US2747726A - Endless-belt conveyors - Google Patents

Description

May 29, 1956 s. D. ROBINS 2,747,726

ENDLESS-BELT CONVEYORS Filed July 5, 1952 8 Sheets-Sheet l llll INVENTOR. SAMUEL DA v/s Ros/N5 A 770R NE Y5 May 29, 1956 s. D. ROBINS ENDLESS-BELT CONVEYORS 8 Sheets-Sheet 2 Filed July 3, 1952 May 29, 1956 s. D. ROBINS ENDLESS-BELT CONVEYORS 8 Sheets-Sheet 3 Filed July 5, 1952 INK BT01? SAMUEL 0/2 v15 Foam/s S. D. ROBINS ENDLESS-BELT CONVEYORS May 29, 1956 8 Sheets-Sheet 4 Filed July 3, 1952 8 KM 0 o 71/ E WW. Q\ V \l o 0 m w 0 w m M w \\w m v g A: g. =3 8 n w L L w L g TTORNEY? May 29, 1956 s. D. ROBINS ENDLESS-BELT CONVEYORS 8 Sheets-Sheet 5 Filed July 3, 1952 E R5 mm 00m N 0 mm T .N W/T IA 0 A L E a W a W/ V: B

'l'lll I I IIII IIOIII Ill- y 1956 s. D. ROBINS 2,747,726

ENDLESS-BELT CONVEYORS Filed July 5, 1952 8 Sheets-Sheet 6 a! INVENTOR.

5AMUL DAV/5 Ros/N3 /l TTOENEYS.

May 29, 1956 s. D. ROBlNS ENDLESS-BELT CONVEYORS 8 Shuts-Sheet 7 Filed July 3, 1952 5 Mo n N Z mw D g H U a M A u 5 m 9 TTOR/VEYS y 1956 s. D. ROBINS 2,747,726

ENDLESS-BELT CONVEYORS Filed July 3, 1952 8 Sheets-Sheet 8 INVENTOR.

- 5AMUL DAV/5 Ra /Ms A TTO/E'NEYS United States Patent ENDLESS-BELT CONVEYORS Samuel Davis Robins, Lawrence, N. Y.

Application July 3, 1952, Serial No. 297,064

6 Claims. (Cl. 198-203) This invention relates to endless-belt conveyor or elevator systems of utility for transporting minerals or other materials over long distances, horizontal or inclined, and it relates more particularly to such systems in which an endless moving cradle belt is wholly supported both in its upper run and its lower run by wheels or rollers which run upon tracks and is combined with an endless moving propelling cable or cables, together with means for connecting and disconnecting the belt and cable or cables, so that the belt may be cable driven.

It is among the objects of this invention to enable a positive powerful frictional connection of the belt to the cable or cables to be made that will be proof against slippage even at such severe angles as 30 to the horizontal at which the belt may be inclined in its path of travel; to multiply the useful life of the cable many times and as much as ten or even more times beyond that which has heretofore been considered possible for cables in beltconveyor usage; and, to enable a continuous conveyor belt to be operated when desired around curves in plan equally as well as in elevation, without having to terminate the belt at any point intermediate the starting and ending stations of the belt. The latter is a novel and very valuable feature heretofore unknown of accomplishment in any belt-conveyor and one serving to eliminate the severe wear attendant upon such operation when attempted heretofore.

These and other objects of this invention are accomplished, in part through the provision of certain new and useful improvements in the construction and arrangement of the belt, its cradles, the cable and tracks of such systems, and in part through the provision of certain new and useful weight-actuated tong means. for connecting and disconnecting the belt and cable possessing a basic mechanical advantage and a two-direction gripping action enabling the belt to support the cable or cables and yet be driven thereby both in itsupper arm and its lower run, whose grip upon the cable in either case is a tune-- tion of the basic mechanical advantage it possesses and is in proportion to the loading of. the belt, and that may easily engage and as easily disengage the cable without damage to the cable, slippage or jamming.

In accordance with this invention the belt conveyor system comprises in its broad aspects three major components, namely, a track-borne cradle-belt assembly, tracks with supporting structure, and a drive cable or cables each with its associated drive machines and takeup sheave.

Thetrack-borne cradle-belt assembly as embodied is an integral assembly of an untensionedendless belt fixedly secured to the required number of articulated tong-forming cradles of this invention disposed at suitable intervals along the belt. I

The drive cable asembodied comprises a bare endless wire rope. A single rope is ordinarily preferred, but two or more may be used if desired. It is made endless by a long splice as in conventional ropeways, tramways, or power transmission systems. There are no attachments 2,747,726 Patented May 29,

of any kind to the rope, such as are found on mono ca ble tramways. Therefore, the more efiicient types of drive may be used, high initial tensioning being unnecessary. Everything about the rope, its drives, sheaves, etc., follows established good engineering custom. The rope at no time has to engage a sheave tangentially but on the contrary takes at least a quarter wrap on sheaves. It is supported throughout the run of the conveyor by the cradle-belt assembly. It is not subject to contamination or wear ad should have at least a 10-year life.

