US2729435A

US2729435A - Transit concrete mixer

Info

Publication number: US2729435A
Application number: US327092A
Authority: US
Inventors: Henry C Harbers; Edward D Sharpe
Original assignee: COOK BROS EQUIPMENT CO
Current assignee: COOK BROS EQUIPMENT Co
Priority date: 1952-12-20
Filing date: 1952-12-20
Publication date: 1956-01-03
Anticipated expiration: 1973-01-03

Description

1955 H. c. HARBERS ET AL 2,729,435

TRANSIT CONCRETE MIXER Filed Decv 20, 1952 SSheets-Sheet 1 Have) C. H4255es,

0144420 D. .SHAQPE,

INVENTORS ATTORNE).

1956 H. c. HARBERS ET AL 2,729,435

TRANSIT CONCRETE MIXER Filed Dec. 20, 1952 3 Sheets-Sheet 2 OOOOOO HENQY C. 132125525, DWAQD D. HA/QPE, i.) E

IN V EN TORS.

14 TTOQNE Y.

fi H. c. HARBERS ET AL wzww TRANSIT CQNCRETE MIXER Filed Dec. 20, 1952 3 Sheets-Sheet 3 fNvExv'roes; LEA/E) C. .IJA-QBERS,

$8 DWAQO D. SHAQPE,

Arrow/vs).

United States PatentO TRANSIT CONCRETE MIXER Henry C. Harbers, Pasadena, and Edward D. Sharpe,

South Pasadena, Calif., assignors to Cook Bros. Equip- ;nent C0., Los Angeles, Calif., a corporation of Caliornra Application December 20, 1952, Serial No. 327,092 14 Claims. (Cl. 259172) This invention relates to transit concrete mixers of the type in which a mixing drum is supported on the rear end of a motor truck and driven in one direction for charging and mixing concrete therein, and in the reverse direction for discharging the concrete therefrom.

In such mixers it is highly desirable to drive the drum in either direction through a mechanical mechanism connected to the forward end of the truck engine shaft, since such mechanism not only delivers the requisite horsepower to the drum for driving it tomeet all conditions of charging, mixing and discharging, but it also enables the drum to be driven whether the truck ismoving or at a standstill, thereby providing the particular advantage of discharging concrete from the drum at thejob either continuously or intermittently, without regard to truck movement which is of great value in curb and gutter work.

Such a mechanical drum driving mechanism would have long since gone into general use were it not for the fact that due to the remoteness of the drum in respect to the front end of the truck engine shaft, the mechanism must of necessity consist of many parts which present mechanical difliculties, and, hence, is prohibitively expensive to construct and maintain.

It is, of course, possible to employ a hydraulic mechanism in place of the mechanical mechanism and to actuate the former from the forward end of the engine shaft. However, because of the high pressures required in a hydraulic mechanism to drive the drum for all conditions of charging, mixing and discharging, such a mechanism becomes impractical due to the large fluid supply required to be carried on the truck, the large and expensive motor and pump necessary, and the detrimental temperatures to which the fluid becomes heated because of the high fluid pressures necessary to the drums operation.

When a mechanical or hydraulic mechanism of the above described type is employed, that further important advantage is attained of effecting continuous rotation of the drum during transit of the mixerv to a job. In the conventional drum driving mechanism where the power is taken off of the gear transmission, each time the clutch is disengaged and the transmission moved into neutral incident to stopping forward travel of the truck, or when changing gears for different driving speeds, fl1e force exerted by the weight of the concrete resting on the blades at the rising side of the drum, operates to rotate the drum in the reverse direction. Thus when the transmission is again put into gear and the clutch released, sudden stresses 2,729,435 Patented Jan. 3, 1956 lic mechanisms to drivingly connect it alone to the drum,

all depending upon the drum driving requirements at any particular time. Thus the driving means of this inven: tion provides the advantages of both a hydraulic mechanism and a mechanical mechanism, and the disadvantages of neither.

It is also a purpose of this invention to provide in conjunction with the hydraulic mechanism, a mechanism for raising and lowering the discharge chute of the mixer to eliminate manual actuation thereof.

