GB2374385A

GB2374385A - I.c. engine exhaust component for removing sparks and attenuating noise

Info

Publication number: GB2374385A
Application number: GB0108905A
Authority: GB
Inventors: Kenneth Alfred Robson
Original assignee: Cardale Group Ltd
Current assignee: Cardale Group Ltd
Priority date: 2001-04-10
Filing date: 2001-04-10
Publication date: 2002-10-16
Also published as: GB0108905D0

Abstract

The exhaust component comprises a hollow vessel 12 with an inlet 18 and an outlet 20 and containing a gas permeable silencer 22 and a gas permeable cyclone type spark arrestor 24. The spark arrestor 24 includes a casing 30, a gas conduit 42, a frustum of a cone 44 and a trap 46 for solid matter. The casing 30 has an inlet 50 and an outlet 56 and defines a flow path, for exhaust gas, between the inlet and outlet. The conduit 42 is positioned inside the casing 30 and has openings 54, 56 at both ends. The frustum 44 is attached at its wider end to an inner wall of the casing 30 and at its narrower end to an outer wall of the conduit 42, so that it surrounds the conduit and is closed at the narrower end. The frustum 44 also has an outlets 60. Exhaust gases passing through the spark arrestor swirl inside the frustum 44. The trap 46 is branched from the flow path so that solid matter entrained in the swirling gas inside the frustum 44 passes to the trap 46 before gas exits the spark arrestor via the outlet 56.

Description

INTERNAL COMBUSTION ENGINE EXHAUST COMPONENT The invention relates to an internal combustion ("i. c.") engine exhaust component.

I. c. engines produce gaseous exhaust products. In most vehicles these exhaust gases are passed through silencer units before being released into the atmosphere. Silencers are used to absorb and attenuate the noise of combustion. There are several designs of silencers. Some of these include annular spaces filled with sound absorbing materials or a plurality of sound attenuating chambers.

As well as exhaust gases, i. c. engines may emit sparks and solid products of combustion, such as (usually hot) carbon or other particles. In many vehicles, such particles simply pass through the exhaust system and are discharged into the environment. However, this is undesirable for vehicles that are used in environments where the discharge of sparks could prove hazardous, for example, in high flammability environments and in dusty atmospheres. High flammability environments occur, for example, in the holds of ships and in chemical plants. Dusty environments occur, for example, in mines, granaries and fabric mills. Therefore, vehicles that are used in this type of environment have spark arrestors fitted in the exhaust system. Spark arrestors prevent sparks from being discharged into the atmosphere, by separating hot and glowing particles from the exhaust gas stream.

There are two types of separation techniques that are used in spark arrestors.

The respective separation techniques involve use of filters; and cyclones.

The filter based spark arrestor comprises a chamber filled with a heat resistant material, such as continuous strand stainless steel, to filter out

glowing particles from the exhaust gas stream. Filter based spark arrestors are easily blocked by the captured particles and therefore tend to have short life spans and need to be frequently replaced.

The cyclone type spark arrestor comprises a conical member housed within the arrestor. The outer walls of the cyclone and the inner walls of the

arrestor casing define a chamber, which is commonly called the' collection chamber". In the cyclone type spark arrestor, a cyclonic motion is imparted to the exhaust gases as they enter the cyclone and travel along its inner surface. The linear velocity remains constant, but the angular velocity increases as gases travel towards the apex of the cyclone, thus increasing the centrifugal force on the particles. The particles are released into the collection chamber when they exit the cyclone. The particles remain in the collection chamber and the gases, cleared of any sparks or solid products of combustion, escape.

The cyclone type spark arrestor generally has a longer life span than the filter type spark arrestor and does not need to be replaced as frequently. However, in many vehicles there is very little space available in which to fit a separate spark arrestor. This space constraint makes fitting a spark arrestor in an exhaust system difficult, especially when carried out as a modification of an existing exhaust system.

US 4,393, 652 discloses an exhaust system comprising an upstream muffler chamber, an intermediate, removable spark and moisture arrestor chamber and a downstream gas purifier chamber. The three components are positioned in an elongate hollow casing, which may be directly coupled to the vehicle exhaust tract. The spark arrestor is a filter type spark arrestor and therefore has a limited life span.

