WO2013045070A1

WO2013045070A1 - Drive for the drum of a concrete mixer

Info

Publication number: WO2013045070A1
Application number: PCT/EP2012/003994
Authority: WO
Inventors: Luigino Pozzo
Original assignee: Pmp Pro-Mec S.P.A.
Priority date: 2011-09-30
Filing date: 2012-09-25
Publication date: 2013-04-04
Also published as: ITUD20110151A1

Abstract

Drive (1) for the drum (3) of a concrete mixer (8) comprising a multistage epicyclic gear-reduction device which comprises at least two reduction stages of which a first reduction stage (9, 10, 11) and a power stage (15, 16, 17, 21), the first reduction stage (9, 10, 11) being housed within a box (19) of the drive comprising fastening means (25) to the frame (7) of the concrete mixer (8), the first reduction stage (9, 10, 11) comprising a power takeoff for the connection of a motor (2), the drive (1) comprising a fixing flange (23) of the drum (3) in which the coupling between the power stage (15, 16, 17, 21) and the fixing flange (23) of the drum (3) occurs by means of a joint (22) comprising a misaligning grooved coupling (38) allowing a misalignment between the axis (34) of the drive (1) and the axis (35) of the drum (3), such misalignment involving the misalignment of the flange (23) with respect to the components of the power stage (15, 16, 17, 21), the power stage (15, 16, 17, 21) transmitting the rotational motion to the flange (23) in a reciprocal misalignment condition of one with respect to the other one in absence of misalignment conditions between the first reduction stage (9, 10, 11) and the power stage (15, 16, 17, 21).

Description

DESCRIPTION

DRIVE FOR THE DRUM OF A CONCRETE MIXER

Technical field

The present invention relates to a drive according to the characteristics of the pre- characterizing part of claim 1.

The present invention also relates to a concrete mixer provided with a concrete mixing rotating drum which is provided with a drive, according to the characteristics of the pre-characterizing part of claim 11.

Prior art

In the field of the drives and in particular of driving systems for the rotation of a drum of a concrete mixer, it is known the combination of a drive system with a hydraulic motor for rotating the drum of the concrete mixer within which the continuous mixing occurs of the concrete which is contained into the drum itself. The rotation occurs in two directions, one direction being intended for mixing and one direction and being intended for discharging the concrete which is contained into the drum.

The drum must be operated with a maximum rotational speed of 14-20 rpm and a maximum torque ranging from 30000 Nm up to 60000 Nm and beyond, depending on the capacity of the mixing drum itself. The drum can be 3 to 4 m long, for example and without limitation to the application of the present invention, and it is secured at its ends on a frame with tractor for the road transportation of concrete. A key feature to be observed is that the rotation speed of the drum must be independent from the operating speed of the engine of the tractor vehicle. Due to the fact that on the tractor a power take-off is not available which is able to supply the speed and torque which are required for the operation of the drum, the usually adopted solution consists in interposing a system consisting of a hydraulic pump and a hydraulic motor between the engine of the tractor vehicle and the drum. The axial piston hydraulic motor is the most commonly used because it represents the best compromise between power output, size and costs. A hydraulic motor of this type is able to provide maximum power at speeds that are between 1800 and 2500 rpm. Due to the rotation speed of the drum and the rotation speed of the hydraulic motor it is necessary to interpose a mechanical reducer between them which ensures a minimum reduction ratio of about 1 :100. For this kind of use a planetary gear reducer with multiple reduction stages is typically used, due to size and reliability reasons. The gear unit constituting the drive system is usually coaxially installed with respect to the drum and at an external position with respect to the inner compartment of the drum, while solutions are present in which the hydraulic motor is placed in an aligned condition with respect to the drive system as well as solutions in which the hydraulic motor is arranged in an axially offset position with respect to the drive system. The installation occurs in correspondence with the opposite side of the drum with respect to the introduction and extraction mouth of the concrete.

Patent SU 1364486 describes a drive for a mixing drum of a concrete mixer vehicle in which part of the gears is fixed internally to the body of the drum, wherein the first and the second stage of the gear unit are positioned in an outer shell, and the third stage is located within an shell which is located internally to the drum, the outer shell having a wall thickness greater than the thickness of the wall of the inner shell.

