Patent EA-003536-B1 (EA)
Title: Vehicle mounted plastics drum for concrete mixing and methods of manufacture thereof
Inventor: RODGERS WILLIAM
IPC: B01F29/60
Filed: 2000-10-09
Abstract: 1. A heavy duty rotary concrete mixing drum capable of attachment to a vehicle; the drum comprising a first end which engages a vehicle powered drive assembly which rotates said drum for mixing of said concrete and a second end from which mixed concrete is discharged; wherein said drum is manufactured from at least one layer of plastics material; wherein the drum includes a wall having integral internal formations which promote mixing and discharge of said concrete and an inner surface which promotes mixing of the concrete. 2. A heavy duty rotary concrete mixing drum according to claim 1 wherein the drum comprises an inner layer of elastomeric material and an external structural layer. 3. A heavy duty rotary concrete mixing drum according to claim 2 wherein said internal layer includes a polyurethane elastomer. 4. A heavy duty rotary concrete mixing drum according to claim 3 wherein said external structural layer includes a fibre reinforced composite exterior. A heavy duty rotary concrete mixing drum according to claim 4 wherein the wall of the drum includes fibreglass filament windings applied about said drum outside said inner polyurethane layer. 6. A heavy duty rotary concrete mixing drum according to claim 5 wherein said wall includes between said inner layer and said outer structural layer a bonding layer. 7. A heavy duty rotary concrete mixing drum according to claim 6 wherein said integral internal formations comprise helical blades extending from said inner layer. 8. A heavy duty rotary concrete mixing drum according to claim 7 wherein said integral helical blades have a variable pitch dimension of between 0.5- 2 meters. 9. A heavy duty rotary concrete mixing drum according to claim 8 wherein the strength of the structural layer of said drum is around 600MPa at a drum wall thickness of approximately 8mm. 10. A heavy duty rotary concrete mixing drum according to claim 9 wherein said polyurethane layer is approximately 2-8mm thick and said fibreglass filament windings are formed from a layer of approximately 2-8mm thickness. 11. A heavy duty rotary concrete mixing drum according to claim 10 wherein an inner surface of the polyurethane drum provides wear resistance and promotes mixing of the contents of the concrete at the concrete/wall boundary layer. 12. A heavy duty rotary concrete mixing drum according to claim 11 wherein the weight of the drum is such that when full, the total weight of the plastics drum and contents is lighter than steel drum of an equivalent size when full. 13. A heavy duty rotary concrete mixing drum according to claim 12 wherein said blades are formed by said elastomeric material and define a hollow internal cavity in each helical blade. 14. A heavy duty rotary concrete mixing drum according to claim 13 wherein said helical blades include a bonding layer adjacent said inner polyurethane layer and a structural layer adjacent said bonding layer. A heavy duty rotary concrete mixing drum according to claim 14 wherein said helical blades include a fibre reinforced tension member disposed in said cavity outside said structural layer and along the length of the blade. 16. A heavy duty rotary concrete mixing drum according to claim 12 wherein said blades are solid core along the full length of the blades. 17. A heavy duty rotary concrete mixing drum according to claim 16 wherein said solid core blades further include embedded therein a continuous glass fibre reinforced elastomer disposed along the length of said blade. 18. A heavy duty rotary concrete mixing drum according to claim 15 wherein the drum is manufactured in three sections from three separate molds, the first of said sections forming an end which engages said drive assembly for mixing said drum, the second said sections including said opening for discharge of said concrete from said drum and the third of said sections providing an intermediate junction between the first and second parts. 19. A heavy duty rotary concrete mixing drum for mounting on a vehicle; the drum comprising an opening at one end for discharging concrete mixed in said drum, and at the other end means for engaging a drive assembly which rotates the drum for mixing and discharging concrete; wherein, the drum includes a wall manufactured using at least one base mold from layers of plastics materials ; wherein the drum further includes blades integrally attached which outstand from an internal surface of the wall of the drum and form an archimedian screw disposed such that when the drum is rotated in a first direction the concrete contents are mixed and when the drum is rotated in a second direction the concrete is discharged from said drum; and wherein the internal surface of the drum is formed from an elastomer which promotes mixing of the concrete at a concrete/drum boundary layer; and wherein, the total weight of the drum and contents when full is lighter than