GB2043003A

GB2043003A - Track laying vehicle

Info

Publication number: GB2043003A
Application number: GB8003934A
Authority: GB
Original assignee: Caterpillar Mitsubishi Ltd
Current assignee: Caterpillar Mitsubishi Ltd
Priority date: 1979-02-16
Filing date: 1980-02-06
Publication date: 1980-10-01
Also published as: JPS55110028A; IT8019806A0; IT1148753B; FR2449021A1

Abstract

A track laying vehicle has an endless track entrained around a driving sprocket (14) and an idler wheel. The track comprises a plurality of articulated elements each having a pair of laterally spaced links (2) connected by a track shoe (6) and pivotally coupled to the links of adjacent elements in the track by pins having bushings thereon. Each element also has a noise-suppressing assembly comprising a hardened wear-resistant outer tubular portion (3), and an inner resilient portion (4) secured thereto, and means (5) for rotatably mounting the noise- suppressing assembly between the pair of links (2) at a position to contact the sprocket (14) between adjacent teeth of the sprocket prior to contact of the sprocket by the trailing bushing, and to contact the circumference of the idler wheel prior to contact by an idler-engaging surface of the element. <IMAGE>

Description

SPECIFICATION Track laying vehicle This invention relates to track laying vehicles having noise suppression assemblies rotatably carried between opposing track links.

Several attempts have been made in recent years to provide reduced noise track mechanisms. For example, U.S. Patent Specification No. 3,567,294 issued March 2, 1971 to F.E. Simpson et al discloses a track mechanism in which a rigid intermediate drive pin is provided to reduce impact energy losses when the driven bushing member strikes the sprocket, thus reducing wear on the external surface of a track bushing and horsepower losses. However, this track mechanism results in contact between the steel members and is not fully effective in reducing the noise level.

U.S. Patent Specification No. 4,035,036 issued July 12, 1977 by R.L. Boggs et al discloses a rotatable resilient tubular cushion member intermediate the drive bushings intended to reduce noise created by the bushings impacting upon the drive sprocket and the idler. This solution is effective in reducing noise, but its effectiveness is limited by the durability of the resilient material, particularly in severe operating environments.

Japanese Utiiity Model Publication No. Sho 50-51321 by Chagawa et al published May 19, 1975 shows a U-shaped resilient cushion member attached to the mid-portion of the inner wall of each track shoe. The cushion member is effective in reducing noise but has limited life because of the abrasive wear resulting from the sliding that takes place between the cushion member and the sprocket tooth with each engagement and disengagement.

According to the present invention, a track laying vehicle has an endless track entrained around a driving sprocket and an idler wheel, the track comprising a plurality of articulated elements each having a pair of laterally spaced links connected by a track shoe and pivotally coupled to the links of adjacent elements inthe track by pins having bushings thereon; wherein each element also has a noisesuppressing assembly comprising a hardened wear-resistant outer tubular portion, and an inner resilient portion secured thereto, and means for rotatably mounting the noise-suppressing assembly between the pair of links at a position to contact the sprocket between adjacent teeth of the sprocket prior to contact of the sprocket by the traiiing bushing, and to contact the circumference of the idler wheel prior to contact by an idler-engaging surface of the element.

Four examples of vehicles in accordance with the present invention are illustrated in the accompanying drawings, in which: Figure 1 is a part sectional side view of part of an endless track of one example; Figure 2 is a section taken on the line A-B in Figure 1; Figure 2A is a transverse section showing the track engaging an idler wheel; Figure 3 is an enlarged side view of the part of the track shown in Figure 2; Figure 4 is a side view of a part of a track of a second example; Figure 5 is a top plan view of the part of the example shown in Figure 4; Figure 6 is an end view of the part of the example shown in Figure 4; Figure 7 is a view similar to Figure 5 but of a third example; Figure 8 is a transverse part sectional view of the part of the example shown in Figure 7;; Figure 9 is a perspective view of part of the Figure 7 example; Figure 10 is a view similar to Figure 5 but of a fourth example; Figure 11 is a transverse elevation of the part of the fourth example shown in Figure 1 0; and, Figure 12 is a side elevation of the part of the fourth example shown in Figure 10.

