Tool holder for a tool assembly and a tool assembly including a tool holder

Abstract

The present invention relates to a tool holder (12) for a tool assembly (10), wherein the tool holder (12) comprises: a tubular element (20) having a cavity (26) and a central axis (16); a damping mass (28) configured within the cavity (26) and radially movable with respect to the central axis (16) and the tubular element (20); and an adapter (22) having a rear portion (34) fixed to the tubular element (20) and a front portion (32) for connection to an end effector (14) of the tool assembly (10), wherein the rear portion (34) includes an opening (40) and the damping mass (28) is at least partially received in the opening (40) with a radial gap. and an elastic element (42) positioned between the adapter (22) and the damping mass (28), wherein the elastic element (42) is configured to support the damping mass (28) and dampen radial vibration movements of the damping mass (28) relative to the tubular element (20), and the elastic element (42) comprises a front surface (44) substantially perpendicular to the central axis (16) and a rear surface (46) substantially perpendicular to the central axis (16).

Description

Technology Field

[0001] The present invention generally relates to a tool holder. In particular, a tool holder having an adapter having an opening for receiving a damping mass, a tool assembly comprising such a tool holder, a tool holder having an adapter integrated with a tubular element, a tool assembly comprising such a tool holder, a tool holder having a damping mass that balances before assembling the damping mass to the tubular element, and a tool assembly comprising such a tool holder are provided. Background Technology

[0002] Tool assemblies can be used in various machining processes such as milling, turning, boring, grinding, and drilling. Machining vibration, also known as chatter, occurs naturally during machining operations and corresponds to the relative movement between the workpiece and the cutting tool assembly. Tool assemblies often use material removal rate / productivity as a key performance indicator. A high material removal rate requires high speed, high depth of cut, and high feed rates. All three of these parameters tend to increase vibration in the machining process.

[0003] Vibrations cause waves to form on the machined surface. Additionally, vibrations of the tool assembly are often harmful and can damage the workpiece and / or the tool assembly itself.

[0004] To dampen the vibration of the tool assembly, the tool assembly may include a tool holder having a damping mass inside. Vibrational kinetic energy is transferred to the damping mass to stabilize the movement of the tool assembly.

[0005] WO2019168448A1 discloses a mass damper for a cutting tool, the mass damper comprising at least one damping mass; and at least one spring element configured to support the damping mass. The damping mass may be chamfered at each end. The problem to be solved

[0006] One objective of the present invention is to provide a tool holder for a tool assembly with improved performance.

[0007] Another objective of the present invention is to provide a tool holder for a tool assembly having improved surface finish capability.

[0008] Another objective of the present invention is to provide a tool holder for a tool assembly having improved damping performance.

[0009] Another objective of the present invention is to provide a tool holder for a tool assembly that allows a damping mass to be positioned close to the end effector of the tool assembly.

[0010] Another objective of the present invention is to provide a tool holder for a tool assembly with high rigidity.

[0011] Another objective of the present invention is to provide a tool holder for a tool assembly having improved balancing.

[0012] Another objective of the present invention is to provide a tool holder for a tool assembly that requires little to no service over a long period of time.

[0013] Another objective of the present invention is to provide a tool holder for a tool assembly that enables simple and / or reliable alignment of a damping mass to a tubular element.

[0014] Another objective of the present invention is to provide a tool holder for a tool assembly having a simple, cost-effective, and reliable design.

[0015] Another objective of the present invention is to provide a tool holder for a tool assembly that enables a simple, cost-effective, and reliable assembly.

[0016] Another objective of the present invention is to provide a tool holder for a tool assembly that enables simple, cost-effective, and reliable production.

[0017] Another objective of the present invention is to provide a tool holder for a tool assembly that solves some or all of the aforementioned objectives in combination.

[0018] Another objective of the present invention is to provide a tool assembly comprising a tool holder that solves one, some, or all of the aforementioned objectives in combination. means of solving the problem

[0019] According to one embodiment, a tool holder for a tool assembly is provided, the tool holder comprising: a tubular element having a cavity and a central axis; a damping mass configured within the cavity and movable radially with respect to the central axis and the tubular element; and an adapter having a rear part fixed to the tubular element and a front part for connection to an end effector of the tool assembly, wherein the rear part comprises an opening and the damping mass is at least partially received in the opening with a radial clearance. and an elastic element positioned between the adapter and the damping mass (28), the elastic element is configured to support the damping mass and damp radial vibrational movements of the damping mass with respect to the tubular element, and the elastic element comprises a front surface substantially perpendicular or perpendicular to the central axis and a rear surface substantially perpendicular or perpendicular to the central axis.

[0020] In many conventional tool holders, the adapter is inserted into a tubular element via an interference fit or transition fit and then secured to the tubular element by a pin. These tool holders require pins with a diameter of at least 5 mm. To increase the safety factor, the number of pins is increased or the diameter of the pins is increased. This requires a length of the rear portion of the adapter along the central axis to be extended. This increased length, in turn, requires the damping mass to be located further away from the end effector.

[0021] Since the damping mass of the tool holder according to this embodiment is at least partially accommodated in the opening of the adapter, the damping mass can be located further forward from the tool holder. Thus, the damping mass can be located closer to the front part of the adapter and, consequently, closer to the end effector of the tool assembly. This allows the distance between the point where an external force acts on the tool assembly during machining and the reaction force area of ​​the damping mass to be shortened. For example, compared to WO 2019168448 A1, this distance can be reduced to 4 mm. In the design of the tool holder, every single millimeter reduction has a significant impact on the performance of the tool holder. Reducing this distance by 4 mm can reduce the amplitude of vibration acceleration of the tool holder during machining by more than 10%, and the maximum vibration displacement of the tool assembly can also be reduced by more than 30%.

