Flexible Track Belts

Abstract

Circular support belts having internal, wound inextensible filaments encased in elastomer retain a plurality of circumferentially disposed track shoes which are attached to these support belts through an elastomeric couple in which shaped keepers are employed to compressively load the elastomer at the couple to secure the track shoes to the internal inextensible filaments of the support belts. A dense elastomer insulated joint is formed wherein direct physical contact by the track shoes and/or the keepers with these filaments is avoided and a resulting couple is obtained which prevents slipping movement between the track shoes and the filaments. The resulting track belt system can be employed about the periphery of pneumatic tire carcasses to increase traction, protect the carcass, etc.

Description

BACKGROUND OF THE INVENTION

Subsequent to the perfection of pneumatic tires, a number of track type devices have been developed for utilization over these types of tires. Generally, these innovations were designed for a specific purpose, such as anti-skid or nonskid functions, protective or shielding functions and/or traction-increasing functions when mounted about the periphery of a pneumatic tire carcass.

Many of these innovations in the prior art employed metal caps, cups or shoes retained about the outer periphery of the tire through some type of circular supporting system, such as links, cables, chains, rings, etc. Typical systems are illustrated in U.S. Pat. No. 873,919 issued to Arnold, U.S. Pat. No. 1,114,983 issued to Grisingher, U.S. Pat. No. 1,407,529 issued to Greenfield, U.S. Pat. No. 1,566,559 issued to Prime, U.S. Pat. No. 2,679,881 issued to Gagne, and U.S. Pat. No. 2,118,776 issued to Eastwick. Most of these innovations were designed for inclement weather conditions and are not suitable for work vehicles capable of high tractive effort wherein their utilization would be required for extended periods, especially in earth-working environments.

Some other innovations were designed for work vehicles and include the tire tracks illustrated in U.S. Pat. No. 2,745,460 issued to Koenig and U.S. Pat. No. 2,764,209 issued to Armington. In these structures, articulated joints are employed to connect track shoes in a circle which can be placed about the periphery of a pneumatic tire carcass. Besides being bulky structures, these systems tend to be expensive in both initial costs and maintenance costs required for the pivoted joints. Localized loadings in the joints may often be excessive and, if the interference fit between the pneumatic tire and the "circle of track" is such that it radially constrains the carcass, the resulting preload on the joints is added to the tractive effort transmitted between the tire and the ground through the track and its joints. As a result, a short service-life in earth-working environments can be expected from the prior art conventional systems of this type.

Replaceable, flexible belt structures also were developed for use with pneumatic tires. Some of these belt structures are shown in U.S. Pat. No. 1,234,193 issued to Mass, U.S. Pat. No. 1,311,750 issued to Brashear, and U.S. Pat. No. 2,609,026 issued to Luchsinger-Caballero, some of which include metal track shoes or elements in the belts as shown in U.S. Pat. No. 1,262,011 issued to Bruce. Some of these systems were designed for use with track laying vehicles as well as over penumatic tire carcasses, as illustrated in U.S. Pat. Nos. 2,273,949 and 2,273,950 issued to Galanot et al., U.S. Pat. No. 2,728,612 issued to Howe et al, and U.S. Pat. No. 3,387,897 issued to Reid.

It is useful to distinguish for classification between the pivoted or hinged track shoes as illustrated in the above-referenced U.S. Pat. No. 2,764,209 and those structures employing flexible connections between the track shoes that offer more freedom of movement between the adjacent track shoes, not being restrained to the pivot axis.

The current invention is primarily related to the latter type having limited universal relative movement between adjacent track shoes and is designed to overcome many of the troublesome problems experienced with the prior art systems.

Difficulties in the prior art structures of this type are often experienced in achieving the desired flexibility in the support system along with adequate strength and service-life when these devices are employed in earth-working vehicles. Another major problem is the connection mechanisms between the belt support systems and the track shoes or elements which often deteriorate quickly leading to failure of these structures.

In particular, an object of the instant invention is the provision of a highly flexible support belt system that has sufficient strength to adequately hold the circumferentially disposed track shoes and radial preloads from the supporting pneumatic carcass while also providing the needed service-life required in earth-working vehicles.

