Thin section bearing unit

Abstract

A thin-section bearing unit (10) for a multi-strand machine, the bearing unit having a central rotation axis (A) and comprising: - a fixed inner ring (20); - a rotatable flanged outer ring (30), the axial dimension of which is less than the axial dimension of the inner ring (20); - a first (41) and a second (42) column of rolling elements (40) axially close to each other, wherein the axial distance (D2) between the rolling elements (40) of the first column (41) and the rolling elements (40) of the second column (42) is between 0.8 mm and 0.9 mm; - a first (43) and a second (44) cage for holding the rolling elements (40) of the respective first (41) and second (42) column, the cages (43, 44) being made of plastic material and being configured to hold the rolling elements (40) on only one side of the rolling elements of the respective column (41, 42); - only two sealing shields (50, 50'), arranged on axially opposite sides of the bearing unit (10) and interposed between the inner ring (20) and the outer ring (30).

Description

Technical Field

[0001] This invention relates to a thin-section bearing unit.

[0002] In particular, the present invention relates to a thin-section bearing unit for multiwire machines, which will be referred to in this specification without prejudice to their general applicability. Background Technology

[0003] In a multi-wire cutting machine, blocks of stone material (such as stone, marble, concrete, etc.) are cut into slabs by the action of diamond cutting wires. The diamond cutting wires are positioned parallel to each other along the cutting path and are pulled along this path by tensioner pulleys. To produce slabs with very thin thicknesses, the tensioner pulleys are assembled as a set, one next to the other in the axial direction, on a common support shaft and are rotatable relative to the support shaft by the interposition of corresponding thin-section bearing units.

[0004] Therefore, the known thin-section bearing units for multi-line machines are also mounted in sets, one next to the other, along a corresponding common central axis of rotation defined by the support shaft. Although the corresponding outer diameters of the thin-section bearing units are quite large, they must have very small axial thicknesses to allow the tensioner pulleys to be mounted as close to each other as possible in the axial direction. The combination of large diameter and small axial thickness requires particularly complex technical solutions to ensure consistent high performance.

[0005] This bearing unit includes:

[0006] - Corresponding fixed (stationary) inner rings are configured to be axially adjacent to each other;

[0007] - A corresponding rotatable outer ring, the axial dimension of which is slightly smaller than that of the corresponding inner ring, so that it can rotate independently of each other and allow the corresponding tensioner pulley to rotate independently;

[0008] - A row of rolling elements, preferably balls, is positioned between an inner and outer ring to allow relative rotation between the inner and outer rings, wherein the rolling elements are held in place by a cage made of pressed steel, the cage surrounding the rolling elements on two axially opposite sides of the row; and

[0009] - Corresponding shielding elements are configured on the axially opposite sides of the row of rolling elements and placed between the relevant inner and outer rings to prevent contaminating materials (such as water mixed with stone powder) from entering the bearing unit and to prevent internal grease from dispersing outward.

[0010] Each outer ring has a corresponding support flange connected to the associated pulley, while each inner ring is laterally defined by a corresponding annular surface positioned to directly contact the annular surface of the inner ring of the axially adjacent bearing unit.

[0011] Reducing the axial thickness of these bearing units is a primary objective of the solution designed for multi-wire machines, as each bearing unit corresponds to a pulley, and each pulley corresponds to a diamond wire. This means that any further reduction in the axial thickness of the bearing units allows for a corresponding reduction in the axial bulk of the pulleys, and thus a reduction in the center-to-center distance between the diamond wires. Ultimately, further reductions in the axial thickness of the bearing units will enable the production of increasingly thinner (or slenderer) slabs of the stone material.

[0012] However, reducing the axial thickness of the bearing unit means reducing the diameter of the rolling elements, and thus reducing the load capacity of the bearing unit. Summary of the Invention

[0013] The purpose of this invention is to produce a thin-section bearing unit that overcomes the above-mentioned shortcomings and is entirely beneficial to the production efficiency of related multi-line machines.

