Concrete trowel

Abstract

A concrete trowel including: a drive assembly including a drive shaft; a rotor including a plurality of blades and rotatably operably coupled to the drive assembly for rotating about a rotational axis; and a blade pitch adjustment assembly configured to adjust a pitch of each of the plurality of blades, the blade pitch adjustment assembly including a yoke configured to move relative to the rotor between a first position in which each of the plurality of blades is in in a first orientation and a second position in which each of the plurality of blades is in a second orientation; a drive piston configured to move from a retracted position to an extended position to move the yoke from the first position to the second position; and an eddy drive assembly driven by the drive shaft, the eddy drive assembly configured to move the drive piston to the extended position.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority to U.S. Provisional Patent Application No. 63 / 771,476, filed Mar. 13, 2025, the entire contents of which are incorporated herein by reference.FIELD OF THE INVENTION

[0002] The present invention relates to powered concrete trowels, and more particularly to battery powered concrete trowels.BACKGROUND OF THE INVENTION

[0003] Powered concrete trowels are typically used for finishing concrete surfaces and generally include a gas-powered motor mounted on a frame or “cage” that surrounds a rotor having a plurality of concrete trowel blades. The rotor is rotatably driven by the rotatable output of the motor, which rotates the blades on a concrete surface. The trowel is controlled by an operator via a handle extending from the frame.SUMMARY OF THE INVENTION

[0004] In some aspects, the techniques described herein relate to a concrete trowel including: a frame; a drive assembly mounted on the frame and including a drive shaft; a rotor including a plurality of blades, the rotor rotatably operably coupled to the drive assembly for rotating about a rotational axis; and a blade pitch adjustment assembly configured to adjust a pitch of each of the plurality of blades, the blade pitch adjustment assembly including a yoke configured to move relative to the rotor between a first position in which each of the plurality of blades is in in a first orientation and a second position in which each of the plurality of blades is in a second orientation; a drive piston configured to move from a retracted position to an extended position to move the yoke from the first position to the second position; and an eddy drive assembly driven by the drive shaft, the eddy drive assembly configured to move the drive piston to the extended position.

[0005] In some aspects, the techniques described herein relate to a concrete trowel including: a frame; a drive assembly mounted on the frame and including a drive shaft; a rotor including a plurality of blades, the rotor rotatably operably coupled to the drive assembly for rotating about a rotational axis; and a blade pitch adjustment assembly configured to adjust a pitch of each of the plurality of blades, the blade pitch adjustment assembly including a yoke configured to move relative to the rotor between a first position in which each of the plurality of blades is in in a first orientation and a second position in which each of the plurality of blades is in a second orientation; an eddy drive assembly driven by the drive shaft, the eddy drive assembly configured to move the yoke from the first position to the second position; and a control valve assembly configured to be movable between a closed position and an open position, wherein when the control valve assembly is in the closed position, the eddy drive assembly is not actuatable and thus the yoke is prevented from moving from the first position to the second position, and wherein when the control valve assembly is in the open position, the eddy drive assembly is actuatable and thus the yoke is movable from the first position to the second position to thereby move each of the plurality of blades from the first orientation to the second orientation.

[0006] In some aspects, the techniques described herein relate to a concrete trowel including: a frame; a drive assembly mounted on the frame and including a drive shaft; a rotor including a plurality of blades, the rotor rotatably operably coupled to the drive assembly for rotating about a rotational axis; and a blade pitch adjustment assembly configured to adjust a pitch of each of the plurality of blades, the blade pitch adjustment assembly including a yoke configured to move relative to the rotor between a first position in which each of the plurality of blades is in in a first orientation and a second position in which each of the plurality of blades is in a second orientation, a drive plate coupled to the drive shaft for rotation therewith and formed from a magnetically permeable or conductive metal material, and a driven rotor movable relative to the drive plate and including a support substrate and at least one magnetic element, wherein rotation of the drive plate by the drive shaft causes rotation of the driven rotor via an eddy current at the at least one magnetic element, and wherein rotation of the driven rotor causes the yoke to move from the first position to the second position and thereby to move each of the plurality of blades from the first orientation to the second orientation.

[0007] Other features and aspects of the invention will become apparent by consideration of the following detailed description and accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1 is perspective view of a concrete trowel according to an embodiment of the invention.

[0009] FIG. 2 is a perspective view of a portion of the concrete trowel of FIG. 1 coupled to a rotor.

[0010] FIG. 3 is side view of a drive assembly and a blade pitch adjustment assembly of the concrete trowel of FIG. 1.

[0011] FIG. 4 is a cross-sectional view of the drive assembly of FIG. 3 taken along the line 4-4 of FIG. 3.

[0012] FIG. 5 is a schematic of an alternative drive assembly for use with the concrete trowel of FIG. 1.

[0013] FIG. 6 is a perspective view of a portion of the blade pitch adjustment assembly of FIG. 3.

[0014] FIG. 7 is a cross-sectional view of the blade pitch adjustment assembly of FIG. 3 taken along the line 4-4 of FIG. 3.

[0015] FIG. 8 is another cross-sectional view of the blade pitch adjustment assembly of FIG. 3 taken along the line 4-4 of FIG. 3.

[0016] FIG. 9 is a cross-sectional view of the blade pitch adjustment assembly of FIG. 3 taken along the line 7-7 of FIG. 3.

[0017] FIG. 10 illustrates a control valve assembly of the blade pitch adjustment assembly of FIG. 3 including a valve and a pin.

[0018] FIG. 11 is a schematic of the blade pitch adjustment assembly of FIG. 3.

[0019] FIG. 12 is a schematic of the blade pitch adjustment assembly of FIG. 3 when a motor of the drive assembly is started.

[0020] FIG. 13 is a schematic of a drive piston of the blade pitch adjustment assembly of FIG. 3 in a retracted position, an unloader of the blade pitch adjustment assembly of FIG. 3 in an extended position, and a control valve assembly of the blade pitch adjustment assembly of FIG. 3 in a closed position.

[0021] FIG. 14 is a schematic of the drive piston of the blade pitch adjustment assembly of FIG. 3 in the retracted position, the unloader of the blade pitch adjustment assembly of FIG. 3 in a retracted position, and the control valve assembly of the blade pitch adjustment assembly of FIG. 3 in the closed position.

[0022] FIG. 15 is a schematic of the blade pitch adjustment assembly of FIG. 3 when the blade pitch adjustment assembly is increasing a pitch of the blades of the rotor.

[0023] FIG. 16 is a schematic of the drive piston of the blade pitch adjustment assembly of FIG. 3 in the retracted position, the unloader of the blade pitch adjustment assembly of FIG. 3 in the retracted position, and the control valve assembly of the blade pitch adjustment assembly of FIG. 3 in the closed position.

[0024] FIG. 17 is a schematic of the drive piston of the blade pitch adjustment assembly of FIG. 3 in the retracted position, the unloader of the blade pitch adjustment assembly of FIG. 3 in the extended position, and the control valve assembly of the blade pitch adjustment assembly of FIG. 3 in the open position.

[0025] FIG. 18 is a schematic of the drive piston of the blade pitch adjustment assembly of FIG. 3 in an extended position, the unloader of the blade pitch adjustment assembly of FIG. 3 in the retracted position, and the control valve assembly of the blade pitch adjustment assembly of FIG. 3 in the closed position.

[0026] FIG. 19 is a schematic of the drive piston of the blade pitch adjustment assembly of FIG. 3 in the retracted position, the unloader of the blade pitch adjustment assembly of FIG. 3 in the extended position, and the control valve assembly of the blade pitch adjustment assembly of FIG. 3 in the open position.

[0027] FIG. 20 is a schematic of the drive piston of the blade pitch adjustment assembly of FIG. 3 in the extended position, the unloader of the blade pitch adjustment assembly of FIG. 3 in the retracted position, and the control valve assembly of the blade pitch adjustment assembly of FIG. 3 in the closed position.

[0028] Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.DETAILED DESCRIPTION

[0029] FIG. 1 illustrates a concrete trowel 10 including a frame 12. The frame 12 supports a drive assembly 16 (FIGS. 2 and 3) for driving a rotor 20 having a plurality of blades 24 and adjusting the pitch of the blades 24. A handle assembly 28 including a post 32 extends obliquely from the frame 12 and handlebars 36 coupled to the post 32. The handle assembly 28 extends from the frame 12 and is used to control the concrete trowel 10.

[0030] With respect to FIG. 1, the frame 12 includes a drive housing 40 and a gear housing 44 coupled to the drive housing 40. With respect to FIGS. 2 and 3, the frame 12 supports the drive assembly 16. In the illustrated embodiment, the drive assembly 16 includes a motor 48, a clutch 52, and a gear assembly 56. The motor 48 is at least partially positioned within an interior of the drive housing 40 and the gear assembly 56 is supported within an interior of the gear housing 44. Although not shown, the gear housing 44 may include a cover 190 (not shown) that separates the interior of the drive housing 40 from the interior of the gear housing 44.

[0031] The drive assembly 16 may be powered by a battery pack (not shown) supported by the frame 12 and in selective electrical communication with the motor 48 to provide electrical power to the motor 48. In some embodiments of the trowel 10, the battery pack and the motor 48 can be configured as an 80 Volt high power battery pack and motor 48. It is to be understood that drive assembly 16 may be a combustion engine and in such a case, in lieu of a battery pack, the concrete trowel 10 may include a fuel cell and a fuel injection system, or carburetion system, in fluid communication with the engine.

[0032] The drive assembly 16 is operable to drive the rotor 20 to rotate the blades 24 relative to the concrete. As shown in FIG. 2, the rotor 20 also includes a tilt plate 60. In some case, the rotor 20 also has a blade guard 64. When the rotor 20 is driven, the blades 24 level and compact the material of the support surface (e.g., concrete). The drive assembly 16 is also operable to adjust the pitch of the blades 24. The drive assembly 16 adjusts a plane of each of the blades 24 relative to the concrete to adjust the pitch of the blades 24. In a first orientation, the plane of each of the blades 24 is generally parallel to a plane of the work surface of the concrete, while in a second orientation, the plane of each of the blades 24 is generally angled relative to the plane of the work surface of the concrete. In some embodiments, the drive assembly 16 may be operable to drive one or more accessories, such as a grinder or polisher, separately from driving the rotor 20.

[0033] With respect to FIG. 4, the drive assembly 16 includes a drive shaft 80. In the illustrated embodiment, the drive shaft 80 extends from the motor 48 and defines a drive axis A. In the illustrated embodiment, the drive axis A is perpendicular to the work surface. In the illustrated embodiment, the motor 48 is positioned within the drive housing 40 (FIG. 1) and the drive shaft 80 is positioned within the gear housing 44 (FIGS. 1 and 2). In the illustrated embodiment the motor 48 is a brushless direct current electric motor. In other embodiments of the concrete trowel 10, the motor 48 can be configured as a brushed motor, or any other type of electric motor known to someone having ordinary skill in the art.

