Abstract:
A power trowel is provided for finishing concrete. The trowel can be used to finish concrete at different stages of hardening. The handle of the trowel is rotated both to adjust the speed of rotation of the trowel blades and the cant of the trowel blades.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   N/A. 
   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   N/A. 
   INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC (See 37 CFR 1.52(e)(5) and MPEP 608.05 
   N/A. 
   BACKGROUND OF THE INVENTION 
   (1) Field of the Invention 
   This invention relates to a method and apparatus for finishing freshly poured concrete. 
   More particularly, the invention relates to a concrete finishing method in which a power trowel floats on the liquid-particulate surface of wet concrete to produce a smooth, level surface finish prior to the concrete&#39;s hardening. 
   In another respect, the invention relates to a method for finishing freshly poured concrete in which a power trowel is provided with blades which can be canted during the finishing of concrete so the power trowel can be adapted for finishing concrete at different stages of hardening. 
   (2) Description of Related Art Including Information Disclosed under 37 CFR 1.97 and 1.98. 
   My U.S. Pat. No. 4,740,348 describes a power trowel for finishing concrete. The power trowel is light weight, and includes a throttle controlled by rotating the handle. While the power trowel set forth in U.S. Pat. No. 4,740,348 is, due to its light weight, especially useful, the power trowel is more difficult to use when concrete becomes stiff as it dries and sets. One way to compensate for the hardening of concrete is to alter the cant of the blades on the power trowel. In conventional trowels, this is accomplished by stopping the trowel and manually adjusting the position of the blades. This procedure is time consuming and can be impractical, especially when the concrete is hardening rapidly. 
   Accordingly, it would be highly desirable to provide an improved method and apparatus for adapting a light weight power trowel of the type described in U.S. Pat. No. 4,740,348 to permit the ready adjustment of the cant of the blades in order to permit the trowel to be used continuously while freshly poured concrete hardens. 
   Therefore, it is a principal object of the invention to provide an improved power trowel for finishing freshly poured concrete. 
   Another object of the invention is to provide a method and apparatus for adjusting the blades of a power trowel simultaneously with operating the power trowel to finish concrete. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
     These and other, further and more specific objects and advantages of the invention will be apparent from the following detailed description of the invention, taken in conjunction with the drawings, in which: 
       FIG. 1  is perspective view illustrating a power trowel constructed in accordance with the principles of the invention; 
       FIG. 2  is a bottom perspective view of the power trowel of  FIG. 1  illustrating further construction details thereof; 
       FIG. 3  is a perspective view of the power trowel of  FIG. 1  illustrating further construction details thereof; 
       FIG. 4  is an exploded perspective view illustrating the hub assembly of the power trowel of  FIG. 1 ; 
       FIG. 5  is a section view of the hub assembly of  FIG. 4  illustrating the mode of operation thereof; 
       FIG. 6  is a bottom view of the intermediate ball bearing adjustment plate used in the hub assembly of  FIGS. 5 and 6  to adjust the cant of the power trowel blades; 
       FIG. 7  is a top view of the top ball bearing adjustment plate used in the hub assembly of  FIGS. 5 and 6 , the top ball bearing adjustment plate being identical to the bottom ball bearing adjustment plate; 
       FIG. 8  is an exploded perspective view of the ratchet assembly used in the power trowel of the invention to adjust the cant of the power trowel blades; and, 
       FIG. 9  is a perspective view illustrating the functioning of the handle used on the power trowel of the invention. 
   

   BRIEF DESCRIPTION OF THE INVENTION 
   Briefly, in accordance with my invention, I provide an improved power trowel including a frame including a hub; a rotatable handle having a distal end and having a proximate end attached to the frame; a plurality of spaced apart blades pivotally mounted on and radially extending from the hub, each of the blades having a lower surface area; a transmission assembly mounted on the frame and operatively associated with the blades to pivot and alter the cant of the blades; a cable for activating the transmission assembly to pivot and alter the cant of the blades; a control assembly interconnecting the cable and the handle such that when the handle is rotated, the control assembly displaces the cable to activate the transmission assembly and pivot and alter the cant of the blades; and, an engine mounted on the frame and operatively associated with and rotating the hub. 