Another important object is the provision of an elastomeric couple between the inextensible reinforcing filaments in the flexible support belts and the track shoes which provides an insulation between these parts without slippage therebetween.

Also, it is an object to provide flexible track belt which is compatible with large earth-working vehicles having considerable drawbar horsepower that require considerable tractive effort be developed across the track belts.

Another object is provision of a flexible track belt which can be manufactured economically in all sizes.

SUMMARY OF THE INVENTION

A flexible track belt includes several flexible circular support belts with each belt having internal inextensible reinforcing filaments wound therein and encased in elastomer, a plurality of track shoes circumferentially arranged about the circular support belts and oriented transversely thereto and attaching means for each track shoe to couple it to the support belts, the attaching means having shaped retaining means for receiving the support belt and clamping means to compressively load the elastomer encasing the reinforcing filaments whereby a dense elastomeric couple between the track shoes and the filaments is formed through the attaching means without direct physical contact due to the insulation provided by the elastomer. The retaining means for the support belts must be shaped in a manner to prevent the extrusion of the elastomer when it undergoes compressive loading in the area of the elastomeric couple so adequate density is achieved to prevent slippage of the attaching means relative to the reinforcing filaments in the support belts.

The resulting flexible track belts can be employed about the periphery of a pneumatic tire carcass to form a reliable track encircled tire combination for work vehicle. Radially reinforced tire carcasses are preferred in such a track encircled tire combination, with filament wound tube tire carcasses combining with the track belts to form the most preferred and superior performing arrangement when the track belts are used in this manner.

Other applications of these track belt systems are also possible.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective of a work vehicle with the flexible track belts mounted on its pneumatic tires illustrating an earth-working environmental application thereof;

FIG. 2 is a section through a belted tire of one of the wheels of the work vehicle shown in FIG. 1 with parts broken away;

FIG. 3 is a broken away elevation of the belted tire shown in FIG. 1;

FIG. 4 is an exploded section of an alternate embodiment of the flexible track belt;

FIG. 5 is an elevation of the flexible track belt in which the retaining member or keeper is extended to limit the travel of an adjacent track shoe due to an overlapping relationship;

FIGS. 6 and 6A are perspectives illustrating another embodiment of the flexible track belt in which only two support belts are employed;

FIG. 7 is an enlarged section of a sidewall retention device which can be employed in place of the centering lugs illustrated in FIGS. 6 and 6A with the two support belt embodiments;

FIG. 8 is a broken away perspective of an individual support belt illustrating some of its internal construction details;

FIG. 9 is a perspective of a filament winding machine for fabricating the support belts;

FIG. 10 is a section of a support belt having fabric disposed between the layers or plies of reinforcing filaments;

FIG. 11 is a broken away perspective of a portion of the drum of the machine illustrated in FIG. 9 showing the simultaneous application of multiple reinforcing filaments;

FIGS. 12 and 13 illustrate in section and elevation, respectively, a belleville spring clamping device to compressively load the elastomer in the elastomeric couple;

FIG. 14 is an elevation of an arcuate retaining means which will shorten the support belts as the track shoes with a compatible surface are tightened against the retaining means; and

FIG. 15 is a perspective of a filament wound tube-tire carcass providing the most preferred carcass with which the track belt can be combined.

DESCRIPTION OF AN EMBODIMENT

An earth-working machine 20 is illustrated in FIG. 1 wherein flexible track belts 21 have been assembled on its pneumatic tire carcasses 22. This is one of the principal environmental applications for which the current flexible track belts were designed. Depending on the aggressiveness of the grousers on the track shoes of the track belt and soil or roadbed conditions, the flexible track belts may appreciably increase the tractive effort capability of such a vehicle. In some situations, this increased capability can exceed the structural capability of the drive train. Of course, in other environments, such as smooth concrete surfaces, the tractive effort may be much less than a contemporary vehicle with conventional rubber tires. Therefore, it should be appreciated that the flexible track belts of this invention, which employ a unique elastomer couple, are usually employed in specialized applications wherein large economies can be experienced through their use, for example in rock work where conventional rubber tires are often cut and punctured, or situations where rubber tires do not give adequate traction due to the surface conditions.

