NZ738378A - Towel Rail - Google Patents

Abstract

towel rail (1) including a body (3), and a heating element (11) passing through at least a portion of the body (3), wherein the heating element (11) has a variable resistance that changes as the ambient temperature changes, such that the heat output of the towel rail (1) is limited at a maximum. To be accompanied, when published, by Figure 2 of the drawings. To be accompanied, when published, by Figure 2 of the drawings.

Description

TOWEL RAIL The present invention relates to a towel rail. In particular, the present invention relates to an electric heated towel rail.

Electric heated towel rails have one or more bars with heating elements passing through them. When the power to the towel rail is turned on, current flows through the heating element, heating the bar. This is different to water heated towel rails, which are plumbed into a hot water system, such as a central heating system, and dual fuel towel rails, which operate on the same principle as an immersion heater. Electric towel rails are simple to manufacture and install, since they do not require plumbing or water tight seals, and can be operated separately from a hot water system.

It is desirable to limit the maximum surface temperature of an electric towel rail. If the towel rail gets too hot, users can be burnt if they touch or fall against it. This can be particularly problematic in situations where the users are young or vulnerable, such as care homes. A high surface temperature on the towel rail may also cause damage to towels, if left on the rail for long periods.

Typically, systems using electrical heating elements can limit the output temperature by either using a thermostatically controlled duty cycle or a fixed resistance heating element.

A thermostatically controlled duty cycle makes use of a temperature sensor. As the maximum or target temperature is reached, the heating element is cyclically switched on and off to control the temperature so that it stabilises. In the example of a towel rail the temperature sensor should be provided on a front face of the rail, and relatively centrally, so that it is in a position where the user is most likely to touch the rail. However, it can be difficult to install the temperature sensor in such a position, and the sensor would disturb the aesthetic appearance of the towel rail.

Therefore, electric towel rails typically use fixed resistance heating elements. In this case, the resistance of the heating element is a constant value, and thus the maximum output is limited. However, the maximum output is only limited in free air – when the rail is not covered. Towel rails are typically made from materials which have low heat losses, and so the maximum surface temperature of the towel rail increases when it is covered, as shown in Figure 1.

In this example, the towel rail is turned on at t0, and the temperature stabilises around 40°C. A towel is put on the towel rail at t1, and the temperature starts to increase, and quickly reaches temperatures between 60 and 70°C, risking damaging the towel.

Even when the towel is removed, the surface temperature does not immediately drop, and so the towel rail continues to pose a hazard to users as discussed above, and without removing the towel, the temperature will continue to increase.

According to first aspect of the invention, there is provided a towel rail including a body, and a heating element passing through at least a portion of the body, wherein the heating element has a variable resistance that changes as the ambient temperature changes, such that the heat output of the towel rail is limited at a maximum.

The heating element may include: a live conducting core; a return conducting core; and one or more linking elements arranged to connect the live conducting core and return conducting core to form a complete circuit, wherein the resistance of the one or more linking elements has a variable resistance that changes as the ambient temperature changes, such that the heat output of the towel rail is limited at a maximum.

The one or more linking elements may be provided along at least a portion of the length of the heating element.

The resistance of the conducting cores may be substantially independent of the ambient temperature.

The one or more linking elements may comprise a matrix of variable resistance conducting material, encasing the live conducting core and return conducting core, such that the live conducting core and return conducting core are in electrical contact with each other through the matrix only.

The variable resistance conducting material may comprise a material, including carbon as a constituent component.

The heating element may be provided with an insulation jacket covering the conducting cores and one or more linking elements.

The heating element may include a junction region for connecting to a power supply, wherein the one or more linking elements do not extend into the junction region.

In the junction region, each conducting core may be provided with an insulation jacket along at least a portion of the length of the conducting cores.

The body may include: two or more support bars arranged to extend, when installed, parallel to each other and to a wall on which the towel rail is mounted; and one or more joining sections, connecting the support bars. The heating element may pass through each of the support bars, and may pass between the support bars through a joining section. The linking elements are omitted in the section of heating element passing through the joining sections, such that the heating element is more flexible in these regions.

