Patent Grant
6938656
This invention relates generally to the forest industry, and more specifically, to wood processing machines having rotating heads used in sawmills. Within this industry, various sizes and shapes of chipping, cutting and planing devices having knives are used to make, for example, lumber from logs and to produce wood chips, wafers, or flakes. The wood chips, wafers, or flakes may then be used in the formation of pulp, waferboard, oriented-strand board or other products.
Rotating chipping, planing and cutting heads employed in sawmill wood processing machines generally fall into two categories; cylindrical and conical. Cylindrical heads typically have a plurality of cutting knives mounted on the outer periphery of a cylindrical head. The knives are mounted parallel to the axis of rotation and form a cutting cylinder as the head rotates. Conical heads are characterized in that the knife blades are mounted to a rotating head to form a truncated cone when the head spins. Typically present at one end are finishing knives or circular saws which are mounted perpendicular to the cone axis. In machines having either cylindrical or conical heads, wood to be processed is advanced by a feeding mechanism into the path of the knives where it is planed, chipped, cut or the like. Examples of such devices, which are quite widespread in the industry, are illustrated in the following U.S. patents:
In general, the purpose of such chipping, planing, and cutting heads is to produce a predetermined finish on the wood being processed and/or to produce chips, wafers, or flakes of a predetermined size. Both results require a precise positioning of the wood being processed relative to the knife edge working the wood. Specifically, three main variables determine the size of any wood particles produced. The first is the rotational speed of the head, the second is the linear speed at which the wood is advanced into the path of the knives by the feed mechanism of the machine, and the third is the number of knives on the head. For a given head with a fixed number of knives, if the speed of the head is increased at the same feed rate, smaller sized chips, wafers, or flakes will be produced because the wood will advance less for each cut. If the speed of the feed mechanism is increased for the same head speed, larger particles will be produced because the wood will advance more during each pass of the knife. To produce wood chips, wafers, or flakes of a consistent and predetermined size thus requires uniform head and feed speeds. Similarly, variations in head or feed speed can change the quality and accuracy of the finish of the wood being processed.
In some machines, particularly those with chipping heads, problems arise from the extreme cutting forces applied by the knives during processing. This can cause irregular movement of the wood, which in turn, results in uneven sized wood chips and a reduced quality of cut lumber. Although such irregular movement is normally limited by the grip of the feed mechanism on the wood or other guide mechanisms, the machine often includes a secondary means to limit any such irregular movement to a maximum predetermined and acceptable amount. This secondary means is typically in the form of a limiting surface on the wood processing head against which the wood can abut to restrict abnormal movement. Often, the component on which this surface is mounted is referred to as a limiter.
In most such machines, such limiting surfaces are incorporated into the periphery of the head so as to be able to abut against the cut surfaces of the wood being processed. Such limiting surfaces are formed so as to avoid contact with the wood under normal machine operation to prevent detrimental jostling of the wood being processed and minimize wear. However should excessive abnormal movement occur, the wood being processed abuts the surface which prevents the wood from advancing further during the knife strike or from being drawn into the cutting head. These surfaces are subject to significant forces and are traditionally formed integral with the head and so cannot be replaced or changed. An example of a cylindrical chipping head with an integral limiter is shown in U.S. Pat. No. 2,817,305 to I. W. Ferguson and J. W. McNaughton.
Like cylindrical designs, conical chipping heads also include limiting surfaces as an integral part of the head. However some designs make use of replaceable fixed components, sometimes referred to as wear plates, rather than incorporating the limiting surfaces as a permanent part of the head. An example of such a conical chipping head may be found in U.S. Pat. No. 5,511,597 to Key Knife Inc. These chipping heads are provided with replaceable, but fixed, wear plates against which the wood being processed may abut during chipping. As per the teachings of this patent, this affords the advantage that the wear plates can be replaced in the event that excessive wear occurs on the limiting surfaces.