[0014] The thin-section bearing unit for a multi-line machine according to the present invention has the features set forth in the appended claims. Attached Figure Description

[0015] The invention will now be described with reference to the accompanying drawings, which illustrate non-limiting embodiments of the invention, in which:

[0016] - Figure 1 A thin-section bearing unit according to a preferred embodiment of the present invention is shown in cross-section.

[0017] - Figure 2 yes Figure 1 A three-dimensional view of the cage of the bearing unit.

[0018] - Figure 3 Shown in cross-section and magnified scale Figure 1 Details of the bearing unit, and

[0019] - Figure 4 It includes Figure 1 A partial cross-sectional view of a multi-line machine with a thin-section bearing unit. Detailed Implementation

[0020] Reference Figure 1 Reference numeral 10 in the figure generally indicates a bearing unit with a thin cross section.

[0021] The bearing unit 10 occupies very little space in the axial direction, so that it can be installed together with other identical bearing units in the idler unit of the multiline machine. The idler unit may include two or more than one hundred (e.g., thirty to one hundred and fifteen) bearing units 10, all of which are identical to each other and are placed side by side along a corresponding common central axis of rotation A.

[0022] The thin-section bearing unit 10 of the present invention can be advantageously used in multi-wire machines, the following description of which will be made by way of example with reference to such a machine without prejudice to its general applicability. In such a multi-wire machine, blocks of stone material are cut into slabs by the action of diamond cutting wires positioned parallel to each other along the blocks and pulled on these blocks by tensioner pulleys 100. To produce these slabs, the tensioner pulleys are assembled in sets, one on each side in the axial direction, on a common support shaft (not shown) defining a central axis A, and are rotatable relative to the support shaft by means of the insertion of the corresponding bearing unit 10.

[0023] Throughout this specification and claims, terms and expressions indicating position and direction, such as “radial,” “axial,” or “lateral,” should be understood in reference to the axis of rotation A.

[0024] According to the present invention and as Figure 1 As shown, the bearing unit 10 includes:

[0025] - A stationary inner ring 20 is mounted on the fixed shaft of a multi-line machine (multi-line machines are known and therefore not shown in the figure);

[0026] - A rotatable flanged outer ring 30, the axial thickness S2 of the outer ring 30 being smaller than the axial thickness S1 of the inner ring 20, and the outer ring 30 together with the inner ring 20 defining a cylindrical cavity 90.

[0027] - Two columns of 41 and 42 rolling elements 40;

[0028] - Two cages 43 and 44 for holding the rolling element 40;

[0029] - Two shields 50, 50' are configured on opposite axial sides of the bearing unit 10 and positioned between the inner ring 20 and the outer ring 30. Only two shields 50, 50' are present, instead of four shields as in the prior art where a bearing unit has a pair of bearings with a single row of rolling elements (where the corresponding shields are configured on opposite axial sides of each row).

[0030] The inner ring 20 is provided with a first raceway 22 and a second raceway 23 on the radially outer side, in which the rolling elements 40 of the corresponding first row 41 and second row 42 roll. On each side L of the bearing unit 10, the inner ring 20 is axially defined by two annular surfaces 21 and 21' arranged in series from the outer side of the bearing unit 10 toward the axis A, with the two surfaces 21' set back axially relative to the surface 21. Furthermore, the inner ring 20 is radially inner defined by a cylindrical surface 24 coaxial with the axis A and orthogonal to the two annular surfaces 21, and radially outer defined by a surface 25, which is also cylindrical, coaxial with the axis A, and orthogonal to the two annular surfaces 21, and includes the first raceway 22 and the second raceway 23 of the inner ring 20.

[0031] The outer ring 30 is provided with a first raceway 32 and a second raceway 33 radially inward, in which the rolling elements 40 of the corresponding first row 41 and second row 42 roll. The raceways 32 and 33 of the outer ring 30 radially face the corresponding raceways 22 and 23 of the inner ring. Furthermore, on each side L of the bearing unit 10, the flanged outer ring 30 is axially defined by an annular surface 34 orthogonal to the axis A. The flanged outer ring 30 is radially outward defined by a cylindrical surface 35 coaxial with the axis A and orthogonal to the annular surface 34, and radially inward defined by a surface 36, which is also cylindrical, coaxial with the axis A and orthogonal to the annular surface 34, and includes the first raceway 32 and the second raceway 33 of the outer ring 30. The outer ring 30 also has a support flange 31 that extends radially outward from the outer ring 30 transverse to axis A and is connected to a portion 101 of the pulley 100 of the multi-thread machine that is radially inward.

