WO2017065618A1

WO2017065618A1 - Improvements in and relating to concrete finishing machines

Info

Publication number: WO2017065618A1
Application number: PCT/NZ2016/050167
Authority: WO
Inventors: Jeremy Rodney BAKER; Dion Ross JONES
Original assignee: Baker Jeremy Rodney; Jones Dion Ross
Priority date: 2015-10-16
Filing date: 2016-10-13
Publication date: 2017-04-20

Abstract

The present invention relates to improvements in and relating to concrete finishing machines and in particular to an improved pan/blade arrangement for a power trowel/float and a method of using the same.

Description

Improvements in and Relating to Concrete Finishing Machines

TECHNICAL FIELD

BACKGROUND ART

Concrete finishing machines are well known in the concrete industry for the efficient finishing off of concrete foundation slabs, these machines are typically referred to as power trowels or power floats. For ease of reading the term power trowel will be used throughout this specification, however it should be understood that this term refers, in general, to any rotary concrete finishing machine including a motor driven rotatable hub that attaches to a concrete working attachment.

After pouring the concrete it begins to set, at first becoming less fluid and more plastic in consistency, before setting further and slowly transitioning to a fully hardened state. Before it fully hardens, the concrete must be levelled and the surface must be made smooth, taking account of the changing properties of the concrete. The process of levelling and/or smoothing the surface of poured concrete is referred to as "finishing".

Depending on the stage of finishing, the concrete working attachment of the power trowel will typically comprise either: · a pan/float disc; or

• a trowel blade assembly.

The pan/float disc consists of a circular flat sheet of steel with an upturned lip. One surface of the sheet of steel is configured to engage with the rotating arms of the motor drive of the power trowel, and the other surface of the sheet of steel is featureless and is designed to flatten substantially fluid-like concrete.

Following the initial pour of concrete, and whilst the concrete is still substantially fluid-like in consistency, the pan is first used to uniformly level the concrete over the extents of the foundation surface. The advantage of using a pan at this stage is that the weight of the concrete finishing machine is supported on the fluid concrete through the large flat contact surface provided by the pan.

As the concrete becomes sufficiently plastic to support the weight of the concrete finishing machine through the trowel blades only, the pan is typically exchanged for a trowel blade assembly. Such an assembly typically consists of four trowel blades extending radially from the hub of the machine. The trowel blades allow the user to provide a smoother finish to the concrete than can be achieved with the pan alone. Different types of blades are available and may be used to achieve different levels of smoothness of finish.

In order to exchange the pan for the trowel blade assembly the machine must be stopped and the pan must be disengaged from the arms of the motor drive of the power trowel, thereby interrupting the concrete finishing process. The pan may be attached directly to the arms (direct attachment) or can be engaged to trowel blades pre-mounted to the arms through brackets (bracket attachment). For direct attachment models, the trowel blades must then be installed to the arms of the motor drive of the power trowel. The machine is then restarted and the concrete can be finished using the blades. This delay can be problematic when finishing large surfaces of fresh concrete in which the hardness of the concrete can vary considerably from one edge to the opposite edge.

Furthermore, the concrete finishing machines are very heavy and unwieldy, making it difficult to manoeuvre the machine to engage and disengage the pan to and from the arms of the power trowel and/or the trowel blades. The process of engaging and disengaging the pan is also messy due to the machine having been used in wet concrete. By way of further background, the concrete finishing machine will typically include a pitch adjustment mechanism to which the trowel blades are attached. The pitch adjustment mechanism allows the pitch of the trowel blades to be adjusted with respect to the concrete. Initially the trowel blades are operated substantially parallel and flat with respect to the concrete surface, this maximises the surface area of the blades that is in contact with the concrete surface. As the concrete becomes increasingly harder it is able to support a greater surface load. Adjusting the pitch of the blades correspondingly changes the proportion of blade surface that is in contact with the surface of the concrete. As the pitch angle is increased the machine's weight is supported by a smaller contact patch.

Past concrete finishing machines typically have trowel blades fitted to the pitch adjustment mechanism. A pan is used that includes an attachment mechanism that engages with the trowel blades when they are positioned with a substantially flat pitch angle (bracket attachment).

A further problem with this arrangement is that the pan can experience accelerated wear if the pitch of the trowel blades is not flat when used with a pan.

It is an object of the present invention to address one or more of the foregoing problems or at least to provide the public with a useful choice.

