GB2180006A - Automatic/manual choke conversion - Google Patents

Abstract

A kit is provided to convert an automatic choke carburettor to manual operation. The kit may be used with different carburettors, the differences being in respect of the direction of movement of the choke pin 48, i.e. clockwise or anti-clockwise, the radial spacing of the pin about its centre of movement, the diameter of the pin, the angular relationship of the parts relative to the vehicle parts, and even different diameters of the generally tubular body to which the kit is to be fixed. In Figure 3 a part 44 can engage with the choke pin 48 in either of the two illustrated positions, the part 44 making contact with the pin at any of a range of positions spaced along a radius from the turning centre 74, and being spring loaded for turning either clockwise or anti-clockwise. Body part 12 has flutes 20 to enable it to be mounted (by screws 22) in the most appropriate orientation on the carburettor body. <IMAGE>

Description

SPECIFICATION Automatic/manual choke conversion This invention relates to a choke controls for i.c. en gine carburettors.

Many motorcars are today fitted with automatic choke controls which usually have a chamberwith a waterjacket connected to the engine cooled system, and/orcontaining an electrically heated element,the chamber housing containing a pin which is coupled to a bi-metal spring so that temperature variation in the chambercausesthe spring to displacethe pin, and that pin is connected through appropriate mechanism to the choke. The effect is intended to be that when the engine is cold, maximum choke is applied, and as the engine warms up and hencethecoolant temperature increases, the choke effect is reduced down to zero beyond a predetermined temperature.

These arrangements are sometimes unreliable with newvehicles and/or ones which are well maintained, but become increasingly unsatisfactory with older and less well maintained vehicles especially as parts wear. Problems then arise with starting the engine, and with heavy fuel consu m ption . There is consequ- entlyan existing well established trade in the manufacture and supply of conversion kits allowing the choke actuating pin to be displaced manually, usually by a Bowden cable after removing thewater jacket. The disadvantage with these arrangements is simplythatalmosteach design ofcarburettorand each different model of vehicle requires a different conversation kit.This is because ofthe different parameters involved making one kituniqueto a particular situation. The object of the invention is to provide a more versatile kit capable of use with at least a plurality of different carburettors and/or vehicles.

According to a first aspect of the invention, a conversion kit comprises a spool connectibleto a Bowden cable or likeforturning the spool, and an arm for engagement with the choke actuating pin of a carburettor, characterised in that the arm includes an abutment surface extending generally radially from a pivotofthearmforcontactingthe pin at any of a number of positions along the length ofthe abut ment surface according to the radial distance of the axis ofthe pin from the pivotal axis of the pin. By these means a firstvariablefrom one design to anothercan be accommodated, namely the provision of pins at different radial distances from the pivotal axis.

Preferably the pin is made captive to the arm by the tail of a spring wound about the pivot ofthe arm,the tail extending generally parallel with said abutment surface, wherebythe pin can be arm actuated in one direction and spring displaced in the opposite direction.

Preferably a pair of radiating arms is provided and said spring is a torsion spring having coils would about said pivot and with one tail engaged with one ofthe arms and the otherfor engaging the choke actuating pin. According to a feature ofthe invention the spring is symmetrical and this meansthatone arm and one tail ofthe spring will be used ifthe pin has to be actuated in one direction e.g. clockwise, and vice verse where the choke actuating pin has to be turned in the opposite direction that is counter clockwise. Bythese means in combination the use of pins at different radial distances and moved in different directions can be accommodated.

Said abutment surface may lie parallel to a radius from a centre of rotation of the spool, the spacing re lative to that radius being equal to the expected radial dimension of the pin.

In some cases a pin extension may be provided to effectively lengthen the pin, and such extensionswill be co-axial with the pin.

Preferably the arm, or each of the arms if more than one is provided, have a recess receiving an extremity ofthetail ofthe spring so that the choke actuating pin is trapped between the arm and spring and the extremity ofthe tail enters the recess and bythese means the invention can accommodate pins of differentactual diameter.

The Bowden cable may enter the structure ofthe conversion kit generally tangentially via a guide part having alternative cable paths so as to accommodate one and the same kit for use with carburettors where the pin is turned in opposite directionsforactuation, i.e. the clockwise and anticlockwise cases, and variations in the possible angle through which the arm can beturned, corresponding to the total angular movement between minimum and maximum choke positions can be provided by presetting one extreme position of movement ofthe arm relative to a fixed stop provided in the structure ofthe conversion.In general,a movementofl80'lesssuchangulardim- ension as corresponds to the width of the stop components can be provided, and hence the normal maximum movement of about 1 10" presents no problem.