Alternatively, the body may include a single support bar arranged to extend, when installed, parallel to a wall on which the towel rail is mounted.. The body may include a mounting portion, extending perpendicular to the support bar at a first end of the body, for securing the towel rail to the wall. The mounting portion may be provided at a first end of the body. A second end of the body, opposite the first end, may be arranged to be spaced from the wall.

The resistance of the heating element may increase as the ambient temperature increases, such that, in use with a constant voltage supply, current reduces as ambient temperature increases.

The resistance of the heating element may be variable along the length of the heating element.

The towel rail may include two or more heating elements.

The heating element may be arranged to maintain a surface temperature of between 30 degrees Celsius and 40 degrees Celsius on the surface of the body, in free air.

The heating element may be arranged such that the surface temperature of the surface of the body increases by 10 degrees Celsius or less, in a region where the body is covered.

The body may be formed of metal.

It will be appreciated that features described in relation to a particular aspect of the invention can also be applied to other aspects of the invention.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 illustrates the surface temperature of a fixed resistance towel rail over time as it is turned on, and later covered by a towel; Figure 2 illustrates an example of a towel rail according to an example embodiment; Figure 3A illustrates a schematic view of the heating element used in the towel rail of Figure 2; Figure 3B illustrates a cut-through view of the heating element of Figure 3A in a first region; Figure 3C illustrates a cut-through view of the heating element of Figure 3A in a second region; and Figure 4 illustrates the surface temperature of the towel rail of Figure 2 over time as it is turned on, later covered by a towel, and then uncovered.

Figure 2 illustrates a perspective view of a portion of a towel rail 1. The towel rail 1 includes a body 3 in the form of a tubular bar, defined by a cylindrical wall 3a. The body 3 includes a first section 5 extending in a first direction, and a second section 7 extending perpendicular to the first section 5. It will be appreciated that the second section 7 can extend for any suitable length, although only a portion of the second section 7 is shown. The body can be one piece, bent to the desired shape, or separate pieces joined by welding, adhesive or any other suitable means.

In use, the towel rail 1 is installed so that the first section 5 (a mounting portion) extends away from the wall on which the towel rail 1 is mounted, and the second section 7 (a support bar) extends along the wall. Towels, or other items, can be hung over at least part of the support bar 7.

The body 3 of the towel rail 1 is hollow in construction, defining a through passage 9.

In Figure 2, a portion of the wall 3a on an upper surface is removed at A, to show the through passage 9. A heating element 11 is provided within the through passage 9, along the length of the body 3. The heating element 11 is connected to a power supply (not shown). When the power is turned on, current flows through the heating element 11, heating the body 3.

Any suitable power supply may be used, such as a mains power supply. In some examples, the voltage of the mains power supply is stepped down to a lower value for safety reasons. This may be by a transformer or other suitable means provided before the heating element. For example, the mains voltage may be 230V, and the voltage in the heating element 11 may be 12V.

The body 3 may be mounted to the wall in any suitable manner. For example, a stud or support (not shown) may be fixed to the wall. The support may have a spigot section projecting out from the wall. The support may be fixed over an existing wall covering (such as tiles) or underneath the wall covering, with only the spigot projecting out. In use, the mounting portion 5 is fitted over the stud or spigot, and secured to it, for example by screws provided through fitting holes 13.

A cable for connecting the heating element 11 to the power supply may be fed through the spigot, and connected to the heating element 11 through an end 15 of the body 3.

Alternatively, the heating element 11 may be fed through an opening (not shown) in the wall 3a, adjacent the end 15, and connected to the power supply.

In one example, only one end of the body 3 is fixed to the wall, and the other end is free, so that the bar is “L” shaped when viewed from above. The free end may be closed by a part of the towel rail wall 3a. In other examples, the body 3 may include a third section (not shown) parallel to the first section 5 and forming a second mounting portion, such that both ends of the body 3 may be secured to the wall, and the bar is “U” shaped when viewed from above.

