US2404843A

US2404843A - Pressure switch

Info

Publication number: US2404843A
Application number: US546797A
Authority: US
Inventors: Matthew W Huber
Original assignee: New York Air Brake LLC
Current assignee: New York Air Brake LLC
Priority date: 1944-07-27
Filing date: 1944-07-27
Publication date: 1946-07-30
Anticipated expiration: 1963-07-30
Also published as: GB594490A

Description

July 30, 1946. M. w. HUBER 2,404,843

PRESSURE SWITCH y Filed Jqly 27, 1944 ai 'f mijn@ '24 55 34 U @if 4Z 41 :Snnentor Madheww Huber BH 190,? Liam.

Patented July 30, 1946 PRESSURE SWITCH Matthew W. Huber, Watertown, N. Y., assignor to The New York Air Brake Company, a corporation of New Jersey Appiication July 27, 1944, SerialNo. 546,797

(Cl. 20G-83) 3 Claims.

This invention relates to pressure switches, and particularly to a pressure actuated switch of the micro-motion type.

There are available several commercial switch mechanisms of the snap action type, which are characterized by the ability to handle rather large currents and which shift reversely in response to motion of the actuating member (usually a plunger) through a very small range.

Fluid pressures up to four or five thousand pounds per square inch are in commercial use today and the trend is upward. A spring loaded abutment subject to such pressures may have a rather small range of motion, say 3/54 and still afford several times the motion required to actuate such a switch. The invention takes advantage of this fact by interposing between the abutment and the switch a variable ratio lever mechanism which changes the distance the abutment must move to trip the switch. If the required motion is small, the sensitivity is said to be high. The ability to adjust sensitivity facilities precise setting of the device for particular conditions.

For large adjustments of sensitivity the switch is shifted relatively to the lever fulcrum. This can be done in various ways but in the example illustrated the switch is simply reversed on its mount changing the point cf engagement of the switch plunger with the lever. For smaller changes of sensitivity the fulcrum is shifted. The fulcrum adjustment is so contrived that the trip point of the switch, relatively to the total range of motion of the abutment, can also be adjusted.

The precise form of the device is affected by the pressure to which the switch must respond, the permissible variation of such pressure, the character of the control effected by the switch and similar details, but a switch intended to Open and close as pressure shifts across 3,000 pounds per square inch is illustrated in the accompanying drawing as typical.

In the drawing- Fig. 1 is a plan View.

Fig. 2 is a section on the line 2-2 of Fig. 3.

Fig. 3 is a section on the line 3-3 of Fig. 1.

Fig. 4 is a view similar to Fig. 3 showing the switch reversed to reduce the sensitivity.

Fig. 5 is a fragmentary View similar to a portion of Fig. 4 showing a different :adjustment of the fulcrum The housing for the switch mechanism might be described as bottle shaped having a cylindrical body II which houses the switch mechanism and the neck l2 which houses the pressure responsive mechanism. The body II merges into v a mounting plate I3 with holes I4 for attaching screws. The lower end of the body II is closed by a removable plate I5 attached by screws.

The upper end of the neck I2 is threaded to receive a union fitting i5 by means of which the pressure line I'l is placed in communication with the bore lli above a pressure responsive diaphragm I9. This diaphragm is made of some oil resisting rubber-like plastic and is clamped between a seat 2l and an annular seating disc 22 by means of a member 23 which is screwed into the neck I2 from below and which serves as a clamp for the diaphragm and as a guide for 4the pressure stem 24.

This stem 24 has a domed head 25 which engages the central portion of the diaphragm I9 and which is limited in its downward motion by a ange 28. A shoulder 21 bears against a spring seat 28. A 'coil compression spring 29 reacts against the spring seat 28 and against a similar seat held by'ring 3| threaded into the lower end of the neck l2. This is locked in its adjusted position by the locking member 32.

The stress on spring 29 is so adjusted that the plunger 24 will respond at the desired pressure, here assumed to be 3,000 pounds per square inch. The stem 24 is guided in the spring seat 3| and extends through the locking member 32. Its lower end engages a lever 33 which is mounted within the body I I on an adjustable fulcrum.

