U.S. patent number 3,590,647 [Application Number 04/784,736] was granted by the patent office on 1971-07-06 for snap-action switch-operating mechanism.
This patent grant is currently assigned to Sterer Engineering and Manufacturing Company. Invention is credited to Carl Eugene Monnich.
United States Patent |
3,590,647 |
Monnich |
July 6, 1971 |
SNAP-ACTION SWITCH-OPERATING MECHANISM
Abstract
A switch-actuating mechanism is designed to give a snap action
to either make or break an electrical circuit in a fast, positive
manner. The switch is held firmly open or closed until the time of
actuation is reached and is thus insulated from the adverse effects
of shock and vibration. The operating mechanism is especially
adapted to operate overcenter types of switches wherein the switch
contacts are subject to chatter when near the center of shifting
position.
Inventors: |
Monnich; Carl Eugene (Granada
Hills, CA) |
Assignee: |
Sterer Engineering and
Manufacturing Company (Los Angeles, CA)
|
Family
ID: |
25133373 |
Appl.
No.: |
04/784,736 |
Filed: |
December 18, 1968 |
Current U.S.
Class: |
74/80;
74/100.1 |
Current CPC
Class: |
H01H
5/00 (20130101); F16H 35/14 (20130101); H01H
35/38 (20130101); Y10T 74/18896 (20150115); Y10T
74/18496 (20150115) |
Current International
Class: |
H01H
35/38 (20060101); F16H 35/00 (20060101); H01H
35/24 (20060101); H01H 5/00 (20060101); F16H
35/14 (20060101); F16h 021/44 () |
Field of
Search: |
;74/100 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Mattern, Jr.; Fred C.
Assistant Examiner: Ratliff, Jr.; Wesley S.
Claims
I claim:
1. A bidirectional snap-action-operating mechanism for controlling
movement of a switch are or the like between two positions,
comprising:
a fixed pivot;
a lever mounted to swing about the pivot and having means
permitting bodily movement of the lever relative to the pivot;
a switch arm engaged by and moved by said lever;
a control member mounted for bidirectional movement in response to
an externally applied force and having a surface parallel to the
direction of bidirectional movement engageable with the lever in a
first position in which the lever engages and holds the switch arm
in a first position;
a first biasing means normally urging the control member into a
position in which it engages the lever on said surface;
and a second biasing means biasing the lever toward said engagement
with the control member and shifting the lever bodily away from the
switch arm and about the pivot into a second position when travel
of the control member moves said surface thereon out of contact
with the lever, whereby the switch arm is released by the lever to
move to an alternate position.
2. A snap-action-operating mechanism as in claim 1 that also
includes
stop means limiting swinging motion of the lever about the pivot
under the urging of the second biasing means.
3. A snap-action-operating mechanism as in claim 1 in which the
control member is mounted for rectilinear movement.
4. A snap-action-operating mechanism as in claim 1 in which the
control member is a rotor mounted for angular movement.
5. A snap-action-operating mechanism as in claim 1 in which the
control member is provided with a shoulder at one end of said
surface thereon, said shoulder engaging the lever on the return
movement of the control member to rock the lever and return the
lever to engagement with said surface.
6. A pressure-responsive switch mechanism comprising:
a switch having a contact shift arm;
an operating member movable in response to an externally applied
pressure and having a rectilinear surface;
a switch actuating lever engageable with the shift arm and having a
rectilinear surface engageable with the first said rectilinear
surface;
pivot means mounting the lever for combined angular and bodily
shifting movement relative to the pivot;
a first biasing means urging the operating member to a position
engaging the actuating lever;
and a second biasing means urging the lever away from the shift arm
and toward the operating member.
7. A pressure-responsive switch mechanism as in claim 6 in which
the operating member has a surface parallel to the direction of
member travel engaged by the actuating lever and terminating
abruptly at a shoulder whereby the actuating lever is displaced in
a direction away from the shift arm when the operating member
disengages the actuating lever by movement in response to applied
pressure and in opposition to the first biasing means.
8. A pressure-responsive switch mechanism as in claim 7 in which
the shoulder on the operating member engages the actuating lever
after said displacement and during subsequent return movement of
the control member by the first biasing means to return the lever
to its initial position.
9. A pressure-responsive switch mechanism as in claim 8 in which
initial movement of the actuating lever to its initial position is
angular movement about the pivot means.
10. A snap-action-operating mechanism as in claim 1 in which the
lever has an opening wide enough in one dimension to snugly receive
the pivot and permit swinging movement of the lever about the
pivot, the opening being elongated transversely of said dimension
to permit the lever to move bodily relative to the pivot;
the switch arm engaging the lever at a position to be moved by said
bodily movement of the lever.
