AU2006235894B2 - A locking assembly for locking an output flange of a drive system against rotation - Google Patents

Abstract

A mixer assembly I having two looking assemblies 24 for physically locking a drum 12 of the mixer assembly I against rotation is disclosed. The mixer assembly 1 5 comprises a support 14 in the form of a support frame and the drum 12 which is rotatably mounted on the support 14. The front end 23 of the drum 12 is driven to rotate by means of a hydraulic motor and a hydraulic gearbox 20 through an output flange. 22 that is mounted on the front end of the barrel 12 by means of a plurality of bolts 40. Each locking assembly 24 comprises a slide 44 that is mounted on the 10 support 14, and an arm 26 that is mounted on the slide 44 in a way that permits the arm 26 to be slidably displaced relative to the slide 44. The arm 26 includes an arm locking formation which is a bracket 32 at an upper end thereof. The bracket 32 engages a passive locking formation that is formed by some of the bolt heads 40 on* the gearbox flange 22 to look the gearbox flange 22 and drum 12 against rotation 15 relative to the support frame 14. The arm 24 may be manually slidable between an unlocked position in which the arm bracket 32 is spaced away from the passive locking formation and a locked position in which the arm bracket 32 is engaged with the bolt heads 40. FIG 1 FOR PUBLICATION ~~>s iS / a .49

Description

1 A LOCKING ASSEMBLY FOR LOCKING AN OUTPUT FLANGE OF A DRIVE SYSTEM AGAINST ROTATION FIELD OF THE INVENTION 5 This invention relates to a locking assembly for locking an output flange .of a drive system against rotation. This invention also extends to mixer assembly having a drum that can be locked against rotation and also a method for -resisting rotation of a drum of a mixer assembly. Finally the invention also extends to a vehicle having a 10 mixer assembly mounted thereon. This invention relates particularly but not exclusively to a looking assembly for locking a drum of a concrete transport truck against rotation, e.g. while maintenance work is carried out by maintenance workers within the drum. It will therefore be convenient to 15 hereinafter describe the invention with reference to this example application. However at the same time it is to be clearly appreciated that the invention is capable.of broader application. For example the invention could be'applied to mixer assemblies other than those mounted on concrete transport trucks. 20 The invention could find application in any situation where a gearbox flange is desired to be locked against rotation. This could include a gearbox flange mounted to a rotary drum or mill or kiln. Another application of the invention could be to a gearbox flange that is used to rotate a carousel. The varied nature of the example applications make clear the very broad scope of the Invention. It would clearly be very difficult if not 25 impossible to itemise all the different possible applications of the invention in this specification. BACKGROUND TO THE INVENTION 30 Settable cementitious materials such as concrete and cement are widely used as construction materials around the world. Such materials together with reinforced steel are used to form ferro-concrete structures.

2 Concrete and cement is mixed into a slurry in a botching plant and this slurry is then transported to the building site where it is poured into an open topped frame, e. g. formwork, and allowed to set. The concrete or cement has a tendency to set and thus 5 it has to be regularly turned while it is being transported to the pour site to resist it from setting.

A contrivance known as a concrete transport truck is used to transport the cementitious material from the batching plant to the building site where it is required 10 to be poured. The transport truck has a drum mounted on the chassis which is constantly rotated when it is filled with concrete to resist setting of the cementitious material while it is being.transported to the pour site. The drum in effect is positioned lying on its side and therefore rotates about a broadly 15 horizontal axis. The drum has a number of internal baffles and flights mounted on its inner surface that help to lift the material up as the barrel rotates and then permit it to fall back when it reaches a certain.height in the barrel. Conveniently the drum of the mixer assembly is rotated by a drive means in the form 20 of a hydraulic motor through a hydraulic gear box that is mounted on the front of the drum. The hydraulic motor is driven by power from the primary drive of the concrete transport truck. More specifically drive from the engine is transferred to the hydraulic motor by means of a power take off shaft. The drive of the hydraulic motor is then transferred through to the gearbox which has a ratio that will rotate the drum at an 25 appropriate speed. The gearbox has an output flange that is directly coupled to the drum so that rotation of the output flange of the gearbox causes the drum to rotate. More specifically the output flange is coupled to the drum by means of a plurality of bolts that are passed 30 through the flange and into the drum around a circumferential edge region of the flange. This provides a strong attachment of the drive to the drum that can withstand the torque generated when a fully loaded drum is caused to rotate.

3 During day to day operation of a concrete transport truck some of the settable material carried in the drum sets and hardens on the inside surface of the drum. Over time this layer of hardened material increases in thickness and eventually a point is 5 reached where it is desirable to remove this layer of hardened material. To do this it is usual for workers to enter into the drum and physically chip off and remove the hardened material from the drum. 10 It will readily be appreciated that it would be very dangerous if the drum was inadvertently started up and caused to rotate while a worker was inside the drum, e.g. performing the maintenance operations described above. The worker would be at great risk of being injured or killed. The Applicant is aware of one instance in Australia where a worker doing maintenance work inside a barrel was decapitated when the 15 barrel started rotating while they were in' the barrel. Currently the only safety system available to workers entering into. the interior of the barrel is to take the ignition keys for the truck and put them in their pockets when they go into the barrel. However this is not a satisfactory solution to this problem. 20 As a result there is a move by occupational health and safety authorities and also managers in companies working with concrete transport trucks to provide a system or contrivance that will provide some assurance to a worker that the drum will not be caused to rotate while they are working inside the drum. 25 Clearly therefore it would be advantageous if a contrivance could be devised that enabled a worker to have some assurance that the drum would be held in' a fixed stationary position such that it could not rotate while they were working inside the drum.

