US3040918A

US3040918A - Material handling machine

Info

Publication number: US3040918A
Application number: US739751A
Authority: US
Inventors: Daniel M Schwartz; Donald E Hendrickson; James D Brown
Original assignee: Eimco Corp
Current assignee: Eimco Corp
Priority date: 1958-06-04
Filing date: 1958-06-04
Publication date: 1962-06-26
Anticipated expiration: 1979-06-26
Also published as: BE579128A

Description

2 1962 D. M. SCHWARTZ ETAL 3,

' MATERIAL HANDLING MACHINE Filed. June 4, 1958 11 Sheets-Sheet 1 INVENTORS DANIEL M. SCHWARTZ DONALD E. HENDRICKSON JAMES 0. BROWN ATTORNEYS June 26, 1962 Filed June 4, 1958 D. M. SCHWARTZ ETAL MATERIAL HANDLING MACHINE 11 Sheets-Sheet 2 INVENTORS DANIEL MSCHWARTZ DONALD E. HENDRIGKSON BY JAMES 0. BROWN ATTORNEYS June 26,1962 D. M. SCHWARTZ ETAL 3,040,918

MATERIAL HANDLING MACHINE Filed June 4, 1958 11 Sheets-Sheet 3 INVENTORS DANIEL M. SCHWARTZ DONALD eusuomcxsou JAMES usnowu %M7.,A@// M4 4M ATTORNEYS June 26, 1962 D. M. SCHWARTZ ETAL 3,040,918

' MATERIAL HANDLING MACHINE Filed June 4, 1958 ll Sheets-Sheet 4 IEL M. SCHWARTZ BY DONALD E.HENDR|CKSON JAMES D. BROWN M ld K/MK ATTORNEYS June 26, 1962 D. M. SCHWARTZ ETAL 3,040,918

MATERIAL HANDLING MACHINE 11 Sheets-Sheet 5 Filed June 4, 1958 DANIEL M. SCHWARTZ DONALD E. HENDRIGKSON JAMES D. BROWN fi wa/f W ATTORNEYS June 1962 D. M. SCHWARTZ ETAL 3,040,913

MATERIAL HANDLING MACHINE Filed June 4, 1958 ll Sheets-Sheet 6 INVENTORS DANIEL M. SCHWARTZ BY DONALD E. HENDRICKSON JAMES D. BROWN ATTORNEYS June 26, 1962 D. M. SCHWARTZ ETAL 3,040,918

MATERIAL HANDLING MACHINE ll Sheets-Sheet 7 Filed June 4, 1958 INVENTORJ DANIEL M. SCHWARTZ DONALD E. HENDRICKSON JAMES D. BROWN //M 7:- JM

KT 'r RNEYS J1me 1962 D. M. SCHWARTZ ETAL 3,040,913

MATERIAL HANDLING MACHINE Filed June 4,1958 11 Sheets-Sheet 8 INVENTORS DANIEL MSGHWARTZ BY DONALD E.HENDRICKSON JAMES 0. BROWN M %M ATTORNEYS June 1962 D. M. SCHWARTZ ETAL 3,040,918

MATERIAL HANDLING MACHINE Filed June 4, 1958 11 Sheets-Sheet 9 INVENTORJ' DANIEL M. SCHWARTZ DONALD E. HENDRICKSON JAMES D. BROWN A MA,

ATTORNEYS June 26, 1962 D. SCHWARTZ ETAL. 3,040,918

MATERIAL HANDLING MACHINE Filed June 4, 1958 Y 11 Sheets-Sheet 1o INVENTORS DANIEL M.SCHWARTZ DONALD E. HENDRIOKSON BY JAMES 0. BROWN A/MA ,JW

ATTORNEYS June 26, 1962 D. M. SCHWARTZ ETAL 3,040,913

MATERIAL HANDLING MACHINE Filed June 4, 1958. ll Sheets-Sheet 11 INVENTORS DANlEL M. SCHWARTZ B DONALD EHENDRICKSON JAMES D. BROWN ma/ J ATTORNEYS United States Patent 3,040,918 MATERIAL HANDLING MACHINE Daniel M. Schwartz, Donald E. Hendrickson, and James D. Brown, Salt Lake City, Utah, assignors to the Eimco Corporation, Salt Lake City, Utah, a corporation of Delaware Filed June 4, 1958, Ser. No. 739,751 1 Claim. (Cl. 214-131) This invention relates to material handling machines of the type having a material gathering device pivot-ally mounted from a low material gathering position to an elevated material dumping position.

