US2269776A

US2269776A - Control mechanism

Info

Publication number: US2269776A
Application number: US230723A
Authority: US
Inventors: Herbert E Lindemann
Original assignee: Perfex Corp
Current assignee: Perfex Corp
Priority date: 1938-09-19
Filing date: 1938-09-19
Publication date: 1942-01-13
Anticipated expiration: 1959-01-13

Description

Jan. 13, 1942. H. E. LINDEMAN N 76 CONTROL MECHANISM Filed Sept.v 19, 1938 2 Sheets-Sheet 1 *3 INVENTOR.

BY HarbfilELz'ndsmann ATTORNEY.

Jan. 13, 1942.

H. E. LI'NDEMANN CONTROL MECHANISM 2 Sheets-Sheet 2 Filed Sept. '19, 1958 HErbETELincf TTORNEY.

Patented Jan. 13, 1942 UNITED STATES PATENT. OFFICE Herbert E. Lindemann, Milwaukee, Wis, asaignor to Perfex Corporation, Milwaukee, Win, a corporation of Wisconsin Application September 1 26 Claims.

This invention relates in general to control mechanisms but more particularly to physical the production of a new and improved control mechanism adapted for heavy duty service.

A further object is to provide a control mech- 9, 1938, Serial No. 230,723

anism which is extremely sensitive and accurate.

in its response to variations in physical conditions over a wide range.

An additional object is to provide improved regulating means for a control mechanism whereby the operation of the device can be accurately predetermined. o

A further object of the invention is to provide improved switch operating mechanism for automatic snap action switches.

Another object is to design a control mechanism which will be capable of directly handling line voltage loads through its switching mechanism for-'controlling motors and other apparatus without the use of a relay.

Another object is to provide a snap acting switch mechanism including elements which ean be arranged to either open or close the switch contacts upon a movement of the switch actuator in a given direction.

Dther objects and advantages reside incertain novel features of construction, arrangement and combination of the parts which will be hereinafter more fully described and particularly pointed out in the appended claims. It has been Fig. 'l is a bottom view. with the cover removed;

Fig. 8 is another bottom view with the switching elements shown in closed position.

Fig. 9 is a view of the'adjusting elements shown in extended perspective relationship;

Fig. 10 is a side view of a portion of a modified construction in which ,the switching elements are normally closed;

Figv 11 is an end view of the modification;

while Fig. 12 is a, fragmentary bottom portion of Fig. 1 with the operating arm removed.

In its preferred form the control mechanism comprises a rectangular base 5, preferably formed of some molded insulation product having a shallow depression 8 formed in its front surface. On the rear side a flange l extends around ,the surface of the base and forms a depression 8 so that the various terminal and mounting screws are protected by the flange I when the instrument is mounted in place.- The device is usually supported on a flat wall surface (not shown) and is provided with bosses or proiectinrportions 9 and it for engaging the wall or 'a mounting plate (not shown) fastened to the wall. Mountingscrews and I2 extend from the front side of the base 5 and are adapted to thread into the mounting plate. The bosses 9 and Ill are arranged so that the elements on the base are not subjected to strains or stresses caused by uneven wall surfaces.

A U-shaped metal bracket l3 (see 9) is secured to the base 5 in the depression 6. by

chosen by way of example to illustrate and describe the invention in connection with a physical condition responsive mechanism such as a room thermostat in which a charged'bellows is uti lized as the controlling medium. In another of its forms the control mechanism may be arranged to respond to humidity, pressure, or other physical conditions.

A preferred embodiment of the control mechanism will now be described in connection with the accompanying drawings in which:

Fig. 1 is a front elevation of the control mechanism; I

Fig. 2 is a side view of the device with the cover in section;

Fig. 3 is a sectional side view line 3-3 of F18. i;

Fig. 4 is a fragmentary view of taken along the the top portion of the device;

Fig. 5 is 2 full rear elevation of the control device;

Pig. 6 s a top view with the cover in section;

means of a pair of supporting screws ll ,(Fig. 5) threaded from the rear side of the base. The bracket I3 is provided with outwardly projecting arm portions l5 and It to which are attached steel spring hinges I1 and I8 respectively. A-- relat vely stiil' operating arm I! is arranged parallel to the base 5 and has one end riveted to the other ends of the spring hinges IT and It so that the operating arm is pivoted by means of these hinges. By providing this spring hinge type of construction for pivoting the arm I! the control operates with greater accuracy and sensitivity due to the fact that no lost motion or loose connections are present. For the purp'ou of actuating the operating arm I! a physical condition responsive means shown here in the form of a thermostatic element or bellows II, is

provided. This bellows 2| is filled with a highly volatile gas or liquid which has the inherent moves the free end of the operating arm I! in a direction away from the base. The bellows 2| is provided at its lower end as shown in Fig. 3, with a small tube 22 which extends into a cylindrical projection 23 formed in the base 5. A

hollow metal stud 24 surrounds the tube 22 and forms a connecting link for supporting the bottom of the bellowson the projection 23 with its axis perpendicular to the base. This projection 22 also serves to thermally insulate the bellows 'from the base. After the expansible medium is oted end of the operating arm I! as shown. By

connecting the bellows substantially adjacent the fulcrum point of the arm [9, the arm multiplies the motion of the bellows in a large ratio, and consequently it is moved with very slight motion of the bellows.