The tracks, as embodied, are firmly supported through the length of the conveyor as by stringers of the track supporting structure, and may consist merely of fiat bars. The track supporting structure, as embodied, is of whatever structural arrangement and type is best suited for the locale in and conditions under which it is to be used. It may rest on the ground, act as a truss to bridge short spans, or be suspended by cables to cross great spans.

The articulated tong-forming cradles possess certain salient and novel features as regards both design and functions. Thus, the ease with which the cradle belt assembly can engage and disengage the drive cable, or the facility of the cradle belt assembly to travel around the terminal pulleys, arises from the concept of the articulated cradle with its cable'engaging tongs.

The cradle structure in accordance with this invention may be singly or doubly articulated. in its singly articulated form each cradle half may comprise an angle bar, a wheel and axle assembly, a tong, and a clamp plate. The tong and clamp plate are below the belt being bolted to the angle bar which is above the belt. Thus, the belt is sandwiched between the parts of the assembled cradle; The wheel and axle assembly is secured to the outer end of the unit.

In order that the several functional requirements of the articulated cradle structure may be fully understood, it should be noted that a troughed belt cannot be reversed on itself at the terminals without flattening itself where it wraps the pulley. Hence, one reason for having the cradle of articulate form. Another reason exists for articulation of the cradle, namely, to permit engaging the drive cable and holding it tightly enough to ensure no slip. With the articulated cradle in accordance with this invention, when the cable is engaged, the cradle becomes a rigid beam, but when the cable is disengaged, the cradle is unlocked and free to articulate, that is, go into a flat position for rounding terminals, and return to a troughed section for the straightaway top and bottom runs.

The cradle serves as a moving support for the belt and its load on the carrying run and for the empty belt on its return run. Moreover, in accordance with this-invention, the cradle serves not only to support the drive cable throughout both runs but to grip the cable with sufiicient pressure to secure slip-free traction from the cable.

The tractive pull is highest where the belt is on the steepest incline, and added tractive pull must be exerted in starting where acceleration is added to the weight load plus the friction load. I i

In accordance with this invention, the distance from a tong hinge or fulcrum of the cradle to the cable may be referred to as the tong lever arm, and the distance between this point and either rail of the track system may be referred to as the load lever arm. The shorter the tong lever arm and the longer the load lever arm, the higher the gripping force between the tong jaws and the cable. Advantageously, a tong lever arm of about one twentysixth of the track gauge may be used. This gives anv loaded belt causes a tighter bite than the empty belt. Thus, the tractive force required is a direct function of the basic mechanical advantage offered by the tong lever arm-weight lever arm ratio, and is in proportion to the loading of the belt.

In accordance with one embodiment of this invention, the tong jaws, which for convenience may be designated as right-hand and left-hand jaws, have each a right-hand lobe and a left-hand lobe forming therebetween a socket for the cable enabling a two-direction action. Thus, in the right-side-up or load-carrying position of the cradles, the jaws lock the drive cable in shear with the cable bearing against the left lobe of the right-hand jaw and the right lobe of the left-hand jaw. But when the cradle is inverted, gravity still acting down, the shear load is reversed, and the opposite lobes bear on the cable.

Means are provided for releasing or disengaging the connection between the belt and cable at certain points in the circuit, and rc-engaging at others. Release points are upstream of head, tail or intermediate drive stations, while rte-engagement points lie downstream of said stations. In order not to chafe or wear either the faces of the tong jaws or the drive cable itself, it is of the utmost importance that engagement or disengagement, whichever the case may be, be smooth and deliberate. Advantageously, the releasing means may be in the form of a separate set of gently rising rails or rollers, or a gently rising endless belt unit, acting upwardly on the central portion of I the cradle to relieve the load on the tong jaws and gradually spread them apart to an open position. Then, but not till then, the cradle wheels encounter a corresponding gentle rise in the track serving with the rails to lift the open jaws clear of the cable. As the cradle and the drive rope are always traveling at the same speed, the release, if performed as outlined, occurs with no scuifing or other deleterious effect either on the tong jaws or the cable. In the inverted position of the cradle, the release may be effected by the same form of releasing means, or the wheels may be pushed or crowded together to raise the central portion of the cradle thereby to release the grip on the cable. The same principles apply to engagement, but in the reverse manner, and the same applies at all stations whether head, tail, or intermediate drive stations.