[0032] Two rows of rolling elements 40 (preferably balls) 41, 42 are arranged inside the cavity 90 and positioned between the inner ring 20 and the outer ring 30 to allow the inner and outer rings to rotate relative to each other about axis A. The rolling elements 40 have the same diameter as rolling elements in known solutions to achieve the same load capacity. Clearly, the total load that can be supported by the bearing unit 10 is equivalent to the load that can be supported by two bearing units of a known type (i.e., with a single row of balls). To minimize the axial volume of the bearing unit, the rolling elements 40 of the first row 41 and the second row 42 are positioned as close as possible to each other axially, thus minimizing the axial distance D2 between the first row 41 and the second row 42 (e.g., ...). Figure 3 (As shown) to be minimized. However, at the same time, it must be ensured that there is no interference between the rolling elements in different columns. In this invention, this trade-off (minimum axial distance / axial interference between two rolling elements in different columns) is achieved by limiting the allowable range of the axial distance D2 to between 0.8 mm and 0.9 mm.

[0033] Cages 43 and 44, made of plastic material, hold the rolling elements in their respective circumferential positions. These cages are designed to reduce the axial bulk of the bearing unit and have limited axial and radial volume themselves. Specifically, and referring to... Figure 2 , Figure 2A first cage 43 is shown (the following description also applies to a second cage 44, which is identical to and mirrors the first cage 43). Each cage 43, 44 further includes a frame 45 with a circular base and a plurality of tenons 46 integral with the frame, axially facing away from the frame in a single direction (axially inward). The tenons 46 are circumferentially spaced and define a plurality of alveoli 47 in pairs between them to retain corresponding rolling elements. The fact that the tenons 46 face away from the frame 45 only in the axially inward direction and thus retain the rolling elements only on one side of the row of rolling elements (as a reminder, in known solutions, a press steel cage surrounds the rolling elements on opposite axial sides of this row) allows for a reduction in the axial volume of the cages 43, 44. The base frame 45 is a continuous annular structural element extending circumferentially about axis A, forming a solid base and providing the cage with the necessary rigidity to retain the equidistant rolling elements. The base frame 45 is defined radially inward by a first cylindrical surface 45a, radially outward by a second cylindrical surface 45b, and axially by an annular surface 45c transverse to axis A. On the other hand, the tenons 46 that receive and hold the rolling element between them must exhibit substantially resilient behavior, allowing the tenons to move apart to allow insertion of the ball, and then close substantially again around the ball to hold it within the associated recess 47. The tenons 46 are circumferentially spaced and have a curved shape. Two circumferentially adjacent tenons 46 have corresponding concave surfaces 46' facing each other, and each recess 47 is defined by a pair of circumferentially adjacent tenons 42.

[0034] Of the two sealing shields 50 and 50', the first sealing shield 50 is axially outwardly positioned relative to the first row 41 rolling elements 40, and the second sealing shield 50' is axially outwardly positioned relative to the second row 42 rolling elements 40. The sealing shields 50 and 50' serve both to prevent contaminating materials (e.g., water mixed with stone powder) from entering the cavity 90 of the bearing unit 10 and to prevent the grease contained within the cavity 90 from dispersing outwards. The sealing shields 50 and 50' are mounted on the outer ring 30, and therefore the sealing shields themselves are rotatable.

[0035] Reference Figure 3 Each sealing shield 50, 50' comprises, in series (or sequentially) from the outer ring 30 toward axis A:

[0036] - The first flange portion 51 mounted on the outer ring 30

[0037] - The inclined portion 52 is stably connected to the first flange portion 51.

[0038] - The second flange portion 53 is stably connected to the inclined portion by means of its radially outer edge 53b, and is provided with an axially inner annular surface 53a, and

[0039] - The cylindrical portion 54 interacts with the inner ring, defining a channel (meatus) on the surface that serves as a labyrinth seal.