Description
BACKGROUND OF THE INVENTION
The present invention relates generally to electrical
switch-operating mechanism and is more especially concerned with
mechanism adapted to give a positive mechanical action to an
overcenter type of switch.
A typical application of the present invention is to a
pressure-responsive electrical switch, although it will be realized
that in the broad aspect of the invention, the external force or
quantity being monitored is immaterial. It is customary in a
pressure-responsive switch to open and close the switch contacts
with an overcenter type of mechanism. The switch is generally
operated by a movable member which moves gradually over a
predetermined range of travel in response to fluid pressure,
although it may equally respond to some other external physical
quantity or value, such as mass, flow rate, temperature, mechanical
movement, or the like.
In the usual designs of an overcenter type of switch, as the switch
approaches its actuation point, the force holding the electrical
contacts together decreases progressively until the switch snaps
overcenter. As the switch approaches the center or shift point, the
low value of the force acting to hold the contacts together makes
them vulnerable to chattering from external vibration or shock.
This same condition is also true of known switch designs which
employ an overcenter device to shift the switch contacts and which
is actuated by an overcenter device such as the Belleville washer.
In this arrangement, the actuation device is subject to chatter in
response to vibration or shock as it approaches the overcenter
shift point.
It is obvious that chatter of the contacts has many disadvantages.
Not only do the contacts wear or possibly stick from arcing but
also false or premature signals are given out by the switch. If the
switch is in a system where it is held for prolonged periods just
short of the actuation point, then fatigue and wear of the
actuating device for the switch contacts often results.
Hence, it is a general object of the present invention to provide a
switch-actuating mechanism which eliminates the adverse results of
shock and vibration on a switch where the contacts are shifted by
means of an overcenter type of movement.
It is a further object of the present invention to provide a
switch-operating mechanism which effects a positive mechanical
operation of an overcenter type of switch at a predetermined point
but which holds the contacts firmly open or closed until the point
of actuation is reached.
A further object of the present invention is to provide a
switch-operating mechanism of novel design which is particularly
adapted to a pressure response and which effects positive operation
of the switch at a predetermined point or value of the
pressure.
SUMMARY OF THE INVENTION
The switch-operating mechanism of the present invention is a
snap-action mechanism capable of operating the switch in either of
two directions of travel and comprises a fixed pivot, a lever
mounted to swing about the pivot, an operating or control member
mounted for bidirectional movement in response to some measured
value, a first biasing means normally urging the operating member
into a position in which it engages the lever, and a second biasing
member biasing the lever toward engagement with the operating
member. When the operating member moves in response to external
pressure or other measured value, there is initially no movement of
the lever since the lever and operating member engage each other on
surfaces which are held parallel to the direction of movement of
the operating member. However, the surface on the operating member
terminates in a shoulder; and when the operating member moves
sufficiently to drop the lever off the shoulder, the second biasing
means suddenly shifts the lever about the fixed pivot and away from
the switch into a second position which allows the overcenter
mechanism of the switch to operate to shift the contacts.
Upon return movement of the operating member, the lever swings
about the fixed pivot until it assumes a position such that the
second biasing means can snap the lever back to its initial
position, whereupon the switch arm is again actuated suddenly to
return the switch contacts to their original positions. Swinging
motion of the lever about the pivot under the urging of the second
biasing means is limited by a fixed stop means.
DESCRIPTION OF THE DRAWING
The present invention will be more readily understood by reference
to the following description and to the annexed drawing, in
which:
FIG. 1 is a longitudinal median section of a pressure-actuated
switch embodying a preferred form of the present invention;
FIG. 2 is a transverse section on line 2-2 of FIG. 1;
FIG. 3 is a fragmentary diagrammatic view illustrating two extreme
positions of the lever reached in response to travel of the control
member illustrating on and off positions of the switch;
FIG. 4 is a diagrammatic view similar to FIG. 3 illustrating an
intermediate position of the lever on the return stroke of the
operating member; and
FIG. 5 is a diagrammatic view illustrating a variational form of
the invention.
DESCRIPTION OF A PREFERRED EMBODIMENT
Referring now to the drawing, and particularly to FIGS. 1 and 2, it
will be seen that the pressure-responsive switch indicated
generally at 10 is enclosed in a housing having two parts, a base
11 and a cuplike enclosure 12. The two parts are joined together in
any suitable manner, as by a threaded connection at 14. Base 11 is
provided with a threaded coupling 15 for mounting the valve on the
wall of a vessel containing fluid under pressure, the end of the
base being open for unrestricted access to the fluid under
pressure.
Base 11 has a center post or guide 16 upon which piston 17 is
slidably mounted. As will be more fully apparent, piston 17 is the
control or actuating member which moves in response to fluid
pressure to actuate the switch.
