Device for mechanical overload protection, and manufacturing method therefor

Abstract

The present invention relates to a device for mechanical overload protection in a drive train of a machine tool, wherein the drive train has an output side having an output shaft and a drive side having a motor shaft. The output shaft is operatively connected to the motor shaft via a connecting means, wherein the device for mechanical overload protection is formed by a press connection between the connecting means on one side and the motor shaft or the output shaft on the other side. The invention also relates to a method for manufacturing such a device for mechanical overload protection in a machine tool. The invention can significantly reduce the peak torques that occur, preferably for short periods, in the drive train, and protect the machine tool and its mechanical components from damage in the event of a blockage.

Description

[0001] MECHANICAL OVERLOAD PROTECTION DEVICE AND MANUFACTURING METHOD THEREFOR

[0002] The present invention relates to a device for mechanical overload protection in a drive train of a machine tool, wherein the drive train has an output side with an output shaft and a drive side with a motor shaft. The output shaft is operatively connected to the motor shaft via a connecting means, wherein the device for mechanical overload protection is formed by a press connection between the connecting means on one side and the motor shaft or the output shaft on the other side. In a second aspect, the invention relates to a method for producing such a device for mechanical overload protection in a machine tool. With the invention, the peak torques in the drive train, which preferably occur briefly, can be considerably reduced and the machine tool and its mechanical components can be protected from damage in the event of a blockage.

[0003] Background of the invention:

[0004] In the field of machine tools, mechanical slip clutches are known to protect the machine tool and its components from high mechanical loads, for example if the machine tool tool blocks or becomes jammed in the surface being machined ("blocking event"). The protection provided by a mechanical slip clutch is based in particular on the fact that the drive train is mechanically disconnected if a blocking event occurs or if a blocking event is detected. With such mechanical slip clutches, on the one hand, the drive train of the machine tool can be protected from the high mechanical loads that occur in such a blocking event. On the other hand, the user of the machine tool can also be protected from possible injuries if the drive train is mechanically disconnected by the slip clutch in the event of a blockage.

[0005] However, with the advancement of technology in the field of machine tools, there is a move to no longer provide mechanical solutions for individual applications, but rather to use electronic and / or mechatronic solutions. For example, electronic slip clutch solutions and solutions for regulating the torque in the machine tool are known in the state of the art. While these functions or solutions are capable of protecting the user from the effects that can occur in the event of a jam, these electronic and / or mechatronic solutions are often unable to limit the peak torques in the machine tool's drive train, which often occur for very short periods.This inability is due in particular to the fact that the electronic and / or mechatronic solutions cannot achieve a mechanical separation of the drive train, as can, for example, a mechanical slip clutch.

[0006] Dealing with such short-term peak torques in the drive train, when a mechanical slip clutch is to be dispensed with, poses a particular challenge for core drilling machines or other machine tools with torsionally rigid tools. For example, core drilling machines use a core bit as a tool. Such core bits comprise a hollow cylinder with which a cylindrical core can be cut out of the substrate to be machined. However, such core bits are comparatively torsionally rigid, so the large forces that can occur when the machine tool tool blocks or jams in the substrate to be machined can only be absorbed to a limited extent by the core bit.The forces not absorbed by the drill bit are disadvantageously introduced into the drive train and can cause damage to the machine tool or its components.

[0007] To prevent such damage, the prior art has proposed designing the mechanical components of the machine tool's drive train to be particularly robust. This is intended to ensure that even very high peak torques or forces that may occur in the event of a jam can be absorbed by the machine tool's mechanical components without causing damage to the machine tool or its components. However, it has been shown that machine tools with such robust and therefore usually oversized mechanical components are very heavy. This can make handling such machine tools significantly more difficult or reduce the time a user can work with the machine tool.

[0008] The object underlying the present invention is to overcome the above-described deficiencies and disadvantages of the prior art and to provide a machine tool in which the effects of briefly occurring peak torques in the drive train can be reduced, particularly in machine tools with torsionally rigid tools. Furthermore, the machine tool to be provided should be particularly light and compact, so that handling of the machine tool is facilitated and the period of time a user can work with the machine tool can be extended. In particular, a machine tool should be provided in which, despite the presence of electronic and / or mechatronic functions, effective protection of the drive train of the machine tool against mechanical damage in the event of a blockage can be enabled.

[0009] The problem is solved by the subject matter of the independent claims. Advantageous embodiments of the subject matter of the independent claims can be found in the dependent claims.

