NO784387L - CARBURETOR COMPONENTS AND CARBURETOR - Google Patents

Description

Carburettor.

The present invention relates to carburettors and the main purpose of the invention is to improve the fine distribution

of the fuel and its mixture with the air, so that the fuel and air are evenly distributed to all cylinders in a multi-cylinder engine.

When an internal combustion engine operates with a mixture ratio that is on the lean side of the stoichiometric value, the content of NOX, HC and CO in the engine's exhaust gases is reduced.

As these components are usually considered to be the most harmful, it is desirable for air pollution reasons that the engine works with a lean mixture. However, this causes the engine to become more susceptible to deviations from an even distribution of the fuel and air. When a carbureted engine is tuned for a fuel-air ratio that is significantly leaner than the stoichiometric value, some cylinders will get such a lean mixture that after-ignition occurs.

The root of this problem is insufficient breakdown and distribution of the fuel in the carburettor. Part of the fuel, which is not sufficiently distributed in the air through the carburettor, can follow different paths along the inner walls of the carburettor and, with different settings of the throttle, tend to go only to some of the cylinders, which will then work with a richer mixture on the others the cost of the cylinders. The difficulties encountered in solving this problem are illustrated by the very large number of different carburetor designs that have seen the light of day in connection with attempts to achieve a more even fuel distribution..That the problem is not. solved in an acceptable way, is evident from the fact that the car industry often switches to a newer carburettor design and that the insignificant older ones are completely abandoned. It must therefore already be emphasized here that the improved operating conditions that can be achieved with the invention, with smooth engine running, low emission values, lean mixture ratios without the risk of after-ignition, and optimal fuel economy, are surprising and unexpected. An experimental car, which had a conventional engine, fitted with a carburettor according to the invention, was shown

to meet the requirements for the maximum permissible content of harmful components in the exhaust gases set by the government of the United States and by the state government of California, without the need for catalytic converters or other regulatory devices.

A carburettor according to the invention has a carburettor passage with an upstream air valve and a downstream of this arranged throttle, whereby a fuel exhaustion zone is formed between these two. The air valve is provided with fuel leaching openings that open into the zone. The air valve, or air damper, is normally held in a closed position by suitable biasing means, but opens more or less under the influence of the air flow through the air damper. This also varies the supplied amount of fuel.

When the fuel discharge openings are located on the surface of the air damper, the movements of these orifices and the air damper can be coordinated, whereby it becomes possible at all times to

feed the fuel out within the area where the air velocity is highest. This implies a difference compared to known carburetors with variable venturi tubes, which have fixed fuel distribution devices in the zone between the air damper and the throttle, through which the fuel under certain conditions, for example when idling, will be introduced into an area with relatively low air velocity.

According to a preferred embodiment of the invention, the air damper contains a distribution channel which extends along or close to one of the edges of the damper, past which the air flow passes. The fuel outlet openings can then be distributed along the edge surface and each one be connected to the distribution channel. Preferably, such mouths are found along a significant part of the total length of the edge, so that fuel is introduced across practically the entire air flow. The fuel goes to the aforementioned channel through passages in the air damper and through its shaft.

The air damper itself can be cast in plastic, as is the case here

a preferred construction material. The damper can then be designed

in two halves, the whole or part of the cross-section of the respective mouths, channels and passages being located on the inside of one half, while the rest is located on the inside of the other half. This makes it possible to avoid expensive drilling work and to produce air dampers with such internal passages, even when the dampers are curved or have other irregular shapes.

In a multi-layer damper of the type just mentioned, the problem in connection with achieving effective sealing between the various passages can be suitably solved by providing at least some of them with internal casings. Such a casing can be connected to a side opening in a hollow shaft that carries the air damper, and can extend from the shaft to the distribution channel.

When the fuel discharge openings are arranged in the edge of the air damper, this should be provided with shallow grooves, which mainly extend in the direction of the air flow. The local increases in the air flow that occur at these tracks will counteract any tendencies towards variations along the damper edge.

You can also provide the damper edge with a groove that extends approximately at right angles to the direction of the air flow and is located next to the upstream side of the damper. With such a design, the turbulence over the edge is increased and the air is concentrated

to the first-mentioned grooves and/or a pressure difference is provided between the air that passes along the upper side of the damper and the air that flows between the air damper and the throttle.

It is known to protect air dampers in carburettors with a variable venturi tube against re-ignition by making openings in the air damper and arranging a flexible flap valve on the upstream side. This flap acts as a non-return valve which remains closed under normal operating conditions and opens and thereby diverts the internal excess pressure in the carburettor during re-ignition. A carburettor according to the invention can be provided with such a flap valve and with several elongated, mainly parallel slots. This gives you a large open area when the flap is open, without the flexible flap having to span a large opening, as is the case when the damper has large circular holes. The slits reduce or completely eliminate the risk of the flap being deformed,

with associated leakage. The result is improved operating conditions.

Regardless of how these protective openings in

in the damper design, it is appropriate to hold the flap firmly using a spring clamp, which is mainly C-shaped.

Sometimes it is desirable to use a damper body that is curved, seen from the side. If such a damper is to be provided with protection against kickback, it is advantageous to cast the flap in a flexible material and to adapt the underside to the contour of the oyer side of the damper body.

The aforementioned biasing means can be of any suitable type and can for example consist of a counterweight, an air spring, a torsion bar, a spiral spring, etc. The biasing means should appropriately be located between the upper side of the air damper and an attachment point higher up. Preferably used

a spring which can be connected to the air damper, either directly or indirectly, via suitable connecting means, for example a tie rod, connected to a swing arm on the damper. This swing arm moves between two vertical planes when the damper moves from the closed to the open position. The drawbar's upper end is attached to a movable upper pivot pin which is arranged in such a way that it can move up and down in the space between the two mentioned vertical planes. This upper pivot pin should be appropriately arranged so that when the air damper is turned from the closed to the open position, the tie rod must be pivoted from a position in which it is inclined to the left of the vertical plane, through the vertical plane, and to a position in which it leans to the right. Alternatively, the drawbar can swing from right to left. According to a particularly preferred embodiment, the upper pivot pin is located on a movable member which can perform a reciprocating movement on a vertical pin above the damper. The spring can be a compression or a tension spring and in the latter case the spring can be connected between the movable member and an upper attachment point...

Optionally, the carburettor can be provided with a device which determines the position to which the air damper moves in the closing direction under the influence of the biasing member. In its rest position, the air damper is slightly open, so that sufficient air and fuel for idling can pass. A carburettor according to the invention does not need to be supplied with a choke, but if this is missing, the construction should be made so that the air damper can take a completely closed position when the engine is to be started. A corresponding device then keeps the air damper slightly open when idling and completely closed when the engine is switched off or turned over by the starter motor. Such a device can also limit the position of the air damper, so that it closes to the same idle position regardless of whether it closes quickly or slowly.

