US3693874A

US3693874A - Fuel control system and control device therefor or the like

Info

Publication number: US3693874A
Application number: US93238A
Authority: US
Inventors: Raymond J Fox
Original assignee: Robertshaw Controls Co
Current assignee: Robertshaw Controls Co
Priority date: 1970-11-27
Filing date: 1970-11-27
Publication date: 1972-09-26
Anticipated expiration: 1989-09-26

Abstract

A control device for directing fuel from a source thereof to pilot burner means and to main burner means, the control device having a movable selector which is adapted to be moved in one direction from an ''''off'''' position thereof through a ''''cooking range'''' thereof to a ''''pilot off'''' position thereof. The control device has stop means for preventing uninterrupted movement of the selector from the ''''cooking range'''' thereof into the ''''pilot off'''' position thereof to prevent accidental pilot outage whereby the operator must axially move the selector before he can move the same from the ''''cooking range'''' thereof into the ''''pilot off'''' position thereof.

Description

United States Patent Fox [451 Sept. 26, 1972 FUEL CONTROL SYSTEM AND CONTROL DEVICE THEREFOR OR THE LIKE Inventor: Raymond J. Fox, Irwin, Pa.

Robertshaw Controls Richmond, Va.

Filed: Nov. 27, 1970 Appl. No.: 93,238

Assignee: Company,

US. Cl 4236/15 A, 137/625.46, 251/96 Int. Cl. ..F23 n 5/24, Fl6k 35/02 Field of Search ..'..137/65, 66, DIG. 6, 625.46;

References Cited UNITED STATES PATENTS 6/1937 Pratt et al. l 37/D1G. 6 10/1961 Wright et al ..l37/66 12/1961 lves ..25l/96 X 2/1966 Allingham' ..25 l/96 X 3,602,239 8/1971 Battersby et al ..25l/96 X Primary Examiner-M. Cary Nelson Assistant Examiner-David R. Matthews Attorney-Auzville Jackson, Jr., Robert L. Marben and Candor, Candor & Tassone ABSTRACT A control device for directing fuel from a source thereof to pilot burner means and to. main burner means, the control device having amovable selector which is adapted to be moved in one direction from an off" position thereof through a cooking range" thereof to a pilot off position thereof. The control device has stop means for preventing uninterrupted movement of the selector from the cooking range A thereof into the pilot off position thereof to prevent accidental pilot outage whereby the operator must axially move the selector before he can move the same from the cooking range thereof into the pilot off position thereof.

20 Claims, 10 Drawing Figures PATENTEDSEP26 I972 SHEET 1 BF 3 INVENTOR. RAYMOND J. FOX

MM :TM

HIS ATTORNEYS PATENTEDSEPZG I972 SHEET 2 [IF 3 INVENTOR. RAYMOND J. FOX

HIS ATTORNEYS PATENTEUSEPZB I972 SHEET 3 [IF 3 HIS ATTORNEYS FUEL CONTROL SYSTEM AND CONTROL DEVICE THEREFOR OR THE LIKE This invention relates to a fuel control system for a fuel burning cooking apparatus and the like as well as to an improved control device for such a control system or the like. 7

It is well known that fuel control systems are pro-' vided with a control device which when disposed in the off position thereof prevents the flow of fuel from a source thereof to a main burner means while still maintaining fuel interconnection between the fuel source and a pilot burner means so that when the control device is subsequently moved to a cooking range position thereof, the main burner means can be ignited by the pilot burner means without requiring the pilot burner to be lit by the housewife or the like each time the main bumer is to be utilized for cooking purposes and the like. However, such control device salso provide a selector position thereof wherein the fuel source is also disconnected from the pilot burner means in order to provide complete flame outage for the cooking apparatus for various purposes, such as when transporting house trailers containing such cooking apparatus or the like.

However, it has been found that such prior known control devices require the user to rotate the control device in one direction thereof for cooking operations and in an opposite direction to provide for pilot outage whereby complicated mechanism is provided for the control device.

According to the teachings of this invention, however, a control device is provided wherein the selector means is movable in just one direction from an off" position thereof through a cooking-range position thereof into a pilot off position, the control device having means to prevent uninterrupted movement of the selector means from the cooking range position thereof into the pilot off position thereof to prevent accidental pilot outage when the user merely intended to select a high cooking temperature, such as broil and the like.

