US2168053A

US2168053A - Endless track mechanism

Info

Publication number: US2168053A
Application number: US741388A
Authority: US
Inventors: Oscar L Starr; Jose Mission San; Grothe Walter; Harmon S Eberhard
Original assignee: Caterpillar Tractor Co
Current assignee: Caterpillar Inc
Priority date: 1934-08-25
Filing date: 1934-08-25
Publication date: 1939-08-01
Anticipated expiration: 1956-08-01

Description

Aug. 1, 1939. o. STARR ET AL ENDLESS TRACK MECHANI SM 3 Shets-Sheet 1 Filed Aug. 25, 1934 n S. 0 h Mrer fi/ M 05 N. a s m WL T rm A "a m OWH g- 1, 1939- o. L. STARR ET AL 2,163,053

ENDLESS TRACK MECHANISM Filed Aug. 25, 1954 131 /z/ uzz 3 Sheets-Sheet .3

I. I 135 I 225 ,74 I 134 28 A f 53/ M2 g2 l 6' R156 a4 INVENTORS. Oscar L. J'Iarr Wal-fer firo'f'he y Harmon 5. Eberhard ate...

1 .4 TA E 2,168,053 V j ENDLESS TRA K MECHANISM Oscar L. Starr, Mission San Jose, Walter Grothe,

. Alameda, Calif., and Harmon .S. Eberhard,

Peoria, 111., assignors to Caterpillar Tractor 00.,

San Leandro, Califi, a corporation of California ApplicationAugust 25, :1934, Serial No. 741,388

18 Claims. ((1365-10) This invention relates to an improved endless track mechanism, and more particularly to an improved track link construction in self-laying endless track mechanism of a track type vehicle,

such as a tractor.

Introduction and general description Each link forming part of an endless track mechanismof a track-type tractor, is usually.

formed of an intermediate full width rail por tion, and end portions of reduced width adapted to be pivotally connected with reduced width end portions of adjacent links to providea rail in which there are joints between adjacent links,

each joint including a pairv of longitudinally ,4

spaced gaps. The endless track includes a pair of rails thus formed, and turns about a final drive sprocket and a front idler wheel. Heretofore, the

travels over the gaps in a rail joint, it. can not find support on more than half full. rail width throughout its entire travel over the joint. This is so because if the reduced width end portions are each of half full rail width, then obviously when the roller travels over either joint gap, it

is supportedon only a half full rail width. Should one of the reduced width-end portions be of less than half full rail width and the other greater than half full rail width, the roller is supported on the end portion of less than half full rail width as it travels over the gap at theside of such less than habf full rail width end portion.

Also, in such prior construction, when a weight bearing track roller travels over one gap, its entire weight will be supported for a period of time solely on the reduced width end portion overlapping an end of such gap. Thus, such reduced width end portion will have a region -where it is subjected to greater roller pressure per unit area than the unit pressure on the full width rail portion of the link. As a result, such region will wear more rapidly, and the rail surface of such region will be lowered below the plane of the rail surface of the full width rail portion .of the link. This results in pounding of the roller against portions of the links which bound the gap, thereby creating destructive forces causing premature breakdown-of the joint. As each joint includes a plurality of such gaps, it is seen that the roller will be supportedsolely on one link end portion of reduced width as it travels over one gap, and

s then solely on another reduced width end portion as it travels overanother gap. The transference of weight from onereduced width end portion to another causes a shearing effect between adjacent pivotally conected links, having a destructive action on the members pivotally connecting the track link assemblies.

The link of our invention is so constructed as to overcome the disadvantages pointed out above, and provide a joint oflong life. In our improved construction, the reduced width end portions of thelinks have their rail extremities so formed as to, be oblique with respect to the sides of the link, and underlap the full width rail portion of an adjacent link, to provide more than half full width rail suport for a track roller throughout its, entire passage over a joint without widening the rail width of the joint beyondthe full width rail portion of the links. The surfaces under the full width rail portion of a link adapted to be underlapped by the oblique surfaces on the reduced width end portions of adjacent links, are arranged to ,have an obliqueness complementary and substantially parallel, to that on such reduced width end portions, and thus form diagonal wiping joints in which, by virtue of such underlapping, the wearing qualities of the joint are -maintained, asthe railwears. In the embodiment'of the invention illustrated, thewide gaps which previously existed in links prior to our invention are filled by end bosses or rail end projections, each of which hasan oblique rail edge, and an obliquesurfa'ce at its extremity.

It has been found that cast metal links are not satisfactory for long life; and, as a result, forged metal links have been relied upon to provide material of desirable strength and durability.

