EP3107687B1

EP3107687B1 - Improved mandrel for sizing, smoothing or polishing stone materials with rotating abrasive heads

Info

Publication number: EP3107687B1
Application number: EP15714276.1A
Authority: EP
Inventors: Giambattista PEDRINI
Original assignee: Pedrini SpA ad Unico Socio
Current assignee: Pedrini SpA ad Unico Socio
Priority date: 2014-02-18
Filing date: 2015-02-18
Publication date: 2018-04-11
Anticipated expiration: 2035-02-18
Also published as: WO2015124990A1; BR112016018894B1; CN106170369B; ES2676081T3; CN106170369A; EP3107687A1

Description

Field of the invention

The invention relates to an inherently balanced mandrel bearing heads for sizing, smoothing or polishing natural stone materials and/or ceramic tiles, namely a mandrel put in rotation on the surface being worked to transmit the rotation to said heads with a rotation axis normal to the surface to be worked, such as slabs, strips or tiles of granite, hard stones, marble or porcelain stoneware, which is made particularly advantageous in the balancing and adjustment both during assembly and operation to perform delicate operations of sizing of the thickness of the materials, smoothing or polishing of the surfaces that require high precision.

Prior art

The prior art includes mandrels for supporting and driving the most varied types of heads with a rotation axis normal to the surface being worked wherein the activation of the mandrel occurs with a belt drive and therefore with the need to arrange the related electric motor on an axis parallel with respect to the rotation axis of the mandrel. As a consequence, most of the mass of the complex that is mobile and adjustable with respect to the surface being worked, that is to say, the mandrel, electric motor and rotating head complex, has a centre of gravity resulting forcedly far from the axis of the mandrel. Hence results a particular sensitivity of said complex to the vibrations transmitted by the abrasive tools to said head and finally supported by the supporting structure to which said mandrel is fixed, there resulting a vibrating elastic mass. A direct consequence and first problem lies in the difficulty to eliminate the effect of said vibrations, when they are not absorbed by said supporting structure, which cause working flaws on the material. Not least, the off-axis position of the motor allows to use standard electric motors and to make pass in the holed shaft of the mandrel the pipe for feeding the cooling water to the abrasive tools of said head.
A second problem appears in the mandrels known in the prior art at the moment of their assembly onto said supporting structure. Said structure is made up of a suitably bent and welded sheet metal and has the seat of fixing of said mandrel to be adjusted to the exact position required in the working of the material; therefore it is necessary to position in a correct way said mandrel on said supporting structure and in the art it is known to shim on the sides the flange of fixing of the tubular housing of said mandrel to said structure, in such a way as to compensate for small differences or building errors of said metal supporting structure. Said operation is uncomfortable and requires a considerable testing work with successive attempts to reach the exact laying and position required for the axis of the mandrel.
An additional problem lies in having at one's disposal a movement device along the axis of the mandrel and, therefore, of the head, motor and mandrel complex to adjust the working action on the surface being worked. In fact, all the axial adjustment devices of the known mandrels have pneumatic or hydraulic actuating cylinders adjacent and outside the body of the mandrel, in order to adjust the tools for the required working action both with a fixed position, as required in sizing, or with pressure, as occurs in smoothing and polishing. The action of said actuating cylinder is out of the axis of the mandrel creating greater stress to the supporting structure and to the body of the mandrel to which it is obviously joined. The mass of the mandrel, it being too off-axis with respect to the line of action of said actuating cylinder, amplifies vibrations.
In the prior art, in order to solve the aforementioned problems, the document EP 1536916 is known, which describes a mandrel for supporting rotating heads in which a pair of electric motors is placed in a balanced way on the mobile body, in the vertical direction, of the mandrel; a gear transmission connects the driving shafts of the electric motors to the mandrel itself; the motion in the vertical direction is realized with a pneumatic piston coaxial to the mandrel; finally, the sleeve for mounting the mandrel on the structure of the machine that houses it has a pair of curved surfaces for the fine adjustment of the position of the axis of the mandrel on the structure of the machine at the moment of assembly.
Moreover, the constitution of such a mandrel is expensive in the working both for the construction of the coaxial cylinder/piston, which must be made to fit the size of the mandrel, and for the realization of the gear transmission that, if it actually realizes a very good balance, has remarkable making and/or maintenance costs.
In the prior art mandrels for rotating abrasive heads are known in which a pair of actuating cylinders are adjacent to the sleeve of the vertically sliding mandrel and operate in the flange of connection of the mandrel to the transmission of motion from a pair of electric motors to the mandrel advantageously made by means of belts alternatively connected to one of the driving pulleys of one of the motors and to the other driving pulley of the other motor. Moreover, the heads mounted on said mandrels are also, often, replaced with others, which are always rotating, but which due to the different shape of the abrasive elements need a different transmission ratio in said belt drive. That is to say, in replacing the head mounted on the mandrel one also has to modify the transmission, in such a way as to put in movement the abrasive elements with the most effective operating speed. With a belt drive of the known type, although balanced, the variation of the transmission ratio is complex and long having to act on the driving pulleys of each motor and/or on the driven pulley connected to the shaft of the mandrel, in such a way as to considerably increase the time for replacing the rotating head with the drive as said.
Furthermore, the mandrel with the connected head has a considerable inertia at the moment of start, in such a way as to require the detachment of the head with the abrasive elements from the surface being worked to prevent damaging it. Moreover, the start and stop occur even several times in the work shift for various reasons besides that of start after a technical intervention and/or a maintenance intervention. It was found that as at start the inertia of the electric motors-drive-mandrel shaft-rotating head complex with the abrasive elements is high, the start must be carried out in a position far from the surface being worked.
Such prior art is susceptible of remarkable improvements concerning the possibility to overcome the above-described drawbacks.
From everything stated above derives the need to solve the technical problem of finding an arrangement of the parts of the mandrel, for abrasive tool heads, that besides realizing an inherent balancing of the mandrel and of the means connected to it, motor and related head, enables a safe and fast change of the transmission ratio between the electric motors and the mandrel and, therefore, of the head.
Moreover, along with said technical problem the new mandrel can allow to eliminate vibrations of the head at start due to inertia.
These realizations, moreover, having to be obtained with low costs with respect to those of construction of the mandrel described in the prior art.