[0010] Description of the invention:

[0011] According to the invention, a device for mechanical overload protection is provided in a drive train of a machine tool. The drive train has an output side with an output shaft and a drive side with a motor shaft. The device for mechanical overload protection is preferably also referred to as a "mechanical overload protection" within the meaning of the invention and is characterized in that the output shaft is operatively connected to the motor shaft via a connecting means, wherein the device for mechanical overload protection is formed by a press connection between the connecting means on one side and the motor shaft or the output shaft on the other side. The connecting means can preferably be a gear or a bushing provided specifically for this purpose.It is preferred within the meaning of the invention that the output shaft is drivable by the motor shaft via a gear, wherein the device for mechanical overload protection in this embodiment of the invention can be formed by a press connection between the gear on one side and the motor shaft or the output shaft on the other side. It can also be preferred within the meaning of the invention that the mechanical overload protection does not require a gear if the motor shaft and the output shaft are operatively connected to one another via a bushing as a connecting means. The proposed device is advantageously designed to disconnect the drive train in the event of an overload or blockage. A so-called triggering torque of this mechanical overload protection is preferably designed such that the drive train of the machine tool is not disconnected during normal operation of the machine tool.According to the invention, it is preferred that the proposed mechanical overload protection device only triggers in the event of extremely severe blocking events in order to protect the machine tool and / or its components from damage. In particular, the invention can be used to reliably limit the torque in the drive train without the mechanical components of the machine tool having to be robust, large, heavy, and possibly oversized. As a result, the invention can provide a particularly compact machine tool that is comfortable to hold and allows for extended periods of work with the machine tool. It was completely surprising that the proposed mechanical overload protection device can be used particularly in machine tools with torsionally rigid tools.Tests have shown that the proposed mechanical overload protection provides particularly good protection for core drilling machines that can be connected to a core bit. Of course, the invention can also be used in other machine tools, such as screwdrivers or cordless screwdrivers.

[0012] The formulation that the mechanical overload protection device is formed on one side by the output shaft or the motor shaft includes the case where more than these two shafts are provided in the transmission unit of the machine tool. For example, the machine tool can comprise intermediate shafts with which the rotary movement or the torque of the motor shaft can be transmitted to the output shaft and which are preferably provided between the motor shaft and the output shaft. If the machine tool has such intermediate shafts, it can also be preferred within the meaning of the invention for the press connection of the mechanical overload protection device to be formed between the connecting means on the one side and one of the shafts of the transmission unit of the machine tool on the other side.In other words, the press connection of the mechanical overload protection device can be formed between a bushing or a gear as a connecting means on one side and the motor shaft, the output shaft or an intermediate shaft on the other side.

[0013] With the invention, the peak torques in the drive train, which preferably occur briefly, can be considerably reduced. The invention represents a mechanical device for disconnecting the drive train of the machine tool in the event of a jam, wherein the invention can provide effective protection of the drive train of the machine tool against mechanical damage in the event of a jam, despite the presence of electronic and / or mechatronic functions. In particular, the invention can reduce the torque in the drive train, so that the mechanics of the machine tool can be effectively protected in the event of a jam. Within the meaning of the invention, it is preferred that the output side of the drive train is oriented towards a tool of the machine tool and the drive side of the drive train is oriented towards a motor of the machine tool (see also: Fig. 2).The output side of the drive train preferably represents a "slow" or "slow-rotating" side of the drive train, while the input side of the drive train represents the "fast" or "fast-rotating" side of the drive train. The fast side of the drive train is connected to the machine tool's motor via the motor shaft, while the slow side of the drive train is connected to the machine tool's tool via the output shaft. The machine tool can, for example, be a core drilling machine that uses a core bit as its tool. The fast side of the drive train can preferably also be referred to as the "motor side" of the machine tool's drive train.

[0014] If the device for mechanical overload protection has a gear as a connecting means, it is preferred within the meaning of the invention that the device for mechanical overload protection can also have a coupling sleeve which is positively connected to the gear. In the context of the present invention, a press connection can be created in this way between the output shaft of the mechanical overload protection device and a coupling sleeve. The coupling sleeve is positively connected to the gear. The gear is thus connected to the output shaft via the coupling sleeve, so that the output shaft rotates when the gear connected to it is driven from the outside. In the context of the present invention, this external drive is provided by the motor shaft of the drive train of the machine tool, which in turn is driven to rotate by the motor of the machine tool.The rotation of the machine tool's motor drives the motor shaft to rotate. The pinions of the motor shaft mesh with the spaces between the teeth of the gear, transferring the rotation of the motor shaft to the gear and the connected output shaft.

