CA1042509A - Means for calibrating pressure switches at extra-low pressure settings - Google Patents
Means for calibrating pressure switches at extra-low pressure settingsInfo
- Publication number
- CA1042509A CA1042509A CA210,980A CA210980A CA1042509A CA 1042509 A CA1042509 A CA 1042509A CA 210980 A CA210980 A CA 210980A CA 1042509 A CA1042509 A CA 1042509A
- Authority
- CA
- Canada
- Prior art keywords
- lever
- switch
- plunger
- low
- pressure
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H35/00—Switches operated by change of a physical condition
- H01H35/24—Switches operated by change of fluid pressure, by fluid pressure waves, or by change of fluid flow
- H01H35/26—Details
- H01H35/2607—Means for adjustment of "ON" or "OFF" operating pressure
- H01H35/2614—Means for adjustment of "ON" or "OFF" operating pressure by varying the bias on the pressure sensitive element
Landscapes
- Physics & Mathematics (AREA)
- Fluid Mechanics (AREA)
- Switches Operated By Changes In Physical Conditions (AREA)
Abstract
ABSTRACT
A simplified calibration mechanism is provided for a pressure switch using an adjustable, spring-biased plunger arrangement for controlling the trip force and hence the pressure to which the switch responds. The mechanism includes an especially configured lever pivoted at one end, contacting an especially shaped cam as a follower at its other end and the plunger at its mid portion. A first calibration device is provided at the lever's pivoted end to adjust the normal low-high pressure settings of the switch. Another calibration device is provided to isolate the lever and cam from the plunger for effecting a precise setting of the pressure switch at extra-low pressures.
A simplified calibration mechanism is provided for a pressure switch using an adjustable, spring-biased plunger arrangement for controlling the trip force and hence the pressure to which the switch responds. The mechanism includes an especially configured lever pivoted at one end, contacting an especially shaped cam as a follower at its other end and the plunger at its mid portion. A first calibration device is provided at the lever's pivoted end to adjust the normal low-high pressure settings of the switch. Another calibration device is provided to isolate the lever and cam from the plunger for effecting a precise setting of the pressure switch at extra-low pressures.
Description
104;~509 This invention relates generally to pressure switches and more particularly to a mechanism for calibrating same at two different pressure ranges.
The invention is particularly applicable to pressure switches used for controlling the water-fill level of washing machines, dishwashers and like domestic appliances, and will be described with particular reference thereto. However, it will be appreciated by those skilled in the art that the invention may have broader applications and may be employed as a calibration - -mechanism for any type of control switch which must be actuated over a range of varying conditions sensed by the switch.
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Heretofore pressure switches used in domestic appliances have commonly employed a cam associated with a lever-follower acting on the general plunger arrangement to establish various ~' water levels between "high and low" pressure settings of the switch. Accordingly, means have been provided in such arrange-~1 . ' -ments to calibrate the switches, usually at the high range end, at the factory. With the advent of "mini-wash" loads in such .! 20 appliances, it became necessary to provide additional means to sense extra-low water levels (pressures). Additional structures had to be provided to calibrate such switches at this setting j because the general cam arrangement was not sufficiently sensitive i~ to such extra-low pressures. This has been accomplished by ~ ' .
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The invention is particularly applicable to pressure switches used for controlling the water-fill level of washing machines, dishwashers and like domestic appliances, and will be described with particular reference thereto. However, it will be appreciated by those skilled in the art that the invention may have broader applications and may be employed as a calibration - -mechanism for any type of control switch which must be actuated over a range of varying conditions sensed by the switch.
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Heretofore pressure switches used in domestic appliances have commonly employed a cam associated with a lever-follower acting on the general plunger arrangement to establish various ~' water levels between "high and low" pressure settings of the switch. Accordingly, means have been provided in such arrange-~1 . ' -ments to calibrate the switches, usually at the high range end, at the factory. With the advent of "mini-wash" loads in such .! 20 appliances, it became necessary to provide additional means to sense extra-low water levels (pressures). Additional structures had to be provided to calibrate such switches at this setting j because the general cam arrangement was not sufficiently sensitive i~ to such extra-low pressures. This has been accomplished by ~ ' .
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, 104;~SU9 providing complex lever arranqements which rock about a first axis between "hi~h and low" settings and about a second axis at the "extra-low" setting to null the cam arrangement. Such arrangements, however, do not isolate the lever-follower, and wear, slight calibration slip between high and low settings, etc., adversely affect the delicate extra-low setting. Furthermore, additional mechanisms, such as ratchet and pawl arrangement, had to be provided with the cam to prevent a l'loose", water-fill operator knob at the appliance console. Finally, the general arrangement of such mechanism could easily result in the electrical leads connected to the switch terminals fouling the lever mechanism to hinder operation thereof or alternatively be shorted thereagainst.
It is thus a principal object of the subject invention to provide a calibration mechanism for a pressure switch which overcomes all of the above-noted disadvantages while being extremely simple in design for ease in manufacture and assembly.