Patent US4006946 describes a roller bearing for the shaft of a cement-mixer drum, universally jointed on a shaft of a planetary-gear train driving the drum shaft through a gear coupling with arcuate teeth, in which the roller bearing is provided with an inner ring which is fixed to the shaft of the drum and with an outer ring which is fixed on a surrounding drive housing, such outer ring being axially split into two halves each accommodating a set of barrel-shaped rollers which are held in respective cages, peripherally offset from each other.

Patent DE8326270 discloses a planetary gear with power take-off which acts on a first stage consists of a central inner gear, planetary-gears and planetary-gear supports, in which the rotation movement of the planetary-gear support occurs through a curved teeth coupling using a spherical bearing for the output coupling, and further in which the shaft of the output joint protrudes towards the inside of the gear being supported on a spherical bearing with a convex radius of curvature and the planetary-gear support being axially supported through roller bearings.

Patent DE2948936 describes a planetary gear in which the rotation axis lies on the pins of the planetary-gear support of the last stage of the drive, and wherein in correspondence with such coupling a ring is present which has with an outer arcuated profile rotatably associated with a counter-shaped supporting profile.

Patent US4124304 describes a device for driving a drum of a concrete mixer vehicle comprising a casing fixedly mounted on the vehicle frame and a driving shaft connected to the drum by a universal coupling consisting of a driving member concentrically connected to the driving shaft and rotatably supported by the casing through a self-aligning roller bearing, and a driven member which is fixed to the driven drum which engages with the driving member with a spherical bearing disposed there between, the self-aligning roller bearing and spherical bushing being concentrically arranged to rotate about a common center of rotation, and the connecting means being arranged on a reference plane in which the center of rotation lies.

Patent US3788610 describes a lubricant system for the support unit of a concrete mixer vehicle comprising a lubricant chamber enclosing the drive connection between the drive shaft and drum.

Problems of the prior art

Prior art solutions have many problems. One problem is relative to the overall size of the concrete mixer vehicle and to its weight. The size of the drive, while apparently looking negligible if compared to the overall size of the concrete mixer vehicle, are very important because it is necessary to provide enough space on the frame of the concrete mixer vehicle to house the drive and the corresponding hydraulic motor, in an intermediate position between the concrete containing drum and the operating cab. Prior art solutions involve a considerable space required for the installation of such devices, with the consequence that it is necessary to use greater drum supporting frames with further increasing of costs and increasing of weights and consumption. Some prior art solutions for solving this problem have adopted configurations with integrated gear-motors, transverse or inverted arrangement of the motor with respect to the drive with a conical coupling, but such solutions are often complex, heavy and expensive, and in addition they involve maintenance problems for the various interested members and devices.

Additionally it should be noted that the drum is mounted on roller supports which allow its rotation and which support the weight of the drum and the concrete contained in it. Part of the weight is also released on the drive system. A further drawback is due to the fact that, during the movement of the mixer on the road, the drum, the frame and the drive system are subject to high stresses with the consequence that torsion phenomena occurs involving the frame of the concrete mixer vehicle itself. As a consequence reciprocal movements are present between the rotating drum and the support frame on which also the drive system and hydraulic motor are fixed. To solve this problem, prior art solutions provide for the use of an assembly which is known as bell coupling joint, which allows the drive of the rotational motion and at the same time allows the reciprocal displacement between the drum and part of the drive system which is fixed to the frame. This solution is constructively complex and heavy because the bell coupling joint must also be able to support and release at least a part of the weight of the drum and of the concrete which is contained into it. In order to solve this problem, some prior art solutions provide the use of a drive system which is coupled to the vehicle frame by means of elastic means, such as rubber pads having a great thickness. By means of the elastic deformation of these bearing pads the reciprocal movements are allowed between the drum and the frame of the vehicle. These systems, although appearing as simple systems, are subject to many problems with reference to the limitation of the allowed movements by the elastic means to avoid that an excessive displacement could cause excessive stresses of the components with possible detachments of the same. Further such elastic means may be subject to premature aging resulting in the loss of their functionality, due to the fact that they are exposed to temperature change, sun, weather conditions, etc. In addition, the need to provide sizes of the pads suitable for the application and sizes of the mechanical components able to withstand the induced vibrations, at least in part compromises the economic benefits obtained by the adoption of such systems, so as to cause this solution to be more expensive than conventional systems, in addition to the fact that no reduction of the weights and of the overall dimensions is not provided for the group comprising the drive and the hydraulic motor.