A connecting lever 21 for adjusting the operating range of the thermostat is pivoted by pin 28 to a pair of small bracket ears 2! formed in bracket l3. lever 21 is connected to a stifliy tensioned coil spring 3| arranged perpendicularly to the base and the other end of which is threaded around an adJusting stud 32. Stud 22 in turn is held to the operating arm is by a calibration adjusting screw 33. Screw 33 is arranged between the ends of the arm l9, and turning it adjusts the tension of coil spring 3| any desired amount for calibration purposes as will be pointed out.

The free end of operating arm I! has an insulating block 34 attached to it by means of sup porting screws 55 and the other end of "the block 34 has an armature and movable contact bracket 35 secured to it by the screws 31. v The bracket 36 is bent in the shape shown with two parallel offset surfaces connected by an angular portion so that the surfaces are on different planes. It is movable together with the operating arm 19 in a direction away from and towards the base. In order to limit the outward movement of the operating arm l9 beyond a fixed point, a stop bracket 28 is provided which is secured by screw- 39 to the base 5. A projecting stop portion ll formed in one end of the armature bracket 25 engages a slot in the stop bracket 38 for the purpose stated.

A magnetic armature 42 is formed on the end of bracket 36 and is arranged with a pair of outwardly extended ear portions 13. These ears provide a means for pivoting a rigid bar or connecting arm 44 through the medium of a pivoting pin '45 extending through ear portions 48 and similar extensions formed on rigid bar 44. A flexible contact arm 46 is arranged at one side of bar 44 (see Fig. '7) and is riveted at 1 to the rigid bar II. A contact point 48 is riveted to rigid bar 60 N and flexible arm I. A second contact point 49 is secured to the free end of the flexible arm II but is slightly separated from the bar I be-, cause the free end of bar 44 is offset from flexible arm 45. and arrangement of elements it is seen that movement of the end of operating arm l9 results in the contact points 45 and 4| being moved in a direction perpendicular to the base. Arranged on the base in operative relation to movable contact points II and 45 are fixed contact points 5| and 52. Fixed contact point II is supported on the end of an adjustable contact stud 53 which threads into the top of a contact supporting bracket ll. A slot is cut inthe top of contact The lower end of this connecting '2 With the foregoing construction bracket 54 (see Fig. 12) where the stud 53 is threaded, in order that the threads of the stud may be resiliently and tightly gripped and thereby hold the stud in its adjusted position. The contact bracket 54 extends through the base 5 to the rear side thereof where it is secured by a pair of screws 55 threaded into a bottom portion of the contact bracket from the front of the base. A terminal screw 56 also threads into bracket 54 at the rear of the base and providesa means for the attachment of a connecting wire (not shown) The other contact point 52 is arranged in a similar manner with contact stud 51 threaded into the split top portion of supporting contact brack et 58 which in turn is secured to the base by means of supporting screws 59. At the rear side of the base a terminal screw 6! threads into contact bracket 58 for the connection of an electrical wire (not shown). I

The stud 51 is provided with a lug 62 (Fig. 12) having a screw driver slot therein for the purpose of adjusting the differential of the control device as will be hereinafter pointed out. Lug i2 is arranged to cooperate with the scale markings v 63 stamped upon the top of contact bracket 55. The top bi'.stud 53 is provided with a hexagonal head portion to facilitate turning the stud so that the height of contact .5! may be varied with respect to the base.

Arranged between the two sets of contact points and adjacent the armature I2 is a permanent horseshoe magnet 84. It is supported by a washer and clamping screw 55 (see Fig. 3) threaded into supporting bracket 66 which in turn is mounted upon the base by a pair of screws 61 threaded from the rear of the base 5'. The poles of magnet 64 are arranged so as to influence the armature 42 to assist'in providing snap action to the opening and closing of the contact points.

At the upper end of the base 5 a cam disc 68 is positioned. It 'is preferably molded of some suitable insulation product and arranged to be rotatable about an axis perpendicular to the base aperture III in the base 5 (see Fig. 9) provides a bearing surface for a brass stud 1i molded into and extending from the rear side of cam disc 6!. A circular groove I2 is formed near the end of stud H and is engaged at the rear of base 5 by the forked end of a tensioned leaf spring II. Spring 13 in turn is secured to the rear side of the base by a pair of screws 14. The upper end of the spring 13 is flexed away from the base in order that it may resiliently hold the cam disc 68 in frictional engagement'with the depressed portion 5 in the front side of the base. A narrow -circular bearing surface 15, on the rear of the v the rear of the cam disc 58. It has a knurled periphery-in order to facilitate manual manipulation of the same and also a series of temperature indicating numerals stamped on its front surface as shown. The number dial II has a large opening in its center together with a slot I1 cut in theside of the opening. A stop member "ll formed in the rear side of the cam disc 55 extends through the slot 11 so that whenever number dial I5 is rotated the cam disc 5| is likewise rotated. A dish shaped spring washer 19 is positioned between the front of the number disc II and the rear side of cam disc 6| so that it closely embraces the outside of the bearing surface portion II. The purpose of this spring washer 18 is to prevent binding or straining the cam disc in its adjusted position and also to prevent the number dial 18 from loosely rattling in its position since the washer tends to resiliently urge bo h discs apart.

A pair of stepped shoulder portions 8| and 82 are formed upon the upper front surface of the base and serve as a bearing surface for the number dial when it is rotated. The rotary position of number dial 16 is limited in either direction by the stop I8 on cam disc 88 which extends through notch 11 and engages notches 88 cut in the bracket I3 as shown in-Fig. 9. It is occasionally desirable, for the purpose of preventing unauthorized manipulation of the number dial I6, that the dial be locked in a particular set position. For thispurpose a clamping member 84 (Fig. 1) is provided which engages the front side of number dial I8 and clamps the dial tightly to the base surface 82 whenclamping' screw 85 is tightened on it. Due to the fact that the number dial 18 is not rigidly connectedto cam disc 68 this clamping arrangement will not disturb the adjustment of cam disc 88.