4 SUMMARY OF THE INVENTION According to one aspect of this invention there is provided a mixer for mixing 5 materials therein, comprising; a drum that is mounted for rotation on a support; at least one drum safety arrangement for locking the drum against rotation on the support when maintenance is carried out on the drum, including a locking arm having one end that is mounted on the support and another end that can be engaged with 10 the drum, the locking arm being moveable on the support between a locked position in which the other end is free of engagement with the drum and a locked position in which the other end is engaged with the drum, whereby to resist rotation of the drum on the support; and a locking device that can lock the locking arm in the locking position to prevent a 15 person other than a supervisor from moving the locking arm out of the locked position whereby to avoid a situation where the drum is caused to rotate by a person while a worker is located within the drum. The locking device may be a padlock. For example the padlock may be a key 20 operated padlock or a combination operated padlock. The locking device can also be used to lock the locking arm in the unlocked position. The drum safety arrangement may further include a guide mounted on the support for 25 guiding movement of the locking arm between the unlocked and locked positions. The guide may comprise a guide formation which is mounted on the support and a sliding element which is received within the guide formation, and the sliding element may slide along the guide formation to guide movement of the locking arm between 30 the locked and unlocked positions.

5 The sliding element may include a locking bracket which can be engaged with the locking device when the locking arm is locked in either the locked or unlocked positions, and another locking bracket which can also be engaged with the locking device when the locking arm is locked in either the locked or unlocked positions. 5 The other end of the locking arm may include a drum engaging formation, and the drum may include a complementary arm engaging formation that is spaced away from the axis of rotation of the drum. The drum engaging formation may be engaged with the complementary arm engaging formation when the locking arm is in the 10 locked position whereby to lock the drum against rotation. The locking arm may have a longitudinal axis and the drum engaging formation may extend transverse to the longitudinal axis, and the drum engaging formation may define at least one opening within which the complementary arm engaging formation 15 can be received. The drum engaging formation may define a plurality of openings that are spaced apart from each other in a line on the drum engaging formation, each of which can be engaged with a complementary arm engaging formation on the drum. The drum may 20 have a drive flange on an end thereof and the drive flange may be mounted on the drum by a plurality of bolts that project away from the surrounding surface of the drive flange. The bolt heads may form the complementary arm engaging formation on the drum, and each opening may have a bolt received therein to engage the other end of the locking arm with the drum. 25 The mixer may have two said drum safety arrangements that are positioned spaced apart from each other in a direction of the circumference of the drum. For example the two drum safety arrangements may be positioned on opposite sides of the drum. 30 According to another aspect of this invention there is provided a vehicle for transporting a settable cementitious material, including: 6 a vehicle chassis; a support that is a drum support mounted on the chassis; a drum that is mounted for rotation on the support, the drum being orientated so that it lies on its side having one end that is closed and another end that is open through 5 which material is fed into the drum and through which material is discharged from the drum; at least one drum safety arrangement for locking the drum against rotation on the support when maintenance is carried out on the drum, the locking arrangement including a locking arm having one end that is mounted on the support and another 10 end that can be engaged with the drum, the locking arm being moveable on the support between a locked position in which the other end is free of engagement with the drum and a locked position in which the other end is engaged with the drum whereby to resist rotation of the drum on the support; and a locking device that can lock the locking arm in the locking position to prevent any 15 person other than a supervisor from moving the locking arm out of the locked position whereby to avoid a situation where the drum is caused to rotate by a person while a worker is located within the drum. The locking device may be a padlock. 20 The drum safety arrangement may further include a guide mounted on the support for guiding movement of the locking arm between the unlocked and locked positions. The guide may comprise a guide formation which is mounted on the support and a sliding element which is complementary to the guide formation which is operatively 25 connected to the locking arm, and the sliding element may be received within and may slide along the guide formation to displace the locking arm between the locked and unlocked positions. The other end of the locking arm may include a drum engaging formation for 30 engaging a complementary arm engaging formation on the drum that is spaced away from the axis of rotation of the drum so that the locking arm holds the drum against rotation when drum engaging and arm engaging formations are engaged.

