Abstract:
An agricultural rake basket flotation system that employs tension springs to support a portion of the weight of the rake basket, toward the lateral ends thereof, thus allowing for a more sensitive and complete response to encounters with obstacles and irregularities in the ground level.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to header flotation systems for pull-type crop-treating equipment in the agricultural industry, and particularly to a header flotation system for use with a pull-type agricultural rake. 
     BACKGROUND OF THE INVENTION 
     As a rake is pulled through the field of crop, the rake reel, supported within the basket, is rotated with the tines moving as close to the ground as possible to maximize crop handling. It is a common shortcoming of pull-type rakes to exhibit poor flotation characteristics, and thus frequently the tines contact the ground, often resulting in costly downtime and repairs. 
     Header flotation is a desirable design characteristic that permits the header to move vertically whenever an obstacle is encountered or the ground is uneven over the length of the header. “Lateral” flotation is a refinement whereby one end of the header may rise, for example upon encountering uneven ground, without causing the other end to rise as much as the first end, i.e., the header is allowed to follow the contour of the ground. Neither flotation nor lateral flotation are of much importance or value in the operation of equipment unless these features are enhanced by the necessary degree of sensitivity. More specifically, flotation is almost a valueless concept unless the flotation structure, or mechanism, is sufficiently sensitive to quickly react to encounters with obstacles and/or uneven ground. 
     Many agricultural rakes incorporate a compression spring as part of the basket lifting linkage to assist in raising the rake over obstacles encountered in the field such as rocks, gopher mounds, branches, etc. Attention is directed to U.S. Pat. Nos. 2,829,486; 2,781,626; 2,657,518 and 2,595,788 for examples of compression springs used in such systems. The primary problem encountered when using a compression spring in a flotation system is that it has too large a spring constant to adequately lift the rake basket over an obstacle, so the rake basket does not, in fact, float, as is desirable and was intended for the equipment represented in those patents. A compression spring is also not adjustable for different types of terrain or heavy add-on options, such as castor wheels and additional tines. Thus, the primary drawback of a compression system is that it lacks the necessary sensitivity. 
     Since flotation is a major feature, and one of the most desirable characteristics of an agricultural rake and other similar agricultural devices, improvements are usually found to be commercially and operationally important. 
     It would be desirable and beneficial to provide a flotation system for an agricultural rake that would overcome the above-noted disadvantages of known rake flotation systems. 
     SUMMARY OF THE INVENTION 
     Accordingly, one object of the present invention is to provide an agricultural rake with an improved flotation system that will reduce the frequency of contact of rake tines with the ground and other objects. 
     Another object of the instant invention is to provide a flotation system for an agricultural rake that employs tension springs rather than compression springs to improve the lateral flotation characteristics of the rake basket. 
     A further object of the instant invention is to provide an improved tension spring flotation system for use with agricultural rakes and other similar pull-type equipment. 
     These and other objects, features and advantages are accomplished according to the instant invention by providing an agricultural rake basket flotation system that employs tension springs to support a portion of the weight of the rake basket, toward the lateral ends thereof, thus allowing for a more sensitive and complete response to encounters with obstacles and irregularities in the ground level. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The advantages of this invention will be apparent upon consideration of the following detailed description of the invention, especially when taken in conjunction with the accompanying drawings wherein: 
     FIG. 1 is a top plan view of an exemplary prior art rake; 
     FIG. 2 is an enlarged view of that portion of FIG. 1 enclosed in circle  2 , showing the details of the prior art header lift mechanism; 
     FIG. 3 is a view of FIG. 2 taken along line  3 — 3 , showing the header lift mechanism, the flotation mechanism and the height adjustment mechanism of the prior art; 
     FIG. 4 is a top plan view of an exemplary rake employing the principles of the instant invention; 
     FIG. 5 is an enlarged view of that portion of FIG. 4 enclosed in circle  5 , showing details of the flotation, height adjustment and header lift mechanisms of the instant invention; 
     FIG. 6 is a view of FIG. 5 taken along line  6 — 6 , showing additional details of the flotation, header lift and height adjustment mechanisms of the instant invention; 
     FIG. 7 is a cross-sectional view of the height adjustment mechanism, taken along line  7 — 7  of FIG. 5; and 
     FIG. 8 is a partial cross-sectional view of the tension spring in two different positions of flotation. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Any reference herein to the terms “left” or “right” are used as a matter of mere convenience, and are determined by standing at the rear of the machine facing in its normal direction of travel. The side delivery rake shown as prior art in FIGS. 1 through 3 is part of a unitized rake implement commonly used in the agricultural industry today, and as generally shown, for example, in U.S. Pat. No. 4,723,402 (which is incorporated herein in its entirety by reference). Side delivery rakes have, of course, been around for many years, and can be found operating as individual machines or in a unitized structure usually employing two rakes. The individual stand-alone rakes would have a slightly modified frame, and would be supported by at least two wheels. 
     Referring now to the drawings and particularly to FIG. 1, a top plan view of a well-known prior art rake can be seen as it would be used in a unitized rake structure. A frame arm, or tongue,  10  supports a conventional side delivery rake basket  20  driven by a hydraulic motor, not shown. Frame arm  10  may be attached directly to a prime mover, such as a tractor, through a common frame with another rake, as characteristic of the unitized rake disclosed in the &#39;402 patent incorporated above. The hydraulic motor and plumbing is conventional in nature and has not, in order to promote clarity and simplicity, been depicted in any of the drawings (see the &#39;402 patent for details). The rake basket  20  is supported by a main frame assembly  30  movably mounted on wheel spindle  27  positioned at the rearward end of frame arm  10 . Main frame assembly  30  is connected to rake basket  20  by a header lift mechanism  40  to permit a generally vertical movement of the rake basket  20  relative to the ground upon which wheel  11  rests, i.e., raising and lowering. Hydraulic lift cylinder  39 , operatively associated with header lift mechanism  40 , provides a conventional lift force for moving the rake basket relative to the ground. The flotation spring  50 , also operatively associated with header lift mechanism  40 , provides conventional flotation, as will be described further below, for rake basket  20 . As can be seen more clearly in FIG. 1, each end of the main frame assembly  30  includes a header lift mechanism  40 . Since, as will be discussed below, each header lift mechanism also includes a flotation mechanism, the rake basket  20  is provided with some degree of the lateral flotation. 
