US 3760855 A
This invention relates to a centering apparatus for peeler logs with substantially noncircular cross sections, nonuniform taper and noncircular sweep. The mantle of a log is represented by the peripheries of a number of cross sections. Each periphery is determined by a number of points on the periphery. Each point is sensed by a displacement transmitter and simultaneously duplicated in a log mantle duplicating unit, so that the duplicated periphery is represented by points with chords in between. Simultaneously, with the duplication of the log mantle, two special free floating variable diameter cylinders, with inherent expansion forces in each and a common axis for both, are contracted by the chords for the duplication of the peripheries. The variable diameter cylinders have in their final position, within the duplicated log mantle, maximum diameters and their common axis is the peeling axis for the log.
Description (OCR text may contain errors)
United States Patent Nilberg Sept. 25, 1973 1 APPARATUS FOR CENTERING IRREGULAR PEELER LOGS Inventor: Reinhold Hermann Nilberg, 463
Beachview Dr., Vancouver, BC, Canada Filed: Sept. 14, 1970 Appl. No.: 71,698
 References Cited UNITED STATES PATENTS 6/1962 Graham 144/209 A 5/1963 Pearson... 144/209 R 4/1970 Don 144/209 A Primary Examiner-Donald R. Schran  ABSTRACT This invention relates to a centering apparatus for peeler logs with substantially noncircular cross sections, nonuniform taper and noncircular sweep. The mantle of a log is represented by the peripheries of a number of cross sections. Each periphery is determined by a number of points on the periphery. Each point is sensed by a displacement transmitter and simultaneously duplicated in a log mantle duplicating unit, so that the duplicated periphery is represented by points with chords in between. Simultaneously, with the duplication of the log mantle, two special free floating variable diameter cylinders, with inherent expansion forces in each and a common axis for both, are contracted by the chords for the duplication of the peripheries. The variable diameter cylinders have in their final position, within the duplicated log mantle, maximum diameters and their common axis is the peeling axis for the log.
7 Claims, 5 Drawing Figures s i ll" umuImmm F 1 1 1111111 llllllll rig 6'" A o 0 $045,) n hi PATEN TED $EP25 9 3 SHEET 3 BF 5 PATENIED SEPZS I976 SHEET '4 BF 5 APPARATUS FOR CENTERING IRREGULAR PEELER LOGS A centering apparatus is part of a lathe for rotary peeling of veneer. The log is chucked, at each end, in the lathe and the center points of the chucks determine the peeling axis.
The amount of continuous full width veneer recovered, along the full length of the log, depends on the position of the peeling axis within the mantle of the log. The purpose of a centering apparatus is to find a peeling axis that gives the maximum recovery of full width veneer. The ideal peeling axis is determined by a straight cylinder, as long as the log and fully surrounded by the log mantle and positioned within the mantle so that its diameter is a maximum.
If the log is tapered, so that one end is substantially larger than the other, then a centering apparatus must operate in such a manner that in addition to the maximum recovery of full width veneer, an optimum of half width veneeris recovered at the larger end of the log.
The only known method for centering of logs with non-circular cross sections is the optical centering method. This method applies two fixed projectors, facing each other on a common axis called the datum axis, at a distance exceeding the length of the log. The datum axis is parallel to the lathe axis, it is generally in the same horizontal plane with the lathe axis and it has a fixed distance from the lathe axis. The log is positioned between the projectors on two supports. Each projector puts on the nearest end face of the log a series of concentric circles. Each log support is shifted by the operator horizontally and vertically so that within the periphery of the end face appears the largest possible circle. The log is centered and transferred to the lathe.
The advantage of the optical method is that an experienced operator easily puts the maximum circle onto Automatic centering consists essentially of finding the center points of the maximum circles in the peripheries of two critical cross sections of the log. One cross section is positioned at about 15 percent of the log length from one end and the other is at the same distance from the other end. These two center points determine adequately the peeling axis for logs with uniform taper and circular sweep. The above mentioned cross sections must have a point of symmetry for correct conventional centering. There is no centering apparatus available for irregular or nonsymmetric cross sections.
Nonsymmetric cross sections, such as eg shaped cross-sections and cross sections with knots, introduce incorrect centering. It has been estimated that the losses from incorrect centering of logs with irregular cross sections, sweep and taper, exceed 5 percent of the total amount of continuous full width veneer recovered. The best quality of veneer is obtained early and correct geometrical centering would increase the of the total amount of best quality veneer recovered.