7 The drum engaging formation may define a plurality of openings that are spaced apart from each other in a line on the drum engaging formation. The drum may have a drive flange on an end thereof and the drive flange may be mounted on the drum by 5 a plurality of bolts that project away from the surrounding surface of the drive flange. The bolt heads may form a complementary arm engaging formation such that each of the openings in the drum engaging formation can be engaged with a bolt. The drum and the drum safety arrangement may include any one or more of the 10 features of the drum and the drum safety arrangement of the mixer defined in the first aspect of the invention above. According to another aspect of this invention, for a mixer having a drum that is mounted for rotation on a support, there is provided a drum safety arrangement 15 including: a locking arm having one end that is mounted on the support and another end that can be engaged with the drum, the locking arm being moveable on the support between a locked position in which the other end of the locking arm is free of 20 engagement with the drum and a locked position in which the other end of the locking arm is engaged with the drum to resist rotation of the drum on the support; and a locking device that can lock the locking arm in the locked position to prevent a person other than a supervisor from moving the locking arm out of the locked position whereby to avoid a situation where the drum is caused to rotate by the unauthorized 25 user while a worker is located within the drum. The locking device may be a padlock. The drum safety arrangement may further include a guide mounted on the support for 30 guiding movement of the locking arm between the unlocked and locked positions, and the guide may comprise a guide formation which is mounted on the support and a sliding element which is complementary to the guide formation which is operatively 8 connected to the locking arm, and the sliding element may be received within and slides along the guide formation to displace the locking arm between the locked and unlocked positions. 5 The other end of the locking arm may include a drum engaging formation for engaging a complementary arm engaging formation on the drum that is spaced away from the axis of rotation of the drum so that the locking arm holds the drum against rotation when drum engaging and arm engaging formations are engaged. 10 The drum engaging formation may define a plurality of openings that are spaced apart from each other in a line on the drum engaging formation. The drum may have a drive flange on an end thereof and the drive flange may be mounted on the drum by a plurality of bolts that project away from the surrounding surface of the drive flange. The bolt heads may form the complementary arm engaging formations such that each 15 of the openings in the drum engaging formation can be engaged with a bolt. The drum safety arrangement may include any one or more of the features of the drum and the drum safety arrangement of the mixer defined in the first aspect of the invention above. 20 For a mixer having a drum that is mounted for rotation on a support, according to another aspect of the invention there is provided a method of locking the drum against rotation on the support, including: 25 providing a locking arm having one end that is fixed to the support and another end remote from said one end; and fixing said other end of the arm to the drum in a way that the locking arm holds the drum against rotation. 30 The method may include locking the locking arm in its position fixed to the drum by means of a locking device, 9 The mixer may include a guide mounted on the support for guiding movement of the locking arm between the unlocked and locked positions, and locking the locking arm in the locked position may include locking the locking arm to the guide by means of a padlock. 5 The drum may include a drive flange having a plurality of bolts projecting from the bolt flange and the locking arm includes a drum engaging formation may comprise a plurality of openings, and fixing said other end of the arm to the drum may include receiving a said bolt within each opening to hold the drum against rotation. 10 According to another aspect of this invention there is provided a locking assembly for locking an output flange of a drive system against rotation, the locking assembly comprising: 15 a slide for mounting on a support; and an arm that is mounted on the slide in a way that permits the arm to be slidably displaced relative to the slide, the arm including an arm locking formation thereon spaced away from the slide, for lockingly engaging a passive locking 20 formation on a component of the drive system, the arm being slidable between an unlocked position in which the arm locking formation is spaced away from the passive locking formation and a locked position in which the arm locking formation is engaged with the passive locking formation whereby to lock the drive train against rotation relative to the support. 25 Thus the slide is mounted on the support on which the drive system is mounted and the locking formation engages a passive locking formation on the actual drive system. This physically resists rotation of the drive system relative to the support when the drive system is engaged. 30 10 The slide may comprise a slide block defining an elongate slot and the arm may have a slide formation that is complementary to the slot and which is slidingly received within the slot. 5 The locking formation on the arm may comprise at least one opening defined in the arm that is sized to be passed over a said passive locking formation that is a projection projecting out from the component of the drive system. The component of the drive system to which the arm is locked may be an output 10 flange, e.g. an output flange on the gearbox. The locking formation may comprise a plurality of openings and each opening may be sized to be passed over a bolt head on the output flange, e.g. with some clearance thereby to resist rotation of the output flange. In one form the locking formation 15 defines two to four openings, e.g. of substantially circular configuration, sized to receive hex heads of the bolts with some clearance. It is not necessary for the openings in the locking formations to be complementary to the shape of the passive locking formations received therein. 20 The arm in turn may comprise a support portion that extends parallel to the slot in the slide block and a locking formation portion forming said locking formation. The locking formation portion may extend substantially perpendicular to the support portion. 25 The arm may include a locking handle that extends away from the arm substantially perpendicular there to and the locking handle may be pivotal relative to the arm. The slide block may further include check means for checking movement of the arm slide formation within the slide block in each of the locked and unlocked positions. 30 The check formations may include transverse slots extending away from the main slot within which the locking handle can be received to position the arm in respectively the locked and unlocked positions.

11 Yet further the locking assembly may include locking means for locking the arm in each of the locked and unlocked positions. 5 The locking means may be a lock that comprises a bracket on the arm and a complementary bracket on the locking handle that can be locked together when the arm is in each of the locked and unlocked positions and the arm is effectively then locked in either the locked or the unlocked position as the case may be. The lock needs to be moved from the locked to the unlocked position and back again. The 10 locking means may include padlocks for padlocking the bracket on the arm to the locking handle. The locking assembly may be manually moved from the unlocked to the locked position, e.g. by a user. This may be accomplished by a user grabbing hold of the arm 15 and physically moving it forward and backward in the slide. Optionally the arm may include a handle formation, e.g. a knob, mounted thereon which can be held by a user to assist them to move the arm backwards and forwards. The handle may project laterally outwardly away from the arm and may be positioned a short distance above the slide. 20 Optionally the locking assembly may include means for driving the arm backwards and forwards between the locked and unlocked positions. The drive means maybe in the form of a pneumatic drive, a linear actuator or a 25 hydraulic drive. According to another aspect of this invention there is provided a mixer assembly comprising: 30 a support; a drum rotatably mounted on the support; 12 a drive means for driving the drum to rotate driveably connected to one end of the drum; and a means for holding the drum against rotation relative to the support that can be moved between an unlocked position in which the drum can rotate without 5 interference and a locked position in which the drum is held against rotation. The mixer assembly may be suitable for mixing slurry, particulate materials or liquid. The slurry may be a settable cementitious material, such as concrete or cement. The particulate material may be free of liquid. For example the particulate materials could 10 be aggregate or powder or stone. The liquid material may be a homogeneous liquid or it may be an emulsion. For example the liquid may be paint. The support may be in the form of a support frame. The support frame is designed to be mounted on a support surface, e.g. a broadly planar support surface be it a floor or 15 a chassis of a vehicle. The drum may have a longitudinal axis about which it rotates and the longitudinal axis may be substantially horizontally extending, i.e. the drum may be supported lying on its side. 20 The drum may have an opening through which material is charged into the drum and discharged from the drum. The opening may be positioned on an end of the drum opposed to the end on which the drive is mounted. 25 The drive means may comprise a hydraulic motor driveably coupled to a gearbox which has an output flange. The output flange of the gearbox may be operatively coupled to the drum, e.g. directly. Specifically the output flange may be bolted onto the end of the drum by means of a plurality of bolts located at spaced intervals around a circumferential edge region of the output flange. 30 The holding means may be a locking means that physically locks the drum against rotation relative to the support.

13 The locking means may comprise at least one locking assembly comprising a slide that is mounted on the support, and an arm that is mounted on the slide in a way that permits the arm to be slidably displaced relative to the slide, the arm including an arm 5 locking formation spaced away from the slide, for lockingly engaging a passive locking formation on a component of the drive system. The arm may be slidable between an unlocked position in which the arm locking formation is spaced away from the passive locking formation and a locked position in 10 which the arm locking formation is engaged with the passive locking formation whereby to lock the drive train against rotation relative to the support. The passive locking formation may be formed by a formation on the drive means or a formation on the barrel. 15 The passive locking formation on the drive means may comprise at least one projection projecting outward proud of the gearbox output flange. The passive locking formation may comprise a plurality of said projections projecting outward proud of the flange, e.g. a bolt heads on the output flange. 20 Instead the passive locking formation on the barrel may be formed by projections projecting out from the surface of the barrel. The projections may be positioned towards the end of the barrel to which the drive means is mounted. 25 The locking means may comprise one locking assembly on a left side of the barrel and another locking assembly on the right side of the barrel. Thus the two locking assemblies lock the output flange on its left and right sides and this confers considerable strength on the locking means as a whole, 30 The mixer assembly may be a concrete mixer or a cement mixer that is mounted on a transport truck. In such a mixer the drum has a horizontally extending rotational axis.

