US3846600A - Means for calibrating pressure switches at extra-low pressure settings - Google Patents

Means for calibrating pressure switches at extra-low pressure settings Download PDF

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Publication number
US3846600A
US3846600A US00408787A US40878773A US3846600A US 3846600 A US3846600 A US 3846600A US 00408787 A US00408787 A US 00408787A US 40878773 A US40878773 A US 40878773A US 3846600 A US3846600 A US 3846600A
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US
United States
Prior art keywords
lever
switch
low
plunger
cam
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 - Lifetime
Application number
US00408787A
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English (en)
Inventor
L Kolze
W Jones
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Eaton Corp
Original Assignee
Eaton Corp
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Eaton Corp filed Critical Eaton Corp
Priority to US00408787A priority Critical patent/US3846600A/en
Priority to CA210,980A priority patent/CA1042509A/en
Priority to AU74541/74A priority patent/AU484713B2/en
Priority to JP49122325A priority patent/JPS5067975A/ja
Application granted granted Critical
Publication of US3846600A publication Critical patent/US3846600A/en
Priority to AU24549/77A priority patent/AU504926B2/en
Priority to US05/916,992 priority patent/USRE30207E/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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

Definitions

  • 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.
  • First calibration means are provided in the lev'ers pivoted end to adjust the normal low-high pressure settings of the switch.
  • Second calibration means are provided to isolate the lever and cam from the plunger for effecting a precise setting of the pressure switch at extra-low pressures.
  • the invention is particularly applicable to pressure switches used for controlling the water-fill level of washing machines, dishwashers and like domestic appliance's, 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.
  • an actuating mechanism provided for a pressure switch of the type using an adjustable spring-biased plunger arrangement for controlling the trip force and hence the pressure to which the switch responds.
  • the calibration mechanism includes an especially configured lever pivoted in an adjustable manner at one end to the switch housing portion from which the plunger arrangement extends. The opposite lever end acts as a follower to engage a cam mounted on a bracket to the housing; the cam controlling normal low-high" pressure settings of the switch. Accordingly calibration of the low-high settings is achieved by adjusting the space between the leverspivoted end and the upper housing surface.
  • a second calibration screw is provided in the cam bracket which limits the upward movement of the plunger arrangement and accordingly establishes the extra-low pressure setting. The cam is cut with a deep notch in the extra-low setting whereby the cam is rendered ineffective to exert a bias on the follower end of the lever.
  • a spring is provided between the plunger portion and pivoted end of the lever arm which acts to bias the lever arm upwardly against the cam.
  • the extra-low calibration screw is positioned over the plunger and adapted to pass through an especially configured slot in the lever arm adjacent the plunger. The lever arm is thus isolated from the plunger when the cam is moved into its extra-low setting because the spring biases the lever off the plunger while the extra-low calibration screw passes through the slot to contact the plunger and adjust the pressure accordingly.
  • the spring biases the follower end of the lever into an especially configured slot formed in the cam at the extra-low pressure setting thereof.
  • the bracket configuration and housing configuration is constructed to effectively surround the calibration mechanism and thus fully shield the field wiring from being caught therein. This permits the switch to be mounted in difficult locations on the console. Additionally the bracket may be universally applied to those switches not employing a mini-wash cycle and still shield the field wire from the rotating cam to prevent damage thereof.
  • Another object of the subject invention in conjunction with the last mentioned object is to provide positive locking means for the calibration mechanism when the switch is placed in an extra-low" pressure setting.
  • Still another object of the subject invention is to provide shielding means in the calibration mechanism of a pressure switch to prevent fouling and failing of the field wiring connected to the switch.
  • FIG. 1 is a top plan view of the calibration mechanism of the subject invention
  • FIG. 2 is a sectioned view of the calibration mechanism taken along line 2-2 of FIG. 1;
  • FIG. 3 is an end view of the calibration mechanism taken along line 3-3 of FIG. 1 to show the cam profile
  • FIG. 4 is a longitudinally sectioned view of the actuating lever employed in the calibration mechanism.
  • FIG. 1 a calibration mechanism mounted onto a generally flat housing surface 12 of a pressure switch 14.
  • pressure switch l4 because pressure switch l4, 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 plungerarrangement 15 controls the trip force and hence the pressure to which switch 14 responds.
  • One such plunger arrangement is shown in FIG. 2 and includes a first spring 16 received within a bore vl7 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 bias 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, the 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.
  • the calibration mechanism 10 of the subject invention as best shown in FIGS. 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 calibration screw 32 for adjusting an extra-low pressure setting.
  • Mounting bracket 24 has a generally flat base 33 secured-to housing-surface 12 by a pair'of screws. Ex-
  • a known U-shaped bracket portion 34 for journalling the shaft 35 of cam 26 as best shown in FIG. 2.
  • the forward leg 34A of the U-shaped bracket portion at the upper end thereof is formed into a stepped flange 36 for mounting-pressure switch 14 to the console of an appliance.
  • Longitudinally extending atone side of mounting bracket 24 is a vertical wall portion 37 which is parallel to the longi tudinal centerline 38 of shaft 35 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 when the switch is snapped.
  • wall portion 37 is spaced from centerline 38 a distance approximately equal to the maximum diameter of cam 26.