[0040] Since the diameter of the rolling element in the bearing unit 10 according to the invention is the same as in the known solution so as not to impair the load capacity of the bearing unit, the design solution described above and further elaborated below for convenience is such that the axial thickness of the bearing unit is less than the sum of the axial thicknesses of a pair of bearing units with a single row of rolling elements according to the prior art.

[0041] First, the bearing unit according to the invention requires only two sealing shields, while the equivalent known solution consisting of two bearing units with single-row balls facing each other axially requires a total of four sealing shields (two sealing shields per unit). Therefore, compared to the equivalent known solution, this solution can eliminate two sealing shields, and in this way, the total axial thickness of the bearing unit 10 with double-row rolling elements can be reduced by the axial volume of the two unused sealing shields.

[0042] Omitting the two sealing shields does not compromise the sealing efficiency of the bearing unit 10: the bearing unit 10 is protected on both axially opposite sides by sealing shields placed between the inner ring 20 and the outer ring 30, and the design is unchanged from the prior art, which has proven to be perfectly adequate.

[0043] By designing the retainers 43 and 44 such that the tenon 46 holds the rolling element 40 only on one side of the rolling elements 41 in rows 41 and 42, a further axial reduction in the total thickness is achieved.

[0044] Furthermore, two other features of the present invention help to reduce the total axial volume of the bearing unit 10:

[0045] a) The retainers 43 and 44 are designed such that their radial extension is less than the radial extension of the second flanged portion 53 of the sealing shields 50 and 50'. In other words, the diameter of the second cylindrical surface 45b of the frame 45 of the retainers 43 and 44 is less than the diameter of the circumference of the radially outer edge 53b of the second flanged portion 53 of the shields 50 and 50'. This is achieved by making the retainers 43 and 44 asymmetrical with respect to the plane P tangent to the circumference C of the center of the rolling element 40. This prevents the retainers 43 and 44 from contacting the inclined portion 52. Therefore, the retainers 43 and 44 can be placed axially close to the shields 50 and 50', in other words, minimizing the axial distance D1 between the annular surface 45c of the frame 45 of the retainers 43 and 44 and the annular surface 53a of the second flanged portion 53 of the shields 50 and 50'.

[0046] (b) The inclined portions 52 of the sealing shields 50, 50' have axial protrusions, the length L of which is minimized. However, at the same time, the required rigidity of the shields 50, 50' must be ensured, hence the need for the inclined portions 52. In this invention, this trade-off is achieved by limiting the allowable range of length L between 1.5 mm and 3 mm (minimum axial length of the inclined portion / sufficient rigidity of the shield).

[0047] By omitting the two sealing shields along with the other configurations described, a reduction in the axial volume of bearing unit 10 is ensured, which is quite significant and equal to approximately 20% of the axial thickness relative to known solutions.

[0048] Therefore, and also refer to Figure 4 Compared to known solutions, the bearing unit 10 with double-row rolling elements can therefore reduce the axial volume for the same load capacity. Thus, a pulley 100 with substantially the same axial volume as the bearing unit 10 can be provided, and the pulley 100 is provided with a first channel 105 and a second channel 110 for receiving diamond wires in each channel (for simplicity, the diamond wires are not depicted but are schematically shown by the corresponding axes of symmetry X, X'). Therefore, the center-to-center distance between the diamond wires of the pulley 100 and the center-to-center distance between the diamond wires of adjacent pulleys will be smaller than the center-to-center distance between the diamond wires in known solutions (bearing units with paired single-row rolling elements). Therefore, the bearing unit 10 with double-row rolling elements according to the invention makes it possible to design multi-line machines capable of producing stone slabs thinner than those obtainable using known solutions.

[0049] Compared to the stiffness of a bearing unit with a single row of rolling elements, this solution also improves the overall stiffness of the bearing unit. In fact, since the outer ring is supported by two rows of balls, the oscillation of the outer ring 30 is significantly reduced in the event of vibrations caused by a multi-row machine. This is because the solution with two rows of balls creates two contact points on the inner ring and two contact points on the outer ring. Compared to the case of a solution with a single row of balls and a single contact point per ring, this reduces the maximum elastic deflection that the outermost radial point of the support flange 31 (and therefore the outermost radial point of the pulley 100) can have. Therefore, the bearing unit according to the invention has much greater stiffness than the standard solution. Consequently, the cutting of stone materials will be more precise.

