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Патент USA US2122700

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July 5, 1938.
C. A. SCHAEFER
2,122,700
ELECTRIC SWITCH
Filed Nov. 2, 1936
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BY
INVENTOR.
Carl ?f 5c%aefrn
ATTORNEY.
‘' 2,122,700
Patented July 5, 1938
PATENT OFFICE
UNITED STATES
2,122,700
ELECTRIC SWITCH
'Carl A. Schaefer, Detroit, Mich, assignor to
Square D Company, Detroit, Micln, a corpora
tion of Michigan
Application November 2, 1936, Serial No. 108,764 g
(0]. 200-83)
' 5 Claims.
This invention relates to electric switches auto
matically operable‘ in response to an external
condition.
is rigidly mounted on the arm 1 and is adapted '
.
One object of the present invention is to pro
5 vide an improved form of electric switch operat
ing with a snap action in response to external
pressure variations.
Another object of the invention is to provide
an improved form of high pressure cutout switch
10 used in conjunction with a normal pressure re
sponsive switch but having individual contacts.
Other objects and features of the invention will
be readily apparent to those skilled in the art
from the following speci?cation and appended
15 drawing illustrating certain preferred embodi
ments of the invention in which:
Figure l is a front elevational'view of a switch
assembly according to the present invention with
the front cover removed and parts broken away
20 to show internal parts.
.
Figure 2 is a horizontal sectional view on the
line II—1I of Figure 1.
Figure 3 is a diagrammatic view showing the
control system.v
ing arm 8 toward engaged position. For moving
the contacts to the disengaged position a pin it
_
The normal pressure responsive mechanism
shown in Figure 1 is more fully described and
claimed in applicant's co-pending application,
Serial No. 77,723, ?led May 4, 1936 for Electric
switches. This switch embodies an insulating
30 enclosure l for the switching mechanism ‘and an
operating means comprising a normal pressure re
sponsive assembly generally indicated at 4 and
the switch is provided with a further protective
device comprising a high pressure responsive cut
35 out indicated generally at 5. Within the enclo
sure I is mounted a conducting bracket 6 having
a pair of arms 1 and 8 pivotally mounted thereon
to be engaged by an insulating portion l1 on a
lever I 8 pivoted to a ?xed part. A compression
spring 19 biases the lever 18 downwardly and is
provided‘ with an adjusting screw 2! for adjust
ing the range of operation of the device. The
normal pressure responsive unit comprises a
chamber 22 having a bellows 23 therein. A pin
24 is connected to the bellows and is adapted to
press against the under side of the lever 18. A
spring 25 is adapted to be adjusted by a knurled
nut 26 which may be provided for varying the
15
limits of the range variation of the device.
The high pressure cutout unit according to the
present invention comprises a separate and dis
tinct switching mechanism actuated upon the
attainment of a predetermined maximum pres
sure to open its contacts. This switch comprises
an enclosure 21 having connected to the bottom
thereof a bellows chamber 28 within which is dis
posed an expansible bellows 29 having connected
thereto a pin 3| for actuating the switching mem
ber. About the pin 3| is disposed a compression
spring 32 opposing movement of the pin and
adjustable by means of a threaded cylinder 33
through which the pin 3| projects. Within the
chamber 21 is disposed an insulating block 30
‘on which are disposed spaced contacts electrically
connected to the terminals 34 and 35. The base
30 is supported on a metallic bracket 36 and
within this bracket is hingedly mounted a link
31 having arms 38 at either side of its opposite
end and a centrally disposed bearing point 39.
An adjusting member 4| is threaded into the en
closure 21 and is provided with a similar bearing
by means of the trunnion ends of studs l0 thread- ' point 42.
ed into the upstanding walls of. the bracket.
40 These arms thus rotate about the same pivotal
axis and are disposed as shown in generally par
allel relation and connected together with a lost
motion connection by the headed movable con
tact surface described hereinafter. The arm 8 is
45 a conducting arm carrying a contact surface 9
thereon at the forward side of the magnetic
arm 1, which contact surface is headed or other
wise restricted in its movement with respect to
the arm 1. A stationary magnet II is provided
50 for attracting the arm 1. A stationary contact 12
is mounted on a resilient arm 13 and a cam 14
is provided for adjusting the position of the sta
tionary contact 12 and hence the vair gap between
the magnetic arm 1 and the permanent magnet
I 55 II. A light tension spring 15 biases the conduct-'
In
0
A compression spring 43 is provided
with bearing seats 44 at its ends which receive
the bearing points 39 and 42. The link 31 and 40
the spring 43 thus comprise an over center toggle
adjustable through the member 4|. A pair of
tension springs 45 bias the arms 38 to’ a fixed
part of the enclosure. Upon the link 31 as by
means of the knife-edged pivots 40 is mounted
a contact member 46 including an insulating por-_
tion 41 carrying a contact plate adapted to bridge
the stationary contacts on the base 33. A pair
of light tension springs 48 are mounted at the
contact side of the knife-edged mounting of the 1'
contact arm 46 and have their opposite ends con
nected to ?xed points on the enclosure. An
adjustable stop 49 is positioned to engage the
contact arm 46 at the side opposite the contact
carrying portion thereto.
