Eccentrically adjustable tool chuck

Abstract

Eccentrically adjustable tool chuck (10), comprising: - a housing (12) which has a connection (16) to the rotary drive and defines an axis of rotation (17); - a shaft (20) which is rotatably mounted in the housing (12), wherein the axis of rotation of the shaft (20) is arranged eccentrically parallel to the axis of rotation (17) of the housing (12); - a tool holder (26) in the shaft (20) for receiving a tool (18), which is arranged eccentrically parallel to the axis of rotation of the shaft (20); - a fixing device (27) for securing the tool (18) in a predetermined position within the tool holder (26) that is secured against rotation; - an adjusting device (36) for angular adjustment of the shaft (20) relative to the housing (12);- wherein the shaft (20) is angularly oriented between a first position in which the tool holder (26) is centrally aligned with the axis of rotation (17) of the housing (12) and a second position in which the tool holder (26) is arranged eccentrically parallel offset with respect to the axis of rotation (17) of the housing (12) and wherein the tool chuck (10) is balanced in the first position with respect to the axis of rotation (17) of the housing (12).

Description

The invention relates to an eccentrically adjustable tool chuck, in which the tool holder is adjustable between a centrally oriented position, which is suitable for drilling, for example, and between an eccentrically offset position, which is suitable for turning or deburring, for example.DE 10 2015 013 247 A1 discloses a drill with counter-boring function and a drilling method for lightweight materials, whereby on the one hand a drilling process can be carried out in a centrally aligned position of the drill and on the other hand a drilling to finished size takes place with an eccentrically offset position with a particularly laterally ground-free cutting edge in the opposite direction of rotation.Such drills are used in particular in lightweight construction in order to avoid raggeding of the bore during production in the case of multilayer materials which contain, for example, a titanium layer and a carbon fibre layer. In aircraft construction, for example, numerous such bores are to be made in multi-layered materials. In the aforementioned known drill, the changeover between a centrally aligned drilling operation and an eccentrically offset operation takes place by a reversal of the direction of rotation by means of a corresponding drill chuck.The reversal of the direction of rotation in particular has proven disadvantageous here, since this has the result that sufficient chip removal is no longer ensured in the case of the reverse direction of rotation. This is because the chips are no longer conveyed outwards, as in the usual operation, but rather run into the workpiece. This results in only a very limited punching time of the drill. In addition, there is no longer any balancing in the eccentric offset of the drilling tool, which is why the field of use is limited to a maximum of approximately 4000 U / min.EP 0 075 061 A1 discloses a further drill with a deburring facility and a drill chuck, with the result that an adjustment between a centered position for drilling and an off-center position for deburring is made possible. For adjustment between the two positions, the drill chuck has an outer sleeve in which an inner sleeve is held, wherein the two sleeves are coupled to one another in a rotationally fixed manner via a transverse pin. A contact means is used for the switching, by means of which a movement between the two positions and a latching takes place.Such a chuck is of relatively complicated construction and has an imbalance, for which reason the range of insertion is greatly limited.EP 0 103 291 A1 discloses a further chuck which enables a drilling tool to be adjusted between a centered and an off-center position. In this case, a clamping unit for receiving the drilling tool is pivotably coupled to a drive shaft. The clamping unit comprises a clamping cone having a spherical circumferential surface which is held in an inner cylindrical surface of a cup-shaped region of a drive element. A displacement movement between the two positions is generated by means of a pneumatic piston-cylinder unit.This drill chuck is also of relatively complicated construction and has an imbalance, for which reason the setting range is greatly limited.An eccentrically adjustable workpiece chuck is known from DE 10 2006 011 057 A1, having a housing which has a connection for the rotary drive and defines an axis of rotation; having a shaft which is rotatably mounted in the housing, an axis of rotation of the shaft being arranged offset eccentrically in parallel with respect to the axis of rotation of the housing; having a tool receptacle in the shaft for receiving a tool which is arranged offset eccentrically in parallel with respect to the axis of rotation of the shaft; having a fixing device for fixing the tool in a predetermined position within the tool receptacle which is secured against rotation; and having an adjusting device for the angular adjustment of the shaft relative to the housing. An adjustment of the eccentricity is effected here by an angular adjustment of the shaft relative to the housing.However, this is a workpiece chuck whose features are not necessarily transferable to a tool chuck, since other requirements regarding stability, runout, etc. are placed on tool