US2117514A - Thermostatic switching mechanism - Google Patents

Description

May 17, 1938. s. c. SHIPLEY 1 2,117,514

THERMOSTATIC SWITCHING MECHANISM Original Filed April 20, 1932 2 Sheets-Sheet l gm vendor SylvanuC. Shipley dttoimq May 17, 1938.

s. c. SHIPLEY 2,117,514

THERMOSTATIC SWITCHING MECHANISM Original Filed April 20, 1932 2 Sheets-Sheet 2 x4 I a i r I m v1 I l l I 1 I I m I I I I E l L II N N m N w a h s 9,

I 2 2 h v N v 0 a 7' w N m T, m m o t i' '0 '0 '0 N a m v g Q w on m gwmntoz I I Sylvanus C. Shlpley Patented May 17, 1938 THERMOSTATIC SWITCHING MECHANISM Sylvanus C. Shipley, Minneapolis. Minn, assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Original application April 20, 1932, Serial No.

606,440. Patent No.

2,063,898, December 15,

1936. Divided and this application August 1, 1934, Serial No. 737,917

18 Claims.

' The present invention relates to improvements in control devices, such as a thermostatic switching mechanism.

One of the objects of the present invention is the provision of a switching mechanism which is moved to a new circuit; controlling position upon the occurrence of an abnormal or undesired condition, the arrangement being such that the switch can then be manually returned to and latched in its original position while the abnormal or undesired condition persists, the switch being automatically returned to normal control whenever the condition returns to a normal or desired state.

.5 Another object of the invention is the provision of a thermostatic switch that is moved to a new circuit controlling condition or position when the temperature to which the thermostatic actuator thereof responds becomes abnormal, providing manual means by which the switch can be returned to and latched in its original position while the temperature remains abnormal, the arrangement being such that the switch is unlatched and returned to the control of the thermal actuator whenever the temperature thereafter returns to normal.

Another object of the invention is the provision of a mercury switch that is operated by a suitable actuator through a lost-motion connec- 30 tion and providing a friction mounting for the mercury switch that is sufliciently positive to maintain the mercury switch in any position to which it is moved whereby to prevent movement of the switch by the lead wires of the mercury 3.; switch.

A further object is the provision of an improved differential adjustment of the lost-motion type.

Other objects of the invention include the general improvement of thermostatic switching 0 mechanisms, particularly those types in which a single thermal actuator operates a plurality of switches.

Other objects of the invention will be found 5 in the description, the drawings and the appended claims.

The present application is a division of my copending application Ser. No. 606,440, filed April 20th, 1932, now Patent No. 2,063,898, December 50 15, 1936 and entitled Control system for automatic stokers".

For a more complete understanding of the invention, reference may be had to the following detailed description and accompanying drawings,

5 in which Fig. 1 is a front view of my improved switching mechanism;

Fig. 2 is a longitudinal section of my improved switching mechanism taken about on line 2-2 of Fig. 1;

Fig. 3 is a fragmentary front view showing the look-out switch held closed by the manually operable means; and

Fig. 4 shows one of the details of my improved switching mechanism.

The switching mechanism of the present invention is particularly adapted for controlling a stoker, and will be explained in this connection. Referring to the drawings, the switching mechanism is housed in a case I, which is provided with an opening surrounded by flange 2, secured in place by screws 3. A tubular extension 4 is provided with an expanded end 5 and this tubular extension surrounds and partially covers the opening in case I, the flange 2 operating to hold the tubular extension in place. A disc 6 substantially fills the opening in case I and abuts the periphery of the expanded end 5 of tubular extension 4 and this disc is held in place by means of washers l which are secured by screws 3. An operating handle 8 is secured to disc 6 by any suitable means, such as rivets, and extends through a slot 9 in case i and terminates in an indicator 10. A tubular member II, which is concentric with and inside of extension 4, is s'ecured at one end to disc 6, by means of inturned lugs, as shown at l2, and its other end is secured to one end of a helically coiled bimetallic element I3 as indicated at M. A shaft 15 has one of its ends secured to the free end of bimetallic element 13, as shown at I6, and extends through the coil formed by this element, through disc 6, operating handle 8 and into the interior of case I. A scale plate I1 is secured to the interior of case I by any suitable means, such as the screws shown at E8, and extends through slot 9 in case I. Scale plate I! is provided with high, low and intermediate graduatio'ns forco-operation with indicator III in order that the base temperature to which the device responds may be adjusted.