Besides acting as a shield in certain environments, the track belt provides increased machine stability, improved floatation, and better steering response in many applications. Better load distribution in the footprint also is achieved which contributes their many advantages.

Prior art devices have traditionally been incapable of attaching or retaining the individual track shoes on flexible belts for extended periods of time without resulting in belt failure due to slippage between the shoes and the support systems or wear in the support system. If the support reinforcing such as cables are physically gripped with sufficient force to prevent slippage, it is often crushed, flattened or nicked encouraging its failure contiguous to such attachments. If the support system is not physically secured, the track shoes tend to slip causing excessive wear and/or flexure therein. In addition, the prior art designs, because of the above factors and others, are normally incapable of achieving some uniform load distribution on the reinforcing members or filaments of the support systems. Because the reinforcing flexible support system must be substantially inextensible in order for the track belt to be retained on tire carcass, if combined therewith, and provide sufficient strength to allow the transfer of torque between the tire carcass and the track shoes, prior art devices often employed large cables or wires which resulted in poor load distribution causing failures.

In FIG. 2, the different construction of the instant invention can be seen in detail wherein track shoe 30 with grousers 31 is attached with tap bolts 32 to a retainer member or a keeper 33 having channels 34 for receiving the supporting belts 35, which in this embodiment are connected together by a thin elastomer web between the channels in the keepers, but are shown as independent belts in FIG. 4, an alternate embodiment.

The space A between the track shoe base 30a and the tops of the ridges 36 of the keeper 33 is critical with reference to the thickness of the individual belts, since it would be impossible to obtain the desired preload or compressive loading on the elastomer surrounding the reinforcing filaments of the support belts 35 for the elastomeric couple necessary to join the track shoes and the support belts in a manner which is compatible with the small diameter inextensible reinforcing employed in this invention, if this space or gap was not present.

In the elastomeric couple, high torques can be transferred between the inextensible reinforcing filaments within the belts and the individual track shoes without direct physical contact by placing the encasing elastomer under high compressive loading, preferably from 1,500-5,000 psi, in the area of the couples. Since the elastomer is substantially incompressible and exhibits resiliency through elastomer "flow," it is necessary that the couple employ means to prevent the flow (extrusion) of the elastomer if a satisfactory couple is to be achieved. The individual channel 34 in the keepers closed by the cooperating base 30a of the track shoe 30 "contains" the elastomer, except along the generally parallel axes of its internal reinforcing filaments (the open ends of the channels). The adhesion of the elastomer to the reinforcing filaments and the friction developed due to a high ratio of reinforcing filaments to elastomer by cross sectional area in the support belt prevents the extrusion of the elastomer from the open ends of the channels. The filaments are preferably brass-plated to improve elastomer adhesion thereto.

As a result of this arrangement, as the tap bolts 32 are tightened, a compressive loading on the elastomer in each couple can be developed so long as the necessary relationship of gap A and the thickness of the supporting belt is present. Normally, the tap bolts are torqued to achieve at least 1,500 psi compressive load in the elastomer in the couples. As the number of belts are decreased (decreasing belt areas in the couples), the corresponding preload must be increased. In the two-belt design illustrated in FIGS. 6 and 6A, compressive loading on the elastomer in the couple is increased to between 4,000 and 5,000 psi or higher to compensate for the reduced coupling area.

Due to stress relaxation in the elastomer, it normally will be necessary to torque the tap bolts 32 at periodic intervals to maintain the desired compressive loading on the elastomer in the elastomeric couples. In FIGS. 12 and 13, the desired loading on the couple is maintained continuously by a belleville retaining system. Rivets 40 replace tap bolts 32 in this embodiment, and extend from the track shoe 30 through bores 41 in the keeper 33 so they project from the outer surface of the keeper. Each rivet has an integral head 43 and is assembled in its bore with belleville springs 44 nested thereon so they can be compressed against the outer surface of the keeper as the head is moved toward the keeper. The rivets which fit loosely in their respective bores are positioned to extend through apertures 45 in the associated track shoe after the support belts 35 are placed in channels 34 of the keeper. A press is then employed to compress the belleville springs and the ends of the rivets extending through track shoes are peened to secure the rivets in their associated track shoes, after which the assembled parts are removed from the press. The belleville springs will maintain the desired compressive loading in the elastomer couple and compensate for any stress relaxation in the elastomer as it occurs. Thus, this arrangement eliminates the necessity of torquing the tap bolts 32 at periodic intervals. Obviously, the belleville springs and rivets can be counter sunk in the keeper to provide a smooth undersurface where keeper engages the supporting pneumatic carcass.