According to the present invention there is provided a calibration mechanism for a pressure switch of the type having a spring-biased plunger arranged adjustable to sense different pressures to which the switch responds. The mechanism includes means for establishing and calibrating normal "low-to-high'l pressure settings of the switch, the ; "low-to-high" pressure settina means including lever means for adjusting the plun~er and selectively operative cam means in association with the lever means to provide a "low-to-;` high" range of settings. The lever means includes a lever adapted for pivotal movement at one end thereof with respect to the switch, the lever having the opposite end thereof
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, 104;~SU9 providing complex lever arranqements which rock about a first axis between "hi~h and low" settings and about a second axis at the "extra-low" setting to null the cam arrangement. Such arrangements, however, do not isolate the lever-follower, and wear, slight calibration slip between high and low settings, etc., adversely affect the delicate extra-low setting. Furthermore, additional mechanisms, such as ratchet and pawl arrangement, had to be provided with the cam to prevent a l'loose", water-fill operator knob at the appliance console. Finally, the general arrangement of such mechanism could easily result in the electrical leads connected to the switch terminals fouling the lever mechanism to hinder operation thereof or alternatively be shorted thereagainst.
It is thus a principal object of the subject invention to provide a calibration mechanism for a pressure switch which overcomes all of the above-noted disadvantages while being extremely simple in design for ease in manufacture and assembly.
According to the present invention there is provided a calibration mechanism for a pressure switch of the type having a spring-biased plunger arranged adjustable to sense different pressures to which the switch responds. The mechanism includes means for establishing and calibrating normal "low-to-high'l pressure settings of the switch, the ; "low-to-high" pressure settina means including lever means for adjusting the plun~er and selectively operative cam means in association with the lever means to provide a "low-to-;` high" range of settings. The lever means includes a lever adapted for pivotal movement at one end thereof with respect to the switch, the lever having the opposite end thereof
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engaging the cam as a follower with portions thereof intermediate the ends contacting the plunger. Means pivotally mount the one lever end to the switch about a single pivot point, the pivot means including adjustable means operable, upon adjustment, to move the pivot point of the lever with respect to the plunger for varying the spring biasing of the plunger.
According to one aspect of the invention ~here is provided means for establishing the calibrating an "extra-low" pressure setting for the switch, the "extra-low" pressure setting means effective to isolate the lever and the cam means from acting on the plunger when the "extra-low" pressure setting-means is operative.
The invention may take physical form in certain parts and arrangement of parts, one embodiment of which will be described in detail herein and illustrated in the accompanying drawings which form a part hereof and wherein:
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~04ZS09 FIGURE 1 is a top plan view of the calibration mechanism of the sub~ect invention;
FIGURE 2 is a sectioned view of the calibration mechanism taken along line 2-2 of FIGURE l;
FIGURE 3 is an end view of the calibration mechanism taken along line 3-3 of FIGURE 1 to show the cam profile; and FIGURE 4 is a longitudinally sectioned view of the actuating lever employed in the calibration mechanism.
Referring now to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only and not for the purpose of limiting same, there is shown in FIGURE 1 a calibration mechanism 10 mounted onto a generally flat housing sur~ace 12 of a pressure switch 14.
Because pressure switch 14, by itself, does not form an essential feature of the subject invention and since its construction is known to those skilled in the art, the details of the switch are not shown herein. It is important only to understand that an adjustable spring-biased plunger arrangement 15 controls the trip force and hence the pressure to which switch :
14 responds. One such plunger arrangement is shown in FIGURE 2 and includes a first spring 16 received within a bore 17 formed in a boss 18 extending from the generally flat housing portion surface 12. The bottom end of first spring 16 acts against a switch blade (not shown) usually by means of an actuator 19 to normally ;. ' :
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104ZSt~9 b~as the switch blade into a first snapped position. The precompression force of spring 16 and thus the switch trip pressure is calibrated by the distance a plunger 20 extends within bore 17 to compress the spring. Opposing the spring force is pressure, determined by the water level in the tub, as sensed by a diaphragm (not shown) which exerts a force on the opposite~side of the switch blade. As the water-fill ;-level increases, thè diaphragm force becomes large enough to overcome the spring precompression and slight movement of the diaphragm thereafter moves the switch blade toggle mechanism pass center to snap the switch.
lhe calibrat-ion mechanism 10 of the subject invention as best shown in FIGURES 1 and 2 includes an especially configured mounting bracket 24 housing and journalling a cam 26 therein; a lever 28 operatively associated with cam 26; a primary calibration screw 30 for _~ adjusting normal "low-high" pressure settings and a secondary calibratîon screw 32 for adjusting an "extra-low~' pressure settingO
~ountin~ bracket 24 has a generally flat base 33 secure~ to housing surface 12 by a pair of screws.
- Extending upwardly from base 33 is a known U-shaped bracket ~ portion 34 for ~ournalling the shaft 35 of cam 26 as best I ~ ~hown in FIGURE 2. The forward leg 34A of the U-shaped 25 i bracket portion at the upper end thereof is formed into a stepped flange 36 for mounting pressure switch 14 to the j ~
J ~ onsole of an appliance. Longitudinally extending at one 1, i ~ ¦~ side of mounting bracket 24 is a vertical wall portion 37 ` -11 . .. I
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. I 73-CO~-106 1 1 ` 1042S09 which is parallel to the longitudinal centerline 38 of shaft 3S and lever 28. Vertical wall portion 37 is positioned on . . the side of housing surface 12 which contains known terminal ; connections X,Y, and Z for completing appropriate circuitry j when the switch is snapped. Importantly wall portion 37 is spaced from centerline 38 a distance approximately equal to the maximum diameter of cam 26. At the upperpart of the rearward end of vertical wall portion 37 there is provided a right angled tab portion 39 which receives in threaded engagement therethrough the secondary calibration screw 32. . -The lever 28 of calibration mechanism 10 is shown . in FIGURES 1,2 and 4 and may best be defined as having a -. pivoted end portion 42, a follower end portion 43 at the , opposite end of the lever and a mid portion 44 adap~ed to j 15 contact plunger 20.
