US2450718A - Hoist - Google Patents

Description

V. L. DARNELL HOIST Oct. 5, 1948.

7 Sheets-Sheet 1 Filed Aug. 20. 1942 Oct. 5, 1948,

v. DARNELL HOIST Filed Aug. 20, 1942 7 Sheets-Sheet 2 Oct. 5, 1948.

v. L. DARNELL 7 Sheets-Sheet 5 Filed Aug. 20, 1942 QM MN V(- L. DARNELL HOIST 7 Sheets-Sheet 4 Filed Aug. .20. 1942 Oct. 5, 1948. v. L. DARNELL 2,450,718

v HOIST Filed Aug. 20. 1942 Sheets-Sheet 5 DC UNA-4 0: LINE&

- Oct. 5, 1948. v. L. DARNELL 2,450,718

HOIST Filed Aug. 20, 1942 '7 Sheets-Sheet 6 INVENTOR.

TTORNEY.

V. L. DARNELL Oct. '5, 1948.

7 Sheets-Sheet 7 Filed Aug. 20. 1942 .Tfi i f h. V 1:. k;

INVENTOR. QM

5. rlfllflflllIlllflllllllttli I w Patented Oct. 5, 1948 HOIST Victor L. Darnell, Centerville, Ohio, assignor to The Master Electric Company, Dayton, Ohio, a corporation of Ohio Application August 20, 1942, Serial No. 455,421

12 Claims.

and hoisting equipment of the dual drum type which is capable of a wide range of general application, but which is especially useful for loading bombs into the bomb bay of an airplane, and analogous purposes.

Obviously, the elevation and stowing of loaded bombs which weigh from one hundred to two thousand pounds or more each necessitates careful handling and accurate manipulation to avoid concussion or premature dropping of the bomb. Han-d operation of bomb hoisting apparatus as heretofore commonly employed is slow and laborious, and requires a long time as compared with the present power driven apparatus. In the present instance electric motive means is ordinarily employed for the hoist apparatus, but

for emergency use an alternative manual operating mechanism is provided. Coordinated safety devices prevent retraction of the cable in event of failure of the electrical power supply or failure of the human factor in manual operation.

As herein illustrated, the preferred embodiment of the invention includes a pair of independently revoluble winding drums onto which are wound the opposite ends of a single hoist cable common thereto, having therein a medial bight. The drums are operable in unison or difierentially by optionally selective electric motor or hand crank actuating means. Associated with the winding drum is brake mechanism automatically effective alternately with either of the optional actuating mechanisms. The brake mechanism becomes automatically efiective to hold the drums at rest with the load in elevated position upon failure of the electric current supply or interruption of the motor energizing circuit. The manual actuating means may be operatively engaged and maintained in driving condition only so long as the brake mechanism is manually maintained ineffective, and upon failure of the operator to so hold the brake mechanism, the latter is reengaged to arrest the drums and hold the load, and the manual actuating device is automatically disengaged. By unison rotation of the drum to retrieve or pay out the connected cable ends uniformly, the bomb or other work load suspended in the bight of the cable may be raised or lowered. However, by differential rotation ofthe drums the suspended work body or bomb may be rotated in either direction as may be necessary to present a hanger eye of the bomb in vertically aligned relation above a suspension hook or latch for engagement therewith. During rotation of the drums level winding friction rollers having peripheral speed greater than that of the drums assures uniform distribution of the cable coils in tight engagement with the drums.

While the invention is herein shown and described primarily in its application to loading bombs onto an airplane, it is to be understood that such reference is for illustrative purposes, with no intent to unduly limit the scope or application of the invention which is not limited thereto, but i capable of general hoist, drag line operation or other alternative operation.

The object of the invention is to improve the construction as well as the means and mode of operation of hoist apparatus and power operated winches, where-by such apparatus may not only be economically manufactured, but will be more efficient in use, automatic in operation, uniform in action, having relatively few operating parts, and be unlikely to get out of repair.

A further object of the invention is to provide a hoist apparatus or power winch assembly of compact form and relatively light Weight, and high power, which may be either portable or permanently installed.

