US2532859A

US2532859A - Thermostatic switch

Info

Publication number: US2532859A
Application number: US745368A
Authority: US
Inventors: John O Rosche
Original assignee: Honeywell Inc
Current assignee: Honeywell Inc
Priority date: 1947-05-02
Filing date: 1947-05-02
Publication date: 1950-12-05
Anticipated expiration: 1967-12-05

Description

Dec. 59 i956 Filed May 2, 1947 J. Q. Rossi-ga THERMOSTATIC SWITCH 2 Sheets-Sheet l NVENTOR. daf/N 0. 5056/15 @i MMM,

Deco 59 1950 J. o. assai-1E 2532,85?)

THERMOSTATIC SWITCH Filed May 2, 1947 2 Sheets-Sheet 2 I N VEN TOR.

5? W JOHN 0. ffmc/f5 Patented Dec. 5, 1950 UNITED STATES PATENT OFFICE THERMOSTATIC SWITCI John 0. Rasche, Cedar Rapids, Iowa, assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application May 2, 1947, Serial'No. 745,368

16l Claims. 1

This invention relates to automatic control devices, and particularly to that class of devices wherein a plurality of controlV functions are accomplished from a single condition responsive element.

An object of the invention is` to provide an improved device of the class in which a plurality of switching functions are performed sequentially as a condition changes, for example, a combination fan and high limit control for a warm air furnace actuated by a temperature responsive element.

Another object is to provide improved means whereby the control point of oneswitch may be varied without affecting the control point of another'switch actuated by the same sensitive element.

Another object is to provide' a combination fan and limit switch for forced warm air furnaces in which the limit switch controlA point adjustment has no effect on the fan switch control point although a normally stationary portion of the temperature responsive element" is adjusted to adjust the limit switch control point.

A further object is to provide a combination switch in whichV one portion of' a sensitive element is moved to adjust the control point of a switch actuated by a second portion of the element, together with a novel linkage between the second portion'of theA element andanother switch whereby adjustment of' the control point of the first switch does not affect the control point of the second switch.

A still further object is'to provide a novel arrangement for turning a fan switch to on position without regard to temperature.

These and other objects of the present invention will readily become apparent as the following description is read in the light ofthe accompanyingy drawings, inv which:

Figure-1 is an elevation, partly in section, of a temperature responsive switching device incorporating the various features of the invention'.

Figure 2 is a section taken substantially on line 2-2 of Figure 1*.

Figure 3 is a fragmentary section taken substantially on line 3*-3 of Figure l with the limit switch operating mechanism omitted.

Figure 4 is a fragmentarysection taken on line 4-d of Figure 2 showing the two limit switches.

The device to be described is a combination control for warm air furnaces, in which a helical bimetal element operates a fan switch to supply warm air to a space being heated when the bonnet temperature of the furnace is high enough so that the air delivered will produce a heating effect. The same bimetal element serves to actuate limit switches to stop the supply of fuel to the furnace when the bonnet temperature reaches predetermined values. It has been found that more uniform temperature can be maintained in the space being heated if the limit switch is set to stop the burner when the bonnet temperature reaches a value at which the air being suppliedl isV just capable of supplying the required heat to take care of the heat loss. |This, of course, will vary with outdoor weather conditions. Hence it is desirable to adjust the limit switch control point in accordance withA the severity of prevailing weather conditions. On the other hand, there is no necessity for adjusting the control point of the fan switch in accordance with weather conditions.

The limit switch control point is adjusted by rotating a member that carries one end of a bimetal helix so-that a member rotated on ternperature change by the other end of the helix will actuate the limit switch at the selected temperature. This arrangement is often referred toasa back end adjustment. The novelty of the' present invention lies in the fan switch operating linkage that permits the bimetal helix to actuate that switch at a temperatureV that is substantially unaifected by the adjustment of the bimetal helix for determining limit switch control point. To this end a lever having an arcuate portion engaging theV fan switch is pivoted on the member which adjusts the position of the normally stationary portion of the bimetal helix. Changes in temperature are effective to move the arcuate portion of this lever radially to actuate the fan switch,.but adjustment of the position of the bimetal-helix to determine the limit switch control point merely rotates the arcuate portion of this lever with respect to the fan switch without actuating it.