Thus, as the loaded belt approaches a selected station in its upper run, it disengages, rises with the tongs clear of the drive cable, lowers a short distance beyond the station, and reengages the cable. If the track at the drive station is curved in plan, the belt, being free of the cable, is also free to traverse the curve without interference from the cable and, if desired, the cable may be led around suitable pulleys to and through booster drive located externally of the track and thence back to the track structure. On the return run at the same station, the belt disengages, lowers with the tongs clear of the drive cable, rises a short distance beyond the station and reengages the cable. Here also the cable is free to be led around pulleys outside the track.

In the accompanying drawings which form part of the instant specification, and are to be read in conjunction therewith, and in which like numbers refer to like parts throughout the several views:

Fig. 1 is a fragmentary view in side elevation at the driving end (discharge end) of a preferred embodiment of endless-belt conveyor system in accordance with this invention, certain of the parts being broken away in order to show more clearly the construction and arrangements of other parts;

Fig. 2 is a view in plan of the embodiment shown in Fig. 1;

Fig. 3 is a view in section taken along the line 3-3 of Fig. 1, and showing details of upper and lower track'- borne articulated tong-forming cradle structures each with its tongs in driving engagement with the cable of the systern;

Fig. 4 is a part sectional view in plan taken along the line 4-4 of Fig. 3 and showing the manner in which the cradle tongs grip the cable on its return run;

Fig. 5 is a part sectional view in elevation taken along the line 55 of Fig. l and showing the flattened condition of the cradle structures in transport around the tail pulleys;

Fig. 6 is a part sectional view in elevation taken along the line 6-6 of Fig. l and showing a cradle structure of the upper run in the last stage of its cable disengaging run, and showing a cradle structure of the lower run in the initial stage of its cable engaging run;

Figs. 7 and 7a are broken diagrammatic views in elevation which taken together show a complete endless cablebelt conveyor system in accordance with this invention but omitting the cable system for clarity of showing, the system embodying a horizontally curved section in Fig. 7 and a vertically curved section in Fig. 7a in each of which the articulated cradle belt assembly is disengaged from the drive cable and caused to follow a curved path;

Figs. 8 and 8a are broken diagrammatic views in elevation of the cable system of the unit shown in Figs. 7 and 7a, the view showing the intermediate drive systems for the cable in the horizontally curved section, Fig. 8, and in the vertically curved section, Fig. 8a;

Figs. 9 and 9a are broken diagrammatic views in plan of the cable system of Figs. 8 and 8a, respectively;

Fig. 10 is a view in vertical section through a modified form of endless cable-belt conveyor system in accordance with this invention, the section plane corresponding generally to that of Fig. 3 and the view showing a double cable system in which a pair of double articulated cradle structures are in a cable-engaging position in their upper and lower runs, respectively;

Fig. 11 is a fragmentary view in plan with parts in section taken along the line 1111 of Fig. 10;

Fig. 12 is a fragmentary view in section taken along the line 1212 of Fig. 10;

Fig. 13 is a view in vertical section of the modification shown in Fig. 10, the section plane corresponding generally to that of Fig. 6 to show the cradle structures in a cable disengaged position corresponding to that of the cradle structures of Fig. 6;

Fig. 14 is a view in vertical section of the modification shown in Fig. 10, the section plane corresponding generally to that of Fig. 5 to show the cradle structures of the upper and lower runs, respectively, in flattened condition in transport around the tail pulleys of the belt system;

Fig. 15 is a view in vertical section of another form of endless cable-belt conveyor system in accordance with this invention, the section plane corresponding generally to that of Fig. 3 and the view showing a double tong cradle structure for use with a single cable system having horizontally offset upper and lower cradle runs, respectively;

Fig. 16 is a fragmentary view in plan taken along the line 1616 of Fig. 15; and,

Fig. 17 is a fragmentary view in elevation taken along the line 1717 of Fig. 15.

Referring now more particularly to Figs. 1 to 9 inclusive of the accompanying drawings, upper and lower suitably vertically spaced tracks 1 and 2, respectively, are supported at suitable intervals by a suitable framework comprising vertical posts 3, horizontal stringers 4 and longitudinal stringers 5. The tracks 1 and 2 extend over whatever distance is desired between a pair of coaxial spaced head pulleys 6 at one end and a corresponding pair of tail pulleys 7 at the other. The tracks may be straightaway and horizontal, or inclined, or include curved sections either horizontally or vertically curved as required by the terrain. As here preferably embodied, the tracks comprise straightaway sections S1 and S2 connected by a horizontally curved section H as is best seen by the diagrammatic showing of Fig. 7, and a vertically curved section V connecting the straightaway section S2 with an inclined section I, as is best seen in Fig. 7a. The curved sections as shown each constitute an intermediate drive station as will more fully appear hereinafter, although as many additional intermediate drive stations may be employed as are necessary having regard to the length of the conveyor system.