A further object is to provide an apparatus of great strength and rapidity of operation.

A further object of the invention is to provide a hoist apparatus and method of operation, whereby the work load may be raised and lowered under control and while suspended may be turned or rotatively adjusted to an optional extent.

A further object of the invention is to provide automatic safety means operative upon failure of either power or manual actuating means, which is operative to maintain the work load suspended in its adjusted position.

A further object of the invention is to provide an improved level winding device for the winding drum by which the cable convolutions are uniformly laid.

A further object of the invention is to provide an improved method of cable control and mode of manipulation of the work load while suspended upon the hoist cable.

A further object of the invention is to provide hoist equipment embodying the advantageous structural features and the inherent meritorious characteristics and the mode of operation herein described.

With the above primary and other incidental objects in view as will more fully appear in the specification, the invention intended to be protected by Letters Patent consists of the feasee ers I tures of construction, the parts and combinations thereof and :the mode of operation, or :their equivalents, as hereinafter described or illus-.

' trated in the accompanying drawings.

In the drawings, wherein are shown the pre-. ferred but obviously not necessarily the only forms of embodiment of the invention;

I Fig-.1 is aperspective view of-an assembled hoist unit in which the present invention is incorporated. Fig; 2 is a vertical sectional view thereof.

Fig. 3 is a front elevation, partly in sectiomof the assembled unit. I I

I Fig. 4 is a rear end elevationviewed from the right of Fig. 2 with the housing cover removed, illustrating thedriving gear train to the respectlvewinding drums- I I At its rear end the rotor shaft 5 carries adriv- I ing gear pinion H), which meshes with a gear wheel Il mounted upona short shaft l2 journaled ini bearings l3 in: the wallsof the. gear. I housing. The shaft l2 also embodies a gear pintion' 14 with which intermeshes an idler gear mounted upon a second short shaft I6 journaled I I I I in bearings I! also in the walls of the gear hous-- ingr The intermediate shaft I 6 .is formed with through the tapered hub .or large boss l in which I Fig. 5 is a detail perspective view of the inter-- energizing and synchronizing circuit for the I power motors. I

an. integral gear pinion I 8, with which inter.-

meshes a driven gear lasecured to the revoluble winding drum shaft 20 which extends axially it is journaled. Secured to the forward end of the driven shaft 20 for unison rotation is a winding drum 2| :which surrounds and encloses the. conical hub 4. The winding drum is providedwith ahelical peripheralgroove to receive one endof thehoist cable 2:2. II I 'Ihere are twodrivingmotors, as described, and two driven winding drums. Separate power transmission systems connect the respective; elec- .Fig. 8 is a side elevation of a; modified form of I embodiment of the invention.

- Fig. ;9.is a side elevation partly in section of the embodiment shown in Fig. 8.

Fig. 10 is an end elevation. I I. Fig. 11 is an electrical circuit diagram of the 'dual; drive synchronizing feature in simplified form.

Like parts are indicated by similar characters of reference throughoutthe several views.

I The present hoist unit is adapted to be either I permanently or demountably secured upon an airplane, for operation of I itsdriving .motorsby current supplied from the. power iplant of the plane or from the electrical supply system of the air field or other outside source of electrical energy. Heretofore it has required one to several hours to load and secure a large size bomb in the bomb bay of an airplane, whereas by the present power operated unit it is possible to hoist and secure such bomb in a comparatively few minutes. This time factor is highly important when a plane has returned for replenishment of its bomb supply in the midst of an aerial engagement, or when the landing field or bomb supply station is under bombardment. Under such conditions, the interruption of the power current to the motors or injury or death of the operator would prove disastrous in the event a partially raised bomb was allowed to drop. This is prevented by present automatic safety devices. The ability to manipulate or turn the bomb or other load while suspended in elevated position is highly advantageous.

Referring to the drawings, I is the main frame of the unit, at the rear of which is a gear housing 2 for the speed reducing transmission gear trains, while at the lower portion of the frame are two forwardly projecting motor housings 3. Immediately above the motor housings are two forwardly projecting conical hubs 4 to support the winding drums.

