Background Art Surfacing machinery is used to perform surface operations on workpieces, for example, to sand or plane lumber, planks, panels, etc. Such surfacing machinery typically includes upper and lower heads for cutting or sanding the workpieces, and a feed assembly for advancing the workpiece through the heads. The feed assembly preferably provides a self-centering effect so that whatever amount of material is being removed, one-half will be removed from each side, thereby maximizing yield.

Self-centering feed assemblies for abrasive grinding machines are disclosed in U. S. Patent No. 4,322,919 issued to Gerber on April 6,1982 and in U. S. Patent No. 4,640,056 issued to Stump on February 3,1987, both of which are herein

incorporated by reference. These prior art feed assemblies allowed each workpiece to float or center at the sanding head position and to thereby achieve equal stock removal on each side of each board. Because the abrasive belt heads themselves had a self-centering effect, these feed assemblies were required to provide the necessary horizontal forces required to feed each board, but follow the surface of each board so as to not interfere with the centering effect at the abrasive belt heads.

However, when used in connection with cutting heads, as opposed to sanding or grinding heads, these prior art feed assemblies were not adequate to achieve the desired individual centering result, since the cutting heads do not provide a self- centering effect. This is due to the fact that when using cutting heads instead of abrasive heads, the vertical forces on the workpiece are exactly the opposite, as a cutting head tries to pull the board into the cutter, whereas an abrasive head tries to push the board away from the abrasive belt. As a result, the cutting heads would remove an unequal amount from each side and tend to gouge or otherwise cut the workpiece unevenly, especially if the workpiece is uneven, warped or contains other variations.

In an attempt to compensate for such problems, the cutting heads normally are displaced relative to each other, as opposed to the desired position of directly opposing each other, resulting in uneven stock removal from each side.

Accordingly, there is a need in a cutting head planer machine for a method and apparatus to adequately center and feed

workpieces to the cutting head assembly so that an equal amount of material will be removed from both sides of each and every board independent of individual board thickness variations. The present invention fulfills such a need.

Disclosure of the Invention The present invention comprises a centering sectional shoe assembly for use in surfacing machinery, and in particular a planer machine having cutting heads. The shoe assembly is positioned in close proximity to the cutting heads (which directly oppose each other), and between the cutting heads and a centering feed assembly. The shoe assembly includes a plurality of individually movable pressure shoe sets, each set comprising an upper shoe and a lower shoe. Each shoe set is operatively connected to a closed circuit, double rod end hydraulic cylinder assembly which selectively and independently positions the shoe set responsive to the surface to the workpiece. A means for exerting a force is also operatively connected to each shoe set to provide a centering force. In use, as the upper or lower shoe of a shoe set is forced away from the centerline of the workpiece, the opposing shoe would automatically move the same amount. The shoe assembly thus centers each and every workpiece independent of the amount of stock removal required. Further, it is desirable that the feed assembly of the present invention likewise includes a closed circuit, double rod end hydraulic cylinder assembly to improve centering of the workpiece by the feed assembly.

Accordingly, it is the principle object of the present invention to provide a method and apparatus for positioning workpieces in surfacing machinery.

It is a further object of the invention to provide a centering assembly for centering workpieces in a planer machine.

It is also an object of the invention to provide a centering sectional shoe assembly that adjusts for individual workpiece thicknesses and widths allowing multiple workpieces to be centered and planed at the same time by a planer machine having opposed cutting heads.

It is an additional object of the present invention to provide a closed circuit, double rod end hydraulic cylinder assembly for a centering sectional shoe assembly.

It is another object of the present invention to provide an improved centering feed assembly having a closed circuit, double rod end hydraulic cylinder assembly.

Numerous other advantages and features of the invention will become readily apparent from the detailed description of the preferred embodiment of the invention, from the claims, and from the accompanying drawings in which like numerals are employed to designate like parts throughout the same.

Brief Description of the Drainas A fuller understanding of the foregoing may be had by reference to the accompanying drawings wherein: FIGURE 1 is a side view of the present invention.

FIGURE 2 is a top view of the present invention in the absence of the hydraulic cylinder assemblies.

Mode (s) of Carrying Out the Invention While the invention is susceptible of embodiment in many different forms, there is shown in the drawings and will be described herein in detail a preferred embodiment of the invention. It should be understood however that the present disclosure is to be considered an exemplification of the principles of the invention and is not intended to limit the spirit and scope of the invention and/or claims of the embodiment illustrated.

Figure 1 illustrates a side view of the present invention 10 in use in a cutting head planer machine having a cutting head assembly 20 defined by directly opposed upper cutting head 30a and lower cutting head 30b. The cutting heads each include cutting teeth 32a and 32b respectively, are suitably mounted and driven as is commonly known in the art. The cutting heads are mounted at any desired distance from each other, to define the thickness or height of the finished workpiece. For example, if the cutting heads are set one inch apart, then a workpiece with a thickness greater than one inch will have a thickness of one inch after passing through the workpiece.

