Replaceable cement-trowel blade trailing edge
TECHNICAL FIELD 
     This invention relates to cement-trowel blades and in particular to a motorized rotational cement-trowel blade with a replaceable trailing edge. 
     RELATED TECHNOLOGY 
     Motorized cement trowels generally are comprised of four trowel blades that are rotated by a trowel engine or motor. The leading edge in the direction of rotation is bent upwards to prevent it from digging into cement that is being troweled. Initially, when the cement is most wet, the rotating blades are rotated while being held in a flat condition parallel to the surface of cement being troweled. This is known as floating. Then as the cement becomes harder and drier, the blades are turned to increasing angles between the blade surface and the cement surface. This is called finishing. Combination trowel blades are employed to achieve both the floating and the finishing with such machines. 
     Motorized cement trowels generally are provided also with an adjustment wheel knob linked mechanically to a geared rotor wheel for varying the angle of the blades as they are being rotated. In handle-operated models, the adjustment wheel is on a handle generally. In riding models, the adjustment wheel may be positioned at various convenient locations. 
     The trowel blades do not wear out rapidly at their front sections because there is more contact surface of the blade when the blades are in a flat condition for floating and the wet cement is less abrasive than the drier cement. However, when the blades are tipped upwards at the front, only a small portion of the aft section of the blades is in contact with the cement and the cement is highly abrasive as it dries when finishing cement troweling. A great portion of troweling is finishing under these high-wear conditions. As a result, the entire trowel blade must be re-worked or replaced often to compensate for wear of mostly the aft section of blades. Reworking and replacing blades is highly expensive for both the material and the labor time required. 
     Various forms of attachable boots have been attempted but abandoned because an expensive boot section had to be discarded when only the trailing edge was worn. 
     There is a great need, therefore, for a replaceable trowel blade with a conveniently and reliably replaceable trailing edge. This invention fills this need and other in an improved replaceable cement-trowel blade. 
     SUMMARY OF THE INVENTION 
     One object of this invention is to provide a cement trowel blade with a replaceable trailing-edge. 
     Another object of this invention is to provide a replaceable trailing edge of a cement-trowel blade with high use-life. 
     Another object of this invention is to provide a replaceable trailing edge of a cement-trowel blade with improved cement-finishing characteristics. 
     Another object of this invention is to provide a cement-trowel blade with a wide selection of attachable trailing edges for various and different types of cement finishing. 
     Another object of this invention is to provide a cement-trowel blade that is attachable to a wide variety of motorized trowel machines. 
     Anther object of this invention is to provide a trowel blade with a trailing-edge easily attachable and detachable with a quick-disconnect means. 
     Still another object of this invention is to provide a conventional trowel blade with a means for attachment of a replaceable trailing-edge section. 
     In this invention, a combination trowel blade is provided with a replaceable trailing-edge section that is attachable to the aft edge of a trowel blade to accomplish these and other objectives. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is a bottom view of a conventional motorized rotational troweling machine with this invention of replaceable trowel blades attached. 
     FIG. 2 is an end view of this invention employing a quick-disconnect means. 
     FIG. 3 is a top view of the embodiment of the invention illustrated in FIG 2. 
     FIG. 4 is an end view of the attachable blade illustrated in FIGS. 2 and 3 but without the trailing-edge section attached. 
     FIG. 5 is a top view of the attachable blade illustrated in FIG. 4 without the trailing-edge section attached. 
     FIG. 6 is an end view of a trailing-edge section of the embodiment of the invention illustrated in FIGS. 2 and 3. 
     FIG. 7 is a top view of the trailing-edge section illustrated in FIG. 6. 
     FIG. 8 is an end view of an embodiment of the invention adapted to utilize conventional trowel blades that have been suitably modified. 
     FIG. 9 is a top view of the embodiment illustrated in FIG. 8. 
     FIG. 10 is an end view of an embodiment of the invention employing a conventional flat-heat bolt, rather than a quick-disconnect means for attachment of the trailing-edge section. 
     FIG. 11 is a top view of the embodiment of the invention illustrated in FIG 10. 
     FIG. 12 is an end view of an embodiment of the invention with a modified means for tightening the quick-disconnect of the trailing edge section to the trowel blade. 
     FIG. 13 is a top view of the embodiment illustrated in FIG. 12. 
     FIG. 14 is a sectional view of the means for tightening the quick-disconnect feature illustrated in FIGS. 12 and 13. 
     FIG. 15 is an end view of a thickened trailing-edge section for achieving higher wear while yet providing flexibility of a thinner front section of the trowel blade. 
     FIG. 16 is an end view of a circular trailing-edge section of the trowel blade. 
     FIG. 17 is an end view of the trailing-edge section with graduated thickness. 
     FIG. 18 is an end view of a trailing-edge section with both graduated-thickness and circular surface for enhancing smoothness of finishing and long use-life. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENT 
     Referring to FIG. 1, a replaceable cement-trowel blade 1 is provided with a replaceable trailing edge 2. The replaceable trowel blade 1 is attachable to a conventional motorized gear rotor 3 by attachment shafts 4. This is a bottom view that blocks view of an engine that provides rotational power to the motorized gear rotor 3 in conventional practice. Typically, a handle shaft 5 with a handle 6 houses a control shaft that can be rotated by blade-control knob 7 to cause the blade 1 and trailing edge to be either flat against a cement surface being troweled or for an upwardly-bent leading edge 8 to be raised. A circular guard 9 is positioned at the outside diameter of rotation of the blades 1 to prevent their contact with outside objects when the blades are being rotated. There are also conventional riding models of motorized rotary trowel blades that function similarly in relation to the rotational features and adjustment of the angle of the blade. This invention is related to the structure of the blade, not the rotary mechanism or adjustment of the angle of the blades in relation to the surface of cement being troweled. 