A further purpose of this invention is to provide in association with the hydraulic mechanism, an actuating mechanism for a gate to close and open the discharge end of the drum according as the latter is rotated in a charging and mixing direction, or in a discharging direction.

Only one form of transit concrete mixer will be described herein, and the novel features thereof pointed out in claims.

In the accompanying drawings:

Fig. l is a view showing in side elevation a transit concrete mixer having applied thereto one form of drum driving means, and gate and chute actuating means embodying this invention. I

Fig. 2'is a top plan view of the mixer chassis with the drum driving means, chute actuating means, and gate actuating means applied thereto.

Fig. 3 is an enlarged fragmentary perspective view showing the interlocking means for the control levers of the invention.

Fig. 4 is an enlarged plan sectional view of the control levers and interlocking means therefor.

Fig. 5 is a perspective view showing the invention schematically as applied to those parts of the mixer necessary to its operation. V

Fig. '6 is an enlarged view showing the control valve units of the invention in horizontal section.

Fig. 7 is a sectional view taken on the line 7--7 of Fig. 6.

Having specific reference to the drawings, the truck mixer shown in Figs. 1 and 2 is conventional in that the rear wheels 15 are driven from the engine 16 located at the forward end of the truck, through a clutch 17 operatively connecting the rear end of the engine shaft to a transmission 18 of the gear type selectively operable by lever 19 to drive a shaft 20 which extends rearwardly and is operatively connected to the rear wheels through a difierential 21.

Supported on the rear end of the truck frame for rotation about an inclined axis, is a mixing drum 22 having an open upper rear end through which the drum is adapted to be charged with concrete, mixed or unmixed, from a hopper 23 supported on a frame 24 fixed on the truck frame. The drum 22 is provided interiorly with spiral blades 25 shown in broken lines in Fig. 1, and under rotation of the drum in one direction these blades operate to feed the concrete inwardly from the open end of the drum as it is fed thereto by the hopper 23, and also to agitate the concrete and prevent setting thereof during transit of the truck to a job. When the drum is rotated in the other direction the concrete is discharged from the rear end of the drum into a chute 26. To prevent accidental discharge of concrete from the drum during transit of the truck to a job, its rear end is partly closed bya gate 27 which isadapted to beopened to permit concrete to be discharged from the drum.

This invention consists in the main of two driving mechanisms for the drum 22, one'a hydraulic mechanism, and the other a mechanical'mechanism, and both of which are actuated by the engine 16. The hydraulic mechanism comprises a rotary pump 28 driven from afront end extension 29; of the engine shaft, through a chain and sprocket connection 30. Fluid is supplied to the pump 28 by a'feed line'31 connectedto a fluidsupply tank '32, and fluid under pressure is discharged from the pump through a pressure line 33 which extends'rearwardiy of the truck to a valve unit 34. As will be described later herein,'the valve unit 34 is connected to a second valve unit 35, and the latteris'connected to the tank32 through a'return line 36.

The valve unit 35 directionally controls the circulation of pressure fiuid from the pump 28 to'and from a fiuid motor 37 through lines '38 and 39. The motor 37 is of the conventional rotary gear type, and one gear thereof is fixed to a shaft 40 for driving 'the latter. 'From this shaft 40 motion is transmitted to a transverse shaft 41 through suitable gearing 42', and theshaft 41,in'turn, is operatively connected to athird shaft 43 through suitablegearing 44'. The shaft 43-is operatively connected to the forwardend of the'drum 22 through a chain and sprocket -connection'45. These several elements, notincluding the motor 37, constitute a drum rotating mechanism which is adapted to be driven either by the motor or the mechanical mechanism of this invention tobe later described herein, and, hence, such rotating mechanism is common to both the hydraulic mechanism and the mechanical mechanism.

The valve unit 34 is provided for thepurpose of controlling the supply ofpressure fluid to a conventional ram 46 comprising acylinder 47 and a piston 48, the fluid being delivered and returned from the cylinder at either sideof the piston by

pipes

49 and 50. As shown in- Fig. 1, one end of the cylinder 47 is mounted on the rear end of the truck by a swivel connection 51-so that it 'can be moved verticallyand-horizontally the rod 48a of the piston 48 pivotally-connectedas at 52 to the chute. The chute 26:is.swivelly mounted'on the rear end of the truck,.as.-indicated at 26a, sothat it can-be adjusted horizontally as well as vertically to discharge concrete to any point desired within the-range ofadjustment provided'by the swivel mounting.

