US2107540A - Power take-off - Google Patents

Description

Feb. 8, 1938. E. H. LlC-HTENBERG POWER JAKE-OFF" Filed Dec. 22, 1953 5 Sheets-Sheet 1 dbtowwqa Feb. 8, 1938. E. H. LICHTENBERG POWER TAKE OFF Filed Dec. 22, 1933 5 Sheets'-Sheet 2 Feb. 8, 1938. I LICHTENBERG 2,107,540

POWER TAKE-OFF Filed Dec. 22, 1953 5 Sheets-Sheet 3 gwomtoc 58, E. H. :LICHTENBE'RG 2,107,540

POWER TAKE-DEF Filed Dec. 22, 1933 5 Sheets-Sheet 4 Patented 'Feb. 8, 1938 PATENT OFFICE rowan TAKE-OFF llrlch H. Lichtenberg, Milwaukee, Wis assignor to Koehrlng Company, Milwaukee, Win. a corporation Application December 22, 1933, Serial No. 703,655

12 Claims. (01. 83-73) This invention relates to power take-oil means and control instrumentalities therefor, and is particularly adapted for use in connection with mixing machines, however is not limited to such 6 specific employment and may be used in other capacities if so desired.

The teachings of this invention are especially applicable for use in connection with that class of machines known as bituminous mixers that are peculiar to other types of mixing machine in that the mixing drum is held stationary during mixing' operations and agitation is obtained through power driven blades. ever, is rotatable to various positions to allow the discharge and charging thereof and this invention is concerned primarily with means for so moving the drum. Heretofore this task has been carried out manually through gear and hand wheel arrangements that did not contribute considerably toward speeding up the interval of handling the material, which embraced the period beginning with-loading and ending with complete discharge. To say the least, the task was laborious even though these simple mechanical devices were employed, and without doubt, movement of the drum was slow, and as a corrolary tothis thought, control over the drum was not positive so that itcould be stopped at a predetermined point. It is to be appreciated that these mixing drums handle at least six to twelve cubic feet of, material and the momentum imparted arising from the overbalancing of the load as the drum rotates to discharge position may be more than the operator can control. It is the aim of: this invention then, to provide means for rotating and controlling the rotation of such a device as the mixing drum of a bituminous mixer and by virtue of which anadvantageous application of power may be obtained for moving the drum to its various positions while at the same t me affording means for positively controlling the momentum.

In realizing the above desideratum, I have devised a novel form of power take-off. which may be driven from the prime mover ,of the mixer to actuate the mixing drum. In connection with this power take-oil, I have devised certain control instrumentalities that in one form are effective to effect a positive application of power for rotating the heavily loaded drum to dumping position under perfect control for stopping the same at a predetermined point. This form of apparatus includes instrumentalities by means ofwhich an instantaneous application of force may be given to the empty drum to return it The drum, howto loading position. In other words, the unloaded drum may be kicked? to occasion the free rotation thereof to loading position. A slightly different control arrangement affords a positive application of power for rotation of the drum in one direction and stopping-oi the drum is made incident to the rotation thereof to a predetermined point. v

Other objects and advantageous features of this invention will be found in the following detailed description and accompanying drawings, wherein like characters 'of reference indicate like parts, and wherein- Figure 1 is a perspective view of a bituminous mixer embodying my novel power take-01f arrangement for rotating the mixing drum, with the preferred form of control instrumentalities associated therewith.

Figure 2 is a sectional view of my power takeoff unit, showing the preferred form of control instrumentalities therefor.

Figure 3 is a front elevation of the operating levers.

Figure 4 is a fragmentary view showing the positional relation of the operating parts at one stage in the operation.

Figure 5 is a front view of the power takeoif unit disclosing the positional relation of the parts at another stage in the sequence of operation.

- Figure 6 is a section taken on the line 6-4 of Figure 3.

Figure '7 15.9. fragmentary elevation showing a modified form of control mechanism for the power unit.

Figure 8 is a partial section taken on the line 8-3 of Figure 7.

Figure 9 is a section of a. modified form of power take-oil? arrangement and operating in- 1 strumentalltles.

Figure 10.is a view of the control instrumentalities for the'brake of Figure 9, or 1 to 8 mclusive. v

Figure 11 is a fragmentary elevation of another form of control mechanism for the unit of Figure 9. I

Figure 12 is an elevation of another form of .control instrumentalities for the power take-oi! unit.

