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(11) | EP 0 941 807 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Apparatus for surfacing hard materials |
| (57) Apparatus (A) for surfacing and polishing stone, marbles and other hard materials
in the form of blocks, plates or sheets. The apparatus comprises a mechanism for causing
a rubbing or grinding block (1), retained in a socket (11) on an arm (18), to execute
a combination of rotative and oscillating movement along a surface to be treated,
each arm (18) carrying at least one treatment block (1) each. Each block (1) makes
a constantly translating parallel self cleansing line contact with said surface to
be treated for performing a rubbing or grinding action thereon. The socket (11) is
so mounted, that tangential and radial forces carried over from the grinding blocks
(1) into said socket (11), are uniformly translated from the same into each arm (18).
Said forces are there uniformly absorbed by at least dual and at least partly cylindrical
reaction elements (16a, 16b) on said arms during said rotating and oscillating movement
of each said grinding block. |
[0001] The present invention relates to an apparatus for surfacing and polishing stone, marbles and other hard materials in the form of blocks, plates or sheets, with a mechanism for causing a rubbing or grinding tool to execute a combination of a rotative and oscillating movement along a surface to be treated, said tool including any number of arms carrying at least one treatment block each, having a constantly translating parallel self cleansing line contact with said surface to be treated for performing a rubbing or grinding action thereon.
[0002] Apparatuses for surfacing or polishing stones etc. usually include a rotating grinding head comprising a cylindrical disc having mounted thereon a number of rubbing or grinding blocks which during rotation of the disc are pressed against the surface to be treated under simultaneous supply of water to the working zone of the grinding blocks. The grinding blocks are provided with a grinding portion comprising diamond grains or other abrasive grains, the abrasive effect being obtained by moving said grinding block or blocks over a surface to be polished and at the same time pressing the grinding blocks against said surface.
[0003] In the most simple apparatuses of this kind, the grinding surface of the grinding blocks is plane, said blocks being rigidly or rotatably attached to the grinding head. One serious disadvantage inherent in this design is that dirt and mud will collect underneath and in front of the grinding blocks, thus tending to clog the pores of the grinding blocks, thereby preventing accurate grinding action of said grinding blocks.
[0004] It has been found that the disadvantage mentioned above can be eliminated if the grinding blocks, in addition to being rotated about the rotational axis of the grinding head, also are made to move with respect to the grinding head. This relative movement may include different types of movement. The grinding blocks may thus be made to rotate about any additional axis or to perform an oscillating movement in the radial or in the tangential direction with respect to the grinding head. In such cases the grinding blocks are designed so as to provide linear contact between the grinding blocks and the surface to be treated, which results in increased pressure against the surface and improved grinding action. This also results in that the grinding blocks will be kept clean due to the fact that mud and grinding dust formed at the grinding action, is discharged radially under the influence of the centrifugal forces instead of clogging the abrasive surface of the grinding blocks.
[0005] Known apparatuses of this kind usually include a grinding head provided with a number of grinding blocks, e.g. four grinding blocks, which are supported at the ends of arms which are pivotably mounted on axes extending radially with respect to the grinding head. Said arms are shaped as double-armed levers, the opposite end of which co-operates with an executor mechanism that is supported by the grinding head and during rotation thereof is caused to positively pivot the grinding blocks back and forth along a certain angle as a consequence of the rotation of the grinding head. Such an apparatus is disclosed in US-A-4 965 965. Due to the relative movement between the axis of the grinding head and the arms of the executor mechanism, the arms, supporting the grinding blocks at the ends thereof, are caused to perform a swinging or oscillating movement about said radially extending axes. Said grinding head is driven by means of an electric motor. Known grinding heads of this kind may include two, four or six grinding blocks, the grinding head having a diameter of 200-600 mm and being driven for rotation with a rotary speed of 200-600 rpm. Each grinding block may e.g. be made to perform one full oscillation for every fifteen revolutions of the grinding head.
[0006] Even if known grinding heads for surfacing stone etc. including excenter mechanisms of the kind mentioned above provides a satisfactory oscillatory movement to the grinding blocks, an important disadvantage is that the mechanism, i.e. each socket, for retaining a grinding block is subjected to heavy mechanical wear, which results in high maintenance, deadlock and servicing costs as well as in a short lifetime of at least parts of the apparatus.
[0007] The object of the present invention is to provide a grinding head for surfacing or polishing stone, marbles, etc. of the kind mentioned initially, including a mechanism for oscillating the grinding blocks, in which the disadvantages of the known apparatuses, mainly the heavy wear of the socket retainers that results in high maintenance and service costs as well as in a short lifetime of the apparatus in essence are eliminated.