In FIGS. 6 and 6A wherein only two support belts are employed, centering lugs 46 are utilized in the central portion of each track shoe 30 on its base surface 30a which are received in a cooperating groove (not shown) in the supporting pneumatic tire carcass. Because the frictional engagement of the base surfaces of the track shoes against the periphery of the tire carcass may not be sufficient to prevent transverse shifting of the track belt on the tire carcass under certain loading conditions, a centering lug or device is desirable in some environmental applications.

An alternate centering device which cooperates with the sidewall of the pneumatic tire carcass 22 is illustrated in FIG. 7. In this device, the retaining member or keeper 33 having the shaped channel 34 for the flexible support belt 35, includes a radially inwardly projecting leg 33a which engages the sidewall of the tire carcass 22 at point B which is well below the crown C of the tire carcass with the track belt assembled thereon. This arrangement will also prevent transverse displacement of the track belt on the tire carcass under certain loading conditions. Also, in FIG. 7, set screws 47 are employed to lock tap bolts 32 in place after they are properly torqued to prevent them from working loose which could cause the flexible support belt to fail.

The construction of the flexible support belts 35 is important in order to achieve prolonged service-life from the resulting track belt, and the details of their construction and fabrication are best shown in FIGS. 8, 9, 10 and 11. As indicated previously, these support belts have internal inextensible reinforcing filaments 50 which are encased in elastomer 51. In prior art devices, the reinforcing typically has been large diameter cables or wires. By contrast, the instant invention employs very small diameter wires, or cables by comparison, usually brass plated, to improve the adhesion of the elastomer thereto, which are preferably wound in a helical manner in the belts forming a series of connected loops. Mono-filament steel wires having high tensile strength and a diameter from 0.005 to 0.050 inch are normally utilized to form the helically wound reinforcing filaments in the support belts. Several of these filaments may be first twisted loosely together and applied in the same manner as a single filament.

In the drawings, the diameters of the reinforcing filaments 50 are exaggerated for purposes of illustration and their density in the cross-section reduced for clarity. The flexible support belts can be fabricated on the winding machine 60 shown in FIG. 9. A motor 61 drives a drum 62 of an appropriate diameter on which a thin layer of elastomer is applied to its peripheral flat surface 63. Thereafter, a layer or ply of reinforcing is applied by helically winding the wire 50 from spool 64 on the previously-applied elastomer layer through the level winding guide 65. After the reinforcing ply or layer is completed, another thin ply or layer of elastomer is placed over the resulting wire ply and the helical wire winding operation is repeated. Reference is now made to FIG. 10 where the layers or plys E of elastomer 51 and layers or plys W of the wires 50 are clearly illustrated in the resulting laminated or sandwich structure of the support belts 35. In FIG. 11, a bobbin 66 is employed to helically wind multiple wires 50 to speed the fabrication of the belts, and it should also be appreciated that the thickness of the elastomer plys E are exaggerated for the purpose of illustration. Normally, the elastomer layers will be in the range of 0.050 to 0.250 inches and will lose their individual identity when the belts are fabricated due to fusion with adjacent layer through the wire plies.

It is improtant to recognize that the belts are fabricated so the wire filaments 50 will be insulated from one another by the elastomer as graphically illustrated in FIG. 10 wherein layers F of fabric have been placed between the wire plies W to make the belts somewhat more resistant to elastomer flow. Even if several wires are applied loosely twisted together, the elastomer will still tend to insulate them from one another. Generally, the elastomer is applied in an uncured condition, and after the belt is finished, the drum can be wrapped with shrink tape if desired, and the belt is then cured by removing the drum from the winding machine 60 and placing it in an autoclave.

