US2711792A - Veneer clippers - Google Patents

Description

June 28, 1955 J. B. MOFALL VENEER CLIPPERS 4 Sheets-Sheet 1 Filed May 1, 1951 INVENTOR. J05 B. MFFALL A T OE /EKS June 28, 1955 J, B. MOFALL 2,711,792

WENEER CLIPPERS Filed May 1, 1951 4 Sheets-Sheet 5 INVENTOR. JOE 5. M FAZ L June 28, 1955 .J. B. M FALL 2,711,792

VENEER CLIPPERS Filed May 1, 1951 4 Sheets-Sheet 4 INVENToR. J05 5. M F LL 2,711,792 VENEER CLIPPERS Joe B. McFall, Seattle, Wash., assignor to United States Plywood Corporation, Seattle, Wash, a corporation of New York Application May 1, 1951, Serial No. 224,036 14 Claims. (Cl. 164-48) This invention relates to a clipper for cutting veneer, and especially to a quick-acting precision clipper having various advantages over those previously employed.

A particular feature of the clipper construction is that the blade moves from beneath a veneer sheet upward into contact with it during the cutting operation, and the blade has a very short cutting stroke. is a rubber surface roll which has the dual action of serving as a backing for the blade and of smoothing the veneer substantially into planar condition prior to the cutting action.

An object of the invention is to mount the cutting blade so that despite its weight it can be moved swiftly during the cutting stroke and returned, and this object is accomplished by utilizing coacting and complementary forces to move the blade, including counterbalancing the weight of the blade.

A more specific object is to effect reciprocation of the blade by double-acting push-pull electromagnetic mechamsm.

During the clipping operation it is an object to guide the veneer accurately and to hold it in substantially planar condition during clipping, while at the same time preventing injury to the guiding mechanism by providing safety operation in the event that excessively thick stock attempts to pass through the cutting zone.

A further object is to provide such clipper mechanism which will aiford easy and quick access to the cutting blade and its associated parts for replacement of the blade or servicing of other parts of the machine.

Still another object is to provide a mechanism which,

while very effective, is of simple and rugged construction and may be very compact because the operating parts, such as the blade and its reciprocating mechanism, are located beneath the path of veneer travel, so that they may be most directly and effectively supported and braced.

Particular features of the clipper include the use of compression springs to balance the blade weight and to supplement the force exerted by the blade reciprocating mechanism, which preferably is of the electromagnetic type, and the provision of a rubber-surfaced roll above the blade, power driven to assist in feeding the veneer to the cutting zone, to hold the veneer substantially fiat during cutting, and to serve as a backing for the knife.

Further advantages and features of the machine will be pointed out in the following description of a preferred embodiment of the clipper shown in the drawings.

Figure 1 is a plan view of the clipper with parts broken away to show structural details.

Figure 2 is an elevation view of the clipper viewed from the discharge side, and Figure 3 is a transverse sectional view through the clipper taken on line 33 of Figure 1.

Figure 4 is a detailed transverse sectional view through a fragmentary portion of the clipper, taken on line 44 of Figure 5, and Figure 5 is a detail sectional view of a fragmentary portion of the clipper taken perpendicular to the view of Figure 4 and on line 5-5 of that figure.

Figure 6 is a plan view of electromagnetic blade reciprocating mechanism with parts broken away, taken on line 6-6 of Figure 7, and Figure 7 is an elevation view of the same mechanism taken on line 77 of Figure 6.

Figure 8 is a wiring diagram of the control mechanism Coacting with the blade States Patent 0 2,711,792; Patented June 28, 1955 for the electromagnetic blade reciprocating mechanism;

In conventional veener clippers the veneer is carried by conveyor mechanism in a sheet, usually one hundred inches in width, and of varying and indeterminate length. Such veneer usually is rotary cut from a log, and the grain extends Widthwise of the sheet and transversely of its direction of movement. The clipping operation has two principal functions, first to enable major defects in the veneer sheet to be removed, and, second, to divide the more or less continuous sheet into strips of a width transversely of the grain appropriate for fabricating into plywood.

