US3034354A - Humidity indicators and humidistats - Google Patents

Description

y 1962 c. K. STROBEL. ET AL 3,034,354

HUMIDITY INDICATORS AND HUMIDISTATS Filed Dec. 10, 1957 4 Sheets-Sheet 1 H i 1?- "1M 30 1 mmlllll ia/M 'May 15, 1962 C. K. STROBEL ET AL HUMIDITY INDICATORS AND HUMIDISTATS Filed Dec. 10, 1957 4 Sheets-Sheet I5 ATTGMK y 1962 c. K. STROBEL ET AL 3,034,354

HUMIDITY INDICATORS AND HUMIDISTATS Filed Dec. 10, 1957 4 Sheets-Sheet 4 malls- I fim'lesKSbubel, 6'uyi'60nnerf Rama/119111271061.

United States Patent HUMIDITY INDICATORS AND HUMIDISTATS Charles K. Strobe], Pittsburgh, and Guy F. Conner and Robert G. McMichael, Jeannette, Pa., assignors to Robertshaw-Fulton Controls Company, Richmond, Va.,

a corporation of Delaware Filed Dec. 10, 1957, Ser. No. 701,839 8 Claims. (Cl. 73-337) This invention relates to humidity indicators and humidistats. More particularly, it relates to humidity responsive devices that are compact, rugged, low in cost, and precise in operation. a

It is an object of this invention to indicate relative humidity and control it at any predetermined value.

It is another object of this invention to indicate the humidity independently of control.

It is a further object of this invention to maintain the humidity within a predetermined range.

It is a still further object of this invention to produce a humidity indicator having a linear characteristic.

It is a still further object of this invention to provide a compact humidity indicating device having a relatively long sensing element.

In a preferred embodiment of this invention, a mounting plate is provided with a step cam which is rotatable thereon; A humidity responsive element and aspring are connected to the step cam. The element changes length in response to a humidity change to rotate the step cam and a humidity indicator which is attached thereto. A manually operable member is also rotatably mounted on the plate and carries a switch which operates appropriate air conditioning equipment. The manually operable member is set at a predetermined position which indicates a predetermined humidity. When the humidity reaches this predetermined value, the step cam will actuate the switch to operate the conditioning equipment. i Otherobjects and advantages of this invention will become apparent from the following detailed description taken in connection with the accompanying drawings wherein:

FIG. 1 is a front elevation view of an embodiment of this invention;

FIG. 2 is a side elevation view of the embodiment of the invention shown in FIG. 1;

FIG. 3 is a front elevation view of another embodiment of this invention;

FIG. 4 is a side elevation view of the embodiment of this invention shown in FIG. 3;

FIG. 5 is a front'elevation view of still another em-* bodiment of this invention;

FIG. 6 is a side elevation view of theembodiment of this invention shown in FIG. 5;

FIG. 7 is a front elevation view of still another embodiment of this invention;

FIG. 8 is a side elevation view of the embodiment of this invention shown in FIG. 7;

FIG. 8a is a sectional view taken on line 8a-8a of FIG. 8;

FIG. 9 is a front elevation view of still another embodiment of this invention with its cover removed;

FIG. 9a is a perspective view of the lower portion of the embodiment shown in FIG. 9;

FIG. 10 is a front elevation view of the embodiment of this invention shown in FIG. 9 with the cover thereon; and

FIG. 11 is a sectional view taken on line 11-11 of FIG. 10. p

The devices which will be described and referred to as humidistats are combination relative humidity indicating the side.

ice

and controlling units, whereas the humidity indicators described merely indicate relative humidity.

Referring more particularly to FIGS. 1 and 2 and the humidistat shown thereby, a base member 10 is provided with an upwardly extending mounting plate 12. Mounting plate 12 is rectangular in shape and is provided with a scale member 14 which takes the form of a semicircular strip. The scale member 14 has its ends secured to the mounting plate 12 adjacent a side thereof by any suitable means, such as screws 16, and extends outwardly from Any suitable indicia, such as markings 18, are provided on member 14 for the purpose of providing a calibrated scale.

