WO2009071093A1

WO2009071093A1 - Grinding apparatus and apparatus for grinding a surface on plate-shaped items

Info

Publication number: WO2009071093A1
Application number: PCT/DK2008/050291
Authority: WO
Inventors: Poul Erik Jespersen
Original assignee: Flex Trim A/S
Priority date: 2007-12-04
Filing date: 2008-12-04
Publication date: 2009-06-11
Also published as: DK200701732A; DK178006B1

Abstract

Grinding tool (2) for grinding a surface of plate-shaped items and with a circular grinding surface (17) for rotation in a plane perpendicular to the rotary axis of the grinding tool, including a support means (16) adapted to support a grinding member (8), preferably a abrasive paper, and which has a circular central area corresponding to the grinding surface (17) and a ring-shaped rim area (18) with a frusto-conical surface, the frusto-conical rim area (18) forming an angle between 3 and 25°.

Description

GRINDING APPARATUS AND APPARATUS FOR GRINDING A SURFACE ON PLATE-SHAPED ITEMS

Field of the Invention The present invention concerns a grinding tool for grinding a surface of plate-shaped items and having a circular grinding surface for rotation in a plane perpendicular to the rotary axis of the grinding tool, where the grinding tool includes a support means adapted to support a grinding member, preferably a abrasive paper, and which has a circular central area corresponding to the grinding surface and a ring-shaped rim area with a frusto-conical surface.

The invention furthermore concerns an apparatus for grinding a surface of plate- shaped items, including a transport unit with a support face for the items and a carrier arrangement with a number of grinding tools arranged across the transport unit and supported on an endless transport means for moving the grinding tools in an annular movement in parallel with the support face, each of the grinding tools being adapted for rotating about an axis in a plane perpendicularly to the support plane and with a circular grinding face for rotating in a plane perpendicular to the rotary axis of the grinding tool in a plane parallel with the support plane.

The invention also concerns use of such a tool in such an apparatus.

Background of the Invention

By industrial grinding or sanding of plate-shaped items that include edges, roundings and surfaces, e.g. table tops, different types of grinding apparatuses are used which may grind the entire item in one run through the grinding apparatus. In order to achieve a nice surface, it is important that the grinding apparatus does not leave any distinct marks coming from the direction of grinding.

There are e.g. grinding apparatuses with a number of rollers, either with surrounding abrasive paper or with a number of grinding members that are disposed in the longitudinal direction of the roller. In order to avoid that the directions of grinding of the rollers are the same, the grinding apparatus is designed either with rollers typically rotating opposite each other, or rollers set at different angles in relation to the surface. The disadvantage of these types of rollers is that they consume a large amount of abrasive paper, whereby the abrasive paper is to be replaced often. This causes stop in production and increases the costs of grinding.

Furthermore, the grinding apparatus will not be worn evenly along the roller, in particular if items with different dimensions are to be ground. Typically, the abrasive paper will be worn most at the centre part of the roller.

In WO 99/22905 and EP 0 471 641 there is described another kind of grinding apparatus where a number of rotating rollers are disposed about a vertical shaft connected to a drive unit such that the rollers, besides rotating about their own shaft, rotate in the horizontal plane about the vertical shaft.

By rotating the roller about two shafts, it is attempted to avoid distinct grinding marks. In WO 99/22905, the rollers are rotating in mutually different directions with different speeds.

The disadvantage of this is that the rotating rollers with direction of rotation opposite the rotation in the horizontal plane will have greater grinding effect than the rollers having direction of rotation in the same direction as the rotation in the horizontal plane.

In EP 0 471 641 are used a number of grinding arrangements where each grinding arrangement consists of a number of rotating rollers rotating about a vertical shaft. In order to ensure grinding of the entire item, these grinding arrangements are arranged with overlap, causing uneven grinding, since there are areas of the item which are ground more than once. The disadvantage of both of the above grinding apparatuses is that they, in order to grind broad items, are to have long rollers, implying that the motor units for these rollers are to be correspondingly larger. This results in a larger capital cost of the grinding apparatus and a greater energy consumption.

In US 2002/0068515 there is described a surface processing apparatus, where either a bar with a grinding drum and/or a bar with a number of circular grinding brushes are used for surface processing a mainly flat item, and where the grinding brushes are shown arranged in two mutually displaced rows such that the grinding area of the second row of grinding brushes just overlap the grinding area of the first row of grinding brushes.

