Method and machining apparatus for use especially in the sanding of items of wood in a sanding machine

Abstract: In order to be able to sand the surface of an item (3) uniformly smooth, a sanding machine is used with sanding tools in the form of sanding rollers (29) which are rotated as well as turned in the same plane, and which at the same time herewith are also moved in a reciprocating manner transversely to and parallel with the direction in which the item is conveyed, whereby during the working stroke the sanding elements on the sanding rollers (29) will sand at all possible contact angles in relation to the item (3). The risk of sanding damage such as marks and grooves as a result of over-sanding, or the possible lack of sanding as a result of too sporadic contact, is herewith reduced, and the best possible result is achieved. Furthermore, the wear on the sanding rollers (29) is completely uniform, whereby their endurance is extended. For the movement of the sanding rollers (29), there is used an apparatus comprising a motor-driven crank arm (7) which, in sliding engagement with a carriage which supports the sanding rollers (29), can drive the carriage forwards and backwards on rails (4) which extend transversely to the machine (1). There is hereby achieved a stable and robust construction which also gives the sanding rollers (29) an expedient movement characteristic, which compensates for the predominantly longitudinal sanding movements to which the items are exposed in the outer areas.

Description: The invention relates to a method of sanding, especially the sanding of items of wood in a sanding machine, where the items are conveyed on a plane such as a vacuum plane at the same time that the sanding tools sweep the surface of the items, said sanding tools comprising a number of sanding rollers, each secured to a spindle, and where the spindles are mounted radially outwards from a drive, and in such a manner that the individual sanding rollers rotate around the spindle axes and are also turned around an axis of rotation which extends at right-angles to the spindle axes and to the surface of the plane. The invention also relates to a sanding apparatus for use in the execution of the method. Methods and apparatuses of this kind are known, e.g. from DK-B-156 703, and are used especially in the sanding of the surfaces of items of wood, which while secured on a plane are machined by sanding rollers during their composite movement over the upper surfaces. In order to be able to machine items with irregular surfaces such as recesses, profiles and flutes, the machining must be effected as carefully as possible out of regard for the preservation of the sharp edges, but at the same time it must be effective enough to ensure that all surfaces, including the irregular surfaces, are machined to the necessary degree. For this purpose, the sanding rollers preferably used are made up of equally-long, flexible sanding threads or sanding bands which extend radially from a core, and which constitute the sanding roller. Such sanding rollers are secured to individual spindles which are mounted on a drive in such a manner that the rollers project outwards from the drive like spokes from a hub. Mounted in this way, the sanding rollers can be made to rotate on their spindles, while at the same time all of the sanding rollers simultaneously rotate around an axis which extends at right-angles to the sanding spindles. Items placed on a belt are now able to be fed in under the sanding rollers, which by their composite movement will machine the items from several directions. In correctly dimensioned machines, this method results in satisfactory sanding, but there are difficulties with items which are placed on the belt in such a manner that they pass closely by the axis of rotation of the sanding rollers, and in the area for the rollers' outer turning track. In these positions, the predominant direction of sanding executed by the rollers will be the transverse and the longitudinal respectively in relation to the feeding direction of the belt. Furthermore, the ends of the sanding rollers have a relatively high speed of rotation, whereby the result of the sanding can be inferior in the outer positions. Therefore, if the need exists for a completely perfect surface finish, the items must be sanded again or placed in another position, or use must be made of machines which are provided with several sanding heads which can be mounted in a staggered manner in relation to the feeding direction of the belt. A sanding apparatus is known from FR-A-2 584 965 for the sanding of plane stone items, which apparatus is of a different kind than the one described in the preamble. The known sanding apparatus has a number of sanding tools whose axes are at right angles to a conveyor and thus to the surface of the stone items. Each sanding tool is driven by a separate motor, and two of the sanding tools can be displaced in a direction parallel with the movement of the conveyor away from and towards the row of the other sanding tools. At the beginning of a sanding process the frontmost sanding tool is positioned at a distance from the others, and while the stone item is being conveyed under the sanding tools, this distance is reduced at approximately the same speed as the travelling speed of the stone items. Since all sanding tools are moved forwards and backwards across the direction of motion of the stone items, the frontmost sanding tool is to begin with only moved from side to side on the frontmost part of the stone item, and subsequently - when the frontmost sanding tool has been reached by the others - all the sanding tools move in a zigzag course above the stone item, after which the last sanding tool increases its distance to the other sanding tools when this has reached the rear edge of the stone item, so that the rear edge like the frontmost edge is finally polished in a transverse motion. This known sanding apparatus has due to its many motors a very complex construction and is unsuited for the sanding of such items which have depressions in the surface. Moreover, the transverse motion of the sanding tools takes place at a uniform speed and in straight lines between the turning points of the