The position-determining device may include a moveable stop member which can be moved between a first position, in which it prevents the air damper from closing past the idle position, and a second position, in which it is moved away, so that the biasing member can close the air damper more. complete. This stop means can either affect the air damper led directly, by entering its path of movement, or - which is preferred - indirectly, by affecting the biasing means and preventing it from closing the air damper past the idle position. The stop device can be maneuvered manually or mechanically, for example affected by the choke, by a spring and solenoid, by a pneumatic motor, etc.

Any suitable fuel portioning system can be used, but preferably a system according to US patent document no. 3 7 52 4 51 is used. This system is improved and adapted to the carburettor according to the invention.

A preferred embodiment of the fuel portioning system operates with a rotatable arm, the free end of which cooperates with a ramp or cam surface. Furthermore, a hollow shaft is included, which constitutes the air damper's pivot shaft and is connected partly with the inside of the damper, partly with a fuel chamber, in which the arm is connected to the hollow shaft. The ramp is located inside the fuel chamber and helps to regulate the flow of fuel from there into a bore in the arm, from where the fuel continues via the hollow shaft to the outlet openings on the air damper.

As already mentioned, the device just described, which is known in and of itself, can be improved by applying the invention. The improvement may concern the arm, the comb surface or both.

The fuel portioning system of the type just mentioned is often criticized because the large machining costs required to achieve sufficient accuracy in the gap between the free end of the fuel capture arm and the cam surface.

Deviations as small as 0.005 mm from the nominal value can cause incorrect mixture control at idle. However, the invention improves the system by reducing the tolerance requirements, which is done by means of a spring-loaded ball at the free end of the arm. The ball is in rolling contact with the edge surface where organs are arranged that limit the ball's lateral movements.

The most recently described construction can also be used with other carburettor types. than according to the invention and the same applies to the improvement of the comb surface made here. Known carburetors with a fuel portioning system of the type discussed here have a common wall between the carburetor passage and fuel. the chamber, which wall extends from the cam surface to the shaft that carries the fuel arm. If the arm and this wall expand to different degrees due to heat, the clearance between the arm and the ramp is affected. To compensate for these differences, the ramp's fastening means can be carried by the same axle as the arm.

By choosing material with suitable coefficients of thermal expansion for the arm's and ramp's suspension means, it is possible either to control the temperature-related changes in clearance size in the desired way or to minimize the changes, for example you want a fatter fuel mixture, when the engine and carburettor are cold, and a leaner fuel mixture when hot, a fuel arm with a higher coefficient of thermal expansion than the material in the ramp's suspension member can be chosen. One way to do this is to make the arm in series-connected segments of plastic and metal. Alternatively, a longer fuel arm can be used, which consists entirely of metal, while the suspension member consists of a material with a significantly lower expansion coefficient, for example invar. The arm can then be made of steel or aluminium. Any material combination that reduces clearance at high temperatures and increases it at low temperatures is appropriate. Alternatively, one can choose material that tends to keep the clearance constant regardless of the temperature and thereby rely on other devices to facilitate starting the engine, for example the position-determining device for the air damper described above or a fuel enrichment device, which will be described below.

As already mentioned, the carburettor passage and the fuel chamber are often separated by a common wall. Pulsations in the fuel-air mixture, which from the intake pipe propagate backwards to the carburettor, can transfer heat through this wall to the suspension member of the ramp. If the ramp is in contact with the wall and the fuel arm is not, this can cause the ramp to become hotter than the arm during the engine's warm-up period. This causes the clearance between arm and ramp to change successively. According to a characteristic of the invention, the suspension member of the ramp is further into the fuel chamber counted from the wall, so that liquid fuel can pass between the wall and the suspension member. The circulating fuel can then keep the suspension member at essentially the same temperature as the arm.

According to another characteristic of the invention, a special fuel enrichment system is used when starting the engine. This includes a line extending from a fuel reservoir to a fuel enrichment port in the intake manifold. The fuel supply can, for example, be made up of the fuel in the fuel chamber, which contains an arm and ramp, a conventional fuel valve and a float for level regulation. The port can be in the intake line between the air damper and the throttle or elsewhere, which will be described in more detail below.

According to a particularly preferred embodiment, it is

in series with the aforementioned shut-off valve arranged a needle valve and a throttle opening for regulating the maximum flow of the enrichment fuel to the port. The line up to this can be ventilated when enrichment is not to take place. However, it is even better to use both the shut-off valve and the needle valve in a hollow, cylindrical detail, the aforementioned opening being located at one end of the cylinder.

Regardless of which type of shut-off valve is used, the needle valve can be made of a plastic material or of another material with a relatively high thermal expansion coefficient, so that the needle and mouth together react to temperature changes. At higher temperatures, when the needle has expanded in the longitudinal direction, the pre-set clearance between the needle and the mouth will therefore be reduced, whereby the available amount of enrichment fuel is automatically reduced. The opposite applies that when the engine is cold and the needle valve is shortened, the distance between the needle and the mouth will be greater, so that enrichment fuel is available.

The throttle can be made in a number of different ways, but should preferably be arranged and designed in such a way that, regardless of whether the throttle is open or closed, its upper limiting surface will be inclined sufficiently so that fuel can flow off it. Eddy currents that form downstream of the air damper tend to retain liquid fuel on the upper side of the throttle. The slope should therefore be sufficiently large to overcome the impact of these eddy currents, either alone or in combination with other measures. Such a measure, which is based on deliberate air leakage, is described in more detail below.

Certain advantages can be achieved if the throttle has

a vaulted underside, which is largely located at a constant radial distance from the damper's axis of rotation. It then becomes easier to seal between the underside and nearby parts of the carburettor housing. Has the throttle parallel ends, which is

perpendicular to the axis of rotation, the maintenance of the seal between these ends and the carburettor housing is facilitated. When the base is arranged radially in relation to the throttle shaft and the ends are perpendicular to it, the achievement of sealing is facilitated both at the base and at the ends and it is particularly appropriate to have a continuous sealing body in contact with these ends, the base and the carburettor housing. This is particularly advantageous when the carburettor housing is molded in plastic, after which a lip seal can then be arranged in a groove in the housing, which seal rests against the ends of the damper and the underside at the edge of the carburettor passage.

The throttle can be hollow or homogeneous. When its underside is corrugated as mentioned above, it may have an open or closed back, which is on one side of the said seal, whereby the upper side, the ends and the radial underside are all held together air-tight on the opposite side of the seal. The area of the back side should at least approximately match the top side. Assuming that the pressure on the top and back side is substantially the same, the resulting forces attempting to turn the damper clockwise and counterclockwise will be substantially balanced. When the damper is hollow and its back side is open, these pressure forces will affect the upper side and the bottom, which form the upper side of the damper. An open back also reduces the damper's weight and facilitates molding of the damper in plastic material.