Forging of a metal link having theinwardly extendingv oblique extremities at the ends of the reduced width'end portions of the link, presents the problem of removalof the link from the forging die. Our invention, therefore, includes the construction of a track link having the advantageous features previously discussed but which can be forged without manufacturing difficulty. We accomplish this by placing each end portion of the rail forging line which extends over an oblique extremity on a reduced Width end portion, closely adjacent and substantially parallel to a side face of the link, with one forging line end portion at one side of the link and the other at the opposite side of the link. Our manner of forging enables final construction of the link withoutsubsequent special machining operations;

only the conventional machining operations being necessary. Should one desire to employ a non-forged link, the constructional shape of our link can still be utilized to provide for the advantageous features of our invention.

Objects of invention The invention has for its objects, among others,

the provision of an improved:

Endless track mechanism constructed to promote long life and-efficient operation;

Endless track mechanism of economical construction free of excess weight;

Rail joint between adjacent pivotally connected links of the track, formed to provide ample rail surface engageable with track rollers, to enhance wearing qualities of the track and thereby provide long life;

Rail joint capable of accomplishing the foregoing described object, and which is-still of substantially full rail width to form part of a rail offull uniform rail width throughout;

Rail joint over which the track rollers can travel without pounding against edges of the joint when the track and rollers have become worn;

Track link constructed to cooperate with ad- Jacent links to provide any of the foregoing described objectsj. I

Forged metal track link to provide any of the foregoing described objects.

Having enumerated some of the objects and having described principles of construction of our invention, we shall now refer to the drawings for a more detailed description of our invention, as embodied in one of its forms.

Description of figures Figs. 1 through 6 illustrate the track construction.

Fig. 1 is a side elevation of a portion of the endless track.

Fig. 2 is a fragmentary plan view taken as indicated by line 2-2 in Fig. 1.

Fig. 3 is a fragmentary section taken in the plane indicated by the line 33 in Fig. 1. Fig. 4 is a vertical transverse section taken in the plane indicated by the line 44 in Fig. 1.

Fig. 5 a vertical transverse section taken in planes indicated by the lines 55 and 5-5' in Fig. 1; the left half of Fig. 5 being taken in planes indicated by line 55 and the right half being taken in planes indicated by line 5'5'.

Fig. 6 is a vertical transverse section taken in the plane indicated by the line 6-6 in Fig. 1.

Figs. 7 through illustrate the track link construction, a right-hand link being selected for illustration.

Fig. 7 is a right side elevation of the link.

Fig. 8 is an elevational view of the inside of the link.

Fig. 9 is a sectional view taken in the plane Endless track Each endless track mechanism of a track-type tractor generally includes an endless self-laying track supported around an associated track frame, by means of a front idler wheel mounted at the front of the track frame and a driving sprocket at the rear thereof; the weight of the tractor being transmitted to the ground stretch of the track through a plurality of weight bearing track rollers running on spaced rails of the track. The driving sprocket serves to propel the tractor over the endless track, and to pick up the track and feed its upper reachforwardly over the front idler wheel which guides the re-laying thereof. If desired, the upper stretch of the track between the front idler and drive sprocket can be supported by suitable track carrier rollers.

Figs. 1 through 6 illustrate the construction of a track link assembly of our invention, a plurality of which when pivotally connected together form the endless track. Suchassembly comprises track shoe I06 secured to the outer edges of left-hand link I01 and right-hand link I08, by cap screws I09. Lock washers H0 are preferably interposed between the cap screw heads and the ground face of the track shoe. Grouser I II (Fig. 1), integral with shoe I06, is formed to retain its earth penetrating ability after considerable wear. The ground-engaging end III of the grouser is substantially flat or non-pointed; and its sides III diverge with gradual taper toward the base of the grouser which is not materially wider than end III'. Hence, the width .of end I I I does not increase unduly as grouser III wears, which would be the case with a relatively sharp pointed end heretofore employed. Cap screws I09 have non-circular or flat sided heads to facilitate fastening thereof by a suitable instrument, such as a wrench. Each head is formed with convexly shaped end surface I I2; the contour of each surface IIZ being initially such as to correspond to the contour, which wear on the head would cause during operation of the track. Such contour is preferably substantially spherical. As a result, ground drag which might be caused by the heads when the track is new is reduced 3&0 a minimum. Track links I01 and I08 of each assembly are symmetrical with respect to each other, to thereby form left-hand and right-hand links, respectively. As can be seen more clearly from Figs. 2

and 4, one pair of reduced width end portions (preferably the front end) of a pair of links forming a link assembly are at the inner sides of the links, and are overlapped or embraced by outer reduced width end portions at the rear of the links of the adjacent pair of links, to provide full width rail joints of butt-lap construction. The inner reduced width end portions are connected by bushing II3 press-fitted in such portions; and the outer reduced end portions are connected by pin II4 journalled in bushing 3 to provide the pivotal connection between adjacent pairs of links. From Fig. 4, it will be seen that pin I'll is longer than bushing H3, so that the pin ends can be press-fitted in the outer reduced width end portions. Bushing H3 and pin H4 are described more fully hereinafter.

M aster pin invention, at least one of the link connecting pins is specially constructed to provide by itself the master connecting element, thus permitting all the links forming the same rail of the track to be of like construction and completely interchangeable.

