GB2186900A

GB2186900A - Road sweeping vehicle incorporating a sound attenuation system

Info

Publication number: GB2186900A
Application number: GB08702609A
Authority: GB
Inventors: Anthony James Duthie; Michael Sandford
Original assignee: JOHNSTON ENG Ltd
Current assignee: JOHNSTON ENG Ltd
Priority date: 1986-02-20
Filing date: 1987-02-05
Publication date: 1987-08-26
Also published as: EP0234782A2; GB8702609D0; EP0234782B1; US4779303A; GB8604229D0; DE3764487D1; GB2186900B; EP0234782A3

Description

GB2186900A 1

SPECIFICATION tion and a stowed position.

The suction type road sweeping vehicle may Improvements in road sweeping vehicles also comprise a suction conduit and pick up nozzle on either side of the vehicle, means for The invention relates to suction type road 70 separately closing off one end of each conduit sweeping vehicles and more particularly to to prevent refuse from passing through the such vehicles incorporating a sound attenua- conduit when it is closed, and brush means tion system. on either side of the vehicle operable such Many known road sweeping vehicles oper- that one brush rotates in the operating posi ate by means of an exhauster fan generating a 75 tion whilst the other is in the stowed position.

vacuum within an air tight container, which is The perforated panel preferably has holes of mounted on the chassis of the vehicle, and a diameter suitable to shift a dominant noise sucks the debris through suction conduits frequency to a predetermined higher range.

from the road. By the very nature of this sys- The perforated panel may also be a mesh tem, the construction and operation of suction 80 comprising holes of a diameter in the range 4 type road sweeping machines makes them to 5 mm with a hole density of greater than noisy vehicles, due to the fact that most of 20,000 holes/M2 and preferably comprises them are equipped with two engines, one for holes of diameter 4.75 mm.

propelling the vehicle, the other for driving the The attenuation duct is preferably lined with suction fan and sweeping machinary. It has 85 an absorbtive material, or a purpose noise at however been established that the major tenuating material matched to suppress the sound producing elements of such machines dominant noise frequencies and is between are usually the flow of air into the debris pick 20mm and 5Omm thick, preferably being up nozzle and the discharge of air from the 25mrn thick.

exhauster fan outlet, which combined can ac- 90 The invention further comprises a method of count for up to 80% of the total sound emisattenuating the sound emission from a suction sion from the road sweeper. type road sweeping vehicle comprising the Since it is important that the flow of dis- steps of passing the air from an exhauster fan charged air is not hindered, in order to main- into an expansion duct and effecting a shift of tain suction efficiency of the system, many 95 the frequency of the sound of the air to a road sweeping vehicles incorporate no form of higher frequency range by means of a perfo sound attenuation system at all. rated panel and attenuating the high frequency Other machines incorporate some form of sound by means of a duct lined with an ab duct or enclosure to attenuate the sound. But sorlative layer.

the sound of the air leaving the fan outlet is 100 A preferred embodiment of the invention usually in a low frequency range of approxi- will now be described in detail with reference mately 250-500 hz, and to properly attenuate to the accompanying drawing in which:

sound of this frequency, would require a very Figure 1 is a schematic side view of a typi long duct with a thick noise absorbing lining, cal road sweeping vehicle.

the construction and incorporation of which is 105 Figure 2 is a schematic perspective view of some what impractical. a road sweeping vehicle incorporating a sound Thus, the present invention provides a sucattenuation system, but with certain parts om tion type road sweeping vehicle comprising a mited.

self propelled chassis, an air tight container The basic road sweeping vehicle in which mounted on the chassis and communicating 110 the present invention is incorporated is as de with a fan for generating a vaccum within said scribed in GB 1592775 and shown in Fig. 1.

container, at least one suction conduit extend- A dual sweep suction road sweeping vehicle ing at one end into the container and being 10 comprises a self propelled chassis 11 in provided at the other end with a suction pick- cluding road wheels 12 and drivers cab 13, up nozzle, and a sound attentuation system 115 on which are mounted a tipping body 15, a connected to an outlet of the fan, comprising fan housing 16, suction equipment 17, a wide an expansion duct inside which is mounted a sweep brush 18 and a pair of channel brushes perforated panel which is connected to an at- 19, one located on either side of the vehicle.

