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(11) | EP 3 373 699 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | METHOD OF MANUFACTURING A HEATER, AND HEATER |
| (57) A heater comprising a first coil wound on a first support structure (S1) to obtain
a first mounted coil (C1) having a first outer dimension, a second support structure
(S2) overlapping the first support structure (S1), and a second coil wound on the
second support structure (S2) to obtain a second mounted coil (C2) having a second
outer dimension exceeding the first outer dimension, the second mounted coil (C2)
overlapping the first mounted coil (C1). The first support structure (S1) may be obtained
by combining first support plates at mutual angles to obtain first support positions
around which the first coil (C1) can be wound. The second support structure (S2) may
be obtained by mounting second support plates alongside corresponding halves of the
first support plates to obtain second support positions around which the second coil
(C2) can be wound. Preferably, support positions where the first coil (C1) is suspended
on the first support structure (S1) are aligned with respective support positions
where the second coil (C2) is suspended on the second support structure (S2). The
step of mounting the second support structure (S2) may include further fixating the
first mounted coil (C1).
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FIELD OF THE INVENTION
BACKGROUND OF THE INVENTION
[0002] Hairdryers are made by placing a heater and fan serial into an open duct. A typical heater is made from a heating wire, like the common OCR25A15, which is coiled and wrapped around a mica frame to fit the limited dimensions of the duct.
SUMMARY OF THE INVENTION
[0003] It is, inter alia, an object of the invention to provide a very compact heater. The invention is defined by the independent claims. Advantageous embodiments are defined in the dependent claims.
[0004] One aspect of the invention provides a heater which comprises a first coil wound on a first support structure to obtain a first mounted coil having a first outer dimension, a second support structure overlapping the first support structure, and a second coil wound on the second support structure to obtain a second mounted coil having a second outer dimension exceeding the first outer diameter, the second mounted coil overlapping the first mounted coil. The first support structure may be obtained by combining e.g. three first support plates at mutual angles of e.g. 60° to obtain e.g. six first support positions around which the first coil can be wound. The second support structure may be obtained by mounting e.g. six second support plates alongside corresponding halves of the three first support plates to obtain e.g. six second support positions around which the second coil can be wound. Preferably, support positions where the first coil is suspended on the first support structure are aligned on lines radially extending from the center with respective support positions where the second coil is suspended on the second support structure. The step of mounting the second support structure may include fixating the first mounted coil.
[0005] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
DESCRIPTION OF EMBODIMENTS
[0007] In the embodiment shown in the drawings, the heater volume is reduced by winding the coil in two diameters with independent pitches so as to wind as compact as possible. In that case one first winds a coil as compact as possible on an inner frame followed by a similar exercise on the outer frame with the next coil.
[0008] In the shown embodiments, two heating coils C1, C2 with different dimensions are wound on different, but connected, frames or support structures S1, S2. In this case the windings are not positioned in an inner outer sequence, but one coil C1 is placed in the inner diameter position while the other coil C2 is placed in the outer diameter position with an independent pitch from each other. Thus the spacing between the coils C 1, C2 is different, which results in an adapted construction as will be discussed below.
[0009] The support structure S1, S2 includes a mica frame which is able to fixate a relatively fragile inner coil C1 and a relatively rigid outer coil C2, both with a different pitch (coil to coil distance) to obtain a very compact heater. This implies the frame is built in two steps: inner coil C1 first, then outer coil C2, and fixate the more fragile inner coil C1 at more points than the outer coil C2. The mica is shaped in such a way that assembly can be done by hand, without riveting the parts together.
[0010] First, various mica parts are placed together to form an inner mica support structures S1. Around this inner frame S1 the relatively fragile heater coil C1 is wound. After the inner coil C1 has been placed, another support structures S2 is built on top of this inner frame S1, which locks the inner heater coil C1 even more at the bottom side of this outer frame S2, while the relatively rigid coil C2 is wound around the outer support structures S2 at sufficient distance to prevent contact between the two coils C1, C2 from occurring.
[0011] This is done by wrapping the heating coil C1, C2 in two independent layers. This wrapping is done manually, and to make it most simple to wrap the coil, first the hexagon shaped mica frame S1 of the inner coil C1 is build. The smaller coil C1 is wrapped around and fixated at the 6 mica walls. The inner coil C1 is additional fixated by 6 other mica sheets forming the hexagonal frame S2 of the main heating coil C2. Then, the outer heater coil C2 is wrapped around the frame S2.
[0012] As most clearly shown in Figs. 3, 4, 5, the first coil C1 has a first diameter, and the second coil C2 has a second diameter exceeding the first diameter. The first coil C1 is wound for a first number of windings around the first support structure S1, and the second coil C2 is wound for a second number of windings around the second support structure S2. In the shown embodiments, the second number of windings is about half the first number of windings, but other ratios are alternatively possible.
[0013] In one embodiment, the wire used for the inner coil C1 has a diameter of 0.32 mm and a length of 6.8 m, while the wire used for the outer coil C2 has a diameter of 0.55 mm and a length of 5.9 m. The outer diameter of the heater is 45 or 48 mm, and its height is 53 or 55 mm. The coil diameters are in general 10 - 15 times the wire diameter. The coils used for our design thus have coil diameters of 3.2 mm and 5.5 mm both with a length of about 35 cm.
