Abstract:
A vibratory mechanism  26  is provided for a compacting work machine  10 . The vibratory mechanism  26  includes a first/outer eccentric weight  50  and a second/inner eccentric weight  80 . The second weight  80  has a cavity  88  with a movable mass  90  that when rotated in a first direction  124  opposes the first eccentric weight  50  and when rotated in a second direction  126  the movable mass  90  combines with the first eccentric  50 . The second eccentric weight  80  is also manually indexable relative to the first eccentric  50  to a plurality of distinct positions giving a plurality of different amplitude vibratory impact forces when rotated in either of the first and second directions  124,126.

Description:
TECHNICAL FIELD  
         [0001]    This invention relates to a vibratory mechanism for a compacting machine and more specifically to a vibratory mechanism that is selectable between a variety of distinct amplitude and frequency settings.  
         BACKGROUND  
         [0002]    Compacting work machines are supported on one or more rotating drums that are used to roll over compactable materials, such as soil and aggregates, during the fabrication of roadways. The rotating drums include vibratory mechanisms mounted coaxially within the rolling drum to increase the compacting force during operation. It is desirable to have a mechanism that is adjustable so as to vary the amplitude and frequency of the compacting force so that the compacting machine is always at peak efficiency.  
           [0003]    Many different vibratory mechanisms have been developed and used that create variable amplitude and frequency vibratory forces for compacting. However, many of these mechanisms are complicated and use a number of moving parts to index one eccentric weight relative to another to obtain a variable amplitude force. One such mechanism is disclosed in U.S. Pat. No. 4,481,835 issues on Nov. 13, 1985 and assigned to Dynapac Maskin AB. This system utilizes a first/outer cylindrical eccentric weight coaxially aligned with a second/inner cylindrical eccentric weight, both weights are rotatably supported on a shaft. The weights are drivingly connected to the shaft by a pin that is diametrically positioned through spiral grooves in the outer weight and a pair of spiral grooves in the inner weight and the shaft. The grooves in the outer weight spiral in the opposite direction of the outer weight. The rod of a single action hydraulic cylinder is positioned in an axial hollow opening of the shaft so as to push against the pin. When the rod is extended the outer weight and the inner weight index relative to one another via the spiral grooves. A spring is used to return the weights to a fixed position. This system is effective but complicated and requires a hydraulic cylinder to be rotatably mounted coaxial with a fluid drive motor that propels a rolling drum.  
           [0004]    The present invention is directed to overcome one or more of the problems as set forth above.  
         SUMMARY OF THE INVENTION  
         [0005]    In one aspect of the present invention a vibratory mechanism is provided. The vibratory mechanism includes a first eccentric weight having a first and a second stub shaft, which are rotatably supported by a pair of bearings.  
           [0006]    A second eccentric weight is coaxially rotatably supported on a shaft positioned within the first eccentric weight. A movable mass is contained within a hollow cavity in the second eccentric weight. An adjustment shaft is coaxially positioned within the first stub shaft and is operatively connected to the first and second eccentric weights and used for indexing the second eccentric weight relative to the first eccentric weight. Lastly, a motor is attached with the second stub shaft. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    [0007]FIG. 1 is a side elevational view of a work machine embodying the present invention;  
         [0008]    [0008]FIG. 2 shows an axial cross section view taken along line  2 - 2  through a rolling drum of the compacting machine of FIG. 1 embodying the present invention;  
         [0009]    [0009]FIG. 3 is an enlarged view of the vibratory mechanism shown in FIG. 2;  
         [0010]    [0010]FIG. 4 is an enlarged view taken along lines  4  of FIG. 3;  
         [0011]    [0011]FIG. 4 a  is an enlarged view taken along lines  4 - 4  of FIG. 3 with the driver shown in an indexable orientation;  
         [0012]    [0012]FIG. 5 is cross sectional view taken along line S-S of FIG. 2 showing the location of the movable mass in a first location and with the second eccentric indexed to position one relative to the first eccentric weight;  
         [0013]    [0013]FIG. 6 is cross sectional view taken along line S-S of FIG. 2 showing the location of the movable mass in a second location and with the second eccentric indexed to position two relative to the first eccentric weight;  
         [0014]    [0014]FIG. 7 is cross sectional view taken along line S-S of FIG. 2 showing the location of the movable mass in a first location and with the second eccentric indexed to position one relative to the first eccentric weight; and  
         [0015]    [0015]FIG. 8 is cross sectional view taken along line S-S of FIG. 2 showing the location of the movable mass in a second location and with the second eccentric indexed to position two relative to the first eccentric weight. 
