The invention relates to a wire saw according to the preamble of claim 1 and a method for manufacturing a wire saw according to the preamble of claim 25.

EP2826582B1 discloses a wire saw comprising a cutting heat having a frame body and four openings for receiving a set of wire guide cylinders. The frame body is made of mineral casting and is combined with four bearing box sleeves and one or more temperature control shields. The frame body has two openings 102 provided for rotational axes 103. The bearing box sleeves 130 are provided in the openings 102, typically by gluing and/or press fitting. The forces acting on the wire guide rollers and between the wire guide rollers are introduced via the bearing box sleeves into the frame body. The temperature control shield has only cooling/heating function. The disadvantage of such a construction is that a very massive frame body has to be used in order to reliably absorb the forces resulting from the wire tension within the wire web (a wire web may consist of several thousand loop sections yielding loads of several tons). These forces act in a direction between the rotational axis of the wire guide rollers and will otherwise cause deformation of the frame body made of mineral casting. Frame deformation causes the wire guide rollers to be less well aligned, impairing the cutting quality.

CH690419A5 discloses a wire saw which is integrated in a frame constituted by a monobloc box structure made of a material with a low coefficient of expansion. The frame has an internal thermostatically controlled fluid circuit. The frame has four symmetrically located access openings forming four columns. The wire guide cylinders supported at their ends by bearings are integrated in the frame.

EP2546014A1 discloses an apparatus for driving a wire or wire-like objects that may be part of a wire saw.

WO2014087340A2 discloses a wire management system which may be part of a wire saw.

The object of the invention is to overcome problems arising if materials such as mineral casting or other materials having lower Youngs's modulus are used for making the frame of the wire saw. It is an aim of the invention to use a frame having lower weight and/or lower density and/or to allow easier frame manufacturing (casting) but at the same time to ensure high cutting quality by overcoming the problem of frame deformation. The manufacture of the wire saw should by easy and allow high flexibility during the manufacturing process. Also, the construction of the frame should take as little space as possible so that the wire guide rollers can be located closely together if needed.

The object is achieved by a wire saw as mentioned at the beginning in that the wire saw comprises at least one common bearing block, in which a first bearing supporting the first wire guide roller and a second bearing supporting the second wire guide roller are accommodated, wherein the at least one common bearing block is made of a second material and is mounted to the frame, wherein Young's modulus of the second material is higher, preferably at least 3 times higher, than Young's modulus of the first material.

Both wire guide rollers (spanning the cutting field) are supported at least at one of their ends by a common bearing block. In such a way the forces acting on the wire guide rollers due to the tension of cutting wire are introduced into the common bearing block, i.e. the common bearing block takes up these forces and the frame is relieved from forces and vibrations acting between the wire guide rollers. The common bearing block is preferably formed from one piece. The bearings (for the wire guide rollers) are accommodated within openings formed in the common bearing block. The common bearing block has the shape of eye-glasses or eye-glass-like shape.

In a preferred embodiment, the bearing block has a first opening and a second opening, wherein the first bearing is completely embedded within the first opening and the second bearing is completely embedded within the second opening. In such a manner a very stable construction is achieved. The forces acting between the wire guide rollers due to the tension of cutting field (i.e. radial forces) are entirely introduced into the common bearing block.

Preferably, in all directions extending perpendicular to the rotational axis of the wire guide rollers each of the first bearing and the second bearing is distanced from the first material of the frame by the second material of the bearing block. With other words: each of the first bearing and the second bearing is surrounded along its entire circumference, by the second material of the bearing block; or: Radially the bearings are completely enclosed by the second material of the bearing block. Again, a very stable construction is achieved. The frame is relieved from forces acting between the wire guide rollers due to the tension of cutting field.

Preferably, the first bearing and the second bearing are entirely supported by the common bearing block. The bearings are completely held by the common bearing block, i.e. they are not in contact with the frame. This ensures that forces acting between the wire guide rollers due to the tension of cutting field don't effect the first material of the frame.

The principle of the invention will be described with two wire guide rollers. However, in the case of three or four wire guide rollers the common bearing block may also accommodate a third or fourth bearing.

With the inventive solution the frame can be designed much slimmer und thus place-saving and lower-weighted than is the case in prior art. It is of course preferred that a first common bearing block supports the wire guide rollers at one of their ends and a second common bearing block supports the wire guide rollers a the other of their ends. The advantageous effect of the invention thus can be realized on both ends of the wire guide rollers.

