ACOUSTIC SHIELDING FOR A TRACKED VEHICLE

Field of the Invention

The present invention relates generally to noise attenuation for tracked vehicles and more particularly to acoustic shielding for such vehicles.

The invention has been developed primarily for use in acoustic shielding for a dozer, and will be described hereinafter with reference to this application. However, it will be appreciated that the invention is not limited to this particular application and may also be applied, for example, to tracked military vehicles, such as tanks, as well as to other tracked vehicles.

Background of the Invention

Known dozers typically include two tracks, each of which extends around at least a drive wheel and an idler wheel. In two-wheeled, or "low-drive", track systems, the rear wheel includes a drive sprocket for progressing the track, and a front idler wheel around which the track is driven by the drive wheel. In three-wheeled, or "high-drive", track systems, a second idler wheel is provided and the track defines a triangle extending around the three wheels. In known three-wheeled systems, the drive wheel is usually located at the apex of the triangle, with the two idler wheels defining the base of the triangle.

As the tracked vehicle moves, track noise is generated predominantly by the action of the track chain on the drive sprocket. However, secondary noise is also produced as the track chain passes around the idler wheel(s) and over track support rollers.

Engagement of the track with the ground serves to dampen the tracks and thereby reduce the amount of track noise generated. This reduction of track noise due to ground engagement is significantly more pronounced in two-wheeled track systems where the drive wheel is located adjacent the ground. However, the degree of damping provided by ground engagement is appreciably less in three-wheeled systems where the drive wheel is elevated from the ground. Accordingly, known three-wheeled track systems tend to exhibit higher track noise than known two-wheeled systems.

It is also noted that any noise that is not absorbed by ground engagement tends to be projected relatively large distances, especially when atmospheric temperature inversions occur, such as on cold nights.

Object of the Invention It is the object of the present invention to overcome or substantially ameliorate one or more of the disadvantages of the prior art.

Summary of the Invention

Accordingly, in a first aspect, the invention provides acoustic shielding for a tracked vehicle having a body, a drive wheel having a drive sprocket, at least one idler wheel, and a track extending around the drive wheel and the idler wheel and being driven by the drive sprocket, said acoustic shielding comprising: a first acoustic shielding element adapted for fixed connection relative to the body of the tracked vehicle and at least partially enclosing the drive wheel and the track.

In a second aspect, the invention provides a tracked vehicle comprising: a body; a drive wheel having a drive sprocket; at least one idler wheel; a track extending around the drive wheel and the idler wheel and being driven by the drive sprocket; acoustic shielding comprising a first acoustic shielding element adapted for fixed connection relative to the body and at least partially enclosing the drive wheel and the track.

Preferably, the first acoustic shielding element extends from the body to at least partially enclose an outer side of the drive wheel. More preferably, the first shielding element is generally trapezoidal, with its longer side being adjacent the vehicle body and its shorter adjacent the drive wheel. In a preferred form, the first shielding element completely encloses the outer side of the drive wheel.

Preferably, the shielding includes a second acoustic shielding element adapted for fixed connection relative to the body and at least partially enclosing a front portion of the drive wheel. In some embodiments, the second shielding element is fixedly connected to the body, and in other embodiments to the first shielding element.

Preferably, the shielding includes a third acoustic shielding element adapted for fixed connection relative to the body and at least partially enclosing a rear portion of the drive wheel. In some embodiments, the third shielding element is fixedly connected to the body, and in other embodiments to the first and second shielding elements.

Preferably, the shielding includes a fourth acoustic shielding element adapted for fixed connection relative to the body and at least partially enclosing a top portion of the drive wheel, hi a preferred form, the fourth shielding element is fixedly connected to the body, and the first shielding element is adapted for fixedly connection to the body by being fixedly connected to the fourth shielding element, hi a preferred form, the first, second, third and fourth shielding elements define an integral acoustic shield around the drive wheel.

In some embodiments, the shielding element(s) are formed from a plurality of shielding portions, while in other embodiments a single shielding portion forms each shielding element.

Preferably, the shielding element(s) comprise a noise barrier material, hi a preferred form, the noise barrier material is a relatively flexible material such as rubber. However, in some embodiments the barrier material is a stiffer material, such as steel.

Preferably, the shielding element(s) also comprise a noise absorption material, hi a preferred form, the noise absorption material is a relatively deformable material, such as an elastomeric material, hi some preferred embodiments, the noise absorption material comprises one or more material selected from the group comprising: rubber, plastics, glass fibre, rock fibre and derivatives thereof.

Preferably, the shielding is connected to the body by a flexible suspension frame. More preferably, the suspension frame is adapted to withstand side-impact while minimising permanent damage to the shielding elements by flexing to absorb impact forces.

Preferably, the shielding includes deflector elements to direct track noise in a predetermined direction. More preferably, the deflector elements direct track noise toward the noise absorption material, hi some embodiments, the deflector elements are

connected to the shielding element(s) and extend inwardly from the shielding elements toward the drive wheel. In other embodiments, the deflector elements are embedded in the shielding element(s). In yet further embodiments, the noise barrier material defines the deflector elements.

Preferably, the shielding element(s) extend downwardly from an upper part of the body. However, in alternative embodiments, the shielding element(s) extend upwardly from a portion of the body to which the idler wheels are mounted.

Preferably, the tracked vehicle includes two idler wheels and the drive wheel is elevated with respect to the idler wheels, such that in use the idler wheels are located adjacent the ground and the drive wheel is elevated with respect to the ground.