     Referring to FIG. 2, the attachable trailing edge 2 is attached to a raisedstep aft portion 10 of the replaceable trowel blade 1 by means of a quickdisconnect bolt shaft 11 and quick-disconnect bolt head 12. A blade attachment boss 13 is attachable to attachment shaft 4 by shaft bolts 14. 
     Referring to FIG. 3, attachment of the replaceable trailing edge 2 to the blade 1 is achieved by inserting bolt head 12 through bolt-head orifice 15 when the trailing edge 2 is off-centered inwardly from a blade inside edge 16 and then forcibly sliding the trailing edge 2 towards a blade outside edge 17 and thereby causing the bolt shafts 11 to enter angled quick-disconnect channels 18. Quick-disconnect channels 18 are at an angle preferably less than 4 degrees from parallel to trowel-blade aft edge 19, such that travel of the trailing edge 2 and, therefore, travel of the bolt shaft 11 outwardly towards the blade outside edge 17 causes the trailing edge 2 to move in the direction of the blade aft edge 19. 
     Referring to FIG. 4, the trowel blade 1 is illustrated from an end view without the attachment shaft 4 and without the bolt heads 12. 
     Referring to FIG. 5, the trowel blade 1 is illustrated from a top view without the attachment shaft 4 and without the bolt heads 12. The angled quick-disconnect channels 18 can be viewed more thoroughly without the bolt heads 12. The shaft boss can be provided with select fastener orifices 20 for various models of motorized trowels and attachment shafts 4. A raised-step aft edge 21 is extended sufficiently to hold the trailing edge rigidly in combination with the bolt shaft 11 and the bolt head 12. 
     Referring to FIG. 6, the bolt shaft 11 and head 12 are illustrated extending vertically from the top surface of the trailing edge 2 separately in an end view. 
     Referring to FIG. 7, a top view of the trailing edge 2 illustrates the bolt heads 12 before they are inserted into bolt-had orifices 15. 
     Referring to FIGS. 2-7, the action of the quick-disconnect is such that a trailing-edge front 22 is caused to come in contact with a raised-step contact wall 23 by movement of the trailing edge in the direction of the blade outside edge 17. Rotation of the blade 1 causes the trailing edge 2 to travel outwardly also, such that operation of the motorized trowel causes the blades to increase in rigidness of attachment, rather than to become loose from working conditions. Disconnecting the trailing edge 2 from the blade 1 is accomplished by tapping the trailing edge inwardly towards the geared rotor 3 and then sliding it further inwardly until the bolt heads 12 are in line with the bolt-head orifices 15 and the trailing edge 2 can be removed. 
     Referring in FIGS. 8 and 9, a means for attachment of the trailing edge 2 to the trowel blade 1 with less machinery required for making the components is shown in assembly end and top views. A flat connector member 24 is overlayed on the top surfaces of the blade 1 and the trailing edge 2. Flat-head connector bolts 25 are then inserted into countersunk bolt-head orifice 26 and bolt orifice 27 and tightened against fastener nut 28. 
     Referring to FIGS. 10 and 11, a means for attachment of the trailing edge 2 to the trowel blade 1 with few fastener elements is shown in assembly end and top views. The raised-step aft portion 10 is provided with bolt orifices 27 and the trailing edge 2 is provided with countersunk bolt-head orifices 27. Flat-head bolts 25 are then inserted through these fastener orifices and a fastener nut 28 is tightened against the raised-step aft portion 10. 
     Referring to FIGS. 12, 13 and 14. the quick-disconnect means is provided with a parallel bolt-shaft orifices 29 with walls parallel to the raised-step contact wall 23 and the trailing-edge front 22. Sloped orifice edges 30 at the sides of the parallel bolt-short orifices 29 provide a tightening effect when quick-disconnect bolt head 12 is inserted into bolt-head orifice 15 and the quick-disconnect bolt shafts 11 are pressured selectively in the direction of the blade outside edge 17 by pressure applied against the trailing edge 2. This causes the quick-disconnect bolt head 12 to travel from a low end 31 to a high end 32 of the sloped orifice edges and thereby tighten the bolt head 12 with respect to the trailing edge 2 to which the bolt shaft 11 is connected. Rotational travel of the blade 1 against cement being troweled causes the trailing edge 2 to be further tightened and to remain tight against the blade 1. Removing the trailing edge 2 is accomplished by pressuring it in the opposite direction to move the bolt head 12 from the high end 32 to the low end 31 such that bolt head 12 can then be removed through bolt-head orifice 15. 
     Referring to FIGS. 2-7, the angled quick-disconnect channels 18 can be provided with sloped orifice edges 30 having a low end 31 and a high end 32 also. Using both angled and sloped quick-disconnect channels has an advantage of tightening the trailing edge 2 against the bottom of the raised-step aft portion 10 in addition to tightening it against the raised-step contact wall 23. This provides vertical rigidity as well as horizontal rigidity in relationship to contact between the blade 1 and the trailing edge 2. 
     Referring to FIG. 15, a thick trailing edge 33 can be utilized to provide longer use-life and a more rigid troweling surface while yet allowing flexibility of the blade 1 in the vicinity of the blade attachment boss 13. 
     Referring to FIG. 16, a circular trailing edge 34 can be utilized to provide increased finish smoothness of the cement. 
     Referring to FIG. 17, a graduated-thickness trailing edge 35 can be utilized to provide increased use-life at the highest wear point without additional weight of material for an entire trailing edge. 
     Referring to FIG. 18, a graduated-thickness circular trailing edge 36 can be utilized to increased smoothness with minimal weight of material and to provide also the flexibility of the blade 1 that can aid the trowelling process.