Aim of the invention

The aim of the present invention is to solve the above mentioned problems and disadvantages of the prior art systems, providing a drive for a drum of a concrete mixer which is compact and reliable allowing a reduction of the overall sizes.

A further aim of the present invention is to allow an effective releasing of the portion of the weight of the drum of the concrete mixer which weights down over the drive while ensuring a reduction of the drive itself while maintaining its reliability.

Concept of the invention

The aim is reached with the characteristics of the main claim of the compact drive for the drum of a concrete miser. The sub-claims represent advantageous solutions.

Advantageous effects of the invention

The solution according to the present invention, by the considerable creative contribution whose effect constitutes an immediate and not-negligible technical progress, presents various advantages

First, a greater compactness of the concrete mixer can be obtained. This allows, among other things, a reduction of its length and therefore a better exploitation of the space which is available for the arrangement of the components for the same total length of the vehicle, greater efficiency in the management of masses, greater maneuverability.

Furthermore a consistent reduction in weight of the drive is allowed, which advantageously has a lower weight of about 40% if compared to prior art systems.

Furthermore a reduction of the length of the drive as a whole is allowed, reducing the axial size of the drum and drive assembly, this reduction being estimated as being about a 40% reduction in overall dimensions if compared to prior art systems. Description of the drawings

It is hereinafter described an embodiment with reference to the included drawings to be considered as a non-limiting example of the present invention in which:

Fig 1 schematically represents a concrete mixer vehicle comprising the drive according to the present invention.

Fig 2 schematically represents a drum for a concrete mixer comprising the drive according to the present invention.

Fig 3 represents the detail which is indicated with "A" in Fig 2.

Fig 4 is a schematic exploded view of the drive according to the present invention. Fig 5 is a schematic sectional view of a first embodiment of the drive according to the present invention.

Fig 6 is a schematic sectional view of a second embodiment of the drive according to the present invention.

Fig 7, Fig 8, Fig 9 schematically represent in section the reciprocal movement which is allowed between the components of the drive according to the present invention with reference to the bearings.

Fig 10, Fig 11 schematically represent in section the reciprocal movement which is allowed between the components of the drive according to the present invention with reference to the grooved coupling in an alignment condition. Fig 11 represents the detail which is indicated with "B" in Fig 10.

Fig 12, Fig 13, Fig 14 schematically represent in section the reciprocal movement which is allowed between the components of the drive according to the present invention with reference to the grooved coupling in a misalignment condition. Fig 13 represents the detail which is indicated with "C" in Fig 12. Fig 14 represents the detail which is indicated with "D" in Fig 12.

Description of the invention

Referring to the figures (Fig. 1), the concrete mixer (8) consists of a tractor vehicle (6) which is operated by a respective motor (4) of the tractor vehicle and a frame (7) on which the rotating drum (3) is mounted resting on supports (5). The rotation of the drum (3) occurs (Fig. 2, Fig 3) by means of a drive system (1) driven by a respective hydraulic motor (2), which puts in rotation the drum (3) of the concrete mixer (8) within which the continuous mixing occurs of the concrete which is contained in the drum (3) itself. The rotation occurs in two directions, one direction being intended for mixing and one direction and being intended for discharging the concrete which is contained into the drum. Preferably, but not necessarily, the motor which puts in rotation the drum (3) is a hydraulic motor, even more preferably an axial piston hydraulic motor. Since the drum (3) must be operated with a rotation speed approximately but not limitatively comprised in the range of about 14 rpm to 20 rpm and. with a maximum torque ranging from 30000 Nm up to 60000 Nm and since the hydraulic motor (2) is able to provide maximum power at speeds that are between 1800 rpm and 2500 rpm, it is necessary to interpose a mechanical reducer between them which ensures a minimum reduction ratio of about 1 :100. The solution according to the present invention provides the interposition of a drive system (1 ) consisting of a planetary gear unit with multiple reduction stages. The gear unit constituting the drive system (1 ) is preferably installed according to a coaxial arrangement with respect to the drum (3) in correspondence of the opposite side of the drum (3) with respect to the introduction and extraction mouth of the concrete.

