Self Centering Planer Apparatus

The present invention relates to the field of processing lumber and more particularly to the art of planing lumber to a desired thickness. In greater particularity, the invention relates to blade planers and particularly to dual sided blade planers wherein both sides of a piece of lumber are planed in a single operation. Even more particularly, the present invention relates to such a blade planer wherein the blade planers remove an equal amount of wood from each side of the lumber.

Planers and sanders are well known in the art and their function in shaping wood to a desired thickness is well known. Blade planers are well known and it is generally accepted that such planers require less power to operate than do belt planers or sanders. It is clear that to achieve double sided planing of the lumber in a single operation, the planer apparatus on each side of the lumber must remove an amount of wood relative to the centerline of the wood. Many centering apparatus have been proposed for use in such planers, but none have been found to be totally satisfactory for use with blade planers. My U.S. Pat. No. 4,417,680 shows an excellent feed mechanism for a belt sander, however, even this apparatus is not completely compatible with a blade planer.

Two problems not present in belt sanders confront the use of a blade planer. First, the cutting action of the blades imparts a discontinuous series of input forces to the lumber which causes oscillation unless the lumber is firmly held in position. Therefore blade planers cannot be mounted in direct opposition as are the belt sanders of my previous invention. Secondly, when lumber which is already very close to or slightly less than the desired thickness is fed into a blade planer apparatus, the staggered configuration of the blade planers requires that the lumber be supported adjacent at least one of the blade planers. Oftentimes this results in the lumber being aligned along one side thereof rather than along the centerline and consequently, with a thin board, one of the blade planers removes an excessive amount of wood thereby reducing the thickness beyond a usable level. For example, a planer may be set to plane boards having a thickness of 15/16ths inches or greater into boards having a thickness of 3/4 inches, with the first blade planer set to remove 1/8 inch and the second set to remove 1/16 inch or vice versa. If a board having a thickness of 13/16" reaches the planer, the first blade planer removes 1/8" resulting in a "scant" board having a thickness of 11/16". Considerable numbers of "scant" boards are produced daily by planers which are incapable of properly centering lumber.

It is the object of the invention to provide a means for centering lumber fed into a blade planer which will assure that equal amounts of wood are removed from each side of the piece of lumber.

More specifically, it is the object of my invention to provide an apparatus which will center lumber for equal planing of both sides regardless of the thickness of the lumber so as to eliminate scant boards.

Another object of the invention is to provide an efficient blade planer which can achieve the above objects.

My improved apparatus utilizes an upper and lower frame assembly with the upper portion being movable vertically relative to the lower frame. Each frame member carries a conventional blade planer and a plurality of feed rollers which include rubber tires, pinwheel rollers, and steel rollers. The spacing between the upper and lower frame members defines the thickness of the resultant board and the datum plane. Lumber fed into apparatus embodying my invention is centered on the datum line by a pair of guide shoes which are interconnected such that as one shoe moves, it forces the other shoe to move a like distance from the datum plane. In one embodiment, the shoes are hydraulically connected and in other embodiments, they are mechanically linked.

Apparatus embodying features of my invention are illustrated in the accompanying drawings which form a portion of this invention and wherein:

FIG. 1 is a side elevation of a planer apparatus partially cut away to show the feed and alignment means;

FIG. 2 is a schematic depiction of the center mechanism utilizing a hydraulic connection;

FIG. 3 is a schematic elevation of a mechanical centering system;

FIG. 4 is a plan view of the system shown in FIG. 3;

FIG. 5 is a partial sectional view along line 5--5 of FIG. 1;

FIG. 6 is a plan view of the guide members; and

FIG. 7 is a detail of the guide members.

Referring to FIG. 1, my invention is shown in the form of a board planer 10 which utilizes a pair of conventionally driven blade planers 11 and 12. The board planer has a lower frame assembly 13 and an upper frame assembly 14 with four corner columns 16 supporting the upper frame assembly 14. Each corner column 16 rests on a jack 17 and each jack 17 is ganged to the other three jacks such that the four corner columns are raised and lowered by the same amount at the same time. As may be seen, blade planer 12 is carried by the upper frame assembly 14, thus the elevation of the upper frame assembly 14 above the lower frame assembly determines the vertical separation between the blade planers 11 and 12 which equals the thickness of the finished board. It is thus apparent that the separation may be varied as desired to yield finished lumber of virtually any thickness.