[0015] Alternatively, there can be a press connection of the mechanical overload protection device between the motor shaft and the coupling sleeve, wherein the motor shaft is positively connected to the gear via the coupling sleeve. This allows rotation of the motor shaft to be transmitted to the output shaft via the gear. If the mechanical overload protection device comprises a bushing as a connecting means, a press connection can be formed between the bushing and the motor shaft or the output shaft in order to transmit the rotational movement of the motor shaft to the output shaft. In a preferred embodiment of the invention, the device for mechanical overload protection can have a coupling sleeve which is positively connected to the gear, wherein the output shaft is connected to the coupling sleeve via a press connection.In this preferred embodiment of the invention, the mechanical overload protection device is located on the output side of the drive train, wherein the output side of the drive train represents the slower rotating side of the drive train. In the context of the invention, this preferably means that the device is provided on the output side of the drive train, i.e. on the side oriented in the direction of the tool of the machine tool. In this way, a slip angle sufficient to limit the torque in the drive train can be achieved while at the same time placing low demands on the thermal stability and seizure behavior of the press connection. The invention makes it possible to provide a particularly durable overload protection device in a machine tool which, moreover, can be easily manufactured and integrated into the machine tool due to the comparatively large installation space available.The provision of mechanical overload protection on the output side may be preferred due to the lower speeds occurring there and the larger installation space available.

[0016] The mechanical overload protection device can also be located on the drive side of the drive train. This is the case when the mechanical overload protection device is formed by a press connection between the connecting means on one side and the motor shaft on the other. This embodiment of the invention is particularly preferred when limited installation space is available on the output side.

[0017] According to the invention, it is preferred that the press connection between the output or motor shaft of the proposed devices and the gear or coupling sleeve is designed such that the maximum torque expected in the drive train is reliably transmitted under normal operating conditions. Furthermore, the proposed mechanical overload protection device is configured to limit the torque M of the press connection to be transmitted in the drive train to a value M_Limit, where M_Limit is smaller than the torque M_B that occurs in the event of a blockage ("blocking torque"). This design of the device or the press connection between the connection partners enables effective protection of the machine tool or its components in the drive train. In contrast to the mechanical slip clutch, the proposed mechanical overload protection device is preferably not designed for continuous operation.Rather, in the context of the present invention, it is intended that the torque M in the drive train is limited by the invention only in the event of extremely large overloads or blocking events. It is preferred within the meaning of the invention that the proposed mechanical overload protection device slips in the event of a blocking event, thus limiting the torque in the drive train.

[0018] According to the invention, it is preferred that the press connection comprises a first and a second sliding partner, wherein the first sliding partner is a component of the output shaft or the motor shaft and comprises a first sliding surface, and the second sliding partner is a component of the gear or the coupling sleeve and comprises a second sliding surface, wherein preferably at least one of the friction surfaces can have a surface coating. The surface coating can preferably be selected from a group comprising: hard chromium plating, nitriding, additional phosphating and / or nitrocarburizing, without being limited thereto. Particularly preferably, a molybdenum coating can be used between the gear and a shaft of the power train of the machine tool in order to ensure optimal adhesion or friction between the sliding partners.With the molybdenum coating, seizure between the sliding partners can be effectively reduced or prevented. In addition, further slipping of the sliding partners of the press connection can be prevented, so that the machine tool or its motor can advantageously be brought to a standstill within milliseconds. It was completely surprising that such rapid braking of the machine tool or its motor can be achieved while at the same time maintaining a compact design. The invention therefore enables significantly faster braking times than with couplings with bronze disks, as used in conventional machine tools from the prior art. The molybdenum coating is shown, for example, in Fig. 5, whereby in the preferred embodiment of the invention shown in Fig. 5, the molybdenum coating is present at least partially between the gear and the output shaft.

[0019] The first and second sliding partners can preferably also be referred to as "friction partners" within the meaning of the invention, whereby the sliding or friction partners form a sliding or friction pair. The sliding or friction pair preferably has a suitable material pairing, whereby the individual sliding or friction partners for forming the press connection can preferably comprise tool steel, sintered material, case-hardened steel and / or tempered steel. In principle, the use of a variety of metals or metal alloys as sliding or friction partners is conceivable in the context of the present invention. It is preferred within the meaning of the invention that the materials can comprise metals or metal alloys from different primary forming processes.It is preferred in the sense of the invention that the first sliding surface of the first sliding partner is arranged on an outer side of the output shaft, while the second sliding surface of the second sliding partner is arranged on an inner side of the coupling sleeve, so that the sliding or friction surfaces are arranged opposite or in contact with one another.