A cam plate 19, which is secured to a collar IBa, is mounted on the free end of shaft l5 by means of said collar. The cam plate 19 is substantially semi-circular in shape but has a cam surface provided in its periphery, as shown at 20. Cam plate I9 is also provided with a slot 2| of irregular shape. The slot 21 is provided with a straight radial portion 22, a lower arcuate portion 23, a curved side 24, and an elongated portion 25. The peculiar form of this slot has a very definite purpose which will be brought out hereinafter. A bracket 26 is secured to case I below shaft I5 and is provided with an upwardly extended portion 21 provided with an opening actuated member 3| is pivoted on pin 28 and the upwardly extending legs thereof are provided with slots 32. A pin 33 extends through the slots 32 and into slot 2| and also clamps an indicator 34 to one of the legs of member 3|, which indicator co-operates with graduations 35 carried by said leg. A star shaped friction washer 36 is next placed on pin 28 followed by a mercury switch holder 31 and then a washer 38 after which pin 28 is peened over. Leaf spring 29 exerts pressure against member 3| so that member 3| and switch holder 31 are coupled together by means of friction washer 36 and at all times rotate together about pin 28. The pressure exerted by leaf spring 29 is sufiicient to maintain member 3| and mercury switch holder 37 in any position to which they may be moved. A mercury switch 39 is carried by holder 31. This mercury switch will hereinafter be termed the fire maintaining switch.

The operation of this part of the device is as follows: With the indicator I0 set at any desired point, temperature changes at the bimetallic element l3 result in rotation of shaft |5 which in turn rotates cam plate I9. The edges formed by slot 2| engage pin 33 to move member 3| and in turn tilt the mercury switch 39. It will be noted that the graduations 35 are evenly spaced and in order for each graduation to represent the same number of degrees in temperature change, it has been necessary to provide the peculiar configuration of slot 2|. With pin 33 moved up to such a position that indicator 34 is opposite graduation A, the extended end of pin 33 will be in the elongated portion designated 25 of slot 2|. Under these conditions, as cam plate I9 is rotated back and forth in response to temperature changes at bimetallic element |3, fire maintaining switch 39 will be tilted back and forth without any lost motion. As indicator 34 is moved downwardly to positions B, C, D, etc., the end of pin' 33 will move into progressively wider parts of the slot 2| so that there will be an increased amount of lost motion between cam.plate l9 and pin 33 so as to provide an adjustable diiferential in the operation of fire maintaining switch 39. It has been formerly stated the pressure exerted by leaf spring 29 is suflicient to hold fire maintaining switch 39 and member 3| in any position to which they may be moved by the lost motionconnection provided by pin 33 and slot 2|. In former instruments, the mercury switch, after having moved past the center, has been allowed to continue rotating by gravity to the extent of the lost motion connection. This feature has been eliminated herein for a specific reason since it has been found that the lead wires to themercury switch tend to hold the mercury switch in some one of its positions and even tend to move the switch back to such position when the force acting thereon has been removed. The pressure set up by leaf spring 29 is sufficient to overcome this tendency of the leads of the mercury switch and curate operation of the instrument. Adjustment of indicator l0 rotates tubular member II to adjust the fixed end of the bimetallic element |3 so as to change the base temperature setting of the instrument.

A bell-crank 40 is pivoted on a pin 4| carried by case and has a substantially horizontal arm to which is secured a mercury switch holder 42, which in turn carries a mercury switch 43. This mercury switch will hereafter be termed the look-out switch. The other arm of the bellcrank is substantially vertically disposed and is provided with an adjustable extension 44 which carries a pin 45 at its end, the pin being adapted to cooperate or ride upon the periphery of cam plate I9. A cam 46 is pivoted to cam plate H), as shown at 41, and is biased normally into engagement with a pin 48 by means of a coiled spring 49. The cam 46, when it is in engagement with pin 48, serves as an extension of the periphery of cam plate l9, so that in effect the periphery of the cam plate l9 extends in a perfect radius beyond the cut-in cam portion 20. A bracket 50 is secured to the lowermost portion of case and Journals a vertical movable rod 5| which is normally biased to move downwardly by means of a spring 52, one end of which abuts the bracket 50 and the other end of which abuts a washer secured to or an enlarged portion 53 formed in rod 5|. The upper portion of rod 5| is slotted as at 54 to pivotally receive a catch 55. Catch 55 is provided with a downwardly extending finger 56 and also with a notch 51 located at its upper portion. The substantially horizontal arm of bellcrank 40 is provided with a bent-over extension 58 which overlies catch 55 and under certain conditions engages notch 51. I