[0034] Further with respect to FIG. 4, the clutch 52 is positioned between the drive shaft 80 and includes a driven shaft 84, which has a plurality of gear teeth 88 extending outwardly therefrom. The clutch 52 is configured to operably couple the driven shaft 84 to the drive shaft 80 when a speed of the motor 48 is greater than or equal to a predetermined speed (e.g., 7000 rpm). In one example, though not shown in detail, the clutch 52 is a centrifugal clutch and includes a drum 92, a plurality of shoes (not shown in detail), and a plurality of springs 96. The driven shaft 84 is fixedly (e.g., integrally) coupled to and extends from the drum 92. The drive shaft 80 extends through the drum 92 and the driven shaft 84. The shoes are each movably coupled to the drive shaft 80 at a first end. Each of the springs 96 is coupled between adjacent shoes at the respective second ends. When the speed of the motor 48 is less than the predetermined speed, the drive shaft 80 rotates, but the driven shaft 84 does not. As the speed of the motor 48 increases to the predetermined speed, and exceeds the predetermined speed, the centrifugal force on the shoes becomes greater than a force of the springs 96, thereby allowing the second ends of the shoes to move into cam grooves (not shown) in the drum 92. Accordingly, when the speed of the motor 48 is greater than the predetermined speed, the drive shaft 80 is operably coupled to the drum 92 causing the drum 92, and therefore the driven shaft 84, to rotate with the drive shaft 80.

[0035] With respect to FIGS. 3 and 4, the gear assembly 56 is positioned within the gear housing 44 and is surrounded by lubricating fluid (e.g., oil). The gear assembly 56 includes a first driven gear 110 that is engaged with the driven shaft 84 of the motor 48 and a second driven gear 114 that is engaged with the first driven gear 110. The first driven gear 110 includes a first portion 110a and a second portion 110b extending from the first portion 110a. The first portion 110a has a first dimension and a first plurality of gear teeth 116. The second portion 110b has a second dimension and a second plurality of gear teeth 120. The first gear teeth 116 meshes with gear teeth 88 of the driven shaft 84. The second gear teeth 120 mesh with gear teeth 124 of the second driven gear 114. The first driven gear 110 defines an axis B that is parallel to the drive axis A. Similarly, the second driven gear 114 defines an axis C that is parallel to both the drive axis A and the axis B of the first driven gear 110. The first driven gear 110 provides a gear reduction ratio to the second driven gear 114.

[0036] The second driven gear 114 is operably couplable to the rotor 20 such that actuation of the motor 48 rotates the rotor 20 to thereby rotate the blades 24. That is, actuation of the motor 48 rotates the drive shaft 80, which in turn rotates the driven shaft 84, the first driven gear 110, and the second driven gear 114.

[0037] In other embodiments (such as shown in FIG. 5), the drive assembly 16 may further include a third driven gear 130 configured to be driven by the second driven gear 114. In such case, the third driven gear 130 may be operably couplable to the rotor 20 such that actuation of the motor 48 rotates the rotor 20 to thereby rotate the blades 24. That is, actuation of the motor 48 rotates the drive shaft 80, which in turn rotates the first driven gear 110, the second driven gear 114, and the third driven gear 130 to rotate the rotor 20. Moreover, the rotor 20 may be removable, such that an accessory can be operably coupled to and driven by the second driven gear 114. The accessory may be a grinder or a polisher. When the operator wishes to operate the trowel 10 to level and compact the concrete, the rotor 20 having the blades 24 is operably coupled to the drive assembly 16 via the third driven gear 130. When the operator wishes to smooth or polish the concrete the operator removes the rotor 20 and operably couples the accessory to the drive assembly 16 via the second driven gear 114.

[0038] With respect to FIGS. 3, 6, and 7, the drive assembly 16 is also operably coupled to a blade pitch adjustment assembly 150 for adjusting the pitch of the blades 24 relative to the rotor 20. The blade pitch adjustment assembly 150 includes an eddy drive assembly 154, a gear pump 158, an accumulator piston 162, an unloader 166, a control valve assembly 170, a drive piston 174, and a yoke 178. The yoke 178 is positioned between the gear housing 44 and the rotor 20 and configured to selectively engage the tilt plate 60 coupled to the rotor 20 to adjust the pitch of the blades 24. In the illustrate embodiment, the yoke 178 is pivotably coupled to the gear housing 44.

[0039] An adjustment housing 182 supports the accumulator piston 162, the unloader 166, the control valve assembly 170, and the drive piston 174. The drive piston 174 is configured to move (e.g., pivot) the yoke 178 to selectively engage the tilt plate 60. The drive piston 174 is configured to selectively move (e.g., pivot) the yoke 178 from a first position to a second position. In the first position, the yoke 178 to does not engage (e.g., is adjacent to or contacting but not exerting a force on) the tilt plate 60 and thus the blades 24 are in the first orientation. In the second position, the yoke 178 engages (e.g., contacts) the tilt plate 60 with a force and thus the blades 24 are in the second orientation. The yoke 178 is biased by a biasing mechanism (e.g., a spring, not shown) into the first position. The eddy drive assembly 154 is configured to drive the gear pump 158 to adjust the pressure within the adjustment housing 182, which can adjust the position of the drive piston 174. The position of the drive piston 174 is used to adjust the pitch of the blades 24 and to maintain the desired pitch of the blades 24, as will be discussed in greater detail below.

[0040] The adjustment housing 182 is collectively defined by a base 186 and a cover 190. As shown in FIG. 8, the adjustment housing 182 has a first chamber 200 (FIG. 6), a second chamber 204, a third chamber 208, and a fourth chamber 212. The first chamber 200 movably receives the accumulator piston 162. Together, the first chamber 200 and the accumulator piston 162 define an accumulator. The second chamber 204 movably receives the unloader 166. The third chamber 208 movably receives the control valve assembly 170. The fourth chamber 212 movably receives the drive piston 174.

[0041] The adjustment housing 182 supports the gear pump 158. The gear pump 158 includes a drive gear 220 that drives a driven gear 224. As shown in FIG. 9, the cover 190 of the adjustment housing 182 has a pump inlet 228, a pump outlet 232, and a channel 236 that defines a first fluid flow path (FIG. 6). The pump inlet 228 is in fluid communication with the interior of the gear housing 44 to receive pressurized fluid therefrom. The pump inlet 228 is in fluid communication with the pump outlet 232 via the gear pump 158. The pump outlet 232 is in communication with the first fluid flow path 236. The first fluid flow path 236 is in selective communication with the first chamber 200, the second chamber 204, and the third chamber 208. Thus, fluid drawn in through the pump inlet 228 via the gear pump 158 is pressurized and guided to the first fluid flow path 236 and then selectively distributed into the respective chamber, as will be discussed in greater detail below. The first chamber 200, the second chamber 204, and the third chamber 208 are in fluid communication with one another via the first fluid flow path 236. The third chamber 208 is in fluid communication with the fourth chamber 212 via a second fluid flow path 240 (FIGS. 19 and 20). The third chamber 208 is also in fluid communication with an interior of the gear housing 44 via a third fluid flow path 244 (FIG. 20).

[0042] The accumulator piston 162 is positioned and movable within the first chamber 200. The first chamber 200 has a first end adjacent the cover and a second end opposite the first end. The first fluid flow path 236 is in communication with the first end of the first chamber 200. A biasing mechanism (e.g., a nitrogen source or a spring, not shown) is positioned between the second end of the first chamber 200 and the accumulator piston 162 to bias the accumulator piston 162 towards the first end. In other embodiments, the first chamber 200 includes an accumulator bladder instead of the accumulator piston 162. Pressurized fluid is guided to the first chamber 200 via the first fluid flow path 236 until the accumulator piston 162 reaches a steady-state position in which the pressurized fluid has a predetermined volume and a predetermined pressure therein.

[0043] With respect to FIG. 8, the unloader 166 is positioned within and movable relative to the second chamber 204. The second chamber 204 has a first end extending through the cover 190 and a second end opposite the first end. The unloader 166 includes a first end and a second end opposite the first end. The unloader 166 includes an unloader piston 260 at the second end and an unloader stem 264 extending from the unloader piston 260 towards the first end. The unloader stem 264 extends through an opening 268 of the second chamber 204 of the adjustment housing 182 (e.g., the cover 190). A biasing mechanism (e.g., a spring or multiple springs, not shown) is positioned between the second end of the second chamber 204 and the unloader piston 260. The unloader 166 is movable between a retracted position (FIG. 14) in which the unloader piston 260 is closer to the second end than the first end and an extended position (FIG. 8) in which the unloader piston 260 is closer to the first end than the second end. The biasing mechanism biases the unloader 166 into the extended position. The first fluid flow path 236 guides pressurized fluid to the second chamber 204 between a location adjacent the first end and the unloader piston 260. With control valve assembly 170 in a closed position (discussed in greater detail below), when the accumulator piston 162 reaches the steady state position, pressurized fluid then moves via the first fluid flow path 236 to the second chamber 204 to move the unloader 166 from the extended to retracted position. When the unloader 166 reaches the retracted position, the pressure within the adjustment housing 182 maintains the predetermined pressure of the pressurized fluid therein.

[0044] As discussed in greater detail below, the eddy drive assembly 154 is operably coupled to the unloader 166. The unloader 166 is also configured to be fixedly or matingly coupled to a drive gear 220 of the gear pump 158.

[0045] As shown in FIGS. 3 and 4, the eddy drive assembly 154 is operably coupled to the drive shaft 80 of the motor 48. The eddy drive assembly 154 is positioned within the gear housing 44 but outside the adjustment housing 182. The eddy drive assembly 154 includes a drive plate 300 and a driven rotor 304.

[0046] With respect to FIG. 4, the drive plate 300 is operably coupled to the drive shaft 80. The drive plate 300 may be fixed to drive shaft 80 and, thus, rotate simultaneously to or in concert with drive shaft 80 about the drive axis A. Thus, the drive shaft 80 and the drive plate 300 may be coaxial. As shown, the drive plate 300 may include or be provided as a magnetically permeable or conductive disk that extends radially from drive shaft 80 (or drive axis A generally). In other words, a disk formed from a magnetically permeable or conductive metal (e.g., non-ferrous metal) may be included with or provided as the drive plate 300.

