Claims:
It is claimed and desired to secure by Letters Patent
1. In apparatus for stacking thin, flexible sheets in a uniform, aligned stack, comprising a sheet receiving platform means for conveying individual sheets to a location directly above said platform and transferring them to the platform to form a stack thereon,
2. The apparatus of claim 1, wherein said platform is vertically movable and lowered during the collection of a stack to accommodate increase in stack height, and wherein the means in the platform to remove the crown comprises multiple sections in the platform moved into a substantially common inclined plane with lowering of the platform to a predetermined elevation.
3. The apparatus of claim 2, wherein said platform comprises multiple rollers with tops of the rollers providing means supporting the stack in the platform, said rollers being journaled for rotation about axes that promote rolling movement of a stack supported on the rollers downwardly along said plane.
4. In apparatus for stacking thin, flexible sheets in uniform, aligned stack, including a sheet receiving platform, and means for conveying sheets to a location directly above said platform and transferring them to the platform to form a stack thereon, the improvement comprising
5. The apparatus of claim 4, wherein said rollers are journaled for rotation about axes substantially paralleling the axis of said crown.
Description:
BACKGROUND OF THE INVENTION
The invention relates to improved sheet stacking apparatus. More particularly, the invention concerns stacking apparatus which is especially useful for stacking sheets of thin, flexible material, such as veneer, in a uniform, aligned stack.
A need exists in industry, and particularly in the wood industry, for means capable of handling thin, flexible sheets and placing such sheets in stacks with the lateral edges of the sheets arranged in vertical alignment. Furthermore, it is desirable that such sheets be handled without folding the surfaces of the sheets or damaging the edges thereof.
Numerous stacking and sheet handling equipments have been designed for use in the wood industry where large numbers of veneer sheets must be automatically processed by various equipment and placed in stacks for convenient handling. However, the stacking and aligning apparatus used in conjunction with such equipment is not completely satisfactory. In the usual stacking apparatus, sheets of veneer are transferred intermittently over a stacking area and then dropped onto the top of a stack. However, due to the lightness and flexibility of veneer, the veneer sheets tend to sail sideways as they drop down onto the stack. Consequently, the sheets do not drop upon the stack with their edges in accurate alignment. Furthermore, due to the flexibility of the sheets and because of their inherent curl, most operations performed to align the sheets after they are in the stack result in buckling and bending of the sheets. Thus, if sufficient force is applied to the edge of the stack to move the thin sheets laterally with respect to the stack, damage often occurs to the edges and the surfaces of individual sheets.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to provide sheet handling and alignment means which overcome the disadvantages of conventional apparatus.
It is another object of the invention to provide an improved means for rapidly handling thin, flexible sheets of material and placing such sheets in an aligned stack.
It is a further object of the invention to provide in a sheet stacking apparatus means for positioning sheets in the stack with the edges of the sheets arranged in substantially vertical alignment.
It is yet another object of the invention to provide means for arranging the edges of a plurality of stacked sheets in alignment without buckling the sheets or damaging the edges of the sheets.
These and other objects of the invention are attained by alignment apparatus which is especially designed for use in conjunction with sheet stacking equipment wherein sheets of thin, flexible material, such as veneer, are conveyed over a stacking area and dropped on the top of a stacking platform or already formed stack. Posts adjacent either end of the stacking area guide the ends of the sheets into substantial alignment with the stack when the sheets are dropped. The center of the stacking platform is elevated or crowned so that sheets dropped upon the platform are flexed or bent along an axis substantially transverse to the length of the sheet. This serves to stiffen the sheets along that axis. Means is provided on one side of the stacking area for bringing an impact arm into contact with the upper sheets to move them against a fence or stop provided on the opposite side of the stack. As the sheets are driven against the fence, they are aligned with the edge of the stack. Due to the stiffness imparted to the sheets by the bend, the impact arm aligns the sheets with the stack without buckling the sheets or damaging the edges thereof. Means is provided for transferring the stack to a handling platform when a predetermined number of sheets have been accumulated.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects and advantages of the invention will become apparent from the following detailed description of the invention, taken in conjunction with the accompanying drawings, wherein:
FIG. 1 is a side elevation view of sheet stacking apparatus designed in accordance with the invention;
FIG. 2 is an end elevation view of the apparatus taken along lines 2--2 in FIG. 1; and
FIG. 3 is an enlarged fragmentary view of the sheet alignment apparatus taken along lines 3--3 in FIG. 2.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the drawings, one preferred embodiment of the invention is illustrated in the form of a sheet stacking and alignment apparatus generally indicated at 10. The alignment apparatus generally comprises an elevator conveyor 12 adapted for intermittently receiving sheets to be stacked from a conveyor line, not illustrated. A transfer conveyor 14 is provided, and a roller bar assembly generally indicated at 16 is provided for retaining the sheets in contact with the bottom surface of the transfer conveyor. A retractable bar or stop 18 is provided in the path of the leading edge of the incoming sheets whereby the sheets can be stopped substantially over a stack 20 formed on a scissor lift stacking platform 22. As electrical switch 19 is secured adjacent bar 18, adapted to produce a signal, upon contact between a sheet and stop 18, for controlling the roller bar assembly. The sheets are lowered or dropped upon the top of the stack by operation of the roller bar assembly with their edges in approximate alignment with the already formed stack. The added sheets are then aligned by means of an impact arm generally indicated at 24. A reject chute 26 is provided to receive any sheets that are moved through the apparatus with stop 18 retracted. An outflow conveyor 28 is provided to receive the completed stacks from the stacking platform.
