US2973877A - Unloader - Google Patents

Description

March 7, 1961 B. A. ROSE 2,973,877

UNLOADER Original Filed July 22, 1958 7 Sheets-Sheet 1 INVENTOR Bennie A. Rose March 7, 1961 B. A. ROSE 2,973,877

UNLOADER Original Filed July 22, 1958 7 Sheets-Sheet 2 Fig.2.

INVENTOR Bennie A. Rose B. A. ROSE March 7, 1961 UNLOADER 7 Sheets-Sheet 3 Original Filed July 22, 1958 INVENTOR Bennie A. Rose March 7, 1961 B. A. ROSE 2,973,877

Bennie A. Rose B. A. ROSE UNLOADER March 7, 1961 7 Sheets-Sheet 5 Original Filed July 22, 1958 INVENTOR Bennie A. Rose ZMAW B. A. ROSE March 7, 1961 UNLOADER 7 Sheets-Sheet 6 Original Filed July 22, 1958 H mm 8* w I m mm 5 1 mm 5 mo 0m 5 3. m9 m9 m9 HIS ATTORNEYS Mar h 7, 1 B. A. ROSE 2,973,877

UNLOADER Original Filed July 22, 1958 7 Sheets-Sheet 7 Fig.l0.

'2' I20 ll? H8 H9 INVENTOR' Bennie A."Rose UNLOADER Bennie A. Rose, Mount Lebanon, Pa., assign'or to Heyl & Patterson, Inc., Pittsburgh, Pa., a corporation of Pennsylvania Continuation of application Ser. No. 750,072, July 22, 1958. This application June 8, 1959, Ser. No. 818,763

11 Claims. (Cl. 214656) This invention relates to an unloader, particularly an unloader for removing bulk material from receptacles such as the holds of vessels, railway cars, trucks, etc.

vMy unloader has especial utility in unloading bulk cargo from the holds of vessels and for purposes of explanation and illustration will be described as so embodied. This application is a continuation of my copending application Serial No. 750,072, filed July 22, 1958, now abandoned.

This invention is an improvement over that of my Patent No. 2,796,180. That patent discloses an unloader comprising a base, a generally horizontally oriented boom connected with the base for movement of at least an end of the boom to difierent elevations, said end of the boom projecting outwardly from the base and being free of undersupport so as to be adapted to extend over a ship, a material receiving hopper carried by the boom,

' conveying means carried by the boom for conveying material from the hopper to a delivery point, a generally vertically oriented stern, connections between the stem and the boom through which the stemis carried by the boom, means for shifting the connections to move the stem between an outward and downward position and an inward and upward position generally above the hopper, material carrying means carried by the stem at the lower portion thereof and means for operating the material carrying means.

I provide control means for automatically controlling the lowering of the material carrying means whereby such means are lowered at relatively high speed until within a predetermined distance of the material being unloaded whereupon the speed of lowering of the. material carrying means is materially reduced so that the material carrying means are moving relatively slowly at the time of engaging the material- This makes for high unloading efliciency while at the same time decreasing the likelihood of damage to the unloader through the material carrying means striking the material being unloaded while moving at high speed. Degradation of the material being unloaded through impact of the material carrying means therewith is also minimized.

I also provide for automatically compensating for lowering of the level of the material being unloaded during successive cycles of operating of the unloader so that the control means for controlling the lowering of the material carrying means is effective upon each cycle of operation of the unloader to slow up the movement of the material carrying means when the material carrying means reaches a position removed a predetermined distance from the material to be carried orlunloaded regardless of the level of the latter.

My unloader comprises material carrying means, which may be a bucket, and lowering means, which may include a stem carrying the bucket at its lower end, for lowering the material carrying means toward the material to be carried preparatory to picking up some of the material. I provide control means for controlling the lowering means to determine the speed of lowering of the material carrying means, the control means having a 7 means becoming effective when the material carrying means move to a position a predetermined distance removed from the material to be carried to reduce the speed of lowering of the material carrying means so that the material carrying means will be moving relatively slowly when such means engage the material. The control means may have electric contact means and means rendering the electric contact means efiective when the material carrying means move to a position a predetermined distance removed from the material to be carried to reduce the speed of lowering of the material" carrying means. The control means may have cam means operable consonantly with lowering of the material carrying means'and means operated by the cam means when the materialcarrying means move to a position a predetermined distance removed from the material to be carried to reduce the speed of lowering of the ma terial carrying means.

