Abstract:
An improved method of mounting the cutting head of a sod harvester with respect to the conveyor employs a single ball joint between the cutting head and the conveyor, and a pair of side links spaced outwardly of the conveyor and arranged to constrain the cutting head against lateral displacement with respect to the conveyor. Preferably, the links are adjustable in length to permit vertical and lateral adjustment of the cutting head with respect to the conveyor, e.g. “tracking” of the cutting head.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to sod harvesters. 
     BACKGROUND OF THE INVENTION 
     Sod harvesters have been commercially available for a long time, and usually are designed as self-propelled machines or as a cutting unit which can be attached to a conventional tractor. In either case, the harvester has a cutting head which includes (a) a generally-horizontal knife to undercut the sod at a specified depth, (b) side cutting blades or coulters to cut the edges of the sod strip, and (c) a roller to support the weight of the cutting head and to establish the thickness of the sod strip. Cut strips of sod are delivered onto a conveyor which conveys the strips rearwardly and upwardly away from the cutting head, for collection. 
     Sod harvesters have used a variety of methods to follow the contour of the ground; in general, the objective is to allow the operator to cut a thin strip of sod without the risk of scalping, or cutting too thinly on occasion. Some harvesters, commonly referred to as “conventional” or “fixed head” harvesters, have the cutting head rigidly connected to the conveyor frame. Examples of this type of harvester are the harvester described in U.S. Pat. No. 3,540,535, the Brouwer model 1555, and the Kesmac model 2100. These harvesters include a pivoting “ball joint” connection at the rear of the conveyor, which allows the cutting head to rise and fall with undulations in the direction of motion of the harvester. A “track rod” connects the cutting head or conveyor to the tractor with pivoting ball joints and holds the cutting head parallel to the direction of motion. These pivot joints also allow the conveyor and cutting head frame to rock from side to side to follow undulations perpendicular to the direction of motion of the harvester. The axis about which the conveyor and cutter assembly rotates is defined by the location of the centres of the rear pivot point and the track rod connection to the cutting head or conveyor. Since this axis is not horizontal, the cutting knives turn away from being exactly perpendicular to the direction of travel when the head pivots, resulting in damage to the edges of the sod strip. 
     This problem is addressed by harvesters that are commonly referred to as “floating head”, or “pivoting head”, harvesters, which have a pivoting connection between the cutting head frame and the conveyor frame. U.S. Pat. Nos. 4,621,696, 3,807,504, and 4,892,152 disclose harvesters of this type, in which the cutting head can tilt about a horizontal pivot axis. The cutting knives and roller no longer pivot front-to-back. However, since the axis of tilt lies at some distance above ground level, the cutting head can be induced to pivot by a side load on the knives and roller, such as would happen if sod is being cut on a curve, as is common with center-pivot irrigation sod cultivation. This can result in scalping. 
     One attempt to solve the floating head problem is disclosed in U.S. Pat. No. 6,112,825. This patent describes a floating head design in which the pivoting connection between the cutting head and the conveyor is angled, such that the pivot axis intersects the knife. It should be noted, however, that a side load on the knives and roller can induce the whole assembly to pivot on an axis defined by the front and rear support ball joints, causing scalping. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide improvements intended to address the problems of prior art sod harvesters. In particular, the invention provides an improved manner of mounting the cutting head to the conveyor to control uniformity in the thickness of sod strips being harvested. 
     The sod harvester of the invention includes a drive unit for moving the harvester in a forward direction, a cutting head for cutting a strip of sod from the ground as the harvester moves in said forward direction, and conveyor means disposed rearwardly of the cutting head for receiving cut strips of sod from the cutting head and conveying the strips rearwardly for collection. The invention provides means for connecting the conveyor and the cutting head, comprising a ball joint disposed on a longitudinal centre line of the cutting head and a pair of laterally spaced links, each connected at one end to the conveyor means and at the opposite end to the cutting head at respective connection points that are selected to constrain the cutting head laterally with respect to the conveyor means, while permitting lateral tilting of the cutting head about the ball joint to accommodate lateral unevenness in the ground. 
     In other words, the invention provides an improved means of connecting the cutting head and the conveyor to allow free flotation of the ground-following roller and cutting knives, with substantially reduced scalping and damage to edges of the sod strip. 