It is a principal object of the invention to provide a rugged, self-propelled machine for loading bulk material which is particularly adapted for use in mines and tunnels where due to limited headroom and confined spaces, compactness, mobility and ease of control are essential features.

Another object of the invention is to provide such a machine for lifting, transporting and loading bulk materials in substantial quantities.

Another object of the invention is to provide an improved material handling machine having a pivotally mounted loader arm, and a conveyor adapted to receive the-mucked material and transport it upwardly and rearwardly.

A further object is to provide such a device wherein the support means for the material gathering structure provides the front support for the material conveying device.

Another object is to provide a device wherein support means for the material gathering structure has integral bumper plate means and the material gathering structure is provided with shock absorbing means which contact the bumper plate means during each cycle of said material gathering structure.

Another object is to provide such a machine having an improved fail-safe power cut-off structure with continually biasing means urging the cut-off structure to the off position so arranged that should means holding the cut-off structure to on fail, the cut-off structure would immediately move to the power off position.

A further object is to provide such a machine wherein the drive mechanism for the material gathering and discharging mechanism and/ or the drive mechanism for the material conveying structure are located on the opposite side of the machine from the manual controls for the operator.

A further object is to provide such a-machine having improved power cut-off means and an improved electrical control system for electrically actuated machines.

These and other objects and advantages are provided in a material handling machine including a main frame, a shaft extending transversely across one end of said main frame, a housing secured to the main frame supporting the transverse shaft intermediate the extended ends thereof, an arm secured to each end of said shaft and supporting a material handling device between the extended ends thereof, a member having a curvilinear outer surface secured to one of the arms, flexible draft means trained about the curvilinear surface and connected to power actuated traction means carried by the main frame to pivot the arms and material handling device from a low material gathering position to an elevated material discharge position and to such a machine including conveyor means supported by the housing for the transversely extending shaft with the conveyor means adapted to receive material from the material handling device in its elevated discharge position.

The invention will be more particularly described in 3,040,918 Patented June 26, 1962 reference to the accompanying illustrative embodiments of the invention wherein:

FIG. 1 is a side elevational view of a machine incorporating the principles of the invention with the control panel removed;

FIG. 2 is a side elevational view of the other side of the material handling machine with the shovel bucket in the material discharge position;

FIG. 3 is an enlarged fragmentary front elevational view of the machine shown in FIGS. 1 and 2;

FIG. 4 is a fragmentary top plan view of the front end of the machine shown in FIGS. 1 and 2;

FIG. 5 is an enlarged fragmentary sectional view of the front end portion of the material handling machine of the invention;

FIG. 6 is a section substantially on line 66 of FIG. 5;

FIG. 7 is a section substantially on line 77 of FIG. 5;

FIG. 8 is an enlarged fragmentary detailed view of one of the idler roller tensioning mechanisms shown in FIG. 7;

FIG. 9 is a top plan view of the machine shown in FIGS. 1 and 2;

FIG. 10 is an enlarged fragmentary view in partial section of the rearward portion of the conveyor; and

FIG. 11 is a diagrammatic view of an electric circuit for interconnecting an electric actuated bucket motor with manual and automatic control means.

Referring to the illustrative embodiments of the invention, there is shown a material handling and excavating apparatus embodying the principles of the invention which generally comprises a main frame 10 mounted on paired laterally extending crawler frames 12 and 14 carrying selflaying

endless traction chains

16 and 18. The main frame may be pivotally mounted to the crawler frames as disclosed in US. Patent No. 2,833,361, D. M. Schwartz, whereby the crawler frames may pivot relative to the body 10 with each of the

crawler tracks

16 and 18 being 4 individually connected to a pair of selectively operable motors, one of which is shown in FIG. 1 and generally designated 2%. Each of the motors is connected through suitable gear trains to a drive sprocket 22 positioned at the rearward end of the crawler frames, all as more fully described in Patent No. 2,833,361, hereinabove referred to.