An endless conveyor belt 8 runs between and over the head and tail pulleys 6 and 7, respectively, to provide upper and lower runs 811 and 8L respectively, and may be suitably initially lightly tensioned as by counterweight means 9 connected to and operating on the tail pulley shaft 10 in known manner. The diameter of the head and tail pulleys and the spacing of the upper and lower tracks is suitably coordinated to place the upper run 8a of the belt above the upper track 1 and the lower run ill of the belt below the lower track 2.

An endless drive cable 11 extends between and over a tail pulley 12, a head pulley 13, and suitably disposed upper and lower sets of tail idler pulleys l-tu and 141, head idler pulleys 15a and 151 and intermediate drive idler pulleys 16M and 161 to provide upper and lower cable runs 11a and 111. The cable runs are vertically aligned midway between the rails of the tracks 1 and 2 except at booster or intermediate drive stations such as those in the curved sections H and V whereat the cable runs llu and 111 are diverted laterally outside the track, by the idler pulley sets 16M and 161, respectively, as best appears in Figs. 9 and 9a.

The tail pulley 12 and the head pulley 13 for the cable are each preferably located outside the track supporting structure. The head pulley 13 is journalled in bearing supports 17 and 18. The tail pulley shaft 19 is suitably adjustably mounted to permit tensioning of the cable as by the counterweight means 19 connected to and operating on the pulley shaft 19 in known manner.

The intermediate or booster drive for the cable 11 at each of the curved track sections H and V preferably comprises a pair of annularly grooved cable drums 2t) and 21 located wholly outside the track supporting structure and journalled for rotation on parallel axes. The cable drum 2t} is power-driven as by an electric motor 22 acting through a suitable reduction gearing 23. The upper run 111: of the cable 11 is guided onto and off of the drums and 21, respectively, by means of the upper set of idler pulleys 1611 in a manner which will be clearly apparent from Figs. 8, 8a, 9 and 9a. The cable makes several half wraps, advantageously five or more, around each drum. Thus, the necessary tractive effort is imparted to the upper run of the cable at the upstream side of the drum 29. On the downstream side of the drum 21, the tension in the upper run is only that imparted to it by the succeeding downstream booster station, or head drive. The lower run 11[ of the cable is led out of and back into its normal running position centrally of the track by the. lower set of idler pulleys 161 so as to run around and completely clear the booster or intermediate drive station.

Articulated cradle structures 24 spaced at suitable intervals along the endless belt 8 form therewith an inseparable cradle-belt assembly. The cradle structures 24 are identical and. each structure is symmetrical, both halves being identical. In accordance with the illustrative embodiment thereof depicted in Figs. 39 inclusive, each half comprises upper and lower beam members 25 and 26, respectively, between which the belt 8 is sandwiched. Advantageously the beam member 26 may be a flat plate, and the beam member 25 may be an angle iron, as shown. They are secured. together so as to clamp the belt 8 therebetween, as by means of rivets 27, bolts, or other suitable securing means passing therethrough.

A wheel and axle assembly comprised of a flanged wheel 28 is attached to each cradle half at the outer end of the beam member 26 for rolling engagement of the wheel 28 with the rails of the upper track 1 in the outward movement of the belt toward the head pulley, and

for rolling engagement with the rails of the lower track 2 on the return run of the belt.

A tong member 29 attached to each cradle half at the inner end of the beam member 26 comprises a tong jaw 30 and a cam follower member 31, by which opening and closing of the tong jaw is effected. The tong jaws 30 have their pivotal connection 32 with each other in the vertical plane of symmetry of the cradle structure 24, in which plane the axis of the upper and lower runs 11a and Ill, respectively, of the cable 11 also lies. The tong pivot 32 is vertically spaced from the cable 11 above the cable in the upper run, and below the cable in the lower run, as clearly appears in Fig. 3.

Each tong jaw 30 is preferably provided also with a pair of cable-engaging lobes 33 and 34 providing therebetween a recess 35 for receiving the drive cable 11. Each jaw is also provided with a stop lug 36 serving to limit the extent of angular movement of the jaws 30 to a determined amount in either direction, as will more fully appear hereinafter.

The camfollower members 31 as here preferably embodied each comprise a roller 37 having an arcuate surface and adapted to ride upon a tong camming rail 38 for the purpose of opening or closing the tong jaws in engaging, or disengaging, the tongs with or from the cable in its upper run at the head, tail and intermediate drive stations of the conveyor system.

The tong-camming rails 33 are disposed in pairs at the required stations along the conveyor, one at each side of the cable 11 in its upper run, as best appears in Figs. 2 and 6. The rails of each pair are suitably supported on and in parallel relation to each other, as by longitudinal stringers 39 (Fig. 6) secured to the horizontal stringers 4.

