Abstract:
A vibration generating machine and method of use is provided. The vibration generating machine includes a work piece such as screed blade and a vibration generator for imparting vibrations to the work piece. The machine is guided by a handle mounted on the work piece by a monolithic handle mount. The monolithic handle mount includes a lower section for mounting directly or indirectly to the work piece, an upper section at least indirectly supporting a handgrip, and an intermediate section having a partial coil that reduce the transmission of vibrations therethrough.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates generally to hand guided vibratory machines and, more particularly, relates to a vibratory machine with monolithic handle mount that reduces the transmission of vibrations to the operator. The invention additionally relates to a method of operating such a machine. 
         [0003]    2. Discussion of the Related Art 
         [0004]    Many hand guided machines employ vibratory action. Examples of such machine include vibratory plates or tampers for compacting soil and vibratory wet screeds for leveling and smoothing freshly poured concrete. While these various machines may differ in purpose and function, they all employ a vibratory generator to impart vibrations to a work piece such as a ground-engaging plate or shoe or a concrete-engaging blade. 
         [0005]    One specific example of a known hand guided vibratory machine is a vibratory wet screed. The vibratory wet screed employs an elongated blade that extends over a surface of freshly poured wet concrete. A motor, mounted above the blade, activates a vibration generator, which in turn imparts a vibration through the elongated blade. An operator grasps a handle extending above the elongated blade, and pulls the vibrating elongated blade over the concrete surface while simultaneously walking backwards. As a result, the vibratory action of the blade smoothes and levels the wet concrete. 
         [0006]    Prior to the introduction of the vibratory wet screed, the process of screeding wet concrete was a manual task. Manual wet screeding typically involved at least two laborers dragging opposite ends of an elongated piece of two-by-four lumber board over a rough surface of wet concrete. Additional laborers would shovel and rake the concrete into position ahead of the approaching screeding board, to ensure that no voids or shallow areas remained in the smooth surface of the concrete after the screeding board had passed. This manual wet screeding process is labor intensive, requiring at least two individuals positioned at opposite ends to drag the screeding board. On average, this manual process would limit a crew of six laborers to pouring and screeding a slab of 6,000 to 8,000 square feet per day. Furthermore, this manual approach is time consuming, physically fatiguing, and often results in uneven or inconsistence results, due in part to the lack of vibration imparted onto the wet concrete surface. Additionally, manual manipulation of concrete typically requires additional water to be added to the concrete mixture, as to increase the workability of the uncured concrete product. However, increasing the water component results in both prolonged curing times as well as increases the presence of voids or weaknesses within the resulting cured concrete slab. 
         [0007]    As a result of the many disadvantages of manual wet screeding, the use of vibratory wet screed machines has become an industry standard. However, operation of vibratory wet screed machines presents drawbacks of their own. Most notably, the vibration produced by the vibration generator is not localized to the elongated blade, but rather is transmitted throughout the entire wet screed machine, including through the handle mounts to the handle. According to this undesirable vibration, an individual operating a vibratory wet screed may become fatigued after operating the vibratory wet screed for a prolonged period of time. To ensure that operators are not exposed to such fatiguing effects, regulatory and standard setting agencies in the United States, Europe, and elsewhere have issued guidelines relating to the operation of vibrating tools. These guidelines indicate that machines which impart a hand-arm vibration (HAV) value of 5.0 or greater onto the operator must comply with additional reporting requirements and operating limitations. 
         [0008]    To reduce this undesired vibration, some vibratory wet screed machines utilize resilient mounting components between the handle mounts and the screed blade and/or at other locations in the vibrational path from the screed blade to the handles to insulate the handles from vibration. However, these resilient mounting components reduce the ability of the operator to adequately control the pitch, direction and rotation of the elongated blade. Specifically, the “give” of these elements leads to movement of the handles relative to the screed blade, resulting in a reduction in responsiveness. Furthermore, these additional components add unnecessary weight to the machine. Added weight is undesirable because it is generally preferable to make vibratory wet screeds and other hand guided machines as light as possible to reduce operator effort. 
         [0009]    Despite these prior attempts to limit the transmission of vibrations to the handles of hand operated vibratory machines, there remains need for improvement. In light of the foregoing, a handle mount configured to reduce the transmission of vibration originating in the vibration generating component of the portable hand operated machine is desired. 