[0022] The material removal rate of the tool assembly is inversely related to the maximum vibration displacement. Therefore, if the maximum vibration displacement of the tool assembly is reduced by 30%, productivity improves by more than 30%. Accordingly, the tool holder according to this embodiment has improved surface finishing capabilities.

[0023] Furthermore, due to the substantially perpendicular orientation of the front and rear surfaces of the elastic element, the elastic element will primarily experience shear stress when transmitting vibrations to the damping mass. This allows the elastic element to become thinner, contributing to a reduction in the distance between the damping mass and the end effector. The substantially perpendicular surfaces may form an angle of 80 to 100 degrees, for example, 85 to 95 degrees, with respect to the central axis.

[0024] In this way, the tool holder is optimized for improved vibration damping performance. At the same time, the tool holder enables a design that satisfies the requirements for rigidity, modularity, fatigue strength, balancing of the damping mass, and / or coolant conduction.

[0025] The opening may be circular. The opening may have an inner diameter larger than the outer diameter of the damping mass to establish radial clearance. In this way, the damping mass is configured to move within both the cavity and the opening. In addition to radial movement, the damping mass may also move axially about a central axis.

[0026] The rear portion may be connected directly or indirectly to the tubular element. The rear portion may be connected to the front end of the tubular element. The tubular element, adapter, and elastic element may each be concentric with the central axis.

[0027] The tool holder may further include a tail lock. The tool holder may further include a back end.

[0028] The tool holder may further include a central fluid pipe. The fluid pipe may be configured to deliver coolant toward the end effector. The adapter may include one or more coolant channels for delivering coolant from the fluid pipe to the end effector.

[0029] The damping mass may include a mass cavity. In this case, a fluid pipe may pass through the mass cavity. The fluid pipe may be rigidly connected to the adapter and the tail lock, respectively, by, for example, threads and / or glue.

[0030] The front portion of the adapter may include an interface for connecting the adapter to an end effector. The interface may be a standard arbor interface. The end effector may be secured to the front portion with bolts. As used herein, the front direction of the tool assembly faces the end effector, and the rear direction of the tool assembly faces the opposite direction, e.g., the rear end.

[0031] The elastic element located between the adapter and the damping mass can be called a front elastic element. The tool holder may include only one elastic element between the adapter and the damping mass.

[0032] The rear portion may be secured to a tubular element by a screw. To this end, the rear portion or the component secured to the rear portion may include an external thread, and the tubular element or the component secured to the tubular element may include an internal thread configured to engage screw-type with the external thread. An opening may be formed radially within the external thread. The opening may overlap at least partially with the external thread along the central axis. A major length of the opening along the central axis, such as the entire length of the opening, may overlap with the external thread along the central axis.

[0033] Alternatively, the rear portion or the component fixed to the rear portion may include a female thread, and the tubular element or the component fixed to the tubular element may include a male thread configured to engage screw-type with the female thread.

[0034] Alternatively or additionally, the rear portion may be secured to the tubular element by engineering fits such as cold welding, glue, clearance fit, or interference fit. A fixed joint may be formed using brazing or adhesive to lock the relative movement between the adapter and the tubular element. It is also possible to use a pin that does not protrude into the opening.

[0035] The tubular element may be configured to be fixed to the rear end. To this end, the rear end may include a male thread, and the tubular element may include an internal rear thread configured to engage screw-type with the male thread of the rear end.

[0036] The tool holder may further include a plate positioned between the adapter and the damping mass. In this case, the elastic element may be positioned between the plate and the damping mass. The plate may be a thermal insulation plate. The plate may be circular. The plate may be rigid. The largest dimension of the plate perpendicular to the central axis may be at least four times, for example, at least ten times, the thickness of the plate.

[0037] A plate located between the adapter and the damping mass can be called a front plate. In addition to the front plate between the adapter and the damping mass, the tool holder may further include a rear plate between the damping mass and the tail lock.

[0038] Each plate can be made of a material with low thermal conductivity, such as glass, plastic, wood fiber, or other engineering materials. Each plate can also be formed of a metal or non-metal material coated with a surface layer of an insulating coating.

[0039] The rear portion may include an adapter aperture. In this case, the plate may be seated in the adapter aperture. This enables improved alignment with the center axis of the damping mass, thereby improving the performance of the tool assembly. The inner diameter of the adapter aperture may be smaller than the inner diameter of the opening. The adapter aperture may be circular.

[0040] The plate can be positioned relative to the adapter by an engineering fit. The engineering fit can be an interference fit, an intermediate fit, or a loose fit. The plate can be seated in the adapter aperture by an engineering fit. Alternatively, or additionally, the plate can be positioned on the fluid pipe by an engineering fit. In either case, the engineering fit contributes to aligning the damping mass with the central axis.

[0041] The elastic element may have a thickness of less than 2 mm, for example, less than 1.5 mm. In addition to the front elastic element between the adapter and the damping mass, the tool holder may further include a rear elastic element between the damping mass and the tail lock. If a rear plate is provided, the rear elastic element may be configured between the damping mass and the rear plate.