Each of the tong camming rails 38 is of a configuration to provide, intermediate its ends, an inclined surface portion 40 upon which the roller 37 of a given cam follower member is adapted to ride and be raised or lowered, as the case may be. For the purpose of opening the tongs in the upper run, a given pair of the rails 38 is disposed so that the inclined surface portion 40 of each will present an upwardly inclined surface to the advancing roller and thus raise it, or vice versa. Advantageously, each tong camming rail 38 terminates at each end of its inclined portion 40 in a straightaway portion 41 serving to guide the roller into and out of the inclined camming portion of the rail.

As will be apparent from Fig. 3, the cradle structures 24 in their upper run are supported in a troughed condition by the wheels 28 upon the rails of the upper trackl wherein the weight of the cradle-belt assembly, plus its load, acts downwardly. Because the cradle is articulated at the pivot 32', this downward load functions to cause the tongs 30 to grip the drive cable 11 tightly, and the cradle constitutes a track-borne rigid beam supporing both the load and the-cable. The greater the loading, the greater the gripping action of the tongs on the cable.

In accordance with this invention however, the 'grip of the tongues on the cable in its upper run may be released at any convenient point in order to permit the cradles to be entirely freed from the cable. The cradles when thus freed may be caused to assume a flattened condition for passage around the head and tail pulleys, or to enable the cradles in a troughed state to follow freely a curvature in the track whether the curvature be in the vertical or horizontal plane. Moreover, by freeing the cradle structures from the cable at selected points it is possible to lead the cable outside the track suporting structure at the head and tail of the conveyor and at intermediate drive stations for relieving the stress in the cable at such stations and to make it possible to employ successfully and in a commercially feasible manner, an endless belt of light weight'and low cost covering many miles of terrain. To this end therefore, the tracks 1 and 2 are provided with ramps 42 for elevating or lowering the tongs 30 as may be required, between opposite extremes of position in one of which the cable lies wholly outside the tong socket 35 and in the other of which the cable is seated in the tong socket. In the illustrative embodiment of this invention as depicted in Figs. 7 and 7a, the ramps 42 are disposed at the head and tail stations, respectively, and at the entrance and exit of the intermediate drive stations H and V at which, in the illustrated embodiment, the track is curved.

The ramps 42 in the upper track 1 are positionally coordinated with the camming rails 38 so that the action of the latter either precedes or follows the action of the former. In order that the coordinated action of the ramps and camming rails on a given cradle in transit on the upper track may be clear, reference may be had to Figs. 1, 3, 5, 6 and 7a in particular. In Fig. 7a, particularly with reference to the uncoupling ramp 42 of the track 1 located just ahead of the head pulley 6, it will be noted that the camming rail 38 is disposed so that its inclined portion 40 precedes the upwardly inclined ramp 42. Thus, as a given cradle moves toward the pulley 6 on the level portion of the track 1 preceding the inclined portion 40 of the camming rail 38, the tongs 30 firmly grip the cable 11 in the position shown in Fig. 3. In this position the cable 11 is wholly contained in the sockets 35 of the tong jaws and is gripped between the left-hand lobe 33 of the right-hand tong jaw and the right-hand lobe 33 of the left-hand tong jaw, as seen in Fig. 3. The force with which the tong jaws grip the cable is a function of the loading of the belt and the basic mechanical advantage offered by the articulated cradle and its cable-gripping tongs. As the cradle advances, the camming rollers 37 meet the inclined portion 40 of the camming rails 38. As the rollers travel up the incline, the cradle halves are fulcrumed on the rails of the track to raise the pivot point 32, thus articulating the cradle halves on the pivot point and releasing the grip of the tong jaws on the cable. Then and only then, the wheels 28 of the advancing cradle meet the uncoupling ramps 42. As the cradle moves up the ramp, the tongs 30 are gradually lifted clear of and preferably above the cable as to the position shown in Fig. 6. The track 1 may continue on for a short distance at its new level beyond the ramp, as desired.

As the cradle continues its forward movement toward the axially-spaced head pulleys 6, the articulation of the cradle permits it to flatten until at the head pulleys 6 it is in a fully flattened position as shown in Fig. 5, to round the pulleys. The latter are suitably spaced axially to receive therebetween the tong structure of the cradle throughout its travel on the head pulleys.

Upon completing its travel on the head pulleys, the cradle is in an inverted but still flattened position as appears in Fig. 5. In this position, the stop lug 36 on each tong jaw abuts firmly against the body portion 43 of its companion tong jaw to prevent troughing of the cradle structure and thus serves to maintain the cradle structure in its flattened condition as it leaves the underside of the head pulleys 6.

