Abstract:
A power riding trowel for finishing concrete comprising rotors turned by gearboxes driven by gearbox driveshaft&#39;s linked to the moor output by CVT gear ratio control. The motor output shaft drives a first jackshaft driven at a higher speed than the motor RPM. A CVT pulley assembly comprising first and second CVT pulleys and a CVT belt entrained between them has a first CVT pulley driven by the first jackshaft. A second jackshaft splined to the second CVT pulley drives the gearbox driveshaft at a speed lower than said second jackshaft to operate the rotor means at a proper speed and torque.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This utility patent application is based upon, and claims filing date priority from, a prior U.S. Provisional Patent application entitled “Riding Trowel CVT Clutch Module,” by inventor Jeffrey Lynn Fielder, Ser. No. 61/884,456, filed Sep. 30, 2013, which is hereby incorporated by reference as if fully set forth herein. 
    
    
     BACKGROUND OF THE INVENTION 
     I. Field of the Invention 
     The present invention relates generally to motorized riding trowels for finishing concrete. More particularly, the present invention relates to transmissions for powered riding trowels of the type classified in United States Patent Class 404, Subclass 112, and particularly to CVT transmission systems for such trowels. 
     II. Description of the Prior Art 
     It has long been recognized by those skilled in the art that freshly placed concrete must be appropriately finished. Proper and timely finishing insures that desired surface characteristics including appropriate smoothness and flatness are achieved. Motorized riding trowels are ideal for finishing very large areas of plastic concrete quickly and efficiently, and such trowels have become a standard in the industry. 
     A typical power riding trowel comprises two or more bladed rotors that project downwardly and frictionally contact the concrete surface for finishing. These rotors are driven by one or more motors mounted on the frame. Typically the motors drive suitable reduction gearboxes (i.e., 20:1 reduction) to power the rotors. The riding trowel operator sits on top of the frame and controls trowel movement with a steering system that tilts the axis of rotation of the rotors. The weight of the trowel and the operator is transmitted frictionally to the concrete by the revolving blades. The unbalanced frictional forces caused by rotor tilting enable the trowel to be steered. 
     Holz, in U.S. Pat. No. 4,046,484 shows a pioneer, twin rotor, self propelled riding trowel. U.S. Pat. No. 3,936,212, also issued to Holz, shows a three rotor riding trowel powered by a single motor. Although the designs depicted in the latter two Holz patents were pioneers in the riding trowel arts, the devices were difficult to steer and control. 
     Prior U.S. Pat. No. 5,108,220 owned by Allen Engineering Corporation, the same assignee as in this case, relates to an improved, fast steering system for riding trowels. Its steering system enhances riding trowel maneuverability and control. The latter fast steering riding trowel is also the subject of U.S. Pat. No. Des. 323,510 owned by Allen Engineering Corporation. 
     Allen Engineering Corporation U.S. Pat. No. 5,613,801 issued Mar. 25, 1997 discloses a power riding trowel equipped with twin motors. The latter design employs a separate motor to power each rotor. Steering is accomplished with structure similar to that depicted in U.S. Pat. No. 5,108,220 previously discussed. 
     Allen U.S. Pat. No. 5,480,257 depicts a twin engine powered riding trowel whose guard structure is equipped with an obstruction clearance system. When troweling areas characterized by projecting hazards such as pipes or ducts, or when it is necessary to trowel hard-to-reach areas adjacent walls or the like, the guard clearance structure may be retracted to apply the blades closer to the target region. 
     Allen U.S. Pat. No. 5,685,667 depicts a twin engine riding trowel using “contra rotation.” For enhanced stability and steering, the rotors rotate in a direction opposite from that normally expected in the art. 
     As freshly poured concrete “sets,” it soon becomes hard enough to support the weight of the specialized finishing trowel, so pan finishing can begin. By starting panning while concrete is still “green,” within one to several hours after pouring depending upon the concrete mixture involved, “super-flat” and “super-smooth” floors can be achieved. The advent of more stringent concrete surface finish specifications using “F” numbers to specify flatness (ff) and levelness (fl), dictates the use of pans on a widespread basis. 
