Abstract:
Hair-care appliances such as curling tongs are provided. The hair care appliances include a heating device that is controlled in dependence on temperature by a thermostat adjacent to the heating device. The thermostat may be shielded thermally from the heating device by a partition wall.

Description:
This application is filed under 35 USC §371 from PCT application number EP01/02676, filed Mar. 9, 2001, and claims priority under 35 USC §119 from German application number 10012192.6, filed Mar. 13, 2000. 

   The invention relates to a hair-care appliance, for example curling tongs. 
   BACKGROUND 
   Hair-care appliances in the form of curling tongs are known, for example, from DE-38 43 186 C2. Arranged within the tubular heating rod, laterally alongside the heating device, which comprises a tubular burner housing, is a rod-like thermostat which runs in the longitudinal direction of the heating device. The thermostat is designed as a control rod and, at one end, is connected mechanically to a valve device. The control rod controls the valve device in dependence on temperature, and the valve device, in turn, regulates the feed of gas to the heating device. The temperature of the curling tongs and/or the temperature of the heating rod is regulated in this way. 
   In the case of these curling tongs, the heating device emits its thermal energy in the form of heat radiation and free convection both to the tubular heating rod and directly to the thermostat. The influence of the heat of the heating device on the expansion of the control rod is thus considerably greater than the influence of the heat which flows from the heating rod to the control rod. On account of this arrangement, the controller obtains the largest percentage of its temperature information from the heating device, which may be configured as an open flame or as a catalyst. Accordingly, the heat acting directly on the control rod from the heating device may result in the control rod being regulated down all too prematurely, with the result that the heating rod does not heat up quickly enough. Following this regulating-down operation, the dwell time until the valve device is regulated up is then comparatively long because the cooling of the control rod, and thus the opening of the valve device, takes up a certain period of time in which rapid heating of the heating rod is diminished. 
   It is also found that the temperature of the heating rod during operation is not always the optimum temperature for sufficient curl shaping, i.e. the temperature of the heating rod may be too high or else also too low, because the system is self-limiting during reheating and thus only regulates the temperature of the heating rod moderately well. 
   SUMMARY 
   The invention features hair-care appliances, for example curling tongs, in which the temperature of the heating rod can be better detected and the heating rod can thus be heated up more quickly. During operation, in preferred hair-care appliances the heating rod maintains a substantially uniform temperature without undesired temperature peaks occurring either upward or downward. 
   In one aspect of the invention, the hair-care appliance includes a heating device, and a thermostat that is shielded thermally from the heating device by a partition wall. With the temperature shielding of the thermostat by a partition wall, most of the thermal energy of the heating device, which is preferably in the form of heat radiation and free convection, passes both into the heating rod and into the partition wall, but no longer directly into the thermostat. This thermal energy introduced is then distributed uniformly, by means of heat conduction, both into the heating rod and into the partition wall. It is only then that, from there, some of the thermal energy passes into the thermostat, which, for its part, heats up correspondingly. During cooling of the heating device, the heating rod and the partition wall and, in dependence on the two last-mentioned parts, also the thermostat cools. 
   The thermostat thus obtains its temperature to the greatest extent from the temperature of the partition wall and the heating rod. The thermostat regulates the flow of gas up and down in dependence on the temperature of the heating rod, this preferably being the case when a state of thermal equilibrium has been established between the temperature of the heating rod, the partition wall and the temperature of the thermostat. As a result, this system reacts more quickly to changes in the temperature at the heating rod and no longer predominantly to changes in the temperature at the heating device. The thermostat accordingly obtains its data rather more from the temperature of the heating rod and the partition wall than from the temperature of the heating device. The temperature of the heating rod can be regulated more precisely as a result. 
   A further advantage is that upon cold adjustment of the thermostat, following the production and assembly of the hair-care appliance, the setting of a large number of series-production appliances is approximated or simplified, i.e. virtually no more cold adjustment is necessary or it can be carried out considerably more quickly on the appliances produced since the tolerances which inevitably result during production and assembly and the temperature peaks, which generally are now less frequent and/or less high, have a considerably lesser effect on the regulating behavior of the hair-care appliance. 