Means are provided for troughing the cradle upwardly as it commences its return run so that the tong may be positioned properly for reengagement with the drive cable in its lower or return run. The embodied means is disposed in the vertical plane of symmetry of the cradles between the head pulleys 6 and the beginning of the return track 2, and is adapted to maintain the pivot connection 32 of the belt at substantially the pitch line level of the head pulley at which the belt leaves the head pulleys, while leaving the cradle halves free to articulate downwardly by their own weight on the pivot connection 32 until they attain the inverted troughed position in which the recesses 35 in the tong jaws are aligned ready for coupling to the return run 111 of the cable, as indicated in Fig. 6. When this position has been attained, the wheels 28 of the advancing inverted cradle meet the rails of the lower track 2, and coupling of the cradle to the cable may proceed. As here preferably embodied, the

troughing means comprises a series of rollers 44 between the pulleys 6 and the track 2, each supported on a suitable structural member 45 at the same elevation and in the plane of symmetry of the cradles at the head pulley end. The top of each roller is at a level corresponding substantially to the tangent to the pitch line of the pulleys 6 at the point of departure of the belt therefrom.

Each cradle 24 on attaining the desired inverted position shown in Fig. 6 enters upon the track 2 (see Fig. 1) which is preferably provided with an approach section 46 for a short distance to maintain the wheels 28 at the same elevation preparatory to the cradle being coupled by the tongs 30 to the return run 111 of the cable. The gauge of the track 2 over the approach section 46 is selected to maintain the tongs 30 in their open cable-receiving position shown in Fig, 6. The flanged wheels 28 make this possible since the cradle in its inverted position tends to flatten out under its own weight. This is resisted by the rails of the track 2 bearing against the wheel flanges.

The coupling ramp 42 at the end of the approach section 46 serves to raise each cradle until the lower run 111 of the cable is seated in the aligned cable recesses 35. The gauge of the track 2 then gradually widens as shown in Fig. 6, until at the top of the ramp the normal running gauge is reached. During this interval, the tong jaws 30 of the cradle are caused by the weight of the cradle to grip the cable tightly therebetween in the condition shown in Fig. 3. From then on, until the cradle is to be uncoupled from the cable, the cradle is track-borne and towed by the cable which it supports.

When uncoupling of the cradle is necessary as, for example, at the intermediate drive station of the vertically curved track section V, Fig. 7a, the downwardly inclined uncoupling ramp 42 at the entrance to this section is gauged first to squeeze the wheels 28 together so as to release the grip of the tong jaws on the cable and place them in a position to be lowered freely away from the cable, and then to lower the cradle down the incline until the jaws lie completely below the cable. The recoupling ramp 42 at the end of the section V functions precisely in the manner of the coupling ramp at the beginning of the return track 2. Moreover, it will be apparent that the coupling and uncoupling of the cradles 24 and lower cable run 111 at any desired station along the return run follows the principles outlined above.

In accordance with this invention also, the coupling and uncoupling ramps 42 of the upper and lower tracks are arranged in pairs so that the coupling and uncoupling operations on the respective tracks will occur substantially simultaneously. This is of particular importance at the beginning and end of a curved section of the track or at any intermediate drive station.

It will be apparent from the foregoing that through the medium of this invention, the drive cable 11 may be led to the sides of the track structure at any desired location and, by the use of an intermediate drive, the cable tension maintained within permissive limits. Moreover, since the cradle construction is such that the cable engaging jaws lie beneath the cradle, it is possible for the cradle-belt assembly to be endless over whatever distance is desired, and for the drive cable to be endless also and located between the upper and lower runs of the endless belt where it may be diverted laterally to booster stations as required.

In the embodiment of this invention shown in Figs. l0-14 inclusive, there is depicted a double articulated troughed cradle structure for use with dual cable flights in both its upper and lower runs under heavy duty conditions where the loads are heavy, the inclines steep, or the like. The cable 11 is endless as in the previous case but is suitably reeved as by the use of oppositely inclined drive and tail pulleys in known manner, to provide parallel flights of cable in both upper and lower runs. The cradle, symmetrical about its center line, comprises the combination with the endless belt 8 of an upper beam member 47 and a lower beam structure between which the belt 8 is clamped. The lower beam structure as here preferably embodied comprises a camming member 48 carrying at its opposite ends a pair of camming roller 49, the member 48 being secured to the upper beam member 47 as by bolts 50. The lower beam structure further comprises at each end of the camming member 48, a tong member 51 also bolted or otherwise suitably secured to the upper beam member 47 and having pivotally connected thereto by a pivot pin 53, a wheel-carrying tong member 52. Each tong member is preferably channel shaped for strength and is of a configuration to provide, as to each, a pair of parallel tong jaws each having inner and outer lobes 54 and 55, respectively, providing aligned cable recesses 56. As in the case of the singly articulated cradle, the cable 11 when seated in the recesses 56 is clamped during its upper run between the inner tong jaw lobes 54 of the tong member 52 and the outer tong jaw lobes 55 of the tong member 51. The arrangement however provides greater gripping area on the cable. The clamping is in the opposite direction however during the lower run of the cable, as is shown in Fig. 10.

