Abstract:
A turf aerator with a reciprocating drive mechanism comprising a substantially rigid tine leg pivotally mounted at an upper end to a drive assembly arranged to reciprocate the tine leg along its longitudinal axis, the drive assembly comprising a reciprocating drive member to which the tine leg is pivotally attached at a first point along the drive member, the drive member being pivotally connected at a second point to a first eccentric and at a third point to a second eccentric, the third point being located intermediate the first and second points and the first and second eccentrics being rotated in synchronism, to reciprocate the first point on the drive member both vertically and while reducing the extent of horizontal reciprocation of the first point on the drive member.

Description:
[0001]    The present invention relates generally to greenkeeping equipment and in particular the invention provides an improved reciprocating drive for a turf aeration device.  
         BACKGROUND OF THE INVENTION  
         [0002]    It is well known that in the cultivation of turf surfaces aeration of the root system is required from time to time to relieve compaction and enable penetration of nutrients beneath the surface mat of the turf. A variety of mechanisms have been used in the past to achieve this end, all of which generally include tines carried in some type of mechanism that allows periodic spiking of the surface. These mechanisms have increased in sophistication over the years from simple tine rollers comprising a drum with a plurality of tines located pointing radially outwardly from its surface to elaborate reciprocating mechanisms.  
           [0003]    A basic problem with tine rollers and, which has been overcome to a certain degree by some more advanced systems is that of tearing which occurs when the tine does not enter and exit the turf vertically but instead passes through an arc while it is in the ground. This action damages the turf surface and makes it less useful for its intended purpose during the period immediately following aeration. It is also highly desirable that turf aerators be able to operate quickly in order to minimise the cost of this operation and enable the operation to be performed more regularly. Another cost related factor is the reliability of the equipment which typically decreases with increased speed and is adversely affected by the typically dirty environment in which the equipment must operate, making lubricants applied to bearing surfaces become like grinding pastes which rather than increasing the life of the bearing surface tend to decrease that life rapidly.  
           [0004]    In one prior art arrangement an aerator has a plurality of tines located at the ends of tine legs which are reciprocated by a crank shaft and arranged transversely of the aerator. The tine legs are each slidably mounted towards their lower end in a guide which is in turn reciprocated fore and aft to keep the tine leg vertical while it is in engagement with the ground. The prior art tine legs are articulated to accommodate the differing relative horizontal speeds of the crank shaft and the leg guides which maintain the lower portion of the legs in vertical orientation. Typically when an aerator is required to penetrate the ground at 50 mm spacings, the machine can only move forward 50 mm for every revolution of the crank shaft and therefore a relatively high tine speed is required for reasonable rate of coverage. Due to their mechanical arrangement, prior art machines were subject to higher rates of wear and fixed hole arrangements limited by a single cam.  
           [0005]    The reciprocating drive mechanism of the present invention is designed to ameliorate or overcome some or all of these deficiencies in prior art equipment.  
         SUMMARY OF THE INVENTION  
         [0006]    The present invention consists in a turf aerator with a reciprocating drive mechanism comprising a substantially rigid tine leg pivotally mounted at an upper end to a drive assembly arranged to reciprocate the tine leg along its longitudinal axis, the drive assembly comprising a reciprocating drive member to which the tine leg is pivotally attached at a first point along the drive member, the drive member being pivotally connected at a second point to a first eccentric and at a third point to a second eccentric, the third point being located intermediate the first and second points and the first and second eccentrics being rotated in synchronism, to reciprocate the first point on the drive member both vertically and while reducing the extent of horizontal reciprocation of the first point on the drive member.  
           [0007]    In a preferred embodiment, the diameter of the path of rotation of the first eccentric is less than the path of rotation of the second eccentric, and the two eccentrics preferably rotate in the same direction.  
           [0008]    In various embodiments, the timing of the eccentrics relative to one another may be varied in order to adjust the operation of the tine leg and in particular, the timing may be adjusted in a given embodiment depending upon the conditions in which the aerator is operating.  
           [0009]    The lower end of the tine leg is able to move in a rearward direction to allow the tine to move relative to the machine while the tine is in the ground. The tine leg is biased to a forward position such that when the tine leaves the ground, the tine leg returns toward the forward end of its travel ready for re-engagement with the ground. Biasing may be by a variety of spring arrangements. In one embodiment, the biasing may be by way of a rosta tensioner including a resilient member mounted to a frame of the machine and having a tensioner arm depending from the resilient member and a roller on the end of the tensioner arm, the roller contacting a rear surface of the tine leg when the tine is in its rest position.  