       SUMMARY OF THE INVENTION 
       [0010]    One or more of the above-identified needs are met by providing an improved handle mount for use in a vibratory machine that reduces the transmission undesirable vibrations to the machine&#39;s handles. The apparatus is ideally suited for use with vibratory wet screeds, but is usable with other vibratory hand operated machines as well such as tampers and vibratory plate compactors. 
         [0011]    In accordance with a first aspect of the invention, a handle mount is configured for mounting on a portable vibratory machine having a vibration generator that produces a vibration along an attached workpiece. The handle mount comprises a monolithic element having a partial coil located along its length. The partial coil is flanked by a lower section mounted at least indirectly to the workpiece, and an upper section at least indirectly bears a handgrip for use by the operator. The partial coil effectively acts a spring that reduces the transmission of vibrations originating at the vibration generator. 
         [0012]    In accordance with another aspect of the invention, the monolithic handle mount may include additional curved elements, allowing the handgrips to be positioned in an ergonomically preferred location for the use of the operator. 
         [0013]    The partial coil and any additional curved elements may further provide a protective guard protecting the side of the machine&#39;s engine. Furthermore, the additional curved elements may effectively orient the partial coil to lie in a preferred plane to maximize vibration reduction in that plane. 
         [0014]    In accordance with yet another aspect of the invention, a method of operating a vibratory hand operated machine is provided having a vibration absorbing handle mount located between the vibration generator and the handle grips that are held by the operator. 
         [0015]    These and other objects, advantages, and features of the invention will become apparent to those skilled in the art from the detailed description and the accompanying drawings. It should be understood, however, that the detailed description and accompanying drawings, while indicating preferred embodiments of the present invention, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    A preferred exemplary embodiment of the invention is illustrated in the accompanying drawings in which like reference numerals represent like parts throughout, and in which: 
           [0017]      FIG. 1  is a front plan view of a hand guided vibratory machine constructed in accordance with a preferred embodiment of the invention; 
           [0018]      FIG. 2  is a perspective view of the machine of  FIG. 1 ; 
           [0019]      FIG. 3  is a right-side elevation view of the machine of  FIG. 1  with an operator; 
           [0020]      FIG. 4  is a partially exploded perspective view the machine of  FIG. 1 ; 
           [0021]      FIG. 5  is a perspective view of a lower handle mount of a handle assembly of the machine of  FIGS. 1-4 , viewed from in front of, below, and from the left side of the handle mount; 
           [0022]      FIG. 6  is a front elevation view of the handle mount of  FIG. 5 ; 
           [0023]      FIG. 7  is a graph indicating the HAV measured at the upper section of the of the lower handle mount of various embodiments, including a preferred embodiment of the invention; 
           [0024]      FIG. 8  is a graph indicating the HAV measured at both the lower section and the upper section of the of the lower handle mount, in accordance with a embodiment known in the prior art, and 
           [0025]      FIG. 9  is a graph indicating the HAV measured at both the lower section and the upper section of the of the handle mount, in accordance with a preferred embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0026]    A wide variety of handle mounts for vibrating hand operated machines could be constructed in accordance with the invention as defined by the claims. Hence, while the preferred embodiments of the invention will now be described with reference to a portable vibratory wet screed machine, it should be understood that the invention is in no way so limited. For instance, it is also usable with a variety of different portable vibratory machines that are potentially subject to undesired vibration transmission through the handle. 
         [0027]      FIG. 1  illustrates a front plan view of a handle  20  constructed in accordance with one embodiment of the invention. Generally, the vibratory wet screed machine  22  includes an engine  24  coupled to a vibration generator  26 . The vibration generator  26  typically includes an eccentric mass that is driven to rotate by an output shaft of the engine  24 . The engine  24  and vibration generator  26  are mounted on a frame  28  located at a center of an elongated blade  30 . A handle assembly  32  is attached to the frame  28  at its lower end  34 , and terminates in handgrips  36  at its upper end, located at its upper section  38 . In operation, the elongated blade  30  is passed over a freshly poured wet concrete surface as vibrations are imparted to the blade  30  by the engine  24  and the vibration generator  26 , thus leveling and partially smoothing the wet concrete. Blade  30  orientation and movement are controlled by an operator  40  grasping the handle assembly  32 . 