By employing the small diameter wires 50 to form the reinforcing filaments in the support belts 35, excellent flexibility is obtained with adequate strength since these individual wires have tensile strengths from 275,000 to 425,000 psi. Because of their small diameters, the wires in the belts develop little internal stress during bending in contrast to large diameter, prior art wires or cables wherein the outside diameter (OD) of the cable reinforcing rings are under tension while the inner diameter (ID) is under compression as the track belt passes through the footprint of the tires. This condition causes loads to be unevenly distributed in larger diameter reinforcing filaments causing failure.

By contrast, the wire plies W of the reinforcing filaments of the support belt of this invention are parallel to the bending axis as the track belts pass through the footprint and are also very close to the neutral bending axis. Generally, it is preferred that these wire plies be located close to the neutral bending axis of the support belts 35 so that more even load distribution on all of the plies can occur. As a result, thick support belts are less desirable than the thinner belts.

Because of the small diameter of the wires 50 forming the reinforcing filaments, it can be appreciated that a physical connection between the track shoes and the reinforcing filaments would be difficult without damaging the latter. However the previously described elastomeric couple enables this attachment to be accomplished without damage to the reinforcing filaments and in joints that eliminate slippage between the shoes and the reinforcing filaments.

The elastomer 51 protects and insulates the reinforcing filaments from the track shoes and their associated keepers while the compressive loading on the elastomer forms a non-slip couple between them. While many compositions are suitable, the elastomer generally employed in the support belts is a natural rubber composition having the following characteristics:

Modulus 300% 1519 Tensile Strength 4023 Elongation 562% Durometer (Shore A) 63 Compression set (25%) 22 hrs. at 158.degree.F. 31.3 Specific Gravity 1.10

A suitable composition is:

Substance Parts by Weight Natural Rubber 100.00 N285 40.0 Textract 2 5.0 Flexone 3C 1.0 Thermoflex A 1.0 Stearic Acid 3.0 Zinc Oxide 5.0 Dipac 1.0 Sulfur 2.5 Total: 158.5

This composition is cured at 280.degree.F. from 2.5 to 8.0 hours, depending on thickness.

The composition of the elastomers employed between the support belts in some embodiments (see FIGS. 2 and 3) can vary from that set forth above.

Track belts made according to this invention have been successfully field tested in earth-working environments, and were found suitable for rock work on a loader having a 64-inch tire carcass.

In some applications where full drawbar loads may be transmitted through a single track shoe coupled to the belt supports, it may be desirable to bond the elastomer in the support belts 35 to the channels 34 in the retainer elements or keepers 33 (see FIGS. 2 and 3). Such a bond increases the capacity to transfer torque through the elastomeric couple without slippage, and the keepers are fabricated with the belts on the drum 62.

Also, the wires 50 may be pre-coated with elastomer before they are wound in the belts. Usually this pre-coating is preferred when several of the wires are applied as a loosely twisted cable having several strands. Such small cables are substantially inextensible in comparison to large cable or wire rope, used in the prior art, and function substantially the same as the individual wires, especially when their individual wires are insulated from each other by the elastomer so the fatigue life of the wires will not be reduced due to fretting.

Normally, the completed track belt is assembled on a pneumatic tire carcass having a design profile somewhat larger than the ID of the track belt, by partially collapsing the conventional tire carcass. After the track belt is in place, the tire is inflated and the radial growth of the carcass is constricted by the track belt to a diameter under its normal design profile. In a tire carcass employing radial reinforcing, a similar technique may be employed by also restricting its radial growth with the track belt.

In particular the instant track belt can be advantageously combined with a radially reinforced tire carcass, such as disclosed in U.S. Pat. No. 2,874,742 issued to Lugli when the track belt of this invention is employed in place of the tread belt shown in Lugli. Like the tread belt shown in Lugli the track belt of this invention will be sized to constrict the carcass to an oval configuration when assembled thereon. The pressure in the carcass will adequately secure the track belt on the tire preventing both circumferential and transverse slippage on the carcass. The disclosures of Lugli concerning the carcass construction is incorporated herein by reference.

