EP0046604B1

EP0046604B1 - Tool for roughing, smoothing and polishing solid surfaces, particularly adapted for stony materials

Info

Publication number: EP0046604B1
Application number: EP81200684A
Authority: EP
Inventors: Ermanno Pacini
Original assignee: Individual
Current assignee: Individual
Priority date: 1980-08-25
Filing date: 1981-06-18
Publication date: 1984-12-19
Also published as: IT8024268A0; IT1132464B; EP0046604A1; ATE10815T1; DE3167810D1

Abstract

A rotating plate (1) carries a plurality of truncated-cone rollers (11) arranged in radial position and rotated about their own axes. The sense of rotation of the rollers is chosen in such a way as to give the rollers (11) a peripheral speed having such a direction as to combine with the peripheral speed of the plate (1) to produce equal working speeds in all the points of the lower generating line (22) of the rollers (11).

Description

The present invention relates to a tool for roughing, smoothing and polishing solid surfaces, particularly adapted for stony materials.
The roughing, smoothing and polishing operations are, as known, the last stages of the working of stony materials and substantially serve, in the order, to have a planar surface, to remove the surface roughnesses and, finally, to obtain a specular surface.
The most widespread type of tool for these operations consists of a horizontal circular plate provided with rotary and translatory motion, which supports at its lower face a circumferential succession of variously arranged abrasive segments or small abrasive discs, called "satellites", which are rotated about their own axes, in opposite sense with respect to the sense of rotation of the supporting plate.
The tool with abrasive discs is more expensive than that with abrasive segments, but it shows the advantage of compensating at least partially, through the contrary rotation of the satellites, the difference between the peripheral speeds of points at different distances from the center of rotation of the plate.
The latter feature is particularly important, since the peripheral speed really represents one of the most important data of those rules for the employment of diamond tools, which were published the first time in 1971 by Assodiam, Italian association of the manufacturers of diamond tools, and are now carefully followed by technicians in all the world.
An unfavourable feature of the above said tools with rotating plate however consists in that the abrading material is always in contact with the material being worked and, therefore, allows the cooling water neither to wash the abrasive elements well nor to remove the mud efficiently. The latter, by coming between the material being worked and the abrasive, reduces the capacity of penetration of the single points and therefore, the output per hour.
In order to obviate partially this drawback, it is necessary to exert on the slab to be roughed a high pressure, which may give rise to breakages if the slab, due to a bad sawing, has a concavity at its resting face.
Far from this type is another tool, which is mainly used for roughing the tiles and substantially consists of a cylinder with horizontal axis, which carries at its periphery a plurality of diamond segments which define a total working width equal to 45, 60 or 70 cms. As a result of the rotation of the cylinder, the abrasive segments remove from the rough tiles, placed on an underlying belt conveyor, a thickness depending on the height of the axis of rotation of the cylinder.
In this case, all the abrasive material works at the same peripheral speed, which may be chosen in such a way as to be as close as possible to the optimum, and this is certainly one of the reasons which cause a higher output per hour and a longer duration of this tool with respect to the tools with horizontal plate.
Moreover, the abrasive remains in contact with the material being worked only along a generating line of the cylinder and for extremely short times, so that the mud, after having been diluted greatly by the cooling water, is immediately removed as a result of the same rotation of the cylinder.
Finally, still for the same reason, i.e. since the area of contact is very restricted, it is not necessary to press strongly the tool on the slab, with consequent danger of breakage in order to obtain a given optimal value of Kgs/cm².
In front of these advantages, however, the above described tool shows the serious drawback of a limited working width. In fact, it is apparent that, while a horizontal plate can translate in every direction, i.e., it has 360° of movement, a cylinder can do so only in directions substantially perpendicular to its axis of rotation.
It has recently appeared on the market a new tool, which consists of a normal horizontal plate provided with abrasive elements with horizontal axis, which are radially arranged with respect to the axis of rotation of the plate and have a lower section in the form of a circular arc of about 25°. Said abrasive elements are rotated about their own axes through an angle of 25° in alternated senses, with the result that the contact between the abrasive and the material to be worked occurs continuously along generating lines and the working speed of each single grain of abrasive depends both on its distance from the axis of the plate and on the sense of rotation imparted to the abrasive element in that precise instant. The working speed is thus variable from one to another grain and, for a same abrasive grain, from one to another instant.