At present, wear plates, or limiters, whether integral with the head or affixed as replaceable components, are formed with a limiting surface, or set of surfaces, designed for a specific set of operating conditions which include wood feed rate, head speed and cutting location. Any variation in chip size or cutting location (due to a size change in the wood being fed into the head) will influence the shape of the limiting surface required to maintain clearance with the normal wood advancement while effectively limiting abnormal wood movement. Often, small changes in operating conditions can require a different limiter if acceptable performance is to be achieved. Thus, if an operator decides to change any wood processing settings to improve speed, quality, or to suit the specific type or size of wood being processed, the manufacturer may be required to service the machine and, if possible, replace the existing limiters with ones more appropriately sized and shaped to the new shape of limiting surface required to limit abnormal wood movement for the new operating conditions.
However, in practice, the machine manufacturers are unable to anticipate all variations in operating conditions. Thus, limiters are only available with surfaces having predetermined increments of change of shape (which increments and shape are set by the manufacturer and not the operator). These set increments may at best only approximate what the operator needs. This can result in limiters being mismatched to operating conditions yielding limiting surfaces which can reduce-the effectiveness of the machine or worse, interfere with its normal and proper operation. Often, the operator is unable to make corrections very easily as significant waiting periods are involved to allow for new limiters to be manufactured and delivered. For machines with limiting surfaces formed integral with the head, no flexibility exists to adjust for different operating conditions whatsoever.
According to a recent U.S. Pat. No. 6,164,352 to Key Knife Inc., a wood surfacing method and apparatus which includes a projecting surface on a cutting head located behind the knife can be formed. The projecting surface is adapted to make contact with the wood with a force that is substantially constant as the wood is fed to the machine. The constant force is achieved, according to the teachings of this patent, by having the surface recede radially inward from the cutting circle of the knives at a rate that corresponds to the speed of the relative linear translation of the wood relative to the angular position of the cutting head.
The advantage claimed with such an apparatus is that a constant supporting force can be developed from the intentional contact of a projecting surface with the wood being processed such that it may resist the cutting forces developed by the knives in order that an increased quality of surface be produced. However, for a constant supporting force to be achieved, the component of the relative movement of the wood in a direction that is radial to the head must coincide exactly with the radial recession of the projecting surface. This can only occur for linear translation that occurs at a specific offset distance from the head centre. Should this offset distance be altered as a result in a change in wood dimensions, the projecting surface would either lose contact with the wood completely or hinder normal wood advancement. While offering an improved surfacing method for wood processing devices where such ideal, stable, and fixed operating conditions occur, this invention does not offer a practical and effective solution for the control of abnormal wood movement across a range of operating conditions.
What is desired is a method and apparatus for varying the limiting surfaces on the cutting heads to accommodate variations in operating conditions, such as feed rate and head speed, to allow for a flexible and effective means to limit abnormal wood movement. Most preferably the method and apparatus should be variable across a range of machine settings and operating conditions including changes in wood size, chip size, wood species, and wood temperature. In addition, most preferably the adjustment can be made to existing components, by the operator, without requiring any new parts or servicing from the manufacturer. Such a device should be reliable and secure against the extreme forces generated during contact with the wood when limiting abnormal wood movement. Further, such a device should be simple to adjust, without the need for special tools by the operator, and without requiring the de-mounting, removal and replacement of various fixed components. Moreover, the apparatus should be constructed so as to be adaptable to the range of cylindrical and conical head sizes in use in the industry.
According to the present invention an adjustable limiting surface can be provided which can limit the abnormal movement of wood being processed during operation. In one embodiment, the limiting surface is releasably mounted to the cutting head in a way that allows the limiting surface to be released, pivoted about a pivot-axis to a new position and resecured. By pivoting the limiting surface, the pitch, or radial rate of recession of the limiting surface can be altered to suit any new operating conditions. Thus, where a change in operating conditions requires a different rate of recession for the limiting surface, the position of the limiting surface can be adjusted to achieve the desired result. In this manner an effective limiting device over a range of operating conditions can be provided for the control of undesired wood movement during processing. In another embodiment the position of the limiting surface can be moved relative to a centre of rotation by translation, which alters in an analogous fashion the rate of recession to accommodate changes in operating conditions.