A further feature involves a stationary member that engages the above mentioned lever and serves as a fulcrum to pivot the lever and actuate the fanswitch irrespective of temperature if the limit switch adjusting mechanism is turned to one extreme position.

While the device to be described employs two limit switches that open at different temperatures and arevr adapted for connection in a circuit with a two stage room thermostat, the invention is not so limited.

Referring now to the various gures of the drawing, a casing l0 has a supporting tube Il suitably secured to the rear surfacev thereof.

The tube Il is adapted for insertion in the bonnet oi a warm air furnace, and suitable means, not shown, are provided to secure the tube Il to a furnace so that its rearwardly extending portion l2 is located within the furnace bonnet at a point where representative temperatures are encountered. The rearward extension l2 of the tube Il is suitably apertured so that furnace air may circulate freely over a bimetal helix |13 located in the extension I2. One end oi the bimetal helix Ill is secured to a bracket I5 that extends from a tube member IE which is journaled at its left hand end in the casing IG and at its right hand end has a plate I3 secured thereto. The plate I8 serves as a bearing in the supporting tube ll for the right hand end of the tube I5. The opposite end of the bimetal helix I is secured to a rod 2l] which is journaled in the plate I8 and also in a plate 22 secured to the left hand end of the tube I6. The left hand end of rod 2B terminates within casing lil. It will be seen that changes in temperature aiecting the bimetal helix I4 will rotate the rod 2Q with respect to the tube I6. Also it will be seen that for any given temperature of the bimetal helix I, the rod 20 will assume a predetermined position with respect to the tube I5.

Another plate 23 is adjustably secured to the plate 22 by means of a screw 243, so that the angular relationship between the plates 22 and 23 may be adjusted about the axis of the tube I. Another plate 25 is pivoted on the tube lli between the plate 22 and the frame I. An eccentric 2 pivoted in the plate 26 and engaging an aperture in the plate 23 serves to adjust the angular relationship between the

plates

23 and 25 about the axis of the tube I6. A spring washer 29 maintains the

plates

23 and 25 in their adjusted relationship. The adjustment between the plates 22 and 23 is a factory calibration adjustment and is accomplished by loosening the screw 24, inserting a special tool in a hole 3l in the plate 2t and in notches or apertures 32 in plate 22 to move the plate 22 with respect to the plate 23, plate 23 being held nxed to plate 6 by the eccentric l. This adjustment may suitably be made with the

plates

23 and 25 positioned so that a pointere is opposite a zero indicia upon the plate 2E. In the normal operation of the device the

plates

22, 23, and 25 are positioned as a unit and together with the tube I6 may be considered a single member for adjustably positioning one end of the bimetal helix I.

The plate 2e has a downwardly extending sector provided with gear teeth 36 that cooperate with a pinion 3l. A shaft 39 carrying the pinion El is journaled in a bracket Eil which is secured to upper and lower portions of the frame I by screws di. A leaf spring i2 engaging the casing iii and the shaft 39 maintains shaft 39, pinion Sl and plate 26 in adjusted position. Rotation of shaft 3S rotates

plates

26, 23 and 22 and therefore shifts the tube I6 and the bimetal element An insulating panel 45 is secured in the upper part oi the casing l0 and carries the fan and limit switching mechanisms. The fan switch, indicated at el, may be a unitary snap switch such as described in Baak Patent 2,318,734 and has terminals i8 and i9 that may be connected to screws l and 52 on the panel 45. The switch is ci the normally open type and is provided with a push button 5S that serves to close the switch on slight upward movement. The panel e5 also carries a bracket 55 that has an outwardly extending pivot pin 5t secured thereto at its lower extremity. A switch actuating lever 58 is pivoted on the pin 5E. The lever 5S carries two identical resilient switch arms 59 and Sil that may be relatively adjusted with respect to the lever 5t. The arm 59 may be adjusted by means of a screw '62 that is threaded in an upward extension 63 of the lever 53. A similar adjustment is provided for the arm 6l). t will be seen that tightening the screw 62 will move the arm 59 in a counterclockwise direction with respect to the lever 58. A pair of armatures Yiili and t5 are connected at the upper ends of the arms 5&3 and @il by means of insulating portions 6 and 5i. iress

back blades

68 and 69 are secured to the armatures Eli and 65 and carry contacts 'IQ and ll that cooperate with stationary contacts l2 and The stationary contacts l2 and i3 are carried by conducting brackets lt and l5 secured to the insulating panel :l5 and are suitably connected to terminal screws 16 and 'il on the panel 115. A pair oi' permanent magnets it and i9 carried on the brackets "lil and 'l5 serve to cooperate with the armatures 5t and E5 to cause the contacts to engage and disengage with a snap action. Wires 8c and SI connect the armatures and press back blades with a terminal 32 on the panel [l5 and this terminal may be connected to a terminal screw 83 also on the panel 45. A spring 8 acting between the bracket 55 and the lever 58 biases the lever 58 in a direction to close the contacts.