Master pin I2I (Figs. 1 and 6) has end recesses I22, preferably of frusto-conical taper; the end of the pin about each recess I22 being slotted at I23. Tapered plugs or wedges I24 are driven into recesses I22 to expand the ends of pin I2I so as to wedge securely such recessed ends within track links I01 and I08; the slots I23 facilitating expansion of the pin ends for this purpose. Each plug I24 is preferably provided with threaded aperture I26 in the outer end thereof,

to receive a suitable implement for extractingthe plug when it is desired to disassemble the track. Threaded aperture I26 in plug I2I-also allows the use of a cap screw or thelike which can be screwed into the aperture until its head contacts the'outer end of the plug, to provide an abutment head against which a hammer or the like can be struck for driving the plug into place without injury to the threads thereof.

After assembly, aperture I26 is preferably sealed by plug I21 of cork or other readily removable packing material, toprevent entry of mud, dirt and the like. It is to be noted that the ends of master pin I2I do not extend out-' wardly beyond the outer sides or faces of track links I01 and I08. Therefore, it cannot interfere with the outside track roller flanges employed by us.

Track link and rail The spaced oppositely positioned track links of each link assembly, although similarly formed -as to structural features, differ only in being right-hand and left-hand rail forming links. As

the structures are similar, only the right-hand link will be described in detail; it being underformed to provide a finished track link by cer- By a special tain simple machining operations. construction of the link and .a special arrangement of the forging parting line along the link,

certain desirable features are imparted to the link without the use of special machining operations. Only conventional machining operations are desirable after the link is forged, namely, to

'form a flat shoe engaging surface on the outer edge of the link, a flat planar rail surface on the inner edge thereof, to finish the apertures which receive the track pin and the track bushing, and to provide tapped holes for the cap screws which secure the track shoe to the links.

Each link has a rail the intermediate portion of which is of full rail width; and end portions of the link are of reduced rail width. One reduced width end portion' has a side edge forming a straight line continuation of one side edge of the intermediate full width rail portion, while the opposite reduced width end portion has a side edge which forms a straight line continuation of the opposite'side edge of the full width rail portion. Thus, at each end of the link, there is a recess at one side thereof and a reduced width end portion at the opposite side, to enable adjacent links of a track to be butt-lap fitted and pivotally connected for the provision of full width rail joints. The extremities of the reduced width end portions are formed to cooperate with adjacent links, to providerail surfaces throughoutthe joints of the character previously discussed,

substantially full rail, uniform width, namely, the;

maximum rail width of the entire rail formed by a plurality of links connected end to end.

. Rear end portion I33 is at the outer side of the link and is of reduced uniform width; and its outside rail edge portion I33 forms a straight continuation of the outside rail edge portion I32 of intermediate portion I32. Thus, an end recess I33 (Fig. 9) is provided at the rear end ofthe link adjacent reduced portion I33. Frontend reduced width portion I34 is at the inner side of the link,'and is consequently diagonally opposite to reduced width portion I33; end recess I34 (Fig. 9), diagonally opposite end recess I33, being formed at the end of the link adjacent reduced portion I34. Reduced portion I34 has inside rail edge portion I34 forming a straight continuation of inside rail edge portion I32 of intermediate portion I32. Outside rail edge portions I32 and I33 are substantially parallel to inside rail edge portions I32 and I34 Hence, each link has parallel side edges forming the side edges of the rail.-

Each of reduced width end portions I33 and I34 is of substantially one-half full rail width, thus enabling adjacentlinks to be connected together, in the manner shown in Fig. 2, to provide buttlap rail joints of substantially full, uniform rail width.

Outer edge portion I35 (Figs. '1 and 8) of the link provides the track shoe engaging portion, and has flat surface I36 to engage track shoe I06. In the front reduced width end portion I34 of the link, rail portion I3I and shoeportion I35 are integral with bushing receiving eye or boss I31 formed with machined aperture I38 for a link connecting bushing; while in the rear reduced width end portion, portions I3I and I35 are integral with pin receiving boss or eye I39 formed with machined aperture I40 fora link connecting pin. Centrally thereof, the link is apertured to allow for escape of foreign material as the track operates; the apertured portion being braced by intermediate reenforcing web I46 integrally joined to rail portion I3I and to shoe portion I35. Thus, apertures I41 and I48 extend from one side face of the link through the other side face. Such apertures are not obstructed by the fastening means securing shoe I06 to the link, because the heads of cap screws I09 engage shoe I06; and their threaded ends, secured in shoe engaging portions I35 of the link, do not project into apertures I41 and I48. Consequently,

the full size of apertures I41 and dis available to allow" escape of foreign material.

As'seen in Figs. 9 and 10, reenforcing web I46 is shaped so as to offer minimum resistance to the escape of foreign material, which occurs as the driving sprocket teeth engage the link connecting made much narrower than edge portion I49 facing the outside of the link; and side faces I50 of the web are perfectly smooth and planar.