Thevalve unit 34 comprises a valvehousing 53 in the longitudinal bore 53a of which is a spool valve 54 movable .axially by a lever 55 to occupy a neutral position and either of two extreme positions. As best shown in Fig. 6, the housing 53 is provided with aninlet port '55a to which connects the pressure line 33 to the bore 53a. The. housing.5 3 is also providedwith two passageways 56 at one side of the bore 53a, and a third passageway 57 at; the,other sideofthe bore. At the same side of the bore as the passageway 57 are two upwardly extending passageways 58 and 58a connected respectively to the

lines

49 and 50.

The valve unit 35 likewise comprises a housing 59 in the. longitudinal bore 59a of which is a spool valve 60 operable by a lever 61 to occupy a neutral position and either of two extreme positions. This housing 59 is provided with a passageway 62 which, through a port 63 is connected to the passageway 57 of the unit 34, At the other side of the bore 59a a pair of upwardly extending

passageways

64 and 64a are provided and positioned upon opposite side of a horizontal passageway 65. Througha port 66 this passageway is placed in communication with the return line 36. The

passageways

64 and 64a lead from the bore 59a to the lines 38. and 39, respectively, in order that fluid can be supplied .to the motor'37 in either direction from the pressure line.33 under the control, of course, of the valve 60, and .returned to the tank 32 through the line 36.

Included in thehydraulic mechanism is a fluid-means for opening and closing the gate 27, that comprises a ram 67 which, as shown in Figs. 1 and 5, has the piston rod 67a thereof operatively connected to an arm 68 pivoted as at 69 on the frame 24, and secured to the gate 27 so that according as the piston is moved upwardly or downwardly the gate will beclosed or opened. Pressure fluid is supplied to and returned from the ram 67 by lines 70 and 70:: connected respectively to the

lines

38 and 39 so that depending upon the direction of fluid supply to the pump 37 the gate will be opened or closed, as will be more fully described hereinafter.

As will be seen in Figs. 1 and 2, the

valve units

34 and 35 are situated at the rear end of the truck in order that the operator, while standing in an observing position at the rear of the truck, can, through the

levers

55 and 61, manipulate the valves 54 and 60 to control thedelivery of pressure fluid from the pump 28 to the motor 37' andthe ram 46 particularly to eliect discharge of concrete from the drum at the job, and to adjust the chute 26 vertically to discharge the concrete at any desired elevation.

As an additional actuating means for the valve 60, a second control lever 71 is situated in the cab of the truclnpivoted as at 72, and operatively connected to the lever 61 by rods 73 and 74 and a bell-crank lever 75. This lever 71 enables the driver of the truck, while seated in the cab, to operate the valve 60, while in position to operate the lever 19 and the clutch 17 to effect forward movement of the truck as and when necessary.

The mechanical drum driving mechanism of this invention comprises a conventional power take-otf unit generally indicated at 76, and having the drive gears 77 thereof (see Fig. 5) operated by the driving gears of the transmission 18, and driven gears 78 splined on the forward end of the shaft '49. The gears 78 are, by a lever 79 pivoted as at 80, shiftable from a neutral position to a forward position in which the shaft 40 drives the drum 22 through theintermediate mechanism, in a direction for charging the drum with concrete and mixing thereof. The lever 70 is also movable to a reverse position in which the shaft 40 is reversely driven to drive the drum '22 in the other direction to discharge concrete therefrom.