[0008] Another object of the present invention is to provide a grinding head of the kind mentioned in which the magnitude of the oscillatory movement of the grinding blocks may be considerably increased.
[0009] These and other objects of the invention are obtained by designing an apparatus for surfacing and polishing of stone, marbles etc. in accordance with the features specified in the appended claims.
[0010] According to the invention said socket is so mounted, that both tangential and radial forces carried over from the grinding blocks into tapering grooves of said carrier, are uniformly translated from the same into each arm where they are uniformly absorbed by at least dual and at least partly cylindrical reaction elements, being constantly brought along together with the rotating and oscillating movement of said grinding blocks.
[0011] By implementing the invention it is possible to increase the working angle of the grinding blocks to as much as +/-15° as compared with an absolute maximum of +/-6° with previous arrangements. This is possible while still a much better reliability than before is gained.
[0012] Below the invention will be described with reference to the embodiment illustrated on the enclosed set of drawings, on which
FIG 1 schematically shows the principle used in an apparatus according to the present invention for imparting a rotative and oscillatory movement to grinding blocks for surfacing and polishing stone material,
FIG 2 is an overall vertical side view of an apparatus according to the invention, and
Fig 3 shows a central cross-section corresponding to Fig 2.
[0013] As mentioned above one object of the invention is to provide a simple mechanism for imparting a considerably increased oscillatory movement to grinding blocks for surfacing or polishing stone, marbles etc., and simultaneously increasing the reliability thereof. By increasing the oscillatory movement the efficiency of an apparatus according to the invention will be much increased.
[0014] FIG 1 schematically shows the principles used when designing said mechanism. To obtain a fuller understanding of the following explanation of the principle illustrated in FIG 1, reference is also made to FIGS 2 and 3 since all reference numerals referred to are not indicated in FIG 1 but may be found in FIGS 2 or 3.
[0015] FIG 1 discloses two grinding blocks 1 disposed opposite each other and in line with each other. Each grinding block 1 is rigidly attached to a lever L, extending in direction upwards in relation to the surface S and being attached at the opposite end to a shaft 3, extending in parallel with and at a certain distance above said block 1. Each shaft 3 is journalled in a bearing 4, rigidly supported by a housing H, shown in FIG 2. Rigidly attached to the opposite end of each shaft 3 is a guiding rod 5, extending from said shaft 3 in direction upwards through an elongated slot 6 in a circular disc 7, excentrically disposed inside the housing H. Said disc 7 is supported in said housing H by means of a vertical drive shaft 8, centrally disposed in said housing and supported in the upper part thereof by means of a bearing 8' providing radial as well as axial support. The disc 7 is attached to said drive shaft by means of an excenter 9, which is rotatably supported in a bearing in the central part of said disc. In FIG 1 said excenter 9 is illustrated as a crank web rotatably attached to the center point 10 of said disc 7. Supposing that the bearings 4 and the housing H are held stationary, a rotation of shaft 8, as indicated by the arrow in the upper part of FIG 1, will cause the center point 10 of the disc 7 to move along a circular path, indicated in FIG 1 by a broken circular line. Since the disc 7 by keeping an arm 18, connected to the excenter 9, stationary, the disc 7, indirectly connected to arms 2 is prevented from rotating together with the housing H, whereby each and every point or part of said disc 7 is caused to follow a corresponding circular path as the central point 10. This means that also the slots 6 in the disc 7 will move along a corresponding circular path thus imparting a tilting or oscillating movement to the guide rods 5 between two angular positions, defining a total working angle α for each grinding block 1(α/2≤15° according to the above comparison between the invention and the prior art). Thus it is the relative rotational movement between the housing H and the shaft 8 that imparts the oscillating movement to the grinding blocks 1. In the embodiment according to FIGS 2 and 3, this relative rotational movement is combined with a varying balance of moments between each pair of grinding blocks 1, further increasing the support of this oscillating movement. The above mentioned angular limit positions are determined by the design of the elongated slots 6, which slots determine the outer limits for the movement of the guiding rods 5.