The most desirable combination of the track belt of this invention with a pneumatic tube tire carcass is with a filament reinforced, helically wound tube tire carcass disclosed in the assignee's U.S. copending Pat. application Ser. No. 835,499 filed June 23, 1969 by Charles E. Grawey. When the instant track belt is combined with the tube tire carcass disclosed in the referenced patent application a superior wheel unit is formed for heavy duty application in work vehicles which can be easily converted for lighter duty application by removing the track belt and replacing it with the tread belt disclosed in that application. The disclosure of the above-referenced patent application is incorporated herein by reference for disclosing the full details of this superior tube tire carcass.

With the above type carcasses the track belts are preloaded and, therefore, must be strong enough to accept the torque through the track shoes along with the preload which in a 64-inch tire could be in the range of 100,000 pounds. Using the small diameter steel wires wound helically in the belts, the necessary belt strength can be obtained for the required service condition with these types of carcasses.

Since it may be difficult to collapse the tire carcass to assemble a heavy track belt thereon, it is possible to assemble the track shoes and belts on the tire carcass if the keepers 33 include arcuate surfaces in their channels to shorten the belts as the tap bolts 32 are tightened to achieve the compressive loading. An example of a suitable arrangement is illustrated in FIG. 14. Since the portion of flexible support belts within the central sections of the keepers is maintained immobile, the resulting arcuate path of the belts in these areas presents no difficulties.

In FIG. 2, the full belted embodiment is illustrated wherein the keepers 33 are essentially molded in the belt so the ID of the belt has a rubber surface 70 that engages a substantial portion of the crown C of the tire carcass 22. In such an embodiment, the coefficient of friction between the mating rubber surfaces is generally sufficient to prevent transverse movement of the track belt on the carcass and insure adequate drive to transmit the necessary torque. In FIG. 4, a lug 71 is employed in the central portion of each keeper 33 and is received in a circumferential groove 72 in the tire carcass.

When the instant track belts are used over conventional bias angled tire carcasses which shorten their circumference when deflected, the track belts, having a constant circumference, may tend to shift laterally (transversely) on these type carcasses. As a result the centering devices described above will be typically employed with bias angle tire carcasses, and not with the non-belted radial carcasses. On bias angle tire carcasses and belted radial tire carcasses the drive between track belt and the carcass may not be so positive. Thus some small amount of slippage may be expected between these carcasses and the track belt. Positive drive may be enhanced by a mechanical lug connection (not shown) between the track belt and these carcasses, if desired.

In the embodiment illustrated in FIG. 5, the keepers 33 have extended portions 33b in between the flexible support belts 35 which, with the underside of the associated track shoe 30, form a limiting stop that limits the degree of movement of adjacent track shoes, preventing a shearing action on the support belts when high radial deflecting loadings act on a single track shoe. Similar structures may be utilized with the dual support belt design illustrated in FIGS. 6 and 6A. In fact, track belts so configured could be employed in a track laying vehicle with appropriate modifications (see FIG. 6A).

Within the channel 34 of the keepers 33, the support belts 35 are held immobile with the bending or flexing occurring where the support belts exit from these channels and the portions thereof extending between the keepers. The neutral bending axis N of a support belt is illustrated by a broken line in FIG. 8 and is essentially in the middle of each support belt. When bending occurs along this axis, some shifting of both the bending axis and the individual wires in the belt matrix can be expected as the load distributes on these reinforcing filaments. It is suspected that through elastomer flow the individual wires shift slightly to redistribute the load with the outer ply W moving toward the bending axis through the elastomer since this requires no net volume change within the elastomeric couple. Since each reinforcing filament or groups thereof can be considered independently, the above analysis may be somewhat simplistic, but it does serve to illustrate that the couple is not rigid in the sense of metal physically clamped against the filament. In this couple, the wires can and do move to some extent along their axis during bending of the belts thereby lessening high localized tension and/or compressive loading on individual wires.

The construction of the preferred tire carcass 80 is shown in FIG. 15. It has an oval shape with an inextensible filament 81 helically wound around a torus-shaped elastomer liner 82 and the resulting loops covered with an outer elastomer casing 83. The air chamber is inflated through valve stem 84 and when the carcass is mounted on a rim with the track belt encircling its outer periphery the oval configuration is maintained as the tire is pressurized since the track belt is inextensible. Deflection of this tube tire carcass occurs in the sidewalls and allows the outer circumference of the carcass to remain substantially constant, becoming less oval in the portions of the carcass away from the deflection point. Thus the track belt is tightly retained on the carcass. An internal bumper 85 may be employed to limit the deflection and a centering rib 86 may be employed with cooperating rim structures to position the tire carcass thereon. Roll restraining hoops 87 at the base of the sidewalls and positioned inside the helically wound reinforcing prevent the carcass from rolling off the rim due to lateral loadings.