The Young's modulus of the common bearing block(s) can be selected such, that the rotational axis of the wire guide rollers hardly shift upon stringing the cutting wire around the wire guide rollers. The selection will depend upon wire tension, length and diameter of wire guide rollers, type of material to be cut, etc.. In a preferred embodiment the second material (forming the common bearing block) is made of metal, preferably steel, such as spheroidal cast iron, ductile cast iron, etc..

Preferably, the second material is made of cast iron or cast steel, preferably spheroidal cast iron or ductile cast iron, in order to resist the strong forces acting on the common bearing block.

In a preferred embodiment the first wire guide roller and the second wire guide roller each comprise a plurality of wire guiding grooves running around the surface of the wire guide roller, wherein wire guiding grooves receive the ends of the wire sections forming the cutting field, wherein preferably the number of wire guiding grooves formed on a wire guide roller is larger than 500, preferably larger than 1000, more preferably larger than 2000. The wire sections of the cutting field are parallel to each other. Such a wire saw is used for making wafers from a (semiconductor) brick or ingot. Other typical materials cut with a wire saw are sapphire, boron, quartz, and rare earth metals.

Apart from the first and second wire guide roller the wire saw may comprise also further wire guiding-, deflection-, tension-, storing-, working- rollers.

Further advantages of the invention are that forces may be better and uniformly taken up by the frame and that the weight and/or dimensions (particularly thickness) of the frame may be reduced. Thus, also a considerable reduction in costs may be achieved. Moreover, the invention increases "parallelism" and/or "perpendicularity" of the wire guide rollers.

Also, the distance between the wire guide rollers may be reduced, because less material (as measures in volume) is needed, in order to achieve the stiffness and rigidity, which are necessary for high cutting quality.

The distance between the axis of the wire guide rollers, i.e. the distance between the bearings within a common bearing block, can be selected flexible. Whereas the design of the frame stays always the same, the design of the common bearing block (particularly the distance between the rotational axes) can be adapted according to customer wishes. In a preferred embodiment the at least one common bearing block is replaceably mounted to the frame. Preferably, the at least one common bearing block is embedded in a recess formed in the frame. Here, a strong and stable connection between the common bearing block(s) and the frame is achieved. Moreover, this embodiment is characterized by a place-saving design.

Preferably, the wire saw comprises two common bearing blocks, wherein each bearing block accommodates a first bearing supporting the first wire guide roller and a second bearing supporting the second wire guide roller, wherein one of the bearing blocks supports the wire guide rollers at one of their ends and the other bearing block supports the wire guide rollers at the other of their ends. Here, the advantageous effect of the invention, is realized at both ends of the wire guide rollers. The opposing frame portions each carrying or accommodating a common bearing block are prevented from deformation due to forces acting between the wire guide rollers (spanning the cutting field).

Preferably, the first material is mineral casting and the second material is a metal, preferably steel. Mineral casting usually has a Young's modulus ranging between 30 and 45 kN/mm ² . Steel has a Young's modulus around 210 kN/mm ² . The combination mineral casting (frame) and steel (common bearing block) is therefore a preferred embodiment.

Preferably, the common bearing block is surrounded, preferably along its entire circumference, by the first material of the frame. Here, a strong and immoveable connection between the frame (first material) and the common bearing block (second material) may be established. Preferably, the at least one common bearing block is glued into the recess or recasted within the recess, preferably by the same material as used for the frame. The glue/ cast material may consist e.g. of mineral casting mass (liquid or pasty) that is introduced into the recess after the frame has already been completed.

Preferably, the outside of the common bearing block and/or the inner wall of the recess have a groove, preferably a circumferentially running groove, which is filled with glue or cast material.

Preferably, the wire guide rollers extend between opposing frame walls of the frame, wherein in each frame wall a recess is formed in which a common bearing block supporting the wire guide rollers is embedded.

Preferably, the frame has an opening, preferably adjacent to, more preferably above the at least one common bearing block, for moving the piece of material into the cutting area of the wire saw, wherein preferably at least one of the common bearing block(s) has an indentation adjacent to the opening. In this embodiment introduction of the piece of material (e.g. ingot, brick or core) usually glued to a workpiece holder / fixture attachment into the cutting area of the wire saw is facilitated.