A collar 85 as seen in Figure 1 carrying a bracket 85 is secured to the left end of the rod 2@ that is positioned by the bimetal helix Isl. The bracket 25 carries an arm 8l' that extends upwardly to the axis of the rod 2i). A lever 39 is pivoted to the arm 87 on an axis in line with the axis of the rod 28. The lever 39 is adjustable with respect to the arm 8l by means 0I" a screw 96 threaded in the arm 8l and abutting a portion of the lever 39. A spring 9i holds the lever S9 in its adjusted position against the screw gil. The outer end 0I the lever 89 is adapted to abut an angular extension 93 of the limit switch actuating lever 58 to open the limit switches. It will be seen that the temperature at which the lever 8s abuts the portion 93 of the' lever 53 will depend on the adjusted position of the tube I6 that carries one end of the bimetal helix lli.A

The bracket 85 also carries an arm 95, best seen in Figures l and 3, that extends upwardly to a point in line with the axis of the rod 2t. A lever is pivoted to the arm 95 on an axis in line with the axis of the rod 2t. The angular relation between the lever 98 and the arm 95 may be adjusted by means of a screw 99 that is threaded in a portion oi the arm 95 and abuts a portion of the lever e8. A spring lill extending between the arm 9E and the lever S8 tends to keep the lever 28 in engagement with the screw 9. The spring II also serves as a strain release as will be hereinafter described.

A lever 65 having an arcuate portion H56 and a depending abutment portion E58 is pivoted in the plate 25 on a pin lll. The arcuate portion It is adapted to engage the button 53 of the fan switch 'l, and the abutment portion ISS is positioned for engagement by the lever S8 that is positioned by the helical bimetal element I4. It will be seen that when the lever 98 engages portion IS of lever 55 and raises the lever to engage the button 53 of the fan switch il that the temperature at which the fan switch button 53 is actuated will depend only on the temperatures at thebimetal I 4.. Adjustment; of thetube. I6 by means of shaft 39; gears 31 andy 3B,.and.plate 26 willrmove the pivot. H0. of the lever |05 a corre.- sponding amount torotatethe arcuate portion |053I of the lever |05Y with respect to the button 5310i the fan switch without moving the button in orfout with respect to the switch 41.

The; lever 98 willl engage thev portion |08 of thev lever |05 to actuate the fan switch before the lever |353v engages the portionI 93` of the limit switch actuating lever 53. The above mentioned strain` release comprising the springl IOI, arm 96, screw S9 and-lever 93 permits continued rotation of the rod 20 and arm 90 after the lever 98` is stopped bythe fan switch button 53 and portion |08' of the lever |05.

A post I I 5 carried by the casing I0 is positioned to engage the lever |05 when plate 26 is adjusted to itsextreme counterclockwise position as shown inY Figure 3. When the pin I I carrying the lever is moved to this position the post I|5 acts as a ulcrum to pivot the lever |05 in a counterclockwise direction about the pin IIO and raise the arcuate portie-n |05 of the lever |05 to actuate the button 53 of the fan switch 41 to close the fan switch regardless of temperature. It will be noted at this point `that the lever 08, which under normal operation of the device engages the portion |08 of the lever |05 to actuate the fan swtchis now out of engagement therewith. By this arrangement the fan circuit may be energized to circulate air through a house to obtain a cooling effect during hot weather conditions. The post I5 may be eccentrically mounted with respect to the casing |I0 to obtain proper correlation between movement of the plate 25 and actuation of the fan switch.

A suitable cover may cooperate with the casing I0 to enclose the mechanism. A knob I|8 may be provided on the outside of the cover I'II.