[0042] Each elastic element can be configured to convert vibration energy into heat. Each elastic element can have frequency-dependent stiffness. In this way, a self-tuning effect can be obtained. For example, the elastic element may have frequency-dependent stiffness such that the resonance frequency of the damping mass substantially matches or matches the vibration frequency of the tool holder over a vibration frequency range of 100 Hz to 1000 Hz. A material having such frequency-dependent stiffness may have a structural size of 100 nm or less in at least one dimension.

[0043] Each elastic element may comprise a material having a shear modulus of less than one-third of its Young's modulus. This allows the thickness of the elastic element to be thin when displaced substantially perpendicular to the central axis. Consequently, the reaction region of the damping mass can be located closer to the end effector. Each elastic element may be a viscoelastic element.

[0044] The rear surface can be directly connected to the damping mass. By doing so, a reaction region of the damping mass is provided at the interface between the rear surface and the damping mass.

[0045] The damping mass may be balanced before the damping mass is assembled into the tubular element. The balancing may be of any type according to the present invention, particularly by providing one or more balancing apertures to the damping mass.

[0046] The tool holder may further include a lateral stiffness ring, and the damping mass may include a groove, and the lateral stiffness ring may be seated in the groove and contact a tubular element. The lateral stiffness ring may be configured to facilitate alignment of the damping mass and the central axis.

[0047] The tool holder may include a plurality of such lateral stiffness rings, and the damping mass may include a plurality of such grooves, and one of the lateral stiffness rings may be provided in each groove. By using multiple lateral stiffness rings, the gravitational and centrifugal forces of the heavier damping mass can be offset.

[0048] The lateral stiffness ring can contribute less than 30% of the total stiffness to support the damping mass.

[0049] According to a further embodiment, a tool assembly comprising an end effector and a tool holder having an adapter having an opening for receiving a damping mass according to the present invention is provided. Examples of the end effector according to the present invention are a milling head, a boring head, a drilling head, a turning head, and a grinding head.

[0050] According to another embodiment, a tool holder for a tool assembly is provided, the tool holder comprising: a tubular element having a cavity and a central axis; a damping mass configured within the cavity and movable radially with respect to the central axis and the tubular element; an adapter having a rear portion formed integrally with the tubular element and a front portion for connection to an end effector of the tool assembly; and an elastic element positioned between the adapter and the damping mass, wherein the elastic element is configured to support the damping mass and damp radial vibration movements of the damping mass with respect to the tubular element, and the elastic element comprises a front surface substantially perpendicular or perpendicular to the central axis and a rear surface substantially perpendicular or perpendicular to the central axis. The damping mass and the elastic element may be configured according to the first embodiment.

[0051] Since the adapter and the tubular element are formed integrally according to this embodiment, the damping mass can be positioned further forward from the tool holder. In this way, the damping mass can be positioned close to the front part of the adapter and, accordingly, close to the end effector of the tool assembly. The integrated adapter and the tubular element can be referred to as an integrated member or unitary body.

[0052] The tool holder may further include a plate positioned between the adapter and the damping mass. The rear portion may include an adapter aperture. In this case, the plate may be seated on the adapter aperture. This enables improved alignment with the center axis of the damping mass, thereby improving the performance of the tool assembly. The adapter aperture may be circular. The plate and the adapter aperture may be configured according to the first embodiment.

[0053] The plate can be positioned against the adapter by an engineering fit. The engineering fit can be an interference fit, an intermediate fit, or a loose fit.

[0054] The elastic element may have a thickness of less than 2 mm, for example, less than 1.5 mm. The rear surface may be directly connected to the damping mass.

[0055] The damping mass may be balanced before the damping mass is assembled into the tubular element. The balancing may be of any type according to the present invention, particularly by providing one or more balancing apertures to the damping mass.

[0056] The tool holder may further include a lateral stiffness ring, and the damping mass may include a groove, and the lateral stiffness ring may be seated in the groove and contact a tubular element. The lateral stiffness ring may be configured to facilitate alignment of the damping mass and the central axis. The lateral stiffness ring may contribute less than 30% of the total stiffness to support the damping mass.

[0057] According to an additional embodiment, a tool assembly comprising an end effector and a tool holder having an adapter integrated with a tubular element according to the present invention is provided.

[0058] According to another embodiment, a tool holder for a tool assembly is provided, the tool holder comprising: a tubular element having a cavity and a central axis; and a damping mass configured within the cavity and radially movable about the central axis and about the tubular element, wherein the damping mass is balanced before assembly of the damping mass to the tubular element.

[0059] In tool holders of the prior art, the damping mass is unbalanced after manufacturing but before the assembly of the tool holder. Unbalance of more than 100 g*mm (gram-millimeter) is very common in damping masses with a total mass of 1.5 kg, which is due to inaccuracies in the machining process and diffusion of material elements within the damping mass. For example, a tool assembly with a damping mass having an unbalance of 100 g*mm, rotating at 6,000 rpm, and a vibration frequency mode close to 100 Hz applies a cyclic load to the tool holder at 100 Hz. This cyclic load will bring the tool assembly into a resonance mode that is very detrimental to the life of the tool assembly and / or the supporting structures for it.