This construction of a surface treatment apparatus entails non-uniform surface treatment, since the grinding areas of the two rows of grinding brushes overlap each other slightly, and that only one grinding of the surface of the item occurs.

This means that the apparatus will not ensure an efficient grinding/deburring of edges and roundings of an item, as e.g. a stationary grinding drum may only grind the surface and forward facing edges/roundings, and a bar with overlapping grinding area of the grinding brushes only ensures a grinding of large parts of the surface once.

Moreover, a grinding tool for grinding a surface of plate-shaped items and having a circular grinding surface for rotation in a plane perpendicular to the rotary axis of the grinding tool will not be capable of grinding the items conveyed in a so-called continuous grinder where the items lying on a conveyor belt are passed in under a bar upon which the grinding tools are mounted. The edges on the grinding tools will strike the side edges on the items. The construction is thus complicated by an elevating bar which is difficult to control. Even in such a situation it will not be possible to grind the items in an accurate way if they vary a little in thickness.

For plane grinding it is common to use broad belt polishers. However, in practice it has appeared that these often impart transverse stripes to the ground items. For items with good finish without grinding marks it has hitherto only been necessary to use a manual finishing treatment.

In US 4065882 is disclosed a grinding tool for use in grinding machines where the tool is provided with abrasive paper having a circular central area which is the active part of the abrasive paper, and a rim area with slits. The rim area is adapted by removal of parts during the slitting operation such that it can be folded in over the edge of the tool without forming an overlap. The rim area then forms an active corner or edge.

The drawbacks of this are that the abrasive paper is to be adapted very accurately by slitting in order to avoid overlap and that the positioning of the abrasive paper on the support means during mounting has to be done with great precision.

Object of the Invention

It is the purpose of the present invention to indicate a grinding tool and a grinding apparatus which are simple in structure, which may plane grind an items with edges, roundings and burrs in a uniform way without any grinding marks on the ground surfaces, and which at the same time is easy to apply, where the item is inserted under the grinding tool in a direction in parallel with the grinding surface, and where slitting the grinding paper is avoided.

Description of the Invention

According to the present invention, this is achieved by a grinding tool of the kind mentioned in the introduction which is peculiar in that the frusto-conical rim area forms an angle between 3 and 25° with the grinding surface.

The grinding apparatus according to the invention is peculiar in that the grinding tool includes a support means adapted for supporting a grinding member, preferably an abrasive sheet or a abrasive paper, and which has a circular central area corresponding to the grinding surface and a ring-shaped rim area with a frusto-conical surface.

This provides an appropriate hipping or sloping surface so that the grinding tool does not hit the edge of the item, but instead is moved in over the item, and which may have a contact pressure against the item during the grinding operation. Furthermore, it is achieved that the grinding member can be formed by a circular flat piece of paper or abrasive fabric without slits, as the angle of the frusto-conical rim area is not greater than the grinding member can be adapted to the shape of the support means by pressing it on it. This provides that the grinding member is simple to make, easy to use and place on the support means as no particular accuracy is required.

Due to the frusto-conical surface, a grinding tool in a grinding apparatus will be moved in over the edge of a plate-shaped item simultaneously with deburring the edge. The grinding tool provides a grinding result with high quality, for example such as known from eccentric grinders. However, by using several heads, the circular grinding marks known from the use of eccentric grinders are avoided.

In a preferred embodiment of the invention, the grinding tool is peculiar in that the frusto-conical rim area forms an angle between 3 and 25°, preferably between 5 and 10°, with the grinding surface. This provides an appropriate hipping or sloping surface such that the grinding tool does not hit the edge of the item, but instead is moved in over the item, and such as to have a contact pressure against the item during the grinding operation.

In a further embodiment of the invention the grinding tool is peculiar in that the support means includes a resilient layer upon which the abrasive paper is mounted. This feature enables adaptation to a slightly deviating thickness on the item and will also provide that the item is ground with a grinding pressure that may be adjusted by suitable choice of the resilient layer. Alternatively, the grinding tool may include a resilient suspension, preferably an air cylinder.

In a further embodiment of the invention, the grinding tool is peculiar in that the resilient layer has a Shore A between 30 and 60, preferably between 40 and 50. In practice, this has appeared to give a good result of the grinding.

hi a further embodiment of the invention the grinding tool is peculiar in that the grinding member includes abrasive paper which is slit, preferably with largely radially extending slits. The abrasive paper may hereby be adapted more easily to the frustum of a cone at the rim area.