chucks.U.S. Pat. No. 2,945,404 A discloses an eccentrically adjustable tool chuck in which the tool is held on a receptacle offset at an angle to the axis of rotation of the tool chuck, eccentricity taking place by longitudinal adjustment along the offset receptacle.Against this background, the object of the invention is to provide an eccentrically adjustable tool chuck of simple and reliable construction, with which an adjustment of the tool holder between a centrally aligned position and an eccentrically offset position is possible without reversal of the rotational direction. Here, machining at relatively high rotational speeds should also be possible.This object is achieved according to the invention by an eccentrically adjustable tool chuck according to claim 1.The invention is thus completely solved.Due to the off-center arrangement of the shaft rotatably mounted in the housing in combination with the tool holder in the shaft, which is arranged off-center parallel offset with respect to the axis of rotation of the shaft, the tool holder can be adjusted without a reversal of the direction of rotation between a centrally aligned position and an eccentrically offset position by an angular adjustment of the shaft relative to the housing.Such an arrangement enables a simple and reliable construction, while at the same time enabling a high rotational speed in the centrally aligned position, since the tool chuck can be balanced in this position.The balancing is initially ensured by calculation by a corresponding weight distribution of the masses within the tool chuck. In addition, in the centrally oriented position, a balancing treatment is preferably carried out on a balancing machine in order to ensure balanced operation even at high rotational speeds. For this purpose, holes are preferably made in the housing at suitable points in order to achieve a balanced running.In this case, all parts of the tool chuck including the part of a tool accommodated in the tool holder can be balanced. Only the part of a tool outside the tool holder cannot be included in the balancing process.In this way, operation in the first centered position is possible up to high rotational speeds, for example in the range of up to 12,000 U / min or more.According to a further embodiment of the invention, the shaft is angularly displaceable between two stops between the first position, in which the tool holder is aligned centrally with the axis of rotation of the housing, and the second position, in which the tool holder is arranged eccentrically offset with respect to the axis of rotation of the housing.By using two stops, a position of the tool holder aligned centrally with respect to the axis of rotation of the housing can thus be reliably ensured and a precise offset with respect to the axis of rotation of the housing can likewise be ensured by the stop at the other end.According to a further embodiment of the invention, the fixing device comprises a pin which abuts an associated surface of the tool, for example a Weldon surface, and is preferably braced by means of a screw.In this way, a secure fixing of the tool in a predetermined position within the tool holder is ensured.According to a further embodiment of the invention, the stops are formed by two screws held in the housing, which cooperate with a groove on the shaft.This represents a simple and effective limitation of the angle of rotation of the shaft and thus for adjusting the eccentric displacement.According to a further embodiment of the invention, the adjusting device has a slotted guide which converts an axial movement of a drive device into a rotational movement of the shaft.In this way, a simple and reliable angular adjustment of the shaft is ensured.According to a further embodiment of the invention, the drive device can be driven by means of a fluid pressure.Preferably, the drive device has a piston which is movable in the axial direction against a prestressing force.According to a further embodiment of the invention, the piston is guided in an axially movable manner within a cavity of the housing and is axially prestressed by a plurality of spring elements.Preferably, for axial movement of the piston, a fluid under pressure can be supplied into the cavity formed between the piston and the housing.In this way, a simple and reliable adjustment of the tool chuck between the first position aligned with the axis of rotation of the housing and the second eccentrically offset position is made possible.According to a further embodiment of the invention, a fluid connection for a minimum quantity lubrication leading to the tool holder is provided, which can be coupled to the cavity via a first valve.In this way, a minimum quantity lubrication provided in any case on the tool chuck can be used for switching over the tool chuck between the first and second positions.For this purpose, the first valve preferably has a predetermined opening pressure for activation, which is dimensioned such that an axial movement of the piston counter to the prestressing force of the spring elements results when the opening pressure is reached.This measure has the advantage that, in the event of a loss of pressure, the piston is automatically moved back into its starting position by the prestressing force of the spring elements, so that the tool holder is located in the first centrally aligned position.According to a further embodiment of the invention, the first valve is designed to interrupt the fluid supply