[0060] In some prior art tool holders, the damping mass is balanced after being assembled into the tool holder, for example, by inserting the damping mass into a tubular element and connecting the damping mass to a tail lock. To balance the damping mass, one or more holes may be drilled into the damping mass through the tubular element to remove material from the damping mass. However, according to the prior art, it is difficult to achieve accurate balancing of the damping mass by drilling into the damping mass according to the prior art through the tubular element. Furthermore, the holes drilled through the tubular element expose the cavity and the damping mass to the external environment, allowing fluid and dust to enter and potentially degrading the function of the tool holder. The holes drilled through the tubular element can also have a detrimental effect on the overall bending stiffness of the tool holder.

[0061] In contrast, by balancing the damping mass according to this embodiment, the mass of the damping mass can be evenly distributed along the central axis, thereby allowing the tool holder to rotate at high speed with the balancing under control. That is, the damping mass can be balanced to reduce or eliminate the resonance of the damping mass. By balancing the damping mass before installing it on the tubular element, the risk of degrading the function of the tool holder by removing material from the damping mass, for example by drilling through the tubular element, can be reduced. Additionally, the balancing can be performed more accurately. Therefore, the tool holder according to this embodiment has improved surface finishing capabilities.

[0062] The damping mass can be balanced to satisfy balancing class G6.3 according to ISO 1940-1:2003 before assembling the damping mass to the tubular element.

[0063] The damping mass can be balanced to satisfy balancing grade G2.5 according to ISO 1940-1:2003 before assembling the damping mass to the tubular element.

[0064] The damping mass can be balanced to satisfy balancing grade G1 according to ISO 1940-1:2003 before assembling the damping mass to the tubular element.

[0065] The damping mass may include at least one balancing aperture for balancing the damping mass. The damping mass and the at least one balancing aperture may be configured such that the damping mass is better balanced after the at least one balancing aperture is provided than before the at least one balancing aperture is provided.

[0066] At least one of the balancing apertures may be a hole extending radially about the central axis. Alternatively, or additionally, at least one of the balancing apertures may be a blind hole.

[0067] The tool holder may further include a lateral stiffness ring, and the damping mass may include a groove, and the lateral stiffness ring may be seated in the groove and contact a tubular element. The lateral stiffness ring may contribute less than 30% of the total stiffness to support the damping mass.

[0068] According to another aspect, in accordance with the disclosure of the present invention, a tool assembly comprising an end effector and a tool holder is provided, the damping mass having a damping mass that balances before being assembled to a tubular element.

[0069] Any tool assembly according to the present invention may be stationary or rotated when machining a workpiece. Any tool holder or any tool assembly according to the present invention may be modular. Modularity may be used, for example, to attach different types of end effectors and / or different types of rear ends to the tool holder. Because various types of rear ends can be mounted on the tool holder, the tool holder can be easily adjusted to fit into a specific support, such as a machine spindle or tool magazine. Alternatively or additionally, modularity may be used to modify the length and / or diameter of the tool holder, for example, with the same damping mass. Through modularity, the supply chain stock of components for the tool holder or tool assembly can be reduced.

[0070] According to one example, a component kit is provided comprising a tool holder according to the present invention, a first rear end and a second rear end, wherein each of the first rear end and the second rear end can be detachably connected to the tool holder, the first rear end can be connected to a first support of a first size, and the second rear end can be connected to a second support of a second size different from the first size.

[0071] According to additional examples, a component kit is provided comprising a tool holder, a first end effector, and a second end effector according to the present invention, wherein each of the first end effector and the second end effector can be detachably connected to the tool holder, and the first end effector is of a first type and the second end effector is of a second type different from the first type. Brief explanation of the drawing

[0072] Further details, advantages, and aspects of the present invention will become apparent from the following embodiments with reference to the drawings: FIG. 1 schematically shows a perspective view of a tool assembly including a tool holder and an end effector. Figure 2 schematically shows a cross-sectional view of a machine tool. FIG. 3 schematically shows a partial cross-sectional perspective view of a tool assembly. Figure 4 schematically shows a partially disassembled side view of a tool assembly. Figure 5 schematically shows a perspective view of an adapter for a tool holder. FIG. 6 schematically shows a schematic perspective view of another example of a damping mass for a tool holder. FIG. 7 schematically shows a cross-sectional view of another example of a tool holder. FIG. 8 schematically shows a cross-sectional view of another example of a tool holder. Specific details for implementing the invention

[0073] In the following, a tool holder having an adapter having an opening for receiving a damping mass, a tool assembly including such a tool holder, a tool holder having an adapter integrated with a tubular element, a tool assembly including such a tool holder, a tool holder having a damping mass that balances before assembling the damping mass into the tubular element, and a tool assembly including such a tool holder will be described. Identical or similar reference numbers will be used to indicate identical or similar structural features.

[0074] FIG. 1 schematically illustrates a perspective view of a tool assembly (10) illustrated herein as a milling tool. The tool assembly (10) includes a tool holder (12) and an end effector (14), illustrated herein as a milling head, connected to the tool holder (12). FIG. 1 also illustrates a central axis (16) of the tool assembly (10).

[0075] The end effector (14) includes a plurality of cutting teeth (18) for machining a workpiece (not shown). The end effector (14) of this example includes four cutting teeth (18).

[0076] As illustrated in FIG. 1, the tool holder (12) includes a tubular element (20) and an adapter (22). Each of the tubular element (20) and the adapter (22) is concentric with the central axis (16). An end effector (14) is secured to the tubular element (20) by the adapter (22).