     
    
     DETAILED DESCRIPTION  
       [0016]    A work machine  10  for increasing the density of a compactable material  12  such as soil, gravel, or bituminous mixtures an example of which is shown in FIG. 1. The work machine  10  is for example, a double drum vibratory compactor, having a first compacting drum  14  and a second compacting drum  16  rotatably mounted on a main frame  18 . The main frame  18  also supports an engine  20  that has a first and a second fluid pump  22 , 24  conventionally connected thereto.  
         [0017]    The first compacting drum  14  includes a first vibratory mechanism  26  that is operatively connected to a first fluid motor  28 . The second compacting drum  16  includes a second vibratory mechanism  30  that is operatively connected to a second fluid motor  32 . The first and second fluid motors  28 , 32  are operatively connected, as by fluid conduits and control valves not shown, to the first fluid pump  22 . It should be understood that the first and second compacting drums  14 , 16  might have more than one vibratory mechanism per drum without departing from the spirit of the present invention.  
         [0018]    In as much as, the first compacting drum  14  and the second compacting drum  16  are structurally and operatively similar. The description, construction and elements comprising the first compacting drum  14 , as shown in FIG. 2, applies equally to the second compacting drum  16 . Rubber mounts  36  vibrationally isolate the compacting drum  14  from the main frame  18 . The first compacting drum  14  includes a fluid motor  40  that is connected, as by fluid conduits and control valves not shown, to the second fluid pump  24 . For example, the fluid motor  40  is connected to the main frame  18  and operatively connected to the first compacting drum  14  in a known manner. The second fluid pump  24  supplies a pressurized operation fluid, to fluid motor  40  for propelling the work machine  10 . A shaft  44  connects the vibratory mechanism  26  to fluid motor  28 . The first fluid pump  22  supplies a pressurized operation fluid, to fluid motor  28  for supplying rotational power to the first vibratory mechanism  26  thereby imparting a vibratory force on the compacting drum  14 .  
         [0019]    Referring now to FIG. 3, the vibratory mechanism  26  is contained within a housing  46  that is attached to the first compacting drum  26 . A first eccentric weight  50  includes a first and a second stub shaft  52 ,  54  that are rotatably supported by a pair of bearings  56 . As best seen in FIG. 2 the second stub shaft  54  is connected to fluid motor  28  by the shaft  44  and a pair of universal connectors  58 . The first eccentric weight  50  is a two-piece assembly that includes a first section  60  and a second section  62  that are assembled together, as by a plurality of fasteners. The first and second sections  60 , 62  create a cage like assembly that defines an inner cavity  66 . Positioned within the cavity  66  is a shaft  70  that is journalled in a pair of bushings  72 . The bushings  72  are located in a pocket  74  machined on the inner cavity  66  side of the first and second sections  60 , 62  concentric with the stub shafts  52 , 54 . A second eccentric weight  80  is attached to the shaft  70 . Thus, the shaft  70  coaxially rotatably supports the second eccentric weight  80 .  
         [0020]    The second eccentric weight  80 , as best seen in FIGS.  3 - 7 , includes an outer annular ring  82  that is held in concentric relationship to the shaft  70  by a pair of spaced apart side plates  84 . Two radially extending plates  86  are attached to the shaft  70 , the outer annular ring  82  and the spaced apart side plates  84  to form a hollow cavity  88 . The two radially extending plates  86  form a wedge portion dividing the hollow cavity  88 , however it should be understood that a single radially extending plate  86  would work as well. Additionally a casting, not shown, forming the hollow cavity  88  with a pair of machined ends to create the shaft  70  would work as an alternative to the above described assembly of components to form the second eccentric weight  80 . A movable mass  90  is positioned within the hollow cavity  88  of the second eccentric weight  80 . The movable mass  90  is shown, for exemplary purposes, as being a metallic shot however it should be understood that the moveable mass could be metal members, steel balls, liquid metal, sand, pendulum type weight, or a metal slug suspended in a liquid and still retain the functional attributes of the example shown.  