A hole is bored in the mounting plate 12 at a point intermediate the ends of the member 14. A stud 20 is received by the hole and extends outwardly at right angles to the plate 12. A cylindrical shaped rotatable member 22 is mounted on the stud 20 and is provided with an enlarged step cam portion 24. The function of the step camportion 24 will be described hereinafter. A pointer or indicator 26 is also rotatably mounted on the stud 20 and engages the rotatable member 22 for rotation therewith. A pair of nuts 28 are screwed on the ends of the stud 2d and serve to hold the members together and position them relative to the mounting plate 12. The indica tor 26 is provided with several bends therein to associate an end thereof with the markings 18 on member 14.

Means is provided for causing the movement of the indicator 26 relative to the markings 18 in response to a change in the relative humidity. More particularly, a humidity sensitive element or ribbon 30 of any suitable material, such as woven nylon, woven rayon, solid nylon, polyvinyl alcohol film, cellulose acetate, or silk, which changes in length in response to a change in relative humidity, has an end 32 wrapped around the rectangular shaped ring 34 and is sewed back to the ribbon 30 to form a loop connection with the ring 34. Attached to the other side of the ring 34 is a chain 36 which in turn is connected to a pin 38 on the rotatable member 22.

Also attached to the pin 38 is a coil spring 40 which has an end hooked on a pin 42 that is attached to and extends outwardly from the mounting plate 12 adjacent the top thereof. Also at the top of the mounting plate 12 is a pair of bearing members 44, 46 which are bolted to the mounting plate 12 at 48, St). A similar bearing member 52 is secured near the bottom of the mounting plate 12 by a bolt 54. Cylindrical roller members 56, 58, 60 are rotatably mounted on the bearing members 44, 46, 52, respectively. The humidity sensitive element or ribbon 30 is extended overthe roller member 56 at the top of mounting plate 12, around the roller member 60 at the bottom of the mounting plate 12, and then looped over the roller member 58 at the top and fixed back to ribbon 3% by a clamp 62.

or downward on the screw 7th. This causes the plate 66 and the bolt St} in the slot 64 to move the bearing member 46 and the roller member 58 up or down. When the desired adjustment is obtained, the bolt 50 is again tightened to hold the bearing member 46 in place.

The device thus far described is operable merely as a It is now apparent. that coil spring 4i) serves to hold the ribbon 30' in tension. A ribbon take-up and adjustment means is provided 3 humidity indicator. A change in relative humidity will cause a change in length of the humidity responsive element 30 to rotate the pointer 26 relative to markings 18 to indicate the change.

Means is provided to operate appropriate air conditioning equipment when a predetermined humidity is reached. To this end, a substantially sector-shaped member 72 having an index arm 74 formed integral therewith is rotatably mounted on the stud 20' between the mounting plate 12 and the rotatable member 22. The index arm 74 is provided with a clip 76 which cooperates with scale member 14 to hold the sector-shaped member 72 in a fixed position. An end 78 of index arm 74 extends beyond the scale member 14 and is manually operable to rotate the sector-shaped member 72 and move the clip 76 to any desired setting.

A commercially available minature single-pole; doublethrow electrical switch 80 is mounted on the sectorshaped member 72 by means of a mounting member 82 which is provided with a pair of cross-cut slots 84, 86. Two small screws extend through cross-cut slots 84, 86 and secure the mounting member 32 and the switch thereon to the sector-shaped member 72. The cross-cut slots provide an adjustment whereby the switch 89 can be moved to various positions. A C-shaped flange 88 extends from an end of mounting member 82 and a shaft 90 is secured between the legs of the C-shaped fiange'tiS. A cam plate 92 is rotatably mounted on the shaft 96 and rides on step cam 24 of member 22. Means comprising a threaded. upturned flange 94 on sectorshaped member 72 and a screw 96 which is received by the flange 94 and abuts the end of cam plate 92 is provided for adjusting the position of the cam plate 92 relative to the activator 98 of switch 80.