[0077] The tool holder (12) further includes a rear end (24). The rear end (24) may be connected to a support (not shown) for supporting the tool assembly (10). During machining of the workpiece, there is relative rotation between the tool assembly (10) and the workpiece around the central axis (16). That is, the tool assembly (10) may rotate and the workpiece may be stationary, or vice versa.

[0078] FIG. 2 schematically shows a side cross-sectional view of a tool assembly (10). FIG. 3 schematically shows a partial cross-sectional perspective view of a tool assembly (10). As with FIG. 2 and FIG. 3, the tubular element (20) includes a cavity (26). The tubular element (20) is cylindrical.

[0079] The tool assembly (10) further includes a damping mass (28). The damping mass (28) is configured within the cavity (26). During a machining operation by the tool assembly (10), vibration causes the damping mass (28) to move radially about the central axis (16) and about the tubular element (20). Vibration also causes the damping mass (28) to move axially about the central axis (16).

[0080] The damping mass (28) is cylindrical and includes two end surfaces. The damping mass (28) includes a central mass cavity (30). The damping mass (28) may be made of a high-density material such as tungsten alloy.

[0081] The adapter (22) includes a front portion (32) and a rear portion (34). The front portion (32) is positioned closer to the end effector (14), and the rear portion (34) is positioned closer to the rear portion (24).

[0082] The rear portion (34) includes a male screw (36). The tubular element (20) includes a female screw (38). The male screw (36) forms a screw engagement by screwing into the female screw (38). In this way, the adapter (22) is secured to the tubular element (20). The male screw (36) can transmit cutting force to tighten the screw engagement. By doing so, the screw engagement can provide a higher fixing force than conventional solutions using pins to secure the adapter to the tubular element. Due to the pitch sections of the screw engagement, the surface area where shear stress is distributed is larger than that of these prior art solutions. An adhesive may be introduced into the screw engagement to improve the fatigue resistance of the screw engagement.

[0083] The rear portion (34) includes an opening (40). The damping mass (28) is partially accommodated in the opening (40). This allows the distance d between the front end of the damping mass (28) and the front end of the adapter (22) to be reduced. This improves the surface finishing ability of the tool assembly (10).

[0084] A radial clearance is established between the outer diameter of the damping mass (28) and the inner diameter of the opening (40). The opening (40) is circular and concentric with the central axis (16).

[0085] As illustrated in FIGS. 2 and 3, the rear end of the opening (40) is aligned with the rear end of the male screw (36). The front end of the male screw (36) is located in front of the front end of the opening (40). Thus, the opening (40) is radially formed inside the male screw (36). Additionally, the opening (40) and the male screw (36) overlap along the central axis (16).

[0086] The front portion (32) includes a female screw (not shown). The female screw of the front portion (32) can be screwed in by a bolt (not shown) to secure the end effector (14) to the adapter (22).

[0087] The tool holder (12) further includes a front elastic element (42). The front elastic element (42) is configured to damp vibrations of the damping mass (28), particularly radial vibration movements. The front elastic element (42) is configured between the adapter (22) and the damping mass (28). The front elastic element (42) includes a front surface (44) and a rear surface (46). The front surface (44) is firmly connected to the front surface of the damping mass (28). The rear surface (46) is firmly connected to the rear surface of the front plate (48).

[0088] Each of the front surface (44) and the rear surface (46) is perpendicular to the central axis (16). The perpendicular orientation of the front surface (44) and the rear surface (46) to the central axis (16) causes the front elastic element (42) to experience shear stress primarily. This makes it possible for the front elastic element (42) to be made very thin, for example, only 1 mm. Because the front elastic element (42) can be made thin, the damping mass (28) can move much closer to the end effector (14).

[0089] The rear surface (46) is in direct contact with the front end surface of the damping mass (28). The front elastic element (42) is concentric with the center axis (16).

[0090] The tool holder (12) of this example further includes a front plate (48), exemplified here as a circular insulating plate. The front plate (48) is in contact with the adapter (22). The front surface (44) is in direct contact with the rear end surface of the front plate (48). The front plate (48) is concentric with the central axis (16).

[0091] The rear portion (34) of this example further includes an adapter aperture (50). The front plate (48) is accommodated in the adapter aperture (50) by an engineering fit. This improves alignment with the center axis (16) of the damping mass (28).

[0092] The front plate (48) can be locked to the adapter (22) with an adhesive such as instant glue. Alternatively, the front plate (48) may be rotatable relative to the adapter (22). In this case, grease may be applied between the front plate (48) and the adapter aperture (50). The grease enables improved transmission of vibration energy compared to air.

[0093] In this example, the front elastic element (42) is configured between the front plate (48) and the damping mass (28). The front surface (44) is in direct contact with the front plate (48).

[0094] The tool holder (12) of this example further includes a rear plate (52) and a tail lock (54). The rear plate (52) is configured between the damping mass (28) and the tail lock (54). The rear plate (52) has the same configuration as the front plate (48). The rear plate (52) contacts the tail lock (54).

[0095] The tail lock (54) includes a tail lock aperture (56). The rear plate (52) is received in the tail lock aperture (56). This improves alignment with the center axis (16) of the damping mass (28).

[0096] The tool holder (12) of this example further includes a rear elastic element (58). The rear elastic element (58) is configured between the damping mass (28) and the tail lock (54). In this example, the rear elastic element (58) is configured between the damping mass (28) and the rear plate (52). The rear elastic element (58) may have the same configuration as the front elastic element (42). Alternatively, the rear elastic element (58) may differ in size and material compared to the front elastic element (42). Each elastic element (42, 58) may be a viscoelastic element.