The control means may have actuating means be coming predeterminedly effective when the material carrying means move to a position a predetermined distance L removed from the materialto be carried to reduce the speed of lowering of the material carrying means so that the material carryingmeans will be moving relatively slowly when such means engage the material and means affecting the actuating means as the level of the material to be carried changes during successive cycles of operation of the unloader insuring that theactuating' means will become effective when the material carrying means moves to a positionremoved said predetermined distance from the material to be carried regardless of the level of the latter. The control means may have in addition to the actuating means means operating the actuating means when the material carrying means move to a position 'a predetermined distance removed from the material'to be carried to reduce the speed of lowering of the material carrying means so that the material carrying means will be moving relatively slowly when such means engage the material, theoperating means moving con-' stantly with lowering of the material carrying means,

and -means progressively changing the position ,of,the

actuating means as, the level of the material to be carried changes during successive cycles of operation of; v

the unloader insuring that the operating means will be efiective to operate the actuating means when the material carrying means moves to a position said lpredeterw mined distance removed from the material to be carried 1 regardless of the level of the latter. The,a'ctuating means may be operated by cam means moving consonantly with: lowering of thevmaterial carrying means and. having a: portion engaging and bodily moving the actuating means i as the level of the material to be carried changes during, successive cycles of operation of the unloaderinsuring' that the cam means will be effective-to operate the. actu-f ating means when the material carrying means moves to f a position removed said predetermined distance from the material to be carried. I also preferably provide means for. returning the actuating means at the conclusion of an unloading operation and prior to initiation of a succeed= ing unloading operation to a position corresponding to;

maximum height of the level of the material.

of the material to be carried changes during successive cycles of operation of the unloader insuring that the X operating means will be effective to operate the actuating}, means when the materialcarrying means moves to a posi- 2,973,871 Patented Mar. 7,,'1 96 1 ea er? tion removed said predetermined distance from the material to be carried regard-less of the level of the latter. I preferably provide holding means maintaining the actuating means in each position to which it is moved on the mounting means together with means for rendering the holding means inoperative and returning the actuating means at the conclusion of an unloading operation and prior to initiation of a succeeding unloading operation to a position corresponding to maximum height of the level of the material. Friction drag means may be employed to maintain the actuating means in each position to which it is moved on the mounting means and means may be provided for rendering the friction drag means inoperative; spring means may also be provided for returning the actuating means at the conclusion of an unloading operation and prior to initiation of a succeeding unloading operation to a position corresponding to maximum height of the level of the material.

Other details, objects and advantages of the invention will become apparent as the following description of a present preferred embodiment thereof proceeds.

In the accompanying drawings I have shown a present preferred embodiment of the invention in which Figure 1 is a fragmentary side elevational view of an unloader mounted on an unloading dock for removing bulk material from the holds of vessels, the unloader being shown in position with its bucket disposed at the bottom of a hold of a vessel to remove material therefrom;

Figure 2 is a fragmentary side elevational view similar to Figure 1 but showing the bucket in position to discharge material removed from the hold of the vessel to means for conveying the material to a delivery zone;

Figure 3 is an end elevational view of the unloader in the position shown in Figure 1 as viewed from the left in Figure 1, the vessel being omitted in Figure 3;

Figure 4 is a fragmentary vertical transverse crosssectional view to enlarged scale taken on the line IV- -IV of Figure 1;

Figure 5 is a fragmentary vertical transverse crosssectional view to enlarged scale taken on the line V V of Figure 1;

Figure 6 is a fragmentary vertical transverse crosssectional view to enlarged scale taken on the line VI VI of Figure 1;

Figure 7 is a schematic diagram showing the reeving of the unloader;

Figure 8 is a diagrammatic face view of the control means for controlling the lowering means;

Figure 9 is a diagrammatic fragmentary cross-sectional view through the control means for controlling the lower.- ing means; and

' Figure 10 is a wiring diagram of the control means for controlling the lowering means. l l l Referring now more particularly to the drawings, there is shown at 2 an unloading dock alongside water 12 in which floats a cargo vessel 3. The water may be the ocean or a river, lake, canal or other body of water. The water may be influenced by the tides or not, but my invention has especial utility in the unloading of vessels whose elevation relatively to the unloading dock changes substantially due to changes in the tide or rising of the vessel due to decreased displacement as it is being unloaded or for both reasons. The vessel 3 is shown in Figure 1 in solid lines at a relatively high elevation and in chain lines at a relatively low elevation in relation to the unloading dock 2. My unloader, aswill appear from the following description, is adapted for efiiciently unloading the vessel at all elevations in relation to the dock.