14 In another form the mixer assembly may be a mill for particle reduction in mineral processing operations. The mill has a housing that also has a horizontally extending rotational axis. In yet another form the mixer assembly may be a kiln. 5 According to yet another aspect of this invention there is provided a vehicle comprising: a chassis mounted on ground engaging wheels; 10 a mixer assembly having a drum mounted on a support as described above in the preceding aspect of the invention mounted on the chassis, the mixer assembly having a locking assembly for locking the barrel or the drive against rotation relative to the chassis. 15 The drum may be mounted with its longitudinal axis extending in a substantially horizontal direction along the length of the chassis. The mixer assembly may have locking assemblies on left and right sides of the barrel. 20 Further the locking assemblies may have arm locking formations that engage bolt heads on the output flange of a gearbox of the drive mechanism. The vehicle may further include drive means for driving the vehicle along a support surface. 25 The vehicle may include means for resisting the ignition motor of the vehicle from turning while any of the locking assemblies is in the locked position. The ignition resisting means may also resist the ignition from starting the vehicle when any of the locking assemblies is not fully in the unlocked position. The means for resisting 30 ignition may comprise an electrical or electronic circuit with switches located in the slide.

15 Yet further the means for resisting the ignition motor from turning may issue an audio and/or visual alarm if a driver tries to turn the engine on when the vehicle is not in the fully unlocked position. 5 The means for resisting the ignition motor from turning reduces the risk of a person starting the engine to cause the drive to try and rotate the barrel when it is held against rotation by the arm. If the drive was started up while the arm was locked in position then there would be a risk that the drum or the drive would be damaged. This feature is designed to avoid this situation occurring. 10 The vehicle may be a concrete transport truck or a so called cement mixer truck. According to another aspect of this invention there is provided a method of resisting rotation of a drum for a mixer that is rotatably mounted on a support, the method 15 comprising; physically locking the drum against rotation by means of at least one arm that is physically attached to the drum or a component that rotates with the drum and which is also attached to the support on which the drum is rotatably 20 mounted. The mixer may include a drive and an output flange mounted on an end of the drum and the arm may be releasably locked to the output flange on the drum. 25 Specifically the arm may include an arm locking formation defining at least one aperture therein and the output flange may have bolt heads projecting out there from over which the aperture can be passed. The arm may be movably mounted to the support by means of a slide towards one 30 end of the arm. The arm may be removably mounted to the drum or a component that rotates with the drum towards its other end. In particular the arm may be removably locked to the drum or a component that moves with the drum.

16 According to another aspect of this invention there is provided a method of resisting rotation of a drum for a mixer that is rotatably mounted on a support when maintenance is being done inside the drum of the mixer, the method comprising 5 physically locking the drum against rotation by means of at least one arm that is physically attached to the drum or a component that rotates with the drum and which is also physically attached to the support on which the drum rotates. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 10 A mixer assembly for a concrete transport truck comprising a drum mounted on a support and a locking assembly for locking the drum against rotation may manifest itself in a variety of forms. It will be convenient to hereinafter describe in detail a number of preferred embodiments of the invention with reference to the accompanying drawings. The purpose of providing this detailed description is to 15 instruct persons having an interest in the subject matter of the invention how to carry the invention into practical effect. However it is to be clearly understood that the specific nature of this detailed description does not supersede the generality of the preceding broad description. In the drawings: 20 Fig 1 is a three dimensional view of a locking assembly mounted on a concrete transport truck; Fig 2 is a part sectional front view of part of the locking assembly and transport truck of Fig 1; 25 Fig 3 is an exploded three dimensional view of the locking assembly of Fig 1 and the part of the concrete transport truck on which the locking assembly is mounted and the part with which the locking assembly is engaged in the locked position; 30 Fig 4 is a front three dimensional view of a left side locking assembly shown in the locked position locking the barrel against rotation; 17 Fig 5 is a front three dimensional view of a right side locking assembly in the locked position locking the barrel against rotation; 5 Fig 6 illustrates a front three dimensional view of a locking assembly in accordance with another embodiment of the invention mounted to complementary locking formations projecting out from the surface of the barrel or drum of the mixer; 10 Fig 7 illustrates a locking assembly in accordance with yet another embodiment of the invention mounted to a support frame and housing of a comminution apparatus that is a mill; and Fig 8 illustrates a locking assembly in accordance with yet another 15 embodiment of the invention that is mounted to a support frame and rotating carousel. Fig 1 shows a front region of a barrel or drum of a mixer assembly mounted on a concrete transport truck. The mixer assembly is shown generally in the drawings by 20 the reference numeral 1. In the following description the terms barrel and drum shall be used interchangeably and refer to the same thing. Specifically they refer to the mixing container that is mounted on top of the transport truck within which the concrete or cementitious 25 material is contained while being mixed. The concrete transport truck has a cabin with a chassis comprising a pair of parallel chassis rails extending rearward direction from the cabin. The mixer assembly 1 is generally mounted on the chassis rails. 30 The mixer assembly 10 comprises broadly a barrel or drum 12 mounted on a support frame 14 that is commonly referred to in the art as a sub-frame.