Thus, according one aspect of the present invention there is provided a wood processing device comprising:
According to a second aspect of the present invention there is provided a wood processing device comprising:
Further according to another aspect of the present invention there is provided a method of operating a wood processing device having a rotatable head where said rotatable head carries one or more knives which form a curved cut surface in the wood being worked, said wood processing device including a limiting surface for preventing abnormal movement of said wood during processing, said method comprising the steps of:
Reference will now be made to various figures which depict, by way of example only, preferred aspects of the present invention and in which:
Because of the tremendous forces generated during wood processing, it is also necessary to secure the clamping element 32 onto the hub 12. Therefore, there is preferably provided a dovetail tongue and groove joint between the hub 12 and clamping element 32. This arrangement is particularly advantageous as, in conjunction with the dovetail shaped tongue formed by inclined surfaces 38 and 40, the base member 16 can be reliably secured to the hub 12, as described in more detail below, while remaining quite compact. This permits the invention to be used across a broad range of heads including miniature conical heads where the small size of the hub can preclude other mounting arrangements due to the lack of space. This compact attachment is achieved in part by the dovetail base portion of the base member extending in a direction transverse to the axis of rotation of the rotatable head, rather than being parallel to the direction of rotation (i.e. axially) as shown in U.S. Pat. No. 5,816,301. A benefit of the present invention is that it ensures that all the base members can be quickly and easily secured in the same axial position on the hub while providing a mounting which is secure against the significant forces generated during wood processing. To help secure the base members 16, a rear retaining ring 43 may also be used to fasten the outer edges of the base members 16 together.
According to the present invention it is also desirable to permit the position of the base member 16 to be changed on the hub 12. As will be explained in more detail below, changing the position of the base member 16 on the hub 12 changes the position of limiting surface 21 and permits the limiting surface to be positioned to suit specific operating conditions. It shall be understood that in this context, changing a position of a base member 16 comprehends translating the limiting surface 21 on the hub, rotating the limiting surface 21 on the hub, or a combination of both translation and rotation to alter the position of the limiting surface. Further, while reference is made herein to a curved limiting surface, other shapes of limiting surface may also be used. For example, a limiting surface 21 made from a series of flat sections which approximate a curve can also work. Even having one planar section may be acceptable in some cases. However a smoothly curved surface which approximates the form of the curved cut surface in the wood, such as a helix or a spiral of Archimedes, is believed to be the most preferable form of limiting surface.
As shown in
Turning to
It will be understood by those skilled in the art that the anchor post 50 permits the translation of the base member 16 laterally on the hub 12 within the limits established by the slot 56. However, because of clamping element 32, base member 16 is not permitted to move axially (i.e. in a direction parallel to the drive shaft 14). In this way, adjustments can be made to the position of the base member 16 relative to the centre of rotation of the hub 12, without significantly altering the axial position of the finishing knives 20 contacting the wood being fed into the head 10. Translation of the base member 16 on the hub 12 is controlled by threaded rod 58, which acts as a translating member for the base member 16. A yoke 59 is formed in rod 58 which sits in anchor post 50. The yoke 59 permits the rod 58 to spin about its longitudinal axis in the post 50 while restricting any longitudinal movement. As the rod 58 is threaded through base member 16, rotation of the rod 58 translates the base member 16. Thus, by turning rod 58, the base member 16 can be accurately located in a range of positions defined by the slot 56. However it will be understood that the present invention comprehends that other means of translation may be used without departing from the scope of the invention
Turning to
The operation of the first embodiment of the invention can now be understood. Consider that it becomes necessary to adapt the machine to a change in operating conditions, for example to a change in the chip size being produced. In such a case it can now be appreciated that by loosening the bolts 30 the clamping element 32 can be backed off permitting each base member 16 to be translated on the hub 12 by turning rods 58. In this sense each base member 16 will be translated in a direction perpendicular to the axis of rotation of the hub 12 along one of the octagonal flat mounting surfaces. Because of the anchor post 50, the repositioning can only take the form of laterally translating the base member 16 along the flat side the hub 12. In this way, translation of the base member 16 changes the position of the limiting surface 21 relative to the centre of rotation and thus alters the recession of the surface to more properly suit the new operating conditions for the wood being processed in the machine.