The drive (1 ) is constructed (Fig. 4, Fig 5, Fig 6) according to a configuration with planetary-gears and planetary-gears supports. Although in the illustrated embodiments the configuration includes 3 stages of planetary-gears and planetary-gears supports, the present invention should be intended as being also applicable in the case of solutions in which a lower or higher number of stages is present, as for example drive configuration with two stages of planetary-gears and planetary-gears supports, drive configuration with four stages of planetary-gears and planetary-gears supports, etc. In particular, in the illustrated embodiment, the configuration provides that the last stage of the drive, the third stage in the illustrated embodiment, is a stage which is configured with planetary-gears support (17) of the third stage of the fixed type and with a rotating ring-gear (21). In this way, it is the ring-gear (21) itself which transmits the motion to the fixing flange (23) of the drum (3). This transmission is obtained by means of a joint (22) having really reduced axial dimensions which is integral both with the ring-gear (21) and with the fixing flange (23). The joint (22) under discussion, through a specific grooved coupling, allows a misalignment by some degrees between the axis of the drive (1) and the axis of the drum (3) of the concrete mixer (8). The maximum allowed misalignment is preferably at least +/- 2 degrees, even more preferably at least +/- 5 degrees. This allows to take into account the bending of the frame (7) of the concrete mixer (8) which occur during transportation on the road, preventing the stresses transmitted to the drive (1 ) may lead to a blocking of the same or to its premature wearing, as well as preventing anomalous stresses on the supports of the rotating drum (3) to occur.

Advantageously the solution according to the present invention provides that at least the last stage of the epicyclic drive system, that is the power stage of the same, is housed (Fig. 3) within a chamber (26) obtained at the head of the drum (3), namely in correspondence of the side of the drum (3) which is the opposite side with respect to the side on which there is the intake for the introduction and the taking-out of the concrete. Positioning the epicyclic power stage inside the drum (3) it is allowed to free up space to place two more epicyclic stages at the head of the drive (1). In this way a drive (1) or reduction gear can be obtained with an extremely high reduction ratio, which makes it possible to use an input hydraulic motor (2) having a reduced size if compared to current standards. The sum of all these aspects results in a reduction of weight of the drive (1) of about 35%, if compared to current solutions. As a consequence of this, it is apparent the great economic advantage of this product. With the present invention, therefore, a drive (1) or reduction gear is provided which is particularly lightin weight and compact with consequent benefits from the economic point of view, while maintaining or even improving the characteristics of reliability and duration. Furthermore also the axial size outside of the drum (3) of the assembly of drive (1 ) and of the hydraulic motor (2) is reduced of about 40% if compared to current solutions. As previously observed, the power stage is realized according to a configuration with fixed planetary-gears support and rotating ring-gear (21), so that it is the (21) itself which transmits the motion to the fixing flange (23) of the drum (3).

In details, the drive (1) for a concrete mixer according to the present invention comprises a three-stage epicyclic gear, although different embodiments can also be provided having two or four stages. The box (19) of the drive (1) only houses inside (Fig. 4, Fig 5, Fig 6) the first two gear stages:

- the first stage with the respective planetary-gear support (11) of the first stage, planetary-gears (10) of the first stage and pinion (9) of the first stage;

- the second stage with the respective planetary-gear support (14) of the second stage, planetary-gears (13) of the second stage and pinion (12) of the second stage.

The third stage of the drive (1), instead, is advantageously positioned on the opposite side of the fixing flange (23) with respect to first and second stage of the drive (1) and it comprises planetary-gear support (17) of the third stage, planetary-gears (16) of the third stage and pinion (15) of the third stage. In this way, when the drive (1) is installed on the drum (3), the third stage (15, 16, 17, 21) is advantageously housed inside (Fig. 3) a chamber (26) which is obtained at the head of the drum (3). By means of the flange (23) the fixing or coupling on the drum (3) of the concrete mixer (8) occurs for the transmission of motion, while the drive (1) is fixed on the frame (7) of the concrete mixer (8) by means (Fig. 3 , Fig 4, Fig 5, Fig 6) of fastening means (25) obtained at the base of the box (19) of the drive (1) itself.