[0047] With respect to FIGS. 4 and 8, the driven rotor 304 is operably coupled to the unloader 166. As shown, the driven rotor 304 is coupled to the unloader 166 at the first end. The driven rotor 304 is coupled to the unloader stem 264. The driven rotor 304 is rotatable about the drive axis A and axially movable along the drive axis A relative to the drive plate 300 and the adjustment housing 182. The driven rotor 304 is mechanically decoupled from the drive plate 300. The drive plate 300 influences or induces rotation at the driven rotor 304, as will be described in detail below. The driven rotor 304 includes a support substrate 308 (e.g., disk substrate) and one or more magnetic elements (e.g., permanent magnets, not shown). The magnetic elements may be, for instance, fixed to the support substrate 308 to rotate therewith. In some embodiments, the one or more magnetic elements includes a plurality of circumferentially spaced (e.g., equally spaced about the drive axis A) magnetic elements. As shown, the magnetic elements may be embedded within the support substrate 308. The magnetic elements may be arrayed such that the magnetic pole directed or toward the drive plate 300 is alternated. Moreover, the one or more magnetic elements may be magnetically engaged with the drive plate 300. The driven rotor 304 may be rotatably mounted about or extend radially outward from the drive axis A.

[0048] When the unloader 166 is in the extended position, the driven rotor 304 is positioned adjacent to the drive plate 300. That is, the driven rotor 304 is positioned relative to the drive plate 300 by a gap having a predetermined distance or less. When the unloader 166 is in the extended position, rotation of the drive plate 300 via drive shaft 80 of the motor 48 may generate an eddy current at the one or more magnetic elements of the driven rotor 304 (e.g., as would be understood). In turn, rotation of the drive plate 300 may induce the driven rotor 304 to separately rotate (e.g., about the drive axis A). Rotation of the driven rotor 304 thus causes rotation of the unloader 166, which in turn causes rotation of the driven gear 224 of the gear pump 158.

[0049] When the unloader 166 is in the retracted position, the driven rotor 304 is spaced apart from the drive plate 300. That is, the driven rotor 304 is positioned relative to the drive plate 300 by a gap that is greater than the predetermined distance. When the unloader 166 is in the retracted position, the driven rotor 304 is too far away from the drive plate 300 for rotation of the drive plate 300 to generate the eddy current. In turn, rotation of the driven rotor 304 stops thus causing rotation of the unloader 166 and driven gear 224 of the gear pump 158 to stop. As noted above, when the unloader 166 reaches the retracted position, the pressure within the adjustment housing 182 reaches the predetermined pressure. When the gear pump 158 stops, the pressure within the adjustment housing 182 remains at the predetermined pressure.

[0050] The control valve assembly 170 is positioned within and movable relative to the third chamber 208 to adjust the pitch of the blades 24. The third chamber 208 has a first open end extending through the cover 190 and a second open end extending through the base 186. The control valve assembly 170 includes a valve 320 that is movable relative to the third chamber 208 and a pin 324 that is movable relative to the third chamber 208. The valve 320 and the pin 324 are also movable relative to one another.

[0051] With respect to FIGS. 8 and 10, the valve 320 includes a valve body 328 and a valve stem 332 that is coupled to and extends from the valve body 328. The valve body 328 is positioned and movable within the third chamber 208 and the valve stem 332 extends through the first open end of the third chamber 208. Thus, the valve stem 332 extends into the gear housing 44. As shown, the valve 320 has a first end (defined by the valve stem 332), which that is positioned within interior of the gear housing 44, and a second end (defined by the valve body 328), opposite the first end, which is positioned within the third chamber 208. A valve axis D extends between the first end and the second end. The valve body 328 has a recess 340 that extends from the second end towards the first end. As shown in FIG. 10, the recess 340 has a first inner circumferential wall 344 and a second inner circumferential wall 348, each extending from an inner wall of the recess 340. The first inner circumferential wall 344 is positioned between a closed end of the recess 340 and the second inner circumferential wall 348. The second inner circumferential wall 348 is positioned adjacent the second end of the valve 320. The valve body 328 also includes a first outer circumferential wall 352 and a second outer circumferential wall 356. The first outer circumferential wall 352 is positioned between the first end and the second outer circumferential wall 356. The second outer circumferential wall 356 is positioned at (or adjacent to) the second end. The valve body 328 also has a first port 360 and a second port 364 spaced apart from the first port 360 along the valve axis D. Each of the first port 360 and the second port 364 extends through the valve body 328 and is in communication with the recess 340. In the illustrated embodiment, the first port 360 is positioned between the closed end of the recess 340 and the first inner circumferential wall 344. Also, the first port 360 is positioned between the first end of the valve 320 and the first outer circumferential wall 352. The second port 364 is between the first inner circumferential wall 344 and the second inner circumferential wall 348. Also, the second port 364 is positioned between the first outer circumferential wall 352 and the second outer circumferential wall 356.

[0052] The pin 324 is movably received within the recess 340 of the valve body 328 and extends through the second open end of the third chamber 208 to an outside of the gear housing 44. The pin 324 includes a first end and a second end opposite the first end. A pin axis E extends between the first end and the second end. The pin axis E is coincident with the valve axis D. The first end is positioned within the recess 340 of the valve body 328 and the second end is positioned outside of the adjustment housing 182. The pin 324 includes a first portion 380 extending from the first end toward the second end, a second portion 384 extending from the first portion 380 towards the second end, and a third portion 388 extending from the second portion 384 towards the second end. The second portion 384 has a smaller outer dimension than the first portion 380 and the third portion 388. A gasket 392 is positioned within a circumferential groove 396 in the third portion 388 and is positioned between the pin 324 and the adjustment housing 182. The gasket 392 seals the pin 324 with respect to the third chamber 208. A channel 400 extends partially therethrough the pin 324 along the pin axis E. The pin 324 has a first port 404 in communication with the channel 400. The first port 404 is in the adjacent to the first end. The pin 324 has a second port 408 that is in communication with the channel 400. The second port 408 is in the second portion 384.

[0053] The first and second outer circumferential walls 352, 356 create a gap between the valve body 328 and a wall of the third chamber 208. The pin 324 is movably received within the recess 340 of the valve body 328. The first end is positioned within the recess 340. Also, the first portion 380 is positioned within and movable relative to the recess 340. The first and second inner circumferential walls 344, 348 of the recess 340 abut the first portion 380 of the pin 324. Also, the first and second inner circumferential walls 344, 348 create a first gap 420 between the pin 324 (e.g., the second portion thereof) and the inner wall of the valve body 328. The first and second inner circumferential walls 344, 348 create a second gap 424 between the pin 324 and the inner wall of the valve body 328.

[0054] The first fluid flow path 236 (FIGS. 6 and 19) is in fluid communication with the third chamber 208 closer to the first end thereof. The first fluid flow path 236 is in fluid communication with the third chamber 208 between the first end thereof and the first outer circumferential wall 352 of the valve body 328. Accordingly, the first fluid flow path 236 is in selective fluid communication with the recess 340 of the valve body 328 via the first port 360 thereof. The second fluid flow path 240 (FIGS. 19 and 20) is in selective fluid communication with the third chamber 208 and the fourth chamber 212. The second fluid flow path 240 is in fluid communication with the third chamber 208 closer to the second end thereof. The gear housing 44 is in selective fluid communication with the third chamber 208, via the third fluid flow path 244 (FIG. 20), between the first end and the seconds thereof (and between the first and second fluid flow paths 236, 240).

[0055] The valve 320 is movable between a retracted position (FIGS. 16 and 19) and an extended position (FIGS. 17 and 20). In the retracted position, the second end of the valve 320 is at or adjacent to the second end of the third chamber 208. In the retracted position, the second fluid flow path 240 is closed by the valve 320 (e.g., the second outer circumferential wall 356). Thus, the second fluid flow path 240 is not in communication with the third chamber 208. Also, in the retracted position, the third fluid flow path 244 is positioned between the first and second outer circumferential walls 352, 356, so it is open. Thus, the third fluid flow path 244 (FIG. 20) allows communication between the third chamber 208 and the gear housing 44. In the extended position, the second end of the valve 320 is spaced apart from the second end of the third chamber 208. The second fluid flow path 240 is open because the valve 320 is spaced apart from the same. Thus, the second fluid flow path 240 is in communication with the third chamber 208. The third fluid flow path 244 is closed by the valve 320 (e.g., the second outer circumferential wall 356). Thus, communication between the third chamber 208 and the gear housing 44 via the third fluid flow path 244 is prevented.

[0056] The pin 324 is movable relative to the valve 320 between a first position (FIGS. 16, 18, and 20) and a second position (FIGS. 8, 17, and 19). In the first position, the first portion 380 of the pin 324 overlaps the first port 360, which closes the first port 360 so that pressurized fluid cannot flow into the recess 340 of the valve body 328. Accordingly, pressurized fluid cannot flow through into the recess 340 of the valve body 328 and into the channel 400 of the pin 324. Also, when the pin 324 is in the first position, the first inner circumferential wall 344 abuts the first portion 380 of the pin 324 so there are no gaps therebetween, but a gap 428 (FIG. 20) is defined between the second inner circumferential wall 348 and the second portion 384 of the pin 324. In the second position, the first portion 380 of the pin 324 is spaced apart from the first port 360, which opens the first port 360 so that pressurized fluid can flow into the recess 340 of the valve body 328. Accordingly, pressurized fluid can flow into the recess 340 of the valve body 328 and into the channel 400 of the pin 324 via its first port 404. Also, when the pin 324 is in the second position, both the first and second inner circumferential walls 344, 348 abut the first portion 380 of the pin 324 so there are no gaps therebetween.

[0057] In the closed position of the control valve assembly 170, the pin 324 is in the first position such that pressurized fluid cannot flow from the first fluid flow path 236 to the second fluid flow path 240. In the closed position of the control valve assembly 170, the eddy drive assembly 154 is not actuatable, as will be discussed in greater detail below. In the open position of the control valve assembly 170, the pin 324 is in the second position, such that pressurized fluid can flow from the first fluid flow path 236 to the second fluid flow path 240. In the open position of the control valve assembly 170, the eddy drive assembly 154 is actuatable, as will be discussed in greater detail below.

[0058] The drive piston 174 is positioned and movable within the fourth chamber 212, which has a first end adjacent to the cover 190 and a second, opposite end. The drive piston 174 has a rod 440 extending therefrom. The rod 440 extends through the second end of the fourth chamber 212 through aligned openings in the adjustment housing 182 (e.g., the base 186) and the gear housing 44. Accordingly, the rod 440 is at least partially positioned outside of the gear housing 44. The drive piston 174 is movable such that the rod 440 selectively engages the yoke 178. In some embodiments, the drive piston 174 may be coupled to the yoke 178. The drive piston 174 is movable between a retracted position (FIGS. 8, 13, 14, and 19) and an extended position (FIGS. 18 and 20). In the retracted position, the rod 440 does not engage the yoke 178 (e.g., exerts a first force that is substantially zero), such that the yoke 178 is biased into the first position. In the extended position, the rod 440 does engage the yoke 178 (e.g., exerts a second force that is greater than first force), such that the yoke 178 is in the second position. A biasing mechanism (e.g., a spring, not shown) is positioned between the first end of the fourth chamber 212 and the drive piston 174 to bias the accumulator piston 162 towards the first end. The second fluid flow path 240 extends between the third chamber 208 and the fourth chamber 212. As shown, the second fluid flow path 240 extends between a location adjacent to the second end of the third chamber 208 and a location adjacent the first end of the fourth chamber 212.