Operation The' cover IIT may be provided with suitable indicia for'cooperation with a mark on the'knob |18 to indicate the position in which the knob IIS should be set for prevailing weatherV conditions. For instance if the extreme counterclockwise adjustment of knob I I 8, corresponding to the position of the parts shown in Figure 2 of the drawing, the cover may be provided with the word severe indicating the position at which the limit switch is to be set for severe weather conditions. At this setting of the limit switches the furnace temperature is allowed to rise to the maximum safe operating temperature. As the knob is rotated in a clockwise direction from this position it may successively indicate cold, medium, and mild and the control points of the limit switches will be lowered by suitable increments. At the eXtreme clockwise position of the knob IIB the cover may be marked summer cooling, indicating the position of the parts shown in Figure 3 in which the fan switch is positively actuated to on position. With the parts adjusted for severe weather conditions the bimetal helix If may actuate the contacts I0-'I2 to open position at a bonnet temperature of 172 Fahrenheit, while if the knob I I8 is adjusted for mild weather conditions the contacts I0-12 may be opened at 112 F. The second set of limit switch contacts may be adjusted to open at bone net temperatures that are 10 to I5V degrees higher than firstY mentioned limit switch contacts; It will be understood' that the device is equallyv applicable. to singlek stage. limit switch operation, in which case only a single set of limit switch contacts would be used.

It is desirable that the fan switch be. actuated to closed' position at some temperature, during winter operation, at which the air being supplied from the bonnet of-'the furnaceto the room being occupied is at a temperature that will not create a feeling of coolness in the room. Thetemperatureiat which the ian switch. is to be. actuatedis independent ofoutdoor weather conditionsV and it is essential therefore that adjustment of the limit switch control point does not affect the fan control point. With the described mechanism the lever actuated by the bimetal helix engages the portion |08 of the lever |05 and raises it` to actuate the fan switch at a temperature that depends-solely on the temperature of the bimetal helix I4 and is independent of the selected limit control temperature. For instance it may be desirable to have the ian switch cut in vat 102 F., and due to the operating differential of the switch, the circuit may be opened when the tem.- perature drops to 99 F. The desired relation betweenl the operating temperatures of the limit switches and the fan switch may be obtained by suitable adjustment of the screws and 99.

If it is found in a particular installation that the ian switch is turned on at a bonnet temperature that is toolow and the air supplied to the room being heated is too cool the relation between the

plates

25 and 23 may be adjusted by the eccentric 27 to raise the fan control point. This increased bonnet temperature will be indicated by the pointer 34 on the plate 23 and its cooperation with the indicia on the plate 26. This adjustment will also change the control point of the limit switches a corresponding amount but will not be so great a change as to affect the safe operating temperature of the furnace as determined by the high stage limit switch when the knob I I8 is adjusted for severe weather conditions.

The device described provides a very simple mechanism for adjusting the control point ofv the limit switches without affecting the temperature at which the furnace fan is operated. It has been the practice heretofore, when two switches are to be operated by the same element and it is desired to vary the control peint of one of them without affecting the other, to provide more or less complicated linkages between the tempera.- ture responsive elements and the two switches. In that case the one end of the bimetal element isXed and all the adjustment is made between the movable portion of the bimetal and the two switches through two seperate linkages. The present mechanism enables the adjustment for the switch having an adjustable control point to be made by adjusting the normally stationary end of the bimetal as is common practice when only one adjustment is to be made for a single switch.

It is to be understood' that the scope of my invention is not limited by the particular instrument disclosed herewith, that novel features of the invention may take various forms, and that I am to be limited only by the scope of the appendedV claims.

I claim:

1. In a device of the class described, in combination, aiXedY support, rst and second members coaxially pivoted in said support, condition responsive means having portions connected to V7 each of said members for angularly positioning said second member with respect to said rst member, first and second control means carried by said support, said rst control means being actuated by said second member at a value of the condition dependent upon the position of said iirst member with respect to said support, and an actuator for said second control means carried by said first member and rotatable there- With, the portion oi"Y said actuator adapted to engage said second control means being movable transversely to the axis of said members on movement of said second member due to a change in the value oi the condition.

2, In a device ofthe class described, in combination, a xed support, rst and second members coaxially pivoted in said support, condition responsive means having portions connected to each of said members for angularly positioning said second member with respect to said rst rst member with respect to said support, and .1

an actuator for said second control means carried by said first member and rotatable therewith, the portion of said actuator adapted to engage said second control means being of arcuate configuration and being movable transversely to the axis of said members on movement of said second member due to a change in the Value of the condition.