   In some implementations, when the hair-care appliance is heated up, the heating device is only regulated down when the heating rod has virtually reached its optimum hair-treating temperature. In addition, during operation of the hair-care appliance, the valve device, which serves for controlling the heating device, is regulated up and down very precisely and quickly by the thermostat, with the result that the temperature of the heating rod is only exposed to very low temperature fluctuations. This results, on the one hand, in it not being possible, as a result of absent temperature peaks, for hair to be subjected to undue stress, but, on the other hand, in the optimum temperature for quick hair shaping always being maintained to the greatest extent. 
   In some implementations, the partition wall may be thermally connected to the heating rod. In this case, in addition to the heat radiation and free convection, the heat conduction also acts on the partition wall in order for the temperature of the partition wall to be brought into line to the greatest extent with the temperature of the heating rod, account also being taken here of the fact that the wall of the heating device is closer to the partition wall than the entire inner surface of the heating rod. In order nevertheless to reduce these differences in temperature between the heating rod and the partition wall, it may be advantageous for ribs to be provided on the inner surface of the heating rod, said ribs being closer to the heating device and thus, in accordance with the formation of the partition wall, also being able to absorb more heat. As a result, the heating rod is heated more uniformly all the way round and its temperature thus essentially coincides with the temperature at the partition wall. 
   In some cases, the partition wall and the thermostat may run essentially parallel to the tubular heating rod, with the result that the entire length of the heating rod is temperature-monitored and temperature-regulated. This achieves a more uniform temperature for the entire length of the heating rod. In this case, the thermostat preferably comprises a cross-sectionally round control rod, which runs at a distance from, and essentially parallel and, for instance, with correspondingly equal length to, the heating device. Such control rods are used in the type GCC  50  cordless curling tongs which have been commercially available from the applicant for some time now (see Braun&#39;s product range overview “Qualität in guter Form” [Quality in Good Shape], 1999/2000 issue, page 9), so that no further details need be given here. This also applies to the construction of the curling tongs overall, such as the valve device, the catalyst, the heating rod, etc., so that, for an explanation of the curling tongs claimed here, reference can be made to this appliance and/or the latter can also form part of the contents of this application. 
   The partition wall may be of essentially annular design in cross-section, and may be connected integrally to the heating rod via a crosspiece. These features allow straightforward production and attachment of the partition wall to the heating rod. In this case, it is possible for the crosspiece to be advantageously welded to the inner wall of the heating rod or connected integrally thereto. The metallic connection of the crosspiece to the heating rod constitutes a good thermal connection between the partition wall and the heating rod, with the result that it is also the case that the partition wall has virtually the same temperature as the heating rod itself. 
   If desired, the partition wall may have one or more through-passages within the heating rod. Thus, the influence of the heating device on the thermostat may be somewhat increased, with the result that the thermostat reacts somewhat more quickly to the temperature of the heating device. The regulating behavior of the thermostat can be influenced to a considerable extent by the number or width of the through-passage or through-passages, by the wall thickness of the partition wall, by the arrangement of the control rod in the heating tube in relation to the heating device, by the design of the heating rod itself and by the heating output of the heating device per unit of time. In dependence on these variables, the best possible regulating behavior can be determined in tests in order always to obtain an optimum temperature, which is neither too high nor too low, on the outer surface of the heating rod. 
   In some implementations, the through-passage discussed above may be designed as a longitudinal slot, and the thermostat may be designed as a control rod. For example, the through-passage may be formed by just one longitudinal slot, which is dimensioned with such a width that the control rod is already at least in partial view. Thus, as a result of the heat radiation acting on it, the control rod can react more quickly to temperature peaks of the heating device both in the upward and in the downward direction. By virtue of the longitudinal slot formed in the partition wall, it is also possible, as a result of heat radiation, for heat to flow comparatively quickly into the space enclosed by the partition wall in order, in particular during the heating-up operation, to allow quicker heating of the partition wall and thus more precise regulation of the thermostat. 
   In some implementations, one end of the partition wall may be connected integrally to the heating rod, while the other, free end terminates at a distance in front of the inner wall of the heating rod in order to form the longitudinal slot discussed above. Thus, the thermal connection between the partition wall and the heating rod may be reduced, while the thermal influence of the heating device is increased. This improves the regulating behavior of the thermostat. 
   The chamber which closes off the partition wall and in which the control rod runs may have a direct connection to the chamber enclosing the catalyst. This direct connection may produce a good thermal connection, in particular when the longitudinal slot discussed above runs over the entire length of the thermostat. 