18 The support frame 14 is mounted on the chassis rails of the truck. The support frame 14 comprises a framework of support members that project up from the chassis rails. The support frame 14 holds the barrel and its load in a stable position above the 5 chassis rails. The barrel 12 comprises broadly a cylindrical middle section with tapering frusto conical sections disposed at each end of the central section. Further the barrel 12 is in effect lying on its side and rotates broadly about a substantially horizontal axis. 10 The barrel 12 may also tilt down slightly from its rear towards its front. The barrel 12 has a front end 23 that is positioned just behind the cabin of the truck and a rear end that is remote from the cabin of the truck. The front end 23 of the barrel 12 is closed and this is the point at which the drive system for rotating the 15 barrel 12 is driveably connected to the barrel 12. By contrast the rear end defines an opening through which material can be charged into the drum and discharged from the drum. 20 The barrel 12 defines an interior space within which the cementitious material is received. The barrel has a plurality of flights or baffles projecting into the interior space from its interior surface and the flights or baffles assist with lifting and turning material within the barrel. 25 The barrel 12 is rotatably mounted on the support frame 14 by means of supports at both the front and the rear ends of the barrel. The front end is supported by means of a bearing, e.g. a spherical bearing, that rotatably supports the drive mechanism that is driveably connected to the front end of the barrel. 30 The rear end of the barrel has a circumferential track ring that rides on a plurality of support rollers that project up from the support frame 14. Typically there might be two 19 laterally spaced support rollers projecting up from the support roller and the track ring rides along an upper region of the track ring. The barrel or drum is caused to rotate by means of a barrel drive means. In a 5 concrete transport truck the drive means comprises a drive transmission system that includes a hydraulic pump (not shown), that is mounted on the support frame 14, that is driven by power from a power take off shaft on the transport truck. The hydraulic motor 18 in turn is driven by hydraulic fluid from the hydraulic pump. Thus the hydraulic motor is driven ultimately by drive taken off the drive produced by the 10 engine of the truck. The hydraulic motor has an output shaft that is operatively coupled to a hydraulic gearbox 20. The function of the gearbox is to step down the speed of the hydraulic motor so as to cause the drum to rotate at an appropriate speed for mixing the 15 material inside. The gearbox 20 in turn has a gearbox output drive flange 22 that is operatively coupled to the barrel 12. Specifically, the drive flange 22 is bolted to the front end 23 of the barrel 12 by means of a plurality of bolts 40. The bolts 40 are positioned 20 spaced apart from each other, e.g. with approximately equal spacings, around a circumferential edge region of the output flange 22. This way, drive from the take off shaft is transmitted to the gearbox flange 22 and then directly to the barrel 12 causing the barrel 12 to rotate. 25 The above description has focussed on the basic structural features of a concrete transport truck. The following description will focus on the manner in which the barrel or drum can be locked against rotation while maintenance work is being carried out inside the drum 12. 30 20 The mixer assembly 10 includes locking mechanisms or locking assemblies that are indicated generally by the reference numeral 24 for locking the barrel 12 against rotation when they are engaged. 5 In the illustrated embodiments the mixer assembly 10 has two locking assemblies, namely left and right locking assemblies 24 on respectively the left and right sides of the mixer assembly 10 when viewed in the direction of travel of the truck. In Fig I the right locking assembly is visible. 10 Each locking assembly 24 comprises broadly a locking arm 26 having a base that forms a slide formation 30 and an upper end that forms a locking formation. The locking arm 26 is elongate and extends diagonally up from the base 30 to the locking formation. Conveniently the arm may be formed, e.g. cut, from a section of plate steel. The arm may have a handle formation, e.g. in the form of a knob like a door 15 knob, projecting out there from to assist a user to manually move the arm backwards and forwards. The locking assembly also includes a guide means in the form of a slide 44 in which the slide formation 30 on the base of the arm 26 is received for guiding sliding 20 movement of the locking arm 26 between locked and unlocked positions. Each locking formation may comprise a locking bracket 32. The locking bracket 32 defines three formations, e.g. openings 34, 36 and 38 that are sized to be passed over the hex heads of three adjacent bolts 40 on the gearbox flange 22 with a small 25 amount of clearance. The bracket 32 may extend substantially perpendicular to the direction of displacement of the locking arm 26. The bracket 32 also extends transverse to the longitudinal axis 15 of the barrel 12 so as to lie over the surface of the gearbox flange 22. The locking arm 26 and the locking bracket 32 may be a unitary body formed by shaping a single piece of material. 30 The slide formation 30 is fast with the locking arm 26 but will generally be formed separately to the locking arm and be attached there to, e.g. rigidly.

21 In the locked position the locking brackets 32 are passed over the heads of the bolts 40 on the gearbox output flange 22 and lock the gearbox flange 22 and drum 12 against rotation. In the unlocked position the locking bracket 32 is slid away from the 5 bolt heads 40 on the gearbox flange 22 so that the bracket 32 does not interfere with rotation of the gearbox flange 22 and the associated drum 12. The slide formation 30 on the base of the arm is fast with the locking arm 26. Thus, the locking arm 26, the slide formation 30 and the locking bracket 32 are essentially a 10 single unit and move together as one. A locking handle formation 42 is also pivotally mounted on the slide formation 30 at the base of the arm 26. The handle 42 extends out away from the slide formation 30 substantially perpendicular thereto. Thus the handle 42 moves longitudinally together 15 with the slide formation 30 and the locking arm 26 but it is also capable of its own independent pivoting movement on the slide formation 30. Specifically the handle 42 can be pivoted between a horizontal outward extending position and a vertical downward extending position. 20 The slide 44 comprises a slide block defining a primary channel 46 therein for slidingly receiving the slide formation 30 on the base of the arm 26 therein to enable the arm 26 to slide in a longitudinal direction. The slide block also includes transversely extending secondary slots 48, 50 opening into the primary slot 46 at one end. The transverse slot 48, is positioned so as to receive the handle 42 therein 25 when the locking assembly 24 is in the disengaged or unlocked position. Similarly, the transverse slot 50 is positioned so as to be able to receive the handle 42 when the locking mechanism is in the locked position. The slide block in turn is mounted on a member of the support frame by means of 30 fastening elements as shown in the drawings. Conveniently there may be four fastening elements positioned broadly towards the four corners of the slide block.