. Follower end portion 43 is formed in a known I circular configuration to insure proper contact with the ¦
profile of cam 26 and extends through an opening 40 in the ~ ~- . rear leg 34B of U-shaped bracket portion 34. Opening 40 l~ 20 i~ is sufficiently sized to permit unimpeded vertical travel '.
of the follower end which occurs upon rotation of cam 26.
Pivoted end portion 42~as best shown in FIGURE 2 may-.... . .
. be defined ~y a spherical follicle 46 having a central .l ¦ opening 47 extending therethrough. Follicle 46 is adapted - 25 ~ to receive in a pivotable manner the spherical head 49 of , the first calibration screw 30 whlch in turn is self-threaded i~to a bore 48 formed in the especially configured boss 18 ~ i~ housing surface 12.
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lO~Z509 Mid portion 4~ includes an especially configured ~ slot 50 (FIGURE 1), the longitudinally orientated portion thereof 50A having sufficient width to receive a boss 21 (FIGURE 2) extending from the top end 22 of plunger 20 which is especially configured in this respect. Formed on the bottom of lever 28 and on each side of the longitudinally extending portion of H-slot 50 is an arcuate projection 52 (FIGURE 4) which is adapted to engage the top surfac~ 22 of plunger 20 on opposite sides of boss 21. Arcuate projections ; 10 52 have a depth less than the height of boss 21 to insure that the boss will always extend through H-slot 50 and thus prevent ~ -interference therebetween.
Between pivot end 42 and mid portion 44 of lever 28 is a second spring 55. Spring 55 is seated at one end in a second bore 56 formed in housing boss 18 and at its other end is seated -: ..
on lever 28 by a boss 57 which is formed in the underside surface of the lever by punching a hole therethrough. The main body , portion of the lever is strengthened by side rails 58 which impart "channel-like" structural properties to the lever. --The cam profile which is engaged by the follower end 43 - of lever 28 is shown in FIGURE 3. That portion of the cam profile between Points A and B controls the normal "low-high"
settings of the pressure switch which typically occur between -~
pressure ranges from 8 to 16 inches of water. The cam profile ' between Points A and B is shown serrated to provide an "infinite"
water level adjustment between the normal low ahd high ranges of the switch. Positive, mechanical reset of the switch occurs .. ..
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. ' , `' 104;~SQ9 .1en the cam is further rotated over its smooth portion between Points B and C of the cam profile. The cam profile betwee~ Points B and C is a generated curve having greatest radial distance at its stop defined by Point C to assure return of the cam to its maximum high setting level and thus prevent locking of the switch at reset.
When cam 26 is rotated in its opposite direction the follower end 43 will eventually rest at Point E of the cam profile defined as the "mini-wash" or "extra-low" pressure setting. To ensure positive reset of the switch as cam 26 is rotated to its "mini-wash" position, the cam is cut with a lobe indicated at Point D which has a radial distance extending to the cam center 60 approximately equal to the mid point radial distance of the cam profile between Points B and C.
When the device is assembled at the factory, cam 26 is usually rotated to Point B on its profile, the highest pressure setting in the normal "low-high"range. First calibration screw 30 is turned to adjust the position of lever 28 for proper setting of the high pressure thereby establishing the normal "low-high" range. When cam 26 is rotated within its normal "low-high" range and also through its positive reset position i.e. Points A-C, the arcuate projections 52 contact the top end 22 of plunger 20 to accordingly adjust the precompression of first spriny 16 or to establish a solid driving connection to assure positive mechanical reset.
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The cam i9 then rotated into its "extra-low" or "mini-wash" pressure settin~ at Point E. In this cam position, second spring 55 lifts lever projections,52 off the top end 22 of the plunger while forcing the follower end 43 into the cam notch ` defined at Point E. The secondary calibration screw 32 is then self-threaded through an opening in tab portion 39 of mounting bracket to contact the boss end 21 of plunger 20. Thus, second spring 55 which assures good contact between lever end 43 and the cam profile during normal "low-high" pressure range settings 10 also functions in the "extra-low" setting to not only isolate the cam 26 but also the lever 28 from adversely effecting the ;
"extra-low" pressure setting. Extra-low pressure settings between 3.7 and 5.3 inches H2O can be achieved within close tolerance ranges by thus isolating the "low-high" calibration f mechanism from the "extra-low" calibration structure. Thus ,~
-~ the design of first spring 16 which must be responsive to a wide range of pressure settings need only be designed to such pressures since second spring 55 provides the force necessary to maintain the calibration mechanism in "sync". Additionally, the design 20 of second spring 55 is not critical in the sense that same effects the calibration of the switch and thus externally exposing second spring 55 is not harmful to the operation thereof.
Furthermore the use of second spring 55 permits the switch to be locked in its "extra-low position" in an aligned manner.
That is the profile of cam 26 at Point E can be shaped to conform generally to the shape of the follower end 43 of lever 28. Thus cam 26 is in a "locked" position relative to lever 28 and the j ' .
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appliance control knob (not shown) mounted on camshaft 35 is likewise "locked" to assure alignment with its corresponding console dial (also not shown) for properly indicating the "mini-wash" setting.