In operation of the embodiment shown in FIGS. 1 and 2,'the clip 76 on index arm 74 is set at a desired relative humidity as indicated by the markings 18. It should be noted that the switch 30' moves relative to the step of cam portion 24 when clip 76 on the index arm 74 is moved to a different setting since the switch is mounted on the sector-shaped member 72. A change in relative humidity causes a change in length of the humidity sensitive element 30 which is held in tension by coil spring 40. The change in length of humidity sensitive element 30 is converted to rotational movement by means of the rotatable member 22 to which the humidity sensitive element 30 and the coil spring 40 are attached. An indicator 26 which is operable to move with the rotatable member 22 indicates the change in length of the humidity sensitive element, i.e., the relative humidity, on a calibrated scale member 14. When the humidity reaches the value at which the clip 76 of the index arm 74 is set, the. step of cam portion 24 on member 22 will either engage or disengage the cam plate 92 and pivot it about shaft 90 to operate the activator 98 of the electrical switch 80. Movement of the activator'93 of the switch 8% will cause operation of appropriate air conditioning equipment (not shown) to control the humidity. The change in humidity due to the operation of the conditioning equipment will change the length of the humidity sensitive element 30 to rotate the step of cam portion 24 either back out of or back into engagement with the cam plate 92 thereby de-actuating activator 98 and operation of the conditioning equipment will cease.

It is now apparent that the humidistat will control the relative humidity about the point indicated by clip 76 on the locked index arm 74 and if the switch 80 or the conditioning equipment is not in operation, the step of cam portion 24 can pass under the cam plate 92, thus permitting the pointer 26 to indicate the correct relative humidity on the calibrated scale member 14. This construction permits the cam portion 24 to travel beyond the set control point without straining any of the parts of the assembly.

Since commercially available miniature switches usually require either a relatively large motion and weak force, or a small. motion and a strong force to be activated, two designs of'indicating and controlling humidistats were made to accommodate the different characteristics of the various switches. The embodiment of FIGS. 1 and 2, just described, illustrates the former whereas the embodiment of FIGS. 3 and 4 shows the latter.

Referring more particularly to FIGS. 3 and 4, a base, ltitl is provided with an upwardly extending mounting V brated scale 120 thereon.

A slender elongated indicator or pointer 122 having a bend therein to avoid engagement with other parts extends between the outer plate 114 and the inner plate 118 and is associated with the calibrated scale 120. The indicator 122 is 'formed integral with an enlarged cam portion 124 of a rotatable member 126. ,The rotatable member 126 is mounted on a stud 128 which has one end extending through mounting plate 102 near the bottom thereofand is supported thereby and the other end attached to a support bracket 130 which extends upwardly from an end of base 100 and is secured to the base 100 by any suitable means, such as screws 132, 134. Movement of the stud is prevented by nut 136 which is provided on the back of mounting plate 102 and is threaded on the end of stud 128.

Means is provided for rotating member 126 in response to a change in relative humidity. More particularly, a humidity sensitive element or ribbon 138 is strung between a pair of clamps 140, 142 to form a multiple sensing element, in this case having four strands to provide the desired strong force. The clamp is secured to the mounting plate 102 near the top thereof by a pair of bolts 144 (only one shown). Secured to the other clamp 14-2 by screws 146, 148 is a U-shaped connecting member 150 which has a hook 152 extending therefrom. A chain 154' is provided with a small ring 156 on one end which is connected to hook 152 and the chain extends partially around the rotatable member 126 and has its other end attached to a small pin 158 on the rotatable member 126.

The chain 154 is retained'on rotatable. member 126 between cam portion 124 and another enlarged portion 160. Also attached to pin 158 is another chain 162 which is hookedto an end of a coil spring 164. The ooil'spring 164 has its other end attached to a pin 166 which is connected adjacent the top of mounting plate 102 and extends outwardly therefrom. The coil spring 164 serves to hold the multiple sensing element in tension.

, This embodiment thus far described operates as a humidity indicator.

The sensing element changes length in responseto a humidity change tovcause rotation of member 126 to move pointer 122 relative to scale 120.

Means is provided to operate appropriate air conditioning equipment when a predetermined humidity is reached. More particularly, an L-shaped member 168 is rotatably mounted on stud 128 between a reduced portion 170 of a rotatable member 126 and a washer member 172 which is provided adjacent support "bracket 130. The upper portion of the L-shaped member 168 forms an index arm 174 which extends to the underside of the outer plate 114 and has an end extending slightly therebeyond for association with the scale 120. The index arm 174 is provided with a screw (not shown) which projects upwardly into the curved slot '116 in outer plate 114. A knob 176which is slightly larger than slot 116 is provided on the outer side of plate 114 and has internal threads which cooperate with v tightly against the plate 114 to hold the index arm 174 in a set position.

