US2808883A - Rotary veneer clipper - Google Patents

Description

1957 E. w. KNOKEY ROTARY VENEER CLIPPER.

2 Sheets-Sheet 1 Filed Oct. 6, 1954 INVENTOR.

Er win WKnokey BY r/ I Oct. 8, 1957 E. w. KNOKEY ROTARY VENEER. CLIPPER 2 Sheets-Sheet 2 Filed Oct. 6. 1954 INVENTOR. Er Win WKnokey ROTARY VENEER CLIPPER Erwin W. Knokey, Netarts, Oreg., assignor of one-half to Diamond Lumber Company, Portland, Greg, a corporation of Oregon Application October 6, 1954, Serial No. 460,719

1 Claim. (Cl. 164-48) This invention relates to a veneer clipper such as is employed within the plywood industry to clip or cut a continuous sheet of veneer into pieces of preselected size. More particularly, the instant invention concerns an improvement in rotary or circular motion veneer clippers whereby the continuous sheet of veneer is sliced or is severed by what is substantially a side to side motion in contrast with the better known reciprocating or sheartype severance.

One object of my invention is to provide a true rotarytype motion veneer clipper which is capable of operation at speeds heretofore unattainable in the industry in order that the continuous sheet of veneer can be made to travel at a continuous high rate of speed, without stopping, while the clipping progresses, all without damage to or crushing of the fragile and somewhat flimsy veneer sheet.

The production of plywood is a major industry in the Pacific Northwest, which region leads all others in logging operations and in timber resources. The typical plywood board is fabricated from a number of thin layers of veneer which are glued together so the grain of each layer is at right angles to that of the adjacent or abutting layer. Each individual ply or sheet of veneer is the end product resulting from a long and complex procedure. At the plywood mill, this process begins when a log is snaked from the pond, trimmed to length, and the bark removed. Thereafter, the log is fed to a huge veneer lathe where a continuous strip of veneer, usually one-eighth inch thick, is peeled from its revolving periphery. This sheet is cut to lengths commensurate with temporary storage facilities (for example, 1000 foot lengths) and is fed, on belts or conveyors, to horizontal storage racks. These storage racks terminate adjacent the feed belt of the veneer clipper where the elongate continuous sheets are cut to smaller sizes correlated to the dimensions desired in the finished plywood board. At the off-bearing side of the clipper, the pieces of veneer are stacked selectively, according to the cut, predetermined lengths, and are transported to a kiln for drying. The cured pieces then are ready for the final trim and for assembly into plywood boards. It is the veneer clipper per se with which my invention is con cerned.

A typical veneer clipper consists of correlated feed and oif-bearing belts, respectively, which feed the continuous sheet to and convey the cut pieces from a clipper blade assembly. In general, clipper blades may be classified in accordance with the type of motion described by the knife during a cutting operation. For example, a majority of prior clipper blades describe a reciprocating, up and down type motion wherein, sequentially (l) the blade makes a rapid operating down stroke cut through the continuous sheet; (2) the motion of the blade is stopped and is reversed; and (3) the blade describes a rapid return stroke to its original position. A second type of clipper operates with plural knives which rotate and move with the veneer, the axis of rotation being horizontal and extending across the table normal to the direction of travel. A third type of clipper blade is swung on links or otherwise is mounted nited States Patent O 2,808,883 Patented Oct. 1957 for a rotary motion toward and away from the veneer with the cutting edge of a single knife maintained parallel to the flat sheet of veneer. This latter type of motion causes the single knife to swing through an arc, the sheet of veneer being sliced adjacent the lower terminus of this arc-like movement. The first and second types of veneer clippers are described and illustrated in a large number of patents to be found in the reciprocating and rotating motion cutting machine art, and the third type of clipper, somewhat more scarce than either of the first two types, is typified by my previous invention, Serial No. 775,654,

filed September 23, 1947, which invention was dedicated to the public through publication in the Oflicial Gazette of the United States Patent Ofiice issued September 13, 1949.

Rotary motion, single blade veneer clippers have been developed because of the greater speed, larger production volume, and increased accuracy which is possible therewith. For example, it will be apparent that a reciprocating clipper blade must describe a motion which can be summarized as descend, stop, reverse, and return. This type of an operating cycle is limited in speed of accomplishment by the requirement that the motion of the blade be stopped and reversed midway of the cycle. With a single knife, rotary type motion, on the other hand, the blade is not stopped midway of the cycle butrather is caused to travel continuously. At the same time, of course, the rotary-type motion produces a slicing rather than a clipping or crushing type cut. The slicing type cut long has been recognized in the industry as a preferable, cleaner severance.