The upper end of pivoted connecting lever 21 is provided with a small cylinder 86 which is riveted to the lever 21 so that it cannot rotate. This cylinder 86 is arranged to bea-r upon the cam surface 68 due to the tension of the coiled spring 8| and rides along the cam surface whenever dial I6 is rotated. -The cylinder 86' is positioned so as to lie directly on a radial line extending through the axis of the cam disc 88 and because of its rigid connection with the lever 21 it will always bear with the same point of contact upon the cam and thereby enable the calibration of the instrument to be maintained at a constant uniform value regardless of the position to which the cam disc is rotated.

It is desirable that the various elements of the instrument be protected from injury and for this purpose a metal cover 81 is provided. As seen in Fig-'5 a number of reinforcing ribs 88 are formed around the insides of the cover which engage the base 5 and space the cover from it. The bottom of the base 5 is provided with a pair of projections 88 while at the top of the base .a pair of resilient metal clips 8| and 82 are secured thereto and extend outward therefrom. In placing the cover upon the base these clips 8i and 82 first engage the top cover members 88 and are then forced tightly into engagement therewith by the projections 88 on the bottom of the base engaging the ribs 88 on the ,cover. In this manner the cover is resiliently held to the base so it will not be loose or tend to rattle. Likewise, all stresses and strains on the elements mounted on the base are eliminated. In order that the cover may be locked to the base a cover screw 83 is provided which engages a slot in the cover and is threaded into the base through an enlarged portion of the slot so that it is flush with the bottom surface of the cover. The cover 81 as seen in Figs. 4' and 6 surrounds the front and sides of the instrument but is open at the top and bottom to permit the surrounding air to circulate therethrough and contact the bellows. A series of grills 84 are provided across the openings to protect the internal mechanism. A pointer or indicator 85 is likewise formed in the top of the cover in order to indicate the setting of the number dial 16.

Referring now particularly to Fig. 2 the cover '81 is provided on its front surface with a scale plate 86 having the usual temperature gradua- 4 tions marked thereon. The scale plate 88 is arranged so that its lower end rests in a slot 8! formed on the front of the cover 81. The usual thermometer 88 is arranged behind an opening in scale plate 88 and is resiliently held in place by a thermometer guard strip 88 which has an enlarged portion IIII for accommodating the thermometer bulb and also imparting greater resiliency to the strip. The upper end of the thermometer 88 is suitably sealed into an opening in the strip 88. At its upper end thermometer guard 88 is slotted and a clamping screw I82 passes through the slot and a hole in the cover and threads into the upper end of scale plate 88. At the bottom a clamping screw I83 passes through a slotted opening in thermometer guard 88 and threads into the cover. By merely loosening screws I82 and I88 the thermometer strip 88 and likewise the thermometer 88 may be moved up or down in order to calibrate it to agree with the readings on the scale plate 86. This arrangement likewise facilitates the assembly of the aforesaid elements upon the cover.

The manner in which the various calibrating adjustments for the control mechanism are made will now be pointed out. In the initial calibration of the device the instrument is first placed in a testing room where the temperature is maintained at'70 degrees F. The dial I6 is then rotated until the numerical indication is positioned opposite the center one of the graduations I06 marked on the upper end of the base and at which time the designation lfl will be directly on top of the dialand opposite pointer if the cover were on. The calibration adiusting screw 33 is then turned to vary the tension of spring 3i until the operating arm is just closes the contacts at the setting made. The instrument is now set to operate and close the contacts at any temperature indication to which the dial I8 is rotated with respect to pointer 95.

The differential of the device is the change in temperature necessary to cause the bellows to open and close the contacts. To calibrate this diiierential initially the

studs

53 and 5? are ad-= justed to give a small clearance between the armature 42 and magnet 64 with the contacts .closed. The lug B2 is left with its screw driver slot at minimum differential setting on the scale markings 63 and the other stud 53 adjusted to vary the air gap until the correct differential of one or more degrees is obtained. After this calibration the lug 62 may be subsequently rotated across scale 63 to any of the markings to lessen the air gap between the armature and magnet and thereby increase the pull of the magnet so that the differential is widened.

.The construction and arrangement of the various elements constituting the thermostatic switch having been pointed out in detail, their operation will now be explained. Assume for example} that the number dial.1 6 has been rotated to a position such that the temperature indication of 77 degrees has been placed directly on top of the instrument as shown in Fig; 1. Cam disc 88 is ac-' cordingly positioned so as to tilt the adjusting lever 21 a certain amount by means of cylinder 88 riding on the cam surface. Assume likewise that the thermostatic switch has been located in a room so as to maintain the temperature of the same at about '77 degrees. As the temperature of the room drops the bellows fluid reduces its vapor pressure in definite relation to the temperature, and the force exerted against the operating arm I8 by the bellows diminishes, causing the operating arm ill to move under the combined efforts of the spring SI and the magnet 36 toward the magnet until equilibrium of the forces is again established. As the operating arm moves toward the magnet in this manner due to reduction in temperature, a point is reached Whereupon further motion of the operating arm IS, the magnetic effort is greater than the opposing effort of the spring and bellows assembly (referred to the same point on the arm l9), and an unstable state is established. At this time the operating arm I! snaps over toward the magnet, closing the

contacts

48 and 52, and 45 and 5! respectively, with snap action, and the unbalance force between the magnet, and the bellows and spring assembly, is applied to the contacts. The closing of the contacts effects the control of the heating plant whereby an increase or rise of temperature takes place within the room containing the thermostat.