for the duct leading to the tool holder for minimal quantity lubrication upon activation and to apply the fluid pressure to the cavity for axial movement of the piston.In this way, by means of a suitable increase in pressure, on the one hand, the switching over of the tool chuck between the first and second positions is made possible and, on the other hand, when the first valve is activated by a high pressure, a fluid supply for the channel guiding the tool holder is interrupted, so that no adverse influence on the minimum quantity lubrication results.According to another embodiment of the invention, a second valve is provided which is configured to open below the predetermined opening pressure for the first valve to vent the cavity to the outside.In this way, it is ensured that as long as the predetermined opening pressure for activating the first valve is not applied, no movement of the piston against the prestressing force of the spring elements can take place, either, so that a stable position of the first, centrally oriented position is ensured.According to a further embodiment of the invention, a third valve is provided which is designed to vent the cavity between the housing and the piston to the outside in the event of failure of the fluid pressure.In this way, it is ensured in the event of a pressure failure that no adjustment into the second, eccentrically offset position results.According to a further embodiment of the invention, the tool holder is designed as a bore at the outer end of the shaft.This enables a simple reception of a tool, in particular in the form of a drilling tool.It is understood that the features of the invention mentioned above and those still to be explained below can be used not only in the respectively specified combination but also alone or in other combinations without departing from the scope of the invention.Further features and advantages of the invention will become apparent from the following description of a preferred exemplary embodiment with reference to the drawing. It shows. FIG. 1 shows a perspective illustration of a tool chuck according to the invention; FIG. 2 is a longitudinal view of the tool chuck according to FIG. 1 ; FIG. 3 is an enlarged sectional view of the tool chuck according to FIG. 2 along the line III-III; FIG. 4 is a sectional view through the tool chuck according to FIG. 2 along the line IV--IV; FIG. 5 shows a perspective, transversely cut illustration of the tool chuck according to FIG. 4 ; FIG. 6 shows a section through the tool chuck according to FIG. 4 along the line VI-VI in an enlarged illustration; FIG. 7 shows a perspective illustration of the tool chuck according to FIG. 1, but without the housing; FIG. 8 shows a perspective view of the tool chuck according to FIG. 1, but without the housing, viewed from the underside; and FIG. 9 shows a perspective view of the tool chuck according to FIG. 7, without the housing, in a position slightly modified in comparison with FIG. 8.A tool chuck according to the invention is illustrated in FIGS. 1 to 9 and is denoted overall by the numeral 10.According to FIG. 1, the tool chuck 10 has a hollow cylindrical housing 12 which is closed at its first end by a closing flange 14 and at this end has a connection 16 for rotary drive by a machine tool, for example in the form of an HSK connection. At the opposite second end, the housing 12 is closed off by a ring 22 of smaller diameter, in front of which there is a union nut 24 which is screwed to a shaft 20 projecting slightly outwards. Projecting outwardly from the shaft 20 is a tool 18 in the form of a drill.The tool chuck 10 or the housing 12 can be driven to rotate about an axis of rotation 17 by means of the connection 16.According to FIG. 3, a shaft 20 is rotatably mounted within the housing 12 and has an axis of rotation which is arranged eccentrically offset with respect to the axis of rotation 17 of the housing 12, so that a certain eccentricity results.Provided within the shaft 20 at the second, outer end is a tool receptacle 26 in the form of a bore in which a tool 18 can be received. The tool 18 can be fixed in a predetermined rotational position within the tool holder 26, for which purpose a fixing device is provided, which is denoted overall by 27.For this purpose, the tool 18 has, in the region of its tool shank, a flat surface 28, which can be a so-called Weldon receptacle. An associated pin 29 is pressed against the flat surface 28 by means of a screw 30, so that a defined position of the tool 18 within the tool holder 26 or the shaft 20 is obtained.The shaft 20 is angularly displaceable by means of an adjusting device, which is designated overall as 36, between a first position, in which the tool holder 26 is aligned centrally with the axis of rotation 17 of the housing, and a second position, in which the tool holder 26 is arranged eccentrically offset with respect to the axis of rotation 17 of the housing 12. The adjustment angle required for this purpose can be, for example, approximately 30°.The first position and the second position are each limited by stops. To this end, as can be seen in FIGS. 3 to 5, a first screw 32 is received on one side of the housing 12, the end of which engages in an associated groove provided in the surface of the shaft 20. The groove 33 extends over a certain angular range and has a first end 56 and a second end 57.On the opposite side of the housing 12 is received a second screw 34, the end of which in turn engages