DISCLOSURE OF THE INVENTION The present invention relates in part to a combination pan and trowel blade arrangement for a power float. The combination pan and trowel blade arrangement includes a pan having at least one radially extending aperture. The at least one radially extending aperture is configured to allow at least a portion of a trowelling blade to pass through the aperture to engage with a concrete surface to be worked. In use the pitch of the trowelling blade may be adjusted through a range of positions whereby the pan and trowel arrangement may be transitioned, during use, from the pan providing the primary contact surface for working a concrete surface, to the trowelling blade providing the primary contact surface for working the concrete surface. Typically at least 3 apertures and corresponding blades will be present, however the invention should not be seen as being limited to a particular number of apertures or blades. In some embodiments a single aperture may allow two or more blades to pass therethrough. One aspect of the present invention is embodied in a pan for use with a power trowel, the pan comprising a disc having a substantially planar working surface, wherein at least one radially extending aperture is formed in the disc.

In preferred embodiments the radially extending aperture is configured to allow through-passage of at least a portion of a trowelling blade. Through-passage of the trowelling blade may be performed by feeding an edge of the trowelling blade through the aperture, or by adjusting the pitch of the trowelling blade so that the working edge of the trowelling blade moves toward and away from the planar working surface of the pan, the pitch adjustment causing at least an edge of the trowelling blade to move into and out of the aperture.

In some embodiments the aperture may correspond substantially in its dimensions to the length and width of a power trowel trowelling blade. In use the trowelling blade sits within the aperture and coplanar with the plane of the working surface of the pan, substantially closing off the aperture and providing a pan surface area that is proportionally substantially the same as a standard pan that does not have an aperture.

Preferably the aperture may be dimensioned so as to allow for a trowelling blade to be varied in pitch so that at least a portion of the trowelling blade can pass through the aperture. Adjusting the pitch of a trowelling blade within the aperture shifts the load of the concrete finishing machine from the pan.

As used herein, the term "pitch" refers to the angle between the plane of the trowel blade and the plane of the pan. When the combination pan and trowel blade arrangement are used on the initial fluid-like concrete it will be understood that the pitch is generally set to approximately 0° so that the plane of the pan and the plane of the trowel blade are coplanar. As the concrete begins to sets and become more plastic the pitch angle can be increased, for example to 10° or to 20°. Typically, where multiple trowel blades are used, the pitch of each of the trowel blades will be approximately the same.

In preferred embodiments the pan includes at least one pan to power trowel attachment means for attachment of the pan to a rotating drive member of a power trowel. In some embodiments the pan to power trowel attachment means attaches the pan to the rotating drive member of the power trowel substantially independently to the means by which a trowel blade is attached to the power trowel. An example of such substantial independence is provided by a hinge rotating about a captive rod. By removing the captive rod, the remaining component parts of the hinge can be separated. Independent attachment of the pan to the rotating drive member allows the pan and trowel blades to be easily replaced independently of one another. This is useful as trowel blades are typically replaced at a far greater rate than the pans and independent attachment may provide for more efficient trowel blade replacement.

In some embodiments the pan to power trowel attachment means may attach to one or more trowel blades.

In some embodiments the pan to power trowel attachment means may attach to a trowel blade to power trowel engagement means. The trowel blade to power trowel engagement means is preferably configured so that pitch adjustment of the pitch adjustment arm is conferred to the blade through the trowel blade to power trowel attachment means. In some embodiments the trowel blade to power trowel engagement means releasably attaches the trowel blade to a pitch adjustment arm of the power trowel. In some embodiments increasing the pitch adjustment of the pitch adjustment arm of the power trowel results in the trowel blade to power trowel engagement means urging the trowel blade to rotate through the aperture of the pan, thereby increasing the pitch angle. In some embodiments decreasing the pitch adjustment does not apply a force on the trowel blade, in which embodiments the trowel blade may return to be coplanar with the pan due to the weight of the power trowel and the force applied by the concrete surface. Embodiments that share common attachment components between the trowel blade to power trowel engagement means and pan to power trowel attachment means may include a mechanism that allows the trowel blades to be adjusted in pitch relative to the planar surface of the pan.

In preferred embodiments the pan to power trowel engagement means may include a tubular section having a radially directed tube opening, the length of the tube being aligned substantially radially with respect to the pan.

Preferably the tubular section of the pan to power trowel engagement means is configured to receive a portion of a rod through the tube opening.

