Electronic balance which is easily assembled, maintained,...

Details Electronic balance which is easily assembled, maintained,... Electronic balance which is easily assembled, maintained,...

2001-09-21

2004-02-17

Gibson, Randy (Department: 2841)

Weighing scales

Self-positioning

Electrical current generating or modifying

C177S212000, C177S229000, C029S593000

Reexamination Certificate

active

06693245

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon claims the benefit of priority from the prior Japanese Patent Applications No. 2000-299601, filed Sep. 29, 2000; No. 2000-299602 filed Sep. 29, 2000; and No. 2000-299603 filed Sep. 29, 2000, the entire contents of all of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electronic balance for measuring the mass of the substance to be weighed and more specifically, to an electronic balance that is easy to assemble and maintain, and that can be downsized, and in addition to this, an electronic balance with an improved lever that moves from the balancing state during load application, and furthermore, an electronic balance that enables the protection of the spring section of the Roberval's mechanism by improving the mobile range of the Roberval's mechanism which composes the electronic balance.
2. Description of the Related Art
Hitherto, for this kind of electronic balance, “ELECTRONIC BALANCE” disclosed in the U.S. Pat. No. 4,799,561 is well known.
FIG. 23
is a front cross-sectional view showing the “ELECTRONIC BALANCE” disclosed in the U.S. Pat. No. 4,799,561 as the first conventional electronic balance
80
.
FIG. 24
is a perspective view showing to remove the scale plate
89
from FIG.
23
.
That is, as shown in
FIGS. 23 and 24
, the first electronic balance
80
generally comprises a Roberval's mechanism
81
in which the mobile section
81
b
with the scale plate
89
provided moves with respect to the fixed section
81
a,
a lever
83
that operates in linkage with the transfer of the mobile section
81
b,
an electromagnetic coil
85
that moves and controls the lever
83
to be in the balancing state, a position detection sensor (not illustrated) for detecting the balancing state of the lever
83
, and a control section that energizes and controls the electromagnetic coil
85
to calculate and output the mass of the substance to be weighed.
Now the Roberval's mechanism
81
has a pair of upper and lower parallel Roberval's sections
86
formed by hollowing out a metal block such as rectangular aluminum, etc. from the one side to a specified shape as illustrated.
In this Roberval's section
86
, a total of 4 thin-wall spring sections
87
are formed, and when a substance to be weighed is placed on a scale plate
89
of the mobile section
81
b,
the spring section
87
portion is deformed by receiving this load, and the mobile section
81
b
moves downwards with the level condition maintained by the mobile section
81
b.
In linkage with the shift of this mobile section
81
b,
the free end
83
a
of the lever
83
displaces from the balancing position to upwards.
The control section energizes and controls the electromagnetic coil
85
so that the lever
83
is brought to the balancing state based on the output of the position detection sensor, and calculates and outputs the mass of the substance to be weighed in accordance with the current value, etc. to the electromagnetic coil
85
when the lever
83
is in the balancing state.
Hitherto, for this kind of electronic balance, “electronic weighing apparatus” disclosed in the Jpn. Pat. Appln. KOKAI Publication No. 11-51756 is well known.
FIG. 25
is an exploded perspective view of the principle section that shows the “electronic weighing apparatus” disclosed in the Jpn. Pat. Appln. KOKAI Publication No. 11-51756 as the conventional second electronic balance
90
.
That is, as shown in
FIG. 25
, the second electronic balance
90
has the Roberval's mechanism
91
and the lever
92
separately formed.
Now, the lever
92
is installed in the form of linking both side sections of the Roberval's mechanism
91
.
And this lever
92
is held between the Roberval's mechanism
91
and the base member
95
as shown with an illustrated broken line by a plurality of fulcrum member
93
and a suspension member
94
.
The lever
83
in the configuration of the first electronic balance
80
is formed integral with the Roberval's mechanism
81
, whereas in the second electronic balance
90
, it is formed separately from the Roberval's mechanism
91
, but both Roberval's mechanism
81
and Roberval's mechanism
91
are formed by hollowing a rectangular shape aluminum block, etc. from the one section to a specified profile as described above.
Hitherto, for this kind of electronic balance, the “DEVICE FOR REDUCING THE FORCE IN A FORCE-MEASURING APPARATUS, IN PARTICULAR IN A SCALE” disclosed in the U.S. Pat. No. 5,340,951 is well known.
FIG. 26
is a perspective view showing the “Device for Reducing the Force in a Force-measuring Apparatus, in Particular in a Scale” disclosed in the U.S. Pat. No. 4,350,951 as a third conventional electronic balance
100
.
That is, as shown in
FIG. 26
, this third electronic balance
100
has the Roberval's mechanism
101
hollowed and formed from the one side section of a rectangular aluminum block, etc. and at the same time, a lever mounting section
102
is formed.
By mounting a separate lever
103
to this mount section
102
, an electronic balance
100
is constructed.
Now, as shown in
FIGS. 23 and 24
, the lever
83
in the configuration of the first conventional electronic balance
80
is hollowed into a specified shape continuously in the width direction from the one section side of a rectangular aluminum block material, etc.
Consequently, in the first conventional electronic balance
80
, in order to provide the specified rigidity to the lever
83
, the thickness must be increased, causing a problem of increased weight.
That is, because the width of this lever
83
is the same as that of the Roberval's mechanism
81
, it is unable to reduce the weight while maintaining the rigidity.
In addition, in general, in this kind of lever
83
, as the lever length is increased, the load applied to the mobile section
81
b
of the Roberval's mechanism
81
can be attenuated, and at the same time, the measurement accuracy as the electronic balance
80
can be improved by increasing the displacement rate of the free end
83
a
of the lever
83
(hereinafter called the “displacement rate”).
And yet, since with the lever
83
of the first conventional electronic balance
80
with the above-mentioned configuration causes restrictions that the lever length is shorter than the Roberval's mechanism
81
, there is a limit to the improvement of measuring accuracy.
This kind of Roberval's mechanism
81
is formed with the measurement range of the mass of the substance to be weighed previously specified.
In particular, the rigidity of the whole Roberval's mechanism
81
and the spring constant of the spring section
87
are set to fit to the measurement of the mass of the substance to be weighed in the relevant measuring range.
The rigidity of this Roberval's mechanism
81
and the spring constant of the spring section
87
have influences on the start of measurement of the mass of the substance to be measured, that is, the time from when the substance to be weighed is placed until the vibration of the mobile section
81
b
ends to enable the measurement (response time).
However, in the first conventional electronic balance
80
, etc. as described above, the Roberval's mechanism
81
is formed by hollowing a rectangular aluminum block, etc. from the one section into a specified shape and has a configuration to have a total of 4 pieces of thin-wall spring section
87
.
Consequently, in the first conventional electronic balance
80
, etc., there is a problem of damaging the thin-wall spring section
87
if external vibration or impact is applied to the spring section
87
located between the mobile section
81
a
and the fixed section
81
b
when the Roberval's mechanism
81
is being transferred to the subsequent assembly step, etc. after forming the Roberval's mechanism
81
.
This problem occurs not only during transportation but also when an unexpected lo

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