US2661935A - Single motor transit concrete mixer - Google Patents

Description

Dec. 8, 1953 c. WILLARD SINGLE MOTOR TRANSIT CONCRETE MIXER Filed Sept. 27, 1952 TO 90W TAKE OFF GEAR 5 X Patented Dec. 8, 1953 SINGLE MOTOR TRANSIT CONCRETE MIXER" Carl L. Willard, Lynwood, Calif., assignor to Willard Concrete Machinery 00., Ltd., Lynwood, Calif., a corporation of California Application September 27, 1952, Serial No.311,936

This invention relates to transit concrete mixers.

Early in. the development of the concrete mixing art, it became apparent that the mixing could be more economically accomplished at a central plant, particularly one located near gravelv and sand pits, and that the mixed wet concrete be thenhauled in. trucks to the construction jobs onwhich the concrete'was to-be used, and there poured. This method of a central mix location and delivery to the job locations requires that the mixing action be substantially continuous from thetime the cement, aggregate and water are brought together in the mixing drum until thesemi-fluid mass is poured into its final structural position onthe job. The agitation of the continuous mixing action preventssegregation of the. ingredient materials of the concrete, or un-.

may be driven, and in nearly all transit mixers 3 is driven, by a second independently controlled internal combustion motor. But for obvious reasons of economy, of first cost, and of operation, efforts were madefrom the time the first transit mixers were conceived and constructed, to design p a means for driving the mixer by thesame motor which drives the truck. These efforts encountered engineering. difficulties which have never 5 Claims. (01. 259-177) lows; the truck drives the. forward element of a friction clutch. The rear clutch element through a conventional gear shift transmission box is driveconnected to the-truck wheels, usually only the rearv wheels. The truck transmission, is conventionally designed toprovide three, four or'more speeds forward, several speeds in reverse, a neuher of possible speeds.

tral idling position, and may also have an overdrive and an underdrive which-triples this num- A power takeoff atthe front end of the gear shift transmission box is driven by a gear wheel onthe maindrive shaft of the transmission which rotates. at the same speed as the rear friction clutch element.

Thepower takeofiT is combined with a variable speed transmission which is designedv toprovide for one or two forward speeds, one or two reverse speeds (for unloading. the drum), and a neutral idling position. The mixer drum, mountedtothe rear of the cab and extending backward. over the'truck rear wheels, has a ring sprocket wheel,

which is driven by a pinion sprocket, which. is in turn. driven by thepower takeoff through a twospeed gear shift box. This latter feature enables the drum to be driven at a fast speed for initial mixing, and a slow speed for the laterphasesv of the mixing operation, and also and primarily for agitation to prevent. themix from setting or separating while. driving to the job and before it is poured from the. mixer at the. construction site.

No difiiculty is metin controlling the operation of the drum when the truck is stationary ateither end of its, travel between the mixing plant and beensatisfactorily overcome. The basic difficulty has arisen from the desirability of continuously and smoothly driving. the drum without excessive and long continuing variations of speed, and without hindering the operation of, or causing damage to the truck transmissionat those times the construction job. The truck transmission is placed in neutral, the wheels braked, and the drum rotation controlled by the engine throttle, by the gear shift in the power takeoff, and by the two-speed drum gear shift box- But when the truck is in motion and the drum is loaded and turning, and itis desired to shift the truck transmission gears in starting, on bills, or to meet trafiic conditions, the rotation of the forward end of the truck transmission continues after the friction clutchis thrown out, due to the momen- 'tum of the loaded drum whichis power-tied to the forward end of the truck transmission by the power takeoif. The power takeofi cannot, to advantage, be shifted to neutral by the operator, for that operative step will slow down and stop the drum, and the power takeoff must be later shifted back.

While a short cessation of rotation of the drum may not be serious, two extra control steps are required in shifting the power takeoff to and from The motor shaft at the forward end of neutral, which complicates the mental reactions required of the operator. Release of the motor friction clutch incidental to shifting the truck transmission gears does not help the situation, for the forward end of the transmission box shaft continues to rotate under the power of the momentum of the drum, and the driven shaft at the rear of the transmission is driven by the truck wheels, making it dificult and at times im possible to bring into mesh and shift the truck transmission gears. They are not only operating at different speeds, but are both heavily loaded at these different speeds. The gear load due to the momentum of the drum is, of course, greater when the drum is loaded with relatively drymixed concrete. If the clutch is held long enough in the release position while efforts to shift the truck transmission are being made, the drum may stop, and then, due to the weight of the concrete load, it will begin a reversing oscillation which increases the relative difference in speed of the loaded gears and increases the difficulty of smoothly shiftin them, and in fact, of shifting them at all.

