Lapping head with floating grinders for rocky materials, particularly for granite slabs

Abstract: The invention discloses a lapping head with floating grinders consisting of a body (20) within which is attached a ring-gear (7) with inner cogs engaging a pinion gear (6) coupled with a central eccentric collar (10), which in turn is co-axially coupled with a vertical shaft (2) attached to the body (20). The central eccentric collar (10) co-operates through a cylinder-shaped collar (11) and through mechanical connecting means (8,9,16,17) both with planetary eccentric collars (13) attached to the body (20), and with each shaft (18) attached to the support (19) holding each grinder (40), wherein the floating motion of each grinder occurs when the vertical shaft (2) rotates, thereby bringing the body (20) of the lapping head to which it is attached into rotation.

Description: The invention concerns a lapping bead with floating grinders for rocky materials, particularly suited to lap granite slabs. It is a known fact that the lapping of marble, granite and other rocky material slabs is done through lapping heads presenting some abrasive sections. Said lapping heads consist of a main body having a cylindrical or polyhedral shape and supporting a plurality of grinders around its outer periphery. The head is made to rotate around its own vertical axis, so that the grinders around its periphery are also brought into rotation. At the same time each of the grinders is also made to float around a horizontal axis. The lapping of the slab is, therefore, obtained by the abrasive action of the grinders, which combine the rotational motion around a vertical axis with the floating motion on a vertical plane of each one of them. In some of the known types of lapping heads the rotational motion of the head and the floating motion of the grinders are obtained through a kinematic device consisting of a pinion gear engaging at the same time two cogged wheels, which are co-axial to each, one of them being attached to the main head body, while the other one is attached to a cam. When the pinion gear rotates, it causes the rotation of both cogged wheels, causing, therefore, both the rotation of the head main body and the rotation of the cam. While the latter is rotating, it contrasts against some levers which are connected with the grinder-supporting shafts and thereby causes the floating movements of the grinders. Since the two cogged wheels present each a number of cogs slightly differring from each other, the cam rotates with a speed which slightly differs from the speed of the main body of the lapping head. Therefore, the number of floating motions per minute of the grinders is noticeably lower than the number of r.p.m. of the head body. The number of said floating motions is, moreover, reduced in direct proportion to the relative speed between the two cogged wheels and, therefore, in direct proportion to the difference of their numbers of cogs. One of the inconveniences presented by this type of lapping heads is the high maintenance rate they require. In fact, since the pinion gear rotates at a very high speed rate, it needs to be constantly and perfectly lubricated. Should this lubrication be missing even for a short period of time, a rapid damaging of the pinion gear, of the cogged wheels and of the ball bearings would occur, especially because of the particular environment where the device operates, which is characterized by the presence of highly abrasive dust. This inconvenience is avoided by the device described in the italian patent application No. 85561/a/89 in the name of the same inventor of the present patent, wherein the lapping head is made without the pinion gear rotating at a high speed rate, so that the unit providing the rotation of the head and the floatation of the grinders is reduced to the two cogged wheels only. Even the lapping head made in accordance with the mentioned patent application, and the other known lapping heads present further inconveniences, the most important of which is represented by the fact that the cam causing the floating motions of the grinders is very costly to manufacture because it is difficult to obtain its geometrical precision. In fact, should its geometrical shape not be perfect, the grinders would have differing floating motions and, therefore, one grinder would work differently from another. Another inconvenience consists in that the contact between the cam and the grinder-supporting shafts is practically punctiform and it is at any rate limited to a segment of much reduced length. This causes considerable wear and tear of the contact points while the machine is in operation, because of the high specific loads. This also reduces considerably the ability to absorb shocks and dynamic loads. A further inconvenience consists in that the presence of the floating levers activating the grinder-holding shafts extend tangentially and thereby reduce the number of grinders which can be mounted on each lapping head in relation to its diameter. Not the least inconvenience is caused by the fact that the lapping heads of the known type require an accurate setup when they are assembled, particularly concerning the positioning of the floating elements of the grinders in relation to the cam outline. In any case, regardless of the accuracy of both the cam outline and of the assembly, there will always be a small slack which tends to increase as time goes by. The purpose of the present invention is to eliminate said inconveniences and its main purpose, in