Center guide 16 has a central passage 18 which extends axially of
the full length of the guide post in order to introduce fluid under
pressure into the interior of piston 17. This pressure fluid
applies a force of external origin to the piston. A fluidtight
connection between the post and the piston skirt is provided by
suitable sealing means, such as O-ring 20.
A biasing means in the form of compression spring 22 is provided
inside the housing. One end of spring 22 bears against a flange on
piston 17 while the other end of the spring bears against a movable
abutment ring 24. The cup portion 12 of the housing is provided
with a plurality, typically three, of adjustment screws 25 which
are threaded into the wall of housing section 12 and bear at their
inner ends against abutment ring 24. By means of screws 25, the
position of ring 24 can be adjusted to change the loading of the
biasing spring 22 against the piston 17 and this in turn determines
the external pressure at which piston 17 effects operation of the
switch. As will be seen, the point in the piston travel at which
actuation takes place does not change by moving abutment 24.
The forward end of piston 17 is surrounded by sleeve 28 which is
held locked in place in the housing by a transverse pin 29. Sleeve
28 has a longitudinally extending slot 30 which is crossed by a
transversely extending pivot pin 31. Mounted in slot 30 to rock
about pivot 31 is lever 33 which is shown in FIG. 1 as being in
engagement with pin 34. This pin is the operating arm of electrical
switch 35 which may be of any suitable design. Since any one of a
wide variety of commercially available overcenter-type switches may
be used, the switch is not shown in detail. However, for purposes
of description, it will be assumed that operating pin 34 when in
the raised position of FIG. 1 places the switch contacts in the
closed position and when lowered (FIG. 4) places them in the open
position. From the switch, conductors 35a go to a connector mounted
on the housing.
When in the retracted position, piston 17 holds lever 33 in the
raised position of FIGS. 1 and 3 by engagement with lever 33. The
forward or leading end of piston 17 has an enlarged end providing a
cylindrical surface 36 which engages surface 37 on the underside of
the lever. At the rear or left-hand end, surface 36 terminates
abruptly in shoulder 38. Lever 33 has an angular shoulder at 44
(FIG. 3) at the end of surface 37. This shoulder cooperates with
piston shoulder 38 in a manner that will be described.
Centrally of its length, lever 33 has an opening 46 through which
passes pivot 31. Opening 46 is elongated in a direction to permit
bodily movement of the lever, to a limited extent, toward piston 17
but otherwise pivot 31 in the opening restrains the lever to
angular movement about the pivot. One end of opening 46 is
preferably rounded, as shown, to provide bearing against the pivot
pin. The upper edge or external surface of lever 33 has a portion
47 which is a circular arc concentric with the axis of pivot 31
when the lever is seated in the upper end of the opening 46. Pin 34
which operates the contacts of switch 35 is in engagement with
surface 47.
The cylindrical surface on the end of piston 17 is concentric with
piston axis 40 and consequently any element of the cylindrical
surface is parallel to axis 40. Surface 37 on the lever is straight
and when lever 33 is in the raised position shown in solid lines in
FIG. 3 and in contact with piston surface 36, surface 37 on the
lever is placed parallel to the direction of movement of piston 17.
Accordingly, piston movement from the initial or rest position
designated 17a to the advanced position shown in broken lines and
designated as 17b produces no movement of the lever. The two
surfaces 36 and 37 merely slide one on the other, and there is no
movement of lever 33 away from the raised position until piston 17
has advanced sufficiently that lever surface 37 passes off the
cylindrical surface 36 at 38. This happens when the piston has
advanced to the position 17b, and disengagement of the two surfaces
allows the lever suddenly to drop behind shoulder 38. Lever 33 is
now drawn downwardly to the broken-line position of FIG. 3, by the
action of garter spring 41, which is confined in an annular groove
in the periphery of sleeve 28. Garter spring 41 is a coil spring
maintained in tension. The two ends of the spring are connected by
a length 41a of the spring wire which passes over lever 33 at one
side of pivot pin 31. Spring 41 acts as a biasing means which pulls
downwardly on the left-hand end of lever 33, urging surface 37 on
the lever toward and into contact with piston surface 36; but when
the piston and lever are disengaged as just explained, the biasing
action of spring 41 is then able to rock lever 33 in a
counterclockwise direction.
Fixed pivot 31 is within elongated opening 46 in lever 33. The
width of this opening is equal to the diameter of the pivot but it
has a length transverse to the direction of piston travel greater
than the diameter of the pivot pin. This opening is preferably,
though not necessarily, open to one side of the lever, as shown,
for ease of assembly of the parts and also to provide conveniently
an angular corner at shoulder 44 at the forward end of guide
surface 37. The configuration of this shoulder in cooperation with
piston shoulder 38 allows the lever to move with a sudden snap
action from the normal full-line position to the broken-line
position of FIG. 3 under the influence of spring 41 when the piston
and lever are disengaged.
