AU2004284110B2 - Cooling engine exhaust gases - Google Patents

Description

"Extraction Apparatus" Field of the Invention This invention relates to an extraction apparatus, and also to a machine incorporating such an extraction apparatus. 5 The extraction apparatus according to the invention has been devised particularly, although not solely, for use with a machine which has an internal combustion engine discharging hot exhaust gases during operation thereof and which is used to perform cutting and chasing operations on brickwork and masonry. The extraction apparatus may, however also be used to extract exhaust gas from 10 other machinery powered by combustion engines, such as chainsaws and lawnmowers. Through use of this invention, exhaust gases generated by machinery may be dispelled from environments where accumulation of exhaust gases could possibly create hazardous working conditions. 15 Background Art It is common to chase a groove or trench into brickwork and masonry to accommodate service lines such as electrical and other cabling, and water and gas supply lines. Typically, a chasing operation is performed using a machine having one or more cutting blades. 20 A significant amount of dust can be generated during a chasing operation, and water is often used for dust suppression. Typically, water is sprayed into the vicinity of the chasing operation, usually onto the cutting blade or blades. The use of water for dust suppression precludes the use of electrical machinery such as electrical grinders that were previously a preferred option for performing 25 chasing operations.

-2 The inability to use electrical machinery requires that other sources of power be utilised. One suitable source of power is a machine driven by an internal combustion engine. Such a machine does, however, have a disadvantage in that its exhaust gases are potentially dangerous and lethal, particularly when the 5 machine is operated in confined areas. It is against this background, and the difficulties and problems associated therewith, that the present invention has been developed. Disclosure of the Invention According to a first aspect of the invention there is provided an extraction 10 apparatus for a machine from which exhaust gases are discharged during operation thereof, the extraction apparatus comprising a body defining an outlet, an air inlet communicating with the outlet for air flow from the inlet to the outlet, an exhaust gas inlet communicating with the outlet, and injection means for injecting water, the body being configured for cooling by forming a confluence of incoming 15 air from the air inlet, exhaust gas from the exhaust gas inlet and water from the injection means. The machine may be a handheld tool and the extraction apparatus may be an accessory for the tool with the body being configured for forming the confluence. Typically, the exhaust gas is hot and the confluence of the incoming air, the hot 20 exhaust gas and the water is advantageous in that contact of the air flow and water with the hot exhaust gas effects cooling of the exhaust gas. Preferably, air flow from the inlet to the outlet is established by a flow generation means. The flow generation means may be of any appropriate form; for example, it may 25 be a suction source connected to the outlet, or an air delivery source such as a blower connected to the inlet.

-3 The air inlet may receive air from any appropriate source. The incoming air may, for example, be ambient air (such as air from the environment in which the machine is operating), or the incoming air may be air extracted from a containment zone disposed about a tool operated by the machine. In the latter 5 case, the incoming air is likely to be accompanied by dust generated during operation of the tool, and possibly also by water in circumstances where there is use of water for dust suppression. Preferably, the body defines a flow path leading to the outlet, and wherein the air inlet and the exhaust gas inlet both open onto the flow path, and the injection 10 means is adapted to inject water into the flow path. In one arrangement, the flow path may comprise an axial flow passage, with the air inlet being at one end thereof and the outlet being at the other end thereof, such that there is (in use) axial flow of air along the flow passage from the inlet towards the outlet. 15 In another arrangement, the flow path may comprise a flow passage having an initial section commencing at the inlet, and a final section terminating at the outlet, with the two sections being disposed one about the other. The exhaust gas inlet is preferably arranged to deliver exhaust gas into the flow path downstream of the air inlet. In one arrangement, the exhaust gas inlet may 20 be configured to deliver exhaust gas into the flow path in a flow direction corresponding to the axial flow direction of the air. In another arrangement, the exhaust gas inlet may be configured to deliver exhaust gas into the flow path in a flow direction transverse to the axial flow direction of the air. There may also be provision for use of a cooling fluid, typically water. In this 25 regard, the body may have provision for water flow in heat exchange relationship therewith for cooling purposes. For example, there may be a water jacket disposed about at least a portion of the flow path for heat exchange contact therewith.