   In another embodiment of the invention, I provide a power trowel including a frame including a hub; a rotatable handle having a distal end and having a proximate end attached to the frame; a plurality of spaced apart blades pivotally mounted on and radially extending from the hub, each of the blades having a lower surface area; a transmission assembly mounted on the frame and operatively associated with the blades to pivot and alter the cant of the blades; a cable for activating the transmission assembly to pivot and alter the cant of the blades; a control assembly interconnecting the cable and the handle such that when the handle is rotated in a first direction, the control assembly displaces the cable to activate the transmission assembly and pivot and alter the cant of the blades; an engine mounted on the frame, having a throttle, and operatively associated with and rotating the shaft; a cable interconnecting the throttle and the handle such that when the handle is rotated in a direction opposite the first direction the cable is displaced and the throttle is adjusted. 
   In a further embodiment of the invention, I provide an improved method for finishing poured concrete to produce a smooth surface finish on the concrete. The improved method includes the steps of screeding a surface of the poured concrete to preliminarily level the surface of the concrete; moving a bull float over the surface; and, making a pass over the surface with a power trowel. The power trowel includes a frame including a hub; a rotatable handle having a distal end and having a proximate end attached to said frame; a plurality of spaced apart blades pivotally mounted on and radially extending from the hub, each of said blades having a lower surface area; a transmission assembly mounted on the frame and operatively associated with the blades to pivot and alter the cant of the blades; a cable for activating the transmission assembly to pivot and alter the cant of the blades; a control assembly interconnecting the cable and the handle such that when the handle is rotated, the control assembly displaces the cable to activate the transmission assembly and pivot and alter the cant of the blades; and, an engine mounted on the frame and operatively associated with and rotating the hub. The method also includes the step of rotating, while the engine is running and the power trowel is on the concrete, the handle to displace the cable, activate the transmission assembly, and alter the cant of the blades. 
   DETAILED DESCRIPTION OF THE INVENTION 
   Turning now to the drawings, which depict the presently preferred embodiments of the invention for the purpose of illustrating the practice thereof and not by way of limitation of the scope of the invention, and in which like reference characters refer to corresponding elements throughout the several views,  FIGS. 1 and 2  illustrate a power trowel constructed in accordance with the invention and generally indicated by reference character  10 . Trowel  10  includes a frame  9 . Engine  11 , fuel tank  12 , and plate  41  are mounted on frame  9 . A drive shaft  140  ( FIG. 5 ) extends from engine  11 , through an aperture in frame  9 , and to hub  40 . When engine  11  is running, engine  11  turns shaft  140  and hub  40 . Frame  9  can include a safety cage fabricated from tubing made from aluminum or another material. The cage includes concentric circular tubes  31 ,  32 ,  33  welded to radial arms  34 ,  35 ,  36 ,  37 ,  38 . Arcuate tube  39  extends from plate  41  to arm  35 . 
   As is illustrated in  FIG. 3 , tube  39  extends through an arcuate opening  19 B ( FIG. 3 ) formed in sleeve  19  and functions as a guide for sleeve  19  along which opening  19 B travels when sleeve  19  (and the handle  13  in sleeve  19 ) is pivoted about pivot point  25  in the direction of arrows  1 . Flange  19 C at the end of hollow sleeve  19  is pivotally attached by pin  25  intermediate receiving parallel flange pair  24 A and  24 B. 