Summary of the invention

This technical problem is solved, according to the present invention, by an improved mandrel according to claim 1. Moreover, in an additional embodiment: the lobes are advantageously made on an applied ring connected to the upper end of the sliding body of the mandrel.
Furthermore, in an additional advantageous embodiment: a tongue, provided with an axially inclined end, is inserted within a hollow longitudinal to the axis of the mandrel and interposed between the sliding body of the mandrel and its adjustable sleeve; said hollow has at its lower end a correspondingly inclined shape connectable to the end of the tongue.
Finally, in a specific embodiment: in combination with the hollow shaped at its lower end there is between the sliding body of the mandrel and the adjustable sleeve a further tongue and a corresponding hollow, for the aligned guiding in a prearranged position between said sliding body and said adjustable sleeve.

Short description of the drawings

A way of carrying out the invention is shown, by way of example only, in the five drawings enclosed in which:

Figure 1 is a schematic side view of the mandrel, according to the invention, mounted on the structure of the machine and provided with standard electric motors operating said mandrel and holed shaft for the passage of the water feeding pipe;
Figure 2 is a schematic axial section rotated by a right angle with respect to the previous view of the shaft of the mandrel and supporting structure of the machine; the Figure also shows the locking tongue of the mandrel in a lifted position.
Figure 3 is a schematic axial section with the actuating cylinders of the body of the mandrel in which one can see simultaneously the balanced drive, the pneumatic cylinders of vertical positioning of the mandrel and the mandrel with the fixed sleeve and the mobile body sliding in it, which here is shown, for illustration simplicity, with the axial plane of the cylinders coincident with that of the electric motors and belt drive, which are usually made on intersecting axial planes, but not coincident as in the Figure; the Figure also shows the locking tongue of the mandrel in a lifted position;
Figure 4 is a schematic axial section with the actuating cylinders of the body of the mandrel as the previous Figure 3, in which the position of the mandrel is lifted and one can see the locking tongue of the sliding body of the mandrel inserted in the end of its seat;
Figure 5 is a simplified schematic plan view, V-V of Figure 4, of the supporting plate of the belt drive in which one can see that the plate with the drive is centrally connected to the end of the body of the mandrel;
Figure 6 is a schematic view, similar to the previous Figure in which the supporting plate of the belt drive is in a position of rapid replacement, with the fitting to the internal diameter that enables its axial disjointing from the body of the mandrel.

