United States Patent 3861657

In a self-propelled concrete mixer unit a bowl is mounted for rotation on the unit and shifts during transit. A chain drive for rotating the bowl is tensioned along the length of the chain and the driven end of the chain is meshed with a laterally movable drive wheel which is laterally floatable so that a combination of longitudinal and lateral tension on the chain and drive wheel will mount the chain in a proper, operative position relatively to the bowl and drive means notwithstanding shifting movements of the bowl.

Application Number:
Publication Date:
Filing Date:
Primary Class:
Other Classes:
International Classes:
B28C5/42; F16H7/14; (IPC1-7): B28C5/20
Field of Search:
259/175,176,177R,177A,3,14,32,57,81,89,81R,30 74
View Patent Images:
US Patent References:

Primary Examiner:
Jenkins, Robert W.
Attorney, Agent or Firm:
Young, John A.
What is claimed is

1. In a self-propelled concrete mixer unit, a bowl for receiving aggregate therein, means for rotatably mounting said bowl, a chain drive having a drivable connection with said bowl, a motor means also drivably connected with said chain and adapted to transmit driving force to said bowl through said chain, means for exerting tension on said chain and including a lever forming a chain mounting at one end of said chain, spring means yieldably urging said lever in a direction effecting chain tensioning movement of said lever, means forming a floatable lateral drive connection between said chain and a power input to said chain, and spring means yieldably exerting lateral floatable movement of said drive whereby the chain is maintained in its respective drive connection with said bowl and power input to compensate for movements of the bowl on said self-propelled mixer unit.

2. A chain tensioning device in accordance with claim 1 including adjustable means for adjusting the yieldable force exerted against said lever to control the spring tension exerted on said chain.

3. The drive connection in accordance with claim 1 wherein said chain includes flexible lengths providing adjustable movement responsibly to shifting of the bowl whereby said chain remains in drive connection with sprocket wheels on said bowl and driving means respectively.

4. The tensioning device in accordance with claim 1 including a splined driving connection between said driving means and chain and including a sleeve and sprocket wheel laterally movable on said spline connection, and spring means yieldably resisting movement of said sleeve.

5. The chain drive mechanism in accordance with claim 1 including a floatable drive wheel, means forming a drive connection between said floatable drive wheel and one end of said chain, and spring means yieldably resisting such floatable movement whereby the operative drive connection is floatably maintained at the variable positions assumed by said bowl on the self-propelled unit during transport.


Self-propelled concrete mixer units, and particularly those which are adapted to effect a forward discharge of the concrete mixture have become very popular. Specifically, units such as those shown in the Willard U.S. Pat. No. 2,859,949 have proved to be particularly useful in meeting the various requirements of rapid discharge accuracy and convenience utilizing a minimum number of operators. During transit, the aggregate within the mixer bowl is continuously agitated by rotation of the bowl which is mounted for turning on the self-propelled mixer unit. Because of the roughness in terrain which is frequently encountered at a building site, the bowl is frequently twisted or shifted from its normal operative position being thrown to such skewed positions, that the chain drive which causes rotation of the bowl becomes disengaged. Although a chain drive is a strong and inexpensive means for driving the bowl, the frequency of disengagement of the chain owing to a shifting of the bowl position has been a substantial and recurrent problem so that many concrete mixer manufacturers have proposed a direct drive in order to circumvent the problem.

If, however, a means could be devised for preventing the chain from becoming disengaged from the bowl and its associated power driving means, the advantages of a chain drive could be retained while circumventing the previously described shortcomings of a chain drive.


A foremost object of the present invention is to devise a tensioning device which will maintain sufficient tension on the chain drive to reduce the tendency of the chain drive to become disengaged regardless of shifting of the bowl which occurs as the unit is driven over irregular terrain.

Another object of the invention is to provide a floating connection for the drive sprocket associated with one end of the chain drive to compensate for chain movements which must accompany shifting of the bowl in order to maintain the chain in proper operative driving relationship with both the bowl and the drive sprocket.

A further object of the invention is to maintain a proper operative position of the chain drive in a self-propelled concrete mixer unit in order to realize the inherent economy and versatility of the chain drive as compared with a direct drive and yet circumvent the previous chain detachment problems which occurred as the bowl inevitably shifted from its proper position.


FIG. 1 is an isometric view of a self-propelled concrete mixer unit which has the present invention installed thereon;

FIG. 2 is an enlarged sectional detail view taken in the direction of lines 2--2 of FIG. 1;

FIG. 3 is an enlarged sectional detail view of the drive sprocket but with the chain removed, and,

FIG. 4 is an enlarged detail view of the spring and bolt arrangement for tensioning the lever which pivotally receives the sprocket wheel.