     The panning process comprises three different recognizable stages. In the initial “brake open” stage, the rotors are ideally driven between 40 and 65 RPM. As the concrete hardens, the pan floating stage occurs, involving rotor speeds between 70 and 95 RPM. The last phase of pan floating, the “fuzz stage,” uses an increased rotor speed of between 95-125 RPM. At present these RPM requirements are achieved simply by varying motor speed. 
     Pan finishing is normally followed by medium speed blade finishing, after the pans are removed from the rotors. An enhancement is the use of “combo blades” during the intermediate “fuzz stage” as the concrete continues to harden. So-called “combo-blades” are a compromise between pans and normal finishing blades. They present more surface area to the concrete than normal finishing blades, and attack at a less acute angle. The rotors are preferably turned between 100 to 135 RPM at this time. Finishing blades are then used, and they are rotated between 120 to 150 RPM. Finally, the pitch of the blades is changed to a relatively high contact angle, and burnishing begins. This final trowel finishing stage uses rotor speeds of between 135 and 165 RPM. 
     Modern large, high power riding trowels can deliver substantial horsepower. During use, however, the drive train, the gearboxes, the rotors and the motors are subject to substantial stresses. Motor loading varies as the rotor RPM requirements change. Furthermore, ideal rotation speeds can vary depending upon the concrete, whose frictional characteristics vary between the freshly poured and stricken off stage, the subsequent green stages, and the end stages occurring after final curing and hardening. The motors function most efficiently at a given operating point in their characteristic horsepower-RPM and torque-RPM curves. Especially with diesel engines, optimum torque and horsepower requirements are achieved over a limited RPM range. 
     The engines on most riding trowels directly power the reduction drive gear boxes connected to the rotor shafts. The incoming shaft speed of the conventional rotor gear box is the same as the motor output RPM. The gearbox output shaft speed (i.e., rotor speed) is reduced, approximately 20:1. Engine RPM is usually the key variable related to output power. However, with engine speed increases, excessive power may be developed and the finishing mechanism may rotate too fast. For example, the initial panning stage requires relatively high power because of the viscous character of the still-wet concrete, but relatively low rotor speeds are desired. Since the rotors are driven through a fixed ratio, established by the gearbox and pulleys, optimum engine power often cannot be obtained during panning without risking excessive rotor speeds. 
     It has thus proven desirable to provide a CVT riding trowel wherein the engine and gear boxes can operate at ideal speeds over a wide range of finishing conditions. 
     U.S. Pat. No. 5,967,696 Oct. 19, 1999 issued to Allen Engineering Corporation depicts a CVT riding trowel, i.e., a trowel with a variable ratio transmission. The trowel described in the latter patent includes a CVT drive train powering a pair of rotors. The rotors are shaft-driven by reduction gear boxes. The CVT system comprises a variable ratio pulley driven by the motor. A second variable ratio pulley drives the gear box input shaft, with a drive belt entrained between the twin, variable ratio pulleys. Means are provided to change the effective diameters of a pair of belt-coupled pulleys. The varying ratio between the pulleys establishes a variable, overall drive gear ratio. However, it has been found that with the latter design, the CVT pulleys do not operate at a high-enough speed to promote efficiency. 
     Other continuously variable transmission devices not specific to riding trowels are seen in U.S. Pat. Nos. 8,682,549, 8,668,607, 8,686,886, 7,063,633, 6,994,643, 7,081,057, 7,090,600, 6,569,043, 6,120,399, 6,958,025, 6,953,400, 6,155,940, and 5,377,774. 
     It has recently been realized that improved efficiency of the overall power train results where the CVT transmission system, in a riding trowel for example, can operate at what would otherwise be classified as an excessive speed. For example, the first stage couplings or pulleys in a conventional CVT system operate at the drive motor output shaft speed or RPM. Variable gear reduction offered to the gearbox drive shaft then reduces applied RPM from that of the motor. It has been discovered that a CVT system that first increases the RPM speed from the motor, to operate the CVT pulleys at higher-than-expected speed, results in efficiency gains. Subsequent gear reduction to the gearbox drive shaft enables the motor to run at its desired speed at maximum intervals, while facilitating proper gear box speed. At the same time, over-torque of the CVT pulleys is avoided and belt breakage is avoided. 