   The proximate end  15  of the handle  13  is rotatably received in sleeve  19 . Cylindrical foot  16  extends through opening  19 D in sleeve  19  and is fixedly attached to end  15 . Rotating the handle  13  in the directions indicated by arrows Y and Z causes foot  16  to rotate side-to-side simultaneously in opening  19 D, as indicated by arrows X. One end of cable  18  slidably passes through upstanding member  17  and is fixedly connected to foot  16 . The other end of cable  18  is connected to the throttle (not visible) of motor  11 . The handle  13  has an “at rest” or neutral position in which member  16  is centered in elongate aperture  19 D. When the distal end  26  ( FIG. 3 ) of the handle is manually rotated in the direction of arrow Y, member  16  is displaced simultaneously in the direction of arrow Y, pulls on cable  18 , and displaces the throttle to increase the flow of fuel to the engine and to increase the RPM of drive shaft  140 . When the distal end  26  of the handle is manually rotated in the direction of arrow Z back to the “at rest” or neutral position of the handle, the throttle returns to idle or to a pre-set position in which the drive shaft  140  rotates at a lower RPM. In contrast, when the distal end  26  of the handle is manually rotated from its “at rest” or neutral position in the direction of arrow Z, shaft  210  and foot  200  move in the direction of arrow  211 . Shaft  210  interconnects foot  200  and foot  16  and slidably extends through an opening formed in member  17 . When the handle is manually rotated from its “at rest” or neutral position in the direction of arrow Y, shaft  210  pulls foot  200  in a direction opposite that of arrow  211 . When foot  200  moves in this opposite direction, pawl  201  does not engage or turn toothed gear wheel  204 . When, however, foot  200  is moved in the direction of arrow  211  by rotating the handle in the direction of arrow Z from the handle&#39;s neutral position, pawl  201  engages and turns wheel  204 . Since pulley  207  is connected to toothed wheel  204 , pulley  207  turns simultaneously with wheel  204 . Pulley  207  rotates in the direction indicated by arrow  212 , pulling cable  20  in the direction of arrow  213 . When cable  20  is pulled in the direction of arrow  213 , lever arm  22  pivots about pin  180  and the upper end  181  of lever arm  22  ( FIG. 2 ) is displaced in the direction of arrow B. When end  181  is displaced in the direction of arrow B, lower end  182  is displaced in the direction of arrow C. Displacing end  182  in the direction of arrow C pulls hook  184  and tab  21  in the direction of arrow D. As will be described below, pulling tab  21  in the direction of arrow D activates a transmission assembly, causing the blades  50 ,  60 ,  70 ,  80  to rotate to alter the cant of the blades. 
   Pin  202  is provided on pawl  201  so that when foot  200  is displaced a sufficient distance in the direction of arrow  211 , pin  202  rides upwardly on cam surface  205 , disengaging pawl  202  from gear wheel  204 . This prevents tab  21  from being displaced too far in the direction of arrow D (FIG.  2 ). Displacing lever arm  214  ( FIG. 8 ) in the direction of arrow  215  functions to release the ratchet assembly such that wheel  204  can free-wheel and the force of gravity acting on the weight of the power trowel will, when the power trowel is setting on the ground, cause blades  50 ,  60 ,  70 ,  80  to rotate back to their original position where blades  50 ,  60 ,  70 ,  80  are more nearly parallel to the ground and are not as severely canted with respect to the ground. Ratchet assembly  19  includes side  209 . 
   As can be seen, the function of the ratchet assembly  19  is, when the handle is rotated, to activate the transmission assembly in the power trowel to cause the cant of blades  50 ,  60 ,  70 ,  80  to be increased. While the ratchet assembly  19  and transmission assembly disclosed herein are presently preferred, any desired ratchet assembly construction and transmission assembly construction can be operatively associated with the rotation of handle and used to accomplish this function. If desired, a mechanism other than a ratchet assembly can be utilized. 
   In  FIGS. 1 ,  2 , and  4  each blade  50 ,  60 ,  70 ,  80  is fixedly attached to an orthogonal block  53 ,  63 ,  73 ,  83 , respectively. Each blade is of equal shape and dimension, although this need not be the case. Each block is of equal shape and dimension, although this need not be the case. Each block is fixedly secured to a hollow cylindrical member  52 ,  62 ,  72 ,  82 , respectively. Each member  52 ,  62 ,  72 ,  82  is of equal shape and dimension, although this need not be the case. Each member  52 ,  62 ,  72 ,  82  includes an orthogonal opening formed through its center. This orthogonal opening receives the orthogonal end of a control arm. For example, member  62  receives orthogonal end  64  on distal end  68  of arm  65 . End  64  and the opening that receives and conforms to end  64  prevent arm  65  from rotating in member  62  and, consequently, cause member  62  and arm  65  to rotate simultaneously. 
   Each control arm mounted in its associated member  52 ,  62 ,  72 ,  82  is of equal shape and dimension, although this need not be the case. For example, arm  55  has a shape and dimension equal to that of arm  65 . Arms  75  and  85  are not visible in the drawings and extend through hollow members  72  and  82  in the same manner that arms  55  and  65  extend through members  52  and  62 , respectively. 
