Mechanical pitch control

A concrete finishing trowel comprising:

• a drive means having extending therefrom a drive shaft, said drive shaft connecting with and configured to rotate a rotatable blade assembly;
• a rotatable blade assembly adapted to finish a concrete surface, said rotatable blade assembly having a generally vertical axis of rotation and a plurality of radially spaced apart concrete finishing blades extending outwardly from said vertical axis for frictionally contacting said concrete surface, said blades each defining a longitudinal axis generally perpendicular to said vertical axis;
• a pitch controller for varying the pitch of said blades by rotating them about their longitudinal axis, said pitch controller utilizing the rotation of said drive shaft to rotate said blades about their longitudinal axis, said pitch controller comprising a thrust collar, a nut, and a bearing;
• said thrust collar comprising a plate configured to bear downwardly on said rotatable blade assembly thereby varying the pitch of said blades by rotating them about their longitudinal axis, said thrust collar further comprising a hollow shaft able to receive said drive shaft therethrough, said hollow shaft having an exterior surface, said exterior surface threaded;
• said nut configured for threading onto said thrust collar exterior surface, said nut having an upper surface;
• and
• said bearing configured to support a drive means lower surface on said nut upper surface;
• and
• a clutch for selectively engaging and disengaging said pitch controller.

A concrete finishing trowel comprising:

• a drive means having extending therefrom a drive shaft, said drive shaft connecting with and configured to rotate a rotatable blade assembly;
• a rotatable blade assembly adapted to finish a concrete surface, said rotatable blade assembly having a generally vertical axis of rotation and a plurality of radially spaced apart concrete finishing blades extending outwardly from said vertical axis for frictionally contacting said concrete surface, said blades each defining a longitudinal axis generally perpendicular to said vertical axis;
• a pitch controller for varying the pitch of said blades by rotating them about their longitudinal axis, said pitch controller utilizing the rotation of said drive shaft to rotate said blades about their longitudinal axis, said pitch controller comprising a thrust collar, a nut, and a bearing;
• said thrust collar comprising a plate configured to bear downwardly on said rotatable blade assembly thereby varying the pitch of said blades by rotating them about their longitudinal axis, said thrust collar further comprising a hollow shaft able to receive said drive shaft therethrough, said hollow shaft having an exterior surface, said exterior surface threaded;
• said nut configured for threading onto said thrust collar exterior surface, said nut having an upper surface;
• said bearing configured to support a drive means lower surface on said nut upper surface;
• and
• a clutch for selectively engaging and disengaging said pitch controller;
• wherein said nut can be threaded in a first direction on said thrust collar and towards said thrust collar plate, and wherein said nut can be threaded in an opposite, second direction on said thrust collar and away from said thrust collar plate;
• wherein travel in said first direction results in a reduction in the degree of downward bearing upon said rotatable blade assembly by said thrust collar plate thereby resulting in a decrease in pitch;
• wherein travel in said second direction results in an increase in the degree of downward bearing upon said rotatable blade assembly by said thrust collar plate thereby resulting in an increase in pitch;
• wherein said drive means drives said drive shaft thereby rotationally driving said thrust collar and said rotatable blade assembly;
• wherein said clutch is configured to stop said nut while said drive means is driving thereby resulting in travel in said second direction and moving said thrust collar away from said nut;
• and
• wherein said clutch is configured to transmit the rotation of said thrust collar to achieve travel in said second direction thereby drawing the thrust collar nearer said nut.