  • 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 FIGS. 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 adaptedto contact plunger 20.
  • Opening 40 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 FIG. 2 maybe defined by a spherical follicle 46 having a central opening 47 extending therethrough.
  • Follicle 46 is adapted to receive in a pivotable manner the spherical head 49 of the first calibration screw 30 which in turn is self-threaded into a bore 48 formed in the especially configured boss 18 in housing surface 12.
  • Mid portion 44 includes an especially configured H- slot 50 (FIG. 1), the longitudinally orientated portion thereof 50A having sufficient width to receive a boss 21 (FIG. 2) extending from the top end 22 of plunger 20 which is especially configured in this respect.
  • H- slot 50 Formed on the bottom of lever 28 and on each sideof the longitudinally extending portion of H-slot 50 is an arcuate projection 52 (FIG. 4) which is adapted to engage the top surface 22 of plunger 20 on opposite sides of boss 21.
  • Arcuate projections 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.
  • 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 FIG. 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 l6 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 and high ranges of the switch. Positive, mechanical reset of the switch occurs when the cam is further rotated over its smooth portion between Points B and C of the cam profile.
  • the cam profile between Points .13 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.
  • cam 26 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.
  • the arcuate projections 52 contact the top end 22 of plunger 20 to accordingly adjust the precompression of spring 55 which assures good contact between lever end 43 and the cam profile during normal low-high" pressure range settings also functions in the extralow" 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 H O can be achieved within close tolerance ranges by thus isolating the low-high" calibration mechanism from the extra-low" calibration structure.
  • 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 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.
  • 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 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.
  • 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.
  • the cam and bracket arrangement of the subject invention can be constructed of metal parts
  • the cam 36, camshaft 35 and lever 28 are preferably formed of plastic such as polypropylene which has a low co-efficient of friction.
  • 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.
  • said low to high pressure setting means including lever means for adjusting said plunger and cam means operatively associated with said lever means to provide a low to high" range of settings;
  • said extra-low pressure setting means effective to isolate said lever and said cam means from acting on said plunger when said extra-low pressure setting means is operative.
  • lever means includes a lever pivotable at one end to said switch, engaging said cam means at its opposite end as a follower and contacting said plunger about a portion between its ends,
  • said pivotable lever end defined by a follicle therein having a central opening extending through said follicle and a fastener received in threaded engagement with the switch housing and having a head received in said follicle whereby said switch can be calibrated between said low-high pressure settings.
  • said extra-low pressure setting means includes an opening extending through said portion of said lever, adjustable stop means suspended above said opening for contacting said plunger, spring means between said lever and the switch housing and longitudinally positioned between said lever portion and said pivotable end for biasing said lever against said cam means and notch means within said cam means for receiving said follower end of said lever to raise said lever from contact with said plunger.
  • 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 said top end, said boss extending through said opening in said lever, and said portion of said lever having a pair of arcuate projections extending from the underside surface 1 thereof and spaced on diametrically 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.
  • cam means includes a rotatable cam having a first stepped profile receiving said follower end of said lever for establishing said low to high range and a second stepped profile for establishing said extra-low" setting, and
  • said notch means including a notch in said second profile, said notch configured similar to said follower end of said lever for relatively locking said cam and said lever in said extra-low range.
  • the im- 7 provement comprising:
  • bracket means mounted on said pressure switch housing portion in which said plunger arrangement is formed;
  • lever means pinned to said housing portion at one end thereof and acting on the plunger to adjust said pressure switch;
  • cam means mounted on said bracket means and acting on said lever means opposite said pinned end to bias said lever means in opposition to said first spring force of said pressure switch over a low to high range of settings and movable to an extralow position;
  • second calibrating means mounted on said bracket means for calibrating said switch to said extralow" setting and rendering-said cam means ineffective to bias said lever means in opposition to said spring force in said extra-low position.
  • lever means is defined by a generally channelled shaped lever arm having a follicle at one end with an opening extending therethrough, and i 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.
  • said second calibrating means further provides means for rendering ineffective the bearing of said lever on said plunger.
  • a bracket having a base mounted to said generally flat surface; a U-shaped bracket portion extending upwardly from said base; v a-shaft journalled within said U-shaped bracket portion and a cam secured to said shaft, said cam defining a part of said calibration means; an upwardly extending, sidewall portion of said bracket extending generally parallel to said longitudinal centerline and spaced from said shaft a distance approximately equal to the maximum radius of said cam for preventing fouling of said field wires with said, cam.
  • said'housing surface includes an upwardly extending, raised boss portion having first, second, and third bores longitudinally spaced bores formed therein,