Mounted upon the dock 2 and extending generally parallel to the edge of the dock against which the vessel lies are parallel sets of rails 4 upon which a gantry 5 is mounted through wheels 6. Only one of the parallel sets of rails is shown because of the fragmentary nature of the drawings but it will be understood that there is another set to the right of the structure shown in Figures 1 and 2. The gantry is movable parallel to the length of the vwsel on the rails 4 so that all of the holds of the vessel from bow to stem may be unloaded. The gantry 5 carries rails 7 disposed substantially at right angles to the rails 4, i.e., crosswise of the vessel, providing for unloading of each hold throughout the entire width of its hatch or hatches. Mounted on the rails 7 through wheels 8 is a carriage 9. The carriages is movable to selected positions crosswise of the vessel so that by correlated movements of the gantry and carriage all portions of all holds in the vessel can be reached.

The carriage is provided with a delivery chute 10 adapted to receive material which has been unloaded from the vessel as will presently be described and to deliver that material generally downwardly. That material is re ceived by an endless belt conveyor 11 carried by the gantry and extending parallel to the rails 7 so that in all positions of the carriage 9 the chute 10 delivers unloaded material onto the conveyor 11. The conveyor 11 is driven so that the upper or active reach thereof moves toward the right viewing Figure l. It discharges the unloaded material received from the chute 10 through another chute (not shown) which delivers the material at a delivery zone either directly into receptacles such as railroad cars or trucks or onto another conveyor mounted on the dock and extending parallel to the rails 4.

The carriage 9 includes structural framework 13 and a tower 14. Since the tower 14- is to resist stresses acting on its upper portion toward the left as will presently appear the tower is guyed from the right to the structural framework of the carriage by links 15.

A boom 16 is mounted on the carriage, being pivoted to the carriage at 17 for turning movement relatively to the carriage about a horizontal axis parallel to the rails 4. The boom is elongated in the direction crosswise of the vessel and is adapted to be swung in a vertical plane about the axis 17 to raise and lower its left-hand end which carries the primary unloading mechanism as will presently be described. The position of the boom is determined by reeving 18 extending between the top of the tower 14 and links 19 connected with the boom at 20. The recving '18 includes sheaves 21 at the upper ends of the links 19, sheaves 22 at the top of the tower i4 and lines 23 extending about the sheaves 21 and 22 and to a drum 24 (Figure 7) mounted in the carriage. When the left-hand end of the boom 16 viewing Figure 1 is to be lowered the drum 24 is turned in the clockwise direction viewing Figure 7 to pay otf the lines 23 and the left-hand end of the boom moves downwardly due to gravity. When the left-hand end of the boom is to be raised the drum is turned in the counterclockwise direction to wind up the lines 23 and hence shorten the distance between the sheaves 2i and thc sheaves 22 and elevate the end of the boom.

Pivoted to the boom at 25 are opposed identical parallel links 26. The links 26 are pivoted at 31 to a gui'e arm 32 which is carried by the pivot for swinging movement about the axis thereof. Pivoted to the boom at 27 are opposed identical parallel adjustable links or columns 28. The adjustable links or columns 28 are united at their upper portions by a structure 2.3a which has parallel internally threaded bores 29 (Figure 5). Also pivoted to the links 26 and the guide arm 32 at 31 are two identical generally downwardly extending screw jacks 34) which screw into the internally threaded bores 29. By turning the screws 30 in the bores 29 the adjustable links or columns 28 may be adjusted in length. A reversing electric motor 30a is mounted on the structure 234: and through a speed reducer 30b and connections 39c the motor is adapted to turn the screws 3?) in either direction to adjust the length of the links 28.

The length of the adjustable links 23 determines the location of the pivot 31 as the links 26 are of fixed length. As the adjustable links 23 are lengthened the pivot 31 moves upwardly relatively to the boom and also somewhat to the right viewing Figure 1. For each position of the boom 16 there is an optimum position of the pivot 31. As the left-hand end of the boom 16, viewing Figure 1, is lowered the pivot 31 should be raised. The optimum position of the pivot 31 for each position of the boom 16 is that position which results in the stem presently to be described being oriented substantially vertically when the stem is positioned to remove material from a hold of a vessel. Thus the lower the position of the left-hand end of the boom the longer should be the adjustable columns 28 whereby to maintain the stem substantially vertical when it is positioned to remove material from a hold of a vessel.

As will presently appear, only the portion of the guide arm 32 to the left of the pivot 31 viewing Figure 1 functions in operation of the unloader, but since a heavy load is carried by the left-hand end of the guide arm that arm is extended to the right from the pivot 31 and provided with sheaves 33. Cooperating sheaves 34 are carried by the boom and lines 35 extend about the sheaves 33 and 34 and thence about sheaves 36, 37 and 38 to counterweights 39. The counterweights 39 exert downward force on the right-hand end of the guide arm 32 to counteract at least a substantial part of the downward force exerted on the left-hand end of the guide arm.