It is also obvious that if the drum is disconnected by the operator from the motor shaft to free the truck drive from the ill effects of the momentum of the rotating drum, agitation stops, and the power takeoff must again be connected after the meshing of the gears of the truck transmission gear box has been accomplished. This reconnection of the drum to the motor throws an extra load suddenly on the motor, affects the speed pickup of the truck, and may create a driving hazard.

Some of the disadvantages of a positive drive between the motor shaft and the drum have been cited. It has been proposed to place a friction clutch between the motor shaft and the drum, as for instance in the power takeoff box. This however, must be controlled by the operator, increasing the demands upon his attention and complicating the operation of the equipment. It has also been proposed to automatically brake the drum drive when the power takeoff is shifted to neutral, but in this arrangement, the power take-- 011 must be shifted to and from neutral, with the disadvantages cited above.

In spite of these efforts to produce a practicable single motor drive in a transit concrete mixer, the mixers now in use are virtually all equipped with an independent motor drive for the drum. which is significant of the absence at the present time of any successful solution of the operative problems presented in the designof a single motor drive.

This problem of many years standing may be briefly stated as that of so designing a single motor transit concretemixer that control of each of the driven elements, i. e., the truck wheels and the mixer drum, may be achieved without hindrance from the operating movement of the other element.

According to this invention, this problem has been successfully solved by providing a power takeoff from the forward end of the truck drive transmission for driving the mixer drum, also providing an alternate drive for the drum from the truck drive shaft at some point between the truck drive transmission and the truck propelling wheels, and further providing means for selec tively connecting either of these drives, but only one at a time.

In the drawing, which depicts one embodiment 4 of the invention, and is for illustrative purposes only:

Figure 1 is a side elevation of a transit concrete mixer embodying the invention;

Figure 2 is a schematic top plan view of the power plant, and truck wheel and drum drives;

Figure 3 is a perspective view of a portion of the drum drive;

Figure 4 is a perspective view of the control mechanism for the two drum drives;

Figure 5 is a top plan view of this control mechanism shown partly in section; and

Figure 6 is a vertical sectional view taken along the line fi6 of Figure 5.

The truck shown is of conventional design, having a chassis frame II, a cab l2, front steering wheels [3, and rear drive wheels M. An internal combustion motor [5 (see Figures 1 and 2) mounted under the hood it; drives one element of a friction clutch [1, the friction clutch being carried by the rear end of the motor shaft (not shown). The driven element of this clutch is mounted on a shaft (not shown) which extends into the housing It of the truck gear shift assembly or transmission as it is usually termed, and from which power is transmitted at various speeds and in both directions of rotation, to the drive shaft i9, and thence to the rear wheels l4 through the usual universal couplings (one of which is shown at lQa) and differential drive, all in accordance with standard truck design.

In the truck shown in the drawing, an auxiliary transmission 20 is provided, suitably connected to the main transmission l8 by a short drive shaft 2i and universal couplings 22 and 23. It will be understood, however, that as far as this invention is concerned, from a functional standpoint the transmissions l8 and Ziimay be considered as one transmission element of the truck drive.

A power takeoff 24 mounted on the side of the housing i8 is driven by a gear wheel (not shown) rigidly carried by the shaft which extends from the driven friction clutch element into the transmission box It. The initial element of this power takeoff thus rotates at a speed which bears a constant speed ratio to the driven element of the clutch H, and when the clutch H is engaged, also bears a constant speed ratio to the motor. The power takeoff 26 is constructed to transmit rotative movement to a shaft 25 through a gear shift assembly within the housing of the power takeoff. This gear shift assembly may be shifted to a neutral idling position, to one or more positions for driving the shaft 2| in one direction of rotation, and to one or more positions for driving the shaft N in the other direction of rotation, by a control device to be later described.

A mixer drum 26 is mounted to rotate on the truck chassis with its axis in a forwardly and downwardly inclined position. It may be mounted for tilting to unload or may be designed, as is the transit mixer shown in the drawing, for unloading by reversing the direction of its rotation. Since the means for unloading the drum, supplying material and water to the drum, and many other features of the transit mixer may be varied without affecting the nature of the invention, no detailed description of such features will be given here.

The drum has rigidly and coaxially mounted upon it a large sprocket wheel 21 which engages a sprocket chain 28 driven by a small sprocket wheel 29. The sprocket wheel 29 is fixedly carried by .a shaft 30 of a two-speed transmission varies directly as the linear travel speed of the truck.

