Ski boot
BRIEF SUMMARY OF THE INVENTION 
     The present invention relates to a ski boot provided with a device for adjusting the fastening force. 
     Various types of fasteners for fitting the skier&#39;s foot to a ski boot are known. They use a buckle, a wire, an air pack, or a plastic plate, or combinations thereof. 
     The ambient temperature at a skiing surface and the temperature of the foot of a skier change moment by moment while a person is skiing. As they change, the physical properties of the materials of which the ski boot is made (e.g. resin of the outer shell and foam plastic of the inner boot) change. Thus, the fastening force, too, changes. 
     On the other hand, a human foot changes in size in a day. It is usually the smallest in size in the morning and tends to expand toward night. For these reasons, a skier has to continually adjust the fastening force or pressure of the ski boots on his feet. However, a skier had to adjust it resorting only to his feeling or sense. A quantitative adjustment of the fastening pressure was impossible. It could not be easily and quickly adjusted to a desirable pressure. 
     An object of the present invention is to provide a ski boot provided with a device for quantitatively controlling the fastening pressure on the skier&#39;s foot. 
     In accordance with the present invention, there is provided a ski boot comprising: an outer shell; an inner boot; an air pack disposed between the outer shell and the inner boot for fastening the skier&#39;s foot with the air contained therein; and means for quantitatively controlling the fastening pressure on the skier&#39;s foot; the means comprising an air pump connected through a valve to the air pack for supplying air into the air pack, a pressure sensor connected to the air pack for sensing the air pressure in the air pack and giving a signal, and a control circuit operative in response to the signal from the pressure sensor for controlling the valve and the air pump. 
     The pressure sensor detects the air pressure in the air pack and the electric air pump automatically supplies air into the air pack until the air pressure therein reaches a preset value. 
     In accordance with the present invention, a skier can obtain a desired fastening pressure extremely easily. 
    
    
     Other features and advantages of the present invention will become apparent from the following description taken with reference to the accompanying drawings, in which: 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partially cutaway side view of a ski boot embodying the present invention; and 
     FIG. 2 is a circuit diagram of an example of a control circuit for the air pump and the solenoid valve. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, a ski boot embodying the present invention comprises an outer shell 1 of a synthetic resin material, an inner boot 2 inserted in the outer shell, and an air pack 3 comprising a bag of a synthetic resin and material disposed between the outer shell 1 and the inner boot 2 at the front part of the ankle. 
     A pipe 4 has one end connected to the rear portion of the air pack 3. Its other end is connected through a solenoid valve 7 to an electric air pump 8 in a case 5 mounted on the back of the outer shell 1. A pressure sensor 6 is connected to the pipe 4 to sense the pressure in the air pack 3. 
     The case 5 contains a relay unit 9 for controlling the electric air pump 8 and the solenoid valve 7, and a power source 10 for the air pump 8. A suction switch 11 and an exhaust switch 12 are mounted on the case 5. The power source 10 may be a cell or a chargeable cell. An AC power source may be used through an adapter. 
     The electric air pump 8 comprises a motor 13 and a rubber pump 14. The motor 13 has a rotary shaft 15 connected to the pump 14 so as to butt it at an eccentric position. When the motor 13 is actuated, the rubber of the pump is caused to vibrate by the rotary shaft so that air will be supplied through the pipe 4 into the air pack 3. The pressure sensor 6 is provided with a sensor switch 16 and a pressure setting knob 17. 
     Referring to FIG. 2, an example of a control circuit for the air pump 8 and the solenoid valve 7 will be described. 
     The control relay unit 9 has three relay coils RX1L, RX2L and RX3L. When the suction switch 11 is pressed, the relay coil RX1L will be energized, so that its contacts RX1 1 , RX1 2  and RX1 3  will close. Thus, the relay coil RX1L will be kept energized so that the energizing coil of the solenoid valve 7 will be energized to open the solenoid valve. Simultaneously the motor 13 for the air pump 8 will be started to send air into the air pack 3. 
     When the air pressure in the air pack 3, sensed by the pressure sensor 6, reaches the value preset with the pressure setting knob 17, the pressure sensor switch 16 will close, energizing the relay coil RX3L. A contact RX3 1  will open, deenergizing the relay coil RX1L, so that the contacts RX1 2  and RX1 3  will open and the solenoid valve 7 will close. Simultaneously the motor 13 for the air pump 8 will stop. Therefore, the air pressure in the air pack 3 will be equal to the preset pressure. 
     In order to deflate the air pack 3, the exhaust switch 12 is pressed. When it is pressed, the relay coil RX2L will be energized so that its contacts RX2 2   and RX2 4  will open and its contacts RX2 1  and RX2 3  will close. Therefore, with the power for the motor 13 off, the solenoid valve 7 will be opened by its energizing coil so that air will be discharged out of the air pack 3. When the exhaust switch 12 is released, the solenoid valve 7 will close. 
     THus, merely by pressing the suction switch 11, the pressure in the air pack 3 can be easily brought back to the preset value in any situation.