From tests made on an experimental set up, I found that a straight cylinder, continuously expanding diametrically within an irregular periphery, puts itself automatically into the position of the maximum diameter. The basic idea of the new method for automatic centering of logs with nonsymmetric cross sections consists essentially of the duplication of the log mantle and the expansion of a straight cylinder within theduplicated mantle. The axis of this expanded cylinder corresponds then to the peeling axis of the log proper.
Assuming that a log with nonsymmetric cross sections nonuniform taper and noncircular sweep is positioned before a veneer lathe on two supports, each movable horizontally and vertically. In this position the mantle of the log can be represented by the peripheries of a number of parallel cross sections preferably perpendicular to the datum axis of the supports. The higher the number of these peripheries, the better the log mantle is defined for duplication. Each periphery can be represented by a number of points on the periphery with chords in between. The higher the number of points the better the periphery is defined for duplication, especially when knots are present on the periphcry.
The position of each chosen point on one periphery of the log mantle can be determined by conventional linear displacement transmitters. All transmitters for one periphery are preferably in a plane, determined by the periphery, so that the axes of the racks of these transmitters cut the datum axis in one common point. The position of the tip of the rack of each linear displacement transmitter,'in one periphery, can be duplicated by a corresponding linear displacement receiver in the duplicating unit and the gaps between the tips of the racks can be closed with a steel wire under tension, 7
running freely through the tips and representing chords of the periphery. I
The mantle of a cylinder can be represented by straight lines parallel to the axis and at the distance of the cylinder radius. The higher the'number of these 1 straight lines the better the mantle of the cylinder is represented. If all lines representing the mantle of the cylinder are shifted in radial direction at the same rate, so that all lines stay parallel to the axis and equidistant from the axis, then the cylinder is expanding or contracting uniformly. I
In this centering apparatus the'straight line sections, representing the mantle of the cylinder, are rods attached at each end to a system of umbrella type spokes,
so that the common shaft of both umbrella systems is also the axis of the variable diameter cylinder. Shifting of both umbrella systems, at the same rate in same direction along the common shaft, expands or contracts the rodcylinder uniformly. When this cylinder is al lowed to expand itself freely within the duplicated log mantle, then in the final static position the cylinder has the maximum diameter.
In order to recover half width veneer from tapered logs the full length expanding cylinder is supplemented on the same shaft, at one end, with a half length expanding cylinder. This short cylinder is mounted between the spokes and rods of the full length cylinder. The radial expansion force of this short cylinder is made half that of the full length cylinder, to ensure preferred expansion of the full length cylinder. The position of the common axis is sensed by special linear displacement transmitters of the cylinder axis sensing unit and the log is shifted by the supports so that the peeling axis of the log, as determined by the axis of the cylinders, coincides with the datum axis of the supports. The log is centered and ready for transfer to the lathe.
Sensing of the log mantle, its duplication, shifting of the cylinders, and sensing of the cylinder axis are simultaneous operations. The cylinders are contracted, from their largest diameters to maximum positions, by the movement of the chords between the tips of the duplicating racks. The cylinder axis sensing unit shifts the supports of the log after the racks for sensing the log mantle are retracted. The contraction'of the cylinders has no adverse effect on the final position of their common axis.
In drawings which illustrate the embodiments of the invention:
FIG. I is a side view of a log mantle sensing unit and a servo unit for one support.
FIG. 2 is a sectional view of a log mantle'duplicating unit.
FIG. 3 is an enlarged view of one ring in a duplicating unit with displacement receivers for the duplication of the log mantle.
FIG. 4 is an enlarged view of one ring, with transmitters, of a cylinder axis sensing unit.
FIG. 5 is a view of an improved part in the optical centering unit, showing the duplicated periphery of a critical cross section with concentric circles from an optical projector.
The log mantle sensing unit senses the mantle in five cross Sections and consists of five periphery sensing rings. One ring 7, 8 for one cross section is shown by FIG. 1. Two of the cross sections are preferably at the ends of the log, one in the middle and two at about one quarter length from the ends. Two supports 3 are in separate cross sections. The periphery of each cross section is represented by 16 points and each point is sensed by one linear displacement transmitter 9 mounted on a ring 7, 8 consisting of a lower half 7 and an upper half 8. For the purpose of sensing, the upper halves 8 are lowered on the corresponding lower halves 7, after log 2 is rolled along rails l on supports 3.