3. In a device of the class described, in combination, a'xed support, first ,and second members coaxially pivoted in said support, a helical bimetal element having portions connected to each of said members for angularly positioning said second member with respect to said rst member, first and second control means carried by said support, said iirst control means being actuated by said second member at a temperature dependent upon the position of said first member with respect to said support, and an actuator for said second control means pivoted in said rst member, the portion of said actuator adapted to engage said second control means being movable transversely to the axis of said members on movement of said second member due to a change in the value of the condition.

e. In a device of the class described, in combination, a xed support, rst and second members coaxially pivoted in said support, a helical bimetal element having portions connected to each of said members for angularly positioning said second member with respect to said first member, rst and second control means carried by said support, said rst control means being actuated by said second member at a temperature dependent upon the position of said first member with respect to said support, and an actuator for said second control means pivoted in said first member, the portion of said actuator adapted to engage said second control means being of arcuate conguration and being movable transversely to the axis of said members on movement of said second member due to a change in the value of the condition.

5. In a device of the class described, in combination, a xed support, a rst member carried by said support and pivotally adjustable with respect thereto, said member engaging one end of a helical bimetal element, first control means carried by said support, a second member carried by said support and engaging the other end of saidhelical bimetal element so as to be rotatably positioned on temperature changes by said element about the axis on which said rst member is adjustable, said second member being adapted to actuate said rst control means at a temperature depending on the adjustment of said rst member in said support, second control means carried by said support, and a lever pivoted in said nrst member and having an arcuate surface for engaging said second control means that is coaxial with the axis of said members when in control means actuating position, said lever being positioned with respect to said rst member by said second member.

6. In a device of the class described, in combination, a xed support, a first member carried by said support and adjustable with respect thereto, said member engaging an active portion of a condition responsive element, iirst control means carried by said support, a second member positioned with respect to said support by another active portion of said condition responsive element and adapted to actuate said first control means at a value of the condition depending on the adjustment of said rst member relative to said fixed support, second control means, and an actuator for said second control means carried by said first member and adapted to be positioned elrectively with respect to said second control means by said second member.

7. In a device of the class described, in cembination, a fixed support, a helical bimetal element, a first member pivotally adjustable in said support and operatively connected to one end of said element, a second member pivoted in said first member onan axis coincident with the pivotal axis of said rst member in said support, said second member being operatively connected to another portion of said element whereby changes in temperature will cause relative rotation be- .tvveen said members, first and second switches carried by said Support and having actuators operated by movement thereof relative to said sup'- port, said second member being adapted for directly operating said first switch actuator, and a lever pivoted in said first member on an axis parallel to the pivotal axis of said members and movable radially by said second member with respect to the pivotal axis for` operating said second switch actuator, said lever having a portion that is arcuate about the pivotal axis of said members when in switch actuating position, whereby pivotal adjustment of said rst member in said support does not aiiect the temperature at which said second switch is actuated.

8. In a device of the class described, in combination, a fixed support, rst and second members coaxially pivoted in said support, a helical bimetal element having portions operatively connected to each of said members for angularly positioning said second member with respect to said first member, rst and second switches carriedl by said support, said first switch being actuated by said second member at a value of the condition dependent on the position of said first member in said support, a lever pivoted in said first member on an axis parallel to the pivotal axis of said members in said support, an arm extending radially from said second member said lever being movable about its pivot in said Erst member by said arm on temperature change, said lever further having a portion for actuating said second switch that is arcuate about the pivotal axis of said members when in switch actuating position, and means associated with said fixed support for engaging said lever to cause actuation of said second switch independently of temperature upon movement of said first member to a predetermined position relative to said xed support.

9. In a device of the class described, in combination, a fixed support, first and second members coaxially pivoted in said support, a helical bimetal element having portions operatively connected to each of said members for angularly positioning said second member with respect to said rst member, a switch carried by said support, a switch actuating lever pivoted in said first member on an axis parallel to the pivotal axis of said members in said support, an arm extending radially from said second member said lever being movable about its pivot in said rst member by said arm on change in temperature, and means integral with said support for engaging said lever to cause actuation of said switch independently of temperature upon movement of said rst member to a predetermined position relative to said fixed support.