The vehicle carries at its forward end a material handling structure 24 of the type adapted to load or gather material at a low forward position and to discharge the material at an elevated position.

The main frame of the vehicle also supports a material conveying apparatus generally designated 26 adapted to receive material from the material handling device at its forward end 28 and to convey the material upwardly and rearwardly to a discharge end 30 positioned rearwardly of the rear end of the main frame of the vehicle.

The material handling structure 24 will be more fully described with reference to FIGS. 1 through 6. Referring to these drawings, the material handling structure 24 includes a shaft 32 which extends transversely across the front end of the vehicle. The shaft 32 is rotatably mounted in a housing 34 which includes a transverse barrel portion 36 carrying anti-friction bearing means 38 and 49 for the shaft 32 at its extended ends. The shaft 32 has two end portions 42 and 44 which project beyond the

respective bearings

38 and 40.

The shaft assembly also includes conventional rotary seal assemblies 46 and 48 between the barrel portion 36. of the housing and the shaft 32. End portion 44' of shaft 32 has secured thereto an arm 58 while end portion 42 of shaft 32 has secured thereto an arm 60. The opposite end 62 of arm 58 is rigidly secured to a material handling device which is shown in the illustrated form of the invenas a shovel bucket 64. The other arm 60 has its ex- -19 tended end 66 secured to the other side panel of the shovel bucket.

The foregoing construction provides a very satisfactory material digging and discharging unit as the paired

arms

58 and 60 are rigidly connected to the extended ends 42 and 44 of the large transverse shaft 32 while the remote ends 62 and 66 of each arm are interconnected through the rigid bucket structure 64.

Each of the

pivot arms

58 and 60 is adapted to receive a relatively long stroke shock absorbing piston and cylinder unit 61 which includes a cylinder 65, and a piston 66' slidably mounted therein and spring urged to an extended position by internal springs 6 shown in FIG. of the drawings. The face of the pistons 66' are provided with slightly curved surfaces 70 which contact surface 72 on each of a pair of bumper plates 74 formed as integral portions of the housing 34 for the pivot shaft 32.

With the bucket in the position shown in FIG. 1 of the drawings, material is scooped either by pivoting the bucket about the axis of the shaft 32 and/or by crowding the bucket by forward movement of the vehicle into material to be mucked. When the bucket is loaded, the

arms

58 and 60 and the bucket 64 are pivoted upwardly to deposit the mucked material in the bucket 64 into the bin at the forward end 28 of the conveyor mechanism 26. In approaching the discharge position, the curved end surface 70 of each of the pistons 66 contacts its respective bumper plate 74 compressing said pistons against the tension of springs 68 which normally urge the pistons in an outwardly direction. In FIG. 2 of the drawings, the bucket structure is illustrated in its most elevated position.

With the arms and the bucket in the discharge position as shown in FIG. 2, the pistons 66' are substantially fully telescoped within the cylinders 65 and the high discharge momentum of the bucket and pivot arms is effectively absorbed. It will also be appreciated that by securing the bumper plates 74 directly to the large housing 34, the impact shock transmitted to the vehicle during operation of the pivoted bucket material handling device is materially reduced.

The housing 34 includes, in addition to the barrel portion 36 and the pair of bumper plates 74, a pair of

side plates

76 and 78 which extend downwardly and rearwardly from the barrel portion 36 of the housing and which are interconnected at their rearward ends by a connecting plate 80 extending transversely between the pair of

plates

76 and 78. The rear plate 80 projects above and below a web generally designated 82 which web adds rigidity to the housing assembly. The web 82 is more clearly shown in FIG. 4 of the drawings.

The upwardly extending portion of the rear plate 80, designated 84, is provided with a plurality of bores adapted to receive bolts 86 which connect the housing 34, which may be a fabricated structure or a casting, to a plate 88 carried by the front end of the main frame of the vehicle. The depending portion of the end plate 80 is also provided with bores for bolts 90 securing the lower portion of the plate 80 to the forward end of the main frame of the vehicle.