The part of the thermostatic switch just described above comprises the means for shutting down the stoker when the fire goes out. When the fire in the furnace goes out, the temperature of element l3 falls to such a degree that cam plate I9 is rotated in a clockwise direction until pin 45 rides over the periphery of cam 46 and drops against the portion 20 of cam plate l9, which allows bell-crank 40 to. rotate clockwise about pin 4| moving lock-out switch 43 to open circuit position. If, for any reason, the temperature drops far enough to cause the opening of lockout switch 43 and then due to a change of wind direction or for some other cause the fire picks up, increasing the temperature of element I3, cam plate l9 will be rotated in a counter-clockwise direction. Pin 45 will bear against the lower edge of cam 46 rotating the same in a clockwise direction against the action of the spring 49'. On continued rise in temperature, pin 45 will ride up cam surface 20 until it reaches the radial periphery of cam plate 19 whereupon cam 46 will be returned to its normal position abutting pin 48. Cut-out switch 43 is moved to closed position by this action.

It should be noted that there is a temperature differential between opening of lock-out switch 43 and closing thereof under these conditions.

such a point that pin 45 rides ofi' cam 46 which is then in engagement with pin 49 to extend the periphery of plate l9. For lock-out switch 43 to close automatically, however, the temperature must rise sufiiciently for'pin 45 to rotate cam 46 about its pivot and ride up on cam surface 20 until it engages the radial periphery of cam plate l9.

The stoker cannot be operated when lock-out switch 43 has moved to open circuit position as explained in the above-referred to parent application. If the fire goes completely out, it may of course be rekindled manually and built up until the temperature to which element i3 responds has become suificiently high to move lock-out switch 43 to closed circuit position after which automatic operation will be resumed as above explained. Ordinarily, however, it will be desired to only start the fire manually and then let the stoker build up the fire. In order to accomplish this result, it is necessary that lock-out switch 43 may be manually moved to closed circuit position and then maintained in that position until the temperature of element I3 becomes sufllciently high to hold lock-out switch in closed circuit position by means of cam plate l9 and cam 46. If this operation is desired, the rod is moved upwardly until finger 5B of catch 55 rests on bracket 50 and the left hand edge of slot 51 engages the left side of extension 58 and moves bell-crank 40 in counter-clockwise direction un til lock-out switch 43 is in closed circuit position (see Fig. 3). This movement of bell-crank 40 positions pin 45 so that it will readily ride upon cam 46 when the temperature of element l3 has been restored. Rod 5| is maintained in its raised position by finger 56 resting on bracket 50 and finger 56 is held in this position by the engagement of notch 51 with the left side of extension 53. When the temperature of element l3 rises sufliciently, cam 49 will move counterclockwise until it picks up pin 45 and moves it slightly to the left. This causes extension 53 to be 'moved up out of engagement with notch 51 whereupon spring 52 will move rod 5|, down to the position shown in Figure 1.

It will be noted that this combined instrument has several adjustments. First the indicator ill may be moved to adjust what might be called the base temperature at which the fire maintaining switch 33 will be moved to closed position by engagement or pin 33 with straight portion 22 of slot 2i. Adjustment of pin 33 vertically changes the differential between opening and closing movements of switch 39, and lastly, adjustable extension 44 changes the temperature at which lockout switch 43 'will be operated in relation to the base temperature setting.

In order to protect bimetallic element l3 from the corrosive effects of the products of combustion,'a protecting tube 53 may be provided if desired.

While the switching mechanism of the present invention has been described in connection with the controlling of a stoker, it will be apparent that it has many other uses and can be modified in many respects without departing from the invention. I therefore intend to be limited only by the scope of the appended claims.

I claim:

1. A switching mechanism of the class described. comprising, in combination, a condition responsive actuator, a pivoted mercury switch. an adjustable lost motion connection adapted to provide a variable coei'licient of action therebetween, said connection comprising a pin associ ated with said switch and a plate having an irregularly shaped aperture therein into which said pin projects, a scale plate having evenly spaced graduations thereon adjacent said pin, a pointer rigidly aillxed to and carried by said pin cooperating with said scale, said aperture being substantially triangular, one side thereof comprising an arc whereby movement of said pointer and hence said pin any equal distance with respect to said scale plate causes a change in the value of the condition to which said actuator responds in equal amounts corresponding to said equal distance of movement.