     As can also be seen in FIG. 1, a pair of links  37  interconnects main frame assembly  30  and rake basket  20  at spaced apart locations along the longitudinal axis of rake basket  20 . Each such link includes (FIG. 2) a tie rod  38  at both ends thereof that permits manual adjustment of the tilt of rake basket  20 . Generally, these two links should be adjusted to the same length. 
     Referring now more specifically to FIGS. 2 and 3, the header lift mechanism  40  will be further described. A pair of laterally spaced apart lift arms  41  form part of the linkage for raising and lowering the rake basket  20  relative to the main frame  30 . The lift arms  41  are pivotally connected to main frame assembly  30  and support rake basket  20 . Hydraulic lift cylinders  39 , interconnecting main frame assembly  30  and lift arm  27 , provide the necessary force to raise and lower rake basket  20  relative to the ground. Lower link  43  is pivotably connected at a first end to main frame assembly  30  and at a second end to rake basket  20 . 
     A tine height adjustment mechanism  50 , best seen in FIG. 3, provides not only a manual means of adjusting the operating height of the tines relative to the ground, but also provides some small degree of flotation for the rake basket  20 . An elongated partially threaded rod  51  has a handle  52  at the top end thereof and extends through threaded block  54 , through yoke  55 , through lower link  43 , spring  56 , all held together by a nut  58 . The main threaded portion of rod  51  is engaged with the threaded block  54 , and block  54  is, in turn, rotatably pinned to lift arm of  41 . A second threaded portion of rod  51 , at the lower end thereof is engaged by nut  58  to hold the height adjustment mechanism together. Thus, rotation of handle  52  causes threaded block  54 , and lift arm  41 , to move either upwardly or downwardly, modifying the relative positions between rake basket  20  and main frame assembly  30  (i.e., the height of the tines above the ground when in the operating position). Compression spring  56  provides some degree of flotation to the rake basket  20 , but the amount is limited by the free play in the spring due to its length, the amount of basket weight supported by the spring, and the total space between coils. 
     Referring now to FIGS. 4 through 8, the improved flotation system of the instant invention will be described. Reference numerals corresponding to those in prior art FIGS. 1 through 3 refer to similar structure or elements. 
     As best seen in FIG. 6, height adjustment mechanism  60  is comprised of an elongated partially threaded rod  61  which has a handle  52  at the top end thereof and is pivotally affixed at the lower end thereof to lower link  43  by yoke  63 . Rod  61  extends through threaded block  54  as described previously. Rotation of handle  52  raises or lowers rake basket  20  relative to main frame  30  for a fine adjustment of the height of the tines above the ground. 
     Basket tilt is controlled by a single link  37  that interconnects main frame assembly  30  and rake basket  20  at the center of the longitudinal axis of rake basket  20 . 
     Flotation is provided by two laterally spaced apart flotation mechanisms generally identified by reference numerals  70  in FIG.  4 . Flotation mechanism  70  is generally comprised of four components (see FIG.  6 ): tension spring  71 , connector  72 , connector  75  and banana-shaped link  77 . Connector  72  is comprised of an externally threaded block  73 , threaded into and thus held by spring  71 , and of rod  74  that is affixed to main frame assembly  30  by a nut. Connector  78  is comprised of an externally threaded block  75 , like block  73 , that is threaded into spring  71 , and link  76 . Banana-shaped link  77  is pivotally fixed at one in to link  76  and at the other to rake basket  20 . 
     The banana-shaped link, as best seen in FIG. 8, provides protection to the tension spring  71  by adding its length to that of the spring when the rake basket is in its lowermost operating position, thereby preventing the tension spring  71  from being overextended. Link  77  also prevents tension spring  71  from being buckled when the basket is raised into the transport position, i.e., when the spring is collapsed to its solid length. 
     Looking at FIG. 6, handle  52  is rotated manually to fine-tune the height of the tines relative to the ground and operating conditions. Turning the handle adjusts the relative position between lower link  43  and main frame assembly  30 , thereby raising or lowering rake basket  20 . Hydraulic cylinder  39  is used to make the gross adjustment of height for the rake basket  20 , i.e., raising the basket for transport or lowering it into operating position. When the rake basket is in the operating position, the two tension springs  71  are generally in the position shown in this Fig. Lateral flotation is provided by the two spaced apart springs through absorption of the lateral movement of the rake basket by the tension spring. Since the springs are relatively free to expand in length, they can absorb more basket movement, and thus provide more flotation. In the transport position, as best seen in FIG. 8 in phantom, the springs may fully collapse, but, because of the banana-shaped link  77 , do not buckle. 
     Flotation mechanism  70  thus provides lateral flotation to the rake basket as it moves across uneven ground, or when it engages an obstacle such as a rock. 
     It will be understood that changes in the details, materials, steps and arrangements of parts which have been described and illustrated to explain the nature of the invention will occur to and may be made by those skilled in the art upon a reading of this disclosure within the principles and scope of the invention. The foregoing description illustrates the preferred embodiment of the invention; however, concepts, as based upon the description, may be employed in other embodiments without departing from the scope of the invention. Accordingly, the following claims are intended to protect the invention broadly as well as in the specific form shown.