To reduce the possibility of calibration slip during repeated usage of the pressure switch, both calibration screws 30, 32 are self-threaded into their respective bores and a *
sealing substance such as "glyptal" is applied to the threads ~ -of the screws to further reduce the possibility of loosening during use. Furthermore, because both calibration screws are threaded into fixed surfaces (first calibration screw 30 into housing surface 12 and secondary calibration screw 32 into bracket tab portion 39) any tool forces applied to either -~
calibration screw cannot adversely influence the force on first spring 16. This permits quick calibration of the switch during assembly. ~ ~
Furthermore, mounting of the switch into the appliance - -is simplified by the shroud mechanism built into the switch housing. That is, vertical wall portion 37 of mounting bracket 24 prevents field wires (not shown) connected to terminals X,Y,Z
from becoming fouled in the cam mechanism and the boss con-figuration 18 formed in the housing surface portion 12 prevents fouling of the field wires with the lever mechanism. In this manner the possibility of the field wiring hindering the operation of the calibration mechanism and/or being shorted thereagainst is ' remote. Thus the need for wiring harnesses to~be applied in the field to prevent wire fouling is eliminated.
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104;~S(~9 While th~ cam and bracket arrangement of the subject invention can be constructed of metal parts, the cam 36, camsha~t 35 and lever 28 are preferably formed of plastic such as polypropylene which has a low co-efficient of friction.
The use of such plastic not only substantially reduces the cost of the assembly, but also eliminates the need for lubricating or greasing these parts if made from metal. This simplifies the assembly of the device and also prevents foreign matter from accumulating in the grease during use of the switch which, in time, may hinder switch operation.
The invention has been described with reference to a preferred embodiment. Obviously, modifications and alterations will occur to others, upon reading and understanding the -' specification. For example, slot 50 could be eliminated and the extra-low setting be achieved by adjusting screw 32 to contact bracket 28 which inturn would contact plunger 20. Such modification would have to incorporate additional known structure to "lock" cam 26 relative lever 28 in the "extra-low" setting.
It is our intention to include all such modifications and alterations insofar as they come within the scope of the present invention.
It is thus the essence of the invention to provide in - a pressure switch simplified calibration means therefor which ` permit the switch to be adjusted over two pressure ranges with the mechanism employed in effecting one of the pressure ranges being isolated from adversely effecting the mechanism establishing the second pressure range and vice versa.
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engaging the cam as a follower with portions thereof intermediate the ends contacting the plunger. Means pivotally mount the one lever end to the switch about a single pivot point, the pivot means including adjustable means operable, upon adjustment, to move the pivot point of the lever with respect to the plunger for varying the spring biasing of the plunger.
According to one aspect of the invention ~here is provided means for establishing the calibrating an "extra-low" pressure setting for the switch, the "extra-low" pressure setting means effective to isolate the lever and the cam means from acting on the plunger when the "extra-low" pressure setting-means is operative.
The invention may take physical form in certain parts and arrangement of parts, one embodiment of which will be described in detail herein and illustrated in the accompanying drawings which form a part hereof and wherein:
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~04ZS09 FIGURE 1 is a top plan view of the calibration mechanism of the sub~ect invention;
FIGURE 2 is a sectioned view of the calibration mechanism taken along line 2-2 of FIGURE l;
FIGURE 3 is an end view of the calibration mechanism taken along line 3-3 of FIGURE 1 to show the cam profile; and FIGURE 4 is a longitudinally sectioned view of the actuating lever employed in the calibration mechanism.
Referring now to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only and not for the purpose of limiting same, there is shown in FIGURE 1 a calibration mechanism 10 mounted onto a generally flat housing sur~ace 12 of a pressure switch 14.
Because pressure switch 14, by itself, does not form an essential feature of the subject invention and since its construction is known to those skilled in the art, the details of the switch are not shown herein. It is important only to understand that an adjustable spring-biased plunger arrangement 15 controls the trip force and hence the pressure to which switch :
14 responds. One such plunger arrangement is shown in FIGURE 2 and includes a first spring 16 received within a bore 17 formed in a boss 18 extending from the generally flat housing portion surface 12. The bottom end of first spring 16 acts against a switch blade (not shown) usually by means of an actuator 19 to normally ;. ' :
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104ZSt~9 b~as the switch blade into a first snapped position. The precompression force of spring 16 and thus the switch trip pressure is calibrated by the distance a plunger 20 extends within bore 17 to compress the spring. Opposing the spring force is pressure, determined by the water level in the tub, as sensed by a diaphragm (not shown) which exerts a force on the opposite~side of the switch blade. As the water-fill ;-level increases, thè diaphragm force becomes large enough to overcome the spring precompression and slight movement of the diaphragm thereafter moves the switch blade toggle mechanism pass center to snap the switch.
lhe calibrat-ion mechanism 10 of the subject invention as best shown in FIGURES 1 and 2 includes an especially configured mounting bracket 24 housing and journalling a cam 26 therein; a lever 28 operatively associated with cam 26; a primary calibration screw 30 for _~ adjusting normal "low-high" pressure settings and a secondary calibratîon screw 32 for adjusting an "extra-low~' pressure settingO
~ountin~ bracket 24 has a generally flat base 33 secure~ to housing surface 12 by a pair of screws.