The forward edge of each of the

side plates

76 and 78 of the housing 34 is longitudinally channeled to receive thrust stops 92 and 94 which, as shown in FIG. 1, of the drawings, engage a portion of the rear panel of the shovel bucket 64 when the bucket is in its low material gather- -ing position and transmit a substantial portion of the material gathering thrust directly to the housing 34 and thence into the forward end of the main frame 10 of the vehicle. The

thrust elements

92 and 94 may be telescopically mounted in the longitudinal bores in the housing so that the lowermost position of the bucket 64 may be adjusted by removing pins 96 and repositioning the pins in other bores provided in the

thrust members

92 and 94. An upper series of longitudinal bores 98 is provided in the forward edges of the

side plates

76 and 78 so that a more elevated pair of thrust stops may be employed with the device where it is necessary to contact the bucket at a more elevated position than is possible when employing the lowermost thrust stops 92 and 94.

The barrel portion 36 of the housing 34 includes as more clearly shown in FIGS. 3, 5 and 6 an arcuate opening to which is secured a panel structure 104. The upper plate 106 of the panel structure 104 supports a limit, fail-safe cut-01f switch generally designated 108. The switch 108 includes a base portion 110, supporting a standard 111, an arm 112 pivotally mounted thereto, contact means 114 opened and closed by appropriate movement of the arm 112 and a roller 116 mounted on the opposite end of the arm 112 remote from the contact means 114. The arm 112 is spring urged to a switch-open position by a spring 115 whereby the roller 116 is maintained in engagement with the peripheral surface of a cam element 118 secured to the shaft 32. The switch 108 is also so constructed that the roller end of arm 112 is the light end so that the arm is urged by gravity into the switch-open position in the event spring 115 should fail.

The surface of cam 118 includes a cut-back portion 120 which cut-back portion is in contact with the roller 116 of switch 108 substantially at the time the curved ends 70 of the bumper pistons contact the respective faces of their bumper plates 74. The cam member is adjustable around the periphery of the shaft 32 by means of sets of bores in both the cam and shaft so that the point of power cut-off may be varied. As the roller 116 comes into engagement with the cut-back portion 120, spring 115 which normally urges the roller end of arm 112 in an upwardly direction urges the arm to move to the switchopen position. Opening of the switch 108 cuts off the power to the bucket pivoting motor as to be more fully described hereinafter. Further these structures provide a fail-safe system in that should cam 118 be displaced or destroyed, the switch arm 112 is immediately moved to the off position.

The bucket 64 is actuated from the low material gathering position to the elevated dumping position by means of a member 124 carried by the end of pivot arm 60 remote from the bucket 64. Member 124 is provided with a cam shaped outer surface 126 in contact with a flexible draft member shown in the illustrated form of the invention as a flat cable chain 128. One end of the cable chain 128 is pin-connected to the arm 60 by pin 129 and when the bucket is in the low material gathering position as shown, for example, in FIG. 3, the cable chain 128 is trained about the curvilinear surface 126 of the member 124. The curved surface 126 of member 124 is shaped to provide a large effective radius when the bucket is in the low material gathering position and a smaller elfective radius when the bucket is in the material discharge position whereby the pivot arms are provided with variable torque actuating means to provide a high-torque, lowspeed digging portion and a relatively low-torque, highspeed discharge portion, as more fully described in the Daniel M. Schwartz et al. Patent No. 2,746,625 issued May 22, 1956.

The other end of the cable chain 128 is connected to a reel 130 secured to rotate with a shaft 132 extending from, for example, a gear type speed reduction unit 134 which reduction unit is powered by a motor 136. The motor 136 may be fluid pressure actuated or an electric motor or other suitable motors may be employed for rotating the pulley 130. As the pulley 130 is rotated in the direction of the directional arrow in FIG. 2, the cable chain 128 Wraps about itself on the pulley hub raising the bucket and the

arms

58 and 60 from the material gathering to the material discharge position. The form of the reel 130, which permits the cable chain to wrap about the hub of the pulley as the bucket is raised from the low material gathering position to the elevated dumping position augments the torque advantage provided by the curvilinear outer surface 126 of the cam arm 124.