Within each of the motor housings 3 is a r0- tor shaft 5 journaled in bearings G-6. Carried thereon is the motor armature or rotor I, which is surrounded by the usual stator ring 8 having customary windings 9. The motor is of the reversible type and adapted to optionally drive the corresponding winding drum in either direction.

tric motors with the driven drums. The iconstructionissuchthat the winding drums 2| are normally driven in unison; preferably in reverse I II directions to simultaneously retrieve or pay out 'the'opposite ends of the common hoist cable 22.

The cable lengths are preferably extended in close relation from the adjacent sides of the drums. I I I I I To insure uniform distributionand contact of the cable 22 about the respectivewinding drums 1 1 2i, each drum .is provided with a level winding device or cable retainer. comprising a frictional roller 23 having a resilient peripheral face 1 which contacts and rides upon the convolutions of the cable 22 'about the' winding drum. Each roller 231s mounted in an oscillatory frame 24 I. pivoted at 25 and having an upwardly extendingv arm 26.- Interposecl between :the-rockzarms 26 I I of the oscillatory roller frames is a tensioned thrust bar 2! comprising two axially adjustable sections between which a helical tension spring 28 is interposed. The reaction of the tension spring 28 tends to oscillate the roller frames 24 in opposite directions to press the rollers 23 against the cable turns about the respective winding drums.

The rollers 23 are geared to the winding drums for unison rotation but at an increased peripheral speed. Each drum has at its rear end an integral gear 29, which meshes with a gear pinion 30 secured to the end of the corresponding roller 23, but of less pitch diameter than the diameter of the roller. As a result thereof, each roller 23 is afforded a wipLng action upon the convolutions of the cable 22 about the corresponding drum. The surface of the roller being resilient is somewhat distorted or flattened against the drum under the reaction pressure of the spring 28, as is shown in Fig. 3.

The terminal ends of the cable 22 are fixedly secured to the respective winding drums 2 I. Each drum is formed with a terminal shoulder 3| over which the end of the cable is inwardly extended at 32. The end of the cable is formed into an eye 33 which is securely bolted to a lug 34 integral with the drum. In spaced relation with the cable shoulder 3| is a notch or recess 35 in the terminal margin of the drum which is bridged by the final turn of the cable. A cable clamp 36 comprising a strap of metal reversely bent upon itself into a bight is engaged about the cable within such notch or recess, and the overlapped ends of the metal strap are clamped to the end of the windin drum shaft 29 by the retaining nut 31.

The cable 22 isconducted from the windin drums 2| in any desired direction and to any necessary extent over suitably placed guide blocks or sheaves 38, and is formed into a medial dependent bigh't within which the work load is engaged. The medialv cable bight preferably comprises a sling 39 especially adapted to the load to be hoisted, but may be merely a continuing bend of the cable 22.

The start, stop and reverse of the motors is controlled from a distant point by suitable switches and circuit breakers in the motor energizing circuit. Upon unison operation of the electric motors to drive the respective winding drums in winding direction, the standing portions of the cable bigh-t 39 are uniformly retrieved to shorten and hence elevate the cable bight 39. Upon reverse operation of the motors in unison, the bight 39 is lengthened and the work load is lowered.

Conventional bombs have therein longitudinally aligned eye bolts 49 by which the bomb is to be suspended from release hooks or latches 4| in the bomb bay of an airplane. When the bomb is initially engaged Within the bight or sling 39 of the cable, the eye bolts may be in any position of rotation of the bomb. That is, they may be disposed laterally, vertically, or at any inclination, and so not in proper relation for engagement with the suspension books or bomb release latches.

