Cutting – With means to monitor and control operation – Including means to correct the sensed operation
Reexamination Certificate
2001-09-26
2004-03-16
Shoap, Allan N. (Department: 3724)
Cutting
With means to monitor and control operation
Including means to correct the sensed operation
C083S370000, C083S425200, C144S357000
Reexamination Certificate
active
06705190
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the field of trimmers and in particular to an improved lumber trimmer which may include P.E.T. saws.
BACKGROUND OF THE INVENTION
As well-documented in the prior art, there is continual development in devices for optimizing lumber production. Typically the optimization of lumber production is accomplished by either increasing the yield rate or the piece rate, or both. That is, optimization of lumber production is accomplished by maximizing the amount of useable lumber obtained from a single raw workpiece such as a log, and this is often optimized to maximize the amount of useable lumber having the highest resale value. As an example of optimising the piece rate, it is desirable to increase the production rate for example by increasing the efficiency of lumber production, often reflected in the maximum maintainable transfer speed expressed in for example feet per minute, lugs per minute or boards per minute. In optimizing the yield rate, speed and accuracy in implementing the optimized cutting solution is important if not paramount.
In the specific instance of a trimming saw or trimmer having multiple saws, where the accuracy of cut may be desirably measured in the tens of thousandths of an inch to optimize the yield rate, and where the piece rates are high for example on infeed conveyors up to 200 lugs per minute, prior art ending of lumber pieces against a fence for example by the use of ending rolls or angled in-line wheels often result in unacceptable inaccuracy due to bounce-back, tip-crush or the like.
In the prior art applicant is aware of U.S. Pat. No. 5,142,955 which issued Sep. 1, 1992 to Hale for a Lumber Cutter for Removing End Defects and Sawing to Desired Lengths. Hale discloses a root end trim saw extending over the root end edge of a lumber piece conveyor. The saw blade is articulated to move down into or up out of the path of lumber pieces and is slidably mounted to be moved over a two-foot range in one-half inch increments to cut away a defective end portion of a lumber piece. The root end trim saw pre-trims a lumber piece which is then ended against a fence prior to entering a trimmer. In use such a saw suffers from at least two drawbacks, namely, that following pre-trimming by the saw the lumber is then ended against a fence reintroducing inaccuracy in positioning of the lumber piece as it enters the trimmer, and, secondly, that at high piece rates the lateral positioning of the root end trim saw within the range specified will limit the transfer rate. The lumber pieces cannot arrive quicker than the time required for the saw to be moved into position for its next cut. As an example, in a worst case scenario, the saw must be translated across the length of its range between the arrival of adjacent lumber pieces. Thus, at high piece rates, it may be required that the conveyor be slowed down until the root end trim saw can be slid into position, thus adversely affecting the optimum piece rate. Consequently it will be appreciated that the design of Hale may adversely affect not only the accuracy of the yield, and thus the yield rate, but also the piece rate.
SUMMARY OF THE INVENTION
The optimizer controls obtaining the desired yield from a particular raw lumber piece. In order to do so, the optimizer controls the yield and piece rates. In applicant's experience, quite often the optimizer optimizes the cutting solution so as to obtain the most-valuable (i.e. highest yield rate) combination of sawn lumber pieces which may be sawn from the raw lumber piece. Where an end trimmer saw, for example the pre-trimmer root end saw of Hale or a so-called precision end trimmer (“P.E.T.”) saw is employed, that is, an end trimming saw which is laterally translatable relative to the length of an incoming lumber piece, in a worst case scenario must translate for example 12 inches between adjacent arriving lumber pieces, the optimizer may reduce the infeed conveyor speed (i.e. reduce the piece rate) so as to not adversely affect the yield rate. That is, the optimizer adversely affects the piece rate in order to obtain the highest value yield rate. In applicant's view, an overall optimized solution in such an instance may be obtained, firstly, by the optimizer implementing for example a second, as opposed to first, most-valuable default cut where the second or lesser valuable default cuts do not, or have a lesser adverse effect on, the piece rate. It is applicant's view that in the trade-off between a first most-valuable cut and a second or lesser valuable default cut and the trade-off in reducing the piece rate in order to implement the most-valuable cut or maintaining a high piece rate while implementing a second or lesser valuable default cut, a globally optimized result is obtained by maintaining the maximum piece rate and accepting a second or lesser valuable default cut thereby slightly degrading the yield rate. Secondly, rather than merely relying on a single root end or P.E.T. trimming saw, a plurality of root end or P.E.T. saws may be employed.
Use of a plurality such as a pair of P.E.T. saws in conjunction with an active infeed board positioner such as, without intending to be limiting, a live fence or selectively actuable ending rolls or inclined in-line wheels (so called skate wheels), allow for adjacent lumber pieces on the infeed to be end-trimmed, if need be, as for example when two adjacent boards need P.E.T. sawing or a specific (e.g. metric) length is best suited, alternating between for example alternating P.E.T. saws in a pair of such saws. The pair of saws may be opposed facing or may be side-by-side, or may form a subset of a plurality of such saws. Thus, as needed, a first P.E.T. saw may be employed to end-trim a first lumber piece, and a second P.E.T. saw may be employed to end-trim the next adjacent second lumber piece.
The trimmer of the present invention includes a low profile housing which may be accessed for maintenance from the top of the housing by the opening of clam shell doors. The clam shell doors open oppositely so as to pivot about opposite perimeter edges of the top of the housing. The housing defines an upper compartment or cavity which may be closed by closing the clam shell doors. The upper compartment is bisected by a beam, which may be in the form of generally an I-beam. The beam bisects the compartment and runs parallel to perimeter edges about which the clam shell doors pivot.
The vertical webbing of the beam is apertured. The upper flanges of the beam mate with the distal ends of the clam shell doors when the doors are closed. The clam shell doors may be pivoted either manually or with the assistance of actuators known in the art. The floor of the cavity may be sheeted so as to provide a walkway for maintenance personnel. One or more of the clam shell doors may also be sheeted and shaped, so that when fully open, a further walkway is provided along the length of the trimmer housing.
A laterally spaced-apart array of drop saws are mounted along one half of the compartment, that is, on one side of the center beam. The drop saws are rotatably mounted on saw ladders which themselves are pivotally mounted to the beam web. The saw drive motors and the saw ladder actuator are mounted on the opposite side of the beam web, in the other half of the compartment. The actuator may be a cylinder which strokes through an aperture in the beam web so as to drive one end of a bellcrank-shaped saw ladder, the drop saws mounted at the opposite end of the bell crank. The drop saws may be each driven by a pair of drive belts, where the first drive belt extends between the saw hub and the pivoting hub of the saw ladder, and the second drive belt extends from the pivoting hub of the saw ladder to a drive shaft of a drive motor.
In one embodiment of the present invention, a single drive motor drives a pair of first drive belts where each of the pair of first drive belts drive oppositely disposed shafts extending through the pivot hubs of the saw ladders so as to thereby drive a pair of second dri
Halper Paul L.
Henderson Deane R.
Newnes William R.
Alie Ghassen
Coe Newnes McGehee ULC
Edwards Antony G.
Shoap Allan N.
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