movement. However, these solutions are not expedient, since they either require an extra pass through the machine, and herewith sanding time, or larger machines with several sanding systems, which are both more expensive and require more maintenance. By an Italian manufacturer, Viet SpA Italia, a sanding machine especially for wood panels had been demonstrated, which sanding machine comprised six sanding brushes mounted to a vertical rotating axle. Sanding brushes are arranged in three lines on rotating spindles, each two of which are arranged on the same line and said three lines are parallel to each other. The vertical axle of the sanding head is guided by a pneumatic cylinder providing for an oscillating movement of the sanding head in a direction perpendicular to the feet direction of the workpiece. The amplitude of the oscillation movement is about 10 cm and makes the outer edge of the sanding head move to the edge of the conveying belt for the workpieces. For the man skilled in the art the purpose of the oscillating movement of the sanding head is to superimpose a different movement direction to the strongly predominant sanding direction of the brushes which is the same for all the brushes. Said strongly predominant sanding direction is not present in an arrangement where the spindles for the sanding rollers are mounted radially outwards from a drive, as disclosed by DK-B-156 703. It is the object of the invention to overcome the disadvantages and drawbacks of the known methods, and this object is achieved by a method according to claim 1 whereby the sanding rollers are further moved in a reciprocating manner parallel with the plane in a direction transversely to the direction in which the items are conveyed. In accordance with claim 2, the sanding rollers are moved at progressively decreasing and increasing speed towards and away from the extreme positions of the motion, respectively. In a surprisingly simple manner, there is hereby achieved a resulting movement of the sanding rollers which provides a hitherto-unknown good degree of machining in that the longitudinal as well as the transverse motion comprise a circular movement, i.e. a completely uniform and gentle sanding due to the many different sanding directions from which the item is attacked by the tool as well as a considerably higher sanding capacity, in that the items can have a greater extension on the conveyor belt and also be placed on the belt in a more random manner. Together with this enhancement of the sanding effect, and herewith the machine capacity, the wear on the sanding rollers becomes more uniform, in that they are more evenly loaded, whereby the effective sanding time or endurance is considerably increased. Finally, it must be emphasized that sanding tools, where the sanding elements rotate, are held extended by the centrifugal force, and therefore function best at a tangential sanding direction, i.e. a sanding direction which extends transversely to the sanding rollers. This is fulfilled to a higher degree by the circular movement according to the method, the reason being that the resulting movement of the sanding rollers reduces to a minimum that time for which the items, relatively speaking, are moved longitudinally to the sanding rollers as compared to the known methods. As disclosed in claim 3, by allowing the sanding rollers to be moved past the extent of the items, the quality of the sanding becomes better due to the fact that the resulting sanding movement over the outer areas of the items becomes more uniform. As mentioned in preamble, the invention also relates to a sanding apparatus as claimed in claim 4 for use in the execution of the method, the sanding machine being of the kind which comprises a housing with a plane conveyor such as a vacuum plane for conveying of items to be sanded through the machine at the same time that the sanding tools sweep the surface of the items, said tools comprising a number of sanding rollers, each secured to a spindle, and where the spindles are mounted radially outwards from a drive, and in such a manner that the individual sanding rollers rotate around the spindle axes and are also turned around an axis of rotation which extends at right-angles to the spindle axes and to the surface of the conveyer. Additional features are described in claims 5-10. In accordance with claim 7, the sanding machine comprises a carriage on which the spindle drive is mounted, said carriage having two pairs of wheels which run on two rails suspended in the machine, and also an actuator for the movement of the carriage on the rails, said actuator comprising a motor with an arm over the centre of the carriage's path of movement, said arm being in sliding engagement with a slide rail secured on the carriage, so that the turning of the arm around an axis, which is parallel or coincident with the axis of rotation of the spindle drive, effects the reciprocating movement of the carriage. By moving the sanding rollers in a reciprocating manner by means of an arrangement comprising a carriage which can slide on rails in the machine, the movement becomes stable and the construction relatively simple. Furthermore the moving of the carriage by means of a motor-driven crank arm results in a stable carriage movement and a simple construction, and the speed of motion of the carriage becomes extremely expedient, since it is lower at the sides where the movement turns than at the middle, which gives the best possible pattern of movement for the sanding roller operations. As disclosed in claim 8, by suspending the spindle drive in a system of jointly-hinged arms, a simple and rigid construction is achieved. As disclosed in claim 9, by being able to adjust the mutual angle of the arms, the drive can be raised and lowered and herewith the distance of the sanding rollers from the belt. Finally, as disclosed in claim 10, it is expedient to allow the arms to form an isosceles triangle at the one wheel pair and the suspension from the drive, respectively, in that it is hereby ensured that the drive and herewith the spindles are always situated in the same plane during raising and lowering. The invention will now be described in closer detail with reference to the drawing, where fig. 1 shows a