When the bomb has been lifted to a position with its top above the level of the hanger hook or latch 4|, the drums are differentially actuated by retrieving-only one side or the other of the cable bight, while maintaining the other winding drum at rest, or by retrieving one side of the cable bight while paying out the other side by reverse action of the drums, the bomb is made to rotate about its longitudinal axis to sufficient degree topresen't the hanger eye 40 in vertical alignment above the suspension hook 4|, whereupon by lowering the .bomb by unison operation of the drums to pay out the cable ends uniformly, the bomb is lowered until the suspension hook enters the hanger eye of the bomb.

The same methodof rotative manipulation of the load may be employed for other purposes, as for example when stowing cargo in a ships hold, to fit the load relative to previously placed cargo, or for loading equipment onto a truck or car so that it may set level on its bottom or side, as found expedient. Such manipulative action is highly useful in many other non-military operations.

For the purpose of maintaining the cable and work load in adjusted position when the motive power is disconnected, and especially in the e ent thatthe source .ofcurrent supply is destroyed or the energizing circuit accidently interrupted, each of the actuating motors is provided with an electrically controlled automatic brake. The brake is held in ineffective position by electromagnetic influence until interruption of the current supply occurs. Immediately such brake becomes effective under springinfiuence to hold the motors and winding drums against rotation. Located within the forward end of each of the motor housings 3 is a partition wall 42 in which one of the shaft bearings 6 of the rotor shaft 5 is disposed. The partition 42 includes a hub 43 concentric with the shaft 5. Mounted on the hub 43 is a recessed electromagnet core 44, having therein a winding 45 which is connected into the motor circuit.

Associated with the core member 44 is an annular armature plate 46 axially movable relative 6, thereto and attracted toward the electromagnet against the tension of a series of helical springs 4 s. The armature plate is guided in its to and fro motion and held against rotation by a series of studs 41 sliding in bores in the hub 43. Disposed in paralle1 relation with the armature plate 46 is a normally fixed back plate or abutment 49. The back plate 49 adjustably mounted on a screw sleeve 50 for axial adjustment, is held against rotation'by-a stud or pin 5| extending through the plate 49 adjacent the periphery thereof.

Intermediate the armature plate 46 and the back plate'or abutment 49 is interposed a friction disc 52 mounted on hub 53 secured to the motor shaft 5, for unison rotation but axially adjustable relative thereto. The friction disc may rotate freely between the armature plate 46 and abutment 49 in unison with the shaft so long as the electromagnet is energized and. the armature plate remains attracted thereby against the tension of the springs 48. However, when the electrical circuit is interrupted, thereby de-energizing the electromagnet, the springs 48 forcibly press the armature plate against the friction disc and clamp the latter against the abutment plate. This serves'to frictionally lock the motor shaft against rotation, and with it the related driven winding drum, whenever for any reason the supply of electric current is interrupted. The automatic' application of the brake will hold the load in its elevated position and will prevent dropping of the bomb or other suspended body.

Upon accidental interruption of the current supply, the loading of a bomb or other hoist op- I eration may be continued by manual actuation of the hoist apparatus. To enable such emergency operation, there is provided on each motor housing head a supplemental housing or gear cover 54 in which is mounted for relative reciprocatory motion a rotary shaft 55, having at one end thereof a crank handle 56. The shaft 55 carries a bevel gear 51 which is movable into and out of intermeshing relation with a mating gear 51' upon the end of the motor shaft 5, by the reciprocation of said shaft 55. The shaft 55 is automatically retracted to disengage the bevel gears 51.-5'|' by a helical spring 58 surrounding the shaft, and is temporarily held in operating position by a pivoted latch 59 engageable in a peripheral groove 69 in the shaft 55. The crank shaft detent is controlled by adjustment of the brake back plate or abutment 49 to set or release the brake.

Secured to the screw sleeve 50 upon which the abutment or back plate 49 is mounted is a manvual adjusting lever 6| by which the screw sleeve may be partially rotated against the tension of a retracting spring 62 coiled about the projecting end of the screw sleeve with one end attached to the hand lever 6| and the other end anchored to the motor housing.