As those skilled in the art will appreciate, the greater speed possible with a rotary-type clipper is one factor which has made practical the elimination of stop and g0 veneer travel. Thus, the industry in recent years has witnessed a conversion from the former stop and go motion of the veneer sheet itself to a continuous feed or motion while the sheet is cut. That is to say, some older clippers stopped the forward motion of the continuous sheet of veneer during the instant that the cut was made. This stop was considered essential with the slower reciprocating type of clippers, since the veneer itself is flimsy, weak, fragile, and very thin. When a cut is effected, a moving sheet would be pushed against the knife and thus would tend to curl, warp, buckle, or crush the wood fibers.

As the operating speed of the veneer clipper has increased in recent years, this requirement for stopping the moving sheet while a cut is effected has been overcome by various mechanisms. For example, some clippers provide a physical hump or rise immediately before the knife blade whereby the contact of the moving sheet with the edge of the blade will cause the following section of veneer to hump up or bend for the instant that the knife is passing through the sheet to effect a cut. At best, this is a half way etficient measure, however, since broken spaces and checks often are enlarged as the sheet is bent. It thus has been the general purpose or goal of the industry in recent years to produce a veneer clipper which will operate with suflicient speed that the knife will move out of the way without crushing or injuring the flimsy and somewhat fragile moving sheet. The instant invention provides a clipper which, to the best of my knowledge, effects the fastest cutting or slicing cycle yet achieved in the industry, and it is the mechanism which achieves this result which forms the subject matter of the instant invention.

To the above ends, my veneer clipper provides a cut-oif plate and a single horizontally arranged knife blade which are mounted on plural eccentric crank arms. These crank arms generate a swinging or a rotary circular motion of the knife toward and away from the veneer sheet through substantially a full circle while maintaining the cutting edge of the knife parallel with the moving veneer at all' times. The actual slicing motion is effected during the traversal of the lower segment only of the circular motion in order that the elements of the clipper assembly can achieve full moving velocity prior to the instant that the veneer is contacted by the knife edge. The veneer thus can be moved at a constant velocity even while the knife passes through the sheet without danger of injury to the wood fibers or buckling of the veneer.

Referring once more to my previous: invention made available to the public through publication in the Ofiicial Gazette, that veneer clipper also was of the single knife rotary type. As therein described,'the elongated knife bar was carried by plural pivotal links which moved through half circles, the opposite ends of the links carrying a counterweight bar of the identical mass and similar shape as the veneer blade and clipper bar. Thus, by moving the pivoted links, the counterweight bar described a half circle rotary motion in one direction at the same time as the clipper blade and cutoff bar described a half circle rotary motion in the opposite direction. During its day, this assembly was one of the fastest in the industry. It was not, however, without certain inherent disadvantages, one important object of the instant invention being to provide a single knife rotary-type clipper assembly which overcomes these disadvantages while, at the same time, providing an assembly which is even faster and which produces a cleaner, sharper slicing motion.

In appreciation of the improvements afforded by the instant invention, it is necessary to recognize that the distance between the anvil or cutoff plate over which the veneer travels and the lower edge of the knife is known in the art as the throat or clearance of a clipper blade assembly. This throat or clearance dimension has, through experience, become fixed in the industry at approximately three inches. Thus, in substantially all veneer clippers, the knife edge travels three inches down and three inches up while describing an operating cycle. With my previously mentioned dedicated invention, the link-type mechanism thus was fabricated with a six inch length which was pivoted at its center to provide a three inch arm on each side of the pivot. With the link in a substantially horizontal position, the stroke or clearance thus Was three inches. During an actuating cycle, of

course, the link was rotated about the pivot through a half circle (substantially 180 degrees) thereby moving the clipper blade through the required three inch down and up throat or clearance distance. At the same time, it will be evident that the three inch vertical component movement of necessity was combined with a six inch horizontal component since each given point on the knife edge traveled through a half circle the radius of which was three inches and the diameter of which was six inches. The actual severance of the sheet of veneer thus was effected with an amplified or exaggerated side to side clipping motion at the lower extremity of the operating cycle.

