Abstract:
The heating device is connectable to an electrical resistance heating circuit in a ski boot and comprises, at least one battery, a watertight box-like structure, a battery charger, a first circuit adapted for preventing overcharging of the battery, a second circuit adapted for preventing excessive discharging of the battery, and a third circuit adapted for controlling power fed to the electrical resistance heating circuit. The watertight box-like structure is removably associable with a ski boot, connectable to the electric resistance heating circuit, and adapted for containing the battery the first circuit, the second circuit, and the third circuit.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a heating device, particularly for ski boots. 
     Currently known are devices for heating ski boots by using electrical energy. 
     Boots including such known devices comprise an inner boot which comprises an electric resistance heater connected to one or more rechargeable electric batteries. 
     Such batteries are electrically connected to a socket for permitting their recharging, which socket is accessible on the boot, the supply of power to the resistance heater being allowed by operating a suitable switch. 
     The main disadvantage found in such known devices resides in the fact that the ski boot must be placed proximate to an external electric power supply, and that the user must use a battery charger in order to restore the functionality of the batteries. 
     A partial solution to the disadvantage of having to place the boots proximate to a source of electric power, is disclosed by copending U.S. patent application Ser. No 06/861.287 filed on May 9, 1986, now U.S. Pat. No. 4,697,359 wherein a structure of an item of footwear is illustrated which is provided with a seat adapted for removably housing a rechargeable battery, on said structure there being provided a suitable switch intended to selectively allow the supply of power to an electric resistance heating circuit inserted within said item of footwear. 
     Also in this case, however, the disadvantage arises of the need to use an external battery charger for connection between a power supply and the rechargeable battery. 
     SUMMARY OF THE INVENTION 
     The main aim of the present invention is therefore to eliminate all of the disadvantages of known types of heating devices for ski boots. 
     Within the above-cited aim, an object of the invention is to provide a heating device which has means for supplying power to an electric resistor circuit contained within a ski boot and which allows direct recharging of the power which can be restored therein without requiring any external accessories and without the need to place said boot proximate to a power source. 
     A further important object of the invention is to provide a heating device which associates the above described characteristic with that of allowing said recharging in conditions of absolute safety for the user. 
     Another important object of the invention is to provide a device which furthermore allows its quick and easy replacement in case of maintenance, allowing at the same time the user to make use of the ski boots, even during recharging. 
     Another object of the invention is to devise a heating device with small dimensions and which is absolutely safe and reliable while skiing. 
     Still another object of the invention is to provide a heating device which allows an optimum supply of power to the electric resistance heating circuit within the ski boot, without requiring the user to perform said function by continuous and constant use of a switch interposed between said device and said circuit. 
     Not least object is to obtain a device which automatically presents any damage to the battery avoiding possible overcharging or excessive discharging thereof. 
     The aim and the objects mentioned above, as well as others which will become apparent hereinafter, are achieved by a heating device particularly for ski boots, comprising an electrical resistance heating circuit, characterized in that it comprises, in combination, at least one battery, a substantially watertight box-like structure, battery charging means, at least one first circuit adapted for preventing overcharging of said battery, at least one second circuit adapted for preventing excessive discharging of said battery, and at least one third circuit adapted for controlling power fed to said electrical resistance heating circuit, said substantially watertight box-like structure being removably associable with a ski boot, connectable to said electric resistance heating circuit, and adapted for containing said battery, said first circuit, said second circuit, and said third circuit. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further characteristics and advantages of the invention will become apparent from the detailed description of a particular embodiment, illustrated only by way of non-limitative example in the accompanying drawings where: 
     FIG. 1 is a block diagram of the device; 
     FIG. 2 is a perspective view of a particular box-like structure for the same; 
     FIG. 3a shows a wiring diagram of a part of the device according to FIG. 1; 
     FIG. 3b shows the current versus time as supplied by the device to the heating circuit with different power regulations. 