   The heating rod and the partition wall may form a single shaped part. This can result in a tubular heating rod which can be produced particularly straightforwardly as a shaped part, because it does not have to be assembled from a number of parts. It may be particularly advantageous if the shaped part is an extruded part which is produced by extrusion of a material which is supplied by the meter, preferably aluminum or some other material which is a good heat conductor and flows freely for extrusion purposes. 

   
     DESCRIPTION OF DRAWINGS 
     An exemplary embodiment of the invention is described in more detail hereinbelow and is illustrated in the drawing in which: 
       FIG. 1  shows a longitudinal section through curling tongs in the region of the thermostat, designed as a control rod, with its valve device formed at one end, the free end of the heating rod being covered for better demonstration purposes—not in the usual manner—by a closure device, 
       FIG. 2  shows an enlarged plan view, in direction X, of the free end of the heating rod according to  FIG. 1 , and 
       FIG. 3  shows a perspective illustration in direction Y according to  FIG. 1 , although the handle region has been broken away and the illustration is likewise on a larger scale than FIG.  1 . 
   

   DETAILED DESCRIPTION 
   In  FIGS. 1  to  3 , the curling tongs  1  comprise an essentially cup-like mount  4  which has an essentially annular housing  3  inserted into its bore  2 , which is accessible from the right-hand side according to  FIG. 1 , and centered there, said housing serving for accommodating a valve device  5 , which is fastened in the housing  3 , and a thermostat  6 , which is designed as a control rod. The mount  4  is open from the left-hand side according to FIG.  1  and is formed by a blind bore  7  into which a gas cartridge (not illustrated in the drawing) can be inserted. Projecting through the space  8  of the blind bore  7  is a gas tube  10 , which penetrates the base  9  and, when a gas cartridge is inserted, actuates the valve arrangement formed in the gas cartridge (this valve arrangement not being illustrated) and thus produces a gas connection from the gas cartridge to the valve device  5  of the curling tongs  1 . 
   According to  FIG. 1 , the valve device  5  comprises a base-side installation plate  11 , which is screwed to a controller mount  12 , or fastened thereon in some other manner, from the right-hand side. A seal  13  is clamped in between the two parts  11 ,  12  in order for the valve chamber  13 , which is formed by the installation plate  11  and the controller mount  12 , to be sealed in the outward direction. The valve device  5  is centered in an accommodating bore  14  formed in the mount  4 . Located in the valve chamber  13  is a valve piston  15 , which can be displaced to the left counter to the force of a compression spring  16  and thus opens the valve device  5  in order that gas can be fed to the catalyst  17 , via channels which are not illustrated in the drawing, for combustion purposes. 
   According to  FIG. 1 , a threaded bore  18  is formed in the controller mount  12 , and a tube  20 , which encloses a Vacodil rod  19 , is firmly screwed in said threaded bore by means of a thread  21 . The Vacodil rod  19  preferably consists of an iron/nickel alloy and is subjected to a low and constant level of deformation in the event of temperature increase. In contrast, the tube  20  consists of a metal which undergoes a high level of deformation under the action of temperature. Since the free end of the tube  20  and the free end of the Vacodil rod  19  are forced together, as the flattened sections  22  in  FIG. 3  show, the tube  20  extends, in the event of an increase in temperature of the control rod  6 , and in the process carries along with it the Vacodil rod  19 , the length of which deforms to a lesser extent. As a result, the end  23  of the Vacodil rod  19 , said end butting against the valve piston  15 , moves to the right according to FIG.  1 . Since the compression spring  16  always holds the valve piston  15  in the drawing in abutment against the free end  23  of the Vacodil rod  19 , the valve piston  15  also moves to the right according to FIG.  1  and closes the gas line (not illustrated) in the direction of the catalyst  17 , with the result that the latter emits less heat. 
