Quick adjustment mechanism for blade pitch of concrete power trowel

Abstract

A rotary power trowel machine for finishing concrete surfaces and more particularly to a quick adjustment mechanism for the pitch of the blades. The quick adjustment mechanism includes a control lever mounted on the operating handle of the trowel in a position to be easily grasped and operated by a trowel operator. The control lever changes the blade pitch through a mechanical advantage linkage which reduces the force applied to the control lever to adjust the blade pitch. The control lever includes a locking mechanism to lock the control handle and linkage in selected positions to lock the blades at a desired pitch angle. The locking mechanism includes a semicircular guide mounted on the trowel operating handle and extending through openings in the control lever. A locking device on the control lever lockingly engages the guide and is selectively locked and released from an upper end of the control lever.

What is claimed as new is as follows:  
     
         1 . A quick adjustment mechanism for the blade pitch of a rotary power trowel in which said trowel includes radial blades pivotally supported about radial axes to vary the pitch thereof, an operating handle extending upwardly from the trowel in inclined relation to enable an operator to control movement of the trowel, a tension member extending along the operating handle and operatively associated with said blades to pivot the blades to vary their pitch, said quick adjustment mechanism comprising a control lever having a central portion pivotally supported from said operating handle, said lever including a lower end extending below the operating handle and an upper end extending above the operating handle to a position to enable an operator to easily access the upper end of the control lever to exert force thereto to pivotally move said control lever in a pivotal manner, the lower end of said control lever being connected to said tension member through a mechanical advantage linkage to facilitate pivoting the blades from a flat pitch to an angled pitch by lifting the weight of the trowel, and a locking mechanism to releasably lock said control lever in relation to the operating handle in a position to lock said blades at an angle pitch.  
     
     
         2 . The structure as defined in  claim 1 , wherein the upper end of said control lever includes a handle, a trigger mechanism for operating said locking mechanism with the trigger mechanism being associated with the upper end of said control lever to enable an operator of the trowel to manipulate the control lever with either hand while maintaining control of the trowel with the other hand.  
     
     
         3 . The structure as defined in  claim 1 , wherein said locking mechanism includes a semicircular guide mounted on said operating handle, a locking plate mounted on said control lever and including a slot like opening receiving said guide therethrough, the dimensions of said slot like opening enabling relative movement between the control lever and the guide when the locking plate is perpendicular to the guide and preventing movement of the locking member and control lever along the guide when in non-perpendicular relation of the locking member to the guide by edge portions of the slot like opening in the control lever engaging a peripheral edge surface of said guide to lock the control lever in at least one direction, and a trigger mechanism on said control lever to position the locking plate in perpendicular relation to the guide to enable pivotal movement of the control lever.  
     
     
         4 . The structure as defined in  claim 3 , wherein said locking plate and control lever include spring bias means to bias the locking plate to a locking non-perpendicular position in relation to the guide to preclude movement of the control lever in one direction of movement, said trigger mechanism including a pivotal member mounted on said control lever for movement between a position to pivot the locking plate to a release perpendicular position and permit the locking plate to pivot to a locking position.  
     
     
         5 . The structure as defined in  claim 1 , wherein said locking mechanism includes a semicircular guide mounted fixedly on said operating handle and extending through an opening in said control lever, said guide including a plurality of teeth on a peripheral edge surface, said control lever including a spring biased latching pin engaged with said teeth to lock the control lever in pivotal position, said control lever including a latch pin releasing mechanism including a control button extending beyond the upper end of said control lever to enable an operator to depress the button by thumb pressure when grasping the upper end of the control lever to release the control lever from the guide to enable the lever to be pivoted in one direction to increase the pitch of the blades and permitting the weight of the trowel on the blades to move the control lever in the opposite direction to enable the blade pitch to reduce.  
     
     
         6 . A quick adjustment mechanism for the blade pitch of a rotary power trowel in which said trowel includes radial blades pivotally supported about radial axes to vary the pitch thereof, an operating handle extending upwardly from the trowel in inclined relation to enable an operator to control movement of the trowel, a tension member extending along the operating handle and operatively associated with said blades to pivot the blades to vary their pitch, said quick adjustment mechanism comprising a control lever having a central portion pivotally supported from said operating handle, said lever including a lower end extending below the operating handle and an upper end extending above the operating handle to a position to enable an operator to easily access the upper end of the control lever to exert force thereto to pivotally move said control lever in a pivotal manner, the lower end of said control lever being connected to said tension member, and a locking mechanism to releasably lock said control lever in relation to the operating handle in a position to lock said blades at an angle pitch.  
     