- Extending upwardly from base 33 is a known U-shaped bracket ~ portion 34 for ~ournalling the shaft 35 of cam 26 as best I ~ ~hown in FIGURE 2. The forward leg 34A of the U-shaped 25 i bracket portion at the upper end thereof is formed into a stepped flange 36 for mounting pressure switch 14 to the j ~
J ~ onsole of an appliance. Longitudinally extending at one 1, i ~ ¦~ side of mounting bracket 24 is a vertical wall portion 37 ` -11 . .. I
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. I 73-CO~-106 1 1 ` 1042S09 which is parallel to the longitudinal centerline 38 of shaft 3S and lever 28. Vertical wall portion 37 is positioned on . . the side of housing surface 12 which contains known terminal ; connections X,Y, and Z for completing appropriate circuitry j when the switch is snapped. Importantly wall portion 37 is spaced from centerline 38 a distance approximately equal to the maximum diameter of cam 26. At the upperpart of the rearward end of vertical wall portion 37 there is provided a right angled tab portion 39 which receives in threaded engagement therethrough the secondary calibration screw 32. . -The lever 28 of calibration mechanism 10 is shown . in FIGURES 1,2 and 4 and may best be defined as having a -. pivoted end portion 42, a follower end portion 43 at the , opposite end of the lever and a mid portion 44 adap~ed to j 15 contact plunger 20.
. Follower end portion 43 is formed in a known I circular configuration to insure proper contact with the ¦
profile of cam 26 and extends through an opening 40 in the ~ ~- . rear leg 34B of U-shaped bracket portion 34. Opening 40 l~ 20 i~ is sufficiently sized to permit unimpeded vertical travel '.
of the follower end which occurs upon rotation of cam 26.
Pivoted end portion 42~as best shown in FIGURE 2 may-.... . .
. be defined ~y a spherical follicle 46 having a central .l ¦ opening 47 extending therethrough. Follicle 46 is adapted - 25 ~ to receive in a pivotable manner the spherical head 49 of , the first calibration screw 30 whlch in turn is self-threaded i~to a bore 48 formed in the especially configured boss 18 ~ i~ housing surface 12.
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lO~Z509 Mid portion 4~ includes an especially configured ~ slot 50 (FIGURE 1), the longitudinally orientated portion thereof 50A having sufficient width to receive a boss 21 (FIGURE 2) extending from the top end 22 of plunger 20 which is especially configured in this respect. Formed on the bottom of lever 28 and on each side of the longitudinally extending portion of H-slot 50 is an arcuate projection 52 (FIGURE 4) which is adapted to engage the top surfac~ 22 of plunger 20 on opposite sides of boss 21. Arcuate projections ; 10 52 have a depth less than the height of boss 21 to insure that the boss will always extend through H-slot 50 and thus prevent ~ -interference therebetween.
Between pivot end 42 and mid portion 44 of lever 28 is a second spring 55. Spring 55 is seated at one end in a second bore 56 formed in housing boss 18 and at its other end is seated -: ..
on lever 28 by a boss 57 which is formed in the underside surface of the lever by punching a hole therethrough. The main body , portion of the lever is strengthened by side rails 58 which impart "channel-like" structural properties to the lever. --The cam profile which is engaged by the follower end 43 - of lever 28 is shown in FIGURE 3. That portion of the cam profile between Points A and B controls the normal "low-high"
settings of the pressure switch which typically occur between -~
pressure ranges from 8 to 16 inches of water. The cam profile ' between Points A and B is shown serrated to provide an "infinite"
water level adjustment between the normal low ahd high ranges of the switch. Positive, mechanical reset of the switch occurs .. ..
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. ' , `' 104;~SQ9 .1en the cam is further rotated over its smooth portion between Points B and C of the cam profile. The cam profile betwee~ Points B and C is a generated curve having greatest radial distance at its stop defined by Point C to assure return of the cam to its maximum high setting level and thus prevent locking of the switch at reset.
When cam 26 is rotated in its opposite direction the follower end 43 will eventually rest at Point E of the cam profile defined as the "mini-wash" or "extra-low" pressure setting. To ensure positive reset of the switch as cam 26 is rotated to its "mini-wash" position, the cam is cut with a lobe indicated at Point D which has a radial distance extending to the cam center 60 approximately equal to the mid point radial distance of the cam profile between Points B and C.
When the device is assembled at the factory, cam 26 is usually rotated to Point B on its profile, the highest pressure setting in the normal "low-high"range. First calibration screw 30 is turned to adjust the position of lever 28 for proper setting of the high pressure thereby establishing the normal "low-high" range. When cam 26 is rotated within its normal "low-high" range and also through its positive reset position i.e. Points A-C, the arcuate projections 52 contact the top end 22 of plunger 20 to accordingly adjust the precompression of first spriny 16 or to establish a solid driving connection to assure positive mechanical reset.
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The cam i9 then rotated into its "extra-low" or "mini-wash" pressure settin~ at Point E. In this cam position, second spring 55 lifts lever projections,52 off the top end 22 of the plunger while forcing the follower end 43 into the cam notch ` defined at Point E. The secondary calibration screw 32 is then self-threaded through an opening in tab portion 39 of mounting bracket to contact the boss end 21 of plunger 20. Thus, second spring 55 which assures good contact between lever end 43 and the cam profile during normal "low-high" pressure range settings 10 also functions in the "extra-low" setting to not only isolate the cam 26 but also the lever 28 from adversely effecting the ;
"extra-low" pressure setting. Extra-low pressure settings between 3.7 and 5.3 inches H2O can be achieved within close tolerance ranges by thus isolating the "low-high" calibration f mechanism from the "extra-low" calibration structure. Thus ,~
-~ the design of first spring 16 which must be responsive to a wide range of pressure settings need only be designed to such pressures since second spring 55 provides the force necessary to maintain the calibration mechanism in "sync". Additionally, the design 20 of second spring 55 is not critical in the sense that same effects the calibration of the switch and thus externally exposing second spring 55 is not harmful to the operation thereof.