GB 1443652 discloses an exhaust assembly comprising a casing, inlet and outlet tubes, at least one centrifugal separator, a dust collection chamber and a silencer chamber. The centrifugal separator comprises a swirl tube and a gas discharge tube. The swirl tube has a cylindrical portion and a frustoconical portion that is open at one end.

GB 913152 discloses an exhaust unit comprising a vortex tube having a flared outlet, a torpedo-shaped core that lies about a central axis of the vortex tube, a silencer chamber that extends around the vortex tube and an outlet pipe.

GB 594370 discloses a device comprising a casing having an inlet and an outlet, a silencing chamber, a whirl chamber, a discharge conduit and a dirt box.

US 5403557 discloses an exhaust apparatus comprising a cylindrical housing, tubular inlet and outlet members, a particulate trap and a catalytic cell. The particulate trap includes upstream, downstream and intermediate sections. The upstream section is cylindrical and the intermediate section includes the frustum of a cone. The downstream section includes an enlarged diameter section that defines an annular pocket, which acts as a particle trap.

US 3960528 discloses an exhaust apparatus comprising a housing with an inlet and an outlet, at least one cyclone, a solid collection chamber, an inlet plenum, an agglomerate chamber and a resonating chamber. The cyclone is open at both ends.

US 3822531 discloses an exhaust apparatus comprising a housing having an

inlet and an outlet, first and second entrance chambers, a perforated agglomerator conduit, an inertial separator and a separator chamber. The inertial separator comprises a cyclone chamber and a perforated collector conduit.

In many of the devices disclosed in the prior art, the exhaust gases are able to exit the device without passing through the spark arrestor component. The devices, therefore, do not remove sparks and solid products of combustion adequately for use in environments where it is particularly undesirable for the discharge of sparks to occur.

According to an aspect of the invention there is provided an i. c. engine exhaust component comprising a hollow vessel having openings respectively for inlet and egress of exhaust gas, the vessel defining a gas flow path between the inlet and outlet; and the vessel including a gas permeable silencer and a gas permeable cyclone type spark arrestor located such that exhaust gas passing along the gas flow path passes through the silencer and spark arrestor, wherein the spark arrestor includes a casing having an inlet and an outlet and defining a flow path, for exhaust gas, between the inlet and outlet; a gas conduit positioned inside the casing and having openings at both ends; a closed frustum of a cone, attached to an inner wall of the casing at the wider end and attached to an outer wall of the gas conduit at the narrower end, so that it encloses the gas conduit and is closed at the narrower end, and having an outlet such that exhaust gases passing through the spark arrestor swirl inside the frustum; and a trap, for solid matter, that is branched from the flow path whereby solid matter entrained in the swirling gas inside the frustum passes to the trap before gas exits the spark arrestor via the outlet.

An advantage of the invention is that both the spark arrestor and silencer are incorporated into the i. c. engine exhaust component in a single unit, that both removes sparks which are carried in exhaust gases and attenuates the noise of combustion. The provision of both of these functions into a single unit overcomes the space constraints normally associated with separately fitting a spark arrestor in an exhaust system. It also provides a single unit that is easily fitted to the exhaust pipes of the i. c. engine in one fitting. The single unit also occupies less space than two separate components, which is an advantage if the units have to be stored prior to their fitting. The single units also have fewer joints to make and service than two separate components.

A further advantage of the invention is that exhaust gases must flow through the spark arrestor before exiting the exhaust component, so that sparks and solid components of combustion are efficiently removed from the exhaust gases.

The hollow vessel encloses the spark arrestor casing.

In one embodiment of the invention, the inlet of the casing is at an end thereof remote from the silencer, whereby the exhaust gas travels substantially the length of the casing externally thereof before entering the spark arrestor.

In another embodiment of the invention, the inlet of the silencer is at an end thereof remote from the outlet of the casing, whereby the exhaust gas travels substantially the length of the casing externally thereof before entering the silencer.

The gas flow path extends along an inner wall of the frustum from the wider end of the frustum towards the narrower end, through the outlet of the frustum and then, externally from the frustum, back towards the wider end of the frustum by virtue of swirling of the gas.

Preferably, the inlet to the casing perforates the casing near the wider end of the frustum.

In use of the exhaust component, the speed of swirling of the gas adjacent the narrower end of the frustum is greater than at the wider end.

