Electricity: magnetically operated switches – magnets – and electr – Permanent magnet-actuated switches
Reexamination Certificate
2002-01-23
2004-07-06
Donovan, Lincoln (Department: 2832)
Electricity: magnetically operated switches, magnets, and electr
Permanent magnet-actuated switches
C335S153000, C335S207000
Reexamination Certificate
active
06759932
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic sensor switch that is operable in response to external magnetism to turn its contacts on and off, and more particularly, to a magnetic sensor switch of the type that comprises a magnetic sensor responsive to approach of a magnet, electrical contacts, and a driving member for transmitting the movement of the magnetic sensor to the electrical contacts, and is operable in response to the movement of the magnetic sensor to turn the electrical contacts on and off.
2. Description of the Related Art
As is disclosed in Japanese Patent Application Public Disclosure No. hei 6-347559 (347559/1994), for example, a magnetic sensor consisting of a combination of a permanent magnet and a reed switch responsive to magnetism has been heretofore known. As shown in
FIG. 1
, the magnetic sensor disclosed in the Japanese Patent Application Public Disclosure No. 347559/1994 comprises an elongated cylindrical case
71
made of a non-magnetic material, a reed switch
75
disposed in the interior of the case
71
generally in the center thereof, a columnar permanent magnet
73
mounted in the interior of the case
71
at the forward end (left-hand end as viewed in the drawing), a magnetic plate
87
attached to the outer side wall of the enclosure (glass tube in this example)
77
of the reed switch
75
, and a magnetism adjusting permanent magnet
74
mounted at the peripheral area of the glass tube
77
adjacent one end thereof. The two permanent magnets
73
and
74
positioned on the opposite sides of the reed switch
75
are configured such that the opposing sides of the magnets
73
and
74
have the same magnetic polarity. In this example, the magnetic polarities of the opposing sides (the reed switch side) of the two magnets
73
and
74
are set both to be the S magnetic pole.
The reed switch
75
is positioned generally in the center of the case
71
by two spaced rings
76
and
78
both of which are made of heat resistant, electrical insulating material. The root portion of the case
71
is mounted to a sensor mounting base
95
by means of a bushing
91
made of rubber. Lead wires
96
and
99
leading out from reeds
93
and
94
, both being made of a magnetic material, of the reed switch
75
are connected to suitable heat-resistant, insulated wires
89
and
90
, respectively, that extend to the outside through the root portion of the case
71
. As is well known, the forward ends of these reeds
93
and
94
comprise contact portions
79
acting as electrical contacts.
Next, the operation of the magnetic sensor constructed as described above will be briefly explained with reference to
FIGS. 2 and 3
.
FIG. 2
shows magnetic lines of force generated from the magnetic sensor shown in
FIG. 1
when the magnetic sensor is in the standby state in which there is no magnetic substance (object) or magnet in the vicinity around the sensor. From
FIG. 2
, it will be appreciated that there is a very weak magnetic field produced in the vicinity of the contact portions
79
of the reed switch
75
. The distribution of the magnetic lines of force generated from the magnetic sensor during this standby state may be preliminarily adjusted by moving the magnetism adjusting permanent magnet
74
longitudinally of the case
71
. When the magnetic field applied in the vicinity of the contact portions
79
of the reed switch
75
is relatively weak as shown in
FIG. 2
, the contact portions
79
remain open, and hence the reed switch
75
is in the off state.
As a magnetic substance or magnet approaches the vicinity of the magnetic sensor in the standby state, the magnetic field applied to the reed switch
75
changes.
FIG. 3
shows magnetic lines of force generated from the magnetic sensor when two iron balls
97
and
98
being magnetic material approach the vicinity of the forward end of the reed switch
75
. As is apparent from
FIG. 3
, the magnetic field in the vicinity of the contact portions
79
of the reed switch
75
is significantly intensified as compared with that in the standby state. As a result, the reeds
93
and
94
made of a magnetic material magnetically attract and contact each other, and hence the contact portions
79
go to on state. Further, the detailed construction, structure and operation of this magnetic sensor are disclosed in Japanese Patent Application Public Disclosure No. 347559/1994. Accordingly, further description thereof is omitted for purposes of convenience.
This magnetic sensor includes the magnetic plate
87
disposed in the vicinity of the contact portions
79
and the magnetism adjusting permanent magnet
74
positioned at the one end of the reed switch
75
near the base of the case, in addition to the permanent magnet
73
, so that the magnetic field produced by the permanent magnet
73
in the vicinity of the contact portions
79
of the reed switch
75
may be adjusted by the magnetic plate
87
and the magnetism adjusting permanent magnet
74
to control the dynamic or operating sensitivity of the contact portions
79
of the reed switch
75
.
As discussed above, this magnetic sensor is configured such that the magnetic field produced mainly by the permanent magnet
73
is applied directly to the reed switch
75
and the contact portions
79
of the reed switch
75
is controlled to turn on and off by that the applied magnetic field is varied by a magnetic substance or a magnet approaching the magnetic sensor. Otherwise stated, this is a magnetic switch of the type in which the magnetic field applied directly to the reed switch
75
is varied by an approaching magnetic substance or magnet whereby the opposing reeds
93
and
94
of the reed switch
75
are attracted to each other so that the contact portions
79
are controlled to the on position.
It is thus to be understood that the switch of this magnetic sensor would not be turned on unless there occurs a change in the magnetic field to some extent. Further, this magnetic sensor will be turned on, irrespective of the polarity of a magnet approaching the magnetic sensor and even if the approaching object is a magnetic substance or object rather than a magnet. For this reason, the illustrated prior art magnetic sensor can not be used in applications where the switch of the magnetic sensor is required to be turned on and off only when it is approached by a particular magnetic pole of a magnet.
In addition, because the prior art magnetic sensor as described above utilizes a reed switch, it has the disadvantages that the cost of manufacture is correspondingly increased and moreover, in the event of failure of the contact portions, the entire reed switch must be replaced, which leads to an increase in the maintenance cost.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a magnetic sensor switch that does not utilize a switch having its contact portions to which a magnetic field is directly applied such as a reed switch.
Another object of the present invention is to provide a magnetic sensor switch in which its magnetic sensor causes its electrical switch to turn on and off in response to the approach of a particular magnetic pole of a magnet to the magnetic sensor.
In order to accomplish the foregoing objects, in one aspect of the present invention, a magnetic sensor switch is provided which comprises: an elongated magnetic sensor having magnetic poles contrary to each other at opposite ends thereof and mounted for rotation through predetermined angles in clockwise and counter-clockwise directions; a movable contact piece including a pair of contact blades; a pair of fixed contact pieces located in opposition to the pair of contact blades of the movable contact piece, respectively; a common contact piece electrically connected to the movable contact piece; a driving member transmitting the movement of the magnetic sensor to the movable contact piece; an auxiliary magnet located on a longitudinal extension line of the magnetic sensor and mounted such that it can be moved toward and away
Donovan Lincoln
Gallagher & Lathrop
Lathrop, Esq. David N.
Sagami Electric Co., Ltd.
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