Furthermore the use of second spring 55 permits the switch to be locked in its "extra-low position" in an aligned manner.
That is the profile of cam 26 at Point E can be shaped to conform generally to the shape of the follower end 43 of lever 28. Thus cam 26 is in a "locked" position relative to lever 28 and the j ' .
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appliance control knob (not shown) mounted on camshaft 35 is likewise "locked" to assure alignment with its corresponding console dial (also not shown) for properly indicating the "mini-wash" setting.
To reduce the possibility of calibration slip during repeated usage of the pressure switch, both calibration screws 30, 32 are self-threaded into their respective bores and a *
sealing substance such as "glyptal" is applied to the threads ~ -of the screws to further reduce the possibility of loosening during use. Furthermore, because both calibration screws are threaded into fixed surfaces (first calibration screw 30 into housing surface 12 and secondary calibration screw 32 into bracket tab portion 39) any tool forces applied to either -~
calibration screw cannot adversely influence the force on first spring 16. This permits quick calibration of the switch during assembly. ~ ~
Furthermore, mounting of the switch into the appliance - -is simplified by the shroud mechanism built into the switch housing. That is, vertical wall portion 37 of mounting bracket 24 prevents field wires (not shown) connected to terminals X,Y,Z
from becoming fouled in the cam mechanism and the boss con-figuration 18 formed in the housing surface portion 12 prevents fouling of the field wires with the lever mechanism. In this manner the possibility of the field wiring hindering the operation of the calibration mechanism and/or being shorted thereagainst is ' remote. Thus the need for wiring harnesses to~be applied in the field to prevent wire fouling is eliminated.
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~ Trade Mark :
cm~
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104;~S(~9 While th~ cam and bracket arrangement of the subject invention can be constructed of metal parts, the cam 36, camsha~t 35 and lever 28 are preferably formed of plastic such as polypropylene which has a low co-efficient of friction.
The use of such plastic not only substantially reduces the cost of the assembly, but also eliminates the need for lubricating or greasing these parts if made from metal. This simplifies the assembly of the device and also prevents foreign matter from accumulating in the grease during use of the switch which, in time, may hinder switch operation.
The invention has been described with reference to a preferred embodiment. Obviously, modifications and alterations will occur to others, upon reading and understanding the -' specification. For example, slot 50 could be eliminated and the extra-low setting be achieved by adjusting screw 32 to contact bracket 28 which inturn would contact plunger 20. Such modification would have to incorporate additional known structure to "lock" cam 26 relative lever 28 in the "extra-low" setting.
It is our intention to include all such modifications and alterations insofar as they come within the scope of the present invention.
It is thus the essence of the invention to provide in - a pressure switch simplified calibration means therefor which ` permit the switch to be adjusted over two pressure ranges with the mechanism employed in effecting one of the pressure ranges being isolated from adversely effecting the mechanism establishing the second pressure range and vice versa.
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Claims (11)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A calibration mechanism for a pressure switch of the type having a spring-biased plunger arrangement adjustable to sense different pressures to which said switch responds, said mechanism comprising:
(a) means for establishing and calibrating normal "low-to-high" pressure settings of said switch, said "low-to-high" pressure setting means including lever means for adjust-ing said plunger and selectively operative cam means in associa-tion with said lever means to provide a "low-to-high" range of settings, wherein said lever means includes a lever adapted for pivotal movement at one end thereof with respect to said switch, said lever having the opposite end thereof engaging said cam as a follower with portions thereof intermediate said ends contact-ing said plunger, and (b) means pivotally mounting said one lever end to said switch about a single pivot point, said pivot means including adjustable means operable, upon adjustment, to move the pivot point of said lever with respect to said plunger for varying the spring biasing of said plunger.
(a) means for establishing and calibrating normal "low-to-high" pressure settings of said switch, said "low-to-high" pressure setting means including lever means for adjust-ing said plunger and selectively operative cam means in associa-tion with said lever means to provide a "low-to-high" range of settings, wherein said lever means includes a lever adapted for pivotal movement at one end thereof with respect to said switch, said lever having the opposite end thereof engaging said cam as a follower with portions thereof intermediate said ends contact-ing said plunger, and (b) means pivotally mounting said one lever end to said switch about a single pivot point, said pivot means including adjustable means operable, upon adjustment, to move the pivot point of said lever with respect to said plunger for varying the spring biasing of said plunger.
2. The calibration mechanism defined in claim 1, wherein, (a) said lever means includes means biasing said other end of said lever in contact with said cam means; and, (b) said cam means includes notch means operative when said cam means is selectively moved to certain positions to cause said lever to operatively move said plunger.
3. The calibration mechanism defined in claim 1, wherein said cam means includes a rotatable cam having 2 stepped profile with said follower end of said lever received thereon for estab-lishing said low-to-high range of pressure settings.