in an associated annular circumferential groove 35 on the shaft 20. This second groove 35 has a first end 58 and a second end 59.As can be seen from FIG. 4, it is thus possible to adjust the shaft 20 between the first position, shown in the figures, in which the tool holder 26 is aligned centrally with the axis of rotation 17 of the housing 12, and the second position, in which an eccentric offset of the tool holder 26 with respect to the axis of rotation 17 of the housing 12 results. In this case, the first position is limited by a stop of the second screw 34 at the first end 58 of the associated groove 35. Furthermore, the second position is limited by a stop of the first screw 32 at the second end 57 of the first groove 33.For adjusting the shaft 20 between the first position and the second position, an adjusting device according to FIG. 3 is used, which is designated as a whole as 36. the adjusting device 36 has a drive device 37, by means of which a piston 38, which is accommodated within a cavity 40 of the housing 12 in an axially displaceable manner, is displaceable along an inner surface 41 of the cavity 40 by means of a fluid pressure. The piston 38 is prestressed in the direction of the first position by a total of five spring elements 42, which are each of identical construction and the arrangement of which can be seen in particular from FIGS. 4 and 5, such that the piston 38 moves to the right under the action of the spring force according to FIG. 3 and bears against an inner flange 49.An axial movement of the piston 38 within the cavity 40, which is generated by a fluid pressure, leads to a rotation of the shaft 20 relative to the housing 12, for which purpose a slotted guide, which is denoted overall by 52, is provided on one side of the shaft 20. The slide guide has a screw 54 which is held in the shaft 20 and engages in an associated, oblique guide groove 53 of the piston 38. If the piston 38 thus moves to the left against the action of the spring elements 42 from the position shown in FIG. 3, this leads to a rotational movement of the shaft 20 relative to the housing 12.In order to move the shaft 20 between the first position and the second position, the drive device 37 is provided, which enables a movement of the piston 38 by means of fluid pressure against the prestressing force of the spring elements 42.For this purpose, a minimum quantity lubrication MMS provided on the tool chuck 10 is used. A central fluid connection 44 for the MMS is connected to the cavity 40 via a first valve 46 and an associated channel 55. From the fluid connection 44, a connecting channel 51 leads via the first valve 46 to a central lubricant channel 50 for MMS, which leads to the tool holder 26. The ends of the central lubricant passage 50 and the connecting passage 51 are closed by respective plugs 48 and 47.In the position shown in FIG. 3, the compressed air, via which the MMS is fed, can thus pass via the first valve 46 into the central lubricant channel 50. In normal operation, the MMS is operated, for example, with an air pressure of approximately 2 bar. If the pressure within the MMS is now increased to a predetermined operating pressure, so that the force of the spring elements 42 can be overcome, for example to a pressure of 5 bar, the first valve 46 switches through and allows the fluid pressure to overflow via the connecting channel 55 into the cavity 40, while at the same time the connection to the central lubricant channel 50 is closed via the connecting channel 51.The pressure within the cavity 40 thus leads to a movement of the piston 38 counter to the prestressing force of the spring elements 42 and, as a result of the slotted guide 52, leads to a rotation of the shaft 20 relative to the housing 12, the piston 38 itself being secured against rotation by means of a screw 64 held in the housing 12 and engaging in an axially running groove 66 on the piston 38.In order that no force is exerted on the cylinder 38 below the predetermined activation pressure, which leads to the rotation of the shaft 20, an associated second valve 60, which can be seen in FIG. 6, is designed to effect venting of the cavity 40 to the connection 44 for the MMS until shortly below the opening pressure of the first valve 46.A third valve 62, which can likewise be seen in FIG. 6, is provided for venting the channel 50 leading to the tool holder 26 to the outside in the event of a drop in the pressure of the fluid for the MMS.The housing 12 is sealed off from the outside on the tool side, for which purpose a seal 23 is provided, which is held by a ring 22 which is screwed onto the shaft 20. In addition, a union nut 24 screwed onto the outside of the shaft 20 serves to secure the ring 22.The tool chuck 10 is balanced in the first position, in which the tool holder 26 is aligned centrally with the axis of rotation 17 of the housing 12, for which purpose the mass distribution within the tool chuck 10 is adapted by means of suitable bores or projections such that a balanced state results. Before the tool chuck is put into operation, it is preferably additionally finely balanced on a balancing machine in order to ensure balanced running even at high rotational speeds.Due to the special construction of the drive device 37, a drop in the fluid pressure leads to the piston 38 moving under the action of the spring elements 42 into its right-hand starting position, so that the first, centrally aligned position of the tool holder 26 results.