Clippers are employed at two principal locations in a plywood plant, first to cut into strips the sheet veneer which is peeled from a log by the rotary cutting operation.

Second, dried veneer is cut in connection with an edgejoining or splicing operation, either to produce strips of appropriate width before the joining operation or strips are joined into a continuous sheet which is then cut into sections of appropriate width for fabricating into plywood sheets. Particularly when veneer is dry it tends to warp or buckle, although even green veneer has this tendency to a lesser degree. In order to cut a veneer sheet to leave straight edges it is important that the veneer sheet be substantially flat at the cut location. In the usual veneer clipper the blade descends onto the sheet being conveyed,

' and it is very difiicult to hold the veneer fiat adjacent to such a blade because occasionally the edge of one sheet of veneer will overlap the edge of another sheet, or some foreign object will fall onto a veneer sheet, which would jam or strain positive hold-down mechanism overlying the veneer being conveyed.

Another difiiculty experienced with the usual veneer clipper, particularly where it is operating on warped veneer, is the length of time during which the blade is in e and returned upward sufliciently to clear the veneer.

During the down stroke of the blade the veneer may be fed forward somewhat to scrape under the blade, but during the retracting motion of at least one inch in such a situation the cut edge of the veneer on the infeed side of the clipper is held against movement, so that if the veneer conveyor continues to run, the veneer is buckled on the infeed side of the clipper, which may cause rupturing of the veneer. If the veneer conveyor were stopped.

to prevent such occurrence for each clipping operation,

) the turning action of the veneer lathe, which is continuous, would be upset. 0n the contrary, the faster the veneer conveyor moves, the more serious are the results of such interruption in veneer movement at the clipper caused by prolonged engagement of the cut edge of the veneer with the clipper blade.

The present clipper has a blade 1 which is located below the belts 2, cooperating to feed the veneer V to the clipper, and a hold-down roll 3 spanning the veneer supply conveyor may therefore be located at the cutting zone. Several advantages are obtained by this arrange ment, the first being that the veneer to be cut is held A third advantage is that by mechanism to be described the blade can be moved more rapidly than it is practical to move an overhead blade, thus further reducing the time of blade contact with the veneer for a given stroke. As a result there is only negligible interruption in movement of the veneer at the cutting zone during a clipping operation, so that there is practically no buckling of the veneer, and consequently rupture of it is avoided, although a more accurate cut is obtained. Despite these advantages jamming of the veneer beneath the hold-down mechanism is avoided, even though veneer edges should overlap or a foreign object on the veneer should pass under the hold-down roll 3.

The infeed or supply conveyor belts 2 preferably are chains, each link of which is faced with a small plate, which plates cooperate to form virtually a continuous surface strip lengthwise of the direction of conveyor movement. These chains are guided for movement along supporting bars 20, disposed in a vertical plane as shown in Figures 3 and 4. Each of these bars is supported at one end for swinging about the axis of shaft 21 carrying drive sprockets or pulleys for driving the chains 2. The swinging end of each bar is supported by a rod 22 pivoted to the swinging bar end and having a plunger 23 carried by its lower end. This plunger is guided for vertical reciprocation in a cylinder 24 which houses a spring 25 reacting between the bottom of the cylinder and the plunger 23. The springs 25 for the several rods 22 are sufiiciently strong to support the conveyors 7; through the several rods 22 under normal loads, but if an excessive thickness of material should tend to pass under and be wedged against roll 3, one or more of the springs 25 could yield, enabling the corresponding bar 20 to swing about shaft 21 so that its conveyor 2 will be depressed at the roll 3 to enable the unusual thickness of material to pass beneath it without damaging any of the mechanism. The cutting edge of knife 1 in its retracted position and discharge or output conveyor 4 will be spaced below the lower periphery of roll 3 suificiently far as to afford ample clearance for any such unusual thickness of the veneer or foreign object likely to be deposited on veneer carried by the conveyor belts 2.