In a further aspect the invention provides a trowel blade for use with a power trowel, the trowel blade including: a trowel blade to pan attachment means configured to allow attachment of the trowel blade to a pan comprising a disc having a substantially planar working surface, wherein at least one radially extending aperture is formed in the disc, wherein the trowel blade to pan attachment means allows the pitch of the trowel blade to be varied relative to the pan so that at least a portion of the trowel moves through the at least one radially extending aperture.

The trowel blade to pan attachment means may include a turned edge for engagement in a hinge.

A further aspect of the present invention is embodied in a trowel blade for use with a power trowel, the trowel blade including: · a trowel blade to power trowel engagement means configured to engage the trowel blade by a pitch adjustment arm of the power trowel, wherein pitch adjustment of the pitch adjustment arm is conferred to the blade through the trowel blade to power trowel engagement means, and

• a pan attachment means configured to attach the trowel blade to a pan, wherein the pan

attachment means allows the pitch of the trowel blade to be varied relative to the pan.

In preferred embodiments the trowel blade to power trowel engagement means includes a tubular section having an opening aligned along the length of a leading edge of the trowel blade. In use, alignment of the opening of the tubular section along a leading edge of the trowel blade results in the tube rotating about its axis when the pitch of the trowel blade is adjusted. Preferably the tubular section of the trowel blade to power trowel engagement means is configured to receive a portion of a rod through the tube opening. This configuration allows the rod to rotate within the tubular section of the trowel blade to power trowel engagement means when, in use, the pitch of the trowel blade is adjusted. In one aspect the present invention provides a pan and blade assembly for use with a power trowel, the pan and blade assembly comprising:

• a pan comprising a disc having a substantially planar working surface, wherein at least one radially extending aperture is formed in the disc

• at least one trowel blade including: o a trowel blade to power trowel engagement means configured so that the movement of a pitch adjustment arm of the power trowel acts on the trowel blade, and o a trowel blade to pan attachment means configured to attach the trowel blade to the pan, wherein the trowel blade is attached to the pan through the trowel blade to pan attachment means such that the or each of the at least one radially extending apertures has one of the at least one trowel blades positioned within it, and wherein, in use, increasing the pitch adjustment of the pitch adjustment arm causes an engaged at least one trowel blade to increase in pitch and pass through one of the at least one radially extending aperture.

In some embodiments the trowel blade to power trowel engagement means attaches the pan through a hinge which also engages the blade to pan attachment means.

In preferred embodiments the arm is configured to provide:

• rotational force to the pan and to the trowel blade; and

• pitch adjustment to the trowel blade.

A further aspect of the present invention is embodied in a pan and blade assembly for use with a power trowel, the pan and blade assembly comprising:

• a pan comprising a disc having a substantially planar working surface, wherein at least one radially extending aperture is formed in the disc • at least one trowel blade including: o a trowel blade to power trowel engagements means configured so that the movement of a pitch adjustment arm of the power trowel acts on the trowel blade, and o a pan attachment configured to attach the trowel blade to the pan, wherein the pan attachment attaches the pan to an at least one trowel blade such that each of the at least one radially extending apertures has one of the at least one trowel blades positioned within it, and wherein, in use, pitch adjustment of the pitch adjustment arm causes an attached at least one trowel blade to adjust in pitch and pass through one of the at least one radially extending aperture.

In some embodiments the trowel blade to power trowel engagements means is configured to attach the trowel blade to a pitch adjustment arm of the power trowel.

In preferred embodiments the pan includes a pan to blade attachment means in the form of a tubular section configured to align coaxially with the blade pan attachment means.

In preferred embodiments the pan attachment means and trowel blade to power trowel engagement means comprise tubular sections, wherein when the pan is attached to the trowel blade to power trowel engagement means the tubular sections are aligned substantially coaxially.

Preferably attachment between the pan and trowel blade pan attachment means comprises passing a rod through the coaxially aligned tubular sections. Such a rod may be held captive through friction, a split pin, bolt or similar.

According to a further aspect the present invention is embodied in a power trowel including a pan and trowel blade assembly.

