US2473075A - Condition responsive switch - Google Patents

Description

June 14, 1949. J. 0. Row-1E: 73,

CONDITION RESPONSIVE SWITCH Filed Sept. 13, 1943 2 Sheets-Sh'et 1 I'snventor JOHN 0. I705CH (Ittorncg June 14, 1949. J o, I 2,473,075

CONDITION RESPONSIVE Sw-I'TQH Filed Sept. 15, 1943 2 Sheets-Sheet 2 g 76 47 f5 7 39 6 {22; :7 Q 4 j/ 65 4,? if

A n in Del Gttorneg Patented June 14, 1949 CONDITION RESPONSIVE-SWITCH John O. Rosche, Minneapolis, Minn., assignor to Minneapolis-Honeywell Regulator Company, .Minneapolis, Minn, a corporation of Delaware Application September 13, 1943, Serial Nob502097 6 Claims. 1

This invention relates toan improvement in a control device of the type-known as slip-friction or lost motion devices. It is particularly adapted for use in condition responsive controls but may also be'used in other motion transmitting devices.

In the operation of condition responsive devices such as are used in controlling the electric circuits of fluid fuel burners, pilot mechanisms, or other conditionresponsive devices, it is important that-the impulse necessary to bring about a change of conditions be positively transmitted with a minimum amount of energy and that the means to accomplish this :be of such a nature as to be free of the. necessityof constant cleaning, adjustment or lubrication; in order to obtain dependable results. Furthermore, in the operation of a furnace control it is desirable to have a temperature responsive control which, on the initial starting of combustion, will permit the fire to develop to a reasonable extent before opening the starting circuit andwill thereafter commence a recycling of the circuit at predetermined intervals dependent upon the temperature Within the furnace.

In similar devices of the prior art, the slip friction connection generally consisted of spring pressed washers biased against the circuit controlling mechanism. In the operation of these devices the extent of the spring pressure was critical. If it'was too great, the amount of friction created prevented the proper operation of the control mechanism, and on the other hand Where it was not suiiicientthe mechanism became inoperative upon reverse movement. Furthermore, where the friction was dependent upon two circular disks or washers, the extent of the friction was not equal across the surfaces, and in those regions where it became greatly concentrated the metal had a tendency to snowball. The devices of the prior art had the further disadvantage that where they were utilized tooperate a number of switches the manner in which the switches were located was such that a greater amount of energy was required where it was necessary to move a plurality of switches to open circuit position or vice versa.

In the development of my invention, I have discovered what I believe to be a new method of establishing aslip-friction connection. for the operationof the circuitcontrolling means or other control devices-dependent upon a slip-friction connection. Furthermore, I have developed .a circuit controlling means wherein .a plurality of circuits maybe moved from. one position to an other with arelativelysmall and approximately constant amount'ofenergy.

The principal objectof my invention is to provide an improved slipz-friction control device which will transmit an impulseswith a minimum loss of energy.

Another object of this invention is to provide an improved slip-friction connection between an element actuated by a'condition responsive device or other power driven device whereby one or more electric switches may be actuated by a relatively slight movement of the-elements and wherein continued movement of the elements in the same direction is not injurious to the switches or to the driving element.

Another object of my invention is to provide in a temperature responsive control device, manually operable means for timing the recycling of the circuits operated-by said device.

With these and other objects in view, reference is made to the accompanying drawings illustrating a preferred'embodiment of this invention, wherein:

Figure 1 is a side elevation of the-device showing the relationship between the slip-friction connection. and. the1Icondition' responsive device;

Figure 2 is a front elevation of the instrument cover showing .the manually controlled adjustment cams for timing the recycling and ignition circuits;

Figure 3 is. a front elevation taken along the line 3-3 ofiFigure 1 showing an enlarged view of the slip-friction. control: mechanism and the switches operated thereby;

Figurel shows. a cross-section of the slip-friction connection taken along. the 1ines4-4 of Figure 3;

Figure 5 sho ws-a side elevation of the cold contact 'switchcontrollingmechanism taken alon the lines 55 ofFigu-re '3, showing the nest of switches in open contact position;

Figure 6 is a side elevation taken along the lines 6-6 of Figure 3 showing the hot switch in closed contact position.

Similar reference characters refer to similar parts throughout the several views of the drawing.

Suitably fastened to the rear of an insulating base It, as shown in Figure 1 is a mounting sleeve H,. to which. is. connectedone end" of a bimetallic helix generally indicated at It. The other end [4 of the helix is secured-to an actuatingrod l5 which extends longitudinally within the helix. and sleeveH-andthrough an opening in the base It, and secured against lateral movement by the collar Hi.