There are also known further tools, which, even though they have not substantially been put into practice, are however known as described in the patent literature. Among them, there should be cited those of the German patents DE-C-801498, DE-C-651894 and DE-C-1115608, which include rollers with conical head, which are rotated about almost vertical oblique axes distributed along the circumference of a supporting plate, which rotates in turn about a vertical axis. None of these tools is however able to ensure the desired equality of working speed to all the abrasive grains, so that the working cannot be other than uneven and the consumption of abrasive irregular.
There is finally to keep in mind the French patent FR-A-140781 1, which describes and shows a tool with rotating horizontal plate, provided with short radially-arranged truncated-cone abrasive rollers, which work at respective generating tines., Con^lrarity to what explained in the specification and illustrated by designating arrows in Figure 1, however, the constructional arrangement shown in Figure 2 is such as to give the single truncated-cone rollers senses of rotation which do not annul but, if any, increase the speed inequalities produced by the rotation of the plate at the single points of the generating lines of the rollers. In the tool of the above said French patent either, therefore, there is not found the desired evenness of working speed for a perfect working and an even consumption of abrasive.
Substantially for glass polishing purposes there is further known a machine, disclosed in FR-A-817793, in which a plurality of frusto-conical abrasive rollers extend approximately radially of the axis of rotation of a support plate with their major bases faced towards the center of the plate and are rotated in the same sense as the plate, so that the surface speeds of the plate and the rollers are additive to produce a uniform value along the roller generating line in contact with the worked material, and which has the features of the pre-characterizing part of Claim 1.
This solution however is not completely satisfactory, since the above explained disposition of the frusto-conical rollers causes the material to enter the zone of influence of the abrasive rollers at their minor bases, which obviously carry a lower amount of abrasive material and, on the other hand, are subjected to the first, comparatively stronger impact with the material. This causes a rapid and uneven wear of the abrasive rollers and, at the same time, limits the abrading capacity of the machine during working.
In addition, the disposition of the major bases of the rollers close to the inner shorter circumference of the annular space of the plate causes a clear limitation of the number of rollers, which can be associated to the plate.
Bearing this in mind, the object of the present invention is to realize a roughing, smoothing and polishing tool, which ensures uniform working capacity throughout the working area without suffering the drawbacks of the above indicated prior art.
According to the invention, such an object is attained by means of a tool, comprising a horizontal plate rotatable about a vertical axis, a plurality of truncated-cone working rollers rotatably supported by said plate with a lower generating line arranged parallel to the plate plane below said plate, and drive means for rotating said rollers about their own axes at speeds in selected ratio with the rotation speed of the plate the rollers extending substantially radially and the ratio being such that all of the points of said lower generating lines of the rollers have substantially equal speeds of movement with respect to the surface to be worked, characterized in that said rollers are arranged with their major bases towards the outside of the plate and are rotated about their own axes in a sense opposite to that of rotation of the plate, so that the rotation speeds of the rollers and the plate are subtractive at said lower generating line of the rollers.
Otherwise stated, the sense of rotation of the rollers about their own axes is chosen in such a way that along their lower generating lines, which are the "working lines" of the tool, the peripheral speed due to the rotation of the plate and that due to the rotation of the rollers are subtracted from one another. The combined disposition of the truncated-cone rollers with their major bases towards the outside of the plate, on the other hand, results in that the maximum speed value is subtracted from the maximum speed value and the minimum speed value is subtracted from the minimum speed value to cause the difference to become uniform from one to the other end of the roller.
A proper selection of the diameter ratio of the rollers and of the speeds of rotation of the plate and the rollers can finally make said difference exactly constant along the lower generating line of the rollers.
The tool is thus able to work perfectly and an even consumption of the abrasive is obtained.
According to an embodiment of the present invention, moreover, it is possible to make the tool in two parts, the lower one of which, supporting the truncated-cone rollers, can be removed to allow the substitution of the abrasive or even, if necessary, the substitution of the rollers. These operations are thus made extremely rapid to full advantage of the productivity of the tool and the machine including the latter. Two exemplary embodiments of the tool according to the invention are illustrated for better clarity, but without any limiting intention, in the enclosed drawings, in which:

Figure 1 shows a tool according to the invention as horizontally sectioned along line I-I of Figure 2;
Figure 2 shows an enlarged detail of said tool as vertically sectioned along line II-II of Figure 1;
Figure 3 shows another detail of said tool as sectioned along line III-III of Figure 1;
Figure 4 shows in diametral vertical section another embodiment of the tool according to the invention, of the type made in two detachable parts;
Figure 5 shows the same embodiment with the lower part detached from the upper part.

With reference to Figures 1 to 3, a horizontal plate 1 provided with radial windows 2 is fixed below a rotatable, substantially cup-like, inner support 3, which is rotated about its own vertical axis 19, coincident with that of the plate, as guided by a stationary, cup-like, outer support 4, to which the inner support 3 is rotatably connected through bearings 5 and 6. Along the central rod or sleeve 7 of the rotatable support 3 there is supplied in conventional manner cooling and washing water, which reaches through radial bores 8 the annular peripheral chamber 9 formed between the lateral lower flaring 10 of the rotatable support 3 and the underlying plate 1.
In the above said annular chamber 9, at said radial windows 2, there are housed truncated-cone abrasive rollers 11, which are radially arranged with their major bases faced to the outside and their lower generating lines 22 projecting below the plate 1 through the windows 2 and parallel to the plate plane (Figure 2).
Each roller 11 has end pins 12 and 13 rotatably supported by the rotatable support 3 through sealed bearings 14 and 15.
The outer pin 12 even exists from the rotatable inner support 3, ending with a pinion 16 in engagement with a crown gear 17 carried by an annular plate 18 made integral with the stationary outer support 4.
The (for example, anticlockwise) rotation of the rotatable support 3 and the plate 1 is thus able to cause an opposite-sense (i.e. clockwise) rotation of each roller 11 about its own axes, at a speed much higher than that of the plate 1. It follows that the lower generating line of each roller, which is engaged with the underlying surface being worked, is subjected to two peripheral speeds of opposite signs, of which that due to the rotation of the plate, which is the lower one, is subtracted from that due to the rotation of the roller about its own axis, which is the higher one.
It is thus made possible to obtain that equality of working speed at all the points of the lower generating line of the rollers 11, which is an essential condition to attain the desired working uniformity, as well as an even consumption of the abrasive material of the rollers.
To this end, it is however necessary to provide for a proper sizing of the rollers 11 too, particularly as regards the ratio of their base diameters, as well as a proper choice of the speed of rotation of the plate and the rollers. More precisely, it is necessary to take into account the following formulae, which can be obtained through simple reasonings, once called d₁ and d₂ the diameters of the minor and major bases of the rollers 11, D₁ and D₂ the diameters of the plate 1 at said minor and major bases (or, more precisely, at the points A and B of the lower generating lines of the rollers), Np and N_µ the speeds of rotation of the plate 1 and the rollers 11 (in the senses indicated by the arrows 20 and 21 in Figure 1), expressed in rpm, V_P1 and V_P2 the peripheral speeds of the plate 1 at the diameters D, and D₂, expressed in ms/sec, V_R1 and V_R2 the peripheral speeds of the rollers 11 at the diameters d₁ and d₂, expressed in ms/sec, and V, the working speed which is desired to have at every point of the lower generating line of the rollers 11.
It is apparent, in fact, that the speed of rotation of each roller 11 about its own axis confers the most internal point A of the same roller a peripheral velocity V_R1 given by the following formula:
and directed from left to right looking at Figure 3.
The rotation of the plate 1, on the other hand, confers the same point A an oppositely directed peripheral speed V_P1, which is given by the following formula:
The resulting peripheral speed, further directed from left to right in Figure 3 because the peripheral speed of the roller as due to its rotation about its own axis is higher than that due to the rotation of the plate, is obviously given by V_R1―V_P1.
In order to make it equal to the desired value V_L, it is therefore necessary that the following relation is satisfied:
This can be obtained in the planning stage by establishing the several parameters according to the experience and constructional requirements and bearing in mind that d, cannot obviously be chosen too small.
Repeating the same reasonings for the more external point B of each roller 11, there is obtained the similar relation:
from which, once established D₂, there can easily be obtained the value of d₂ which allows the same speed V_L to be granted to the point B also.
Since the speeds of the end points A and B are equal to one another and to the desired speed, this obviously holds true for all the other points of the lower generating line of each roller 11 too, i.e. the entire generating line has an equal peripheral working speed. This allows the tool the best working conditions with uniform removal of material and likewise uniform consumption of abrasive. At the same time, should an uneven consumption of abrasive occur, it would be possible to remedy promptly by changing the ratio of the two end diameters (d,, d_Z) of the abrasive rollers, possibly with a simple addition of abrasive where necessary.
During working, cooling and washing water is fed at controlled pressure to the inside of the rod 7 of the rotatable support 3 and from here, through the bores 8, to the annular chamber 9 and then, through the windows 2, on the surface being worked. It is thus obtained an efficient washing and cooling of the abrasive rollers, which are immersed in cold and clean water during the most part of their time of rotation, as well as a certain dilution of the mud, which is produced in a minimum amount, since only one generating line of the rollers is in contact with the material, and is progressively removed because of the same water and the rotating movement of the abrasive rollers.