Preferably, the web is of triangular cross section, with the apex thereof at the inside of the link; the smooth, planar sides I50 diverging outwardly toward the'wider outside edge I 43 The extremities of reduced width end portions I33 and I34 are specially formed to cooperate with adjacent links to provide our novel weartaklng, rail-joint construction. Reduced width end portion I34 has an end boss I5I forming a rail'end projection; and reduced width end portion I33 has a similar rail end projection boss I52. Projection I5I (Fig. 7) is formed with a convex substantially frust'o-conical surface I56 generated about the axis of aperture I38. Consequently, surface I56 is obliquely disposed with respect to the axis of aperture I33 and to the longitudinal line of the track or rail. It is also obliquely disposed with respect to the line of contact which a track roller makes with the rail as it travels thereover, and to both the parallel side rail edges I32 and I32 of the full width rail portion I32. The part of convex surface I56 of greatest radius is at outside edge I34 of reduced width end portion I34, to cause such surface to slant inwardly from the outside edge.

Each oblique convex surface I56 of one link is adapted to underlap a complementary oblique concave surface formed underneath the rail surface of the full width rail portion I32 of the adjacent link. As seen in Figs. 2 and 8, such complementary obli'que concave surface is indicated at I51. Surface I51 is at the same side of the link'as surface I56, and is of frusto-conical shape; the axis of generation being coincident with the axis of aperture I40. Also, surface I51 is substantially parallel to surface I56. Surfaces I56 and I51 are of such complementary shape that the distance between any selected corresponding points thereof (distance A, for example, in Fig. 8 taken between two points lying in a line parallel to a side edge of the rail), is substantially the same. Such distance, as illustrated by example line A, is also substantially equal to the pitch of the track link; the pitch being indicated by line B in Fig. 8. The pitch line is only suflici ently greater to provide for clearance between surface I51 of one link and complementary surface I56B of an adjacent link. In the example of link shown, the pitch B is 8 inches, and the distance A is substantially 7.75 inches so that a total clearance of about .25 inch obtains to allow pivotal movement between adjacent links.

From the preceding description, it is seen that at one side of the rail of the link are formed a convex oblique surface at one end and a complementary concave surface at the opposite end; the convex surface of one link being adapted to underlap the concave surface on an adjacent link. The opposite side of the rail is also similarly provided with complementary oblique surfaces. Projection I52 is formed with convex, substantially frusto-conical surface I6I (Figs. 2 and 8) slanting inwardly from the outside edge I33 of reduced width portion I33; and comple- .mentary oblique concave surface I 62 is formed under the rail surface of the full width rail portion I32 to be underlapped by a complementary convex surface on an adjacent link. Surfaces I6I and I62 are also parallel; and the distance between any selected corresponding points on surfaces I6I and I62 is substantially equal to the distance between any such points on surfaces I56 and I51. Also, each of the surfaces is gen.-

erated about the axis of the link aperture I33 or I40 adjacent to such surface.

With particular reference to Figs. 2, '1 and 8, it will be noted that obliqueconvex surface I66 terminates at the rail surface in a similarly oblique or diagonally disposed rail end edge III; and oblique concave surface I61 terminates at the rail surface in similarly oblique rail end edge I12 parallel to rail end edge "I. Oblique surfaces I62 and I6I terminate similarly in obliquely disposed parallel rail end edges I13 and I14; all of edges I1I, I12, I13 and I14 being parallel with respect to each other and lying substantially in the plane of the rail surface of the link, to provide the end edges of the rail surface of the link. In this connection, it will be observed (Fig. 9) that edges I12 and I13 form edges which cooperate to bound, respectively, end recesses I33 and I34; the end recesses being adapted to receive reduced width end portions of adjacent links.

The described construction of each link enables adjacent links, as previously pointed out, to be connected end to end to provide butt-lap joints of substantially full rail width. Particular reference is made to Figs. 1, 2 and 3 in the following detailed description of the rail joint between adjacent links. In Fig. 2, the links to the left and right of link I08 and their parts corresponding to those already described for link I08, are indicated by the same reference numerals. However, the left link and its parts are distinguished by letter B and the right by letter A.

Because the distance between corresponding points on surfaces I56 and I51, and on surfaces I6I and I62, is substantially equal to the pitch of the link, the links can be connected with oblique concave surface 523 under therail surface'of the full width rail portion of link I 08B, substantially parallel to and in close proximity to complementary oblique convex surface I6I on reduced width end portion I33 of link I08. The oblique rail end edges I13B and I14 are substantially parallel and closely spaced apart, so that the end of edge I14 which is adjacent the side edge of the rail, or, in other words, the outer end portion, overlaps the inner end portion of the adjacent rail end edge I13B. 'Also, the outer part of surface I6I overlaps the inner part of surface I62B. Furthermore, by virtue of the projection boss I52 on which convex surface I6I is formed, the concavity at concave surface I62B under the full width rail surface of link I08B, is substantially completely filled by the boss. The relationship which exists between the other complementary curved surfaces and rail end edges of adjacent links is the same as that described, as is shown in Fig. 2.

