Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The present invention relates to calibration
mechanisms of the cam-type such as are used for pressure
switches and, more particularly, to an improved configur-
ation of the camshaft and support bracket which simplifies
and facilitates assembly of the mechanism.
Conventional actuation mechanisms for pressure
switches such as illustrated in U.S. Patent No. 3,846,600
and assigned to the assignee of the present invention have
utilized stamped metal support brackets, cams, plunger
adjustment and cam follower mechanisms and metal camshafts.
Typically, as in the mechanism of the above-cited patent,
the camshaft is assembled with the support bracket, and then
the cam member is placed on the projecting end of the camshaft
which is then coined or staked to maintain the cam rigidlv
attached to the camshaft, which normally must be lubricated
where it engages the support bracket. Although such actu-
ation mechanisms have been generally satisfactory in
operation, the necessity for lubricating the metal parts is
undesirable from a processing standpoint, the manufacturing
expense of the metal stampings and machined shaft is
excessive, and the need to stake the cam to the shaf t merely
requires additional assembly steps and equipment, further
diminishing the economic feasibility of the actuation
mechanism.
The use of plastic moldings for the support bracket
and cam assembly has been considered as a means of eliminating
the need for lubrication, but until the present invention,
the use of such plastic parts has not provided an~ particular
advantage from the standpoint of the assembly process.
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Accordingly, it is an object of the present
invention to provide an actuation mechanism, such as is
used for pressure switches, in which the assembly of the
cam, camshaft and support brack~t is greatly simplified
and may be performed manually, without the need for
expansive jigs, fixtures and assembly equipment such as
staking presses.
It is a more specific object of the present
invention to provide a calibration mechanism in which the
10 ~/ configuration of the support bracket and camshaft are
utilized to retain the cam assembly in its assembled
position during normal operational rotation of the cam -
assembly.
According to the present invention there is
provided an adjustment assembly in a pressure switch having
a spring-biased plunger arrangement and a pivotally mounted
lever operably connected to the plunger for adjusting
the position of the plunger. The assembly includes a
bracket means mounted to the pressure switch, the bracket
~ 20 means including a mounting member having a bore therethrough.
; There is further provided cam means including a cam member
; having first and second stop surfaces, a shaft connected
to the cam member, and a lobed portion extending radially
from the shaft and axially spaced from the cam member a
predetermined amount. The lobed portion is angularly offset
from the angular displacement defined between the first and
second stop surfaces. The cam member, the shaft and the
lobed portion may be an integral one-piece assembly. The
mounting member has a radially extending slot opening to
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the bore and has the shaft and the lobed portion receivable
therethrough. The lever has one end thereof engaging the
cam member as a follower for limiting rotation thereof
between the first and second stop surfaces. The spring-
biased plunger engages the lever intermediate the ends
thereof for movement therewith. The cam member is operative
while engaging the lever follower end to maintain the lobed
portion angularly offset with respect to the slot, the lobed
portion and the cam member so as to axially retain the cam
means to the mounting member.
During the assembly, the slot is circumferentially
oriented to receive the projection when the cam assembly is
in the assembly orientation and permits the projection to
- pass axially therethrough as the cam assembly is moved
axially to the assembled position. The support bracket
and slot are configured to permit rotations of the cam
assemblyl when the cam assembly is in the assembled position,
to the range of rotational orientations. In this condition,
the projection is out of circumferential alignment with the
slot and prevents substantial axial movement of the cam assembly.
In one specific embodiment of the invention an
actuator arm has a bore and a slot communicating therewith
for receiving the camshaft and projection. The actuator arm
also defines a radial projection circumferentially and
axially aligned with the projection on the camshaft. The
actuator arm is spring-biased to a predetermined angular
position with respect to the support bracket in which the
projection on the shaft is disengaged from the projection
on the actuator arm and also angularly offset from the
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actuator arm slot. After the cam assembly has rotated
through a portion of its total angular displacement, the
shaft projection thenengages the actuator arm projection and
rotates it through a given angular displacement. Through-
out the complete range of camshaft angular displacement the
shaft projection remains in abutment with a transverse
shoulder adjacent the bore in the actuator arm, thereb~
axially retaining the camshaft to the support bracket.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a top plan view of the calibration
mechanism of the present invention; -
Fig. 2 is a cross-sectional view of the calibration
mechanism taken on section lines 2-2 of Fig. l;
Fig. 3 is a partial view taken along section lines
3-3 of Fig. l;
Fig. ~ is a partial top plan view of a second
embodimen L of the invention;
Fig. 5 is a partial end view taken along section
lines 5-5 of Fig. 4;
Fig. 6 is an enlarged partial view of the actuator
arm; and
Fig. 7 is a cross-sectional view taken along
section lines 7-7 of Pig. 6.
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DETAILED DESCRIPTION
Referring now to Figs. 1 and 2, there is shown gen-
erally by reference numeral 10 a calibration mechanism mounted
on a pressure switch 12. The calibration mechanism lO in-
cludes a pivotally mounted lever 14, a cam member 16, a cam-
shaft 18, and a support bracket indicated generally by refer-
ence numeral 20. The pressure switch 12, forming no part of
this invention, includes a spring-biased plunger 22 slidably
received in a bore 24 formed in an upper housing section 26
f pressure switch 12. AS shown in Fig. 2, a biasing spring
28 has its upper end reacting against the bottom surface of
- plunger 22 and its bottom end reacting against the top sur-
face of an actuator member 30. A switch blade tnot shown)
is disposed intermediate the bottom surface of actuator 30
and the top surface of a diaphragm (not shown). The dia-
phragm is responsive to pressures developed by varying water
`~ levels. A second biasing spring 32 is mounted between upper
; housing 26 and lever 14 and functions to continuously maintain
an upward biasing force upon the lever 14. Lever 14 is pivot-
- 20 ally mounted at its right end by a fastener 34 having a
spherical head 36 which seats against a corresponding spher-
ical follicle 38 having a central opening 40 through which
fastener 34 is received. A cam follower 42 is formed by the
left end of lever 14 and is continuously biased against cam
16 by spring 32 and, during a portion of its pivotal movement,
by spring 28. A pair of downwardl~ extendîng tabs 44 engage
the top surface of plunger 22.