for a steel drum of an equivalent volume when full. 20. A vehicle mounted rotary concrete mixing drum having an opening at one end for discharge of concrete therefrom and at the other end means for engaging a drive assembly so as to rotate the drum for mixing and discharge of concrete; wherein, the drum includes a wall manufactured from layers of plastics material using three base moulds and further includes detachable or integrally attached blades which outstand from an inner surface of said wall; the vanes forming an archimedian spiral disposed such that when the drum is rotated in a first direction the concrete contents are mixed and when the drum is rotated in a second direction, the concrete discharged from said drum; and wherein the internal surface of the drum includes a polyurethane elastomer layer which promotes mixing of the contents of the concrete at the concrete boundary layer; and wherein the weight of the drum is such that when full, the total weight of the drum and contents is lighter than for a steel drum of an equivalent size when full. 21. A heavy duty rotary concrete mixing drum according to claim 20 wherein the drum is manufactured in three separate parts from said three separate molds, the first of said parts forming an end which engages said drive assembly, the second said parts including the opening for discharge of said concrete from said drum and the third of said parts providing an intermediate junction between the first and second parts. 22. A heavy duty rotary concrete mixing drum according to claim 21 wherein the wall of said drum includes an inner layer of elastomer, an intermediate chemical bonding layer and an exterior layer of a composite of resin and high strength wound fibre reinforcement. 23. A heavy duty rotary concrete mixing drum according to claim 22 wherein each said molds may be formed from materials selected from, expanded polystyrene, fibreglass, steel, rigid polyurethane foam. 24. A vehicle mounted rotary concrete mixing drum having an opening at one end for discharging concrete and at the other end means for engaging a drive assembly so as to rotate the drum for mixing and discharging concrete; wherein, the drum is manufactured from three moulds and comprises a first plastics material such as fibreglass forming an outer surface of the drum and a second plastics material such as polyurethane or like elastomer forming an inner surface of the drum; wherein the outer and inner surfaces together form a wall of the drum and wherein the drum further includes detachable or integrally attached blades which extend inwardly from the wall of the drum forming an archimedian screw disposed such that when the drum is rotated in a first direction, the concrete contents are mixed and when the drum is rotated in a second direction the contents are discharged from said drum; and wherein the inner polyurethane surface of the drum provides wear resistance and promoted mixing of the contents of the concrete at the concrete boundary layer; and wherein the weight of the drum is such that when full, the total weight of the plastics drum and contents is lighter than for a steel drum of an equivalent or smaller size when full. 25. A method of manufacture of a vehicle mounted plastics concrete mixing drum comprising the steps of; a) preparing a mould having a surface defining an internal profile of said drum which includes a wall having recesses which provide a mold part for continuous helical mixing blades included in said drum: b) applying a release agent to an outer surface of said mould; c) applying over said release agent a plastics layer in liquid form and allowing said plastics layer to set against the mould so as to form a first layer of a wall of said drum; d) applying a bonding layer to said plastics layer; e) applying a fibre reinforced composite layer to said bonding layer; and f) removing the mold from the interior of said drum. 26. A method according to claim 23 comprising the further step prior to step a) of forming said mold from expanded polystyrene. 27. A method according to claim 26 comprising the further step of placing a fibre reinforced member along a concave tip of said helical mixing blade. 28. A method according to claim 27 comprising the further step prior to application of fibre reinforced composite layer of moving said drum formed about said mold to a grit blasting chamber wherein a grit jet is traversed over the drum to prepare an outer surface of said drum with a bonding agent to receive said outer layer. 29. A method according to claim 28 wherein the drum is manufactured from three molded parts, two of which comprise end parts of the drum and a third comprising a central part for location between said end parts. 30. A method according to claim 29 wherein each mould part has a formation which imparts to the drum pan formed by the mould part, a part spiral extending inwardly from the wall of the drum part such that when the drum parts are engaged together, an internal archimedian spiral is formed wherein the moulds are configured such that when the dru