US2975251A - Pressure switch - Google Patents

Description

March 14, 1961 w BELLER r 2,975,251

PRESSURE SWITCH Filed Feb. 20, 1958 3 Sheets-Sheet l INVENTORS W\LBERT E BELLER United States i atent PRESSURE SWITCH Wilbert E. Beller, Park Ridge, and Edwin A. Ostrowski, Mount Prospect, Ill., assignors to Controls Company at America, Schiller Park, 111., a corporation of Delaare Filed Feb. 20, 1958, Ser. No. 716,361 6 Claims. (Cl. 200-83) Still another object of the invention is to provide for operation of precision snap stype switches in response to movement of a pressure responsive diaphragm without transmitting to the switches the large thrust of the diaphragm.

Other objects and advantages will be pointed out in, or be apparent from, the specification and claims, as will obvious modifications of the single embodiment shown in the drawings, in which:

Figure 1 is a top view of the present pressure operated switch;

Figure 2 is a vertical section through the pressure switch taken on line 2-2 of Figure 1; t

Figure 3 is a vertical section through the pressure switch taken on line 33 in Figure 2;

Figure 4 is a fragmentary vertical section taken on line 4-4 in Figure 2;

Figure 5 is similar to Figure 4 and is taken on line 55 in Figure 2; V v

Figure 6 is a fragmentary bottom view of the switch mechanism'as seen from line 66 in Figure 5;

Figure 7- is a section taken on line 7-7 in Figure 2;

Figure 8 is a fragmentary view showing the positions of the parts after the low pressure switch has been actu-J ated and-prior to operative engagement of the second loading spring acting in opposition to the diaphragm force; and 3 g Figure 9 is a view similarto Figure 8 showing'the position of the parts after the high pressure switch has been actuated and also illustrates the manner in which the diaphragrn is opposed by two springs in the high pressure range. a a a 7 Referring to the drawings now in detail, the pressure sensing diaphragm 10 is contained in a housing 12 including theinlet spud14 adapted for connection to the pressure source andwelded or otherwise connected to the lowerhousinghalf 16 to which the upper half 18 is crimped to. capturethe beaded edge of the diaphragm 10. The upper half ofthe diaphragm housing is centrally apertured to permit the reduced diameter portion 20. of plunger 22...to pass therethrough so the recess in the bottom'oi theeplunger may fit over the boss 24 on the diaphragm pad 26. It will be appreciated that pressure on'the'underside of the diaphragm will flex the diaphragm upwardly. It will also be appreciated that the diaphragm housing including the diaphragm can be completely assembled as a separate sub-assembly.

The switch case 28'is crimped to the diaphragm housing with the seal 30 captured by the crimping process to prevent dirt from getting on the switch contacts located inside the switch case.

2,975,251 Patented Mar. 14, 1961 An annular insulating support block 32 is fixed on the underside of the switch case by a pair of rivets 34, 34 with the central aperture of the block guiding plunger 22. The support block is provided with terminal bosses 36 which project through cooperating-holes in the switch case to position the terminals on the exterior of the case.

Upward motion of the plunger as the pressure under diaphragm 10 increases is first opposed by spring 38 which is compressed between the raised portion 40 of the switch case and the spring seat cup 42 fitting over the upper reduced diameter portion 44 of plunger 22. After spring 38 has been compressed sufficiently for shoulder 46 on the plunger to contact the spring seat washer 48 further movement of the plunger is opposed both by the spring 38 and by spring 50. Thus, the first range of movement of the plunger is opposed by spring 38 while subsequent motion of the plunger is opposed by both spring 38 and spring 50. Therefore, a low pressure can actuate the plunger up to the point where shoulder 46 engages washer 48 and thereafter a higher pressure is required to move the'plunger. This characteristic is utilized in obtaining a substantial dilterential in operating pressures for the switches.