Referring particularly to FIG. 1 the elevator conveyor 12 is a conventional unit suitably supported at a slight incline and is designed to transport sheets, such as sheet 30, into contact with the bottom surface of transfer conveyer 14. The elevator conveyor can comprise two or more endless belts 32 supported upon and driven in unison by drive rollers 33 attached to shaft 34 at the upper end of the elevator. Shaft 34 is rotated by a conventional motor 35 coupled to the end of the shaft. Belts 32 can be provided with cleats or lugs to engage the trailing edge of the sheets, if desired. However, the incline of the elevator is shallow and belts having rubber or composition covers with relatively high frictional surfaces can be used to handle veneer sheets without lugs.
The transfer conveyor 14 is suspended over the stacking area from a framework, generally indicated at 36. The framework includes legs 38, end members 39, and side members 40. All of the framework members can be constructed of channel or angle steel and are secured together by conventional means such as welded joints.
Channel extensions 41 are secured on either side of the framework to side members 40. A bearing plate 44 is secured at the end of each extension in depending relationship thereto and serves as a base for a bearing 45. A drive shaft 48 is journaled in bearings 45 on the left side of the framework as viewed in FIG. 1 and an idler shaft 50 is journaled in bearings 45 on the right side of the framework. A pair of drive rollers 52 are secured to the drive shaft and, in similar fashion, a pair of idler rollers 54 are secured to the idler shaft at the opposite side of the framework.
A transfer conveyor belt 55 is supported on each set of drive and idler rollers, with the belts adapted to be rotated in unison by a motor 56 secured at one end of drive shaft 48. The belts are preferably constructed of composition or rubber material which will frictionally engage and move the sheets when the latter are retained in contact with the lower surfaces of the belts.
Roller bar assemblies 16 are provided respectively at each end of the stack, as illustrated in FIG. 2, for retaining the sheets in contact with the underside of the transfer conveyor belts. Only one of the roller bar assemblies will be described in detail, it being understood that the other assembly is of similar construction and is arranged in complementary relationship to the assembly described. Like elements of the other roller bar assembly are designated by like primed numerals.
Roller bar assembly 16, as shown in FIGS. 1 and 2 includes two roller bars 61, 62 each attached to and suspended between a pair of spaced apart endless chains (one shown at 63). The chains are supported for rotation in a counterclockwise (as seen in FIG. 2) direction by a drive roller assembly 67 and two idler roller assemblies 68, 69. The idler roller assemblies are secured by suitable means to the framework. The drive roller assembly comprises a drive shaft 70 that is rotatably supported in bearings 65, 66 secured to the legs of the frame. A motor 71 is provided at the end of drive shaft 70 for rotation thereof. Roller bars 61, 62 are pivotally secured at each end between the link-type chains spaced apart one-half the distance around the periphery of the chains.
Each roller bar generally comprises two side members 73, having rollers 74 journaled therebetween on pins 76. The rollers are spaced above the midline of members 73 whereby the rollers are exposed for contact with the bottom surface of the sheets. In addition, in the arrangement illustrated, the roller bars are pivotably secured to the chains at a point above the center of gravity of the roller bars. Mounted in this manner the roller bars are normally disposed with the exposed portions of the rollers extending upwardly. Furthermore, this attitude of the rollers is maintained as the roller bars traverse the orbital path described by the chains. Accordingly, rollers 74 are always maintained in contact with the surface of a sheet supported upon the roller bars as the chains are rotated to drop the sheet on the stack.
End alignment assemblies 80, 81 are arranged at either end of the stack as viewed in FIG. 2, each being secured to the framework. Each assembly includes a ram 86 having an extensible shaft 87 to which is attached a deflection plate 83 having a flared upper portion 84. Rams 86 are of conventional design, such as air or hydraulic rams designed for power operation in both directions. The rams are normally operated so that plates 83 are located near the ends of the stack. Accordingly, as panels are dropped upon the top of the stack, the flared portions 84 of the plates engage the ends of the panel and guide them downwardly onto the stack in approximately aligned relationship therewith.
