More particularly, it relates to a flexible drive assembly, and to a mechanism incorporating the flexible drive assembly, in particular a vibrator for vibrating fluid cementitious material.

According to a first aspect of the invention, there is provided a flexible drive assembly which includes : an elongated flexible core for the transmission of rotation and torque from one end of the assembly to the other end thereof; a plurality of bearings in which the core is journalled and supported, the bearings being spaced longitudinally in series along the length of the core; a support supporting the bearings; and an elongated reinforcing sheath extending circumferentially around the core and extending along the length of the core, the sheath permitting bending of the core and the sheath restricting radial expansion of the core in response to the transmission of rotation and torque by the core.

The support may be an elongated flexible tube within which the core and the bearings are located, the bearings being supported by the tube and the core being supported by the bearings such that the core is radially inwardly spaced from the tube, a peripheral space being defined between the radially outwardly facing surface of the core and the opposed radially inwardly facing surface of the tube.

Typically, the tube and bearings are of circular outline in cross-section, the inner diameter of the tube being larger than the outer diameter of the bearings, a spacing ring being located between a radially outwardly facing circumferentially extending periphery of each bearing and the opposed inner surface of the tube.

Instead, a radially outwardly facing circumferentially extending periphery of each bearing may abut the inner surface of the tube.

Preferably, the tube has an inner diameter of 10-50 mm, when the assembly is intended for use in a vibrator as described hereunder.

Typically, the flexible core comprises a multiplicity of longitudinally extending strands which are interconnected to form a rope or cable. The strands may be metal strands interconnected in an arrangement which permits torque to be transmitted by the core substantially equally effectively in either rotational direction, in particular so that there is not materially greater tendency for the core to unravel when transmitting torque in one rotational direction when compared with the other.

The sheath may be a helically wound elongated element having coils which are spaced along the length of the sheath from one another. Typically, each element is a metal wire.

In a particular embodiment, the series of bearings may have end bearings at opposite ends thereof which are spaced longitudinally inwardly from the ends of the core, the reinforcing sheath comprising a series of longitudinally spaced sheath portions, the sheath portions extending respectively between neighboring bearings and between the end bearings and the ends of the core, radial expansion of the core at positions located between neighboring sheath portions being restricted by the bearings.

Each bearing may be anchored against longitudinal displacement thereof relative to the core, e. g. by clamping radially inwardly on to the core or sheath.

To this end, each bearing may be anchored by means of a locking collar on which a radially inwardly facing surface of the bearing seats, the locking collar exerting a radially inward compressive force on the core, optionally indirectly via the sheath, to anchor the collar longitudinally in place. Each locking collar may comprise a ring of arcuate segments, radially inwardly facing surfaces of the segments together defining a circular cylindrical clamping surface, clamping engaging the core or sheath, radially outwardly facing surfaces of the segments being tapered so that together they form a frusto-conical bearing seat for the associated bearing, against which seat the inner periphery of the bearing is clamping wedged.

Preferably, each bearing is a roller bearing having an inner race anchored longitudinally relative to the core and an outer race. In this specification the term roller bearing is to be construed broadly as covering bearings having inner and outer bearing races separated from each other not only by rollers, but by balls, i. e. as covering ball bearings as well.

The bearings may be equally longitudinally spaced along the core, the spacing between neighboring bearings being 35-150 mm, suitable for a vibrator as described hereunder. Preferably, the distance between neighboring bearings is 50-100 mm, the tube having an inner diameter of 10 to 50 mm.

The assembly may include a clamping element clamped to at least one end of the core or sheath, each clamping element exerting a radially inwardly clamping force on the core or sheath. Typically, each clamping element is a sleeve which has been radially inwardly compressed on to the radially outwardly facing circumferentially extending surface of the associated end of the core or sheath, the sleeve being c-axial with the core or sheath.

According to a second aspect of the invention, there is provided a mechanism for transmitting rotation and torque, the mechanism including : a rotary drive member operatively connected to one end of the core of a flexible drive assembly as described above for supplying rotation and torque to the core; and a driven member operatively connected to the other end of the core of the assembly, for receiving rotation and torque from the core, the driven member being rotatable, via the drive assembly, in response to rotation of the drive member.

The mechanism may form part of a vibrator for vibrating fluid cementitious material, the driven member being a vibration head for vibrating in response to rotation thereof.

According to a third aspect of the invention, there is provided a vibrator for vibrating fluid cementitious material, which vibrator includes: a rotary drive member; a flexible drive assembly as described above, the core having an end connected to the drive member for receiving rotation and torque from the drive member; and a vibration head connected to the other end of the core of the flexible drive assembly for receiving rotation and torque from the core, the vibration head being rotatable, via the drive shaft assembly, in response to rotation of the drive member, to cause vibration of the vibration head.