The boom carries two parallel endless conveyors 40 for conveying material to the chute 10. The conveyors 40 are trained about sheaves 41 and 42, the latter being driven, and a slack take-up 42a is provided for each conveyor. The conveyors 40 discharge into the chute in any position of the boom. Material is delivered to the conveyors 40 by two parallel feeder conveyors 43. Each of the feeder conveyors 43 delivers the material through one of a pair of parallel chutes 44 onto the corresponding conveyor 40. Two side-by-side hoppers 45 receive material unloaded from the vessel by the means now to be described and direct that material to the feeder conveyors 43 whence it passes through the chutes 44 onto the conveyors 49, through the chute 10 onto the conveyor 11 and to the delivery zone.

At opposite sides of the hoppers 45 are drive arms 47 of generally L shape as shown in Figure 1. Each of the drive arms 47 has a relatively short leg and a relatively long leg. The two drive arms ,47 are identical, each' being pivoted to the boom at 46 at the end of its short leg. The ends of the longlegs of the drive arms 47 are pivoted at 48 to a guide 49. Also, the left-hand end of the guide arm 32 is pivoted to the guide 49 at 50. Thus the guide arm 32 and thedrive arms 47 carry and control the movement of the guide 49.

The boom 16 carries a motive unit 51, which may, for example, be an electric motor with a speed reducer, driving a shaft 52 to which are fixed two driving herringbone pinions 53. The pinions 53 respectively mesh with driven herringbone gears 54 fixed to a shaft 55. Also fixed to the shaft 55 are opposed cranks 56 each of which is connected through a link 57 with the corresponding drivearm 47. Each link 57 is pivoted to the corresponding crank 56 at 58 and to the corresponding drive arm 47 at 59.

The cranks 56 determine the positions of the drive arms 47 and also of the guide arm 32 and the guide 49. The cranks 56 are shown in Figure 1 fully extended toward and in alignment with the links 57 so that the pivot 59 is at the maximum distance from the shaft 55. With the cranks 56 so positioned the guide 49 is in its extreme lefthand position viewing Figure 1 and is oriented with its axis substantially vertical. When the cranks 56 are turned through 180 the drive arms 47 are moved to the position shown in Figure 2 and the guide 49 is moved somewhat upwardly and toward the right and tilted with its lower extremity extending somewhat toward the right and substantially directly above the hoppers 45.

A stem 60 is carried by the guide 49 and is movable up and 'down relatively thereto, being guided in such the stem hoisting drum 67 and thence extend about sheaves 68 and 69 and about sheaves 70 carrying counter weights (not shown), the lines 63 being dead-ended to the carriage at 72. Thus when the drum 67 is turned in the clockwise direction viewing Figure 7 the stem 60 is raised in the guide 49 while when the drum 67 is turned in the counterclockwise direction the stem 60 isallowed to move downwardly in the guide 49 through the' action of gravity.

The stem 60 carries at its lower end a bucket which may for example be a-conventional clamshell bucket and which is designated generally by reference numeral 73. The bucket is adapted to be opened and closed in.

conventional manner by a line 74 passing about bucket dome sheaves 75 and bucket crosshead sheaves 76, one end of the line extending about a sheave 77 carried by the guide 49 and being dead-ended to the guide 49 at 78. The other end of the line 74 passes about sheaves 79, 80, 81 and 82 to a bucket closing drum 83 mounted in the carriage.

There is shown in Figure 1 an operators station 84 where the operator may observe the unloading operation as it progresses and manipulate controls for moving the gantry along the dock, for moving the carriage in and out on the rails 7 mounted on the gantry, for raising and lowering the boom, for lengthening and shortening the adjustable links 28, for operating the cranks 56 to move the guide 49, for raising and lowering the stem and for opening and closing bucket. I

As above explained, the boom is positioned consonantly with the level of the material being unloaded and for each position of the boom the adjustable links'28 are adjusted so that when the stem 60 projects into the hold as shown in Figure 1 it will be substantially vertical.

With the cranks 56 in the position of Figure 1 and hence with the guide 49 in the position of that figure, being positioned relatively outwardly and downwardly and with its axis substantially vertical, the stem- 60 is lowered into the hold with the bucket 73 open. The bucket is closed to fill it with material whereupon the stem is; raised to withdraw the bucket filled with material from the hold.