[0017] FIG 2 discloses the main parts of the apparatus according to the invention. The apparatus is shown in a partial side view with its overall arrangement A for imparting said oscillating movement to grinding blocks contained in sockets 11. For simplicity reasons the grinding blocks, to be contained in these sockets 11, are not shown. In this embodiment the apparatus comprise two arms 2 arranged perpendicularly to each other. As is shown by the arm 2 situated in the middle of FIG 2, its socket 11 has a tapered dove-tail groove 12 for the mounting of said grinding block. Due to said taper, from the center and out, a grinding block can be retained in a socket 11 due only to its location and the fact that as a consequence of the rotation its arm is fixed harder and harder to the socket due to the centrifugal force as the rotational speed of the arm increases. Thus due to said dove-tail configuration there never is never any play between the sockets and their grinding blocks. Also the arm 2 and the shaft 3, schematically shown and described in connection with FIG 1, can be identified in FIG 2. As is best seen in FIG 2, due to its eccentric movement, each arm 2 is given an oscillatory movement from an angle of +α/2 to -α/2 during its rotation.
[0018] This movement is at the same time the cause of the effectiveness with this kind of surfacing or polishing and the root to the problems with low reliability with apparatuses of this kind, however, now solved by this invention. It has been found that the load changes experienced by each grinding block during its service life generate a kind of infinitesimal pumping movement between each grinding block and its socket, giving rise to penetration of water and particles in the small space there between, very quickly giving rise to degradation of both the socket and the grinding block, thus shortening the lifetime of each.
[0019] In FIG 2, reaction elements 13 can be seen constituting part of the solution to keep the grinding blocks and their sockets in a fixed relationship. The details of this solution are, however, more clearly seen and described in connection with FIG 3 below.
[0020] Consequently FIG 3 shows a partial central cross section corresponding to FIG 2, and reveals relevant internal details of the apparatus according to the invention. Also this illustration lacks the surfacing or grinding blocks needed when using the apparatus. The mounting of the sockets 11 is, however, clearly shown. Constituted of three main parts each, one center socket mount 14 and two side portions 15, are heavily bolted together. The side portion 15 on the trailing side of each grinding block unit has between itself and each socket 11 two springs 23 that can withold aproximately 150N, which is the approximate load from the carrier during service at full speed. The purpose of the springs 23 is to achieve a dampening effect during running in of new grinding blocks. The interstitium between the socket 11 and each side portion is filled with Teflon®-sealings 22.
[0021] Each socket 11 is held in two "vertical" cylindrical bearing blocks 16a and 16b, each in itself held to the arm 2 with bolts 17 either in a thread 17a or with a nut 17b on the outside, as on the reaction element 13. Due to the physical extension of the reaction element 13, it is necessary to manufacture each arm 2 in at least two parts in order to make drilling for the shaft 3 possible. The upper part of each arm 2 and the rest of each arm are as a consequence preferably mounted together with bolts and nuts, the mounting surface therebetween preferably also comprising steering pins and holes (not shown). The first bearing block 16a is fixed to the arm 2, which also is the case with the second bearing block 16b. In the interstitium between each of these blocks and each reaction element liners 20 are fixed on either one of the parts working together. As also can be seen from FIG 3, vertical compression springs 19 are arranged between each socket 11 and its arm 2 for making the initial contact between the surface S to be treated and the surfacing or polishing blocks 1 as lenient as possible when initialising a working operation. The springs 19 also serves to balance potential irregularities on the surface S to be treated. Irregularities small as 0,01 mm, causes severe strokes to the grinding head. Finally, also a felt gasket 24 is arranged at the inner end of each socket 11 for stopping stone material together with water to penetrate the space 25 between the sockets 11 and their arms 2.
1. Apparatus for surfacing and polishing stone, marbles and other hard materials in the
form of blocks, plates or sheets, comprising a mechanism for causing a rubbing or
grinding block (1), retained in a socket (11) on an arm (18), to execute a combination
of rotative and oscillating movement along a surface to be treated, each arm (2) carrying
at least one treatment block , each block (1) making a constantly translating parallel
self cleansing line contact with said surface to be treated for performing a rubbing
or grinding action thereon, characterised in that, said socket (11) is so mounted, that tangential and radial forces carried
over from the grinding blocks (1) into said socket (11), are uniformly translated
from the same into each arm (18) where they are uniformly absorbed by at least dual
and at least partly cylindrical reaction elements (16a, 16b) on said arms during said
rotating an oscillating movement of each said grinding block (1).
2. Apparatus according to claim 1, characterised in that such reaction elements (16a, 16b) have a greater length the more peripheral
they are arranged.
3. Apparatus according to claim 2, characterised in that the mean-thickness of the reaction elements (16a, 16b) is greater the more
peripheral they are arranged.
4. Apparatus according to anyone of the preceding claims characterised in that each socket (11) comprise a dove-tail groove (12), for achieving a positive
retainment of grinding elements due to its rotational movement.