The lower portion of L-shaped member 168 serves as a mounting plate for an appropriate miniature electrical switch 178. A pair of screws 180, 182 extend through appropriate washers and a pair of cross-cut slots 184, 186 provided on the lower portion of L-shaped member 168 and firmly secure the switch 178 thereto. A cam plate 188 which is attached tofswitch 178 by any suitable means,

such as screws 198, 192, has one side riding on cam portion 124 and the other side engageable with an activator 194 of switch 178 to cause activation thereof when the step of cam portion 124 engages or disengages the cam plate 188.

In operation of the embodiment shown in FIGS. 3 and 4, the knob 176 is loosened and the index arm 174 is moved to a desired relative humidity setting as indicated by the calibrated scale 120. The knob 1'76 is then tightened to lock index arm 174 in this position. A change in the setting of index arm 174 results in movement of the To this end, a humidity sensitive element or ribbon 232 is strung between a clamp 234, which is fixed by any suitable means 236 to the mounting plate 198 near the bottom thereof, and a triangular shaped holder 238 to form a four strand sensing element. The triangular shaped holder 238 is hung on one end of an arm 240 which is pivotally mounted adjacent the top of mounting plate 198 by any suitable means, such as a nut and bolt 242.

Another humidity sensitive element 244 is strung between a clamp 246 and a triangular holder 248' which is similar to holder 238 to form a second four strand sensing element which is shorter than the first. The triangular holder 248 is hung on the other end of pivot arm 240 and a chain 250 is connected to the clamp 246 by any suitable means 252 and is looped around the rotatable member 224 and attached to a coil spring 254.

' The coil spring is hooked on a pin 256 which is connected switch 178 and cam plate 188 relative to the step of cam Y portion 124. As the relative humidity rises, the length of the multiple humidity sensing element 138 increases. The linear change is converted to rotational movement of rotatable member 126 and step cam portion 124 thereof. The pointer 122 which is formed on step earn portion 124 moves relative to scale 120 to indicate the relative humidity. When the humidity reaches the value at which the index arm 174 is set, the step of cam portion 124 moves out of engagement with the cam plate 188 to actuate the activator 194 of switch 178. This in turn causes operation of appropriate air conditioning equipment which is connected to the switch 178 to decrease the humidity. When the humidity decreases to the value at which the index arm 174 is set, the step of cam portion 124 will again engage the cam plate 188 to turn off the air conditioning equipment. It is obvious that conditioning equipment which will humidity the air may be used. In this case, the step of cam portion 124 will engage cam plate 188 to turn on the conditioning equipment when the humidity drops to the set value.

It is now apparent that the humidstat will control the relative humidity about a point indicated by the index arm 174 and that the correct relative humidity will be indicated by the pointer 122 whether or not switch 17 8 or the conditioning equipment is in operation.

The humidistats thus far described have controlled the humidity around the. particular humidity setting. The embodiment shown in FIGS. '5 and 6, however, controls the humidity within a predetermined range. Referring more particularly to FIGS. 5 and 6, a base 196 is provided at one end with an upwardly extending mounting plate 198. A U-shaped member 200 has its legs attached intermediate the ends of mounting plate 198 by any suitable means, such as rivets 202, 204-. The U-shaped member 2 00 is provided with a curved slot 206 in the body thereof and a calibrated scale 208 located above the curved slot 206. A stud 210 has one end secured to the mounting plate 198 at 212 midway between the base 196 and the U-shaped member 200 and the other end extending through an aperture adjacent an end of support bracket 214. The other end of support bracket 214 is adjustably connected at 216 to an angular member 218 which, is secured at 226) to the other end of base 196. The adjustable connection comprises a vertical slot 222 which is provided in the upstanding leg of angularmember 218 to permit the connecting bolt to be movable therein to adjust the height of support bracket 214. Mounted on the stud 210 is a cylindrical shaped rotatable member 224 having an enlarged stepped cam portion 226 for a purpose to be described hereinafter. Formed on the stepped cam portion 226 is an indicator or pointer 228 which is bent at 230 to associate the end thereof with the scale 208.