[0059] In operation, as shown in FIGS. 12-14, the operator starts the motor 48 with blades 24 of the rotor 20 in the first orientation. When the operator starts the motor 48, the unloader 166 is in the extended position and the control valve assembly 170 is in the closed position (e.g., the pin 324 is in the first position) with the valve 320 in the retracted position. When the motor 48 first starts, the motor 48 speed is below the predetermined speed, so the drive shaft 80 rotates, but the driven shaft 84 does not. Rotation of the drive shaft 80, causes rotation of the drive plate 300. Because the unloader 166 is in the extended position, rotation of the drive plate 300 causes rotation of the driven rotor 304 and unloader 166, which thus causes actuation of the gear pump 158. Actuation of the gear pump 158 causes fluid to move from the interior of the gear housing 44 through the pump inlet 228 and to be pressurized by the gear pump. The pressurized fluid moves from the pump inlet 228 to the pump outlet 232 and is moved through the first fluid flow path 236 to the first chamber 200 to move the accumulator piston 162 towards the second end of the first chamber 200. When the accumulator piston 162 reaches the steady-state position, the pressurized fluid is guided by the first flow path to the unloader 166 to move the unloader 166 from the extended position to the retracted position. This stops the gear pump 158 and prevents pressurized fluid from continuing to enter the adjustment housing 182. When the accumulator piston 162 is in the steady-state and the unloader 166 is in the retracted state, the predetermined pressure is achieved within the adjustment housing 182. As noted above, when the gear pump 158 stops, the predetermined pressure within the adjustment housing 182 remains. With the motor 48 equal to or greater than the predetermined speed, the rotor 20 (or one of the accessories) is driven by the respective gear.

[0060] As shown in FIGS. 15-19, to adjust the pitch of blades 24 from the first orientation to the second orientation, the control valve assembly 170 moves from the closed position to the open position. That is, the valve 320 moves in a first direction of arrow 500 from the retracted position to the extended position. When the valve 320 moves, the pin 324 remains in place, such that the control valve assembly 170 is in the open position (e.g., the pin 324 is in the second position). With the control valve assembly 170 in the open position, the first fluid flow path 236 communicates with the third chamber 208, which decreases the pressure within the adjustment housing 182 to below the predetermined pressure. Accordingly, the unloader 166 is moved via the biasing mechanism to the extended position causing the driven rotor 304 to rotate with the drive plate 300. Rotation of the driven rotor 304 causes rotation of the unloader 166 and thus the unloader 166 drives the gear pump 158 to move pressurized fluid from the pump inlet 228 into the first fluid flow path 236. Since the control valve assembly 170 is in the open position, the pressurized fluid enters the third chamber 208 and then enters the recess 340 of the valve body 328 via the first port 360 of thereof. Pressurized fluid is then moved through the pin 324 to the fourth chamber 212 via the first port 404 in the pin 324, the channel 400, the second port of the pin 324, and the second fluid flow path 240. As the pressurized fluid moves into the fourth chamber 212, it moves the drive piston 174 from the retracted position to the extended position to move the yoke 178 from the first position to the second position. Accordingly, the blades 24 move from the first orientation to the second orientation. Once drive piston 174 reaches the extended position, continued introduction of the pressurized fluid moves the pin 324 in the first direction of arrow 500 (FIG. 19) from the second position to the first position until the pin 324 closes the first port 360. With the first port 360 closed, the control valve assembly 170 is once again in the closed position. When the first port 360 closes, the pressurized fluid being introduced into the housing adjustment housing 182 causes the pressure in the adjustment housing 182 to increase to the predetermined pressure. Once the predetermined pressure is reached the unloader 166 moves from the extended position to the retracted position to stop the gear pump 158, as discussed above. The predetermined pressure in the adjustment housing 182 remains, which maintains the pitch of the blades 24 of the rotor 20 in the second orientation.

[0061] As shown in FIG. 20, to adjust the pitch of blades 24 from the second orientation to the first orientation, the valve 320, with the pin 324 in the first position, moves in a second direction of arrow 504 from the extended position to the retracted position. Because the pin 324 remains in the first position, the control valve assembly 170 remains closed as the valve 320 moves to the retracted position. Accordingly, the pressure within the adjustment housing 182 does not change. As the valve 320 moves to the retracted position, the third fluid flow path 244 opens allowing pressurized fluid from the fourth chamber 212 to move through the second fluid flow path 240 to the third fluid flow path 244 through the second port 364 in the valve body 328. Accordingly, fluid can be discharged to the gear housing 44. As fluid moves out of the fourth chamber 212, the biasing mechanism within the fourth chamber 212 moves the drive piston 174 from the extended position back to the retracted position, such that the yoke 178, via the bias of its biasing mechanism, moves from the second position back to the first position. Accordingly, the blades 24 move from the second orientation to the first orientation. Once drive piston 174 reaches the retracted position, the control valve assembly 170 remains closed with the valve 320 in the retracted position. Because the first port 360 remains closed, the predetermined pressure in the adjustment housing 182 remains, which maintains the pitch of the blades 24 of the rotor 20 in the first orientation after the same is achieved.

[0062] The valve 320 can be moved between the extended and retracted positions by any suitable mechanism. For example, the valve 320 may be movable via a small pull cable accessible on the frame 12 or handle assembly 28, a fork linkage, an adjustment knob accessible on the frame 12 or the handle assembly 28, a drive screw (e.g., an electric motor), a solenoid, or another suitable mechanism.

[0063] The benefits of this power trowel 10 design are several. First, the clutch 52 enables the motor 48 to drive two features without a secondary motor. That is, the motor 48 is able to drive the rotor 20 without a secondary motor 48 and the blade pitch adjustment assembly 150. Additionally, the drive of the pitch assembly is a low duty drive due to the clutch 52. Additionally, with exception of the yoke 178, the elements of the blade pitch adjustment assembly 150 are enclosed within the frame 12 (e.g., the gear housing 44), so they are protected from dust and debris from the concrete. The control valve assembly 170 can be actuated by a manual actuator, if desired, that requires minimal force (e.g., less than manual actuators for conventional adjustment assemblies). The blade pitch adjustment assembly described herein is more energy efficient by avoiding excessive oil flow and associated energy loss through pressure relief and unloading valve systems. The eddy current drive allows the trowel 10 to stop pumping oil once the accumulator achieves its predetermined pressure. The trowel 10 is lighter weight. Also, with fewer components to assemble, maintain, and replace, there is less wear and tear of the components, which increases long-term reliability of the trowel 10.

[0064] Various features of the invention are set forth in the following claims.

Examples

Embodiment Construction

[0029]FIG. 1 illustrates a concrete trowel 10 including a frame 12. The frame 12 supports a drive assembly 16 (FIGS. 2 and 3) for driving a rotor 20 having a plurality of blades 24 and adjusting the pitch of the blades 24. A handle assembly 28 including a post 32 extends obliquely from the frame 12 and handlebars 36 coupled to the post 32. The handle assembly 28 extends from the frame 12 and is used to control the concrete trowel 10.

[0030]With respect to FIG. 1, the frame 12 includes a drive housing 40 and a gear housing 44 coupled to the drive housing 40. With respect to FIGS. 2 and 3, the frame 12 supports the drive assembly 16. In the illustrated embodiment, the drive assembly 16 includes a motor 48, a clutch 52, and a gear assembly 56. The motor 48 is at least partially positioned within an interior of the drive housing 40 and the gear assembly 56 is supported within an interior of the gear housing 44. Although not shown, the gear housing 44 may include a cover 190 (not shown) t...

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority to U.S. Provisional Patent Application No. 63 / 771,476, filed Mar. 13, 2025, the entire contents of which are incorporated herein by reference.FIELD OF THE INVENTION

[0002] The present invention relates to powered concrete trowels, and more particularly to battery powered concrete trowels.BACKGROUND OF THE INVENTION

[0003] Powered concrete trowels are typically used for finishing concrete surfaces and generally include a gas-powered motor mounted on a frame or “cage” that surrounds a rotor having a plurality of concrete trowel blades. The rotor is rotatably driven by the rotatable output of the motor, which rotates the blades on a concrete surface. The trowel is controlled by an operator via a handle extending from the frame.SUMMARY OF THE INVENTION

[0004] In some aspects, the techniques described herein relate to a concrete trowel including: a frame; a drive assembly mounted on the frame and including a drive shaft; a rotor including a plurality of blades, the rotor rotatably operably coupled to the drive assembly for rotating about a rotational axis; and a blade pitch adjustment assembly configured to adjust a pitch of each of the plurality of blades, the blade pitch adjustment assembly including a yoke configured to move relative to the rotor between a first position in which each of the plurality of blades is in in a first orientation and a second position in which each of the plurality of blades is in a second orientation; a drive piston configured to move from a retracted position to an extended position to move the yoke from the first position to the second position; and an eddy drive assembly driven by the drive shaft, the eddy drive assembly configured to move the drive piston to the extended position.

[0005] In some aspects, the techniques described herein relate to a concrete trowel including: a frame; a drive assembly mounted on the frame and including a drive shaft; a rotor including a plurality of blades, the rotor rotatably operably coupled to the drive assembly for rotating about a rotational axis; and a blade pitch adjustment assembly configured to adjust a pitch of each of the plurality of blades, the blade pitch adjustment assembly including a yoke configured to move relative to the rotor between a first position in which each of the plurality of blades is in in a first orientation and a second position in which each of the plurality of blades is in a second orientation; an eddy drive assembly driven by the drive shaft, the eddy drive assembly configured to move the yoke from the first position to the second position; and a control valve assembly configured to be movable between a closed position and an open position, wherein when the control valve assembly is in the closed position, the eddy drive assembly is not actuatable and thus the yoke is prevented from moving from the first position to the second position, and wherein when the control valve assembly is in the open position, the eddy drive assembly is actuatable and thus the yoke is movable from the first position to the second position to thereby move each of the plurality of blades from the first orientation to the second orientation.

[0006] In some aspects, the techniques described herein relate to a concrete trowel including: a frame; a drive assembly mounted on the frame and including a drive shaft; a rotor including a plurality of blades, the rotor rotatably operably coupled to the drive assembly for rotating about a rotational axis; and a blade pitch adjustment assembly configured to adjust a pitch of each of the plurality of blades, the blade pitch adjustment assembly including a yoke configured to move relative to the rotor between a first position in which each of the plurality of blades is in in a first orientation and a second position in which each of the plurality of blades is in a second orientation, a drive plate coupled to the drive shaft for rotation therewith and formed from a magnetically permeable or conductive metal material, and a driven rotor movable relative to the drive plate and including a support substrate and at least one magnetic element, wherein rotation of the drive plate by the drive shaft causes rotation of the driven rotor via an eddy current at the at least one magnetic element, and wherein rotation of the driven rotor causes the yoke to move from the first position to the second position and thereby to move each of the plurality of blades from the first orientation to the second orientation.