particular, is the disclosure of a lapping head with floating grinders, presenting a simpler and less costly construction than the laping heads of the known type. Another purpose is to disclose a lapping head able to stand shocks and accidental dynamic loads without being damaged. Another purpose is for the lapping head according to the invention not to require difficult adjustments or adaptations at the time of its assembly. Another purpose of the invention is for the lapping head to operate reliably and to require as little maintenance as possible. Not the least purpose is for the lapping head of the invention to allow the assembly of a higher number of floating grinders than the lapping heads of the known type having the same peripheral dimensions. The described purposes and others which will become better understood hereafter are reached by the disclosure of a lapping head with floating grinders, which, in accordance with the patent claims, includes: a main body consisting of a lower box, which is closed by an upper lid attached to it and presenting an axial hole, a ring gear having its inner cogs attached to the inner face of the lid and being co-axial with its axial hole; an eccentric flange attached to the base of the lapping machine and presenting an axial hole and being freely coupled within the axial hole of the upper lid; a vertical shaft coupled with a power take-off, passing co-axially through the hole of the eccentric flange with which it is coupled by means of bearings, said shaft having one of its ends attached to the lower box through connecting means; a pinion gear engaging with the ring gear having inner cogs, and coupled outwardly with the eccentric flange by means of bearings; a plurality of grinders arranged around the periphery of the lower box, each being attached to a support being held by a shaft connected to the kinematic elements conveying the motion, which are contained within the lower box, and is characterized in that a central eccentric collar, which is coupled with the shaft at the latter intermediate length and is rigidly attached to the pinion gear by means of connecting elements, co-operates through a cylinder-shaped collar and through mechanical connecting means with both eccentrical planetary rings coupled with the lower box, and with each shaft connected with the support of the grinders, and makes possible the floating motion of each grinder when the vertical shaft rotates and causes the rotation of the main body of the lapping head to which it is attached. According to a preferred embodiment of the invention, the central eccentric collar is rigidly connected with the pinion gear through a pin connection and its outer diameter, which is eccentric in relation to the inner hole within which it is coupled with the vertical shaft, is slidingly keyed within a cylinder-shaped collar. The cylinder-shaped collar is bound through pivots to planetary eccentric collars, preferably three in number, which are lodged within seats which are machined within the lower box. The central eccentric collar and the planetary eccentric collars present the same degree of eccentricity, so that, while the central eccentric collar is rotating, the cylinder shaped collar to which it is keyed is forced to follow it and each part of its surface performs in relation to the lower box a plurality of revolutions having a radius corresponding to the value of eccentricity of the eccentric collars. One or more pistons are arranged each within a radial slot obtained within the cylinder-shaped collar and they are connected with levers, which are connected in turn with the shafts supporting the grinders. Through the levers which are connected with the shafts supporting the grinders, said pistons transmit to the latter only the tangential component of the rotating motion of the cylinder-shaped collar, thereby making the floating motion of the grinders possible. Advantageously, according to the described embodiment, a very simple and inexpensive lapping head is obtained, which does not require complex adjustment and setup operations while it is being assembled. Also advantageously the lapping head according to the invention does not require much maintenance when used, although it presents a high degree of reliability, a reduced rate of wear and tear and a high capability of absorbing dynamic loads and shocks. Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and the specific example, while indicating a preferred embodiment of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description and from the drawings, wherein: Fig. 1 shows a longitudinal cross-section of the lapping head according to the invention; Fig. 2 is a plan view of the lapping head of Fig. 1, cross-sectioned on a trasversal plane. With reference to the Figs. 1 and 2 it can be observed that the lapping head according to the invention, which is indicated as a whole with 1, presents a body 20 containing all the kinematic elements and consisting of a lower box 22, on the top of which is attached through suitable means, for instance screws 25, an upper lid 21 presenting a central axial hole 23. Whithin hole 23 of the upper lid 21 is assembled an eccentric flange 3 which is not allowed to rotate, since it is attached by means of a pin 4 to a fork 5, which in turn is solidly attached to the base 24 of the lapping machine. A ring gear with inner cogs 7 is attached to the inner face of the upper lid 21. Therefore, said ring gear is also attached to the lower box 22 and to the body 20 of the lapping head. The pinion gear 6 