The conveyor belt drive shaft 21 is turned by a sprocket 26, driven by chain 27 from a motor-driven sprocket 28. Since the individual chains 2 are pushed around their circuits by their drive sprockets or pulleys on shaft 21, it is necessary that these chains be maintained quite tight, and for this purpose tighteners 29 are carried by bars 20 and adjustable relative to such bars, as indicated in Figure 3, to vary the tension of the chains individually.

Coaxial with sprocket 28 is a second sprocket 39 mounted on the same driven shaft to drive a chain 31 which turns sprocket 32 fixed on shaft 49 at the discharge side of the clipper. This shaft carries a further sprocket 33 driving chain 34 to turn sprocket 35 on countershaft 35 above shaft 40. This countershaft carries gear 35", meshing with gear 36, carried by shaft 37, also located above shaft and parallel to such shaft and countershaft 35'. Gear 36 is not secured to shaft 37, however, but rather is secured to a sprocket 36 which drives chain 38, which in turn drives sprocket 39 fixed on roll shaft 3'. The sizes of sprockets 32 and 30 are such that shaft 40 preferably will be turned at the same speed and in the same direction as shaft 21 driving the supply conveyor chains 2. Sprockets 41, fixed to shaft 40, can then be of the same size as the sprockets driving supply conveyor chains 2, and the discharge conveyor chains 4 can be of the same type as the supply conveyor chain 2 which is shown in Figure 4. Likewise these discharge conveyor chains can be supported and guided by bars 42 disposed in spaced vertical planes. Moreover, the chains 2 and tcan be aligned in the direction of movement of the veneer, as shown in Figure l, and by the drive mechanism described they will be driven at the same speed. As shown in Figures 3 and 4, however, it is preferred that discharge conveyor chains be located substantially lower than the supply conveyor chains 2 in order to avoid any possibility of material being jammed on the discharge conveyor. Fingers 43 may project toward the knife to a location adjacent to its surface on the discharge side so as to prevent even a narrow strip of veneer from dropping between such surface of the knife and the conveyor 4. Preferably these fingers are inclined downwardly toward the conveyor somewhat, so that even a narrow strip will slide onto the conveyor to be carried positively away from the knife blade.

The gears 35 and 36, interposed in the driving mechanism for roll 3, preferably are of the same size, so that they serve merely to reverse the direction of rotation of shaft 3' so that it will turn in the direction opposite the rotative direction of shafts 21 and 40. The sizes of sprockets 35, 3-6 and 39 will be selected with reference to the size of roll 3, such that the peripheral speed of this roll will be equal to the linear speed of chains 2. While, as mentioned above, it is preferred that the linear speed of chains 4 be the same as the speed of linear chains 2, this is not essential so long as chains 4 move at least as rapidly as chains 2. The discharge speed can, if desired, be faster than the speed of the supply conveyors.

The spacing between the lower periphery of roll 3 and the upper surface of the supply conveyor chains 2 need exceed only slightly the thickness of veneer which usually is one-eighth of an inch or less in thickness and seldom exceeds one quarter of an inch. The spacing between the supply conveyor and the bottom of roll 3 may therefore be between one-quarter and three-eighths inches, bearing in mind that if the edges of the veneer sheets overlap, the supply conveyor supporting arms 20 can swing downwardly to relieve excessive pressure between such conveyor and the roll 3 as explained previously. The roll 3, therefore, can be fixedly supported in this position.

While the roll 3 can be mounted stationarily, it is preferred that a further precaution be taken to prevent damage to the machine under very extraordinary conditions. For all practical purposes it may be assumed that the roll 3 is stationary, but it is maintained in the position shown only by its own weight, which is considerable. Thus shaft 3' is carried by arms 37' at its opposite ends, which are secured to shaft 37. This shaft is journaled for rotation so that roll 3 may be swung from the solid line position shown in Figure 3 upward in counterclockwise direction until the arms 37 assume the dotted line positions shown in that figure. The lowered or operative position of the roll will be established by a stop 37", carried by shaft 37, which is engageable with a shaft journal box. This stop may be adjusted to vary the operative position of the roll and may engage a suitable abutment at the opposite side of the shaft journal to limit swinging movement of the roll in a counterclockwise direction from its operative position.