The hydraulic motor (2) is fixed on the box (19) of the drive (1) in correspondence with the cover (18) which closes the inside of the box (19) containing the first stage (9, 10, 11) and containing the second stage (12, 13, 14) of the drive (1). The shaft (32) of said motor (2) couples (Fig. 4, Fig. 5, Fig. 6) with the pinion (9) of the first stage which is supported on the cover (18) by means of a fifth bearing (31 ). The pinion (9) of the first stage couples with corresponding planetary-gears (10) of the first stage which in turn transmit the motion to a planetary gear-support (1 1 ) of the first stage by means of sliding on first bearings (27). The planetary gear-support (1 1 ) of the first stage in turn transmits the motion to the pinion (12) of the second stage. The pinion (12) of the second stage couples with corresponding planetary-gears (13) of the second stage which in turn transmit the motion to a planetary gear-support (14) of the second stage by means of sliding on second bearings (28). The planetary gear-support (14) of the second stage in turn transmits the motion to the pinion (15) of the third stage. The pinion (15) of the third stage couples with corresponding planetary-gears (16) of the third stage which in turn transmit the motion to the ring-gear (21 ) by means of sliding on third bearings (29). Finally, the ring-gear (21 ) puts in rotation the drum (3) of the concrete mixer (8). The planetary gear-support (17) of the third stage is therefore stationary and integral with the central body (24) of the drive. A closing shell-guard (20) is fixed to the ring-gear (21 ) to close the head of the drive (1 ).

Advantageously the need is prevented for complex solutions of the bell coupling joint type to allow the transmission of the rotational motion and at the same time to also allow the reciprocal displacement between the drum and the fixed portion of the drive which is integral with the frame of the concrete mixer. Indeed the releasing of the portion of the weight of the drum (3) which weights down on the drive (1) occurs by means of the flange (23), which releases the weight on the central body (24) of the drive by means of fourth bearing (30), and, as a consequence, the weight is released through the central body (24) on the box (19) down to the support (5) which is installed on the frame (7) of the concrete mixer (8).

Advantageously the fourth bearings (30) are shaped to allow (Fig. 7, Fig. 8, Fig. 9, Fig. 1 1 , Fig. 13, Fig. 14) a misalignment by some degrees between the axis (34) of the drive (1 ) and the axis (35) of the drum (3) by means of a sliding movement with inclination of the base of the flange (23) with respect to the central body (24). The maximum allowed misalignment is preferably of at least +1-2 degrees, even more preferably at least +/-5 degrees. The fourth bearings (30) are roll bearings. In the preferred embodiment of the present invention (Fig. 6), the fourth bearings (30) are roll bearings with two bearers of rolling bodies, but different embodiments are possible as for example (Fig. 5) roll bearings with a single bearer of rolling bodies. The misalignment is allowed to occur (Fig. 8, Fig. 9) in both directions, that is with deviation angles (33) between the axis (34) of the drive (1 ) and the axis (35) of the drum (3) preferably included in a range from - 2 degrees to + 2 degrees, even more preferably in a range from - 5 degrees to + 5 degrees. The joint (22), by means of a special grooved coupling, allows to obtain a misalignment between the axis (34) of the drive (1 ) and the axis (35) of the drum (3) in such a way that the misalignment involves the flange (23) but not the ring-gear (21 ). In this way the ring-gear (21 ) is free to rotate in order to transmit the motion to the flange (23), while the flange (23) beside receiving the rotational motion from the ring-gear (21 ) is able to undergo the indicated misalignment.

By way of summary the present invention relates to a drive (1) for the drum (3) of a concrete mixer (8) comprising a multistage epicyclic gear-reduction device which comprises at least two reduction stages of which:

- a first reduction stage (9, 10, 11);

- a power stage (15, 16, 17, 21).