As the temperature of the room rises, the beilows fluid increases its vapor pressure in relation to the temperature and the force exerted against the operating arm l9 by the bellows increases.

-When the bellows temperature reaches 77 degrees plus the differential for which the instrument is set, the bellows effort Just exceeds the opposing spring and magnetic efforts and the arm I9 snaps outward. Since the magnetic effort drops much more rapidly than the spring and bellows assembly forces as the arm i9 moves outward, the unbalance force on the arm I9 becomes quite large aiter a short amount of travel and considerable acceleration'is imparted to the arm and movable assembly, causlng it to move and open the contacts with a fast snap action.

Returning now to the action taking place as the contacts are closed, the movable contact 49 on the free end of resilient arm 46 engages its as sociated fixed contact SI and a slight wiping action takes place until the rigid bar 4| engages the rear end of contact 49. The other movable contact 48 engages the fixed contact 52 with a wiping action due to the leveling effect produced by the pivot 45. As seen clearly in Fig. 8 which shows the contacts in their closed position, magnet 64 maintains armature 42 within its influence without touching the same because it is held away from it by the contacts engaging each other. Due to this magnetic attraction the contacts are not subjected to vibration or shock but are held tightly inintimate engagement. The resilient arm 4 forms an electrical bridge circuit which extends from a connecting wire (not shown) attached to terminal screw 58, through contact plate ll, contact stud ll, contacts SI and I8, resilient arm 48, contacts II and ",stud 51, contact Dlate II to the other terminal screw BI and a wire attached thereto. Due to the poor contact between rigid bar and the rear 01 contact 49 most 01' the current flows through the flexible arm 40.

when the contacts are opened by the-operating arm II, the bellows exerts its force against the combined tension of spring {I and the pull of the magnet. When a point. is reached shortly be- Your] the balance of eilort between these elements the armature l2 rapidly moves away from the influence o! the magnet. Because of the resiliency of flexible arm 40 and the time it takes .101 the end of rigid bar 44 to move away from the rear side oithe contact I, the contacts remain'closed for a short interval of time after the aforesaid balance of effort has been passed and open after the rigid bar 44 has had time to accelerate. In this manner the contacts are separated with a distinctive snap action.

By providing this snap action corrosion, arcing and pitting of the contacts is obviated. The device operates more accurately and-positively without fluttering of the contacts and should there be any tendency for the contacts to stick or become slightly welded together, they are immediatcly separated due to the pivotal arrangement of the rigid arm M which acts to pry them apart. Also because of the iact that'it only necessary to open one set of contacts to interrupt the bridge circuit controlled by the instrument, either set of contacts may remain lightly in on gagement with the associated iii ed contact in case the instrument not mounted a level position. The ioregoing advantages render the device suitable for handling relatively high loads without the use of relays.

In the construction described the elements of the control device are such that the contacts are closed upon a drop in room temperature and are opened when the temperature drops as pointed out. It occasionally desirable that this arrangement be reversed so that the contacts will be closed upon a temperature rise and opened upon a fall in temperature, such as in a refrigoration system for example. This reverse operation may be easily and conveniently accomplished in the instant arrangement as shown in the modifications Figs. 10 and 11. The screws 31 are merely removed, the armature bracket 36 reversed, and the screws inserted and tightened again so that the armature bracket extends towards the base. The contact points 48 and I! now extend upwardly into engagement with the bottom of

studs

53 and 61 which are provided at this point with contact points I04 and I05. The magnet clamping screw 65 is likewise loosened to permit the magnet 6| to be rotated so that its poles extend toward the base in operative relation to the armature 42 as shown. Clamping screw B5'is then tightened to hold the magnet in this position. The armature bracket 36 is so shaped that it comprises two parallel fiat portions arranged in different planes, oiIset from one another and connected by an angular flat portion between the ends. The portion or the bracket connected to the block 34 by screws 31 is arranged on a plane which is substantially on a line with the top surfaces of the

contact brack ets

54 and 58 and therefor at the approximate center point between the

studs

53 and 51. This arrangement it is seen permits the armature end .of the bracket 36 to be placed in association with either end of the contact studs to operate the contacts, without the necessity of bending the same or of adjusting the studs to diiierent elevations from the base to accommodate the bracket. It is therefore seen that without the introduction 01' any auxiliary elements or new parts the com trol device is arranged for universal adaption in which a different control may be efiected by merely reversing certain elements.

It is sometimes necessary that the manual manipulation of the number dial 18 be limited so that the mechanism cannot exercise its control either beyond or below a maximum or minimum temperature value. To provide for this limitation a stop I0! is formed on the number dial 16 at any point where it is required. As shown in Fig. 1 the stop I01 engages tho'clampin: member 84 when the dial 18 is rotated to a temperature reading or about 77 degrees. The

mounting of the bellows.

stop I01 prevents any movement of the dial beyond this point.

Contributing factors to the ability of the device to control heavy loads and yet operate on small temperature changes are the following: A high sealing effort or arresting force is obtained which prevents the contacts from bouncing after they have made contact. Lost motion in the operating beam is prevented by the use of spring hinges. Unwanted flexure of the beam support I5 is prevented, although lightweight supports are used, by the method of mounting the bellows perpendicular to the base to allow the use ,of a support which is stressed principally in tension.