The tong member 51 is provided with a shelf portion 57 upon which trough portions 58 of the belt are supported when the cradle is in its flattened condition for passage around a head or tail pulley 59 as shown in Fig. 14.

Each tong member 52 is of a configuration to support or hold the respective trough portions 58 of the belt at a suitable angle in both the upper and lower runs of the belt and to this end is provided with an extended surface portion 60 slidably engaging the under surface of the respective trough portions. Thus, as the tong member 52 is caused to pivot on the pin 53, the trough portion 58 in engagement therewith is freely movable with respect thereto.

Each tong member 52 carries a wheel 61 which the cradle may be supported by, and travel on, the tracks 1 and 2. A stop lug 62 is suitably located on each tong member 62 through which it passes from side to side, to engage the shelf portion 57 of the tong member 51 at one extreme of angular movement, and engage the tong jaw lobes 55 of the same member at the other extreme.

It will be apparent that the weight of the cradle acting down on the tong pivot pins 53 will cause the tong jaws to come together both in the upright position and the inverted position of the cradle structure in Fig. 13. By suitably locating camming rails 63 (Fig. 13) to coact with the camming rollers 49 after the manner described for the singly articulated cradle, the engaging and disengaging of the cable by the tongs may be readily effected, as will be apparent to those skilled in the art. Likewise, through the employment of coupling and uncoupling ramps as previously described, the cradle may be raised from or lowered onto the cable flights in its upper run to effect the desired coupling and uncoupling at head, tail and intermediate drive stations. Thus, the freed cable flights may be diverted outwardly to booster stations, or head and tail pulleys, as required.

In Figs. 15-17 inclusive, there is depicted a modified form of single articulated cradle structure 24 adapted for use in a conveyor system in accordance with this invention in which the endless cable 11 has its upper and lower runs horizontally offset at equal distances to the left and right respectively of the plane of symmetry of the cradle, as shown in Fig. 15.

The cradle tong means as here preferably embodied is or are characterized by a pair of tong members 29, one having a doubled lobed tong jaw 30 comprising spaced pairs of lobes 64 and 65 spaced apart a distance sufiicient to span the cable 11 both in its upper and its lower runs.

The other tong member 29 has-its tong jaw 30 provided with a single pair of lobes 66 extending therefrom a distance sufiicient to form separate cable recesses 67 with the lobes 64 and 65 respectively. Thus, articulation of the cradle halves on the tong pivot 32 enables the tongs to grip the cable 11 between the lobes 66 and 64 in its upper 10 run and between the lobes 66 and 65 in its lower run. In either case, the gripping action is a direct function of the loading of the belt 8 and the basic mechanical advantage of the track-borne articulated cradle-belt assembly.

Articulation of the cradle to effect coupling and uncoupling of the tongs may be effected as described for the embodiment of Figs. 1-9, and to this end the tong lobe 64 carries a camming roller 68 which may also function as a troughing roller in co-action with the troughing rail 69. Likewise, a stop pin 70 carried by the tong lobes 65 is adapted to co-act with abutments 71 on the other tong member to limit the angular movement of the cradle halves between a flattened condition in transport over head and tail pulleys and a condition of maximum troughing during coupling and uncoupling of cradle and cable.

The cradle 24 is supported as shown upon the tracks 1 and 2. In order to eifect improved tracking of the cradlebelt assembly, particularly over track sections curved in azimuth, the assembly may comprise an articulated wheel assembly 72, advantageously embodying double-flanged or sheave-type wheels arranged in tandem fore and aft of a vertical spindle. In such case, the rails of the tracks 1 and 2 and the wheels may be of a configuration in crosssection adapting them to nesting with each other so as to minimize derailing. Such a construction is embodied in the assembly of Fig. 15 wherein tandem wheels 73 are mounted on a truck 74 journalled by a vertical spindle 75 to a mounting plate 76 secured to the cradle structure extremities. Thus, relative pivotal movement between the wheel trucks 74 and the mounting plate 76 may follow as the cradle-belt assembly traverses curves. Moreover, by the use of tandem wheels, a lower load intensity and more effective load distribution with lessened track wear, is attainable.

It will be noted that in the tong designs thus far described, the hinge axis is close to the belt but not so close but that a local distortion of the belt occurs as a result of cradle articulation. In narrow belts, 24" wide and under, this distortion is not objectionable but where Wide belts, say 60", are used, the proportionate belt thickness leads to excessive distortion unless the pin axis is practically coincident with the neutral axis of the belt structure. Advantageously, such an ideal hinge location may be obtained by cutting a rectangular hole in the belt to provide space for the hinge and, if desired, for passage of the tong halves therethrough for attachment to the top of the belt. Moreover, in such a design, the hinge itself may be dispensed with and the tong halves permitted to abut at the hinge point in rocker fashion. The easy flexing of the belt thus obtained outweighs the disadvantage of having to punch a hole in the belt. In this form the gravity loading of the upper run leads to a compressive abutment of the tong halves while on the lower run with the cradle inverted the gravity loading tends to pull them apart, which tensile load is taken in the belt itself.