In particular, one embodiment of this invention provides a control device for directing fuel from a source thereof to pilot burner means and to main burner means, the control device having a movable selector means which is adapted to be moved in one direction from an off position thereof through a cooking range position to a pilot off position thereof. The control device has a valve means operatively associated with the selector means so that when the selector means is in the off position thereof, the valve means is adapted to interconnect the fuel source to only the pilot burner means. The selector means when in a cooking range position thereof causes the valve means to be adapted to interconnect the fuel source to the pilot burner means and to the main burner means. The valve means is adapted to disconnect the fuel source from both the pilot burner means and the main burner means when the selector means is in the pilot off position thereof.

The control device is provided with a stop means which prevents uninterrupted movement of the selector means from the cooking range position thereof into the pilot off" position thereof so that the operator must axially move the selector means relative to the control device to clear such stop means for movement of the selector means into the pilot .off" position whereby accidental pilot outage of the control system of this invention is prevented by the control device of this invention.

Accordingly, it is an object of this invention to provide an improved fuel control system having one or more of the novel features of this invention as set forth above or hereinafter shown or described.

Another object of this invention is to provide an improved control device having one or more of the novel features set forth above or hereinafter shown or described.

Other objects, uses and advantages of this invention are apparent from a reading of this description which proceeds with reference to the accompanying drawing forming a part thereof and wherein:

FIG. 1 is a front view of the control device of this in-- vention.

FIG. 2 is a cross-sectional view taken along line 2-2 of FIG. 1. a g

FIG. 3 is a fragmentary, cross-sectional view taken on line 3-3 of FIG. 2 with the selector knob being removed therefrom.

FIG. 4 is a cross-sectional view taken on line 4-4 of FIG. 2 and schematically illustrates the control system of this invention.

FIG. 5 is an exploded perspective view of the parts of FIG. 3 that form part of the control device of this invention.

FIG. 6 is a cross-sectional view taken on line 6-6 of FIG. 2, FIG. 6 illustrating the control device in its of position.

FIG. 7 is a front view similar to FIG. 6 with background details of the control device removed and illustrating the control device set in its broil" position.

FIG. 8 is a view similar to' FIG. 4 and illustrates the control device when in the -broil" position of FIG. 7.

FIG. 9 is a view similar to FIG. 7 and illustrates the control device in the pilot off" position thereof.

FIG. 10 is a view similar to FIG. 8 and illustrates the control device in its pilot off position.

While the various features of this invention are hereinafter described and illustrated as being particularly adapted to provide a control device for a fuel burning apparatus, it is to be understood that the various features of this invention can be utilized singly or in any combination thereof to provide control means for other apparatus as desired.

Therefore, this invention is not to be limited to only the embodiment illustrated in the drawings, because the drawings are merely utilized .to illustrate one of the wide variety of uses of this invention.

Referring now to FIGS. 1 and 2, the improved control device of this invention is generally indicated by the reference numeral 20 and comprises a housing means 21 formed from a plurality of parts and having an inlet 22 interrupting a flat valve surface 23 thereof and being adapted to be interconnected to a fuel source 64, FIG. 4, by suitable conduit means 25 whereby the control device 20 is adapted to be utilized in the fuel control system of this invention which is generally indicated by the reference numeral 26 in FIG. 4. Such fuel control system 26 comprises a main burner means 27 and a pilot burner means 28 operatively associated with the main burner means 27 in a manner conventional in the art to ignite fuel that initially issues from the main burner means 27.

The flat valve surface 23 of the housing means 21 is also interrupted by an arcuate recess 24 that is in fluid communication with the inlet 22 as illustrated in FIG. 4 for a purpose hereinafter described. Two other arcuate recesses 29-and 30 are provided in the flat valve face 23 of the housing means 21 with the arcuate recess 29 being interconnected to an outlet 31 that is adapted to be interconnected by a conduit means 32 to the main burner means 27, the control device having conventional thermostatic valve means disposed intermediate the recess 29 andthe conduit means 32 to thermostatically control the flow of fuel to the main burner means 27. Similarly, the arcuate recess 30 is fluidly interconnected to an outlet 33 that is adapted to be interconnected by a conduit means 34 to the pilot burner means 28. However, the control device.20 does not thermostatically controlthe flow of 'fuel to the pilot burner means 28 so that the pilot burner means 28 will be continuously operating unless the control device 20 is in its pilot off" position as will be apparenthereinafter.