     SUMMARY OF THE INVENTION 
     This invention provides a continuously variable ratio transmission (i.e., “CVT”) module ideally for powered concrete finishing riding trowels and the like that couples between the drive motor or motors and the lower drive train. CVT modules may be employed with single engine or multiple engine riding trowels, and they are ideal for diesel applications, natural gas engines, and traditional gasoline powered motors. 
     The preferred riding trowel comprises one or more engines for powering downwardly projecting rotors whose blades frictionally contact the concrete surface. The rotors are driven by reduction gear boxes that are shaft activated. By tilting the rotors steering forces are developed. The CVT module is mechanically interposed between the motor output shaft and the lower gear box input shaft, being connected with conventional V-belts entrained about suitably positioned pulleys. 
     The CVT configuration facilitates higher power applications by reducing the torque and subsequently the belt tension in the CVT. Belt tension is directly related to the torque on the rotating pulleys. Power is the product of torque and speed. Therefore increasing the speed of the CVT pulleys will result in lower torque. The CVT module input section steps up the applied motor speed, rather than stepping it down. With the enhanced CVT first stage input speed, and resultant torque and RPM characteristics, overall efficiency is achieved. Subsequent CVT pulley sections reduce speed sufficiently to drive the gearbox shafts at a desired speed. 
     Thus a basic object of my invention is to increase efficiency of a powered riding trowel, or other motor-powered device, when employing a CVT transmission. 
     A basic object of my invention is to provide a CVT module for power finishing trowels or similar motor-powered equipment. 
     It is also an object to accommodate larger engines in a riding trowel of the type described. It is a feature of the invention that engines up to sixty horsepower may be employed without damaging the drive train. 
     A related object is to optimize trowel efficiency and CVT efficiency by allowing the CVT transmission to operate at speeds higher than the motor output shaft speed, and to gear down the output speed to match the required rotor gearbox speed. 
     Another related object is to properly modify the torque and rotational speed of key components in a complex CVT-equipped powered riding trowel. 
     Yet another object is to provide an enhanced, modular CVT system ideal for riding trowels that enables the rotors to operate at a variety of speeds while allowing the drive motor or motors to operate at optimum speeds. 
     Another important object is to provide a CVT system whereby motor speeds can be varied during concrete finishing operations, while rotor speeds are substantially maintained. 
     Conversely, an important object is to enable rotor speed to be varied substantially as desired during different finishing stages, while maintaining substantially constant motor speed and motor torque. 
     A basic object, that is intertwined with all of the above, is to increase the efficiency of a CVT power unit by allowing it to run at higher-than-normal speeds (i.e., 6000 RPM) while maintaining the proper motor and gearbox speeds employed by the riding trowel. 
     Another basic object of my invention is to provide an optimum, overall gear ratio at all times during the riding trowel finishing process. 
     Another important object is to lock the drive train into different gear ratios that are selected during different finishing stages to maintain the desired operating parameters. 
     A related object is to provide a CVT module for ridding trowels that is ideal either during panning or blading. 
     A still further object of our invention is to provide a CVT module for riding trowels that increases production and efficiency. 
     A still further object of my invention is to provide a modularized CVT system of the character described that may be quickly installed or removed from riding trowels during service and/or maintenance. 