         [0028]    The engine  24  of this exemplary embodiment, as seen in  FIGS. 1-4 , is a 4-stroke internal combustion engine of the type generally used for vibratory wet screeds. The engine  24  includes an engine block  102 , crankcase  104 , fuel tank  106 , clutch housing  108 , and carburetor (not shown). A clutch is coupled to a drive shaft (not shown), which in turn is coupled to the input shaft  110  of the vibration generator  26 . The engine  24  may also include a starter  112 . Engine speed is controlled by an externally located throttle actuation lever  114 . 
         [0029]    Referring especially to  FIG. 4 ; the vibration generator  26  of the illustrated embodiment preferably includes an imbalance functionally coupled to the input shaft  110 . The input shaft  110  is rotationally coupled to the drive shaft of the engine  24  at a flex joint (not shown). The imbalance of the vibration generator  26  may consist of a either adjustable or fixed weights contained within an external housing  116 . 
         [0030]    As mentioned above, the engine  24  and vibration generator  26  of an illustrated embodiment are coupled to the elongated blade via a frame  28 . Referring to  FIG. 4 , the frame  28  includes a support bracket  118  that is fastened to the upper surface of the screed blade and extends in a forward-aft plane above the screed blade  30 . The support bracket  118  has a series of apertures  120  configured to receive fastener elements  122  such as bolts therein. The upper surface of the support bracket  118  is configured to receive a mounting plate  124  thereon. The mounting plate  124  also includes a series of apertures  126 , located at positions consistent with those of the support bracket  118 , such that fastener elements  128  could pass through both aperture sets and couple the support bracket  118  to the mounting plate  124 . The engine  24  is received on the center of the upper surface of the mounting plate  124 , and may be supported by the shaft housing  130 . In this configuration, the vibration generator  26  extends below the support bracket  118 , such that it is in indirect operational engagement with the elongated blade  30  by way of the support bracket  118 . Additionally, the mounting plate  124  extends laterally beyond the engine  24 , thereby providing a handle assembly  32  mounting surface disposed on either side of the engine  24 . A pair of vibration inhibitors  132  are located between the support bracket  118  and the engine mounting plate  124  in order to absorb undesirable vibrations originating at the vibration generator  26 , located below the support bracket  118 . The vibration inhibitors  132  of this embodiment take the form of two rectangular rubber pads or shock mounts that extend the width of the frame  28 . They may have a Durometer rating of 50. 
         [0031]    As previously indicated, and illustrated in  FIGS. 1-3 , the elongated blade  30  is affixed to the engine  24 , vibration generator  26  and handle assembly  32  via the support bracket  118 . The blade  30  or screed of this embodiment is formed from extruded aluminum and is of an L-shaped cross section, having a vertical portion at a leading edge  134  thereof and a horizontal portion that extends forwardly from vertical portion to a trailing edge  136 . The leading edge  134  of the elongated blade  30 , i.e. that edge which first engages the freshly poured wet concrete, is positioned along the rear of the vibratory wet screed  22 , and is directed nearest the location of the operator  40 . The trailing edge  136  of the elongated blade  30  is positioned along the front of the vibratory wet screed, farthest from the location of the operator  40 . The horizontal portion of the elongated blade  30  may be comprised of flat surfaces, or may include raised rails  138  to provide additional structural support and additional means for vibration transmission along the length of the elongated blade  30 . Mounting holes  140  are formed in the central portion of the vertical portion for receiving the fasteners  122  for the mounting bracket  118 . 
         [0032]    Referring to  FIGS. 1 ,  2 , and  4 , the handle assembly  32  of this embodiment includes left and right subassemblies  200 L and  200 R located on either side of the engine  24  and connected to one another by a cross-bar  201 . The handle assembly  32  may further include a pivoting kickstand  202  for supporting the vibratory wet screed machine  22  in an upright orientation when not in operation. Each handle subassembly  200 L or  200 R includes a handgrip  36 , an upper handle mount  204 , and a lower handle mount  206 . Handles  208  are mounted on the upper ends of the upper handle mounts  204  and receive the handgrips  36 . The throttle actuation lever  114  is coupled to one of the handles  208  adjacent the associated handgrips  36 . The lower handle mount  206  of each handle assembly  32  terminates in a mounting bracket  210  configured to be attached to a handle assembly-mounting surface of the mounting plate  124 , disposed on either side of the engine  24 . The mounting bracket  210  is attached to the mounting plate  124  with traditional threaded fasteners  212 . The left and right subassemblies  200 L and  200 R are substantial mirror images of one another. The left lower handle mount  206  will now be detailed, it being understood that the description thereof applies equally to the right handle mount  206 . 