The invention will now be illustrated by way of example, with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a schematic view of a vibrator for vibrating fluid cementitious material in accordance with the invention; Figure 2 is a schematic longitudinal section on an enlarged scale of a portion of a flexible drive assembly forming part of the vibrator of Figure 1, in the direction of line II-II in Figure 3; Figure 3 is a schematic cross-section of the flexible drive assembly of Figure 2, in the direction of line 111-111 in Figure 2; and Figure 4 is a schematic longitudinal section of an end portion of the flexible drive shaft assembly of Figure 2.

In the drawings, reference numeral 10 generally indicates a vibrator for vibrating fluid cementitious material, such as concrete or cement in a fluid state, in accordance with the invention. The vibrator 10 includes a rotary drive assembly 20 which is powered by an output shaft 12 of a motor 14.

The vibrator 10 also includes a vibration head 16 which has a conventional hammer and anvil arrangement wherein a hammer (not shown) is eccentrically rotatably located within an anvil 18. The vibration head 16 thus vibrates in the usual way in response to the application of torque and rotation to the hammer which rotates the hammer eccentrically within the anvil 18.

The shaft 12 is connected to the vibration head 16 by means of a flexible drive assembly 20. The drive assembly 20 includes an elongated flexible core in the form of a cable 22 which is connected to the shaft 12 at one end 24 of the cable 22 and is connected to the hammer of the vibration head 16 at the other end 26 of the cable 22. In conventional fashion, the cable 22 comprises a multiplicity of longitudinally extending metal strands 28 which are interconnected in an arrangement which permits torque and rotation to be transmitted by the cable 22 substantially equally efficiently in either rotational direction. Such cables are colloquially referred to in the art as non-spin wire ropes.

The cable 22 is located within a support in the form of an elongated flexible tube 30, the cable 22 being radially inwardly spaced from the wall of the tube 30. In this case the tube 30 is a single steel-wire-reinforced 1 1/4 inch hydraulic hose which is circular in cross-section and has an inner diameter of about 32 mm, a wall thickness of about 3.2 mm, and a length of about 6 m.

The cable 22 is supported in the tube 30 by a plurality of bearings 32 spaced longitudinally in series along the length of the cable 22. The bearings 32 support the cable 22 such that an annular peripheral space is defined between the radially outwardly surface of the cable 22 and the opposed radially inwardly facing surface of the tube 30. The bearings 32 are roller bearings, each having a radially outer race 36 running freely on an inner race 34 by means of a ring of balls 38 held captive between the races 34,36.

The inner race 34 of each bearing 32 is anchored and locked relative to the cable 22 by means of a locking collar 40 located between the radially inner periphery of the inner race 34 and the cable 22. The locking collar 40 comprises a ring of arcuate segments 42 which are angularly spaced apart, so that the locking collar 40 is radially inwardly compressible. Radially outwardly facing surfaces 44 of the segments 42 are tapered, so that together they form a longitudinally split frusto-conical bearing seat against which the radially inner periphery of the inner race 34 of the associated bearing 32 is clamping wedged. For clarity of illustration, the taper of the segments 42 is exaggerated in Figure 2. The locking collar 40 thus exerts a radially inward clamping force on the cable 22 to anchor the collar 40, and thus the associated bearing 32, to the cable 22. The bearings 32 are equally longitudinally spaced along the cable 22, the spacing between neighboring bearings 32 being about 75 mm.

As can best be seen in Figure 3 of the drawings, the inner diameter of the tube 30 is larger than the outer diameter of the bearings 32, a spacing ring 46 being located between the radially outwardly facing periphery of each bearing 32 and the opposed radially inwardly facing surface of the tube 30. The outer race 36 of each bearing 32 fits tightly into the associated spacing ring 46, while the spacing ring 46 in turn fits tightly into the tube 30, so that the spacing ring 46 effectively connects the outer race 36 to the tube 30.

The assembly 20 further includes a series of longitudinally spaced sheath portions 48 (Figure 2). Each sheath portion 48 extends circumferentially around the cable 22 and extends longitudinally along the cable 22 between the bearings 32 of a neighboring pair of the bearings 32. For ease of illustration, the cross-section of Figure 3 is at a position such that the sheath portions 48 are not shown in Figure 3 of the drawings. In this example, each sheath portion 48 is a helically-wound elongated metal wire having coils which are longitudinally spaced along the length of the sheath portion 48 from one another. The sheath portions 48 are sufficiently loosely wound and spaced from one another so that neighboring coils of the sheath portions 48 do not contact each other when the cable 22 is bent. In the present case, each sheath portion 48 is a loosely wound copper coil which has been heat-treated in a softening process, in order to increase the flexibility of the sheath portion 48. It is important to appreciate that, although each sheath portion 48 has the appearance of a length of spring, it does not function as a spring in the drive assembly 20, where, due to the tensile strength of the copper wire, the sheath portions 48 act in use rather to restrict radial expansion of the cable 22 in response to transmission of rotation and torque by the cable 22, any spring-like characteristics of the sheath portions being irrelevant. It will be appreciated that the bearings 32, via their locking collars 40, also restrict radial expansion of the cable 22 where the respective bearings 32 engage the cable 22, so that the series of sheath portions 48, and the interspersed bearings 32, effectively together form a sheath extending along the full length of the cable 22.

