Means for calibrating pressure switches at extra-low pressure settings

Claim 2

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: 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 adjusting said plunger and cam means operatively associated with said lever means to provide a ''''low to high'''' range of settings; and means for establishing and calibrating an ''''extra-low'''' pressure setting for said switch, 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.

Claim 3

The calibration mechanism of claim 1 wherein said 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.

Claim 4

The calibration mechanism of claim 2 wherein 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.

Claim 5

The calibration mechanism of claim 3 wherein said lever and said cam means are formed of plastic having a low co-efficient of friction.

Claim 6

The calibration mechanism of claim 3 wherein 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 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.

Claim 7

The calibration mechanism of claim 3 wherein said 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.

Claim 8

The calibration mechanism of claim 6 wherein said extra-low setting is within the range of 3.7 to 5.3 in. H2O pressure.

Claim 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; 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 ''''extra-low'''' position; first calibrating means at said pinned end of lever means to determine the maximum high setting of said device; and second calibrating means mounted on said bracket means for calibrating said switch to said ''''extra-low'''' setting and rendering said cam means ineffective to bias said lever means in opposition to said spring force in said ''''extra-low'''' position.

Claim 10

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; 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 ''''extra-low'''' position; first calibrating means at said pinned end of lever means to determine the maximum high setting of said device; and second calibrating means mounted on said bracket means for calibrating said switch to said ''''extra-low'''' setting and rendering said cam means ineffective to bias said lever means in opposition to said spring force in said ''''extra-low'''' position.

Claim 11

The pressure switch of claim 8 wherein said lever means is defined by a generally channelled shaped lever arm 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.

Claim 12

The pressure switch of claim 9 wherein a second spring is compressed between said first housing portion and said lever to exert a bias on said lever in the same direction as said first spring, and said second calibrating means further provides means for rendering ineffective the bearing of said lever on said plunger.

Claim 13

The pressure switch of claim 10 wherein said second calibrating means further includes said cam means relatively locking said lever therewith when said switch is in said extra-low setting.

Claim 14

In a pressure switch of the type having a generally flat housing surface, said housing having a bore therein, an adjustable, spring-biased plunger extending partially within said bore for establishing the effective force which determines the pressure at which said switch responds, calibration means for adjusting the position of said plunger, and electrical terminals on one side of the longitudinal centerline of said housing for receiving field wires to complete switch circuitry, the improvement comprising: a bracket having a base mounted to said generally flat surface; a U-shaped bracket portion extending upwardly from said base; 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.

Claim 15

In a pressure switch of the type having a generally flat housing surface, said housing having a bore therein, an adjustable, spring-biased plunger extending partially within said bore for establishing the effective force which determines the pressure at which said switch responds, calibration means for adjusting the position of said plunger, and electrical terminals on one side of the longitudinal centerline of said housing for receiving field wires to complete switch circuitry, the improvement comprising: a bracket having a base mounted to said generally flat surface; a U-shaped bracket portion extending upwardly from said base; 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.

Claim 16

The pressure switch of claim 12 wherein said housing surface includes an upwardly extending, raised boss portion having first, second, and third bores longitudinally spaced bores formed therein, said plunger extending partially within said bore, said calibration mechanism including a lever having one end engaging said cam, its opposite end pivotable about a fastener, extending therethrough, and a mid-portion thereof adapted to contact said plunger, said fastener received within said second bore, and a spring received partially within said third bore spaced between said first and second bores and compressed against the underside of said lever whereby said raised portion of said housing prevents fouling of said field wires within the lever mechanism.