         [0033]    Turning now to  FIGS. 6-7 , the left lower handle mount  206  takes the form of a monolithic element. A “monolithic element” as used herein means that the element in question (the lower handle mount  206  in the present case) is formed from a single piece without the use of removable fasteners such as bolts or screws. That does not necessarily mean that the element must be formed from a single structure. For example, it could take the form of multiple tubing sections of the same or different materials that are welded together. In the illustrated embodiment, however, the monolithic handle  214  is fabricated of a single continuous piece of hollow metal contoured tube, which is welded to the mounting bracket  210  at the lower section. The tube is contoured by bending to have upper and lower straight sections  216 ,  218  separated from one another by a partial coil  220  and intermediate segments  222 ,  224 . The partial coil  220  acts as a spring for reducing the transmission of vibrations to the upper straight section  216 . The upper intermediate segment  222  includes a short straight section  226  at the upper end of the partial coil  220  and a curved section  228  that serves as a “break” that assures that the associated short straight section  226  is non-tangential to the partial coil  220 . Similarly, the lower intermediate segment  224  includes a short straight section  230  at the lower end of the partial coil and a curved section  232  that serves as a “break” that assures that the associated short straight section  230  is non-tangential to the partial coil  220 . Specifically, the combination of the partial coil  220 , curved sections  228 ,  232  and interposed short straight sections  226 ,  230  within the monolithic handle  214  results in forming of an indirect path of vibration travel between the vibration generator  26  and the operator  40 . This collective shape of the monolithic handle  214  further changes the mode shape of the system, moving excitation frequencies out of the range of operation of the engine  24  for the application. These intermediate segments  222 ,  224  also assure that the upper and lower section  216 ,  218  of the lower handle mount  206  are oriented in a manner that assures alignment of the mounting bracket  210  with the mounting plate  124  and also assure extension of the upper handle mount  204  in a direction that assures the desired ergonomic positioning of the handle  208  and handgrips  36 . 
         [0034]    The partial coil  220  includes a curvature having a radius of approximately 3.0 inches. The partial coil  220  is oriented such that it exhibits a degree of leaf spring-like flexibility while in operation, sufficient for reducing the transmission of vibrations along the handle assembly  32 . The partial coil  220  simultaneously exhibits a significant degree of rigidity as to allow the static load of the machine  22  to be transmitted to the handgrips  36  without deflection and not inhibit an operator&#39;s manipulation of the machine  22 . The partial coil  220  is oriented such that it lies in and effectively dampens two axes of undesired vibration, namely the vertical axis of the machine  22  and the fore-and-aft axis of the machine  22 . It is also considered within the scope of the invention that the partial coil  220  additionally could be oriented to lie in a third axis of undesired vibration, namely the longitudinal axis of the machine  22 . Such undesirable vibration may originate in the vibration generator  26  and/or the engine  24 . The partial coil  220  of the illustrated embodiment exhibits a spring constant of approximately 0.80 kg/mm along the fore-and-aft axis of the machine  22 , 0.76 kg/mm along the longitudinal axis of the machine  22 , and 0.40 kg/mm along the vertical axis of the machine  22 . The partial coil  220  of the illustrated embodiment exhibits an arc length maximized to suppress undesirable vibration without sacrificing maneuvering control. That arc length is 149.8 mm at the centerline of the monolithic handle  214 , in the illustrated embodiment, but could vary significantly, such as between 75 and 250 mm. That arc angle is 112.3 degrees in the illustrated embodiment, but could vary significantly, such as between 75 and 200 degrees. Accordingly, the illustrated embodiment of the partial coil  220  will sufficiently suppress vibrations oriented in the along a vertical axis and a fore-and-aft axis of the machine  22 , without imparting significant reduction on operator  40  steering torque. This reduction in undesirable vibrations will result in diminished occurrence of fatigue experienced by an operator  40 . The intermediate curved segments  222 ,  224  may, if desired, also have a radius of approximately 3.0 inches, hence facilitating fabrication by permitting the use of the same bending tool to form all curved sections. However, the arc length of the additional curved segments  222 ,  224  can be much less than that of the partial coil  220 , as see in  FIGS. 6-7 . In an illustrated embodiment, the arc length of the upper intermediate curved segments  222  is 46.3 mm at the centerline of the monolithic handle  214 , and has an arc angle of 34.8 degrees. In the illustrated embodiment, the arc length of the lower intermediate curved segments  224  is 46.7 mm at the centerline of the monolithic handle  214 , and has an arc angle of 35.1 degrees. However, various alternative arc angles and arc lengths of the intermediate curved segments  222 ,  224  are considered within the scope of this invention. The section of the handle mount  206  between the bottom end of the lower curved section  232  to the upper end of the upper curved section  228  preferably has a length of about 350 mm. 