Radial expansion of the cable 22 is thus inhibited along its entire length.

Although the sheath in this example comprises the series of sheath portions 48, the sheath can naturally instead be formed by a continuous element which extends circumferentially around the cable 22 and extends longitudinally along the full length of the cable 22. This continuous element can, for instance, be a continuous loosely wound helical wire, or a continuous sleeve or skin of a plastics material which is sufficiently strong to resist radial expansion of the cable 22 in use. In such case, the bearings 32 will be clamped, via the locking collars 40, and indirectly via the sheath, on to the cable 22.

At each end 24,26 of the cable 22, a clamping element in the form of a sleeve 50 (Figure 4) is clamped to the cable 22, each sleeve 50 exerting a radially inwardly clamping force on the cable 22. The sleeves 50 are aluminum tubes which have been radially inwardly compressed in a crimping process on to the radially outwardly facing surface of the associated ends 24,26 of the cable 22.

The sleeves 50 are connected to the output shaft 12 of the motor 14 and to the hammer of the vibration head 16 respectively. Figure 4 shows the connection of one end 24 of the cable 22 to the shaft 12, the associated sleeve 50 being received in a socket 52 in the end of the shaft 12. The sleeve 50 is connected to to shaft 12 by fasteners (not shown) passed through radially extending holes 54 in the socket 52, the fasteners clamping on to the sleeve 50. As can be seen in Figure 4 of the drawings, the tube 30 is connected to the motor 14 (not shown in Figure 4) by a tubular fitting 56 having an end received in the end of the tube 30, and locked thereto by a strap 59. The tubular fitting 56 covers the connection between the shaft 12 and the cable 22, the shaft 12 being supported there by roller bearings 58 housed in the tubular fitting 56.

In use, the shaft 12 is drivingly rotated by the motor 14. The shaft 12, via the associated sleeve 50, applies torque and rotation to the one end 24 of the cable 22. This torque and rotation are transmitted by the cable 22, via a sleeve similar to the sleeve 50 and connected to the other end 26 of the cable 22, to the hammer of the vibration head 16. The cable 22 thus rotates relative to the tube 30, which is stationary, so that the vibration head 16 can be safely manoeuvered about a construction site. Radial expansion of the cable 22, i. e. flaring or bulging, is restricted by the sheath portions 48 and by the bearings 32. Longitudinal movement of the bearings 32 relative to the cable 22 is restricted by anchoring of the bearings 32 to the cable 22 by the associated locking collars 40.

It is an advantage of the flexible drive assembly 20, as described with reference to the drawings, that it provides a flexible drive for transmitting torque and rotation in a safe and effective manner. The Applicant has found that conventional flexible drive assemblies, which have relatively rotating parts in contact with one another, are prone to failure, posing a threat to the safety of persons in the vicinity of the drive assemblies. The Applicant has also found that failure of such drive assemblies often occurs due to bulging or flaring of cables forming part of the assemblies. This bulging or flaring is inhibited, if not prevented, by the sheath portions 48 and bearings 32 of the drive assembly 20. The Applicant has found, furthermore, that the drive assembly 20 can be made to be capable of transmitting torque and rotation when bent through angles of up to 720°.

The Applicant further believes, without being bound by theory, that this bulging or flaring of the cable 22 is caused by slippage of the strands 28 of the cable 22 relative to one another. The sleeves 50, which are clamped onto the ends 24,26 of the cable 22, and the locking collars 40, which exert a clamping force on the cable 22, serve to resist such slippage. The clamping forces of the respective locking collars 40 are generated when, during assembly of the drive shaft assembly 20, the bearings 32 are forced in a longitudinal direction on to the respective tapered bearing seats, so that the ring of arcuate segments 42 contracts radially inwardly, clamping onto the cable 22.

Although the flexible drive assembly 20 is illustrated in the drawings as forming part of a vibrator 10, it will be appreciated that the drive shaft assembly can find application in a variety of different mechanisms. For instance, the drive shaft assembly may be used drivingly to connect the engine of a motor vehicle to the wheels of the vehicle. It will be appreciated that, in such case, the support for the bearings will be provided by bearing housings forming part of or mounted on the chassis of the vehicle, so that no tube 30 is required to provide rigidity to the drive shaft assembly, and the tube 30 can be omitted. The need for universal- and/or CV joints in the drive train of a vehicle can thus be avoided.