Thus, each rail joint between ends of two adjacent links, by virtue of the oblique extremities formed on the cooperating and overlapping reduced width end portions on-such links, comprises two pairs of substantially parallel and obliquely disposed rail end edges and surfaces. One of such pairs, for example, comprises oblique rail end edges I 13B and I14 and the oblique curved surfaces associated therewith, which extend from the outside edge of the rail to a location between the side edges of the rail; and the other of such pairs comprises edges I1|B and I12 and the surfaces associated therewith, which extend from the inner or opposite side edge of the rail to another location between the side edges.

It will benoted from Fig. 2 that the angle of in Fig. 5) throughout its travel over an entire rail joint or pivotal connection between ends of adjacent links. For illustration, line X indicates the line of contact of the roller with the rail, just at the point where the outside end portion of the roller passes over the outer portion of the gap between rail end edges H33 and I14. At this position, it will be observed that substantially all of the roller is supported on the rail surface of link I 083 and adjacent both side edges of the rail. As the roller proceeds in the direction of arrow W, it is seen, as indicated by line of contact Y, that before it passes completely over'edge "33, it finds support on reduced width portion I33 0! link I88 closely adjacent the outside edge of the rail, and is still supported adjacent both side edges 'of the rail.

When the roller travels to the location where it just passes completely over edge "33, indicated by line 'of contact Z, it still finds support adjacent both side edges of the rail, and onboth reduced example) as it traverses a portion of the extremity of reducedwidth end portion I33 of link I08 also traverses a portion of the adjacent link 108B. Materially increased unit pressure on a re-' duced width end portion I33 or I 343 is therefore obviated, to eliminate more rapid wear of such portion as the roller passes over the rail gap ad jacent thereto. This results in substantially complete elimination of the roller pounding action which has heretofore existed, to increase'mate rially the life of the rail. Furthermora because of the provision of the projecting bosses I52 and I5I upon which, respective convex oblique surfaces I6I and I56 are formed, and which substantially fill the concavities under adjacent links cooperating therewith, sufficient material obtains to provide ample support for the rollers over the joint gaps. In comparison with joints which have heretofore characterized endless self-laying track constructions, we have found that theimproved joint construction of our invention serves-to increase the life of the track materially; the average increase of life being about 25%. I

A joint of the character described wherein substantially constant and uniform spacing exists between the opposing end surfaces during flexing of the joint as pivotal movement between connected links occurs, is termed in the art, a wiping joint, from the fact that foreign material tending to lodge in the space between such surfaces of the joint and act as a wedge to spread the elements, cannot enter during thepivotal flexing and is wiped away by the action of the cooperatingwiping surfaces of the joint. The oblique character of such surfaces presents the added advantage of greater wiping area, besides providing a joint between links enabling the gradual transfer of load on. the rails as the track rollers travel from link to link, which is of the utmost importance in adding to the useful life of the track, as noted above.

The above construction can be readily obtained in a forged track link, without special machining from forging, placed in an advantageous location. To accomplish the above purpose, the parting line along the rail portion of the link, indicated at C in Figs. 2 and 9, is formed to extend for a short distance, from end point D, substantially parallel to and closely adjacent the outer side of the link to point D beyond edge I14, then diagonally across the rail surface to point E ahead of edge HI, and then substantially parallel to and closely adjacent to the inner side of the link to point E. Points D and E are located at the outermost parts of respective oblique surfaces IBI and I58. Thus, the parting line along the rail surface has extremities or end portions on oblique surfaces ISI and I58; and such line extremities lie inlvertical planes which are very close to and substantially coincide with the respective side faces of the link. The spacing of the parting line from the side faces of the links is made as small as possible-at the ends of the link; such spacing being just enough'to provide sufficient depth for good filling of material in the die during forging. In this connection, it will be observed that the outer portions oi. diagonally opposite end sur- 25 faces I58 and liljare slightly bevelled as indicated at M to facilitate filling.

Across the bottom-or track shoe engaging face of the link, the parting line is indicated at F in Fig. 10. It is seen (Figs. 9 and 10) that the parting line around the front end of the link lies entirely in a vertical plane closely adjacent the inner face or side of the link; while the parting line at the rear end of the link passes from point D adjacent the outer face of the link diagonally down line G to point H on the pitch line of the link (Fig. 8) and adjacent the inner face of the link (Figs. 9 and 10). In Figs. 9 and 10, the part-' ing line on the interior surfaces of the link, formed by apertures I38, I48, I41 and I48, is indicated at J and K.

The endless track of our invention is designed to cooperate with track rollers having outside roller flanges only, namely, flanges which engage only the outside edges of the spaced rails which form each endless track. This avoids flange interference with the track bushings, heretofore characterizing constructions with inside track roller flanges, and enables the provision of increased bushing diameter between the rails for obtaining strength .of construction. The outside faces of the track links are formed free of projections which would, otherwise, cause interference with such outside roller flanges as wear occurs on both the rollers and the rails.