- 4 The injection means for the injection of water into the flow path, may comprise of one or more water injection nozzles in a side wall of the flow path. The or each injection nozzle may receive water for injection from the water jacket in the body. The or each injection nozzle may be disposed between the water jacket and the 5 flow path. The injected water may also serve to perform a filtering function on the exhaust gas, dissolving a portion of the exhaust therein. Water used for cooling but not injected into the flow path may subsequently be used for dust suppression where appropriate. 10 Water may be delivered to the apparatus by way of a flexible water delivery line. The apparatus may incorporate a filter or scrubber for treating the exhaust gas before being dispelled. This may allow the hazardous components to be extracted from the exhaust gas before it is dispelled. It may even allow for the exhaust gas to be dispelled within the same environment without increasing the 15 hazard to the operator. This may be particularly useful when the machinery is used in underground locations. Where the extraction apparatus is used with a flow generation means comprising a suction source, the outlet may be connected to the suction source by way of a suction hose. Cooling of the exhaust gas is desirable if not essential, in such a 20 case for, otherwise heat could cause damage to the suction hose and possibly also the suction source. The suction hose and the water delivery line may be conveniently connected together for handling as a single unit. This may be achieved by accommodating the water delivery line in the suction hose for at least part of the length thereof. 25 Where the apparatus is used with a flow generation means comprising a blower, the inlet may be connected to the blower by way of a blower hose. Alternatively, the blower may be incorporated in, or mounted on, the machine and connected directly to the inlet. In such an arrangement, the blower may be driven by the -5 engine of the machine. A discharge hose may be fitted to the outlet for conveying the mixture of air and exhaust gases discharging therefrom away, such as for example to a remote location, possibly outside of the environment in which the machine is being operated. 5 The extraction apparatus according to the invention may be provided as a discrete unit that can be fitted to a machine powered by an internal combustion engine. Alternatively, the extraction apparatus according to the invention can be incorporated as an integral part of a machine powered by an internal combustion engine; for example, the extraction apparatus may be incorporated as a feature of 10 a new machine or retro-fitted as an attachment to an existing machine. According to a second aspect of the invention there is provided an extraction apparatus for a handheld machine having an internal combustion engine from which hot exhaust gases are discharged during operation thereof, the extraction apparatus comprising a body defining a flow path terminating at an outlet, 15 injection means for injecting water, an air inlet communicating with the flow path, whereby a flow generation means communicating with the flow path can induce an air flow from the inlet to the outlet, and an exhaust gas inlet communicating with the outlet, wherein the extraction apparatus is configured for forming a confluence of incoming air from the air inlet, exhaust gas from the exhaust gas 20 inlet and water from the injection means. According to a third aspect of the invention there is provided a machine having an internal combustion engine from which hot exhaust gases are discharged during operation thereof, the machine further having an extraction apparatus according to the first or second aspect of the invention. 25 According to a fourth aspect of the invention, there is provided a machine for performing a working operation on a workpiece, the machine comprising a tool receiving means for receiving a tool for performing the working operation, an internal combustion engine operable to drive the tool, the engine having an exhaust through which exhaust gas is discharged during operation thereof, 30 injection means for injecting water, a flow path having an outlet, the flow path being in fluid communication with the engine exhaust, the flow path also being in -6 fluid communication with an air inlet, whereby in use there is confluence in the flow path of water from the injection means and incoming air and exhaust gas, prior to discharge thereof through the outlet. The machine may further comprise means for delivering water into the vicinity of 5 the tool for suppression of dust generated thereby. The machine may still further comprise a shroud disposed about the tool for containment of the dust and also the dust suppression water, and an extraction line communicating at one end thereof with the shroud and at the other end thereof with the air inlet, for extracting dust and dust suppression water carried by 10 air drawn into the shroud and conveyed to the air inlet under the influence of a flow generation means such as a suction source or a blower. Brief Description of the Drawings The invention will be better understood by reference to the following description of several specific embodiments thereof as shown in the accompanying drawings in 15 which: Figure 1 is a schematic side elevational view showing the extraction apparatus according to a first embodiment fitted onto a machine; Figure 2 is a perspective view of the extraction apparatus according to the first embodiment, viewed from one side thereof; 20 Figure 3 is a side elevational view of the extraction apparatus; Figure 4 is a plan view of the extraction apparatus; Figure 5 is an elevational view from the outlet end of the extraction apparatus; Figure 6 is an elevational view from the inlet end of the extraction 25 apparatus; -7 Figure 7 is a sectional view on line 7-7 of Figure 5; Figure 8 is a schematic view illustrating the machine shown in Figure 1 fitted with the extraction apparatus according to the first embodiment, in operation; 5 Figure 9 is a schematic sectional view of an extraction apparatus according to a second embodiment; Figure 10 is a schematic sectional plan view of an extraction apparatus according to a third embodiment; and Figure 11 is a partially sectioned elevational view of the extraction 10 apparatus shown in Figure 10. Best Mode(s) for Carrying Out the Invention Referring to Figures 1 to 8 of the drawings, there is shown an extraction apparatus 1 according to a first embodiment. The apparatus 1 is an attachment for a cutting machine 2 for performing cutting and chasing operations on wall and 15 floor surfaces. The cutting machine 2 typically comprises a work head 3 and a body 4 carrying the work head. The body 4 incorporates a drive unit 5 in the form of an internal combustion engine (typically a petrol engine) having an exhaust line 6 (hidden in Figure 1 by the apparatus 1, and therefore depicted in dotted outline). 20 The work head 3 receives and supports a cutting tool 7, typically in the form of a cutting blade. The apparatus 1 comprises a body 11 having a tubular portion 12 defining a central flow passage 13 which provides a flow path. The flow passage 13 extends axially between two ends, at one of which there is provided an air inlet 14 and at 25 the other of which there is provided an outlet 15.

