US2854225A - Automatic choke system for a carburetor - Google Patents

Description

Sept. 30, 1958 F. sKAY 2,854,225

AUTOMATIC CHOKE FR A CARBURETOR Filed June 13, 1955 3 Sheets-Sheet 1 I 22 k fo j I 42| 7a i 44 fi 34 @6l i 4a' 46 47' 4a (fo ,4 @45:12 e@ f8 l /0 5 fg 66 6d I 64 7d a 64 S F. SKAY 2,854,225

AuToMATzc cHoxE SYSTEM Foa A CARBURETQR Filed June 13, 1955 I5 Sheets-Sheet 2 *5f-h A:

. INVENTOR.

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AUTOMATIC cHoxa SYSTEM FOR A CARBURETOR Filed June 13, 1955 3 Sheets-Sheet 3 i 'I 40 y 1,

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o l ne I I 64 United States AU'IMATIC CHUKE SYSTEM FOR A CARBUREIOR Frank Skay, Detroit, Mich., assigner to Holley Carburetor Company, Detroit, Mich., a corporation of Michigan Application .inne 13, 1955, Serial No. 514,925

i8 Claims. (Cl. 261-39) The present invention relates to an automatic choke system for a carburetor.

It is an object of the present invention to provide an automatic choke having three reaction periods; namely, an instant reaction to vacuum at initial start, a slow modulated reaction to existing vacuum and engine temperature during initial warm up, and finally, fast direct action responsive solely to temperature when approaching operating temperature.

It is a further object of the present invention to provide an automatic choke system including a thermostat and provided with means for controlling the maximum heat applied to the thermostat as well as preventing bleeding of atmosphere below the carburetor throttle plate.

lt is a further object of the present invention to provide an automatic choke system including temperature responsive means effective to prevent closing of the choke under heavy load such for example as encountered when climbing a long steep hill.

lt is a further object of the present invention to provide a choke system including means responsive solely to engine temperature which prevents closure of the choke after the engine reaches full operating temperature until the engine has cooled.

It is a further object of the present invention to provide an automatic choke system comprising a small compact assembly suitable for installation in hitherto inaccessible locations.

lt is a further object of the present invention to provide an automatic choke system characterized by an increase in the economy of rnanufacturc and characterized also by the ease of service in the "eld,

it is a further object of the present invention to provide an automatic choke system including a thermally expansible and contractable device movable as a unit in response to variations in manifold vacuum.

lt is a further object of the present invention to use a thermally responsive device in the form of a cylinder movable in a piston subjected to manifold vacuum so as to obtain movement of the thermally responsive device as a unit in response to changes in manifold vacuum.

it is a further object of the present invention to provide in a choke system a thermostat having one heat sensitive end, said thermostat having its heat sensitive end exposed in a pressure cham er adapted to receive air heated in accordance with engine temperature at a pressure dependent upon manifold vacuum.

Other objects and features of the invention will become apparent as the description proceeds, especially when taken in conjunction with the accompanying drawings, wherein:

Figure l is a side elevation of a carburetor with part of the automatic choke mechanism shown in section.

Figure lA is a sectional view through the thermally responsive device employed in the automatic choke system.

Figure 2 is a fragmentary elevational view as seen from the right in Figure l, with parts in section.

Figure 3 is a fragmentary plan view of the carburetor and automatic choke mechanism.

Figures 4, 5 and 6 are elevational sectional views similar to Figure l showing the movable parts of the automatic choke system in different operating positions.

Figure 7 is an elevational sectional view showing a modification of the structure illustrated in Figures 1 6.

Figure 8 is a fragmentary elevational view partly in section showing yet another embodiment of the present invention.

Figure 9 is a fragmentary plan View of a portion of the carburetor with the cover plate of the automatic choke mechanism removed.