Assoon as the stem has reached asufficient height to allow the guide 49 to be swung upwardly and inwardly I without the stem or bucket striking against any portion of the apparatus the cranks 56 are turned 180 and the guide 49 is swung upwardly and inwardly to position the closed bucket filled with material above the hoppers 451' That position of the bucket is shown in Figure 2. With the bucket thus positioned the bucket is opened and the material is discharged into the hoppers 45 whence it passes out to the feeder conveyors 43, through the chutes 44 onto the conveyors 40, through the chute 10 onto the conveyor 11 and to the delivery zone. The cranks 56 are then turned through 186 to the position shown in Figure l, returning the guide 49 to the position of that figure whereupon the stem 60 is again lowered for repetition of the cycle.

The stem hoisting drum 67 is mounted to rotate on coaxial trunnions one of which is shown diagrammatically at 84 in Figure 9, that trunnion being journaled in a bearing 85 mounted in the carriage 9. The drum 67 is driven by means presently to be described connected with the trunnion at the opposite end of the drum. Fixed to g the trunnion 84 is a pinion 86 meshing with a gear 8 7 H carried by a shaft 88 journaled for rotation in a bean" The lines 63 then i ing :89 mounted in the carriag 9- Fix d to the shaft 88 is a dished disc 90 having at a portion of its periphery an inner 1 91 andfan outer superimposed cam 92 for a pnrposepresently to be described.

Mounted in the carriage 9 is a bracket 93 having therethrough a circular opening 94 through which passes a pin 95 which is keyed to the bracket at 96 but free to partake of limited axial movement with respect thereto, i. e., in the right and left hand direction viewing Figure 9. The pin 95 has a head 97 and next the head a flange 98. Projecting toward the right viewing Figure 9 about the central portion of the pin and integral with the bracket 93 is a hub 99 against which the flange 98 lies as shown in that figure. Mounted upon the hub 99 for rotation thereabout and also about the axis of the pin 95 is an arm 100 whose outer end extends beyond the periphery of the dished disc 90 and has pivoted thereto at 101 a bell crank lever 102 having a generally upwardly extending arm 103 and a generally horizontally extending arm 104. A coil spring 105 urges the bell crank lever 102 to turn in the counterclockwise direction viewing Figure 8. The arm 100 carries in fixed position thereon an electric contact element 106, and a cooperating electirc contact element 107 is mounted on the end of the arm 103 of the bell crank lever 102 as shown in Figure 8. Mounted on the arm 104 of the bell crank lever 102 is a cam following roller 108 disposed in the path of the cams 91 and 92. A coil spring 109 connected between the head 97 and the arm 100 urges the arm at all times to turn in the clockwise direction viewing Figure 8. Stops 110 and 111 on the carriage 9 limit the turning movement of the arm 100 in the clockwise and counterclockwise directions respectively viewing Figure 8.

The left hand end of the pin 95 viewing Figure 9 is threaded at 112 and has a nut 113 applied thereto. Surrounding the pin between the nut 113 and the bracket 93 is a flanged disc 114 normally maintained spaced from the bracket 93 by a compression coil spring 115 which draws the flange 98 of the pin 95 toward the left viewing Figure 9 to exert a frictional drag on the hub portion of the arm 100 cooperating with the bracket 93 to hold the arm 100 against turning under the action of the spring 109. A solenoid 116 adapted to be energized at will is effective when it is energized to draw the flanged disc 114 toward the right viewing Figure 9. Such movement of the flanged disc 114 results in reduction of the pressure or frictional drag of the flange 98 of the pin 95 against the hub portion of the arm 100 and allows the spring 109 to move the arm 100 in the clockwise direction viewing Figure 8.

When the disc 90 turns in the counterclockwise direction viewing Figure 8 the inner cam 91 first engages the cam following roller 108 and turns the bell crank lever 102 through a small angle in the clockwise direction viewing Figure 8 which separates the electric contact element 107 from the electric contact element 106. As the disc 90 continues its movement in the counterclockwise direction viewing Figure 8 the outer cam 92 engages the cam following roller 108. The strength of the spring 105 is determined relatively to the frictional engagement of the hub portion of the arm 100 between the flange 98 of the pin 95 and the bracket 93 that normally when the outer cam 92 engages the cam following roller 108 such engagement causes the entire arm 100 to turn in the counterclockwise direction viewing Figure 8. In case of emergency, as when the disc 90 might continue to turn in the counterclockwise direction viewing Figure 8 after the arm 100 had come to rest against the stop 111 the cam following roller 108 could ride up over the outer cam 102, but normally that will not occur.