A rotatable valve member 35 is carried by the housing means 21 and has a flat valve surface 36 disposed in sliding and sealing relation with the flat valve surface 23 of the housing 21, the valve member 35 being rotatably mounted to the housing means 21 by a shaft means 37 splined thereto and being utilized for thermostatically setting the control device 20 so that the same will direct fuel to the main burner means 27 only when the temperature of the oven or the likereceiving the main burner means 27 is below the'temperature setting of the control device 20 with such oven temperature being sensed by suitable temperature sensing means 38 in a cpnventional manner. Conversely, the temperature setting means 37 prevents the fuel from being directed to the main burner means 27 when the temperature sensing means 38 senses a temperature in the oven above the selected temperature of the control device 20 in a conventional manner. Thus, it can be seen that the temperature sensing means 38 of the control device 20 while not forming a part of this invention does control the outlet 31 to block the outlet 31 from the fuel source 64 when the temperature in the'oven is above the selected temperature and to interconnect or unblock the outlet 31 when the temperature in the oven is below the selected temperature.

The face 36 of the valve member 35, as illustrated in FIG. 3, has an arcuate recess 39 formed therein and is provided with a plurality of recesses 40 on the outer periphery thereof which receive tongue extensions 41 of a cup-shaped drive member 42 rotatably carried by the housing means 21 and having a C-shape shaft means 43 for interconnecting to a selector knob 44 of the control device 20 whereby rotation of the knob 44 rotates the drive member 42, valve member 35 and temperature setting shaft 37 in unison. A cup-shaped casing member 45 is disposed over the drive member 42 and is adapted vto be fastened to the housing means 21 by suitable fastening means 46.

The casing 45 has a slot means" 47 passing therethrough and through which the shaft extension 43 of the drive member 42 extends in the manner illustrated in FIG. 2 to interconnect to the selector knob 44.

A compression spring 48 is disposed between the valve member 35 and the drive member 42 to tend to urge the drive member 42 axially away from the valve member 35 and against the closed end portion 49 of the casing 45. In order to seal the opening 50 passing through the valve member 35 from the exterior of the housing 21, a hat-shaped casing member 51 is disposed over the valve member 35 at the tubular portion 52 thereof and compresses an annular sealing member 53 therebetween whereby the casing member or hatshaped member 51 isdisposed between the compression spring 48 and the valve member 35.

The arcuate recess 39 in the valve surface 36 of the valve member 35 is so constructed and arranged that when the selector knob 44 is disposed in the off position illustrated in FIGS. 4 and 6, the arcuate slot 39 of the valve member35 is in fluid communication with the fuel inlet recess 24 of the valve surface 23 of the housing 21 and also is in fluid communication with the recess 30 that leads to the pilot burner means 28 so that the pilot burner 28 can be continuously operating. However, the recess 39 is out of communication with the recess 29 that is adapted to lead to the main burner means 27 so that no fuel can be directed to the main burner means 27 when the selector means 44 is in its off position.

When the selector knob 44 is disposed in any of the cooking temperature positions thereof, such as at the end of the cooking temperature position which is the broil position illustrated in FIG. 8, the recess 39 of the valve member 35 bridges the inlet recess 24 with both

recesses

29 and 30 so that fuel is adapted to be directed to both burner means 27 and 28 in any of the cooking range positions of the selector knob 44.

When the selector knob-44 is disposed in the pilot off position as illustrated in FIGS. 9 and 10 in a manner hereinafter described, the recess 39 of the valve member 35 is disposed completely out of communication with both

recesses

29 and 30 so that no fuel can be directed to either the pilot burner means 28 or main burner means 27 for the reasons previously set forth. a

The slot 47 through the end 49 of the stationary casing member 45 is so constructed and arranged that the same defines a first stop projection 54 that extends radially inwardly into the slot 47 and has opposed side edges '55 and 56. The drive member 42 has an outwardly directed tang 57 that is adapted to be received in the slot 47 in the casing 45 and abuts against the side 55 of the projection 54 when the selector knob 44 is disposed in the off position illustrated in FIG. 6 so as to limit clockwise movement of the selector knob 44 when viewing FIG. 6. However, when the control knob 44 is moved in a counterclockwise direction from FIG. 6 to the pilot off position illustrated in FIG. 9, it can be seen that the tang 57 of the drive member 42 abuts against the side 56 of the projection 54 so as tolimit counterclockwise movement of the selector knob 44.

