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Патент USA US2405014

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`July 30, 1946.
M. J. CAPARONE
2,405,014
SNAP ’ACTION MECHANISM
' Filed May :5, 1944
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Patented July 30, 1.946
2,405,014
UNITED STATES PATENT OFFICE
2,405,014
SNAP ACTION MECHANISM
Michael J. Caparone, Pasadena, Calif., assignor to
Grayson Heat Control, Ltd., Lynwood, Calif., a,
corporation of California
Application May 3, 1944, Serial No. 533,976
5 Claims.
(Cl. 74-100)
1
2
This invention relates to snap-acting mecha
nisms and, more particularly, to overcenter spring
jections I6 formed on a channel-shaped base
member I8 which is positioned within the frame
I0 and extends substantially parallel with the
side wall I4. Preferably, the base member I 8 is
and lever 'devices for operating valves or switches.
A common form of overcenter snap mechanism
embodies a frame` having main and secondary 5 supported for rocking movement relative to the
levers fulcrumed therein and connected by a
frame I4 andy for this purpose, the projections
spring in such manner that gradual movement of
I I3 thereof are provided with. notched portions
the main lever carries the spring from side to
20 which bear upon knife-edged portions 22
side of the fulcrum of the secondary lever to pro
formed on the adjacent edges of the slots I2.
duce a snap action therein. The torque required 10 The base member I8 may be adjusted on its bear
merely to overcome friction and inertia of the
ings by means of a set screw 24 which projects
secondary lever at the beginning of the snap ac
through the side wall I4 of the frame and is mov
tion is insufficient to permit this lever to exert
able into engagement with the base IB at a point
any appreciable force. It is only after the snap
remote from the projections I6.
action has progressed sufficiently to increase the 15
A main lever 26 of considerably less width than
torque that the secondary lever can perform use
the width of the frame ID is mounted centrallir
ful work. The necessity for such travel on the
thereof and extends from the base I8 to the op
part of the secondary lever to increase the torque
posite side wall 28 of the frame I9. A knife
magnitude reduces the force of the snap action
edged portion 30 formed on one end of the main
and limits the power and. usefulness of such de 20 lever .26 cooperates with a V-shaped notch or
vices for various applications,
»
bearing 32 formed in the side wall 28 approxi
An object of this invention is to cause the snap
mately midway between the ends thereof- The
mechanism to exert its maximum force at the
opposite end of the main lever 26 is bent at sub
instant that snap movement occurs.
stantially a right angle to the lever body and
Another object of the invention is to utilize
projects between the side walls of the base I8
substantially the full stroke of the secondary
forming a free end movable in an arcuate path.
lever to perform useful work.
This end has a countersunk opening 34 formed
Another object of the invention is to retain
therein and the adjacent edge is suitably notched
the simplicity of existing snap mechanisms while
to provide a suspension point 36 for one end of
improving the action thereof.
30 a tension spring 38 which is hooked therearound.
Another object of the invention is to render the
The opposite end of the spring 38 is hooked
magnitude of the force exerted by the snap lever
around a similar suspension point 40 formed by
either variable or fixed, as desired.
a countersunk aperture intermediate the ends of
Other objects and advantages will become ap
a secondary lever 42. The secondary lever 42 is
parent from the following description taken in
forked between the suspension point 40 and the
connection with the accompanying drawing,
lower end thereof to provide clearance for the
wherein
spring 38. The forked ends of the secondary
Fig. 1 is a front elevation of the improved
lever 42 are provided with knife edges 44 for co
snap-acting mechanism;
operation with V-shaped notches or bearings 46
Fig. 2 is a section taken on the line 2_2 of 40 formed in the side walls of the base member I8
Fig.1;
approximately midway between the projections
Fig. 3 is a section similar to Fig. 2 but show
IB and the opposite ends. The spring member
38 is normally under tension and serves to force
ing the mechanism in another operating position;
Fig. 4 is a section similar to Fig. 2 but show
ing the snap mechanism in still another operat
ing position;
the main lever 26 upwardly against its bearing
Preferably, the bearings 32 and 46 for the
main and secondary levers are in axial alignment
and, in the normal or unoperated position of the
snap mechanism shown in Fig. 2, the spring 38
45 32.
Fig. 5 is a section taken on the line 5-5 of
Fig~ 1.