22 The mixer assembly 10 also includes padlock brackets 56, 58 on each of the handle 42 and the locking arm 26 for enabling an operator to padlock the locking mechanism 24 in the locked position. The padlock may be a key operated lock or a combination lock. This key or combination lock that locks the handle in position provides operators 5 and workers with added assurance that unauthorised tampering with the lock assembly including moving the arm 26 to an unlocked position would not readily take place while an operator was inside the drum 12. In the illustrated embodiment the locking assembly 24 and specifically the arm 26 is 10 manually moved between the locked and unlocked positions by a user or operator. The slide 44 guides or directs the movement of the slide formation 30 between the two longitudinally spaced slots 48, and 50 to facilitate the change between the locked and unlocked positions. 15 In another embodiment that has not been illustrated the locking assembly 24 has a drive means in the form of a linear actuator or a hydraulic drive to drive the arm 26 between the locked and unlocked positions. The locking assembly 24 also has a damage prevention means or mechanism to 20 resist the drive means (for rotating the drum) from being activated when one or more locking assemblies are in the locked position (where they physically lock the drum against rotation). The damage prevention means includes a circuit and switch, e.g. in the form of a 25 micro-switch 52, that is operatively connected to the ignition circuit of the vehicle to resist the ignition from being energised when the locking assembly is not in the unlocked position. The micro-switch 52 can be located in the transverse slot 50 corresponding to the 30 locked position. This switch 52 is closed or activated when the locking assembly 24 is in the locked position and is coupled to the ignition circuit in a way that stops the starter motor from being energised and this in turn prevents the drive for the mixer 23 assembly 10 from being turned on and started. The damage prevention means may also have an audio and/or visual alarm for alerting an operator if they try and turn the ignition while one or more of the locking assemblies is in the locked position in addition to cutting out the ignition circuit as described above. 5 in another form the switch may be positioned in the slot 48 and act to close the ignition circuit permitting the ignition to be switched on only when the handle 42 is fully received in the slot 48 and in the unlocked position. 10 Thus, the damage prevention means is designed to avoid damage to the drive including gearbox if an operator turns the ignition key on when one or more locking assemblies 24 are still in the engaged positions. If this situation occurred while a locking assembly was in the locked position this could cause failure and/or 15 damage to the gearbox. In use the locking mechanism or assemblies 24 are brought into use when maintenance workers want to enter into the interior of the barrel. Typically this maintenance work might involve chipping away and removing a layer of hardened 20 excess concrete that has hardened set on the interior surface of the barrel 12. Before an operator enters the barrel 12 the locking arms 24 from the locking mechanisms 24 on the left and right sides of the barrel 12 are moved from the unlocked to the locked positions. To do this an operator manually pivots the handle 25 42 up out of the slot 48 in the block 44 corresponding to the unlocked position and then slides the locking arm 26 in a direction towards the barrel 12. This slides the slide formation 30 along the primary slot 46 until the handle 42 is aligned with the locking slot 50. The handle 42 is then turned down into the secondary slot 50 to the point where it is fully received in the slot 50 and pointing vertically downwards. So 30 long as the handle formation 42 is received in the slot 50 in this fashion the locking mechanism will stay in the locked position.

24 This action causes the locking formation that is a bracket 32 to move up and over the flange 22 on the barrel 12. The openings 34, 36, 38 in the locking bracket 32 are aligned with three bolt heads 40 and passed over the bolt heads 40 such that the bolt heads 40 are laterally restrained by the bracket 32. This effectively locks the flange 5 22 against rotation if anyone were to switch on the engine and the drive to the barrel 12. To make sure that the handle 42 stays in the slot 50 and the locking assembly 24 stays in the locked position a key operated padlock 62 can be passed through the 10 padlock brackets 56, 58 on the arm 26 and the handle 42. This stops the handle 42 from being pivoted up away from the vertically downward position and prevents the locking mechanism 24 from being manually moved back to the unlocked position by an unauthorised user. The operators going into the interior of the barrel to work can keep control and/or custody of the key for the padlock while they are in the barrel. 15 If any person tried to start up rotation of the barrel while it was in the locked position the arm would physically hold the barrel against rotation and it would not turn. If the damage prevention means was fitted the ignition system would be cut and drive 20 to the barrel would be disabled. Further the person trying to start the engine would be alerted by an audio and/or visual alarm, e.g. on a dash or the like. Thus, the locking mechanisms physically lock the barrel against rotation and there are also other systems in place that are designed to warn and/or stop an operator from 25 trying to start up the barrel when a said locking mechanism is in the locked position. When the maintenance work is complete the authorised operator can remove the padlock from the handle 42 and arm 26. This then enables the operator to pivot the handle 42 up to a position where it is aligned with the primary slot 46 and slide the 30 slide formation 30 on the arm 26 along the primary slot 46 back to the first secondary slot 48. The handle 42 is then pivoted down until it is received within the slot 48 effectively locking the locking mechanism in the unlocked position.

25 The truck and mixer assembly can then be used in the usual way to transport batch loads of concrete or cement in slurry form from a batching plant to a pour site. The locking mechanisms 24 do not interfere in any way with the gearbox flange 22 and 5 thus do not hinder rotation of the barrel 12. Fig 6 illustrates a locking assembly in accordance with a second embodiment of the invention. As this embodiment is structurally and functionally very similar to the first embodiment described above the same reference numerals will be used to refer to 10 the same components unless otherwise indicated. In fact the following description will focus on the differences between the two embodiments. 15 In Fig 6 the locking arm 26 and the locking bracket 32 on the end of the arm 26 are configured to engage complementary locking formations on the barrel surface that project out from the barrel surface as distinct from the hex heads on the bolts of the gearbox flange. 20 These formations are positioned radially outward of the gearbox output flange and may comprise formations that are welded to the barrel by means of strong fillet welds. In this embodiment the locking arm locks directly onto the barrel and holds it against rotation rather than the flange. As the point at which the barrel is locked is spaced 25 away from the point at which drive is applied by the drive transmission to the barrel a moment will be applied and the attachment will have to be stronger than in the Fig 1 embodiment to hold the drum against rotation when drive is applied through the drive system. 30 Fig 7 illustrates a locking assembly in accordance with another embodiment of the invention.