Means is provided to move the pointer 228 relative to the scale 208 in response to a change in relative humidity.

to the mounting plate 198 near the top thereof by any suitable means 258. The coil spring 254 holds the humidity sensitive elements 232, 244 in tension and the chain 258, by frictional engagement, causes rotation of the rotatable member 224 upon change in length of the humidity sensitive elements 232, 244. A pin (not shown) may be provided on the rotatable member 224 to cooperate with the chain 250 for insuring rotation of memher 224 upon movement of the chain 250.

The embodiment thus far described operates as a humidity indicator. A change in humidity causes a change in the length of the sensing elements 232, 244 and rotates member 224 to move pointer 228 relative to scale 208.

Means is provided to maintain the relative humidity within the predetermined range. More particularly, a pair of L-shaped members 260, 262 are rotatably mounted on stud 21!) adjacent rotatable member 224. Appropriate washers are provided and a nut 264 holds the parts in place. The upwardly extending portions of the L-shaped members 260, 262 form index arms 266, 268 having clips 270, 272 on the ends thereof. The index arms 266, 268 are bent so that the clips 270, 272 extend into slot 206 and are attached to the body of U-shaped member 200. The clips 270, 272 are operable to be manually moved to various settings as indicated by scale 298. Miniature electrical switches 2 74-, 276, which operate appropriate air conditioning equipment (not shown), are mounted on the other legs of L-shaped members 260, 262 by suitable fastening means 278, 280. The switches 274, 276 are provided with cam plates 282, 284 which have one side riding on stepped cam portion 226 and the other side engageable with switch activators 286, 288.

In operation of the humidistat shown in FIGS. 5 and 6, the clips 270, 272 are manually set to desired position to indicate a humidity range on scale 208. This moves the cam plates 282, 284 relative to the steps of the cam portion 226. If the humidity is within the range set by clips 270, 272, both of the steps on cam portion 226 will be out of engagement with their respective cam plates 282, 284 and the air conditioning equipment (not shown) will not be in operation. However, should the humidity rise above the value set by clip 270, the increase in length of the humidity sensitive elements 232, 244 will cause rotation of member 224 and step cam portion 226 thereof and a step of cam portion 226 will engage cam plate 282 to actuate activator 286. This will operate the switch274 to turn on appropriate air conditioning equipment (not shown) to dry the air. The conditioning equipment will remain in operation until the air is dry enough to move the step 226 out of engagement with the cam plate 282.

On the other hand, should the humidity fall below the value set by clip 272, the decrease in length of the humidity sensitive elements 232, 244 will cause cam portion 226 to move a step thereof into engagement with cam plate 284 to actuate switch activator 288. This will operate the conditioning equipment (not shown) to humidify a the air. The conditioning equipment will remain in operation until the air is humid enough to cause rotation of the step out of engagement with the cam plate 284. As in the previously described embodiments, the correct relative humidity will be indicated by pointer 228 irrespective of operation of switches 274, 276 or the conditioning equipment.

This embodiment is particularly advantageous because the lag or overshoot of either or both of the humidifying or dehumidifying equipment can be compensatedfor by correct selection of the control points. Therefore, it is apparent that this embodiment can control the humidity within a predetermined range.

The embodiments heretofore described have been humidistats whereas the embodiments hereinafter are merely humidity indicators.

Referring more particularly to FIGS. 7, 8, and 8a, a base 290 is provided with a mounting plate 292 extending upwardly from the center thereof. A stud 294 is mounted near the top of mounting plate 292 by any suitable fastening means, such as a nut'296. A roller member 298 is rotatably secured on stud 294 by a pair of nuts 380. A humidity sensitive element 302 which changes length substantially linearly with changes in humidity has one end wrapped around a stud 304 which is attached to the mounting plate 292 near the bottom thereof by any suitable fastening means 386 and the end is secured back to the humidity sensitive element 382 by a clamp 388 to form a loop connection with stud 384. The other end of humidity sensitive element 302 extends over the roller member 298.