2. A switching device of the class described, comprising in combination, a condition responsive actuator, switch means, an adjustable lost motion connection adapted to provide a variable coeflicient of actuation therebetween, said connection comprising a pin associated with said switching means and vertically movable with respect thereto and a plate having an irregularly shaped aperture therein into which said pin projects, said aperture being substantially in the shape of a triangle, a scale plate having evenly spaced graduations therein adjacent said pin, a pointer rigidly affixed to and carried by said pin cooperating with said scale, one side of said triangular shaped aperture being in the form of an arc whereby movement of said pointer and hence said pin any equal distance with respect to said scale plate causes a change in the value of the condition to which said actuator responds in equal amounts, said aperture also having an extending portion at the apex thereof of a width substantially equal to the diameter of the pin whereby upon predetermined movement of said pin to engage said aperture said. lost motion connection becomes a relatively positive connection.

3. In combination, an actuator movable in conformity to changes in a condition, a switch operable to open and closed position thereby, a carrier for said switch, an extension on said carrier, manually operable latch means to latch said switch in closed position when said actuator would normally cause said switch to assume open position, said latch means comprising a manually movable rod and a catch pivoted thereto, said catch being adapted to engage said extension, and means controlled by said actuator to release said extension from said catch when said actuator returns to a position in which it would normally place the switch in closed position.

4. A switching mechanism of the class described, comprising in combination, an actuator, a plate rotated thereby, a first switch, an adjustable lost motion connection between said plate and said first switch to provide an adjustable differential between opening and closing move-'- ments of said switch, a second switch, mechanism cooperating with said second switch and the periphery of said plate for operating said second switch and manually operable mechanism associated with said second switch for auxiliary operation thereof under certain predetermined conditions.

5. In combination, an actuator movable in conformity to changes in a condition, a switch operable to open and closed position thereby, a carrier for said switch, an extension on said carrier, manually operable latch means to latch said switch in closed position when said actuator would normally cause said switch to assume open position, said latch means comprising a manually movable rod and a catch pivoted thereto, said catch being adapted to engage said extension, and means controlled by said actuator to release said extension from said catch wh in said actuator returns to a position in which it would nor mally place the switch in closed position, said means comprising a cam movable by said actuator adapted to abut said carrier to move said extension.

6. A switching mechanism of the class described, comprising, in combination, an actuator, a pivoted mercury switch, and an adjustable lost motion connection adapted to provide a variable coefficient of action therebetween, said connection comprising a pin associated with said switch and a plate having an irregularly shaped aperture therein into which said pin projects, said aperture being substantially triangular, and one side thereof comprising an are.

7. A switching device of the class described, comprising, in combination, an actuator, a pivoted mercury switch and an adjustable lost motion connection adapted to provide a variable efiicient of actuation therebetween, said connection comprising a pin associated with said switch and vertically adjustable with respect thereto and a plate having an irregularly shaped aperture therein into which said pin projects, said aperture being substantially in the shape of an unequally sided triangle one side thereof. being vertically disposed relative to the line of movement of said pin, the base and'one leg of said triangle being curved.

8. A switching device of the class described, comprising, in combination, an actuator, switch means and an adjustable lost motion connection adapted to provide a variable coefficient of actuation therebetween, said connection comprising a pin associated with said switch, and vertically movable with respect thereto and a plate having an irregularly shaped aperture therein into which said pin projects, said aperture being substantiallyin the shape of a triangle, and having an extending portion at the apex thereof of a width substantially equal to the diameter of the pin,

whereby upon a predetermined adjustment said pin engages in said portion and said lost motion connection becomes a relatively positive connection.

9. A device of the character described, comprising in combination, a condition responsive actuator, a switch, a cam having a high and a low surface with a relatively gradual incline therebetween revolvable bysaid actuator, a cam segment pivotally mounted on said cam adjacent a junction of said high and lowsurfaces, said seg- .ment having a relatively abrupt incline and covering when in one position said gradual incline between said high and low surfaces of said cam, said segment being operable to move said switch, the arrangement being such that upon rotation of said cam bylsaid actuator in. one direction said cam follower rides from said high surface upon said cam segment and moves to said low surface with a relatively abrupt movement, but upon rotation of. said cam by said actuator when said cam follower rides upon a low surface of said cam, said cam follower rotates said segment about said pivot and rides up said relatively gradual incline to said high surface.

10. A device of the character described, in combination, a condition responsive actuator, a switclna cam having a high and a low'surface with a relatively gradual incline therebetween revolvable by said actuator, a cam segment pivotally mounted on said cam adjacent ajunction of said high and low surfaces, said segment having said cam segment and moves to said low surface with a relatively abruptmovement, but upon rotation of. said cam by said actuator when said cam follower rides upon a low surface of said cam, said cam follower rotates said segment about said pivot and rides up said relatively gradual incline to said high surface, and resilient means normally biasing said cam segment to said gradual incline covering position.