4. The calibration mechanism defined in claim 1, wherein said pivot means includes, (a) means defining a first pivot surface adjacent said one end of said lever; and (b) fastener means received through said lever and threadedly engaging said switch, said fastener means including means defining a second pivot surface contacting said first pivot surface.
5. In a pressure switch of the type having housing means including pressure responsive means with switch means actuatable upon movement of said pressure responsive means, and plunger means movably mounted on said housing means, and means variably biasing said plunger means, said bias being determina-tive of the pressure at which said switch is actuated, the im-provement comprising:
(a) bracket means mounted on said pressure switch housing;
(b) lever means having one end thereof pivoted on said housing means and having portions thereof contacting said plunger means for adjusting said pressure switch;
(c) means pivotally mounting said one lever end to said housing about a single pivot point;
(d) cam means mounted on said bracket means and contacting the end of said lever means opposite said pivoted end, and exerting a force thereon in opposition to said bias; and (e) calibrating means disposed at said pivotal end of said lever means, said calibrating means being operative, upon adjustment thereof, to move the pivot point of said lever means for determining the high and low actuation pressures of said switch.
(a) bracket means mounted on said pressure switch housing;
(b) lever means having one end thereof pivoted on said housing means and having portions thereof contacting said plunger means for adjusting said pressure switch;
(c) means pivotally mounting said one lever end to said housing about a single pivot point;
(d) cam means mounted on said bracket means and contacting the end of said lever means opposite said pivoted end, and exerting a force thereon in opposition to said bias; and (e) calibrating means disposed at said pivotal end of said lever means, said calibrating means being operative, upon adjustment thereof, to move the pivot point of said lever means for determining the high and low actuation pressures of said switch.
6. A calibration mechanism for a pressure switch of the type having a spring-biased plunger arrangement adjustable to sense different pressures to which said switch responds, said mechanism comprising:
(a) means for establishing and calibrating normal "low-to-high" pressure settings of said switch, said "low-to-high" pressure setting means including lever means for adjust-ing said plunger and selectively operative cam means in associa-tion with said lever means to provide a "low-to-high" range of settings, wherein said lever means includes a lever adapted for pivotal movement at one end thereof with respect to said switch, said lever having the opposite end thereof engaging said cam as a follower, with portions thereof intermediate said ends con-tacting said plunger; and (b) means pivotally mounting said one lever end to said switch about a single pivot point, said pivot means includ-ing adjustable means operable upon adjustment to move the pivot center of said lever with respect to said plunger for varying the spring biasing of said plunger; and (c) means for establishing and calibrating an "extra-low" pressure setting for said switch, said "extra-low" pressure setting means effective to isolate said one lever and said cam means from acting on said plunger when said "extra-low" pressure setting means is operative.
(a) means for establishing and calibrating normal "low-to-high" pressure settings of said switch, said "low-to-high" pressure setting means including lever means for adjust-ing said plunger and selectively operative cam means in associa-tion with said lever means to provide a "low-to-high" range of settings, wherein said lever means includes a lever adapted for pivotal movement at one end thereof with respect to said switch, said lever having the opposite end thereof engaging said cam as a follower, with portions thereof intermediate said ends con-tacting said plunger; and (b) means pivotally mounting said one lever end to said switch about a single pivot point, said pivot means includ-ing adjustable means operable upon adjustment to move the pivot center of said lever with respect to said plunger for varying the spring biasing of said plunger; and (c) means for establishing and calibrating an "extra-low" pressure setting for said switch, said "extra-low" pressure setting means effective to isolate said one lever and said cam means from acting on said plunger when said "extra-low" pressure setting means is operative.
7. The calibration mechanism defined in claim 6, wherein said extra-low pressure setting means includes, (a) an opening extending through said lever;
(b) adjustable stop means suspended above said opening for contacting said plunger;
(c) spring means disposed between said lever and said switch and located longitudinally along said lever between said opening and said pivotable end for biasing said lever against said cam means; and (d) latch means within said cam means for receiving said follower end of said lever to raise said lever from contact with said plunger.
(b) adjustable stop means suspended above said opening for contacting said plunger;
(c) spring means disposed between said lever and said switch and located longitudinally along said lever between said opening and said pivotable end for biasing said lever against said cam means; and (d) latch means within said cam means for receiving said follower end of said lever to raise said lever from contact with said plunger.
8. The calibration mechanism defined in claim 7, wherein (a) said plunger arrangement includes said plunger partially received within a bore in the switch housing, said plunger having an exposed top end and a boss extending through said top end, said boss extending through said opening in said lever, and (b) said lever having a pair of arcuate projections extending from the underside surface thereof and spaced on dia-metrically opposite sides of said opening, said projections straddling said boss of said plunger and contacting said top surface of said plunger when said low-to-high pressure setting means are operable.