Further advantages result from the presently preferred embodiment which is illustrated in Figures 4 and 5. According with the latter Figures, in fact, the tool is made in two separable parts 31 and 32, which are normally fixed to one another by a nut 33 screwed onto the threaded end 34 of a pin 35, which projects downwards from the upper part 31 and passes through a central bore 36 of the lower part 32.
More precisely, the upper part 31 comprises a stationary support 37 and a rotatable support 38, which include respective upwardly extending tubular rods 39 and 40, which are coaxially arranged and rotatably coupled to one another through a bearing 41. The rotatable support in turn rotatably carries three shafts 42, which are radially arranged at circumferentially spaced positions and on which a conical pinion 43, engaged with a conical crown gear 44 of the stationary support 37, and a cylindrical gear 45 are rigidly mounted.
The lower part 32 in turn comprises a support 46, which is rotated along with the rotatable support 38 of the upper part 31 as made integral therewith by the pin 35 and the nut 33. Said support 46 rotatably carries three shafts 47, which are radially arranged at circumferentially spaced positions, exactly below the shafts 42 of the upper part 31. On each shaft 47 there are fixed a cylindrical gear 48, engaged with the above mentioned gear 45, and a truncated-cone roller 49 provided with abrasive coating 50. As can be detected from Figure 4, the shafts 47 are slightly inclined with respect to the horizontal working plane 51, so that each truncated-cone roller 49 has a generating line completely engaged with the same working plane, as it happened to the rollers 11 of the tool of Figures 1 to 3.
A plate 52 fixed to the support 46 completely closes the lower part 32 of the tool, allowing only a minimum section of the rollers 49 around the working generating line to project through the radial windows 53.
There is finally provided a feed system for the cooling and washing water, which system extends within the rotatable support 38 of the upper part 31 of the tool in the form of channels 54 and 55 and ends above the rollers 49 into a roller housing chamber 56 (Figure 4).
The mode of operation of the tool illustrated in Figures 4 and 5 is conceptually identical to that of the tool illustrated in Figures 1 to 3, i.e. the rotation of the rotatable support 39, and therefore of the plate 52, about its own vertical axis causes a corresponding rotation of the rollers 49 about their almost horizontal axes. This time, however, it happens to the shafts 42 to receive the latter rotary motion as a result of the engagement of the pinions 43 with the stationary crown gear 44 and to transmit the same to the truncated-cone rollers 49 through the connection between the gears 45 and 48. It is easy to verify that, if the rotatable support 38 is rotated in the sense indicated by the arrow 61 in Figure 4, the shafts 42 are obliged to rotate at higher speed in the sense indicated by the arrow 62 in the same figure and the rollers 49 are finally obliged to rotate about their own axes in the sense indicated by the arrow 63, i.e. in the same sense as the rollers 11 of Figure 1 upon an identical rotation of the rotatable support 13. There further result therefore a speed subtraction and compensation and, with a suitable choice of size and speed, the possibility of obtaining the desired equality of speed in all the points of the lower generating line of the rollers.
Moreover, it is possible to detach rapidly the lower part 32 from the upper one 31 for the rapid substitution of the abrasive and, if necessary, of the same rollers 49.
In Figures 4 and 5, and still more in Figures 1 to 3, there is given a generic representation of the abrasive coating of the rollers, since the features of the present invention are totally independent from the type of abrasive which is used. For mere indication it is however to be considered particularly useful and efficient to realize the abrasive coating in the form of one or more helixes wound about the rollers. With such a helix-like arrangement, in fact, there is obtained the important result of causing a thrust of the mud outwards, which is particularly useful during the roughing, when the single rollers should remove great amounts of material and meet with very irregular surfaces. Through the spaces between the helixes, the mud can easily move outwards and thus go out of the working area. It is moreover to be noted that, as a result of the helix-like construction of the abrasive coating, the direction and the sense of the peripheral velocity vector are slightly different from those of the work vector of the abrasive grain, which has consequently a solid support. Finally, since the contact area is limited, it is possible to obtain a good working pressure of the abrasive even with a low weight of the tool.

Claims

1. Tool for roughing, smoothing and polishing solid surfaces, comprising a horizontal plate (1) rotatable about a vertical axis (19), a plurality of truncated-cone working rollers (11) rotatably supported by said plate (1) with a lower generating line (22) arranged parallel to the plate plane below said plate, and drive means (16, 18) for rotating said rollers (11) about their own axes at speeds in selected ratio with the rotation speed of the plate the rollers extending substantially radially and the ratio being such that all the points of said lower generating lines of the rollers have substantially equal speeds of movement with respect to the surface to be worked (1), characterized in that said rollers (11) are arranged with their major bases towards the outside of the plate (1) and are rotated about their own axes in a sense opposite to that of rotation of the plate (1 ), so that the rotation speeds of the rollers (11) and the plate (1) are subtractive at said lower generating line (22) of the rollers (11).

2. Tool according to Claim 1, characterized in that said drive means (16, 18) are selected so as to rotate said rollers (11) about their own axes at a speed higher than that of rotation of the plate (1).

3. Tool according to Claim 1, characterized in that said rollers (11) are provided with abrasive coating made in the form of one or more helixes wound about the rollers.