A pair of circular members 319, 312 are rotatably mounted on shaft 294 on either side of roller member 298. A bridge member 314 is secured to the circular members 310, 312 by suitable fastening means 316. A hearing block 318 is provided between the roller member 298 and the bridge member 314 and a screw 320 extends through bridge member 314 to press the bearing block 318 against the roller member 298 to hold the humidity sensitive element 392 in place. A coil spring 322 which holds the humidity sensitive element in tension has one end connected to the bridge member 314 by suitable fastening means 324 and the other end hooked to a stud 326 which is secured at the bottom of mounting plate 292.

An indicator or pointer 328 is formed on the'circular member 310 and is associated with a curved member 338 which has a calibration scale 332 thereon and is connected near the top of mounting plate 292 by suitable fastening means 334. The curved member 330 is concentric with the roller member 298, in other Words, the stud 294 is the center of curvature of the curved member 330.

In operation of the embodiment shown in FIGS. 7, 8,

and 8a, a change in the relative humidity causes a change in the length of humidity sensitive element 302. This linear change is converted to rotational movement by roller member 298 to move the pointer 328 relative to the scale 332 to indicate the relative humidity. The humidity indicator will have a linear characteristic since the lever arm (the perpendicular distance from the sensing element 302 to the fulcrum, i.e., the stud 294) remains constant, the scale is concentric, and the sensing element 302 changes length substantially linearly with the bottom thereof by any suitable means 364. A roller v member 366 which is rotatably mounted on stud 362 is provided with an indicator or pointer 368 formed on an end thereof. The pointer 368 extends beneath the curved slot and may be viewed externally of the cover 350. A member 370 is also formed in the roller member 366 and defines a slot 372. A projection 374 extends upwardly-from an end member 370 and has an aperture which fixedly receives an end of a spiral spring 376. The other end of spiral spring 376 is secured to mounting plate 334 by a screw 378. Any suitable humidity sensitive element 388 has an end wound around roller member 366 and threaded through slot 372 to fix the end of the humidity sensitive element 380. The humidity sensitive element 388 extends over a roller member 382 which is rotatably mounted on a stud 384. The stud 384 is adjustably connected in a diagonal slot 386 near the top of mounting plate 334 by any suitable fastening means 388. The other end of the humidity sensing element 380 is fixedly threaded to a slotted pin 390which has a retaining Washer 392 thereon. The slotted pin 39%) is attached to the mounting plate 334 adjacent the bottom thereof by a out 394.

In operation of the humidity indicator shown in FIGS. 9 through 11, any suitable sensing element 388 has one end fixed in a slotted pin 398, extends over roller 382 and has the other end fixed around roller 366. A change in relative humidity will cause a change in length of sensing element 380 to rotate pointer 368 which is on roller 366. The pointer will move relative to concentric scales 358, 360 to indicate the relative humidity. In the situation shown, the relative humidity will be read on the upper scale 358. However, a different type or a shorter sensing element 380 may be used, in which case,

the lower scale will be read. A shorter pointer 368 may be provided in the latter case. A length adjustment of the sensing element 380 may be made merely by loosening the fastening means 388 and sliding the shaft 384 to the desired position in slot 386 and re-tightening the fasteningmeans 388.

It is now apparent that a rugged, compact unit has been provided that has a relatively long sensing element which will indicate the humidity with reasonable accuracy.

While various embodiments of this invention have been shown and described, it is apparent that many changes may be made in the constructionand operation without departing from the scope of this invention as defined by the appended claims.