The slot 47 through the end 49 of the casing 45 also defines a pair of arcuate stops or

projections

58 and 59 with the arcuate stop 58 being disposed adjacent the longer projection 54 on the side 55 thereof and the arcuate section 59 being disposed on the opposite side of the projection 54.

The drive'member has another tang or projection 60 extending therefrom which is adapted to abut against the side 61 of the projection or stop means 58 in the manner illustrated in FIG. 6 when the control knob 44 is disposed in the offf position and, thus, tend to prevent direct rotational movement of the selector means 44 from the off position illustrated in FIG. 6 in a counterclockwise direction. However, the length of the projection 60 is relatively small so that the operator need only slightly axially move the selector knob 44 inwardly relative to the control device to move the drive member 42 axially toward the valve member 35 to have the tang 60 clear the stop means 58 of the casing 45 and thereby permit the selector 44 to be rotated from the off position thereof to any of the temperature positions, the tang 60 completely clearing the arcuate portion or stop means 58 of the casing 45 at the lowest temperature selection position of the knob 44 so that there is no impediment to the rotational movement of the selector knob 44 in the temperature range position thereof. i

In order to insure that when the selector 44 is moved from its "off position toward a temperature setting position thereof, the valve member will be rotated sufficiently to interconnect the fuel inlet slot 24 to the main burner slot 29, the arcuate stop'58 is angled so that once the tang 60 of the drive member 42 is behind the same, the angled stop58 cams the tang 60 to automatically drive the drive member 42 in a counterclockwise direction a distance sufficient for the desired rotation of the valve member 35, the compression spring 48 providing the necessary drive force for such camming action between the tang 60 and angled stop means 58.

However, when the operator rotates the selector knob 44 to the broil position thereof, the projection 60 now engages against the side 62 of the arcuate stop '59 of the casing 45 as illustrated in FIG. 7 so that the operator will not rotate the knob 44 beyond the broil position thereof to accidentally move the same to the pilot off position thereof. However, in order to move the selector knob 44 from the broil position illustrated in FIG. 7 to the pilot off position of FIG. 9, the

operator must push axially inwardly on the selector knob 44 to cause the drive member 42 to move toward the valve member 35 and thereby have the tang 60 clear to the edge 62 of the stop means 59 and permit the same to be rotated from the broil position of FIG. 7 to the pilot off position of FIG. 9. When the projection 60 engages against the rear side of the arcuate portion 59 of the casing 45 as the knob 44 is being rotated from the broil position to the pilot off position, such engagement between the tang 60 and the relatively long stop means 59 provides feel" to the selector knob 44 to indicate to the user that the same is being knob 44 from the pilot off position thereof back toward a temperature operating position of the selector moved in resistance to the pilot off position so that the drive member 42 has been pushed outwardly by the compression spring 48. Thus, to now turn the selector knob 44, the member, knob 44 must be moved axially inwardly to clear the tang 60 from the edge 63 of the arcuate stop means 59 in the manner previously described.

Thus, it can be seen that this invention provides means on the control device 20 to prevent the same from being accidentally moved to and from a pilot off position thereof and thereby accidentally cause a pilot outage which adverse situation must be corrected before the control device 20 can be utilized to control the burner means 27 and 28 in the manner previously described.

Accordingly, it can be seen that this invention not only provides an improved fuel control system, but also this invention provides an improved control device for such a control system or the like.

forms may be utilized all coming within the scope of the claims which follow.

What is claimed is:

l. A control device for directing fuel from a source thereof to pilot burner means and to main burner means, said control device having a movable selector means'which is adapted to be moved in one direction from an off position thereof through a cookingrange" having multiple temperature selection positions to a pilot off position thereof, said control device having thermostatic control means operatively associated with said selector means for controlling the temperature output effect of said main burner means in relation to the cooking temperature setting of said selector means, said controldevice having valve means opera- .tively associated with said selector means so that when said selector means is in said off position thereof said valve means is adapted to interconnect said source to only said pilot burner means, said valve means being adapted to interconnect said source to said pilot burner means and said main burner means when said selector means is in any one of said temperature selection positions of said cooking range, said valve means being adapted to disconnect said source from said pilot burner means and said main burner means when said selector means is in said pilot off" position, said control device having means for preventing uninterrupted movement of said selector means from said cooking range thereof into said pilot off position thereof to prevent accidental pilot outage.