Where the body 3 includes two ends for connecting the body 3 to the wall, the heating element 11 may be connected to the power supply at either of the ends, or both ends.

Typically the body 3 is formed of a material that can absorb and conduct heat from the heating element 11. For example, the body may be metals such as stainless steel.

In the example shown, the body 3 is formed of a single tubular bar, with a single support bar 7. However, it will be appreciated that this is by way of example only, and the bar may be any shaped cross-section, such as square or rectangular. It will also be appreciated that the towel rail 1 may be any shape when viewed from above. For example, the towel rail 1 may be T-shaped, with the support bar 7 extending in both directions from the mounting portion 5. Alternatively, the towel rail may be of a more complicated shape including multiple bars, such as a ladder shape, with multiple towel rail bars extending parallel to the wall on which the rail is mounted, joining sections (curved or straight) extending between the towel rail bars, and multiple support points to mount the towel rail 1 from the wall.

Figures 3A to 3C show the heating element 11 in more detail. Figure 3A shows a portion of the heating element 11. The heating element 11 comprises 3 sections The first section is a heating region 17. The heating region 17 is the part of the heating element 11 that provides a heat output, and so all or substantially all of the heating element 11 passing through the body 3 of the towel rail 1 is taken up by the heating region 17. Figure 3B shows a cross-section of the heating element 11 through the heating region 17.

The second section is a junction region 19, which is used to connect the heating element to the power supply. In the assembled rail 1, this section may be formed inside the through passage, near the end 15 of the body 3, or outside the body 3.

Whilst there may be some heating output from the junction region 19, this will be insignificant compared to the output in the heating region 17. Figure 3C shows a cross- section of the heating element 11 through the junction region 19.

The third section is a transition region 21, which forms a join between the junction region 19 and the heating region 17.

The heating element 11 comprises a pair of conducting cores 23, 25. In the junction region 19, each conducting core 23, 25 is surrounded by an insulating shield 27, 29. In the heating region 17 the conducting cores 23, 25 are encased in a variable resistance conducting material 31, which in turn is surrounded by an insulation shield 33. The variable resistance conducting material 31 is formed in a material matrix, and in one example, is extruded around the conducting cores 23, 25. It will be appreciated that the insulation shields 27, 29, 33 are electrically insulating, but not thermally.

The heating element 11 may connect to the power supply in any suitable manner. For example, in the junction region 19, the separate cores 23, 25 may end in a plug or socket, which connects to a socket or plug of a power supply, transformer, or power supply cable. Alternatively, each core 23, 25 may end in a separate plug. In yet further examples, the conducting cores 23, 25 of the may be connected to power supply or power supply cable by soldering or any other suitable joining means. The connection may be protected by heat shrink or other protective covering.

The junction region 19 forms a first end of the heating element 11, with a second end at the far end of the heating region 17. The variable resistance conducting material 31 extends from the transition region 21 to the second end of heating element 11. In the transition region 21, the individual insulation shields 27, 29, 33 are not included. The transition region 21 may be covered by heat shrink 35 or another protective insulating material.

In the heating element 11, a first of the cores 23 forms a live core, whilst the second forms a neutral core. The conducting cores 23 are both in electrical contact with the variable resistance conducting material 31 throughout the heating region 17, but are not in direct contact with each other. The conducting cores 23, 25 are only in electrical contact via the variable resistance conducting material 31. Therefore, a complete electrical circuit is formed by using the variable resistance conducting material 31 as a link between the cores 23, 25, and current passes from a power source, through the live core 23, and then back through the neutral core 25. The neutral core 25 may be referred to as a return core.

The resistance of the conducting cores 23, 25 is constant in any temperature within the operating range of the rail 1. However, the resistance of the variable resistance conducting material 31 alters depending on the ambient temperature. The ambient temperature is the temperature of the environment immediately surrounding the variable resistance conducting material 31. In the case of the towel rail 1 shown in Figure 2, this may be the temperature of the variable resistance conducting material 31 itself, the temperature in the through passage, 9, the temperature of the body 3, or the air (or towel) immediately surrounding the body 3.