[0007] Other features and aspects of the invention will become apparent by consideration of the following detailed description and accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1 is perspective view of a concrete trowel according to an embodiment of the invention.

[0009] FIG. 2 is a perspective view of a portion of the concrete trowel of FIG. 1 coupled to a rotor.

[0010] FIG. 3 is side view of a drive assembly and a blade pitch adjustment assembly of the concrete trowel of FIG. 1.

[0011] FIG. 4 is a cross-sectional view of the drive assembly of FIG. 3 taken along the line 4-4 of FIG. 3.

[0012] FIG. 5 is a schematic of an alternative drive assembly for use with the concrete trowel of FIG. 1.

[0013] FIG. 6 is a perspective view of a portion of the blade pitch adjustment assembly of FIG. 3.

[0014] FIG. 7 is a cross-sectional view of the blade pitch adjustment assembly of FIG. 3 taken along the line 4-4 of FIG. 3.

[0015] FIG. 8 is another cross-sectional view of the blade pitch adjustment assembly of FIG. 3 taken along the line 4-4 of FIG. 3.

[0016] FIG. 9 is a cross-sectional view of the blade pitch adjustment assembly of FIG. 3 taken along the line 7-7 of FIG. 3.

[0017] FIG. 10 illustrates a control valve assembly of the blade pitch adjustment assembly of FIG. 3 including a valve and a pin.

[0018] FIG. 11 is a schematic of the blade pitch adjustment assembly of FIG. 3.

[0019] FIG. 12 is a schematic of the blade pitch adjustment assembly of FIG. 3 when a motor of the drive assembly is started.

[0020] FIG. 13 is a schematic of a drive piston of the blade pitch adjustment assembly of FIG. 3 in a retracted position, an unloader of the blade pitch adjustment assembly of FIG. 3 in an extended position, and a control valve assembly of the blade pitch adjustment assembly of FIG. 3 in a closed position.

[0021] FIG. 14 is a schematic of the drive piston of the blade pitch adjustment assembly of FIG. 3 in the retracted position, the unloader of the blade pitch adjustment assembly of FIG. 3 in a retracted position, and the control valve assembly of the blade pitch adjustment assembly of FIG. 3 in the closed position.

[0022] FIG. 15 is a schematic of the blade pitch adjustment assembly of FIG. 3 when the blade pitch adjustment assembly is increasing a pitch of the blades of the rotor.

[0023] FIG. 16 is a schematic of the drive piston of the blade pitch adjustment assembly of FIG. 3 in the retracted position, the unloader of the blade pitch adjustment assembly of FIG. 3 in the retracted position, and the control valve assembly of the blade pitch adjustment assembly of FIG. 3 in the closed position.

[0024] FIG. 17 is a schematic of the drive piston of the blade pitch adjustment assembly of FIG. 3 in the retracted position, the unloader of the blade pitch adjustment assembly of FIG. 3 in the extended position, and the control valve assembly of the blade pitch adjustment assembly of FIG. 3 in the open position.

[0025] FIG. 18 is a schematic of the drive piston of the blade pitch adjustment assembly of FIG. 3 in an extended position, the unloader of the blade pitch adjustment assembly of FIG. 3 in the retracted position, and the control valve assembly of the blade pitch adjustment assembly of FIG. 3 in the closed position.

[0026] FIG. 19 is a schematic of the drive piston of the blade pitch adjustment assembly of FIG. 3 in the retracted position, the unloader of the blade pitch adjustment assembly of FIG. 3 in the extended position, and the control valve assembly of the blade pitch adjustment assembly of FIG. 3 in the open position.

[0027] FIG. 20 is a schematic of the drive piston of the blade pitch adjustment assembly of FIG. 3 in the extended position, the unloader of the blade pitch adjustment assembly of FIG. 3 in the retracted position, and the control valve assembly of the blade pitch adjustment assembly of FIG. 3 in the closed position.

[0028] Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.DETAILED DESCRIPTION

[0029] FIG. 1 illustrates a concrete trowel 10 including a frame 12. The frame 12 supports a drive assembly 16 (FIGS. 2 and 3) for driving a rotor 20 having a plurality of blades 24 and adjusting the pitch of the blades 24. A handle assembly 28 including a post 32 extends obliquely from the frame 12 and handlebars 36 coupled to the post 32. The handle assembly 28 extends from the frame 12 and is used to control the concrete trowel 10.

[0030] With respect to FIG. 1, the frame 12 includes a drive housing 40 and a gear housing 44 coupled to the drive housing 40. With respect to FIGS. 2 and 3, the frame 12 supports the drive assembly 16. In the illustrated embodiment, the drive assembly 16 includes a motor 48, a clutch 52, and a gear assembly 56. The motor 48 is at least partially positioned within an interior of the drive housing 40 and the gear assembly 56 is supported within an interior of the gear housing 44. Although not shown, the gear housing 44 may include a cover 190 (not shown) that separates the interior of the drive housing 40 from the interior of the gear housing 44.

[0031] The drive assembly 16 may be powered by a battery pack (not shown) supported by the frame 12 and in selective electrical communication with the motor 48 to provide electrical power to the motor 48. In some embodiments of the trowel 10, the battery pack and the motor 48 can be configured as an 80 Volt high power battery pack and motor 48. It is to be understood that drive assembly 16 may be a combustion engine and in such a case, in lieu of a battery pack, the concrete trowel 10 may include a fuel cell and a fuel injection system, or carburetion system, in fluid communication with the engine.

[0032] The drive assembly 16 is operable to drive the rotor 20 to rotate the blades 24 relative to the concrete. As shown in FIG. 2, the rotor 20 also includes a tilt plate 60. In some case, the rotor 20 also has a blade guard 64. When the rotor 20 is driven, the blades 24 level and compact the material of the support surface (e.g., concrete). The drive assembly 16 is also operable to adjust the pitch of the blades 24. The drive assembly 16 adjusts a plane of each of the blades 24 relative to the concrete to adjust the pitch of the blades 24. In a first orientation, the plane of each of the blades 24 is generally parallel to a plane of the work surface of the concrete, while in a second orientation, the plane of each of the blades 24 is generally angled relative to the plane of the work surface of the concrete. In some embodiments, the drive assembly 16 may be operable to drive one or more accessories, such as a grinder or polisher, separately from driving the rotor 20.

[0033] With respect to FIG. 4, the drive assembly 16 includes a drive shaft 80. In the illustrated embodiment, the drive shaft 80 extends from the motor 48 and defines a drive axis A. In the illustrated embodiment, the drive axis A is perpendicular to the work surface. In the illustrated embodiment, the motor 48 is positioned within the drive housing 40 (FIG. 1) and the drive shaft 80 is positioned within the gear housing 44 (FIGS. 1 and 2). In the illustrated embodiment the motor 48 is a brushless direct current electric motor. In other embodiments of the concrete trowel 10, the motor 48 can be configured as a brushed motor, or any other type of electric motor known to someone having ordinary skill in the art.

[0034] Further with respect to FIG. 4, the clutch 52 is positioned between the drive shaft 80 and includes a driven shaft 84, which has a plurality of gear teeth 88 extending outwardly therefrom. The clutch 52 is configured to operably couple the driven shaft 84 to the drive shaft 80 when a speed of the motor 48 is greater than or equal to a predetermined speed (e.g., 7000 rpm). In one example, though not shown in detail, the clutch 52 is a centrifugal clutch and includes a drum 92, a plurality of shoes (not shown in detail), and a plurality of springs 96. The driven shaft 84 is fixedly (e.g., integrally) coupled to and extends from the drum 92. The drive shaft 80 extends through the drum 92 and the driven shaft 84. The shoes are each movably coupled to the drive shaft 80 at a first end. Each of the springs 96 is coupled between adjacent shoes at the respective second ends. When the speed of the motor 48 is less than the predetermined speed, the drive shaft 80 rotates, but the driven shaft 84 does not. As the speed of the motor 48 increases to the predetermined speed, and exceeds the predetermined speed, the centrifugal force on the shoes becomes greater than a force of the springs 96, thereby allowing the second ends of the shoes to move into cam grooves (not shown) in the drum 92. Accordingly, when the speed of the motor 48 is greater than the predetermined speed, the drive shaft 80 is operably coupled to the drum 92 causing the drum 92, and therefore the driven shaft 84, to rotate with the drive shaft 80.

[0035] With respect to FIGS. 3 and 4, the gear assembly 56 is positioned within the gear housing 44 and is surrounded by lubricating fluid (e.g., oil). The gear assembly 56 includes a first driven gear 110 that is engaged with the driven shaft 84 of the motor 48 and a second driven gear 114 that is engaged with the first driven gear 110. The first driven gear 110 includes a first portion 110a and a second portion 110b extending from the first portion 110a. The first portion 110a has a first dimension and a first plurality of gear teeth 116. The second portion 110b has a second dimension and a second plurality of gear teeth 120. The first gear teeth 116 meshes with gear teeth 88 of the driven shaft 84. The second gear teeth 120 mesh with gear teeth 124 of the second driven gear 114. The first driven gear 110 defines an axis B that is parallel to the drive axis A. Similarly, the second driven gear 114 defines an axis C that is parallel to both the drive axis A and the axis B of the first driven gear 110. The first driven gear 110 provides a gear reduction ratio to the second driven gear 114.

[0036] The second driven gear 114 is operably couplable to the rotor 20 such that actuation of the motor 48 rotates the rotor 20 to thereby rotate the blades 24. That is, actuation of the motor 48 rotates the drive shaft 80, which in turn rotates the driven shaft 84, the first driven gear 110, and the second driven gear 114.

[0037] In other embodiments (such as shown in FIG. 5), the drive assembly 16 may further include a third driven gear 130 configured to be driven by the second driven gear 114. In such case, the third driven gear 130 may be operably couplable to the rotor 20 such that actuation of the motor 48 rotates the rotor 20 to thereby rotate the blades 24. That is, actuation of the motor 48 rotates the drive shaft 80, which in turn rotates the first driven gear 110, the second driven gear 114, and the third driven gear 130 to rotate the rotor 20. Moreover, the rotor 20 may be removable, such that an accessory can be operably coupled to and driven by the second driven gear 114. The accessory may be a grinder or a polisher. When the operator wishes to operate the trowel 10 to level and compact the concrete, the rotor 20 having the blades 24 is operably coupled to the drive assembly 16 via the third driven gear 130. When the operator wishes to smooth or polish the concrete the operator removes the rotor 20 and operably couples the accessory to the drive assembly 16 via the second driven gear 114.