In a further embodiment of the invention the grinding tool is peculiar in that the grinding member is provided with holes, and that corresponding holes are provided in the support means for sucking off grinding dust.

In a further embodiment of the invention, the grinding tool is peculiar in that the rim area of the support means is between 10 and 17 mm wide and has an inclination between 2 and 5mm. This is typically used in a grinding tool with a diameter between 100 and 180 mm, preferably around 150 mm.

In a further embodiment of the invention, the grinding tool is peculiar by including a motor. Each single tool may hereby optionally be rotated in one or the other direction, independently of other tools in an apparatus.

These grinding tools are connected with a support arrangement that holds the grinding tools at a desired position in relation to the surface of the item. A large number of tools may be used in a simple way in one machine, e.g. a continuously operating grinder.

The grinding tools are circular and have support means that support grinding wheels and are connected to the grinding motors such that the grinding wheels in use are disposed in parallel with a surface of the item to be ground, preferably in a horizontal plane.

In order to grind the whole item in one run, the support arrangement includes an endless conveying means for the grinding heads, the conveying means being driven by the a moving motor.

This entails that the individual grinding tools, besides that they may rotate about their own vertical shaft, can be moved horizontally and transversely of the workpiece which is conveyed through the apparatus resting on the support plane. The support plane can be formed by a conveyor belt or by rollers or by any other kind of conveyor suited for supporting and transporting items through the grinding apparatus. The horizontal movement of the grinding tools transversely of the workpiece occurs in direction perpendicularly to the vertical shaft of the grinding members. This ensures that the entire item is ground in one run through the grinding apparatus.

As the conveying means is an endless course providing that the grinding heads are moved around from one side to the opposite side and back again to the first side, so that the item is surface treated by two rows of grinding tools that are moved over the workpiece in opposite directions in one run.

In that way is achieved a very even grinding of the item, since the second row of grinding heads will typically grind in opposite direction and thereby remove possible grinding marks made by the first row of grinding heads.

In a grinding apparatus, the annular movement of the rotating grinding tools will thus cause a grinding which has appeared to provide a surprisingly finely ground surface without leaving grinding marks.

An item may thus be ground in just one run by a grinding apparatus. If desired, the grinding apparatus may constitute part of a machine which is made with more serially mounted grinding apparatuses. In such a machine, the grinding apparatus according to the invention will constitute the last grinding apparatus in the machine.

It is preferred that each tool is driven by its own motor. Hereby it is possible to have the same or different direction of rotation of each single grinding tool in an apparatus. This may be controlled in a control unit.

For example: - every other grinding tool may have the same direction of rotation, while the intermediate grinding tools have opposite direction of rotation, or every third grinding tool may have the same direction of rotation, while the intermediate grinding tools have an opposite direction of rotation. The different directions of rotation of successive grinding tools cause that the grinding apparatus advantageously may be used in deburring and grinding edges and roundings.

The lateral movement of the grinding tools is to be adjusted to the speed with which the item is moved through the grinding apparatus, so that the grinding tools are moved at least so fast that the item is provided at least two grinding actions, and so that there are no areas on the item which are not ground.

In order to move the grinding tools transversely of the conveying direction of the item through the apparatus, the conveying means is constituted by a number of drive chains or belts which are adapted to engage a drive wheel driven by the moving motors.

In a preferred embodiment of the invention, four of these drive wheels are disposed rectangularly in the support frame, so that grinding tools connected to the conveying means are moved transversely of the item at first, and then back transversely across the item.

If the conveying means is a drive chain, the drive wheel will be sprocket wheels engaging the drive chain, thereby driving the conveying means with grinding heads around.

If the conveying means is a drive belt in the shape of a V-belt, the drive wheels will either be smooth drive wheels which by means of the resisting force between V-belt and drive wheel will drive the conveying means with grinding tools around, or be a toothed drive wheel engaging a toothed side of the V-belt.

Alternatively, the conveying means may be wires or wide belts or similar where the drive wheel is a narrow drive wheel or a roller, respectively.

Instead of having the drive wheels set up rectangularly in the support frame, the drive wheels may be envisaged set up in other polygonal arrangements, as for example: - three drive wheels disposed as a triangle, or - five drive wheels disposed as a pentagon.

Alternatively, there may only be used two drive wheels which the conveying means are running around, so that the two rows of grinding tools are disposed in immediate succession. This puts demands on the grinding tools so that they do not have too great diameter as the grinding tools otherwise cannot pass each other transversely of the item.