Linear displacement transmitter 9, FIG. 1, is air pressure operated, in such a manner that a positive pressure pushes rack 12 with rack tip 13 on the log and a negative pressure retracts the rack. Rack 12 is operating an electrical potentiometer 14, so that the voltage output of the potentiometer is proportional to the linear displacement of the rack tip 13. This voltage operates the servo mechanism 22, 23 in FIG. 2 of the corresponding displacement receiver 21 mounted on ring of the duplicating unit. When the potentiometer voltage from 23 is exactly the same as from 14 then tip 24 of receiver rack 21 has travelled the same distance as tip 13 of transmitter rack 12. The log mantle sensing tip 13 of rack 12 is a roller of the same diameter as the roller 24 in FIG. 2, if the duplication is one to one. The mantle duplicating unit, as shown by FIG. 2, consists of as many periphery duplicating rings 20 as there are periphery sensing rings 7, 8 in the mantle sensing unit. Each periphery duplicating ring 20 with its linear displacement receivers 21 corresponds to one periphery sensing ring 7, 8 with the same number of transmitters 9, so that each transmitter has a corresponding receiver.
The lower end of the displacement receiver 21 in FIG. 3 is a grooved roller 24 carrying a wire 25 under tension. This wire closes the periphery between the duplicated points of one cross section. The wire is in continuous to and fro movement in order to reduce friction between rods 30 and wire 25 during contraction of the cylinder 29. The duplicating unit is also lubricated by oil mist from an oil spray so that the effect of friction, on the expanding forces of the cylinders, becomes negligible.
Variable diameter cylinders 29 and 31, FIG. 2, have a common hollow shaft 32. The full length cylinder 29 is mounted in between the half length cylinder 31. Cylinder 31 consists of rods 33 and spokes 34. Supports 35 and 36, for pivoted spokes, are fixed to the shaft 32. Supports 37 and 38 are movable on the shaft and interconnected within the slotted shaft 32 by means of rod 39, to ensure that 37 and 38 move exactly at the same rate. Each spoke of cylinder 31 is connected by means of pivots 40 at one end to a rod 33 and at the other end to a support, in such a manner that any expansion or contraction of the cylinder will keep rods 33 parallel to and equidistant from shaft 32. The full length variable diameter cylinder 29 has a similar construction. Fixed supports 35 and 36 are common to both cylinders. Expansion and contraction of these cylinders are independent from each other. The log is loaded on supports 3 so that the larger end of the log corresponds to the half length cylinder in the duplicator. If two half length cylinders are used so that one is at each end of the cylinder unit, with the full length cylinder in between, then the position of the larger end of the log is not critical anymore.
As shown by FIG. 2, the lower end of the common shaft 32 is attached to a float 41 in an oil tank 42. The float 41 and the balancing weight 43 are so designed that the shaft 32 with both cylinders is free from tilting forces when not vertical, so as to adjust itself freely to any tilted position as determined by the expansion or contraction of the cylinders within the duplicated log mantle. Same free adjustment can also be achieved by horizontal suspension of the cylinder unit in oil, so that it floats submerged whereby the cylinders are expanded by spring action.
Both cylinders 29 and 31,.FIG. 2, are expanded by the weight of their rods and spokes to their largest diameters as determined by the fully retracted displacement receivers 21. The axis of the common shaft 32 represents in this case the duplicated datum axis 6 of supports 3, in FIG. 1. Duplication of the log mantle by receivers 21 results simultaneously in contraction of both cylinders 29 and 31. When the transmitters 9 and receivers 21 stop moving, then both cylinders occupy their correct positions in the duplicated log mantle. The full length cylinder 29, has within the duplicated log mantle, its maximum diameter and the half length cylinder 31, its optimum diameter. The final position of the common shaft 32 corresponds to the required peeling axis and this position is determined by linear displacement transmitters on rings 44 and 55 of the cylinder axis sensing unit.
