US2358032A - Power element - Google Patents

Description

7 S p 9 I J. J; ROTHWELL' ETAL 2,358,032

POWER ELEMENT Filed Sept. 22. 1942 I6 /4 l2 l0 8 6 4 2 a 4-07 8./% /2.2/ /6.28

Patented Sept. 12, 1944 UNITED. STATES PATENT-OFFICES POWER ELEMENT I John Joseph Rothwcll, Elkhart, and Wilbur Warren Wood, Middlebury, Ind., assignors to' Penn Electric Switch 00., Goshen, Ind., a corporation of Iowa Application September 22, 1942, Serial No. 459,333

Claims.

Our present invention relates -'to a power element which is compensated against pressure changes in control devices and the like, as on control switches for refrigerating equipment of ture being considerably less expensive to manufacture and install, and securing a minimization of variation due to change in ambient pressure as distinguished. from the possibility of exactly counteracting such change in air pressure and thereby providing one hundred percent compensation, as in the Shaw Patent No. 2,204,951.

A further object is to provide means to minimize the effect of ambient atmospheric pressure on one side of a power diaphragm 0r bellows open to atmosphere, where the other side of the powerdiaphragm or bellows is subjected to a variable pressure for controlling the position of the diaphragm or bellows and thereby operating a control device or the like.

More specifically, it is our object to provide head of the diaphragm or bellows. being secured a compensating diaphragm arrangement which;

minimizes ambient air pressure change by the exposure of a minimum of surface to outside atmosphere.

With these and other objects in view, our invention consists in the construction, arrangement and combination of the various parts of our device whereby the objects contemplated are attained, as hereinafter more fully set .forth, pointed out in our claims and illustrated in the accompanying drawing, wherein:

Figure 1 is a front elevation of a control device, such as a refrigerant compressor motor controlling switch, having our compensated power element illustrated in connection therewith;

Figure 2 is an enlarged sectional view of the power element to show, particularly, a compensating means therefor; and

Figure 3 is a graphic view showing, for the switch, and of such a switch when our compensating means is applied thereto.

On'the accompanying drawing we have used the reference numeral ID to indicate a switch housing wherein a switch arm I2 is pivoted to a bracket M which, in turn, is supported on a bar l5 of insulating material. The switch arm I2 is operated by a power element PE, consisting of a diaphragm or bellows housing IG' anda diaphragm l'l therein. The diaphragm has been illustrated as one of the bellows type, its periphery being soldered to the housing l6 and the at 18 to an actuating stem IS. The actuating stem l9 engages a bell crank 2|! pivoted at 2| and retained in engagement with the actuating stem by a range spring 22. The spring 22 is adjustable by means of an adjusting rod 23 and a control knob 24' thereon. The bellows housing I6. has a fitting 25 secured thereto, by means of which pressure is introduced into the bellows housing for collapsing the diaphragm H as the pressure builds up. The fitting 25 may be connected in the usual manner by copper tubing or the like, to the low side line of a refrigeration system, or to anysuitable temperature or pressure responsive device which would efie'ct a" build-up of pressure within the housing I6 for the purposeof actuating the switcharm l2. The" switch arm l2 carries contacts 26, in the usual manner, for engagement and disengagement with respect to stationary contacts 21, depending. upon the position of the'switch arm, as fully disclosed in the- Shaw patent hereinbefore mentioned.

'We have provided the power element PE with a compensating means in" the form of a pair of plates 28 and 29 interposed between the diaphragm housing l6 and the switch housing [0.

Screws 3!) pass through aubase flange 3| of the bellows housing I6 and through the plates: 28-

and 29 adjacent the corners of the plates, the plates being substantially square and the flange 3| likewise being substantially square. 'Between the plates 28 and29 is a compensating diaphragm 32, the periphery of which is sealed between the plates by a head 33 on the plate 28, and the central portion of which is sealed relative to the plates by a bead orflaredpart 34 of the plate 28. The center of the comperlsatingdiaphragm 32 has an opening 35 therethrough, slightly smaller than the actuating stem I9, so that this opening,

due to the inherent resiliency of the compensating diaphragm, seals against the surface of the stem.v The diaphragm 32 may be made of rubber or similar material for this purpose, and, if; found desirable, may be vulcanized to the stem. We. have found, however, that the bellows. ,ll,

V I6 which forms a pressure chamber'for the diasection of the actuating stem, being the area diaphragm, whereas the plate 29 is soldered to the bellows housing IE to prevent any leakage at in most installations, has but a small travel, and therefore never moves so far as to stretch the central part of the compensating diaphragm within the bead 34 to such a point that the opening 35 shifts relative to the actuating stem.

