Conveyors: power-driven – Conveyor system for arranging or rearranging stream of items – By longitudinally respacing successive articles in stream
Reexamination Certificate
1998-06-22
2001-04-24
Ellis, Christopher P. (Department: 3651)
Conveyors: power-driven
Conveyor system for arranging or rearranging stream of items
By longitudinally respacing successive articles in stream
C198S577000
Reexamination Certificate
active
06220423
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a system to be used as a load sensor and regulator, in front of a high piece count transversal type lumber separator such as, for instance, the one described in U.S. Pat. No. 5,518,106 (B. Allard), dated May 21, 1996. The incoming material consists of four-faced or two-faced lumber pieces carried forward laterally in a single layer by parallel chains, towards the separator whose function is to pick out individually each piece of lumber from the incoming stream and to deposit it in turn between rows of lugs affixed on parallel carry-off chains synchronized with the offloading sequence of the separator.
BACKGROUND OF THE INVENTION
Among the transversal type lumber separators in use today, the apparatus which is the object of the heretofore quoted US patent is considered one of the most efficient performers in the industry, being known to reach piece counts up to 120 per minute, in its original mode of installation. Performance figures, however, have so far been largely influenced by two basic factors particular to the operating conditions, namely: a) the width and length variations of the pieces in the lumber supply, and b) the quality of material flow control in front of the separator. Inadequate regulation of the incoming lumber flow can produce opposite negative effects such as, on the one hand, lack of material at the loading point or, on the other hand, overlapping of pieces due to pressure build up in front of the separating device. It is well known in the industry that a flow of material consisting exclusively of 2″×4″ stock of uniform 8′ length, does not present as many handling problems as does a production in dimensions from, for example, 1″×4″ to 2″×10″, in 8′ to 16′ mixed lengths, and that the capacity of any type of feed system may be greatly affected by the lumber dimension diversity factor.
In any event, and whatever might be the limitations of present day feed systems, production advances in sawmilling have made it necessary to raise the piece count for lumber separators from a ceiling of some 120 pieces per minute, under best conditions, to numbers above 180 per minute; in other words, an increase of some 50% in operating potential is required. This need for extra piece handling capacity stems not only from the process of industrial integration which has caused individual mills to grow in size, but also from a forest resource conservation principle which dictates that more lumber should be produced from the small logs available, including the usable portion of tree tops. While this procedure results in larger production volumes, it also causes a disproportionate increase in the number of pieces to be handled through the various manufacturing stages.
Beyond the need for ever shorter loading/offloading cycles in lumber feeding devices, a further condition is imposed on these systems as a result of present high conversion rate policies which have now firmly established such processes as curved sawing (producing bowed pieces) and marginal edging (causing imperfect squaring off) as basic rules of production. As a consequence, the overall production volume in a modem sawmill contains an important proportion of rough sawn pieces having shape irregularities to be corrected in the final processes of length trimming and kiln stacking. The industry is therefore faced with an urgent need for performance improvements in feeding systems to all processes, more particularly the final ones, where the total mill production is to be separated into a succession of individual pieces for trimming, sorting and stacking.
OBJECTS AND STATEMENT OF THE INVENTION
An object of the present invention is to overcome the performance limitations of board and cant separating feeders presently in use, by means of an auxiliary system which provides precise flow regulation of the input material as well as accurate positional control of individual pieces in the loading area of the lumber separator.
This auxiliary system is located after a lumber supply transfer which itself follows a preliminary unscrambler providing single layering of the pieces. It comprises a first transfer section somewhat shorter than the minimum length of lumber transported; this is followed by a second section which carries the pieces through to the lumber separating device. These two transfer sections used for load control and piece positioning are individually driven (as well as the supply transfer) and all three are equipped with suitably disposed banks of closely spaced presence sensors.
The functions of the above described arrangement can generally be stated as follows:
to insure a continuous, regulated flow of lumber from the supply zone to the loading point in front of the separator;
to prevent “fanning out” (when several pieces of lumber remain together at one end, while spreading away from one another at the opposite end) and “jackstrawing” (a criss-cross situation existing in a group of lumber pieces) of pieces, which are most likely to occur in random length productions;
to maintain close spacing of the pieces but also prevent pressure build-up between them or against the front of the separator; and
to provide optimal positioning of the leading piece once it reaches the loading area, and thereafter the proper forward speed with regard to the loading sequence.
The present invention relates to a system for sensing lumber pieces and regulating their movement laterally towards a loading station of a lumber separating device which engages individual lumber pieces to deposit the pieces at a controlled rate on a subsequent process feeding apparatus, the system comprising:
an individually driven first transfer section following a controlled lumber supply transfer; the first transfer section having first lumber conveying means and a first driving unit possessing instantaneous speed modulation and reversal capability;
an individually driven second transfer section downstream of the first transfer section and upstream of the separating device; the second transfer section having second lumber conveying means and a second driving unit possessing instantaneous speed modulation and reversal capability;
first lumber detecting means located along the first transfer section for assessing lumber flow conditions along the first section;
second lumber detecting means located along the second transfer section for assessing lumber flow conditions along the second section and for monitoring position of the leading piece in front of the loading station; and
computer means responsive to the first and second detecting means and associated with the first and second driving units to command acceleration, stoppage or reversal of the first and second conveying means.
In one form of the invention, the system also includes third lumber detecting means located in the lumber supply transfer, for controlling the output of lumber to said first transfer section. These third detecting means are linked to the computer means to cause forward/reverse movement or stoppage of the lumber supply transfer individual driving unit hereby designated as the third driving unit.
A critical characteristic of the lumber flow control system consists in the performance of the detecting means in providing full information on load conditions, such as gaps between pieces, skewing of individual pieces and exact position of the leading piece throughout the loading sequence. The combination of such “total situation” scanning with an “all cases” computer program, plus instantaneous mechanical response provided by the particular characteristics of the first and second driving units, constitutes the basis of the present invention and also the required condition for reaching its objective of higher lumber separator performance.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that this detailed description, while indicating pref
Brisson Maurice
Gagnon Andre
Denis Compact Chicoutimi Inc.
Ellis Christopher P.
Farkas & Manelli PLLC
Taltavull W. Warren
Tran Khoi H.
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