The knife blade 1, as mentioned previously, is disposed beneath roll 3, and its cutting edge preferably lies substantially in the vertical diametral plane of roll 3 in its operative position. As shown in Figure 4, the blade lies close alongside the supply conveyor chains 2, but clearance must be permitted for the curved sections of these chains between their working stretches and their return stretches. A nosing 10 is therefore provided to bridge the space between the ends of the working stretches of chains 2 and the path of the knife blade 1. Such blade is carried by an angle mounting bar 11, being secured thereto by bolts 12, so that the blade may be removed readily for sharpening, or a dull blade readily replaced by a sharp blade.

As has been mentioned above, the width of the veneer sheet to be clipped ordinarily is approximately one hundred inches. This represents quite a great span, yet in order to obtain a clean out throughout the width of the veneer sheet the blade must be held rigidly against bending at the middle. It is necessary, therefore, to provide a rigid blade supporting structure which should be supported at reasonably closely spaced intervals along its length. If the clipper blade is mounted above the path of the veneer sheet, it is necessary not only to provide mechanism for keeping the blade straight, but to withstand the forces produced by the thrust of the blade during its rapid movement, while preventing any appreciable sagging in the middle of the blade. Such structure must therefore be quite massive, which presents a difficult problem in overhead blade clippers, requiring that they be quite deep. As a result the clipper structure as a whole is high.

By mounting the clipper blade beneath the path of veneer travel, however, as in the present installation, it

is not necessary to suspend the blade supporting structure.

In order to enable workmen to handle veneer on the conveyor readily, such as to remove clipped strips of the veneer, it is necessary that the veneer conveyors be at a reasonable working height, such as two and one-half to three and one-half feet, in any event. vides ample space to accommodate a rigid mounting for the clipper blade supporting structure.

In Figures 2 and 3 the blade supporting structure is shown to be carried by trusswork 13 of any suitable type. Projecting upwardly from this trusswork are bosses 14 serving as mountings for blade actuating mechanism interengaged between the knife-supporting truss structure and the knife itself. Such actuating mechanism, however, does not support the knife, but, on the contrary, at all times exerts a downward force on the knife'when in its lower position.

The knife is actually supported by springs 15 mounted on opposite sides of the knife and at intervals along its length. Projecting from opposite sides of the knife blade mount 11 are feet 16 which rest on the upper ends of the respective springs 15, and these springs are supported in cups 17, supported on the beam or truss 13 and adjustable in height relative to it to vary the pressure exerted by the springs upward against the feet 16. The force of these compression springs 15 exerted collectively preferably will more than offset the weight of the knife and its associated structure, not only in its lower position, but also in its extreme upper position. At all times, therefore, these springs not only will counterbalance the weight of the moving parts of the knife mechanism, but in addition will urge the knife upward even when it is raised to its upper limiting position. The knife actuating mechanism, therefore, on the upper stroke of the knife releases the springs so that their force can be used to move the blade upward, and in addition may assist the springs to overcome the inertia of the movable clipper parts. During descent of the knife the actuating mechanism will supplement the weight of the moving clipper parts to compress the springs.

The actuating mechanism includes a bar 5 interconnecting a plurality of toggle joints having their upper ends connected to eyes 18 projecting downward from the clipper blade mounting bar 11, and their lower ends connected to the bosses 14 on the beam 13. The extended length of the toggle joints is such that the sharpened edge of the blade 1 will just touch the roller 3 when the blade is in its uppermost position, as shown in Figure 5. This upper position of the blade may be adjusted as the blade is worn by sharpening, for example, by providing slots in the blade through which the bolts 12 pass. As indicated in Figure 2, the toggle joints break or buckle in opposite directions from fully extended position, so that the bar 5 will be moved in only one direction during a complete stroke of the blade, including its movement upward from its lowermost position and return to such position.

