Measuring and testing – Liquid level or depth gauge – Float
Reexamination Certificate
1999-01-20
2001-09-18
Williams, Hezron (Department: 2856)
Measuring and testing
Liquid level or depth gauge
Float
C073S305000, C073S314000, C073SDIG005, C073S319000
Reexamination Certificate
active
06289731
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the invention
This invention relates to a liquid level detector, particularly to a liquid level detector that performs non-contact and non-friction measurement with advantages in excellent durability, simple structure, high resolution, low cost, and easy fabrication.
2. Description of the prior art
As shown in
FIG. 1
, a prior liquid level detector mainly comprises a main body
10
, a float ball
12
, a connecting rod
14
, a sensing head
16
, a Ni—Cr coil
18
, a pivot
20
, and a signal wire
22
. A circular casing is provided at lower end of the main body
10
for accommodating the Ni—Cr coil
18
, which is formed by winding Ni—Cr wire on a Bakelite plate, and the pivot
20
is positioned at the center portion of the circular casing, wherein the connecting rod
14
is passing through the pivot
20
and attached thereto; and one end of the connecting rod
14
is extended and pivot-jointed with the float ball
12
, while the other end of the connecting rod is coupled with the sensing head
16
, which is propped by a spring to keep in touch with the arc shaped Ni—Cr coil
18
. When the prior liquid level detector is applied to somewhere, say an oil tank, the float ball
12
is floating in the oil and the sensing head
16
is touching the Ni—Cr coil
18
. Position of the floating ball
12
ascends or descends according to the liquid level to drive the sensing head
16
fixed at the connecting rod
14
to slide and contact on the Ni—Cr coil. Any change in impedance owing to displacement of the sensing head
16
will be transmitted via a signal wire
22
for being read on a display apparatus that will display data of liquid quantity. The defects of the abovesaid prior liquid level detector shall include: a complicated structure for applying the float ball
12
, the connecting rod
14
, the sensing head
16
, the Ni—Cr coil
18
, etc; high cost; shortened durability due to possible fracture of the Ni—Cr coil
18
that is whetted in the long term by touching of the sensing head
16
; non-uniformity of the arc shaped Bakelite plate that may cause a clearance problem between the sensing head
16
and the Ni—Cr coil
18
—the detector may fail to detect if clearance is too big, or, the coil may be fractured owing to friction if the clearance is too small; when the detector being applied under a quaking condition, such as in a mobile car, wherein the detector may be impaired or malfunctioned due to out of order of internal components.
In view of the above imperfections, the inventor is benefited with years of manufacturing experience in related field to have an improved construction of this invention developed and proposed.
SUMMARY OF THE INVENTION
This invention is proposed to provide a liquid level detector, wherein a float ball is moving up or down in an internal tube without substantial contact with an external coil. The non-contact induction can avoid any fracture of the coil for prolonging the durability and refrain from quakes for keeping at an integral, usable and precise condition.
Another object of this invention is to provide a liquid level detector, which avails itself of the movable float ball in the internal tube for mutual induction with the external coil for obtaining a high resolution and more precise result by reading inductance values at different positions.
Another more object of this invention is to provide a liquid level detector without complicated components, so that the structure can be simplified for easy fabrication and low cost purposes.
A further object of this invention is to provide a liquid level detector, wherein the induced signal of the float ball and the coil can be converted internally into a voltage value to drive a display apparatus directly, or can be converted by an external conversion circuit.
A further more object of this invention is to provide a liquid level detector, wherein the length of the internal tube and coil can be changed to meet some special requirement or usage in order to enlarge its application scope.
A liquid level detector of this invention backed with the above described advantages comprises: an internal tube, a coil wound on the internal tube, an external tube, a float ball, a base, and an upper fixing socket, etc, wherein a magnetic material coated float ball is disposed in the coil wound internal tube, which is enclosed by an external tube. A plurality of air apertures and a thread portion are formed at upper end of the internal tube, where the thread portion is commensurate with a tapped hole in the upper fixing socket. The bottom end of the internal tube is coupled with the base, which is provided with a plurality of infiltration holes, while those two ends of the external tube are glue-sealed to form an isolated space for protection of the coil outside the internal tube. A circular wall is provided at top end of the upper fixing socket for reception of a printed circuit board. When detecting, the float ball is moving up or down according to liquid level, and the mutual inductance change in the coil will be converted by the printed circuit board in the upper fixing socket into voltage value to be displayed on the external display apparatus.
REFERENCES:
patent: 3024659 (1962-03-01), White
patent: 4845986 (1989-07-01), Hayashi et al.
patent: 5718146 (1998-02-01), Liang
patent: 5848549 (1998-12-01), Nyce et al.
patent: 5862702 (1999-01-01), Liang
Loo Dennis
Pro-Techtor Inter-national Services
Williams Hezron
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