Referring more particularly to the drawing,
is located on the right-hand side of the center
the conventional parts of a snap-acting mecha 50 line of these bearings as viewed in
2.
nism are shown as comprising a channel-shaped
The free end of the secondary lever 42 opposite
frame I0 having a pair of spaced slots I2 ex
the knife-edge 44 is bent substantially perpen
tending through the bottom wall thereof adja
dicular to the lever body and extends in the op
cent the one side wall I4 thereof.
The slots I2
are each adapted to receive one of a pair of pro- Y
posite direction from the free end of the main
lever 26 to form an operating portion 48. The
2,405,014c
operating portion 48 is provided with an aperture
50 through which the knife-edged portion 30 of
the main lever freely projects. The operating
portion 48 is adapted for operative engagement
in accordance with the movement of the control
device as represented by the push rod 58.
To this end, means are provided to apply a
restraining force to the secondary lever 42 to
prevent any movement thereof until sufficient
spring tension has been established to overcome
the force -exerted by the means. Under such con
with the device to be operated, such as a switch
or the valve 56 shown in broken linesl in the
drawing, As indicated in Fig. 4 the valve 56 is
moved off its "seat in response to operation of the
snap mechanism and may be returned by action
of a spring (not shown).
__ v
ditions, it will be apparent that the mechanism
lo vcannot attain a condition of substantial equilib
The secondary lever 42 is further provided with
an elongated aperture 52 overlying and connected
to aperture 4l and in axial alignment with an
aperture 54 formed in the frame I0. The aper
tures 52 and 54 are adapted to providefreev ac
cess to the main lever 26 from the exterior of
the frame IIJ in order thatV gradual'movement
may be imparted thereto by suitable means. Such
movement may result from pressure applied to
the main lever 25 by a control device for the
>valve or switch to be operated and the broken
lines in the drawing are intended to represent the
actuating portion‘or push rod 58 cfa thermostat
or other control device suitable for this purpose.
In the operation of the mechanism so far de
scribed, the parts are moved from the normal or
unoperated position shown in Fig. 2 to thefully
«operated position shown in Fig. 4 by pressure
applied to the main lever 26 by the push rod 58.
The valve 56 to be operated is shown in Fig. 2
as being in closed position and the operating
end 48 of the secondary lever is shown as slightly
spacedtherefrom.
4
valve 56 or for operating a switch or other device
Movement of the push rod
58 to the left as viewed in Fig. 2 will cause grad
ual movement of the main lever 26 to the left as ;
it pivots in its bearing 32 and the suspension
point 36 of the spring 38 will move correspond
ingly in an arcuate path until it is 'in substantial
alignment with the knife-edge 44 of the second
ary lever 42. The centerline of this position is
designated by the broken line A-A in Fig. 2,
it being noted that the secondary lever 42 would
not partake of the gradual movement due to the
component of force acting to produce a clockwise
-~rium and the dead center position is eliminated.
>,In-this embodiment, the means so provided may
take the form of a permanent magnet 60 com
prising a pair of pole faces 62 connected by a
bar portion 64. The magnet 60 is mounted on the
frame I0 in any suitable location to exert mag
netic force -upon the secondary lever 42 and is
shown herein as being intermediate the push rod
'58 and the side wall 28 of the frame. It will be
apparent, however, that such location of the mag
net 60 may be varied to change the operating
force exerted by the secondary lever 42 and that
magnets of different size and magnetism may be
substituted for the same purpose.
The pole faces 62 may project through aper
tures 66 formed in the frame I0 at the desired
location and a retaining clip 68 of sheet material
may extend around the bar portion 64 and
through slots provided therefor in the frame I0
and be swaged into close engagement with the
frame l0 on the inner wall thereof to secure the
magnet in position.
In the operation of the improved snap-action
mechanism described, the suspension point 36
must travel overcenter across the line A--A with
out any movement being imparted to the sec
ondary lever 42 due to the magnetic force of
the magnet 6i) acting thereon. The main lever
» 26 continues to move to the left, as shown in Fig.
3 of the drawing, until suflicient spring tension
has been established by such movement relative
to the secondary lever 42 to overcome the restrain
ing force of the magnet 60. It is apparent that
the total force that can be exerted by the sec
ondary >lever 42 at the instant that snap action
When
suspension
point
35
«fr
rotation of lever 42.
is aligned with knife-edge 44 the mechanism has --occurs is equal to the magnetic force acting on
the secondary lever 42. 'In this invention move
reached> a dead center position thus placing the
ment of the parts to dead center is prevented and
parts in substantial equilibrium. Continued pres
the snap mechanism is enabled to exert its maxi
eure applied by the push rod 58 to the main le
ver 26 will cause the suspension point 36 to travel 50 mum force at the instant that snap action occurs.