When the throttle has a corrugated underside as mentioned above, it is appropriate to arrange a lip in the transition between the upper and lower sides. This lip can, for example, be made up of an interruption in the curved underside, which forms an undercut at this edge of the upper side past which the air flows. The presence of such a lip also facilitates the removal of liquid fuel, which may flow along, the upper side of the damper, from the damper, so that such fuel does not flow down along the curved underside. If this is undercut below the lip, so that the tip of the lip is mainly located on or within the projected circular arc of the underside, then it is possible to avoid unbalance e-forces that would otherwise attempt to spontaneously open the damper.

If the upper edge of the lip is curved, this can help to reduce noise by reducing or eliminating pulsations and turbulence in the intake pipe.

The air damper and the throttle can be carried by axles, as the air damper's shaft can be located outside the throttle. With reference to a vertical line roughly midway through the area through which the intake air flows, when both dampers are fully open, these relative positions can be described so that the shaft of the air damper is at a greater horizontal distance from the reference line than the shaft of the throttle is. This offers several advantages. Thus, for example, it becomes easier to construct the shaft bearing for both damper shafts. without the air damper's shaft needing to be placed so high above the throttle or so far in that the air damper would reduce the available area in the carburettor passage. If the throttle shaft is placed inside the air damper, the horizontal space requirement for the throttle is reduced, so that the transverse dimension of the carburettor housing can be reduced. Such a location also means that the throttle is less exposed to pressure waves during kickback with a corresponding reduction in the forces which then affect the throttle shaft and the rest of the structure. Less force is required to open the throttle and overcome the difference between the suction force and the pressure on the upstream side of the throttle. The damper shafts are subjected to minor stresses. If the air damper's biasing device includes swing arms (the draw rods mentioned above), then a certain change in the angle between these rods and the top of the damper occurs when the damper moves from the closed to the open position. This angle change affects the force vector that the biasing member exerts on the air damper. When its shaft is outside the throttle shaft, the air damper can be fitted with a longer arm,

which in turn reduces the just mentioned angle change.

From what has been said above, it should be concluded that the outward displacement of the air damper's shaft provides certain advantages, which can occur regardless of the type of biasing means used, and that a further advantage is achieved when such a position of the shaft is used in combination with f pre-tensioning means which include pivotable drawbars, and vertically movable suspension means.

When using offset damper shafts, the air damper, seen in side view, should have a vaulted or bent shape, so that this damper extends over the throttle shaft and down into the carburettor passage when both dampers are open. The air damper can, for example, have a gooseneck-shaped profile. This reduces the space that must be found between the underside of the air damper and the upper side of the gas damper when both dampers are closed, as the air damper can rest against the upper side of the throttle when both dampers are fully open, whereby the reduction in area is minimal.

Regardless of where the air damper shaft is located, it is often appropriate to make both dampers in a plastic material and to provide their pivot shafts with button-shaped extensions. These extensions can, for example, be around bores in the dampers, through which the shafts pass. According to a preferred embodiment, the carburettor has such an extension on the throttle and a nearby one on the air damper, whereby there is a small clearance between the bores. This clearance is sufficiently small to direct the main part of the air flow

around the edge of the air damper instead of around the expansion, but large enough to allow some of the air to pass

around the extension above the upper side of the throttle, whereby fuel is removed from there in the manner described above. The clearance can also be eliminated by means of seals on one or both of the extensions. Such sealing means can be arranged so that they move towards or away from the sealing contact depending on whether the engine is stationary or running. The seal can, for example, be located on one of the extensions in the main case parallel to the shaft, so that the seal comes into contact with the opposite extension when the throttle and air damper are closed, and is released from it when the dampers are opened, so that no friction occurs.

Each of the two dampers can consist of one or more movable members. The air damper can consist of a single body, which cooperates with a nearby part of the carburettor housing, but it can also consist of several damper members, which either cooperate with each other or with one or more parts of the carburettor housing or both. The same applies to the throttle.

When using such split dampers, the movements of the various parts should be synchronised. This can be done with the help of various machine elements known within carburettor technology, for example gears, chains or wires. In carburettors with a split air damper, these synchronizing devices can advantageously also form the biasing devices. As the latter include a vertically movable detail and tie rods as mentioned above, the upper joint points for the tie rods for each such air damper part can be on one and the same movable detail and therefore move synchronously. According to a preferred embodiment, the synchronizing device for the parts of the throttle may consist of a joint system which reverses the direction of rotation and which has an arm on a first throttle shaft, a crank arm on the second throttle shaft and a coupling link which is arranged so that when the crank arm moves in one direction, then the lever arm moves in the opposite direction. Such a joint system cannot keep the dampers synchronized over the entire movement range, but works satisfactorily if it is adjusted so that the dampers are in phase in the closed position.

In carburettors with several air dampers and throttles, each damper member can have its own pivot shaft, which shafts should ideally be located at the edges of and/or outside the curved plane which corresponds to an upward projection of the contour line to the outlet of the intake passage.

The intake passage can be divided into two branches by means of a vertical partition. Each branch contains air dampers and throttles, the axes of which lie in planes that are parallel to those of the partition.

When there is such an intermediate wall, it is appropriate to let the ends of the individual parts of the throttle, set in the closed position, extend below And close to the lower edge of the intermediate wall. The advantage here is that an axial flow quantity is then maintained even if the dampers do not open and close exactly synchronously. Such a design makes the setting of the joint mechanism between the two throttles more critical and reduces or eliminates the risk of impact through back suction on the air dampers, which impact could otherwise amplify any differences in the fuel flow between the two branches.

Another construction, which can be used when the carburettor has an intermediate wall and separate air dampers in the branches on both sides of this, means that each air damper member is supplied with a separate fuel portioning system. This makes it possible to introduce a coal-hydrogen-containing fuel into both carburettor passages or also only into one, while alcohol is introduced into the other. In the latter case, the peak value is reduced by. the engine's combustion temperature, so that the content of N0X in the exhaust gases is greatly reduced or essentially eliminated.

The invention shall be described in more detail with reference to the exemplary embodiments shown in the drawings.