Loosely journaled on the screw sleeve 59 adjacent to the brake hand lever 6| is a collar 63. At one side thereof is a radial finger 64 to which is connected one end of a helical retractile spring 65, the opposite end of which is connected with the brake lever 6|. At its top the collar 63 has therein an elongated notch 66. Adjustably secured to the hand lever 6| is a plate 61 havin therein a stud 68 which projects Within the elongated notch and serves by engagement with one side of the notch to retract the collar through a partial rotation upon oscillation of the hand lever under retractive influence of the coil spring 62. The elongated notch 66 enables the lever 6| to be aim-ifs 7' moved through a limited range of adjustment independently of the collar, against the yielding resistance of both springs 62 and 65. The stud carrying plate 61 is adjustable relative to the hand lever by means of the clamp screws 69, whereby the position of the stud 68 may be changed and with it the rotative adjustment of the collar 63 relative to the hand laver. To maintain the radial relation of the plat 61, it is bifurcated and disposed in straddle relation with the sleeve Opposite the spring engaging finger 64 the collar 63 carries a radial arm 70 which is oscillated with the collar. At its extremity is a hole H into which projects a reduced end 12 of the pivoted crank shaft latch 59. The latch plate 59 has therein a key hole slot 13, the medial enlargement of which is of suificient size for the crank shaft to pass longitudinally therethrough. The terminal slots of the opening 13 have width substantially equal to the neck of the shaft within the peripheral groove 60 thereof.

The crank shaft has a reduced end 14 of the same size as the reduction within the peripheral slot 60, affording a terminal shoulder upon the shaft. The retraction of the brake lever 61 and collar 63 under influence of the springs 62 and 65 elevates the arm and normally holds the latch plate 59 elevated incident to engagement of its end 12 in the hole H of the arm 10. The reduced end of the crank shaft is thus engaged in the lower extension of the key hole slot 13. In this relation the lower margin of the key hole slot of the latch plate overlaps the terminal shoulder of the crank shaft to normally prevent longitudinal thrust movement thereof necessary to interengage the bevel gears 51--5'|'. The manual actuating means is thus locked in inoperative condition. The crank shaft is unlocked by manual adjustment of the brake lever 6| to a mid-stroke posi tion. The collar 63 being partially rotated by the spring 65 as the lever is initially moved, lowers the arm 10 and with it the latch plate until the medial enlargement of the key hole slot is aligned with the crank shaft. The crank shaft is then manually thrust longitudinally through the key hole slot of the latch plate against the yielding resistanceof the spring 58, until the peripheral groove 60 of the shaft is in the plane of the latch plate 59. Upon further oscillation of the brake lever, the upper margin of the medial enlargement of the key hole slot is depressed into the peripheral groove 60 of the shaft, thereby locking the latter against retraction under influence of the spring 58, so long as the brake lever is manually held in its finally operated position. During such further and final movement of the brake lever, the arm 10 and the collar 63 are held against further rotation by the described locking engagement of the latch plate with the crank shaft while the stud 68 continues to advance within the elongated marginal notch 65. Such further movement of the brake lever retracts the brake back plate or abutment 49 by partial rotation of the screw sleeve 50 and releases the brake. The operated position of the several parts is shown by the right hand assembly in Figs. 1 and 3.

The engagement of the latch plate 59 within the peripheral groove 60 temporarily locks the bevel gears 51 and 51 in intermeshing engagement, and the winding drums may be rotated by manual effort. However, upon release of the brake lever, which may be intentional or accidental, the brake lever is immediately returned to its original position, the latch is disengaged and the crank shaft retracted by the spring 58 to its original position, and by reverse rotation of the screw sleeve 50 incident to return of the lever 6|, the brake mechanism is automatically reset to arrest and hold the winding drums and the suspended load in their adjusted positions. Thus, in event that the operator is injured or killed while manually operating the hoist, and the brake lever is so released, it operates as a safety device to prevent dropping the bomb or other load.

Likewise, the control switch for the power drive mechanism is preferably one which automatically opens the motor circuit upon release, and such that the motor continues to operate only so long as the control switch is held closed. Therefore, release of the control switch or a break in the energizing circuit will effect automatic operation of the brake to arrest and hold the winding drums and the suspended load.