When disengaged from piston surface 38, lever 33 is moved bodily
toward piston 17 by spring 41 and with respect to the fixed pivot
31 because of the elongated nature of the opening 46 in the body. A
stop pin 45 is provided at the right hand of the lever; and in the
construction shown, this forms a fulcrum about which the lever
rocks when in contact with the pin, under the biasing action of
spring 41. After piston 17 has advanced from the normal or starting
position at 17a toward the right in the drawing sufficiently to
disengage lever 33, as at 17b, the piston can continue movement in
this direction without causing any movement of the operating lever.
The range of overtravel can be as much as desired for any
reason.
Assuming now that the fluid pressure exerted through passage 18 on
piston 17 decreases, the piston is retracted by the action of
biasing spring 22. This return movement of the piston toward the
left from 17b holds shoulder 38 on the piston in engagement with
shoulder 44 on the lever. Because of this engagement, retraction of
the piston from advanced position 17b to position 17c of FIG. 4
causes lever 33 to rock clockwise about pivot 31 from the
broken-line position to the full-line position of that figure.
During this movement, pin 31 is held at the end of the elongated
opening 46 in the piston so that the lever merely rocks in a
clockwise direction around the fixed axis of pivot 31 without
producing any movement of switch arm 34. This rocking causes the
left-hand end of the lever to rise in opposition to the force
exerted by spring 41.
Lifting the end of the lever raises it with respect to the piston
until shoulder 44 moves upwardly off the corner of the piston at
shoulder 38 to the piston shown in FIG. 4. At the instant that the
lower angular corner of the lever rides up onto cylindrical surface
36, on the piston, the force of spring 41 is sufficient to suddenly
return the lever with a snap action to the full-line position of
FIG. 3. This counterclockwise rotation of the lever under the
influence of biasing spring 41 returns lever surface 37 into
engagement with piston surface 36. Overtravel of the lever is
prevented by engagement with stop 45. This movement causes the
central portion of the lever to rise with respect to pivot 31 as
the lever returns to its initial position, and this rising movement
at the center of the lever returns switch arm 34 to the raised or
closed position.
The arcuate surface 47 on the outer central surface of the lever is
concentric with the center of pivot 31 when the lever is seated on
the pivot pin at the end of opening 46, as in FIG. 4. Consequently,
the clockwise rotation of the lever during retraction of the piston
creates no movement of switch arm 34 even though in engagement with
the lever. The switch arm is actuated only when the lever is
returned by snap action from the solid-line position of FIG. 4 to
the dotted line position therein, which is the initial position
shown in FIG. 3.
As lever 33 is rocked counterclockwise by spring 41 to bring lever
surface 37 against piston surface 36, the lever moves in part by
rocking about the corner between shoulder 44 and surface 37 which
causes the central portion of the lever to rise. This lifts arcuate
surface 47 which in turn raises switch arm 34 from the lower or
open position to the raised or closed position of the switch
contacts. This returns the switch to the initial condition.
This last-described motion of lever 33 takes place as piston 17
reaches the position 17c of FIG. 4 and normally piston 17 will
continue to the left to return fully to its initial rest or
starting position 17a. During movement from position 17c to
position 17a, no movement of lever 33 occurs, for reasons already
stated.
It will be obvious that the principles involved in the present
invention may be embodied in other specific constructions than
illustrated. As an example of some of the modifications that may be
made, within the scope of the present invention, there is
illustrated in FIG. 5 a variational embodiment. The departures or
changes from the embodiment already described will be mentioned;
otherwise, the construction of the switch of FIG. 5 is the same as
already described.
The operating member in this case is disc 51 rotatably mounted on
shaft 52 to turn about the axis of the shaft in response to torque
applied to the shaft by means not shown. The peripheral surface of
the disc is a circular arc, and this surface is parallel to the
direction of movement of the member 51. This surface engages the
surface 53 on the lever 54. The lever is actuated upon rotation of
disc 51 sufficient to cause lever 54 to pass off peripheral surface
53 and drop over shoulder 55 on the disc.
When the lever and operating member disengage, the movement of the
lever is the same as already described, the biasing means in this
case being compression spring 57 bearing downwardly upon the
left-hand end of lever 54 and also bearing against a fixed abutment
58.
The return motion of disc 51, that is counterclockwise rotation of
the disc, takes place under the influence of spiral spring 60 which
is the biasing means exerting a return force on the disc 51. Upon
the return movement, the action of the lever 54 in restoring switch
arm 34 to the closed position from the open position is the same as
already described.
From the foregoing description, it will be apparent that other
changes in the construction and arrangement of parts constituting
the present invention may occur to persons skilled in the art
without departing from the spirit and scope of the present
invention.
* * * * *