The first reduction stage (9, 10, 1 1 ) is housed within a box (19) of the drive comprising fastening means (25) to the frame (7) of the concrete mixer (8); the first reduction stage (9, 10, 11) comprises a power takeoff for the connection of a motor (2); the drive comprises a fixing flange (23) of the drum (3). The coupling between the power stage (15, 16, 17, 21) and the fixing flange (23) of the drum (3) occurs by means of a joint (22) comprising (Fig. 10, Fig. 11 , Fig. 12, Fig. 13, Fig. 14) a misaligning grooved coupling (38) allowing a misalignment between the axis (34) of the drive (1 ) and the axis (35) of the drum (3), such misalignment involving the misalignment of the flange (23) with respect to the components of the power stage (15, 16, 17, 21 ), the power stage (15, 16, 17, 21) transmitting the rotational motion to the flange (23) in a reciprocal misalignment condition of one with respect to the other one in absence of misalignment conditions between said first reduction stage (9, 10, 11 ) and said power stage (15, 16, 17, 21). Therefore, advantageously the present invention refers to an epicyclic gear-reduction device which operates on a floating ring-gear which also acts as a casing of the reduction device itself. Therefore the power stage (15, 16, 17, 21) is made according to a configuration with fixed planetary gear-support and a floating rotating ring-gear (21), in which the ring-gear (21) transmits the rotational motion from the power stage (15, 16, 17, 21) to the fixing flange (23) of the drum (3). Advantageously the ring-gear (21) is located circumferentially outside with respect to the elements of the power stage (15, 16, 17, 21), in such a way that the ring-gear (21) constitutes the casing of the drive.

The grooved coupling (38) preferably (Fig. 10, Fig. 11 , Fig. 12, Fig. 13, Fig. 14) consists of:

- a groove (37) obtained on the power stage (15, 16, 17, 21) in correspondence of the element (21) which transmits the rotational motion from the power stage (15, 16, 17, 21 ) to the fixing flange (23) of the drum (3);

- a guiding element (36) obtained on the joint (22).

The guiding element (36) drives the reciprocal misalignment movement between the joint (22) and the element (21) which transmits the rotational motion to the fixing flange (23) of the drum (3), the guiding element (36) sliding in said groove (37).

Preferably (Fig. 10, Fig. 11) an end-stop element (39) is also provided which is obtained in correspondence of a central body (24) of the drive (1). The end-stop element (39) limits the misalignment of the flange (23) with respect to the components of the power stage (15, 16, 17, 21) in correspondence with a maximum misalignment position.

Advantageously, in the solution according to the present invention, at least the power stage (15, 16, 17, 21) is located at the opposite side of the first reduction stage (9, 10, 11) with respect to the longitudinal position of the fixing flange (23) of the drum (3), the power stage (15, 16, 17, 21) being placed internally to the drum (3) within a chamber (26) obtained at the head of the drum (3), namely in correspondence of the side of the drum (3) which is the opposite side with respect to the side on which there is the intake for the introduction and the taking-out of the content of the drum (3). It will be apparent that while on the preferred embodiment of the present invention only the power stage (15, 16, 17, 21 ) is placed internally to the chamber (26) of the drum (3), in alternative solutions (not represented), also an additional stage of the drive can be provided to be housed inside the same chamber (26).

Advantageously, in the drive (1) for the drum (3) of a concrete mixer (8) according to the present invention, the coupling between the power stage (15, 16, 17, 21 ) and the fixing flange (23) of the drum (3) occurs by means of a joint (22) comprising a misaligning grooved coupling allowing a misalignment between the axis (34) of the drive (1 ) and the axis (35) of the drum (3), such misalignment involving the misalignment of the flange (23) with respect to the components of the power stage (15, 16, 17, 21 ), the power stage (15, 16, 17, 21) transmitting the rotational motion to the flange (23) in a reciprocal misalignment condition of one with respect to the other one in absence of misalignment conditions between the first reduction stage (9, 10, 11 ) and the power stage (15, 16, 17, 21 ). The misalignment between the axis (34) of said drive (1) and the axis (35) of said drum (3) is allowed in a bi-directional way, the misalignment being allowed to occur in both directions, with deviation angles (33) between the axis (34) of the drive (1 ) and the axis (35) of the drum (3) preferably included in a range from - 5 degrees to + 5 degrees, even more preferably in a range from - 3 degrees to + 3 degrees.

Advantageously, the solution according to the present invention allows to obtain an effective releasing of the portion of the weight of the drum of the concrete mixer which weights down on the drive, at the same time allowing a decreasing of the gear itself keeping its reliability unchanged. Indeed, in the solution according to the present invention, the function relative to the transmission of the motion from the motor to the drum and the function relative to the release of the weight of the drum of the concrete mixer and its content are reciprocally free. This allows to obtain a drive having reduced weight and size with all the advantages coming from a reduced price, greater reliability and saving of space.

