Title:
VENEER STACKER
United States Patent 3698708


Abstract:
Apparatus for sorting and stacking veneer sheets comprising a vacuum infeed conveyor transporting individual sheets of veneer width-wise to a position above a scissors lift table whereupon parallel-motion knockdown arms are actuated to force the sheet loose from the vacuum conveyor and down onto the top of a pile forming on the lift. Squaring of the pile of sheets into a uniform stack is accomplished by the knockdown arms which move the forward lateral edge of the sheet up against a fixed stop acting in conjunction with a pair of actuatable even-ender pusher arms which align the longitudinal edges of the sheet. When a predetermined pile height is reached, as determined by the downward indexing of the scissors lift, the completed pile is discharged from the apparatus by an outfeed conveyor. While the pile is being discharged a pair of accumulator members are moved into position beneath the knockdown arms so as to temporarily support and retain the initial several sheets of a new pile as the scissors lift is discharged and recycled to the position where it is ready to receive the new pile in formation. A modification of the apparatus provides one or more additional bin locations adjacent the first bin location to receive and segregate the veneer sheets into stacks according to size or other criterion.



Inventors:
BRAWN PHILIP E
Application Number:
05/107319
Publication Date:
10/17/1972
Filing Date:
01/18/1971
Assignee:
CAROTHERS SHEET METAL CO.
Primary Class:
Other Classes:
271/189, 271/197, 414/790, 414/790.8, 414/793.1
International Classes:
B65H29/32; B65H31/30; B65H31/32; B65H31/34; (IPC1-7): B65H29/32
Field of Search:
209/82 271
View Patent Images:



Primary Examiner:
Schacher, Richard A.
Claims:
What is claimed is

1. Apparatus for stacking veneer sheets comprising:

2. In an apparatus for stacking veneer sheets inside a bin wherein individual sheets of veneer are horizontally transported to a predetermined position above said bin and then are deposited on top of a pile formed of said sheets, and accumulator means are provided for temporarily supporting the initial sheets of a new pile while a completed pile of sheets is removed from said bin, the improvement wherein said accumulator means comprises:

Description:
BACKGROUND OF THE INVENTION

This invention relates to improvements in a veneer stacker for stacking individual sheets or plies of veneer into a uniform pile, and thereafter outfeeding the pile so formed so that it can be strapped, transferred to a dolly or forklift truck or otherwise handled for further processing. More specifically, the veneer stacker of the present invention provides improved means for ensuring that a uniformly-aligned stack of veneer is formed and that the operation of the infeed supplying individual sheets of veneer to the stacker apparatus is not delayed or interrupted while a completed stack of veneer is discharged from the apparatus. Additionally, a modification of the invention extends the apparatus to cover a plurality of bin locations so that veneer sheets fed into the apparatus can be sorted and stacked according to size, grade, moisture content or other criteria for segregation.

Devices for sorting and stacking veneer sheets or plies as they are received from the dryer or the green chain end of the clipper of a veneer line are known to the art and shown for example in Stickney U.S. Pat. No. 3,508,648 and Keller U.S. Pat. No. 3,540,567. Generally speaking, the major difficulties encountered with prior art sorters/stackers of the type described are that (1) they do not satisfactorily align the sheets both longitudinally and laterally so as to form a satisfactorily squared-up stack, and (2) the operation of the apparatus must be interrupted or slowed down, or alternatively an additional holding bin location provided, while a completed stack is removed from the apparatus. Accordingly, a real need exists in the forest products industry for a veneer stacker which will consistently and reliably form individual sheets of veneer into a uniformly-aligned stack which can thereafter be removed from the apparatus in a manner which will avoid disruption or slow-down of the production line.

SUMMARY OF THE PRESENT INVENTION

The present invention is directed to a veneer stacker of the general type described in which a vacuum infeed conveyor transports individual sheets of veneer along their lateral (i.e., transverse-to-the-grain) dimension to a position above a scissors lift table whereupon parallel-motion knockdown arms are actuated to force the sheet loose from the conveyor and down onto the top of a pile forming on the lift table. Even-ending pusher arms acting on the longitudinal (parallel-to-the-grain) sides of the veneer sheet, in conjunction with the parallel-motion knockdown arms and an anti-kickback element for receiving and holding the forward lateral edge of the veneer sheet, ensure uniform longitudinal and transverse alignment of each sheet delivered onto the stack. Accumulator means in the form of actuatable arm elements are provided for temporarily supporting the initial several sheets forming a new pile while the previously-formed stack of veneer is discharged from the apparatus so as to thereby avoid the necessity for interrupting or slowing down the operation of the apparatus, or alternatively providing a temporary holding bin location while a completed stack is removed. In a modification of the apparatus, additional in-line bin locations are provided, each capable of forming a stack of veneer from sheets of predetermined size, so as to provide a sorting capability for the apparatus wherein veneer sheets infeeding to the apparatus of diverse size, grade, moisture content, or other criteria can be segregated according to the sorting criteria and stacked into uniform piles.