2. A control device as set forth in claim 1 wherein said means for preventing uninterrupted movement of said selector means comprises detent means.

3. A control device as set forth in claim 1 wherein said selector means is rotatably movable through said positions thereof, said means for preventing uninterrupted movement of said selector means comprising means for causing said selector means to be axially moved before being rotatably movable from said cooking range to said pilot off position thereof.

4. A control device as set forth in claim 3 wherein said control device also has means preventing uninterrupted movement of said selector means from said ofi position thereof into said cooking range.

While the form of the invention now preferred has 1 been disclosed as required by the patent statutes, other I 5. A control device as set forth in claim 4 wherein said means for preventing uninterrupted movement of said selector means from said off position thereof to said cooking range also comprises means for causing said selector means to be axially moved before being rotated from said off position to said cooking range. v

6. A control device as set forth in claim 1 wherein said valve means comprises a rotatable valve member, said selector means comprises a rotatable drive member splined to said valve member whereby said drive member and said valve member rotate in unison while said drive member is adapted to be axially moved relative to said valve member.

7. A control device as set forth in claim 6 wherein said means for preventing uninterrupted movement of said selector means comprises stop means carried by said control device and disposed in the path of movement of said rotatable drive member whereby said drive member must be axially moved relative to said valve member to clear said stop means.

8. A control device as set forth in claim 7'wherein a spring means is disposed between said valve member and said drive member to tend to maintain said drive member axially spaced from said valve member.

9. A control device as setforth in claim 8 wherein said control device has a stationary member, said spring means urging said drive member against said stationary member to limit the axial spacing of saiddrive member relative to said valve member, said stationary member having said stop means thereon.

10. A control device as set forth in claim 9 wherein said stationary member has a slot therethrough, said drive member having a tang for normally projecting through said slot, said slot defining said stop means as a projection that prevents normal movement of said tang in said slot.

11. A control system comprising a source of fuel, pilot burner means, main burner means, and a control device operatively interconnected to said source and to both of said burner means for directing fuel from said source to said pilot burner means and to said main burner means, said control device having a movable selector means which is adapted to be moved in one direction from an off position thereof through a cooking range having multiple temperature selection positions to a pilot off position thereof, said control device having thermostatic control means operatively associated with said selector means for controlling the temperature output effect of said main'bumer means in relation to the cooking temperature setting of said selector means, said control device having valve means operatively associated with said selector means so that when said selector means is in said ofi position thereof said valve means interconnect said source to only said pilot burner means, said valve means interconnectingsaidsource tosaid pilot burner means and said main burner means when said selector means is in any one of said temperature selection positions of said cooking range", said valve means disconnecting said source from said pilot burner means and said main burner means when said selector means is in said "pilot off" position, said control device having means for preventing uninterrupted movement of said selector means from said c gokin range" thereof into said pilot off" position ereo to prevent accidental pilot outage.

12. A control system as set forth in claim 11 wherein said means for preventing uninterrupted movement of said selector means comprises detent means.

13. A control system as set forth in claim 11 wherein said selector means is rotatably movable through said positions thereof, said means for preventing uninterrupted movement of said selector means comprising said means for preventing uninterrupted movement of said selector means from said off position thereof to said cooking range also comprises means for causing said selector means to be axially moved before being rotated from said off position to said cooking rangeiil v 16. A control system as set forth in claim. 11 wherein said valve means comprises a rotatable valve member, said selector means comprises a rotatable drive member splined to saidvalve member whereby said drive member and'said valve member rotate in unison while said drive member is adapted to-be axially moved relative to said valve member.

17. A control device as set forth in claim 16 wherein said means for preventing uninterrupted movement of said selector means comprises stop means carried by said control device and disposed in the path of movement of said rotatable drive member whereby said drive member must be axially moved relative to said valve member to clear said stop means.

18. A control system as set forth in claim 17 wherein a spring means is disposed between said valve member and said drive member to tend to maintain said drive member axially spaced from said valve member.