sanding machine according to the invention seen from the feed-in or the outlet end, fig. 2 shows the machine seen from above in a section II-II in fig. 1, and fig. 3 shows a perspective illustration of the sanding machine according to the invention. An example of a sanding machine for the execution of the method according to the invention is shown in figs. 1 and 2. The machine 1 comprises a frame which is built into a housing with a through-going channel. In the bottom of said channel there is disposed a conveyor belt 2. In the example shown, the belt is a commonly-known endless rubber belt which is provided with a number of suction holes for suction from underneath, so that items 3 placed on the belt will be secured on the belt without the need for further fastening. As shown, the belt 2 can be moved through the machine 1, so that the items can be machined inside the machine. To effect the machining, in the machine's upper part there is mounted a machining apparatus comprising a motor 6 with an arm 7 secured to the motor shaft. At the end of the arm 7 there is mounted a pivot 8 supporting an underlying slide shoe 10 or the like which can grip around a slide rail 11, in that said slide rail 11 extends longitudinally with the machine as shown in fig. 2. The slide rail 11 is secured to a bracket 12, see fig. 1, which in turn is secured to a fixed part 13 on the movable sanding and moving equipment itself, which in principle is illustrated in fig. 3. The axis of rotation 9 of the pivot 8 is substantially coincident with the axis of rotation of the spindle drive 26. The spindle drive 26 comprises a housing from which spindles 28 project outwardly, and on which can be secured sanding elements in the form of rollers 29, as shown in figs. 1 and 2. As indicated by the arrows, the spindles 28 alternately rotate the one way and the other way around, while at the same time all of the spindles are turned around by means of a drive 27 with a motor 25. A motor 24 is mounted for the rotation of the spindles via the drive. The whole of this spindle drive 26 is suspended in journals 23 at the end of two supporting arms 22, which at their opposite ends are pivotally connected to a wheel axle 16 with a first pair of wheels 5. At the middle of the arms 22 there are linked a pair of shorter arms 20, the opposite ends of which are provided with a wheel axle 15 with a second pair of wheels 5. These two pairs of wheels 5, 16; 5, 15 can rest on two guide rails 4 which extend transversely to the machine 1 and therewith the path of movement of the belt 2, as shown in fig. 2. The wheel axle 15 with the second pair of wheels extends through a pair of guide slots 14 in the fixed part 13. Also linked to the wheel axle 15 are the legs of a yoke 17 which in the centre is in threaded engagement with a spindle 18 which can be turned by a motor 19. The end of the spindle 18 is linked loosely to the other wheel axle 16 with the first pair of wheels. There is hereby formed a raising and lowering arrangement for the spindle drive, which by turning of the threaded spindle 18 results either in a lengthening of the arms 20 and 22 and thus a raising of the spindle drive 26, or a shortening for the lowering of the spindle drive 26. The distance from the mutual pivot joint 21 of the arms 20 and 22 to the wheel axle 15 is the same as the distance to the journal 23 for the drive 26, whereby it is ensured that the spindles 28 will always be in the same plane. As mentioned, the moving arrangement for the carriage comprises a rotatable arm 7 which can drive the slide shoe 10 on the slide rail 11 around in a circular movement, as shown in fig. 2. The carriage with the wheels 5 will hereby roll on the guide rails 4 from the one end of the rails to the other, between the fully-drawn position to that shown with stippled lines in figs. 1 and 2. As will appear from the drawing, the sanding rollers 29 are moved a distance past the extent of the items 3 along the breadth of the belt, whereby the sanding is effected within the movement pattern of the rollers 29, and preferably some distance inside. Instead of the described machining apparatus comprising a carriage on rails which extends transversely to the feeding direction of the belt by means of an actuator, other forms of movement arrangements can be used. The spindle drive will thus be connected to a turning arrangement which gives the drive a rotating circular movement over the belt, or a reciprocating movement in an arcuate path transversely to the feeding direction of the belt. The following is a description of the method. The sanding rollers 29 are made to rotate by means of the motor 24, and are turned around the axis of rotation 9 by means of the motor 25. The moving arrangement for the carriage can now be activated by starting the motor 6 on the machine 1, whereby the carriage will move in a reciprocating manner on the guide rails 4. Items 3 can now be placed on the belt 2, which can be moved to traverse through the machine by means of a suitable driving arrangement (not shown). The sanding rollers 29 can now be lowered by means of the motor 19 until a suitable contact is established between the sanding elements on the rollers and the items. The sanding movement, which is described by the individual sanding elements on the rollers 29, comprises both a rotation around the spindle axle and a turning movement around the centre axis 9 of the drive, whereby the area shown in fully-drawn lines in figs. 1 and 2 is swept, and also a reciprocating transverse movement for sweeping between the the fully-drawn area and the area shown with stippled lines. The result achieved hereby is the especially effective sanding mentioned above, in that the sanding is effected by a relatively constant speed of contact between the item and the individual sanding elements, which is due to the expedient equalization of the speed components during the movement reversals of the carriage. In addition to the advantage of the more uniform sanding in the full extent of the belt 2, which reduces sanding damage and increases the efficiency, a considerably more uniform wear is achieved on the sanding rollers 29, which therefore require less frequent replacement, which results in low operational expenses.