Preferably, the exhaust component is connected to the vehicle so that the frustum extends generally vertically with the narrower end below the wider end. This ensures that solid matter falls away from the flow path into the trap, where it remains, so that the solid matter is not picked up again by the gas flow.

The trap is branched from the gas flow path and includes an enclosure surrounding, but spaced from, the closed narrower end of the frustum, whereby solid matter near the said end may pass through the frustum outlet and into the enclosure, away from the flow path.

Preferably, the cross-sectional area of each of the individual components of the exhaust component, through which the exhaust gas flows in use, is less than the area of the immediately preceding component through which the gas flows.

It is especially preferred that the cross-sectional area of each of the individual components of the exhaust component, through which the exhaust gas flows in use, is smaller, by 10% than the area of the said

immediately preceding component.

According to a further aspect of the invention there is provided a method of assembling the exhaust component according to one embodiment of the invention including the steps of (i) positioning the frustum over the gas conduit to provide a first sub-assembly, (ii) positioning the first subassembly inside the casing to provide a second sub-assembly, (iii) attaching the inlet pipe to the second sub-assembly at the closed end of the casing to provide a third sub-assembly and (iv) positioning the third sub-assembly inside the housing to provide the exhaust component.

According to yet a further aspect of the invention there is provided a method of assembling the exhaust component according to another embodiment of the invention including the steps of (i) positioning the frustum over the gas conduit to provide a first sub-assembly, (ii) positioning a baffle over the pipe to provide a second sub-assembly, (iii) attaching the first sub-assembly to the second sub-assembly on opposite sides of a plate, so that each of the gas conduit and the pipe is terminated by the plate to provide a third sub-assembly, (iv) positioning the third sub-assembly inside the casing to provide a fourth sub-assembly, (v) positioning the fourth subassembly inside the housing to provide a fifth sub-assembly and (vi) positioning the outlet pipe in the housing, at the opposite end to the inlet pipe to provide the exhaust component.

The cyclone type spark arrestor is efficient at removing sparks and solid particles and has a long lifetime in use because it does not become blocked

by the captured particles. A cyclone type spark arrestor also suffers less from build up of captured particles. Consequently the cyclone type of spark arrestor does not cause increases in engine exhaust back pressure. An increase in back pressure would affect engine performance and can

eventually cause complete power loss.

Examples of i. c. engine exhaust components according to preferred embodiments of the invention will now be described, by way of nonlimiting example, with reference to Figures 1 to 5 in which: Figure 1 is a cross-sectional view of an i. c. engine exhaust component, wherein the gas flows through the silencer before the spark arrestor, which shows the gas flow path through the component, according to an embodiment of the invention.

Figure 2 is a cross-sectional view of the inlet to the spark arrestor casing, which shows the gas flow path through the inlet, according to an embodiment of the invention.

Figure 3 shows the assembly sequence of the i. c. engine exhaust component according to Figure 1.

Figure 4 is a cross-sectional view of an i. c. engine exhaust component, wherein the gas flows through the spark arrestor before the silencer, which shows the gas flow path through the component, according to an embodiment of the invention.

Figure 5 shows the assembly sequence of the i. c. engine exhaust component according to Figure 4.

An i. c. engine exhaust component (herein"exhaust component 10") according to an embodiment of the invention is shown in Figure 1. In this embodiment of the invention, the gas flows through the silencer before flowing through the spark arrestor.

The exhaust component 10 includes a housing 12 that has an inlet end 14 and an outlet end 16.

The housing 12 is preferably substantially cylindrical in shape. The preferred cylindrical shape may alternatively be of oval cross section.

The inlet 14 and outlet 16 ends of the housing 12 have openings 18, 20 so that, in use of the exhaust component 10, exhaust gases can pass through the housing 12.

A silencer 22 and a cyclone type spark arrestor 24 (herein"spark arrestor 24") are positioned inside the housing 12.

An inlet pipe 26 passes through the inlet end 14 of the housing 12 and is terminated by connection to the closed end 28 of the spark arrestor casing 30, which will be described in more detail below. The inlet pipe 26 is narrower than the width of the inlet end 14 of the housing 12. The ratio of the width of the inlet pipe 26 to the width of the housing 12 is selected to ensure that the correct level of back pressure is achieved so that the gases flow through the exhaust component 10 efficiently. A suitable ratio can be readily determined by the skilled person in any particular case.