   According to  FIG. 1 , the heating rod  25 , which comprises a tubular shaped part, is supported on the housing  3 , in a housing bore  24 , and extends from there to the right according to FIG.  1 . The heating rod  25  is produced as an extruded part in an extruder and thus, in cross section, has a cross-sectional shape which is adapted to the conditions of the curling tongs  1  and has different wall thicknesses, as FIGS.  2  and  3  show. As can also be seen from  FIGS. 2 and 3 , the control rod  6  is arranged on the left alongside a heating device  17 , designed as a catalyst, and runs essentially parallel to the longitudinal axis  26  of the heating rod  25 . The cross-sectional profile of the heating rod  25  runs symmetrically in relation to the longitudinal axis  26 . According to  FIGS. 2 and 3 , the center point  27  ( FIG. 2 ) of the catalyst  17  is located to the right of the longitudinal axis  26 , while the center point  28  of the control rod  6  is formed to the left of the longitudinal axis  26  in the heating rod  25 . As can also be seen from  FIG. 1 , the control rod  6  runs approximately over half the length of the heating rod  25 , while the free end  29  of the catalyst  17  terminates a few millimeters in front of the free end  30  of the control rod  6 . The catalyst  17  is retained in a carrier  31 , which is firmly connected to the housing  3  via fastening rods  32  formed on it (FIG.  2 ). 
   Fastened rotatably on the top side of the housing  3 , according to  FIGS. 1  to  3 , is a button  33  which, via its extension  34 , engages in a double-walled clamp  35  and thus firmly connects the latter to the button  33 . The inner surface  36  of the clamp  35  butts against the top side of the outer surface  37  of the heating rod  25  when the button  33  is not actuated. This is achieved by a spring  38  ( FIG. 1 ) which acts on the button  33  and is supported on the mount  4 . At the free end of the clamp  35 , an end cap  42  engages in the gap  41  formed by the two walls  39 ,  40 , said end cap serving as a handle for the curling tongs  1  and as a means of protecting a user against burning. The end cap  42  is firmly connected to the clamp  35 , for example, by crimping, adhesive bonding, a screw connection or some other fastening method. The handle  61  of the curling tongs  1  forms the outer surface of the mount  4 . 
   According to  FIGS. 1  to  3 , the heating rod  25  has openings  44 , via which the heat emitted by the catalyst  17  during operation can escape. In order to give a view into the interior  45  of the heating rod  25  from the free end  43 , the closure cap  47 , which would otherwise be inserted into the inner wall  46  of the appliance in its complete state, has been omitted and is only illustrated by dashed lines. 
   According to  FIGS. 2 and 3 , a partition wall  49  extends from the inner wall  46  of the heating rod  25  into the interior  45 , said partition wall only partially enclosing the control rod  6  and running over a circular-ring arc which corresponds approximately to the length of a quarter-circle. In this way, only approximately half the surface of the control rod  6  is exposed to the direct heat radiation of the catalyst  17 , while the other half is covered by the partition wall  49 . The wall surface  50 , which is directed toward the control rod  6 , runs at a predetermined distance from, and concentrically in relation to, the control rod  6 , this resulting in the formation, between the two parts, of an intermediate gap  51  in the form of an annular segment, although it is also possible for this gap to assume some other form. 
   According to  FIG. 2 , the line  52 , which runs concentrically in relation to the control rod  6 , constitutes a bore in the housing  3  via which the control rod  6  penetrates through a sleeve  62  and passes to the valve device  5 . The partition wall  49  is connected integrally to the heating rod  25 . Furthermore, corresponding profiles  53  are integrally formed on the inner wall  48 , these profiles serving for centering, accommodating and adapting the components formed in the interior  45  of the heating rod  25 , as has already been mentioned above. 
   According to  FIG. 2 , the housing  3  has diametrically opposite recesses  54 ,  55 , the button  33  being embedded in the recess  54  and an ignition slide  56  being embedded in the recess  55 , said ignition slide being connected, via lever mechanisms which are not illustrated in the drawing, to an ignition device, which is not illustrated in the drawing either. 
   According to  FIGS. 2 and 3 , the partition wall  49  is connected to the inner wall  46  of the heating rod  25  via a crosspiece  58 , with the result that the heat is thereby introduced from the heating rod (heat conduction). The free end  60  of the partition wall  49  terminates at a distance in front of the inner wall  46  of the heating rod  25  located opposite it and thus forms a longitudinal slot  59 . 
