Low-Emission Propane-Driven Power Trowel

Abstract

A power trowel for treating a concrete surface includes a support frame configured to be moved on the concrete surface. A propane supply vessel is supported by the support frame and is configured to contain propane. The propane supply vessel is positioned to reduce obstructions to the operator's view of the concrete surface. An internal combustion engine is supported by the support frame and is in fluid communication with the propane supply vessel to receive propane therefrom to power the internal combustion engine. One or more rotatable shafts are driven by the internal combustion engine, and one or more trowel blades connect to the one or more rotatable shafts so as to rotate therewith.

1 . A power trowel for treating a concrete surface, the power trowel comprising:
 a support frame;   a propane supply vessel supported by the support frame and being configured to contain propane;   an internal combustion engine supported by the support frame and in fluid communication with the propane supply vessel to receive propane therefrom to power the internal combustion engine;   one or more rotatable shafts driven by the internal combustion engine; and   one or more trowel blades connected to the one or more rotatable shafts so as to rotate therewith.   
     
     
         2 . The power trowel of  claim 1 , further comprising a fuel regulator in fluid communication with the propane supply vessel and the internal combustion engine to receive propane from the propane supply vessel and deliver propane to the internal combustion engine. 
     
     
         3 . The power trowel of  claim 2 , further comprising a vacuum conduit in fluid communication with the internal combustion engine and the fuel regulator to transmit suction from the internal combustion engine to the fuel regulator, and wherein the fuel regulator includes a vacuum-actuated valve being actuatable in response to the suction to permit propane to exit the fuel regulator and move toward the internal combustion engine. 
     
     
         4 . The power trowel of  claim 3 , wherein the internal combustion engine further comprises a carburetor in fluid communication with the fuel regulator to receive propane from the fuel regulator, and wherein the vacuum conduit connects to the carburetor to transmit the suction from the carburetor to the fuel regulator. 
     
     
         5 . The power trowel of  claim 1 , wherein the internal combustion engine includes one or more hardened valve seats. 
     
     
         6 . The power trowel of  claim 1 , further comprising an operator handle supported by the support frame and configured to be manipulated by an operator to move the power trowel on the concrete surface, and the operator handle defines a vertical plane intersecting the operator handle and at least one of the one or more rotatable shafts. 
     
     
         7 . The power trowel of  claim 6 , wherein the at least one rotatable shaft defines a rotation axis for the one or more trowel blades, the propane supply vessel is disposed in a region intersected by the vertical plane and having an angular width of at most 90 degrees about the rotation axis. 
     
     
         8 . The power trowel of  claim 6 , wherein the propane supply vessel is disposed such that it is intersected by the vertical plane. 
     
     
         9 . The power trowel of  claim 8 , wherein the internal combustion engine is disposed between the propane supply vessel and the operator handle. 
     
     
         10 . The power trowel of  claim 1 , wherein one of the one or more rotatable shafts defines a rotation axis for the one or more trowel blades, and the center of gravity of the power trowel is disposed along the rotation axis. 
     
     
         11 . A power trowel for treating a concrete surface, the power trowel comprising:
 a support frame including a propane vessel support configured to support a vessel containing propane;   a fuel regulator supported by the support frame and configured to receive propane from the vessel, the fuel regulator including a vacuum-actuated valve being actuatable to permit propane to exit the fuel regulator;   an internal combustion engine supported by the support frame and in fluid communication with the fuel regulator to receive propane exiting the fuel regulator to power the internal combustion engine;   a vacuum conduit in fluid communication with the internal combustion engine and the fuel regulator to transmit suction from the internal combustion engine to the fuel regulator;   one or more rotatable shafts driven by the internal combustion engine;   one or more trowel blades connected to the one or more rotatable shafts so as to rotate therewith; and   wherein the vacuum-actuated valve is responsive to the suction from the internal combustion engine to control delivery of propane to the internal combustion engine.   
     
     
         12 . The power trowel of  claim 11 , wherein the fuel regulator further includes a vacuum switch operatively connected to the vacuum conduit and actuatable in response to the suction to actuate the vacuum-actuated valve. 
     
     
         13 . The power trowel of  claim 12 , further comprising a battery supported by the support frame and operatively connected to the vacuum switch and the internal combustion engine. 
     
     
         14 . The power trowel of  claim 12 , wherein the internal combustion engine further comprises a carburetor in fluid communication with the fuel regulator to receive propane from the fuel regulator, and wherein the vacuum conduit connects the carburetor and the vacuum switch such that the carburetor transmits suction to the vacuum switch. 
     
     
         15 . The power trowel of  claim 11 , wherein the propane vessel support is a mounting platform configured to support the vessel thereabove, and further comprising a releasable strap configured to extend about the vessel to thereby secure the vessel to the support frame. 
     
     
         16 . A power trowel for treating a concrete surface, the power trowel comprising:
 a support frame having a front section and a rear section;   a propane supply vessel configured to contain propane and being supported by the support frame such that the propane supply vessel is disposed in one of two vessel placement regions defined by the support frame, a first of the vessel placement regions being defined by the rear section of the support frame, and a second of the vessel placement regions being defined by the front section of the support frame and having an angular width of at most 90 degrees about the rotation axis;   an internal combustion engine supported by the support frame and in fluid communication with the propane supply vessel to receive propane therefrom to power the internal combustion engine;   one or more rotatable shafts driven by the internal combustion engine to rotate about a rotation axis;   one or more trowel blades connected to the one or more rotatable shafts so as to rotate therewith; and   an operator handle supported by the rear section of the support frame.   
     
     
         17 . The power trowel of  claim 16 , wherein the propane supply vessel and the internal combustion engine are positioned relative to the support frame such that the center of gravity of the power trowel is disposed along the rotation axis. 
     
     
         18 . The power trowel of  claim 16 , wherein the operator handle defines a vertical plane that intersects the vessel placement regions. 
     
     
         19 . The power trowel of  claim 18 , wherein the first vessel placement region has a width perpendicular to the vertical plane of at most 12 inches. 
     
     
         20 . The power trowel of  claim 16 , where the first vessel placement region extends rearwardly from a rear of the internal combustion engine and the second vessel placement region extends forwardly from a front of the internal combustion engine.