A centering shoe assembly 40 is shown positioned in close proximity to the cutting heads. Assembly 40 comprises a series

of shoe sets, positioned across the width of the machine, each set made up of upper shoe 42a and lower shoe 42b. The shoes 42a and 42b are mounted for pivotable movement about pivots 44a and 44b respectively. Movement of each set of shoes is effected as described below by closed circuit, double rod end hydraulic cylinder assemblies 50 operatively connected to each shoe set.

The shoes assemblies are mounted such that the minimum distance between the upper and lower shoes is less than the distance between the cutting heads. For example, if the distance between the cutting heads is one inch, then the minimum distance between the upper and lower shoes would be less than one inch, such as 7/8 inches. In such an example, a workpiece having an initial thickness of less than one inch will pass through the machine unaffected, i. e, without contacting the cutting heads.

In the prior art, a workpiece originally thinner than desired would still contact the surfacing heads and be made even thinner.

Assembly 50 comprises an upper double rod end hydraulic cylinder 52a and a lower double rod end hydraulic cylinder 52b.

Each cylinder 52a and 52b contains a fluid (such as oil or any suitable liquid or gas) filled first chamber 54a and 54b and second chamber 56a and 56b respectively, separated by a piston 58a and 58b respectively. Pistons 58a and 58b move piston rods 60a and 60b respectively, which are pivotably attached to a shoe mount 62a and 62b respectively, by pivot 64a and 64b respectively, to control movement of shoes 42a and 42b.

Cylinders 52a and 52b are operatively connected by a first conduit 66 and a second conduit 68. First conduit 66 provides fluid communication between first chamber 54a and second chamber 56b, while second conduit 68 provides fluid communication between second chamber 56a and first chamber 54b. In this manner, as one of the pistons 58a and 58b move, the other piston moves the same amount in the same direction relative to the center line (i. e, both move either away from the centerline or towards the centerline), since the volume of the fluid in the first chambers 54a and 54b and the volume in the second chambers 56a and 56b remain equal. Thus, if shoe 42a is forced away from centerline 17 by workpiece 15, piston 58a moves, forcing fluid out of first chamber 54a, through conduit 66, and into second chamber 56b.

This in turn moves piston 52b, forcing fluid out of first chamber 54b, through conduit 68 and into second chamber 56a, thus moving shoe 42b away from the center line the same distance as shoe 42a.

To provide a centering force, a means 70 for exerting pressure on the shoes is operatively connected to at least one of the shoes 42a and 42b. Means 70 preferably takes the form of an air cylinder 72 having piston 74 which moves piston rod 76 pivotably attached to the shoe at shoe mount 78 by pivot 79.

Air cylinder 72 selectively provides adjustable pressure to the shoes to help produce the desired centering effect.

Also illustrated in Figure 1 is a centering feed assembly 80 having a plurality of staggered drive wheel sets, of the general type as described in U. S. Patent No. 4,322,919. It

should be understood that a feed mechanism of the general type as described in U. S. Patent No. 4,640,056 could also be used.

The feed assembly 80 however differs from these prior art feed assemblies in that they are operatively controlled by another closed circuit double rod end hydraulic cylinder assembly 90. Accordingly, opposing drive wheels 82a and 82b are mounted on drive shafts 84a and 84b respectively, and are driven by any suitable means as is known in the art. Drive wheels 82a and 82b are mounted at the and of an L-shaped link 86a and 86b respectively, which pivot at link mounts 88a and 88b respectively about link pivots 89a and 89b respectively.

Assembly 90 comprises an upper double rod end hydraulic cylinder 92a and a lower double rod end hydraulic cylinder 92b.

Each cylinder 92a and 92b contains a fluid filled first chamber 94a and 94b and second chamber 96a and 96b respectively, separated by a piston 98a and 98b respectively. Pistons 98a and 98b move piston rods 100a and 100b respectively, which are pivotably attached to the other end of link 86a and 86b respectively, by pivot 104a and 104b respectively, to control movement of drive wheels 82a and 82b.

Cylinders 92a and 92b are operatively connected by a first conduit 106 and a second conduit 108. First conduit 106 provides fluid communication between first chamber 94a and second chamber 96b, while second conduit 108 provides fluid communication between second chamber 96a and first chamber 94b. Thus when one drive wheel moves away from the centerline 17, the opposite wheel

move away from the centerline an equal distance. This provides an improved centering effect of the workpiece 15 as it is moved through the cutting heads 30a and 30b, and into exit shoe assembly 120, which supports, stabilizes, guides and provides a flattening effect to the finished workpiece as it exits the cutting head assembly 20.

Figure 2 is a top view of the present invention, in the absence of assemblies 50 and 90, and means 70, illustrating the relative location of the staggered drive wheels 82a, the sectional shoes 42a, and the cutting head 30a. As can be seen, the sectional shoes are located between the cutting head and the drive wheels, in close proximity to the cutting head. It should be understood that the drive wheels need not be staggered, but could be aligned.

It should be understood that the embodiments herein described are merely illustrative of the principles of the present invention. Various modifications may be made by those skilled in the art without departing from the spirit or scope of the claims which follow.