The above described requirement for substantially twice the horizontal component of travel as compared to the vertical component of travel of a rotary-type knife now has come to be recognized as a disadvantage or limitation. As will be appreciated by those skilled in the art, the hardness and the strength of the veneer varies with the species of wood. Thus, with certain species of wood, the veneer sheet is flimsy, weak, and somewhat yielding in texture. With the above described link or half circle motion clipper blade, the extreme component of side to side motion sometimes exhibited a tendency to chop, to slide, or to move the sheet of veneer sideways during the cutting of the blade through the veneer. It thus is one object of the instant invention to provide a mechanism which will limit the lateral or sidewise component of the blade movement consistent with the requirement for a normal throat or clearance in order to eliminate this tendency to chop, slide, or move the sheet *4 of veneer sidewise when the veneer is a species of wood not easily cut.

Another object of my invention is to provide a rotarytype veneer clipper wherein the motion of the clipper blade describes substantially a full circle, in contrast with a half circle, in order that the throat or clearance of the blade will allow an increased vertical component of motion or travel before the knife actually contacts the wood. In sum total, this provision allows the clipper assembly to be operated at a higher rate of speed and, during each cycle of operation, to achieve a maximum velocity before the moment of actual contact of the blade with the traveling sheet of veneer so as to effect a clean severance.

Another object of my invention is to provide a rotarytype veneer clipper wherein the use of 'counterweights is eliminated and the overall mass of the clipper blade is held to a minimum so as to produce a minimum inertia of the moving parts and thus to allow the assembly to accelerate and to move faster.

In accordance with the last described inventive object, it will be recognized that the moment of inertia of a body is a function and is directly related to the mass of that body. Furthermore, inertia is that property of a body by virtue of which the body tends to continue in a state of rest or motion in which it may be placed until acted upon by some external force. A veneer clipper assembly, including all moving parts and counterweights, if any, can be considered to be such a body for purposes of examination and evaluation. By eliminating the use of a counterweight in the instant assembly, I have reduced the inertia to a minimum and, accordingly, have minimized the resistance to movement or to change of direction of the clipper 'blade assembly. This minimal inertia construction allows the clipper blade to come up to full operating velocity and to achieve a higher maximum velocity with the same application of power. Further, since the motion of the moving blade is in a circle rather than in a straight line, down and up, the motion is more or less continuous and uninterrupted. This allows a higher velocity.

Yet another object of my invention is to provide a rotary motion type veneer clipper wherein the conveyor for moving the sheet of veneer is reeved about pulleys which are located on the off-bearing sides of the clipper blade assembly in order to minimize the collection of trash and debris on these pulleys during the operation of the clipper blade. The need for this provision is emphasized by the higher operating speed of the blade assembly of the instant invention and by the necessity for a smooth, uninterrupted movement of the sheet of veneer if full advantage is to be taken of this blade speed.

These and other objects and advantages of my invention will be described with reference to the accompanying drawings, wherein:

Fig. 1 is a back elevation or what is termed in the indnstry an outfeed view showing the complete veneer clipper and conveyor system, together with the twin air motor actuation cylinders therefor;

Fig. 2 is an enlarged and somewhat diagrammatic view of the knife edge in motion as it slices through a sheet of veneer, the rotary motion of the cutoff plate, knife and gears being indicated diagrammatically by direction arrows in order to illustrate the function of the mechanism; and

Fig. 3 is a section detail, taken substantially on the line 33 of Fig. 1, showing the cutoff plate, gib plate, and the crank arm means whereby the rotary motion of a spur gear is transferred to an eccentric rotary-type motion of the knife blade, this figure further illustrating the location of the feed belt conveyor pulley on the offbearing side of the clipper assembly whereby trash and debris generated by the operation of the clipper blade is inhibited from accumulating on the pulley and thus slowing or limiting efiective operation of the high speed conveyor system. 7 r

In general orientation, the veneer clipper of Fig. l is located in a plywood mill intermediate the lathe which peels the continuous strip of veneer from the revolving periphery of a log and the sorting table from which pieces of green veneer are stacked selectively according to predetermined lengths cut by the clipper. In-this figure, the plural feed belts are indicated at and the off bearing belts at 6. These belts are rotated by a common drive shaft 7 through appropriate pulleys such as illustrated at 8 in Fig. 3. As indicated in this figure, the drive and the idler pulleys (not shown) are located on opposite sides of and are spaced from the clipper blade assembly generally identified at K. It is the function of the feed belts 5 to deliver the continuous sheet of veneer to the clipper blade assembly and of the offbearing belts 6 to remove the clipped or cut pieces of veneer to an end point of use. Appropriate motor drive mechanism to elfect this function may be provided by an electric motor or the like, as will be appreciated by those skilled in the veneer clipper art.