[0020] By selecting a suitable material for the first and second sliding or friction partners, which together form the press connection between the output shaft and the coupling shell, the slippage of the proposed mechanical overload protection device can be promoted, allowing the drive train to be disconnected in the event of a jam and the torque transmitted in the drive train to be limited. This effectively protects the machine tool and its mechanical components from damage in the event of a jam.

[0021] According to the invention, it is preferred that the material of the coupling sleeve be selected from a group comprising: steel, brass, bronze, and ceramic. The coupling sleeve is preferably designed as a bushing or can have the shape of a bushing.

[0022] Due to manufacturing reasons, the triggering range of the mechanical overload protection device may exhibit undesirably wide variations. This undesirably wide variation in the triggering range of the proposed device is due in particular to manufacturing tolerances. The undesirably wide variation in the triggering range can be reduced by providing the press connection with an outer surface onto which a clamping ring can be pressed. This allows the triggering range of the mechanical overload protection device to be adjusted and reduces the wide variation in the triggering range caused by manufacturing tolerances. According to the invention, it is preferred that the clamping ring be pressed on in a force- and / or displacement-controlled manner. Furthermore, the outer surface can comprise a conical angle.In other words, as a remedy against manufacturing-related tolerances, a preferably force-controlled pressing on of an external clamping ring can be carried out, whereby the clamping ring can be pressed onto an external, preferably flat, cone angle of the press connection.

[0023] According to the invention, it is preferred that the clamping ring is designed as a conical ring that is pressed onto the outer surface of the press connection in a force-controlled manner, thus limiting the triggering range of the mechanical overload protection device. Alternatively or additionally, according to the invention, it may be preferred that the clamping ring is pressed onto the outer surface of the press connection in a path-controlled manner, so that the triggering range of the mechanical overload protection device is advantageously limited in this way. Preferably, an outer surface of the bushing is also conical. In particular, the invention can achieve a very small deviation when triggering the mechanical overload protection device.This very small deviation when triggering the mechanical overload protection device can advantageously be achieved by adjusting the torque to be transmitted and / or a desired trigger value of the mechanical overload protection device with a very small deviation during the pressing-on process. During the pressing-on process, a force F is applied to the preferably conical clamping ring. This pressing-on process can be carried out with a defined force F and / or along a defined path S. A hydraulic press, for example, can be used for this. The higher the force F applied to the clamping ring, the greater the torque M that can later be transmitted with the resulting press connection of a shaft of the transmission unit of the machine tool on the one side and a gear and / or coupling sleeve on the other side.The term "force-controlled" in the sense of the invention preferably means that the clamping ring is pushed axially onto the outer conical area of ​​the bushing up to a defined press-on force. The term "path-controlled" in the sense of the invention preferably means that the clamping ring is pushed axially onto the outer conical area of ​​the bushing for a defined path. The clamping area is preferably arranged directly above the contact area of ​​the shafts and the coupling sleeve. Since the cone angle on the outside of the bushing is known, the radial preload of the connection between the output or motor shaft and the coupling sleeve can be adjusted in this way with the help of the applied press-on force or the defined displacement path. The clamping ring can be pushed over a cone so that the press fit, which forms the connection between the shaft and the clamping ring, can be advantageously increased.Preferably, the clamping ring is pushed onto the shaft with a defined pressing force and / or for a specific travel distance, thereby securing it to the shaft. The cone advantageously has an inclined surface, the inclination of which is determined by the cone angle (see Figure 6).

[0024] In a second aspect, the invention relates to a method for producing a mechanical overload protection device. The terms, definitions, and technical advantages introduced for the mechanical overload protection device preferably apply analogously to the manufacturing method.The manufacturing process is characterized by the following process steps: a) producing a press connection between the output shaft or the motor shaft on the one side and the coupling sleeve of the device on the other side, b) recording the press-on force required to produce the press connection, c) determining the release torque of the device, d) calculating a press-on force and / or a displacement path for the clamping ring, e) pressing the clamping ring onto the press connection between the output shaft or the motor shaft and the coupling sleeve of the device with the previously calculated press-on force and / or the previously calculated displacement path, f) re-determining the release torque of the device.