26 Again as this embodiment is structurally and functionally very similar to the first embodiment described above the same reference numerals will be used to refer to the same components unless otherwise indicated. 5 In Fig 7 a rotating drive shaft with an output flange is drivably coupled to an end of a housing of a mill or kiln apparatus. The housing of the mill or kiln has a cylindrical configuration and is rotated about the longitudinal axis of the cylindrical body. The housing is driven by means of a drive system similar to that shown in Fig 1 with 10 a drive shaft operatively coupled to a gearbox, e.g. a hydraulic gearbox with a gearbox output flange. The gearbox output flange is then mounted on an end of the housing of the mill or kiln. The mill has locking assemblies mounted to each of left and right sides of the output 15 flange of the gearbox and this provides a physical restraint against rotation of the housing while the locking assemblies are being used to lock it against rotation. Mills, kilns and the like require periodic maintenance to be done on the interior of the housing. This can be required to repair or replace worn linings of the housing due to 20 the collisions occurring within the mill. To do this a worker will enter into the interior of the mill and a system is necessary to ensure that the housing is not caused to be rotated while the worker is inside the housing. Fig 8 illustrates a locking assembly in accordance with another embodiment of the 25 invention. Again as this embodiment is structurally and functionally very similar to the first embodiment described above the same reference numerals will be used to refer to the same components unless otherwise indicated. In Fig 8 the locking assembly is mounted on a carousel. The carousel has a central 30 hub with arms extending outward there from, The central hub is rotated by a drive system that is similar to that used to rotate the drum of the mixer in Fig 1. Basically an 27 output flange is driveably coupled to the hub so that rotation of the shaft causes the hub and thereby also the arms of the carousel to rotate. The carousel has two locking assemblies mounted thereto much like those in Fig 1. 5 The locking assemblies have an arm with a base mounted on a stationary support frame and a locking formation for locking to the hub spaced from the base. In use the locking formations are passed over the bolt heads on the output flange and lock it against rotation. 10 Thus the locking arms physically lock the carousel against rotation when maintenance work is being done to avoid the risk of injury to maintenance workers. An advantage of the locking mechanism 24 described above is that it is relatively simple and can be manually operated yet it is still very effective. It provides a strong 15 and robust lock against rotation of the barrel 12 when maintenance is being carried out on the barrel 12 and maintenance workers are inside the barrel 12. Yet further it physically locks the barrel against rotation which is what is desired by both workplace safety authorities and operators of concrete transport trucks. Further, the locking mechanism 24 will not add a huge amount of additional cost to the cost of building a 20 concrete transport truck. A further advantage of the locking mechanism 24 described above is that it locks the barrel 12 at or very close to the point where the rotational drive is applied to the barrel 12 of the mixer assembly 10. As a result of this structural feature, it is able to 25 withstand high levels of torque. It is obviously very important that the locking mechanism 24 has the strength to withstand the torque imparted by the drive mechanism to the barrel 12 without failing. Where the locking formation on the locking arm is passed over a complementary locking formation on the barrel radially outward of the gearbox flange then the moment applied by the drive to the locking formation 30 would be considerably greater.

28 Further if the locking mechanism 24 was located at the rear of the barrel 12 the shear forces and the moment applied by the drive at the front of the barrel 12 to the rear locking mechanism would be substantially greater than that to a locking mechanism at the front adjacent the drive. Thus the risk of such a locking mechanism failing over 5 time would be proportionately greater. A yet further advantage of the mixer assembly 10 described above, is that it has a switch that prevents the engine being started when one or more said locking mechanisms 24 are in the locked position. Basically when the locking arm 24 is not in 10 the unlocked position, the switches co-operate with the ignition switch and circuit to stop the engine being started. Further, the dash of the vehicle may have a light and/or audio alarm indicating that the locking mechanism 24 is still in the locked position when someone tries to start the engine. 15 In the specification the term "comprising " shall be understood to have a broad meaning similar to the term "including" and will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. This definition also applies to variations on the term "comprising" such as "comprise" and "comprises". 20 The reference to prior art in this specification is not and should not be taken as an acknowledgment or any form of suggestion that the referenced prior art forms part of the common general knowledge in Australia. 25 It will of course be realised that the above has been given only by way of illustrative example of the invention and that all such modifications and variations thereto as would be apparent to persons skilled in the art, are deemed to fall within the broad scope and ambit of the invention as is herein set forth. 30

Claims (26)

1. A mixer for mixing materials therein, comprising; 5 a drum that is mounted for rotation on a support; at least one drum safety arrangement for locking the drum against rotation on the support when maintenance is carried out on the drum, including a locking arm having one end that is mounted on the support and another end that can be engaged 10 with the drum, the locking arm being moveable on the support between a locked position in which the other end is free of engagement with the drum and a locked position in which the other end is engaged with the drum, whereby to resist rotation of the drum on the support; and a locking device that can lock the locking arm in the locking position to prevent 15 a person other than a supervisor from moving the locking arm out of the locked position whereby to avoid a situation where the drum is caused to rotate by a person while a worker is located within the drum.

2. A mixer according to claim 1, wherein the locking device is a padlock that is a 20 key operated padlock or a combination operated padlock.

3. A mixer according to claim 1 or claim 2, wherein the locking device can also be used to lock the locking arm in the unlocked position. 25

4. A mixer according to any one of claims I to 3, wherein the drum safety arrangement further includes a guide mounted on the support for guiding movement of the locking arm between the unlocked and locked positions.

5. A mixer according to claim 4, wherein the guide comprises a guide formation 30 which is mounted on the support and a sliding element which is received within the guide formation, and the sliding element slides along the guide formation to guide movement of the locking arm between the locked and unlocked positions. 30

6. A mixer according to claim 5, wherein the sliding element includes a locking bracket which can be engaged with the locking device when the locking arm is locked in either the locked or unlocked positions, and another locking bracket which can also be engaged with the locking device when the locking arm is locked in either the 5 locked or unlocked positions,

7. A mixer according to any one of claims 1 to 6, wherein the other end of the locking arm includes a drum engaging formation, and the drum includes a complementary arm engaging formation that is spaced away from the axis of rotation 10 of the drum, and the drum engaging formation is engaged with the complementary arm engaging formation when the locking arm is in the locked position whereby to lock the drum against rotation.