The present invention is applicable to conventional carburetors and no eiort is made to illustrate or describe any of the conventional details of the carburetor. For purposes of completeness however, the automatic choke system is illustrated as associated with a down-draft carburetor which, as usual, is connected to the intake manifold of an internal combustion engine. As is well under.- stood in the art, operation of the automatic choke is controlled by manifold vacuum and operating temperature of the engine. As best seen in Figures 1 3, the automatic choke mechanism comprises a casting itl fastened or otherwise secured to a pad i2 provided on the body of the carburetor by screws indicated at i4. The carburetor includes a main air iiow passage lo adapted to be substantially cornpleteiy closed by a choke plate ld mounted on a pivot support ZG having an axis at 22, as seen in Figure l. lt will be observedl that the pivot axis of the choke plate 21.3 is off-center and arranged such that a downward flow of air tends to hold the choke plate in open position. The body of the carburetor is provided with a stud 2st having a chamber 26 provided therein. A mounting pin 23 has an inner threaded end securing the pin centrally of the chamber and delining an annular space for the reception of a coil spring 35i one end of which is turned to extend axially and is retained in a recess 32. The pin 28 has its outer end provided with a slotted head 34% to facilitate assembly ofthe construction. Mounted on the pin 2f) is a bell crank 36.

The choke plate l is fastened by screws 38 to a pivot shaft and rigidly secured to the outer end of theV pivot shaft is an arm du. The arrn 4i) is provided with an elongated slot for the reception of a pin 42 carried adjacent the end of an arm le of the bell crank 36. The bell crank includes a second arm portion 46 having an elongatedslot 47 therein receiving the end of an operating rod 48 as will subsequently be described. The outer end 49 of the coil spring 3i) is turned outwardly and is received in a hole in the bell crank 36. The spring 3i? is arranged to apply a torque tending to rotate the bell crank 36 clockwise as seen in Figure l, or in other words, to apply forces tending to close the choke plate 18.

In general, it is suicient to note at this time that the rod 48 is movable up and down in response to variations in engine conditions such as manifold vacuum,y engine ternperature, or a combination of the two. Upward movement of the rod 4S from the position illustrated in Figure l results in counterclockwise movement of the bell crank 36 about the axis of pivot pin 28. This in turn imparts clockwise rotation to the arm dit xedly secured to the pivot shaft of the choke plate with resultant opening movement of the choke plate. The elongated slot which receives the pin 42 of the bell crank permits the above described movement.

Referring now more particularly to Figure 1 there is provided a thermally expansible and contractable device indicated generally at Si). No claim is made to the details of this device, since it is available on the market under the trade name Vernathermfi It is described in Vony Wangenheim Patent 2,714,759. This device includes a cylindrical portion 52 which operates as a piston in a cylinder 54 formed Iin the casting 10. The space within the casting below the cylindrical portion 52 is connected to atmosphere by a vent indicated at 56. The space within the casting above the piston 52 is connected to manifold vacuum by a substantially unrestricted passage indicated at 58. Also communicating with the space above the piston is a passage 59 extending through a nipple 60 and provided with a calibrated restriction 61.

Referring now to Figure lA, the thermally responsive device 50 is formed with the cylindrical portion 52 in the form of a cup receiving a quantity of thermally expansible and contractable substantially incompressible material 62 disclosed inthe Van Wangenheim patent as a mixture of Wax and metal powders. The `open end of the cylindrical cup portion 52 is closed by a generally tubular extension 63 in which is slidably received a rod 64. The rod 64 is provided with an annular groove or lateral grooves rev ceiving a ring 65, the purpose of which will subsequently appear. Suitable yieldable sealing means 66 are provided at the inner end of the bore through the tubular extension 63 which permits expansion of the material 62 to move the rod 64 outwardly. Upon cooling of the thermally responsive material 62, inward movement of the rod 64 and sealing means 66 is accomplished by external spring means.

j Referring again to Figure 1 it will be observed that the thermally responsive device 50 is in-the present instance mounted with the rod 64 thereof extending downwardly into a generally tubular rod receiving seat orrecess 68 provided with a lateral relief extension 70. At the upper end of the recess 68 is a spring seat A72 and interposed between the spring seat 72 and the ring 65 'is a compression spring 74.

It is a characteristic of the thermally responsive device 50 and the actuating material 62 thereof-that substantial pressure is required to restore its relatively movable elements to contracted position when it cools following thermal expansion. It will be appreciated that the coil spring 30 acting .through the bell crank 36 and rod 48 applies pressure downwardly to the upper or thermally sensitive end of the device. At the same time, upward pressure is applied thereto by the compression spring 74. The springs 30 and 74 may be selected of such strength to apply any desired compressive force to the thermally sensitive device without `affecting its sensitivity and freedom of movement in response to changes in manifold vacuum.