We claim:

1. In a humidity responsive device, the combination comprising a mounting plate, a step earn 1 rotatably mounted on said plate and movable in response to humidity variations, a humidity element having an end connected to said plate and another end connected to said step cam for movingsame, a resilient element having one end connected to said plate and another end connected to said step cam for biasing said step cam for movement in a direction to tension said humidity element, an indicator movable with said step cam for indicating the humidity, switch means having activator means disposed to be actuated by movement of said step cam, and switch mounting means rotatably mounted on said plate for moving said switch means relative to said step cam to determine the angle of rotation of said step cam at which said activator means is actuated. Y

2. The device of claim 1 wherein said switch means is adjustably mounted in cross-type slots 'in said switch mounting means to enable adjustment of said switchmeans relative to said step cam independently of said switch mounting means. 7

t 3. In a humidity responsive device, the combination comprising a mounting plate, a step cam rotatably mounted on said plate and movable in response to humidity variations, a humidity element having an end 9, connected to said plate and another end connected to said step cam for moving same, a resilient element having one end connected to said plate and another end connected to said step cam for biasing said step cam for movement in a direction to tension said humidity element, an indicator movable with said step cam for indicating the humidity, a pivoted member movable about its pivot by said step cam, switch means having activator means disposed to be actuated by movement of said pivoted member, and means mounting said switch means and said pivoted member and rotatably mounted on saidplate for moving said pivoted member relative to said step cam to determine the angle of rotation of said step cam at which said activator means 1 I is actuated.

4. The device of claim 3 wherein means is provided for moving, said pivoted member about its pivot independently of said step cam.

V i 5-. In a humidity responsive device, the combination comprising a mounting plate, a step cam mounted on said plate and rotatable in response to variations in the relative humidity, a pair of switch means each having an activator element disposed to be actuated respectively by said step cam, a pair of manually operable members rotatably mounted on said plate and respectively corresponding to each of said switch means for mounting same, each of said manually operable members being movable relative to said step cam to determine the angle of rotation of said step cam at which each of said activator elements is actuated.

6. In a humidity responsive device, the combination comprising a mounting element, rotatable indicator means carried by said mounting element, a scale member carried by saidmounting element and cooperable with said indicator means, humidity sensitive means supported on said mounting element and operatively connected for rotating said indicator means relative to said scale member to indicate changes in a relative humidity, indexing means mounted for rotation on a common axis with said indicator means and being cooperable with said scale member to index a predetermined relative humidity setting, switch means mounted for movement with said indexing means and having activator means thereon, and switch actuating means mounted for movement with said indicator means and being operable for causing actuation of said switch activator means at said predetermined relative humidity as sensed by said humidity sensitive means.

7. In a humidity responsive device, the combination comprising a mounting element, rotatable indicator means carried by said mounting element, a scale member carried by said mounting element and cooperable with said indicausing actuation of said switch activator means at said I cator means, humidity sensitive means upported on said mounting element, roller means rotatable by said humidity sensitive means and operatively connected for rotating said indicator means relative to said scale member to indicate changes in relative humidity, indexing means mounted for rotation on a common axis with said indicator means and being cooperable with said scale memher to index a predetermined relative humidity setting, switch means mounted for movement with said indexing means and having activator means thereon, and switch actuating means carried by said roller means for movement with said indicator means and being operable for predetermined relative humidity as sensed by said humidity sensitive means.

8. In a humidity responsive device, the combination comprising a mounting element, rotatable indicator means carried by said mounting element, a scale member carried by said mounting element and cooperable with said indicator means, humidity sensitive means supported on said mounting element, roller means rotatable by said humidity sensitive means and operatively connected for rotating said indicator means relative to said scale memher to indicate changes in relative humidity, indexing means mounted for rotation on a common axis with said indicator means and being cooperable with said scale member to index a predetermined relative humidity setting, switch means mounted for movement with said indexing means and having activator means thereon, and switch actuating means carried by said roller means for movementwith said indicator means, said switch actuating means including a cam portion operatively engageable with said switch activator means for actuating said switch activator means at said predetermined relative humidity as sensed by said humidity sensitive means.

References Cited in the file of this patent UNITED STATES PATENTS 639,935 Renzo Dec. 26, 1899 1,955,615 Ulrich Apr. 17, 1934 1,966,931 Mills July 17, 1934 1,998,340 Streb et a1. Apr. 16, 1935 2,503,273 Johnson Apr. 11, 1950 2,651,941 Windsor et a1 Sept. 15, 1953 2,780,687 Keenan Feb. 5, 1957 2,781,664 Ogden et a1. Feb. 19, 1957 2,887,544 Gustavsson May 19, 1959 FOREIGN PATENTS 101,234 Germany Jan. 20, 1899 1,153,712 France Oct. 13, 1957

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