The improved slip-friction device comprises two eccentrically shaped members 28 and 2| which are preferably formed of Bakelite or other similar insulating material. Referring to Figures 3 and 4, these members are mounted upon a sleeve 22 and secured against lateral movement by an abutment 23 at one end, and a washer '24 at the other end. A reduced end of the sleeve 25 is driven down against the washer 24 so as to secure the assembly. A non-corrosive washer 26 separates the two elements. The members 2!} and 2| have a common central aperture 2! which is sufii-ciently large so that the members may slidably fit over the outer eriphery of the member 22. Radially extending outwardly from the aperture 27 are a plurality of apertures 28 which hold the frictional elements.

Frictional elements are formed of carbon blocks inserted in the apertures 28 of the members 23 and 2!. Their inner ends are flush with the member 22 and are formed with a curved surface designed to comply with the outer periphery of the member One of the carbon elements of each member is resiliently held in abutment with the member 22 by a spring 32 and secured by a screw 33". The screws 33 may be rotated to adjust the tension of s ring 32 and thereby adjust the resilient force exerted by the combined efforts of the three friction blocks 39. The slip frictional assembly is secured to the rod i5, by the cotter pin 29 which extends through the sleeve 22 and rod |5.

I consider it an important feature of my invention that the frictional elements should be non-metallic although I recognize that certain soft metals and graphite impregnated metals might be substituted. Furthermore, I consider it important that the frictional elements be radially disposed about the central core member and that one of the frictional elements be resiliently held against said core member, thus the wear on the frictional elements will always be evenly divided and may be maintained by the resilient member.

The member 2! has a pair of lugs or abutments 3 5 and 35 and the member 223 has similar lugs or abutments and 38, all of which extend outwardly from said members and serve as stops as will hereinafter be explained. Extending outwardly from the side of the member 25 is a long arm 39 which serves as a switch actuating member. Extending outwardly from the member 2| and on the opposite side is a shorter arm 40, which also serves as a switch actuating arm. Although shown in the present application as switch actuating arms, these elements may be used in other applications for the control of other pilot means.

Situated on the base It, and suitably fastened thereto adjacent the arm 39, as shown in Figures 3 and 6, are switch holding members 4| and 52. A pair of resilient switch blades 53 and M, having contact points and 35, are suitably fastened to the holding members in such manner as to be normally biased to an open contact position but are movable to a closed position with a very small amount of effort. These contacts are commonly referred to as the hot contacts when the device of the present invention is used in the control of an oil burner.

On the opposite side of the slip friction assembly and also suitably fastened to the base ID, as shown in Figures 3 and 5, are a group of switches which form what are commonly referred to s cold contacts in an oil burner control. They consist of holding members 41, 48 and 49, and a pair of resilient blades 50 and 5|, which are suitably fastened to the members 48 and 49 in such a manner as to be in a normally open circuit position when no force is being exerted against them. Contact points 52, 53, 54 and 55 are mounted respectively on the member l"! and the blades 50 and 5|.

A novel arrangement for operating the cold contacts is shown in Figure 5 in the form of a rockable arm 55 which is pivotally mounted at 51, to a base 58. The arm has on its outer portion a pair of oppositely extending shoulders 59 and 5d, and on its inner portion a pair of feet 6| and 32 designed to prevent injury to the arm 56. A spring 63 fastened to a bent portion of the member 49 and connected at its other end to the shoulder fin, maintains the arm 56 in such a position with regard to the switches 50 and 5| as to resiliently hold them in closed contact position against the member 41.

As will hereafter be explained, when the arm d8 of the member 2| exerts pressure against the shoulder 59, the arm 55 moving on the pivot 5'1 begins to move downward against the tension of the spring 63. Under normal conditions as the spring 63 is extended its tension would constantly increase, but as the arm 56 moves on the pivot 51, the fulcrum formed between the opposite ends of the spring and the pivot moves inwardly towards the pivot and approximately counter-balances the increasing spring tension so that the force needed by the arm to move the rest of switches forming the cold contacts to open circuit position would remain approximately constant for all three blades. Furthermore, as the arm 56 is depressed it will be noticed that upon the initial movement contacts 54 and 55 remain together but contact 53 moves away from contact 52. On further movement blade 5| separates from blade which is firmly secured to the holding member 68, so that contact disengages from contact 54.