         [0035]    It should be noted that the partial coil  220  and intermediate curved segments  222 ,  224  of the handle mount  206  also serve as a guard that extends along the sides of the engine  24 , thereby preventing damage to the engine  24  if the screed machine  22  were to fall or be placed on its side when not in operation. Also, the intermediate curved segment  222  located between the partial coil  220  and the upper section  216  may direct the handle mount  206  upwards, to provide an ergonomic orientation of the handle  208  and handgrips  36 , for engagement by the operator  40 . 
         [0036]    In operation, an operator  40  starts the engine  24 , and engagement of the clutch causes the drive shaft to rotate. Manipulating the throttle actuation lever  114  adjusts the operating speed of the engine drive shaft, which ranges from 4,000 to 8,000 rpm, and more preferably 6,000 to 7,000 rpm in standard operating conditions. The rotation of the drive shaft causes the input shaft  110  of the vibration generator  26  to rotate. The input shaft  110  then rotates the imbalance located within the vibration generator  26  to produce vibrations. The vibrations are transmitted to elongated blade  30  and propagate through the blade  30  in a generally sinusoidal pattern. These vibrations typically have a magnitude of about 9-13 HAV at standard engine operating speeds of, e.g., 6,500 rpm. Some of these vibrations are transmitted to the mounting plate  124  through the support bracket  118  and thence to the lower section  34  of the handle assembly  32 , i.e. the lower section  218  of the lower handle mounts  206 . However, a substantial portion of those vibrations are damped by the partial coils  220  in the lower handle mounts  206 . The magnitude of the vibrations induced by the vibration generator  26  are proportional to the speed at which the engine  24  drive shaft rotates. In addition to generating increased vibrations in the vibration generator  26 , an engine  24  running at high speed may also form significant vibration that will be distributed throughout the vibratory wet screed  22 . Specifically, an engine  24  operating at a speed greater than 6,000 rpm may impart a vibration of between 2.0 and 3.0 HAV into the mounting plate  124  and thus to the lower ends of the lower section  218  of the lower handle mounts  206 . Accordingly, at optimal operating speed, the partial coil  220  of the handle mounts  206  may suppress vibrations originating in the engine  24 , as well as those vibrations originating in the vibration generator  26 . 
         [0037]    Tests have confirmed that that partial coil  220  of each lower handle mount  206  is capable of significantly reducing the transmission of vibrations transmitted to the lower handle mount  206  by the vibration generator  26  and the engine  24 . In fact, assuming an input vibration at the lower section  218  of the lower handle mounts  206  of 14 HAV, tests have shown that the vibrations at the upper section  216  of the lower handle mounts  206  are reduced to less than 10 HAV. In fact, those vibrations are reduced to less than 7 HAV and even less than 5 HAV. In these tests, the engine  24  was operated at a series of operational speeds. At these specified operational speeds, hand-arm vibration (HAV) values were measured first at the location of the lower section  34  of the handle assembly  32 , i.e. the lower section  218  of the lower handle mount  206 . A second set of HAV values was measured at the location of the handgrips  36 , i.e. upper section of the handle  208 . The operational speed of the engine  24  was recording in rotations per minute (rpm) and the hand-arm vibration value was measure in units of meters per second squared (m/ŝ2). The results of this test are reflected in tabular form in Table 1 and graphically in  FIGS. 7 and 9 . Specifically,  FIG. 7  includes graph  300 , which depicts the HAV values measured at the location of the handgrips  36 , over an engine  24  operational speed ranging from 5,000 rpm to 8,000 rpm. Dashed line  302  represents the vibrations measured at the handgrips  36  for a vibratory wet screed comprising relatively straight lower handle mounts, lacking a partial coil  220 , as is known in the prior art. Broken line  304  represents the vibrations measured at the handgrips  36  for an alternative vibratory wet screed embodiment comprising lower handle mounts, incorporating a 4.0 inch radius within the prior art design using a relatively straight lower handle mount. Solid line  306  represents the vibrations measured at the handgrips  36  of the vibratory wet screed  22  of the present invention, comprising a partial coil  220  having a radius of 3.0 inches. 
         [0038]      FIG. 9  includes graph  320 , which depicts the HAV values measured at the vibratory wet screed  22  of the present invention, over an engine  24  operational speed ranging from 5,000 rpm to 8,000 rpm. Broken line  322  represents the vibration measured at the lower section  218  of the lower handle mount  206 . Solid line  324  represents the corresponding vibration measured at the location of the handgrips  36 , after the vibrations have been dampened by the partial coil  220 . 
         [0000]    
       