Preferably, the wire saw has at least one cutting wire spool for temporarily storing cutting wire, wherein the cutting wire spool is in co-operation with the wire guide rollers via the cutting wire and is arranged in a space separated from and/or arranged below the cutting area of the wire saw. Preferably, the wire saw has at least two cutting wire spools for temporarily storing cutting wire: a wire supply spool (unused wire) and a wire reservoir spool (used wire). Usually also deflection and/or tension spools are provided in a wire saw. The advantage of this embodiment is that the wire saw can be designed very compactly and in a place-saving manner, if the spool(s) are arranged below the cutting area, i.e. the area in which the wire guide rollers and the cutting field are arranged. The arrangement below the cutting area becomes possible, because the frame can be dimensioned lower-weighted and thus more space- saving. The cutting wire has a shorter path between the wire guide rollers and the at least one cutting wire spool, resulting in shorter tolerance chains and making alignment of spools and/or pulleys easier.

Preferably, the shape of the at least one common bearing block is essentially rectangular or oval.

Preferably, the width of the at least common bearing block is at least 1,5 times, preferably at least 2 times, larger than its height. As "width of the common bearing block" the dimension parallel to the direction between the axis of the wire guide rollers is understood. Usually, the cutting field is horizontal and thus also the width of the common bearing block is a horizontal dimension.

Preferably, the width of the at least one common bearing block is larger than the sum of the distance between the rotational axis of the wire guiding rollers and at least once, preferably 1.5 times the diameter of a wire guiding roller. This embodiment implies that bearing blocks of different distances between first and second bearing may be used during manufacture of the wire saw, enabling the wire saw to be tailor made to customer specifications in a late stage of the manufacturing process. The size of the recess formed in the frame may be the same for all frames produced within a cycle. However, there is the option to use different bearing blocks for example bearing blocks having the same width and/or height but different distance between the bearings. Also the bearing block may be made stronger if harder materials are cut. Here, high flexibility is achieved for the customer.

Preferably, the recess is formed as going-through opening within a frame wall of frame and/or wherein the common bearing block is embedded within the recess in a form-fitting manner, preferably leaving space for an adhesive. The support of the common bearing block within the frame is reliable, stable and immoveable.

Preferably, the width (i.e. dimension parallel to the connection line between the axis of the wire guide rollers) of the recess formed in the frame is at least 10% larger than the width of the common bearing block, preferably at least 15% larger, even more preferably at least 20% larger. Here, also "smaller" bearing blocks may be used. The free space(s) between bearing block and frame may be filled by intermediate pieces (placeholder). The common bearing block may have cooperating/positioning portions for positioning it in the recess so that its positioning can be established correctly, even if the recess is (much) larger than the common bearing block.

Thus, in a preferred embodiment the at least one common bearing block has at least one positioning structure cooperating with a corresponding (preferably form-fitting) positioning structure formed at the frame.

In a preferred embodiment at least one, preferably each, of the first bearing and the second bearing is enclosed by a sleeve, which in radial direction separates the respective bearing from the material of the common bearing block, wherein preferably the sleeve is with its outer surface in direct contact with the material of the common bearing block. The sleeve(s) helps to evenly distribute the forces acting from the bearings on the common bearing block.

In a preferred embodiment the wire saw has at least one motor for driving at least one of the wire guide rollers, wherein the motor is attached to the common bearing block, wherein preferably the motor is completely supported by the common bearing block. In such a way the frame is also decoupled from the driving forces. It is preferred, if the whole weight of the motor is carried by the common bearing block.

In a preferred embodiment the common bearing block has a weight of at least 100kg, preferably of at least 150kg, more preferred of at least 180kg. The large weight of the common bearing block ensures a stable construction which is not only capable of taking up forces acting between the wire guide rollers but also reduces transfer of vibrations to the frame (large inertia).

In a preferred embodiment the common bearing block has in direction of the rotational axes of the bearings a thickness of at least 150mm, preferably of at least 180mm. Such a massive common bearing block reliably absorbs the forces resulting from the wire tension within the wire web (a wire web may consist of several thousand loop sections yielding loads of several tons). The same holds for the following embodiment.

In a preferred embodiment the volume portion of the common bearing block which extends between the bearings amounts to at least 5.000cm ³ , preferably to at least 7.500cm ³ . Said volume portion is defined as the portion which is laterally bordered by the bearings and in vertical direction by an upper plane, which includes the uppermost points of both bearings, and by a lower plane which includes the lowermost points of both bearings.

In a preferred embodiment at least one lead-through, preferably a channel, is formed within the common bearing block, wherein preferably the lead-through is adapted to accommodate a cable and/or a cooling medium and/or a pressurized medium. Here, the common bearing block has additional function(s). One of these functions may be cooling of the bearings by means of a (circulating) cooling medium, preferably cooling fluid. Preferably, an end of a lead-through within the common bearing block is coupled to an end of a lead-through formed within the frame.