It will be noted that the controls 143 for the pivot arm loader; 139 for the conveyor; and 141 for the groundengaging crawler units of the vehicle are positioned on that side of the machine remote from the cam arm 124, its flexible draft means 128 and the reel whereby the operator standing or seated on platform is in a protected position relative to the actuating mechanisms of the improved machine of the invention. it will further be seen that through the use of a single cam arm 124 and maintaining the entire drive mechanism for the pivot arm on the side of the vehicle remote from the operator permits the operator to obtain an unobstructed view of the material being mucked.

The Conveyor Mechanism:

The upper surface of the rearward portion of

side plates

76 and 78 are provided with

integral bosses

100 and 102 for interconnecting and supporting the forward end of the conveyor 26 to the material handling machine as to be more fully described hereinafter.

The conveyor 26 includes spaced

side walls

131 and 131, the lower ends of which flare outwardly to provide a material receiving bin having

side walls

133 and 133 and a front end wall 138. The side walls 133 and 133' and the end wall 138 are shaped to provide a substantially enclosed receiver for the bucket 64 when the

bucket arms

58 and 60 are in the bucket discharge position as shown in FIG. 2 of the drawings.

Between the

side walls

131 and 131 is a bed plate 140 suitably supported on transverse structural members 141. The bed 140 receives, on the upper surface thereof, an endless conveyor chain 142 provided with laterally extending chain flights 144 which gather the material discharged into the hopper and conveys the material upwardly and rearwardly to the discharge end 30. The return flight of the endless conveyor chain 142 is below the deck plate 140 as shown, for example, in FIG. 5 of the drawings.

Positioned at the forward end 28 of the conveyor is an idler shaft 148 which is reciprocally mounted in front conveyor support members generally designated 150 and 152. Each of the side plates of

support members

150 and 152 of the conveyor is provided with a

wing portion

154 and 156, respectively. These wing portions are bored and connected by pins 158 between the

bosses

100 and 102 of the housing structure 34. The rearward portion of the conveyor 26 is secured to the rearward deck portion of the main frame 10 of the vehicle by vertically extending structural members 160. The lower ends of the members 160 are pin connected as at 164 to the rear end 166 of the main frame 10 of the vehicle while the upper ends are pin connected as at 168 to a bracket 170 secured to each

side

131 and 131 of the conveyor.

By pin connecting the conveyor 26 at its rearward end to the main frame of the vehicle through the vertically extending structural members 160 and at its forward end to the housing 34 stresses and strains placed upon the vehicle when operating on unlevel ground and the like are kept to a minimum as relative movement is permitted at the points of the plural pin connections.

The front idler shaft 148 has a centrally positioned sprocket formed thereon to provide a guide for directing the passage of the flexible conveyor chain 142 about the forward end of the conveyor structure and to insure rotation of idler shaft 148 with movement of conveyor chain 142. The extended ends 182 of the shaft 148 are rotatably mounted in bearings 184 maintained in bearing blocks 1 86 provided with quadrangular ends 188 which are slidably received in an elongated trackway 190 formed in each of the front mounting members 150' and 152 for the conveyor. The trackways 190 formed in each of the

support members

150 and 152 are provided with enlarged portions 192 at their rearward ends whereby the bearing blocks 18 6 may be inserted in their respective trackways.

As more clearly shown in FIG. 7, the rearwardly extending portions of each of the bearing retaining blocks 186 is provided with plural bosses designated 194, 196 and 198. Bosses 194 are received in the bifurcated ends 200 of guide shafts 202 which control the longitudinal reciprocating movement of the bearing blocks 186. The bifurcated ends 200 are bored and connected by pins 204 to bearing block bosses 194. The bifurcated end 200 of each guide shaft 202 is also provided with a lower seat for spring 206 while the other end of each spring abuts the end 208 of its respective conveyor support element. Each of the ends 208 is :bored to receive a sleeve 210 to pnotect the threaded portion 212 of the guide rods 202 during reciprocation of the guide rods in the bores in the end plates 208. The rearwardmost end of each sleeve 210 engages a capstan nut 214, threadedly mounted on the extended ends of the threaded portions of the guide rods 202 externally of the end plates 208.