The conveyor system above described lies substantially in the same plane as the surface of the top of a table 9 and thus functions to move a sheet of veneer over what can be seen to be a substantially horizontal table top. In conjunction therewith, the main structural elements of the clipper blade assembly consist of the frame members indicated in general at F in Figs. 1 and 3. These frame members stand up on the floor of the plywood mill in order efliciently to hold and to position the operating and moving elements of the clipper blade assembly.

Adjacent the top of Fig. l, I have illustrated a pair of air motors or piston and cylinder units 10. These motors are mounted end to end with the respective piston rods 11 thereof aligned and pivotally joined, as at- 12, to a pair of spur type gear actuation means 13. An appropriate motor control valve is provided at 14 'to regulate the supply and exhaust of air pressure via the four hoses 15 to the two air motors 10. A supply tank 16 and exhaust line' 17 connect with the valve 14 and the hoses 15, air flowing thereto and therefrom as indicated by the arrows in Fig. 1. Thus, an appropriate actuation of the valve 14 will supply air simultaneously to the right end of both motors 10 while exhausting the air from the opposite ends thereof. An opposite manipulation of the valve 14 will supply air to the left end of both motors 10 while exhausting air from the right ends thereof. Since the piston rods 11 define pitrnans, these various actuations of the air motor 10 will rotate the two large spur type gear actuation means 13 in either direction selectively. That is to say, both of these gears 13 rotate either counterclockwise or clockwise at the same time in accord with the movements of the motors 10.

In order to accommodate the limited pivotal movement of each air motor 10 during an actuating cycle, pivotalmounting therefore is provided at 18. Additionally, it will be noted that one of the piston rods 11 is in tension while the other is in compression during each operating cycle of the clipper blade assembly. This factor provides a more balanced construction and tends to eliminate 'slackness or sloppiness in the fitting of the vafious parts. 7

Referring now to Fig. 3, it will be noted that each of the large spur type actuation means 13 is journaled, as at 19, and is meshed with a pair of smaller spur gears 20. Thus, each of the large gears 13 is a driver which rotates -a pair of the smaller spur gears 20. In this manner, rotary motion is translated to four of the small spur gears 20 simultaneously during actuation of the clipper blade assembly.

Referring now to Fig. 3, each of the small spur gears 20 is keyed to a horizontal drive shaft 21, the ends of which are carried in roller bearings 22. The shaft 21,

in turn, terminates in a circular plate 23 having integral therewith'a short horizontal driven arm 24. As can be seen in Fig. 3, the short arm 24 is off center or eccentric with respect to the axis of rotation of the drive shaft 21- and, together with the plate 23, thereby defines an eccentric crank arm means.

In joinder of the short driven arm 24 and the knife blade K, the clipper blade assembly includes an elongated cutoff plate 25. The knife K detachably is joined thereto, as by bolts 26, and the arm 24 is carried in roller bearings 27. Retention of these latter bearings is effected by means of a housing 28 and cover 29, both of which detachably are secured as by bolts 30 and 31. Thus, the end. ofthe crank arm 24 effectively is 'journaled in bearings 27 which are carried within an aperture formed in the cutoff plate 25. By utilizing this type of anassembly, I am enabled to remove the bearing assembly 27 quickly and without disturbing the remainder of the clipper assembly merely by removing the cover plate 29 and the nut which is threaded upon the end of the arm 24. It will be appreciated that considerable force is transmitted in rotationby this bearing assembly 27 and thatthis force will become evident by wear. Accordingly, this provision for removal and replacement of the entire bearing is of importance to the practical continued operation of the clipper blade assembly.

During an operating cycle of the cutoff plate 25 and knife K, a bearing surface and guide is provided by a vertically disposed gib plate 32. This gib plate provides a plane smooth surface against which the corresponding plane smooth surface of the cutoff plate 25 will rub and bear. The sliding contact thereby provided restrains the cutoff plate to movement in a plane which, as shown in Fig. 3, is vertical. Additionally, looseness in the parts can be taken up by an adjustnientwhich will move the gib 32 slightly to the left as viewed in Fig. 3. This adjustment is effected by means of a plurality of threaded lock and bolt assemblies 33. The bolt of each of these assemblies bears upon the top of the gib and is received in threads tapped into the aforementioned frame F. Additionally, the gib 32 is formed with an oblique or sloping back face, as can be seen in dashed outline in Fig. 3. Movement of the gib to the left is effected by tightening the bolt assemblies 33 to move the gib downwardly upon the sloping back face. Thus, the cutoff plate 25 and knife K will retain their vertical disposition yet Will be moved or adjusted slightly to the left with respect to the frame F and associated mechanism. In actual practice, an adjustment of the bolts 33 is effected only when some wear of the parts has made the assembly loose or sloppy in fit.