         
               
             
               
               
               
             
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Vibration Reduction of Handle Comprising a Partial Coil 
               
             
          
           
               
                 Engine Operational 
                 HAV Value at Lower 
                 HAV Value at Upper 
               
               
                 Speed 
                 Section of Handle 
                 Section of Handle 
               
               
                 (rpm) 
                 (m/s{circumflex over ( )}2) 
                 (m/s{circumflex over ( )}2) 
               
               
                   
               
             
          
           
               
                 5,000 
                 8.1 
                 4.8 
               
               
                 5,500 
                 7.6 
                 6.1 
               
               
                 6,000 
                 14.3 
                 4.7 
               
               
                 6,500 
                 15.7 
                 3.7 
               
               
                 7,000 
                 14.7 
                 3.5 
               
               
                 7,500 
                 13.8 
                 4.4 
               
               
                 8,000 
                 13.7 
                 5.8 
               
               
                   
               
             
          
         
       
     
         [0039]    The previous test was then repeated while utilizing a vibratory wet screed comprising relatively straight lower handle mounts, lacking a partial coil, as is known in the prior art. Specifically, the handle had essentially the shape of the handle illustrated in U.S. Pat. No. 7,175,365. The results of this test are reflected in tabular form in Table 2 and graphically in  FIGS. 7 and 8 .  FIG. 8  includes graph  310 , which depicts the HAV values measured utilizing a vibratory wet screed comprising relatively straight lower handle mounts, lacking a partial coil, as is known in the prior art, over an engine  24  operational speed ranging from 5,000 rpm to 8,000 rpm. Broken line  312  represents the vibration measured at the lower section of the lower handle mount. Solid line  314  represents the corresponding vibration measured at the location of the handgrips, after the vibrations have been transmitted through the handle assembly. 
         [0000]    
       