   The proximate end  56 ,  66 ,  76  (not visible),  86  of each arm  55 ,  65 ,  75 ,  85  is positioned inside hub  40 . Each arm  55 ,  65 ,  75 ,  85  rotatably extends through a hollow cylindrical support member  51 ,  61 ,  71 ,  81 , respectively. Each support member  51 ,  61 ,  71 ,  81  is fixedly secured to and outwardly depends from hub  40 . A semi-spherical bearing surface  57 ,  67 ,  77  (not visible),  87  is fixedly secured to the top of proximate ends  56 ,  66 ,  76 ,  86 , respectively. Ends  56 ,  66 ,  76 ,  86  each extend inwardly, and if desired upwardly, from inner cylindrical wall  41  of hub  40  so that when a bearing surface  57 ,  67 ,  77 ,  87  and its associated end  56 ,  66 ,  76 ,  86 , respectively, is downwardly pivoted in the direction of arrow V in  FIG. 5 , arm  55 ,  65 ,  75 ,  85 , as the case may be, rotates in the manner indicated by arrows P and Q in FIG.  4 . When an arm  55 ,  65 ,  75 ,  85  rotates, the blade  50 ,  60 ,  70 ,  80  mounted on the arm also rotates, increasing the cant of the blade with respect to the surface of concrete being finished. For example, when proximate end  86  and bearing surface  87  are downwardly pivoted through an arc in the direction indicated by arrow R in  FIG. 4 , member  82  and block  83  rotate or pivot simultaneously with the distal end of arm  85  in the direction indicated by arrow T, and edge  80 A pivots upwardly through an arc in the direction indicated by arrow S. When edge  80 A pivots upwardly, the cant of blade  80  is increased with respect to the surface of concrete being finished with the power trowel of the invention. Similarly, downwardly depressing arm  66  causes blade  60  to cant such that edge  60 A moves upwardly in the direction of arrow H ( FIG. 2 ) and edge  60 B moves downwardly in the direction of arrow G. Downwardly depressing arm  56  causes blade  50  to cant such that edge  50 A moves downwardly in the direction of arrow E and edge  50 B moves upwardly in the direction of arrow F. 
   The transmission assembly that functions to displace arms  56 ,  66 ,  76 ,  86  is shown in more detail in  FIGS. 4  to  7 . The transmission assembly includes members  100  and  123 ; plates  111 ,  112 ,  113 ; circular race  127  with bearings  128  rotatably set therein; circular flat washer  130 ; and, ball bearings  119  to  122 . Upper plate  111  is identical to lower plate  113 . Member  100  includes neck  102 , upper flat circular surface  103 , lower conical surface  104 , and externally threaded cylindrical surface  101 . Member  123  includes upper conical surface  125  (opposed to conical surface  104  in FIG.  5 ), inner cylindrical surface  124  and outer cylindrical surface  124 A. Surface  124  slides over outer cylindrical surface  42 . 
   As shown in  FIG. 6 , plate  112  includes tab  21  with aperture  21 A formed therethrough to receive hook  184 . Plate  112  also includes arcuate openings  190  to  193  formed at equal intervals in plate  112 . Each opening  190  to  193  extends completely through plate  112 . 
   In  FIG. 7 , plate  111  (and therefore plate  113 ) includes tab  114  and includes radial grooves or openings  115  to  118  each extending completely through plate  111 . Openings  115  to  118  are formed at equal intervals in plate  111 . As shown in  FIG. 5 , tabs  114  of plates  111  and  113  in registration are stacked one on top of the other. In  FIG. 2 , the stacked tabs  114  are indicated by reference character  26  and extend through opening  114  formed in the frame  9 . Since frame  9  is fixed during operation of the power trowel, tabs  114  remain in fixed position in opening  114 , preventing plates  111  and  113  from rotating. 
