TECHNICAL FIELD

Th©: present invention concerns a conc ete riding finishing trow©! for finlshihg .newly-laid (i,e, urvcured) concrete before or while it is curing/hardening. The concrete finishing $ trowel Includes attest: one rotor assembly comprising a rotor shaft with at least one rotor blade thereon for finishing newiy~iaid concrete, whereby the at least one rotor assembly is driven b at least one motor.

BACKGROUND OF THE .INVENTION

A. coherete finishing trowel _: (also known as a ' ^' power fioaf , ^pew r trowef ^!: helicopter",0 Trowel machine", "concrete finisher" or "concrete floor finisher") is used ^' to apply a smooth finish to concrete. The concrete finishing Trowel can be a riding trowel that is used by art operator sitting on a seat on the machine or a walk-behind trowel that is used by an operator walking behind the machine.. 5 Riding trowel typicall include a seif-pro elie mobile frame including a deck. At least two rotor assemblies are moypted on an underside of the deck. Each rotor assembly includes a driven shaft extending downwardly from the deck an a plurality of trowel blades mounte on and extending radially outwardly from the bottom: en of the driven shaft and supported or? me surface to be panned and finished. The weight of the riding0: trowel and the operator is transmitted fhctionaiiy to the: Underlying surface by the rotating blades, thereby smoothing the underlying surface. Th driven shafts of the rotor assemblies are driven by one or more ieseS- or petrohdrlven engines mounted on the frame o that it can (power- and time-wise) be used substantiall continuously for at least 3-3 hours; The one or more desai- o petro dfiyen engines are: typicall linked: to the:5 drive shafts via a worm gear mechanism or hydraulic m ans

For example, US patent: no. 6 250 844 concerns a concrete fihishing trowe that has one or more driven- rotor assemblies coupled to a gasoline-powered internal combustion via a torque transfer system. The torque transfer system includes: at least one flexibl shaft,0: such s a fiexilsle wound wire shaft. The flexible shaft bends to accommodate tilting movement of the associated rotor assembly that occurs upon a steering operation.: Such a rotor d ive: System comprising a gasoiin^-powefed internal combustion engine m k s the riding trowel noisy to use, arid worm gear mechanisms give rise to-substantial power losses in th rotor drive system.

5 SUMMARY OF THE INVENTIOM

An object of the invention is to provide an improved concrete finishing riding trowel fo finishing newly-laid (; e. urvcured) concrete before or while it is eg ring /hardening. 0 This object is achieved by a concrete finishing: tiding trowel comprising at (east one rotor assembly comprising a rotor shaft with at least one rotor biade for finishing (i.e. panning and finishing or just finishing (smoothing and polishing and/or grinding anef/or washing;} a surface mounted thereon:, whe eb the at least one rotor Assemb y is driven fey at least one battery-powered electric motor.

5

An etectrtc mot or is mbch quieter, cleaner, lighter and less talfcy than a dieseh or petrol- driven motor, it requires no fuel tank and does ^; hot produce any exhau t fumes and it has a much higher torque than a dieseh or petrohdhven motor. By supplying electrical power th a feast one motor from batteries instead of sab ^' i&s, no cables will trail the ndlng trowel.0 A trailing cable can limit the movement of the riding trowel, d¾rnag© the surface being subjected to a finishing treatment, and get twisted around the rotor blades of the riding trowel.

A concrete finishing riding trowel usuall has a size of 200χ ®5ί130 cm, it, it occupies aS volume: of at least on cubic metre, and weighs at least 400 kg (when hot carrying driver). It; is arranged to carry a driver (having weight of 70-100 k§ or more), A conc ete finishing riding trowel is usually idrfven using two levers and a foet~co trol|ed accelerator that controls power output and speed. The concrete finishing riding trowel can be moved sideward, forward, backward and diagonally _* and ft can be spun around using the levers,0

The at least one battery-powered electric motor is preferably a multi-speed motor, such s •a two-, three-- or four-speed motor, and it ma have a constant o variable torque o horsepower. According to an embodiment; of the invention the motor is; arranged to at least. ie pdranl provide a higher torgue, such as two or three times th normal operating5 torque, on demand. For example, a concrete finishing riding trowel can start to get stuck in a newiy-taici concrete surface if left standing thereon. By temporarily increasing the torque of the at least one tatter - owered electric motor (for a few seconds for example} when an operator wants to move the concrete finishing riding trowel, the machine can be moved out of the: wet; newly-laid: concrete, it is not as simp e to increase the torque of a diesef> or petrol-driven moto since this may result in the undestred overheating of transmission components, suc : as salts and/Or qehtfifpgal cl tcr es.