Since the shaft 40 can be driven in either direction by the unit 76 or the motor 37, it is necessary to provide some means which will prevent the unit from being connected to the shaft to drive it in a direction opposed to the direction in which it is being driven by the motor. For this purpose a latch is provided comprising a stationary keeper 81'f ormed on a plate 82, and a U-shaped latch member 83 pivoted as at 84 on the lever 79so as to be movable from the position shown in Fig.3 to that shown in Fig. 4. In the Fig. 3 position the member 83 engages the keeper81 to lock the lever 79 against movementin either direction'from a neutral position. In the position shown in Fig. 4 the member 83 locks the

levers

79 and 71 to each other so that .movement of either lever effects corresponding movement of the other lever. It will, of course, be understood that both levers must be in neutral position before the latch member can be moved to the lever interlocking position shown in Fig. 4. While the

levers

71 and 79 are shown in Fig. 5 ashaving separate pivots 72 and 80, in practice'they have a common pivot in the form of a pin 85 with its ends fixed inthe plate 82 and a second plate 86, as-shown in Figs. 3 and 4.

The operation of the invention is as follows:

To charge the drum with concrete from a source situated above thehopper 23, it is first necessary to set the druminto rotation in a forward direction, that is, counterclockwise as when viewedin Fig. 5, so that theconcreteisjfedforwardly in the drum under the action of the blades 25. During this charging operation the concrete fiows into the rear end of the drum at a point above the gate 27, it being understood that the gate is mater closed during this operation. If the concrete is premixed then it is only necessary to drive the drum at a relatively low speed, and to do so the hydraulic mecl1anism alone provides the necessary power for the purpose.

Normally the two valves 54 and 60 occupy the neutral positions shown in Fig. 6 so that fluid from the pressure line 33 is free to circulate through" the valves and their housings 53 and 59 back to the tank 32. In the neutral position of the valve 54 the passageways 58 are closed to block fluid in the ram cylinder 47. To set the motor 37 into operation for driving the drum 22 in the direction required for charging, the valve 60 is moved to an extreme position in which pressure fluid from the bore 59a can pass through that passageway 64 into the line 39, fluid from the discharge side of the motor returning to the line 36 through the line 38, passageway 64a, bore 59a, and passageway 65; t

The

lever

61 and 71 being interconnected as described, the valve 60 can be moved to the aforesaid'extreme position by either lever, but the latch member" 83 must be first swung clear of the lever 71 to the position shown in Fig. 3. In this position of the latch member the lever 79 is locked in neutral position so that it cannot be accidentally moved to set the mechanical mechanism into operation in opposition to the motor 37.

With pressure fluid circulating through the motor 37 in the direction above described such fluid is also supplied to the ram 67 and in such direction as to maintain the gate 27 in closed position.

If the drum is being charged with concrete that has not been premixed, the drum must be rotated at a greater speed to effect proper mixing thereof, thus requiring greater power than can be developed by the hydraulic mechanism alone. Therefore, to drive theldrum as required, the mechanical mechanism is now employed to assist the hydraulic mechanism. The mechanical mechanism can be set into operation by first restoring the lever 71 to neutral position whereupon, the latch member 83 is swung to the position shown in Fig. 4 so as to interlock the

levers

71 and 79. By now moving either lever forwardly the two levers are moved together, the lever 71 moving the valve 60 to the aforedescribed position for circulating pressure fluid through the motor 37 to rotate the drum in a forward direction, and the lever 79 shifting the power take-off unit 76 to drive the shaft 40 in the same direction as driven by' themotor; Accordingly, mechanical and hydraulic mechanisms are coupled one to the other to drive the drum at the required speed for thorough mixing of the unmixed concrete with which the drum is being charged.

Once the drum has been charged with pro-mixed concrete or unmixed concrete and the latter thoroughly mixed in the drum, the truck is ready to travel to the job, butsince during such travel it is only necessary to drive the drum at a relatively low speed so as to keep the concrete therein agitated to prevent setting thereof, the mechanical mechanism may be disconnected from the shaft 40 and only the hydraulic mechanism maintained in operation. To accomplish this the

