Abstract:
A cutter head assembly comprising a first longitudinal member; a second hollow longitudinal member provided with at least one aperture, being coaxial with the first longitudinal member and radially spaced apart therefrom; cup-shaped elements fixedly mounted to a corresponding aperture and to the first longitudinal member; blade holders to removably secure a rotatable blade to the cutter head. These blade holders are designed so as to improve mulching action and resistance to impacts of the cutter head, for use in land clearing and in any operation involving mechanical vegetation cutting.

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to land clearing and to any operation involving mechanical vegetation cutting. More specifically, the present invention is concerned with a cutter head assembly for such operations. 
     BACKGROUND OF THE INVENTION 
     Felling and mulching operations are conventionally performed using a removable cutter head fixed on a self-propelled vehicle that is either wheeled or tracked, for example. There are two types of equipment known in the art and readily available on the market for felling and mulching operations: vertical shaft cutter heads, usually mounted to the side of the vehicle, and horizontal shaft cutter heads, usually mounted to the front of the vehicle. 
     Vertical shaft cutter heads are generally similar to lawn mowers and will not be further discussed herein. 
     Horizontal shaft cutter heads are generally made of a horizontal rotor around which blades are attached by means of blade retaining devices. This rotor is typically driven in rotation by a hydraulic motor. The blade retaining devices are commonly made from long rods on which the blades are aligned out, side by side on the same row, or following a spiral design. 
     The cutter heads mentioned hereinabove have several drawbacks. More specifically, changing a single worn out blade can be complex and time-consuming. It often results in the user changing all the blades of a same row at once, no matter if they require being replaced or not, in order to avoid repeating the process within a short period of time and so as to prevent decreased cutting efficiency. 
     Moreover, the mechanical resistance of the above mentioned cutter heads to repeated impacts is limited because the rotor is generally made of a single hollow tube. Also, since the width of the rotor rarely exceeds 1.5 meters, the resulting cutting surface is insufficient for works on large terrains. This type of rotors is generally designed for domestic use more than for industrial applications. 
     In addition, the method of attachment of the cutter blades presented in the prior art does not satisfactorily meet the requirements of both simplicity and resistance to impacts. More precisely, the relatively wide interspaces provided between adjacent cutter blades, while enhancing the overall cutting surface of the device, may cause chips of wood or other foreign matters such as steel fence, roots, wire and the like, to be caught in these interspaces, which may reduce the efficiency of the cutter in use. Also, when performing cutting operation, such a design may result in projections of wood chips harmful to people standing around. 
     Efforts have been made in order to solve the above problems. In particular, the flail cutter described by Dallman, in his European Patent no. 0,951,815 issued in 1999, has a coaxial structure that comprises a rotation shaft inserted into a pair of hollow tubes. However, while permitting an easy set up of the cutter blade holding devices, this structure is not designed to sustain great impacts. 
     The prior art was also concerned with improving the shape of the cutter blade holders. Bachmans, in his patent GB 2,307,630 issued in 1997, describes an assembly comprising a hollow tube provided with apertures that receive cup-shaped elements welded by their bottom base to said tube. The walls of these elements extend beyond the diameter of the tube to form the cutter blade holders. 
     In spite of previous improvements, the mechanical resistance to impact of such assemblies is still often insufficient, and the design of the blade holders is not optimized in order to grant smooth unobstructed flow of the chipped wood and hence efficiency of the cutter head. 
     There is therefore a need for a cutter head that would be powerful, tough and safe enough to allow industrial work. 
     OBJECTS OF THE INVENTION 
     An object of the present invention is therefore to provide an improved cutter head assembly. 
     SUMMARY OF THE INVENTION 
     More specifically, in accordance with the present invention, there is provided a cutter head assembly comprising: 
     a first longitudinal member; 
     a second hollow longitudinal member provided with at least one aperture, said second longitudinal member being coaxial with said first longitudinal member and radially spaced apart therefrom; 
     at least one cup-shaped element comprising four side-walls, each said at least one cup-shaped element being fixedly mounted to both a corresponding one of said at least one aperture and said first longitudinal member; and 
     at least one cutter blade mounted in said at least one cup-shaped element. 