The bar 5 may be reciprocated lengthwise to move the toggle joints 50 by various means, so long as such means operate very rapidly. Heretofore, air cylinders have usually been used to operate clipper blade reciprocating mechanism, but this medium requires provision of Such height proan air compressor, compressed air storage tank, and come pressed air distribution pipes, which makes a relatively expensive installation. It is preferred, therefore, that electromagnetic means be utilized to reciprocate'bar 5, since electricity is readily available to most veneer clipper installations. The electromagnetic actuating mechanism shown best in Figures 6 and 7 may be controlled by electric control mechanism such as shown diagrammatically in Figure 8. An electromagnetic installation is provided at each end of the clipper, which coact during each stroke so that the magnetic means at one end of the bar exerts a pushing force while the means at the other end of the bar exerts a pulling force. in addition, the electromagnetic means serve to hold the bar 5 in one or the other of its extreme endwise positions between cutting operations.

Each of the electromagnetic means includes a laminated core 51 fixed at the end of the clipper, and on which is mounted the stationary coil including a winding 6a of small wire and a winding 6b of large wire. Cooperating with this magnet is the movable magnet structure including the reciprocable soft iron core 52 having ears 53, one at each end. These ears are apertured to receive slidably guide rods 54 mounted on the clipper frame.

This movable core element carries the coil 50, which cooperates with coils 6a and 6b. The movable core is connected by a pivot 55 extending through ears 56 to a link 57, the opposite end of which is pivotally connected by a pin 58 to the adjacent end of bar 5.

It will be evident that the lengthwise movement of bar 5 is limited by the stroke of movable core member 52. Suitable stops, not shown, may therefore be provided to limit movement of the cores in each direction and to snub such movement as the desired downward limiting blade position is reached. Endwise reciprocation of the blade mount 11 as the bar 5 moves is prevented by guides 59 which may be in the form of a cylinder mounted on the clipper frame, extending slidably through a sleeve carried by the blade supporting bar.

The electrical control mechanism for the electromagnet coils 6a, 6b and 60 is illustrated in Figure 8. This mechanism consists of three principal circuits: one a low-voltage, continuously energized circuit, the second a highvoltage, alternating current, intermittently-energized circuit, and the third a control circuit. The low-voltage circuit 61, from thirty to seventy volts direct current, connects in series the circuit 6a of each stationary coil and the two coils 60, carried by the respective movable cores 52. No. 12 wire is satisfactory for all these coils, and a switch 62 is closed all the time the clipper is operating and is opened when the clipper is not in use.

The coils 6b are wound with much heavier wire, for example No. 4 Wire of many more turns than coils 6a. These coils are connected in series in alternately energized ignitron tube circuits. One circuit, for example, includes the transformer 7a, connected to the 440-volt source 70, and two ignitron tubes 71a and 72a, connected to the opposite ends of the secondary winding of transformer 7a. A common lead from these tubes is then connected to one of the coils 6b, which coils are interconnected by a common lead 73. The opposite end of the other coil 6b is connected by a lead 74a to a center tap on the secondary winding of transformer 7a. Similarly, the primary Winding of transformer 7b is connected across the 440-volt A. C. line 70, and opposite ends of the transformer secondary winding are connected to ignitron tubes 71b and 72!). These two tubes are then connected to the same terminal of a coil 61; as is lead 74a, and the coil terminal to which tubes 71a and 72a are connected is also connected to the lead 74b in circuit with the center tap of the secondary winding of transformer 7b.

The control circuit includes an igniting control 75a for tubes 71a and 72a, and an igniting control 7511 for tubes 71b and 7212. In series with the ingiting control 75a is connected a switch 76a of a double-pole, doublethrow switch, and an automatic timer 77a. Similarly, in series with igniting control 75b is connected the switch 76b of the double-pole, double-throw switch, and an automatic timer 77b. The opposite terminals of igniting controls 75a and 75b are connected to one side of the ll-volt A. C. control circuit source 78.