In Figs. 6, 9 and 10 is shown a modification wherein the dual winding drums are disposed in axial alignment with each other and are actuated by a single driving motor, which may be connected at will with the driving drums independently or simultaneously through associated worm gear drive mechanism which i automatically effective to hold the drums and suspended load in operated position.

Referring to Figs. 8 and 9, the peripherally grooved winding drums 15-15 are mounted for rotation upon a hollow shaft I6 secured in upstanding end frames 11. Connected with each of the drums is a worm wheel 18 which meshes with a worm 19 upon a vertical shaft in the end frame 11. Beneath the drums I5 i an electric motor 8|, to theopposite heads of which the end frames 71 are secured. The vertical shafts 80 carry at their lower ends worm wheels 82 with which mesh driving Worms connected to the motor shaft 83 by intermediate driving clutches 84. The clutches 84 are separately operable by manual levers 85 to individually connect the respective winding drums with the motor. The hoist cable is arranged a before described, with its ends wound upon the respective drums and a dependent bight in the intermediate portion in which the load to be lifted is suspended.

By simultaneously retrieving the cable uniformly upon both winding drums, the load is lifted or conversely lowered by uniformly paying out the cable from both drums. However, by driving the drums differentially, the load may be rotated to greater or less degree as it is being raised or lowered. In the event of power failure, a hand crank may be applied to the motor shaft at 86 for manual actuation.

As hereinbefore described, it is variously necessary during operation to employ either of the two motors, which are series wound, independently or to operate the motors simultaneously. During simultaneous operation, it is highly desirable, for reasons heretofore explained, that the motors operate at synchronous speeds. This necessitates an equalizing system, the operation of which is delayed until the armature potential of the respective motors reaches a predetermined value. In the event it becomes necessary to start one motor while the other is operating at normal speed, if the equalizing circuit is closed at the moment the second motor is energized, momentarily there would occur a large difference of potential between the respective motor circuits and a heavy flow of current through the equalizing circuit. This would likely result in a destructive flash or are at the relay contact point, as well as at the brushes of the motor being started. By delaying the closing of the relay contact until the armature potential reaches a predetermined value, the potential difference is reduced to a safe value and equalization occurs without arcing.

Referring to the accompanying circuit diagrams, wherein 1 and 1' indicate the armatures of the series wound direct current motors |-8--9, of which 9 and 9 are the field windings, relay coils 81 and 81' are shunted across each motor armature. Circuit make and break contacts 88 and 88' controlled by the relay coils are included in a paralleling circuit line interconnecting the respective motors. The clutch control coils 43 are connected in parallel with the respective motor circuits. The motors are independently controlled by distantly located double throw switches 89 and 89', which according to the direction of operation serve to reverse the rotation of the motors.

When a single switch 89 or 89' is closed, the corresponding series motor will operate at a speed dependent upon the load and speed torque characteristic of the motor. The corresponding relay 8'! or 81, as the case may be, being connected across the armature circuit and designed so that its contact 88 or 88 closes only when the potential across the armature reaches a predetermined value, cannot alone close the paralleling or equalizing circuit in which both circuit closers 88 and 88' are included. Consequently, the paralleling operation is not completed while either motor is being operated singly. When, however, both motors are placed in operation, each relay 8! and 81' is energized as soon as the potential across its associated armature reache the predetermined value. Upon closing both relay contacts the paralleling circuit is completed and the potential across the respective motor armatures is equalized.

The respective motorshave similar characteristics, but may be unequally loaded. Under such condition, if not equalized there may be a distinct difference between the speed of the respective motors due to speed torque characteristics of series wound motors. The paralleling operation effected by closing of both relays tends to equalize not only the potential across the armatures, but that across the series fields as well. Thus, the motors are made to operate at substantially equal speeds, even though the loads on the two motors may differ. The current flow through the equalizing circuit will vary with the difference between the loads imposed upon the respective motors. In Fig. 11 the equalizing system is shown reduced to its fundamental form for clarity and ease of understanding.