           [0010]    The resilient member has a torsional distortion applied to it as the tine leg moves rearward and pushes the roller and tensioner arm rearwards, whereby the resilient member exerts a restoring force on the tine leg via the tensioner arm and roller.  
           [0011]    A similar rosta tensioner is also located in front of the tine leg such that the tensioner applies a restoring force in the rearward direction if the tine leg moves forward of its rest position.  
           [0012]    In a second, preferred embodiment, the biasing may be effected by way of a resiliently flexibly mounted guide arrangement. The guide arrangement may comprise a pair of rollers. One roller may be mounted on each side of the tine leg. Each roller may be rotatably mounted at the end of a roller arm. A plurality of coil springs may be connected to the roller and/or its arm for drawing the roller into abutment with the tine leg and for exerting a restoring force on the tine leg.  
           [0013]    This guide arrangement may also serve to damp rapid horizontal reciprocatory motion of the tine leg when the aerator is rapidly traversing a surface, in use. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which:  
         [0015]    [0015]FIG. 1 illustrates a perspective view of a first embodiment of the invention comprising an aerator arranged to be carried by, or towed behind a vehicle provided with a three point hitch;  
         [0016]    [0016]FIG. 2 is a side elevation of the aerator mechanism at one point in a cycle of operation;  
         [0017]    [0017]FIG. 3 is a side elevation of the aerator mechanism of FIG. 2 showing paths of various components during a cycle of operation;  
         [0018]    [0018]FIG. 4 illustrates a perspective view of a second embodiment of the invention comprising a self propelled turf aerator;  
         [0019]    [0019]FIG. 5 illustrates a perspective view of a “ride on” embodiment of the invention;  
         [0020]    [0020]FIG. 6 illustrates a side elevation of the aerator mechanism at its lowest point in its cycle of operation; and  
         [0021]    [0021]FIG. 7 illustrates a schematic, side view of a guide arrangement of the version of the aerator mechanism of FIG. 6. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]    Referring to FIG. 1, a first implementation of the invention is illustrated in which an aerator  11  of the type towed behind a tractor or similar vehicle is shown. In this embodiment, mounting points  12 ,  13 ,  14  are provided for attachment to the three point hitch of the towing vehicle and an input shaft  15  is arranged to connect to a power take-off of the towing vehicle. The aerator mechanism  16  is mounted on a chassis  17  and the rear wheels  21  (see FIG. 2) are mounted on a ram  18 , extending below a bracket  57  on the chassis  17  and connected by resilient connection  19 , such that when the towing vehicle raises the three point hitch, the chassis  17  raises but the wheels or a roller  21  connected to the ram  18  may be lowered to remain in contact with the ground to help support the aerator.  
         [0023]    Referring to FIG. 2, an embodiment of the invention is illustrated wherein the aerator mechanism is shown in detail at a point of its cycle where the aerator tines  31  are fully lowered into the turf surface  52 . The mechanism is mounted on a frame  32  extending above the chassis  17  and includes a substantially horizontally extending reciprocating drive member  33  connected to a rotating eccentric  57  at one end by a pivotal connection  34 , and a substantially vertical tine leg  35  connected at its upper end to the opposite end of the drive member  33  by a pivotal connection  36 . The tines  31  are mounted in a tine clamp  42  connected to the lower end of the tine leg  35 . A push rod  37  extends between a pivotable connection  58  on the drive member  33  and the pivotable connection  59  on a crank  38  to drive the driver member  33  and thereby the tine leg  35  in reciprocating motion. The crank  38  is connected to a coaxial chain wheel  39  which is driven via chains  48 , chain wheel  51  and gearbox  41  and power take-off connection  15  and the eccentric  57  is similarly connected to a coaxial chain wheel  44 , chain  45 , chain wheel  63  and the gearbox  41 . The eccentric  57  also includes a counter balance  47  to minimise vibration caused by the horizontal reciprocation of the drive member  33 .  