Detailed description of a preferred embodiment

In Figures 1 to 4, 1 indicates the mandrel for supporting in rotation a head with abrasive tools of the known type, not shown, to the metal structure 2 of a generic machine tool for sizing, smoothing and/or polishing stone materials of granite, hard stones or marble, or even tiles of porcelain stoneware; said mandrel is fixed to the structure 2 by means of an adjustable sleeve 3 provided with a spherical surface 4 in the upper end for the position of rest of a flange 5 on an applied ring 6, which is spherical too and is welded to said metal structure 2 of support of the mandrels with the abrasive tool heads of the machine. The fixing of said flange 5 is made by means of screws 7 that clamp it to the mandrel 1 in the precise position of adjustment on the working surface of the machine tool, while, at the other lower end of said sleeve 3, the guiding occurs by the contact of a spherical band 8 of a casing 10 external to the adjustable sleeve, with a cylindrical seat of an applied ring 9 in the supporting metal structure 2.
The Figures also show a body 12, of said mandrel 1, sliding along the axis of the adjustable sleeve 3 under the action of two pneumatic cylinders 13 connected by means of the end of the rod 14 to an upper flange 15, which in its turn is connected to said body 12 of the mandrel, the upper flange also supporting a balanced belt drive 16. Said body 12, in addition to the upper flange 15, supports a pair of electric motors 17 operating the rotation of the mandrel by means of said drive; a tongue 18, interposed between said adjustable sleeve 3 and the body of the mandrel 12 within a slot 19, obtained in the sliding surface of the body 12, enables the reciprocal axial sliding and prevents rotation. The adjustable sleeve 3 has on the external casing 10 in the lower part of the mandrel 1, to house in a telescopic way, a circular case 11 in its axial motion of lowering and lifting as it is connected to the lower end of the body 12 of the mandrel: the external casing 10 also realizes the guiding contact between said adjustable sleeve 3 with the band 8 on the ring 9 in spherical contact.
A further tongue 20, provided with an axially inclined end 21, is inserted in a different position with respect to the tongue 18 within a hollow 22 longitudinal to the axis of the mandrel; said hollow has at the lower end 23 a shape inclined as and connectable to the end 21 of the tongue 20. The sliding of the mandrel 1 upwards, for the detachment of the head from the surface being worked, can be seen in Figure 4 so as to connect and eliminate the clearances of guiding with the rotation between the sleeve 3 and the body 12 of the mandrel axially sliding therein. The inclined end 21 of the tongue 20 couples with the lower end 23 of the hollow 22 and prevents oscillations or vibrations when the mandrel, the motors and the connected head start rotating.
One can see, moreover, a holed shaft 24 coaxial to said body 12 of the mandrel and coupled with it in rotation by means of upper 25 and lower rolling bearings 26 and 27; a hole 28 of the shaft allows the passage of a water feeding pipe 29 to said head with the abrasive tools; the head is fixed in a removable way, as known, to the end flange 30 of the holed shaft 24 for the activation in rotation; while a reaction pin, as known in the art, is counteracted by a tooth, integral and axially sliding with the body 12 of the mandrel, in such a way as to transmit the necessary rotation torque to said head; moreover, said tooth and reaction pin are not shown as it has already been said for the rotating head with abrasive tools, since they are known in the art.
The balanced drive 16 is made by means of supports 31 of the electric motors 17 connected in diametrically opposite positions with respect to the shaft 24 on the flange 15. Each shaft of electric motor 17 has a driving pulley 32 or 33 having a diameter suitable to transmit the desired rotation drive to the shaft 24 of the mandrel 1; on the shaft 24 a pulley 34 is fitted having a greater diameter with a number of circumferential grooves for V belts 35 or 36 equal to the sum of the number of grooves present on the driving pulleys 32 and 33, fitted on the shafts of the electric motors; the number of the grooves is an even number for the pulley 34, while the number of the grooves on the driving pulleys is half the number of the grooves on the pulley 34: five grooves in each pulley 32 or 33 are shown in the Figure. The V belts present in the pulley 34, in the Figure provided with ten grooves, are housed in an alternate way on grooves corresponding to those of the driving pulleys 32 and 33 aligned to them; that is to say, all the belts 35 and 36 are housed in the grooves of the pulley 34, fitted on the shaft 24 of the mandrel 1, and are subdivided in an alternate way, 35 in the driving pulley 32 and 36 in the driving pulley 33, fitted on the driving shafts of the electric motors 17. Therefore, as one can see in the Figures, of the ten grooves present in the pulley 34 five belts are coupled on the pulley of a motor and the other five belts on the pulley of the motor diametrically opposite to the axis of the mandrel 1.
In Figures 5 and 6 one can see the coupling between the supporting plate 15 of the belt drive 16 with the body 12 sliding within the sleeve 3. The coupling 37 occurs by disjointing the screws 38 that clamp the radial lobes 39 to the lugs 40 made in the centre of the supporting plate 15; in the Figures one can see four lobes 39 and as many ports 41 to allow the passage of the lobes 39 with clearance in the ports 41 between the lugs 40, after the disjointing of the coupling by removing the screws 38 and rotating the supporting plate 15 by an angle sufficient to match the lobes 39 with the ports 41 as in Figure 6.
