GB2231013A

GB2231013A - Track for endless track vehicles, in particular for small-dimensions endless track vehicles

Info

Publication number: GB2231013A
Application number: GB9003916A
Authority: GB
Inventors: Ugo Bisi
Original assignee: Berco SpA
Current assignee: Berco SpA
Priority date: 1989-02-24
Filing date: 1990-02-21
Publication date: 1990-11-07
Anticipated expiration: 2010-02-21
Also published as: DE9001983U1; IT215729Z2; NL194544C; NL9000403A; GB9003916D0; NL194544B; FR2643605A3; BE1003669A6; IT8920629V0; JPH02128689U; GB2231013B; FR2643605B3; ES1014789U; JP2524271Y2; ES1014789Y

Abstract

The track (1), in particular for small-dimensions endless track vehicles, comprises a plurality of mutually hinged track links (2). Each track link comprises a sole (3), a ferrule (4), arms (5) connected at one end to the ferrule (4) and having hinge eyelets (6) at the other. The hinge eyelets (6) of a track link (2) are linked with the ferrules (4) of the adjacent track link (2) by means of pins which make it possible adjacent track links to articulatedly move. Except for pin, the components of each track link are cast as one single piece, giving the track link (2) a monolithic structure. <IMAGE>

Description

"TRACK FOR CATERPILLAR/ VEHICLES, IN PARTICULAR FOR

SMALL-DIMENSIONS CATERPILLAR/VEHfCLES" The prevent invention relates to a track for f 0 r

caterpillarl vehicles, in particular for caterpiLlar

vehicles of small dimensions.

The presently used tracks are composed by a plurality of elements connected with one another, such as track links, pins, ferrules, bushes, soles, screws, nuts, and still other elements. The presence of a plurality of interconnected elements endows the track with a very good functionality both from the viewpoint of the maintenance, and from the viewpoint of the use of said track.

Furthermore, it offers the possibility of replacing worn parts of the track, thus the useful life of said track being extended, and the degree of efficiency of the same track being maintained high and constant.

Furthermore, the presence of a plurality of elements of suitable shape gives the track a particularly flexible structure, capable of perfectly articulating on the drive wheel according to an involute outline which is the one which enables the caterpillar

vehicle to move with an as low as possible energy consumption, and without vibrations.

Unfortunately, manufacturing a track composed by a large number of elements results to be more and more complex and expensive with decreasing track dimensions.

In order to reasonably limit the costs, the smalldimensions tracks, hence for small-dimensions caterpillar

machines, are accomplished according to simplified structures, which anyway display limited flexibility characteristics.

Owing to the poor flexibility during rhe motion, suck types of traks articulate arond th rve drive whee! following the involute line to an only approximate extent. Owing to this matter of fact, the tracks does net result to be sufficiently engaged by the drive wheel, which causes vibrations which are transmitted to the structure of the machine, and the intensity of which increases with increasing machine speed.

Furthermore, the simplified engagement of the surfaces of the track which get coupled with the trackguide rollers causes the track to warp, in particular at high speeds, with the phenomena of wearing being increased, and strong vibrations being transmitted to the structure of the machine.

These simplified-structure tracks therefore offer satisfactory performances only in case of very slow vehicles, and anyway when the traveling distance is limited.

The purpose of the instant finding is of providing a track capable of obviating the above drawbacks, i.e., which is capable of being accomplished by means of a limited number of elements, and is therefore simple and cheap, but which is simultaneously flexible enough, so as to get engaged with the drive wheel according to an involute outline, and therefore to allow the machine to travel at a high speed.

Such a purpose is achieved by means of a track for

caterpillarZ vehicles, in in particular for caterpillar

vehicles of small dimensions, in which the transmission of the motion to the track is accomplished by means of at least one toothed drive wheel and a return wheel is provided, in which, between said two wheels a plurality of track guide rollers are installed, with said track comprising a plurality of track links articulated relatively to one another, characterized in that each track link is constituted by one single cast piece comprising a sole-shaped portion, a ferrule-shaped portion, two arm-shaped portions having first ends structured as one single piece with the ferrule portion and second ends each defining a portion of hinge-eyelet shape, with said hinge-eyelet-shaped portions having mutually opposite inner surfaces mutually spaced apart by a slightly longer length than the axial length of the ferrule portion in order to enable adjacent track links to get articulatedly coupled through a respective articulation pin running through the ferrule portion of a track link and the hinge-eyelet portions of the adjacent track link, with said arm portions defining sliding surfaces parallel and opposite to the sole portion and said ferrule portion defining a cylindrical outer surface on which the teeth of the drive wheel act according to an involute outline.

The invention is illustrated for merely exemplifying, and non-limitative, purposes in the figures of the hereto attached drawing tables, in which Figure 1 shows a perspective bottom view of two track links accomplished according to the invention, hinged to each other; Figure 2 shows a partially sectional bottom view of the track links of Figure 1: Figure 3 shows a front view of the track links; Figure 4 schematically shows a track according te the present invention, applied to the carriage of a

caterpillarvehicLe.

Referring to the above mentioned figures, the trick according to the invention, generally indicated by the reference numeral 1, comprises a plurality of track links 2 hinged with each other and driven by a drive wheel 11.

The track links 2 are engaged by track-guide rollers 14, and are returned by a return wheel 15. Each track link 2 (see, in particular, Figure 2), comprises a sole-shaped portion 3, a ferrule-shaped portion 4, two ar-rn-shaped portions 5, and two portions having the shape of hinge eyelets 6, and a pin 7.