As the stern hoisting drum 67 turns in the clockwise direction viewing Figure 9 to pay out the line 63 and thus lower the stem 60 carrying the bucket 73 the pinion 36 which is fixed to the trunnion '84 of the drum 67 turns the gear 87 in the counterclockwise direction viewing Figure 8. But since the dished disc is fixed to the gear 87 it turns with the gear. When the unloader is beginning to unload material, as from the hold of a ship, and the level of the material at the beginning of the unloading operation is at the upper portion of the hold, the arm is at or near the stop or substantially in the position in which it is shown in Figure 8. When the bucket '73 reaches a point a predetermined distance from the material to be unloaded the inner cam 91 raises the cam following roller 108 to separate the electric contact element 107 from the electric contact element 106. Separa tion of those electric contact elements results through mechanism presently to be described in slowing down of the speed of movement of the bucket 73 so that the bucket strikes the material at reduced speed and hence with reduced impact. The unloader through its mechanism above referred to closes the bucket about a portion of the material and the drum 67 turns in the counterclockwise direction viewing Figure 8 winding up the lines 63 and raising the bucket which operates as explained above to discharge its contents into the hoppers 45.

On the succeeding cycle the level of the material in the hold of the ship is slightly lower and hence the bucket goes downwardly slightly farther than on the preceding cycle. Such additional downward movement of the bucket, which is accompanied by turning of the drum 67 in the clockwise direction viewing Figure 8 somewhat farther than upon the preceding cycle, results in the outer cam 92 engaging the cam following roller 108 and pushing the arm 100 a short distance toward the left viewing Figure 8. The arm is held in the position to which it is thus pushed by the gripping of the hub portion of the arm between the flange 98 of the pin 95 and the bracket 93 under the action of the spring 115.

As the level of the material in the ships hold gets lower and lower the arm 100 is on succeeding cycles pushed farther and farther to the left or in the counterclockwise direction viewing Figure 8 until when the hold is empty it reaches an extreme position. The mechanism thus automatically insures that regardless of the height of the material in the ships hold the bucket will upon each cycle of operation of the unloader through operation of control mechanism presently to be described move downwardly at relatively high speed to a position a predeter' mined distance above the surface of the material whereupon the speed of downward movement of the bucket will be slowed so that it moves relatively slowly at the time of engaging the material. As the level of the material lowers the bucket moves down to a lower and lower position upon successive cycles but its speed of downward movement is always decreased when the bucket reaches a point a predetermined distance above the then level of the material.

At the end of unloading of a hold of the ship when a new sequence of unloading operations is to be commenced in unloading another hold which at the beginning of such sequence of operations is relatively full of material so that the bucket is to begin its work at a level much higher than the level at which it finished unloading the preceding hold the solenoid 116 is energized, drawing the flanged disc 114 toward the right viewing Figure 9 and relieving the frictional engagement on the hub portion of the arm 100 between the flange 98 of the pin 95 and the bracket 93 permitting the spring 109 to return the arm 100 to its position against the stop 110.

Figure 10 is a wiring diagram showing the electrical operation of the control means for controlling the speed of lowering the bucket. The drum 67 is driven through a suitable gear reduction drive by a direct current electric motor 117 having a shunt field 118 excited by a suitable source of direct current 119. The motor 117 receives electric power from a direct current shunt wound adjustable voltage generator 120 having a shunt field 121. The direction of rotation of the motor 117 is determined by the polarity of the generator voltage and the speed of the motor is determined by the magnitude of the generator voltage. The polarity and magnitude of the generator voltage are determined by the direction of flow and magnitude of current in the generator field 121. That current is provided by an exciter generator 122. The exciter generator 122 is driven by an alternating current squirrel cage motor 123 coupled to its shaft and receiving power from a separate source 124. The exciter generator 122 is provided with a field coil 125 which may be electrified at different intensities in proportion to a desired efiect as will now be explained.

The excitation of the field coil 125 of the exciter generator 122 afiects the speed of the bucket hoist motor 117 by changing the output of the exciter generator 122 which changes the electrification of the shunt field 121 of the generator 120 which in turn afiects the magnitude of the output voltage of the generator 120 and hence the speed of the bucket hoist motor 117. The field coil 125 receives excitation from a direct current source 127. In the excitation circuit are arranged in parallel a resistor 128 and the cooperating electric contact elements 106 and 107 (see Figure 8) so that with the electric contact element 107 closed against the electric contact element 106 as shown in Figure 8 no current flows in resistor 128. This condition results in full voltage, full speed lowering of the bucket. When the bucket is lowered to where the inner cam 91 (Figure 8) causes separation of the electric contact element 107 from the electric contact element 106 the resistor 128 becomes electrically effective in series with the field 125 and the voltage and speed of the system are reduced to the preset value desired for the bucket 73 to strike the material being unloaded.