     These and other objects and advantages of the present invention, along with features of novelty appurtenant thereto, will appear or become apparent in the course of the following descriptive sections. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the following drawings, which form a part of the specification and which are to be construed in conjunction therewith, and in which like reference numerals have been employed throughout wherever possible to indicate like parts in the various views: 
         FIG. 1  is a frontal isometric view of a typical motorized, riding trowel equipped with my new CVT gearing system, with portions thereof shown in section or broken away for clarity or omitted for brevity; 
         FIG. 2  is a rear isometric view of the concrete finishing trowel of  FIG. 1 , equipped with my new CVT gearing system, with portions thereof shown in section or broken away for clarity or omitted for brevity; 
         FIG. 3  is an enlarged, fragmentary, left frontal isometric view of the preferred CVT power module, with portions thereof shown in section or broken away for clarity or omitted for brevity; 
         FIG. 4  is an enlarged, fragmentary, top isometric view of the preferred CVT power module, with portions thereof shown in section or broken away for clarity or omitted for brevity; 
         FIG. 5  is an enlarged, fragmentary, right frontal isometric view of the preferred CVT power module, with portions thereof shown in section or broken away for clarity or omitted for brevity; 
         FIG. 6  is an enlarged, fragmentary, rear isometric view of the preferred CVT power module, with portions thereof shown in section or broken away for clarity or omitted for brevity; 
         FIGS. 7 and 8  are exploded isometric assembly views, with portions thereof shown in section or broken away for clarity or omitted for brevity; 
         FIG. 9  is a fragmentary, frontal exploded isometric and diagrammatic view of an alternative embodiment of a CVT trowel; 
         FIG. 10  is a fragmentary, rear exploded isometric and diagrammatic view of an alternative embodiment of a CVT trowel; 
         FIG. 11  is a fragmentary rear left isometric view of the trowel of  FIGS. 8 and 9 ; and, 
         FIG. 12  is a fragmentary front right isometric view of the trowel of  FIGS. 8-10 . 
     
    
    
     DETAILED DESCRIPTION 
     The subject matter of this patent is related to one or more of the following U.S. Pat. Nos. D323,510 issued January 1992; U.S. Pat. No. 3,936,212 issued February 1976; U.S. Pat. No. 4,046,484 issued Sep. 6, 1977; U.S. Pat. No. 4,312,603 issued Jan. 26, 1982; U.S. Pat. No. 4,556,339 issued Dec. 3, 1985; U.S. Pat. No. 4,676,691 issued Jun. 10, 1987; U.S. Pat. No. 4,710,055 issued Dec. 1, 1987, U.S. Pat. No. 5,108,220 issued Apr. 28, 1992; U.S. Pat. No. 5,238,323 issued Aug. 24, 1993; U.S. Pat. No. 5,405,216 issued Apr. 11, 1995; U.S. Pat. No. 5,480,257 issued Jan. 2, 1996; U.S. Pat. No. 5,480,258 issued Jan. 2, 1996; U.S. Pat. No. 5,613,801 issued Mar. 25, 1997; U.S. Pat. No. 5,658,089 issued Aug. 19, 1997; U.S. Pat. No. 5,685,667 issued Nov. 11, 1997; U.S. Pat. No. 5,803,658 issued Sep. 8, 1998; U.S. Pat. No. 5,934,823 issued Aug. 10, 1999; U.S. Pat. No. 5,967,696 issued Oct. 19, 1999, U.S. Pat. No. 5,988,938 issued Nov. 23, 1999; and, U.S. Pat. No. 6,019,545 issued Feb. 1, 2000. For purposes of disclosure, and compliance with enablement and disclosure requirements of 35 USC Sec. 112 et. Seq., the foregoing patents are hereby incorporated by reference as if fully set forth herein. 
     The subject matter of this patent is also related to one or more of the following other references: “Hi-Lo Variable Speed Pulley Drives” brochure by Hi-Lo Manufacturing Co. Prtd. November 1994; “TS 78 Multi-Lap Ride-On Power Trowel” Spec Sheet by Bartell Powell Products; Bartell “Power Trowels” Brochure “Speed Selector Inc.&#39;s “Variable Speed Drives &amp; Accessories” Brochure form 910-1-9; For purposes of disclosure, and compliance with 35 USC Sec. 112, the foregoing references are hereby incorporated by reference as if fully set forth herein 
       FIG. 1  shows a typical dual rotor riding trowel  20  incorporating my new CVT transmission module variable gearing system. Common structural details relating to riding trowel motors, rotors, steering, rotor tilting, etc. are explained in detail in the above-cited references. It should be appreciated that trowel  20  may comprise either modern hydraulic steering, or it may employ the older manual steering arrangements such as that illustrated in U.S. Pat. No. 5,108,220. The drive engine may be diesel, gasoline, or gas powered. A variety of other differences between various riding trowels known in the art exist as well, but few of these are relevant to the employment of my CVT module. 