which engages the inner cogs of the ring gear 7 is coupled by means of bearing with the outer part of the eccentric flange 3, while a vertical shaft 2 is coupled through bearings with the inside of the hole 31 of the same eccentric flange 3. Said shaft is attached to the lower box 22 by means of suitabble connecting mechanical elements, for instance a nut 33 which is screwed on the thread 34 of its lower end. It can, therefore, be understood how, by causing the rotation of the vertical shaft 2, if its end 50 is connected with a power take-off belonging to the lapping machine, the entire body 20 is also brought into rotation, so that the ring gear 7, engaging the pinion gear 6, causes the latter to rotate. It can be observed, especially in Fig. 1, that the pinion gear 6 is completely contained within the inner diameter of the ring gear 7 and, therefore, presents a smaller number of cogs than the latter. As a consequence, when the body 20 and, therefore, the ring gear 7 rotate, the pinion gear 6 rotates at a speed rate which slightly exceeds the speed of body 20, the difference in speed varying in relation to the difference in the number of cogs between the ring gear 7 and the pinion gear 6. It will also be observed that a radial slot 8 is machined on the pinion gear 6. A pivot 9 is bound within said slot and it is fixed within a seat 42 which is obtained within a central eccentric collar 10, which is slidingly keyed around the intermediate diameter 35 of the vertical shaft 2 preferably through the interposition of a bearing 36. Pivot 9 allows pinion gear 6, while rotating, to bring the central eccentric collar 10 into rotation, too. Therefore collar 10 also has a rotating movement in relation to the intermediate diameter 35 of the shaft 2, which acts as its rotational pivot. The central eccentric collar 10 in turn is keyed , preferably through a bearing 38, within the cylinder-shaped collar 11, which is bound to the lower box 22 by means of three pins 12, each of which is connected with its own planetary eccentric collars 13, lodged within suitable seats 36 machined within the lower box 22. Said planetary eccentric collars 13, as can be observed more closely in Fig. 2, are arranged one in relation to the other preferably at an alpha angle measuring 120 degrees around the center of the rotational vertical shaft 2. It will, however, be specifically pointed out that this embodiment can be varied, in that the number of planetary eccentric collars 13 can be in a number differring from three. The central eccentric 10 and the planetary eccentrics 13 present the same degree of eccentricity 14, so that the cylinder-shaped collar 11 is forced to follow the central eccentric collar 10 during its rotational movement and each of its points describes, therefore, a circular trajectory having a radius, the value of which equals the value of the eccentricity 14. Therefore, when the vertical shaft 2 is brought into rotation, it causes the rotation of the body 20 of the lapping head and of the ring gear 7, which is attached to it, of the pinion gear 6 engaging the ring gear 7, of the central eccentric collar 10 connected with the pinion gear 6 and of the cylinder-shaped collar 11, which is coupled with the central eccentric 10, all of these elements turning around one and the same vertical axis 36. Moreover, at the same time while this rotation around the vertical axis 6 is taking place, each point of the cylinder-shaped collar 11 describes, in relation to the lower box 22, a circumference having a radius equalling the degree of eccentricity 14 of the central eccentric collar 10 and of the planetary eccentric collars 13. Some horizontal slots 15 having a radial arrangement are machined within the cylinder-shaped collar 11. In the embodiment illustrated in Fig. 2 they are four in number and are arranged at an angle of 90 degrees from each other. In this case, too, the embodiment can be varied, by matching the number of slots with the number of grinders 40 to be assembled, depending on the outer dimensions of the body 20 of the lapping head, as will be better explained hereafter. Each of the slots 15 lodges a cylinder piston 16 complete with a transversal hole 41, into which a lever 17 is inserted and attached to a shaft 18. It has been said that, while the central shaft 2 is rotating, each point of the cylinder-shaped collar 11 describes, in relation to the lower box 22, a circumference having a radius equalling the degree of eccentricity 14 of the eccentric collars 10 and 13. It is known that each circular motion can be broken out into the sum of two elementary motions, one of them being radial while the other one is tangential. Therefore, with reference to each cylinder 16 lodged within each slot 15, it is bound to the cylinder-shaped collar 11, as far as its tangential motions are concerned, since, because it is lodged within the mentioned slot 15, it is forced to follow the cylinder-shaped collar 11 during its rotation. Said cylinder 16, on the contrary, is free to move radially within slot 15, since the lever 17 to which it is bound is free to move within the slot 28 obtained underneath slot 15. As a consequence of this, it happens that the cylinder-shaped collar 11 during its rotation imparts to cylinder 16 exclusively the tangential component of its circular motion, while the radial component is nullified by the fact that the connection between the cylinder 16 and the slot 15 is sliding, so that no force is transmitted. The result of this is that the circular motion of the cylinder-shaped