Itis desired when the engine is cold and not running for the parts to assume the position illustrated in Figure l. Accordingly, forces developed by the spring 30 are suicient to overcome the force of the spring 74 and the device 50 is moved downwardly to a position determined by engagement between the lower end of its rod 64 and the Vlower end of the seat 68. Since it is assumed that the device is cold, it will be in its contracted position and accordingly, the bell crank 36 will be in its extreme position of clockwise movement and the choke plate 18 is closed. While the forces exerted by the springs 30 and 74 may be substantial, they may nevertheless bein subis effective on the upper end of the piston 52 to counterbalance the resultant or differential between the springs 3() and 74. Itis of course appreciated that this position of balance is also effected by other variables such for example as the pressure of .the air flowing into the carburetor on the off-center chokeplate.

As the engine continues to run, the choke plate is gradually opened by the expansion of the thermostatic device 50 which forces the rod or plunger 64 down-- wardly so that the ring 65 tends to compress the spring 74. The spring rates of the springs 30 and 74 are so selected that' expansion of the thermally responsive device 50 with resultant compression or further tensioning of the springs 30 and 74 results in a reduction in spring differential or resultant acting on the thermally responsive device 50. Thus, thermal expansion of the device without any increase in manifold vacuum results in further opening movement of the choke plate. However, during this period thermal eiciency of the engine, increases With a resultant increase in manifold vacuum so that an increasing vacuum is present in the cylinder above the piston 52. Thus, the choke plate moves toward open position in a gradual modulated manner in accordance with increase in engine temperature and increase in manifold vacuum.

It will be noted that while the ring 65 acts directly` against the spring 74, it does not act directly to move the thermostatic device 50 upwardly. In the absence of an increased manifold vacuum above the piston, expansion of thedevice is partially absorbed in the thermostatic modulated spring 74. This results in a desirable sensing of engine eciency and slows up opening of the choke plate -as precisely as required.

A bottom of the seat 68 and where some thermalexpanstantial balance so that relatively small forces derived from manifold vacuum may result Vin substantial movement of the thermally responsive-device.

It will be recalled that the passage 58 whichV connects the chamber above the piston to manifold vacuum is substantially unrestricted. On the other hand, the passage 59 which connects the chamber to a source of heated air sion of the device 50 has been indicated. Also, in this igure, the choke plate 18 is illustrated as having opened slightly from the position shown in Figure 4.

During further warm up operation heat is transferred from the chamber in the cylinder above the device 50 to the heat sensitive material 62 in the device with resultant expansion thereof. When the temperature has slightly exceeded that assumed to exist in the arrangement of elements illustrated in Figure 5, the lower end of the rod 64 engages the bottom of the seat 68 as illustrated in Figure 6. At this time further expansion of the device 50 results in direct upward movement of the rod 48 and corresponding counterclockwise rotation of the bell crank 36 until the arm 40 of the choke plate 18 is swung to the position corresponding the full open position of the choke. Thus, when the operating temperature of the engine reaches a predetermined minimum, Vfurther increase in engine temperature results in rapid and direct opening movement of the choke plate. Moreover, it will be observed that so long as the thermostatic device 50 remains at the temperature corresponding to the expanded condition illustrated in Figure 6,V

the choke plate will remain open. In other words, it is impossible for the choke plate to close during a period when the engine is stopped unless and until the temperature of the engine falls below a predetermined degree.

It will also be observed from an inspection of Figure 6 that thermal expansion of the device 50 has resulted in full upward movement of the piston portion 52 thereof to a position in which it shuts otf the restricted passage 61 which admits heated air to the piston,v as well as the part of the passage connected toV engine manifold. In

other words, when the required temperature to accomplish full opening of the choke plate is attained, the thermostatic device is no longer subjected to heat. Thus, it is the maximum temperature to which the thermostatic device is subjected, irrespective of how much higher temperature may be achieved by the engine.

It will also be observed that in the position illustrated in Figure 6 the cylindrical portion 52 of the thermostatic device has engaged the underside of a ring which has associated therewith a sealing gasket 82 and a retainer plate 34. This construction operates as a yieldable abutment for the upper end of the expansible device.