The drawings show

fig. 1 a vertical section, perpendicular to the throttle axis, of a single carburettor,

fig. 2 corresponds to fig. 1, but shows a dual carburettor,

fig. 3 shows a perspective view of a carburettor which is considered to be the best embodiment,

fig. 4 shows the carburettor according to fig. 3 seen in perspective and viewed from the same direction, but with the lid, the fuel-port ionization system, the air dampers, their biasing devices and the dampers removed, while at the same time part of the carburettor housing is left out so that the internal construction can be seen,

fig. 5 shows an exploded perspective view of one of the air valves in the carburettor according to fig. 3,

fig. 6 shows in a perspective view details of the dampers, certain other details being indicated by dashed lines,

fig. 7 shows on a larger scale one of the air dampers according to fig. 6,

fig. 8 shows on a larger scale and in a perspective view part of the carburettor's cover, the air damper and its biasing means according to the design in fig. 3,

fig. 9 shows a section along the line 9-9 in fig. 8,

fig. 10 shows a partially exploded perspective view of the device according to fig. 3 and shows the detailed construction of the air damper, the fuel portioning system and associated connecting device,

fig. 11, which corresponds to a part of fig. 2, shows the air damper and throttle in the positions they take at idle,

fig. 12 shows the fuel lever in fig. 10 seen from the side,

fig. 13 shows a cross-section through the lower end of the fuel arm,

fig. 14 shows a section along the line 14-14 in fig.

13,

fig. 15 schematically shows the construction of a conventional fuel priming system with swing arm and ramp,

fig. 16 shows a longitudinal section through the lower end of a fuel arm with associated ramp in the embodiment shown in fig. 10, 12, 13 and 14,

the curves in fig. 17 shows the difference between the systems according to fig. 15 and 16 regarding the sensitivity to deviations in the dimensions of the ramp,

fig. 18 shows on a larger scale and in perspective the part of fig. 4 which contains the float chamber with floats, fuel valves, fuel arms and ramps,

fig. 19 shows part of fig. 2 with the addition of tet-.' ning devices at the damper ends,

fig. 20 shows a perspective view of some details of the carburettor in fig. 3,

fig. 21 shows a principle core for a fuel enrichment system,

fig. 22 shows a partially exploded perspective view

of the fuel enrichment system in the carburettor according to fig. 3, and

fig. 23 shows a section along the line 23-23 in fig.22.

The carburettor in fig. 1 has a housing 1 with a lid 3 and an intermediate gasket 2. The lid has an inlet opening 4

and a flange 5 for mounting an air filter, not shown. The inlet 4 leads to a carburettor passage 6 which extends around the carburettor housing to an outlet 7 which is connected to the engine's

intake pipe.

An air damper 11 is arranged in the upper part of the passage 6. This can be of any suitable shape. However, it appropriately has a thickening 12 and a main part thus made in one piece with an upper side 15, a lower side 16, an end surface 14 and a single edge 21.

The air damper has fuel discharge openings and passages for the transport of fuel to these openings, which can for example be located on separate pipelines which are attached to the damper itself. Alternatively, the openings can be taken out in the damper body itself. In fig. 1, the openings 22 are arranged in the edge part 21 and communicate with a trunk line 23 which is supplied with fuel through a passage 24, which is likewise arranged inside the damper.

The air damper is carried by a shaft 25. The shaft enters an opening 13 which extends through the thickening 12. This shaft is suspended in the wall 8 and in the opposite wall of the carburettor housing, not shown. At least one end of the shaft 25 can be permanently stored in the wall and has . an internal bore 26 which communicates partly with an external fuel source, partly with the passage 24.

Between the two mentioned walls extends a second shaft 29 which carries a throttle 30. This can have any suitable shape and for example have an upper side 31, a lower side 32, a back side 33 and a gable side 34 (the opposite gable side is not shown). The throttle has a lip-like protrusion 40 which cooperates with a stop stop 36 in the carburettor housing to limit the movement of the throttle in the closed position.

The carburettor is usually connected to the intake pipe in an internal combustion engine, for example a car engine. The shaft 29 is thereby connected to an appropriate maneuvering device, for example an accelerator pedal, a gas regulator or an automatically working regulator.

The air damper 11 and the throttle 30 are shown in their closed positions. If you turn the throttle shaft 29 clockwise, the throttle 30 will be opened to fully open position 30a. The negative pressure in the intake pipe acts on the underside 16 of the air damper and tries to keep the damper in the fully open position 1a, whereby, however, an opposing force must be overcome. This force is provided by biasing means which will be described in more detail below.

Fuel in portioned quantities passes through the bore 26, the passages 24 and 23 as well as the mouths 22 and out into the air, which is caused to flow downwards by the negative pressure in the engine's intake pipe. Thanks to the fact that the fuel outlet openings are located on the air damper, the fuel can be dispensed in a fuel discharge zone where the air moves very quickly, which facilitates the fine distribution of the fuel.

As can be seen from fig. 2, the invention can be conveniently applied to carburettors with several dampers. The one in fig. 2 shows the design of a carburettor housing 41 with a lid 43 and an intermediate gasket 42. 44 denotes the inlet opening in the carburettor housing's upper mounting flange 45. The passage 46 inside the carburettor is divided into two passages 47 and 48 by means of an intermediate wall 49. The intake air passes through each of these two carburettor passages, past the air dampers 11 and the throttle dampers 30 and then continues through the outlet 50. A carburettor according to the invention can have more than two passages with associated dampers.

Fig. 3 shows a carburettor according to a preferred embodiment. It can be made in any suitable material, but many of its various details, including the carburettor housing 51 and the lid 59, preferably consist of a rigid impact- and heat-resistant plastic, for example polyphenyl sulphide. The carburettor has a mounting flange 52. The risk of this being bent or pinched to pieces is reduced by the use of a fastening device with clamps 54. Such a clamp has a first foot 55 which rests against the upper side of the flange 52, a slightly longer foot 56 which extends down into a recess 53 without reaching the bottom thereof, and a third foot 57 which rests against the machined surface of the intake pipe which surrounds the carburettor. By inserting a screw into the hole 58 and screwing it into a threaded hole in the aforementioned surface of the intake pipe, the carburettor can be fitted tightly without exposing the edges of the flange 52 to bending forces. The clamping forces will be transferred to the flange through the first foot 55 which is located reassuringly within the edge of the flange.

The lid 59 is fixed by means of screws 60. An elevation 61 and a corresponding recess 62 in the lid support the shaft 63 of a fuel enrichment system which will be described in more detail below. The lid 59 also has an upper bridge 67 which is supported by legs 64, 65 and 66, with intermediate air inlet openings

72. The legs 64-6 6, which are made in one with the lid and of the same

material like this, extends obliquely upwards and inwards and merges into a horizontal plate 68, which below has a thickening 69. This acts as storage for a pin 70 and for various setting screws which will be described in more detail below. The pin 70 has; thread 71 for connecting an air filter not shown

which covers the bridge and seals against an annular ledge 73 at the lower ends of the legs.

The carburettor has a first air damper 75, a second air damper 76, an intermediate wall 77 and biasing means 80. In this case, the pin 70 has a smooth part 81 which from the thickening fin 69 extends down towards the wall 77 and carries a yoke 82 which can slide up and down on the smooth part 81. The yoke has two arms 83 and 84, which extend over the air dampers 75, 76

and each includes a joint location 85. From each of these joint locations, a tie rod 86 and 87 respectively extends.