         [0024]    Rotation of the crank  38  causes reciprocation of the driver member  33  via the push rod  37  and subsequently this causes the tine leg to reciprocate substantially vertically. Horizontal reciprocation of the end of the driver member  33  having the connection  36  is effectively damped by the rotation of the eccentric  57  so that a vertical throw of said end of the drive member  33  is much greater than a horizontal throw of said end. Reciprocation is controlled in synchronisation with forward motion of the aerator such that a uniform pattern of holes is punched in the turf surface  52  as the aerator advances. As the implement moves forward with the tines  31  inserted in the ground, the tines move backward relative to the implement. After the tines  31  are retracted from the ground they are moved forward by rosta tensioner  55  until the tine leg  35  strikes the rosta tensioner  53  which decelerates the lower end of the tine leg  35  prior to the tines  31  being reinserted into the turf surface  52 . The rosta tensioner  53  includes a torsion block  61  formed of resilient material mounted at one end to the frame  32  (or a bracket or member extending from the frame), a tensioner arm  62  extending from the torsion block  61  and a roller  64  which abuts the tine leg  35  at least when it approaches its forwardmost position. In some embodiments, the roller  64  may remain in contact with the tine leg  35  at substantially all times. However, it will be appreciated that the decelerating force generated by the torsion block  61  will be greater as the roller  64  is moved forward by the tine leg  35 .  
         [0025]    When the tine leg  35  leaves the ground, its forward motion is effected by a return mechanism comprising the rosta tensioner  55 . The rosta tensioner  55  includes a torsion block  56 , a tensioner arm  65  and a roller  66  which act similarly to those of the forward rosta tensioner  53 . However, rosta tensioner  55  is located behind the tine leg  35  and, preferably, the roller  66  remains in contact with the tine leg  35  substantially all of the time, to push the tine leg forward when it leaves the ground and to continuously and smoothly push it towards the forward extremity of its travel.  
         [0026]    The forward rosta tensioner  53  and the rearward tensioner  55  operate against each other with one or the other having a predominant effect on the motion of the tine leg  35  depending upon its position at the time. The relative effect of each rosta tensioner  53 ,  55  may be varied by varying the stiffness of the torsion blocks  61 ,  56  and the length of the tensioner arms  62 ,  65 .  
         [0027]    When the aerator  11  is set at its normal operating height, the wheels or roller  21  will be in contact with the ground  52  to help support the aerator (or in self-propelled models, to substantially fully support the aerator). When aeration is not in progress, the jack  18  is extended to raise the chassis  17  sufficiently to lift all of the tines clear of the ground, regardless of their position in the aeration cycle. In the case of the tractor mounted model of FIGS. 1 &amp; 2, this would be carried out in conjunction with the raising of the  3  point hitch, connected to the mounting points  12 , 13   14 .  
         [0028]    It should be noted that while one tine leg  35  is illustrated for the sake of simplicity, typically 2, 4, or more tine legs and their associated drive mechanisms as described above, will be provided side by side in the chassis  17 . These mechanisms are operated at the same speed (they are driven off one gearbox), but will typically have their operating cycles offset such that the load on the drive components is distributed over the cycle and not subjected to the shock of all tines hitting the ground and being driven in simultaneously. This also reduces the lifting force created as the tines are driven into hard earth.  
         [0029]    Referring to FIG. 3, the mechanism of FIG. 2 is depicted (with some parts removed) and path tracings for some points in the mechanism superimposed. It will be noted that in operation, as described here, the chain wheel  44  and the chain wheel  39  rotate in the same direction. However, it is also possible to have these wheels counter rotate and/or to alter their timing relative to one another, to vary the hole pattern, or tine penetration and exit characteristics. However, in the present embodiment, the chain wheels are timed to operate in complete synchronism with both reaching bottom dead centre at the same time.  
         [0030]    Under these circumstances, the pivot point  36  at the top of the tine leg follows the path  136  during one cycle of operation, and a point near the lower end of the tine leg will follow the path  135  assuming no ground engagement.  
         [0031]    Turning to FIG. 4, a self propelled, “walk-behind” version of the aerator is illustrated. In this embodiment, again the aerator mechanism  16  is mounted on a chassis  17  and ram  18  resiliently connected to the chassis carries the wheels on a roller  21 . In this embodiment, the front of the implement is supported on a single or double wheel  23  mounted at the lower end of a post  24  rotatably mounted through the forward end of the chassis  17 .  
         [0032]    A control arm  25  extends from and is pivotally connected to the upper end of the post  24  and includes a plurality of control levers  26  used to operate the implement. A motor  27  is provided to drive the aerator mechanism and to propel the implement via the rear wheels  21 .  