The main purpose of our compensating constructionis to minimize the effiective area inside the diaphragm l'l orv on the opposite side thereof from the power side within the bellows housing phragm or bellows. This is accomplished by making the stem I9 relatively small and keeping the openings 36 and 31 in the plates 28 andZS as small as possible, and yet permit the necessary flexing of the centralportion of the compensating diaphragm as the stem I9 reciprocates. This is accomplished by using the relatively rigid plates 28 and 29 sealed with relation to the compensating diaphragm so that only the'center por-. tion defined by the bead 34 is responsive to at-' mospheric pressure, this portion, plus the crossaffected. 7

The bead 33 further seals the compensatingthispoint. The result is an area defined by the head 34 being affected by ambient air pressure as distinguished from the entire inner surface of the diaphragm or bellows l1. By way of illustration, reference is made to Figure 3 for the purpose of comparing apower element minus our compensating diaphragm with one including our compensating diaphragm. Theline CI indicates, the cut-in point of the first mentioned control, deviceand CO thecut-out point thereof. It will be noted that at sea level the cut-in pressure may be approximately 14 pounds and the cut-out pressure approximately .5 pounds. As. the alti.-

tude increases, the cut-in and cut-out points decrease until at abut 40,000 feet, the cut-in point v is only approximately 1 /2 pounds, whereas the cut-out point has receded to a vacuum represented by 15 inches of mercury. This is a considerable change in the operating range of the switch, and is due to the difierence'in'elevation causing a difference in atmospheric air pressurer H A switch operating under these conditions is and is therefore objectionable. Many installations can readily permit a half pound change in V the operating pressure between sea level and 40,000 feet, whereas two, three or more pounds of change is undesirable.

Some changes may be made in the construction and arrangement of the parts of our device without departing from the real spirit and purpose of our invention, and it is our intention to cover by of said bellows, means to minimize the effect of ambient atmospheric air pressure changes on said other side of said \bellows comprising a compensating diaphragm surrounding said stem. and means for supporting said diaphragm so that it is insealing relationship with said stern and the open end of said bellows and so that it is held rigid for substantially its entire distance across Y the open end of the bellows to minimize the effective area of said bellows acted upon by ambientatmospheric air pressure.

2. In a power element of the class described, a

diaphragm, a; variable chamber on one side thereof, an actuating stem projecting from the other side of said diaphragm, and means to minimize the effect of ambient atmospheric air pressure changes on said other side thereof comprising a compensating diaphragm surrounding said actuating stem and supported from a point closely adjacent thereto to the periphery of the compensating diaphragm in order to minimize the effective area of said power diaphragm acted upon byam-bient atmospheric air pressure, said unsatisfactory in connection with refrigeration mechanism or the like,- and it is desirable to' minimize the change. 'We have found, with our compensating diaphragm, that the cut-in and cut-out points will recede much less as altitude increases, and this'is shown graphically bythe lines CI and 00'. The recession of CI is from approximately 14 pounds to approximately 13 tinguished from the full compensation possible 05 with more complicated, mechanismfsuch as an opposingbellows. Although we have illustrated our power element in connection with a refrigeration'switch, it may be used on other power applications, such as hydraulic brakes on aeroplanes, etc., and in connection with refrigeration mechanism and other devices to be controlled in accordance with pressure or temperature changes-where a change in altitude afl'ects the compensating diapli ra'gm spanning said other side of said diaphragm and isolating it from atmosphere.

3. In a power element, a diaphragm, an actuating stem projecting from one side thereof, a pressure chamber against the other side thereof,

and means for substantially reducing the exposure of said first side of said diaphragm comprising a compensating diaphragm spanning said first side, means for supporting said compensating diaphragm closely adjacent said actuating 0 pensating diaphragm adjacent the edges of said openings, and said compensating diaphragm being sealed relative to said stem,'the arrangement being such as to isolate said other side of th compensating diaphragm from atmosphere.

4.-In a power element of the character disclosed, a, power bellows, an actuating stem projecting, from one side thereof, said side being open, aipressure chamber against the other side thereof, and means for substantially reducing the exposure of said open side of said power 'bellows to ambient atmosphere comprising a com- 7 operation of -a switch or similar control dev c pensating diaphragm'surrounding said stem, and

means for supporting said diaphragm so that it w is in sealing relationship with said stem and the open end of said bellows and so that it is held' rigid for substantially its entire distance across the open end of the bellows, said supporting means including a pair of plates on opposite sides of said diaphragm and spanning said power bellows, said plates having central openings slightly larger than said actuating stem and sealed relative to said diaphragm adjacent the edges of said openings.

5. In-a power element, a diaphragm, an actuating stem projecting from one side thereof, a pressure chamber against the other side thereof, and means for minimizing the exposure of said first side of said diaphragm to atmosphere comprising a compensating diaphragm spanning said first side, and a pair of plates on opposite sides of said compensating diaphragm for supporting it, said plates spanning said compensating diaphragm and having central openings slightly larger than said actuating stem, said stem being phragm from atmosphere.

JOHN JOSEPH ROTHWELL. WILBUR WARREN WOOD.

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