The assembly of the complete mandrel 1 to the supporting metal structure 2 occurs by introducing the adjustable sleeve 3 into said structure 2 and by clamping the screws 7 after aligning it in the correct vertical adjustment position with respect to the working surface of the machine. The screws 7 clamp the flange 5 of the adjustable sleeve 3 within holes having a diameter considerably greater than their own shank and with large washers 48 also enabling the clamping with substantial reciprocal inclinations between said metal structure 2 and said adjustable sleeve 3. The clamping of said screws 7 allows to lock the position, also inclined, of said adjustable sleeve by swinging in the spherical contact 4 between the flange 5 of the adjustable sleeve and the ring 6 fixed to said structure 2. At the other end of the adjustable sleeve the spherical band 8 allows the adjustable sleeve to take said inclined position without losing the contact with the corresponding cylindrical surface in the ring 9 with which it is coupled.
The balanced belt drive 16 works as a usual belt drive, but the arrangement of the masses of the electric motors 17, as ballast resting on the supporting plate 15, allows to act with greater effectiveness in the working steps that a specific machine has to perform on the surface of the stone materials being worked. In fact, the mass of the electric motors and of the drive has the centre of gravity coincident with the rotation axis of the shaft 24 of the mandrel 1. Moreover, the arrangement of the belts in an alternate way on the pulley 33, fitted on the shaft 24, towards the driving pulley 32 or towards the driving pulley 33, allows to balance the draw of the belts on the rotation axis of the pulleys in the drive where they are inserted; that is to say, the described arrangement allows also in the presence of a means, namely the belt drive, which by itself generates unbalance, to remain well balanced for the symmetry of the masses, of the forces and of the necessary reactions of the supporting plate 15 to make effective the drive 16 between the two electric motors of the standard type and the mandrel 1 that needs feeding of water inside its rotating shaft 24, to enable the correct operation of the rotating head with abrasive elements.
Moreover, the presence of the tongue 20 with the inclined lower end 21 allows to eliminate the vibration at the moment of the starting in rotation of the motors 17, drive 16, shaft 24 and rotating head with abrasive elements complex. This locking is practical and rapid in its application, in fact, the tongue 20, as shown in Figure 4, removes the possibility of rotational movements due to the minimum clearance in the sliding coupling of the body 12 of the mandrel with respect to the sleeve 3 that is fixed as said to the metal structure 2. Obviously the stop of the vibration at start occurs only in the preferred starting position in which the body 12 of the mandrel is completely lifted.
Furthermore, the shape of the coupling between the supporting plate 15 of the belt drive 16 and the body 12 of the mandrel enables a fast replacement of the drive 16 to adjust the actual gear ratio to the specific rotation need that may be required from a rotating head with abrasive elements. With the rotation of the supporting plate 15 and the disjointing of the coupling 37, the lobes 39 can be disjointed from the coupling for their passage in the ports 41 provided on the supporting plate 15. The lobes 39 are advantageously made on an applied ring 42 connected to the upper end 43 of the sliding body 12 of the mandrel. The plate has the lugs 40 provided with threaded holes 44 to house the screws 38 when tightened.
The advantages of a balanced mandrel bearing heads for sizing, smoothing or polishing natural stone materials and/or ceramic tiles described above, are summarized in a practical, simple and robust construction that allows to realize the necessary fine adjustment of the position exactly vertical to the working surface of the machine in which the mandrel 1 is inserted; this construction also allows to use driving means that are certainly less expensive than a gear drive as known in the art, in such a way as to make the on-site maintenance of the working machine of the stone materials for their sizing, smoothing or polishing very economical.
Moreover, the presence of the tongue 20 with the inclined end 21 combined with the hollow 22 that has the similarly inclined lower end 23, realizes in a simple and effective way the solution to the technical problem of limiting the vibrations at the start of the rotation of the complex of the motors 17, belt drive 16, holed shaft 24 and rotating head with the abrasive elements that are set in movement.
Finally, the use of the disjointable coupling 37 allows to make practical and fast the maintenance of the improved mandrel for rotating heads with abrasive elements, in such a way as to realize a precise rotation speed of the head for its most correct use.
Obviously, a person skilled in the art can make several changes to an improved mandrel for sizing, smoothing or polishing stone materials with rotating abrasive heads in order to meet specific and contingent needs, said changes being all contained within the scope of protection of the present invention as defined by the following claims.

