Abstract:
A wood chipping apparatus includes a housing having a chipping chamber and an air chamber isolated by a fixed partition wall of the housing. A chipping drum is supported for rotation in the chipping chamber. A fan is supported for rotation in the fan chamber. The chambers have adjacent outlets that communicate with a discharge chute. Wood chips exiting the chipping chamber are received in the chute and are entrained by air issuing from the fan chamber to carry the chips along the chute. A baffle separates the outlets of the chambers and ensures that the air from the fan chamber does not backflow into the chipping chamber through its material outlet.

Description:
This invention relates generally to drum-type wood chippers and more particularly to the handling of the wood chips during discharge. 
     BACKGROUND OF THE INVENTION 
     Drum-type wood chippers of the kind typically used to chip tree limbs and other wood debris include a housing having an internal chamber in which a chipper drum is supported for driven rotation. The drum carries a plurality of cutting knives spaced about its perimeter which, when wood debris is fed into the chamber, reduce the limbs and such to chips. The chips are discharged through an outlet in the chamber and transported by their momentum along a discharge chute for collection, typically in a chamber or bin, such as that provided on a towing vehicle used to transport the chipper. 
     As the type of wood and size of the chips can vary, it is not uncommon for some of the chips to be too light such that they have insufficient momentum to travel the length of the discharge chute and collect in the chamber. One proposed solution to the problem has been to add fan blades to the side of the drum in order to generate a flow of air in the chipping chamber to help carry the chips along. The flow of air, however, is difficult to control and in some cases an undesirable backflow develops wherein dust and light debris is discharged through the material inlet. 
     Another proposal has been to equip such chippers with a fan external to the housing that is driven off the drum shaft and is coupled by a hose to the discharge chute for creating an air flow in the chute downstream of the outlet which acts to draw and carry the chips along and into the collection bin. While such external fan devices are effective at entraining the chips, there is not always room enough on the chipper apparatus to accommodate the mounting of the external fan assembly. Further, the necessity for an additional air hose from the fan to the discharge chamber detracts from the appearance of the chipper apparatus, is prone to damage, and adds to the maintenance and cost of the apparatus. 
     SUMMARY OF THE INVENTION 
     Apparatus for reducing wood debris to chips comprises a support frame having a housing mounted thereon with an internal chipping chamber having a circumferentially extending chamber wall. A chipping drum is supported for driven rotation within the chamber and communicates with a material inlet provided in the chamber wall for introducing wood debris into the chipper chamber for reduction to chips by the drum. A material outlet is provided in the wall for discharging the wood chips from the chamber. A discharge chute is coupled at a receiving end thereof to the housing in communication with the material outlet for receiving and guiding the chips outwardly of the housing to an opposite discharge end of the chute. 
     According to a characterizing feature of the invention, the apparatus includes a chip entrainment system comprising an internal fan chamber provided in the housing adjacent the chipping chamber that is isolated from the chipping chamber by a fixed partition wall of the housing. A fan is supported for driven rotation within the fan chamber and is operative to draw air into the air chamber through an air inlet of the fan chamber and to discharge a high velocity flow of air through an outlet of the fan chamber in communication with the receiving end of the discharge chute. A baffle is provided in the chute between the chipping and fan outlets of the housing. Air entering the chute from the fan chamber joins the flow of chips issuing from the drum chamber at a location downstream of the material outlet of the chipping chamber so as to entrain the chips and carry them forward toward the discharge end of the chute. The baffle prevents the stream of air from backflowing into the chipping chamber through the material outlet thereof. 
     The invention offers several advantages over the known prior art chip handling systems, including integrated the air flow system into the housing, eliminating space problems associated with externally mounted fans and the necessity for an external air hose to communicate with the chute. The fixed partition wall and baffle ensure that the air flow generated by the fan entrains the chips as desired downstream of the material outlet, while preventing the air flow from entering the chipping chamber and causing debris to be ejected through the material inlet. 
    
    
     THE DRAWINGS 
     A presently preferred embodiment of the invention is disclosed in the following description and in the accompanying drawings, wherein: 
     FIG. 1 is a side elevational perspective view of a chipping apparatus constructed according to a presently preferred embodiment of the invention; 
     FIG. 2 is an enlarged fragmentary elevation view of the apparatus shown partly broken away; and 
     FIG. 3 is a fragmentary end view, shown partly broken away taken generally along lines  3 — 3  of FIG.  2 . 
    