-8 As shown in Figure 8, the apparatus 1 according to the embodiment is operated in conjunction with a flow generation means 16 for generating an air flow from the air inlet 14 to the outlet 15. In this embodiment, the flow generation means 16 comprises a suction source such as a vacuum pump 17, the suction inlet of which 5 is connected to the outlet 15 by a suction hose 18. A discharge hose 19 is connected to the outlet of the vacuum pump 17 for conveying the discharge thereof to a remote location. The body 11 further comprises an exhaust gas inlet 21 having an intake end 23 and a discharge end 25. The intake end 23 is adapted for communication to the 10 exhaust line 6 of the engine 5. While not shown in the drawings, a coupling is provided for securing the body 11 to the machine 2 with the intake end 23 of the exhaust gas inlet 21 communicating with the engine exhaust line 6. The exhaust gas inlet 21 has a first tubular section 24 extending into the flow 15 passage 13 from the intake end 23 of the inlet 21 and a second tubular section 26 extending along the flow passage 13 to terminate at the discharge end 25 of the inlet 21. The second tubular section 26 is closed at the outer end thereof by an end wall 27 of generally conical configuration with the apex thereof disposed inwardly. The exhaust gas inlet 21 opens laterally onto the flow passage 13 20 through circumferentially spaced ports 28 in the second tubular section 26 adjacent the end wall 27. By virtue of its configuration, the end wall 27 acts to deflect oncoming exhaust gas towards the ports 28. With the arrangement of the air inlet 14 and the exhaust gas inlet 21, there is confluence (in the flow passage 13) of incoming air (as an air stream) and exhaust 25 gas (as an exhaust gas stream). The incoming air and exhaust gas streams combine in the flow passage 13 and exit through the outlet 15 as a common stream flowing along the suction hose under the influence of the vacuum pump. The confluence of the incoming air and the hot exhaust gas streams is advantageous in that contact of the cooler air stream with the hot exhaust gas 30 stream effects cooling of the exhaust gas. Additionally, the cooler air dilutes the -9 hot exhaust gas, and the temperature of the resultant combined air/exhaust gas stream is lower than that of the exhaust gas alone. The body 11 has provision for water flow in heat exchange relationship therewith for cooling purposes. Specifically, the body 11 incorporates a water jacket 31 5 disposed about the flow passage 13. Water flows through the water jacket 31 between a water inlet 33 and a water outlet 35. The water inlet 33 is connected into a flexible water delivery line (not shown). Water discharging from the outlet 35 is conveyed away along a discharge line coupled thereto and can be used for dust suppression purposes about the tool 7. 10 There is also provision for injection of water into the flow passage 13 to further assist cooling of the hot exhaust gas. In this embodiment, water is injected into the flow passage 13 through an injection nozzle 37 adapted to receive water for injection from the water jacket 31 in the body 11. The injection nozzle 37 is provided on the side wall 39 of the flow passage 15 at a location upstream of the 15 exhaust gas inlet 21. The location of the injection nozzle 37 relative to the discharge end 25 is intended to reduce any possibility of injected water entering the exhaust system of the engine in the event of the engine not being operational while water injection is occurring. The injected water is conveyed along the flow passage 13 to the outlet 15 and 20 then along the suction hose, together with the air and exhaust gas. The provision of cooling for the exhaust gas using water may be selective, in that apparatus 1 may be operated either with, or without, the delivery of water to the water jacket 31 for heat exchange and water injection. This can be controlled by a suitable control valve (not shown) in the water supply line. 25 In addition to creating fluid flow along the flow passage 13 as well as the suction hose, the suction effect provided by the vacuum pump may also provide noise suppression for the cutting machine. The apparatus 1 can be operated with the air inlet 14 opening directly to atmosphere at the location where the machine is being used. In other words, air is -10 drawn directly into the flow passage 13 through the air inlet 14 under the influence of suction created by the vacuum pump. The apparatus 1 can be operated in another way, where the air inlet 14 is connected to a shroud provided about the cutting blade 7 so as to communicate 5 with a containment zone defined within the shroud. The shroud 8 encloses part of the cutting blade and has an opening beyond which the cutting blade extends. The purpose of the shroud 8 is to contain the dust and, if water is used for dust suppression, to also contain slurry generated by the water used to suppress the dust. With this arrangement, air is drawn from within the containment zone 10 defined about the cutting blade by the shroud. The air is likely to be accompanied by dust generated during operation of the blade, and possibly also water and/or slurry in circumstances where there is use of water for dust suppression. There may be a filtering process performed at the vacuum pump to filter the slurry and solid particles from the air and exhaust gas. The vacuum pump may have a 15 discharge line through which the filtered air and exhaust gas are discharged to atmosphere. The first embodiment has been described with reference to its use in conjunction with a flow generation means 16 in the form of a suction source connected to the outlet 15 of flow passage 13, thereby to cause induction of air into the air inlet 14 20 and generate an air flow along the flow passage. An alternative arrangement for generating an air flow along flow passage 13 may involve delivery of air to the inlet 14, such as by way of a blower communicating therewith. With such an arrangement, a discharge hose may be connected to the outlet 15, for the purpose of conveying away the mixture (being air and exhaust gas, and possibly 25 also dust and water) discharged therefrom. Referring now to figure 9, there is shown apparatus 40 according to a second embodiment. The second embodiment is different from the first embodiment in that it is designed for operation with a larger cutting machine, such as, for example, a floor saw for performing cutting and chasing operations in a floor 30 surface.

