Abrading – Rigid tool – Rotary disk
Reexamination Certificate
2000-01-28
2001-07-31
Banks, Derris H. (Department: 3723)
Abrading
Rigid tool
Rotary disk
C451S548000, C451S904000, C015S179000, C015S183000, C015S230160, C015S004000
Reexamination Certificate
active
06267660
ABSTRACT:
The present invention concerns a rotatable grinding or polishing tool with grinding elements each mounted in a cylinder surface, which grinding elements comprise flaps of abrasive cloth and support brushes having substantially the same radial extension as the flaps and provided in close contact with these flaps.
The invention furthermore concerns an apparatus comprising support means for advancing an item with a certain thickness to be ground or polished and a rotatable grinding or polishing tool mounted above the support means and having grinding elements that are mounted in a cylinder surface, the grinding elements comprising flaps of abrasive cloth and support brushes which have substantially the same radial extension as the flaps and which are provided in close contact with these flaps.
Furthermore, the invention concerns a method for grinding plane substantially plane items by using a grinding or polishing tool according to any preceding claim which is pressed against the item.
By grinding or polishing plane items in apparatuses according to prior art, the items are placed on a rolling table, a belt conveyor or the like, whereby they are continually passed through the apparatus. The grinding elements of the rotating tool are brought into contact with the surface. Today this is only used for grinding or polishing items with profiled surfaces where it is possible for the grinding flaps to perform an efficient grinding at the bottom and at the sides of the profile of the surface.
It is prior art to make rotatable grinding or polishing tools, preferably for the furniture industry, where grinding elements constituted by flaps of abrasive cloth or sandpaper and reinforcing support brushes are disposed in axial direction of the rotatable tool. Such tools are traditionally used in connection with grinding or polishing profiled items. These tools are not capable of performing stronger and more aggressive grinding or polishing of plane items.
Therefore, belt polishers are used for grinding and polishing plane items, by which it is possible to exert a relatively large pressure on the back side of a rotating belt-shaped sandpaper which is thus pressed against the surface to be ground or polished. Because of friction and thereby heat formation, there is a great risk that varnish sticks to the sandpaper and renders it unserviceable after short time of use. The belt polishers are furthermore disadvantageous as they only are usable for grinding /polishing of substantially plane surfaces.
In certain situations by the plane grinding there is a wish for achieving a so-called flamed surface, i.e. with variation in the surface structure depending on the hardness and veining of the wood, and possibly on the kinds of varnish used and the varnish thicknesses. In order to achieve a flamed surface one has previously used segmented thrust pads in wide band polishers. Such segmented thrust pads imply, however, complicated and in certain circumstances costly constructions in connection with grinding and polishing wood in the furniture industry.
With prior art rotating polishing tools it is possible to perform an intermediate polishing or an intermediate grinding of varnished items. This, however, requires great rotational speeds in order to achieve sufficient grinding efficiency. Hereby heat formation occurs so that ground varnish and dust sticks between the grinding grains on the flaps. The heat formation may be reduced by reducing the rotational speed of the rotating tool. However, this implies that the grinding or polishing may not be performed with necessary efficiency and quality. The surface after the grinding or polishing may thus be non-uniform depending on variation in hardness of the treated surface.
The purpose of the present invention is to provide a grinding or polishing tool and an apparatus of the kind mentioned in the introduction which makes possible to perform plane polishing or plane grinding, particularly of varnished surfaces, without the problems of heat formation and clogging of the grinding elements, and which is capable of establishing a so-called flamed surface on a wood item in a technically simple way.
This purpose is achieved with a rotatable grinding or polishing tool which is peculiar in that between each grinding element there is provided a holding element which has substantially shorter radial extension than the grinding elements and which comprises holding means with a substantially greater stiffness in tangential direction than the support brushes.
The apparatus according to the invention is peculiar in that between each grinding element there is provided a holding element having substantially shorter radial extension than the grinding elements and comprising holding means with a substantially greater stiffness in tangential direction than the support brushes.
The method according to the invention is peculiar in that the tool is pressed against the item with such a force that the grinding flaps and the support brushes are bent in over the upper side of the holding element.
By using the holding elements it is possible to thrust the tool against the item with such a pressure that the grinding flaps and the support brushes are bent in over the upper side of the holding elements.
The grinding elements and the holding elements may be directly fastened in the cylinder surface or be fastened thereto via mouldings which may be accommodated in undercut grooves in the cylinder surface.
By using a tool according to the present invention it is possible to press the grinding or polishing tool against the surface of an item with relatively great force in order to establish a relatively large grinding/polishing pressure. At the same time, the rotational speed of the rotating tool may be reduced considerably. This correspondingly reduces the heat formation. Then it becomes possible to perform grinding or polishing of the item with great efficiency and without risk of too large heat formation. Therefore, it is possible to achieve efficiency and quality as known from plane grinding with belt polishers.
The holding elements are preferably provided in a holder which may be accommodated in undercut grooves between the grinding elements. The holding brushes extend likewise axially along the grinding or polishing tool. However, the holding brushes extend radially only about half as far out as the flaps and the reinforcing support brushes. The holding brushes and the grinding elements are arranged with mutual radial length so that there is no risk of the grinding flaps of the tool coming into contact with support means for advancing the item through an apparatus.
In a preferred embodiment, the tool is peculiar in that the holding element is an additional brush, and that the holding means are brush hairs.
The tool according to the invention thus has grinding/polishing flaps which are support by reinforcing support brushes. As in the prior art grinding or polishing tools, the flaps and the reinforcing support brushes have substantially the same radial length as the flaps, however, are a little longer than the support brushes. When brush hairs are used for the holding element, these will have a lesser radial length than the flaps and the reinforcing support brushes, respectively. Thereby a substantially greater stiffness in tangential direction appears as compared with the reinforcing support brushes. Hereby the brush hairs in the holding brushes are not bent, and thereby it becomes possible to support the grinding flaps and the support brushes against the upper side of the holding brushes. It is possible to use an optional combination of shorter brush hair and/or stiffer brush hairs in order to achieve the desired stiffness.
The holding brushes in the present invention are preferably fastened to solid brush holders or raised ribs extending radially outward over a certain distance over the cylinder surface of the roller of the tool, and where the brush hairs extend radially further outward from the solid brush holders. By using raised ribs or letting the solid brush holder extend a certain d
Banks Derris H.
Creighton Wray James
Narasimhan Meera P.
Wilson Lee
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