[0025] It is preferred within the meaning of the invention that the proposed manufacturing method is used, in particular, to produce the press connection between the output shaft or the motor shaft of the drive train and the coupling sleeve. As a result, within the scope of the proposed manufacturing method, in particular the gear, which can be driven by the motor shaft of the machine tool, is connected to the output shaft or the motor shaft via the coupling sleeve. Preferably, in the context of the proposed manufacturing method, the gear is pressed onto the output shaft or the motor shaft, wherein the coupling sleeve can be inserted between the gear and the output shaft or the motor shaft. The press-on force required to produce the press-on connection is measured, wherein this press-on force required to produce the press-on connection is preferably referred to as the "first press-on force" in the context of the present invention.The initial press-on force can preferably be measured using a servo press. Forces of up to 30 kilonewtons (kN) can be used, for example, with a measurement accuracy of 1% of the applied force.

[0026] The triggering torque of the resulting press connection is then checked by determining the triggering torque of the mechanical overload protection device. This method step is preferably also referred to as "checking" the triggering torque of the mechanical overload protection device within the meaning of the invention. The triggering torque can be checked, for example, using a torque measuring shaft, wherein the torque measuring shaft is preferably configured to determine a triggering torque.

[0027] The pressing force and / or the displacement path for the clamping ring can then be calculated, whereby the pressing force and / or the displacement path required for pressing on the clamping ring are preferably referred to as the "second pressing force" and / or "second displacement path" within the meaning of the invention. A software solution or a computer program product can be used to calculate a fictitious pressing force or a fictitious displacement path, which can then be used for pressing on the clamping ring. The clamping ring is then pressed onto the press connection between the output shaft and the coupling sleeve of the mechanical overload protection device using the previously calculated pressing force and / or the previously calculated displacement path.

[0028] The tripping torque of the mechanical overload protection device is then checked again to determine whether any deviations in the tripping torque and / or tolerances have been reduced. If, for example, the repeated tripping torque check reveals that the tripping torque is too low, the clamping ring can be pressed on again with a greater pressing force to increase the tripping torque of the mechanical overload protection device. The modified tripping torque can then be measured or checked again. These last steps can be repeated until the desired tripping torque and / or minimal deviations in the tripping torque are achieved.

[0029] Advantageously, the proposed method can provide an effective device for mechanical overload protection in a drive train of a machine tool, which has particularly small deviations of the triggering torque in the event of a blockage.

[0030] In one embodiment, the invention relates to a device for mechanical overload protection in a drive train of a machine tool, wherein the output shaft can be driven by the motor shaft via a gear and the gear can be pressed directly onto the output shaft. In this configuration, the component pair consisting of output shaft and gear forms a mechanical overload protection device. The connection between the output shaft and the gear can preferably be established via a press connection, wherein the mechanical overload protection can then preferably be directly integrated into the press connection between gear and shaft. The coupling sleeve can be omitted in this embodiment of the invention, thereby reducing the complexity of the device and simplifying its manufacture.

[0031] In a further embodiment of the invention, the device for mechanical overload protection can be arranged on the drive side of the drive train. The mechanical overload protection can then be formed by the component pair motor shaft and gear, wherein a coupling sleeve between the motor shaft and the gear can be used or not. If a coupling sleeve is used, it is preferred within the meaning of the invention that the coupling sleeve is positively connected to the gear and the motor shaft is connected to the coupling sleeve via a press connection. Providing the mechanical overload protection on the drive side of the drive train can be preferred above all if integration on the output side is not possible, for example because there is insufficient installation space available on the output side.

[0032] In a further embodiment of the invention, the output shaft can be driven by the motor shaft via a gear, wherein the device for mechanical overload protection has a coupling sleeve which is positively connected to the gear, wherein the output shaft is connected to the coupling sleeve via a press connection.

[0033] Further advantages emerge from the following description of the figures. The figures, the description, and the claims contain numerous features in combination. The skilled person will also expediently consider the features individually and combine them into further meaningful combinations.

[0034] In the figures, identical and similar components are numbered with the same reference numerals.

[0035] They show:

[0036] Fig. 1 View of a preferred embodiment of the device for mechanical overload protection

[0037] Fig. 2 Side view of a preferred embodiment of the device for mechanical overload protection

[0038] Fig. 3 Detailed view of a preferred embodiment of the device for mechanical overload protection

[0039] Fig. 4 View of a preferred embodiment of the device for mechanical overload protection with clamping ring

[0040] Fig. 5 View of a preferred embodiment of the device for mechanical overload protection with clamping ring to show the arrangement of the molybdenum coating

[0041] Fig. 6 View of a preferred embodiment of the device for mechanical overload protection with clamping ring to show the cone angle

[0042] Implementation examples and figure descriptions:

[0043] Figure 1 shows a preferred embodiment of the device 10 for mechanical overload protection. Shown in particular is a mechanical overload protection device 10 that is arranged on the output side 20 of the drive train. Figure 1 shows in particular the output side 20 and the drive side 30 of the drive train (without reference numerals) of a machine tool (not shown). The output side 20 of the drive train has an output shaft 22 that can be connected to a motor shaft 32 on the drive side 30 of the drive train via a gear 40a. For this purpose, the motor shaft 32 can have a pinion 34 on the side facing away from the motor, which can engage with the teeth of the gear 40a. In this way, a rotational movement of the motor shaft 32 on the drive side 30 of the drive train is transmitted to the output side 20 and the output shaft 22.The gear 40a can be considered a connecting means 40 for connecting the motor shaft 32 and the output shaft 22. Alternatively, a bushing 40b (not shown) can be used to transmit the rotational movement and / or the torque of the motor shaft 32 to the output shaft 22. The mechanical unit for transmitting the rotational movement and / or the torque of the motor 14 of the machine tool to the tool holder 12 is preferably referred to as a "transmission unit 60" within the meaning of the invention. The transmission unit 60 of the machine tool preferably comprises the motor shaft 32, the output shaft 22, and any intermediate shafts, as well as the device 10 for mechanical overload protection and its connecting means 40, such as gears 40a or bushings 40b. The figures particularly illustrate the embodiment of the invention in which the connecting means 40 is designed as a gear 40a.The transmission unit 60 of the machine tool shown in the figures comprises in particular a motor shaft 32 and an output shaft 22. However, the proposed device 10 for mechanical overload protection can in particular also comprise intermediate shafts (not shown) which, in addition to the motor shaft 32 and the output shaft 22, are used to transmit the rotary movement and / or the torque of the motor 14 to the tool of the machine tool.

[0044] The motor shaft 32 can, for example, have a number of Z = 11 teeth. The gear 40a can, for example, have a number of Z = 58 teeth. Of course, other combinations of numbers of teeth are also conceivable. The aforementioned combination of eleven teeth on the motor shaft 32 and fifty-eight teeth on the gear 40a of the proposed overload protection device 10 has proven particularly suitable for transmitting the torques that occur, but also for enabling disconnection of the drive train in the event of a blockage. The rotation of the motor 14 (see Fig. 2) of the machine tool drives the motor shaft 32 to rotate. The teeth 34 of the motor shaft 32 engage in the spaces between the teeth of the gear 40a, so that the rotational movement of the motor shaft 32 is transmitted to the gear 40a and the output shaft 22 connected to it.

[0045] The gear 40a is positively connected to a coupling sleeve 42, which in turn is connected to the output shaft 22 by means of a press connection 44. In this way, the gear 40a is connected to the output shaft 22, so that a rotational movement of the gear 40a also leads to a rotational movement of the output shaft 22 on the output side 20 of the drive train.

[0046] Figure 2 shows a side view of a preferred embodiment of the device 10 for mechanical overload protection, wherein this mechanical overload protection is also arranged on the output side 20 of the drive train. Figure 2 also shows a possible arrangement of the drive train within the machine tool (not shown). On the left side of Figure 2, a holder 12 for a tool of the machine tool is indicated. The machine tool can be, for example, a core drilling machine. The tool of the machine tool can, for example, be formed by a drill bit, wherein a drill bit represents a comparatively torsionally rigid tool. The tool holder 12 is preferably arranged at a first end of the output shaft 22 of the drive train, while the second end of the output shaft 22 forms an end of the output shaft 22 facing away from the tool holder.At this end facing away from the tool holder, the output shaft 22 is connected to a coupling sleeve 42, the connection being formed by a press connection 44. In other words, there is a press connection 44 between the output shaft 22 and the coupling sleeve 42. The coupling sleeve 42 is also positively connected to a gear 40a, which can be driven via a motor shaft 32 of the drive side 30 of the drive train. The motor shaft 32 has a pinion 34 at its first end, which can interact with the gear 40a to transmit a rotary motion. At its second end, the motor shaft 32 is connected to the motor 14 of the machine tool. Due to the rotational speed of the motor 14 of the machine tool, the drive side 30 with the motor shaft 32 represents the fast-rotating side of the drive train, while the output side 20 with the output shaft 22 represents the slow-rotating side of the drive train.

[0047] Figure 3 shows a detailed view of a preferred embodiment of the device 10 for mechanical overload protection. The press connection 44 between the output shaft 22 and the coupling sleeve 42 allows the output shaft 22 and the coupling sleeve 42 to slide or rub against each other.