When the towel rail 1 is covered, the covering traps heat, increasing ambient temperature. This, in turn, means that a lower output is required from the heating element 11 to maintain a constant temperature. Therefore, as the ambient temperature increases, the resistance of the variable resistance conducting material 31 changes to reduce the heat (power) output of the heating element 11. Conversely, when the covering is removed, heat is no longer trapped, and so the ambient temperature reduces, and more output is required from the heating element 11 to maintain a constant temperature. Therefore, when the ambient temperature decreases, the resistance of the variable resistance conducting material 31 changes to increase the heat output.

In an example with a constant voltage power supply, the resistance of the variable resistance material 31 increases as the ambient temperature increases. This reduces the current flowing through the heating element, reducing the overall heat output. When the ambient temperature decreases, the resistance of the variable resistance material 31 decreases, increasing current flow and thus heat output.

In an example with constant current power supply, the resistance of the variable resistance material 31 decreases as the ambient temperature increases, reducing power output. Conversely, when the ambient temperature decreases, the resistance of the variable resistance material 31 increases, increasing heat output.

In the following, the operation of the towel rail 1 will be discussed in relation to constant voltage mode. However, it will be appreciated that both constant voltage and constant current mode may be used.

Figure 4 shows the heat profile 37 of a towel rail 1 including a heating element 11 as discussed above. As discussed in relation to Figure 1, the temperature is measured on the surface of the body 3, and the towel rail 1 is turned on at t0.

The towel rail 1 quickly reaches and stabilises at a temperature of 35°C. The power supply to the towel rail 1 is always on, and so once the stable temperature has been reached, the resistance of the variable resistance conducting material 31 stabilises, and a constant temperature is maintained as the ambient temperature varies.

At time t1, a towel is put onto the towel rail 1. As discussed in relation to Figure 1, putting a towel on the towel rail 1 traps heat. This increases the ambient temperature..

As a result of the ambient temperature increasing, the resistance of the variable resistance conducting material 31 increases, reducing the current flow through the heating element, hence reducing the heat output from the heating element 11.

Initially, there is a slight drop in temperature, as the increase in temperature from the towel rail causes a jump in the resistance. The temperature then increases, and stabilises at approximately 40°C. This is in contrast to the constant resistance rail, shown in Figure 1. Within the period that the rail 1 shown in Figures 3A to 3C stabilises in temperature at 40°C, the unregulated rail reaches 55°C, and continues to increases in output, rather than stabilising.

The variable resistance of the variable resistance conducting material 31 is an innate property of the material, and so the change in the heating element 11 is almost instantaneous. Therefore, embodiments of the heating element 11 provide a self- regulating output, effectively providing a feedback loop that limits the surface temperature the towel rail 1 can reach.

Embodiments of the regulated rail 1 reduce the risk of injury to users, or damage to the towel. It also achieves regulation of the output without the need for sensors that can be complex to install, require complex thermostats to use, and which can be unsightly.

At t2 in Figure 4, the towel is taken off the rail 1. This causes a reduction in the ambient temperature, increasing the power output of the heating element 11. The temperature drops back to and stabilises at 35°C within five to ten minutes. This is unlike the unregulated example, which takes significantly longer to cool, meaning the rail continues to pose a risk.

The variation in the heat output is caused by the change in resistance of the variable resistance material 31. The variable resistance material 31 extends along the length of the heating region 17. Since the ambient temperature can vary along this length, the resistance of the variable resistance heating material 31, and hence the power output of the heating element 11 can also vary along this length. Therefore, the regulated heating element 11 can maintain a constant surface temperature along the length of the body 3, regardless of whether it is partially covered and partially uncovered. This is unlike the unregulated example, where covered sections will have a significantly hotter surface temperature than uncovered sections.

