Electronic balance

Details Electronic balance Electronic balance

1999-11-22

2001-10-23

Gibson, Randy W. (Department: 2859)

Weighing scales

Self-positioning

Spring

Reexamination Certificate

active

06307165

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 10-338,954, filed Nov. 30, 1998, entitled “Electronic Balance.” The contents of that application are incorporated herein by reference in their entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electronic balance which includes a plurality of Roberval's chains.
2. Discussion of the Background
Many of conventional electronic balances and scales utilize a Roberval's chain (also called a “parallel guide”) to support a balance pan in order to limit the movement of the balance pan on which a mass is placed. The Roberval's chain includes a fixed pillar, a movable pillar, and upper and lower beams. The fixed pillar is fixed to or integrated into a frame of the scale. The movable pillar is supported by the fixed pillar via the upper and lower beams which are substantially in parallel with each other. Each beam is connected to the fixed pillar at one end and to the movable pillar at the other end through each fulcrum. The movable pillar supports the balance pan. Thus, the load applied to the balance pan is transmitted to an electric load detector through the movable pillar and a lever.
Japanese Unexamined Utility Model Publication (Kokai) No. 63-35,924 discloses a Roberval's chain which is constructed by assembling separate pieces of a fixed pillar, a movable pillar, and upper and lower beams. Japanese Unexamined Patent Publication (Kokai) No. 63-277,936 discloses a Roberval's chain which has a single piece construction carved out from a single flat plate. The contents of these references are incorporated herein by reference in their entirety.
In these balances, however, it is difficult to make an adjustment because an adjustment of an offset error in the longitudinal direction of the upper and lower beams affects an offset error in the transverse direction of the upper and lower beams or vise versa.
SUMMARY OF THE INVENTION
According to one aspect of the invention, an electronic balance includes a first Roberval's chain, a second Roberval's chain connected to the first Roberval's chain, and a detector. The first Roberval's chain includes a first fixed pillar, a plurality of first beams, and a first movable pillar supported by the first fixed pillar via the plurality of first beams. The first beams extends substantially in parallel with each other and in a first extending direction. The first movable pillar is configured to receive a load to be measured. The second Roberval's chain includes a second fixed pillar, a plurality of second beams, and a second movable pillar supported by the second fixed pillar via the plurality of second beams. The plurality of second beams extends substantially in parallel with each other and in a second extending direction substantially perpendicular to the first extending direction of the plurality of first beams. The second movable pillar is connected to the first movable pillar. The detector is configured to detect the load electrically via a movement of the first movable pillar.
According to another aspect of the invention, a scale includes a housing and an electronic balance provided in the housing. The housing has a circumferential portion, and first and second side portions at both ends of the circumferential portion. The electronic balance includes a first Roberval's chain, a second Roberval's chain connected to the first Roberval's chain, and a detector. The first Roberval's chain includes a first fixed pillar fixed to the housing, a plurality of first beams, and a first movable pillar supported by the first fixed pillar via the plurality of first beams. The first beams extends substantially in parallel with each other and in a first extending direction. The first movable pillar is configured to receive a load to be measured. The second Roberval's chain includes a second fixed pillar fixed to the housing, a plurality of second beams, and a second movable pillar supported by the second fixed pillar via the plurality of second beams. The plurality of second beams extends substantially in parallel with each other and in a second extending direction substantially perpendicular to the first extending direction of the plurality of first beams. The second movable pillar is connected to the first movable pillar. The detector is configured to detect the load electrically via a movement of the first movable pillar.


REFERENCES:
patent: 4632198 (1986-12-01), Uchimura
patent: 4690230 (1987-09-01), Uchimura et al.
patent: 4813505 (1989-03-01), S{umlaut over (o )}dler et al.
patent: 5183125 (1993-02-01), Schurr
patent: 5646375 (1997-07-01), Neuman
patent: 5736685 (1998-04-01), Nakajima

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