U.S. patent number 3,912,894 [Application Number 05/464,730] was granted by the patent office on 1975-10-14 for convertible switch.
This patent grant is currently assigned to Westinghouse Electric Corporation. Invention is credited to Walter J. Kellogg, John H. Mullen.
United States Patent |
3,912,894 |
Mullen , et al. |
October 14, 1975 |
Convertible switch
Abstract
A convertible electric switch characterized by relatively
movable contacts movable between open and closed positions. A
contact carrier carrying one of the contacts and having a hole with
a pair of opposite sides forming cam-following surfaces extending
transversely to the direction of movement of the contact carrier. A
contact actuator extending through the hole and having a pair of
cam surfaces located at angularly disposed positions on the
actuator to effect movement of the movable contact to one of the
open and closed positions. The contact actuator is rotatable within
the hole to present one or the other of the pair of cam surfaces to
one or the other of the pair of cam follower surfaces.
Inventors: |
Mullen; John H. (Beaver,
PA), Kellogg; Walter J. (Beaver, PA) |
Assignee: |
Westinghouse Electric
Corporation (Pittsburgh, PA)
|
Family
ID: |
23845016 |
Appl.
No.: |
05/464,730 |
Filed: |
April 26, 1974 |
Current U.S.
Class: |
200/533; 200/280;
200/534 |
Current CPC
Class: |
H01H
11/0012 (20130101); H01H 3/001 (20130101) |
Current International
Class: |
H01H
11/00 (20060101); H01H 3/00 (20060101); H01H
003/42 () |
Field of
Search: |
;200/153LA,4R,280 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Schaefer; Robert K.
Assistant Examiner: Smith; William J.
Attorney, Agent or Firm: Johns; L. P.
Claims
What is claimed is:
1. A convertible switch comprising an insulating housing, fixed and
movable contacts movable between open and closed positions,
mounting means mounting the movable contact between open and closed
positions and comprising a contact carrier having a pair of spaced
cam follower surfaces extending transversely to the direction of
movement of the movable contact, a contact actuator having one cam
surface on one side thereof and another cam surface on the other
side thereof, the cam surfaces being operable on opposite sides of
the contact carrier, the contact actuator being movable
longitudinally to effect movement of the contact carrier, the one
cam surface moving the contact carrier to one of the open and
closed positions of the contacts when the actuator is moved in one
direction, the other cam surface moving the contact carrier to the
other of the open and closed positions of the contacts when the
actuator is moved in the other direction, the contact actuator also
being rotatable to turn the cam surfaces to diametrically opposite
sides of the actuator, the contact carrier being biased in one
direction against the contact actuator, and the actuator being
movable against the cam surfaces to effect movement of the movable
contact to one of the open and closed positions.
2. The convertible switch of claim 1, in which the contact carrier
is movable longitudinally in a direction that is transverse to the
movement of the contact actuator.
3. The convertible switch of claim 2, in which the contact carrier
comprises aperture means through which the contact actuator
extends.
4. The convertible switch of claim 3, in which the aperture means
is a hole and the cam follower surfaces are disposed along opposite
sides of the hole.
5. The convertible switch of claim 4, in which the contact actuator
is rotatable to present one or the other of the cam surfaces to one
or the other of the cam follower surfaces.
6. The convertible switch of claim 2, in which the mounting means
is biased in one of the open and closed positions.
7. The convertible switch of claim 6, in which the mounting means
is biased in the open position.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to electrical switching devices and, more
particularly, to switches which are convertible from normally open
to normally closed conditions.
2. Description of the Prior Art
Selective switches of the cam type are particularly useful in
control switching programs. U.S. Pat. Nos. 2,991,343, 3,539,736,
and 3,675,168 disclose cam operated switches of the type generally
involved in this invention. An advantage of such switches is that a
switch actuator or plunger on which the cams are mounted moves
transversely to the direction of movement of the contacts, thereby
minimizing contact bounce which heretofore has been a source of
arcing between contacts.
Notwithstanding various attempts to eliminate arcing, it is
recognized that the possibility or arcing and resultant welding
between contacts is an ever present problem. The disadvantage of
that problem is not avoided by most switches disclosed in the prior
art, because the cam operation is useful only for moving the cams
against a kick-out spring which does not have sufficient force to
separate contacts if they are welded together. Thus, selective
switches of the cam type would be more foolproof if the cam
surfaces were also used to separate the contacts when necessary
such as where they weld together.
SUMMARY OF THE INVENTION
Generally, in accordance with this invention it has been found that
the foregoing problem may be satisfied by providing a convertible
switch comprising an insulating housing, fixed and movable contacts
within the housing and movable between open and closed positions,
mounting means mounting the movable contacts between open and
closed positions and comprising a contact carrier having aperture
means including a pair of spaced cam follower surfaces disposed
along opposite sides of the aperture means, the cam follower
surfaces extending transversely to the direction of movement of the
movable contacts, a contact actuator having diametrically opposite
pair of cam surfaces which are movable against one of the spaced
cam follower surfaces to effect movement of the movable contact to
one of the open and closed positions, the contact actuator
extending through the aperture means and being rotatable to present
one or the other of the cam surfaces to one or the other of the cam
follower surfaces, and the cam actuator being biased longitudinally
to a position corresponding to the bias position of the contact
carrier.
