Measuring and testing – Center of gravity; turning moment; metacentric height
Reexamination Certificate
2001-01-09
2003-09-02
Lefkowitz, Edward (Department: 2855)
Measuring and testing
Center of gravity; turning moment; metacentric height
Reexamination Certificate
active
06612157
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a small free fall sensor detecting a fall of portable electronic equipment such as notebook type personal computers.
2. Description of the Prior Art
There is a possibility that when the above-described portable electronic equipment falls during use, recording data is seriously damaged even if a component in equipment is not almost damaged. For example, a hard disk drive used as a storage device for the above-mentioned portable electronic equipment has recently been improved in tolerance of shock of an impact. However, when recording data is written or read, a disc head supported by an arm seeks with a slight gap between it and the disc surface of a hard disc drive. Accordingly, there is a possibility that a small shock not exceeding the aforesaid mechanical tolerance may bring the distal end of the disc head into contact with the disc to thereby damage either one or both of them. As a countermeasure to prevent the damage, the head is moved to an inner radius landing zone provided around the disc before the shock acts thereon. This countermeasure can render a risk of damage minimum. However, in order that the above-mentioned countermeasure may be carried out, a process for moving the head to the inner radius landing zone is required before a stage where the disc head is subjected to a shock due to the fall. Accordingly, a sensor is required which can detect the falling equipment.
An accelerometer is one of the aforesaid sensors. The prior art has proposed various types of acceleration sensors. For example, the acceleration sensors include those of the mechanical type including a steel ball or weight. Many of the accelerometers of this type are responsive only to a transverse acceleration, whereas few of them are responsive to a gravitational acceleration. Moreover, many of the accelerometers responsive to the gravitational acceleration detect an impact acceleration in a case where a substance has fallen but very few of them can detect the falling substance before subjection to shock due to fall. For example, Japanese Patent Publication No. 8-321236A discloses a seismic switch as shown in FIG.
13
. The disclosed seismic switch
101
comprises a coil spring
102
and a bob
103
supported by the coil spring
102
. In the seismic switch
101
, an electric circuit is made when the bob
103
is in contact with an umbrella electrode
104
disposed around the bob. However, the aforesaid seismic switch can detect only the transverse acceleration. More specifically, when the gravitational acceleration is detected by the aforesaid seismic switch, an apparent change in the weight of the bob is detected by the aforesaid seismic switch. However, in order that a decrease in the weight due to the fall may especially be detected, the coil spring needs to sufficiently change for even a slight change in the weight due to the fall as well as to support the weight of the bob. For example, the coil spring
102
needs to change its length in Japanese Patent Publication No. 8-321236A, whereupon selection of a spring constant is difficult.
Japanese Patent Publication No. 8-249995A discloses an oscillation detecting switch as shown in FIG.
14
. The oscillation detecting switch
111
comprises a coil spring
112
having a distal end supporting an L-shaped support rod
113
further supporting a moving contact member
114
. In response to a three-dimensional oscillation, the moving contact member
114
is brought into contact with a fixed contact member
115
so that a signal is delivered. However, when the switch having the above-described structure is used as a free fall sensor, a posture of the mounted sensor is fixed. For example, when the aforesaid switch
111
stands erect, is inverted and is inclined 90 degrees, the coil spring is compressed, extended and bent respectively. As a result, it is difficult to uniform sensor characteristic at the respective postures. On the other hand, it is desirable that the sensor detecting the falling state of the equipment should have the same characteristic when it is erect and inverted. It is further desirable that the sensor should have a sufficient freedom in the posture thereof.
A sensor such as the conventional accelerometer is adapted to be mounted on a large equipment. Such an equipment has a determined posture in the practical use. However, when used with a hard disk drive provided in a notebook personal computer, for example, the aforesaid sensor is supposed to be erect and inverted in the hard disk drive for the reason of limitation in the location of the sensor or the like. Further, when such a hard disk drive is utilized for a recent space-saving desktop personal computer, there is a possibility that the hard disk drive is used in a sideways arrangement for the reason of limitation in an accommodating space. Accordingly, the sensor, which is limited in the posture thereof, also limits the posture of equipment on which it is mounted, thereby reducing the usability thereof. Therefore, a sensor has been desired which has less limitation in the posture thereof in use.
The conventional acceleration sensors include, other than that described above, a servo acceleration sensor in which a bob is held by magnetic force and a feedback control is performed so that the bob is maintained at a constant position according to a detected acceleration. The conventional acceleration sensors further include an acceleration sensor in which warping of an optical fiber is utilized. However, each acceleration sensor consumes a large amount of electricity because of its structure and has difficulty in being rendered so small that it can be used in the portable electronic equipment.
Further, the prior art has proposed various types of small acceleration sensors using semiconductor elements. For example, a cantilever includes a bob section in a distal end thereof and a detecting section near a root thereof. The detecting section detects, as an amount of strain, a deformation of the cantilever due to a change in the acceleration. However, an impact acceleration a fallen object suffers the moment it has fallen on a floor is easily one thousand times larger that the gravitational acceleration or more. Further, when the equipment is placed on a desk in a normal use, an impact acceleration the acceleration sensor undergoes is ten times larger than the gravitational acceleration or more. On the other hand, the prior art has provided acceleration sensors with a structure that can detect a small change in the acceleration such as an apparent decrease in the weight. This type of acceleration sensor has a fragile structure for holding the bob. Accordingly, it is difficult to repeatedly use this type of acceleration sensor even after it has undergone such a large impact as described above. Of course, there is a possibility that the sensor may be damaged to thereby loose its original function when subjected to a small impact in its normal use. Further, these acceleration sensors also have the above-described problem of posture. In particular, the prior art has provided no sensors which can achieve the same characteristic when it is disposed laterally as when it is vertically, except a combination of a plurality of sensors.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide a free fall sensor having a superior utility.
The present invention provides a free fall sensor comprising a movable electrode including a plurality of moving portions disposed on a circumference at regular intervals so as to be equidistant from a central axis, a fixed electrode disposed outside the movable electrode so as to be brought into contact with and separated from the movable electrode, an inertial member located inside the moving portions of the movable electrode, and a buffer preventing the inertial member from contacting the fixed electrode so that the moving portions serving as movable electrodes are held between the fixed electrode and the inertial member thereby to be prevented from being pre
Takeda Teruyuki
Urano Mitsuhiro
Dickens Charlene
Foley & Lardner
Lefkowitz Edward
Ubukata Industries Co., Ltd.
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