In the example discussed above, a single heating element 11 is provided along the body 3. In an alternative example, two or more heating elements may be provided in parallel. Figure 4 also shows the heat profile 39 of a towel rail 1 including two self- regulating heating elements 11.

As can be seen from the second profile in Figure 4, the towel rail 1 with two self- regulating elements stabilises at a higher temperature (approximately 40°C without a towel, and 48°C with the towel). However, the overall self-regulating effect is maintained. Increasing the number of heating elements 11 simply increases the surface temperatures at which the towel rail 1 stabilises.

In yet further examples, the heating element 11 may have a plurality of live cores 23 coupled to the single neutral core 25 in a single heating element 11. Again, this increases the power, but the overall regulating effect is maintained.

The free air (no covering) and restricted air (covered) temperatures can be controlled by choice of the resistance of the live core 23 and the neutral core 25, and the choice of the variable resistance conducting material 31 at a nominal reference temperature.

This is controlled by the material and structural composition of the cores 23, 25 and variable resistance conducting material 31.

Typically, the heating element(s) 11 is arranged to reach and maintain a surface temperature of between 30°C and 45°C without a towel (free air). In one example, the temperature maintained in free air will be between approximately 30°C and 40°C. In a further example, the temperature maintained in free air will be between approximately °C and 40°C. The heating element 11 is also arranged such that the maximum temperature increase with a towel (restricted air) is 10°C or less. In one example, the maximum temperature increase may be 5°C or less. The heating element(s) 11 should be arranged so that the surface temperature never exceeds 50°C. In one example, the surface temperature of a towel rail 1 including two heating elements 11 will never exceed 50°C, and the surface temperature on a towel rail 1 including a single heating element 11 will never exceed 40°C.

In one example, the live cores 23 is formed of intertwined strands of a Nickel/Copper alloy. The resistance can be varied by varying the Nickel:Copper ratio, and the number and size of strands.

In one example, the neutral core 23 is a copper wire, either stranded or single core.

The resistance can be varied by varying number and size of strands.

Any material which shows suitable variation in the resistance with changes in the ambient temperature may be used. In one example, the variable resistance conducting material 31 is a carbon based material. In one example, the heating element 11 may be based on the HTLe cable, from the Wuhu Jiahong New Material Company Limited, although a braided earth shield is not required.

A specific resistance conductor may also be provided to control the overall resistance of the heating element 11.

In the above description, the conducting cores 23, 25 are provided through a matrix formed by the variable resistance conducting material 31, such that the cores 23, 25 are encased by the variable resistance conducting material 31. This is just one example of forming a self-regulating heating element 11.

In other examples, any suitable link or linking elements having a temperature variable resistance, provided along the length of the heating portion 17, may be used to connect the conducting cores 23, 25. The resistance of the linking element(s) should be variable without having to actively measure the temperature, for example using a sensor.

In one example, there may be a number of separate discrete regions of the variable resistance conducting material 31 provided along the length of the heating portion 17.

In other examples, discrete linking elements which have a temperature variable resistance may be used. In yet further examples, one or both of the conducting cores 23, 25 may be formed of the variable resistance conducting material, as well as or instead of the link between the cores 23, 25.

In some examples, there may be parts of the heating portion 17 which do not include links between the conducting cores 23, 25, such that these portions do not heat up. For example, this may be at bends or other features in the body 3 where a towel is unlikely to be hung.

Optionally, the heating element 11 may include an earth core or an earth shield, or the shield may be omitted.

The construction of the heating element 11 is given by way of example only. In some examples, the junction region 19 and transition region 21 may be omitted, and the heating region 17 may connect directly to the power supply or power supply cable.

Also, the size of the transition region 21 may be any suitable size, if included, and any suitable means may be used to transition from the heating region 17 to the junction region 19 if included.

In some examples, the conducting cores 23, 25 in the junction region 17 may be encased in a further insulation shield or covering, so that the individual wires are not visible or accessible.