65
2
2,122,700
A stationary stop 5| is provided for limiting
the downward movement of the link 31. lThe pin
Ii is provided with a pointed end received within
a cooperating groove in the link 51.
10
The operation of the normally responsive pres
sure switch is as follows:
The parts as shown in Figure 1 are in the closed
circuit position. Upon a decrease in. pressure
within the bellows chamber 22 the lever I! will
move downwardly under the bias of the spring
I. whereupon the insulating portion i1 will en
gage with the pin IS on the lever ‘l and rotate
this arm in a clockwise direction until it engages
with the conducting arm 5 whereupon the arms
‘I and I move together and move the contact
surface 5 which is rigid with the arm 5 into its
disengaged position. Similarly, when the pres
sure within the bellows chamber 22 increases
while the contacts are maintained in the oil
20 position the lever l8 will be moved upwardly,
thus permitting the contacts to be moved into
engaged position under the bias of the spring i5.
Due to the rapidly increasing force of the magnet
II as the contacts move toward engagement the
25 meeting of the contact surfaces will concur with
a snap action under the in?uence of the perma
nent magnet ll. Movement of the cam surface
l4 will move the stationary contact relative to
the magnet and by varying the air gap will vary
30 the differential of pressure to which the switch
I:
operates. . The compression spring I! is adjusta
ble to vary the range of operation of the device.
The spring 25 is adjustable to raise or lower the
limits of the range of operation of the device.
The operation of the high pressure cutout
mechanism is as follows:
The parts as shown in Figure 1 are in the closed
circuit position. Upon the attainment of a pre
determined maximum condition within the bel
40 lows chamber 25 the pin 3| will be moved up
wardly and by its engagement with the link 31
will move this link and contact arm 36 in an up
ward direction. When the ‘toggle formed by the
spring 43 and the link 31 approaches its dead
45 center position the force necessary to move it will
50
rapidly decrease so that the movement thereof
will occur quickly. At this time the contact lever
45 will engage the stop 45 and cause rotation of
the contact lever about its knife-edge support to
move the bridging contact plate to disengaged
position. Upon decrease in pressure within the
bellows chamber 25 the parts will automatically
reverse themselves and move to bridging engage
ment with the stationary contacts. In the'open
55
ing operation, it is to be noted that contact pres
sure is maintained until the contact lever sharp
ly engages the adjustable stop 49 whereupon the
lever is rapidly rotated about its knife-edge
60 mounting. The springs 45 are not ‘absolutely
essential to the operation of the device but with
out them the contact opening action is apt to be
rather sluggish since at the instant of operation
the force necessary to move the link 31 and the
~ contact lever upwardly is increased by the in
sure at which the contacts will be open and that
at ‘which they will be closed.
Figure 3 illustrates diagrammatically a system
employing the pressure switch assembly which
has previously been described. This comprises a
motor 52 vwhich may constitute a refrigerator
compressor motor, or any other electrical trans
lating device adapted to be connected to a line
through a contactor 55 having a magnet coil 54
for effecting closing of the contact. In addition
to the normal pressure switch 55 and the high
pressure cutout 55 a manual three point switch
5'! having terminals 58 and 59 and a movable
switching arm 5| is provided. With the switching
arm placed in a neutral position as shown in 15
Figure 3 the control circuit through the coil 54
will be manually opened and the translating de
vice will remain disconnected frciua the line.
Upon movement of the switching arm 6| into en
gagement with the terminal 59 the control cir
cuit through the coil 54 will be closed with both
the normal pressure switch 55 and the high pres
sure cutout 58 in series with the coil. This is the
normal automatic operating connection for the
circuit as it is seen that with this connection if
the pressures within the bellows chambers 28
and 22 are at certain values both the controlling
contacts will be closed and the circuit will be com
pleted through the coil 54 thus connecting the
motor to the line through the contactor 53. Upon 30
a suitable decrease in pressure in the normal
pressure switch 55 its contacts will be opened,
thus opening the control circuit, whereupon the
contactor 53 will open and disconnect the motor
from the line. This is the normal automatic op~
eration of the device wherein the motor is con~
nected to and disconnected from the line in re
sponse to variations in p1. assure within the bel
lows 22. Upon the attainment of a predetermined
maximum pressure within the bellows 28 the high
pressure cutout 55 will operate to open its con
tacts, thus opening the control circuit to discon
nect the motor, regardless of the condition of the
normal pressure switch and these contacts will
remain open until the pressure within the bellows .