It would be advantageous if the two rows of grinding tools are moving transversely of the item at a certain distance, since there will be time and room for abraded material from the first row of grinding tools to be removed from the item, for example by suction, and thus not prevent the second row of grinding heads from performing an optimal grinding. Suction may e.g. be effected through rollers upon which the item is resting when running through the machine.

Instead of having drive wheels that are connected to a moving motor in every corner of the support frame, some of these drive wheels may be idlers which are only provided for guiding the conveying means.

hi a preferred embodiment of the invention, the conveying means is a wide toothed belt running on two large sprocket wheels arranged with one sprocket wheel at each side of the grinding apparatus. The grinding tools are disposed on the toothed belt.

Since a grinding apparatus is to be used on items with different thickness, it includes an apparatus frame in which the support arrangement is adjustable in height, provided by means of a number of displacing actuators.

As the support frame with grinding heads has a considerable weight, a number of displacing actuators are applied for elevating/lowering the support frame in the apparatus frame. This implies that the support frame may be disposed at a set level in the apparatus frame, whereby the grinding tools may be disposed so that they grind an exact thickness off the item.

The displacing actuators may be cylinders, rack and pinion arrangements, mechanical rocker arrangements, rotational arrangements or similar, which may be driven hydraulically, pneumatically or electrically.

The fact that the support frame can be adjusted in height makes it easy to bring the support frame up to a level at which it is easy to replace grinding tools or grinding members in the tools.

The grinding members may be constituted by abrasive paper which is mounted on a support means, e.g. by means of Velcro faces, or in other ways that enable rapid replacement of the grinding members.

The support means may be designed with a hub/pin connected with the shaft of the grinding motors, e.g. by a screw socket, bayonet socket, spring lock or in other ways that enable rapid mounting/dismounting.

In these ways grinding members and/or the grinding tools may be readily replaced so that it is not required with long interruptions in production when grinding members or grinding tools are to be changed.

A grinding apparatus according to the present invention may find application in the wood industry, but may also find application with other industries where there are surfaces to be ground, e.g. in the automobile industry where sheet parts for vehicles are to be ground.

Description of the Drawing The invention will then be explained in more detail with reference to the accompanying drawing, where: Fig. 1 shows a perspective view of a grinding apparatus according to the invention,

Fig. 2 shows a sectional view of the grinding apparatus in Fig. 1,

Fig. 3 shows a side view of the grinding apparatus in Fig. 1 ,

Fig. 4 shows additional side views of the grinding apparatus in Fig. 1, Fig. 5 shows a perspective view of a grinding head with grinding tool,

Fig. 6 shows an alternative support frame,

Fig. 7 shows a grinding apparatus,

Fig. 8 shows a plan view of the support means with grinding member,

Fig. 9 shows a second side view of the support means with grinding member, and Fig. 10 shows a plan view of a grinding member with slits.

Detailed Description of the Invention

On Figs. 1-4 is shown a grinding apparatus 1 that includes a number of grinding heads 6 which are constituted by a grinding motor 3 and grinding tool 2 with associated support means 16 and grinding member 8.

Each grinding head 6 is suspended in the support frame 4 along a conveying means 9 with a sheet part 14.

Conveying means 9 is adapted to engage drive wheels 11 that are driven by moving motors 5.

In the shown embodiment of the grinding apparatus 1 there are two drive wheels 11 and two idlers 10 disposed in a rectangle so that the grinding heads 6 are moved perpendicularly and transversely of the feeding direction A of a workpiece or item (not shown). Drive wheels 11 are disposed at opposite corners of the support frame 4.

The conveying means 9 is shown as two chains engaging an upper and a lower set of drive wheels 11a, lib/idlers 10a, 10b, respectively, which are shown as sprocket wheels.

In order to keep the grinding heads 6 in a vertical position so that the grinding elements 8 are parallel with the surface of the item (not shown), the apparatus frame 7 is provided with a wire/a belt 13 preventing the grinding heads 6 from lateral deflections.

The support frame 4 is connected with the apparatus frame 7 via drive wheels 11/idlers 10 and frame part 15, and is adjustable in height by means of cylinder 12.

Fig. 5 shows a grinding head 6 with associated grinding tool 2 which is driven by a motor 3. The grinding head is provided on a plate 21 that constitutes the connection between the grinding head 6 and the support frame (not shown).