Lumber is fed into the apparatus in the direction indicated by arrow A and is engaged by input rollers 18 and 19 which are driven for rotation by a motor, not shown. The rollers 18 are rubber tire-like rollers whereas the rollers 19 are pinwheel rollers of the type disclosed in my prior U.S. Pat. No. 4,417,680. These input rollers urge the lumber along a feed path through the apparatus generally along the datum plane defined by the centerline between blade planers 11 and 12. Positioned intermediate pinwheel rollers 19 and lower blade planer 11 are a plurality of pairs of shoes 21 or guides which are spaced equidistantly from the datum plane. The shoes 21 are elongated members, shown more precisely in FIG. 7, having a generally planar surface 20 and a sloping forward surface 25 beveled at approximately 7.degree. counter to the surface 25 of the opposing shoe. The paired shoes are connected as explained more fully herein such that the shoes move concomitantly toward and away from the datum plane. Howver, it should be noted that the upper shoes extend somewhat over the lower blade planer 11 such that the lumber is held firmly against the blade planar 11 and is not subject to oscillation or displacement due to impact with the blades of the blade planer 11. Downstream of the lower blade planer 11 the board is supported on a platen 22 and urged along the feed path toward upper blade planer 12 by an intermedidate set of driven rollers 23 and 24 with roller being of the rubber tire type and rollers 24 being of the pinwheel type. Output rollers 26 and 27 discharge the board from the apparatus. Each of these rollers are steel rollers with selected rollers 26 being driven. The plurality of rollers and shoes insure that the boards are held firmly and do not oscillate with the impact of the blade planers, thus the surfaces of the boards are not marred by the apparatus. Although not disclosed or claimed in the present application, it is noteworthy to mention that the thickness of the boards planed by the apparatus may be set to within 0.005" and displayed on a digital readout.

Such fine tolerance in a blade planer requires that the boards be accurately aligned as they pass both blade planers 11 and 12. This alignment is accomplished through the use of the shoes 21. Each shoe is mounted to its associated frame on link members 31 and 32, which are pivotally mounted on transverse shafts 33 and 34 respectively, such that the planer face 20 of the shoe remains parallel to the datum plane at all times. Link members 32 have an extension or centering arm 36 which serves to transfer motion of the shoe 21 to a centering mechanism. The centering mechanism may be either hydraulic or mechanical in nature.

A hydraulic centering system is schematically depicted in FIG. 2. Note that centering arm 36 is urged against a stop member 37 by an air cylinder 38. The shoes 21 are in a reference centered position when arm 36 abuts the stop member 37. That is, the shoes 21 are at their minimum separation for the particular board thickness desired. In this position, the shoes 21 are spaced relative to the blade planers 11 and 12 such that a board having the desired thickness or less would pass through the apparatus without being touched by either planer and the faces 20 are nearly tangent to the arc formed by the associated planer 11 or 12.

The distal end 39 of arm 36 is connected to a piston rod 41 of a double acting hydraulic cylinder 41. A cylinder piston 43 is conventionally moved by rod 41. For clarity, the upper frame components have been given a suffix "a" and the lower frame components a suffix "b". The upper and lower cylinder 42a and b of a pair of shoes 21a and b are connected by a set of hydraulic lines 44 such that movement of arm 36a away from stop member 37a creates pressure in cylinder 42a which is transmitted to cylinder 42b to urge arm 36b away from stop member 37b. The hydraulic pressure is in equilibrium only when shoes 21a and b are equally displaced from their centered reference points, thus whenever a board enters between the shoes, it is held with its centerline coinciding with the datum plane, and equal amounts of wood are removed by each blade planer 11 and 12.

Connected to each cylinder via the hydraulic lines 44a and b and a set of check valves 46 is a pressurized reservoir which replenishes the hydraulic fluid in the event of a leak in one of the cylinders. Also, it is necessary to be certain that the pressure in the system is equalized, thus a photocell 47 senses the absence of lumber at the entrant portion of the shoes 21 and opens a valve 48 between the lines 44a and b to equalize the pressure therein as the shoes 21 are reset by the air cylinders 38a and b, which may be driven by shop air or any other convenient source. It is to be understood that arms 36 may be urged into engagement with stop members 37 by a variety of biasing devices other than air cylinder 38.

FIGS. 3 and 4 illustrate a mechanical embodiment wherein arms 36 are biased against stop member 37 by springs 51a and b (note that the weight of the board may necessitate spring 51b bing slightly stronger than spring 51a) and is connected to a rod 52 which translates the pivotal motion of the arm 36 into horizontal motion. The rod 52 is in turn connected to a bell crank 53 or like device which is pivotally connected to a lever arm 54 connected to a vertical shaft 56. The vertical shaft 56 is splined and fits within a sleeve 57 such that the combined length of the shaft 56 and sleeve 57 may be varied in accordance with the vertical displacement of the upper frame member 14. Identical members connect the centering arms 36 of the lower shoes 21 to the sleeve 57. It may be seen that if either shoe 21 is displaced toward or away from its reference centered position, the mechanical linkage associated therewith will cause the shaft 56 and sleeve 57 to rotate which, in turn, causes the opposing shoe and its linkage to move the same amount. It will be appreciated that several variations of the mechanical linkage may be constructed as long as the connection between the upper and lower shoe linkage can be varied with the elevation of the upper frame assembly.

While I have shown my invention in two forms, it will be obvious to those skilled in the art that it is not so limited but is susceptible of various changes and modifications without departing from the spirit thereof.