In a particular embodiment of the invention, the housing 12 and the inlet pipe 26 are cylindrical in shape and the housing 12 has a diameter of 150 mm and the inlet 26 has a diameter of 69. 85 mm.

The length of the inlet pipe 26 that extends beyond the housing 12 may, optionally, include fittings to enable it to mate with an adaptor. This allows the exhaust component 10 to be fitted to a range of vehicles.

The inlet pipe 26 has perforations 32 in the length of pipe that lies between the inlet end 14 of the housing 12 and the baffle 34, which will be described in more detail below. The perforations 32 allow gas to travel out of the inlet pipe 26 and into a chamber 36, in use. Chamber 36 is defined by an inner wall of the housing 12, an outer wall of the inlet pipe 26 and the baffle 34.

Preferably, the perforations 32 are arranged regularly along the inlet pipe 26 to allow for even distribution of the gas in use.

The gas travels at a controlled rate according to the spacing and number of perforations 32 in the inlet pipe 26, and according to the flow volume and pressure of gas emitted by the engine to which the exhaust component is connected. A suitable spacing and number of perforations can be readily determined by the skilled person in any particular case.

In a particular embodiment of the invention, the inlet pipe 26 is cylindrical in shape, has an inside diameter of 66.65 mm and comprises eight rows of twelve circular perforations each having a diameter of 6.3 mm. The total cross-sectional area of the perforations 32 represents a 10% reduction in size compared to the cross-sectional area of the inlet pipe 26.

The baffle 34 includes perforations 38, which allow gas to travel from the chamber 36 into the annular space 40 in use. The annular space 40 is discussed in more detail below. Baffle 34 controls the back-pressure so that the gases may flow through the silencer 22 at a controlled rate. The baffle 34 attenuates the noise of combustion and also provides rigidity and support to the inlet pipe 26. Preferably, the exhaust component 10 comprises one baffle 34, although more than one baffle could be included if appropriate.

The gas travels at a controlled rate according to the spacing and number of perforations 38 in the baffle 34, and according to the volume and pressure

of gas emitted by the engine to which the exhaust component is connected. A suitable spacing and number of perforations can be readily determined by the skilled person in any particular case. Preferably, the perforations 38 are arranged regularly on the baffle 34 to allow for even distribution of the gas in use.

In a particular embodiment of the invention, the baffle 34 includes six circular perforations each having a diameter of 24 mm. The total crosssectional area of the perforations 38 in the baffle 34 represents a 10% reduction in size compared to the total cross-sectional area of the perforations 32 in the inlet pipe 26.

The spark arrestor 24 comprises a casing 30, a gas conduit 42 positioned inside the casing 30, a frustum of a cone 44 and a trap 46.

The casing 30 has a closed end 28 and an open end 48. The dimensions of the casing 30 are smaller than the dimensions of the housing 12, so that the casing 30 fits inside the housing 12. The space between the outside of the casing 30 and the inside of the housing 12 defines the annular space 40.

The length of the casing 30 is selected so that the overall exhaust component 10 is as compact as possible, whilst still allowing gases to flow through the unit efficiently. The size of the annular space 40 will vary according to the gas flow requirements of the particular unit and/or application. A suitable size of the annular space can be readily determined by the skilled person in any particular case.

In a particular embodiment of the invention, the housing 12 and the casing 30 are cylindrical in shape, the housing 12 has a cross sectional area of 17671 mm2, the casing 30 has a cross sectional area of 15175 mm2 and the annular space 40 has a cross sectional area of 2442 mm2. The total cross-

sectional area of the annular space 40 represents a 10% reduction in size compared to the cross-sectional area of the perforations 38 in the baffle 34.

The casing 30 has an inlet 50 positioned towards the outlet end 48, which admits gases from the annular space 40 into a chamber 52. Chamber 52 is defined by an inner wall of the frustum 44 and an outer wall of the gas conduit 42.