Claims

Mandrel for sizing, smoothing or polishing stone materials with rotating abrasive heads, comprising: a sleeve (3) within which a body (12) of the mandrel is arranged slidingly which in its turn is provided with a shaft (24) at whose end a rotating head with abrasive tools is applied; a pair of actuating cylinders (13) for the positioning of said mandrel (1), that is to say, of the head connected to it, on the supporting metal structure (2); a pair of electric motors (17) for the activation in rotation of the mandrel and a drive from said motors to the shaft (24) of the mandrel; wherein said motors are coupled in rotation with the shaft of the mandrel with a belt drive; characterised in that it has the coupling between a supporting plate (15) of the belt drive (16) connected to the body (12) of the mandrel arranged slidingly within said adjustable sleeve (3), realized by a disjointable coupling (37) in which screws (38) clamp radial lobes (39) of the body of the mandrel to lugs (40), which are made in the centre of the supporting plate (15); the radial lobes (39) are alternated with ports (41) to allow the passage with clearance of the lugs (40), during the disjointing of the coupling with the rotation of the supporting plate (15) with respect to said lobes.
Mandrel, according to claim 1, in which the lobes (39) are advantageously made on an applied ring (42) connected to the upper end (43) of the slidingly arranged body (12) of the mandrel.
Mandrel, according to one of the claims 1 or 2, in which a tongue (20), provided with an axially inclined end (21), is inserted within a hollow (22) longitudinal to the axis of the mandrel and interposed between the slidingly arranged body (12) of the mandrel and its adjustable sleeve (3); said hollow having at its lower end (23) a correspondingly inclined shape connectable to the end (21) of the tongue (20).
Mandrel, according to claim 3, in which in combination with the hollow (22) shaped at its upper end there is between the slidingly arranged body (12) of the mandrel (1) and the adjustable sleeve (3) a further tongue (18) and a corresponding hollow (19) for the aligned guiding in a prearranged position between said slidingly arranged body and said adjustable sleeve.