         
               
             
               
               
               
             
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Vibration Reduction of Handle Not Comprising 
               
               
                 a Partial Coil (Prior Art) 
               
             
          
           
               
                 Engine Operational 
                 HAV Value at Lower 
                 HAV Value at Upper 
               
               
                 Speed 
                 Section of Handle 
                 Section of Handle 
               
               
                 (rpm) 
                 (m/s{circumflex over ( )}2) 
                 (m/s{circumflex over ( )}2) 
               
               
                   
               
             
          
           
               
                 5,000 
                 7.6 
                 5.3 
               
               
                 5,500 
                 8.6 
                 6.8 
               
               
                 6,000 
                 10.3 
                 11.3 
               
               
                 6,500 
                 11.6 
                 14.9 
               
               
                 7,000 
                 8.5 
                 9.3 
               
               
                 7,500 
                 6.6 
                 4.3 
               
               
                 8,000 
                 5.5 
                 7.9 
               
               
                   
               
             
          
         
       
     
         [0040]    As indicated in Table 1 and by the lines  306  in  FIG. 7 , the test results show that, when the engine is operated at a speed of between 6,000 and 7,000 rpm, the ideal operating speed of a vibratory wet screed machine, the resulting HAV vibration measured at the handgrips is less than or equal to 4.7 m/ŝ2, for the lower handle mount having a partial coil as described above. Furthermore, the test results from Table 1 indicate that the average reduction in HAV vibration measurement from the lower handle mount, as compared to the handgrip each handle subassembly, is 62.7 percent, over the entire engine operation speed spectrum, for the handle comprising the partial coil. Alternatively, as indicated in Table 2, the test results show that the vibratory wet screed comprising a traditional relatively straight lower handle mount, without a partial coil, exhibited a peak HAV value of 14.9 m/ŝ2 while operating at 6,500 rpm. Furthermore, the test results from Table 2 indicate that the average reduction in HAV vibration measurement from the lower section of the handle, as compared to the upper section of the handle is only 3.6 percent, over the entire engine operation speed spectrum, for the handle comprising the traditional straight handle, without a partial coil. The use of the lower handle mount with the integral partial coil thus reduces vibrations at the upper portions of the handle by 62.7 percent on average and by 75.1 percent at the “sweet spot” of engine operation at 6,500 RPM. 
         [0041]    Further tests have confirmed that that partial coil  220  of each lower handle mount  206  is capable of significantly reducing the transmission of vibrations transmitted to the lower handle mount  206  by the vibration generator  26  and the engine  24 , while exhibiting decreased deflection in response to operator  40  applied force. In this test, the handle assembly  32  according to the illustrated embodiment of the present invention was fastened to a fixed location at the mounting bracket  210 . The height of the handle  208  of the right handle subassembly  200 R was then measured to establish a baseline value. In order to simulate the twist motion of an operator trying to maneuver only one side of the blade, weight of 30 lbs. (13.61 kg) was then suspended from the right hand grip of the handle  208 , and a deflection distance of 17.0 mm was measured in the handle assembly  32 , along the fore-and-aft axis of the machine  22 . The test was then repeated with the handle assembly  32  repositioned to measure deflection about the vertical and horizontal axis of the machine  22 . The results of these tests are reflected below in Table 3. According to the measurements obtained, the spring constant values of the handle assembly  32 , including a partial coil  220 , in accordance with the present invention were calculated for each axis of the machine  22 . These spring constant values are similarly presented in Table 3. 
         [0000]    
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 Deflection of a Handle Assembly Comprising a Partial Coil 
               
             
          
           
               
                   
                 Undeflected 
                 Deflected 
                   
                   
               
               
                   
                 Height of 
                 Height of 
                 Change in 
               
               
                   