[0038] With respect to FIGS. 3, 6, and 7, the drive assembly 16 is also operably coupled to a blade pitch adjustment assembly 150 for adjusting the pitch of the blades 24 relative to the rotor 20. The blade pitch adjustment assembly 150 includes an eddy drive assembly 154, a gear pump 158, an accumulator piston 162, an unloader 166, a control valve assembly 170, a drive piston 174, and a yoke 178. The yoke 178 is positioned between the gear housing 44 and the rotor 20 and configured to selectively engage the tilt plate 60 coupled to the rotor 20 to adjust the pitch of the blades 24. In the illustrate embodiment, the yoke 178 is pivotably coupled to the gear housing 44.

[0039] An adjustment housing 182 supports the accumulator piston 162, the unloader 166, the control valve assembly 170, and the drive piston 174. The drive piston 174 is configured to move (e.g., pivot) the yoke 178 to selectively engage the tilt plate 60. The drive piston 174 is configured to selectively move (e.g., pivot) the yoke 178 from a first position to a second position. In the first position, the yoke 178 to does not engage (e.g., is adjacent to or contacting but not exerting a force on) the tilt plate 60 and thus the blades 24 are in the first orientation. In the second position, the yoke 178 engages (e.g., contacts) the tilt plate 60 with a force and thus the blades 24 are in the second orientation. The yoke 178 is biased by a biasing mechanism (e.g., a spring, not shown) into the first position. The eddy drive assembly 154 is configured to drive the gear pump 158 to adjust the pressure within the adjustment housing 182, which can adjust the position of the drive piston 174. The position of the drive piston 174 is used to adjust the pitch of the blades 24 and to maintain the desired pitch of the blades 24, as will be discussed in greater detail below.

[0040] The adjustment housing 182 is collectively defined by a base 186 and a cover 190. As shown in FIG. 8, the adjustment housing 182 has a first chamber 200 (FIG. 6), a second chamber 204, a third chamber 208, and a fourth chamber 212. The first chamber 200 movably receives the accumulator piston 162. Together, the first chamber 200 and the accumulator piston 162 define an accumulator. The second chamber 204 movably receives the unloader 166. The third chamber 208 movably receives the control valve assembly 170. The fourth chamber 212 movably receives the drive piston 174.

[0041] The adjustment housing 182 supports the gear pump 158. The gear pump 158 includes a drive gear 220 that drives a driven gear 224. As shown in FIG. 9, the cover 190 of the adjustment housing 182 has a pump inlet 228, a pump outlet 232, and a channel 236 that defines a first fluid flow path (FIG. 6). The pump inlet 228 is in fluid communication with the interior of the gear housing 44 to receive pressurized fluid therefrom. The pump inlet 228 is in fluid communication with the pump outlet 232 via the gear pump 158. The pump outlet 232 is in communication with the first fluid flow path 236. The first fluid flow path 236 is in selective communication with the first chamber 200, the second chamber 204, and the third chamber 208. Thus, fluid drawn in through the pump inlet 228 via the gear pump 158 is pressurized and guided to the first fluid flow path 236 and then selectively distributed into the respective chamber, as will be discussed in greater detail below. The first chamber 200, the second chamber 204, and the third chamber 208 are in fluid communication with one another via the first fluid flow path 236. The third chamber 208 is in fluid communication with the fourth chamber 212 via a second fluid flow path 240 (FIGS. 19 and 20). The third chamber 208 is also in fluid communication with an interior of the gear housing 44 via a third fluid flow path 244 (FIG. 20).

[0042] The accumulator piston 162 is positioned and movable within the first chamber 200. The first chamber 200 has a first end adjacent the cover and a second end opposite the first end. The first fluid flow path 236 is in communication with the first end of the first chamber 200. A biasing mechanism (e.g., a nitrogen source or a spring, not shown) is positioned between the second end of the first chamber 200 and the accumulator piston 162 to bias the accumulator piston 162 towards the first end. In other embodiments, the first chamber 200 includes an accumulator bladder instead of the accumulator piston 162. Pressurized fluid is guided to the first chamber 200 via the first fluid flow path 236 until the accumulator piston 162 reaches a steady-state position in which the pressurized fluid has a predetermined volume and a predetermined pressure therein.

[0043] With respect to FIG. 8, the unloader 166 is positioned within and movable relative to the second chamber 204. The second chamber 204 has a first end extending through the cover 190 and a second end opposite the first end. The unloader 166 includes a first end and a second end opposite the first end. The unloader 166 includes an unloader piston 260 at the second end and an unloader stem 264 extending from the unloader piston 260 towards the first end. The unloader stem 264 extends through an opening 268 of the second chamber 204 of the adjustment housing 182 (e.g., the cover 190). A biasing mechanism (e.g., a spring or multiple springs, not shown) is positioned between the second end of the second chamber 204 and the unloader piston 260. The unloader 166 is movable between a retracted position (FIG. 14) in which the unloader piston 260 is closer to the second end than the first end and an extended position (FIG. 8) in which the unloader piston 260 is closer to the first end than the second end. The biasing mechanism biases the unloader 166 into the extended position. The first fluid flow path 236 guides pressurized fluid to the second chamber 204 between a location adjacent the first end and the unloader piston 260. With control valve assembly 170 in a closed position (discussed in greater detail below), when the accumulator piston 162 reaches the steady state position, pressurized fluid then moves via the first fluid flow path 236 to the second chamber 204 to move the unloader 166 from the extended to retracted position. When the unloader 166 reaches the retracted position, the pressure within the adjustment housing 182 maintains the predetermined pressure of the pressurized fluid therein.

[0044] As discussed in greater detail below, the eddy drive assembly 154 is operably coupled to the unloader 166. The unloader 166 is also configured to be fixedly or matingly coupled to a drive gear 220 of the gear pump 158.

[0045] As shown in FIGS. 3 and 4, the eddy drive assembly 154 is operably coupled to the drive shaft 80 of the motor 48. The eddy drive assembly 154 is positioned within the gear housing 44 but outside the adjustment housing 182. The eddy drive assembly 154 includes a drive plate 300 and a driven rotor 304.

[0046] With respect to FIG. 4, the drive plate 300 is operably coupled to the drive shaft 80. The drive plate 300 may be fixed to drive shaft 80 and, thus, rotate simultaneously to or in concert with drive shaft 80 about the drive axis A. Thus, the drive shaft 80 and the drive plate 300 may be coaxial. As shown, the drive plate 300 may include or be provided as a magnetically permeable or conductive disk that extends radially from drive shaft 80 (or drive axis A generally). In other words, a disk formed from a magnetically permeable or conductive metal (e.g., non-ferrous metal) may be included with or provided as the drive plate 300.

[0047] With respect to FIGS. 4 and 8, the driven rotor 304 is operably coupled to the unloader 166. As shown, the driven rotor 304 is coupled to the unloader 166 at the first end. The driven rotor 304 is coupled to the unloader stem 264. The driven rotor 304 is rotatable about the drive axis A and axially movable along the drive axis A relative to the drive plate 300 and the adjustment housing 182. The driven rotor 304 is mechanically decoupled from the drive plate 300. The drive plate 300 influences or induces rotation at the driven rotor 304, as will be described in detail below. The driven rotor 304 includes a support substrate 308 (e.g., disk substrate) and one or more magnetic elements (e.g., permanent magnets, not shown). The magnetic elements may be, for instance, fixed to the support substrate 308 to rotate therewith. In some embodiments, the one or more magnetic elements includes a plurality of circumferentially spaced (e.g., equally spaced about the drive axis A) magnetic elements. As shown, the magnetic elements may be embedded within the support substrate 308. The magnetic elements may be arrayed such that the magnetic pole directed or toward the drive plate 300 is alternated. Moreover, the one or more magnetic elements may be magnetically engaged with the drive plate 300. The driven rotor 304 may be rotatably mounted about or extend radially outward from the drive axis A.

[0048] When the unloader 166 is in the extended position, the driven rotor 304 is positioned adjacent to the drive plate 300. That is, the driven rotor 304 is positioned relative to the drive plate 300 by a gap having a predetermined distance or less. When the unloader 166 is in the extended position, rotation of the drive plate 300 via drive shaft 80 of the motor 48 may generate an eddy current at the one or more magnetic elements of the driven rotor 304 (e.g., as would be understood). In turn, rotation of the drive plate 300 may induce the driven rotor 304 to separately rotate (e.g., about the drive axis A). Rotation of the driven rotor 304 thus causes rotation of the unloader 166, which in turn causes rotation of the driven gear 224 of the gear pump 158.

[0049] When the unloader 166 is in the retracted position, the driven rotor 304 is spaced apart from the drive plate 300. That is, the driven rotor 304 is positioned relative to the drive plate 300 by a gap that is greater than the predetermined distance. When the unloader 166 is in the retracted position, the driven rotor 304 is too far away from the drive plate 300 for rotation of the drive plate 300 to generate the eddy current. In turn, rotation of the driven rotor 304 stops thus causing rotation of the unloader 166 and driven gear 224 of the gear pump 158 to stop. As noted above, when the unloader 166 reaches the retracted position, the pressure within the adjustment housing 182 reaches the predetermined pressure. When the gear pump 158 stops, the pressure within the adjustment housing 182 remains at the predetermined pressure.

[0050] The control valve assembly 170 is positioned within and movable relative to the third chamber 208 to adjust the pitch of the blades 24. The third chamber 208 has a first open end extending through the cover 190 and a second open end extending through the base 186. The control valve assembly 170 includes a valve 320 that is movable relative to the third chamber 208 and a pin 324 that is movable relative to the third chamber 208. The valve 320 and the pin 324 are also movable relative to one another.

[0051] With respect to FIGS. 8 and 10, the valve 320 includes a valve body 328 and a valve stem 332 that is coupled to and extends from the valve body 328. The valve body 328 is positioned and movable within the third chamber 208 and the valve stem 332 extends through the first open end of the third chamber 208. Thus, the valve stem 332 extends into the gear housing 44. As shown, the valve 320 has a first end (defined by the valve stem 332), which that is positioned within interior of the gear housing 44, and a second end (defined by the valve body 328), opposite the first end, which is positioned within the third chamber 208. A valve axis D extends between the first end and the second end. The valve body 328 has a recess 340 that extends from the second end towards the first end. As shown in FIG. 10, the recess 340 has a first inner circumferential wall 344 and a second inner circumferential wall 348, each extending from an inner wall of the recess 340. The first inner circumferential wall 344 is positioned between a closed end of the recess 340 and the second inner circumferential wall 348. The second inner circumferential wall 348 is positioned adjacent the second end of the valve 320. The valve body 328 also includes a first outer circumferential wall 352 and a second outer circumferential wall 356. The first outer circumferential wall 352 is positioned between the first end and the second outer circumferential wall 356. The second outer circumferential wall 356 is positioned at (or adjacent to) the second end. The valve body 328 also has a first port 360 and a second port 364 spaced apart from the first port 360 along the valve axis D. Each of the first port 360 and the second port 364 extends through the valve body 328 and is in communication with the recess 340. In the illustrated embodiment, the first port 360 is positioned between the closed end of the recess 340 and the first inner circumferential wall 344. Also, the first port 360 is positioned between the first end of the valve 320 and the first outer circumferential wall 352. The second port 364 is between the first inner circumferential wall 344 and the second inner circumferential wall 348. Also, the second port 364 is positioned between the first outer circumferential wall 352 and the second outer circumferential wall 356.