As seen in Figs. 5 and 7, the outer end of boss I38 which receives the linkconnecting pin, is so disposed with respect to the outside edge of the rail thereover, as to preclude interference with outside track roller flange I19 as wear occurs. The end of the boss lies in substantially the same upright plane as the outside edge of the rail; and the outside edge of the rail is bevelled at I8I and a portion of boss I39 is similarly bevelled at I8 IA, to

i provide a desirable slanting face portion for cooperation with .complementary bevelled or slanting inside face I8l' of track roller flange l19. Relief groove I84 is formed in the outside face of the link between bevelled surfaces I8I and IBIA, to avoid any possibilityof flange interference, and to reduce weight'inasmuch as the additional material is not required for providing strength. Thus, the outside track roller flanges I18 can be made sufliciently long to hold the rollers on the rails of the track- Preferably, we 7 employ outside roller flanges long enough to overlap the portions of 75 bosses I 39 adjacent the rails and to overlap the portion of bushings. 3 between the rails.

Since only outside roller flanges are employed and because the outside faces of the links are formed to preclude flange interference, the material utilized to provide the wear takingportion of the rail need be only of a depth sufllcient to provide for such wear; no excess depth being necessary (as would be the case where inside roller flanges are employed) to avoid premature interi'erence of inside roller flanges with bushings -I I3 after wear on the rails and track rollers. Consequently, saving in weight of the link is effected; and, also, the full depth of the rail portion is available for wear, thus materially increasing the life of the track in comparison with self-laying tracks heretofore employed. The average increase of life by virtue of the outside roller flanges only, and the outside face link construction which avoids interference with such outside flanges, is about 25% and since the improved joint construction increases the life of the track about 25%, it is seen that the total average increase of track life enabled by such two features, is about 50%.

Elimination of inside track roller flanges also enables enlargement, whenever desirable, of the diameter of the portion of each bushing 3 between the rails, to provide strength of constructween the rails.

tion. In the track mechanism chosen for illustration and which is adapted for use with atractor designed for heavy duty work, such as bulldozing, we employ bushings I I3 of enlarged diameter be- However, increased height of the link and consequent increase in weight thereof, is avoided by providing reduced diameter ends- I86 (Fig. 4) on each bushing H3; such ends being press-flttedin the links of each pair. Also, reduced bushing ends I86 enable the pitch line to be maintained a minimum practical distance above the ground. This is so because if increased diameter bushings of constant diameter from end to end were employed, the diameter of bushing bosses l 31 would have to be made larger, with consequent increase in height and weight of the link, and

SUMMARY From the foregoing description, it is seen that many features of our invention cooperate in providing an improved wear-resisting track mechanism capable of having long life. The improved rail joint construction is one of such features. Another feature is the provision of outside track roller flanges only 'and the elimination of inside roller flanges, which also enables minimum practical depth of material for the rail portion of each link, particularly in view of the fact that the outside faces of the links are shaped to avoid interference with such outside track roller flanges upon wear of the rollers and track. Bushings of increased diameter between the rails cooperate to Therefore, we claim as our invention: 1. A link for an endless self-laying track having a full width rail portion for supporting a weight bearing roller, and a portion at each end of such link of reduced width for pivotal cooperation with a corresponding part of an adjacent link, the extremities of such end portions being formed to cooperate with adJacent pivotally connected links to provide a rail surface throughout each pivotal connection of more than one-half the full width of the rail portion.

2. A link for an endless self-laying track having a rail portion of full uniform width for supporting a weight bearing roller, and a portion at each end of such link of reduced width for pivotal cooperation with a corresponding part of an adjacent link to provide with such part a rail joint of substantially the same uniform width as that of the rail portion, the extremities of such end portions being formed to cooperate with adjacent pivotally connected links to provide a rail surface throughout each pivotal connection of more than one-half the full width of the rail portion.

3. A link for an endless self-laying track hav-' ing a full width rail portion for supporting a weight bearing roller, and a portion at each end of such link of reduced width for pivotal cooperation with a corresponding part of an adjacent link, each of said end portions having at its extremity a rail end edge disposed obliquely with respect to a side edge of the full width rail portion to cooperate with a complementary oblique edge of an adjacent pivotally connected link to provide an oblique wiping joint.

4. A link for an endless self-laying track having a full width railportion for supporting a.

weight bearing roller, and a portion at each end of such link of reduced width for pivotal cooperation with a corresponding part of an adjacent link; each of said end portions having at its extremity a rail end edge disposed obliquely with respect to a side edge of the full width rail portion, and a similarly oblique convex surface formed adjacent the rail surface thereof to underlap the full width rail portion of an adjacent pivotally connected link.