levers

71 and 79 are first restored to neutral position whereupon, the latch member 83 is swung to the position shown in Fig. 3 to lock the lever 79 in neutral position and free the lever 71 for independent operation. The lever 71 is now moved to actuate the valve 60 so as toset the motor the case in most instances, it can be accomplished by the hydraulic mechanism alone. To do this the. lever 61 is actuated by the operator while standing at the rear end of the truck in a position to move the chute 26 iQfllC desired horizontal position, and to also actuate the lever for lowering and elevating thechute to position the V .6 discharge end thereof at the required elevation for a particularjob. 1 1 'I- Actuation of the lever-61 is such as' to move the valve 60 to the other extreme position wherein pressure fluid from the bore 59a can pass to the passageway64a and from the latter to line 38 to drive the motor-'37 in the opposite direction to that previously driven so as to drive the drum in a reverse direction and discharge concrete therefrom into the chute. It will be understood that the fluid as discharged from the motor is returned to'the tank 32 through line 39, passageway 64, bore 59a, passageway 65, port 66, and line 36.

To permit concrete discharge from the drum, the gate 27, of course, has to be opened, and this is eflected automatically" and simultaneously' With driving of the motor 37, since part of the pressure fluid flowing to the motor 37 passes into the line 70 and thence to the cylinder 47 at the top side of the piston 48.

.To operate the ram 46 for adjusting the chute 26 vertically, the valve 54 is moved by the lever 55 from neutral position to one extreme position or'the other, depending upon whether it is desired to raiseor lower the chute. To raise the chute the valve 54 is moved to that extreme position necessary to place the passageway 58 in communication with the bore 53a so that pressure fluid from the bore will flow to the lower end of the ram cylinder 47 through the line 49. Fluid from the upper end of the cylinder 47 is returned by the line 50 to the passageway 58a and finally to the return line 36 through the valve unit 35 as will be obvious from a consideration of Fig. 6. Manifestly, movement of the valve 54 to the other extrerne position eifects circulation of the fluid in the opposite direction to that effected for raising the chute, and thus the ram 46 is made operable to lower the chute.

It is important to note that the construction of the valves 54 and 60, middle arrangement of ports and passageways in the housings 53 and 59 are such that irrespective of the position of the valve 54, fluid can pass to the housing 59 for operation of the motor 37 in either direc tion as controlled by adjustment of the valve 60.

From the foregoing operation of the hydraulic mechanism to rotate the drum 22 for concrete discharge, it will be apparent that such discharge is possible irrespective of whether the truck is moving or at a standstill, since the pump 28 is at all times driven by the engine 16. This is of great advantage in pouring concrete for curb and gutter work.

If a job requires a rapid'rate of concrete pouring, naturally the rotational speed of the drum must be increased beyond that possible by the hydraulic mechanism. Therefore, it is necessary to resort to the mechanical mechanism to assist the hydraulic mechanism to that end. 'Accordingly, .the power take-off unit 76 is now drivingly connected to the shaft 40 by first restoring the lever 71 to neutral position to discontinue operation of the motor 37 and allow interlocking of the lever with the lever 79,

so that when the lever 79 is moved to reverse position to effect reverse driving of the drum, the lever 71 will likewise be moved to reverse position causing the motor 37 to be driven by the-pressure fluid in the same direction as the unit 76 drives the shaft 40. This insures the two mechanisms driving the shaft 40 in the same direction, and thus prevents the two mechanisms opposing each other and mutilating the gears and other parts of the mechanisms.

Although only one form of transit concrete mixer is shown and described herein, it is to be understood that various changes and modifications of the mechanical drum driving means and the hydraulic drum driving means as well as the controls therefor, may be made herein without departing from the spirit of the invention and the spirit and scope of the appended claims.

What is claimed is: a 1. In a transit concrete mixer: a truck; an engine for propelling the truck; a transmission mechanism; a drum rotatably mounted on the truck; mechanical means con- .nected loathe-transmission mechanism; thydraulic means connected to the-forwardend-of-the engine shaft; afirst controltmeans for the mechanical meansselectively operable-to connect thelatter tothe drumcto drive .the same in either direction; a second control means .for the hydraulic means selectively operable toconnect the latter to thedrum to drive thesame in either direction; 'and a means movable toone positionin which it interlocks'the two control means toeach other for simultaneous operation, and another position in whichthe first control means vis-locked'againstoperation-and the second control means released for-operation.