     FIGS. 4 to 11 are perspective views illustrating eight possible different solutions for the accommodation of the box-like structure on the ski boot. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to the above described figures, the heating device 1, particularly for ski boots 2, comprises a battery charger 3 of the switching type, which allows recharging with voltage values ranging from 12 to 24 volts DC, and from 100 to 240 volts AC with automatic voltage level compensation. Said battery charger 3 comprises an automatic charge-cut off circuit 4 adapted to prevent overcharging of the battery and controlled by the charging time and/or the battery temperature, so as to stop charging when the charging time and/or the battery temperature exceed preset values. This battery charger 3 may be of any type suitable for allowing recharging of the battery through connection to an external, AC or DC, power supply; for example it may be the same as the battery charger incorporated in the shaver HP 1335 manufactured by Philips Shave. 
     The batteries, indicated at 5, are electrically connected, through line 40, to the battery charger 3 and, through line 41, to an automatic switch circuit 6 intended t cut off feeding of the heating resistor circuit 8 and thus to stop discharge of the batteries when the voltage across the batteries 5 falls below the present value, said automatic switch circuit allowing protection of the batteries, by preventing excessive discharge thereof. 
     The heating device 1 furthermore comprises a control circuit 7 for regulating the power fed to the resistor heating circuit 8 arranged in the ski boot 2. 
     The function of this control circuit 7 is thus to adjust the temperature within the ski boot according to the requirements of the user. 
     Advantageously, the control circuit 7 is of the nondissipating type, so as to allow the user, besides the adjustment of the temperature within the ski boot, also to increase the life of the batteries 5. 
     An illustrative embodiment of circuits 6 and 7 is shown in FIG. 3a, wherein section A corresponds to the automatic switch circuit 6 and sections B and C form the control circuit 7. 
     In detail, as visible, section A, fed on line 41, comprises a first transistor 45 which, biased by resistors 46-49, sets the operation threshold of the device. First transistor 45 drives, through resistors 50, 51, second transistor 52 which, during normal operation, is in the ON state and drives sections B and C. In this state, LED 53 is switched on. When the voltage of the batteries and thus the voltage drop on leads 41 falls below the operation threshold of section A, transistor 52 is switched off, thereby switching off sections B and C so as to stop feeding of the heater circuit 8. Resistor 49 of the NTC type is intended to thermally compensate transistor 45. 
     Section B defines the power regulation portion and includes a differential amplifier circuit driven by resistor 52 through transistor 59 and comprising transistors 54 and 55 and resistors 56-58 and capacitor 57 forming with the transistors 54,55 a self-exciter structure. Regulation of the duty cycle of this structure is obtained through potentiometer 60 which allows selection of the reference voltage of the differential amplifier circuit. The variable-width pulse fed by transistor 55 are then supplied, through resistor 61, to the base of transistor 62 of sections C. Potentiometer 60 is furthermore mechanically coupled to switch 70 arranged on line 41 to interrupt current flow. 
     This section C defines the final power section and includes a first, gain portion formed by transistors 62 and 63, and a second, power section formed by transistor 64 connected with its collector electrode to line 65 leading to the heating circuit 8. Resistor 66, of the NTC type, is connected between the base and emitter of transistor 64 and is intended to protect the latter against short-circuits by limiting the base current. 
     Thus, by acting on the potentiometer 60, connected to a knob 12 it is possible to reduce the current on the load as illustrated in FIG. 3a, wherein the current pulses have a duration Δt which is a function of the angular position of the knob 12 connected to potentiometer 60, said adjustment allowing power supply for desired periods of time and thus achieving different temperatures in the boot. 
     In this manner, the user merely needs to select, by means of the knob 12, the setting deemed optimum, the control circuit 7 supplying power as selected until the voltage fed by the batteries falls below the set threshold and automatic switch circuit 6 causes switching off of control circuit 7 and therefore the resistor heating circuit 8. 
     The battery charger 3, the batteries 5, the circuits 4, 6 and 7 are all enclosed within a watertight box-like structure 11 carrying the control knob 12 for the potentiometer 60 and pins 13, in electrical contact with line 65, for connection to the heating circuit 8. The box-like structure 11 further carries a lamp 14 connected to the battery charger 3 and the LED 53 forming part, as already explained, of control circuit 7 for verifying the charge and the discharge of the batteries. According to the present embodiment, pins 13 may be used also to connect the device to an external recharging power supply, but further electrical connection elements may be instead provided for this purpose. 
     Advantageously, the box-like structure 11 has the shape of a parallelpipedon with external projections or ribs 15 adapted to facilitate gripping by the user. 