' 5. A link for an endless self-laying track having a full width rail portion, a portion at each end of the link of reduced width and having a rail projection adjacent the rail surface thereof, each projection being formed with a. convex curved surface, and a concave surface formed at each end of the link under the rail surface of the.

full width rail portion, all of said curved surfaces being disposed obliquely with respect to a side edge of. the full width rail portion and terminating in similarly oblique substantially parallel edges providing end edges of the rail surface, each convex surface at an end of the link being of a shape complementary to that of the concave surface at the opposite end of the link to enable .said link to be connected to like links with adjacent end edges and adjacent curved surfaces of adjacent links substantially parallel and in close proximity.

6. An endless self-laying track comprising a plurality of connected links, each link having an intermediate full width rail portion and end portions of reduced width cooperating with reduced width end portions of adjacent links to provide butt-lap railjoints of full rail width throughout; each joint including a pair of adjacent oppositely disposed rail end portions extending in thickness from one side edge of the rail to a location between the side edges of the rail, and another 3 side edge of the rail to another. location between the side edges of the r ail,-said-: oppositely disposed" v end portions being so spaced and angularly positioned with respect to the longitudinal line of the-rail as to provide throughoutthejoint a. rail surface of more thanron'emalf the full rail width. .'l-. A'forged'metal linkfor an endlss'self-laying track having .a full widthrailiportion, and a portion atea'ch end of such link of reduced width; v the forging parting line along the railfsurfaoe of theli nk having an end portionat .onesi'de of the li'nk and another fend portion at theopposite '15" side of" the link, each end portion; of" such line being closely adjacent toasidejofithe linkk 8. Aflforged metal'linkj' for an endlessself ilayingtrack having-lafull width-rail portionya J-po'rtion'; of reducedwidthatone side and end -of v o 'the link, and anotherjportion of reduced width at the opposite side andqend ofthelinkyeach of 7 said end portions haying adjacent its;ex tremity I a', surface oblique to a side-edge of the. full width rail portion; the forging partingfline 'alongthe ,rail surface of the link having. end portions on V I said oblique surfaces, each of such line'end por-,

' jtions being closely adjacent a and parallel to a side of the link. r 1 I :9. A forged metal linkfor an endless self-laying track having a full width rail-portion, a por-' ---tion of-jreduced width atone side and end of the r a and another portion of reduced'width at i the oppositesideand end of the link-the outside edge of each of such end portions forming a' straight and smooth continuation of a side edge of the'full width rail portion; each of such end portions having adjacent its'extremity a convex surface slanting inwardly from the outside edge thereof; the forging parting line having portions closely adjacent to.the outside, edges of such con- 'vex surfaces.

H A link for an endless'self- -laying track hav- 'ing a full width rail portion, a portion adjacent 1 I one side and end of thelink iof reduced-widthand v H said 1 reduced width portion including said rail projection havingsa surface, -.lying in the'plane of the rail. su'rface of saidffullfwidthgrail portion, e. asecond-portion'adjacent' theODDQSitC side and 7 95a rail projection with a surface in' the plane of having a rail. projection continuous therewith;

end-ofith'e linkof redu'cedwidth 1 and also having said'fullwidth rail surface, each projection terminatingin a f surface extending obliquely inwardlyfrorn adjacent the, associated-side of the link, an oblique surface formed under'and'adjacent-the rail surface ofthe full "width rail portion at a location adjacent said one end ofthe link and adjacent theside opposite the reduced a width rail portion which is adjacentsaid one end of the link, and a second-obliquesurface formed under and adjacent the rail surface of the full width rail portion at a location adjacent said opposite end of the link and-adjacent the side opposite the second reduced width rail portion which is adjacent saidiopposite end of the link, each of said oblique surfaces under the full width rail portion of the link extending obliquely cut wardly from adjacent thea'ssoci'ated side of the complementary shape to provide the same [disa I tance betweenany selected corresponding'point'sf thereof, whereby said linkcanb'e pivotally con-L o -I- .ne'cted'with similar links with each oblique sure link, the oblique surfaces at the same of each of opposite sides of the link being of-substantially substantially face on a rail projection underlappingjthe associatedoblique surface formed under the full rail surface of an adjacent similar linkto thereby [provide-long wearing rail joints.

;- 11.A.forged metal link'for an endless self laying track having -a'- full width-rail portion, a .-portionadjacent one side and end-of the link -"of reduced width-and 'havingea rail projection adjacent the rail surface thereof, a second por--' tion adjacent the opposite-side and end of the link of "reduced width and; having a rail projec- "tion adjacentthe rail; surface thereof, each'projection terminatingin 'a surface extending obliquelyinward-1y" from: adjacent the associated side of the linkin- .addition,toihavinga surface of. the link-andadjacentthe sideopposite the reduced width fraiivportion which is adjacent said one end of the link, anda secondv oblique surface formed under and-adjacent the rail surface ofthe full width railportion at a location adjacent said Opposite end of the link and adjacent the a side opposite the second reduced width rail portion which is adjacent said opposite end of the linkQeach of saidoblique surfaces under. the full width rail portion ofv the link 'extending'obli'quely outwardly from adjacent the associated side of the link, the oblique surfaces at the same of each of opposite sides of the link being ofsubstantially complementary shape to provide the same distance between any selected corresponding points thereof, whereby said link can'be pivotally connected with similar links with ,each, oblique surface on a rail projection underlapping the associated obliquesurface formed under the full rail surface of an adjacent similar link to thereby provide long-wearing rail joints; the forging parting line along the rail surface of the link having end portions on. the oblique surfaces on the rail. projectionaeach of said line end por-.

tionsbeing-closely adjacent and substantially paralleitoa side .of the link whereby the forged link can be removed from the die even though such obli'que surfaces extend inwardly.