It is therefore a principal objective of the present invention to provide a new and improved stacker for veneer sheets and like material which is of economical design, minimizes the possibility of damage or degrade of the veneer in the stacking process, builds up a more compact and uniformly-aligned pile, and provides means for rapidly discharging a completed stack without disrupting or delaying the regular flow of material infeeding into the apparatus.

It is a principal feature of the present invention to provide a veneer stacker of the type described wherein accumulator means are provided for temporarily supporting and retaining the initial group of sheets forming the beginning of a new pile while the completed pile previously formed is outfed from the apparatus.

It is a further feature of the present invention to provide in a stacker apparatus of the improved type described means for sorting the individual veneer sheets according to one or more criteria such as size, species, moisture content and the like and thereafter stacking them into uniform piles at designated bin locations.

The foregoing and other objectives, features and advantages of the present invention will be more readily understood upon consideration of the following detailed description of the invention, taken into conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an end elevational view of an illustrative embodiment of the veneer stacker of the present invention with the accumulator elements shown in the operative position.

FIG. 1A is an end sectional view of the main portion of the veneer stacker with the accumulator element shown in the retracted position.

FIG. 2 is a side elevational view of the veneer stacker, with the outfeed conveyor mechanism removed for the sake of clarity.

FIG. 3 is a top plan view of the veneer stacker.

FIG. 4 is a detail sectional view of one of the vacuum infeed conveyor belts taken along the line 4--4 in FIG. 3.

FIG. 5 is an underview of the vacuum conveyor belt taken along the line 5--5 in FIG. 4.

FIG. 6 is an enlarged side view showing details of the knockdown arm mechanism of the veneer stacker.

FIG. 7 is an enlarged end view showing details of the accumulator mechanism.

FIG. 8 is a partial side elevational view showing a modified form of accumulator mechanism for use with a one or two-bin capacity veneer stacker.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings, particularly FIGS. 1-3 initially, an exemplary embodiment of the veneer stacker apparatus comprises a skeletal framework of metal girders and tubing 11 defining two respective bin locations 12, 14 for the stacking of veneer into two piles segregated according to size or other criteria. Illustratively, the sorting may be on the basis of width with the first bin location 12 receiving sheets of 54 -inch width and the second bin location 14 receiving sheets of 27 -inch width, which sizes are the standard sheet widths employed in the domestic veneer industry for faces, centers and backs in the lay-up of veneer into 4-by- 8 foot plywood panels.

The stacker apparatus is typically located to receive veneer sheets directly from either a veneer dryer or the green chain end of a veneer production line. The infeeding of veneer into the entry end of the stacker is accomplished with a vacuum conveyor 16, the details of which are described hereinafter, which transports the individual sheets width-wise along their transverse-to-the-grain dimension, by the application of negative pressure or suction to the top surface thereof, to a position directly above the designated bin location 12 or 14, depending upon the size of the veneer sheet. At this point a pair of knockdown arms 18 is actuated by the tripping of limit switch 29a to press the veneer sheet loose from the vacuum conveyor and force the sheet downward and forward until its leading lateral edge (see FIG. 6) abuts against a fixed stop 50. The sheet is retained in abutting position against the stop 50 by means of a spring-biased serrated jaw element 22a attached to the frame and pressing downward on the forward edge of the veneer pile to prevent kickback of the sheet after it has been brought against the rest 50. A pair of auxiliary spring arm elements 24 having a vertically-depending leg 24a assist in maintaining the the veneer sheet in as the stack is formed.

Immediately after the veneer sheet is removed from the conveyor infeed 16 by the action of the knockdown arms 18, the longitudinal (parallel-to-the-grain) edges of each veneer sheet 28 is aligned by the energization of actuators 30a operating even-ender pusher arms 30 which, through a time delay after the tripping of limit switch 29, simultaneously retract and then move inwardly toward each other to align the veneer sheet therebetween. After the veneer has been pushed under the anti-kickback jaw 22, and up against the stop 50 the even-ender pusher arms 30 remain in the extended position bearing against the longitudinal edges of the top plies in the stack thus retaining the veneer sheets in a uniformly-aligned pile as additional sheets are added.

The veneer stack 28 is supported on a scissors lift table 23 which indexes downward, upon triggering of limit switch 47, in regular increments as the pile builds up. The top of the scissors lift table 23 is formed of a plurality of spaced free-turning rollers 25 aligned parallel to the lateral or short dimension of the sheet to facilitate lengthwise removal of the completed stack of veneer from the side of the apparatus.