Turning to
Of most importance, the lateral displacement “T” has an effect on the rate of recession of the limiting surface 21. As drawn there are three positions for the limiting surface 21 at 21′, 21″ and 21′″ each of which corresponds to respective knife edge positions 18′, 18″, and 18′″ and has a different rate of recession relative to the centre of rotation C. Surface 21′ has the least rate of recession and 21′″ has the greatest. It can be seen that the difference in cutting circles defined by cutting radii A, B, and D and the maximum point of recession of the cam limiting surface 21′, 21″, and 21′″ can be increased or decreased for a relatively constant angular rotation “θ”. In this fashion, the amount surfaces 21′, 21″, and 21′″ will recede radially inward for a fixed amount of angular rotation can be varied. By altering the rate of radial recession of the limiting surface, the movement of the wood in a direction that is radial to the head is thereby limited. For any given cutting location on the head, this restricts the maximum chip length produced. As will be understood by those skilled in the art, the maximum chip length, or limited chip length will only occur if feed rate of the wood from the feed mechanism is such that the limiting surface 21 defines the position of the wood.
It should be appreciated that in this embodiment of the present invention that the knives 18, 20 are mounted to the base member 16, which carries limiting surface 21. This allows the radial rate of recession of both the limiting surface 21 and the outward projecting surface of the knife 18 to be varied simultaneously, and in unison, simply by translating the position of the base member 16 on the hub 12. Moving the base member 16 forward, relative to the direction of rotation of the hub 12, will increase the rate of recession of both the knife 18 and the limiting surface 21, whereas moving the member 16, rearward (relative to the rotation direction of the hub 12) will reduce the rate of recession. What has been discovered is that all points on the displaced limiting surface 21 are within very close proximity to their ideal theoretical position at each point in the translation. In other words, the variance in the rate of recession of the limiting surface 21 is appropriate for the change in position of the knife 18 when they are moved together. Thus, to place the limiting surface 21 in the correct position requires knowing the cutting location on the head 10 and then adjusting the base member 16 to the appropriate position to achieve the desired limited chip length.
The effect of translation on the rate of recession of the knife 18 is best illustrated by examining the clearance angle, or relief angle, that is formed between the wood flow and the top (outward projecting) surface of the knife 18. In
The first element of the structure 139 is a knife 140 in a knife clamping assembly 142 which is held in a pocket 144 by a pair of fasteners 146 (of which only one can be seen in FIG. 9). The knife clamping assembly includes an upper clamping element 148 and a lower clamping element 150. In an adjacent pocket 152, a combination wear element and chip guide 154 is held in place by a second pair of fasteners 156 (of which only one is visible in FIG. 9). Drive shaft 136 is connected to a drive mechanism (not shown) which rotates the head in the direction of arrow 158.
Located between each of the knives 140 is a base member, or limiter, 161 on which is mounted a limiting surface 160. Unlike the previous embodiment, the base member 161 does not carry the knives. The limiter 161 includes a position adjustor assembly 162 to pivot the limiter 161 to alter the radial rate of recession of the limiting surface 160. The position adjustor assembly includes a pair of foundation screws 163 and locking screws 165 of which only one can be seen in FIG. 9. To reposition the limiter 161 the foundation screws 163 may be rotated in or out to pivot limiter 161 about pivot pin 168. Thus the pivot pin 168 defines a pivot axis R for limiter 161, which is generally parallel to the axis of rotation of the drive shaft 136. The foundation screws 163 are each threaded into threaded holes 167 in segment 133. The limiter 161 is caught (or locked) between the locking screws 165 and the foundation screws 163. By rotation, the locked position can be raised or lowered permitting adjustment of the limiting surface 160.
The pivot pin 168 is located in a curved toe 170 of the limiter 161. In turn the curved toe 170 is located in a curved recess 172 formed in the segment 133. The curved toe 170 and the curved recess 172 are made of complementary sizes and shapes so that the limiter 161 is permitted a limited range of positional adjustment relative to the segment 133. It can now be appreciated that the radial recession of the limiting surface 160 can be made to recede more steeply or more gradually depending upon the need.
The operation of this embodiment can now be understood. Consider the situation where the operator adjusts a machine setting, such as the head speed or the log feed advancement rate, to suit various operating conditions such as the size of wood being processed or the size of chip desired. The machine can then be started and observations made on the effectiveness of the limiting surface 160 on restricting abnormal movement of the wood, having regard to the chip size, feed rate and head speed. Typically a change of operating conditions will result in the curved limiting surface 160 either receding too slowly or too quickly causing the normal wood flow to be hindered or insufficiently limiting abnormal movement. If a discrepancy is identified, the machine can be stopped and the locking screws 165 loosened to unclamp or unlock the limiter 161. The foundation screws 163 can then be raised or lowered in the threaded holes 167 of segment 133 pivoting the limiter 161 about the pivot pin 168. Once a new position for the limiter 161 is established, the locking screws 163 can be secured to lock the limiter 161 again against any further movement relative to the segment 133.