Claims: Method of sanding, especially the sanding of items of wood in a sanding machine (1), where the items (3) are conveyed on a plane (2) such as a vacuum plane at the same time that the sanding tools (26, 28, 29) sweep the surface of the items (3), said sanding tools (26, 28, 29) comprising a number of sanding rollers (29), each secured to a spindle (28), and where the spindles (28) are mounted radially outwards from a drive (26), and in such a manner that the individual sanding rollers (29) rotate around the spindle (28) axes and are also turned around an axis (9) of rotation which extends at right-angles to the spindle (28) axes and to the surface of the plane (2), characterized in that the sanding rollers (29) are further moved in a reciprocating manner parallel with the plane (2) in a direction transversely to the direction in which the items (3) are conveyed. Method according to claim 1, characterized in that the reciprocating movement of the sanding rollers (29) is performed at a progressively decreasing and increasing speed towards and away from the extreme positions of the motion, respectively. Method according to claim 1 or 2, characterized in that the length of the reciprocating movement is so great that the sanding rollers (29) are moved out over the extent of the plane (2) in the direction of the reciprocal movement. Sanding machine, especially for sanding items of wood, comprising a plane (2) such as a vacuum plane, on which the items (3) are conveyed at the same time that sanding tools (28, 29) sweep the surface of the items (3), said sanding tools (26, 28, 29) comprising a number of sanding rollers (29), each secured to a spindle (28), said spindles (28) being mounted radially outwards from a spindle drive (26) and in such a manner that the individual sanding rollers (29) rotate around the spindle (28) axes and are also turned arround an axis (9) of rotation which extends at right-angles to the spindle (28) axes and to the surface of the plane 2, characterized by the spindle drive (26) moving the sanding rollers (29) in a reciprocating manner parallel with the plane (2) with an additional component of movement in a direction transversely to the direction in which the items (3) are conveyed. Sanding machine according to claim 4, charac terized in that the spindle drive (26) comprises a motor (6) and an arm (7) rotated by the motor (6) and connected to the axis (9) of rotation. Sanding machine according to claim 4 or 5, characterized in that the spindle drive (26) is connected to a turning arrangement which gives the spindle drive (26) a rotating circular movement over the plane (2). Sanding machine according to claim 5, characterized in that the sanding machine (1) comprises a carriage (5, 15, 16, 17, 20, 22) on which the spindle drive (26) is mounted, said carriage having two pairs of wheels (5) which run on two rails (4) suspended in the machine (1), and also an actuator (6, 7, 10, 11) for the movement of the carriage on the rails (4), said actuator (6, 7) comprising a motor (6) with an arm (7) over the centre of the carriage's path of movement, said arm (7) being in sliding engagement with a slide rail (11) secured on the carriage (5, 15, 16, 17, 20, 22), so that the turning of the arm (7) around an axis (8), which is parallel or coincident with the axis (9) of rotation of the spindle drive (26), effects the reciprocating movement of the carriage (5, 15, 16, 17, 20, 22). Sanding machine according to claim 7, charac terized in that the spindle drive (26) is suspended at the one end (23) of two first arms (22), which at their opposite ends support, by means of an axle (16), the first wheel pair (5, 16) of the carriage (5, 15, 16, 17, 20, 22), and where the second wheel pair (5, 15) of the carriage (5, 15, 16, 17, 20, 22) is mounted, by means of an axle (15), in the end of two second arms (20), which at their opposite ends are linked (21) to the first arms (22) which support the drive (26). Sanding machine according to claim 8, charac terized in that the angle between the two sets of arms (20 and 22) can be varied for the raising and lowering of the drive (26). Sanding machine according to claims 8 and 9, cha racterized in that the distance between the linkage (21) of the second arms (20) to the first arms (22) and the suspension (23) of the drive (26) on the first arms (22) corresponds to the distance between the linkage (21) and the wheel pair (5, 15) on the second arms (20).

Inventors: HUNDEBOL KELD OTTING, HUNDEBOL, KELD OTTING
Applicants: HH PATENT AS, HH PATENT A/S
Application year: 1991
Main classification: B24B41
IPC codes: B24B41, B24B7