,Figure 13 is a view similar to that of Figure 12, showing the control instrumentalitiea in one position of adjustment.

Figure 14 is an end view of'the appartus shown in Figures 12 and 13.

As a foreword, I propose to transmit power from a source to the drum of a bituminous mixer for rotating the same through a planetary gearing arrangement. I have proposed, however, several types of control instrumentalities for op erating this planetary gearing mechanism. Accordingly, Figures 1 to 6 inclusive are devoted 'to the preferred form of power take-off unit embodying the planetary gear transmission mechanism and the control instrumentalities therefor. Figures 7 and 8 disclose the modified form of control instrumentalities for the power take-off iing slightly diiferent ends than that advanced for the disclosures of the other figures. Figure 10 is devoted, to a brake control that may be adapted to use on any one of the power take-offs shown.

Referring specifically now to Figures 1 .to 6, I

have shown in Figure 1 one type of apparatus which is especially adapted to employ my novel oeptionof stub'shafts 4 that carry the gear mem-,

power take-oil mechanism. This apparatus is known as a bituminous mixer and embodies a motor A mounted on a chassis B which supports a mixing drum 0 within which is arranged an agitator D. The drum C and agitator D are mounted on a common shaft E driven by the motor .A and supported in suitable bearings mounted on the framework in a manner which will be clearly apparent. For the purposes of explanation, the shaft E. Figure 2, may be considered as the main shaft in this power take-oil" arrangement, andupon which the various elements of the power take-off are arranged, albeit it will be understood that the shaft E may not necessarily be the main shaft of'an apparatus such as that'disclosed in Figure 1, and may be, if desired, a stub shaft with proper coupling argtalngiements' for connecting the same to a drive This power take-off arrangement mounted on the shaft E embodies a planetary gear system wherein the arresting of rotation of one part will cause the rotation of a driven part in one direction and wherein a movement of the driven.

part in a reverse direction is also obtained whilst the main shaft continues to rotate in one directiononly.

The arrangement which I preferably employ includes a circular gear carryingmember I mounted on the shaft E and freely rotatable with respect thereto. Endwise movement of this member off the shaft is prevented by a washer 2 retained in position by a cotter-key or equivalent v.means. The radial'face of the member I is provided with'a series of drilled bosses 3' for the rebers 5: The arrangement and number of these gears is optional and they may be placed at 180" as disclosed inr'l 'ignreior at the latter arrangement embodying three of the members. The member I is .iurther formed with a peripheral flangeTupon-which are mounted in side by side relationithe'friction band members I and 8 respectively, to be hereinafter mentioned. The peripheral flange 65in this embodiment, extends inwardly and overlies a circular driven'member 8 having gear teeth I 0 cut on the underside of the peripheral flange 60, said teeth meshing with the planetary gears 5 The flange 68 on the left side of the web ofiers a braking surface encompassed by band 6!. The member 9 is keyed to the sleeve ll of the driven member 12 by virtue of the key M, the sleeve being in turn mounted on roller bearings l5 spacing the same on the shaft. The member I2 is disc-like in configuration and is intended to be bolted by a bolt and nut arrangement at It to some device to be driven, say for instance, the drum C of the bituminous mixer.

To support the power unit, I have provided a bracket member N which may be secured to some part of the frame of the mixer or to any convenient .support if the device is not employed with a mixer, and which encomposses the sleeve ii in the zone 20. The planetary gears 5 areeach in mesh with a main shaft gear 2! keyed on the shaft E which constitutes the driving gear for rotating the planetary gears and the other parts of the apparatus.

The controls for the friction band members land 8 are best shown in Figures 2 to 5 inclusive, and it is to be pointed out that the controls for the band I are separate and independent from the controls for the band 8 albeit the controls for the band I are effective to operate the control for the band 8 for a particular purpose to be hereinafter brought out. Accordingly, with reference to Figs. 2'and 3, the control members for the band I include a lever 22 pivoted as at 23 on a support member 24 which takes the configuration shown in Figure 6 and which is drilled in its lower flange is pivotally connected as at 26 to the looped end 21 of the band 1 whereas the opposing looped end 28 of this same band is connected by a pin 29 to the upper end of the'support 24. It will be obvious that by moving "the long arm of the lever 22 downwardly, the band will be tightened about the peripheral flange 6 to arrest the rotation thereof. v