This fulcrum comprises an eccentric journal 34 formed on the inner end of a screw 35 which is threaded into a boss 36 formed within the body Il (see Fig. 2). The lever 33 is held in assembled relation with the journal 34 by a second boss 3l formed within the body Il. The screw 35 is locked in its adjusted positions by a check nut 33.

The switch element is an ordinary micro-motion switch whose body appears at 4l. It is tripped by depressing a push button or plunger 42 which extends through a guide in its upper surface. The body 4I is mounted against the lug 39 and a companion lug 40 by a pair of screws 43. The leads from the switch are indicated at 44.

As will be apparent from an inspection of Figures 3 and 4 the switch 4I may be mounted in the body l l in either of two positions. In the position of Figure 3 motion of the plunger 24 is multiplied so that this is a high sensitivity setting. In the position of Figure 4 the motion of the plunger 24 is reduced giving a low sensitivity setting. In either of these positions the trip point 42 of the switch may be coordinated with the motion of the plunger 2s by turning the screw 35 so as to raise or lower the axis of the journal 34 on which the lever 33 turns.

As indicated in Figure it is also possible to turn the screw 35 180 degrees so as to position the journal 3s to the left of the axis of screw 35 instead of to the right thereof as is indicated in Figures 3 and 4. This adjustment is one of minor eiect as compared to reversal of the switch body 4i.

In either arrangement it is possible toI raise and lower the axis of the journal 34 so as to control the trip point of the switch, and the precise pressure at which it trips.

The screws |15 (see Figures 1 and 2) are merely closure plugs and are needed because tapped holes which receive the screws 43 must be drilled and tapped through from the outside of the case.

The invention provides a vary simple structure which may be manufactured at moderate cost. The stress on the spring 29 may be readily adjusted by adjusting the spring seat 3|. By using interchangeable springs 29 of diiierent strengths a very wide range of pressures may be handled. The adjustment of the journal 34 is effected by a very simple means and permits a precise setting of the trip point of the switch. The adjustability of the switch with reference to the lever permits adjustment of sensitivity. While a very simple two position adjustment is shown, it is obvious that any means permitting a shift of the push button 42 in the direction of the length of the lever 33 might be used to adjust sensitivity. The embodimeni-I illustrated is chosen for its simplicity' and because it ciers a suiiicient range of adjustment for ordinary commercial purposes.

What is claimed is:

l. In a pressure switch, the combination of a movable abutment; means for subjecting said abutment in one direction to a variable fluid pressure; yielding means for biasing said abutment in opposition to said pressure; a snap acting switch; a mechanical connection between said abutment and switch, and including a lever having a fulcrum; and means for shifting said fulcrum in a circular orbit.

2, In a pressure-operated switch, the combination of a movable abutment; means for subjecting said abutment to a variable fluid pressure, acting thereon in one direction; a spring serving to bias said abutment in the opposite direction; adjustable means for stressing said spring; a motion transmitting member shiftable by said abutment; means for limiting the motion of said transmitting member; a snap-acting switch having an actuator shiftable past the trip point of the switch in both directions; a lever interposed between said transmitting member and said actuator; and a fulcrum for the lever shiftable to vary the relation of the trip point of the switch to the position of said transmitting member.

3. In a pressure-operated switch, the combination of a movable abutment; means for subjecting said abutment to a variable fluid pressure, acting thereon in one direction; a spring serving to bias said abutment in the opposite direction; adjustable means for stressing said spring; a motion transmitting member shiftable by said abutment; means for limiting the motion of said transmitting member; a snap-acting switch having an actuator shiftable past the trip point of the switch in both directions; a lever interposed between said transmitting member and said actuator; and a shiftable fulcrum for the lever, said fulcrum having at least two settings in which respectively it establishes different motion ratios between the transmitting member and the switch actuator, said fulcrum being shiftable in each setting in a direction to vary the relation of the trip point of the switch to the position of said transmitting member.

MATTHEW W. HUBER.