2.- In a transit concrete mixer: .a truck; 'an engine-for propelling the truck; a transmission mechanism; a-drum rotatably mounted -on .the-rtruck; mechanical means connected to the transmission mechanism and including a snafu-hydraulic means connected to the shaft of said engine and including a motor; "a first control means for the mechanical means selectively operable to connect the latter to the drum to drive the same in either direction; a second control means for the hydraulic means selectively operable to connect the motor to the drum to drive the same in either direction; and a latching device manuallytmovable to one position in-which it interlocks the two control means with each other for simultaneous operation to causethe mechanical means to assist the hydraulic means in driving said drum, and anotherposition in which the first control means is locked-against operation and the second control means released for operation.

3. In a transit concrete mixer: a truckyan engine for propelling the truck; a selective transmission for drivingly able to drive said mechanism ineither direction; hydraulic means permanently connected to the shaft of said engine and including a motor drivingly connected to said mechanism, and a valve selectively operable to cause the motor to drive said mechanism in either direction; and means so controlling actuation of the valve and said unit that both of said means can be connected to said mechanism -to drive the latter simultaneously in one direction orthe other.

4. Means for driving the drum of. a transit' concrete .mixer fr'omthe truck engine, including: a selective power 'takc-oif unit; a hydraulic pump adapted to be constantly driven by said engine; a hydraulic motor selectively driven in either direction by said pump; mechanism operatively connecting the drum-to said motor and "said unit; a first means controlling directional operation of said'motor; a

second means controlling directional operation of said unit; and athird means'for so controlling operation of the first-and second means that said-unit andsaid motor can be caused to drive said.mechanismsimultaneously in one direction or the other, or the motor alone in'either direc tion.

5. in a transitmixer: a truck; an 'engine;:: drum rotatably mounted on the truck and having an open rear end; a. gate'for'closing said end; a hydraulic system in- -cluding asourceof fluid, aipump connected to said source and drivingly connectedto the-engine, a'motor operated by the pump and drivingly connected to the-drum, a ram for-closing and opening the gate, and a valve selectively controlling circulation of pressure fluid from the pump to the'motor and return to said source in either direction, and simultaneously-from'the pump to the ram and return to said source 'in' 'either direction, so that according as "tltedi'umis' rotated in 'onedirection or the otherby'the motorfthe ram will 'be "operated to close or open'the gate.

6. In 'a"transitmixer: a truck; an engine; a selective "transmissiomfor drivingly conneeting'the engine to the truck; a'fdrumrotatably mounted'onLthe truck and having an. open rear end; a gate'for closing said end; a chute stvivelly mounted at the, rear end of the truck; a rotating mechanism for the drum; ahydraulic circuit including a source ofifluirl, .a :purnppermanently driven by theen- .ginc, a motor operatively connected to said mechanism, a ram foractuating the gate, a second ram for raising and lowering the chute; a valve for directionally controllling the circulation of pressure fluid from the pump to themotordn eitherldirectionand itsreturn to-said source, and simultaneously .to thegaterani in either'direction and its returnto'said source,so that according as the drum .isrrotatedinone direction or the other, thegate ram will be simultaneously operated to close or open-the gate; and a second valve for controlling the circulation of pressure'fiuid from the pump to .thesecond ram in either direction and its return to said source.

7. In .a transitmixer: a truck; an engine; a selective transmission fordrivingly connecting the engine to the truck; a drumrotatably mounted on the .truckandihaving an open vrear .end; agate forclosing vsaid end; a chute swivelly mounted at the reartcndofthe truck; arotating mechanism for thedrum; .a hydraulic circuitincludinga source of fluid, a .pump permanently driven-by the en- :gine, a motoroperatively connected to said mechanism, a ram for actuating .thegate, a second ramtor raising andloweringthemhute; avalve for directionally controlling the circulation of pressure .fiuid from the pump to the motor in either-direction, and its returnto said source,

and simultaneously to the. gate ram in either direction and its return to said source, so that according as the drum is rotated-in oneadirectionor the other, the gate ram will operatettoclose or 'open-thegate; a'second'valve-for controllingthe-circulation of pressurefluid from the pumpto the second ramin either direction and'its return to said sourcepsaid valves having fluidpassagcs so-arranged relatively' that the second valvecan be actuated to raise or lower the chute without interfering with circulation of fluid toand .from the motor in either direction.