     Preferably, the conveyor is pivotally mounted so that its leading end can move up and down to follow ground contours, but is constrained from side to side movement, as in most floating head harvesters. The ball joint is located below the conveyor and behind the cutting head, and the two links are to the outside of the conveyor, located at a distance vertically from the ball joint. The links constrain the cutting head to remain perpendicular to the direction of travel, while at the same time allowing it to rock from side to side in response to changes in ground contour. 
     This mounting arrangement does not create a discrete axis about which the cutting heat pivots in relation to the conveyor frame. A notional pivot axis can be defined as an axis that intersects the center ball joint, is oriented in the direction of travel, and is angled downward at the same angle as the two links in their centre positions (cutting head horizontal). The actual rocking of the cutting head will deviate from this notional axis to the extent that the ends of the links connected to the cutting head frame deviate from a plane normal to the notional axis as the cutting head rocks. With the notional axis oriented to approximately the bottom of the ground-following roller, substantially less “induced pivoting” is experienced relative to prior floating heads. 
     An advantage of the preferred embodiment of the invention over a single pivot shaft between the cutting head frame and the conveyor frame is that it permits greater ground clearance. 
     A further advantage is that adjustable links provide a means of adjusting the vertical distance between the back of a “sod guide” that is usually provided at the rear of the cutting head to the leading end of the conveyor. As the links are shortened, the sod guide moves up relative to the conveyor. This relationship is important to the smooth and gentle transfer of sod from the cutting blade to the conveyor. Prior art sod harvesters have no way of adjusting that relationship without changing the depth of cut. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     In order that the invention may be more clearly understood, reference will now be made to the accompanying drawings which illustrate a particular preferred embodiments of the invention by way of example, in contrast with the prior art. 
     In the drawings: 
     FIG. 1 is a schematic side elevational view of one form of prior art sod harvester; 
     FIG. 1 a  is an end elevational view in the direction of arrow A in FIG. 1; 
     FIG. 2 is a view similar to FIG. 1 illustrating a second form of prior art sod harvester; 
     FIG. 2 a  is a view generally in the direction of B in FIG. 2; 
     FIG. 3 is a view similar to FIGS. 1 and 2 illustrating a third form of prior art sod harvester; 
     FIG. 3 a  is an enlarged view of the gage roller of FIG. 3; 
     FIG. 3 b  is a plan view of the gage roller in FIG. 3; 
     FIG. 4 is a side elevational view similar to FIGS. 1,  2  and  3  but illustrating a sod harvester in accordance with a preferred embodiment of the present invention; 
     FIG. 5 is an elevational view in the direction of arrow D in FIG. 4; 
     FIG. 6 is a plan view of the gage roller in FIG. 4; 
     FIGS. 7 and 8 are plan and front elevational views corresponding to FIG. 4; 
     FIG. 9 is a view similar to FIG. 8 showing the cutting head of the harvester in a tilted position; and, 
     FIG. 10 is a perspective view of a practical example of the sod harvester as seen from the right and above in FIG.  4 . 
    
    
     All of the views show a sod harvester in the form of a cutting unit which is designed to be attached to a conventional tractor. The tractor itself is not shown in detail but typically is disposed to the left of the cutting unit in the direction of travel of the harvester, as indicated in ghost outline at T in FIG.  7 . The tractor itself and the manner in which the cutting unit is coupled to the tractor are not part of the present invention. Reference may be made to the prior patents cited herein to illustrate mounting of the cutting unit to a tractor. The disclosures of those patents are incorporated herein by reference. 
     DESCRIPTION OF THE PRIOR ART 
     FIGS. 1 to  3  show three types of prior art sod harvesters which are compared with the present invention. For the purpose of comparison, all of the harvesters are assumed to have a gage roller which is an 8″ in diameter by 16″ wide and which tilts up 0.50 inches on the outside edge. While the actual dimension of displacement sideways will vary with geometry, using a consistent assumption will illustrate the different results inherent in the designs. 
     FIG. 1 illustrates a fixed head harvester, known commercially as the Brouwer 1555, Brouwer 1550, Brouwer 1500, Brouwer A3A, Texas conventional, among others. The axis of rotation is defined by the rear and front support ball joints, and it falls significantly above the gage roller, in this case 13 inches. From FIG. 1 a,  it can be seen that a 0.50 inch vertical rise requires a 0.76 inch horizontal displacement. 