The double-pole, double-throw switch 76a, 76b is energized by the ratchet relay 79, which will shift the switch alternately to close switch 76a and switch 76b on successive energizations of the relay coil. This relay may be energized manually at will by closing a switch 3 to connect the relay coil across the energizing current source 78. In parallel with manual control switch 8 may be connected an automatic switch mechanism 80, energized by suitable measuring or cycling mechanism. Thus, for example, the element 89 could be cam control switch synchronized with movement of the feed conveyor chains 22, such that when they have moved a predetermined distance, for example, twenty-five or fifty inches, the switch of the mechanism 80 would be closed to energize the relay 79.

A safety switch 81 may be included in the control circuit, which is normally closed, but can be opened by a switch actuating abutment 82 carried by one of rods 22. Alternatively, a safety switch 8?. may be incorporated in the control circuit for each of rods 22, such switches being connected in series. When, as previously explained, an unusual thickness of material wedges against the roll 3, the rod 22 in the vicinity of the excessive thickness, or all the rods 22 will be moved downward by swinging of bars 20 carrying chains 2. Opening of a switch 8 would then prevent energization of relay coil 79 during passage of the excessive thickness material so that the clipper would not be overloaded by the blade trying to out such excessive thickness material.

As shown best in Figures 4 and 5, the roll 3 has a reasonably thick facing of rubber, and the knife blade 1 is adjusted relative to its supporting bar 11 such that, when the links of the toggle joints are in extended alignment, the cutting edge of the knife will bear against the rubber surface of the roll. The diameter of the roll is quite large, and because the cutter blade will operate at non-uniform intervals it will strike the periphery of the roll at different locations practically every operation of the clipper. Any appreciable cutting of the rubber surface is thus avoided as the roll serves as the backing for the cutting knife, and the rubber surface of the roll will not be worn quickly.

When the veneer is moved into the convergent space between the supply conveyor 2 and the periphery of roll 3, as indicated by the arrow in Figure 4, any exceptionally warped or wrinkled portions of the veneer sheet will be engaged by the surface of the roll, and the veneer sheet at the cutting zone of minimum clearance between the roll and. the nosing 10 will be held substantially flat. When the desired location for a cut in the veneer has reached the cutting zone, the operator will close the manual switch 3, or the automatic switch 80 will close to complete the circuit from the source 78 to the relay coil 79, assuming that the switch 81 is closed. If the parts are in the position shown in Figures 2, 6, 7 and 8 at that time with the bar fully to the left as the clipper is seen from the discharge side, the doublepole, doublethrow switch will be shifted to close a circuit through the ignitor control mechanism 75b to ignite the ignitron tubes 71b and 72b. Switch 62 having been closed prior to initiating operation of the clipper, coils 6a and 60 at both ends of the clipper will be energized. Now, however, both coils 6b will also be energized by direct current supplied by the ignitrons which will flow in a direction so that the right coil 6b will attract the right coil 60, and the left coil 6b will repel the left coil 60. Immediately, therefore, the magnets thus energized will drive bar 5 to the right, swinging the toggle joints from the solid line positions shown in Figure 2 to the broken line positions shown in that figure.

Prior to cnergization of the coils 6b as described, energization of the left coil 6a and the left coil 60 will produce a magnetic flux attracting the two magnets at the left, but relatively weak as compared to the flux produced by energization of the coils 6b. The magnetism produced by coils 6a and 69 thus juxtaposed, however, will be sufiiciently in excess of the magnetism produced by the similarly energized coils 6a and 60 at the right of the clipper as seen in Figure 8, as to hold springs 15 compressed with the clipper blade in its lower position as seen in Figure 3. Immediately upon energization of the coils 6b in the manner described, however, as the bar 5 begins to move to the right, the force produced by springs 15 supplemented by the expanding force of the toggle joints will raise the clipper blade quickly to its position shown in Figures 4 and 5. Thus the blade will have cut across the veneer, severing the piece along the line in the cutting zone so quickly that there will be only negligible interruption in movement of the severed edge on the feed side of the cutting zone, even though the conveyor chains 2 continue to move at a reasonably rapid speed.