12.'A link for an'endless self-laying trackhavinga'full width rail portion, a portion at an end,

of. the link of reduced width and having a rail projection adjacent the rail surface thereof to extend said rail surface substantially across the gap which would otherwise occur between connecting links of a similar type having a full width rail portion and a-less than full width rail portion.

.13. A link foran endless self-laying track having a full width rail portion, a portion at an end of "the link of reduced width and having a rail projection adjacent the rail surface thereof to extend said rail surface substantially across the gap which would otherwise occur between connecting links of a similar type having a full width rail portion and a less than a full width rail portion, said extended surface having at its extremity a boundary which is oblique to the perpendicular to the side boundaries of said full ,widthportionfof said rail surface.

' 1'1. A link adapted for pivotal connection with similar links to form an endless self-laying track having a rail surface for supporting a weight bearing roller, comprisingv an intermediate portion of full rail "width, and portions of less than full rail width: extending 'from'diagonally {opposite corners of said-full rail .width portion, each of said less than full'width portions bein continuous with said full width portion and having a rail surface lying substantially in the plane of the rail surface of said full width portion and terminating adjacent the end thereof in a wiping surf-ace obliquely disposed with respect to the sides of said link, each of the unextended end portions of said intermediate full width portion having an oblique wiping surface in complementary relationship with the oblique wiping end surface of that less than full width portion adjacent the same side of said link for providing an oblique wiping joint between successive links.

15. A link adapted for pivotal connection with similar links to form an endless self-laying track having a rail surface for the support of a weight bearing roller, said link having at least a portion adjacent one end terminating in a convex curved surface oblique to the side walls of said link and a portion adjacent the opposite end terminating in a concave curved surface the curvature of which is complementary to said first curved oblique surface to provide an oblique wiping joint between connected links.

16. A track-type tractor track link adapted for pivotal connection with similar links and having a full width rail portion and end portions of reduced width at diagonally opposite corners, each of the portions of reduced width terminating at its extremity in a convex oblique surface and an oblique edge at the rail surface, and the full width rail portion of the link terminating at diagonally opposite corners thereof in oblique edges at the rail surface from which extend oblique concave surfaces lying underneath the rail surface of said full width rail portion, the curvature of the oblique surfaces at each side of the link being substantially complementary and the distances between corresponding points on the oblique surfaces at either side of the link being substantially the same as that between similar points on the oblique surfaces at the opposite side of the link to provide a diagonal wiping joint at each extremity when said .link is pivotally connected with links of similar construction.

17. A forged track-type tractor track link adapted for pivotal connection with similar links and having a full width rail portion and end portions of reduced width at diagonally opposite corners, each of the portions of reduced width terminating at its extremity in a convex oblique surface and an oblique edge at the rail surface, and the full width rail portion of the link terminating at diagonally opposite corners thereof in oblique edges at the rail surface from which extend oblique concave surfaces lying underneath the rail surface of said full width rail portion, the curvature of the oblique surfaces at each side of the link being substantially complementary and the distances between corresponding points on the oblique surfaces at either side of the link being substantially the same as that between similar points on. the oblique surfaces at the opposite side of the link to provide a diagonal wiping joint at each extremity when said link is pivotally connected with links of similar construction, said link having a forging parting line close to a side wall of said link at each end.

18. A link adapted for pivotal connection with similar links to form an endless self-laying track having a rail surface for supporting a weight bearing roller, comprising 'an intermediate portion of full rail width, and portions of less than full rail width extending from portions of opposite ends of said full rail width portion, each of said less than full rail width portions being continuous with said full rail width portion and having a rail surface lying substantially in the plane of the rail surface of said full rail width portion and terminating adjacent the end thereof in a wiping surface obliquely disposed with respect to the sides of said link, each of the unextended end portions of said intermediate full rail width portion having an oblique wiping surface shaped to complement the wiping surface on an adjacent less than full rail width portion of an adjacent similar link to be pivotally connected thereto and each of the oblique wiping surfaces on the less than full rail width portions of said link also being shaped to complement the wiping surface on the adjacent unextended end portion of an adjacent similar link to be pivotally connected thereto for providing an oblique wiping joint between successive links.

OSCAR- L. STARR. WALTER. GROTHE. HARMON S. EBERHARD.