When the lift table 23 has indexed downward to a point where a pile of predetermined height (e.g., 30 inches) has been formed, limit switch 39 is thereupon triggered, causing the scissors lift to continue downward until it bottoms out and at the same time bringing into position beneath the infeed conveyor 16 the arms 35 of an accumulator mechanism, the details of which are hereinafter described, for receiving and temporarily supporting the initial group of sheets of a new pile of veneer while the previously-formed stack 28 is removed automatically from the bin location. (During the time the veneer is being temporarily stacked on the accumulator limit switch 42 is maintained triggered which de-activates limit switch 47 controlling the indexing of the scissors lift table 23.) Discharge of the completed stack after the scissors table 23 has bottomed out is effected by actuation through limit switch 45 of the drive 40 of an endless chain conveyor 43 which transports the completed stack 28, along its longitudinal dimension, off of the rollers 25 formed into the top of the scissors lift and out of the bin area, and thence onto roller support tables 36 where the completed stack can thereafter be outfed to another conveyor, or transferred to a forklift truck or dolly, as desired.

As the completed stack of veneer 28 moves away from the bin area its trailing edge releases limit switch 45 causing the scissors lift table 23 to commence rising back upward. The lift table continues rising until it triggers limit switch 48 which stops the upward movement of the lift and simultaneously causes the respective accumulator arms 35 to move out from under the pile of veneer which has been stacked thereon during the time while the previously-completed load was being lowered and discharged, and to gently deposit it onto the now fully recycled lift table.

While the scissors lift is recycling the return to the upward position to receive the new stack of veneer, the previously-completed pile continues to move on the outfeed conveyor 43 until trailing edge of the veneer releases a limit switch 41 and the stack stops, resting on the roller support tables 36.

Returning now to the details of the stacker construction, the vacuum infeed conveyor 16 comprises a plenum chamber 15 on the top of the apparatus which has a negative pressure created therein by an air blower (not shown). The plenum is connected by ducts 13 on the top periphery of the stacker frame 15 to a plurality of air boxes 17 spaced in rows extending along the direction of travel of the veneer sheets as they feed into the apparatus. The bottom of each of these air boxes 17 is perforated with a plurality of small spaced apertures 19. An endless conveyor belt 20, supported on pulleys 26 and driven by motor 27, travels immediately beneath each of the longitudinally-extending air boxes and is perforated along its length with a corresponding array of spaced openings 21 so that the veneer sheet 28 is held under vacuum and conveyed by the traveling belts 20.

As previously mentioned, the veneer sheet 28 is carried into the apparatus by the vacuum infeed conveyor 16 until it reaches a position above its designated bin location whereupon limit switch 29a is tripped which actuates the knockdown arms 18. Referring to FIG. 6, the knockdown arms each comprises a horizontal runner arm 18' which is pivotally supported for parallel-motion action at two points along its length by arm members 19a, 18b which in turn are pivotally connected to the support frame 11. A forwardly projecting spring finger 22 depends from the leading edge of the runner 18' to assist in the lateral alignment of the sheet into the stack. An extension 18c of one of the swing arms 18a is connected to a pneumatic or fluid-operated actuator 31. The actuator rod is normally extended so that the knockdown arm 18 associated therewith is held elevated above the plane of the conveyor belts 20 in the non-operative position.

Upon energization of the actuator 31 when limit switch 29a is tripped, the actuator rod retracts, causing the horizontal runner 18' of the knockdown arm 18 to move downward through the plane of the conveyor belts forcing the veneer sheet loose and onto the top of the veneer stack 28. The parallel-motion movement of the knockdown arm causes the runner to contact the veneer sheet along a substantial length thereof, rather than at just one point, thus ensuring that the sheet is maintained substantially horizontal as it is deposited by the pair of concurrently-acting knockdown arms or to the top of the pile. The continuing downward arcuate motion of the swing arms 18a, 18b about their respective pivot points slides the sheet forward by the action of the projecting spring finger 22 until its leading edge abuts against the fixed stop 20. Reversal of the actuator 31 then quickly retracts the knockdown arm 18 back upward beyond the plane of the conveyor belt into the nonoperative-position ready for the next actuating signal from the limit switch 29a.