While I have shown and described a present preferred embodiment of the invention it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied within the scope of the following claims.

I claim:

1. In an unloader comprising material carrying means and lowering means for lowering the material carrying means toward the material to be carried preparatory to picking up some of the material, control means'for controlling the lowering means to determine the speed of lowering of the material carrying means, the control means having means becoming effective when the material carrying means move to a position a predetermined distance removed from the material to be carried as the level of the material lowers as the unloading progresses to reduce the speed of lowering of the material carrying means so that the material carrying means will be moving relatively slowly when such means engage the material.

2. In an unloader comprising material carrying means and lowering means for lowering the material carrying means toward the material to be carried preparatory to picking up some of the material, control means for controlling the lowering means to determine the speed of lowering of the material carrying means, the control means having electric contact means and means rendering the electric contact means effective when the material carrying means move to a position a predetermined distance removed from the material to be carried as the level of the material lowers as the unloading progresses to reduce the speed of lowering of the material carrying means so that the material carrying means will be moving relatively slowly when such means engage the material.

3. In an unloader comprising material carrying means and lowering means for lowering the material carrying means toward the material to be carried preparatory to picking up' some of the material, control means for controlling the lowering means to determine the speed of lowering of the material carrying means, the control means having cam means operable consonantly with move to a position a predetermined distance removed from the material to be carried as the level of the mate 1 rial lowers as the unloading progresses to reduce the speed of lowering of the material carrying means so that the material carrying means will be moving relatively slowly when such means engage the material. p

4. In an unloader comprising material carrying means and lowering means for lowering the material carrying means toward the material to be carried preparatory to picking up some of the material, control means for controlling the lowering means to determine the speed of lowering of the material carrying means, the control means having actuating means becoming predeterminedly efiective when the material carrying means move to a position a predetermined distance removed from thematerial to be carried to reduce the speed of lowering of the material carrying means so that the material carrying means will be moving relatively slowly when such means engage the material and means affecting theactuating means as the level of the material to be carried changes during successive cycles of operation of the unloader insuring that the actuating means will become efiective when the material carrying means moves to a position removed said predetermined distance from the material to be carried regardless of the level of the latter.

and lowering means for lowering the material carrying means toward the material to be carried preparatory to picking up some of the material, control means for controlling the lowering means to determine the speed of lowering of the materialcarrying means, the control means engage the material, the operating means moving consonantly with lowering of the material carrying means,

and means progressively changing the position of the' actuating means as the level of the material to be carried changes during successive cycles of operation of the unloader insuring that the operating means will be effective to operate the actuating means when the material carrying means moves to a position removed said predetermined distance from the material to be carried regardless of the level of the latter.

6. In an unloader comprising material carrying means and lowering means for lowering the material carrying means toward the'material to be carried preparatory to picking up some of the material, control means for controlling the lowering means to determine the speed of lowering of the material carrying means, the control means having actuating means and cam means operating the actuating means when the material carrying means move to a position a predetermined distance removed 7 from the material to be carried to reduce the speed of lowering of the material carrying means so that the material carrying means will be moving relatively slowly when such means engage the material, the cam means. moving consonantly with lowering of the material carry-r ing means, the cam means having a portion engaging" and bodily moving the actuating means as the level of' the material to be carried changes during successive cycles of operation of the unloader insuring that the cam means will be effective to operate the actuating means when the material carrying means moves to a position" i removed said predetermined distance from the materialy to be carried regardless of the level of the latter.

, 7. In an unloader comprising material carrying means' and lowering means for lowering the material carrying means toward the material to be carried prepara- 5. In an unloader comprising material carrying means "11 tory to picking up some of the material, control means for controlling the lowering means to determine the speed of lowering of the material carrying means, the control means having actuating means and means opi crating the actuating means when the material carrying means move to a position a predetermined distance removed from the material to be carried to reduce the speed of lowering of the material carrying means so that the material carrying means will be moving relatively slowly when such means engage the material, the operating means moving consonantly with lowering of the material carrying means, means progressively changing the position of the actuating means as .the level of the material to be carried changes during successive cycles of operation of the unloader insuring that the operating means will be effective to operate the actuat ing means when the material carrying means moves to a position removed said predetermined distance from the material to be carried regardless of the level of the latter and means for returning the actuating means at the conclusion of an unloading operation and prior to initiation of a succeeding unloading operation to a position corresponding to maximum height of the level of the material.