A self-propelled concrete mixer in it designated generally by reference numeral 10 and of the general construction disclosed in Willard U.S. Pat. No. 2,859,949 is arranged so that the driver is located in a cab 12 so that the concrete mixture within a bowl 14 is dischargeable through a chute 16 controlled also by the operator within the cab 12 and in full view of the driver. The driver can then maneuver the unit 10 through the forward steering wheels 18 and thus discharge the concrete mix at the proper location in a convenient and accurate manner. The bowl 14 is mounted on bearings (not shown) at the upper end 19 and lower end 20, and the bowl is driven by means of a chain drive 22. Chain drive 22 consists of a plurality of links 24 which are articulated together to permit a limited angular movement of one link with respect to the adjacent interconnected link to impart greater flexibility to the chain as it moves endlessly around sprocket wheel 24 secured to the lower end 20 of bowl 14 and to the drive sprocket wheel 26.

The sprocket wheel 26 is mounted on a lever 28 which is pivotally secured at 30 to an arm 32 (FIG. 2). The lever 28 is biased in a clockwise direction (FIG. 2) about pivot 30 by a spring 34 which bears at one end against a flange 36 and at the other end against a nut 38 which is received on threaded portion 40 of a bolt 42. The compression load of spring 34 is adjustable by the operative position of nut 38 which is moved on the threaded bolt until generating the correct amount of spring force on the lever 28 which in turn establishes the degree of tension on chain 22. After the nut 38 is positioned at the proper location to generate the desired force of spring 34 the nut is then locked in place by a lock nut 43 which is also received on threaded bolt 40.

The bolt 40 is connected through a pin 45 to the end 44 of lever 28 (FIG. 4). The bolt 40 can also pass through opening 50 (FIG. 4) of flange 36 to permit a slight flexing of the chain in an opposite direction when the lever 28 is moved counterclockwise on 30 (FIG. 2).

The drive sprocket wheel 26 (FIG. 3) has teeth 54 which pass through openings in the links of chain 22 to forcibly drive the chain and the sprocket wheel 24 secured to bowl 14. The drive sprocket 26 is mounted on an integral sleeve 56 splined to a shaft 58 which is driven in some suitable manner (not a part of this present invention). The sleeve 56 and sprocket wheel 26 can shift axially in either direction as indicated by the double arrow headed line 60 (FIG. 3).

The described floating, or lateral movement by the sprocket wheel 26 contributes to the maintenance of a proper driving relationship between the teeth 54 and the links of the chain since, as the bowl 14 shifts there is a tendency to develop a twisting action on the chain 14 and the twist is alleviated by the articulated connection between the chain links and the ability of the sprocket wheel 26 (FIG. 3) to shift on the drive shaft 58 in the direction of the double arrow headed line 60.

Therefore, as the bowl 14 shifts back and forth on its bearings the proper chain tension is maintained by the spring tension 34 and the chain links are maintained in driving connection with the drive sprocket wheel 24 and drive sprocket wheel 26, since the chain links can flex slightly and the sprocket wheel 26 can shift slightly on shaft 58. The drive sprocket wheel 26 is positioned and arranged to float against the resistance of a spring 64 which is compressed between abutment 66 and an annular shoulder 68 which acts through a spacer 70 located between the drive sprocket wheel 26 and the abutment 68. The sprocket 26, sleeve 56 and spacer 70 are all integral parts. Because the parts in FIG. 3 are at an angle the purpose of the spring 64 is to sustain the weight of the parts. Therefore, the sprocket wheel 26 can adjust itself laterally against the action of the spring 64. The sprocket wheel 26 will, however, always be returned to the center position shown in FIG. 3, this being the normal position of the sprocket wheel 26 which occurs when the bowl 14 is properly mounted and positioned.


In operation, as the self-propelled concrete mixer is driven onto the building site, it frequently happens that the terrain is irregular and consequently the wheels of the mixer unit are at different elevations and this will cause the bowl 14 to be shifted at an angle on its mounting bearings.

Normally, this inadvertent (but inevitable) shift of the bowl 14 will cause the chain drive 22 to tend to slip off of the teeth of the associated sprocket wheels 24 and 26. In the present invention, however, such disengagement is prevented since the drive sprocket wheel 26 can shift laterally (FIG. 3) against the resistance of spring 64. The sprocket wheel 26 is further caused to move in a clock-wise direction (FIG. 2) under the action of the spring 34 thus maintaining tension on the chain drive 22. Consequently, the shifting of the bowl 14 on its bearings is compensated for by the lateral (FIG. 3) and longitudinal (FIG. 22) movements of the sprocket wheel 26 under the action of the springs 64 and 34 respectively. As a result, the incidence of chain disengagement from the sprocket wheels is materially reduced and hence the inevitable shifting of the bowl is not accompanied by chain disengagement to the extent previously experienced.

It is, therefore, possible to retain the economy and verstaility of a chain drive without experiencing the disengagement problems which were previously encountered.

Although the present invention has been illustrated and described in connection with a few selected example embodiments, it will be understood that these are illustrative of the invention and are by no means restrictive thereof. It is reasonably to be expected that those skilled in this art can make numerous revisions and adaptations of the invention and it is intended that such revisions and adaptations will be included within the scope of the following claims as equivalents of the invention.