The control instrumentalities for contracting the band 8 include a lever 30 mounted on a bracket 3|, Figure 2, formed as a part of the member 9, the said member 30 being mounted thereon by means of a pivot pin 32. The long arm of the lever 30 is provided with a long pin 30', Fig. 2, which overlies and is intended to contact with the arm 22 when the same is in a substantially horizontal position as shown in Fig. 3. The short .arm of the lever 38 is connected by a pin 33 to the looped end 34 of the band 8. The opposing end of the band 8 is connected by a pin 35 to the bracket member 3|. Obviously by moving the long arm of the lever 30 upwardly the band 8 is caused to contract and grip .the peripheral I flange 6. v

A drilled boss 20' onthe support I9'receives a pin 84 which pivotally supports an-operating handle 63 for the brake band 65, Figure 10. The

handle is in the form of a bell crankand the drum in the position of Figure '1,' namely, theloading position or the position which it occupies during the mixing period. Let it be pointed out that'the relative positions of the parts of the power take-oif controls, particularly the small lever 30, isas shown therein, with this lever lying in the upper right quadrant of the circle. Whenthe lever 22 is pressed downwardly totighten the band I, the rotation of the disc I is stopped and the planetary gears 5 are compelled to rotate about-their axes in a counter-clockwise direction, assuming that the main gear 2| is rotating in a clockwise direction. As a result, the member 9 Figure 2, will be rotated in a counter-clockwise direction, thus moving the small lever 30 to the left as well as the mixing drum, and the lever 22 is held down until the drum reaches proper discharge position. At this time the lever 30 should be in the vicinity of the lever 22 as shown in Figure 3 and stopping of the drum is obtained through the brake lever 63 and associated band 6i. It is of importance that the lever 30 be not tripped at this time and that it come to rest either in engagement with the lever 22 or in such position that it may be engaged and actuated by the lever 22. The drum is now in a position to empty and after the contents have been discharged therefrom, it is desirable to return the unloaded receptacle to the position shown in Figure 1, where it may be recharged for subsequent mixing operations. To so return the drum, the lever 22 is lifted upwardly by the operator after first releasing the brake, whereupon the long arm of the lever 30 is lifted and the band 8 tightened. As the band 8 tightens, the rotation of the member I is stopped and the planetary gears 5 are locked with respect to the main shaft gear 2i and the internal gear l0, Figure 2, whereupon the whole planetary gearing assembly is rotated in a clock-wise direction with the shaft E. With the parts so locked, the planetary gearing arrangement does not operate as such for transmitting motion so that it may be said that it is rendered inoperative for this phase of transmitting power. To continue, as long as the small lever 30 is under the influence of the lever 22, force will be transmitted to the drum for rotating it to loading position. This action imparts a kick to the drum and as soon .as the lever 38 is carried above the lever 22 the band 8 is released and the drum is free to rotate under its own momentum to loading position where it is stopped through the use of the braking elements disclosed. As soon as the band 8 is released, the planetary gearing mechanism is restored to idle position and is not effective to transmit power. Obviously, by this arrangement I obtain apositive application of force for moving the heavily loaded drum to discharging positiomand I control the momentum so that the drum cannot get out of hand and move past discharging position through the power take-off unit as well as the braking instrumentalities.

I propose analternate control arrangement for the power take-oif'unit of the-type shown in Figures 1 to 6, and reference may be had to Figures 7 and-8 as disclosing the arrangement.

In this showing the support 24 mounts a lever of the first class having its fulcrum in the middle on the pin 40, the lever having a short arm 4i and a long arm 42. In this instance the lever is prov vided with a bifurcated part 43 pivotally connected by a bolt member 44 to one end of the brake band I. The other end of the brake band is connected as at 45 to' the support 24. Obviously, by pulling up on the long arm of the lever,

the'brake band is contracted to grip the peripheral flange and accomplish the rotation of the mixingdrum to the left, orin a counter-clock-.

wise direction, as hereinbefore set out. A slightly different control arrangement is shown for the band 8, and the support ii of Flgure.2 which is of the lever 50 the band 8 may be tightened.

This. may be accomplished by pressing downwardly on the lever 42 which brings the short armportion 4| to engagement with the pin 53' mounted o'n'thelong arm of the lever 50. This will effect a reverse rotation of the drum in the manner described with regard to the device of Figures 1 to 6, wherein a kick is imparted to the drum for effecting the free rotation thereof to loading position.