     According to another aspect of the present invention, there is provided a blade holder to removably secure a cutting blade into a generally longitudinal cutter head provided with a plurality of apertures separated by interspaces; said blade holder comprising: 
     a fin-shaped top surface; 
     a bottom surface to be mounted to said cutter head; and 
     lateral surfaces that are configured to receive a cutting blade; 
     wherein said blade holder has a longitudinal width that completely fills the interspace between two consecutive apertures of said cutter head. 
     Other objects, advantages and features of the present invention will become more apparent upon reading of the following nonrestrictive description of preferred embodiments thereof, given by way of example only with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the appended drawings: 
     FIG. 1 is a top view of a cutting head assembly according to an embodiment of the present invention; 
     FIG. 2 is a part-sectional and part-exploded tri-dimensional view of the cutting head assembly of FIG. 1; 
     FIG. 3 is an end view of the cutter head assembly of FIG. 1; and 
     FIG. 4 is a cross sectional view taken along line  4 — 4  of FIG.  1 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In a nutshell, the present invention is generally concerned with a horizontal cutter head assembly comprising coaxial inner and outer tubes and cutter blade holders so configured as to increase cutter efficiency and wear life of the cutter head assembly. 
     Turning now more specifically to FIGS. 1 and 2 of the appended drawings, the structure of a cutter head assembly  10  according to an embodiment of the present invention will be described. 
     The cutter head assembly  10  comprises an outer tube  12  and an inner longitudinal member shown in our example as an inner hollow tube  14 , coaxially mounted inside the outer tube  12  and radially spaced apart from it. Two end caps  16  and  17  are provided at opposite longitudinal ends of the tubes  12  and  14  and are secured to both tubes  12  and  14 . These end caps  16  and  17  include threaded apertures  19 . 
     It should be noted that the assembly of the present invention does not display any central shaft. Instead, the driving shaft of the assembly comprises two lateral mounting elements  16   a  (only one shown in FIG. 2) each mounted to a corresponding end cap  16  and  17  as will be described hereinbelow. 
     The outer tube  12  is provided with rectangular-shaped apertures  18  circumferentially located in spiral patterns around the outer tube  12 . Each of these apertures  18  is so designed as to receive a respective cup-shaped element  20 . 
     Each cup-shaped element  20  includes two curved side-walls  22  and two flat side-walls  24 . These side-walls  22  and  24  are advantageously secured to one another, via welding for example, before being mounted to the tubes  12  and  14 . 
     As can be better seen from FIG. 4 of the appended drawings, the cup shape elements  20  do not include a bottom wall, but the lower portions of the side-walls  22  and  24  are secured to the inner tube  14  via welding, for example. Similarly, the upper portion of the side-walls  22  and  24  are secured to the outer tube  12  via welding. 
     As will be apparent to one skilled in the art, by welding the cub shape elements to both the outer and inner tubes  12  and  14 , a stronger cutter head assembly is produced. 
     In the interspaces  26  between consecutive apertures  18  of the outer tube  12  are mounted cutter blade holders  28 . These cutter blade holders  28  are therefore located according to a spiral pattern circumferentially around the tube  12  (as can be best seen on FIG.  3 ). 
     The holders  28  are independent and integral elements, comprising a concave base  30  that fits the shape of the outer tube  12  and a top convex surface  32  that protrudes outward beyond the diameter of the tube  12 . This protruding surface  32  is generally fin-shaped. 
     Moreover the cutter blade holders  28  are so longitudinally sized in width that once in place they completely fill the interspaces  26  between consecutive apertures  18  on the tube  12  (see FIG.  1 ). 
     The concave base  30  of the blade holders  28  include beveled surfaces  31 , as can be better seen from FIG. 1, allowing a better welding of the holders  28  to the outer tube  12 . 
     The side of the blade holders  28  includes a first rounded aperture  34  provided with a D-shaped shoulder  35  on a first lateral surface of the blade holder  28 , configured and sized to receive the D-shaped head  36  of a threaded fastener  38 . The blade holder  28  also includes a second rounded aperture  40  provided with a round shoulder  41  on a second surface of the blade holder  28 , the purpose of which will be described hereinbelow. 