[0052] The pin 324 is movably received within the recess 340 of the valve body 328 and extends through the second open end of the third chamber 208 to an outside of the gear housing 44. The pin 324 includes a first end and a second end opposite the first end. A pin axis E extends between the first end and the second end. The pin axis E is coincident with the valve axis D. The first end is positioned within the recess 340 of the valve body 328 and the second end is positioned outside of the adjustment housing 182. The pin 324 includes a first portion 380 extending from the first end toward the second end, a second portion 384 extending from the first portion 380 towards the second end, and a third portion 388 extending from the second portion 384 towards the second end. The second portion 384 has a smaller outer dimension than the first portion 380 and the third portion 388. A gasket 392 is positioned within a circumferential groove 396 in the third portion 388 and is positioned between the pin 324 and the adjustment housing 182. The gasket 392 seals the pin 324 with respect to the third chamber 208. A channel 400 extends partially therethrough the pin 324 along the pin axis E. The pin 324 has a first port 404 in communication with the channel 400. The first port 404 is in the adjacent to the first end. The pin 324 has a second port 408 that is in communication with the channel 400. The second port 408 is in the second portion 384.

[0053] The first and second outer circumferential walls 352, 356 create a gap between the valve body 328 and a wall of the third chamber 208. The pin 324 is movably received within the recess 340 of the valve body 328. The first end is positioned within the recess 340. Also, the first portion 380 is positioned within and movable relative to the recess 340. The first and second inner circumferential walls 344, 348 of the recess 340 abut the first portion 380 of the pin 324. Also, the first and second inner circumferential walls 344, 348 create a first gap 420 between the pin 324 (e.g., the second portion thereof) and the inner wall of the valve body 328. The first and second inner circumferential walls 344, 348 create a second gap 424 between the pin 324 and the inner wall of the valve body 328.

[0054] The first fluid flow path 236 (FIGS. 6 and 19) is in fluid communication with the third chamber 208 closer to the first end thereof. The first fluid flow path 236 is in fluid communication with the third chamber 208 between the first end thereof and the first outer circumferential wall 352 of the valve body 328. Accordingly, the first fluid flow path 236 is in selective fluid communication with the recess 340 of the valve body 328 via the first port 360 thereof. The second fluid flow path 240 (FIGS. 19 and 20) is in selective fluid communication with the third chamber 208 and the fourth chamber 212. The second fluid flow path 240 is in fluid communication with the third chamber 208 closer to the second end thereof. The gear housing 44 is in selective fluid communication with the third chamber 208, via the third fluid flow path 244 (FIG. 20), between the first end and the seconds thereof (and between the first and second fluid flow paths 236, 240).

[0055] The valve 320 is movable between a retracted position (FIGS. 16 and 19) and an extended position (FIGS. 17 and 20). In the retracted position, the second end of the valve 320 is at or adjacent to the second end of the third chamber 208. In the retracted position, the second fluid flow path 240 is closed by the valve 320 (e.g., the second outer circumferential wall 356). Thus, the second fluid flow path 240 is not in communication with the third chamber 208. Also, in the retracted position, the third fluid flow path 244 is positioned between the first and second outer circumferential walls 352, 356, so it is open. Thus, the third fluid flow path 244 (FIG. 20) allows communication between the third chamber 208 and the gear housing 44. In the extended position, the second end of the valve 320 is spaced apart from the second end of the third chamber 208. The second fluid flow path 240 is open because the valve 320 is spaced apart from the same. Thus, the second fluid flow path 240 is in communication with the third chamber 208. The third fluid flow path 244 is closed by the valve 320 (e.g., the second outer circumferential wall 356). Thus, communication between the third chamber 208 and the gear housing 44 via the third fluid flow path 244 is prevented.

[0056] The pin 324 is movable relative to the valve 320 between a first position (FIGS. 16, 18, and 20) and a second position (FIGS. 8, 17, and 19). In the first position, the first portion 380 of the pin 324 overlaps the first port 360, which closes the first port 360 so that pressurized fluid cannot flow into the recess 340 of the valve body 328. Accordingly, pressurized fluid cannot flow through into the recess 340 of the valve body 328 and into the channel 400 of the pin 324. Also, when the pin 324 is in the first position, the first inner circumferential wall 344 abuts the first portion 380 of the pin 324 so there are no gaps therebetween, but a gap 428 (FIG. 20) is defined between the second inner circumferential wall 348 and the second portion 384 of the pin 324. In the second position, the first portion 380 of the pin 324 is spaced apart from the first port 360, which opens the first port 360 so that pressurized fluid can flow into the recess 340 of the valve body 328. Accordingly, pressurized fluid can flow into the recess 340 of the valve body 328 and into the channel 400 of the pin 324 via its first port 404. Also, when the pin 324 is in the second position, both the first and second inner circumferential walls 344, 348 abut the first portion 380 of the pin 324 so there are no gaps therebetween.

[0057] In the closed position of the control valve assembly 170, the pin 324 is in the first position such that pressurized fluid cannot flow from the first fluid flow path 236 to the second fluid flow path 240. In the closed position of the control valve assembly 170, the eddy drive assembly 154 is not actuatable, as will be discussed in greater detail below. In the open position of the control valve assembly 170, the pin 324 is in the second position, such that pressurized fluid can flow from the first fluid flow path 236 to the second fluid flow path 240. In the open position of the control valve assembly 170, the eddy drive assembly 154 is actuatable, as will be discussed in greater detail below.

[0058] The drive piston 174 is positioned and movable within the fourth chamber 212, which has a first end adjacent to the cover 190 and a second, opposite end. The drive piston 174 has a rod 440 extending therefrom. The rod 440 extends through the second end of the fourth chamber 212 through aligned openings in the adjustment housing 182 (e.g., the base 186) and the gear housing 44. Accordingly, the rod 440 is at least partially positioned outside of the gear housing 44. The drive piston 174 is movable such that the rod 440 selectively engages the yoke 178. In some embodiments, the drive piston 174 may be coupled to the yoke 178. The drive piston 174 is movable between a retracted position (FIGS. 8, 13, 14, and 19) and an extended position (FIGS. 18 and 20). In the retracted position, the rod 440 does not engage the yoke 178 (e.g., exerts a first force that is substantially zero), such that the yoke 178 is biased into the first position. In the extended position, the rod 440 does engage the yoke 178 (e.g., exerts a second force that is greater than first force), such that the yoke 178 is in the second position. A biasing mechanism (e.g., a spring, not shown) is positioned between the first end of the fourth chamber 212 and the drive piston 174 to bias the accumulator piston 162 towards the first end. The second fluid flow path 240 extends between the third chamber 208 and the fourth chamber 212. As shown, the second fluid flow path 240 extends between a location adjacent to the second end of the third chamber 208 and a location adjacent the first end of the fourth chamber 212.

[0059] In operation, as shown in FIGS. 12-14, the operator starts the motor 48 with blades 24 of the rotor 20 in the first orientation. When the operator starts the motor 48, the unloader 166 is in the extended position and the control valve assembly 170 is in the closed position (e.g., the pin 324 is in the first position) with the valve 320 in the retracted position. When the motor 48 first starts, the motor 48 speed is below the predetermined speed, so the drive shaft 80 rotates, but the driven shaft 84 does not. Rotation of the drive shaft 80, causes rotation of the drive plate 300. Because the unloader 166 is in the extended position, rotation of the drive plate 300 causes rotation of the driven rotor 304 and unloader 166, which thus causes actuation of the gear pump 158. Actuation of the gear pump 158 causes fluid to move from the interior of the gear housing 44 through the pump inlet 228 and to be pressurized by the gear pump. The pressurized fluid moves from the pump inlet 228 to the pump outlet 232 and is moved through the first fluid flow path 236 to the first chamber 200 to move the accumulator piston 162 towards the second end of the first chamber 200. When the accumulator piston 162 reaches the steady-state position, the pressurized fluid is guided by the first flow path to the unloader 166 to move the unloader 166 from the extended position to the retracted position. This stops the gear pump 158 and prevents pressurized fluid from continuing to enter the adjustment housing 182. When the accumulator piston 162 is in the steady-state and the unloader 166 is in the retracted state, the predetermined pressure is achieved within the adjustment housing 182. As noted above, when the gear pump 158 stops, the predetermined pressure within the adjustment housing 182 remains. With the motor 48 equal to or greater than the predetermined speed, the rotor 20 (or one of the accessories) is driven by the respective gear.

[0060] As shown in FIGS. 15-19, to adjust the pitch of blades 24 from the first orientation to the second orientation, the control valve assembly 170 moves from the closed position to the open position. That is, the valve 320 moves in a first direction of arrow 500 from the retracted position to the extended position. When the valve 320 moves, the pin 324 remains in place, such that the control valve assembly 170 is in the open position (e.g., the pin 324 is in the second position). With the control valve assembly 170 in the open position, the first fluid flow path 236 communicates with the third chamber 208, which decreases the pressure within the adjustment housing 182 to below the predetermined pressure. Accordingly, the unloader 166 is moved via the biasing mechanism to the extended position causing the driven rotor 304 to rotate with the drive plate 300. Rotation of the driven rotor 304 causes rotation of the unloader 166 and thus the unloader 166 drives the gear pump 158 to move pressurized fluid from the pump inlet 228 into the first fluid flow path 236. Since the control valve assembly 170 is in the open position, the pressurized fluid enters the third chamber 208 and then enters the recess 340 of the valve body 328 via the first port 360 of thereof. Pressurized fluid is then moved through the pin 324 to the fourth chamber 212 via the first port 404 in the pin 324, the channel 400, the second port of the pin 324, and the second fluid flow path 240. As the pressurized fluid moves into the fourth chamber 212, it moves the drive piston 174 from the retracted position to the extended position to move the yoke 178 from the first position to the second position. Accordingly, the blades 24 move from the first orientation to the second orientation. Once drive piston 174 reaches the extended position, continued introduction of the pressurized fluid moves the pin 324 in the first direction of arrow 500 (FIG. 19) from the second position to the first position until the pin 324 closes the first port 360. With the first port 360 closed, the control valve assembly 170 is once again in the closed position. When the first port 360 closes, the pressurized fluid being introduced into the housing adjustment housing 182 causes the pressure in the adjustment housing 182 to increase to the predetermined pressure. Once the predetermined pressure is reached the unloader 166 moves from the extended position to the retracted position to stop the gear pump 158, as discussed above. The predetermined pressure in the adjustment housing 182 remains, which maintains the pitch of the blades 24 of the rotor 20 in the second orientation.