Claims

Eccentrically adjustable tool chuck (10), having: - a housing (12) which has a connection (16) for rotary drive and defines an axis of rotation (17); - a shaft (20) which is rotatably mounted in the housing (12), wherein the axis of rotation of the shaft (20) is arranged offset eccentrically in parallel with respect to the axis of rotation (17) of the housing (12); - a tool receptacle (26) in the shaft (20) for receiving a tool (18), which is arranged offset eccentrically in parallel with respect to the axis of rotation of the shaft (20); - a fixing device (27) for fixing the tool (18) in a predetermined position within the tool receptacle (26), which is secured against rotation; - an adjusting device (36) for the angular adjustment of the shaft (20) relative to the housing (12); wherein the shaft (20) is arranged offset angularly between a first position, in which the tool holder (26) is aligned centrally with the axis of rotation (17) of the housing (12), and a second position, in which the tool holder (26) is arranged eccentrically parallel with respect to the axis of rotation (17) of the housing (12), and wherein the tool chuck (10) is balanced in the first position with respect to the axis of rotation (17) of the housing (12).The tool chuck (10) of claim 1, wherein the shaft (20) is angularly adjustable between the first position and the second position between two stops.Tool chuck (10) according to one of the preceding claims, in which the fixing device (27) comprises a pin (29) which bears against an associated surface (28) of the tool (18).Tool chuck (10) according to Claim 3, in which the pin (29) is clamped by means of a screw (30).Tool chuck (10) according to one of Claims 2 to 4, in which the stops are formed by two screws (32, 34) which are held in the housing (12) and cooperate with a groove (33, 35) on the shaft (20).Tool chuck (10) according to one of the preceding claims, in which the adjusting device (36) has a slotted guide (52) which converts an axial movement of a drive device (37) into a rotational movement of the shaft (20).Tool chuck (10) according to claim 6, in which the drive device (37) can be driven by means of a fluid pressure.Tool chuck (10) according to Claim 6 or 7, in which the drive device (37) has a piston (38) which is movable in the axial direction counter to a prestressing force.Tool chuck (10) according to claim 8, wherein the piston (38) is guided within a cavity (40) of the housing (12) in an axially movable manner and is axially prestressed by a plurality of spring elements (42).Tool chuck (10) according to Claim 9, in which, for the axial movement of the piston (38), a fluid can be fed under pressure into the cavity (40) formed between the piston (38) and the housing (12).Tool chuck (10) according to claim 10, in which a fluid connection (44) for a minimum quantity lubrication leading to the tool holder (26) is provided, which can be coupled to the cavity (40) via a first valve (46).Tool chuck (10) according to Claim 11, in which the first valve (46) has a predetermined opening pressure for activation which is dimensioned such that an axial movement of the piston (38) counter to the prestressing force of the spring elements (42) results when the opening pressure is reached.Tool chuck (10) according to claim 12, wherein the first valve (46) is configured to interrupt the fluid supply for a lubricant channel (50) leading to the tool holder (26) for minimal quantity lubrication upon activation and to apply the fluid pressure to the cavity (40) for axial movement of the piston (38).The tool chuck (10) according to any one of claims 11 to 13, wherein a second valve (60) is provided, which is configured to open below the predetermined opening pressure for the first valve (46) in order to vent the cavity (40) to the outside.Tool chuck (10) according to Claim 14, in which a third valve (62) is provided, which is designed to vent the cavity (40) between the housing (12) and the piston (38) outwards in the event of failure of the fluid pressure.Tool chuck (10) according to one of the preceding claims, in which the tool holder (26) is designed as a bore at the outer end of the shaft (20).

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