On the other hand, by moving the handle 46 downwardly, the end of the lever 50 may be brought into engagement with the lever 4|, Figure 7, and as pressure is further placed on the handle 46 the lever 50 will pivot on the pin 5| and draw the ends of the band 8 together and lock the planetary gear mechanism for clockwise rotation with the main shaft. Hence, the drum may be kicked in a clockwise direction by operation of either handle 46 or lever '42. The brake of Figure 10 may be incorporated. with the assembly and operated in the manner and for the purposes set out with respect to the assembly of Figures 1.to 6.

I have shown in Figure 9 a planetary gearing .assembly that is essentially the same as that shown in Figure 2 except that it does not incorporate the braking arrangement of Figure 10. It is my intention to mount the brake directly upon the peripheral flange of the member 9 that overlies the gear III. In other words, the planetary gearing assembly shown in Figure 9 is intended for a one direction drive, and all of the braking. Accordingly, the elements of the power take-offshown herein .will. be identified by numeral only since they have already been described in the description of Figures 1 to 6. The control instrumentalities for operating this power unit are of two kinds, one form being shown in Figure 11 and another form being shown in Figures 13 and 14. These control apparatus have one feature in common and that is that only a single lever is employed for both clutch and braking operations. In the disclosure of Figure 11 the operation of the brake and clutch is entirely manual, whereas in Figures 13 and 14 the operation of the clutch and brake may be made inciband, and the operation of these bands is ob- I tained through a single'lever .14, Figure 11, that is pivotally mounted upon a support 13 that is similar in construction to the support 24 shown in Figure 6 and ispossessed of the necessary apertures (not shown) for bolting the same to the frame of the machine as disclosed in Figure 1. This bracketis preferably s-shaped and in theupper zone is provided with two inclined ears that receive pins I1 and I8 respectively,the pin ll retaining the looped end of the band 8a and the pin [9 retaining ,the looped end of the band la. The lever '54 which is pivoted at 15 has a short arm portion which is preferably bifurcated and mounts a long pin 16 which receives the other looped ends of the bands Ea and 81:. With this arrangement, when the lever 14 is moved downwardly in the direction of the arrow, the

band 8-1 is contracted, whereas the band la is loading position. The brake 8a may be applied v to stop the drum and hold it in proper unload-- ing position. The drum may then be returned to loading position manually, or, in the event the nature of the mixing apparatus will allow the complete rotation of the drum, power may be again applied through the planetary gear mechanism to rotate the drum. through the remainder of the 360 back to loading position. The small a spring shown at 16a is merely for the purpose of holding the lever 14 in a horizontal or inoperative position.

Referring now to Figures 12 to 14 inclusive, I have shown therein a contr-cl arrangement for the planetary gearing assembly of Figure 9 which preserves the thought of single lever operation for both clutch and brake and has the additional feature of being operated by the drum of the mixer. The support member for this arrangement differs slightly over that of previous arrangements and consists in a member 88 which is to be mounted on the frame of the mixing machine and which has an angularly disposed extension 8! drilled at its end for the reception of a pin 82. The pin 82 mounts the operating member 83, the long arm of which is curved as shown in the illustration in the direction of its length and also in the direction of its width to provide an offset end 84 lying in the vicinity of the mixing drum, see Figure 14. Tins operating end of the handle is intended to be engaged by an abutment member 85 that is formed as a part of the mixing drum and projects outwardly from the radial face 86 thereof as shown. The funclever 88 is pivotally secured to a plate member 98 which forms one element ofan assembly generally indicated by the reference character N, mounted upon .a pin 8| that is in turn mounted upon the support 88 and secured thereto by a nut 92. Now this assembly N includes a second plate 93 which is drilled to receive inspaced relation three rods, 84, 85, and 80. the opposite ends of which are located in the plate 88. This assembly N is intended to rock about the member 8|,

which defines the axis oi rotation, under the urging of the lever 83.- The toggle lever 88 is connected to the assembly through engagement with the rod 85 which is extended beyond the plate 80. The rod 88 also acts as an anchor for one end of a contraction spring 91 and is connected at its other end to the pin 82.

In connecting the bands to this assembly, the connecting rod 88 is sleeved on the rod 86 and attached by means of a nut to one end of the band 8a. The other end of this band is anchored on the center-pin 8|. Likewise, a connecting rod 99' is bolted to one end of the band 1a and connected to the rod 88 at its other end and the other end of this band la is mounted on the a center pin 9!.

With reference to Figure 12, it will be observed that the spring 91 is intended to lie in a straight line position between the pin 82 and the rod 95 so as to bias the toggle toward collapsed position on either side of a centerline drawn between the pin 82 and rod 95. The spring will act to collapse the toggle on either side of its "on-center position.