[0014] Advantageously, the first coil C1 has a second function (which may even be its main function) as a voltage divider or voltage dropper to turn the mains voltage into a voltage suitable for the fan of the hair dryer. The dissipation resulting from this voltage adaptation is advantageously used to heat the air. If different fan speeds need to be provided, different taps on the inner coil C1 can be used for that purpose. The wire diameter of the first coil C1 can be designed in a way suitable for that second function.
[0015] Due to its very compact design the heat transfer needs to be high in order to prevent so called 'red coils' (coils are too hot and start to radiated visible red/orange/yellow light). This can be avoided by increasing the airflow by reducing the flow area of the air in the duct. This is done e.g. by covering/blocking the central part of the duct, to guide the air flow along the coils more vigorously.
[0016] Figs. 6 and 7 illustrate how the heater of Fig. 5 is made. Fig. 6 shows the mica plates used for the support structures S1 (lower row) and S2 (upper row). Fig. 7 first shows that the first support structure S1 is made by combining the 3 mica plates shown in the lower row of Fig. 6. Each of the small grooves on the outer edges forms a support position for the first coil C1. Then, the first coil C1 is wound around the first support structure S1. Next, the mica plates of the second support structure S2 are mounted next to the mica plates of the first support structure S1. Doing so also results in better fixing the windings of the first coil C1 by means of the curves at the inner edges of the plates used for the second support structure S2, while the small grooves in the outer edges of these plates form support positions for the second coil C2. Finally, the second coil C2 is wound around the second support structure S2.
[0017] The embodiment of Figs. 5-7 is more advantageous than the embodiment of Figs. 1-4, because while in the drawings, the wound coils C1, C2 are shown to have circular shapes, in reality they will have a polygon shape, i.e. more along straight lines between support positions where the coils C1, C2 are suspended on the respective support structures S1, S2. In the embodiment of Figs. 1-4, the support positions of the second support structure S2 are between the support positions of the first support structure S1. As a result, if the second coil C2 follows a straight line between its support positions, the second coil C2 has a risk of bumping into the first coil C1 where this first coil C1 is suspended at the support positions of the first support structure S1. In the embodiment of Figs. 5-7, the support positions of the first and second support structures S1, S2 are aligned with each other, so that the distance between the coils C1, C2 is about constant, even if their shapes looks like polygons rather than like circles, so that the risk of the coils C1 and C2 touching one another is less than in the embodiment of Figs. 1-4.
[0018] It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. The invention can be used as a heater for a hair dryer, but it can also be suitable for other appliances with small convectional heaters. While the first and second coils C1, C2 overlap, there is no need for these coils C1, C2 to have the same length. If the inner coil C1 is shorter than the outer coil C2, other components can advantageously be mounted inside the second coil C2. While coil C1 is shown to be thinner than coil C2, they may have identical diameters. While coil C1 is shown to have more windings than coil C2, this is not necessary. The coils C1, C2 may have an oval or elliptical shape instead of a round shape, in which case the outer dimension is not the diameter but another characteristic dimension. In an alternative embodiment, four mica plates are mounted at mutual equal angles of 45° instead of three plates mounted at mutual equal angles of 60°. The overall shape of the heater may be conical instead of cylindrical. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word "comprising" does not exclude the presence of elements or steps other than those listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. In the device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.
1. A method of manufacturing a heater, the method comprising the steps of:
winding a first coil on a first support structure (S1) to obtain a first mounted coil (C1) having a first outer dimension;
mounting a second support structure (S2) on and overlapping the first support structure (S1); and
winding a second coil on the second support structure to obtain a second mounted coil (C2) having a second outer dimension exceeding the first outer dimension, the second mounted coil (C2) overlapping the first mounted coil (C1).
2. A method as claimed in claim 1, wherein the first support structure (S1) is obtained
by combining first support plates at mutual angles to obtain first support positions
around which the first coil (C1) can be wound.
3. A method as claimed in claim 2, wherein the second support structure (S2) is obtained
by mounting second support plates alongside corresponding halves of the first support
plates to obtain second support positions around which the second coil (C2) can be
wound.
4. A method as claimed in any of the preceding claims, wherein the step of mounting the
second support structure (S2) includes further fixating the first mounted coil (C1).
5. A method as claimed in any of the preceding claims, wherein support positions where
the first coil (C1) is suspended on the first support structure (S1) are aligned with
respective support positions where the second coil (C2) is suspended on the second
support structure (S2).
6. A heater comprising:
a first mounted coil (C1) having a first outer dimension wound around a first support structure (S1); and
a second mounted coil (C2) having a second outer diameter wound around a second support structure (S2) overlapping the first support structure (S1), the second outer dimension exceeding the first outer dimension, and the second mounted coil (C2) overlapping the first mounted coil (C1).
7. A heater as claimed in claim 6, wherein the first support structure (S1) comprises
first support plates mounted at mutual angles to obtain first support positions around
which the first coil (C1) can be wound.
8. A heater as claimed in claim 7, wherein the second support structure (S2) comprises
second support plates mounted alongside corresponding halves of the first support
plates to obtain second support positions around which the second coil (C2) can be
wound.
9. A heater as claimed in any of the preceding claims 6-8, wherein support positions
where the first coil (C1) is suspended on the first support structure (S1) are aligned
with respective support positions where the second coil (C2) is suspended on the second
support structure (S2).
10. A heater as claimed in any of the preceding claims 6-9, further comprising a cover
for reducing an airflow through a central area inside the first mounted coil (C1).