     FIG. 2 illustrates a common fixed head design, the Brouwer 1560. The characteristic of an independent cutting head with a horizontal pivot axis relatively low to the ground is also found in U.S. Pat. Nos. 4,621,696 and 4,892,152. In this case, the horizontal displacement around the axis of rotation to accommodate a 0.50 inch rise is reduced to 0.23 inches (FIG. 2 a ). 
     FIG. 3 illustrates a fixed head design known as the Kesmac 2100. In this design, the cutter head is rigidly attached to the conveyor, as in FIG. 1, but the axis of rotation is arranged to intersect the ground close to the gage roller, which eliminates the side shift problem of FIGS. 1 and 2. However, since the pivot axis is at a significant angle relative to horizontal (conservatively assumed to be 30 degrees), the 0.50 inch rise causes the end of the roller to move forward 0.29 inches. As seen FIG. 3 b,  this results in the roller wobbling off square by 0.14 inches. 
     DESCRIPTION OF PREFERRED EMBODIMENT 
     Reference will now be made to FIGS. 4 to  10  in describing particular preferred embodiments of the invention by way of example. For purposes of comparison with the prior art, FIG. 4 is a schematic side elevational view similar to FIGS. 1 to  3 . Later views such as FIGS. 7 to  10 , provide more detail; FIGS. 9 and 10 in particular illustrate a practical form of sod harvester in accordance with the invention. 
     Referring initially to FIG. 4, the sod harvester of the invention is generally indicated by reference numeral  20  and is designed to be mounted alongside a drive unit such as a tractor (“T” in FIG. 7) for movement in a forward direction indicated by arrow  22 . The harvester includes a cutting head  24  for cutting a strip of sod as the harvester moves in the forward direction  22 , and conveyor means generally indicated at  26  disposed rearwardly of the cutting head for receiving cut strips of sod from the cutting head and conveying the strips rearwardly and upwardly for collection. The cutting head  24  and the conveyor means  26  may be of known design and therefore are not illustrated in detail. The invention resides in the provision of means for connecting the conveyor and the cutting head, as will be described. For present purposes, it is sufficient to note that the cutting head  24  includes a cutting head frame  28 , and a gage roller  30  which is mounted below the frame  28 . Roller  30  partially supports the weight of the cutting head and follows the contour of the ground as the harvester moves in the direction of travel  22 . FIG. 4 does not show the undercutting knife or the side blades that are typically provided in association with the gage roller  30 , since these components and their relationship with the gage roller are conventional. 
     The conveyor means  26  includes a conveyor frame  32  which essentially comprises a pair of side frame members  34  (FIG. 10) between which a conveyor belt is supported for conveying cut strips of sod upwardly and rearwardly away from the cutting head. In FIG. 10, the belt itself is not shown but reference numeral  36  indicates sprockets around which the belt travels. A pair of brackets  38  project upwardly from the conveyor side frame members  34  and define a transverse pivot axis  40  (see FIG. 4) at which the conveyor frame is coupled to the drive unit so that the conveyor can pivot up and down to follow ground contours. Side-to-side tilting motion of the conveyor frame is not provided for. 
     In accordance with the present invention, connecting means are provided between the conveyor frame  32  and the cutting head frame  28 , and comprise a spherical ball joint  42  that is disposed on a longitudinal centre line of the cutting head (denoted  44  in FIG.  7 ), and a pair of laterally spaced links  46 ,  48  disposed outwardly of the respective frames  28  and  32  (see FIG.  7 ). Each of the links  46 ,  48  is connected at one end to the conveyor frame and at its opposite end to the cutting head frame. The two connection points for link  46  are denoted  50  and  52 , and the corresponding connection points for link  48  are denoted  54  and  56 . The connection points are selected to constrain the cutting head  24  laterally with respect to the conveyor means while permitting lateral tilting of the cutting head about the ball joint  42  to accommodate lateral unevenness in the ground. 
     FIG. 4 shows the relationship between the ball joint  42 , the link  46  and its pivot points  50  and  52 . When the cutting head  24  is on a horizontal surface, the corresponding link  48  and connection points  54  and  56  at the opposite side of the harvester are in the same position as link  46  and its connection points  50  and  52 . Each of the connection points  50 ,  52 ,  54  and  56  is provided by a ball joint. 
     The centre-line ball joint  42  constrains all points on the cutting head to remain at a constance distance from the ball joint. The two links  46  and  48  connect the conveyor frame  32  to the cutting head frame  28  at a distance vertically from ball joint  42 . These links hold the cutting head frame  28  in the desired position relative to the conveyor means  26  and the direction of travel  22 . 