tenuation duct, whose outlet exhausts to at- The tipping body 15 is a steel moncoque mosphere, the arrangement being such that, in 120 assembly which is pivotable about a horizontal use, expelled air from the fan passes into the axis 21 adjacent its rear end. The body is expansion duct, through the perforated panel mounted on a subframe of steel members 23 and through the attenuation duct before being to which the body is pivotally attached by finally exhausted into the atmosphere. means of flanges 22 depending from the The suction type road sweeping vehicle is 125body. The subframe is rigidly mounted on the preferably provided with brush means chassis 11, which may be any suitable type of mounted on the vehicle forwardly adjacent the vehicle chassis, provided with driving controls suction conduit and comprising a rotatable in the cab 13. The interior of the tipping body brush movably connected to the vehicle chas provides an airtight container for dust etc sis for movement between an operating posi- 130 swept up by the vehicle and is closed off by 2 GB2186900A 2 a rear door 25. The rear door is pivoted from the front of the tipping body 15 to about its upper edge and is operable by a ram which it is rigidly connected and from which it (not shown) in known manner to permit is divided by partition 20. The engine housing egress of material contained in the body when 16 encloses an engine and suction fan 57 it is tipped. A further ram (not shown) con- 70 which are mounted on the subframe 23 and nected between the front part of the tipping apply suction to the interior of the sweeping body 15 and the subframe 23 is operable to body when the vehicle is working. The ancil tip the body. lary hydraulic equipment, fuel tanks, etc., for Protruding from the top of the tipping body the sweeping equipment are also mounted on 15 is a wandering hose 30 comprising a first 75 the subframe within the housing 16.

secton 31 which communicates with the in- Referring now to Fig. 2, which shows a typ- terior of body 15 and is pivotable about a ical suction type road sweeping vehicle as vertical axis. Hingedly connected to the first previously descrbed incorporating a sound at section 31 is a second hose section 32 which tenuation system, it will be appreciated that is L-shaped so that a nozzle 33 of the wan- 80 certain parts have been omitted for clarity but dering hose may be brought adjacent to the are shown in Fig. 1.

ground by pivotal and hinging movement of The outlet duct 51 to the suction fan 57 is the wandering hose. connected to one end of an expansion cham The suction equipment 17 comprises, on ber 52, which is rectangular in cross section each side of the vehicle, a nozzle 35 con- 85 and extends across the front end of the en nected by a conduit 36 to an inlet duct 37 gine housing 16. The other end of the expan into the body 15, the connection being ar- sion chamber 52 connects to an attenuation ranged such that the body may be tipped. The duct 54, which is also rectangular in cross conduits are provided with shutting means 38 section. Where the expansion duct 52 meets for closing off one end thereof to prevent rethe attenuation duct 54 there is fitted a perfo fuse from entering the container via that con- rated panel 53 corrugated to increase its area.

duit. This enables the vehicle to be used to This perforated panel acts to raise the fre sweep either side of the road regardless of quency of the sound of the air. At the other the direction of travel of the vehicle, using one end of the attenuation duct 54 is an angled set of suction equipment only. Wheels 41 are 95 portion 56 to expel exhausted air upwardly provided on a draw bar 40 on to which the away from the vehicle. The attenuation duct nozzle 35 is pivotably mounted, the purpose 54 is provided with splitter panels 55 lined of which is to control the height of the nozzle with a noise absorbing lining 55 which ab above the road surface. The nozzle and wheel sorbs the sound as the air passes through the assembly may be lifted clear of the road by a 100 narrow channels between the splitters within ram 42 when the conduit on that side of the the duct, before being finally exhausted to the vehicle is not in use. atmosphere.

The channel brushes 19 are situated in front The mesh panel, splitter spacing and lining of the nozzles 35 and are movably mounted are matched to ensure that effective noise at to the chassis 11 by means of a bracket and 105 tenuation occurs. The perforated panel area pivotal link system (not shown) to allow float- must be such as to suit the air flow through ing of movement the brushes 19 relative to it, not hindering it, which would reduce the the ground. effectiveness of the sweeper and to ensure The wide sweep brushes 19 are suspended that the frequency of sound is shifted from a from the chassis 11 and mounted for rotation 110 low range, typically 250/500 Hz, to a higher and have means such that they may be raised one around 1000 Hz which can be attenuated off the ground when not in use. by relatively short length ducts lined with a The two sets of brushes 18 and 19 are less bulky thinner material, which may be ac driven by separate hydraulic motors (not commodated within the physical dimension shown). 115 constraints of the equipment.