A cover 10, which is adapted to be fixed to the base 0, has suitably mounted upon its outer surface two adjustable controlling members H and '52 which have abutting extensions 13 and I4, arranged to contact stops l5 and 16 in such a manner as to prevent more than one complete revolution of the members 1| and 12. The purpose of these members and their associated parts are for governing the overtravel in either direction of member 2| by providing adjustable limiting means which abut with protruding portions of member 2| after it has traveled a desired distance. Should the impulse continue after abutment, the slip-friction connection will permit continued movement of the driving member 22 without affecting the position maintained by the member 2|. As will be explained hereafter disk H and its associated parts governs the recycling time and limits the movement of member 2| in a counter-clockwise direction and disk 12 and its associated parts which limit overtravel in a clockwise direction governs the ignition circuit. The disks as shown in Figure 2, indicate adjustments for maximum and minimum times. When adjusted to maximum position for either cam a longer period of overtravel is permitted and consequently a longer period of time must elapse on reverse movement of member 2| and arm 4|) before the particular circuit is affected. The converse is true when adjustmentis made to minimum settings. I

Within the cover are a pair of cams ll and 78 which form the operating elements of the mem- 5. bers H andTZ. They are suitably fastened'thereto by shafts l9 and 80 and are held in frictional arrangement with friction washers 8|-and 82 to abut the extensions-35 and 36 of element 2|: to. adjustably limit the arc within-which the element 2| may rotate,

A central aperture 9|] in the cover opens to a cut 9| on the end of the shaft"|5, to permit.a

screw driver to be inserted for manually resetting the slip-frictional assembly and the switch actu ating mechanisms.

Astationary stop .95, is suitably fastened to the base I'll, at 95, This stop extends between the abutments 3| and 38 of the member. 2|).to limit the rotating movement of said. member.

In operation, the above described device is adapted to fit on the stack of a .furnace or other suitable place where the heatresponsive element will be in the path of the gases of combustion. As-v suming that the furnace is started and ignited-by means not shown, then as the temperature increases, the helix |3 expands and begins to turn in a counter-clockwise direction, The rod l5, secured to the end M of the helix I 3 will likewise rotate in a counter-clockwise;directiorn and being secured to the member 22, by thecotter pin 29, exerts a continuing impulse against said member. As the driving member 22 moves, the friction elements 3B, which are in frictional engagement therewith, causethe members ZILand 2| tomove in the same direction. As the inner member 22 moves not over threeor four degrees, the arm. 39, abutting against the switch 44, moves it toward switch 43 thereby closing the contacts 45 and .46 upon, a small initial movement. Further movement of member thereafter is prevented by; the abutment 38 coming in contactjwith thestop 95, but therod I5 and, the driving member 22 may continueto rotate because of the slip-friction .engagement of the carbonblocks 3ll, which are radiallylocated within themember 2|l,.in radial abutment with the member 22. Simultaneous with the movement of the member 20, the member 2| also commences to move in a counter-clockwise direction passing beyond the point where member 25! closes the hot contacts and until the arm as contacts the shoulder 59 and thereafter forces the arm 56 to rotate downward on the pivot 51, against the tension of the spring 63. As shown in Figure 5, the nest of switches 41, 50 and 5| are biased to a closed contact position by the influence of sprin 63 and as this force is removed by the movement of the arm 40, the switches are moved to an open contact position, commencing with the contacts 53 and 52 and followed by contacts 55 and 54. Further movement of the member 2| and arm 4|] is prevented upon abutment of the element with the cam 11. However, as previously explained the driving member 22 may continue to rotate in a slidable manner against the friction elements 30 which are radially disposed in the member 2|. As the heat within the furnace abates, the helix will contract causing a clockwise rotation of the rod |5 and the members 22, 2|] and 2|. Upon initial clockwise movement of member 20, arm 39 will substantially immediately move away from switch blade 44 allowing contacts 46 and 45 to separate. Continued movement of member 20 will be quickly prevented by abutment 31 engaging stop 95. Upon clockwise movement of member 2|, arm 40 will permit return movement of arm 56 under the influence of spr'mg 63. When sufficient movement has taken place, contacts 55 and 54 will first be closed,-

and then contacts 53 and 52. Arm 40 will continue moving until shoulder 36 engages cam 18; A more detailed description of circuits that maybe controlled by the aforementioned switches will.

be found in U. S. Patent 2,274,177 granted February 24,1942, to JohnM. Wilson.

In the application of my improved control device to different types of fluid fuel burning furnaces and to different grades of fuel I have found. it desirable to provide for an adjustable period of recycling which I attain through the use of the cams I! and Til, and their adjusting members 1| and 12.