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  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Switches Operated By Changes In Physical Conditions (AREA)
US00408787A 1973-10-23 1973-10-23 Means for calibrating pressure switches at extra-low pressure settings Expired - Lifetime US3846600A (en)

Priority Applications (6)

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
CA210,980A CA1042509A (en) 1973-10-23 1974-10-08 Means for calibrating pressure switches at extra-low pressure settings
AU74541/74A AU484713B2 (en) 1973-10-23 1974-10-21 Means for calibrating pressure switches at extra-low pressure settings
JP49122325A JPS5067975A (enrdf_load_stackoverflow) 1973-10-23 1974-10-23
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

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

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Application Number Title Priority Date Filing Date
US05/916,992 Reissue USRE30207E (en) 1973-10-23 1978-06-19 Means for calibrating pressure switches at extra-low pressure settings

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US3846600A true US3846600A (en) 1974-11-05

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US00408787A Expired - Lifetime US3846600A (en) 1973-10-23 1973-10-23 Means for calibrating pressure switches at extra-low pressure settings
US05/916,992 Expired - Lifetime USRE30207E (en) 1973-10-23 1978-06-19 Means for calibrating pressure switches at extra-low pressure settings

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Application Number Title Priority Date Filing Date
US05/916,992 Expired - Lifetime USRE30207E (en) 1973-10-23 1978-06-19 Means for calibrating pressure switches at extra-low pressure settings

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US (2) US3846600A (enrdf_load_stackoverflow)
JP (1) JPS5067975A (enrdf_load_stackoverflow)
AU (1) AU504926B2 (enrdf_load_stackoverflow)
CA (1) CA1042509A (enrdf_load_stackoverflow)

Cited By (6)

* Cited by examiner, † Cited by third party
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
US4159563A (en) * 1976-07-22 1979-07-03 Robertshaw Controls Company Electrical switch construction and method of making the same
WO1979001143A1 (en) * 1978-05-30 1979-12-27 Eaton Corp Calibration mechanism for a pressure switch
US4262178A (en) * 1978-05-30 1981-04-14 Eaton Corporation Calibration mechanism for a pressure switch
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

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS635153Y2 (enrdf_load_stackoverflow) * 1980-11-08 1988-02-12
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

Citations (4)

* Cited by examiner, † Cited by third party
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
US3789171A (en) * 1971-08-24 1974-01-29 Actuated Controls Ltd Pressure switch with operating lever having manually adjustable pre-loading means therefore

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3600536A (en) * 1969-12-22 1971-08-17 Controls Co Of America Calibrating pressure switches at extra low-pressure setting
US3845265A (en) * 1973-07-02 1974-10-29 Controls Co Of America Low profile pressure switch with plunger adjusting means

Patent Citations (4)

* Cited by examiner, † Cited by third party
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
US3789171A (en) * 1971-08-24 1974-01-29 Actuated Controls Ltd Pressure switch with operating lever having manually adjustable pre-loading means therefore

Cited By (6)

* Cited by examiner, † Cited by third party
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
US4159563A (en) * 1976-07-22 1979-07-03 Robertshaw Controls Company Electrical switch construction and method of making the same
WO1979001143A1 (en) * 1978-05-30 1979-12-27 Eaton Corp Calibration mechanism for a pressure switch
US4262178A (en) * 1978-05-30 1981-04-14 Eaton Corporation Calibration mechanism for a pressure switch
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

Also Published As

Publication number Publication date
JPS5067975A (enrdf_load_stackoverflow) 1975-06-06
CA1042509A (en) 1978-11-14
AU2454977A (en) 1977-12-08
USRE30207E (en) 1980-02-05
AU504926B2 (en) 1979-11-01
AU7454174A (en) 1976-04-29

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