- 11 The apparatus 40 comprises a body 41 having a tubular portion 43 defining a central flow passage 45. The flow passage 45 extends axially between two ends, at one of which there is provided an air inlet 47 and at the other of which there is provided an outlet 49. 5 The body 41 further comprises an exhaust gas inlet 51 having an intake end 53 and a discharge end 55. The intake end 53 is adapted for connection to the exhaust line of the engine, and a coupling 57 is provided for that purpose. The exhaust gas inlet 51 is so configured that the discharge end 55 is centrally located within the flow passage 45 as well as opening onto the flow passage 55 in the 10 direction towards the outlet 49. The exhaust gas inlet 51 has a first tubular section 54 extending into the flow passage 45 from the intake end 53 and a second tubular section 56 extending along the flow passage 45 to terminate at the discharge end 55. With the arrangement of the air inlet 47 and the exhaust gas inlet 51, there is 15 confluence (in the flow passage 45) of incoming air and exhaust gas. The incoming air and exhaust gas streams combine in the flow passage 45 and exit through the outlet 49 as a common stream. The body 41 has provision for water flow in heat exchange relationship therewith for cooling purposes. Specifically, the body 41 incorporates a first water jacket 61 20 disposed about a portion of the flow passage 45 downstream of the exhaust gas inlet 51. The body 41 further incorporates a second water jacket 62 about first section 54 of the exhaust gas inlet 51. The two water jackets 61, 62 are interconnected by flow line 63. Water flows through the two water jackets 61, 62 between a water inlet 64 and a 25 water outlet 65. The water inlet 64 and water outlet 65 are connected into a flexible water delivery line (not shown). Water leaving the outlet 65 can be conveyed away and discarded, or alternatively used for other purposes such as dust suppression at the shroud (in the case where the machine has a dust suppression facility).

