Electricity: magnetically operated switches – magnets – and electr – Electromagnetically actuated switches – Vacuum or hermetically sealed type
Reexamination Certificate
2000-03-27
2001-09-18
Barrera, Ramon M. (Department: 2832)
Electricity: magnetically operated switches, magnets, and electr
Electromagnetically actuated switches
Vacuum or hermetically sealed type
C335S202000, C335S205000
Reexamination Certificate
active
06292074
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a switch unit, particularly a reed switch unit to be utilized for detecting a liquid level in a reservoir tank in a master cylinder.
A brake system employed in a driving automobile is so constructed that a brake liquid circulates in a hydraulic circuit which is formed between the master cylinder adapted to be connected to a brake pedal or the like and a wheel cylinder adapted to be connected to a wheel brake. To the master cylinder is fitted a reservoir tank in which the brake liquid is stored to be supplied to the master cylinder.
In order to assure an accurate operation of the brake system, it is necessary that more than a determined amount of the brake liquid is always stored in the reservoir tank. For this reason, there is provided in the reservoir tank a liquid level detecting sensor for detecting the liquid level of the brake liquid stored therein, in order to issue a warning to a driver, etc. when the brake liquid has decreased below a prescribed amount.
The liquid level detecting sensor consists of a float which moves up and down with a vertical movement of the liquid level of the brake liquid and has a permanent magnet, and a reed switch unit having a reed switch for detecting the vertical movement of the float. The reed switch is an electric component of such a structure that its contacts are adapted to be closed when the permanent magnet in the float approaches the reed switch.
A conventional reed switch unit is shown in
FIGS. 1 and 2
.
The reed switch unit
10
is composed of a reed switch
11
and a unit body
12
which is formed of a synthetic resin and on which the reed switch unit
11
is mounted.
The reed switch
11
is so constructed that a contact part
14
of which contacts are adapted to be closed in association with an approach of the permanent magnet is sealed inside a glass tube
16
. In the glass tube
16
is sealed an inert gas (for example, nitrogen gas) in order to prevent oxidation, frosting, etc.
The glass tube
16
is provided at its opposite ends with lead portions
18
which are adapted to be connected to the contact part
14
.
The unit body
12
formed of a synthetic resin comprises a coupler part
12
a
which can be connected to another electric circuit on the right hand in the drawing, and a switch receiving part
12
b
on which the reed switch
11
is adapted to be mounted on the left hand in the drawing.
The switch receiving part
12
b
is provided with metal terminal members
20
to be connected with the respective lead portions
18
,
18
of the reed switch
11
. Each of the terminal members
20
is formed of a plate-like member provided with a slit
22
which can grasp the lead portion
18
and projecting upward from the switch receiving part
12
b
. The terminal members
20
are respectively connected to coupler terminals
23
which are shown by a dotted line in the coupler part
12
a.
The reed switch
11
is fitted to the unit body
12
and fixed by soldering after both the lead portions
18
,
18
have been grasped in the slits
22
of the terminal members
20
. Because the lead portions
18
and the terminal members
20
are fixed by soldering, both physical fixations and electrical connections of the lead portions
18
can be assured.
In order to help positioning of the glass tube
16
when the reed switch
11
is fixed to the terminal members
20
, the unit body
12
has, at a position where the glass tube
16
is to be located, ribs
24
which are integrally formed with the unit body
12
and upwardly project from the switch receiving part
12
b
so as to surround side faces of the glass tube
16
.
By providing the ribs
24
, when the reed switch
11
is mounted, the glass tube
16
is first placed between the ribs
24
, and then fixed by soldering after the lead portions
18
are grasped in the slits
22
of the terminal members
20
. Therefore, the reed switch
11
is securely fixed at a determined position (For example, see a Japanese Patent Unexamined Publication No. Hei.7-220817).
As described above, it has been a conventional manner that the lead portions and the terminal members are fixed by soldering, when the reed switch is mounted on the unit body.
However, there is such a problem that in case the soldering should be conducted at two points at the same time when the lead portions and the terminal members are connected, it is difficult to solder at the two points at the same time because a stress occurs in a direction of pulling the glass tube. There is a further problem that the soldering takes a long heat introducing time into components to be connected, and a line tact in the process will be extended. Moreover, after the soldering has been carried out, the solder will be inevitably splashed, and in case that the solder has entered between the glass tube and the unit body, there will be a fear that the glass tube may be broken. This will lead to a decrease in productivity because scattering of the solder must be detected and so on.
Further, there is still another problem that since the soldering takes a long heat introduing time, the heat will be easily conducted to the glass tube or the connected parts which are in contact with the lead portions, and the inert gas in the glass tube will escape.
Further, a quality control is difficult with the soldering, because it results in a faulty joint in case where the heat introducing time is too short or the faces to be connected are not clean.
In addition to this, a conventional reed switch unit for the reservoir tank has been also known as disclosed, for example, in Japanese Patent Unexamined Publication No. Hei.4-325362.
The conventional reed switch unit for a reservoir tank to be mounted on the reservoir tank is used for storage of operating liquid or the like in a master cylinder. The reed switch unit is contained in a switch housing formed in the reservoir tank in isolation from an interior thereof and comprises a reed switch, a first and a second terminal members and a coupler part.
The first and a second terminal members respectively have a first and a second connecting terminals respectively connected to a first and a second reed parts of the reed switch, and a first and a second coupler terminals at their respective opposite ends. The coupler part is formed of a synthetic resin and connected by molding to an intermediate portion between the first and the second terminal members to receive the first and the second coupler terminals.
In the conventional reed switch unit for the reservoir tank, because the first and the second terminal members to which the coupler part of the synthetic resin is connected by molding are individually manufactured, it has been difficult to accurately set the first and the second terminal members at respective fixed positions in metal molds on occasion of molding the coupler part. This has been a drawback when cut-down of the manufacturing cost is intended.
SUMMARY OF THE INVENTION
Accordingly, this invention has been made in order to solve the above described problems.
It is an object of a first aspect of the present invention to provide a reed switch unit in which the productivity is enhanced and the quality is improved by mounting the reed switch on the unit body without employing the soldering process.
The object can be attained by a reed switch unit for detecting a liquid level in a reservoir of a master cylinder, according to the present invention, which comprises a reed switch including a contact part which is sealingly contained in a glass tube, and lead portions which axially extend from opposite ends of the glass tube, and a unit body provided with terminal members for respectively supporting the lead portions so as to be electrically connectable thereby to fix the reed switch is characterized in that the lead portions and the terminal members are connected with each other by means of a resistance welding.
By employing this construction, the line tact will be shortened, because the heat introducing time into the components to be connected is shorter as compared with th
Amano Tsutomu
Hanaoka Mitsuhiro
Ohta Kazuhiro
Shimizu Atsushi
Barrera Ramon M.
McGuireWoods LLP
Nissin Kogyo Co. Ltd.
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