Usually the automatic choke structure is held in position by a loose ring disposed aboutthe body of the chamber housing the bi-metal spring, with (usually) three screws spaced around the periphery ofthe ring. That ring is detachable after removing the water jacket and/or electrical connections. According to a furtherfeature ofthe invention, the same ring (or one providing the same facility) is used to attach the con- version kit in position, and to this end, the body ofthe conversion kitwhich is used asasubstituteforthe spring accommodating chamber may be provided with a series of stepped diameterflanges, so that the ring can locate the body co-axially, seating on a part icularone ofthe steps according to the actual diame ter of the ring which is either employed with one and the same body or provides the same facility.

To accommodate for the variation in pitch circle diameter containing the axes of the screws from one design to another, the larger of the flanges on the kit body may have a series of parallel flutesthrough which the screws can pass. This gives rise to a further adjustability feature to suit requirements, for if there are say 18 flutes provided, effectively the body ofthe kit can be indexed through 20 angle steps in orderto turn the Bowden cable entry point to a required position in relation to the surrounding structureforpur- poses which will be plain to those skilled in the art from the foregoing discussion.

According to yet anotherfeature ofthe invention, the partcarrying the arm which is to engage with the choke actuating pin is connected to the spool which is turned by the Bowden cable by way of a screw and nut allowing infinitevariation inthe part positions.

Furtherfeatures of the invention will become apparent from a description of a presently preferred embodimentwith reference to the accompanying drawings wherein Figure lisa sectional electation of a conversion kit; Figure2 is a sectional plan of the same taken on the line 2 2 of Figure 1; Figure 3 is a further sectional plan taken on the line 3-3 of Figure 1.

The conversion kit shown in the drawings is designed to be usable with all ofthe different models of automatic choke carburettor at present in reasonably widespread use in Europe as known to the invention (some 13 different designs).

Referring to the drawings, the kit includes an adap tor(notshown) and/or a base plate 10which is used as an intermediate member with only certain ofthe carburettors and is not required with others. The base plate loins apertured to allow the choke actuating pin (notshown in Figure 1)to projectthrough.

The kit comprises a main adapter body 12 which is of a suitable diameterto fit inside the corresponding and complementary part of the carbutettorwith flange 1 4seating on the carburettor. The body has a series of steps 16 to accommodate a loose ring 18 which is intended to be the one originally provided attaching the automatic choke chamber in place or one providing the same facility, and it will be app reciatedthatthering 18 will seat on an appropriate one ofthe steps according to which ofthe rings is used. The ring will automatically centre and locate the body part 12.

As best seen in Figure 2, the body part is provided with a series offlutes 20sothatthe shanks of attach ment screws 22 (Figure 1) can project through app- ropriate flutes to engage in the taped hoies provided in the carburettor body. It will be appreciated that a particularly large diameter ring seating on the largest ofthe steps will involve the screws being clear of the flutes, in which case the construction allows the body 12 to be turned within the ring to any desired position. With the smaller diameter steps, and the screws passing through the flutes, the flutes permit the body to be relocated at approximately 20 intervals because there are 18flutes.

The adapter body 12 is engaged with a cable anchor housing 15 by means ofinturned lugs 24 provided on the part 12 and like lugs 25 on the part 15, these lugs interdigitating and fitting (axially) on either side of a circlip 26 which engages under each ofthese lugs, that is to say below the adapter lugs seen in Figure 1 but above the lugs provided on the housing,to hold the parts togetherwithoutthe nec- essity of using screws.

Generally axially extending through the assembly is a main pivot comprising a lower portion 30 which carries the pin actuating arm (discussed later herein) and an upper portion 32which isjournalled inthe adapter housing and supports the spool.

The arm is best seen in Figure 3 and is symmetrical about the plane PP. On each side ofthe plane there is an actuating arm 44 havintg an actuating face 46to contact the choke actuating pin 48. Figure 3 shows two pins 48, but only one is present according to the model carburettor. Wound about part 30 is the torsion spring 50 which is also symmetrical about the plane PP. On each side of the plane it has a tail 52, one of which abuts the choke actuating pOin 48 and has its extremety bent generally at a right angle to enterthe recess slot 54, and the other tamil contacts the other arm as an abutment stop.