As the repelling magnetism at the left end of the clipper and the attracting magnetism at the right end of the clipper continue, the bar 5 will be moved sufficiently to draw the toggle joints downward again into the broken line positions of Figure 2. By such movement the springs 15 again will be compressed and the knife blade will be withdrawn below the path of the veneer through the clipper. The severed strip of veneer will drop onto the discharge conveyor 4 with its trailing edge resting on fingers 43, and the sheet fed into the veneer will continue between the nosing 10 and the roller 3 until the piece of the next desired width has been fed through the cutting zone. The coils 6a and 60 which are closer together will hold the bar 5 stationary, ready for the next cut after the timing mechanism 77b has interrupted the circuit through the coils 6b.

When the switch 8 or 80 again is closed to energize the coil of relay 79, the double-pole, double-throw switch 76a, 76b will be shifted to the other position, thus closing a circuit through the igniting control 75:: for ignitron tubes 71a and 72a. The direct current supplied by these ignitrons would flow through coils 6b at the two ends of the clipper in series, but in the direction opposite the direction the current flows when supplied by ignitron tubes 71b and 72b. Consequently, even though coils 6a and 60 are energized always with current flowing in the same direction, the energization of coils 6b now would produce a magnetic reaction affording magnetic attraction at the left end of the clipper and magnetic repulsion at the right end, so that again a push and pull force would be exerted on bar 5 to move the links, this time from the broken line position of Figure 2 back to the solid line position, which will effect a further clipping action.

I claim as my invention:

1. A veneer clipper comprising backing means, said backing means comprising a roller disposed above the path of a veneer sheet to be cut, a knife, means supporting said knife beneath said roller, supply conveyor means supported at least in part beneath said roller to form a converging space therewith, driving means for positively moving said conveyor means toward and up to said converging space beneath said roller, and means operable to eifect relative approach movement of said knife and said roller to cut veneer carried by said conveyor means between said roller thereabove and said knife and said conveyor means part therebeneath in the region just beyond said converging space.

2. The veneer clipper defined in claim 1, and means guiding the knife for movement upward across the path of the veneer sheet and into engagement with the roller and for retraction downward again.

3. The veneer clipper defined in claim 2, and yieldable means supporting said supply conveyor means part and operable to yield upon wedging force between said conveyor means part and the roller in excess of a predetermined value.

4. The veneer clipper defined in claim 1, and counterbalancing spring means interposed between the supporting means and the knife and operable to support the knife.

5. The veneer clipper defined in claim 4, and actuating means operatively associated with said knife and movable to one position for moving and holding the knife in a lowered position against the counterbalancing action of the spring means, said actuating means being movable to another position for exerting a raising force on the knife, upplementing the force of the springs, and said actuating means being movable to a third position to move the knife downward again in opposition to the force of the springs.

6. The veneer clipper defined in claim 5, in which the actuating means include a plurality of toggle joints extending between the knife and the knife supporting means.

7. A veneer clipper comprising a rubber-surfaced roll disposed above the path of a veneer sheet to be cut, means rotating said roll, supply conveyor means supported at least in part beneath said roll, means for moving said conveyor means toward said roll at a speed substantially that of the peripheral speed of said roll, a knife disposed below said roll, beside said conveyor means, and beneath the path of the veneer sheet, and means operable to move said knife reciprocally into engagement with the surface of said roll to cut the veneer between said rotating roll and said knife and coming off said conveyor means.

8. The veneer clipper defined in claim 7, and means guiding the roll for bodily movement upward into a position spaced a substantial distance above the path of the veneer sheet.