[0048] In this sense, the output shaft 22 and the coupling sleeve 42 represent friction or sliding partners in a friction or sliding pair. In particular, the output shaft 22 represents a first sliding partner 46, and the output shaft 22 has a first friction or sliding surface 48. The coupling sleeve 42 represents a second sliding partner 50, and the coupling sleeve 42 has a second friction or sliding surface 52. The sliding or friction surfaces 48, 52 form contact surfaces between the output shaft 22 and the coupling sleeve 42, wherein at least one of the sliding or friction surfaces 48, 52 can have a surface coating. The provision of a surface coating represents a measure to ensure a permanently essentially constant triggering torque for disconnecting the drive train in the event of a blockage of the machine tool.The sliding or friction surfaces 48, 52 can, for example, be hard chrome-plated and / or nitrided and / or have a molybdenum coating, without being limited thereto. A further measure to ensure a permanently essentially constant release torque for disengaging the drive train in the event of a blockage of the machine tool consists in the selection of suitable materials for the sliding or friction surfaces 48, 52 of the sliding partners 46, 50. Tool steel or sintered materials, for example, can be used. The coupling sleeve 42, which is preferably pressed between the gear 40a and the output shaft 22, can, for example, comprise steel, brass, bronze and / or ceramic or be made of at least one of the aforementioned materials. Of course, material combinations or alloys for producing the sliding partners 46, 50 or the coupling sleeve 42 are also conceivable.

[0049] Preferably, the materials of the sliding partners 46, 50 or the coupling sleeve 42 are selected such that the mechanical overload protection device 10 is triggered, i.e., disconnects the drive train, particularly in the event of severe blocking. In this way, the torque in the drive train can be limited, and the components of the machine tool are effectively protected from damage in the event of a blocking. A fundamental idea underlying the invention is to limit the torque to be transmitted by the press connection 44 to a value M_Limit that is smaller than the maximum blocking torque M_B. The materials of the sliding partners 46, 50 or the coupling sleeve 42 are selected or designed, in particular, such that the resulting press connection 44 slips in the event of a blocking, thus limiting the torque in the drive train. Figure 4 shows a view of a preferred embodiment of the device 10 for mechanical overload protection with a clamping ring 56.The provision of an additional clamping ring 56 in the area of ​​the press connection 44 can reduce manufacturing-related tolerances of the mechanical overload protection device 10, so that the release torque of the mechanical overload protection device 10 can be more precisely adjusted and controlled by the clamping ring 56. The clamping ring 56 is pressed onto an outer surface 54 of the press connection 44, with the pressing on of the clamping ring 56 being carried out in particular in a force-controlled manner. After the clamping ring 56 has been pressed on, the release torque of the mechanical overload protection device 10 can be measured and, if necessary, the clamping ring 56 can be pressed more firmly, i.e. with a higher pressing force, from the outside onto the press connection 44 in a second or further pressing-on step. The outer surface 54 can, for example, be formed by an outer surface of the coupling sleeve 42.

[0050] The press connection 44 preferably has a preferably flat conical angle 58 onto which the clamping ring 56 can be pressed. In other words, the coupling sleeve 42 may not be completely cylindrical, but rather tapered, so that the coupling sleeve 42 forms a slightly tapered hollow cylinder.

[0051] The slope of the walls of this hollow cylinder is determined by the cone angle 58, which can be in a range from 1 to 5 degrees, preferably 3 degrees. The cone angle 58 is also shown in particular in Fig. 6. The cone angle 58 can also be larger or smaller than the specified angle range, depending on whether a coating is used on the friction partners or not, or depending on the nature or chemical composition of any coating.

[0052] According to the invention, it is preferred that the clamping ring 56 is formed by a conical ring that can be pressed onto the press connection 44 in a force-controlled and / or path-controlled manner in order to be able to adjust the triggering torque of the mechanical overload protection device 10 better and more precisely as an optimal, additional component. According to the invention, the triggering torque represents the torque at which the mechanical overload protection device 10 disconnects the drive train, for example if the tool of the machine tool is blocked or if the tool of the machine tool becomes jammed in the surface to be machined. By disconnecting the drive train by the mechanical overload protection device 10 in this so-called blocking situation, the torque in the drive train can be reliably limited, thus protecting the components of the machine tool from damage.Particularly defined torque limits at which the mechanical overload protection device 10 triggers (“triggering torque”) are helpful in this regard. Such clearly defined torque limits can be provided, in particular, with the help of the force-controlled pressed-on clamping ring 56. The clamping ring 56 can be pressed onto an outer surface 54 of the press connection 44 using an automated assembly process, with torques and forces being measured during the assembly process in order to determine an optimal pressing force and / or an optimal path for pressing the clamping ring 56 onto the press connection 44. In this way, the triggering torque and its accuracy can be improved and, advantageously, adjusted very precisely.