Motion of the plunger is transmitted to the switches by spring loaded beams 52, 54. Beam 52 is fulcrumed on pivot 56 molded in the support block 32 and is loaded by spring 58, tensioned between pin 60 and the beam 52, to ride against the lower shoulder 62 on the plunger and follow motion of the plunger. Beam 52 is utilized to transmit plunger motion to the low pressure switch while beam 54, loaded by spring 64 and pivoted on pivot 66, is utilized to transmit motion to the high pressure switch.

Both switches are of the precision type and may, for example, be of the type construction shown in Wilms Patent No. 2,260,964. Thus, the low pressure switch (see Figure 4) has an integral blade and tongue structure mounted by rivet 68 (which extends through the block 32 to form terminal 70) on the underside of the support block 32 with free end of the blade carrying a contact 72 normally'engaging the contact on the lower end of rivet 74 (forming terminal 76). The blade and tongue are spring loaded by spring 78 to have a snap action in the well known manner. The actuating plunger 80 receives its motion in the upward direction from the spring loaded beam 52 following the plunger while the return motion is imparted by compressed spring 82. When the switch snaps over center the blade moves down into contact with the stop or calibrating screw 84 mounted in the support 86 fixed to the support block 32. This calibrating or stop-screw determines the switch resetting characteristics. v

The high pressure switch is of the same basic construction being mounted by rivet 88 to position contact 90 for engagement with rivet 92 in the normal position. The switch blade and tongue are loaded by spring 94 to have the usual snap action with motion imparted to the tongue by plunger or pin 96 receiving its motion from beam 54 on the up motion and receiving the down motion from thereturn spring 98.

Figure 9 shows the manner in which the switch plunger 80 serves to prevent any overloading or distortion of the switch. Thus, the upper end of the plunger 80 contacts the underside of block 32 to prevent further upward movement of the plunger by the spring loaded beam which (as shown in Figure 9) then ceases to follow the diaphragm plunger 22. The switch is, therefore, doubly protectedfirst the spring force in the beam decreases as the beam moves up and secondly when the plunger stops further movement.

The operation of the present switch mechanism will now be rather apparent. As the pressure on the underside of diaphragm increases plunger 22 will move up opposed by spring 38 acting on the spring seat cup 42. As the plunger moves up both spring loaded beams 52 and 54 will follow the plunger. When beam 52 rises to the snapping point of the low pressure switch the switch will snap over center and contact 72 will break away from rivet 74 and open the circuit. As the plunger continues to rise shoulder 46 of the plunger will engage spring seat washer 48 and the pressure acting On the underside of diaphragm 10 must now overcome the force of both spring 38 and spring 50. Thus, a higher pressure is required to continue the motion of plunger 22. When this higher pressure is obtained and the plunger continues its upward motion spring loaded beam 54 will rise sufficiently to actuate pin 96 to snap the high pressure switch over center and break contact 90 from rivet 92. As the pressure under diaphragm It) falls it will be appreciated that the reverse action obtains.

It will be noted that the force exerted by the pressure actuating diaphragm 10 acts only on springs 38 and 50 and cannot be transmitted to the precision switches. Thus, the switches are protected in all cases against deformation by excessive loading. Indeed, as the pressure goes up the loading on the switches goes down. This is due to the fact that the springs loading the beams 52 and 54 are tensioned and as the beams move up following the motion of the plunger in response to increasing pressure the stress in the beam- loading springs 58 and 64, is, of course, decreased and, therefore, the force acting on the precision switches is decreased. Therefore, with this construction the switches are at all times protected against overloading and the consequent deformation.

It will be appreciated that while the switches here shown are normally closed they could be normally open or, if desired, could be designed as double throw instead of single throw switches. It will also be appreciated that the pressure could be introduced to the upper side of the diaphragm, if desired. Under such circumstances it would be necessary only to reverse the action of the springs to obtain the desired operating characteristics. In some instances space limitations or other design requirements may indicate this type construction as being preferable. It will be obvious that further modifications and changes in the construction will occur to those skilled in the art. For this reason the scope of the invention is not to be limited to the specific embodiment illustrated but it is to be limited only by the scope of the claims.