                 Handles without 
                 Handles with 
                 Height of 
                 Spring 
               
               
                 Axis of 
                 Weight 
                 Weight 
                 Handles 
                 Constant 
               
               
                 Deflection 
                 (mm) 
                 (mm) 
                 (mm) 
                 (kg/mm) 
               
               
                   
               
             
          
           
               
                 Longitudinal 
                 782.0 
                 764.0 
                 18.0 
                 0.76 
               
               
                 Fore-And- 
                 730.0 
                 713.0 
                 17.0 
                 0.80 
               
               
                 Aft 
               
               
                 Vertical 
                 1628.0 
                 1594.0 
                 34.0 
                 0.40 
               
               
                   
               
             
          
         
       
     
         [0042]    The test was then performed while utilizing the handle assembly of a vibratory wet screed comprising relatively straight lower handle mounts, lacking a partial coil, as is known in the prior art. Specifically, the handle assembly had essentially the shape of the handle illustrated in U.S. Pat. No. 7,175,365. After being fastened to a fixed location, the height of the handle was measured to establish a baseline value. A weight of 30 lbs. (13.61 kg) was then suspended from the handgrip of the right handle subassembly, and a deflection distance of 27.0 mm was measured in the handle, along the fore-and-aft axis of the machine. 
         [0043]    The test was then repeated with the handle assembly repositioned to measure deflection about the vertical and horizontal axis of the machine. The results of these tests are reflected below in Table 4. According to the measurements obtained, the spring constant values of the handle assembly, comprising relatively straight lower handle mounts, lacking a partial coil, as is known in the prior art were calculated for each axis of the machine. These spring constant values are similarly presented in Table 4. 
         [0000]    
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 4 
               
             
             
               
                   
               
               
                 Deflection of the Handle Assembly Not 
               
               
                 Comprising a Partial Coil (Prior Art) 
               
             
          
           
               
                   
                 Undeflected 
                 Deflected 
                   
                   
               
               
                   
                 Height of 
                 Height of 
                 Change in 
               
               
                   
                 Handles without 
                 Handles with 
                 Height of 
                 Spring 
               
               
                 Axis of 
                 Weight 
                 Weight 
                 Handles 
                 Constant 
               
               
                 Deflection 
                 (mm) 
                 (mm) 
                 (mm) 
                 (kg/mm) 
               
               
                   
               
             
          
           
               
                 Longitudinal 
                 771.0 
                 755.0 
                 16.0 
                 0.85 
               
               
                 Fore-And- 
                 700.0 
                 673.0 
                 27.0 
                 0.50 
               
               
                 Aft 
               
               
                 Vertical 
                 1730.0 
                 1708.0 
                 22.0 
                 0.62 
               
               
                   
               
             
          
         
       
     
         [0044]    Resultantly, this test demonstrates that the handle assembly  32  of the present invention, incorporating a partial coil  220 , exhibits a 37.0 percent decrease in deflection in the direction of operator pull, i.e. fore-and-aft axis of the machine  22 , as compared to relatively straight lower handle mounts, lacking a partial coil, as is known in the prior art. This decreased deflection along the fore-and-aft axis is consistent with the greater fore-and-aft axis spring constant exhibited in the present invention. In operation, the diminished deflection in the direction of operator pull is realized through improved maneuverability of the machine  22 , according to the present invention. Moreover, the handle assembly  32  of the present invention exhibits a lower spring constant along both the longitudinal and vertical axis of the machine  22 , as compared to the relatively straight lower handle mounts, lacking a partial coil. 
         [0045]    Many changes and modifications could be made to the invention without departing from the spirit thereof. For instance, the handle assembly may be composed entirely of the monolithic handle, or may alternatively the monolithic handle may be combined with additional handle assembly components. The invention is also applicable to vibratory rammers, portable plate compactors, pneumatic vibrators and other similar portable vibratory hand operated machines, which would benefit from reduction in undesirable vibration transmission through a handle as provided in the current invention. The scope of other changes and modifications will become apparent from the appended claims.