[0053] Figure 5 shows a preferred embodiment of the device 10 for mechanical overload protection with clamping ring 56 to illustrate the arrangement of the molybdenum coating 62. In the embodiment of the invention shown in Figure 5, the molybdenum coating 62 is arranged between the gear 40a and the output shaft 22.

[0054] Figure 6 shows a further preferred embodiment of the device 10 for mechanical overload protection with clamping ring 56, wherein in Figure 6 in particular the cone angle 58 and its position are shown.

[0055] List of reference symbols

[0056] 10 Device for mechanical overload protection

[0057] 12 tool holder

[0058] 14 Engine

[0059] 20 Output side

[0060] 22 Output shaft

[0061] 30 Drive side

[0062] 32 Motor shaft

[0063] 34 teeth

[0064] 40 lanyards

[0065] 40a gear

[0066] 40b socket

[0067] 42 coupling sleeve

[0068] 44 Press connection

[0069] 46 first gliding partner

[0070] 48 first sliding surface

[0071] 50 second gliding partner

[0072] 52 second sliding surface

[0073] 54 exterior area

[0074] 56 clamping ring

[0075] 58 cone angle

[0076] 60 transmission unit

[0077] 62 Molybdenum coating

Claims

Patent claims 1. Device (10) for mechanical overload protection in a drive train of a machine tool, wherein the drive train has an output side (20) with an output shaft (22) and a drive side (30) with a motor shaft (32), characterized in that the output shaft (22) is operatively connected to the motor shaft (32) via a connecting means (40), wherein the device (10) for mechanical overload protection is formed by a press connection (44) between the connecting means (40) on one side and the motor shaft (32) or the output shaft (22) on the other side.

2. Device (10) according to claim 1, characterized in that the device (10) for mechanical overload protection further comprises a coupling sleeve (42) which is positively connected to the connecting means (40).

3. Device (10) according to claim 1 or 2, characterized in that the connecting means (40) is formed by a gear (40a) and / or a bushing (40b).

4. Device (10) according to claim 3, characterized in that the press connection (44) comprises a first sliding partner (46) and a second sliding partner (50), wherein the first sliding partner (46) is a component of the output shaft (22) or the motor shaft (32) and comprises a first sliding surface (48) and the second sliding partner (50) is a component of the gear wheel (40a) or the coupling sleeve (42) and comprises a second sliding surface (52), wherein at least one of the sliding surfaces (48, 52) has a surface coating. Device (10) according to claim 4, characterized in that the surface coating is selected from a group comprising: hard chromium plating, nitriding, molybdenum coating, additional phosphating and / or nitrocarburizing. Device (10) according to one of claims 2 to 5, characterized in that a material of the coupling sleeve (42) is selected from a group comprising: steel, brass, bronze and / or ceramic. Device (10) according to one of the preceding claims, characterized in that the device (10) is designed to limit the torque M of the press connection (44) to be transmitted in the drive train to a value M_Limit, wherein M_Limit is smaller than the torque M_B that occurs in the event of a lock.Device (10) according to one of the preceding claims, characterized in that the press connection (44) has an outer surface (54), wherein a clamping ring (56) can be pressed onto this outer surface (54) in order to adjust a triggering range of the device (10). Device (10) according to claim 8, characterized in that the clamping ring (56) can be pressed on in a force-controlled and / or displacement-controlled manner. Device according to claim 8 or 9, characterized in that the outer surface (54) comprises a cone angle (58). Method for producing a device (10) according to one of claims 8 to 10, wherein the method is characterized by the following method steps: a) producing a press connection (44) between the output shaft (22) or the motor shaft (32) on the one side and the coupling sleeve (42) of the device (10) on the other side, b) detecting the press-on force required to produce the press connection (44), c) determining the triggering torque of the device (10), d) calculating a press-on force and / or a displacement path for the clamping ring (56), e) pressing the clamping ring (56) onto the press connection (44) between the output shaft (22) or the motor shaft (32) and the coupling sleeve (42) of the device (10) with the previously calculated press-on force and / or with the previously calculated displacement path, f) re-determining the triggering torque of the device (10).

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