In the above description, the conducting cores 23, 25 have been described as having constant resistance within the operating range of the towel rail 1. It will be appreciated that this simply refers to the fact that the resistance of the cores 23, 25 does not change with temperature. It will be further appreciated that there may be some minor variation due to inconsistencies in power supply, material, construction and the like, but these changes will have a negligible effect on the heat output of the heating element, compared to the change in resistance of the variable resistance conducting material 31 with temperature. Furthermore, the resistance may vary at sufficiently high or low temperatures, which would never be experienced by the towel rail in use (for example, below 0°C and above 100°C).

Also, in the above, the regulated towel rail 1 is described as reaching and stabilising at a constant temperature, when it is first turned on, or when a towel is hung on or taken off the rail 1. The towel rail 1 is also described as having a constant temperature along the length of the body 3. It will be appreciated that there may also be some small temperature variation in this constant temperature. However, this variation will again be negligible when compared to the changes in temperature that occur when turning on, hanging a towel or taking a towel off. It will also be appreciated that a towel is just one example of a covering, and any covering may have the same effect.

Claims (17)

1. A towel rail including a body, and a heating element passing through at least a portion of the body, 5 wherein the heating element has a variable resistance that changes as the ambient temperature changes, such that the heat output of the towel rail is limited at a maximum.

2. The towel rail of claim 1, wherein the heating element includes: 10 a live conducting core; a return conducting core; and one or more linking elements arranged to connect the live conducting core and return conducting core to form a complete circuit, wherein the one or more linking elements has a variable 15 resistance that changes as the ambient temperature changes, such that the heat output of the towel rail is limited at a maximum.

3. The towel rail of claim 2, wherein the one or more linking elements are 20 provided along at least a portion of the length of the heating element.

4. The towel rail of claim 2 or claim 3, wherein the resistance of the conducting cores is substantially independent of the ambient temperature. 25

5. The towel rail of any of claims 2 to 4, wherein the one or more linking elements comprise a matrix of variable resistance conducting material, encasing the live conducting core and return conducting core, such that the live conducting core and return conducting core are in electrical contact with each other through the matrix only.

6. The towel rail of any of claims 2 to 5, wherein the heating element is provided with an insulation jacket covering the conducting cores and one or more linking elements.

7. The towel rail of any of claims 2 to 6, wherein the heating element includes a junction region for connecting to a power supply, wherein the one or more linking elements do not extend into the junction region. 5

8. The towel rail of claim 7, wherein, in the junction region, each conducting core is provided with an insulation jacket along at least a portion of the length of the conducting cores.

9. The towel rail of any of claims 2 to 8, wherein the body includes: 10 two or more support bars arranged to extend, when installed, parallel to each other and to a wall on which the towel rail is mounted; and one or more joining sections, connecting the support bars, wherein the heating element passes through each of the support bars, and passes between the support bars through a joining 15 section; and wherein the linking elements are omitted in the section of heating element passing through the joining sections.

10. The towel rail of any of claims 1 to 8, wherein the body includes a single 20 support bar arranged to extend, when installed, parallel to a wall on which the towel rail is mounted, and wherein the body includes a mounting portion, extending perpendicular to the support bar at a first end of the body, for securing the towel rail to the wall. 25

11. The towel rail of claim 10, wherein a second end of the body, opposite the first end, is arranged to be spaced from the wall.

12. The towel rail of any preceding claim, wherein the resistance of the heating element increases as the ambient temperature increases, such that, in use with a 30 constant voltage supply, current reduces as ambient temperature increases.

13. The towel rail of any preceding claim, wherein the resistance of the heating element is variable along the length of the heating element.

14. The towel rail of any preceding claim, wherein the towel rail includes two or more heating elements.

15. The towel rail of any preceding claim, wherein the heating element is arranged 5 to maintain a surface temperature of between 30 degrees Celsius and 40 degrees Celsius on the surface of the body, in free air.

16. The towel rail of any preceding claim, wherein the heating element is arranged such that the surface temperature of the surface of the body increases by 10 10 degrees Celsius or less, in a region where the body is covered.

17. The towel rail of any preceding claim, wherein the body is formed of metal.