During numerous shifts of the truck transmission gears in starting from the mixing plant, later for stops, such as at road crossings, or in changing speeds in response to changing road grades and trafiic conditions, the ratio of drum speed to truck speed remains constant andtherefore the load on the driven gears of the truck transmission increases and decreases at a uniform rate of change. The driver may therefore ignore the load of the revolving drum on the driven transmission gears, and has only to throw out the clutch and ease the freely turning and unloaded driving gears into mesh with the driven gears of the transmission. Since the driving gears are free of any load but the slight one of their own inertia, this shift is very readily accomplished. It is also to be noticed that the speed of the drum varies only with the speed of the truck while thus in transit from mixing plant to construction site, a variation which is much less than that which takes place under former practice when the drum is coupled with the engine through the power takeoff. Under the former condition, the drum speed may drop to zero or the drum may even rotate in the reverse direction when the main friction clutch is disengaged.

When the truck arrives at the construction site, the main drive shaft isruncoupled from the drum, the power takeoff is shifted to the unloading position with appropriate adjustment of the locking plate 55 and the batch is poured into the forms or other place of deposit. After the drum is emptied of its load of mixed concrete, the power takeoff transmission is placed in neutral, the main truck drive shaft is coupled to the drum, and the equipment is returned to the mixing location with the drum turning slowly at its transit 1.

speed of rotation.

This invention has been described as adapted to a transit concrete mixer of one type in which the-truck is of conventional design as to its power plant, driving mechanism, and controls. invention is applicable to transit concrete mixers of varied design, both as to the mixing elements and as to the transportation elements of the equipment. The invention, therefore, is not limited as to its scope to the particular machinery equipment hereinabove described, but embraces all equipment of the transit concrete mixer class which is described and defined in the appended claims.

I claim:

1. In a transit concrete mixer, the combination of: an automotive vehicle having driving wheels; a motor mounted on the vehicle; a first train of power transmitting devices connecting the motor and the driving wheels of the vehicle, including a variable speed transmission providing for at least one forward driving speed, at least one reverse driving speed, and a neutral non-driving adjustment; a rotary concrete mixing drum mounted on the vehicle; a second train of power transmitting devices connecting the drum to an element of the first train between the motor and the transmission; a third train of power transmitting devices connecting the The 8 drum to an element of the first train of power transmitting devices between the transmission and the wheels; a throw-out clutch in said -sec 0nd train a throw-out clutch in the third train,

a pair of controls for the throw-out clutches, respectively; and a single, two-position member for locking one. of the controls in the throw-out position and simultaneously freeing the other control for operation to the throw-in position when said member is in one position, and vice-i versa.

2. In a transit concrete mixer, the combination of: an automotive vehicle having a motor, a friction clutch, a multiple selective speed, reversible rotation and throw-out transmission, a main drive. shaft and driving wheels connected in the order named; a mixing drum; a power takeoff connecting the drive shaft between the clutch and transmission to the drum, the power takeoff having a transmission providing for rotation in either direction of rotation, and also a throw-out clutch; a power coupling between the main drive shaft and the drum, geared to drive the drum clockwise looking forward, and including a throw-cut clutch; a control for the power takeoff throw-out clutch; a control for the throw-out clutch of said power coupling; and a single, twoposition member for locking one of said controls in the throw-out position and simultaneously freeing the other control for operation to the throw-in position when said locking member is in one of its two positions and vice versa.

3. lhe combination definied in claim 2, in which the transmission is of the type having axially slidable gear wheels with intermeshing teeth.

i. The combination defined in claim 2, in which there is a variable speed transmission providing for at least two speeds of rotation of the drum in the same direction and disposed operatively between the drum on the one hand and both the power takeoff and power coupling on the other hand. I

5. In a concrete transit mixer, the combination of a truck chassis; a motor on the chassis; a friction clutch, an intermediate drive shaft, a variable speed, reversible and throw-out transmission, a main drive shaft and truck driving wheels connected in the order named; a mixing drum; power transmitting devices for the drum; a power takeoff coupling the intermediate shaft and said devices, and having a transmission with at least three position of adjustment, providing for rotation in either direction, and a throwout; a power coupling between the main drive shaft and the said power transmitting devices; a throw-out clutch in said power coupling; two controls for said two last-mentioned throw-outs; and a single, two-position member for locking one of said controls in the throw-out position and simultaneously freeing the other control for operation to the throw-in position when said member is in one of its two positions and vice versa.

CARL L. WHLARD.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,615,315 Shaw Jan, 25, 1927 1,801,162 Jaeger Apr. 14, 1931 1,858,700 Besonson May 17, 1932 1,867,838 Jaeger July 19, 1932 2,013,359 Paris Sept. 3, 1935

Images