Springs 88 and 8 9 affect the yoke 8 2 with an upward force, through which the air dampers 75, 7 6 attempt to assume their upper, closed positions.

In fig. 4 is the carburettor in fig. 3 shown with the lid

and other parts removed, so that the inside of the carburettor housing 51 becomes visible. The house has a front wall 90, a rear wall 91 and gable walls 92 and 93. The gable walls are provided with upward projections 94 and 95. Between these gable walls extends an intermediate wall 77. In the projections 94 and 95 there are recesses 96, 96A, 97 and 97A for shaft units 100 and 110. The shaft unit 100 has support members 101 and 102 for a rotatably mounted air damper shaft 103 and a likewise rotatably mounted throttle shaft 105. The throttle shaft has an extension 106 which extends beyond the support 102, i.e. goes outside the carburettor in the assembled state . The shaft 103 has an extension 104 which projects into the carburettor's fuel chamber. More about this below in connection with fig. 10. The shaft 103 has a bore 107 which communicates with a lateral line 108 which extends into the interior of the air damper. This is explained in more detail below in connection with fig. 5 and 6. The second shaft unit 110 has supports 111 and 112, an air damper shaft 113, a shaft union 114, a

bore 117, a line 118 and a throttle shaft 115 with an extension 116. These details are identical to details 101-108.

The fuel chamber 120 is located on one side of the carburettor, so that the wall 93 is shared by the fuel chamber and the carburettor passage. Otherwise, the fuel chamber is limited by a front wall 121, a side wall 122, a rear wall 123 and a bottom (hidden in the drawing). An intermediate wall 126 divides the chamber into a first side chamber 127 and a second side chamber 128. 125 is a threaded hole for connecting a fuel supply line. The carburettor can work with a single float and a float valve. The carburettor can work with a single float and a float valve in the chamber 127 and with a connection opening (not shown) in the wall 126. If you want to supply the carburettor with double floats, for example when mutually different types of fuel are to be supplied to the two

chambers 127 and 128, the connection opening is omitted and instead both chambers are provided with connections for fuel supply.

To achieve a liquid- and air-tight seal between the carburettor housing 51, the shaft units 100 and 110 and the lid 59, the walls 92, 93 and the shaft units have edge grooves 134 in which gaskets 136, 137 and 138 are inserted.

Fig. 5 shows the air dampers in fig. 3 in detail and shows i.a. that the air damper can be produced in several layers, for example an upper layer 140 and a lower layer 159. The upper layer has an edge part 141 and an underside thereof forms a segment 142 in the bore for the axle. The edge strip 141 also has a flat surface which in size and shape corresponds to a surface 163 on the lower layer 159. The strip 141 also has an upward and downward diverging surface 14 5 intended for retaining a spring clip. The back side 144 extends between the surfaces 143 and 145.

From the edge strip 141, a corrugated disk-shaped part 14 6 extends out with a side 14 7 which corresponds to one end of the air damper, and an upper side 148 which corresponds to the upstream surface of the air damper. Furthermore, there is an underside 149 which is adapted to the surface 158. The disk 146 has several slits 150, separated by narrow strips 151. A central part 152 has a recess 153, in which the lower end of a pull rod 86 or 87 can be fixed.

The lower layer 159 also has an edge strip 157, which partially delimits a segment 160 of the bore surrounding the air damper shaft lo3. Where this segment and the back 161 merge into each other there is a strip 162 which cooperates with a divergent surface 145 on the upper layer 140 for retaining a spring clip.

Like the upper layer, the lower layer has a corrugated disk-like part with an upper side 158, an end surface 156 and a lower side 155. The lower side corresponds to the lower side of the air damper.

Also in the disk-like part 164, elongated slits 165 with intermediate strips 166 are taken out, of the same size as in the layer 140. A central part 170 in the lower layer has an opening 171 sufficiently large to receive the recess 153. The opening 171, the strips 176 and the slits 165 are located in the middle of corresponding details in the upper layer when the two layers are brought together with the side edges 147, 156 arranged in the same plane.

A track 167 extends through the central part 170 in the lower layer 159, from the segment 160 and to another track 168 and delimits a passage which essentially runs perpendicular to the damper shaft. The groove 168 forms a passage which is essentially parallel to the shaft pg and extends along a considerable part, for example at least half of the damper's front edge. Here, several short grooves 169 have also been taken which run perpendicular to the groove 168 and form... discharge openings. The grooves mentioned here can either be found in the upper side of the lower layer 159 or in the lower side of the upper layer 140 or in both of these surfaces. The damper's layered structure makes it possible to design the passage and the openings with the help of grooves, so that the damper can easily be manufactured from a plastic material, for example glass fiber reinforced plastic, without the need for drilling and using simpler molds than would be necessary if the mouths were to be provided using movable pins. The multi-layer construction also facilitates the arrangement of curved passages.

The two layers 140 and 159 are intended to be connected with a shaft 103 whose diameter is adjusted so that the shaft fits exactly between the segments 142 and i'60.

According to a preferred embodiment, a wire 108 is connected to the shaft 103, namely to its internal bore 107. The wire should be shaped so that it can be inserted into the groove 167. When the two layers and the shaft 103 are assembled together and the wire 108 is in place, the layers can be joined, for example by welding. The wire 108 ensures the necessary tightness. As it transports fuel most of the way from the bore 107 to the groove 168, there is no need for a perfect seal between the stroke 140 and the sides of the groove 167.

The slots 150 and 165 have the task of protecting the air damper against kickback. Under normal operating conditions, the slots are covered by flexible flaps 175, 17 6. The flaps have approximately the same size as the upper sides of the dampers and end just before the edge 21, which is more clearly seen in fig. 7. In order for the flaps not to interfere with the function of the tie rods 87, 86, they are provided with recesses 177 and 178 which mean that the recesses 153 are open even when a Jtlaff is in its lower, i.e. closed, position, as the flap 175 is in fig. 6.

The flaps are held in place by spring clamps 17 9, 180 which grip around the flap edge. In fig. 6 shows how the upper arm 181 of the clamp 179 surrounds the edge 182 of the flap 175. The strip 162 facilitates the retention of the clamps.

Fig. 7 shows the grooves found in or near the damper's front edge. The figure shows a corner of an air damper 17 6, built up of two layers as shown in fig. 5 and 6. In the edge 21

there are fuel discharge openings, formed by grooves 169 in the layer 159. Grooves 186 extend mainly parallel to the air flow direction through the surface 21, from the upper side 188 to the lower side 189. These grooves prevent the fuel from passing along the edge during unstable operating conditions.