The advantage of the switch of this invention is that it is not
only convertible from normally open to normally closed positions by
rotating the cam actuator or plunger 180.degree. without
disassembling any part of the switch, but it is operable to
separate the contacts forcibly if the contacts are welded
together.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a vertical sectional view, taken on the line I--I of FIG.
2, and showing the contacts in the open position;
FIG. 2 is a vertical sectional view taken on the line II--II of
FIG. 1;
FIG. 3 is a horizontal sectional view taken on the line III--III of
FIG. 1;
FIG. 4 is a view similar to FIG. 2 of another embodiment of the
invention; and
FIG. 5 is an enlarged plan view taken on the line IV--IV of FIG.
1.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In FIGS. 1 and 2 a convertible switch is generally indicated at 5
and it comprises a housing 7, a contact assembly generally
indicated at 9, and a contact actuator or plunger 11. The housing 7
is composed of electrically insulating material and encloses a
chamber 13 in which the operating parts of the switch are located.
The housing also comprises a plunger-receiver aperture 15, an
access opening 17, and a hole 19, all of which communicate with the
chamber 13.
The contact assembly 9 comprises a pair of stationary contacts 21,
movable contacts 23, and a contact carrier 25 which is slidably
mounted in the chamber 13 for moving the contacts 21, 23 between
open and closed positions. The stationary contacts 21 are mounted
on similar conductors 27 which extend through the housing 7 and are
provided with external terminals 29.
The movable contacts 23 are disposed at opposite ends of a bridging
contact member 31 which extends between the space pair of
stationary contacts 21. The member 31 extends through a window 33
at one end of the contact carrier 25. In the window a compression
spring 35 holds the associated bridging contact member 31 in place
to provide a resilient contacting engagement between the
corresponding movable contacts 23 and the stationary contacts 21 in
a manner similar to that set forth in U.S. Pat. No. 3,296,567. A
spring 37 is disposed between a shoulder 39 on the plunger and the
housing to maintain the contacts 21, 23 in the open position.
However, if the spring 37 is a tension spring, the contacts 21, 23
may be maintained in the closed position.
As shown in FIG. 3 the contact carrier 25 comprises opening means
or hole 41 through which the plunger 11 extends. Inasmuch as the
plunger 11 comprises cam surfaces 43 and 45, opposite surfaces 47
and 49 of the hole 41 are cam follower surfaces which engage the
cam surfaces 43 and 45 when the plunger 11 is operated.
The contact actuator or plunger 11 is an elongated member, the
upper end portion of which extends through the aperture 15 of the
housing 7 where it is retained by suitable biasing means such as a
compression spring 51. The cam surfaces 43 and 45 are located at
diametrically opposite positions on the plunger and at
longitudinally spaced positions thereof. The plunger 11 is movable
longitudinally as well as rotatably as indicated by the arrow 53
(FIG. 1).
In operation, when the plunger 11 is depressed against the spring
51, the surface 49 of the contact carrier 25 follows the inclined
cam surface 45 under the influence of the spring 37 and the
inclined cam surface 43 engages the cam following surface 41 to
move the contact carrier 25 to the broken line position, whereby
the movable contacts 23 close a circuit through the stationary
contacts 21 as shown by the broken line positions 23.
When the plunger 11 is rotated 180.degree., the inclined cam
surfaces 43 and 45 are disposed in the broken line positions as
shown in FIG. 1. Thus, when the plunger 11 is in the uppermost
position, under the force of the spring 51, the contact carrier is
in the broken line position 25 with a circuit closed through the
contacts 21, 23. When the plunger 11 is moved against the spring
51, the cam surface 45 moves from its broken line position and the
cam surface (broken line) 43 engages the cam follower surface 49
and moves the contact carrier 25 to the contact open position
against the pressure of the spring 37. If for any reason the
contacts 21, 23 are welded together, the cam surface 43 may be used
to force them apart.
Moreover, reversing the position of the plunger 11 from the solid
line position to the broken line position of the cam surfaces 43,
45, reverses the condition of the switch 5 from a normally open to
a normally closed condition, as shown more particularly in FIG. 5
the top surface of the plunger may be provided with an indicator or
arrow 55 for indicating whether the plunger is in the normally
closed or normally open position with respect to the contact
carrier 25.
The embodiment of the invention shown in FIG. 4 differs from that
of FIG. 3 in that the movable contacts 23a and stationary contacts
21a are reversed and shown in a closed circuit condition against
the pressure of the spring 37. Thus the plunger 11 is in the
position shown in FIG. 1 with the cam surface 45 in the solid line
position. Manifestly, lowering of the plunger 11 causes separation
of the contacts 21a, 23a under normal conditions in response to
pressure of the spring 37. If the contacts 21a, 23a are slightly
welded together, continued depression of the plunger 11 brings the
cam surface 43 into contact with the cam follower surface 47 and
thereby forces the contacts 21a, 23a apart. Rotation of the plunger
11 to the dotted line position of the cam surfaces 43, 45 enables
closing of the circuit through the contacts 21a, 23a. The indicator
55 (FIG. 5) does not obtain for the embodiment of the invention
shown in FIG. 4.
Accordingly, the convertible switch of this invention provides for
simple conversion of the switch from a normally open to a normally
closed position without the necessity of removing or adding parts
or changing wiring. The convertible switch also provides for means
for readily separating the contacts where they are welded
together.
* * * * *