collar 11 transmits, through piston 16 and its lever 17, to each shaftt 18 a hunting rotational motion around the horizontal axis 39. As a consequence, support 19 on which the grinder 40 is applied accomplishes a hunting motion in a vertical plane which is parallel to the vertical axis 36 around which body 20 and, therefore, the entire lapping head rotate. In another possible embodiment of the invention the hunting plane of support 19 and, therefore, of grinder 40 attached to it can also be arranged with a direction differring from the vertical. It has already been said that the number of slots obtained in the cylinder-shaped collar 11 can be different from four. In fact, it has been observed that the number of these slots is equal to the number of the shafts 18 and , therefore, of the supports 19 with their respective grinders 40, which are assembled on body 20 of the lapping head. Since the support 19 of each grinder 40 has a well defined tangential dimension, it will follow that the maximum number of slots 15 which can be machined in the cylinder-shaped collar 11 is equal to the maximum number of grinders 40 which can be applied to body 20, depending on its outer diameter. From the foregoing description it can be understood that the lapping head according to the invention reaches all the proposed purposes. First of all, the purpose of manufacturing a lapping head presenting a simple construction at a lower cost than the lapping heads of the known type has been reached. It has, in fact, been described that the cam, which while rotating imparts the floating motion to the grinder-supporting shafts has been eliminated. It has been replaced by the central eccentric collar 10, the cylinder-shaped collar 11 keyed to the former and by the planetary eccentric collars 13, all of these elements having a cylindrical outline, which can easily be obtained with a turning operation. The purpose of obtaining a lapping head whose inner components are not subject to much wear and tear has also been reached. In fact, it can be observed that, while in the laping heads of the known type the floating motion of the grinders is obtained because of the contact of the cam against the levers of the shafts through the interposition of contrasting and rolling elements, so that the ensuing contact is practically punctiform, all the inner components of the lapping head according to the invention present very large contact surfaces, extremely reduced specific loads and, as a consequence, irrelevant wear and tear. Again as a consequence of this fact, the lapping head according to the invention is also sturdy enough to stand dynamic loads or accidental shocks, without undergoing any damage. The purpose of obtaining a lapping head not requiring complicated adjustment and setup operations during its assembly has also been reached. In fact, since the kinematic elements of the lapping head according to the invention are obtained by turning and they present cogs, so that they all rotate, they do not present any difficulty of assembly, since they easily match each other if the they have been manufactured with the tolerances required by the drawing. The purpose of obtaining a lapping head whereon more grinders can be assembled than on the lapping heads of the known type, their diameters being the same, has also been reached. In fact, as can be seen by observing the Figs. 1 and 2, the levers 17 activating the shafts 18 connected with the supports 19 of the grinders 40, present an exclusively vertically protruding bulk, while the bulk of the levers activating the shafts supporting the grinders in the lapping heads of the known type develop their bulk in the tangential direction, since they must come into contact through their contrasting elements with the shaped surface of the activating cam. It is easy to understand that this decreases the number of grinders which can be assembled around the periphery of the lapping head body, because of the presence of said levers, which are arranged in a tangential direction. Moreover, it will be observed that the connection between each lever 17 and its respective cylinder 16, sliding within slot 15 in the cylinder-shaped collar 11, presents a much reduced bulk even in the vertical direction of axis 36, as compared to the contrasting elements activating the levers causing the rotation of the grinders in the lapping heads of the known type. Therefore, the lapping head according to the present invention presents also a reduced axial bulk as compared to the lapping heads of the known type, their respective diameters being equal. It has been said that during the manufacturing phase the lapping head according to the invention can be provided around its periphery with any number of grinders 40 and, as a consequence, of shafts 18, depending on the outer diameter of the lapping head and on the bulk of the grinders. It has also been said that, at the discretion of the manufacturer, the number of the planetary eccentric collars 13 belonging to the lapping head can be varied, as can be varied the number of cogs of the pinion gear 6 and of the ring gear 7, so as to obtain the transmission ratio between the two which best suits the specific requirements. Furthermore, the systems connecting and joining the kinematic elements forming the lapping head can be varied and modified in shape and number, while it is understood that, in any case all these modifications and variations will not exceed the spirit and the scope of the present invention, such as it is defined by the following claims.