- 12 There is also provision for injection of water into the flow passage 45 to further assist cooling of the hot exhaust gas. In this embodiment, water is injected into the flow passage 45 through injection nozzles 67 adapted to receive water for injection from the first water jacket 61 in the body 41. The injection nozzles 67 are 5 circumferentially spaced in the side wall 69 of the flow passage 45 at a location downstream of the discharge end 55 of the exhaust gas inlet 51. The location of the injection nozzles 67 relative to the discharge end 25 is intended to reduce any possibility of injected water entering the exhaust system of the engine in the event of the engine not being operational while water injection is occurring. 10 The injected water is conveyed along the flow passage 45 to the outlet 49, together with the air and exhaust gas. As with the first embodiment, the provision of cooling for the exhaust gas using water may be selective, in that apparatus 40 may be operated either with, or without, the delivery of water for heat exchange and water injection. This can be 15 controlled by a suitable control valve (not shown) in the water supply line. Also as with the first embodiment, apparatus 40 can be operated with the air inlet 47 opening onto atmosphere, either directly or via a blower. The apparatus 40 can be operated in another way, where the air inlet 47 is connected to a shroud of the cutting machine so as to communicate with the 20 containment zone defined within the shroud. With this arrangement, air is drawn from within the containment zone. In the embodiments described previously, the extraction apparatus could be arranged for use with either a suction pump or a blower, as previously explained. An extraction apparatus devised particularly for use in conjunction with a blower 25 or other source of air under pressure is the subject of the third embodiment shown in figures 10 and 11. The apparatus 70 according to the third embodiment comprises a body 71 comprising an outer tubular portion 73 and an inner tubular portion 75 spaced - 13 inwardly from the outer tubular portion 73. The outer tubular portion 73 is open at one end 77 thereof and is closed at the other end 79 thereof by an end wall structure 81. The inner tubular portion 75 is supported within the outer tubular portion 73 by 5 radial support webs 83 in circumferentially spaced apart relationship. Further, the inner tubular portion 75 has an inner end 85 spaced from the end wall structure 81, and outer end 87 extending beyond the open end 77 of the outer tubular member 73. With this arrangement, the outer and inner tubular portions 73, 75 cooperate to 10 define a flow passage 89 having an outer passage section 91 defined between the inner and outer tubular portions, an inner passage section 93 defined within the inner tubular portion 75, and a transition passage 97 defined by the space between the inner end 85 of the inner tubular portion 75 and the end wall structure 81. 15 The outer passage section 91 defines an initial flow path section extending from inlet 92 and the inner passage section 93 defines a fluid path section terminating at outlet 94. The support webs 83 do not obstruct the outer passage section 91 of the flow passage 89 because they are in circumferentially spaced apart relationship. 20 The body 71 further comprises an exhaust gas inlet 101 having an intake end 103 and a discharge end 105 opening onto the outer passage section 91 of the flow passage 89. The intake end 103 is adapted for connection to the exhaust line of an engine, and a coupling 107 is provided for that purpose. The body 71 has provision for water flow in heat exchange relationship therewith 25 for cooling purposes. Specifically, the body 71 incorporates a water jacket 109 disposed around part of the outer tubular portion 73 and extending into end wall structure 81. The portion of the water jacket 109 accommodated within the end wall structure 81 is provided by a cavity 113 within the end wall structure.