The object is also achieved with a method for manufacturing a wire saw according to the invention, comprising the step of: mounting the at least one common bearing block to the frame, preferably embedding the at least one common bearing block within the frame, preferably by means of glue.

Preferably, the frame is casted, preferably from mineral casting, and wherein the common bearing block is embedded within the frame subsequently to or during casting the frame.

Preferably, the at least one common bearing block is embedded within a recess formed in the frame, wherein preferably the recess is formed during casting the frame.

Further embodiments of the invention are indicated in the figures and in the dependent claims. The list of reference marks forms part of the disclosure. The invention will now be explained in detail by the drawings. In the drawings: Fig. 1 shows the frame of a wire saw with embedded bearing blocks according to an embodiment of the invention,

Fig.2 shows a wire saw with a frame according to Fig. 1 ,

Fig.3 shows a wire saw with cutting wire spools in a space below the cutting area,

Fig.4 shows an embodiment with a larger distance between the bearing openings in the bearing block,

Fig. 5 shows an embodiment with a shorter distance between the bearing openings in the bearing block,

Fig. 6 shows an embodiment in which the width of the bearing block is smaller than the width of the recess formed in the frame,

Fig.7 shows schematically a method of manufacturing a wire saw, and

Fig. 8 shows a preferred embodiment of the wire saw.

Fig. 2 and 3 show wire saws 10 according to the invention for cutting a piece of material 20, particularly for slicing, squaring and/or bricking a piece of material such as hard brittle and/or semiconductor material. Fig. 1 shows the frame 3 of the wire saw 10 shown in Fig.2.

Wire saw 10 comprises a first wire guide roller 1 and a second wire guide roller 2 for supporting a cutting field 19 formed from cutting wire. A frame 3 supports the wire guide rollers 1, 2 and is made of a first material. The wire guide rollers 1, 2 are rotatably mounted to the frame 3 via bearings 4, 5. The wire saw 10 comprises at least one common bearing block 6, in which a first bearing 4 supporting the first wire guide roller 1 and a second bearing 5 supporting the second wire guide roller 2 are accommodated. In the preferred embodiment of Fig. 1 and 2 the wire saw 10 comprises two common bearing blocks 6, wherein each bearing block 6 accommodates a first bearing 4 supporting the first wire guide roller 1 and a second bearing 5 supporting the second wire guide roller 2. One of the bearing blocks 6 supports the wire guide rollers 1 , 2 at one of their ends and the other bearing block 6 supports the wire guide rollers 1 , 2 at the other of their ends. The bearing blocks 6 each have a first opening 14 (accommodating the first bearing 4) and a second opening 15 (accommodating the second bearing 5). As can be seen from Fig. 1 and 3 the first bearing 4 is completely embedded within the first opening 14 and the second bearing 5 is completely embedded within the second opening 15. In all directions extending perpendicular to the rotational axis of the wire guide rollers 1, 2 each of the first bearing 4 and the second bearing 5 is distanced from the first material of the frame 3 by the second material of the bearing block 6. The first bearing 4 and the second bearing 5 are entirely supported by the common bearing block 6. Each bearing block 6 is mounted to the frame 3. In the preferred embodiment, the bearing blocks 6 are embedded in a recess 7 formed in the frame 3 (Fig. 1). The recess 7 may be formed as going-through opening within a frame wall 8, 9 of frame 3 and the common bearing block 6 may be embedded within the recess 7 in a form- fitting manner.

The common bearing block(s) 6 is/are made of a second material, wherein Young's modulus of the second material (bearing block) is higher, preferably at least 3 times higher, than Young's modulus of the first material (frame).

It is preferred if the first material is mineral casting (having a Young's moduli of approx. 30 - 45 kN/mm ² ) and the second material is a metal, preferably steel (having Young's moduli of approx. 150 - 220 kN/mm ² ). The forces acting between the wire guide rollers 1, 2 due to the tension of cutting field 19 is taken up by the common bearing blocks 6 and the frame 3 is relieved from these forces.

The common bearing block 6 may be surrounded, preferably along its entire circumference, by the first material of frame 3 (Fig. 1). The at least one common bearing block (6) is glued into or recasted (once the common bearing block is in place, the material used for the frame is casted between the frame and the common bearing block) within the recess 7, preferably by the same material as used for the frame 3.

As can be seen from Fig. 2, the wire guide rollers 1, 2 extend between opposing frame walls 8, 9 of frame 3, wherein in each frame wall 8, 9 a recess 7 is formed in which a common bearing block 6 supporting the wire guide rollers 1 , 2 is embedded.