A track 185 extends perpendicular to the air flow direction up to the edge 21. This track has the task of

to increase the turbulence at the edge region as well as to increase the pressure difference between the air damper and the throttle. If the grooves 186 are made deeper, so that they continue past the back side of the strip 187.190, the groove 185 can perform an air-collecting function for the grooves 186.

Figs. 8 and 9 show further construction details of the biasing member 80, which is mentioned above in connection with fig. 3. Fig. 8 shows the pin 70 with its smooth part 81, the yoke 82, the arms 83 and 84, a joint 85, the tie rods 86 and 87 and the springs 88 and 89. All of these details are also shown in fig. 3. However, Fig. 8 also shows the second joint location 79, which is hidden in Fig. 3. Because most of the lid 59 and the entire carburettor housing 51 (with the exception of the intermediate wall 77) have been removed and because an air damper in fig. 8 is cut through, it is possible in fig. 8 clearly see the recess 153 as well as the drawbar 86's lower attachment point.

The recess 153 has a first side wall 193, a similar second side wall (not shown) and a lower wall 192. The wall 192 follows the bottom contours of the two side walls and joins them in an airtight manner, so that the interior of the recess 153, which comes in series with the space above the air damper is pneumatically isolated from the underside. A short pin 191, fixed in the side walls, acts as the drawbar 86's lower joint point.

In fig. 8, the air damper 75 is almost in the closed position. If the throttle is opened to increase the suction force under the air damper 75, the air damper will be turned to its fully open position 75A, which is shown with dotted lines. During this opening movement, the side walls of the recess 153 will exert a downward and outward force on the pull rod 86, so that it is pulled out to its full length 8 6A. When this happens, the tie rod turns from a position to the left and to a position to the right about a vertical plane through the tie rod's upper joint point 85.

The arrow 204 shows how the joint point 85 moves. In the lateral direction, the upper point cannot move, because the fork-shaped arm 83 prevents this. Correspondingly, the second arm 84 controls the details on its side of the pin 70. The sleeve-shaped part 205 of the yoke 82 has a recess 194 below

for the partition wall 77.

The sleeve-shaped part 205 has at its lower end ears 195, 196 where the lower ends of the springs 88 and 89 are attached. The upper end of the spring 88 is attached to the underside of a set screw 197 which is screwed together with a nut sleeve 198. The screw can be reached through a hole 199. Corresponding members can be arranged for the spring 89, but this is not necessary. The biasing member 80 thus tries to keep the air damper 175 in the closed position and the yoke 82 moves upwards or downwards when the air damper 175 is closed and opened.

An arm 200 extends laterally from the sleeve 205. The upper side 201 of the arm is at level with the lower end 203 of the setting screw 202, see fig. 9. The screw acts as a stop screw for

the yoke 8 2 and thus also for the air damper, and the setting can be changed by turning the screw.

Fig. 8 and 9 also show details of an additional device, which can be used, for example, to prevent the biasing means from, when the engine is running, closing the air damper more

. than what corresponds to the idle position, while the air damper, on the other hand, is closed completely during a starting run. This additional device may include an idler screw 210 which extends parallel to the pin 70 and is screwed into a projection 211 and provided with a lock nut 212 and an upper impact end 213. A spade-like member 215 is carried by a rod 216. The rod can move moves back and forth in a horizontal direction in a bore 217 in a wall 18. The wall projects down from the bridge 68. The organ 215 has an opening 219

and a locking part 220, which can be moved into position above the upper end 213 of the idle screw 210. When the shovel 215 is in the position shown in fig. 8 and 9, the screw end 213 can pass through the opening 219 when the stop arm 200 moves upwards to abut against the lower end 203 of the screw 202. If the shovel is in this position, when the engine stops, the biasing device 80 can bring the air damper to the fully closed position, so that maximum suction effect is achieved at the next engine start. When the engine is started and idling, the air damper should be slightly more open. For this purpose, the blade 215 can be pulled slightly away from right to left, so that the part of the blade 220 is located directly above the upper end 213 of the idle screw. The blade 215 then prevents the biasing means from closing the air damper past the idle position.

The rod 216 and the shovel 215 can be maneuvered manually

or by means of a solenoid, a diaphragm motor, etc. When such a special drive device is present, this in turn can be maneuvered automatically or manually. An example of automatic maneuvering can be found in fig. 8.

One can, for example, use a vacuum motor 221,

as in fig. 8 is shown in the exploded part of the sketch, but which is normally attached to the wall 218 and held in place by means of bolts 229 with associated nuts. Inside the vacuum motor is a spring 223 which usually holds the diaphragm 224 in its right end position. The diaphragm is fixed by means of a screw 225 in a threaded hole 226 in the rod 216.

When the engine stops, the spring 223 will normally try

to displace the membrane 224, the rod 216 and the shovel 215 to the position shown in fig. 8 and 9* 1 The vacuum motor 221 is arranged so that the blade 215 is displaced to a position in which its part 220 is in the closing path of the idle screw 210 when the motor is working. This is made possible by means of a wire 227 which connects

the inside of the engine to the left of the diaphragm 224 with a suitable vacuum source, for example the port 228 in the wall 77 inside the carburettor. The spring tension and the diaphragm's area are adapted in relation to each other so that the shovel 215 is held in its outer position until the engine has started, after which the diaphragm will displace the rod 216 and the shovel 215 to the left. As soon as the air damper opens, the non-perforated part of the shovel will be over the idle screw and thereby prevent the air damper from closing past the idle position. ,y

Fig. 10 shows several details from the previous figures, for example the second air damper 76, the pull rod 87 and the intermediate wall 77 in fig. 3. It also shows the parts of the carburettor housing 51 which are shown in fig. 4, including the wall 93, the axle units-101 and the rear wall 91. Furthermore, parts of the fuel chamber 120 are shown, including the walls 122,123 and 126 which form part of the float chamber 128. Fig. 10 also shows the threaded intake opening 232 in the float chamber wall 123. Some of the parts of the air damper 76 as in fig. 5 is shown in an exploded view is in fig. 1.0 shown in assembled state. This applies in particular to the air damper 76 on the shaft 103 as well as the shaft extension 104, the bore 107, the line 108 and the tracks 168 and 169.

The arrows 230 show how the bore 107 in the throttle shaft through the line 108 communicates with the fuel outlets. Fig. 10 also shows the initially mentioned fuel portioning device.

A carburetor according to the invention can be provided with any suitable fuel portioning device, but the type having an arm and a ramp is preferred. Here, the arm unit has a fastening sleeve 237 whose inner wall 238 fits snugly on the shaft extension 104. A bolt 243 that passes through washers 242 and the sleeve 237 has threaded engagement with the bore 107.