    
     DETAILED DESCRIPTION 
     Apparatus for reducing tree limbs, branches, and similar wood debris to chips is shown generally at  10  in FIG.  1  and comprises a support frame  12  mounting a set of wheels  14  and having a coupling  16  at its forward end for coupling the apparatus  10  to a towing vehicle (not shown). While any of a number of towing vehicles would be suitable, the preferred towing vehicle is the type having a collection bin that is open at the back to receive the wood chips discharged from the apparatus  10 , as will be explained further below. 
     A housing  18  is mounted on the frame  12  and includes an internal chipping chamber  20  in which a chipping drum  22  is supported for driven rotation about an axis A, as shown best in FIG.  3 . The chipping chamber  20  includes axially spaced end walls  24 ,  26  and a peripheral circumferentially extending wall  28  joined such as by welding to provide the internal chamber  20 . 
     As shown best in FIG. 1, a material feed chute  30  extends longitudinally rearwardly from the housing  18  to an open end  32  into which wood debris to be chipped is fed by an attendant. Within the chute  30  is a rotatably driven feed drum (not shown) which engages and feeds the wood debris at a predetermined rate into the chipping chamber  20  through a material inlet  34  provided in the peripheral chamber wall  28 . As the wood debris enters the chipping chamber  20 , it encounters the chipping drum  22 . The drum  22  is preferably of the usual type having a cylindrical drum body  36  fixed to a drive shaft  38  and having a circumferentially extending wall  40  generally parallel to and spaced radially from the wall  28  of the housing  18 . A plurality of replaceable chipping knives  42  are mounted about the wall  40  for rotation therewith about the axis A. The shaft  38  extends through and is journaled by the end walls of the housing  18  and is coupled to a drive motor  44  mounted on the frame  12  by a suitable drive connection, such as belt and pulleys  46 ,  48 . 
     The drum  22  is rotated at high velocity in a downwardly, clockwise direction as viewed in FIG. 2, such that the debris fed into the chamber  20  passes beneath the drum  22 . As the wood debris encounters the drum, the knives  42  reduce the material to wood chips. The high velocity of the drum carries the chips through the chamber  20  and ejects them through a material outlet  50  provided in the chamber wall  28  on the opposite side of the housing  18  as that of the material inlet  34 . 
     The apparatus  10  includes a discharge chute  52  coupled at a receiving end  54  thereof to the housing  18  in communication with the material outlet  50  for receiving and guiding the wood chips expelled from the chipping chamber  20  outwardly of the housing  18  to an opposite discharge end  56  of the chute  52 , where they are expelled into an adjacent collection bin, such as that on the towing vehicle. 
     The chipping apparatus  10  thus far described is conventional in construction and operation to existing wood chipping apparatus, such as the E-Z BEEVER® wood chippers manufactured by Morbark, Inc., of Winn, Mich. 
     In order to enhance the flow of the wood chips along the discharge chute  52  to assure that the lighter wood chip material has sufficient momentum to traverse the length of the chute and discharge into the adjacent collection bin of the tow vehicle, the apparatus  10  is provided with a chip entrainment system indicated generally at  58  in FIGS. 2 and 3. The system  58  includes an internal fan chamber  60  provided in the housing  18  axially adjacent the chipping chamber  20 . The fan chamber  60  is preferably formed as an extension of the chipping chamber  20  and includes an outer end wall  62  and an extension  64  of the circumferential wall  28  of the chipping chamber  20 . The end wall  26  of the chipping chamber  20  is internal to the housing  18  and serves as a fixed, solid partition separating the chipper chamber  20  from the fan chamber  60  and thereby preventing air from the fan chamber  60  from entering the chipping chamber  20  through the partition wall  26 . 
     As shown best in FIG. 2, the fan chamber  60  includes a plurality of air inlets  66  formed in the outer end wall  62  of the fan chamber  60  communicating with the external atmosphere to draw air into the chamber  60 . A fan  68  is supported in the chamber  60  for driven rotation, and preferably is fixed to a section of the drive shaft  38  extending through the chamber  60  for conjoint rotation with the drum  22 . The fan  68  includes a disc-like body  70  fixed to the shaft  38  adjacent the partition wall  26  mounting a plurality of fan blades  72  fixed to a side  74  of the body  70  facing away from the chipper chamber  20  for rotation therewith. The fan chamber  60  has an air outlet  76  adjacent the material outlet  50  of the chipper chamber  20 . The receiving end  54  of the discharge chute  52  communicates with the air outlet  76 . A baffle  78  extends form the housing  18  into the discharge chute  52  between the material outlet  50  and air outlet  76 , dividing the receiving end  54  of the discharge chute  52  into a chip side  79  communicating with the chipping chamber  20  and an air side  80  communicating with the fan chamber  60 . The baffle  78  is preferably formed as an extension of the partition wall  26  and terminates within the receiving end  54  of the chute  52  at a free end  82  that is downstream of the material and air outlets  50 ,  76 . 
     In operation, the fan  68  rotates with the drum and draws air into the chamber  60  through the air inlets and discharges a high velocity flow of air into the discharge chute through the air outlet  76  where it is directed by the walls of the discharge chute and the baffle  78  downstream of the chute where it joins with and entrains the flow of wood chips downstream of the free end  82  and carries the chips toward the discharge end  56  of the chute  52  with sufficient velocity and momentum to ensure that the chips are discharged into the adjacent collection bin. The partition wall  26  and baffle  78  ensure that the entrainment air does not enter the chipping chamber  20  and cause undesirable turbulence that would interfere with the flow of the chips through the material outlet  50 , and particularly prevents any such air from entering the chipping chamber and causing dust and light wood debris to be discharged through the material inlet  34  of the apparatus  10 . 
     For purposes of maintenance, it is desirable to be able to selectively secure the drum  22  and fan  60  against rotation relative to the housing  18 . For this purpose, the end wall  62  of the fan chamber  60  is formed with at least one opening  84  that aligns with at least one corresponding opening  86  in the body of the fan  70  for receiving a stop bar or suitable tool therein (not shown) from outside the housing  18 , preventing the fan  68  and thus the drum  22  from rotating about its axis A. 
     The disclosed embodiment is representative of a presently preferred form of the invention, but is intended to be illustrative rather than definitive thereof. The invention is defined in the claims.