Referring now to Figure 7 there is illustrated a generally equivalent arrangement which differs only in that the thermostatic device S0 is mounted in a flexible diaphragm rather than being movable in a cylinder. In this case the space above the diaphragm 90 is indicated at 92 and is connected to a partially unrestricted passage to engine manifold and a restricted passage to a source of air heated in accordance with engine temperature. The space below the diaphragm 90 is designated at Sirand is of course connected to atmosphere. In this case the bell crank 36 is biased by the coil spring 30 precisely as in the embodiment of the invention previously described7 and the thermostatic device S0 is again urged upwardly by a compression spring 74 acting against the ring 65 fixedly connected to the rod 64. The operation of the construction illustrated in Figure 7 is exactly the same as that illustrated in the preceding gures except that the device is not illustrated as including means for cutting off the ports connecting to manifold vacuum and a source of heated air, although this of course may be accomplished by providing such ports in a position to be closed by engagement of the upper end of the device 50 when it moves to limiting position.

Referring now to Figures 8 and 9 there is illustrated a similar automatic choke system wherein like parts bear the same reference numerals as previously applied and will not be described in detail. rangement is provided which effectively prevents the heated air coming in contact with moving parts of `the system. For this purpose the thermally expansible and contractable device 50 is inverted and its operating rod 64 provided with a turned end to extend into the elongated slot 47 of the bell crank 36.

In this case a casting is provided having a cylindrical portion 102 in which the device 50 is slidable as a piston. Surrounding the cylinder 102 is a jacket space 104 into which heated air is drawn through a restricted y passage 106 extending through a threaded nipple 108. The casting 100 is provided with a removable cap or cover 110 adapted to close the upper end of the space 104, this cover including a passage indicated at 112 adapted to extend to communicate with a passage 114 leading to engine manifold. A port 116 is provided to afford communication between the interior of the cylinder 102 and the jacket space 1043-. As a result of theV foregoing construction engine manifold vacuum is applied to exhaust the space within the cylinder 102 above the piston of the device 50 and also to establish vacuum within the jacket space 104 so as to draw heated air into the jacket space to heat the thermally responsive device 50. Inasmuch as the admittance of heated air is through a calibrated restriction 106, the proportion of engine manifold vacuum applied to eect upward movement of the piston in the cylinder is effectively calibrated. At the same time, contamination or fouling of the interior of the cylinder 102 of the piston of the thermally responsive device 50 is eifectively prevented since the heated air is drawn directly from the jacket space to the passage 112 and does flow into ttc within the cylinder 102.

The casting 100 is provided with an upwardly extending boss 120 which forms a locator for a compression spring 122 urging the device 50 upwardly. At the same In this case an ari 6 time the boss 120 is provided with intersecting drilled passages indicated generally at 124 adapted to admit air under atmospheric pressure to the cylinder 102 below the piston.

The position of the parts illustrated in Figure 8 represents the condition of the automatic choke before starting Wh'en the engine is cold. When the engine is rst started and while it remains cold, manifold vacuum admitted in the cylinder above the thermally responsive device moves the device upwardly, thus opening the choke plate a small amount. The position of the device at this time is determined by the position in which the forces developed by manifold vacuum are sufficient to counterbalance the resultant of the forces of the springs 122 and 30. Further operation of the engine with resultant increase in operating temperature results in expansion of the unit 50 and an increase in manifold vacuum with a resultant gradual small additional opening of the choke plate. When the operating temperature of the engine reaches a predetermined point, the device 50 engages the upper end of the boss 120 which acts as a seat therefor, and further expansion of the device results in direct and relatively rapid opening movement of the choke plate to full open position.

The drawings and the foregoing specification constitute a description of the improved automatic choke system for a carburetor in such full, clear, concise and exact terms as to enable any person skilled in the art to practice the invention, the scope of which is indicated by the appended claims.

What I claim as my invention is:

l. A choke plate in a carburetor for an internal combustion engine, automatic control means for positioning the choke plate in accordance with manifold vacuum and operating temperature of the engine, said control means comprising first means responsive initially to engine manifold vacuum to elect partial opening of said plate when said engine is cold, second means responsive to engine temperature to effect continued opening movement of said plate in accordance with increasing temperature and increasing manifold vacuum, and third means operable upon attainment of a minimum engine temperature to move said plate to full open position and to maintain said plate in full open position so long as said minimum engine temperature prevails, said first means comprising a cylinder, a piston-like device movable in said cylinder and operatively connected to said plate, opposed resilient means connected to said device, and means for connecting said cylinder to engine manifold vacuum, said second means comprising relatively longitudinally movable elements making up said device, substantially incompressible thermally expansible means for effecting relative movement of said elements, and means for heating said expansible means in accordance with engine temperature.