[0097] Each elastic element (42, 58) is self-adhesive. The front elastic element (42) is bonded to the front plate (48) and the damping mass (28). The rear elastic element (58) is bonded to the damping mass (28) and the rear plate (52).

[0098] The tool holder (12) further includes a fluid pipe (60). The fluid pipe (60) passes through the mass cavity (30). The fluid pipe (60) also passes through the through holes of each plate (48, 52) and each elastic element (42, 58). The fluid pipe (60) is screw-connected to the adapter (22) and screw-connected to the tail lock (54). By this, the fluid pipe (60) is secured to the adapter (22) and the tail lock (54), respectively. Additionally, sealing glue is provided to these screw connections. The fluid pipe (60) is configured to deliver coolant toward the end effector (14). The fluid pipe (60) is concentric with the central axis (16).

[0099] If the adapter aperture (50) and tail lock aperture (56) are omitted, the front plate (48) and the rear plate (52) can each be fitted into the fluid pipe (60) by an engineering fit. In addition, in this way, the damping mass (28) can be aligned with the center axis (16).

[0100] The adapter (22) further includes coolant channels (62). The coolant channels (62) are configured to provide high-pressure coolant from the fluid pipe (60) to the end effector (14). In this example, the coolant channels (62) each extend parallel to the central axis (16).

[0101] The damping mass (28) includes a groove (64). The groove (64) extends around the circumference of the damping mass (28) and is concentric with the central axis (16). In this example, the groove (64) is located at the center of the damping mass (28) along the central axis (16).

[0102] The tool holder (12) of this example further includes a side rigidity ring (66). The side rigidity ring (66) is seated in the groove (64). The side rigidity ring (66) contacts both the inner surface of the tubular element defining the boundaries of the damping mass (28) and the cavity (26). This improves alignment with the center axis (16) of the damping mass (28).

[0103] The damping mass (28) is supported by elastic elements (42, 58) and a lateral stiffness ring (66). Thus, the supporting stiffness of the damping mass (28) consists of stiffness from the elastic elements (42, 58) and the lateral stiffness ring (66). The lateral stiffness ring (66) preferably contributes less than 30% of the total stiffness for supporting the damping mass (28). Vibration energy is damped by relative motion within each of the elastic elements (42, 58) and the lateral stiffness ring (66).

[0104] The lateral rigidity ring (66) may be made of a material different from the material of the elastic elements (42, 58) or a different grade of the same material (e.g., natural rubber of grades NBR 70 and NBR 90). The lateral rigidity ring (66) may be made of a material having low creep characteristics, such as, for example, natural rubber, silicone rubber, elastomer, or other polymer materials.

[0105] In any case, the elastic elements (42, 58) primarily contribute to converting vibration energy into heat, while the lateral stiffness ring (66) primarily or only responds to the centrifugal force on the damping mass (28) caused by weight drifting of the damping mass (28) and high-speed rotation.

[0106] The elastic elements (42, 58) receive radial movements when the tool assembly (10) is subjected to a periodic load. The elastic elements (42, 58) may be manufactured from a material having frequency-dependent stiffness to provide a self-tuning effect.

[0107] FIG. 4 schematically illustrates a partially disassembled side cross-sectional view of a tool assembly (10). For example, when the tool holder (12) rotates at 10,000 rpm, the damping mass (28) will typically require less than 10 g*mm of balancing to avoid balancing-related problems, such as periodic loads. To balance the damping mass (28), the damping mass (28) is first measured in a balancing machine. In response to the balancing measurement, material is then removed from the damping mass (28) to create one or more balancing apertures (68) at one or more locations along the central axis (16) so that the damping mass (28) is balanced. The damping mass (28) of FIG. 4 includes two balancing apertures (68), each exemplified as a drilled radial blind hole drilled from the outer surface of the damping mass (28).

[0108] The tool holder (12) of this example further includes a damping liquid in the mass cavity (30) between the damping mass (28) and the fluid pipe (60). The damping liquid may be a viscous liquid such as oil. Because the balancing aperture (68) does not extend through the damping mass (28) (in this example, a closed hole), leakage of the damping liquid through the damping mass (28) is prevented.

[0109] The damping mass (28) can be balanced to satisfy balancing grade G6.3 according to ISO 1940-1:2003, balancing grade G2.5, or balancing grade G1. After balancing the damping mass (28), the tool holder (12) is assembled.

[0110] The tool holder (12) may have a mass of, for example, 5.5 kg. In this case, the damping mass (28) may have a mass of 1.5 kg. The mass of the damping mass (28) may be 20% to 40% of the mass of the tool holder (12).

[0111] In the case of a tool holder (12) having a mass of 5.5 kg and a damping mass (28) having a mass of 1.5 kg, the tool holder (12) can be tuned to a vibration frequency of 300 Hz. This means that the total stiffness supporting the mass is approximately 5.3 x 10 6 It means N / m and is determined by the following equation.

[0112]

[0113] Here, K total is the total stiffness (of the elastic elements (42, 58) and the lateral stiffness ring (66) in this example), f is the tuned vibration frequency, and m is the mass of the damping mass (28).