8. A mixer according to claim 7, wherein the locking arm has a longitudinal axis 15 and the drum engaging formation extends transverse to the longitudinal axis, and wherein the drum engaging formation defines at least one opening within which the complementary arm engaging formation can be received.

9. A mixer according to claim 8, wherein the drum engaging formation defines a 20 plurality of openings that are spaced apart from each other in a line on the drum engaging formation, each of which can be engaged with a complementary arm engaging formation on the drum, and wherein the drum has a drive flange on an end thereof and the drive flange is mounted on the drum by a plurality of bolts that project away from the surrounding surface of the drive flange, and wherein said bolt heads 25 form the complementary arm engaging formation on the drum, each opening having a bolt received therein to engage the other end of the locking arm with the drum.

10 A mixer according to any one of claims 1 to 9, having two said drum safety arrangements mounted on the drum that are positioned on opposite sides of the 30 drum.

11. A vehicle for transporting a settable cementitious material, including 31 a vehicle chassis; a support that is a drum support mounted on the chassis; a drum that is mounted for rotation on the support, the drum being orientated 5 so that it lies on its side having one end that is closed and another end that is open through which material is fed into the drum and through which material is discharged from the drum; at least one drum safety arrangement for locking the drum against rotation on the support when maintenance is carried out on the drum, the locking arrangement 10 including a locking arm having one end that is mounted on the support and another end that can be engaged with the drum, the locking arm being moveable on the support between a locked position in which the other end is free of engagement with the drum and a locked position in which the other end is engaged with the drum whereby to resist rotation of the drum on the support; and 15 a locking device that can lock the locking arm in the locking position to prevent any person other than a supervisor from moving the locking arm out of the locked position whereby to avoid a situation where the drum is caused to rotate by a person while a worker is located within the drum. 20

12. A vehicle for transporting a settable cementitious material according to claim 11, wherein the wherein the locking device is a padlock.

13. A vehicle for transporting a settable cementitious material according to claim 11 or claim 12, wherein the drum safety arrangement further includes a guide 25 mounted on the support for guiding movement of the locking arm between the unlocked and locked positions, and the guide comprises a guide formation which is mounted on the support and a sliding element which is complementary to the guide formation which is operatively connected to the locking arm, and the sliding element is received within and slides along the guide formation to displace the locking arm 30 between the locked and unlocked positions. 32

14. A vehicle for transporting a settable cementitious material according to any one of claims 11 to 13, wherein the other end of the locking arm includes a drum engaging formation for engaging a complementary arm engaging formation on the drum that is spaced away from the axis of rotation of the drum so that the locking arm holds the 5 drum against rotation when drum engaging and arm engaging formations are engaged.

15. A mixer according to any one of claim 14, wherein the drum engaging formation defines a plurality of openings that are spaced apart from each other in a 10 line on the drum engaging formation, and wherein the drum has a drive flange on an end thereof and the drive flange is mounted on the drum by a plurality of bolts that project away from the surrounding surface of the drive flange, and wherein said bolt heads form a complementary arm engaging formation such that each of the openings in the drum engaging formation can be engaged with a bolt. 15

16. For a mixer having a drum that is mounted for rotation on a support, there is provided a drum safety arrangement including: a locking arm having one end that is mounted on the support and another end that can be engaged with the drum, the locking arm being moveable on the support 20 between a locked position in which the other end of the locking arm is free of engagement with the drum and a locked position in which the other end of the locking arm is engaged with the drum to resist rotation of the drum on the support; and a locking device that can lock the locking arm in the locked position to prevent a person other than a supervisor from moving the locking arm out of the locked 25 position whereby to avoid a situation where the drum is caused to rotate by the unauthorized user while a worker is located within the drum.

17. A drum safety arrangement according to claim 16, wherein the locking device is a padlock. 30

18. A drum safety arrangement according to claim 16 or claim 17, wherein the drum safety arrangement further includes a guide mounted on the support for guiding 33 movement of the locking arm between the unlocked and locked positions, and the guide comprises a guide formation which is mounted on the support and a sliding element which is complementary to the guide formation which is operatively connected to the locking arm, and the sliding element is received within and slides 5 along the guide formation to displace the locking arm between the locked and unlocked positions.

19. A drum safety arrangement according to any one of claims 16 to 18, wherein the other end of the locking arm includes a drum engaging formation for engaging a 10 complementary arm engaging formation on the drum that is spaced away from the axis of rotation of the drum so that the locking arm holds the drum against rotation when drum engaging and arm engaging formations are engaged.

20. A drum safety arrangement according to claim 19, wherein the drum engaging 15 formation defines a plurality of openings that are spaced apart from each other in a line on the drum engaging formation, and wherein the drum has a drive flange on an end thereof and the drive flange is mounted on the drum by a plurality of bolts that project away from the surrounding surface of the drive flange, and wherein said bolt heads form the complementary arm engaging formations such that each of the 20 openings in the drum engaging formation can be engaged with a bolt.

21. For a mixer having a drum that is mounted for rotation on a support, there is provided a method of locking the drum against rotation on the support, including: 25 providing a locking arm having one end that is fixed to the support and another end remote from said one end; and fixing said other end of the arm to the drum in a way that the locking arm holds the drum against rotation, 30

22. A method of locking the drum against rotation according to claim 21, including locking the locking arm in its position fixed to the drum by means of a locking device. 34

23. A method of locking the drum against rotation according to claim 22, wherein the mixer includes a guide mounted on the support for guiding movement of the locking arm between the unlocked and locked positions, and locking the locking arm in the locked position includes locking the locking arm to the guide by means of a 5 padlock.

24. A method of locking the drum against rotation according to any one of claims 21 to 23, wherein the drum includes a drive flange having a plurality of bolts projecting from the bolt flange and the locking arm includes a drum engaging 10 formation comprising a plurality of openings, and fixing said other end of the arm to the drum includes receiving a said bolt within each opening to hold the drum against rotation.

25. A vehicle for transporting a settable cementitious material having a mixer drum 15 substantially as herein described in the detailed description of the invention with reference to the accompanying drawings.

26. A method of locking a drum that is rotatably mounted on a support against rotation substantially as herein described in the detailed description of the invention 20 with reference to the accompanying drawings.