The present invention relates to track laying vehicles. This form of traction is common for certain types of military and construction vehicles and requires that directional control is achieved by skid-steering, where the track on one side of the vehicle is caused to run at a different speed to the track on the other side of the vehicle to cause the vehicle to turn.
The invention has particular, though not exclusive, application to relatively small sized vehicles of this kind (say with a body length in the order of a metre), also known as robots, which may be used in hazardous or hostile environments for explosive ordnance disposal (EOD), inspection, reconnaissance, communications, rescue or other such tasks under autonomous control or under the control of a human operator located at a safe distance. Typically such robots comprise a self-propelled tracked platform carrying the various items of equipment suited to the task which it is intended to perform—such as manipulators, lights, antennas, cameras, microphones or other sensory devices—and a wireless link or control cable spool to pass commands and data from/to the remote operator. Robots of this kind have to be capable of operating over uneven terrain and manoeuvring within confined spaces, and operating in this respect with the utmost reliability. Tracked vehicles are generally preferred to wheeled vehicles for such tasks due to the greater mobility which they can provide including, in appropriate cases, turning on the spot.
A problem which can arise in the course of operating known vehicles of this kind, however, is shedding of a track, thereby rendering the vehicle immobile. If occurring during the course of an EOD mission, for example, this can cause the mission to be aborted or at best require a second vehicle to be deployed, possibly needing to move the first vehicle before the mission can be continued, and is in any event an outcome to be avoided if at all possible. In this respect the tracks of such vehicles are generally in the form of unitary moulded bands or are composed of a plurality of articulated links (also known as shoes), and are driven by a respective powered sprocket at one or both ends of the vehicle. The body of the vehicle is supported on each side by a series of rollers—known as road wheels—which run on the respective lengths of the tracks which are laid on the ground at any time. At least in the case of articulated tracks, each track link is typically formed with a tang (projection) on its face opposite to its ground-engaging face and the sprockets and road wheels are formed with circumferential grooves—or are disposed in parallel pairs to effectively define such a groove between them—through which the track tangs pass to maintain the correct alignment of the tracks on the vehicle. While this method of track alignment is normally effective so long as the vehicle operates over reasonably even surfaces, if a gap is present under part of one of the tracks—for example when the vehicle crosses a ditch or climbs over an obstacle—the unsupported track can sag under its own weight and corresponding track tangs can escape from the constraints of the road wheel grooves. If one or more tangs then reengage on the “wrong” side of a road wheel—which can occur particularly if the vehicle is also turning because very high lateral loads can be imparted to the tracks by skid steering—the track may become jammed or the following tangs will also tend to become disengaged as the track continues to be driven and the track will be shed.
The present invention seeks to avoid the above-described problem and in one aspect resides in a track laying vehicle comprising an endless driven track on each side of the vehicle and a plurality of road wheels along each side of the vehicle arranged to run on respective said tracks; each track comprising a series of tangs extending oppositely to the ground-engaging surfaces of the track and said road wheels comprising or being arranged to define circumferential grooves through which the tangs of the respective track are arranged to pass when the tracks are driven; and wherein in operation the road wheels are arranged to nip the tangs in the course of their passage through said grooves.
Nipping the tangs with the road wheels in accordance with the invention can act to resist the tangs dropping out of their grooves if a corresponding portion of track is unsupported from below and hence can obviate the risk of a track being shed in such circumstances.
In a preferred embodiment said road wheels are fitted with elastomeric tyres where they are adapted to nip said tangs.
Preferably also the lateral faces of said tangs and the confronting surfaces of said road wheels are both tapered.
The tracks of the vehicle may comprise respective series of articulated links and each said link preferably comprises a said tang located adjacent to the point of articulation of the link.
Preferably also the road wheels are comprised within bogies which are arranged to define a respective pair of said circumferential grooves in series, the spacing of said tangs along the respective track being so related to the spacing of each said pair of grooves that, within each said bogie, there is at least one tang at or close to the position of fullest engagement with at least one said groove at substantially all times.
The invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which:
Referring to
As seen also in
At the nominal rear end of the vehicle 1 a track drive sprocket 8 is provided, driven by an onboard electric motor, and equipped with two parallel circumferential series of teeth 8A which engage in recesses 9 in the opposite flanks of the track links (see also
The body of the vehicle is supported at each side on the lower run of the respective track 3 by a series of three road wheel bogies, each such bogie comprising a pair of bifurcated swing arms 13 pivoted at their apices to the under chassis 14 of the vehicle on an associated rubber torsion block 15 (
Opposite to its track pad 6/7 each track link is formed with a tang 18. These tangs 18 pass through circumferential grooves (not shown) in the drive sprocket 8, idler wheel 10 and guide wheel 12, and through similar grooves effectively defined by the spacing between each parallel pair of road wheels 16, in order to maintain the correct alignment of each track 3 with respect to the vehicle. The tangs 18 are located close to the pivot points of the respective track links 4 and are tapered at their leading and trailing surfaces (as seen in
With further reference to
Various modifications may be made to the illustrated vehicle without departing from the scope of the invention, of which the following are specific examples.
Instead of disposing the road wheels 16 in serial pairs in bogies, the vehicle may be fitted with a series of individual leading or trailing swing arm assemblies along each side, each with a single set of parallel road wheels. These will have the same track retaining capability by nipping the tangs 18 e.g. as indicated in
Although the invention has been described in terms of tracks with a single tang 18 on each link 4, for larger vehicles it may be preferable to have two tangs in parallel on each link. The road wheels will then be in threes rather than pairs, so as to collectively define two parallel grooves corresponding to the two tangs.
Instead of the sprockets 8 driving the respective tracks by engaging the track link flanks as described above, they could be configured to drive by engagement with the tangs 18.
Number | Date | Country | Kind |
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0800408.7 | Jan 2008 | GB | national |