In the case of a two-bin sorter handling two different widths of veneer, for example 54 inch sheets and 27 inch sheets, judicious placement of a second limit switch 29a ', spaced ahead of limit switch 29a by more than the width of the smaller category of sheet and coupled to a coincident circuit for triggering the action of the respective knockdown arms 18, may be provided in the first bin location 12 receiving the wider sheets. This will permit the shorter width sizes of veneer sheet to pass over the first bin location 12 without actuation of its knockdown arms, and onto the second bin location 14 where limit switch 29a (FIG. 2) will be tripped for actuating the knockdown arms associated therewith. The principle of coincident limit switches with variable spacing can of course be extended to a multi-bin stacker handling a variety of sheet widths. Additionally other sorting criteria can be provided, through the use of memory logic and control devices working with inputs corresponding to thickness, moisture content and the like, to segregate veneer sheets into a plurality of stacks of respectively uniform characteristics.

The accumulator mechanism, the details of which are best shown in FIG. 7, comprises on each lateral side of a bin location a pair of pivotable arm members 35 formed of a vertical leg portion 35a and a horizontal arm portion 35b. The vertical leg portion 35a has its lower end pivotally connected to the stationery frame 11 and its upper end pivotally connected for limited articulation to the horizontally-extending arm portion 35b. An actuator 33, directly connected to one of the pair of accumulator arms 35 and coupled to the other of the pair by linkage mechanism 34, provides the means, under control of limit switch 39, for moving the respective arms 35 between the retracted position (shown in dotted lines) and the operative position shown. In the retracted position of the accumulator arms the rod of the actuator 33 is extended, forcing the respective arms outwardly about their pivot points 37 so that the upward terminus of the vertical leg portion 35a of each of the accumulator arms bears against the respective side members of the skeletal support frame 11. Because of the articulation provided by the pivot 32 between the vertical leg portions 35a and the horizontal portion 35b, each of the accumulator arms may be more fully withdrawn from the center of the bin location than if each of the accumulator arms were a rigid member.

Reversal of the actuator 33 swings the pair of actuator arms 35 away from the side walls and into the operative position over the now-completed pile formed on the lift table 23 where the horizontal arm portions 35b of the respective accumulators 35 provide temporary support for the initial sheets of a new pile 28 dropping from the conveyor into the bin location while the stack previously formed therein is removed off the scissors table. A cam 38 is provided for coaction with an associated cam follower 38a carried on each of the accumulator arm 35 so as to maintain the sheet support surface provided by the accumulator arms in a horizontal plane as the respective accumulator arms are moved between their operative and non-operative positions. In this manner the pile of veneer sheets forming a new stack is maintained substantially stationary as the accumulator arms 35 are withdrawn to permit the scissors lift table 23 to move into position and receive the new pile. To effect this the connection in each of the accumulator arms between its horizontal arm portion 35b and its vertical leg portion 35a is provided by a spring-biased coupling 32' permitting a short axial displacement therebetween so as to enable the support plane formed by the respective accumulator arms to be maintained fixed in space as each of the horizontal arm portions 35b is moved between its operative and retracted positions. (In the absence of the cam mechanism and coupling arrangement provided it will be apparent that the support surface formed by the accumulator arms would move vertically as the arms are swung between the operative and retracted positions, thus producing a corresponding displacement in the position of the pile 28 which in turn might interfere with the operation of the knockdown arms 18 or the even-enders pusher arms 30.)

It will be understood that, for each bin location, a total of four such accumulator arms 35 are preferably provided to swing into the center of the bin location to provide a temporary support plane for the initial group of sheets forming a new pile while the previously-formed pile is being unloaded. If desired, it may be feasible to extend the length of the horizontal arm portions 35b of a pair of accumulator for substantially the full width of the veneer sheet and, by using a construction of sufficient load-bearing capacity, accomplish the necessary support with but a single pair of accumulator arms 35 rather than the four depicted in this illustrative embodiment.

FIG. 8 depicts a modified form of accumulator mechanism in which the pivoting arms of the previous embodiment is replaced by a pair of horizontally-reciprocable rods 52 extending from associated hydraulic actuator cylinders 54 which are supported by respective girders 53 and mounted onto the adjacent sides of bin frame 11. In this modification actuation of the respective actuators 54, in response to a control signal received as before from the triggering of limit switch 39, causes the normally-retracted rods 52 to extend across the width of the bin stall 12 forming a temporary support plane for the initial group of sheets 28 of a new pile while the previously-formed stack is discharged and the lift table 23 recycled. Because of the outward horizontal extension of the actuator cylinders 54 beyond the side of the stacker frame 11 it will usually not be feasible, by reason of space and conveyor length considerations, to utilize this modified form of accumulator mechanism except for veneer stackers of only one or two-bin capacity.

The terms and expressions which have been employed in the foregoing abstract and specification are used therein as terms of description and not of limitation, and there is no intention, in use of such terms and expressions, of excluding equivalents of the features shown and described, or portions thereof, it being recognized that the scope of the invention is defined and limited only by the claims which follow.