A contributing factor to the ability of the device to respond to temperaturelchanges without appreciable time lag is the construction and The bellows 2| is constructed with a very low ratio of mass to exposed surface area in order to minimize the heat capacity, and is connected to the rest of the mechanism through members 24 and 25 of small cross sectional area'to minimize the heat transfer.

From the foregoing description of the invention it is apparent that a novel type of control mechanism has been designed in which the elements thereof are compactly arranged, easy to assemble and adjust, and in which relatively heavy loads are readily controlled.

Since only a preferred illustration of the invention has been disclosed it is conceivable that modifications thereof may be readily perceived by those well versed in the art and it is therefore desired that the invention be not limited to the precise structure illustrated and described, but only to the extent of the appended claims.

What is claimed is:

l. A control mechanism of the class described comprising a base, an operating arm arranged parallel to the base, means for effecting move-.

ment of said operating arm perpendicular to the base and in two directions, an armature bracket secured to but insulated from said operating arm and havingan armature on the end thereof, a pair of movable contacts, connecting ar'm means supporting one of the movable contacts from each endthereof, means on the armature for pivotally supporting the connnecting arm means between its ends, a pair of fixed contacts ar-- ranged in operative relation to said movable contacts and engageable therewith responsive to the movement ofthe operating arm, a magnet arranged on the base between the contacts and in operative relation-to the armature for providing snap action to the engagement of said contacts, the engagement of said contacts preventing the actual engagement of the armature with the magnet, and a stop on the base engaged by the armature bracket for limiting the movement of the operating arm when the; contacts are disenaged.

2. A control mechanism of the class described comprising a supporting base, an operatingarm pivoted to the base and arranged parallel thereto, an armature carried at one end of the operating arm and arranged parallel to the base, means for insulating said armature from the arm, a permanent magnet supported on the base in a position to influence the armature, connecting arm means pivoted to the armature, a movable contact carried on each end of the connecting arm means and arranged with the armature between them, a pair of fixed contacts supported on the base in operative relation to the movable contacts and arranged with the magnet between them, resilient physical condition responsive means arranged between the base and the op-' erating arm at a point near the pivot of the operating arm for actuating the operating arm in one direction, different resilient means also arranged between the base and the operating arm at a point near the armature end of the operating arm for actuating the operating arm in another direction, both of said resilient means assisting the magnet to impart snap action to the opening and closing ofthe control contacts, and means for adjusting both of said resilient means.

3. A control mechanism of the class described comprising an elongated base, a physical condition responsive element arranged upon said base at one end thereof, a supporting bracket arranged at the same end of the base, an operating arm having one end hingedly supported from the bracket and having its free end extending toward the opposite end of the base, a control element carried by the free end of the operating arm, a fixed control element on the base arranged in cooperative relation to said first control element, means for associating said physical condition element with said operating arm adjacent the hinged end of the arm whereby the operation of the physical condition responsive element effects the cooperation of the control elements, an adjustable cam rotatively mounted upon the base adjacent the hinged end of the operating arm ror-adjustingthe point at which the condition responsive element is effective to bring about the cooperation of the control elements, an adjustable tension spring connected to the operating arm at a point between its hinged end and its free end, a connecting lever pivoted to the base and having one end connected to the tensionspringand the other end in slidableengagement with said adjustable cam, and means for imparting snap action to the operation of the control elements.

4. A control mechanism of the class described comprising a base, an operating arm-spaced from the base and arranged parallel thereto, means for hinging the operating arm to the base, a bellows secured at one end to the base and having its other end associated with the operat ing arm adjacent its hinge for actuating the same, a spring acting upon the operating arm,

-means on the arm for calibrating the tension ofthe spring, rotatable adjustment means secured to the base, means connecting the adjustment means with the other end of the spring whereby the bellows may be adjusted to predetermine its movement of the operating arm, a contact bracket carried by the operating arm, movable contacts on the contact bracket, fixed contacts on the base in operative relation to the movable contacts, means including the bellows and the spring for imparting snap action to the opening and closing of the contacts, and means associated with the fixed contacts for adjusting the differential operation of the operating arm.

5. A control mechanism of the class described comprising an elongated "base, a U-shaped bracket supported at one end of the base, an opcrating arm arranged in spaced parallel relationship to the base, means for hingedly supporting the operating arm on the U-shaped bracket, an expansible and contractible bellows supported at one of its ends from the base and having its axis arranged perpendicular thereto, means for associating the-other'end of the bellows with the operating arm adjacent its hinge support to actuate the armin one direction of secured to one end of movement, a connecting shaped bracket adjacent tension spring arranged lever pivoted to the U- the bellows support, a perpendicular to the base and connected between one nd of thelever and a point intermediate the ends of the operating arm i'or moving the operating arm in another direction, a manually rotatable disc arranged on the base adjacent the U-shaped bracket with its axis extending perpendicular to the base, a spiral cam on said disc responsive to the rotation of the disc for adiustably moving the other end of the connecting lever to vary the tension of the tension spring, cooperablemeans on the discand the U-shaped bracket for limiting the rotative movement 01' the disc, cooperable contact points supported on the operating arm and on the base and actuated by the movement of the arm, and cooperable magnetic means also supported on the movable end of the operating arm and on the base for imparting snap action to the actua-' tion or the contact points. v