Each of the capstan nuts 214 may also be provided with a pin 216 whereby the nuts may be pin connected to the extended end of its guide rod 202 in a normal operating position In operation of the idler shaft tensioning structure, with the mechanism positioned as shown in FIGS. 7 and 8, the springs 206 maintain a predetermined forward pressure on their respective bearing retaining blocks 1'86 urging the roller forward against the endless conveyor chain 142 while permitting the chain to resiliently give in the event rocks and other foreign material lodge between the chain links which would normally interfere with the passage of the chain about the idler and drive shafts, thus relieving the conveyor chain of unnecessary strains. The tensioning mechanism also provides the means whereby the conveyor chain may be manually placed in a slack condition for easy removal, replacement and repair. To remove the tension on the chain, pins 216, where they are employed, are removed and each of the capstan nuts 214 is screwed toward the bifurcated ends of the guide rods. When the capstan nuts 214 are screwed downwardly until their inner faces are in engagement with the outer surfaces of plates 208 of their respective support members, further rotation of the capstans compress the springs 206 and slide the bearing blocks 186 toward the rearward ends of their tracks 190 formed in the conveyor support elements.

If it is necessary to remove or replace the take-up spring 206, if it has been broken or damaged, this may be readily accomplished without dismantling the whole conveyor.

To remove the spring take-up assembly the pin 204 is first removed. Nut 214 is then turned to compress the spring 206 and move the bifurcated end 200 to the rear until it is clear of boss 194. The whole assembly may then be cocked to the outside in clearance provided in the hole in end plate 208. Nut 214 is then turned in the opposite direction and removed from screw 212, allowing complete disassembly.

To install a new spring the procedure is reversed by tightening nut 214 and compressing the spring 206, at the same time advancing end 200 to the rear until it can be inserted over the boss 194. Turning capstan nut 214 in the opposite direction will allow the spring to expand and the bifurcated end 200 to advance over boss 194 until the pin 204 can be replaced.

As hereinbefore described, each of the bearing blocks 186 also includes

bosses

196 and 198. These bosses are bored to receive the pins 204 which couple the bifurcated ends 200 of the guide rods 202 to the bosses 194. Between each of the pair of bosses 196 and 193, and maintained therein by pins'204, are plates 220 which are interconnected by, a depending rib 222 secured such as by welding to the under surface of a plate 224 corresponding to a front extension of the bed 140 of the conveyor. The most rearward edge of the bed extension 224, designated 226, is tapered to provide a narrow edge for sliding contact with the bed 140. It will also be noted 7 from FIG. 7 that the bed extension 224 overlaps the forward edge of the main bed 140 to insure that as the hearing blocks 186 carrying the idler shaft 148 are caused to reciprocate, by foreign material which may engage the links in the conveyor chain 142 no open space is formed in the conveyor deck.

The conveyor chain 142 is driven from the discharge end 30 of the conveyor by sprocket 227 secured to live shaft 230 rotatably mounted in bearing blocks 232 secured to each side wall of the conveyor. The shaft 230 also has secured thereto a sprocket 233 about which a drive chain 234 is trained. The drive chain 234 extends about a pair of

idler sprockets

236 and 238 and then about a driven sprocket 240 keyed'to the output shaft 242 of a reduction gear unit 244 driven by a motor 246 supported between the vertical support members 160 at the rearward end of the conveyor.

As more clearly shown in FIG. 2, the lower flight of the drive chain 234 passes over chain guides 248 while the upper flight of the drive chain 234 is provided with guide elements 250.