chamber 25 decreases. In many instances it is
desired to connect the motor or other translating
device to the line for continuous operation inde
pendent of the normal pressure switch but main
taining the protection ail’orded by the high pres
sure cutout. This is accomplished by moving the 50
switching arm 5| into engagement with the ter
minal 55 whereupon the coil 54 will be connected
in the control circuit in series with the high pres
sure cutout 55 only and the switch 55 will be ,
shunted from the control circuit. With this
connection the motor will be operated continu
ously until the attainment of the predetermined
maximum pressure within the high pressure cut
out bellows 28 or until the manual switch is oper
ated.
While certain preferred embodiments of the
invention have been speci?cally disclosed, it is
understood that the invention is not limited
creased tension in the springs 48. With the
springs 45 the increased force of springs 48 forms
thereto as many variations will be readily appar—
ent to those skilled in the art and the invention
only a very small part of the force to be overcome is to be given its broadest possible interpretation,
so that they will not slow up the action of the’ within the terms of the following claims.
toggle in effecting quick break of the contacts.
Adjustment of the cylinder 33 will adjust the
‘pressure to which the device will operate to open
the contacts. Adjustment; of the member 4i .will
adjust the tension on the toggle link spring 43
75 and will adjust the differential between the pres
l0
What is claimed is:
'
1. A pressure switch- comprising an element
movable in one direction in response to a pres
sure condition, adjustable spring means for op
posing such movement, a pivoted member mov~
able in response to movement of said element.
means biasing said member in a direction to op
3
‘2,122,700
pose movement thereof by said element, a con
tact arm pivoted on said member, means biasing
said arm to contacts engaged position, over-cen
ter spring means connected to said member and
causing its movement to be snap-like in action,
and a stop engaging said arm when said member
is moved by said element to cause rotation of the
‘ arm against its biasing means to a contacts dis
engaged position.
-
'2. A pressure switch comprising an element
movable in response to a pressure condition,
spring means opposing such movement and ad
justable to vary the range of operation of the
switch, a pivoted member in the path of said ele
15 ment, over-center spring means connected to said
member and adjustable to vary the differential or
operation of said switch, a contact arm pivoted
on said member, biasing means for said arm at
the contact side of its pivotal mounting, and a
20 stoplengaging said arm at the opposite side of
its pivotal mounting to. cause rotation of said
‘arm against said biasing means to contacts dis
engaged position in response to movement of
said member by said element.
25
3. A pressure switch comprising an element
10
movable in response to a pressure condition,
spring means opposing such movement and ad
justable to vary the range of operation of the
switch, a pivoted member operatively connected
30 to'said element, a compression spring intercon
meeting said member and a relatively ?xed part
and movable through its dead center position.
during movement of_ said member to extreme
positions, said compression spring being adjust
36 able to vvary the differential of operation of the
switch, spring means opposing moving of said
member by said element, a contact arm pivoted
on said member, spring means biasing said arm
at the contact side of its pivotal mounting, and
40 a stop engageable with said arm at the opposite
side of its pivotal mounting to effect rotation
thereof to its contacts disengaged position.
4. A pressure switch comprising, an element
movable in response to a pressure condition,
spring means opposing such movement and ad
justable to vary the range or operation or the
switch, a pivoted member operatively connected
to said element, a compression spring intercon
necting said member and a relatively ?xed part
and movable through its dead center position
during movement of said member to extreme
positions, said spring being adjustable to vary
the di?erential of operation of the switch, spring 10
means opposing moving of said member by- said
element, a contact arm pivoted on said member,
spring means biasing said arm at the contact side
of its pivotal mounting, and a stop engageable
with said arm at the opposite side of its pivotal
mounting to e?ect rotation thereof to its con
tacts disengaged position, the spring means bias
ing said member and said arm being su?icient to
overcome the bias of said compression spring
when in the contacts disengaged position so as 20
to e?ect return of said member and engagement
of the contacts when the element is moved by the
?rst mentioned spring means in response to a
reduction in the pressure condition.
5. A pressure switch comprising an element 25
movable in response to a pressure condition,
spring means opposing such movement and ad
justable to vary the range of operation of the
switch, a pivoted member, a compression spring
disposed between the free end of said member and 30
a relatively ?xed part and movable through dead
center position during movement of said member
by said element, said compression spring being
adjustable to vary the differential of operation
of the switch, a contact controlling arm pivoted 35
on said member, biasing means for said arm at
one side of its pivotal mounting, and a stop en
gaging the opposite side of said arm during move
ment of said member by said element to e?'ect
rotation of said arm against said biasing means 40
to actuate the switch contacts.
\ CARL A. SCHAEFER.
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