6. A control mechanism of the class described comprising a supporting base, an operating arm arranged parallel to the base, means for pivoting said operating arm to the base, a bellows arranged between the base and the operating arm with its axis perpendicular to the base and having one end supp rted on the base and the other end associated with the operating arm near its hinge, said bellows adapted to move the operating arm in one direction, an armature bracket carried by said operating arm and having an armature element formed thereon arranged parallel with the base, a pair of movable contacts supported on the armature bracket, a pair of fixed contacts arranged on the base in operative relation to the movable contacts, a spring arranged with its axis perpendicular to the base and connected at one end to the operating arm at a point on the arm between the bellows connection and the armature bracket, said spring effective to move the arm in another direction, a connecting lever pivoted intermediate its ends to the base and having each end movable perpendicular to the base, one end or said lever being connected to the other end of said spring whereby its tension is adjusted by the movement of spiral adjusting cam rotatably supported on the base with its axis perpendicular thereto for moving the other end or the connecting lever, and magnetic means supported on the base in operative relation to the armature for providing snap action to the operation ofxsaid contacts, said movable contacts bridging said fixed contacts to complete an electrical circuit.

7. A control mechanism of the class described comprising an elongated'base, a U-shaped supporting bracket secured to one end of the base and having the two legs extending outwardly therefrom, an operating arm arranged parallel to the base, hinge means connecting the operating arm with the bracket legs, an armature bracket carried by the operating. arm and'arranged parallel to the base, a rigid bar pivoted at its mid-point to said armature bracket and arranged at right angles thereto, a flexible arm the rigid bar and arranged and the armature bracket, the other end of the flexible arm being spaced apart from the rigid bar, a pair of spaced movable contact points secured to opposite ends of the flexible arm, a pair of fixed contact points supported onthe base in operative relation to the movable contact points, a magnet supported on the base between the fixed contacts for influbetween therigid bar ior actuating the encing the armature bracket to impart snap action to the operation of the contacts, a physical condition responsive element having its axis arranged perpendicular to the base and secured at one end thereto and at the other end cooperating with the operating arm adjacent its pivot same, a connecting lever pivoted at its mid-point to the supporting bracket adjacent the condition responsive element, a coiled spring arranged with its axis perpendicular to the base and connected at one end with the connecting lever operating arm at a point between the condition responsive element and the armature bracket, the connection of the spring with the operating arm comprising an adjusting means for calibrating the tension of the spring, a manually rotatable dial having a spiral cam thereon arranged on the base adjacent the supporting bracket with its axis perpendicular to the base, means on the supporting bracket for llmiting 'the rotation of the dial in either direction, the other end of the connecting lever having slidable engagement with the spiral cam whereby the operation of the contacts can be predetermined in accordance with physical condition changes, and locking means on the base adapted to engage the rotatable dial to prevent manual rotation of the same.

8. A control mechanism of the class described comprising a supporting base, an operating arm, means for hingedly supporting the operating arm to the base, means on the base and associated with the operating arm for moving it in either of two directions, an armature bracket carried by the operating arm and having anarrnature formed on the end thereof, switch mechanism comprising movable contacts supported by said armature bracket on each side of the armature and fixed contacts supported on the base, a reversible magnet on the base, in operative relation to the armature for influencing the same and for rendering the switch mechanism snap acting, said fixed and said movable contacts arranged to' move toward engagement and said armature toward said magnet responsive to the movement of the operating arm in a direction toward the base, said armature bracket arranged to be reversible on its support to effect disengagement of the contacts responsive to the same movement of the operating arm'in a direction toward the base when said magnet is reversed.

9. A control mechanism of the class described comprising a base, an operating arm pivoted on the base, an armature bracket carried by the arm, means on the base for moving the arm in a direction either away from or toward the base, movable switching mechanism carried by said armature bracket, fixed switching mechanism supported on the base in operative relation to the movable switching mechanism, said switching mechanism adapted to move into engagement responsive to the movement of the operating arm toward the base, and magnetic means associated with said switch mechanism for rendering the switch mechanism snap acting, said armature bracket adapted to be reversed to open said switching mechanism when the operating arm is moved in a direction toward the base.

10. A control mechanism of the class described comprising a base, an operating arm pivoted to the base, a physical condition responsive element controlling the movement of the operating arm, a pair of fixed contact supports secured to the base and having raised portions arranged parallel to the base, a contact stud extending through and at the other end with the supporting the operating arm on the base,

the raised portion of each contact support, a reversible contact bracket, movable contacts pivotally carried by the reversible contact bracket in operative relation to the contact studs, means for supporting the reversible contact bracket in one manner from the end of the operating arm whereby the movable contacts are moved into association with one end or the contact studs, said means adapted to support the reversible contact bracket in another manner from the operating arm whereby the movable contacts are moved into association with the other end of the contact studs, and means associated with said reversible contact bracket for rendering the contacts snap acting.

11. A control mechanism or the class described comprising a base, an operating arm pivoted to the base, a physical condition responsive element controllingthe movement of the operating arm, a pair of flxed contact brackets secured to the base each having a raised portion arranged parallel to the base, a separate contact stud extending through the raised portion of each iixed contact bracket, a movable contact bracket, means for supporting the movable contact brackat from the movable end of the operating arm, a pair of movable contacts pivotally carried by the. movable contact bracket in operative relation to the contact studs, said movable contact bracket arranged for mounting in either of two positions on the operating arm whereby the movable contacts can bemade to engage either ends or the contact studs and thereby either open or close the contacts on a given change in the physical condition, and means associated with said removable contact bracket for rendering the contacts snap acting.