     The riding trowel  20  comprises a drive engine  22  for powering downwardly projecting, bladed rotors  24  that frictionally contact the concrete surface  23  below. The multiple, radially spaced apart blades  26  projecting from central hubs  28  are driven by gear boxes  30  to treat concrete. Engine  22  is interconnected with the gear boxes  30  via a CVT module generally designated by the reference numeral  29 . The steering system may include a plurality of both manual and hydraulic linkages and actuators. By tilting the rotors appropriately, directional steering forces are developed. The operator&#39;s seat  34  may be mounted above the motor  22  proximate suitable steering handles and controls (not shown). Seat  34  rests upon a subframe  36  supported upon the trowel main frame  40 . 
     U.S. Pat. No. 5,967,696 entitled “Riding Trowel with Variable Ratio Transmission”, issued Oct. 19, 1999 discloses a riding trowel with a CVT pulley system for establishing continuously variable gear ratios. In this device the amount of power that is transferred from the engine to the gearboxes results in excessive torque. The CVT belt breaks with too much torque with larger, modern engines. To operate efficiently the CVT clutch needs to run at a faster RPM. By speeding up the CVT pulley system torque is reduced, and belt pressure or tension is reduced. This results in longer belt life. However, the gearbox shafts must run at a reduced speed. Thus the instant torque converting arrangement uses another pulley, driven by the CVT, to reduce speed and increase torque to the gearbox driveshaft. The pulley and shaft arrangement is disposed in modular form, preferably beneath the operator seat, proximate the lower gearboxes, between the twin rotors. 
     With joint reference now directed to  FIGS. 3-8 , the CVT module  29  is preferably mounted atop a rigid plate  44  that is configured to suitably attach atop the trowel main frame  40 . The power input end of the CVT module has been generally designated by the reference numeral  46  in  FIGS. 4 ,  5 , and  7 . The CVT module is positioned proximate the output end of the engine  22 , the power output flywheel of which has been designated by the reference numeral  50  in  FIG. 7 . The PTO shaft  51  (i.e.  FIG. 8 ) emanating from the flywheel  50  of the engine  22  drives the CVT module. Portions of the engine outer wall  52  are seen in  FIGS. 3-8 . Engine wall  52  supports a pulley idler plate  54  used by the first or input stage of the CVT module. 
     The power input stage of the CVT unit (i.e., the first stage) comprises a pulley  60  that is splined to PTO shaft  51 . A first belt  62  entrained over pulley  60  is coupled to a reduced diameter pulley  64  that is positioned above pulley  60 . Pulley  64  thus rotates faster than PTO  51 . Pulley  64  is splined to a jackshaft  66  that penetrates it and terminates through a bushing  68  in a roller bearing  69  attached to plate  54  proximate the engine. Jackshaft  66  rotates at a higher speed and lower torque than the engine shaft  51 . 
     Jackshaft  66  reaches the second stage  67  ( FIG. 3 ) of the CVT module through a bearing  70  affixed to a support plate  72  mounted atop a vertically extending, intermediate plate  74  that is secured to horizontal plate  44 . Jackshaft  66  terminates within and is splined to a variable drive CVT pulley assembly  84  in CVT module second stage  67 . Pulley  84  can change its effective diameter, varying the speed and torque transmitted to lower pulley  88  by a second or CVT belt  89 . CVT pulley  84  will be driven by jackshaft  66  at a higher speed than the engine shaft  51 , therefore operating at a lower torque. A suitable CVT unit is available from CV Tech Company, Drummondville Quebec Canada. The CVT unit comprises a first and preferably upper pulley  85  with cooperating, conical halves  87 A and  87 B that are axially spaced apart a distance that establishes the belt gear ratio. 
     A second jackshaft  92  positioned below jackshaft  66  is splined through lower CVT pulley  88 . The CVT belt  89  extends to lower CVT pulley  88  from the upper CVT pulley. Jackshaft  92  extends from a roller bearing  95  that is mounted to a vertically oriented plate  97  that is secured to plate  44  near its leftward extreme. Jackshaft  92  extends through a bushing  99  and through intermediate plate  74  to the third stage of the CVT module that has generally been designated by the reference numeral  100  ( FIG. 8 ). 