[0114] If the side stiffness ring (66) is set to have 30% of the total stiffness to support the damping mass (28), the stiffness of the side stiffness ring (66) is approximately 1.6 * 10 6 It is N / m. The gravitational force of the damping mass (28) is about 15 N when the center axis (16) is horizontal. This gravitational force causes a displacement of about 0.01 mm and an allowable unbalance of 15 g*mm.

[0115] If the tool holder (12) includes only one elastic element, namely the front elastic element (42) but not the rear elastic element (58), the support stiffness is reduced and the mass of the damping mass (28) can be reduced. The reduction in the mass of the damping mass (28) will further reduce production costs. The reduction in the mass of the damping mass (28) is also advantageous because the space within the cavity (26) is limited. A lower mass of the damping mass (28) also reduces the static deflection of the tool assembly (10) due to gravity. A lateral stiffness ring (66) may still be provided in the groove (64) to counteract the drifting of the damping mass (28) due to gravity / weight and centrifugal force.

[0116] The stiffness of the front elastic element (42) can be pre-selected to tune the damping mass (28) according to the following equation:

[0117]

[0118] Here, m is the mass of the damping mass (28), k is the stiffness of the forward elastic element (42), and f is the tuned vibration frequency of the tool assembly (10). The mass m of the damping mass (28) can be selected in advance. The tuned vibration frequency f can be determined by the structure of the tool assembly (10).

[0119] FIG. 5 schematically shows a perspective view of the adapter (22). In FIG. 5, the opening (40) and the adapter aperture (50) can be seen more clearly. The inner diameter of the opening (40) is larger than the inner diameter of the adapter aperture (50).

[0120] FIG. 6 schematically illustrates a perspective view of another example of a damping mass (28) for a tool holder (12). In FIG. 6, the damping mass (28) differs from the damping mass (28) in FIG. 2-4 in the position and configuration of the balancing aperture (68). The damping mass (28) in FIG. 6 includes two balancing apertures (68), each configured as a square cut-out in the damping mass (28). Additionally, the balancing aperture (68) is angularly offset with respect to the center axis (16).

[0121] FIG. 7 schematically illustrates a side cross-sectional view of another example of a tool holder (12). The main differences with respect to FIG. 1-5 will be explained. The tool holder (12) of FIG. 7 is for a tool assembly (10) in the form of a milling tool. In FIG. 7, the milling head is omitted. The front portion (32) of the adapter (22) has a larger outer diameter. The outer surface of the front portion (32) is aligned with the outer surface of the tubular element (20). Additionally, the tubular element (20) and the rear portion (24) are formed integrally.

[0122] FIG. 8 schematically illustrates a side cross-sectional view of another example of a tool holder (12). The main differences with respect to FIG. 1-5 will be explained. In FIG. 8, the adapter (22) is formed integrally with the tubular element (20). In addition to the cavity (26), the combined adapter (22) and the tubular element (26) do not include an additional opening (similar to the opening (40) in FIG. 2-5) for accommodating a damping mass (28).

[0123] The integrated adapter (22) and tubular element (20) can be fixed to the rear end (24) in various ways. In FIG. 8, the tubular element (20) includes a rear opening (70) for receiving the rear end (24). The front plate (48), front elastic element (42), damping mass (28), side rigidity ring (66), rear elastic element (58), rear plate (52), and tail lock (54) can be inserted into the tubular element (20) through the rear opening (70).

[0124] The rear opening (70) may include a female screw for screwing into the male screw of the rear end (24). A damping mass (28) is configured between the adapter (22) and the rear opening (70).

[0125] Since the adapter (22) is formed integrally with the tubular element (20), the connection between the adapter (22) and the tubular element (20), which can add length to the tool holder (12), can be avoided. This allows the distance d between the front end of the damping mass (28) and the front end of the adapter (22) to be reduced. This improves the surface finish capability of the tool assembly (10) including the tool holder (12).

[0126] Although the present invention has been described with reference to exemplary embodiments, it will be understood that the invention is not limited to what has been described above. For example, it will be understood that the dimensions of parts may be changed as necessary. Accordingly, the present invention may be limited only by the claims appended herein.