' 12. A control mechanism of the class described comprising a base, an operating arm pivoted to I the base, a physical condition responsive element controlling, the movement of the operating. arm,

a pair of flxed contact supports secured to the base and having raised portions arranged parallel to the base, a contact stud extending through the raised portion of each contact support, a movable contact bracket having two parallel flat portions oflset from one another and connected'by an angular extending portion, a pairoi' movable contacts pivotally supported on one of the flat portions of the bracket, means for supporting the other of the flat portions of the bracket on the arm in a position substantially on a plane with the raised portions or the contact supports whereby the movable contacts are adapted to be moved by the bracket into association with one end of thecontact studs, said bracket arranged to be reversed on its supporting means whereby the movable contacts are adapted to be moved actuated by the operating arm, means for hingedly supporting the operating arm on the base, flexible physical condition responsive means for moving the operating arm in one direction, adjustable flexible means opposing the action of the physical condition responsive means for moving the operating arm in a reverse direction and for adjusting the device to predetermine the physical condition at which the controlmechanism is actuated, means on the base remote from the adjustable flexible means for adjusting the same, lever means pivoted on the base connecting the adjustable flexible means to the adjusting means for applying eflort produced by the remotely located adjusting means to the adjustable flexible means and for reversing the direction of the applied eflort, and means on the base for magnetically biasing the operating arm, said flexible physical condition responsive means and said adjustable flexible means being connected to said operating arm in a manner to eliminate lost motion between the operating armand both flexible means, said physical condition responsive means and said adjustable flexible means additionally cooperating with the magnetic biasing means for rendering the operating arm snap acting in either direction.

15. A device of the class described comprising a base, an operating arm, control mechanism actuated by the operating arm, means for hingedly supporting the operating arm on the base, flexible physical condition responsive means arranged perpendicular to the base and flxed thereto at one end for moving the operating arm.

in one direction, the other end of said physical condition responsive means emglng the opv erating arm near the axis of rotation 01' the op- 1 the top front surface of into association with the other end of the contact.

studs, and means associated with saidreversed' contact bracket for rendering the contacts snap acting.

13. A device of the class a base, an operating arm,

described comprising means for hingedly flexible physical condition responsive means tor moving the operating arm in one direction, an adjustable flexible means opposing the action of the physical condition responsive means for moving the operating arm in a reverse base remote from the adjustable flexible means for adjusting the same, lever means pivoted-on the base connecting the adjustable flexible means to the adjusting means for applying eflort prodirection, means on the -lever means pivoted on the base connecting operating arm,

responsive means erating arm, adjustable flexible means opposing the action of thephysical condition responsive means for moving the operating arm in a reverse direction and for adjusting the device-to predetermine the physical condition at which the control mechanism is actuated, said adjustable flexible means being connected to the operating arm at a point more remote irom its axis of rotation than the point of engagement of the physical condition responsive means, means on the base remote fromthe adjustable flexible means for adjusting the same,

adjustable flexible means to the adjusting means for applying eflort produced by the adjusting means to the adjustable flexible means and for reversing the direction of the applied eflort, and means on the base for magnetically biasing the said flexible physical condition and. said adjustable flexible means being connected to said operatingarm in a manner to eliminate lost motion between the operating arm and both flexible means, said physical condition responsive means and said adjustable flexible means additionally cooperating with the magnetic biasing means to render the operating arm snap acting in either direc tion.

ducedby the remotely located adjusting means 76 16. A control mechanism or the class described the comprising a base, an operating arm arranged parallel to the base, an expansiblc and contractible bellows supported at one end on the base and having its axis perpendicularly disposed thereon, the other end of the bellows connecting with the operating arm for transmitting movement thereto, an adjustable dial having indicia thereon rotatably supported on the base with its axis of rotation perpendicular to the base, a cover for the mechanism, said dial arranged to protrude through the cover to render the indicia readable and the dial accessible for adjustment, a connecting lever pivoted to the base, means on the adjustable dial for moving one end of the connecting lever, a coil spring having its axis perpendicularly disposed with respect to the base connecting the other end of the lever with the operating arm at a point more remote from the connection thereto of the expansible and con tractible bellows, and means for magnetically biasing the operating arm whereby snap action of the operating arm is obtained by the sole co" operative action of the resilien y of the en pansible andcontractible means and coil spring with the magnetic biasing means.

17. A device of the class riescrib a base, an operating arm, control tuated by the operating arm, supporting the operating arm to the base, It lble physical condition responsive means moving the operating arm in. one justable flexible means opposi physical condition responsive the operating arm in a rover adjusting the device to cal condition at which the actuated, a rotary cam t remote from the adjustable ed comprisin vice, said dial arranged to i through the cover to render the indicia re able and the dial. accessible for adjustment, lever pivoted on. the base connecting the adjustable flexible meals to the spiral cam for applying effort produced by the spiral cam to the adjustable flexible means, and means on the base for magnetically biasing the operating arm, said flexible n l sical condition responsive means and said ad ustable next ble means being connected to operating arm in a manner to eliminate lost motion between the operating arm and both flexible meanasaid phys ical condition responsive means and said adj ustable flexible means additionally cooperating with the magnetic biasing means to render the oper ating arm snap acting in either direction.