Support bracket 20 includes outer and inner verti-
cal legs 44 and 46, having bores 48 and 50, respectively,
which are horizontally aligned and also in line with a cen-
tral longitudinal axis through lever 14. Inner vertical leg
46 includes a vertically extending slot 52 having cam follower
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42 extending therethrough. Slot 52 functions to guide the
pivotal motion of lever 14. A keyhole slot 54 is aligned
with slot 52 and communicates with bore 50.
A radially extending projection 56 is formed on
camshaft 18 and has a width permitting entry through keyhole
slot 54. The right transverse edge of projection 56 with r
respect to Fig. 2 is spaced from the face of cam 16 a predeter-
mined amount in order to establish desired camshaft end play
with respect to bracket 20. In the preferred practice of
the invention, cam 16, projection 56 and camshaft 18 are in-
tegrally molded in one piece from a suitable plastic material.
This feature of the invention eliminates the need for lubri- -
cating the camshaft and cam member. A material found to be
particularly suitable is marketed under the trademark
~ZYTEL" by E. I. du Pont de Nemours, Wilmington, Delaware.
As illustrated in Fig. 3, cam member 16 defines
; first and second radially extending stop surfaces 58 and 60,
respectively, which abut the sides of cam follower 42 and
function to limit the angular displacement of camshaft 18.
A circular bead 61 is formed on the transverse face of cam
member 16 and provides a bearing surface for contacting
against inner leg 46. Projection 56 is angularly positioned
within that portion of the cam profile between stop surfaces
58 and 60 not contacted by follower 42. Keyhole slot 54,
aligned with follower 42, remains continuously offset from
projection 56. By maintaining projection 56 angularly off-
set from keyway slot 54, camshaft 18 is axially retained in
bore 50 with inner vertical leg 46 being captured between
projection 56 and cam 16. End play of camshaft 18 can there-
fore be determined by establishing the axial space betweenprojection 56 and the face of cam 16 to an amount slightly
greater than the thickness of inner vertical leg 46.
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The calibration mechanism is assembled by first
aligning projection 56 with keyhole slot 54 and inserting
camshaft 18 through bores 50 and 48 of support bracket 20
until projection 56 clears slot 54. Support bracket 20
with the camshaft mounted therein is then attached to the
upper housing section 26 of the pressure switch. Lever 14
is then aligned over plunger 22 and biasing spring 32 so that
cam follower 42 extends into slot 52 and engages with the
cam profile of cam section 16. Fastener 34 is then in-
serted through opening 40 in lever 14 and threaded intoupper housing section 26. Cam follower 42 is now continu-
ously in engagement with cam 16, thereby limiting the total
angular displacement of the cam to an angle defined between
first and second stop positions 58 and 60.
Referring now to Fig. 4, there is shown a second
embodiment of the invention which includes an actuator arm
62 rotatably mounted on camshaft 64 through a bore 66. As
best shown in Figs. 6 and 7, actuator arm 62 includes a
counterbore 68 which terminates in a transverse shoulder 70.
A slot 72 extends axially through shoulder 70 and permits
projection 76 to pass therethrough. A projection 74 extends
inward radially from bore 68. As illustrated in Fig. 5, cam-
shaft 64 has a radial projection 76 extending therefrom an
amount sufficient to clear bore 68 when the actuator arm is
positioned on camshaft 64. As illustrated in Fig. 4, the
actuator arm projection 74 and the camshaft projection 76
are axially aligned. Actuator arm 62 is biased in the posi-
tion as shown by Fig. 5 and has a connecting linkage 78
attached to its free end with the other end of the linkage
~not shown) connected to an associated appliance control
member. With the actuator arm biased to the position as
shown in Fig. S and with stop surface 58 a~utting follower
42, camshaft 64 can only rotate initially in a counterclock-
wise direction. Continued counterclockwise rotation of cam-
shaft 64 results in projection 76 rotating away from slot 72
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until it abuts projection 74. Further rotation of cam- .;
sha~t 64 is then effective to rotate actuator arm 62
counterclockwise for the remaining portion of cam displace-
ment until stop surface 60 abuts follower 42. Shoulder 70
prevents projection 76 from passing through keyhole slot 54
(identical to first embodiment) as it rotates past align-
ment therewith. By maintaining projection 76 offset from
slot 72 and in axial abutment with shoulder 70, the actu-
ator arm 62 and camshaft 64 are axially retained to the
support bracket.
The second embodiment of the invention is assembled
in a manner identical to that described for the first em-
bodiment wherein projection 76 is aligned with slot 52 in
the support bracket and actuator arm 62 is rotated to per-
mit projection 76 to pass through slot 72. The supportbracket is then attached to the pressure switch followed by
assembly of lever 14.
Modifications and variations of the preferred em-
bodiment will occur to others upon a reading of the specif-
ication, and it is my intention to include all such modi-
fications and alterations insofar as they come within the
scope of the appended claims.
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