Itwill be seen from Figure 3 thatwhicheverwaythe arm is turned, according to which arm contacts the pin, that the spring and arm are effective to provide pin displacement and return. In one direction the arm acting on the tail, opposite to that which is pin engaged winds up the spring so that the othertail displaces the pin, and spring return caused the arm to return the pin.

It will be noted from Figure 2 that the Bowden inner wire is led around the major proportion of the periphery of the spool 60, and is clamped in place by the socket screw 68 with the extreme end of the wire 70 extending diametrical Iy in the spool . The spool is made fast with the pivot by screw 74 engaged in a nut 76 held bythe shape in a complementary socket in the part 30 (Figure 1). Astop shoulder 72 limits move mentofthespool and hencethemaximum angular movement of the choke actuating pin.

Asecondtorsion spring 78 has onetail engaged in the spool at 80 and the other in the cable anchor housing at 82 to return the spool against one angular limit stop.

The adjustments which are possible are as follows: 1. Direction of movement of choke pin, clockwise or anticlockwise by engagement with one or other arm 44, and routeing the cable through one or other guide in the cable anchor housing, with possible reversal of the spool return spring 78.

2. Radial spacing of the pin, by location at different positions along the arm 44.

3. Different diameters of pin, by relative angular movement of arm 44 and the appropriate tail 52.

4. Different loose ring diameters for attachmentvia the stepped body.

5. Different angular relationship ofthe parts by the rotatability of the body in the loose ring, and the infinite adjustability of the spool and cable relative to the arms via screw 74.

6. Different angular relationship ofthe cable to the arms by rotating the whole of the cable anchor housing.

Claims (16)

1. Aconversion kitforconverting an automatic choke carburettor to a manual choke carburettor comprising a spool connectibleto a Bowden cable or likeforturning the spool, and an arm for engagement with the choke actuating pin of a carburettor, characterised in that the arm includes an abutment surface extending generally radially from a pivot ofthe arm for contacting the pin at any of a number of positions along the length of the abutment surface according to the radial distance ofthe axis of the pin from the pivotal axis ofthe pin.

2. A kit as claimed in claim 1 wherein said generally radial abutment surface lies parallel to a radius from a centre of rotation ofthe spool.

3. A kit according to claim 1 wherein an extension is provided forthe pin which is coaxial tothe pin.

4. A kit as claimed in any of claims 1 wherein the pin is made captive to the arm bythetail of a spring wound about the pivot ofthe arm.

5. A kit as claimed in claim 4wherein thetail of the spring extends generally parallel to the abutment surface and the pin can be arm actuated in one direction and spring displaced in the opposite direction.

6. A kit as claimed in claims 4 or 5 wherein the abutment surface is provided with a recess to receive a portion ofthe spring.

7. A kit as claimed in any of claims 1 to 6wherein a pair of radiating arms is provided and said spring is atorsion spring having coils wound about the pivot with one tail engaged with one ofthe arms and the otherforengaging the choke actuating pin.

8. A kit according to claim 7 wherein the spring is symmetrical.

9. A kit as claimed in any preceding claim provided with a guide part having alternative cable paths so that said Bowden cable may extend generallytan gentially and when the Bowden innercable isten- sioned the arm will be moved clockwise or anticlockwise according to which of the alternative paths is occupied by said cable.

10. A kit as claimed in claim 9wherein a stop is provided to limit maximum angular movement of said arm.

11. A kit as claimed in any preceding claim wherein the structure of the kit is arranged to be held in position by a loose ring disposed about a body housing the parts.

12. A kit as claimed in claim wherein said body is provided with a series of stepped diameterfianges.

13. A kit as claimed in claim 11 wherein the largest of the flanges on the kit body has a series of parallel flutes through which attachment screws can pass.

14. A kit as claimed in any preceding claim wherein the spool is connected to the arm by a screw and nut allowing angularvariation between the parts.

15. A kit as claimed in claim 11 wherein the body comprises an outer part and an inner part, both of which are provided with generally radially extending lugs, and the parts are held together by a circlip located between the abutting said lugs.

16. A kit substantially as described with reference to the accompanying drawings.