- 14 Water flows through the water jacket 109 between a water inlet 117 and a water outlet 119. The water inlet 117 is mounted on the end wall structure 81 and extends centrally into the inner tubular portion 75, terminating at a fitting 121 to which the end of a water hose (not shown) can be attached. The inlet 117 5 includes a bore 123 defining a flow path which communicates with the cavity 113 within the end wall structure 81 through ports 125. There is also provision for injection of water into the flow passage 89 to assist cooling of hot exhaust gases. In this regard, water is injected into the flow passage through an injection port 127 provided in the side wall of the water inlet 10 117. In operation of the suction apparatus 70, a blower hose is fitted onto the inlet 92 at end 77 the outer tubular portion 73, and a discharge hose is fitted to the outlet 94 at the outer end 87 of the inner tubular portion 75. Additionally, a water hose is fitted to the water inlet 117. With this arrangement, the three hoses are positioned 15 one within the other as to provide a unitary hose assembly for ease of handling. With the blower operating, an air flow is delivered to the extraction apparatus 70 to flow along the outer passage section 91 at which there is confluence between the air and hot exhaust gas entering through the exhaust gas inlet 101. The mixture passes through the transition passage 97 and then turns around to flow 20 along the inner passage section 93 to the discharge hose fitted to outer end 89 of the inner tubular portion 75. Water if desired for cooling purposes, is injected into the mixture of air and hot exhaust gas via the injection port 127. It should be appreciated that the scope of the invention is not limited to the scope of the embodiments described. 25 While the embodiments have been described in relation to a machine for performing chasing and cutting operations, it should also be understood that the invention might be utilised for machines having tools other than cutting blades, such as for example drilling tools and grinding tools.

-15 Further, the invention may be used with any machine having an engine generating hot exhaust gases that need to be cooled and conveyed away from the location at which the engine is operating. The extraction apparatus according to each of the embodiments described is a 5 discrete unit that is designed to be fitted as an attachment to an existing machine. It should, however, be understood that the extraction apparatus according to the invention could be incorporated as an integral part of a machine; for example, it may be incorporated as a feature of a new machine or retro-fitted as an attachment to an existing machine. 10 Throughout the specification, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

Claims (25)

1. An extraction apparatus for a machine from which exhaust gases are discharged during operation thereof, the extraction apparatus comprising a body defining an outlet, an air inlet communicating with the outlet for air flow 5 from the inlet to the outlet, an exhaust gas inlet communicating with the outlet, and injection means for injecting water, the body being configured for cooling by forming a confluence of incoming air from the air inlet, exhaust gas from the exhaust gas inlet and water from the injection means.

2. An extraction apparatus as claimed in claim 1 wherein the machine is a 10 handheld tool and the extraction apparatus is an accessory for the tool, the body being configured for forming the confluence.

3. An extraction apparatus according to claim 1 or 2 wherein the body defines a flow path leading to the outlet, and wherein the air inlet and the exhaust gas inlet both open onto the flow path, and the injection means is adapted to inject 15 water into the flow path.

4. An extraction apparatus according to claim 3 wherein the flow path comprises an axial flow passage, with the air inlet being at one end thereof and the outlet being at the other end thereof, such that there is in use axial flow of air along the flow passage from the inlet towards the outlet. 20

5. An extraction apparatus according to claim 3 wherein the flow path comprises a flow passage having an initial path section commencing at the inlet, and a final path section terminating at the outlet, with the two path sections being disposed one about the other.