Preferred embodiments of the present invention may provide a number of advantages over the prior art, non-limiting examples of which may include:

• providing a power trowel that can transition seamlessly from pan use to blade use;

• providing a power trowel that is convenient and simple to use;

• providing improved safety by not having exposed blade edges;

• allowing the formation of an intermediate textured finish during the transition between the pan and blade finish; • providing a cleaner machine that does not require an operator to handle the pan or blades when wet with concrete, and

• providing a power trowel that does not require any interruption or swapping of machinery during the concrete finishing process, particularly when finishing large areas of slab such as for commercial applications.

BRIEF DESCRIPTION OF DRAWINGS

Further aspects of the present invention will become apparent from the following description which is given by way of example only and with reference to the accompanying drawings in which:

Figure 1 Is a perspective view of a prior art power trowel having a pan attached; Figure 2 Is a perspective view of the prior art power trowel of Figure 1 with blades attached;

Figure 3 Is a perspective view of a power trowel in accordance with a preferred embodiment of the present invention;

Figure 4 Is a further perspective view of the power trowel shown in Figure 3;

Figure 5 Is a detailed perspective view of a portion of a pan in accordance with a preferred embodiment of the present invention;

Figure 6 Is a detailed perspective view of a portion of a hub and pitch adjustment arm in

accordance with a preferred embodiment of the present invention;

Figure 7 Is a perspective view of a trowel blade in accordance with a preferred embodiment of the present invention, and Figure 8 Is a detailed perspective view of a pan and trowel blade assem bly in accordance with a preferred embodiment of the present invention.

Figure 9 Is a detailed perspective view of a pan and trowel blade assem bly in accordance with a preferred embodiment of the present invention.

Figure 10 Is a plan view of a pan and trowel blade assembly in accordance with a preferred

embodiment of the present invention.

Figure 11 Is a perspective view of a pan and trowel blade assembly in accordance with a preferred embodiment of the present invention. Figure 12 Is a side view of a pan and trowel blade assembly in accordance with a preferred embodiment of the present invention.

Figure 13 Is a detailed cross-sectional view of a pan and trowel blade assembly in accordance with a preferred embodiment of the present invention. Figure 14 Is a perspective view of a trowel blade in accordance with a preferred embodiment of the present invention.

Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.

BEST MODES FOR CARRYING OUT THE INVENTION Referring to Figures 1 and 2 there is shown a power trowel as generally indicated by arrow 1. The power trowel includes a handlebar 2 that attaches to chassis 3 by way of a handle 4. The chassis 3 includes a safety cage 8 to protect the operator from dangerous moving parts. A motor 5, which is shown as a combustion type engine, is attached to the chassis and drives a hub 6. The hub 6 includes four pitch adjustment arms 7a, 7b, 7c, of which 3 are shown in figures 1 and 2. The pitch adjustment arms are configured to rotate about their longitudinal axis. Adjustment of the pitch adjustment arms is typically controlled manually by way of a handlebar 2 mounted actuator, not shown. In use the hub 6 and pitch adjustment arms 7a, 7b and 7c rotate, clockwise in the Figures shown.

Figure 1 shows a first configuration of power trowel 1 whereby a solid pan 9 is attached to the hub 6 and pitch adjustment arms 7a, 7b and 7c. In some embodiments the pan 9 may include brackets for, not shown, into which trowel blades, not shown in figure 1, slot. This allows the pan 9 to be attached to and from the power trowel 1 without the need for tools. Both the direct attachment and bracket attachment embodiments require the pitch adjustment arms 7a, 7b and 7c to be adjusted to a neutral plane, or one where an attached trowel blade is, or would be, substantially parallel to a planar working surface of the pan. The pan shown in figure 1 will typically be a disc having a substantially planar working surface and will be formed of thin steel or the like. A pan is typically used when a concrete surface being worked is recently poured and is substantially fluid like in its consistency. When the concrete is of a fluid like consistency the power trowel 1 must be supported by a large surface area in order for it not to simply sink into the concrete. Figure 2 shows a second configuration of power trowel 1 in which the pan shown in figure 1 has been removed and trowel blades 10a, 10b and 10c have been attached to the pitch adjustment arms 7a, 7b and 7c. The second configuration of the power trowel 1 is used when the concrete being worked has transitioned to a more plastic consistency and is able to support a greater weight on its surface. Initially the second configuration of power trowel 1 is operated with the trowel blades 10a, 10b and 10c pitch adjusted to a substantially neutral, or flat, orientation with respect to the concrete surface being worked. As the concrete becomes increasingly harder the pitch of the blades is adjusted by way of the pitch adjustment arms 7a, 7b and 7c. This has the effect of decreasing the surface area of the trowel blades that are in contact with the surface of the concrete, providing a higher pressure along the region of the trowel blades 10a, 10b and 10c that are in contact with the concrete surface. Referring now to Figures 3 and 4 there is shown a power trowel embodying aspects of the present invention, as generally indicated by arrow 11. Power trowel 11 is of the same general design as the power trowel of Figures 1 and 2 and includes handlebar 2, handle 4, motor 5, chassis 3, hub 6 and pitch adjustment arms 7a, 7b and 7c. The power trowel 11 includes both trowel blades 12a, 12b and 12c as well as pan 13. The pan 13 comprises a disc having a substantially planar working surface, through which radially extending apertures 14a, 14b and 14c are formed. The form of the radially extending apertures are shown more clearly in the detail view of Figure 5. In Figures 2 and 3 the pan attaches directly to the hub 6. The connection is not shown but may take a number of forms, examples of which includes brackets or fixtures extending from the pan 13 that attach to the hub independently of the pitch adjustment arms 7a, 7b, 7c.