     The rocking action of the head  24  and the optimal orientation of the links  46 ,  48  can be best understood by imagining a notional pivot axis  58  located by the center of ball joint  42  and the center of the contact line between the gage roller  30  and the ground. A co-ordinate system can be assigned with the z direction pointing down that notional axis  58 , with the y direction normal to z on a vertical plane, and the x direction horizontal, normal to z, as shown in FIGS. 4 and 5. In order for the cutting head frame to actually pivot about the notional axis, ball joints  52  and  56  would need to travel on the circle formed by the intersection of a plane P normal to the z direction with a sphere centered on ball joint  42  with radius equal to the distance from ball joint  42  to ball joints  52  and  56 . This circle is shown on FIG. 5, with  52 ′ and  56 ′ being the ball joints  52  and  56  in the rotated position. Since the ball joints  52  and  56  are at the end of links  46  and  48 , they are constrained to maintain a constant distance from ball joints  50  and  54 , and therefore will leave that plane P as the head rocks, by some distance in the negative z direction. However, it will be appreciated that the closest approximation to the condition of the cutting head rotating about the notional axis would exist if the links  46  and  48  were perpendicular to the plane P when the cutting head is in the horizontal position. In that case, the negative z distance by which ball joints  52  and  56  leave plane P is minimized. Also, links  46  and  48  should be as long as practical, in order to minimize the deviation from plane P. 
     Links  46  and  48  being perpendicular to plane P is also important because that causes the distance by which the ball joint leaves plane P to be the same for ball joint  52  as for ball joint  56 . If one point moved further in the negative z direction than the other, the cutting head would experience rotation about the y axis, which is undesirable because the cutting head would no longer be parallel to the direction of travel. 
     In order to compare this design with prior art, analysis of side shift and wobble was done with a CAD model rather than simple calculations, since there is no pivoting about an axis. For the same 0.50 rise on one side of the roller, horizontal displacement was 0.09 inches, and the wobble off square was 0.051 inches, as shown in FIG.  6 . This wobble, or “yaw” can be explained by the fact that the notional axis is not exactly horizontal. 
     In summary, the motion of the cutting head  24  includes a minor “yaw” component that is significantly less than what has been calculated for prior art designs. Additionally, as can most clearly be seen from FIG. 4, ground clearance behind the cutter head is substantially improved as compared with prior art arrangements in which a pivot shaft is provided in the area to the left of the ball joint  42  along axis  58 . That whole area can now remain unobstructed. 
     In any of the inventive embodiments, the side links  46  and  48  preferably are adjustable in length so as to permit adjustment of tracking of the cutting head  24  relative to the conveyor frame  32 . The links can also be adjusted to vary the vertical distance between the sod guide (not shown) that is typically provided on the cutting head  24 , and the conveyor  32  to assure smooth and gentle transfer of sod from the cutting head to the conveyor. 
     As noted previously, FIG. 10 shows a practical example of a sod harvester in accordance with the preferred embodiment of the invention. FIG. 10 will not be described in detail since the principal components are well known and not part of the invention. The invention resides in the connecting means between the conveyor frame  32  and the cutting head frame  28 , namely the ball joint  42  and the links  46  and  48 . Those components have been indicated in FIG. 10, as has the gage roller  30  and an associated cutter blade assembly, which is generally denoted  60 . Precise constructional details of the cutting head frame and the conveyor frame will not be described and may vary. A connection point for a track rod connection to the tractor is provided at the opposite side of the cutting head frame  28  from that seen in FIG. 10 in a position corresponding to the point that is denoted  62 . 
     Each of the links  46 ,  48  has an end fitting that is screw-threaded into the main body of the link so that the length of the link can be adjusted. In FIG. 10, the main body of link  46  is denoted  46   a  and the screw-in end fitting is denoted  46   b.  In this embodiment, the link would of course have to be disconnected from the frame in order to effect adjustment. Fitting  46   b  would be screwed into or out of the main body  46   a  and then the link re-connected. The construction of link  48  is essentially the same. 
     It will of course be appreciated that the preceding description relates to a particular preferred embodiment of the invention and that many modifications are possible within the broad scope of the invention. Some of those modifications have been indicated previously and others will be apparent to a person skilled in the art. 
     In particular, it is to be understood that the sod harvester of the invention may be powered other than by a tractor; the harvester may be self-propelled, i.e. have a built-in drive unit.