Fig. 6 shows an alternative support frame 4 on which a number of grinding heads 6 are arranged on a continuous conveying means 9, shown here as a broad toothed belt. The continuous or endless transport means 9 is driven by a moving motor 5 such that the grinding heads 6 move around the support frame 4 while simultaneously the motors 3 on the grinding heads 6 rotate the grinding tools 2. The individual grinding tools 2 are hereby moved in an epicyclical movement.

Fig. 7 shows a grinding apparatus 1 with a transport unit 24 for supporting and possibly feeding a plate-shaped item to be machined. A support arrangement 4 is suspended above the transport unit where a number of grinding tools 2 are moved by an endless conveying means 9 in an annular movement.

Fig. 8 shows a grinding tool with grinding member 8 mounted thereon. The inner circular area constitutes the grinding surface 17 which is in contact with the item. Outside the grinding surface 17 there is a ring-shaped rim area 18 which is designed with an angle in relation to the grinding surface 17 so that it constitutes a frustum of a cone.

Fig. 9 shows the support means 16 with grinding member 8 mounted thereon. The grinding member 8 is secured by Velcro faces, double-adhesive tape or in other ways fastened to the support means 16. In the shown embodiment, the support means consists of a hard part 27 and a resilient layer 19 upon which the grinding member is provided. The support means is made with a collar 28 or the like which enables fastening the grinding tool 2 to a shaft on a grinding head (not shown). In the shown embodiment, the grinding member 8 is provided with a number of holes 22, and the support means 16 is provided with corresponding holes 23 for sucking grinding dust.

Fig. 10 shows a plan view of a grinding member 8. The inner circular area constitutes the grinding surface 17 which is in contact with the item. Outside the grinding surface 17 there is a ring-shaped rim area 18 which is designed with an angle in relation to the grinding surface 17 so that it constitutes a frustum of a cone. In the shown embodiment of the grinding tool a number of slits 26 are provided in the grinding member 8, besides a number of holes 22 for sucking grinding dust. These slits 26 are optional.

Claims

1. A grinding tool (2) for grinding a surface of plate-shaped items and having a circular grinding surface (17) for rotation in a plane perpendicular to the rotary axis of the grinding tool, where the grinding tool (2) includes a support means (16) adapted to support a grinding member (8), preferably a abrasive sheet or sandpaper, and which has a circular central area corresponding to the grinding surface (17) and a ring-shaped rim area (18) with a frusto-conical surface, characterised in that the frusto-conical rim area (18) forms an angle between 3 and 25° with the grinding surface (17).

2. Grinding tool according to claim 1, characterised in that the frusto-conical rim area (18) forms an angle between 5 and 10° with the grinding surface (17).

3. Grinding tool according to claim 1 or 2, characterised in that the support means (16) includes a resilient layer (19) upon which the grinding member (8) is mounted.

4. Grinding tool according to claim 3, characterised in that the resilient layer (19) has a Shore A hardness between 30 and 60, preferably between 40 and 50.

5. Grinding tool according to any preceding claim, characterised in that the grinding member (8) includes abrasive paper which is slit, preferably with largely radially extending slits (26).

6. Grinding tool according to any preceding claim, characterised in that the grinding member (8) is provided with holes (22) and that corresponding holes (23) are provided in the support means (16) for sucking grinding dust.

7. Grinding tool according to any preceding claim, characterised in that the rim area (18) of the support means is between 10 and 17 mm wide and has an inclination between 2 and 5 mm.

8. Grinding tool according to any preceding claim, characterised in that it includes a motor (3).

9. An apparatus (1) for grinding a surface of plate-shaped items, including a transport unit (24) with a support face for the items and a carrier arrangement (4) with a number of grinding tools (2) arranged across the transport unit and supported on an endless transport means (9) for moving the grinding tools (2) in an annular movement in parallel with the support face, each of the grinding tools (2) being adapted for rotating about an axis in a plane perpendicularly to the support plane and with a circular grinding face for rotating in a plane perpendicular to the rotary axis of the grinding tool in a plane parallel with the support plane, characterised in that the grinding tool (2) includes a support means (16) adapted for supporting a grinding member (8), preferably a abrasive paper, and having a circular central area corresponding to the grinding surface (17) and a ring-shaped rim area with a frusto-conical surface (18).

10. Use of a grinding tool (2) according to any of claims 1 - 8 in an apparatus (1) according to claim 9.