Figure 5 shows a detailed partial view showing a segment of the pan 13. Figure 5 shows radially extending aperture 14b, which is dimensioned to fit the length and width of a power float trowelling blade therethrough. The dimensions of the aperture should not however be seen as being limiting and typically vary depending on the dimensions of the pan and the design of the trowelling blades with which it is to be used.

The pan 13 also includes a pan to power float attachment means 15 in the form of a tubular section having a radially directed tube opening 16.

The pan 13 also includes a notch 17 formed in an upturned edge of the pan, the notch substantially aligned with the radially directed tube opening 16. Although Figure 5 shows a single radially extending aperture 14b, power float attachment means 15 and notch 17 it should be understood that these formations are repeated around the pan 13 for each of the apertures 14a, 14b and 14c.

With reference to Figure 6 there is shown a detailed view of a portion of a hub 6 of power trowel 11. The hub 6 includes a pitch adjustment arm 7b that is configured to rotate about its longitudinal axis, as indicated by arrow 18. It should be appreciated that the exact configuration of the hub and pitch adjustment mechanism may vary without departing from the scope of the present application and should not been seen as a limitation of the invention.

Pitch adjustment arm 7b includes a pan to power trowel attachment means 19a, 19b in the form of two tubular sections aligned co-axially below pitch adjustment arm 7b, the tubular sections 19a, 19b also have tabs 20a, 20b depending from them. Any pitch adjustment of the pitch adjustment arm 7b results in the pan to power trowel attachment means 19a, 19b and tabs 20a, 20b also being rotated.

Referring to Figure 7 there is shown a trowel blade 12b having a trowel blade to power float engagement means 21a, 21b in the form of tubular sections having openings coaxially aligned along the length of a leading edge 22 of the trowel blade 12b. The tubular section may be formed as part of the trowel blade or may be welded or otherwise attached to the trowel blade. The trowel blade power float engagement means 21a, 21b is configured to attach the trowel blade to a pitch adjustment arm 7a, 7b, 7c of the power float as well as to attach the trowel blade 12b to a pan 13.

Referring to Figure 8 there is shown a detail view of a pan and blade assembly as generally indicated by arrow 23. In Figure 8 Trowel blade 12b power float engagement means 21a, 21b tubular sections align co-axially with the tubular sections of the trowel blade to power float engagements means 21a, 21b on pitch adjustment arm 7b. Power float attachment means 15 and notch 17 on the pan 13 also align coaxially with the trowel blade to power float engagement means 21a, 21b on pitch adjustment arm 7b. A rod 24 is inserted through the co-axially aligned apertures of the power float attachment means 15, trowel blade to power float engagements means 21a, 21b and pan and trowel attachment means 19a, 19b. The rod 24 is retained in place with friction, a split pin, bolt/nut or the like, not shown. In operation, rotation of the pitch adjustment arm 7b presses tabs 20a, 20b into, or away from, the trowel blade 12b thereby adjusting the pitch of the trowel blade 12b relative to the planar working surface of the pan 13. The rod 24 acts as a pivot axis and rotation of the pitch adjustment arm 7b is not conferred to the pan 13. When the trowel blade 12b pitch is adjusted the trowel blade 12b is rotated through the radially extending aperture 14b. When the power trowel of Figures 3 and 4 is operated on freshly poured concrete, that is substantially fluid in its consistency, the blades 12a, 12b and 12c are adjusted to have a neutral pitch where the blades are substantially coplanar with the planar base of the pan 13. This mode of operation is depicted in Figure 3. As the concrete hardens and becomes more plastic the pitch of the blades 12a, 12b and 12c are adjusted such that they tilt through the longitudinally extending apertures 14a, 14b and 14c. As the pitch of the blades is increased the pan is lifted further away from the concrete surface and the blades 12a, 12b and 12c provide a smaller and smaller contact patch. In this manner the present invention transitions seamlessly from working with a pan style attachment to working with blades.