As shown in Figure 2, the inlet 50 comprises a channel wherein the wall is bent inwardly in the direction that the gas flows in use. Preferably, the wall is bent inwardly at an angle of 450 although other angles are possible within the scope of the invention. The casing 30 may include one or more inlets 50. Preferably, the casing 30 includes six inlets 50. Preferably the shape of the inlet is so chosen as to induce the gas to swirl as it enters the spark arrestor. In the preferred embodiment shown the gas tends to flow in a clockwise direction. However, it would be within the scope of the invention to employ an inlet (and other components of the spark arrestor, as necessary) to induce anticlockwise swirling if desired. The direction of swirling is primarily a function of the location and design of the inlet slots.

In a particular embodiment of the invention, the casing 30 comprises six inlets 50 each having an open area of 366 mm. In this embodiment, each inlet 50 is 20 mm high (dimension A in Figure 2) and 18 mm wide (dimension B in Figure 2). The total open area of the inlets 50 represents a 10% reduction in size compared to the cross-sectional area of the annular space 40.

The gas conduit 42 is open at both ends, having an inlet end 54 and an outlet end 56. The outlet end 56 of the gas conduit 42 is positioned towards the outlet end 16 of the housing 12. The gas conduit 42 extends beyond the

housing 12 so that it acts as the overall outlet for the exhaust component 10.

The wider end of the frustum 44 is attached to an inner wall of the spark arrestor casing 30 via. a carrier plate 58. Alternatively, the wider end of the frustum 44 could be attached directly to an inner wall of the casing 30. The closed, narrower end of the frustum 44 is connected to an outer wall of the inlet end 54 of the gas conduit 42. The frustum 44 is closed and is positioned around the gas conduit 42. This ensures that the gas must flow along an inner wall of the frustum 44 before exiting the exhaust component 10.

The width of the frustum 44 and the ratio of the width of the frustum 44 to the width of the spark arrestor casing 30 are selected to allow gases to flow through the exhaust component 10 efficiently. These dimensions vary according to the gas flow requirements of the particular unit and/or application and can be readily determined by the skilled person in any particular case.

The frustum 44 includes one or more outlets 60 positioned along the walls.

The outlets 60 have the same shape as the inlet 50. The outlets 60 induce a swirling motion in the gas. The preferred number of outlets 60 is determined by the size of the frustum 44 and preferably is selected to give rise to gas swirl directions and velocities that are matched to the engine to which the spark arrestor is attached.

The trap 46 is branched from the gas flow path and includes a collection chamber, which is defined by an outer wall of the frustum 44 and an inner wall of the spark arrestor casing 30. The trap 46 collects the solid particles, whilst the gas flows through the gas conduit 42. Preferably, the solid particles are collected along an inner wall of the casing 30 towards the inlet

end 14 of the housing 12.

In a particular embodiment of the invention, the distance between the baffle 38 and the inlet end 54 of the gas conduit 42 is 25 mm.

The gas conduit 42 passes through the outlet end 16 of the housing 12 and the open end 48 of the spark arrester casing 30. The gas conduit 42 is narrower than the width of the outlet end 16 of the housing 12.

The ratio of the width of the gas conduit 42 to the width of the housing 12 is selected to allow gases to flow through the unit efficiently. A suitable ratio can be readily determined by the skilled person in any particular case. In a particular embodiment of the invention, the gas conduit 42 is cylindrical in shape and has an inside diameter of 60.3 mm.

In use, the exhaust gas flows into the inlet pipe 26 and through the perforations 32 in the inlet pipe 26 into the chamber 36 of the silencer 22. The exhaust gas then flows through the perforations 38 in the baffle 34 and into the annular space 40 between the inside of the housing 12 and the

outside of the spark arrestor casing 30. The size and number of perforations 32, 38 in the inlet pipe 26 and the baffle 34 control the rate of gas flow through the exhaust component 10. The gas flows along the length of the spark arrestor casing 30, towards the outlet end 16 of the housing 12, and through inlet 50 into the chamber 52. The exhaust gas then flows, with a swirling motion, through the chamber 52, along an inner wall of the frustum 44. The swirling of the gas is induced by the louvres 50. The linear velocity remains constant, but the angular velocity increases as the gas travels towards the narrower end of the frustum 44. This increases the centrifugal force on the particles, which continue along this spiral path until they exit the chamber through outlet 60. The particles then fall into the trap

46. The particles remain in the trap 46 and the gases, cleared of any sparks or solid products of combustion, escape through the gas conduit 42.

The exhaust component 10 of the invention may be manufactured according to the sequence of steps shown in Figure 3.