We claim:

1. A pressure actuated switch mechanism comprising,

,a housing including a pressure chamber including a diaphragm, a plunger actuated by the diaphragm, a loading spring acting on the plunger to oppose the pressure, a second loading spring engageable with the plunger only after the plunger has moved a predetermined distance whereby further movement of the plunger requires a higher pressure in said chamber, and switch means actuated by the plunger, said switch means including switch actuating means receiving motion from the plunger, the actuating means having a lost motion connection to the plunger and including stop means effective to prevent continued motion of the actuating means when such continued motion would overload the switch means.

2. A pressure actuated switch mechanism comprising, a housing including a pressure chamber including a diaphragm, a plunger actuated by the diaphragm, a load ing spring acting on the plunger to oppose the pressure, a second loading spring engageable with the plunger only after the plunger has moved a predetermined distance whereby further movement of the plunger requires a higher pressure in said chamber, and switch means actu-- ated by the plunger, the switch means being connected to the plunger by means which disengage the plunger from the switch means upon the occurrence of predetermined high pressures in the pressure chamber.

3. The control apparatus comprising, condition responsive motor means, a plunger deriving motion from the motor means, a housing containing the motor means and the plunger, a spring acting on the plunger to oppose the motor means in its initial movement, a second spring engageable with the plunger only after its initial movement and operative to oppose the continued motion of the plunger, both springs being progressivly stressed during the continued motion whereby the motor means must exert an increased force to actuate the plunger, control means actuated by the plunger in the initial movement of the plunger, control means actuated by the plunger during the continued movement of the plunger, the second spring acting on a washer normally seating on a stationary portion of the housing, the plunger passing through the washer opening freely during the initial plunger movement, said plunger having a shoulder thereon engageable with the washer whereby to oppose the plunger motion with the second spring, the first spring seating against a cup carried on the end of the plunger, said cup having a flange thereon adapted to seat on the washer as the plunger retracts to thereby relieve the plunger of all spring loading.

4. Control apparatus comprising, condition responsive motor means, a plunger deriving motion from the motor means, a housing containing the motor means and the plunger, a spring acting on the plunger to oppose the motor means in its initial movement, a second spring engageable with the plunger only after its initial movement and operative to oppose the continued motion of the plunger, both springs being progressively stressed during the continued motion whereby the motor means must exert an increased force to actuate the plunger, a first switch being connected to the plunger by means preventing transmission of the forces acting on the plunger to the switch, the first switch being actuated inthe initial movement of the plunger, and a second switch being connected to the plunger by means preventing transmission of the forces acting on the plunger to the switch, the second switch being actuated during the continued movement of the plunger.

5. Apparatus according to claim 4 in which the plunger has a shoulder thereon and the beams are spring loaded to follow the plunger as the beam bearsagainst the shoulder. 6. Apparatus according to claim 5 in which each beam is connected to its associated switch by means of an actuating plunger, and including, stop means for stopping the motion of each actuating plunger before the associated switch can be overloaded or deformed.

References Cited in the file of this patent UNITED STATES PATENTS 1,654,523 Bihl Ian. .3, 1928 1,703,235 Heath Feb. 26, 1929 1,870,895 Carson Aug. 9, 1932 2,357,878 Crew Sept. 12, 1944 2,453,861 Rothwell Nov. 16, 1948 2,589,063 Dillman Mar. 11, 1952 2,620,413 Johnson Dec. 2, 1952 2,636,093 Clark et al. Apr. 21, 1953 2,741,678 Schaefer et al Apr. 10, 1956 2,754,383 Beeman July 10, 1956 12,813,944 Tyzack Nov. 19, 1957 2,890,305 'Gutkowski June 9, 1959 2,895,024 'Brown et al July 14, 1959 OTHER REFERENCES German patent, St6636 V111b/21c, Oct. 25, 1956. p t

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