As a small gap is provided between the end of
overcenter to the left across the line A-A. The
'- the valve 56 and the operating end 4S of the
component of force then tends to produce a coun
secondary lever 42 prior to snap action, the sud
ter-clockwise rotation of the secondary lever 42
whereupon the tension spring 38 will snap the ' den release of force as described creates a high
impact force which is usually sufficient to force
operating end 48 of the secondary lever from the
dead center position to the fully operated posi
Such snap action causes
-tion shown in Fig. 4.
the valve 56 to be moved off its seat and to re
main in such position until the push rod 58 re
turns to its former position and permits the mech
anism to resume the normal position shown in
Fig.‘2.
From the foregoing description of the opera
tion of a conventional snap-acting mechanism, it
will be apparent that the operating end 48 of
the secondary lever 42 cannot exert sufñcient
force to overcome the closing spring of valve 55
until the lever has travelled far enough to in
crease its torque to such magnitude as will serve
the purpose. Hence, only a portion of the travel
can be utilized to perform useful work. This
invention is more particularly directed to in
creasing the range of snap-action movement of
the operating lever 42 in order that maximum
force may be delivered thereby for unseating the
the valve off its seat even if it is corroded or
stuck thereto. Such impact would of course be
equally useful in freeing switch contacts which
may have >become similarly corroded or stuck in
closed position. Moreover, due to the increased
force of the snap action provided by this inven
' tion the valve 55 could be moved to its seat under
` the action of a more powerful spring than it is
possible to provide for use with snap mechanisms
of limited snap movement.
It will be understood that various changes
may be made in the arrangement and combina
tion of parts and in the details of construction
herein disclosed within the scope of the appended
claims without departing from the spirit of the
invention.
I claim:
l. Snap-acting mechanism oi the character de
scribed comprising in combination, a pair of levers
pivotally mounted at opposite ends, a tension
2,405,014
spring connecting the free ends of said levers and
adapted to establish snap-action thereof in re
sponse to overcenter movement relative to said
mounting, and means adapted to apply a force
for preventing one of said levers from partici
6
one end thereof, a tension spring connecting the
free ends of said levers and being located on one
side of the centerline of said bearings, said main
lever being adapted upon pivotal movement
thereof to travel overcenter and impart snap
action to said secondary lever, and means adapted
pating in said movement until sufficient spring
tension has been established to overcome said
to exert magnetic force on said secondary lever
force.
to prevent pivotal movement thereof until said
2. Snap-acting mechanism of the character de
main lever has travelled overcenter and estab
scribed comprising in combination, a pair of levers 10 lished suilicient spring tension to overcome said
pivotally mounted at opposite ends, a tension
force.
spring connecting the free ends of said levers
5. Snap-acting mechanism of the character de
and adapted to establish snap-action thereof in
scribed comprising in combination, a frame hav
response to overcenter movement relative to said
ing spaced bearings therein, a main lever having
mounting, and magnetic means for preventing
one end pivotally mounted in one of said bearings
one of said levers from participating in said
and a free end extending adjacent another said
movement until suilîcient spring tension has been
bearing, a secondary lever having one end piv
established to overcome the force exerted by said
otally mounted in said other bearing and a free
means.
end extending adjacent the first one said bear
3. Snap-acting mechanism of the character de 20 ing, a tension spring connecting said free ends
scribed comprising in combination, a pair of levers
and being located on one side of the centerline
pivotally mounted at opposite ends in bearings, a
of said bearings, said levers and spring being so
tension spring connecting the free ends of said
arranged that gradual movement of said main
levers on one side of the centerline of said bear
lever in one direction on its pivotal mounting will
ings, one said connected end being movable over 25 cause the free end thereof to travel overcenter
center to establish snap-action in the other, and
and impart snap-action to said secondary lever,
means adapted to apply a force on the lever hav
and a permanent magnet carried by said frame
ing said other connected end for preventing par
and adapted to exert its magnetic force on said
ticipation thereof in said movement until sunl
secondary lever during a portion of said main
cient spring tension has been established to over 30 lever travel to restrain said secondary lever from
come said force.
pivotal movement until sufilcient spring tension
4. Snap-acting mechanism of the character de
has been established by said main lever travel to
scribed comprising in combination, a main lever,
overcome said force.
a. secondary lever, oppositely disposed bearings
for pivoting said main and secondary levers at 35
MICHAEL J. CAPARONE.
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