The steps by which the exhaust component 10 may be manufactured include: (i) Positioning the frustum 44 over the gas conduit 42 to provide a first sub-assembly 62.

(ii) Positioning the first sub-assembly 62 inside the casing 30 to provide a second sub-assembly 64.

(iii) Attaching the inlet pipe 26 to the second sub-assembly 64 at the closed end 28 of the casing 30 to provide a third sub-assembly 66.

(iv) Positioning the third sub-assembly 66 inside the housing 12 to provide the exhaust component 10.

In a further embodiment of the invention, the i. c. engine exhaust component may provide for exhaust gases to flow through the spark arrestor before flowing through the silencer. This allows the exhaust gas to cool and the high initial energy and pulsation of the gas to decrease before the gas enters the silencer and the annular space. In this embodiment, the solid particles are removed from the exhaust gases before they enter the annular space.

This ensures that the solid particles do not deposit and build up in the annular space, so that the exhaust component may perform efficiently over a longer period of time.

The exhaust component of this embodiment also allows for easier emptying of the particle trap, which is conveniently positioned at one end of the housing. It may be necessary to empty the particle trap when the trap

contains a large number of solid particles, since the gas may otherwise pick up additional particles from the trap and carry them back through the outlet pipe to the exhaust, thus reducing the efficiency of the component. The unit may, optionally, comprise a particle removal feature. An example of a particle removal feature is a removable end plate instead of welded-on end plate 74 visible in Figure 4.

An i. c. engine exhaust component (herein"exhaust component 70") according to a further embodiment of the invention, in which the gases flow through the spark arrestor before flowing through the silencer, is shown in Figure 4.

As described above in relation to the previous embodiment, the exhaust component 70 includes a housing 72 that has an inlet end 74 and an outlet end 76.

The housing 72 is preferably substantially cylindrical in shape. The preferred cylindrical shape may alternatively be of oval cross section.

The inlet 74 and outlet 76 ends of the housing 72 have openings 78,80 so that, in use of the exhaust component 70, exhaust gases can pass through the housing 72.

A cyclone type spark arrestor 82 (herein"spark arrestor 82") and a silencer 84 and are positioned inside the housing 72.

As described above in relation to the previous embodiment, the spark arrestor 82 comprises a casing 86, a gas conduit 88 positioned inside the casing 86, a frustum of a cone 90 and a trap 92.

The casing 86 has a closed end 94 and an open end 96. The dimensions of the casing 86 are selected so that it fits inside the housing 72 and so that the overall exhaust component 70 is as compact as possible. An annular space 98 is defined by the space between the outside of the casing 86 and the inside of the housing 72. The size of the annular space 98 will vary according to the gas flow requirements of the particular unit and/or application. A suitable size of the annular space can be readily determined by the skilled person in any particular case.

The gas conduit 88 has an open end 100 and a closed end 102, which is terminated by connection to a carrier plate 104 positioned inside the casing 86. At the inlet end 74 of the exhaust component 70, the gas conduit 88 extends beyond the housing 72 and acts as the inlet for the whole exhaust component 70.

The gas conduit 88 is narrower than the width of the inlet end 74 of the housing 72. The ratio of the width of the gas conduit 88 to the width of the housing 72 is selected to ensure that the correct level of back pressure is achieved so the gases flow through the exhaust component 70 efficiently. A suitable ratio can be readily determined by the skilled person in any particular case.

The length of the gas conduit 88 that extends beyond the housing 72 may, optionally, include fittings to enable it to mate with an adaptor.

The gas conduit 88 has an inlet 106 positioned towards the closed end 102. The inlet 106 admits gases from the gas conduit 88 into a chamber 108, in use. Chamber 108 is defined by an inner wall of the frustum 90 and an outer wall of the gas conduit 88. The gas conduit 88 may include one or more inlets 106. Preferably, the gas conduit 88 comprises six inlets.

The wider end of the frustum 90 is attached to an inner wall of the casing 86 via a carrier plate 110. Alternatively, the wider end of the frustum 90 may be attached directly to the casing 86. The closed, narrower end of the frustum 90 is connected to an outer wall of gas conduit 88.

The width of the frustum 90 and the ratio of the width of the frustum 90 to the width of the casing 86 are selected to allow gases to flow through the exhaust component 70 efficiently. These dimensions vary according to the gas flow requirements of the particular unit and/or application and can be readily determined by the skilled person in any particular case.