9. In a pressure switch of the type having a plunger arrangement at least partially disposed within a bore formed in a portion of the switch housing and biased by a first spring, the effective force of which determines the pressure at which said switch responds, the improvement comprising:
bracket means mounted on said pressure switch housing portion in which said plunger arrangement is formed;
a lever having means pivotally mounting said lever to said housing portion at one end thereof and about a single pivot point, said lever acting on said plunger to adjust said pressure switch;
cam means mounted on said bracket means and acting on said lever opposite the mounting means to move said lever in opposition to said first spring force of said pressure switch over a "low-to-high" range of settings and movable to an "extra-low" position; 16 means for continuously biasing said lever against said cam means throughout movement of said cam means between said "low-to-high" and said "extra-low" positions;
first calibrating means at the pivotally mounted end of said lever for establishing a maximum high pressure setting of said device; and second calibrating means mounted on said bracket means for calibrating said switch to said "extra-low" setting said second calibrating means effective while said cam means is positioned in said "extra-low" position to isolate said cam means and said lever from acting on said plunger.
bracket means mounted on said pressure switch housing portion in which said plunger arrangement is formed;
a lever having means pivotally mounting said lever to said housing portion at one end thereof and about a single pivot point, said lever acting on said plunger to adjust said pressure switch;
cam means mounted on said bracket means and acting on said lever opposite the mounting means to move said lever in opposition to said first spring force of said pressure switch over a "low-to-high" range of settings and movable to an "extra-low" position; 16 means for continuously biasing said lever against said cam means throughout movement of said cam means between said "low-to-high" and said "extra-low" positions;
first calibrating means at the pivotally mounted end of said lever for establishing a maximum high pressure setting of said device; and second calibrating means mounted on said bracket means for calibrating said switch to said "extra-low" setting said second calibrating means effective while said cam means is positioned in said "extra-low" position to isolate said cam means and said lever from acting on said plunger.
10. The pressure switch of claim 9, wherein said lever is generally channel shaped having a follicle at one end with an opening extending therethrough, and said first calibrating means including a fastener received in threaded engagement with said first housing portion, said fastener having a head received within said follicle.
11. The pressure switch of claim 9 wherein said means for continuously biasing said lever against said cam means in-cludes a second spring compressed between said first housing portion and said lever to exert a bias on said lever in the same direction as said first spring.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US00408787A US3846600A (en) | 1973-10-23 | 1973-10-23 | Means for calibrating pressure switches at extra-low pressure settings |
| US73729376A | 1976-11-01 | 1976-11-01 | |
| AU24549/77A AU504926B2 (en) | 1973-10-23 | 1977-04-22 | Calibrating-pressure switches at extra low pressure settings |
| US05/916,992 USRE30207E (en) | 1973-10-23 | 1978-06-19 | Means for calibrating pressure switches at extra-low pressure settings |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1042509A true CA1042509A (en) | 1978-11-14 |
Family
ID=27422781
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA210,980A Expired CA1042509A (en) | 1973-10-23 | 1974-10-08 | Means for calibrating pressure switches at extra-low pressure settings |
Country Status (4)
| Country | Link |
|---|---|
| US (2) | US3846600A (en) |
| JP (1) | JPS5067975A (en) |
| AU (1) | AU504926B2 (en) |
| CA (1) | CA1042509A (en) |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4024364A (en) * | 1975-11-28 | 1977-05-17 | Eaton Corporation | Pressure switch mechanism and cam stop arrangement therefor |
| US4109121A (en) * | 1976-07-22 | 1978-08-22 | Robertshaw Controls Company | Electrical switch construction and method of making the same |
| JPS55500374A (en) * | 1978-05-30 | 1980-06-26 | ||
| US4262178A (en) * | 1978-05-30 | 1981-04-14 | Eaton Corporation | Calibration mechanism for a pressure switch |
| JPS635153Y2 (en) * | 1980-11-08 | 1988-02-12 | ||
| US4755639A (en) * | 1987-10-28 | 1988-07-05 | Eaton Corporation | Pressure switch with calibration tab |
| US4947674A (en) * | 1988-09-07 | 1990-08-14 | Commonwealth Edison | Limit switch calibration system |
| US7441439B2 (en) * | 2005-02-07 | 2008-10-28 | Richard Dean Mc Farland | Portable pressure switch calibration and diagnostic tool |
| US9640344B2 (en) | 2014-02-07 | 2017-05-02 | Good Day Tools Llc | Portable pressure switch calibration and diagnostic tool |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2375387A (en) * | 1941-10-31 | 1945-05-08 | Cutler Hammer Inc | Circuit controlling device |
| US2919321A (en) * | 1957-09-30 | 1959-12-29 | Tait Mfg Co The | Pressure differential responsive snapacting control for pumps and the like |
| US3046368A (en) * | 1960-03-31 | 1962-07-24 | Penn Controls | Compressor unloader |
| US3600536A (en) * | 1969-12-22 | 1971-08-17 | Controls Co Of America | Calibrating pressure switches at extra low-pressure setting |
| IT964065B (en) * | 1971-08-24 | 1974-01-21 | Actuated Controls Ltd | IMPROVEMENTS TO PRESSURE SENSITIVE SWITCHES |
| US3845265A (en) * | 1973-07-02 | 1974-10-29 | Controls Co Of America | Low profile pressure switch with plunger adjusting means |
-
1973
- 1973-10-23 US US00408787A patent/US3846600A/en not_active Expired - Lifetime
-
1974
- 1974-10-08 CA CA210,980A patent/CA1042509A/en not_active Expired
- 1974-10-23 JP JP49122325A patent/JPS5067975A/ja active Pending
-
1977
- 1977-04-22 AU AU24549/77A patent/AU504926B2/en not_active Expired
-
1978
- 1978-06-19 US US05/916,992 patent/USRE30207E/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| USRE30207E (en) | 1980-02-05 |
| AU2454977A (en) | 1977-12-08 |
| AU504926B2 (en) | 1979-11-01 |
| JPS5067975A (en) | 1975-06-06 |
| US3846600A (en) | 1974-11-05 |
| AU7454174A (en) | 1976-04-29 |
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