6. An extraction apparatus according to any one of claims 3 to 5 wherein the 25 exhaust gas inlet is arranged to deliver exhaust gas into the flow path downstream of the air inlet. -17

7. An extraction apparatus according to claim 4 wherein the exhaust gas inlet is configured to deliver exhaust gas into the flow path in a flow direction corresponding to the axial flow direction of the air.

8. An extraction apparatus according to claim 6 wherein the exhaust gas inlet is 5 configured to deliver exhaust gas into the flow path in a flow direction transverse to the axial flow direction of the air.

9. An extraction apparatus according to any one of the preceding claims wherein the injection means comprises one or more water injection nozzles.

10. An extraction apparatus according to claim 9,wherein the nozzles are 10 disposed in a side wall of that portion of the body defining the flow path.

11. An extraction apparatus according to any one of the preceding claims further comprising cooling means for cooling the body, the cooling means being adapted to pass a cooling fluid in heat exchange relation with the body.

12. An extraction apparatus according to claim 11 wherein the cooling fluid 15 comprises water.

13. An extraction apparatus according to claim 12 wherein the cooling means comprises a water jacket in the body disposed about at least a portion of the flow path for heat exchange contact of the water therewith.

14. An extraction apparatus according to claim 13, wherein the water for injection 20 comprises received water from the water jacket in the body.

15. An extraction apparatus according to claim 14 wherein the water injection nozzles comprise nozzles disposed between the water jacket and the flow path.

16. A combination of an extraction apparatus according to any one of claims 2 to 25 15 and a flow generation means that is external to the handheld tool and the extraction apparatus for generating an air flow from the air inlet to the outlet - 18

17. A combination according to claim 16 wherein the flow generation means comprises a suction source, the outlet being connected to the suction source by way of a suction hose.

18. A combination according to claim 16 wherein the flow generation means 5 comprises a blower, the inlet being connected to the blower by way of a blower hose.

19. A combination according to claim 18 wherein a discharge hose is fitted to the outlet for conveying away the mixture discharging therefrom.

20. An extraction apparatus for a handheld machine having an internal 10 combustion engine from which hot exhaust gases are discharged during operation thereof, the extraction apparatus comprising a body defining a flow path terminating at an outlet, injection means for injecting water, an air inlet communicating with the flow path, whereby a flow generation means communicating with the flow path can induce an air flow from the inlet to the 15 outlet, and an exhaust gas inlet communicating with the outlet, wherein the extraction apparatus is configured for forming a confluence of incoming air from the air inlet, exhaust gas from the exhaust gas inlet and water from the injection means.

21. A machine having an internal combustion engine from which hot exhaust 20 gases are discharged during operation thereof, the machine having an extraction apparatus comprising a body defining an outlet, an air inlet communicating with the outlet for air flow from the inlet to the outlet, an exhaust gas inlet communicating with the outlet, and injection means for injecting water, the body being configured for forming a confluence of 25 incoming air from the air inlet, exhaust gas from the exhaust gas inlet and water from the injection means.

22. A machine for performing a working operation on a workpiece, the machine comprising a tool receiving means for receiving a tool for performing the working operation, an internal combustion engine operable to drive the tool, 30 the engine having an exhaust through which exhaust gas is discharged during -19 operation thereof, injection means for injecting water, a flow path having an outlet, the flow path being in fluid communication with the engine exhaust, the flow path also being in fluid communication with an air inlet, whereby in use there is confluence in the flow path of water from the injection means, and 5 incoming air and exhaust gas, prior to discharge thereof through the outlet.

23. A machine according to claim 22 further comprising means for delivering water into the vicinity of the tool for suppression of dust generated thereby.

24. A machine according to claim 23 further comprising a shroud disposed about the tool for containment of the dust and also the dust suppression water, and 10 an extraction line communicating at one end thereof with the shroud and at the other end thereof with the air inlet, for extracting dust and dust suppression water carried by air drawn into the shroud and conveyed to the air inlet under the influence of a flow generation means.

25. An apparatus or machine substantially as herein described with reference to 15 the accompanying drawings.