The walls of the frustum 90 include one or more outlets 112.

The trap 92 is branched from the gas flow path and includes a collection chamber, which is defined by an inner wall of the inlet end 74 of the housing 72 and an outer wall of the frustum 90. The trap 92 collects the solid particles, whilst the gas flows along the annular space 98.

The silencer 84 includes a pipe 114 positioned inside the casing 86 and a baffle 116. The pipe 114 is positioned on the side of the support plate 104 opposite the spark arrestor 82.

The casing 86 includes perforations 118 in the length of the casing 86 on the side of the support plate 104 opposite the spark arrestor 82. The perforations 118 allow the gas to flow from the annular space 98 into a chamber 120, which is defined by the inside of the casing 86, the carrier plate 104 and the baffle 116.

The pipe 114 is closed at both ends. At the end nearest to the spark arrestor

82, the pipe 114 is terminated by the carrier plate 108 and at the opposite end the pipe 114 is terminated by a plate 122. The pipe 114 comprises perforations 124 along its length, which allow the gas to flow from the chamber 120 and into a chamber 126, in use. Chamber 126 is defined by an inner wall of the housing 72, the baffle 116 and the plate 122.

The gas travels at a controlled rate according to the spacing and number of perforations 118,124 in the casing 86 and the pipe 114 respectively, and according to the volume and pressure of the gas entering the silencer 84. A suitable spacing and number of perforations can be readily determined by the skilled person in any particular case.

An outlet pipe 128 passes through the outlet end 76 of the housing 72. The outlet pipe 128 is narrower than the width of the outlet end 76 of the housing 72. The outlet pipe 128 is supported by brackets 130.

The ratio of the width of the outlet pipe 128 to the width of the housing 72 is selected to allow gases to flow through the unit efficiently. A suitable ratio can be readily determined by the skilled person in any particular case.

In use, the exhaust gas flows into the gas conduit 88 and through the inlet 106 into the chamber 108. The exhaust gas then flows, with a swirling motion, through the chamber 108 and along an inner surface of the frustum 90. The linear velocity remains constant, but the angular velocity increases as gases travel towards the narrower end of the closed frustum of the cone 90. This increases the centrifugal force on the particles, which continue along this spiral path until they exit the frustum 90 through outlet 112. The particles then fall into the trap 92. The particles remain in the trap 92 and the gas, cleared of any sparks or solid products of combustion, travels along the annular space 98 between the inside of the housing 72 and the outside of

the casing 86. The gas then flows through perforations 118 into the chamber 120 and into pipe 114. The gas then flows through perforations 124 into the chamber 126. The perforations 124 control the rate of gas flow through the exhaust component 70. The gases then escape through the outlet pipe 128.

The exhaust component 70 of the invention may be manufactured according to the sequence of steps shown in Figure 5.

The steps by which the exhaust component 70 may be manufactured include: (i) Positioning the frustum 90 over the gas conduit 88 to provide a first sub-assembly 132.

(ii) Positioning a baffle 116 over the pipe 114 to provide a second sub- assembly 134.

(iii) Attaching the first sub-assembly 132 to the second sub-assembly 134 on opposite sides of a plate 108, so that each of the gas conduit 88 and the pipe 114 is terminated by the plate 104 to provide a third sub-assembly 136.

(iv) Positioning the third sub-assembly 136 inside the casing 86 to provide a fourth sub-assembly 138.

(v) Positioning the fourth sub-assembly 138 inside the housing 72 to provide a fifth sub-assembly 140.

(vi) Positioning the outlet pipe 128 in the housing 72, at the opposite end to the gas conduit 88 to provide the exhaust component 70.

According to all embodiments of the invention, the outlet pipe is preferably connected to the vehicle exhaust pipe. It is preferred that the outlet pipe is a vertical stack pipe.

Again according to all embodiments of the invention, in use, the exhaust component is positioned vertically on the i. e. engine so that the frustum extends generally vertically with the narrower end below the wider end.

The dimensions of the various components of the exhaust component can be readily determined by the skilled person in any particular case. The flow volume of the exhaust gas typically reduces by 10% as the gas flows through the exhaust component and cools. This reduction in flow volume should be taken into account when determining the dimensions of the various components of the exhaust component in a particular case in order for the exhaust component to function efficiently.