8. In an unloader comprising material carrying means and lowering means for lowering the material carrying means toward the material to be carried preparatory to picking up some of the material, control means for controlling the lowering'means to determine the speed of lowering of the material carrying means, the control means having actuating means, mounting means carry ing the actuating means having a portion :along which the actuating means may be moved to various positions on the mounting means and means operating the actuating means when the material carrying means move to a position a predetermined distance removed from the material to be carried to reduce the speed of low ering of the material carrying means so that the material carrying means will be moving relatively slowly when such means engage the material, the operating means moving consonantly with lowering of the material carrying means, and means progressively moving the actuating means along the mounting means as the level of the material to be carried changes during successive cycles of operation of the unloader insuring that the op erating means will be effective to operate the actuating means when the material carrying means moves to a position removed said predetermined distance from the material to be carried regardless of the level of the latter.

9. In an unloader comprising material carrying means and lowering means for lowering the material carrying means toward the material to be carried preparatory to picking up some of the material, control means for them trolling the lowering means to determine the speed of lowering of the material carrying means, the control means having actuating means, mounting means carrying the actuating means having a portion along which the actuating means may be moved to various positions on the mounting means, holding means maintaining the actuating means in each position to which it is moved on the mounting means and means operating the actuat ing means when the material carrying means move to a position a predetermined distance removed from the material to be carried to reduce the speed of lowering of the material carrying means so that the material carrying means will be moving relatively slowly when such means engage the material, the operating means moving consonantly with lowering of the material carrying means, means progressively moving the actuating means along the mounting means as the level of the material to be carried changes during successive cycles of operation of the unloader insuring that theoperating 12 means will be effective to operate the actuating means when the material carrying means moves to a position removed said predetermined distance from the material to be carried regardless of the level of the latter and means for rendering the holding means inoperative and returning the actuating means at the conclusion of an unloading operation and prior to initiation of a succeeding unloading operation to a position corresponding to maximum height of the level of the material.

10. In an unloader comprising material carrying means and lowering means for lowering the material carrying means toward the material to be carried preparatory to picking up some of the material, control means for controlling the lowering means to determine the speed of lowering of the material carrying means, the control means having actuating means, mounting means carrying the actuating means having a portion along which the actuating means may be moved to various positions on the mounting means, friction drag means maintaining the actuating means in each position to which it is moved on the mounting means and means operating the actuating means when the material carrying means move to a position a predetermined distance from the material to be carried to reduce the speed of lowering of the material carrying means so that the material carrying means will be moving relatively slowly when such meansengage the material, the operating means moving consonantly with lowering of the material carrying means, means progressively moving the actuating means along the mounting means as the level of the material to be carried changes during successive cycles of operation of the unloader insuring that the operating means will be effective to operate the .actuating means when the material carrying means moves to a position removed said predetermined distance from the material to be carried regardless of the level of the latter, means for rendering the friction drag means inoperative and spring means returning the actuating means at the conclusion of an unloading operation and prior to initiation of a succeeding unloading operation to a position corresponding to maximum height of the level of the material.

11. In an unloader comprising material carrying means and lowering means for lowering the material carrying means toward the material to be carried preparatory to picking up some of the material, control means for controlling the lowering means to determine the speed of lowering of the material carrying means, the control means having actuating means including electric contact means and means including cam means operable consonantly with lowering of the material carrying means rendering the electric contact means effective when the material carrying means move to a position a predetermined distance removed from the material to be carried to reduce the speed of lowering of the material carrying means so that the material carrying means will be moving relatively slowly when such means engage the material and means affecting the electric contact means as the level of the material to be carried changes during successive cycles of operation of the unloader insuring that the actuating means will become efiective when the material carrying means moved to a position removed said predetermined distance from the material to be carried regardless of the level of the latter.

References Cited in the file of this patent UNITED STATES PATENTS Re. 20,630 Hallenbeck Jan. 18, 1938 673,317 Cole et a1. Apr. 30, 1901 2,379,958 Fox July 10, 1945 2,796,180 Rose June 18, 1957 UNITED STATES PATENT OFFICE V CERTIFICATION OF CORRECTION Patent No, 2,973,877 March 7, 1961 Bennie Rose It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below; I

Column 3, line 62, for "changes" read change column 4, line 9', for "'carrlages" read carriage column 6, line 1, for learner-W read carries Signed and sealed this 25th day of July 1961.,

(SEAL) Attest:

ERNEST W. SWIDER Attesting Officer DAVID L. LADD Commissioner of Patents

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