   When tab  21  is at the “neutral” position shown in  FIG. 2 , blades  50 ,  60 ,  70 ,  80  are slightly canted from parallel with respect to the surface of the concrete being finished with the power trowel. In this “neutral” position, the blades are typically canted at a “preset” angle in the range of two degrees to ten degrees. When tab  21  is in the neutral position, ball bearings  119  to  122  are typically positioned near the outer ends  115 A to  118 A of the openings  115  to  118  in plate  111  (and plate  113 ). Plates  111  and  113  are positioned such that each opening in a plate  111  is in registration with an opening in the other plate  113 . When tab  21  is in the neutral position, ball bearings  119  to  122  are also typically positioned near the outer ends  190 A to  193 A of the openings  190  to  193  in plate  112 . When ratchet assembly  119  is operated by rotating the handle to displace hook  184 —and therefore tab  21 —in the direction of arrow D in FIG.  2  and arrow J in  FIG. 4 , tab  21  is displaced. When tab  21  is displaced, the remaining portion of plate  112  simultaneously rotates in the direction of arrow J. Rotating plate  112  in the direction of arrow J causes the ball bearings to move along openings  190  to  193  toward the inner ends  190 B to  193 B of said openings. When the ball bearings  119  to  122  move along openings  190  to  193  toward ends  190 B to  193 B, the bearings also simultaneously roll or slide or move along openings from outer ends  115 B to  118 B toward inner ends  115 B to  118 B. When bearings  119  to  122  move toward the inner ends of openings  190  to  192  and of openings  115  to  118 , the bearings force sloped surface  125  (and washer  130 ) downwardly away from sloped surface  104  (FIG.  5 ). When sloped surface  125  (and member  123 ) are forced downwardly, surface  124  slides over surface  42 , and race  127  and washer  130  are forced downwardly against bearing surfaces  57 ,  67 ,  77 ,  87  to displace downwardly proximate ends  56 ,  66 ,  76 ,  86  in the manner indicated by arrows V ( FIG. 5 ) and R ( FIG. 4 ) to increase the cant blades of  50 ,  60 ,  70 ,  80 . 
   In  FIG. 5 , circular washer  130  rests on bearing surfaces  57 ,  67 ,  77 ,  87 . Apertures  119 ,  194 , and  124 , along with similar apertures formed through race  127  and washer  130 , permit plates  111  to  113 , member  123 , race  127 , and washer  130  to slide up and down along the outer surface  42  of the hollow internally threaded  43  cylindrical member that depends upwardly from the floor  40 A of hub  40 . External threads  101  of member  100  turn into internally threaded  43  cylindrical surface. Member  100  is fixedly attached to drive shaft  140  and rotates simultaneously therewith when engine  11  is operating, as does hub  40 . Plates  111  to  113  do not rotate with hub  40  and shaft  140 . Members  123 ,  127  and washer  130  may rotate with hub  40 , or, rotate at a slower speed due to the friction between bearings  119  to  122  and conical surface  125 . The outer diameter of race  127  and washer  130  are presently, but not necessarily, equal to the outer diameters of plates  111  to  113 . 
   In use, fresh concrete is poured and is screeded to preliminarily level the surface of the concrete. The concrete is then tamped to bring the fines to the surface. A bull float is moved over the surface of the wet concrete. The bull float ordinarily is fabricated from a material generally free of iron. The power trowel of the invention is then passed over the concrete by starting the engine  11  to rotate the blades and by placing the trowel  10  on the horizontally oriented surface of the concrete. The trowel is moved over the surface of the concrete by grasping the distal end  26  of the elongate generally straight, rigid handle and by pulling and pushing the handle  13  to move the trowel over the concrete. The throttle is increased, and the rpm of the blades  50 ,  60 ,  70 ,  80  increased, by manually turning the handle  13  in the direction of arrow Y away from the “at rest” or neutral position of the handle. The cant of blades  50 ,  60 ,  70 ,  80  is increased by turning the handle in the direction of arrow Z to activate ratchet assembly  19  to displace cable  20  and tab  21  to cause the transmission assembly to downwardly displace the proximate ends  56 ,  66 ,  76 ,  86  to cant blades  50 ,  60 ,  70 ,  80  in the manner earlier described. 
     FIG. 9  further illustrates operation of handle  13 . 
   Cables  18 ,  20  can, if desired, each be replaced with a linkage assembly. 
   The handle  13  can consist of a plurality of tube lengths that can telescope, can bolt together, or can otherwise be interconnected. In one preferred embodiment, an end of a cylindrical section of the handle  13  has a reduced diameter that slides into the larger diameter end of a receiving section. The reduced diameter end also is provided with a spring loaded ball bearing that snaps into an opening formed in the larger diameter end of the receiving section when the smaller diameter end slidably seats in the larger diameter end. The ball bearing prevents the smaller diameter end from rotating in the receiving larger diameter end of the receiving section. 
   Having described my invention in such terms as to enable those of skill in the art to make and practice it, and having described the presently preferred embodiments thereof.