Returning now to Fig. 1, it will be noted that the crank arm means 20, 21, 23, 24 are eight in number whereas only four of these are driven bythe large spur gear drivers 13. The remainder of these crank arms are nonpowered guides which serve merely to retain the knife K in a parallel or horizontal relationship with respect to the table 9 during operation. Thus, those crank arms which are idlers (not driven) are identical in structure to the crank arm shown in Fig. 3, except that no large drive gear 13 or small driven spur gear 20 is provided. Instead the structure consists merely of a shaft such as 21, roller bearings 22, a plate 23, an arm 24, and the associated bearing structure 27. In a high speed clipper such as here illustrated, this multiple guide arrangement reduces vibration and produces a smoother operating structure.

' Operation Referring to Figs. 2 and 3, it will be noted that the knife K moves slidably across the edge of an anvil A while elfecting a cutting operation. This anvil could as well be a cutoff bar since both are common in the industry. In these figures, the total vertical component of travel of the knife blade is indicated by the reference letter T. This letter T indicates the dimension of the throat or clearance of the knife above the anvil A and, in a majority of veneer clipper assemblies, the dimension is approximately three inches. Additionally, the movement of the knife K and cutoff plate 25 is shown by direction arrows. As is shown in Fig. 3, the belts and 6 lie in tunnels recessed in table top 9 so that the upper surfaces of said belts lie in the same plane as that of said table top. Said belts underlie the anvil A, and thus the knife K can pass substantially below the upper face of the anvil A without striking the table top or cutting said belts. The peripheral outline of the large spur type actuation gear 13 is shown by a dashed line representation in Fig. 2 as it meshes with the two adjoining smaller spur gears 20. Thus, a rotation of the large spur gear 13 will rotate both of these smaller spur gears 20 simultaneously in order to move the knife K through a rotary or a circular type operating cycle.

In assembling my rotary veneer clipper, I prefer to pro-portion the various gear teeth and the driving and driven rods and crank arms such that a single stroke of the air motors will move the small spur gears 20 through substantially a full circle.

As shown in Fig. 2, this movement is approximately 345 degrees, although it could as well be a full circle of 360 degrees. Thus, I use the term substantial to indicate a movement which is within 15 or degrees of a geometric full circle.

Adjacent the bottom of Fig. 2, direction arrows 34 have been used to indicate the rotary movement traced by a given point on the knife K. Thus, as the air motors 10 move through a full stroke from one extremity to the other, a given point on the knife edge K will move in a circular pattern as traced by the arrows 34. In this connection, itwill be noted that the tangent to the lower limit of the circular motion described by the cutting edge of the knife lies immediately below the sheet of veneer and below the anvil A. This tangent to the lower limit of the circular motion is horizontal and is illustrative of the fact that the sheet of veneer is cut with a rotary slicing motion during the sidewise traversal of the lower segment only of the circle 34. Additionally, Fig. 2 demonstrates that each rotary operating motion of the cutoff plate and knife both begins and ends with the cutting edge of the knife K spaced above the table top 9 and above the veneer a distance which is substantially equal to the diameter of the circle 34. It is this diameter which is identified by the throat T and is substantially equivalent to the diameter of the circle 34.

Various types of manual, automatic or semiautomatic controls can be provided for my veneer clipper, these controls forming no part of the instant invention. Suflice to say, these controls serve to effect an actuation of the air motor control valve 14. For example, one operating cycle is initiated by manipulation of the valve 14 in order simultaneously to feed air pressure to the left side of both motors 10 while exhausting pressure from the right sides thereof. The air motors 10 then move the two piston rods or pitmans 11 toward the right in Fig. 1 causing the large spur gears 13 to rotate in a clockwise direction. This clockwise rotation is transferred to a counterclockwise rotation of the eight driven and idler small gears 20. In Fig. 2, this is the particular operating cycle described by the direction arrows 34 and by the direction arrows associated with the two small gears 20.