         [0021]    Referring back to FIG. 3, an adjustment shaft  92  is slidably positioned within a bore  94  coaxially positioned in the first stub shaft  52 . Adjustment shaft  92  extends through the first stub shaft  52  and has an end piloted into a pilot hole  96  in the shaft  70 . Referring now to FIGS. 4 and 4 a , a spring  100  is slidably disposed about the adjustment shaft  92  and abuts a counter bore  102  positioned adjacent the hollow cavity  88  in the bore  94 . A driver  104  is fixedly attached to the adjustment shaft  92  having one end abutting the spring  100 . Opposite the end abutting the spring  100  the driver  104  has a stepped end, the first step corresponding to a first radially extending face has a key  106  machined therein that engages a slot  108  in the end of shaft  70 . The second step corresponding to a second radially extending face in the driver  104  has a key  110  that engages a pair of slots  112 , one shown, in a bushing  116  that is fastened to the first section  60  of the first eccentric weight  50 . While the driver  104  is disclosed as having keys  106 , 110  that engage slots  108 , 112  it should be understood that other known mechanical equivalents, such as a pin slid into mating holes, splines and the like, for locking the relative movement between the first and second eccentric weights  50 , 80  would work just as well.  
         [0022]    [0022] 21  Also shown in FIG. 1, is a control panel  120  connected to a controller  122  and to the first fluid pump  22  as by wire. The control panel  120 , includes operator inputs such as switches, touch screens and the like, is used by the operator to select between high frequency operation and low frequency operation. When the operator selects high frequency from the control panel  120  the controller  122  sends a signal to the fluid pump  22 . Fluid pump  22  is a variable or dual displacement pump capable of reversing flow direction at the two working ports that rotates the fluid motor  28  in a first direction  124  at a high rotational output speed when the operator selects high frequency. When the operator selects low frequency from the control panel  120 , the controller  122  sends another signal to fluid pump  22  to rotate the fluid motor  28  in a second direction  126  at a lower rotational output speed.  
         [0023]    Referring back to FIG. 2 a hand wheel  130  is attached to the adjustment shaft  92  opposite the driver  104 . The hand wheel  130  is supported by a plurality of spokes  132  that are connected to a hub  134 . The hub  134  is connected to the adjustment shaft  92  in a common manner, as by a retaining nut. The spokes  132  of the hand wheel  130  form a fan  136 .  
         [0024]    Industrial Applicability  
         [0025]    During a given compacting operation and from compacting job to job it is necessary to change the amplitude of the vibratory force being applied, by the compacting work machine  10 , to the compactable material  12 . The vibratory mechanism  26  disclosed herein provides a simple effective mechanism for offering this flexibility and operates as follows. When the operator starts any given compacting operation the first thing is to set the vibratory mechanism  26  to the desired amplitude. This is accomplished by changing the position of the second eccentric weight  80  relative to the first eccentric weight  50 . Pulling back on the hand wheel  130  slides the indexing shaft  92  and the driver  104 , so that the driver  104  pulls against spring  100 . Pulling the driver  104  back disengages the key  110  from slots  112 , while key  106  maintains engagement with slot  108 . The hand wheel  130  is then rotated to the next position changing the position of the second eccentric weight  80  relative to the first eccentric weight  50 , at which time the operator releases the hand wheel  130 , the indexing shaft  92  and the driver  104 . This causes the key  110  to slide into the next one of the pair of slots  112 , locking the position of the second eccentric weight  80  relative to the first eccentric weight  50 . With the exemplary design described the second eccentric weight  80  is indexable in two distinct positions relative to the first eccentric weight  50  as is shown in FIGS. 4 and 6 (first position) and FIGS. 5 and 7 (second position) respectively. However, it should be understood that the same described mechanism could easily have a plurality of indexable positions.  
         [0026]    The operator then selects the frequency of the vibratory mechanism  26  from the control panel  122 . A signal is sent to the controller  122  based on either high frequency or low frequency selection. If high frequency is selected, the controller  122  sends a signal to the first fluid motor  22 . The first fluid pump  22  then provides pressurized fluid to the first fluid motor  28  so that it rotates in the first direction  124  and at a high rotational speed. In the high frequency mode the movable mass  90  in the second eccentric weight  80  shifts to a position so as to opposes the first eccentric weight  50 , as seen in FIGS. 4 and 5. When a low frequency setting is selected the controller  122  sends a signal to the first fluid pump  22  to supply pressurized fluid to the first fluid motor  28  so that it rotates in the second direction  126  and at a low rotational speed as seen in FIGS. 6 and 7. This arrangement provides a control arrangement that is simple to operate and makes it fail proof so that the operator cannot operate the vibratory mechanism  26  at high frequency and high amplitude.  
         [0027]    Additionally, during operation the hand wheel  130  is configured with supporting spokes  132  that operates as a fan  136 . During operation the hand wheel  130  assembly provides cooling air to the vibratory mechanism  26 .