     The box-like structure 11 can be removably associated with ski boots 2, for example at a suitable flat seat 16 provided on the front quarter 17 of th boot and provided with a pair of sockets 18 for the pins 13 adapted to allow the electrical coupling thereof to the circuit 8. 
     FIG. 5 illustrates a ski boot wich is provided, at the rear quarter 19, with a container 20 having a laterally-opening seat 21, configured so as to removably insert the box-like structure 11, also in this case there being provided, inside said seat, suitable sockets for the connection to the circuit 8 of the device 1. 
     FIG. 6 instead illustrates a ski boot 2 having the front quarter 17 with a seat 21 upwardly open and configured so as to removably accommodate and surround the box-like structure 11 so as to protect it from possible shocks during skiing. 
     Naturally, the control knob 12 for the potentiometer, as well as the control lights 14 and 53, are positioned so as to be visible and accessible by the user. 
     FIG. 7 illustrates a ski boot, having the container 20 at a rear portion of the quarter 19, in said embodiment the seat 21 opening towards the interior of the boot 2. 
     A recess is thus defined which is adapted to allow the removable insertion of the box-like structure 11, within said seat 21 there protruding present terminals 22 adapted to allow electrical connection to the pins 13. 
     FIG. 8 illustrates a ski boot 2, on the upper region of the shell 23 thereof adjacent to the front quarter 17 there being provided a seat 16 on which is removably placed a box-like structure 11 provided with sockets for the connection to the heating circuit 8, shaped complementarily with respect to preset pins 24 provided and projecting from said seat 16. 
     FIG. 9 illustrates a ski boot 2, on the upper region of the shell 23 whereof, adjacent to the front quarter 17, is provided, instead, a seat 21 adapted to accommodate the box-like structure 11, the same being protected within said seat, which can be closed by means of a suitable closure 25. 
     Also in this case, suitable pins 24 for the connection to the device 1 of the heating circuit 8 project from said seat 21. 
     FIG. 10 illustrates a ski boot 2, on the rear quarter 19 of which is provided and projects a projection 26 provided with a flat surface 27 facing towards the top of the boot 2, with which the box-like structure 11 is removably associable, by means of the pins 13, said protrusion 26 being provided with suitable sockets for the pins 13 so as to allow electrical connection of the device 1 to the circuit 8 within the boot. 
     FIG. 11 instead illustrates a ski boot 2, provided, at the rear quarter 19, with a container 20, provided with a seat 21 arranged therein and configured so as to removably accommodate the box-like structure 11. 
     Said seat is provided with an opening towards the upper end of the quarter 19. 
     Also in this case, inside the seat 21 suitable sockets are provided for the pins 13 which project from the box-like structure 11, said sockets allowing the electrical connection of the device 1 to the heating circuit 8 within the boot 2. 
     It has thus been observed that the invention achieves the intended aims and objects, a heating device having been provided which is associable with the ski boot, which can be removed therefrom and placed directly at a power source, said device allowing the recharging of the batteries inserted therein without the need of an external battery charger. 
     By virtue of the possibility of power supplies at various voltages, the user may, for example, recharge the batteries by electrically connecting the box-like structure 11 to the battery of the car while travelling towards the skiing resorts. 
     Furthermore, the insertion of the device within a watertight box-like structure prevents any malfunction due to possible water infiltration while skiing. 
     Moreover, if a fault occurs, the user can send the entire box-like structure 11 to be repaired, which in any case will still allow the boot to be used even with the box-like structure 11 removed therefrom. 
     The presence within the device of a circuit for regulation and power supply furthermore allows the user to achieve an optimum heating condition within the ski boot, it being possible to achieve said condition by reducing the current on the load. 
     Moreover, the presence of the automatic cut off and control circuits allows to keep the batteries always efficient even if the user fails to notice an excessively long use thereof or an excessively longlasting connection thereof to a power source. 
     The accommodation of said device within the box-like structure allows its quick and simple application to the ski boot, its modest dimensions not substantially affecting the aesthetic characteristics of the ski boot. 
     Naturally, the materials and the dimensions of the individual components, as well as the components of the individual circuits which compose the heating device, may be any according to specific requirements.