11. A device of the character described, in combination, a condition responsive actuator, a switch, a cam having a high and a low surface with a relatively gradual incline therebetween revolvable by said actuator, a cam segment pivotally mounted on said cam adjacent a junction of said high and low surfaces, said segment having a relatively abrupt incline and covering when in one position, said gradual incline between said high and low surfaces of said cam and said segment being operable to move said switch, the arrangement being such that upon rotation of said cam by said actuator in one direction said cam follower rides from said high surface upon said cam segment and moves to said low surface with a, relatively abrupt movement, but upon rotation of said cam by said actuator when said cam follower rides upon a low surface of said cam, said cam follower rotates said segment about said piv- 0t and rides up said relatively gradual incline to saidhigh surface, spring means normally biasing said cam segment to said gradual incline covering position, and latch means manually operable to hold said cam follower out of engagement with said cam and cam segment irrespective of the position thereof.

12. A switching device comprising, in combination, an actuator, a pivoted mercury switch, lead wires therefor, an adjustable lost motion connection between said actuator and the mercury switch adapted to provide a variable coefficientv of actuation between said switch and said actuator, and means for maintaining said switch in any position to which it is moved by said actuator through said lost motion connection, the action of said means being sufficiently positive to prevent movement of the switch by the lead wires.

13. A switching mechanism of the class described comprising, in combination, an actuator, a plate rotated thereby, a first switch, an adjustable lost motion connection between said plate and said first switch to provide an adjustable differential between opening and closing movements of said switch, a second switch, and mechanism cooperating with said second switch and the periphery of said plate for operating said second switch.

14. A switching mechanism of the class described comprising, in combination, an actuator, a platerotated thereby, the periphery of said plate having a curved portion concentric with the axis of rotation of the plate and a re-entrant portion, a first switch, an adjustable lost motion connection between said first switch and the actuator, a, second switch, mechanism cooperating with the second switch and engaging the periphery of the plate for maintaining said second switch in a first switch operating position when said mechanism engages the curved portion of the periphery and in a second switch operating position when engaging the re-entrant portion, and manually operable means for locking said second switch in the first switch operating position when said mechanism is opposite said re-entrant portion, said means being automatically unlocked when the plate is moved by the actuator to bring the curved portion of its periphery into engagement with said mechanism.

15. A switching mechanism of the class described, comprising, in combination, a first switch, a second switch physically independent of said first switch, an actuator responsive to a physical condition, means associated with said actuator and switches for operating the latter by the former, basic adjusting means for adjusting in unison the values of the physical condition at which said switches will be actuated, and means associated with one of said switches and said actuator for additionally adiusting this switch whereby it will be operated at difierent values of the physical condition with respect to the other switch and the basic adjustment.

16. A switching mechanism. of the class de scribed, comprising, in combination, a first switch, a second switch, an actuator responsive to a physical condition, means associated with said actuator and switches for operating the latter by the former, basic adjusting means for adjusting in unison the values of the physical condition at which said switches will be actuated, means for adjusting the difierential in the variation in the physical condition at which one of said switches will be operated from one circuit controlling position to its other circuit controlling position and vice versa, and means for additionally adjusting the value of the physical condition at which the other of said switches will be operated without disturbing the adjustment of said first named switch.

17. In a switching mechanism of the class described, in combination, a thermostatic element, means for adjustably securing one end of said thermostatic element whereby the position of the relatively movable end thereof for any given temperature may be varied, a first switch, means associated with said switch and thermostatic element for adjustably predetermining the temperature differential at which said switch will be moved to open and closed positions, a second switch, connecting means associated with said second switch and the relatively movable end of the thermostatic element whereby the former is operated by the latter, and means for adjusting said connecting means whereby the position of the relatively movable end of said thermostatic element at which the second switch will be operated may be varied.

18. A switching mechanism of the class described, comprising, in combination, a first switch, a second switch physically independent of said first switch, an actuator responsive to a physical condition, means associated with said actuator and switches for operating the latter by the former basic adjusting means for fixedly adjusting in unison the values of the physical condition at which said switches will be actuated, and means for independently adjusting the dif-- ferential in the variation of the physical con-iition at which one of said switches will be opererated from one circuit controlling position to its other circuit controlling position without affecting the operation of the other switch,

SYLVANUS C. SHIPLEY.

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