8. Means for driving the drum of a transit concrete mixer-from 'the truck engine, including: a selective power take-oft unit;-a=hydraulic pump adapted to be constantly dri-ven bysaid-engine;ahydraulic motor selectively driven tiirection,--or saidzmotor alone inteither direction.

9. -.In a transit concrete mixer: 21 truck;.an engines-for cpropelling the itruckya selective transmission for drivingly connectingdhe engine to-the .rear'wheels of ;the:.truck;?a adru'm rotatably mounted on the truck; drum rotating mechanism; :mechahicalmeans connected to said transmission and including a'p'ower take-oft unit selectively 'operable'ito' drive said mechanism-in either direction;

hydraulicmeans permanently'connected to'the shaft of saiden'gine andiincluding a motor drivingly connected to 'said mechanism, and a-valve movable from a-neutral position to'eith'er oftwo extreme positions for causing "the motor-todrive said-'mechanism-in e'ither direction; a

first lever for actuating the valve; :1 second lever-movable from'a'neutral position to either of two extreme positions for causing said unit to drive said mechanism in either direction; and a latching device having a stationary keeper and a latch member pivoted on the second lever to occupy one position in which it interlocks the two levers. for

simultaneous operation to occupy the same extreme vpositions, and another position in whichlit engages the keeper to lock" the second i levertin i neutral position, and

frees the'firstlever 'for operation.

10. In a transit mixer as embodied in claim 1, wherein the drum has an open rear end; a gate for closing said end; a hydraulic ram for closing and opening the gate; and means so interconnecting the hydraulic means, said ram, and the second control means that according as the latter is operated to connect the hydraulic means to the drum to drive the same in one direction or the other the ram will be operated to open or close the gate.

11. In a transit concrete mixer: a truck; an engine for propelling the truck; a transmission; a drum rotatably mounted on the truck; a mechanism operatively con nected to the drum for driving the same; hydraulic means continuously driven by the engine and selectively connectabie to the mechanism for driving the latter in either direction; mechanical means connected to the transmission and selectively operable to assist the hydraulic means in driving the mechanism in either direction; and manually operable means so controlling operation of the mechanical means and the hydraulic means that the two can be caused to simultaneously drive the mechanism in one direction or the other, or the hydraulic means alone.

12. In a transit concrete mixer: a drum; a first driving means for the drum of relatively low horse power; a second driving means for the drum of relatively high horse power; a first means to operatively connect the first driving means to the drum so as to rotate the latter in either direction; a second means to operatively connect the second driving means to the drum to rotate the latter in either direction; means to connect the first and second means to each other for simultaneous operation to couple both driving means to the drum for driving thereof in the same direction; and means operable to lock the second driving means in a non-connecting position when the second driving means is in a corresponding position.

13. In a transit concrete mixer: a truck; an engine for propelling the truck; a transmission mechanism; a drum rotatably mounted on the truck; mechanical means connected to the transmission mechanism; a hydraulic motor; a first control means for the mechanical means selectively operable to connect the latter to the drum to drive the same in either direction; a second control means for said motor selectively operable to connect the latter to the drum to drive the same in either direction; and means permanently connecting said motor to the engine shaft for constant driving thereby so that the drum can be driven by said motor through operation of the second control means whether the truck is in motion or at a standstill.

14. In a transit concrete mixer: a drum; a first driving means for the drum of relatively low horsepower; a second driving means for the drum of relatively high horsepower; a first means to operatively connect the first driving means to the drum so as to rotate the latter in either direction; a second means to operatively connect the second driving means to the drum to rotate the latter in either direction; and means selectively operable to connect the first and second means to each other for simultaneous operation to couple both driving means to the drum for driving thereof in one direction or the other, or by the first means alone in one direction or the other.

References Cited in the file of this patent UNITED STATES PATENTS 1,036,743 Suudh Aug. 27, 1912 1,232,605 Raddatz July 10, 1917 1,349,924 Swanson Aug. 17, 1920 1,867,838 Jaeger July 19, 1932 2,510,858 Black June 6, 1950