18. A control mechanism of the class described comprising, a base, a supporting bracket secured at one end of the base and having two legs extendlng outwardly therefrom, an operating arm arranged parallel to the base, spring means for hinging the operating arm upon each of the two legs, means for actuatin the operating arm in one direction, lever means having one of its ends arranged to adjust the actuating means, an extension on the supporting bracket having two bracket ears for pivotally supporting the lever means, adjusting means on the base cooperating with the other end of the lever means, said supporting bracket having a pair of notches cut therein, and a stop on the adjusting means engaging the notches to limit the extent of motion or the adjusting means. i

19. A control mechanism of the class described comprising a base, an operating arm pivoted to ill fill

and terminating short hitch/W6 the base, a cylindrical bellows responsive to physical conditions for motivating operating arm, said bellows having a number of convolutions extending around its periphery for rendering the bellows flexible and for providing a large surface for contact with air surrounding the bellows, pivot means fastened to one end of the hellows for engaging the operating arm, a pedestal support on the base having an aperture therein, a tube fastened to the other end of the bellows providing a means for filling th hellows, said tube additionally serving to alig the bellows with the pedestal support by into said aperture, and a hollow metal stud around the tube arranged between the bel ows and the periestal support for spacing ellows from the pedestal support and for assisting in the alig ment of the bellows the?" and said pedestal support being arranger, so to substantially isolate the bellows from the re mainder of the mechanism.

20. A control mocha "'sr stationary contact bras said bracket being formed so t tace may be disposed or bracket, an operating ating arm oscillating is movable contact bracir-e ing arm and carryin a mo sting with a stationary cry contact b1 clret, an ar movable contact bras, braclret being for reversing said move the movable contact y cated at the opposite si e r: tact braclret train their magnet adapted to scope i to provide snap action l c ble contact, and reve; said magnet arranged no for cooperation with. said arm its positions.

21. A. control mechanism comprising has a stationary contact br :et mounted on said base, said bracket being formed so that a contact surface may be disposed on either side of said bracket, an operating arm mounted on sai and terminating short of said bracket, so crating arm oscillating laterally of said a detachable contact bracket mounted o the operating arm and carrying a movable contact cooperating with a stationary contact on said stationary contact bracket, an armature carried by said detachable contact bracket, a magnet adapted to cooperate with said armature to provide snap action movement of the movable contact, and reversible mounting means for said magnet for permitting reversal of the magnet upon change of the detachable contact bracket,

22. A control mechanism comprising a base, a stationary contact bracket mounted on said base, said bracket being formed so that a contact, surface may be disposed on either side of said bracket, an operating arm mounted on said base and terminating short of said bracket, said operating arm oscillating laterally of said contact bracket and having its central position substantially in alignment with said stationary contact bracket, a movable contact bracket attached to said operating arm and carrying a movable contact adapted to cooperate with a stationary contact on said stationary contact bracket, said movable contact bracketrbeing reversible upon e moo .ng m

said operating arm so that the movable contact may cooperate with a contact surface located on either side of said stationary contact bracket.

23. A control mechanism comprising a base, an operating structure spaced from the base and pivoted thereto, a bellows mounted with its axis perpendicular to said base and engaging said tionary contact bracket mounted upon said base,

said bracket having a supporting portion spaced from said base and from said operating arm, a contact stud supported on the supporting portion of said bracket, said bracket being formed so that a contact surface on the contact stud may be disposed on either side of said supporting portion, a detachable contact bracket mounted on said operating arm and carrying a movable contact cooperating with said contact stud, an armature carried by said movable contact bracket, a magnet adapted to cooperate with said armature to provide snap action movement of the movable contact, and reversible mounting means for said magnet for permitting reversal of the magnet upon change of the detachable contact bracket.

- 24. A control mechanism comprising abase, an operating structure spaced from the base and pivoted thereto, a bellows mounted with its axis perpendicular to said base and engaging said operating structure for urging the same in one direction about its pivot, a spring for biasing said operating structure in the opposite direction, adjustment means fixedly secured to the base and associated with said spring, indicating means associated with said adjustment means for indicating the setting of said adjustment means, means including a calibrating screw interposed between said spring and operating structure for calibrating the adjustment means with respect to said indicating means, a portion of said operating structure including an arm extending parallel with the base, a movable contact bracket mounted on said arm and electrically insulated therefrom, said contact bracket carrying a pair of contacts electrically connected with each other, a pair of fixed contacts on the base arranged to be bridged by said movable contacts, and means for causing said fixed and movable contacts to engage and disengage with snap action;

25. A control mechanism comprising a base, an operating arm spaced from the base and pivoted thereto, a bellows mounted on the base, said bellows constantly urging the operating arm in one direction about its pivot, a spring constantly engaging said operating arm for constantly urging said arm in the opposite direction about said pivot, a lever pivoted to the base and engaging said spring for varying its tension, and a cam mounted on the base ,and having a cam surface operatively associated with said lever whereby movement of said cam adjusts the tension of said spring, and control mechanism mounted on said base and controlledby said operating arm.

26.'In a control device, an operating arm,- resilient condition responsive means associated with the operating arm in a. manner constantly urging the same in one direction, electrical switching mechanism operated by said operating arm, adjustable flexible means associated with the operating arm in a manner constantly urging the same in the opposite direction and for adjusting the condition responsive means to predetermine the value of the condition at which the operating arm is actuated, said condition responsive means and said flexible means acting independently and simultaneously on said operating arm for eliminating all lost motion between said arm and each of said means, and magnetic means for biasing the operating arm whereby snap action of the operating arm and of the switching mechanism is obtained by the sole cooperative action of the condition responsive means and the adjustable flexible means with the magnetic means.

HERBERT E. LINDEMANN.