As for the operation, assuming that-the mixing drum is in the position shown in Figure l, in readiness to be moved to the left for unloading, the lever as, which is preferably in the full line position shown in Figure 12, is moved upwardly to the upper dotted line position which flattens the toggle arrangement and shifts the plate assembly to the lower dotted. line position shown, thustightening the clutch hand .la and stopping the rotation of the gear carrier 5 to efi'ect the rotation of the driven part 9 and the drum in a counter=c1ockwise direction. In fact, when the lever 83 is thrown to its upper dotted line positien, the toggle is moved to the left of its center and the spring is effective to retain the toggle in such position to continue the operation of the planetary gearing assembly. Rotation of the drum to the left eventually brings the abutment member 85 into engagement with the operatingend 84 of the lever 83, whereupon the end of the lever is sw-ung downwardly until such time as the toggle is shifted to the right and beyond the center-line between the pins 82 and 95. when the toggle passes over dead-center, the spring is immediately effective to initial- 1; set the brake since it tends to collapse the" teggle and move the plate assembly toward the upper dotted line position of Figure 12. Continned, rotation of the drum, which may arise from the momentum imparted during the positive rotation, mcves the lever 83 to its lower dotted line position, which sets the brake and brings the drum to a stop at the proper position for unloading. .The proper drum position for unloading may vary with mixers of varying type, and hence, the positional relation between the In returning the drum to leading position,

abutment/85 and the lever 83 should. best be determined in actual practice.

it may be first started manually by lifting up on the operating end of the lever 83 which rethe brake and apply the clutch to rotate the drum through the remainder of the 360 to loading position. I

I have described this power take-off unit in the environment of a bitumlnousmixer. before mentioned, these mixers embody a min driven shaft-for the agitator and the drum axis of rotation is the same as that of the shaft. However, in some constructions the drum is supported directly by the heavy framework and the shaft bearings are relieved of the weight of the ber.

drum. The main point to make is that the drum and shaft are independently rotatable, except when coupled through the mechanism herein disclosed.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States, is-

1. In combination with a mixing apparatus of the class described, which includes a frame, a mixing drum mounted on said frame, a driven shaft lying on the axis of rotation of said mixing drum,a prime mover mounted on said frame for rotating said shaft, a power take-off means for coupling said shaft to said drum for selective rotation of said drum, said power take-off including a-gear carrier mounted on said shaft and freely rotatable with relation thereto, a plurality of planetary gears mounted on saidgear carrier, a gear mounted on said main shaft and meshing with said planetary gears, a driven member mounted on said shaft and having a geardriven member, said driven member being keyed thereto, a radial part on said sleeve member, instrumentalities for connecting said radial part to said drum, a support for said sleeve encompassing said sleeve between the radial part and the driven member, and a pair of friction bands, one of which is mounted on said driven member and the other of which is mounted upon said gear carrier, and operating instrumentalities therefor, said first named friction band being effective to hold the said drum against rotation, said second named friction band being effective to hold said gear carrier against rotation and effect the drive of said drum through said planetary gearing, driven member and sleeve mem- 2. In a'mixing apparatus of the class described, a rotatable mixing drum, and means for rotating said drum, comprising a multi-part planetary gear mechanism includingv means for locking the parts of the gear mechanism against relative movement, said last named means coniprising a.fric'tion band mounted on and carried Mom of said parts and releasably connected to another of said parts, control instrumentalities for said friction band, a second friction band for controlling the operation of the planetary gear mechanism, control instrumentalities for said second named friction band, the control instrumentalities of said first named friction band being movable into and out of a position for engagement with the control instrumentalities of the second named friction band.

3. In combination with a rotatable mixing drum, means for rotating said drum, including a driven part, and means for releasably connecting said driven part to said drum, said means including a. friction band coupled for rotation with said'drum and adapted to be contracted about said driven part for rotation therewith, actuating instrumentalities for contracting said friction band, and means for operating said actuating instrumentalities, said actuating instrumentalities being movable into a position for en'- gagement with said last named means and separable therefrom when actuated thereby, said arrangement being of such a nature that when the friction band is contracted about said driven part the drum is connected for rotation in one direction and upon separation of the actuating inof said drum.

strumentalities and the means for operating the same, the friction band is released and the drum is free to rotate under its own momentum.