An arm 238 extends from the sleeve 237. This arm has an internal bore 244 which, as arrows 245 show, is connected to the inside of the sleeve 237 and to the bore 107. 239A

marks the position of the arm in the mounted position.

At the free end of the arm there is a ball valve, consisting of a ball 241 loaded by a spring 240. The ball rests against the upper side of a ramp 233 which is attached to the shaft 103 by means of a suspension device 234. The ramp is kept fixed in position by shoe-like protrusions 235 and 236 in the bottom 231 of the fuel chamber.

The ramp's 2 33 contact surface has such a profile that

its radial distance from the shaft 101 varies along the length of the ramp. This means that the distance between the ramp and the free end of the arm 239 will vary, so that the ball will move forward

and back into the bore 4 2 and through this deliver portions of fuel to the outlet openings 169 - see also fig. 11.

The fuel is mixed with the intake air, as shown by the arrows 246 in fig. 11 and flows past the throttle valve 30 and to the carburettor outlet. When the damper 30 is turned, the suction force acting under the air damper 76 will vary, so that the air damper is opened and closed while overcoming the force from the biasing means 80. This will turn the shaft 103 and the arm 239, and thereby, vary the size of the portion of fuel that is fed into the carburettor through the air damper.

Fig. 12 shows how the ramp 233 is suspended in the shaft 103 by means of the member 234. When there is a distance 247 between this and the carburettor passage wall 93, it will be easier to keep the suspension member and the arm 239 at the same temperature. As explained at the beginning, this provides a more accurate fuel portioning. The designation 276 refers to the previously discussed clearance between the free end of the arm 239 and the ramp 233.

From fig. 13, it appears that the bore 244 in the arm 239 has a further part 269 at the arm's free end 267. In the transition between the bores 244 and 269, a shoulder 268 is formed, against which one end of the spring 240 rests. The opposite spring end rests against the ball 241. The wall of the arm is provided with several openings 273

in the region of a horizontal equatorial plane through the sphere.

As shown in fig. 14, parts 27 5 of the wall of the arm remain between the openings 27 3. Furthermore, the openings do not extend all the way down to the lower end of the arm. There is, on the other hand, a section 274 of the wall which hangs together in the circumferential direction and which prevents the ball from making lateral movements. If the gap between the ball and the extended bore 269's inner wall should be very small, then it must be ensured that the total flow cross-section is sufficient for fuel feeding even with the throttle completely open.

The openings 273 may have a different shape than that shown in fig. 13 and 14. They can also, if the thickness of the arm is sufficient for this, be located at the free end of the arm instead of in the mantle surface.

Fig. 15 shows a known device which can be used instead of the ball-equipped arm described above. Arm 278

in fig. 15 has an internal bore 279 and a lower end 280 intended to move along the upper side 282 of the ramp 281 with an intermediate clearance 283. The arrows show how the fuel flows. The size of the fuel flow depends on several factors. variables, . including the available cross-sectional area. As the ramp is located near the end of the arm, so that the area there

is smaller than the cross-sectional area of the bore 290, the available cross-sectional area marked with dashed lines 284 will be a function of the diameter d of the bore 27 9 and of the height h of the gap 28 3 according to the equation A = 3.14 dh.

In a device according to fig. 15, the gap or clearance 283 at idle can be as small as a few hundredths or thousandths of a millimeter. This means that irregularities in the surface of the ramp have a major impact on the accuracy of the fuel portioning. In practice it has been shown that deviations of the order of 0.005 mm lead to difficulties. The impact of the deviations on the available cross-sectional area

can be calculated with the formula above by replacing h with y, i.e.

you then get the equation A = 3.14 dy.

When, according to a preferred embodiment of the invention, the arm is provided with a ball, the just-mentioned sensitivity becomes significantly less. This is partly evident from fig. 16,

which on a much larger scale shows a section along the line 16-16

in fig. 13 with the spring 269 omitted.

It is assumed that the various details are in the positions shown and deviate from the manufacturing tolerances. The dashed line 290 represents the nominal position of the ramp surface in relation to the end of the arm 239. The distance h represents this deviation. However, the impact that this deviation has on the stream-neighboring area is less than what appears from the above

said formula.

The upper limiting edges of the openings 273 have in fig.

16 the designation 292. The fuel enters between these edges and

the ball, here shown with arrow 293. As the surface of the ball touches obliquely in relation to the edge 292, a certain axial deviation will result in a relatively smaller change in the distance between the edge 292 and the limiting circle 293. The device thus becomes less sensitive to such deviations .

What has been said here is shown graphically in fig. 17,

which shows a comparison between the errors that can occur with the device according to fig. 15 and 16 for various large deviations in the position of the ramp from the nominal value. The diameter of the bore inside the arm is assumed to be turned 0.3 mm in both cases. Along

The x-axis is the ramp's target deviation from the nominal value set on a suitable scale, graduated from 0-26 units. (The value 26 should in practice correspond to approx. 0.7 mm). Along the y-axis, the change in the effective flow area that the imperfections in the ramp give rise to is also set aside on a suitable, relative scale.

The upper curve here refers to fig. 15, while the lower curve applies to fig. 16, i.e. a device according to the invention.

It can be seen that even with a target deviation of 8 units, the area is affected by approx. 6 times as much with the known device as with a device according to the invention. Another way of interpreting this diagram is to say that if in both cases you have the same accuracy during production, then the fuel portioning will be several times more accurate when using a device according to the invention.

Fig. 18 shows a device for level regulation in the float chamber. The device has two floats 248 and 249 in the float chambers 127 and 128. The floats have suspension arms 250 and 251, respectively. Each of these has a saddle-like part 252 and 253, respectively, which extends over the partition wall 126. When the lid of the float housing is mounted, it will hold the float arms against the partition wall. The arm 250 has a hinge 254 from which an arm part 2 55 with a holder 2 56 emanates. A joint pin 2 57 at the end of the arm 255 is connected to a lifting arm 258, which in turn is connected to a valve cone 259 which cooperates with a valve seat 260. The valve seat is located in a threaded hole to which a fuel line 261 is connected. A fuel line 262 is connected to the second float chamber and also otherwise the two halves of the device are identical.

The floats can, for example, consist of cellular plastic.

They work in a conventional way and will maintain a fuel level in the chambers that is suitable for transferring the fuel through the arms 239.

Fig. 19 shows some details of the throttles. Part of the carburettor housing 51 has a groove 300, which essentially runs parallel to the throttle shaft 105. In this groove is. a gasket 302 is arranged. The gasket lies against the underside 32 of the damper 30 in such a way that air is prevented from leaking past here. When the damper's ends 304 are flat and perpendicular to the shaft 105, which is most appropriate, the seal 302 can be provided with a protrusion 303 which extends up to the ends 30, for example up to the shaft 105. Such a protrusion 303 is also shown in fig. 4,

under the shaft 115, and in fig. 20.