From the above description it will be apparent that there is thus provided a device of the character described possessing the particular features of advantage before enumerated as desirable, but which obviously is susceptible of modification in its form, proportions, detail construction and arrangement of parts without departing from the principle involved or sacrificing any of its advantages.

While in order to comply with the statute, the invention has been described in language more or less specific as to structural features, it is to be understood that the invention is not limited to the specific features shown, but that the means and construction herein disclosed comprise the preferred form of several modes of putting the invention into eifect, and the invention i therefore claimed in any of its forms or modifications within the legitimate and valid scope of the appended claims.

Having thus described my invention, I claim:

1. A hoist apparatus wherein dual independently operable winding drums control a hoist cable common thereto the ends of which are wound upon the respective drums and having a medial bight therein to receive a work load are driven by electromotive means in unison in either direction to raise and lower the work load and differentially to rotate the work load while suspended in said bight, electrically operated power means for the drums, an electrical energizing circuit for said electro-motive means, a manual .actuating device for driving the drums independently of the electromotive means, an automatic brake mechanism for arresting and holding the winding drums and suspended load in adjusted position, electromagnetic means for temporarily maintaining the brake mechanism in ineffective condition during operation of the electromotive drive means, and permitting automatic reengagement of the brake mechanism upon interruption of the electric current supply through said circuit, and amanual control device for maintaining the brake mechanism in ineffective condition independently of the electromagnetic means during operation of the manual actuating device for the drums, the brake mechanism being automatically reengageable upon release of the manualcontrol device, the construction and arrangement being such that upon failure of either the electric power supply or of the operator while manually actuating the drums, the brake mechanism is automatically engaged to prevent retrograde motion of the winding drums and suspended work load.

2. A hoist apparatus including a revoluble winding drum, a hoist cable, a portion of which is wound upon the drum, an electric. motor and hand crank for actuating the drum alternately at will, an electrical control circuit for the motor, an electrically controlled brake maintained in inoperative condition by influence of electric current in the motor circuit and operative to arrest and hold the drum in operated position upon interruption of the motor circuit, a manual control device for temporarily holding the brake in ineffective relation independently of the electric current influence, and an interlock mechanism between the manual brake control and the hand crank, the construction and arrangement being such that the hand crank is effective only while the brake is manually held in ineffective relation and is automatically rendered ineffective upon release of the manual brake control device.

3. A hoist apparatus wherein a pair of independently revoluble winding drums control a hoist cable, the opposite ends of which are wound upon the respective drums and has a medial bight formed therein, separate electric motors for independently driving the respective winding drums, an electrical energizing circuit for the electric motors by which the operation of the motors is synchronized, manual actuating means for driving the drums independently of the electric motors, brake mechanism efiective to hold the drums at rest intermediate periods of operation thereof either by electric motor or manual driving devices, and interlock means for preventing operative engagement of the manual actuating device until the brake mechanism isdisengaged and for automatically disengaging the VICTOR L. DARNELL.

REFERENCES CITED The following references are of record in the fiie of this patent:

. UNITED STATES PATENTS Number Name Date 402,688 Schulz May 7, 1889 528,567 Sharp Nov. 6, 1894 568,174 Taylor Sept. 22, 1896 636,023 Cravath Oct. 31, 1899 Number Number 14 Name Date Morgan et a1 Aug. '7, 1900 Hunt Oct. 23, 1906 Hultgren July 16, 1907 Schwinnen June 23, 1914 Miller Jan. 8, 1918 Sivard Jan. 15, 1918 Kittredge Oct. 14, 1919 LEmieux Jan. 20, 1920 Howe Sept. 4, 1923 Cull June 17, 1924 Fl-odin June 30, 1925 Howe Apr. 5, 1932 Kahlerth Dec. 10, 1940 Vickers Oct. 7, 1941 Luebbe Apr. 20, 1943 FOREIGN PATENTS Country Date Italy Mar. 4, 1934 Great Britain Apr. 26, 1934 Great Britain Feb. 24, 1939

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