[0061] As shown in FIG. 20, to adjust the pitch of blades 24 from the second orientation to the first orientation, the valve 320, with the pin 324 in the first position, moves in a second direction of arrow 504 from the extended position to the retracted position. Because the pin 324 remains in the first position, the control valve assembly 170 remains closed as the valve 320 moves to the retracted position. Accordingly, the pressure within the adjustment housing 182 does not change. As the valve 320 moves to the retracted position, the third fluid flow path 244 opens allowing pressurized fluid from the fourth chamber 212 to move through the second fluid flow path 240 to the third fluid flow path 244 through the second port 364 in the valve body 328. Accordingly, fluid can be discharged to the gear housing 44. As fluid moves out of the fourth chamber 212, the biasing mechanism within the fourth chamber 212 moves the drive piston 174 from the extended position back to the retracted position, such that the yoke 178, via the bias of its biasing mechanism, moves from the second position back to the first position. Accordingly, the blades 24 move from the second orientation to the first orientation. Once drive piston 174 reaches the retracted position, the control valve assembly 170 remains closed with the valve 320 in the retracted position. Because the first port 360 remains closed, the predetermined pressure in the adjustment housing 182 remains, which maintains the pitch of the blades 24 of the rotor 20 in the first orientation after the same is achieved.

[0062] The valve 320 can be moved between the extended and retracted positions by any suitable mechanism. For example, the valve 320 may be movable via a small pull cable accessible on the frame 12 or handle assembly 28, a fork linkage, an adjustment knob accessible on the frame 12 or the handle assembly 28, a drive screw (e.g., an electric motor), a solenoid, or another suitable mechanism.

[0063] The benefits of this power trowel 10 design are several. First, the clutch 52 enables the motor 48 to drive two features without a secondary motor. That is, the motor 48 is able to drive the rotor 20 without a secondary motor 48 and the blade pitch adjustment assembly 150. Additionally, the drive of the pitch assembly is a low duty drive due to the clutch 52. Additionally, with exception of the yoke 178, the elements of the blade pitch adjustment assembly 150 are enclosed within the frame 12 (e.g., the gear housing 44), so they are protected from dust and debris from the concrete. The control valve assembly 170 can be actuated by a manual actuator, if desired, that requires minimal force (e.g., less than manual actuators for conventional adjustment assemblies). The blade pitch adjustment assembly described herein is more energy efficient by avoiding excessive oil flow and associated energy loss through pressure relief and unloading valve systems. The eddy current drive allows the trowel 10 to stop pumping oil once the accumulator achieves its predetermined pressure. The trowel 10 is lighter weight. Also, with fewer components to assemble, maintain, and replace, there is less wear and tear of the components, which increases long-term reliability of the trowel 10.

[0064] Various features of the invention are set forth in the following claims.

Examples

Embodiment Construction

[0029]FIG. 1 illustrates a concrete trowel 10 including a frame 12. The frame 12 supports a drive assembly 16 (FIGS. 2 and 3) for driving a rotor 20 having a plurality of blades 24 and adjusting the pitch of the blades 24. A handle assembly 28 including a post 32 extends obliquely from the frame 12 and handlebars 36 coupled to the post 32. The handle assembly 28 extends from the frame 12 and is used to control the concrete trowel 10.

[0030]With respect to FIG. 1, the frame 12 includes a drive housing 40 and a gear housing 44 coupled to the drive housing 40. With respect to FIGS. 2 and 3, the frame 12 supports the drive assembly 16. In the illustrated embodiment, the drive assembly 16 includes a motor 48, a clutch 52, and a gear assembly 56. The motor 48 is at least partially positioned within an interior of the drive housing 40 and the gear assembly 56 is supported within an interior of the gear housing 44. Although not shown, the gear housing 44 may include a cover 190 (not shown) t...

Claims

1. A concrete trowel comprising:a frame;a drive assembly mounted on the frame and including a drive shaft;a rotor including a plurality of blades, the rotor rotatably operably coupled to the drive assembly for rotating about a rotational axis; anda blade pitch adjustment assembly configured to adjust a pitch of each of the plurality of blades, the blade pitch adjustment assembly includinga yoke configured to move relative to the rotor between a first position in which each of the plurality of blades is in in a first orientation and a second position in which each of the plurality of blades is in a second orientation;a drive piston configured to move from a retracted position to an extended position to move the yoke from the first position to the second position; andan eddy drive assembly driven by the drive shaft, the eddy drive assembly configured to move the drive piston to the extended position.

2. The concrete trowel of claim 1, wherein the blade pitch adjustment assembly further includes an accumulator configured to maintain the yoke in either the first position or the second position.

3. The concrete trowel of claim 2, wherein the blade pitch adjustment assembly further includes a gear pump driven by the eddy drive assembly, the gear pump configured to move pressurized fluid to a first side of the drive piston to move the drive piston from the retracted position to the extended position.

4. The concrete trowel of claim 3, wherein the eddy drive assembly includes a drive plate and a driven rotor, wherein the drive plate is coupled to the drive shaft for rotation therewith and formed from a magnetically permeable or conductive metal material, wherein the driven rotor is operably coupled to the gear pump and includes a support substrate and at least one magnetic element, and wherein rotation of the drive plate by the drive shaft causes rotation of the driven rotor via an eddy current at the at least one magnetic element.

5. The concrete trowel of claim 4, wherein the blade pitch adjustment assembly further includes an unloader operably coupled to the driven rotor, wherein the unloader is movable from an extended position to a retracted position, and wherein in the extended position, the driven rotor is adjacent the drive plate to enable the eddy current therebetween and in the retracted position, the driven rotor is spaced apart from the drive plate to prevent the eddy current therebetween.

6. The concrete trowel of claim 5, wherein when the driven rotor is adjacent the drive plate, the driven rotor is rotatable to actuate the gear pump, and when the driven rotor is spaced apart from the drive plate by a predetermined distance, the driven rotor is not rotatable to actuate the gear pump.

7. The concrete trowel of claim 6, wherein actuation of the gear pump causes the pressurized fluid to flow to the accumulator until a steady-state position is reached and then to flow to the unloader to cause the unloader to move the driven rotor away from the drive plate by the predetermined distance to stop the gear pump.

8. The concrete trowel of claim 5, wherein the blade pitch adjustment assembly further includes a control valve assembly that is movable between a closed position and an open position, wherein when the control valve assembly is in the closed position, the pressurized fluid is prevented from moving to the first side of the drive piston to move the drive piston to the extended position, and wherein when the control valve assembly is in the open position, the pressurized fluid is able to move to the first side of the drive piston to move the drive piston to the extended position.

9. The concrete trowel of claim 8, wherein the control valve assembly is in the closed position, the pressurized fluid is able to move from the first side of the drive piston back to the frame to move the drive piston from the extended position to the retracted position, and wherein when the drive piston moves from the extended position back to the retracted position, the yoke is biased from the second position back to the first position to move each of the plurality of blades from the second orientation to the first orientation.

10. The concrete trowel of claim 1, wherein the drive assembly includes a motor and the drive shaft is driven by the motor.

11. The concrete trowel of claim 1, wherein the drive shaft defines a drive axis, and wherein the rotational axis is parallel to the drive axis.

12. A concrete trowel comprising:a frame;a drive assembly mounted on the frame and including a drive shaft;a rotor including a plurality of blades, the rotor rotatably operably coupled to the drive assembly for rotating about a rotational axis; anda blade pitch adjustment assembly configured to adjust a pitch of each of the plurality of blades, the blade pitch adjustment assembly includinga yoke configured to move relative to the rotor between a first position in which each of the plurality of blades is in in a first orientation and a second position in which each of the plurality of blades is in a second orientation;an eddy drive assembly driven by the drive shaft, the eddy drive assembly configured to move the yoke from the first position to the second position; anda control valve assembly configured to be movable between a closed position and an open position,wherein when the control valve assembly is in the closed position, the eddy drive assembly is not actuatable and thus the yoke is prevented from moving from the first position to the second position, andwherein when the control valve assembly is in the open position, the eddy drive assembly is actuatable and thus the yoke is movable from the first position to the second position to thereby move each of the plurality of blades from the first orientation to the second orientation.

13. The concrete trowel of claim 12, wherein the control valve assembly moves in a first direction, the control valve assembly moves from the closed position to the open position, and wherein the control valve assembly moves in a second opposite direction, the control valve assembly maintains the closed position, such that the yoke moves from the second position back to the first position via a spring bias to move each of the plurality of blades from the second orientation to the first orientation.

14. The concrete trowel of claim 12, wherein the eddy drive assembly includes a drive plate and a driven rotor, wherein the drive plate is coupled to the drive shaft for rotation therewith and formed from a magnetically permeable or conductive metal material, wherein the driven rotor operably moves the yoke and includes a support substrate and at least one magnetic element, and wherein rotation of the drive plate by the drive shaft causes rotation of the driven rotor via an eddy current at the at least one magnetic element.

15. The concrete trowel of claim 14, wherein when the driven rotor is adjacent the drive plate, the driven rotor is rotatable, and when the driven rotor is spaced apart from the drive plate by a predetermined distance, the driven rotor is not rotatable.

16. The concrete trowel of claim 12, wherein the blade pitch adjustment assembly further includes an accumulator configured to maintain the yoke in either the first position or the second position.

17. A concrete trowel comprising:a frame;a drive assembly mounted on the frame and including a drive shaft;a rotor including a plurality of blades, the rotor rotatably operably coupled to the drive assembly for rotating about a rotational axis; anda blade pitch adjustment assembly configured to adjust a pitch of each of the plurality of blades, the blade pitch adjustment assembly includinga yoke configured to move relative to the rotor between a first position in which each of the plurality of blades is in in a first orientation and a second position in which each of the plurality of blades is in a second orientation,a drive plate coupled to the drive shaft for rotation therewith and formed from a magnetically permeable or conductive metal material, anda driven rotor movable relative to the drive plate and including a support substrate and at least one magnetic element,wherein rotation of the drive plate by the drive shaft causes rotation of the driven rotor via an eddy current at the at least one magnetic element, andwherein rotation of the driven rotor causes the yoke to move from the first position to the second position and thereby to move each of the plurality of blades from the first orientation to the second orientation.

18. The concrete trowel of claim 17, wherein when the driven rotor is adjacent the drive plate, the driven rotor is rotatable, and when the driven rotor is spaced apart from the drive plate by a predetermined distance, the driven rotor is not rotatable.

19. The concrete trowel of claim 17, wherein the blade pitch adjustment assembly further includes an accumulator configured to maintain the yoke in either the first position or the second position.

20. The concrete trowel of claim 17, wherein the blade pitch adjustment assembly further includes a control valve assembly that is movable between a closed position and an open position, wherein when the control valve assembly is in the closed position, the driven rotor is not rotatable, and wherein when the control valve assembly is in the open position, the driven rotor is rotatable.

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