2. A choke plate in a carburetor for an internal combustion engine, automatic control means for positioning the choke plate in accordance with manifold vacuum and operating temperature of the engine, said control means comprising rst means responsive initially to engine manifold vacuum to effect partial opening of said plete when said engine is cold, second means responsive to engine temperature to effect continued opening movement of said plate in accordance with increasing temperature and increasing manifold vacuum, and third means operable upon attainment of a minimum engine temperature to move said plate to full open position and to maintain said plate in full open position so long as said minimum engine temperature prevails, said first means comprising a cylinder, a piston-like device movable in said cylinder and operatively connected to said plate, opposed resilient means connected to said device, and means for connecting said cylinder to engine manifold vacuum, said second means comprising relatively longitudinally movable elements making up said device, substantially incompressible thermally expansible means for effecting relative movement of said elements, and means for heating said expansiblemeans inaccordance withl engine temperature, said third means comprisinga seat engageable by one end of said device to cause further expansion to result in direct plate opening action.

` 3. A choke plate ina carburetor for an internal combustion engine, automatic controlmeans fortpositioning the choke plate in accordance withV manifold vacuum and operating temperature of the engine, said control means comprising a longitudinally thermally expansible and contractable device actuated by the expansion and contraction of confined substantially incompressible material, linkage connecting one end of said device to said choke plate, support means responsive to manifold vacuum for mounting and guiding said device for longitudinal movement, means for connecting said support means to manifold vacuum to develop forces tending to movevsaid device in a direction to move said choke plate to open position, a seat engageable with one end of said device to limit its movement in a direction to close said choke plate, a irst spring operably connected to said one end of said device and effective to oppose movement of said device toward said seat, and a second spring operably connected to said plate and linkage to .oppose opening of said plate and to apply a force'to the said other end of said device. Y

4. A choke plate in a carburetor for an internal combustion engine, automatic control means for positioning the choke plate in accordance with manifold lvacuum and operating temperature of the engine,'said control means comprising a longitudinally thermally expansible and contractable device actuated by the expansion and contraction of conlinedsubstantially incompressible material,V linkage connecting one end of said device to said choke plate, support means responsive to manifold vacuum for mounting and guiding said device for longitudinal movement, means for connecting said support means to manifold vacuum to develop forces tending to move said device in a direction to move said choke plate to open position, a seat engageable with one end of said device to limit its movement in a direction to close said choke plate, a rst spring operably connected to said one end of said device and eiective to oppose movement of said device toward said seat, a second spring operably connected to said plate and linkage to oppose opening of said plate and to apply a force to the said other end of said device, and means for heating said device in accordance With the operating temperature of the engine.

5. A choke plate in a carburetor for an internal combustion engine, automatic control means for positioning the choke plate in accordance with manifold vacuum and operating temperature of the engine, said control meansV comprising a longitudinally thermally expansible and contractable device actuated by the expansion and contraction of confined substantially incompressible material, linkage connecting one end of said device to said choke plate, support means responsive to manifold vacuum for mounting and guiding said` device for longitudinal movement, means for connecting said support means to manifold vacuum to develop forces tending to move said device in a direction to move said choke plate to open position, a seat engageable with one end of said device to limit its movement in a direction to close said choke plate, a first spring operably connected to said one end of said device and effective to oppose movement of said device toward said seat, a second spring operably'connected to said plate and linkage to oppose opening of said plate and to apply a force to the said other end of said device, and means for heating said device kin accordance with the operating temperature of the engine, said support means comprising a vacuum chamber, means for supplying air heated in accordance with engine temperature to said chamber including a restrictiontoow. of heated air so that vacuum WithinY asse-2er? said chamber isarpredetermined diierental of manifold vacuum.

6. Structure as defined in claim 5 in which said device is of cylindrical form, and said vacuum chamber comprises a cylinder in which sai-d device is movable in the manner of a piston.

