Blade pitch adjustment device

Abstract

A blade pitch adjustment system may adjust the pitch of a plurality of blades. A height adjustment assembly adjusts a distance between a rotatable blade assembly and a thrust collar. Adjusting the distance between the assembly and the collar changes the pitch of the blades of the machine. Two or more blade pitch adjustment systems may be adjusted at the same time, at the same rate. For concurrent adjustment, systems are connected to a rotating member by tension cables. A linear actuator rotates the rotating member, changing the tension on the tension cables, actuating the systems to change the pitch of the blade assemblies. The pitch of the blade assemblies may have an offset or bias which may be adjusted for with a sliding member, which may be powered by a linear actuator. The system may be used with a concrete finishing machine.

1 . A blade pitch adjustment system comprising:
 a thrust collar;   a rotatable blade assembly coaxial with and persistently contacting the thrust collar, the rotatable blade assembly being operatively parallel to the thrust collar, and comprising a plurality of blades that are configured to have an adjustable pitch; and   a height adjustment assembly configured to be coaxial with the thrust collar and the rotatable blade assembly and configured to change a distance between the thrust collar and the rotatable blade assembly such that the thrust collar and the rotatable blade assembly remain operatively parallel to each other before, during, and after a change in distance,   wherein changing the distance between the thrust collar and the rotatable blade assembly adjusts the pitch of the blades.   
   
   
       2 . The blade pitch adjustment system of  claim 1 , wherein the height adjustment assembly is operatively connected to the thrust collar and is configured to adjust the position of the thrust collar with respect to the rotatable blade assembly while keeping the thrust collar operatively parallel to the rotatable blade assembly. 
   
   
       3 . The blade pitch adjustment system of  claim 1 , wherein the height adjustment assembly is operatively connected to the rotatable blade assembly and is configured to adjust the position of the rotatable blade assembly up and down with respect to the thrust collar while keeping the rotatable blade assembly operatively parallel to the thrust collar. 
   
   
       4 . The blade pitch adjustment system of  claim 1 , further comprising power unit mated with a power transfer shaft, the power transfer being connected to the rotatable blade assembly. 
   
   
       5 . The blade pitch adjustment system of  claim 1 , wherein the rotatable blade assembly further comprises a hub connecting to a plurality of rotatable blade arms, each of the rotatable blade arms comprising at least one lever, wherein at least one of the plurality of blades is attached to each rotatable blade arm, and wherein the lever is configured to persistently contact at least a portion of the thrust collar. 
   
   
       6 . The blade pitch adjustment system of  claim 1 , wherein the height adjustment assembly comprises an outer ring, a profile follower, a bearing positioned coaxially with the outer ring, and a height adjustment collar, wherein the height adjustment collar comprises one or more height adjustment profiles, and wherein the profile follower is configured to contact and travel along the height adjustment profiles. 
   
   
       7 . The blade pitch adjustment system of  claim 6 , wherein the profile follower comprises a plurality of cams, a plurality of bearings, or a plurality of complementary ramps. 
   
   
       8 . A blade pitch adjustment system comprising:
 a thrust collar;   a rotatable blade assembly operatively connected to and operatively parallel with the thrust collar, and comprising a plurality of blades that are configured to have an adjustable pitch; and   a height adjustment assembly comprising at least three contact points, operatively forming a movable plane, and being configured to adjust a distance between the thrust collar and the rotatable blade assembly by adjusting the height of the at least three contact points, such that the thrust collar and the rotatable blade assembly remains operatively parallel to each other during and after distance adjustment,   wherein adjusting the distance between the thrust collar and the rotatable blade assembly correspondingly adjusts the pitch of the blades.   
   
   
       9 . The blade pitch adjustment system of  claim 8 , wherein the at least three contact points operatively connect to the thrust collar and are configured to adjust the position of the thrust collar with respect to the rotatable blade assembly while keeping the thrust collar operatively parallel to the rotatable blade assembly. 
   
   
       10 . The blade pitch adjustment system of  claim 8 , wherein the at least three contact points operatively connect to the rotatable blade assembly and are configured to adjust the position of the rotatable blade assembly with respect to the thrust collar while keeping the rotatable blade assembly operatively parallel to the thrust collar. 
   
   
       11 . The blade pitch adjustment system of  claim 8 , wherein the rotatable blade assembly, the thrust collar, and the three contact points are coaxial. 
   
   
       12 . The blade pitch adjustment system of  claim 8 , wherein the height adjustment assembly comprises an outer ring, a bearing operatively connected to the outer ring and positioned coaxially within the outer ring. 
   
   
       13 . A concrete finishing machine comprising:
 a frame;   a guard connected to the frame;   a power unit connected to the frame;   a rotatable blade assembly operatively connected to the power unit and comprising a plurality of blades that are configured to have an adjustable pitch and that are rotatably connected to a hub, the rotatable blade assembly being generally planar;   a thrust collar having a planar rim and being configured to contact at least a portion of the rotatable blade assembly at the planar rim, the planar rim being operatively parallel to the plane of the rotatable blade assembly; and   a height adjustment assembly configured to adjust a distance between the thrust collar and the rotatable blade assembly such that the planar rim of the thrust collar and the plane of the rotatable blade assembly remain operatively parallel to each other during and after distance adjustment.   
   
   
       14 . The concrete finishing machine of  claim 13 , further comprising an actuator configured to actuate the height adjustment assembly. 
   
   
       15 . The concrete finishing machine of  claim 13 , further comprising a plurality of rotatable blade assemblies, a plurality of height adjustment assemblies, and a plurality of thrust collars. 
   
   
       16 . The concrete finishing machine of  claim 13 , wherein the distance between the guard and the concrete surface is substantially the same, regardless of the pitch of the plurality of blades. 
   
   
       17 . The concrete finishing machine of  claim 13 , further comprising a power transfer shaft operatively connected to the power unit and operatively connecting the rotatable blade assembly to the height adjustment assembly. 
   
   
       18 . The concrete finishing machine of  claim 13 , further comprising
 a frame member operatively connected to the frame;   a tension adjustment member connected to the frame member at a connecting point, the tension adjustment member having a plurality of ends;   a plurality of tension cables operatively connected to the plurality of ends of the tension adjustment member; and   a first actuator having a first end connected to the tension adjustment member and a second end connected to the frame member.   
   
   
       19 . The blade pitch adjustment system of  claim 18 , further comprising a mounting member connected to the frame, wherein the frame member is slidably connected to the mounting member. 
   
   
       20 . The blade pitch adjustment system of  claim 19 , further comprising a second actuator, a first end of the second actuator being connected to the mounting member, and a second end of the second actuator being operatively connected to the tension adjustment member.