In the above description reference has been made repeatedly to inextensible reinforcing filaments, such as high tensile strength steel wires having diameters from 0.005 to 0.050 inches, which are employed in the track belt. Other filaments meeting the tensile strength requirements can be employed if they have a total elongation of less than 5 percent. For the purposes of this description a filament or small cable formed of such filaments which have a total elongation of less than 5 percent shall be considered to be inextensible in the context of the invention.

Claims

What is claimed is:

1. A flexible track belt comprising:

at least one flat elastomer endless support belt having a centrally disposed inextensible reinforcing ply of circularly wound inextensible reinforcing filaments in a side-by-side relationship therein to form connected loops of substantially equal diameters forming at least one cylindrical ply with filaments individually encased by elastomer;

a plurality of removable oblong track shoes circumferentially arranged about the outer peripheral surface of said flat support belt at spaced intervals, said track shoes oriented transversely across said support belt and transverse to the axes of said reinforcing filaments in said support belt, and

a plurality of attaching means coupling said track shoes to said support belt, each of said attaching means having an outer belt engaging member and an inner keeper member, each of said inner keeper members having a belt conforming channel recess with a uniform recess cross-section therein, said keeper members arranged at circumferentially spaced intervals about the inner peripheral surface of said support belt and integrally formed with said support belt so elastomer portions of said support belt separate adjacent edges of said keeper means from one another thereby providing a continuous inner surface, each of said keeper members confining in its channel recess the lateral contiguous edges of a portion of said belt having said reinforcing filament encased in elastomer operable to prevent lateral extrusion of elastomer surrounding said reinforcing filaments when said portion is clamped in its contiguous channel recess so elastomer in said portion can be loaded with sufficient force to prevent slippage between said attaching means and said inextensible reinforcing filaments due to a couple formed therebetween as the elastomer is densified by said force.

2. The flexible track belt as described in claim 1 wherein several equal diameter support belts are employed therein with said belts connected together with elastomer webs.

3. The flexible track belt defined in claim 1 wherein the keeper members are bonded to the elastomer endless support belt.

4. The flexible track belt as defined in claim 1 wherein the elastomer is loaded with at least 1,500 PSI to enhance the couple.

5. The flexible track belt as defined in claim 1 wherein the cylindrical ply is disposed within the support belt adjacent to the neutral bending axis of said support belt.

6. The flexible track belt as defined in claim 1 wherein the inner surfaces of the oblong track shoes form the outer belt engaging member of the attaching means.

7. The flexible track belt defined in claim 1 wherein each of the attaching means is adjustable and operable to vary the force on the portion of the elastomer belt within its keeper member.

8. The flexible track belt as defined in claim 1 wherein the inextensible reinforcing filaments are composed of steel wires having diameters from 0.0005 to 0.050 inches.

9. A flexible track belt as defined in claim 1 wherein key means are included attached to the inner periphery of the resulting track belt to prevent lateral shifting thereof on a supporting unit.

10. The flexible track belt as defined in claim 1 wherein the key means include cheek members on opposite sides of the track belt which project radially inward for engagement with the sidewalls of a supporting pneumatic carcass.

11. The flexible track belt as defined in claim 1 wherein the elastomer endless support belt has at least wo cylindrical plies.

12. The flexible support belt defined in claim 11 wherein fabric layers are disposed between adjacent cylindrical plies of the inextensible reinforcing loops.

13. The flexible track belt defined in claim 1 wherein the reinforcing filaments are brass plated and bonded to the surrounding elastomer.

14. The flexible track belt defined in claim 13 wherein cross sectional ratio of reinforcing filaments to elastomer in the support belt is controlled to prevent extrusion of elastomer from the open ends of the keeper members whereby the elastomer confined by each keeper member can be densified to enhance the couple between the attaching means and the individual reinforcing filaments.