In order to reduce the headroom requirements of the material handling machine, in the illustrative embodiment of the present invention, the rearward portion of the conveyor 26 is disposed in a plane generally parallel with the bed of the main frame 10 of the vehicle. Referring particularly to FIG. 10 of the drawings, at the line of juncture 220 between the generally horizontal portion and the inclined portion of the conveyor, the bed 140 of the conveyor 26 is apertured and an idler sprocket generally designated 222 is rotatably mounted in suitable bearings 224 with a segment of the barrel portion 226 of the idler sprocket 222 projecting through the aperture to engage the conveyor chain 142. The toothed portion 228 of the sprocket 222 provides lateral stability to the conveyor chain and the location of the idler sprocket 222 supports the upper conveyor flight of the conveyor chain to minimize wear on the conveyor pan 140 in the area of the conveyor bend from the inclined portion to the generally horizontal portion.

The lower flight 230 of the conveyor chain 142 is also supported in the area of the juncture between the inclined and the horizontal portions of the conveyor structure. The lower flight 230 is supported by a pair of

idler sprockets

232 and 234. Each of these idler sprockets rotate with motion of conveyor chain 142 and each is suitably supported in bearings carried bybrackets generally designated 238 which brackets are secured to the conveyor structure. As more clearly shown in FIG. 10 of the drawings, the lower idler sprocket 232 and the upper idler sprocket 234 for the lower chain flight 230 are positioned generally forwardly and rearwardly of the upper chain flight support and idler sprocket 222, whereby the lower flight 230 of the conveyor chain is elevated and the weight of the lower flight of the conveyor chain is effectively carried minimizing unnecessary loading and wear of the conveyor chain during its return flight.

From the foregoing description, it will be seen that the conveyor fully accomplishes the aims and objects hereinbefore set forth. It will also be apparent that other advantages are inherent in the improved conveyor structure. For example, with the conveyor chain 142 driven by the rear sprocket 227 the tension side of the chain is the upper material conveying flight thereof, whereby the tension required for proper operation of the structure is reduced and in addition the conveyor chain 142 is to a large measure prevented from bunching up .as it drags material being conveyed across the pan 140 V ferring to FIG. 11, the electric bucket motor is generally designated 136E. The electric motor is manually controlled through bucket control level 143 having a bucketup position A, a neutral position B, and a bucket-brake position C. The manual control lever 143 is mechanically linked to a switch 250 which is open when the control handle is in position A and closed when the control handle is in the neutral position B; a switch 252 which is closed when the control handle is in position A, the bucket-up position, and open when the control handle is in positions B or C; and a switch 254 which controls an electric brake for the electric motor 136E. Switch 254 is open when the control handle is in positions A or B and closed when the control handle is in position C, the bucket-brake position. The manual control handle 143 and switches 25%, 252 and 254 are of the type disclosed in U.S. patent application Serial No. 695,956, I. D. Brown.

The control system also includes switch 256 and switch 258 which are both normally open switches and are actuated in unison by a solenoid 260. In FIG. 11, the cam actuated switch 108 is also diagrammatically illustrated.

The following are the electrical connections between the switches 258 252, 254, 256, 258, 262 and 108; the electric motor 136E; and the source S of three-phase electric current: Conductors L L and L, from the source of current are connected to lines T T and T through electric contactor switches 262 actuated by solenoid 264.

Solenoid 264 is energized by current from line L through

lines

268 and 268a, and current from line L through line 266, switch 252, line 270, switch 258 and line 272.

Solenoid 260 for

switches

256 and 258 is energized by current from line L through line 266, switch 250, line 274, line 274a and line 268]) which, in turn, is conneced to line 268. Solenoid 260 is also energized in parallel through line 266, switch 1%, switch 256 and lines 2741) and 274a.

The electric moto 136E is provided with a conventional direct current actuated brake energized by current from

lines

266 and 268 connected to the primary windings of a step-down transformer 280. The secondary winding of the transformer 280 is connected to a conventional dry plate rectifier 282. The direct current output from the dry plate rectifier 282 is connected to the brake- :actuating winding 284 through conductor 286, and conductor Z88.