9. A veneer clipper comprising a supply conveyor, a roll disposed above said supply conveyor a distance slightly greater than the thickness of a veneer sheet to be cut, means rotating said roll to move its lower periphery in the same direction of movement as said supply con veyor and at approximately the same speed, a knife, means movably supporting said knife beneath said roll for guiding the movement thereof from a position below said conveyor upwardly to contact with said roll, said supporting means comprising means biasing said knife upwardly against the force of gravity, and means operable to augment the action of said biasing means so as to move said knife positively from its lower position into its upper position to cut the veneer passing beneath said roll.

10. A veneer clipper comprising backing means disposed above the path of a veneer sheet to be cut, a knife, means supporting said knife beneath said backing means, means operable to effect upward movement of said knife across the path of the veneer sheet and into engagement with said backing means and for retraction downward again, a supply conveyor alongside the knife and baking means and operable to feed a veneer sheet therebetween, and yieldable means supporting said supply conveyor and operable to yield upon wedging force between said conveyor and said backing means in excess of a predetermined value, and said backing means including a pressure roll.

11. A veneer clipper comprising backing means disposed above the path of a veneer sheet to be cut and presenting a moving surface, a knife, means supporting said knife beneath said backing means surface, means operable to effect upward movement of said knife across the path of the veneer sheet and into engagement with said backing means surface and for retraction downward again, and a supply conveyor alongside the knife and backing means surface and operable to feed a veneer sheet therebetween; said supply conveyor comprising a plurality of separately movable veneer sup mounting each of said movable supports for 11 towards and away from said backing means an separate yieldable means sup orting each of aratcly movable supports and operable to y wedging force between each of said supports backing means surface in excess of a value.

12. The veneer clipper defined claim 11, in which each of the separately movable supports comprises endless web drive.

13. The veneer clipper defined in claim 12, in which a common driving means is provided for d ag all of the endless web drives regardless of the pos Ion of any of the separately movable supports and the endless web drive operatively associated therewith.

14. A veneer clipper comprising backing means disposed above the path of a veneer sheet to be cut, a knife, means supporting said knife beneath said backing means, means biasing said knife upwardly against the force of gravity, means operable to effect upward movement of said knife across the path of the veneer sheet and into engagement with said backing means and for retraction downward again, said last named means comprising actuating means moveable in opposite directions generally parallel to said knife to effect such movement thereof completely toward and away from said backing means when moved in either direction, electromagnetic means operable to move said actuating means in either of said directions, said electromagnetic means comprising a pair of coils mounted for movement with said actuating means, a pair of stationary coils each positioned in cooperative relationship with one of said moveable coils, strong electromagnetic energizing means discontinuously operable to energize one said pair of coils always in the same manner and the other pair of coils in opposite manners alternately to effect changing attraction and repulsion between cooperating coils and hence movement of said actuating means in said opposite directions, and weaker electromagnetic energizing means continuously operable to energize said cooperating coils to effect continuous minor attraction between said cooperating coils, the relationship of opposing forces between the continuous weaker electromagnetic force plus the force of gravity on said knife in one direction, with the force of said biasing means in the opposite direction being such that when either set of cooperating coils are adjacent to one another the component of forces is suificient to hold said adjacent coils in such position and said knife in retracted position, while the relationship of opposing forces between the stronger electromagnetic force plus the force of the biasing means in one direction, with that of the weaker electromagnetic force plus the force of gravity in the opposite direction being such that upon each said discontinuous energization the combined major attraction and repulsion of cooperating coils results in a complete movement of said actuating means in one of said directions and hence momentary engagement with said backing means by said knife with sufficient force to cut a veneer sheet therebetween.

References t'lited in the file of this patent UNITED STATES PATENTS 758,156 Taylor Apr. 26, 1904 915,438 Hornor Mar. 16, 1909 1,534,687 Collier Apr. 21, 1925 1,676,260 Glidden July 10, 1928 1,841,853 Stanley Jan. 19, 1932 1,929,114 Hentschell et al. Oct. 3, 1933 2,005,824 Haumann June 25, 1935 2,394,324 Miller Feb. 5, 1946 2,405,598 Miller Aug. 13, 1946 2,532,672 Michael et al. Dec. 5, 1950

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