The present invention further relates to and claims a concrete mixer (8) provided with a mixing drum (3) in which the drum (3) is put in rotation by means of a drive (1) as previously described, that is it relates to a concrete mixer (8) comprising a drive (1) for the drum (3) of a concrete mixer (8) as described in the present description.

Although in the figures explicit reference is made to a concrete mixer of the movable type on a vehicle, that is of the type which is commonly known as a concrete mixer vehicle, it will be apparent that the present invention can be applied to generic concrete mixers and, therefore, to concrete mixers of the fixed or semi-fixed type. Therefore, by means of the term cement mixer it is meant to include all the types of concrete mixers and in particular concrete mixer vehicles, without excluding of fixed or semi-fixed concrete mixers.

The description of the present invention has been made with reference to enclosed figures in a preferred form of execution of the same, but it is evident that many possible alterations, changes and variants will be immediately clear to those skilled in the art of the sector in view of the previous description. So, it should be stressed that the invention is not limited by the previous description, but contains all alterations, changes and variants in accordance with the appended claims.

Used nomenclature

With reference to the identification numbers reported in the enclosed figures, the following nomenclature was used::

1. Drive

2. Hydraulic motor

3. Drum

4. Tractor motor

5. Support

6. Tractor

7. Frame

8. Concrete mixer

9. Pinion of the first stage 10. Planetary-gear of the first stage

11. Planetary-gear support of the first stage

12. Pinion of the second stage

13. Planetary-gear of the second stage 14. Planetary-gear support of the second stage

15. Pinion of the third stage

16. Planetary-gear of the third stage

17. Planetary-gear support of the third stage

18. Cover

19. Box

20. Shell guard

21. Ring-gear

22. Joint

23. Flange or coupling means

24. Central body

25. Fastening means

26. Chamber

27. First bearings

28. Second bearings

29. Third bearings

30. Fourth bearings

31. Fifth bearing

32. Shaft

33. Deviation angle

34. Drive axis

35. Drum axis

36. Guiding element

37. Groove 38. Grooved coupling

39. End-stop element

Claims

1 . Drive (1) for the drum (3) of a concrete mixer (8) comprising a multistage epicyclic gear- reduction device which comprises at least two reduction stages of which:

- a first reduction stage (9, 10, 11 );

- a power stage (15, 16, 17, 21),

said first reduction stage (9, 10, 11 ) being housed within a box (19) of the drive comprising fastening means (25) to the frame (7) of said concrete mixer (8), said first reduction stage (9, 10, 1 1 ) comprising a power takeoff for the connection of a motor (2), said drive comprising a fixing flange (23) of said drum (3) in which the coupling between said power stage (15, 16, 17, 21) and said fixing flange (23) of said drum (3) occurs by means of a joint (22) comprising a misaligning grooved coupling (38) allowing a misalignment between the axis (34) of said drive (1) and the axis (35) of said drum (3), said misalignment involving the misalignment of said flange (23) with respect to the components of said power stage (15, 16, 17, 21), said power stage (15, 16, 17, 21 ) transmitting the rotational motion to said flange (23) in a reciprocal misalignment condition of one with respect to the other one in absence of misalignment conditions between said first reduction stage (9, 10, 11 ) and said power stage (15, 16, 17, 21 ) characterised in that said power stage (15, 16, 17, 21 ) is made according to a configuration with fixed planetary gear-support and a floating rotating ring-gear (21 ), said ring-gear (21 ) transmitting the rotational motion from said power stage (15, 16, 17, 21) to said fixing flange (23) of the drum (3), and further characterised in that said grooved coupling (38) consists of:

- a groove (37) obtained on said power stage (15, 16, 17, 21 ) in correspondence of said ring-gear (21) transmitting the rotational motion from said power stage (15, 16, 17, 21 ) to said fixing flange (23) of the drum (3);

- a guiding element (36) obtained on said joint (22);

said guiding element (36) driving the reciprocal misalignment movement between said joint (22) and said ring-gear (21) transmitting the rotational motion to said fixing flange (23) of the drum (3), said guiding element (36) sliding in said groove (37), said ring-gear (21) being located circumferentially outside with respect to the elements of said power stage (15, 16, 17, 21), said ring-gear (21) being a floating ring-gear constituting the casing of said drive.