' 7. Structure as deiined in claim 5 in which said vacuum chamber comprises a flexible diaphragm to which said device is secured.

j 8. A choke plate in a carburetor for an internal combustion engine, automatic control'means for positioning the choke plate in accordance with manifold vacuum and operating temperature of the engine, said control means comprising a longitudinally thermally expansible and contractable device actuated by the expansion and contraction of confined substantially Vincompressible material, linkage connecting one end of said device to said choke plate, support means responsive to manifold vacnum for mounting and guiding said device for longitudinal movement, means for connecting said support means to manifold vacuum to develop forces tending to move said device in a direction to move said choke plate to open position, a seat engageable with one end of said device to limit its movement in a direction to close said choke plate, a first spring operably connected toV said one end of said device and effective to oppose movement of said device toward said seat, means mounting said device for unitary endwise movement, a seat engageable by one end of said device to limit unitary endwise movement thereof in one direction, opposed re silient means operatively connected to said device to apply an endwise compressive force theretoand a resultant endwise force urging said device toward said seat, vacuum responsive means for urging said `device away from said seat, and motion transmitting means connecting v the other end of said device to said choke plate.

9. A choke plate in a carburetor for an internal combustion engine, automatic control means for positioning,

the choke plate in accordance with manifold vacuum and operating temperature of the engine, said control means comprising a longitudinally thermally expansible means to manifold vacuum to develop forces tendingv to move said device in a direction to movesaid choke plate to open position, a seat engageable with one end of said device to limit its movement in a direction to close said choke plate, a iirst spring operably connected to said one end of said device and elective to oppose movement of said device toward said seat, means mounting said device for unitary endwise movement, a seat engageable by one end of said device to limit unitary endwise movement thereof in one direction, an abutment engageable by the other end of said device to limit expansion thereof, opposed resilient means operatively connected to said device to apply an endwise compressive force .thereto and a resultant endwise force urging said device away from said seat, andl motion'transmitting means connecting the other end of said. device to said choke plate.

l0. A choke plate in a carburetorfor an internal com? bustion engine, automatic control means for positioning the choke plate in accordance with manifold vacuum and operating temperature -of the engine, said control means comprising a cylinder, a piston movable in said cylinder, means for connecting one end of said cylinder to manifold vacuum, said piston comprising elements relatively movable axially `upon change in temperature and actuated by the expansion and contraction of confined substantially incompressible material, a seat at oneend of said cylinder engageable with one elementof said piston, a rst spring operatively connected to said piston to oppose movement thereof into said seat, means connecting the other element of said piston to said choke plate, a second spring operatively connected to said choke plate to oppose opening movement thereof and to oppose movement of said piston as a unit by said rst spring, and means connecting said cylinder at opposite ends of said piston to atmosphere and manifold vacuum.

11. A choke plate in a carburetor for an internal combustion engine, automatic control means for positioning the choke plate in accordance with manifold vacuum and operating temperature of the engine, said control means comprising a cylinder, a piston movable in said cylinder, means for connecting one end of said cylinder to manifold vacuum, said piston comprising elements relatively movable axially upon change in temperature and actuated by the expansion and contraction of conned substantially incompressible material, a seat at one end of said cylinder engageable with one element of said piston, a rst spring operatively connected to said piston to oppose movement thereof into said seat, means connecting the other element of said piston to said choke plate, a second spring operatively connected to said choke plate to oppose opening movement thereof and to oppose movement of said piston as a unit by said rst spring, means connecting said cylinder at opposite ends of said piston to atmosphere and manifold vacuum, and means connecting the end of said piston connected to manifold vacuum to a source of air heated in accordance with engine temperature.

12. A choke plate in a carburetor for an internal combustion engine, automatic control means for positioning the choke plate in accordance with manifold vacuum and operating temperature of the engine, said control means comprising a cylinder, a piston movable in said cylinder, means for connecting one end of said cylinder to manifold vacuum, said pistoncomprising elements relatively movable axially upon change in temperature and actuated by the expansion and contraction of contined substantially incompressible material, a seat at one end of said cylinder engageable with one element of said piston, a first spring operatively connected to said piston to oppose movement thereof into said seat, means connecting the other element of said piston to said choke plate, a second spring operatively connected to said choke plate to oppose opening movement thereof and to oppose movement of said piston as a unit by said rst spring, means connecting said cylinder at opposite ends of said piston to atmosphere and manifold vacuum, means connecting the end of said piston connected to manifold vacuum to a source of air heated in accordance with engine temperature, and means restricting the flow of heated air to control the degree of vacuum available in said cylinder.