         [0033]    Referring to FIG. 5, a “ride on” version of the aerator is illustrated, in which the forward end of the chassis  17  is elongated and an operator&#39;s seat  71  is provided behind the operating arm  25 .  
         [0034]    To avoid problems caused by lubricating oil, all of the pivot points and drive shaft bearings in the mechanisms are manufactured with self lubricating bushes formed of lubrication impregnated nylon and sealed bearings are used wherever required.  
         [0035]    Referring now to FIGS. 6 and 7, a further embodiment of the aerator  11  illustrated in FIGS. 1, 2 and  3  is shown. With reference to FIGS. 1, 2 and  3  like reference numerals refer to like parts, unless otherwise specified. The operation of the aerator mechanism  16  shown in FIG. 6, and in particular the displacement of the tine leg  35  is substantially as described above with reference to FIGS. 2 and 3.  
         [0036]    However, in this embodiment of the invention, each tine leg  31  is mounted on a tine cap  80 . The tine cap  80 , in turn, is pivotally mounted via a pivot point  82  to a bottom of the tine leg  35 .  
         [0037]    A spring housing  84  is mounted ahead (in the direction of movement of the aerator  11 ) of the pivot point  82 . A spring  86  projects from the spring housing  84  and bears down on the tine cap  80 . A resiliently flexible pad  88  is mounted rearwardly of the pivot point  82 .  
         [0038]    To ensure vertical insertion of the tine  31  into the surface  52 , a longitudinal axis of the tine  31  is slightly offset with respect to a longitudinal axis of the tine leg  35 .  
         [0039]    In this embodiment, instead of the rosta tensioners  53  and  55 , a guide mechanism  90  is provided for guiding the lower end of the tine leg  35  and to ensure the required insertion into, and retraction from, the surface  52  of the tine  31 .  
         [0040]    The guide arrangement  90  comprises a pair of rollers  92  and  94 . The roller  92  is mounted behind the tine leg  35  with the roller  94  being mounted ahead of the tine leg  35 . The roller  92  is mounted via an arm  96 , pivotally, on a bracket  98 . Similarly, the roller  94  is mounted pivotally via an arm  100  to a bracket  102 . The roller  92  is biased to the position shown in solid lines in FIG. 7 by a pair of springs  104  and  106  with the spring  104  having a greater spring force than the spring  106 . The maximum arc of travel of the roller  92  is shown in dotted lines in FIG. 7 of the drawings. Similarly, the roller  94  is biased to the position shown in solid lines in FIG. 7 of the drawing by a pair of springs  108  and  110  with the spring  110  having a greater spring force than the spring  108 .  
         [0041]    It is to be noted in FIG. 7 of the drawings that the arrangement of the springs  104 ,  106 ,  108  and  110  are shown schematically. For example, an end  110 . 1  of the spring  110  is connected to the bracket  102  by an arm  116 . Likewise, an end  108 . 1  of the spring  108  is connected to the bracket  102  by an arm  118 . In practice, the arms  116  and  118  overlie each other and extend substantially parallel to each other. The arm  116  is fast with the bracket  102  to pivot together with the bracket  102 . A stopper (not shown) is provided to limit the extension of the spring  110 . A stopper (also not shown) is also provided for limiting the extension of the spring  104 . Both lighter springs  106  and  108  serve to keep their respective rollers  92  and  94  in contact with the tine leg  35  to prevent lash of the leg  35 .  
         [0042]    It will be apparent that, were the roller  94  absent, the rest position of the roller  92  would be the position  92 . 1 . Similarly, if the roller  92  were absent, the rest position of the roller  94  would be the position  94 . 1 .  
         [0043]    The rollers  92  and  94  with their associated springs ensure that the tine legs  31  follow the narrow elliptical path  135  illustrated in FIG. 3 of the drawing to ensure that substantial verticality of the tines  31  is maintained as the tines  31  are inserted into, and removed from, the turf  52  when the aerator  11  traverses the turf  52 .  
         [0044]    By adjusting the ground speed of the aerator  11  and the strength of the springs  104 ,  106 , 108  and  110 , the ground spacing of holes created by the tines  31  can be varied. For very rapid traversal of the turf  52 , chatter of the tine legs  35  is inhibited by means of the spring biased rollers  92  and  94 . The tine legs  35  are also constrained against lateral movement by means of a lined bracket  112  through which the tine leg  35  passes. The bracket  112  is lined with a plastics lining  114  which is also self lubricating. For example, the lining  114  is of PTFE.  
         [0045]    It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.