19. A control system as set forth in claim 18 wherein said control device has a stationary member, said

Claims

1. A control device for directing fuel from a source thereof to pilot burner means and to main burner means, said control device having a movable selector means which is adapted to be moved in one direction from an ''''off'''' position thereof through a ''''cooking range'''' having multiple temperature selection positions to a ''''pilot off'''' position thereof, said control device having thermostatic control means operatively associated with said selector means for controlling the temperature output effect of said main burner means in relation to the cooking temperature setting of said seleCtor means, said control device having valve means operatively associated with said selector means so that when said selector means is in said ''''off'''' position thereof said valve means is adapted to interconnect said source to only said pilot burner means, said valve means being adapted to interconnect said source to said pilot burner means and said main burner means when said selector means is in any one of said temperature selection positions of said ''''cooking range'''', said valve means being adapted to disconnect said source from said pilot burner means and said main burner means when said selector means is in said ''''pilot off'''' position, said control device having means for preventing uninterrupted movement of said selector means from said ''''cooking range'''' thereof into said ''''pilot off'''' position thereof to prevent accidental pilot outage.

3. A control device as set forth in claim 1 wherein said selector means is rotatably movable through said positions thereof, said means for preventing uninterrupted movement of said selector means comprising means for causing said selector means to be axially moved before being rotatably movable from said ''''cooking range'''' to said ''''pilot off'''' position thereof.

4. A control device as set forth in claim 3 wherein said control device also has means preventing uninterrupted movement of said selector means from said ''''off'''' position thereof into said ''''cooking range''''.

5. A control device as set forth in claim 4 wherein said means for preventing uninterrupted movement of said selector means from said ''''off'''' position thereof to said ''''cooking range'''' also comprises means for causing said selector means to be axially moved before being rotated from said ''''off'''' position to said ''''cooking range''''.

8. A control device as set forth in claim 7 wherein a spring means is disposed between said valve member and said drive member to tend to maintain said drive member axially spaced from said valve member.

9. A control device as set forth in claim 8 wherein said control device has a stationary member, said spring means urging said drive member against said stationary member to limit the axial spacing of said drive member relative to said valve member, said stationary member having said stop means thereon.

11. A control system comprising a source of fuel, pilot burner means, main burner means, and a control device operatively interconnected to said source and to both of said burner means for directing fuel from said source to said pilot burner means and to said main burner means, said control device having a movable selector means which is adapted to be moved in one direction from an ''''off'''' position thereof through a ''''cooking range'''' having multiple temperature selection positions to a ''''pilot off'''' position thereof, said control device haVing thermostatic control means operatively associated with said selector means for controlling the temperature output effect of said main burner means in relation to the cooking temperature setting of said selector means, said control device having valve means operatively associated with said selector means so that when said selector means is in said ''''off'''' position thereof said valve means interconnect said source to only said pilot burner means, said valve means interconnecting said source to said pilot burner means and said main burner means when said selector means is in any one of said temperature selection positions of said ''''cooking range'''', said valve means disconnecting said source from said pilot burner means and said main burner means when said selector means is in said ''''pilot off'''' position, said control device having means for preventing uninterrupted movement of said selector means from said ''''cooking range'''' thereof into said ''''pilot off'''' position thereof to prevent accidental pilot outage.

13. A control system as set forth in claim 11 wherein said selector means is rotatably movable through said positions thereof, said means for preventing uninterrupted movement of said selector means comprising means for causing said selector means to be axially moved before being rotatably movable from said ''''cooking range'''' to said ''''pilot off'''' position thereof.

14. A control system as set forth in claim 13 wherein said control device also has means preventing uninterrupted movement of said selector means from said ''''off'''' position thereof into said ''''cooking range''''.

15. A control system as set forth in claim 14 wherein said means for preventing uninterrupted movement of said selector means from said ''''off'''' position thereof to said ''''cooking range'''' also comprises means for causing said selector means to be axially moved before being rotated from said ''''off'''' position to said ''''cooking range''''.

16. A control system as set forth in claim 11 wherein said valve means comprises a rotatable valve member, said selector means comprises a rotatable drive member splined to said valve member whereby said drive member and said valve member rotate in unison while said drive member is adapted to be axially moved relative to said valve member.

19. A control system as set forth in claim 18 wherein said control device has a stationary member, said spring means urging said drive member against said stationary member to limit the axial spacing of said drive member relative to said valve member, said stationary member having said stop means thereon.

20. A control system as set forth in claim 19 wherein said stationary member has a slot therethrough, said drive member having a tang for normally projecting through said slot, said slot defining said stop means as a projection that prevents normal movement of said tang in said slot.