[0050] In summary, according to the solution of the present invention, the bearing unit with double-row balls having optimized geometry enables the reduction of the thickness of the stone slab and the improvement of the cutting accuracy of the slab.

[0051] In addition to the embodiments of the invention described above, it should be understood that many other variations exist. It should also be understood that the described embodiments are merely examples and do not limit the subject matter, application, or possible constructions of the invention. Rather, while the foregoing description enables those skilled in the art to apply the invention according to at least one exemplary construction, it should be understood that many variations of the described components can be proposed without departing from the subject matter of the invention as defined in the appended claims, and interpreted literally and / or according to their legal equivalents.

Claims

1. A thin-section bearing unit (10) for a multi-line machine, the bearing unit having a central rotation axis (A) and comprising: - Fixed inner ring (20); - A rotatable flanged outer ring (30), the axial dimension of which is smaller than that of the inner ring (20); and The bearing unit (10) is characterized in that, in combination, the bearing unit (10) further includes: - Rolling elements (40) of a first column (41) and rolling elements (40) of a second column (42) that are axially close to each other, wherein the axial distance (D2) between the rolling elements (40) of the first column (41) and the rolling elements (40) of the second column (42) is between 0.8 mm and 0.9 mm; - A first retainer (43) and a second retainer (44) for holding the rolling elements (40) of the respective first column (41) and second column (42), the retainers (43, 44) being made of plastic material and configured to hold the rolling elements (40) only on one side of the rolling elements of the respective columns (41, 42). - Only two sealing shields (50, 50') are configured on opposite axial sides of the bearing unit (10) and placed between the inner ring (20) and the outer ring (30).

2. The bearing unit (10) according to claim 1, characterized in that, The first sealing shield (50) is axially outward positioned relative to the rolling element (40) of the first column (41), and the second sealing shield (50') is axially outward positioned relative to the rolling element (40) of the second column (42).

3. The bearing unit (10) according to claim 1 or 2, characterized in that, Each retainer (43, 44) includes a frame (45) with a circular base and a plurality of tenons (46) integral with the frame and axially opposed to the frame in a single axial inward direction. The tenons (46) are spaced apart in the circumferential direction and define a plurality of recesses (47) in pairs between them to retain a corresponding rolling element (40) only on one side of the rolling element of the corresponding column (41, 42).

4. The bearing unit (10) according to any one of the preceding claims, characterized in that, Each sealing shield (50, 50') comprises, in series, the outer ring (30) toward the axis (A): - The first flange portion (51) mounted on the outer ring (30). - The inclined portion (52) is stably connected to the first flange portion (51). - The second flange portion (53) is stably connected to the inclined portion (52), and - Cylindrical section (54).

5. The bearing unit (10) according to claim 4, characterized in that, The inclined portion (52) of the sealing shield (50, 50') has an axial protrusion with a length (L) between 1.5 mm and 3 mm.

6. The bearing unit (10) according to claim 4, characterized in that, The second flange portion (53) is stably connected to the inclined portion by means of its radially outer edge (53b) and is provided with an annular surface (53a) in the axial direction.

7. The bearing unit (10) according to claim 3, characterized in that, The base frame (45) of the retainer (43, 44) is defined radially inward by a first cylindrical surface (45a), radially outward by a second cylindrical surface (45b), and axially by an annular surface (45c) transverse to the axis (A).

8. The bearing unit (10) according to claims 6 and 7, characterized in that, The diameter of the second cylindrical surface (45b) of the frame (45) of the retainer (43, 44) is smaller than the diameter of the circumference of the radially outer edge (53b) of the second flange portion (53) of the sealing shield (50, 50').

9. The bearing unit according to claim 8, characterized in that, The cages (43, 44) are asymmetrical with respect to the plane (P) that is tangent to the circumference (C) of the center of the rolling element (40).

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