     As can be better seen from FIG. 2, the aperture  40  of one blade holder  28  is aligned with the aperture  34  of an adjacent blade holder  28 . 
     The blade holding assembly  42  includes the fastener  38 , a pair of bushings  44  and  46 , a washer  48  and a nut  50 , all used to secure a rotating cutter blade  52  between adjacent blade holders  28 , hence inside the cup-shape element. 
     The bushings  44  and  46 , made of ultra-resistant steel, are advantageously inserted in a press-fit manner inside the apertures  34  and  40  of blade holders  28  so as to protect the blade holders  28  from wear caused by abrasion and vibrations while facilitating blade replacement. In such a fashion, only the bushings wear out and need be replaced. This feature increases the wear life of the cutter blade holders  28  and improves the efficiency of the cutter head assembly  10  since the blades  52  are not stopped in their rotation movements by wear on blade holders  28 . Every blade  52  is mounted individually and easily replaceable. Indeed, once the bushings  44  and  46  are respectively inserted in the apertures  34  and  40 , the blade  52  may be positioned between adjacent blade holders  28 , the fastener may be inserted in the apertures  34  and  40  through apertures of the blade  52 . The washer  48  in then inserted in the shoulder  41  and the nut is mounted to the fastener  38 . 
     As will easily be understood by one skilled in the art, the configuration and position of the apertures  34  and  40  allow each blade  52  to be installed and removed independently. 
     It is to be noted that, as can be seen from FIG. 1, the shoulders  35  and  41  are sufficiently deep that neither the head  36  of the fastener  38  or the nut  50  protrudes from the lateral surfaces of the holder  28 . 
     As can be seen from the dashed line arrow  54  of FIG. 4, the blade  52  can freely rotate and swing back inside the cup-shaped elements  18  whenever an obstacle is hit by the blade  52 . 
     As mentioned hereinabove, the different parts and elements are advantageously fixedly mounted together by welding. Thus the two radially curved sides  22  and two longitudinal side-walls  24  of the cup-shaped element  20  are welded together and to the inner and outer tubes  12  and  14 ; and the concave base  30  of the cutter blade holders  28  are fixedly mounted to the outer tube  12  by welding in the interspaces  26  between consecutive rectangular apertures  18 . 
     Each one of the two lateral mounting elements  16   a  is mounted to a corresponding end cap  16  or  17  by means of a substantially annular end plate  56  provided with apertures  58  corresponding to the threaded apertures  19  of the end caps. Fasteners  60  are used to removably mount the lateral mounting element  16   a  to the end cap. Hence these mounting elements  16   a  are very easily removed and replaced in case of damage or deformation, with a minimum waste of time. 
     The fin-shaped cutter blade holders  28  are designed so that obstacles such as a chip of wood or other foreign matter will gently slide on them instead of impairing the movement of the cutter head  10  or inducing damage to the assembly. Moreover, since they are affixed to the tube  12  in the interspaces  26  between apertures  18  containing the cup-shaped elements  20 , the cutter blade holders  28  contribute to an improved mulching action of the cutter head  10  and permit an unobstructed flow of matter since a full width of wooden object cannot be stuck in the interspaces  26  comprised between the apertures  18  in tube  12 . 
     As a way of example, the overall assembly can have a width of 2.3 meters and be installed directly at the front of a vehicle. The cutter head assembly  10  is advantageously made of resistant material, advantageously ultra-resistant steel, to achieve the mechanical solidity and resistance required for the work to be performed. 
     It will be noted that the presence of the member  14  coaxially located inside the outer tube  12  and spaced apart from it, provides for additional inertia to the assembly. It is also to be noted that even though the member  14  is shown as a cylindrical hollow tube, this is not a limitation of the present invention since a solid tube, having a circular cross-section or not, could be used. 
     Although the present invention has been described hereinabove by way of preferred embodiments thereof, it can be modified, without departing from the spirit and nature of the subject invention as defined in the appended claims.