When the members H and 72 are placed at their.

maximum settings, member 2| and arm were permitted to rotate the maximum extent in eachdirection which is considerably in excess of the distance necessary for the arm 4t to move the switches to open contact position during counterclockwise movement, and considerably more thanis necessary to allow the switches toclose on clockwise movement. The effect of this overtravelis to extend the period of time on reverse motion of the arm 453 before the circuit controlled by the adjusting cam is moved to its other position. On the other hand when the members 1| and .72 are to their minimum adjustment, the movement of member 2| and arm 4|] is limited in its extent of overtravel after opening contacts 54 and 55 on movement in a counter-clockwise direc tion, and after permitting the closure of contacts.

55,. 54, 53 and 52 on clockwise movement.

It should be understood that each of the adjusting disks may be set in a position independent of that assumed by the other member according to the needs of the combustion unit and the fuel? being consumed therein. Furthermore, it should beunderstc-od that the setting of these members should preferably be made by one skilled in the art such as an expert installer or service man, as

maladjustment would tend to make the unit iii-- operative.

It will be seen by the above description that I have attained a condition responsive control device which is responsive to a condition responsive element which is similar in construction and yet positive in its operation which attains the objects which I have set forth. Since there are many other forms which this invention may take as a controlling mechanism and as a means of transmitting power, I therefore desire to be limited by the scope of the appended claims and not by the specific embodiment of the invention disclosed in the present application.

I claim as my invention:

1. In a control device, in cooperation, a unitary drivin member, a first driven member having a limited movement, a second, driven member having a larger movement, means for limiting the movement of said first and second driven members, and means for holding said first and second driven members in frictional engagement with said unitary driving member, said means comprising a plurality of frictional elements radially positioned within said first and second driven members in slip frictional engagement with said driving member, only one of said elements being adjustably spring biased, and said elements being so positioned with relation to each other and said drivin member that the adjustable spring bias of said one element causes an equal distribution 7 1. of frictional engagement among all of said elements.

2. In a condition responsive control device, an element movable in response to a change of condition, a member movable upon impulse of said condition responsive element, a plurality of electrical contacts, each of which is individually mounted on a resilient supporting member, first means biasing said contacts to open circuit position, comprising the resiliency of said supporting members, second means for biasing said contacts in consecutive pairs to closed circuit position, and means by which said member successively moves said pairs of contacts to open circuit position.

3. In a control device, in combination, a driving member, a driven member, and a plurality of electrical contacts, each of which is individually mounted on a resilient supporting member, a first means biasing said contacts to open circuit position, comprising the resiliency of said supporting members, a second means biasin said contacts in consecutive pairs to closed circuit position, and means by which said driven member successively moves said pairs of contacts to open circuit position.

In a condition responsive control device, in combination, an element responsive to a change of condition, a unitary driving member movable upon impulse of said condition responsive element, a pair of driven members positioned about said driving member and being movable by said driving member, at least three radial elements, one of which is spring biased, being disposed in each of said driven members in frictional engagement with said driving member, said elements being so spaced with relation to each other that the pressure formed by the spring bias of said one element maintains an equal tension on all of said elements, a plurality of contacts engageable by one of said driven members, a second plurality of contacts engageable by the other of the driven members, first means biasing said second plurality of contacts to open circuit position,

econd means biasing said second plurality of contacts to closed circuit position.

5. In a control device, comprising in combination, a driving member, a driven member in frictional engagement with said driving member, said ill 8 members being mounted within a partially enclosed casing, a removable cover for enclosing said casing, and means for limiting the frictional travel of said driven member comprising a manually adjustable position indicating memb-er having a first portion mounted on the exterior of said cover, and a second portion mounted on the interior of said cover, said limiting means being operable to limit the movement of said driven member only when said cover is mounted on said casing.

6. In a control device, comprising in combination, a driving member, a driven member in frictional engagement with said driving m mber, said members being mounted in a partially enclosed casing, a removable cover for enclosing said casing, two manually adjustable position indicating dials mounted on the exterior or" said cover for independently indicatin the limit of movement in each direction of said driven member, and two rotatable cams carried on the interior of said cover for engaging different portions of said driven member, said cams being rotatably controlled by said dials and being adapted to limit the movement of said driven member only when said cover mounted on said casing.

JOHN O. ROSCHE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 122,818 Ebbitt 16, 1872 255,196 Ross Mar. 21, 1882 498,372 Ward 1 May 30, 1893 793,601 Moore -1 June 27, 1905 1,011,468 Mattice Dec. 12, 1911 1,256,228 Hensley Feb. 12, 1918 1,373,085 eitch Mar. 29, 1921 1,482,402 Lamb 1 Feb. 5, 1924 1,849,713 Grant Mar. 15, 1932 1,969,968 Dever Aug. 14, 1934 2,091,161 Rube} Aug. 24, 1937 2,199,999 Jensen et al. 1 May '7, 1940 2,302,110 Dow et al Nov. 17, 1942

Images