   Referring to  FIGS. 1 ,  2  and  3 , the curling tongs  1  function as follows: 
   First of all, the valve device  5  is actuated, via a valve slide which is not illustrated in the drawing, such that gas flows into the catalyst  17  via the gas cartridge, the gas tube  10  and the valve device  5 . It should be mentioned here that, in the cold state, the control rod  6  always keeps the valve piston  15  in its open position, but that this position can always be moved into the closed position by a main slide (not illustrated) if the appliance is no longer to be used. The ignition slide is then actuated and, via an ignition mechanism which is not illustrated in the drawing, one or more sparks are produced in the catalyst  17 , these sparks causing the air/gas mixture which is located in the interior  57  of the catalyst  17  to explode. The explosion is followed by the commencement of the catalytic combustion at the catalyst  17 . The catalyst  17  is heated and the heat emitted by it radiates into the interior  45  of the heating rod  25 . 
   Some of the heat irradiates the surface of the control rod  6  directly, while some more of the heat is shielded by the partition wall  49 . The convection and heat radiation emanating from the heating rod  25 , the partition wall  49  and the catalyst  17  heats the control rod  6  until such time as, just before the desired temperature of the heating rod is reached, it slowly actuates the valve device  5  and thus restricts the feed of gas to the catalyst  17 . This takes place because, when the control rod  6  is heated, the tube  20  expands to a considerably greater extent than the Vacodil rod  19 , i.e. the free end  23  of the Vacodil rod  19  is moved to the right according to FIG.  1 . As a result of the force of the compression spring  16 , the valve piston  15  follows this movement, since it is always held in abutment against the Vacodil rod  19 . This results in the feed of gas to the catalyst  17  being regulated down. 
   As a result of the reduction in the catalytic combustion, the catalyst  17  cools and less heat is introduced into the heating rod  25 . It is likewise the case that the level of heat radiation to which the control rod  6  is subjected by the catalyst  17  is lower, with the result that said control rod also cools. At the same time, the heat which is emitted by the heating rod  25  and by the partition wall  49 , and was introduced via the catalyst  17  on account of heat radiation and heat conduction, has a lesser cooling effect on the control rod  6 , with the result that, overall, only a slight reduction in the feed of gas is introduced. 
   If, then, curls are wound around the outer surface  37  of the heating rod  25  at the operating temperature of the latter, although in this case it is necessary for the clamp  35  to be pivoted open in the upward direction by virtue of the button  33  being actuated, heat is emitted to the hair (not illustrated) by the heating rod  25 . At the same time, hot air flows on account of the combustion gases produced during the catalytic combustion, this hot air penetrating outward, likewise into the hair, via the openings  44 . This heats the hair, while the heating rod  25  cools at the same time. 
   Less heat then radiates from the heating rod  25  to the control rod  6 , with the result that, although more heat is now radiated from the catalyst  17  from the other side, said control rod cools overall and, in the process, the length of the tube  20  shortens again. As a result, the free end  23  of the Vacodil rod  19  is displaced to the left according to FIG.  1 . In this case, the valve piston  15  is also displaced to the left, counter to the force of the compression spring  16 , and the channels, which are not illustrated in the drawing, is opened, with the result that more gas can flow into the catalyst  17  again. The catalytic combustion in the catalyst  17  increases and more heat is introduced into the interior  45  again. 
   The control rod  6  is influenced to a considerably greater extent by the temperature of the heating rod  25  than by the temperature of the catalyst  17 , which results in it being possible to avoid temperature peaks and thus in the temperature behavior of the curling tongs  1  as a whole being improved. The dimensions of the partition wall  49  may be made to correspond to the dimensions of the control rod  6 , of the heating rod  25 , of the catalyst  17  and of the other components which are to be heated in the curling tongs  1 , such that in the event of a nevertheless quick heating-up operation, when the desired temperature of the heating rod  25  is reached, the control rod  6  reacts to the temperature quickly enough for the desired temperature of the heating rod to be maintained to the greatest extent. In this case, it is also possible for the partition wall  49  to be attached to the inner wall  48  of the heating rod  25  to a greater or lesser extent via a larger or smaller surface area in order for more or less heat to be introduced into the partition wall  49 , in order that the latter can emit more or less heat to the control rod  6  and the desired temperature of the heating rod thus remains, to the greatest extent, constant. Of course, the distances of the control rod  6  from the inner wall  48  of the heating rod  25 , from the inner wall  50  of the partition wall  49  and from the outer wall of the catalyst  17  are also of critical importance for the purpose of achieving optimum regulating behavior for the curling tongs  1 . These distances, and these dimensions of the components in relation to one another, can only be determined by tests.