Patent Application
20100230523
This invention involves a disc type wood chipper and, in particular, a wood chipping machine that is capable of producing wood chips of a small enough size such that the chips can be economically reduced to wood flour utilizing largely energy supplied to the machine for chipping but typically wasted in the chipping and chip discharge process.
This invention relates to a wood chipping machine that utilizes most of the available and unused internal energy of the machine needed to generate chips of a size that they can be further reduced to wood flour in a single low energy cutting and hammering operation. This reduction to wood flour was historically accomplished by chipping logs or wood scraps into chips having a ¾″ length/width or less and then collecting these chips and hammering them into wood flour in a high horsepower, energy inefficient hammer mill. Hammering whole logs and large chips directly into powder has also been attempted but has proven to be extremely inefficient and results in an extremely low production rate.
Typically disc type chippers having sufficiently large enough production rates suitable for use in economic industrial processes, utilize relatively large diameter discs which are generally in the 72″ (1.8 M) range. Depending on the process involved, between 10 and 40 knives are used to obtain an adequate output rate when the disc is rotated at rim speeds of between 9,200 and 12,000 feet per minute (2800-3600 M/min). Accordingly, these machines require a good deal of energy, a high percentage of which is not consumed or utilized in the chipping process but is discharged from the machine with the chips largely in the form of heat.
It is therefore an object of the present invention to more thoroughly utilize virtually all of the energy supplied to a disc type wood chipper to further reduce the wood particle size normally produced in the chipper.
It is a further object of the present invention to improve large disc type chippers that are used in the production of wood flour.
It is a further object of the present invention to reduce the costs involved in the production of wood chips of a small size for chemical processing or for the production of pelletized fuels.
These and other objects of the present invention are attained in a disc type chipping machine having a chipping disc that contains a plurality of generally radially extending slots passing through the disc between its front face to its back face. The disc is enclosed within a protective casing. A primary knife is located within the front face entrance of each slot and is arranged to cut chips of a desired length from a wood work piece that is brought in contact therewith. A counter knife is mounted immediately behind each primary knife and is arranged to slice each chip longitudinally as the chip passes through the slot thus utilizing the energy normally imparted to the chips. A series of hammers are mounted upon the back face of the disc adjacent to each slot which coact with stationary anvils that are mounted upon the inside of the casing to further break up or pulverize the chips leaving each slot. The chips are then delivered by centrifugal force into a flow channel that surrounds the outer back face and rim of the disc. A series of paddle units are mounted upon the disc with each unit having a wing that passes over the rim of the disc to engage the chip in the flow channel and conducts the chips into a discharge duct. In a further refinement, serrated chip cutters are contained on at least one wall of the flow channel which coact with the wings to further reduce the size of the chips prior to their entering the discharge duct. Here again only the energy normally associated with the chipping operation is utilized in this chip reduction operation. The discharge duct is connected to a separator or chip bin in which the chips are separated from air in the flow stream. A roughened or serrated baffle plate is located at the entrance to the separator or bin upon which the entering chips are impinged to again still further reduce the size of the chips utilizing the kinetic energy stored in the chip stream.
For a better understanding of these and other objects of the present invention reference will be made to the following detailed description of the of the invention which is to be read in association with the accompanying drawings, wherein:
Turning initially to
As further illustrated in
As best shown in
This type of knife holder is relatively simple in design, however it provides for ease of positioning of both knifes so that the blades of the counter knife can be properly aligned with the blade of the primary knife while, at the same time enabling the primary blade to be positioned within the slot to produce chips having a desired length that typically is between ¼″ and ⅝″ (6 and 10 mm). As noted above, as the initially cut chips move through each slot they are cut longitudinally by the blades of the counter knife. As illustrated in
Upon leaving each slot, the chips are directed by the centrifugal force generated by the rotating disc toward the rim of the disc and ultimately into a flow channel 40 (
After the hammering operation is completed, the chips move upwardly in the flow channel into the rim area of the rotating disc. As illustrated in
A close running clearance can be provided between the edges of the blades and the walls of the chamber. A number of serrated sections 70-70 are contained on the inner surface 71 of the top wall of the flow chamber. The serrated sections extend across the entire width of the paddle blades whereby the chips are forced by the rotating disc into contact with the serrations as the paddle blades move thereunder. Here again, due to forces involved and the speed of the disc, the average chip size is further reduced within the chamber before the flow is released to the discharge duct. The upper edge of the paddle blades can also contain serrations 76 to further enhance the effectiveness of the chip reducing process.
As noted above, the disc rim speed of the machine is preferably between 9,200 and 13,000 feet per minute. Accordingly, the chips entering the duct are moving at or slightly below the rim velocity of the disc. A good deal of kinetic energy is thus contained in the exiting flow stream. As shown in
Turning now to
As should be now evident, the chips produced in the present machine undergo a multi-step reduction in size as they move through the machine. Two of the steps involve the slicing of chips from a wooden work piece while the following steps involve further physically breaking down or pulverizing the chips. These steps are all carried out utilizing the energy already supplied to a chipper for chipping but not normally utilized for significant material size reduction by the machine to produce chips of a size such that the chips can pass freely through a sieve having ⅜″ (10 mm) diameter holes. Accordingly, the chips so produced can be more efficiently and rapidly turned into the extremely small sizes necessary in the production of wood pellets or for use in various chemical or industrial processes.
While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof to adapt to particular situations without departing from the scope of the invention. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope and spirit of the appended claims.