The frame 3 may have an opening 11 (here: above at least one common bearing block 6) for moving the piece of material into the cutting area of the wire saw 10. In order optimize the design and the introduction of the piece of material at least one common bearing block 6 may have an indentation 12 adjacent to the opening 11. As can be seen from Fig. 3 the wire saw 10 may have at least one (here: two) cutting wire spool(s) 17, 18 for temporarily storing cutting wire. The cutting wire spools 17, 18 are in co-operation with the wire guide rollers 1 , 2 via the cutting wire and is arranged in a space separated from and arranged below the cutting area of the wire saw 10. The space where the spools 17, 18 are arranged is separated from the cutting area by means of a wall 16.

The shape of the bearing blocks 6 is essentially rectangular or oval. When e.g. three wire guide rollers need to be accommodated, the bearing block may have a general triangular shape (with three recesses). The bearing blocks 6 each have a first opening 14 (accommodating the first bearing 4) and a second opening 15 (accommodating the second bearing 5); see Figs. 4-6. The bearing blocks 6 therefore have eye-glass-like shape.

In Figs.4-6 the flexibility of the bearing block concept is illustrated. Dependent upon customer wishes different bearing blocks 6 may be mounted to the frame 3 (without changing the design of frame 3).

Fig. 4 shows a bearing block 6 with a larger distance between the openings 14, 15.

If the distance between the wire guide rollers 1, 2 has to be smaller, a bearing block according to Fig. 5 may be used. Here, it is preferred that the width of the at least one common bearing block 6 is larger than the sum of the distance between the rotational axis of the wire guiding rollers 1, 2 and at least once, preferably 1.5 times the diameter of a wire guiding roller 1 , 2. In the embodiment of Fig. 6 the width of the recess 7 is larger than the width of the bearing block 6. Here, it may be preferred that the recess 7 formed in the frame 3 is at least 10% larger than the width of the common bearing block 6, preferably at least 15% larger, even more preferably at least 20% larger. The intermediate space may be filled by means of a filling material 13 (e.g. mineral cast material, metal plates, etc.).

Figs.4-6 also show positioning structures 21 formed on the bearing block 6. The positioning structures 21 cooperate with corresponding positioning structures formed at the frame 3.

The invention also relates to a method 100 for manufacturing a wire saw 10 (Fig. 7) comprising: a step 102 of mounting/embedding the at least one common bearing block 6 within the frame 3 that has been previously casted in a step 101. The recess 7 is preferably formed during the casting process 101. The step 102 of embedding the common bearing block 6 is preferably done by means of glue or cast material. The frame 3 may be casted, preferably from mineral casting, and the common bearing block(s) 6 is/are embedded within the frame 3 subsequently to or (alternatively) during casting the frame 3.

Fig. 8 shows an embodiment of a wire saw 10. The bearing 4 is enclosed by a sleeve 24, which in radial direction separates the bearing 4 from the material of the common bearing block 6. The sleeve 24 may be with its outer surface in direct contact with the material of the common bearing block 6.

As can be seen from Fig. 8 the motor 22 for driving the wire guide roller is attached to the common bearing block 6. The motor 22 may be completely supported by the common bearing block 6. As already mentioned the common bearing block 6

- may have a weight of at least 100kg, preferably of at least 150kg, more preferred of at least 180kg, and/or

- may have in direction of the rotational axes of the bearings a thickness of at least 150mm, preferably of at least 180mm.

In a preferred embodiment the volume portion of the common bearing block which extends between the bearings 4, 5 amounts to at least 5.000cm ³ , preferably to at least 7.500cm ³ .

Fig. 8 also shows a lead-through 23 in form of a channel which is formed within the common bearing block 6. The lead-through 23 may accommodate a cable and/or a cooling medium and/or a pressurized medium. An end of a lead-through 23 within the common bearing block 6 may be in communication with an end of a lead-through formed within the frame 3.

The invention is not restricted to these embodiments. Other variants will be obvious for the person skilled in the art and are considered to lie within the scope of the invention as formulated in the following claims. Individual features described in above specification, particularly with respect to the figures may be combined with each other to form other embodiments and/or applied mutatis mutandis to what is described in the claims and to the rest of the description. List of reference first wire guide roller

second wire guide roller

frame

first bearing

second bearing

common bearing block

recess

frame wall

frame wall

wire saw

opening

indentation

filling material

first opening

second opening

wall

supply spool

reservoir spool

cutting field

workpiece

positioning structure

motor

lead-through

sleeve