbon/strip resistance element connected at each terminal end portion thereof to a "cold" strip terminal element sandwiched between a heat radiator/electrical discharge earthing strip and a second adhesive-backed insulating strip in accordance with the method of the preceding paragraphs.

In further describing the invention by way of a preferred embodiment, reference will be made to the accompanying drawings in which: Figure 1 is a perspective view of the components comprising a connection between the ribbon/strip resistance element and "cold" terminal; Figure 2 is a view of the components in assembled form; and Figure 3 is a perspective view of a partially shielded heater element complete with terminal connection and earthing strip ready for installation.

oooa Referring firstly to Figure 3 of the drawings, a completed composite ribbon/strip element i heater 10, complete with terminal connections, is shown ready for installation in situ and subsequent connection to an electrical supply.

The components of the composite strip heater element comprise a backing layer of polyester ))ooi film strip 11 double-sided with acrylic adhesive and approximately 25 mm in width and a thickness somewhat less than 1 mm. A release paper 12 is provided on the adhesive face that is, in use, intended to be bonded to the floor surface.

The electric resistance ribbon/strip element 13 is shown complete with connection 14 to strip terminal 15 overlaid and bonded onto the polyester backing layer 11.

An electrical shield or screen comprising a thin sheet of aluminium 16 is bonded to the polyester backing layer 11 sandwiching the element 13 and electrical connection 14 therebetween. An earth strip terminal (not shown) is electrically coupled to the electrical screen 16 at the end portion of the composite strip 10 adjacent to the electrical connection 14.

The electrical screen 16 is bonded to the strip element 13 by double sided acrylic film 17.

The other end of the composite strip 10 similarly terminates in an electrical connection 14 bonding the terminal to the ribbon element 13.In the example shown, the terminal 15 at one end of the composite strip heater comprises a flat insulated terminal 15 which is intended to be coupled to the phase supply. The other end of the composite strip heater is similarly coupled to a terminal 15 that is connected to the neutral supply. The earth strip terminal is also insulated and coupled to the earth at the electrical socket. Further details regarding installation will be explained hereinafter.

Referring now to Figures 1 and 2 of the drawings, the electrical connection 14 between the element 13 and the strip terminal 15 will be explained in greater detail. It will be seen from the exploded view of Figure 1 that the element 13 and the strip terminal 15 are electrically o:ooo coupled to one another by a soldered portion 16. To this end, the element 13 and "cold" terminal 15 (which are expediently of identical width) are longitudinally overlapped for a short portion, i.e. approx. 50 mm. The soldered portion 16 is approx. 10 mm long. It is not possible to solder the entire length of the overlap as it would be insufficiently flexible to allow the heater strip 10 to be wound onto a storage spool. However, it is necessary to provide mechanical strength for the joint and this is achieved by gluing the remaining portion of the overlap. This is at best achieved by a short portion of double sided flexible adhesive tape 17 interposed between the overlapping strips.

Both the "cold" strip and the heater strip are pre-tinned 16a, 16b at the appropriate places to ensure a good solder joint between these two mating surfaces. Referring to Figure 2, it can be seen that the adhesive tape 17 projects slightly beyond the end of the "cold" terminal (17a) to provide additional strength. However, this is optional.

In the example shown, the strip terminal 15 comprises a length of annealed strip copper. The copper is preferably tinned which avoids any problems associated with the connection of dissimilar metals should the joint ever be exposed to moisture.

It will be appreciated that the resulting connection 14 is relatively thin, being in the order of 1 mm thick. This is an important aspect of the invention as it means that a completed strip heater may be wound onto a carrier, preferably in the form of a spool. The spool may have an internal diameter of approximately 200 mm and may be wound up to a diameter of approximately 600 mm in a typical installation. Prior art methods of achieving the electrical connections 14 negated the possibility of winding the completed heater onto a spool because of the bulky size of the connections.

As previously explained, the resultant composite heater element is suitable for winding onto a •oooo spool for delivery complete to an installation site, whilst also complying with stringent electrical requirements which relate to this type of product.

The heater element is intended to be bonded in a predetermined pattern onto a floor surface at t the site of installation. The desired heat output determines the length of the heater element and the laying pattern matches the length to the size of the room. It is desirable that both ends :°ogoo of the heater element are positioned adjacent convenient connection to an electrical supply.

To this end, it has been found, in use, that the terminal strip elements should be in the order of anything up to 5 m in length to enable the installer to trim to a length suitable for coupling to the electrical supply. In this regard, when the appropriate length has been determined, the insulation is stripped from the end of the terminal which is subsequently coupled to a known electrical connector which itself is suitable for coupling to the electrical supply. It is necessary that the whole installation be electrically coupled to a residual current device for an added degree of protection.

It will be appreciated that the above description is by way of example only. Further modifications may be made to the invention without departing from the scope thereof.

*o* *ooo o•

Claims (6)

1. A method of manufacturing a ribbon/strip heater comprising the steps of:- taking a length of ribbon/strip resistance element; taking a length of"cold" (as herein defined) strip terminal; longitudinally overlapping the first corresponding end portions of the ribbon/strip resistance element and "cold" strip terminal; soldering said overlapping end portions of the ribbon/strip resistance and "cold" strip terminal elements together for at least a portion of their overlapped end portions to form a permanent connection; and repeating steps and for the second corresponding end portions of the ribbon/strip resistance and "cold" strip terminal elements. ooooo: S"2. A method of manufacturing a ribbon/strip heater according to claim 1 wherein the following additional steps are performed:- adhesively bonding together the remainder of the overlapped portions of the ribbon/strip resistance element and "cold" strip terminal; and sandwiching the ribbon/strip resistance element, overlap connections and a portion of the "cold" strip terminals between a first heat radiator/electrical discharge earthing strip and a second adhesive-backed insulating strip and bonding these together to form a composite heater strip; and electrically connecting a conducting earthing strip terminal to one end portion of said heat radiator/electrical discharge earthing strip.

3. A method of manufacturing a ribbon/strip heater according to claim 1 or 2 wherein the ribbon/strip resistance element and the "cold" terminal element are the same width.

4. A method of manufacturing a ribbon/strip heater according to claim 1, 2 or 3 wherein the ribbon/strip resistance element is soldered to the "cold" terminal element at its terminal end portion. A method of manufacturing a ribbon/strip heater according to any one of the preceding claims wherein the ribbon/strip resistance element and heat radiator/electrical discharge earthing strip are made of aluminium.

6. A method of manufacturing a ribbon/strip heater according to any one of the preceding claims wherein the "cold" strip terminal is made of annealed strip copper.

7. A method of manufacturing a ribbon/strip heater according to any one of the preceding claims wherein said second adhesive-backed insulating strip is made of polyester.

8. A composite strip heater comprising a length of ribbon/strip resistance element connected at each terminal end portion thereof to a "cold" strip terminal element sandwiched between a first heat radiator/electrical discharge earthing strip and a second adhesive-backed insulating strip in accordance with the method of the preceding claims. DATED this 27th day of January, 2000. THERMOFLOOR PRODUCTS LTD By their Patent Attorneys MADDERNS MMij