Operation of the bucket control system shown in FIG. 11 is as follows:

When the bucket control handle 143 is in the neutral position, switch 252 is open, switch 250 is closed, solenoid 260 is energized closing switches 258 and 2545. Switch 188 is closed when the bucket is in the low discharge position and the cam wheel of he switch 1% is riding on the high portion of cam 118 away from the low portion 12% of the cam. Contactor coil 264 and the bucket brake 284 are not energized when the handle 143 is in neutral and the bucket after returning by gravity to its lowermost position would remain on the ground.

With the bucket control handle 143 in position A, the bucket-up position, switch 252 is closed, switch 250 is open, solenoid 268 is energized closing switches 2.56 and 258, switch 188 is closed, contaotor solenoid 264 is energized closing switches 262 energizing the bucket motor and the bucket travels upward to the material discharge position. When the bucket reaches the discharge position, the set-back portion 120 of the cam 118 carried by bucket shaft 32 permits the spring-urged cut-cit or limit switch 108 to open which, in turn, deaenergizes solenoid 260 opening switches 256 and 258, thus deenergizing the motor contactor solenoid 264 which, in turn, opens switches 262, de-energizing the electric motor 136E. The bucket may then'return to the ground by gravity.

With the control handle in the brake position C, switch 254 is closed, and the direct current brake for the elec tric motor 136E is energized and the contaotor coil 264 for switches 262 is not energized.

When the manual control handle 143 is in the bucketup position and maintained in that position, the bucket is actuated through the following cycle:

The bucket is elevated from the low material gathering position to the material discharge position where the power to the electric motor is cut off by the opening of limit switch 108 and the bucket returns to the ground or loading position by gravity. In order to complete another cycle of loading and discharging and returning to the loading position, manual control handle 143 must be moved from the bucket-up position to the neutral position B and again moved into the bucket-up position. On returning the control handle 143 to the neutral position B the closing of switch 250 energizes solenoid 260

closing switches

258 and 256 which, in turn, maintain a holding circuit from line L through line 266, switches 108 and 256, lines 27417 and 274a, solenoid 260, lines 2681) and 268 to line L In addition to providing an improved electrical control system for the pivoted bucket loader, the inclusion of the limit switch 108 in the systern as described insures that should mechanical failure occur in any part of the limit switch mechanism due, for example, to breakage or excessive wear of the cam or the cam roller, the circuit holding the solenoid 260 will be opened by the opening of the limit switch 108 deactivating the entire bucket control circuit. The cutoff or limit switch 108 is opened by the force of the spring urging the pivot arm in a direction to open the contacts of the switch or by gravity should the spring normally urging the switch in the open position become inoperative. Further, a break in any one of the plural conductors or lines associated with

switches

250 and 252 will also render the electric bucket motor 136E inoperative.

It will be appreciated that while the electric system has been described with reference to an electric motor 136E having an electric contactor to connect the motor to the power source, pressure fluid motors with electric or pressure fluid operated valves may be substituted for the motor 136E without departing from the scope of this invention.

It will also be appreciated that the new and improved fail-safe cut-oft switch 108 may be employed as the power cut-d means where the prime mover for the material handling structure is a pressure fluid motor, or an internal combustion engine or the like as the fail-safe switch may be connected to a valve in the pressure fluid system or to, nor example, a clutch where an internal combustion engine is employed as the motor means for the pivoted bucket loader.

Having described our invention, what is claimed is:

In a material handling machine of the type wherein a material handling device is secured to a shaft mounted for pivotal movement from a low digging position to an elevated material dumping position and an electric motor is drivably connected to means for rotating said shaft to actuate said material handling device from the low material digging position to the elevated material dumping position and means connecting the electric motor to a source of current; said means connecting said motor to said source including a manually operated switch group including at least two manually operated switch elements, at least two normally open solenoid actuated switch elements, conductor means connecting the source of current to said motor serially through one of said manually operated switch elements and one of said solenoid actuated switch elements, conductor means connecting the source of current to the actuating solenoid through the other of said manually operated switch elements, a power cute-if switch actuated by said material handling device, and conductor means connecting the source of current to the actuating solenoid serially through said power cut-off switch and the other of said solenoid actuated switch elements, and in parallel with the manually operated switch element connected to the actuating solenoid.

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