     
         7 . The structure as defined in  claim 6 , wherein the upper end of said control lever includes a trip handle, a trigger mechanism for operating said locking mechanism with the trigger mechanism being associated with the trip handle at the upper end of said control lever to enable an operator of the trowel to manipulate the control lever with either hand while maintaining control of the trowel with the other hand.  
     
     
         8 . The structure as defined in  claim 6 , wherein said locking mechanism includes a semicircular guide mounted on said operating handle, said control lever including a slot like opening receiving said guide therethrough, a locking plate on said control lever including a slot like opening receiving said guide therethrough, the dimensions of said slot like openings enabling relative movement of the control lever along the guide when the locking plate is perpendicular to the guide and preventing movement of the control lever along the guide when the locking plate is in non-perpendicular relation to the guide by edge portions of the slot like opening in the locking plate engaging a peripheral edge surface of said guide to lock the control lever against pivotal movement in at least one direction, and a trigger mechanism on said control lever to pivot the locking plate into perpendicular relation to the guide to enable pivotal movement of the control lever.  
     
     
         9 . The structure as defined in  claim 8 , wherein said locking plate and control lever include spring bias means therebetween to bias the locking plate to a non-perpendicular locking position in relation to the guide to preclude movement of the control lever in said one direction of movement, said trigger mechanism including a pivotal member mounted on said control lever for movement between a position to pivot the locking plate to a released perpendicular position and to permit the spring bias means to pivot the locking plate to a non-perpendicular locking position.  
     
     
         10 . The structure as defined in  claim 6 , wherein said locking mechanism includes a semicircular guide mounted fixedly on said operating handle, said guide including a plurality of teeth on a peripheral edge surface, said control lever including a spring biased latching pin engaged with said teeth to lock the control lever in pivotal position, said control lever including a latch pin releasing mechanism including a control button extending beyond the upper end of said control lever to enable a trowel operator to depress the button by thumb pressure when grasping the upper end of the control lever to release the control lever from the guide to enable the lever to be pivoted in one direction to increase the blade pitch of the blades and permitting the weight of the trowel on the blades to move the control lever in the opposite direction to reduce the blade pitch.  
     
     
         11 . The structure as defined in  claim 8 , wherein said control lever is connected to said tension member through a mechanical advantage linkage to facilitate change in the blade pitch by exerting a reduced force on the control lever to support the weight of the trowel when increasing and decreasing the blade pitch.  
     
     
         12 . The structure as defined in  claim 11 , wherein said mechanical advantage linkage includes said control lever being pivotally connected to the operating handle at a pivot point closer to a lower end thereof, a connecting rod connected to the lower end of the control lever, a pivot link pivotally mounted on said operating handle, said pivot link including a lower end pivotally connected to said connecting rod and an upper end connected to said tension member, said pivotal mounting of said link on said operating handle being located closer to the upper end of said link.  
     
     
         13 . The structure as defined in  claim 10 , wherein said control lever is connected to said tension member through a mechanical advantage linkage to facilitate change in the blade pitch by exerting a reduced force on the control lever to support the weight of the trowel when increasing and decreasing the blade pitch.  
     
     
         14 . The structure as defined in  claim 13 , wherein said mechanical advantage linkage includes said control lever being pivotally connected to the operating handle at a pivot point closer to a lower end thereof, a connecting rod connected to the lower end of the control lever, a pivot link pivotally mounted ons aid operating handle, said pivot link including a lower end pivotally connected to said connecting rod and an upper end connected to said tension member, said pivotal mounting of said link on said operating handle being located closer to the upper end of said link.  
     
     
         15 . A quick adjustment mechanism for the blade pitch of a rotary power trowel in which said trowel includes radial blades pivotally supported about radial axes to vary the pitch thereof, an operating handle extending upwardly from the trowel in inclined relation to enable an operator to control movement of the trowel, a tension member extending along the operating handle and operatively associated with said blades to pivot the blades to vary their pitch, said quick adjustment mechanism comprising a control lever having a central portion pivotally supported from said operating handle, said lever including a lower end extending below the operating handle and an upper end extending above the operating handle to a position to enable an operator to easily access the upper end of the control lever to exert force thereto to pivotally move said control lever in a pivotal manner, the lower end of said control lever being connected to said tension member through a mechanical advantage linkage to facilitate change in the blade pitch by exerting a reduced force on the control lever to support the weight of the trowel when increasing and decreasing the blade pitch.  
     
     
         16 . The structure as defined in  claim 15 , wherein said mechanical advantage linkage includes said control lever being pivotally connected to the operating handle at a pivot point closer to a lower end thereof, a connecting rod connected to the lower end of the control lever, a pivot link pivotally mounted on said operating handle, said pivot link including a lower end pivotally connected to said connecting rod and an upper end connected to said tension member, said pivotal mounting of said link on said operating handle being located closer to the upper end of said link.