Planes through rings 44 and 55, FIG. 2, are perpendicular to the duplicated datum axis and the center points of these rings are on this axis. Each of these planes corresponds to a plane in the log supports 3. Each of the rings 44 and 55 has four displacement transmitters. Four transmitters on ring 44, shown by FIG. 4, are arranged in pairs 45, 46 and 47, 48. The center determined dete;mined by one pair 45,46 is perpendicular to the center line of the other pair 47, 48 and their common point is the center of the ring. These displacement transmitters touch the cylinder only lightly, if compared with the expansion force of the cylinder, and they follow the expansion and contraction. Half of the difference in travelled distance of the diaplacement transmitters, in one opposing pair, is equal to one coordinate of the cylinder axis with-respect to the center point of the ring. In a similar manner transmitters are arranged on ring 55, FIG. 2.
Displacement transmitter 46, FIG. 4, moves by means of an instant stop electric motor 50 till bar 52 of the racktouches the cylinder rod 33. Bar 52 is provided, along the side it approaches rod 33, with a lever 62 as long as the bar. This lever 62 is movable on hinge 63 at one end at the other end of the bar, this lever perates a switch 64 when the lever is pushed flush with bar 52 by cylinder rod 33. Switch 64 reverses the instant stop motor 50 until no contact is made, reverses again till contact is made and so on. Bar 52 with transmitter rack 46 follows the contraction and expansion of the cylinder, with a very small pressure on the cylinder, until a steady state is achieved as a very short clockwise and counter clockwise oscillation of the motor 50. P0- tentiometer 54 provides the position of bar 52 as a voltage. In the same manner operate all transmitters on rings 44 and 55.
Sensing of the cylinder position by bar 52 can also be achieved by operating rack 46 with air pressure. The
tip of lever 62 isthen the flapper of a conventional air flapper controller valve for moving rack 46.
Centering of the log proper is made by moving supports 3 vertically and horizontally. Servos 22, FIG. 2, of the duplicating unit arede-energized and stopped. All transmitters 9, FIG. 1, are'retracte'd. Servos 15 and 17 of both supports 3 are energized and start moving as required by the signals from transmitters on ring 44 and ring 55. On ring 44, FIG. 4, the voltage difference of opposing potentiometers 53 and 54 is proportional to the vertical coordinate of the cylinder shaft 32 in the plane of ring 44 and the corresponding support 3 is shiftedvertically by servo l untilthe potentiometer 16 of this servo shows the same voltage difference. In the same manner the horizontal" coordinate is sensed as a voltage difference by the potentiometers of transmitters 47 and 48, FIG. 4, and same support 3 is shifted horizontally by means of servo 17 until the potentiometer 18 has the same voltage difference. In a similar manner the transmitters on ring 55 shift the other log support 3. The log is centered. Servos l5 and 17 are deenergized and stopped and the log is transferred, in a conventional manner, to the lathe either by means of carriage or it is grabbed by charging arms. The supports 3 are ready to receive a new log. Servos 22 are energized and all duplicating racks retract, the cylinders expand to their largest diameters and the duplicating unit is ready for a new operation.
The number of cross sections required for adequate duplication of the log mantle depends on the type of logs used. Logs with circular sweep, uniform taper and nonsymmetric cross sections have two critical cross sections at about percent of the length from each end. The center points of the maximum circles in each of these two critical cross sections define the peeling axis. These logs are centered by duplicating the peripheries of these two cross sections, reducing substantially the number of displacement transducers. Only two half length variable diameter cylinders are needed in the cylinder unit, one at each end of the common shaft, and it is not necessary to load the log with the large end on the same support.
Optical centering can be applied to logs with circular sweep, uniform taper and nonsymmetric crosssections by duplicating each of the above mentioned two critical cross sections of the mantle before a corresponding projector, so that the duplicated periphery is perpendicular to the datum'axis of the projector. The projector puts concentric circles 70, FIG. 5 into the duplicated cross section and the log is shifted on the supports, with the sensing unit on the log, so that in each duplication the maximum circle is within the periphery. The log is centered. The-conventionaloptical method does not center swept logs.
Although there has been shown and described herein a preferred form of the invention, it is to be understood that the invention is not' necessarilyconfined thereto, and that any change in the structure and relative arrangement of components are contemplated as being within the scope of the invention, defined by the claims appended.