Both throttles have lip-like protrusions 40, provided by means of undercuts 304. The upper edges 305 of the lips are rounded, which causes pulsations and turbulence in the fuel-air mixture when it passes past the throttle.

From fig. 20 shows that the throttle 30 can have recesses 309, designed to receive the wall parts 192 on the air dampers when both these and the throttle are fully open.

The throttles in fig. 20 is carried by shafts 105 and 115 as shown in fig. 4, with extensions .106 and 116 respectively. In order for the dampers to be able to turn in opposite directions around their axes, these extensions are equipped with lifting arms and a reversing device. This includes an angle arm 310,

which is attached to the shaft part 116 and whose lower arm 311 can be connected, for example, to an accelerator pedal. 312 is the hole for the shaft. The right arm 313 is at 314 articulatedly connected to a link 315 which at 317 is articulatedly connected to a link 319. This has a hole 318 for mounting on the shaft 106. The arrows show that when the arm 311 moves to the right, the arm 319 will move towards the left.

Fig. 21 shows a fuel enrichment system, intended for use when starting the engine. It includes a port 325 in the intermediate wall 77 - fig. 10. This port communicates through a passage 324 with a valve 322 which can connect the port with a ventilation line 323 or with a line 321, connected to a fuel supply 320, for example one of the float chambers. The detailed design of the device can be seen from fig. 22.

Fig. 22 shows a float chamber 128 and parts of its bottom 231. The port 325 in the intermediate wall 77 is through the passage 324 and the passage 326 in the wall 93 connected to a pocket 327 which is located next to the valve chamber 62, see fig. 3. Between rooms 62 and

327, an employment 328 has been arranged.

Inside the valve chamber bore 62 there is a ventilation port 329 and directly outside this a fuel port 332. The port 329

is by means of a short line 323 connected to an opening 330 which communicates with the space 331 above the liquid level of the float chamber 127. The fuel port 322 communicates with a line 334. The line 334 extends into the fuel supply in the float chamber 128. The lower part of the tube 334 end 335 is located at a small distance above bottom 231, so that fuel can enter the pipe.

The fuel enrichment valve 63 has a sleeve 338 which fits snugly into the bore 62, the sleeve's free end 339 abutting the shoulder 328. In the outer surface of the sleeve there is a first port 340 and a second port 341 - fig. 23 - which ports are located in the middle of the ventilation port 329, respectively the fuel port 332. The valve has a valve housing 342, provided with external threads for a nut sleeve 34 3.

The nut 343 holds the valve member 344, which at its otherwise closed inner end 34 5 has an opening 34 6. Furthermore, it has ports 347 and 348 which can be brought into position directly opposite the ports 340 and 341 when an extension 351 of the valve member 344 is turned under influence of a lifting arm 352. A flange 349 holds the valve member 344 in the axial direction. Thread 350 inside the flange 34 9 engages with the needle valve 353 head. The needle 354 extends through the organ 344 past the ports 347 and 348, so that the needle tip 355 is inside the opening 346. However, the diameter of the needle is chosen so that an annular space 356 is formed between the needle and the inner wall of the organ 344.

When the valve is in the position shown in fig. 22, it is connected to space 331. The negative pressure in the engine's intake line draws through port 325 air and fuel vapor through opening 330, line 323, ports 329, 340 and 347, passage 356, opening 346, pocket 327, passages 326 and 324 as well as port 325 and into the carburetor. If the arm 352 is turned 60° clockwise, the ports 340 and 347 will no longer be directly facing each other, and the enrichment port 325 is then disconnected from the room 331. At the same time, the ports 341 and 348 will lie directly facing each other. The negative pressure at the port 325 thus causes a suction of fuel from the float chamber 128 through the line 334, the ports .33 2, 341 and 348, the room 356, the opening 346, the pocket 327, the passages 326 and 324 as well as the port 325 and into the carburettor. This delivery of enrichment fuel continues until arm 352 is returned to its initial position as shown in the drawing.

The needle valve 353 can be adjusted with a screwdriver which is inserted into the open end of the extension tube 351. If the valve 353 consists of a plastic material with a significantly higher coefficient of thermal expansion than the material in the valve body 344, a certain automatic temperature compensation can be obtained.. As the needle valve expands more than the valve body 344 when the temperature rises, the needle valve will then be closer to the mouth 346, so that the amount of enrichment fuel decreases at higher temperatures.

Claims (12)

Carburetor, characterized in that its flow-through passage contains upstream arranged air damper means with means carried by the air dampers for the discharge of fuel in a zone between the air dampers and downstream of these arranged throttle means, in that biasing means are arranged to normally keep the air damper means in a closed position and to set them into different positions under the influence of the air flow that passes by, as fuel portioning means are arranged for regulating the supplied amount of fuel in dependence on the setting position of the air damper. 2. Carburettor according to claim 1, characterized in that the orifices through which the fuel is delivered are arranged in the edges of the air damper members. 3. Carburettor according to claim 2, characterized in that an air damper contains a distribution channel running along one edge, which partly communicates with the fuel the portioning organs, partly with the fuel outlet nozzles. 4. Carburettor according to claim 1, characterized in that each air damper is made up of at least two layers, the fuel outlet openings being at least partially formed by indentations in one or both layers' common interface. 5. Carburettor according to claim 1, characterized in that each air damper is made up of at least two layers, the interface between the layers containing recesses that form passages that communicate with the outlet openings. 6. Carburettor according to claim 3, characterized in that each air damper is made up of at least two layers and that at least part of the distribution channel's cross-section is formed by indentations in one or the other of the layers' common boundary surfaces. 7. Carburetor according to claim 1, characterized in that each air damper element is made up of at least two layers of a synthetic plastic material and that at least part of the cross-section of the passages inside the damper element is provided by recesses in the common interface of one or the second layers, which are joined to each other, in that the internal passages are provided with casing along at least part of their length. 8. Carburettor according to claim 7, characterized in that each air damper member is mounted on a rotatable, hollow shaft, the interior of which is connected to a fuel supply line and to the passages in the interior of the damper. 9. Carburettor according to claim 1, characterized in that the air damper members are provided with openings which are normally kept covered by flaps, but open automatically when back-ignition. 10. Carburettor according to claim 9, characterized in that the openings have the form of slits, the length of which is at least twice as large as the width, which width can be up to approx. 6 mm. 11. Carburettor according to claim 9, characterized in that the fuel outlet openings are located in one edge of the air damper member and that the flaps are attached to the damper along an opposite edge by means of mainly C-shaped clamps. 12. Carburetor according to claim 9, characterized in that the limiting surface arranged upstream of each air damper member is corrugated in a cross-sectional plane that is perpendicular to the axis of the damper, the flaps having a contour adapted to the curved shape.