Brief Description of the Drawings

Preferred embodiments will be described hereinafter, by way of examples only, with reference to the accompanying drawings, in which:

Figure 1 is a side elevation of a tracked vehicle incorporating a preferred embodiment of acoustic shielding;

Figure 2 is a front elevation of the vehicle of Figure 1;

Figure 3 is a rear elevation of the vehicle of Figure 1;

Figure 4 is an enlarged view of the circled portion of Figure 3; and

Figure 5 is similar view to Figure 4, but shown an alternative embodiment of the acoustic shielding.

Preferred Embodiments of the Invention

Referring to the drawings, there is shown a tracked vehicle 40 to which is mounted acoustic shielding 50. The vehicle 40 has a body 41 supported on a high-drive track system 60. However, in alternative embodiments (not shown), the tracked vehicle 40 uses a low-drive track system. The illustrated track system 60 includes a drive wheel 61 having a drive sprocket (not shown), and two idler wheels 62. A track 63 extends around the drive wheel 61 and the idler wheels 62 and is driven by the drive sprocket.

The acoustic shielding 50 includes a first 51, second 52, third 53 and fourth 54 acoustic shielding elements, each of which are fixedly connected relative to the body 41 of the tracked vehicle 40 for shielding, respectively, the side, front, rear and top of the drive wheel 61.

The first shielding element 51 extends from the body 41 to enclose an outer side of the drive wheel 61 and an upper part of the track 63. However, in alternative embodiments, the first shielding element 51 only partially encloses the side of the drive wheel 61. The first shielding element 51 is trapezoidal, with its longer side being adjacent the vehicle body 41 and its shorter side adjacent the drive wheel 61. However, in other embodiments (not shown), the first shielding element 51 is rectangular. In the embodiments illustrated in Figures 1 to 4, the first shielding element 51 is adapted for connection to the body 41 by virtue of being fixedly connected to the fourth shielding element 54, which is connected directly to the body 41. However, in other embodiments, such as that shown in Figure 5, a flexible suspension frame 70 extends generally laterally outwardly from the body 41 to support the first shielding element 51. The suspension frame 70 is adapted to withstand side-impact while minimising permanent damage to the first shielding element 51 by flexing to absorb impact forces.

The second acoustic shielding element 52 extends from the body to partially enclose a front portion of the drive wheel 61. The second shielding element 52 is fixedly connected to the body 41. However, in other embodiments (not shown), the second shielding element 52 is instead connected to the body 41 by virtue of being connected to the first 51 shielding element 51 and/or the suspension frame 70.

The third acoustic shielding element 53 extends from the body 41 to partially enclosing a rear portion of the drive wheel 61. The third shielding element 53 is fixedly connected to the body 41. However, in other embodiments (not shown), the third shielding element 53 is instead connected to the body 41 by virtue of being connected to the first shielding element 51 and/or the suspension frame 70.

The fourth acoustic shielding element 54 is fixedly connected at its laterally innermost end to the body 41 and, in combination with the body 41, encloses a top portion of the drive wheel 61. As mentioned above, in the embodiments shown in Figures 1 to 4, the

fourth shielding element 54 connects the first shielding element 51 to the body 41. However, in the second embodiment illustrated in Figure 5, the fourth shielding element

54 is fixedly connected at its laterally innermost end to the body 41 and has an opposite free end. Accordingly, in the second embodiment, if the shielding 50 is subjected to a side impact force, the fourth shielding element 54 simply slides relative to the suspension frame 70 and the first shielding element 51 to avoid being damaged.

As can be seen from Figures 1, 2 and 3, the first 51, second 52, third 53 and fourth 54 shielding elements define an acoustic shield around the drive wheel 61.

The shielding elements 51, 52, 53 and 54 are each formed from a single shielding portion. However, in alternative embodiments (not shown), each of the shielding elements 51, 52, 53 and 54 is formed from a plurality of shielding portions. The shielding elements 51, 52, 53 and 54 include an outer relatively flexible noise barrier material, such as rubber. However, in alternative embodiments (not shown), the barrier material is a stiffer material, such as steel. The shielding elements also comprise an inner relatively deformable noise absorption material formed from an elastomeric material, in the form of a rubber or plastics derivative. However, in other embodiments (not shown), the noise absorption material is formed from rubber, plastics, glass fibre, rock fibre or derivatives and/or combinations thereof. The noise absorption material serves to absorb noise generated by engagement of the track 63 with the drive wheel 61. The noise barrier material deflects noise to a region within the shielding 50 for absorption by absorption material. The noise barrier material is stiffer than the noise absorption material.

As shown in Figure 4, the shielding elements 51, 52, 53 and 54 include deflector elements

55 arranged to direct noise in a predetermined direction, preferably toward the noise absorption material. In some embodiments, the deflector elements 55 extend inwardly from the shielding elements 51, 52, 53 and 54, toward the drive wheel and in other embodiments, the deflector 55 elements are embedded in the shielding elements 51, 52, 53 and 54. hi yet further embodiments (not shown), the noise barrier material defines the deflector elements.

It will be appreciated that the illustrated embodiments of acoustic shielding provide the advantage of reducing the transmission of track noise to tracked vehicle operators and the

surrounding environment. Accordingly, the risk of damage to hearing health of operators is reduced, as is the environmental impact of operations utilising tracked vehicles.