Referring to Figure 9 there is shown a detail view of a further pan and blade assembly as generally indicated by arrow 25. In Figure 9 trowel blade 12b has a power float engagements means in the form of a blade holder 26. The blade 12b slots into the blade holder 26 and is bolted into place, bolts not shown. The blade holder 26 is also attached to the pitch adjustment arm 7b and to the pan by way of hinge 27.

In operation, rotation of the pitch adjustment arm 7b adjusts the pitch of the blade holder 26, tilting the trowel blade 12b through the aperture 14b and at the same time lifting the pan 13 by way of the hinge 27. Figure 10 shows a plan view of a further pan and blade assembly as generally indicated by arrow 28. The same pan and blade assembly is shown in perspective in Figure 11 and in side view in Figure 12. Figure 10 depicts the location of cross-section A-A shown in Figure 13.

Referring to Figure 10, four trowel blades 29a, 29b, 29c, 29d are configured to hinge at hinge mechanisms 30a, 30,b, 30c, 30d in relation to pan 31. The trowel blades are rotated at the hinge and urged through openings 32a, 32b, 32c, 32d in the pan by the action of trowel blade to power trowel engagements members 33a, 33b, 33c, 33d respectively.

Referring to Figure 11, trowel blade 29d can be rotated about hinge 30d by the downward action of member 33d so that the blade and the pan 31 are not coplanar. Conversely, when member 33d acts upwards, the blade 29d may move so that it become coplanar with pan 31. In those embodiments where member 33d is attached fixedly to blade 29d the two components move in unison. In some embodiments, however, the two components are attached only at the hinge and in those cases it will be appreciated that the two components only act on eachother in compression (co-rotation about the hinge) and otherwise can be pulled apart (contra-rotated about the hinge) in opposite directions.

As shown in Figure 12, trowel blade 29d may be rotated about hinge mechanism 30d by the downward action of member 33d so that the lower edge 34 of the trowel blade 29d extends a significant distance away from the lower surface of the pan 31. The pitch angle may be increased to 10° or 20°, as shown in the figure.

Figure 13 shows a detailed side view through cross-section A-A shown in Figure 10. The ensuing description applies equally to the respective cross-sections through each of trowel blades 29b, 29c, 29d.

Trowel blade 29a rotates about hinge mechanism 30a. The hinge mechanism is formed by a captive rod 34a inserted through: a) the turned edge 36a of the trowel blade 29a; b) a turned edge of pan 31 (not shown); c) a turned edge of member 35a (not shown).

In this way the hinge mechanism consists of three members rotating about an axis provided by captive rod 34a. As force is applied to member 35a so as to rotate it in a downward direction (anticlockwise as shown), trowel blade 29a is urged to also rotate downward (anticlockwise as shown). Conversely, as the force applied to member 35a is relaxed or removed, member 33a can rotate in an upward direction (clockwise as shown), and trowel blade 29a rotates upwards (clockwise as shown).

Typically member 35a and trowel blade 29a are not fixedly attached to each other, being attached only at hinge mechanism 30a. In the arrangement shown in figure 13, each may act on the other in compression, but each may be separated from each other as force is applied to pull them apart, so that they are in contact only about the hinge mechanism 30a.

Member 35a is attached (through weld, rivet, or similar) to member 37a having an engaging clip region 38a in which member 33a may be releasably engaged. Member 33a is provided with a slot 39a and hole 40a (both shown in Figure 10) which are used to fix a pitch adjustment arm 7a which has been inserted in channel 41a. In this way, as the pitch of the adjustment arm 7a is modulated, a rotational force is generated on member 33a which is turn acts through member 38a to impart a rotational force on member 35a thereby rotating the trowel blade 29a about hinge mechanism 30a.