It may take several iterations for an operator to establish an ideal position for the limiter 161. This is because, until the limiter 161 is well positioned, the radial recession of the limiting surface 160 may be insufficient to allow for a clearance to be maintained with the cut wood surfaces during normal wood feed, or excessive such that an undesirable amount of abnormal wood movement can occur. However, if the machine, when operated again does not run acceptably, the operator will be able to shut it off, adjust the position of the limiter 161, and restart the machine immediately thereafter. If there are further refinements to the position required, then further adjustments to the position of the limiter 161 can be made, until the operator is content that abnormal movement has been limited as effectively as possible while ensuring unhindered wood advancement during normal operation.
According to a further aspect of the present invention the position of the limiter 161 can be set with the aid of a scale or other markings associated with the relative position of the limiter 161 on the segment 133. Thus, if the operator has set the limiting surface 160 to a preferred position for a given head speed, wood size and feed rate, the position can be noted and used for future reference. Of course the precise position of the limiter 161 may be affected by other factors, such as a need to balance the elements on the spinning head, so it may not be possible to exactly position the limiter 161 by the scale or markings alone.
In this embodiment, the base member 200 is pivoted about a pivot pin 204 which is similar in function to the pivot pin 168 previously described. Additionally, a position adjustment assembly 206, equivalent to that of the previous embodiment, is used to pivot the base member 200 about the pivot pin 204. The position adjustment assembly includes locking screw 211 which extends into foundation screw 214 screwed into the threaded hole 209 of segment 207. The locking screw 211 includes a head 210, which bears against the bottom of the recess 208 on surface 212 of the base member 200.
If it is desired to adjust the position of the base member 200 to alter the position of the limiting surface 205, the locking screw 211 is backed off, permitting the foundation screw 214 to be threaded outwards to displace the base member 200 outwardly, away from the segment 207. In this way the position of the base member 200 and thus the limiting surface 205 and the knife elements in the pocket 202 can be adjusted on the segment 207 in a fashion similar to the previous embodiment.
It will be appreciated by those skilled in the art that various modifications and alterations of the invention can be made without departing from the broad scope of the appended claims. Some of these have been discussed above and others will be apparent to those skilled in the art. For example, the present invention comprehends an adjustor which adjusts a position of a limiting surface by means of a translational adjustment, a rotational (pivoting) adjustment, or a combination of both. Further the present invention comprehends having the limiting surface integral with a base member that carries the knives, so that the limiting surface and knife position change as the base member is adjusted, as well as having the limiting surface separate from and independently adjustable from the knife. As well, the present invention may be used on all manner of spinning head wood processing machines including those used for the production of chips, flakes, wafers or shavings.
| Number | Name | Date | Kind |
|---|---|---|---|
| 49161 | Shannon | Aug 1865 | A |
| 269315 | Orum | Dec 1882 | A |
| 743374 | Bresman | Nov 1903 | A |
| 3817305 | Ferguson et al. | Jun 1974 | A |
| 3842873 | Valo | Oct 1974 | A |
| 4480667 | Vaittinen et al. | Nov 1984 | A |
| 5511597 | Shantie et al. | Apr 1996 | A |
| 5575320 | Brisson | Nov 1996 | A |
| 5617908 | Toogood | Apr 1997 | A |
| 5662436 | Bishop | Sep 1997 | A |
| 5709255 | Toogood | Jan 1998 | A |
| 5816301 | Stager | Oct 1998 | A |
| 5857508 | Jonkka | Jan 1999 | A |
| 6164352 | Simonsen | Dec 2000 | A |
| 6227267 | Mitchel et al. | May 2001 | B1 |
| Number | Date | Country |
|---|---|---|
| 8902290-9 | Jul 1991 | SE |
| Number | Date | Country | |
|---|---|---|---|
| 20030070728 A1 | Apr 2003 | US |