Claims: A lapping head with floating grinders comprises: a body (20) consisting of a lower box (22) closed at the top by an upper lid (21) attached to it and presenting an axial hole (23); a ring gear (7) with inner cogs, attached to the inner face of the upper lid (21) and co-axial with its axial hole (23); An eccentric flange (3) attached to the base (24) of the lapping machine, presenting an axial hole (31) and freely keyed within the axial hole (23) of the upper lid (21); a vertical shaft (2) coupled with a power take-off passing axially through the hole (31) of the eccentric flange (3) with which it is coupled through bearings (32), said shaft (2) presenting one end (34) which is attached to the lower box (22) through suitable fastening means (33); a pinion gear (6) engaging the ring gear (7) having inner cogs and being coupled with the eccentric flange (3) by means of bearings (61); a plurality of grinders (40) arranged around the periphery of the lower box (22), each being attached to a support (19) supported by a shaft (18) which is connected to the kinematic elements conveying the motion and being contained within the lower box (22), characterized in that a central eccentric collar (10) which is coupled with the vertical shaft (2) at the latter intermediate position and which is rigidly connected with the pinion gear (6) through suitable connecting means (8,9) co-operates through a cylinder-shaped collar (11) and through some mechanical coupling elements (8,9,16,17) both with the planetary eccentric collars (13), coupled with the lower box (22), and with each shaft (18), which is connected with the support (19) holding the grinder (40), wherein the floating motion of each grinder (40) occurs when the vertical shaft (2) rotates and brings into rotation the body (20) of the lapping head to which it is attached. A lapping head with floating grinders according to claim 1, characterized in that a pivot (9) attached within a slot (42) obtained in the central eccentric collar (10) and bound within a radial slot (8) obtained in the pinion gear (6) rigidly connects the central eccentric collar (10) with the pinion gear (6). A lapping head with floating grinders according to claim 2, characterized in that the pivot (9) attached to the central eccentric collar (10) contrasts against the radial slot (8) of the pinion gear (6) within which it is coupled through contact surfaces (51). A lapping head with floating grinders according to claim 1, characterized in that the central eccentric collar (10) is slidingly keyed within the cylinder-shaped collar (11). A lapping head with floating grinders according to claim 1, characterized in that the degree of eccentricity (14) of the central eccentric collar (10) is equal to the degree of eccentricity of each one of the planetary eccentric collars (13). A lapping head with floating grinders according to claim 1, characterized in that the connection between the cylinder-shaped collar (11) and each shaft (18) connected with the support (19) holding each grinder (40) is obtained through a piston (16) sliding within a radial slot (15) machined in the cylinder-shaped collar (11), said piston being coupled with a lever (17) which is attached to the shaft (18) of each support (19) holding each grinder (40).

Inventors: CADO' WALTER, CADO', WALTER
Applicants: BREMA SRL
Application year: 1990
Main classification: B24B41
IPC codes: B24B41