Claims

Claim 1 A tool holder (12) for a tool assembly (10), wherein the tool holder (12) comprises: - a tubular element (20) having a cavity (26) and a central axis (16); - a damping mass (28) configured within the cavity (26) and radially movable with respect to the central axis (16) and the tubular element (20); - an adapter (22) having a rear portion (34) fixed to the tubular element (20) and a front portion (32) for connection to an end effector (14) of the tool assembly (10), wherein the rear portion (34) includes an opening (40) and the damping mass (28) is at least partially received in the opening (40) with a radial gap; and - an elastic element (42) positioned between the adapter (22) and the damping mass (28), wherein the elastic element (42) is configured to support the damping mass (28) and dampen radial vibration movements of the damping mass (28) relative to the tubular element (20), and wherein the elastic element (42) comprises a front surface (44) substantially perpendicular to the central axis (16) and a rear surface (46) substantially perpendicular to the central axis (16), wherein the rear surface (46) is directly connected to the damping mass (28), and the elastic element (42) receives shear stress when transmitting vibrations to the damping mass (28), the tool holder. Claim 2 In claim 1, the rear portion (34) is a tool holder (12) that is fixed to the tubular element (20) by screw threads (36, 38). Claim 3 In paragraph 2, the rear portion (34) is a tool holder (12) that is fixed to the tubular element (20) by an adhesive. Claim 4 A tool holder (12) further comprising a plate (48) positioned between the adapter (22) and the damping mass (28) in any one of claims 1 to 3. Claim 5 In paragraph 4, the rear portion (34) includes an adapter aperture (50), and the plate (48) is a tool holder (12) that is seated on the adapter aperture (50). Claim 6 In paragraph 4, the plate (48) is positioned relative to the adapter (22) by an engineering fit, and the tool holder (12). Claim 7 In any one of claims 1 to 3, the tool holder (12) has a thickness of less than 2 mm, wherein the elastic element (42) is a tool holder (12). Claim 8 In any one of claims 1 to 3, the tool holder (12) has an elastic element (42) having a thickness of less than 1.5 mm. Claim 9 A tool holder (12) characterized in that, in any one of claims 1 to 3, the damping mass (28) is balanced before assembling the damping mass (28) to the tubular element (20). Claim 10 A tool holder (12) according to any one of claims 1 to 3, further comprising a side rigidity ring (66), wherein the damping mass (28) comprises a groove (64), and the side rigidity ring (66) is seated in the groove (64) and contacts the tubular element (20). Claim 11 In claim 10, the side rigidity ring (66) contributes less than 30% of the total rigidity to support the damping mass (28), the tool holder (12). Claim 12 A tool assembly (10) comprising an end effector (14) and a tool holder (12) according to any one of claims 1 to 3. Claim 13 A tool holder (12) for a tool assembly (10), wherein the tool holder (12) comprises: - a tubular element (20) having a cavity (26) and a central axis (16); - a damping mass (28) configured within the cavity (26) and movable radially with respect to the central axis (16) and the tubular element (20); - an adapter (22) having a rear portion (34) formed integrally with the tubular element (20) and a front portion (32) for connection to an end effector (14) of the tool assembly (10); and - an elastic element (42) positioned between the adapter (22) and the damping mass (28), wherein the elastic element (42) is configured to support the damping mass (28) and dampen radial vibration movements of the damping mass (28) relative to the tubular element (20), and wherein the elastic element (42) comprises a front surface (44) substantially perpendicular to the central axis (16) and a rear surface (46) substantially perpendicular to the central axis (16), wherein the rear surface (46) is directly connected to the damping mass (28), and the elastic element (42) receives shear stress when transmitting vibrations to the damping mass (28), the tool holder. Claim 14 A tool holder (12) further comprising a plate (48) positioned between the adapter (22) and the damping mass (28) in claim 13. Claim 15 In claim 14, the rear portion (34) includes an adapter aperture (50), and the plate (48) is a tool holder (12) that is seated on the adapter aperture (50). Claim 16 In claim 14 or 15, the plate (48) is positioned relative to the adapter (22) by an engineering fit, the tool holder (12). Claim 17 In any one of claims 13 to 15, the tool holder (12) has a thickness of less than 2 mm, wherein the elastic element (42) is a tool holder (12). Claim 18 In any one of claims 13 to 15, the tool holder (12) has a thickness of less than 1.5 mm, wherein the elastic element (42) is a tool holder (12). Claim 19 In any one of claims 13 to 15, the damping mass (28) is balanced before assembling the damping mass (28) to the tubular element (20), the tool holder (12). Claim 20 A tool holder according to any one of claims 13 to 15, further comprising a side rigidity ring (66), wherein the damping mass (28) comprises a groove (64), and the side rigidity ring (66) is seated in the groove (64) and contacts the tubular element (20). Claim 21 In claim 20, the side rigidity ring (66) contributes less than 30% of the total rigidity to support the damping mass (28), the tool holder (12). Claim 22 A tool assembly (10) comprising an end effector (14) and a tool holder (12) according to any one of claims 13 to 15. Claim 23 A tool holder (12) for a tool assembly (10), wherein the tool holder (12) comprises: - a tubular element (20) having a cavity (26) and a central axis (16); and - a damping mass (28) configured within the cavity (26) and radially movable with respect to the central axis (16) and the tubular element (20), wherein the damping mass (28) is balanced to satisfy balancing grade G6.3 according to ISO 1940-1:2003 before the damping mass (28) is assembled to the tubular element (20). Claim 24 delete Claim 25 In claim 23, the damping mass (28) is balanced to satisfy balancing grade G2.5 according to ISO 1940-1:2003 before assembling the damping mass (28) to the tubular element (20), the tool holder (12). Claim 26 In paragraph 23, the damping mass (28) is balanced to satisfy balancing grade G1 according to ISO 1940-1:2003 before assembling the damping mass (28) to the tubular element (20), the tool holder (12). Claim 27 In paragraph 23, the tool holder (12) comprises at least one balancing aperture (68) for balancing the damping mass (28). Claim 28 In claim 27, one or more of the balancing apertures (68) are holes extending radially with respect to the central axis (16), in a tool holder (12). Claim 29 In claim 27 or 28, a tool holder (12), wherein at least one of the at least one balancing aperture (68) is a closed hole. Claim 30 A tool holder (12) according to any one of claims 23, 25 to 28, further comprising a side rigidity ring (66), wherein the damping mass (28) comprises a groove (64), and the side rigidity ring (66) is seated in the groove (64) and contacts the tubular element (20). Claim 31 In claim 30, the side rigidity ring (66) contributes less than 30% of the total rigidity to support the damping mass (28), the tool holder (12). Claim 32 A tool assembly (10) comprising an end effector (14) and a tool holder (12) according to any one of claims 23, 25 to 28.

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