4. In combination with a rotatable mixing drum and means for rotating said mixing drum, a control for'said means which comprises a pair of friction bands, one of which is rotatable with respect to the other, operating instrumentalities for each control band, said operating instrumentalities including a pair of pivoted levers, one of said pivoted levers being associated with the movable band and being movable into and out of a position for engaging with the other lever,

said arrangement being of such a nature that the movable band is actuated by the other of said levers through engagement with the lever of the movable band and movement of said movable band effects disengagement of said levers.

5. In a mixing apparatus of the class described which includes a rotatable mixing drum, a driven shaft and a prime mover for rotating said shaft, means for coupling said drum to said shaft for effecting the rotation of said drum which comprises a multi-part planetary gear mechanism, one of said parts being rotatable relative to an other of said parts, means for locking said parts together for simultaneous rotation, said means comprising a friction band supported by one of said parts and adapted to be contracted about the other of said parts and to rotate therewith, a second friction band encompassing one of said parts and adapted to be contracted therearound, actuating instrumentalities for each of said bands, the actuating instrumentalities of the coupling band being movable therewith and toward and away from the other actuating instrumentalities, said first named actuating instrumentalities being operated by said second named actuating instrumentalities and separable upon actuation, whereby said mixing drum may be connected for rotation in one direction.

6. In combination with a rotatable mixing drum,'means for rotating said drum, including a driven part, and means for releasably connecting said driven part to said drum, said means including a friction band coupled for rotation with said drum and adapted to be contracted about said driven part for rotation therewith, actuating instrumentalities for contracting said friction band, and means for operating said actuating instrumentalities, said actuating instrumentalities being movable into a position for engagement with said last named means and separable therefrom when actuated thereby, said arrangement being of such a nature that when the friction band is contracted about said driven .the same, the friction band is released and the drum is free to rotate under its own momentum, and a friction brake for controlling the rotation ,7. In a mixing apparatus, a mixing drum, a

. driven shaft, means for coupling and uncoupling nism for coupling and uncoupling said shaft to said drum, a brake associated with said planetary gear mechanism for controlling the momentum'of said drum, and a single lever for controlhug the operation of the planetary gear mechanism and said brake, said lever being operable by the-rotation of the drum.

9. In a mixing apparatus, the combination with a rotatable mixing drum and a driven shaft, means for connecting said drum to said shaft, control instrumentalities for said means ihclud=- ing ajfriction band and a lever for operating said band, a brake for arresting rotation of said drum, including a friction band, instrumentalities for connecting said last named friction band to said lever, and means on said drum for engaging said lever to move the same to operate said friction bands incident to rotation of said drum.

10. A mixing apparatus which includes a rotatablemixing'drum having a charging opening and wherein the drum is movable from one position to another to bring the charging opening to a position wherein the contents of the drum may be discharged, a driven shaft, means for coupling said shaft to said drum for moving the same to bring the opening therein into positions for-charging and unloading, an abutment on said drum, control instrumentalities for operating said means, including a lever adapted to be engaged by said abutment, a brake associated with said means, instrumentaiities connecting said brake to said lever, said arrangement being of such a nature that as the dnm is rotated to bring the charging opening into a position for emptying, the lever is engaged by the abutment and actuated thereby to render the means inoperative for coupling the drum to the driven shaft and for applying the brake.

11. In apparatus of the class described, a rotatable mixing drum, means for rotating said drum in one direction, and means for imparting momentum to said drum effecting rotation of the drum in the opposite direction, said last mentioned means automatically becoming inoperative after imparting a momentary initial pos-v itive rotation to said drum, but allowing said" latter rotation to continue after the momentum imparting means aforesaid has become inoperative.

12. In a power take-ofl unit, a drive shaft, a gear fixed thereto for rotation therewith, a driven member freely rotatable on and wholly supported by said drive shaft and having an internal ring gear concentrically disposed about the gear on'the drive shaft but in spaced relation to said latter gear, a planetary gear-carry.- ing member also freely rotatable on said drive shaft, planetary gears carried thereby and disposed intermediate the ring gear of the driven member and the fixed gear on the drive shaft and tating the drivenv member in one direction through said gear on the drive shaft, said planetary gears, and said ring gear; said driven member being provided-with a radially extending arm, in combination with additional brake means operatively associated with said planetary gearcarrying member, and'instrumentalities carried by said radially extending arm for controlling said latter brake to efiect rotation of the driven member in the opposite direction.

ERICK 1-1. momma. v

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