The embodiments of the invention for which protection by a patent is claimed are defined as follows:
I. An automatic centering apparatus for veneer logs with substantially noncircular cross sections, nonuniform taper, and noncircular sweep, comprising in combination:
a log mantle sensing unit for the coordinates of points along the peripheries of chosen cross sections,
a log mantle duplicating unit for the duplication of peripheries as determined by the log mantle sensing unit,
a cylinder unit, with one or more variable diameter cylinders on a common shaft within the log mantle duplicating unit, assigned for shifting freely into the position of the maximum diameters,
a cylinder axis sensing unit, as part of the log mantle duplicating unit, for sensing the coordinates of two points on the axis of the cylinder unit.
a servo unit for shifting the log supports corresponding to the signals received from the cylinder axis sensing unit.
2. A centering apparatus as defined in claim 1 wherein said log mantle sensing unit includes a number of parallel rings, surrounding the log, spaced from each other along the datum axis, perpendicular to this axis and with center points on this axis,
each ring of said sensing unit supporting displacement transmitters for sensing points of the periphery of a cross section as determined by the plane of the ring,
said log mantle sensing unit including a lower part and an upper part of half rings,
said upper part separating itself automatically from said lower part by an adequate distance when loading the centered log on the lathe and then charging the supports with a new log,
said upper and lower parts of half rings joining automatically into a rigid sensing unit after charging of a new log,
3. A centering apparatus as defined in claim wherein said log mantle duplicating unit including a number of parallel rings spaced from each other along the duplicated datum axis or reference axis, perpendicular to this axis with center points on this axis,
each ring of said duplicating unit supporting displacement receivers, so that the tips of these receivers are duplicating the points of a periphery as determined by the corresponding displacement transmitters on the corresponding ring of said log mantle sensing unit,
said tip of each displacement receiver of said duplicating unit provided with means for the accomodation of a common wire or stringunder tension said means close the gaps between the points of each duplicated periphery by chords said wire or string adapted to move continuously to reduce the friction between said cylinder unit and wire,
4. A centering apparatus as defined in claim 1 wherein said variable diameter cylinder of said cylinder unit is provided with means for expanding said cylinder radially with respect to the common shaft, whereby said means for expanding do not hinder shifting of wherein said cylinder axis sensing unit comprising two parallel rings spaced from each other along said reference axis and perpendicular to this axis, with center points on this axis, so that the planes of these rings correspond to the planes through the log supports,
said ring of said axis sensing unit is provided with two pairs of displacement transmitters,
said transmitters of each pair opposing each other, so
that when the transmitters of a pair touch the cylinder, then the travel difference of these transmitters is proportional to one coordinate of a point on the axis of the cylinder unit in the plane of the ring,
said cylinder axis sensing unit provided with means for operating said servo unit of the log supports to shift the log so that the peeling axis of the log, as determined by the axis of the cylinder unit, coincides with the datum axis of the supports.
6. An optical centering apparatus for peeler logs with substantially circular sweep, uniform taper and nonsymmetric cross sections, comprising in combination: two movable projectors for optically projecting an image or target of concentric circles on chosen cross sections of the log mantle for the purpose of finding the maximum circle within the periphery of the cross section, two movable log supports with manually operated controls to shift the log so that the center points of the maximum circles in said cross sections of the log are on the datum axis of the supports, wherein the improvement comprises:
means for sensing the coordinates of points along the peripheries of two critical cross sections of a log on two movable supports, whereby the coordinates obtained with said means for sensing are simultaneously duplicated so that each periphery appears before the corresponding projector,
said means for sensing the coordinates designed to move off the log while the log is shifted or transferred to the lathe or another log is loaded on the supports, means for pointwise duplication of the periphery of each critical cross section of the log mantle before the corresponding projector so that the plane of the duplicated periphery is perpendicular to the projector axis, means for shifting said image or target of concentric circles in the plane of the duplicated periphery relative to the periphery so that the largest circle, within the periphery, is a maximum, whereby simultaneously the log is shifted by the supports so that the'center points of the maximum circles, in said critical cross sections of the log, are on the datum axis of the supports. 7. An apparatus for centering irregular peeler logs comprising in combination:
means for sensing the log mantle of the log along the peripheries of substantially irregular cross sections for the purpose of duplicating said peripheries,
means for duplicating of said peripheries of the log mantle for the purpose of finding the peeling axis for maximum veneer recovery,
means for finding said peeling axis within said duplicated peripheries of the log mantle,
means for shifting the peeling axis of the log into the datum axis of the log supports.