13. A choke plate in a carburetor for an internal combustion engine, automatic control means for positioning said plate in accordance with manifold vacuum and a temperature condition of the engine, said means comprising a temperature responsive device having relatively movable members actuated by thermal volume change of confined substantially incompressible material, means mounting one of said members for movement of said device as a unit in plate opening and closing directions, rigid linkage connecting the other of said members to said plate, opposed spring means operatively connected to said device to oppose relative motion between its members due to thermal expansion of said material and to bias said device as a unit in plate closing direction, rigid abutment means engageable by said one member upon predetermined relative movement 'between said 'members due to expansion of said material, and means responsive to manifold vacuum for applying a force to said one member in a direction to open said plate.

14. A choke plate in a carburetor for an internal combustion engine, automatic control means for positioning said plate in accordance with manifold vacuum and av temperature condition of the engine, said means comprising a temperature responsive device having relatively movable members actuated by thermal change, means mounting one of said members for movement of said device as a unit in plate opening and closing directions, rigid linkage connecting the other of said members to said plate, opposed spring means operatively connected to said device to oppose relative motion between its members due to thermal expansion of said material and to bias said device as a unit in plate closing direction', rigid abutment means engageable by said one member upon predetermined relative movement between said members due to an increase of temperature, and means responsive to manifold vacuum for applying a force to said one member in a direction to open said plate.

15. A choke plate in a carburetor for an internal combustion engine, automatic control means for positioning said plate in accordance with manifold vacuum and a temperature condition of the engine, said means comprising a temperature responsive device having relatively movable members actuated by thermal change, means mounting one of said members for movement of said device as a unit in plate opening and closing directions, rigid linkage connecting the other of said members to said plate, spring means operatively connected to said device to bias said `device as a unit in plate closing direction, rigid abutment means engageable by said one member upon predetermined relative movement between said members due to thermal change thereof, and means responsive to manifold vacuum for applying a force to said one member in a direction to open said plate.

16. A choke plate in a carburetor for an internal combustion engine, automatic control means for positioning said plate in accordance with manifold vacuum and a temperature condition of the engine, said means comprising a temperature responsive device having relatively movable members actuated by thermal volume change of confined substantially incompressible material, a closed chamber having a movable wall connected to one of said members for moving said device as a unit in plate opening and closing directions, means for subjecting said movable wal1 to differential pressures dependent on engine manifold vacuum, rigid linkage connecting the other of said members to said plate. opposed spring` means operatively connected to said device to oppose relative motion between its members due to thermal expansion of said material and to bias said device as a unit in plate closing direction, rigid abutment means engageable by said one member upon predetermined relative movement between said members due to expansion of said material.

17. A choke plate in a carburetor for an internal combustion engine, automatic control means for positioning said plate in accordance with manifold vacuum and a temperature condition of the engine, said means comprising a temperature responsive device having relatively movable members actuated by thermal change, means for subjecting said device to an engine temperature, means responsive to engine manifold vacuum mounting one member of said device for movement of said device as a unit in plate opening and closing direction and operable to apply plate opening forces to said one member dependent on manifold vacuum, resilient means urging said device as a unit in plate closing direction, means connecting the other member of said device to said plate, and abutment means limiting movement of said one member in plate closing direction.

18. A choke plate in a carburetor for an internal combustion engine, automatic control means for positioning said plate in accordance with manifold vacuum and a temperature condition of the engine, said means comprising a temperature responsive device having relatively movable members actuated by thermal change, means for subjecting said device to an engine temperature, means responsive to engine manifold Vacuum mounting one member of said device for movement of said device as a unit in plate opening and closing direction and operable to apply plate opening forces to said one member dependent on manifold vacuum, resilient means urging said device as a unit in late closing direction, rigid linkage connecting the other member of said device to said plate, and abutment means limiting movement of said one member in plate closing direction.

References Cited in the file of this patent UNITED 'STATES PATENTS Smith Apr. 28, 1942 Jorgensen etal; Apr. 5, 1955 Boyce Aug. 16, 1955 Schaer et al. Dec. 18, 1956Y

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