According to an embodiment of th invention at least one battery-powered ^■ electric motor of ^" the at least one battery-powered electric motor is arrange to drive the at least one rotor assembly via a planetary gea mechanism whereby power losses (as compared to heft drive systems or worm gear mechanisms) may be avoided.

According to another embodiment of the invention at least one battery-powered electric motor of the at least one battery-powered electric motor is arranged verticall above at least one roto shaft of at least one rotor assembly of said at least one rotor assembly, where the concrete finishing riding trowel is standing on a flat horizontal surface.. At least part of a planetary gear mechanism may also be arranged vertically above at least one rotor shaft of at least one roto assembly of said at least on rotor assembly,, According to another embodiment of the Invention at least one battery-powered electric motor of the at least one battery-powered electric motor is powered by at least one battery having a total voltage of up to 50V, such as at least one lithium ion battery or any other re- c argeabl ba te :, According to n embodiment of th Invention at least one rotor assembly of the at feast one rotor assembly is Individtfally maheuverafele, i.e. the at least one rotor assembly may be Indlvidualy driven and/or tilted and or displaced with respect: to the riding trowel.

According to anothe embodiment of the invention af least a surface of at least mm of the at least on rotor b!ac!e is provided with a material having a lower coefficient of frictio than steel on newfy-iaid concrete, M least a surface of a rotor blad may be provided with plastic ¹ or the entire rotor blad may comprise ^a composite material in order to reduce the friction between the rotor blade and the neWly-iaid concrete s compared to conventional steel rotor blades on: newiydaid concrete. Such a reduction in the friction between rotor blades and newly-laid concrete: will reduce energy consumption during the operation of the concrete finishing iding trowel, which consequently results in lowe running costs and an extension of the time for which a battery of t e concrete finishing riding trowel can be used before it has to be re-charged. According to a further embodiment of the invention at least one rotor assembly of the at least one roto assembly and at least one isatter * powered electric motor of tf -- at least one battery-powered moto is provided as a ti!tab!e and/or dispiaGeabSe unit, i.e. a rotor assembly and a battery-powered electric motor together may be titled or displaced u wa ds, downwards or sideways with: respect to e riding trowel during the steering and/or operation of the riding trowel. The tilting of such a tiitabie/ lsplaceaisie unit can: cause forces imposed on the underlying surface toy the rotating rotor: blades to: propel the concrete finishing riding trowel he need for a flexible s aft between the rotor and motor or a flexible U-jOint is overcome, which in turn improves the power transfer ¹ since a rigid shaft, Le, a substantially non-elastlo shaft that is not intended to bend during the steering or operation of the concrete finishing riding trowel, can be used, Othe components of a concrete finishing riding trowel, such as at least part of a planetary gear mechanism, may also be included in such a tiltabSe and/or dlsplaoeable unit.

According to another embodiment of the invention the concret finishing riding trowel is a riding: trowel and comprises an operator's seat and a plurality of feattferydaowered electric motors, preferably an even numbe of battery-powered electric motors whereby the plurality of battery-powered electric motors is symmetrically distributed around the operator's seat. For example, half of an even number of battery-powere electric motors may be placed on each side of the operator's seat