This dimension reduction contributes to providing the swirling motion of the gases, by maintaining the flow velocity.

Claims

1. An i. c. engine exhaust component comprising a hollow vessel having openings respectively for inlet and egress of exhaust gas, the vessel defining a gas flow path between the inlet and outlet; and the vessel including a gas permeable silencer and a gas permeable cyclone type spark arrestor located such that exhaust gas passing along the gas flow path passes through the silencer and spark arrestor, wherein the spark arrestor includes a casing having an inlet and an outlet and defining a flow path, for exhaust gas, between the inlet and outlet; a gas conduit positioned inside the casing and having openings at both ends; a closed frustum of a cone, attached to an inner wall of the casing at the wider end and attached to an outer wall of the pipe at the narrower end, so that it encloses the pipe and is closed at the narrower end, and having an outlet such that exhaust gases passing through the spark arrestor swirl inside the frustum; and a trap, for solid matter, that is branched from the flow path whereby solid matter entrained in the swirling gas inside the frustum passes to the trap before gas exits the spark arrester via the outlet.

2. An exhaust component according to Claim 1, wherein the hollow vessel encloses the casing.

3. An exhaust component according to Claim 2, wherein the inlet of the casing is at an end thereof remote from the silencer, whereby the exhaust gas travels substantially the length of the casing externally thereof before entering the spark arrestor.

4. An exhaust component according to Claim 2, wherein the inlet of the

silencer is at an end thereof remote from the outlet of the casing, whereby the exhaust gas travels substantially the length of the casing externally thereof before entering the silencer.

5. An exhaust component according to Claim I or any claim dependent therefrom, wherein the flow path extends along an inner wall of the frustum from the wider end of the frustum towards the narrower end, through the outlet of the frustum and then, externally from the frustum, back towards the wider end of the frustum by virtue of swirling of the gas.

6. An exhaust component according to any one of Claims I to 5, wherein the inlet to the casing perforates the casing near the wider end of the frustum.

7. An exhaust component according to Claim 1 or any claim dependent thereon, wherein, in use, the speed of swirling of the gas adjacent the narrower end of the frustum is greater than at the wider end.

8. An exhaust component according to Claim 7, wherein the frustum extends generally vertically with the narrower end below the wider end when the exhaust component is connected to the vehicle.

9. An exhaust component according to Claim I or any claim dependent thereon, wherein the trap is branched from the gas flow path and includes an enclosure surrounding, but spaced from, the closed narrower end of the frustum, whereby solid matter near the said end may pass through the frustum outlet and into the enclosure, away from the flow path.

10. An exhaust component according to any one of Claims I to 9, wherein the cross-sectional area of each of the individual components of the

exhaust component, through which the exhaust gas flows in use, is less than the area of the immediately preceding component through which the gas flows.

11. An exhaust component according to Claim 10, wherein the crosssectional area of each of the individual components of the exhaust component, through which the exhaust gas flows in use, is smaller, by 10% than the area of said immediately preceding component.

12. A method of assembling an exhaust component according to Claim 3 comprising (i) Positioning the frustum over the gas conduit to provide a first sub- assembly.

(ii) Positioning the first sub-assembly inside the casing to provide a second sub-assembly.

(iii) Attaching the inlet pipe to the second sub-assembly at the closed end of the casing to provide a third sub-assembly.

(iv) Positioning the third sub-assembly inside the housing to provide the exhaust component.

13. A method of assembling an exhaust component according to Claim 4 comprising (i) Positioning the frustum over the gas conduit to provide a first sub- assembly.

(ii) Positioning a baffle over the pipe to provide a second sub-assembly.

(iii) Attaching the first sub-assembly to the second sub-assembly on opposite sides of a plate, so that each of the gas conduit and the pipe is terminated by the plate to provide a third sub-assembly.

(iv) Positioning the third sub-assembly inside the casing to provide a fourth sub-assembly.

(v) Positioning the fourth sub-assembly inside the housing to provide a fifth sub-assembly.

(vi) Positioning the outlet pipe in the housing, at the opposite end to the inlet pipe to provide the exhaust component.

14. An exhaust component generally as herein described, with reference to and/or as illustrated in the drawing figure.