The sole portion 3 is formed by two transversal bars 8 united by a membrane 9.

On the membrane 9, and at the middle, or in the nearby of the middle, of the track link, at least one slot 10 is provided.

By means of the slot 10 provided in each sole portion 3, the track 1 results to be self-cleaning, in that the drive wheel 11 is capable of expelling the earth which penetrated between the track links, thus the "packing" effect being limited. In fact, those skilled in the art are well aware of the fact that under particular working conditions, such as on argillaceous ground, straw mixed with wet earth, and so on, the track tends to get jammed.

Under these conditions, the articulation is hindered, and overstresses are generated on the track. On the contrary, the slot 10, by making it possible the material which jams the track to be better discharged, is capable of removing such overstresses.

The sole shaped portion 3, the ferrule portion 4,both arm palicns 5, and both hingeeyelet portions 6 are cast as one single body, with the expensive separate production of the elements, and their assemblage being avoided.

In fact, the arm portions 5 have their first enis cast as one single piece with both of the opposite portions of the ferrule portion 4, and each one of the second ends defines a respective hinge-eyelet portion 6.

The axial length of the ferrule portion 4 is slightly shorter than the distance existing between the mutually opposite inner surfaces of the hinge-eyelet portions 6, in order to enable adjacent links 2 of the track 1 to get coupled with each other. The inner diameter of the ferrule portion 4 and the inner diameter of the hingeeyelet portion 6 are such that, by getting coupled with the pin, they make it possible the same pin to be axially blocked, with simultaneously enabling the mutal articulation of two adjacent track links.

The arm portions 5 are provided with sliding surfaces 13 parallel to, and opposite to the sole portion 3, on which the track sliding rollers 14 rest. The sliding surfaces 13 have a regular and continuous shape, and, besides getting engaged with the rollers 14 -- thus making it possible the vehicle to be supported -- they guide the track 1.

The track 1 is assembled by uniting, through the pins 7, each ferrule portion 4 of a track link 2 with pairs of hinge-eyelet portions 6 of the adjacent track link 2.

When the track 1 is assembled, the external cylindrical surfaces of the ferrule portions 4 constitute the sliding path for the teeth of the drive wheel 11, so that when the machine travels, an engagement results according to a circle involute outline, which facilitates the machine translation movement -- thus enabling said machine to move at an even high speed -- and decreases the wear rate.

The sole 3, which is of the type with two transversal bars 8, represents the best compromise between the ability to get constrained to the ground, and the machine manoeuverability.

The dimensions of the sole 3 can be varied as a function of the several requirements: a "larger" surface area in case the specific pressure applied to ground has to be contained within narrow limits, and a "smaller" surface area if one wants to favour the manoeuverability and decrease the wear rate relatively to the drive wheel and the supporting rollers 14.

The track links 2 can be cast from special cast iron, capable of offering a high flowing ability at its melting point, so as to enable the manufacturer to respect a high precision in the dimensions, reducing, or even getting rid of, further processing steps.

For example, for the intended purpose a cast iron could be used, which has the following chemical composition: C 3.70 Si 2.60 Mn 0.31 Cr 0.028 S 0.014 P 0.029 Ni 1.45 Sn 0.03 Mg 0.076 Cu 0.83 Mo 0.31 By means of an aimed thermal treatment of hardening, a right combination between bainite and residual austenite can be obtained, and characteristics of strength and of tenacity can be reached, which are comparable to those of a structural steel hardened and tempered and surface-hardened. The mechanical characteristics obtained are as follows: R. 1150 N/mm2 HRc. 40 A. 10% The mechanical characteristics obtained make it possible a right compromise to be reached between hardness and tenacity, with a very good wear and fatigue resistance.

It will of course be understood that the present invention has been described above purely by way of example, and modifications of detail can be made within the scope of the invention.

Claims

1 . Track for caterpillar /vehicles, in particular for

caterpillar Zvehacles of small dimensions, in which the transmission of the motion to the track is accomplished by means of at least one toothed drive wheel and a return wheel is provided, in which, between said two wheels a plurality of track guide rollers are installed, with said track comprising a plurality of track links articulated relatively to one another, characterized in that each track link is constituted by one single cast piece comprising a sole-shaped portion a ferrule-shaped portion two arm-shaped portions having first ends structured as one single piece with the ferrule portion and second ends, each of which defines a portion of hinge-eyelet with said hinge-eyeletshaped portions having mutually opposite inner surfaces mutually spaced apart by a slightly longer length than the axial length of the ferrule portion in order to enable adjacent track links to get articulatedly coupled through a respective articulation pin running through the ferrule portion of a track link and the hinge-eyelet portions of the adjacent track link with said arm portions defining sliding surfaces parallel and opposite to the sole portion and said ferrule portion defining a cylindrical outer surface on which the teeth of the drive wheel act according to an involute outline.

2. Track according to claim 1, characterized in that the sole portion comprises two bars united by a membrane

3. Track according to claim 2, characterized in thaT the membrane is provided with at least one slot positioned at, or in the nearby of, its middle.

4. Track according to claim 1, characterized in that it is obtained from a cast iron having the following chemical composition: C = 3.70; Si = 2.60; Mn = 0.31; Cr = 0.028; S = 0.014; P = 0.029; Ni = 1.46; Sn = 0.03; Mg = 0.076; Cu Mo = 0.31.

5. Track according to claim 4, characterized in that it is hardened by means of a thermal hardening treatment.

Track substantially as herein disclosed and illustrated.

7. Track for caterpillar vehicles substantially as hereinbefore described with reference to the accompanying drawings.