Referring to Figures 1 to 3, a track shoe 6 is secured by bolts 7 and 8 to a pair of links 2, to form one element of an endless track. A cylindrical noise suppressing assembly having a resilient internal portion 4 and a hardened wear-resistant outer tubular portion 3 operatively secured thereto is rotatably mounted on a shaft 5 extending between opposite pairs of links 2. The endless track is urged into movement by a sprocket 14 and extends over an idler wheel 14a. The noise suppressing assembly is positioned in such a manner that it contacts the surface between adjacent sprocket teeth, before the adjacent tooth space is contacted by the track bushing, and contacts the circumference of the idler wheel 1 4a before the idler engaging surfaces of links 2 contact the idler wheel.The resilient internal portion 4 of the noise suppressing assembly yields to permit the bushing and the link gradually to contact the sprocket tooth space and idler, respectively, rather than with a severe metal-to-metal impact.

In this example, holes 9,9 for receiving shaft 5 are provided in the walls of opposing links 2, respectively.

The noise suppressing assembly may be attached during assembly of a track chain or after completion of the assembly.

Figures 4 to 6 show a second example, wherein the noise suppressing assembly 3, 4 and shaft 5 are carried by brackets 10 secured to each track shoe 6 between the opposing links 2 as by bolts 11.

Links 2 are attached to the body of track shoe 6 in a conventional manner similar to that shown in the example illustrated in Figures 1 to 3.

Figures 7 to 9 show a third example in which the shaft 5 is supported at the mid portion thereof by the lower extending portion of a V-shaped bracket 12, the upper flat ends of which are secured by bolts 11 to each track shoe 6. The noise suppression assembly is made up of two substantially equal parts rotatably mounted on opposite end portions 5' of the shaft 5, respectively.

Figures 10 to 12 show a fourth example, wherein brackets 10' are each provided with bolt holes 13 through which the bolts 7 and 8 pass to secure each bracket 10' to the respective link 2 and to track shoe 6.

Materials for the internal resilient member are selected from good quality naturai rubbers, synthetic rubbers or plastics. The hardened tube 3 operatively secured over the cylindrical resilient member 4 is preferably formed from a highly wear-resistant plastic or a hardened steel tube whose hardness is above Rockwellc 50.

Durabiiity tests of a prior art inverted U-shaped cushion member, a prior art tubular cushion member, and the hardened tube operatively secured to the resilient member have been carried out in environments having the track shoes packed with mud, and also with little or no mud. The results in hour-life are given below::

a Type of cushion member Packed with mud Slightly mud packed Inverted U-shape 100r L 500Hr 500 X 1300Hr Tubular 500 X 1000Hr Higher than 1 000Hr Hardened tube opera- Higher than Higher than tively secured on 750Hr 1500Hr cylindrical resilient cushion member The test results shows that the cylindrical noise suppressing assembly having a hardened wearresistant tubular outer portion operatively secured to an inner cylindrical resilient portion is more durable and gives longer service life than either the prior art U-shaped cushion member or the prior art tubular member because the resilient portion is protected from wear, breakage and abrasion when it is compressed and deformed.

Claims

1. A track laying vehicle having an endless track entrained around a driving sprocket and an idler wheel, the track comprising a plurality of articulated elements each having a pair of laterally spaced links connected by a track shoe and pivotally coupled to the links of adjacent elements in the track by pins having bushings thereon; wherein each element also has a noise-suppressing assembly comprising a hardened wear-resistant outer tubular portion, and an inner resilient portion secured thereto, and means for rotatably mounting the noise-suppressing assembly between the pair of links at a position to contact the sprocket between adjacent teeth of the sprocket prior to contact of the sprocket by the trailing bushing, and to contact the circumference of the idler wheel prior to contact by an idlerengaging surface of the element.

2. A vehicle according to claim 1, wherein the assembly mounting means comprises a shaft extending between and journalled in the pair of links.

3. A vehicle according to claim 1, wherein the assembly mounting means comprises a shaft rotatably carried by a pair of brackets secured to the track shoe between the links.

4. A vehicle according to claim 3, wherein the brackets are secured to the track shoe by bolts securing the track shoe to the links.

5. A vehicle according to claim 1, wherein the rotatably mounted assembly is formed in two portions, and the assembly mounting means comprises a shaft journalled in a generally V-shaped bracket extending between the two portions and secured to the track shoe.

6. A vehicle according to any one of the preceding claims, wherein the outer portion of the noisesuppressing assembly is cylindrical.

7. A vehicle according to claim 1, substantially as described with reference to any one of the examples illustrated in Figures 1 to 3, 4 to 6, 7 to 9, and 10 to 12 of the accompanying drawings.