The interior of the body 15 is partitioned off A suitable noise absorbent lining is prefera- to form a duct 47, which is flared at its end bly a purpose skinned foam material, for adjacent to rear of the body and the rearmost example open cell foam clad with MYLAR, portion is formed by a mesh grill 50 which which provides a diaphragrm, permitting the extends across the full width of the body at 120 absorption of noise yet allowing the duct to the posithon shown in Fig. 2. Duct 47 is con- be cleaned without affecting the foam.

nected by another duct 48 to a flanged con- In one particular example it was found that nector 49 which is connected to the inlet side using a panel of steel mesh comprising holes of a suction fan, when the body is in its low- of 4.75 mm diameter and with a hole density ered position as shown. 125 of 23810 holes/ M2, a mesh area of 0.5 M2 Extending upwardly into the body at either and thickness of 2 mm and lining the attenua side and adjacent its front end are inlet ducts tion duct with the purpose skinned foam, 37 which are connected to suction conduits achieved a reduction in the fan outlet sound of 36. approximately 10 dBa.

The engine housing or canopy 16 extends 3 GB2186900A 3

Claims

CLAIMS 10. A suction type road sweeping vehicle

1. A suction type road sweeping vehicle as claimed in Claim 9 in which the duct lining comprising a self propelled chassis, an air is 25mm thick.

tight container mounted on the chassis and 11. A method of attentuating the sound communicating with a fan for generating a va- 70 emission from a suction type road sweeping cuum within said container, at least one sucvehicle as claimed in any one of the preceding tion conduit extending at one end into the claims, comprising the steps of passing the air container and being provided at the other end from an exhauster fan into an expansion duct, with a suction pick up nozzle, and a sound effecting a shift in the frequency of the sound attenuation system connected to an outlet of 75 of the air to a higher frequency range by the fan, comprising an expansion duct inside means of a perforated panel and attenuating which is mounted a perforated panel which is the high frequency sound by means of a duct connected to an attenuation duct whose outlet lined with an absoffitive layer.

exhausts to atmosphere, the arrangement be- 12. A suction type road sweeping vehicle ing such that, in use, expelled air from the fan 80 substantially as herein before described with passes into the expansion duct, through the reference to and as shown in the accompany perforated panel and through the attenuation ing drawings.

duct before being finally exhausted into the 13. A method of attenuating the sound atmosphere. emission from a suction type road sweeping

2. A suction type road sweeping vehicle as 85 vehicle substantially as herein before described claimed in Claim 1 having brush means with reference to and as shown in the accommounted on the vehicle forwardly adjacent the panying drawings. suction conduit and comprising a rotatable Printed for Her Majesty's Stationery Office brush movably connected to the vehicle chas- by Burgess & Son (Abingdon) Ltd, Dd 8991685, 1987. 25 sis for movement between an operating posi- Published at The Patent Office, 25 Southampton Buildings, tion and a stowed position. London, WC2A 'I AY, from which copies may be obtained.

3. A suction type road sweeping vehicle as claimed in Claim 2 comprising a suction conduit and pick up nozzle on either side of the vehicle, means for separately closing off one end of each conduit to prevent refuse from passing through the conduit when it is closed and brush means on either side of the vehicle operable such that one such brush is rotating in the operating position whilst the other is in the stowed position.

4. A suction type road sweeping vehicle as claimed in any one of the preceding claims in which the perforated panel has holes of a dia- meter suitable to shift a dominant noise frequency to a predetermined higher range.

5. A suction type road sweeping vehicle as claimed in any one of the preceding claims in which the perforated panel is a mesh compris- ing holes of a diameter in the range 4 to 5 mm with a hole density of greater than 20,000 holes /M2.

6. A suction type road sweeping vehicle as claimed in any one of the preceding claims in which the perforated panel is a mesh comprising holes of diameter 4.75 mm with a hole density of 23,810 holes/M2.

7. A suction type road sweeping vehicle as claimed in any one of the preceding claims in which the attenuation duct is lined with an absoffitive material.

8. A suction type road sweeping vehicle as claimed in any one of the preceding claims in which the attenuation duct is lined with a pur- pose noise attenuating material matched to suppress the dominant noise frequencies.

9. A suction type road sweeping vehicle as claimed in any one of the preceding claims in which the duct lining is between 20mm and 50mm thick.

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