The invention in its broader aspects is not limited to the specific mechanisms shown and described, but departures may be made therefrom within the scope of the accompanying claims without departing from the principles of the invention and without sacrificing its chief advantages.

What is claimed is:

1. A belt-conveyor system for transporting material over long distances, horizontal or inclined, comprising upper and lower tracks; an endless drive cable; a cradlebelt assembly comprising an endless belt and wheeled cradle structures mounted at spaced intervals on said belt for supporting said belt in its upper and lower runs in rolling engagement with said upper and lower tracks, respectively, said cradle structures each being articulated and comprising each at least a pair of rigid beam members disposed cross-wise of said belt and secured thereto in end-to-end relationship to each other, each of said pair of beam members having means forming a tong jaw at its contiguous end, the tong jaws of said beam members together providing a weight-actuated tong for connecting 1 l the cradle structure to said cable at certain points in the belt circuit and disconnecting it at others, each said tong when connected to said cable having its hinge axis located between said cable and said belt and having its jaws constructed and arranged to grip said cable in its upper and lower runs, respectively, between different pairs of gripping surfaces; means for raising and lowering the hinge axis of said cradle structures for releasing the connection between said cradle structures and said cable at certain points in the belt circuit, and reengaging at others; and, means for raising and lowering said cradle structures toward and away from said cable in its upper and lower runs when disconnected from said cable.

2. A belt-conveyor system for transporting material over long distances, horizontal or inclined, comprising upper and lower tracks; an endless drive cable; a cradlebelt assembly comprising an endless belt and wheeled cradle structures mounted at spaced intervals on said belt for supporting said belt in its upper and lower runs in rolling engagement with said upper and lower tracks, respectively, said cradle structures comprising at least two sections disposed in line with one another transversely of the belt and affixed thereto and being articulated for hinging movement in opposite directions from a flattened condition in which they are adapted for passage over head and tail pulleys of the system to upright and inverted troughed positions in the upper and lower runs, respectively, of the belt, said cradle structures comprising tong-forming means providing weight-actuated tongs for connecting said cradle structures to said cable, each said tong having its hinge axis closely adjacent said belt and between said belt and said cable when connected thereto and having its jaws constructed and arranged to grip said cable in its upper and lower runs, respectively, between different pairs of gripping surfaces; and, camming means for initially elevating said cradle structures substantially centrally thereof at selected stations in the circuit of said belt to open said tongs, whereby said cradle structures may be thereafter disengaged from said cable at said stations.

3. A belt-conveyor system in accordance with claim 2 in which said cradle structures additionally comprise cam follower members to be actuated by said camming means for centrally elevating said cradle structures and in which said camming means comprise rail members disposed at said stations and having inclined camming surface portions for engaging said cam follower members at said stations.

4. A belt-conveyor system in accordance with claim 2 in which said stations are located both in the upper run and in the lower run of the belt.

5. A belt-conveyor system in accordance with claim 3 in which said rail members disposed at stations in the upper run of the belt are independent of said upper track and in which said rail members disposed at stations in the lower run of said belt are a part of said lower track.

6. In a belt-conveyor system having head and tail pulleys, an endless belt carried by said pulleys providing an upper carrying run and a lower return run therebetween, an endless drive cable for said belt, and upper and lower tracks disposed lengthwise on said belt: the combination with said belt of a plurality of belt-supporting cradles for said belt, each said cradle comprising at least two rigid belt-supporting sections disposed end-to-end in line with one another transversely of the belt, each said section being fixedly secured to said belt; wheels carried by each said cradle at its outer extremities, said wheels being adapted to run on said lengthwise disposed tracks; lugs carried by said sections at their inner extremities and hingedly interconnecting the sections at a locus closely adjacent to the belt but between said belt and said drive cable for hinging movement of said sections in opposite directions from a flattened condition in which said sections are adapted for passage over the head and tail pulleys of the system to upright and inverted troughed positions in the upper and lower runs, respectively, of the belt, said lugs projecting downward beneath the carrying run of said belt to form at the juncture of said sections a pair of two-directional grippers for pinchingly engaging said driving cable both in the upper carrying run of the belt and in its lower return run, said grippers pinching the cable in the upper carrying run of the belt in proportion to the load moment developed in the span between the tracks, and, in the inverted position of the cradle on the return run the cable is likewise gripped, the load moment being reversed, whereby the belt is driven at each cradle by the cable.

References Cited in the file of this patent UNITED STATES PATENTS 2,609,086 McBride et al Sept. 2, 1952 FOREIGN PATENTS 495,420 Germany Apr. 7, 1930 502,639 Germany Oct. 31, 1930

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