Stack 20 is comprised of a plurality of sheets 30 arranged on a power-operated stacking platform 22 having a base 92. An upper member 94 of the platform assembly serves as a support for a pair of oppositely inclined roller sets, also referred to as platform sections 96, 98, each roller set including plural parallel rollers 110 with tops of these rollers providing the means for supporting a stack. Roller set 96 is fixedly secured at one end to the outer edge of member 94 and is fixedly secured at its other end to an upright member 99 located in the center of the scissor lift platform. Roller set 98 is pivotally secured at one end to upright member 99 and its other end is free. A block 102 is arranged adjacent the platform assembly, having an upper surface 104 arranged beneath the outer end of roller set 98. The scissor lift is normally positioned so that the uppermost portion of the stack is between opposed plates 83. As platform 22 is gradually lowered with the building of the stack to keep the top of the stack at a predetermined level roller sets 96, 98 approach the level of conveyor 28. During the stacking operation the opposite inclines of roller sets 96, 98 serve to elevate or crown the center portion of the stack for a purpose described hereinafter. However, as the platform is lowered the outer end of roller set 98 contacts surface 104 of block 102 and is prevented from being lowered any further. Further lowering of platform 22 causes roller set 98 to become aligned with set 96, elevating one end of stack 20 and causing the latter to slide or roll off of the platform onto conveyor 28. With roller set or platform section 98 aligned with roller set or platform section 96, the two platform sections occupy a common, slightly inclined plane, and the rollers in the platform sections with the sections in this common plane promoting rolling of a stack down to one side and off the platform. The platform is then re-elevated for the purpose of forming a new stack.
Referring particularly to FIG. 3, the impact arm and fences are particularly illustrated. The fence includes two fence members 120, each secured to the framework by an extension 122. Each fence member is arranged in generally vertical alignment with the plane of stop 18, at a location defining the desired edge of stack 20. The fence members are of sufficient length to extend below the upper level of the stack and plates 83. Impact arm assembly 24 includes an elongate arm 126 pivotally secured at its bottom end to a bracket 128 that extends from the framework. A ram 130, such as a hydraulic ram, is secured to the framework with extensible shaft 134 connected at its outer end to arm 126 generally midway of its length. Upon operation of the ram, arm 126 is selectively movable between the retracted position shown in solid outline in FIG. 3, and the extended position shown in dot-dash outline in FIG. 3. The arm includes a front edge 137 having a smooth surface formed thereon, adapted to contact sheets extending beyond the edge of the stack upon operation of ram 130. The lower end of arm 126 is reduced in cross section so that only the upper portion of the arm impacts against the sheets.
In operation of the apparatus described sheets such as sheet 30 are intermittently admitted to the apparatus and transferred up conveyor 12 into contact with the underside of transfer conveyor 14. The positions of the roller bar chains are adjusted so that a roller bar on either side of the apparatus occupies its uppermost position as sheet 30 reaches the top of the elevator conveyor. The roller bar chains are retained in that position and the sheet is driven across the stacking area by the transfer conveyor, being retained in good frictional contact with the bottom of the transfer conveyor by the rollers on the roller bars. As the leading edge of the sheet reaches stop 18, it strikes the stop and is held in a stationary position with slippage occurring between the sheet surface and the transfer conveyor.
As the sheet strikes the bar 18, an electrical signal is generated by switch 19 and is used to actuage the roller stop chain drive motors, causing the roller bars to move downwardly and outwardly with respect to the ends of the sheet. The sheet is supported upon the roller bars until it is lowered approximately over the top of the stack. At that time, the roller bars traverse the lower course of the orbital path described by the roller bar chains and are moved outwardly beyond the end of the sheet. Consequently, the sheet drops upon the top of the stack, guided by plates 83 which engage the ends of the sheet.
After each sheet is dropped, arm 126 is actuated one or more times and comes into contact with the edge of the uppermost sheets on the stack. This serves to move the sheets laterally into contact with fence members 120 whereby the edges of the sheets are aligned with the stack. The force of the arm on the sheets is slight and does not damage the edges of the sheet. Furthermore, due to the stiffness imparted to the sheets by the bend at the center of the stack, the sheets are moved without buckling or bending. Although the apparatus described utilizes and upward bend or bow in the sheets to provide stiffness thereto, it should be apparent that the desired stiffness could be provided by bending the sheets downwardly as well.
The stacking apparatus described and illustrated hereinbefore has special advantages for use with the in sheets, such as veneer sheets. Namely, the tendency to damge the edges of sheets is overcome and the sheets are arranged in an aligned, uniform stack without buckling or damage resulting therefrom. Furthermore, the alignment apparatus does not interfere with the use of the stacking apparatus nor reduce the speed of operation. However, the apparatus could be utilized in other equipments for aligning stacks of cards or paper.