It will be appreciated that, as the arms of the power trowel are driven by the action of the motor about the hub 6, the arm 7a transfers that force through members 33a, to 37a, to 35a to the hinge mechanism to rotate the entire pan and trowel blade attachment of Figure 13 about the hub 6. In this embodiment, the trowel blade to power trowel engagement means of the invention comprises members 33a, 35a and 37a.

Advantageously the design and configuration of the pan and trowel blade attachment of Figure 13 enables the ready removal of the trowel blade following removal of the captive rod 34a. Captive rod 34a may be held in place by friction, captive pin, bolt, or otherwise. Captive rod 34a is designed to remain in position while the power trowel is in operation and rest, until such time as the user wishes to remove it. Typically removal of the captive rod will only be necessary to replace the trowel blade. It will be understood that the trowel blade typically wears out fastest because of the pressure applied to the edge of the blade and the abrasive nature of the concrete surface being worked.

Figure 14 shows a removable trowel blade 29a of the pan and trowel blade attachment of Figure 13, showing the turned edge 36a of the trowel blade 29a. Advantageously, the trowel blade 29a may be sold separately and may be readily replaced on the power trowel and/or pan and trowel blade attachment of Figure 13. In the embodiment shown in Figure 14, the edge 42a is square to the adjacent edges, whereas the edge 43a has a slight curve to it.

The entire disclosures of all applications, patents and publications cited above and below, if any, are herein incorporated by reference.

Reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that that prior art forms part of the common general knowledge in the field of endeavour in any country in the world. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents.

The invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, in any or all combinations of two or more of said parts, elements or features.

Where in the foregoing description reference has been made to integers or components having known equivalents thereof, those integers are herein incorporated as if individually set forth.

It should be noted that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the invention and without diminishing its attendant advantages. It is therefore intended that such changes and modifications be included within the present invention. The invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, in any or all combinations of two or more of said parts, elements or features.

Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof.

Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and the like, are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense, that is to say, in the sense of "including, but not limited to".

Claims

Claims:

1. A pan for a power trowel, the pan comprising a disc having a substantially planar working surface, wherein at least one radially extending aperture is formed in the disc.

2. The pan according to claim 1 wherein the dimensions of the or each radially extending aperture corresponds substantially to the length and width of a power trowel blade.

3. The pan according to claim 1 wherein the or each radially extending aperture is configured to allow at least a portion of a trowelling blade to pass through the aperture to engage with a concrete surface to be worked.

4. The pan according to claim 1 having at least 3 radially extending apertures formed in the disc.

5. The pan according to claim 1 wherein the pan includes at least one pan to power trowel attachment means for attachment of the pan to a rotating drive member of a power trowel.

6. The pan according to claim 5 wherein the at least one pan to power trowel attachment means includes a turned edge for engagement in a hinge.

7. The pan according to claim 1 having at least one pan to trowel blade attachment means.

8. The pan according to claim 7 wherein the blade to pan attachment means includes a turned edge for engagement in a hinge.

9. A trowel blade for use with a power trowel, the trowel blade including: a trowel blade to pan attachment means configured to allow attachment of the trowel blade to a pan comprising a disc having a substantially planar working surface, wherein at least one radially extending aperture is formed in the disc, wherein the trowel blade to pan attachment means allows the pitch of the trowel blade to be varied relative to the pan so that at least a portion of the trowel moves through the at least one radially extending aperture.

10. The trowel blade according to claim 9 wherein the blade to pan attachment means includes a turned edge for engagement in a hinge.

11. A trowel blade to power trowel engagement means configured to allow engagement of a pitch adjustment arm of the power trowel with a trowel blade, wherein pitch adjustment of the pitch adjustment arm is conferred to the trowel blade through the trowel blade to power trowel engagement means.

12. The trowel blade according to claim 11 wherein the trowel blade is configured to be manually disengaged from the trowel blade to power trowel engagement means.

13. A pan and blade assembly for use with a power trowel, the pan and blade assembly comprising:

14. The pan and blade assembly according to claim 13 wherein the trowel blade to power trowel engagement means is attached to the pan through a hinge which also engages the blade to pan attachment means.

15. The pan and blade assembly according to claim 13 wherein the trowel blade to power trowel engagement means includes a tubular section configured to receive a portion of an arm of the power trowel through the tube opening.

16. The pan and blade assembly according to claim 15 wherein the arm is configured to provide rotational force to the pan and to the trowel blade, and is configured to provide pitch adjustment to the trowel blade.