Weighing scales – Self-positioning – Electrical current generating or modifying
Reexamination Certificate
2002-04-12
2004-11-02
Gibson, Randy W. (Department: 2841)
Weighing scales
Self-positioning
Electrical current generating or modifying
C177S238000, C177S255000, C177SDIG009
Reexamination Certificate
active
06812414
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a weighing machine for weighing human bodies and the like.
BACKGROUND ART
In a conventional weighing machine, a strain plate is strained in a manner such that a load from a scale plate on which an object to be weighed, such as a human body, is placed is transmitted to and concentrated on one point by means of a load transmission mechanism (beam balance) that is formed of a plurality of metal plates combined with one another. The change of a resistance value of a strain gauge that is pasted on the strain plate is detected, or the change of capacitance is detected by varying the distance between two electrode plates as the strain plate is displaced, and the change is converted into load.
In the beam balance described above, metal plates are used in combination with one another in a manner such that they are set upright to stand load from the scale plate, and load transmitting metal plates for transmitting the load from the scale plate to a beam metal plate must be constructed as knife edge fittings, so that the balance normally inevitably has a great thickness of 35 mm or more. Further, knife edge portions are subjected to a very high pressure, so that they are forced to deform and wear away after repeated use, thus failing to ensure long-term reliability.
To cope with this, a technique of a thin weighing machine with simple construction and high long-term reliability is described in Publication No. WO00/06977, for example. An outline of this weighing machine will now be described with reference to
FIGS. 13 and 14
.
As shown in
FIG. 13
, a weighing machine
50
is formed in a manner such that a scale plate
51
, one strain plate
52
, and a base plate
53
are combined in layers. The strain plate
52
and the scale plate
51
are fixed in layers with scale plate spacers
54
between them by means of bolts and screws, and the strain plate
52
and the base plate
53
are fixed in layers with base plate spacers
55
between them by means of bolts and screws. The base plate
53
is provided with a circuit portion
56
, which includes control and arithmetic circuits such as a microcomputer, a display portion
57
for displaying the result of computation, and a power source retaining portion
58
, and its plane shape is optional.
Further, the scale plate
51
in the form of a plate is connected to load receiving portions
59
of the strain plate
52
by means of the scale plate spacers
54
. The weighing machine
50
is configured to be a weighing machine that is formed of three flat plates and can be made very thin.
In the case where the weighing machine
50
is placed on a floor surface, leg portions
60
can be provided on a part of the strain plate
52
. For example, one or more leg portions
60
provided on the strain plate
52
can be arranged in any other region(s) of outer frames
61
than regions right under fixing portions
62
to which the base plate
53
is fixed. To attain this, hollow portions
63
are formed in the base plate
53
.
The strain plate
52
is formed integrally of a sensitive portion
66
including a strain gauge
65
for use as sensing means, load transmitting beams
64
connecting with the sensitive portion
66
, and load receiving portions
59
. An upper surface
67
of the one strain plate
52
is provided with a center groove portion
68
, which includes the sensitive portion
66
and is formed extending parallel to a straight line L—L that connects the respective center points C of the load receiving portions
59
. A weight applied to the scale plate
51
is received dispersedly by means of the load receiving portions
59
, the load is caused to act concentratedly on the sensitive portion
66
by means of the load transmitting beams
64
, and strain or deformation of the sensitive portion
66
is picked up as a change of the quantity of electricity by means of the strain gauge
65
.
The load applied to the weighing machine
50
of
FIG. 13
acts on the strain plate
52
. In a weighing machine such as a scale that measures a heavy weight, in particular, screw portions for fixing the strain plate
52
and the base plate
53
are liable to loosened by repeated loading. If the screw portions loosen, the position of the strain plate
52
relative to the base plate member is shifted, so that the way the strain plate
52
is strained changes with every measurement. In consequence, measurements of the same weight involve different ways of transmission to the strain gauge
65
, inevitably causing measurement errors. Further, a shock of a fall or the like also creates gaps between the strain plate
52
and screws, so that the measurement accuracy lacks in reliability.
Another prior art is also described in Publication No. WO00/06977. In this case, a strain plate and a base plate are fixed by means of the following arrangement instead of screwing. As shown in
FIG. 14
, a base plate
53
is in the form of an open-topped box, a strain plate
52
is arranged in the box, and fixing members
70
for preventing vibration and displacement of the strain plate
52
are arranged between the corner portions of the strain plate
52
and a peripheral wall
69
of the base plate
53
.
If sides
70
a
of the fixing members
70
and sides
52
a
of the strain plate
52
are brought intimately into contact with one another, in a weighing machine of the alternative prior art described above, however, the central portion of the strain plate
52
sinks during measurement, and the sides
52
a
of the strain plate
52
warp, thereby pressing the inner sides
70
a
of the fixing members
70
. After repeated use, therefore, gaps are formed between the fixing members
70
and the strain plate
52
, so that the strain plate
52
is dislocated, and the measurement may possibly be subject to dispersion, as in the case of the aforesaid screwing method. If gaps are previously provided between the fixing members
70
and the strain plate
52
to prevent this, however, the position of the strain plate
52
is finely shifted with every measurement, so that measurement errors may possibly occur. A shock of a fall or the like also creates gaps between the fixing members
70
and the strain plate
52
, resulting in the same problem.
DISCLOSURE OF THE INVENTION
The object of the present invention is to provide a thin weighing machine of high-reliability, which stands repeated use and whose measurement accuracy is influenced little by a shock of a fall or the like.
In order to achieve the above object, a weighing machine according to an aspect of the present invention comprises a substantially flat strain plate adapted to be deformed when loaded, a sensor for detecting deformation of the strain plate, a base plate member carrying the strain plate thereon, and a scale plate member located on the upper surface of the strain plate and capable of transmitting load to the strain plate, the sides of the strain plate being held by means of elastic position regulating members, individually.
The weighing machine according to this aspect can adopt the following forms.
The strain plate has a strain-direction regulating portion for regulating the direction of a strain produced in the strain plate as the strain plate is deformed. The sensor is a strain gauge attached to the strain plate corresponding to the strain direction of the strain plate. The position regulating members hold at least the sides of the strain plate which extend at right angles to the strain direction.
The strain plate is formed with at least two sides extending at right angles to the strain direction and opposed to each other across the strain-direction regulating portion, the two sides being held by means of the position regulating members, individually. Further, the position regulating members hold a plurality of portions of the sides of the strain plate perpendicular to the strain direction. Furthermore, the position regulating members hold two portions near the opposite end portions of the sides of the strain plate perpendicular to the strain direction.
The position regulating members
Citizen Watch Co. Ltd.
Gibson Randy W.
Smith , Gambrell & Russell, LLP
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