     Referring now to  FIGS. 5-8 , jackshaft  92  terminates within stage  100  through bearing  102  in a third pulley  104  that is supported by bearing  102  and intermediate plate  74 . A third belt  108  entrained over pulley  104  extends through and beneath plate  44  through an orifice  109  ( FIG. 5 ). Belt  108  reaches a larger diameter, fourth pulley comprising lower gearbox drive pulley  111  that is coupled to the gearbox drive shaft  113 . Gearbox drive shaft  113  is supported by a pair of spaced-apart bearings  116  ( FIGS. 6 ),  118  and  121 . 
     In short, the Allen power transmission system takes the power of the engine, which is supplied at a particular rotating speed and torque, converts it to a higher speed and lower torque which is more suitable for the CVT, then converts back to a lower speed and higher torque which is necessary for the proper speed of the gearboxes and rotors, and maximal efficiency of the trowel. 
     Turning to  FIGS. 9-12 , and alternative embodiment of a module suitable for trowel  20  ( FIG. 1 ) has been designated by the reference numeral  29 B. This embodiment is advantageous when servicing the trowel. CVT power is delivered into the module  29 B from the side opposite that employed with module  29 . 
     The alternative CVT module  29 B is mounted similarly to embodiment  29  discussed above. The power input end of the CVT module  29 B has been generally designated by the reference numeral  46 B. The power output flywheel  50 B ( FIG. 10 ) drives PTO shaft  51 B that is coaxial with flywheel  50 B. Portions of the engine outer wall  52 B are fragmented as in  FIG. 10 . Engine-driven shaft  51 B penetrates a bearing  201  and U-joint assembly  206  and is anchored in thrust bearing  202  and passes through pillow block  203 . Shaft  51 B penetrates taper lock bushing  204  that is coaxially centered within a first pulley  60 B that drives a lower diameter second pulley  64 B via entrained belt  62 B. Pulley  60 B is thus driven by PTO shaft  51 B. Pulley  64 B thus rotates faster than PTO shaft  51 B. Pulley  64 B is splined to a first jackshaft  66 B that penetrates it and terminates through a bushing  69 B  54  proximate the engine. Jackshaft  66 B rotates at a higher speed and lower torque than the engine shaft  51 B. 
     Jackshaft  66  reaches the second stage  67 B ( FIG. 10 ) of the CVT module through a bearing  70 B and terminates within and is splined to a variable drive CVT pulley assembly  84 B in second stage  67 B. Pulley assembly  84 B can change its effective diameter, varying the speed and torque transmitted to lower CVT pulley  88 B by a second or CVT belt  89 B. CVT pulley  84 B will be driven by jackshaft  66 B at a higher speed than the engine shaft  51 B, therefore operating at a lower torque. The CVT unit  84 B comprises a first and preferably upper CVT pulley  85 B with cooperating, conical halves  87 C and  87 D that are axially spaced apart a distance that establishes the belt gear ratio. 
     Preferably a second jackshaft  92 B is positioned below jackshaft  66 B and is splined through lower CVT pulley  88 B. The CVT belt  89 B extends to lower CVT pulley  88  from the upper CVT pulley. Jackshaft  92 B extends from a roller bearing  95 B and extends through a bushing  99 B to the third stage of the CVT module that has generally been designated by the reference numeral  100 B ( FIG. 11 ). 
     Referring now to  FIGS. 10-12 , jackshaft  92 B terminates within stage  100 B through bearing  102 B and runs to a third pulley  104 B. A third belt  108 B entrained over pulley  104 B drives a larger diameter, fourth pulley comprising lower gearbox drive pulley  111 B that is coupled to the gearbox drive shaft  113 B. Gearbox drive shaft  113 B is supported by a pair of spaced-apart bearings  116 B ( FIGS. 10 ,  11 ), and  118 B. The rotors  24 B are gearbox driven by the gearbox shafts  113 B. 
     From the foregoing, it will be seen that this invention is one well adapted to obtain all the ends and objects herein set forth, together with other advantages which are inherent to the structure. 
     It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. 
     As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.