2. Drive (1 ) for the drum (3) of a concrete mixer (8) according to the previous claim characterised in that it includes an end-stop element (39) in correspondence of a central body (24) of said drive (1), said end-stop element (39) limiting said misalignment of said flange (23) with respect to the components of said power stage (15, 16, 17, 21) in correspondence with a maximum misalignment position.

3. Drive (1) for the drum (3) of a concrete mixer (8) according to any of the previous claims characterised in that at least said power stage (15, 16, 17, 21) is located at the opposite side of said first reduction stage (9, 10, 11) with respect to the longitudinal position of said fixing flange (23) of said drum (3), said power stage (15, 16, 17, 21) being placed internally to the drum (3) within a chamber (26) obtained at the head of said drum (3), namely in correspondence of the side of said drum (3) which is the opposite side with respect to the side on which there is the intake for the introduction and the taking-out of the content of said drum (3).

4. Drive (1) for the drum (3) of a concrete mixer (8) according to any of the previous claims characterised in that said misalignment between the axis (34) of said drive (1) and the axis (35) of said drum (3) is allowed in a bi-directional way, said misalignment being allowed to occur in both directions, with deviation angles (33) between the axis (34) of the drive (1) and the axis (35) of the drum (3) preferably included in a range from - 5 degrees to + 5 degrees, even more preferably in a range from - 3 degrees to + 3 degrees.

5. Drive (1) for the drum (3) of a concrete mixer (8) according to any of the previous claims characterised in that said flange (23) is supported in correspondence with said central body (24) of said drive (1) by means of fourth bearings (30) releasing a portion of the weight of said drum (3) through said central body (24) on said box (19).

6. Drive (1 ) for the drum (3) of a concrete mixer (8) according to the previous claim characterised in that said fourth bearings (30) are shaped to allow said misalignment between the axis (34) of the drive (1) and the axis (35) of the drum (3) by means of a sliding movement with inclination of the base of said flange (23) with respect to said central body (24).

7. Drive (1) for the drum (3) of a concrete mixer (8) according to the previous claim characterised in that said fourth bearings (30) are roll bearings with two bearers of rolling bodies.

8. Drive (1) for the drum (3) of a concrete mixer (8) according to any of the previous claims characterised in that said motor (2) is fixed on said box (19) of the drive (1) in correspondence with a cover (18) which closes the inside of said box (19) containing said first stage (9, 10, 11) and containing a second stage (12, 13, 14) of said drive (1), the shaft (32) of said motor (2) coupling with a pinion (9) of said first stage which is supported on said cover (18) by means of a fifth bearing (31), said pinion (9) of said first stage coupling with corresponding planetary-gears (10) of said first stage which in turn transmit the motion to a planetary gear-support (11) of said first stage by means of sliding on first bearings (27), said planetary gear-support (11) of said first stage in turn transmitting the motion to a pinion (12) of said second stage, said pinion (12) of said second stage coupling with corresponding planetary-gears (13) of said second stage which in turn transmit the motion to a planetary gear-support (14) of said second stage by means of sliding on second bearings (28), said planetary gear-support (14) of said second stage in turn transmitting the motion to a pinion (15) of said third stage, said pinion (15) of said third stage coupling with corresponding planetary-gears (16) of said third stage which in turn transmit the motion to said flange (23) by means of sliding on third bearings (29).

9. Drive (1) for the drum (3) of a concrete mixer (8) according to the previous claim characterised in that said planetary-gears (16) of said third stage transmit the motion to said flange (23) by means of said ring-gear (21), said ring-gear (21) putting in rotation said drum (3) of said concrete mixer (8).

10. Drive (1 ) for the drum (3) of a concrete mixer (8) according to any of the previous claims characterised in that said motor (2) is a hydraulic motor, preferably a hydraulic motor with axial pistons.

1 1. Concrete mixer (8) including a mixing drum (3) characterised in that it includes a drive (1) for drum (3) of a concrete mixer (8) according to any of the previous claims.