10. In a device of the class described, in combination, a fixed support, first and second members coaxially pivoted in said support, a helical bimetal element having portions operatively connected to each of said members for angularly positioning said second member with respect to said rst member, a switch carried by said support, a switch actuating lever pivoted in said first member on an axis parallel to the pivotal axis of said members in said support, an arm extending radially from said second member said lever being movable about its pivot in said rst member by said arm on change in temperature, and means integral With said support at a point intermediate the pivotal axes of said members and said lever for engaging said lever to cause actuation of said switch independently of temperature upon movement of said rst member to a predetermined position relative to said xed support.

ll. In a ycontrol device, a condition responsive element having one end normally fixed and the other end moving upon change in the value of the condition to which said element responds, a first control member connected to the movable end of said element, shifting means for movin-g the normally xed end of said element to change the value of the condition at which said rst control member Will be operated by said element, a second control member and a lever interconnecting the shifting means, movable end of said member and second control element to cause operation of said second control member at the same ivalue of the condition upon operation of said shifting means to different positions.

l2. In a control device, a shiftable mount, a condition responsive element having one part connected to said mount and another part movable upon change in the value of the condition to which it responds, a control arm pivoted on said shiftable mount, an actuatingI arm connected to the movable part of said element and movable into and out of engagement with said control arm, a strain release permitting continued movement of said element after engagement of said actuating and control arms, and a member op- 10 erated by said element upon such continued movement.

13. In a control device, an actuator, a shiftable member, a control arm connected to said member, said control arm being moved by said actuator, a control membel operated by said control arm, and a iixed stop engaged by said control arm upon shifting of said shiftable member to a predetermined position, the engagement of said stop by said control arm causing movement of the control arm to operate said control member independently of said actuator.

14. In a control device, an actuator, a shiftable member, a control arm connected to said shiftable member, said control arm being moved by said actuator, a control member operated by said control arm, and a fixed stop engaged by said control ai'm upon shifting of said shiftable member, the engagement of said stop by said control arm causing movement of the control arm to operate said control member independently of said actuator and a second control member operated by Said actuator.

15. In a device of the class described, in com-',- bination, a fixed support, first and second members carried by said support and independently movable with respect thereto, condition responsive means interconnecting said members for relatively positioning said members, rst and second control means carried by said support, said first control means being actuated by said second member at a value of the condition dependent upon the position of said rst member with respect to said support, an actuator for said second control means carried by said first member, and means interconnecting said actuator and said second member for moving said actuator to actuate said second control means upon a change in the value of the condition.

16. In a device of the class described, in combination, a xed support, first and second members coaxially pivoted in said support, condition responsive means having portions connected to each of said members for angularly positioning said second member with respect to said rst member, first and second control means carried by Said support, said first control means being actuated by said second member at a value of the condition dependent upon the position of said first member with respect to said support, and an actuator for said second control means carried by said first member and rotatable therewith, the portion of said actuator adapted to engage said second control means being a curved surface that is movable normal to the pivotal axis of said members on relative movement of said members due to change in condition value.

JOHN O. ROSCHE.

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

UNITED STATES PATENTS Number Name Date 2,034,865 Hart Mar. 24, 1936 2,041,645 Kriechbaum May 19, 1936 2,120,937 Kronmiller June 14, 1938 Certificate of Correction Patent No. 2,532,859 December 5, 1950 JOHN O. ROSCHE It is hereby certified that error appears in the printed specication of the above numbered patent requiring correction as follows:

Column 3, lines 45 and 46, for plate 6 by the eccentric 7 read plate Q6 by the eccentric 27 column 9, lines 53 and 54, for member and second control element read element and second control member;

and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Oce.

Signed and sealed this 3rd day of April, A. D. 1951.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.

Certificate of Correction Patent No. 2,532,859 December 5, 1950 JOHN O. ROSSI-IE It is hereby certified that error appears in the printed specication of the above numbered patent requiring correction as follows:

Column 3, lines 45 and 46, for plate 6 by the eccentric 7 read plate 26' by the eccentric 27 column 9, lines 53 and 54, for member and second control element read element and second control member;

and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Oioe.

Signed and sealed this 3rd day of April, A. D. 1951.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.