According id a further embodiment of the invention the battery-powered electric motor is powered by a plurality of batteries that is arranged to provide at feast 110 ampere-hours of electric charge for at least two hours, According to ah embodiment of the invention at least o e rotor assembly of the at leas one rotor assembly is¾re arranged to be displaceab!e, for example in a direction along the rotor shaft. This ma be advantageous if the concrete finishing riding trowel is being used on a sloping surface, such as a bridge, drainage system, a flight of steps or a gallery, since it at least one rotor assembl ca b displaced: to make the concret finishing riding trowel more stable. When a concrete finishing; riding trowel having a diese!- or petrol-driven engine ss used on a sloping surface, the tilting of the fuel tank and/or oil tanks may caws© the eng:lha ^; id s ut off This problem s avoided when using an electric engine, The: present invention also concerns t e use of a concrete finishing riding trowel according to any of the embodiments of the invention In- art. Indoor or enclosed environment.

BRIEF DESCRIPTION OF THE DRAWI SS

The present invention will hereinafter be Further explained by means of non-limiting examples with reference to the appended figures where;

Figure 1 shows a riding trowel according to an embo iment of the invention, Figure 2 is: a schematic: view of a battery-dnven electric motor arranged above a rotor shaft of a rotor assembly of a riding trowel according to an embodiment of the present Invention,

Figure 3 schematically shows the to of a riding trowel according to an embodiment of the present invention^ it should he noted that the drawings have not been drawn to scale and that the dimensions of certain features have bee exaggerated for the sake of clarity. DETAILED DESCRIPTION OF EMBODIMENTS

Figure 1 shows a neiing trowel 10 sultabje for use in an indoor or enclosed environment The illustrated riding trowel. 10 comprises two rotor assembles: 20 mounted oh ah underside thereof and each comprising: a rotor shaft extending downwards from the deck of the riding trowel with a plurality -of roto blades 14 mounted thereon and extending radially outw rds from the rotor shaft†S; Each rotor assembly 12 is drive by a separata battery-powered electric motor in the illustrated embodiment. The diameter of the rotor blades 14 may for example toe S5 _i: 120 or i SO cm, or any other diameter that is: suitable for a particular application. The fidihg trowel 1:0 comprises an Operator's seat 16 in which an operator sits to steer. and operate the riding trowel l0. Such a riding trowel 10 requires no fuel tank, no electric ca le for connection to an external power source, and no m gears.

Figure 2 shows a rotor s aft 18 of a rotor assembl 12. A battery-powered multi-speed electric motor W of variable torque, such as a 5;§ k or 3 k electric motor, Is arranged vertically above the vertical rotor shaft 18 whereby the output shaft of the battery-powered electric motor 20 may be arrange to drive:ths input shaft of a planetary gea mechanssm 22, at least part of which is also located between the motor 20 and th® rotor shaft 18. The planetary gear mechanism may have a gearratio of 20:1.

According to an embodiment of the invention the battery-powered electric motor 20, the rotor shaft 18 and any rotor blades 14 mounted thereon may be provided as a tillable and/or dispiaceabt unit to aid steering ppe ioris, Tilting such a unit fro side to side or forwards and backwards may b used to stee the riding trowel 10 in the forward/reverse and the left/right directions respectively.

Figure 3 schematically shows the fop of a riding trowel to according to an em odiment of the present invention m which two individually maneuverable arsd/or tilta Se and/or dispiaoeabje battery-powered :eleotric motors 20 are arranged symmetricaliy, one o each side of the Hding trowel operator's seat 16, At least of the rotor assemblies 12 driven by each of the battery-powered electric motors 20 may foe arranged to be di piabeabie, axial i in a direction along its: rotor shaft IS for example.

The battery-powered electric motors 20 are owe ed by a plu ality of batteries M, such as lithium on batteries or an other rechargeable batteries, having a total voltage of u to SO V, such as a four 12 V batteries connected in parallel, Th batteries 24 o battery pack ma be arranged just under and/or behind th operator's: seat 1 for example. The batteries ma be arranged: to provide at feast 110 ampere-hours of electric charge Tor at ieast two hours.

The present: invention also concerns the use of a concrete finishing riding trowel according to any of the embodiments of the invention in an indoor or enclosed environment. Fuftfi&r modifications, of the i ention wit!iin ths scope of me cisios would be apparent a skliecS; erso ,;