During an operating cycle, the knife blade itself also describes a rotary motion as illustrated by the arrows 34. Because it is only the extreme lower segment of this circular motion during which the knife K actually is cutting through the veneer, the entire blade assembly is enabled to come up to full velocity'before it contacts the upper surface of the sheet of veneer. Additionally, it will be noted that the blade assembly and knife movement is one of continuous motion from the instant that the valve 14 first is manipulated until the knife edge K has traversed a complete circular cycle. This absence of a stop in motion, which stop was conventional with reciprocating type clipper blades, allows the entire mechanism to be operated at a much faster speed than prior veneer clippers. For example, I have found that the instant clipper can be operated with such rapidity that but one-twelfth of a second is consumed by each full operating cycle. This speed allows the veneer to continue moving without danger of buckling or crushing of the fragile fibers, and thus is productive of a higher output in the plywood mill.

In summary, it will be seen that I have provided a single knife rotary type veneer clipper which is capable of operation at higher speeds than heretofore has been considered possible. Additionally, the circular motion described by the knife blade is substantially a full circle whereby the same throat or clearance required with all clippers is accommodated yet the total path of travel of the knife is minimized. These factors produce a slicing cut with a minimal sidewise travel and allow the knife assembly to come up to full operating speed prior to the instant that the sheet of veneer is contacted by the knife edge. They thus add to the overall operating speed and efficiency of the clipper. Still further, by providing a feed belt pulley which is on the olfbearing side of the knife rather than immediately adjacent the point of contact of the knife with the anvil, I am enabled to maintain a clean, smooth operating pulley system which is free from accumulated debris and trash in spite of the high rate of productivity. That is to say, my pulley system is free of accumulated debris and trash because they are located at the offbearing side of anvil A and top 9, and is shown in Fig. 3. The trash and debris produced by the cutting action of knife K accumulates at the forward or infeed side of said anvil A. The anvil tends to brush said debris from the upper surface of the clipped veneer and it falls downwardly over the left-hand side of said table top 9. It is thus prevented from falling downwardly on the pulley 8, which is located far to the right of the cutting line of the knife K.

I claim:

In combination with a table having conveyor means for moving a sheet of veneer thereover, an elongated cutoff plate mounted above but movable in a plane toward and away from said table as guided by a single plane guide face on the plate, said cutofi plate carrying a single knife blade with a single cutting edge parallel the surface of said table, a gib plate means parallel to and in sliding contact with said plane guide face only thereby to define a single face bearing surface guiding and restraining said cutoff plate to movement in a plane, means for adjusting said gib plate laterally with regard to said cutoff plate, thereby to maintain the movement of said cutoff plate to movement in said plane, and plural eccentric crank arm means operatively journaled within bearings housed within said cutoif plate to move the cutoff plate in rotation through substantially a full circle while maintaining said cutting edge parallel to the surface of said table, selected ones of said plural eccentric crank arm means including a short horizontal driven arm which extends through and is journaled within an aperture in said cutofi plate carrying a corresponding one of said bearings, each .said driven arm being operatively joined to and parallel with .an elongated horizontal driven shaft having an axis of rotation off center with respect to the axis of the driven arm, selected others of said plural eccentric crank arm means being nonpowered guides and each including a short horizontal idler arm which extends through and is journaled within an aperture in said cutoff plate carrying a corresponding one of said bearings, said nonpowered guides also including an elongated horizontal idler shaft operatively joined to and parallel with each said idler arm but having an axis of rotation oif center with respect to the axis of the corresponding idler arm, a spur gear fixed to each of said selected horizontal drive shafts for rotation therewith, a pair of spur gear actuation means spaced longitudinally of said cutoff plate with each spur gear actuating means operatively meshing with a separate pair of said spur gears fixed to said selected crank arm means to rotate the same in either direction through substantially a full circle of rotation, and a pair of air motor means mounted end to end centrally above said cutofi plate with the piston rods of the motors aligned but extending in opposite directions into pivotal connection with respective ones of said gear actuation means to define pitmans.

References Cited in the file of this patent UNITED STATES PATENTS 84,306 Sanborn Nov. 24, 1868 156,217 Greenman Oct. 27, 1874 1,224,107 Hawkins et a1 Apr. 24, 1917 1,448,404 Hort Mar. 13, 1923 1,467,378 Hanson Sept. 11, 1923 Seybold Mar. 10, 1924 Stanley Jan. 19, 1932 Willgoos Aug. 8, 1939 Bugatti Sept. 23, 1941 Keagle Mar. 11, 1948 Munschauer July 14, 1953 Wikle Feb. 7, 1956 FOREIGN PATENTS Denmark Jan. 21, 1946 OTHER REFERENCES Knokey: Abstract of application Serial Number 775,654,

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