MXPA06011369A - Hydraulic expanding chuck - Google Patents

Abstract

The invention relates to a hydraulic expanding chuck (1), which has a particularly advantageous long, narrow design. The tool end (3) of the expanding chuck (1) is equipped with an expanding bushing (10) that is surrounded by a pressure chamber (12), which can be radially deformed in order to clamp a tool by means of a hydraulic fluid (F) that is contained in said pressure chamber (12). A pressure generation unit (14) is situated at an axial distance from the expanding bushing (10) and a pressure conduction system (13) is provided to transfer pressure from the pressure generation unit (14) to the pressure chamber (12), said pressure conduction system being formed by an annular gap (11) that is concentric with the chuck axis (2).

Description

HYDRAULIC EXPANSION MANDREL DESCRIPTION OF THE INVENTION The invention relates to a hydraulic expansion mandrel for fixing a tool, in particular a drill bit or a milling cutter. A mandrel serves to connect a rotary driven tool to the driving spindle of a machine tool, a mandrel therefore has a pronounced mandrel shaft around which the mandrel and the tool clamped thereon are rotated. In the direction towards this mandrel axis, the mandrel always has one end on the side of the tool that is provided for receiving the tool, as well as one end on the side of the machine, which is shaped for the connection of the mandrel with the spindle of the machine tool, a genus known as chucks themselves form the so-called hydraulic expansion mandrels. In these hydraulic expansion mandrels, the housing for the tool is formed by a thin-walled expansion bushing. The expansion sleeve is surrounded by a pressure chamber that is filled with a pressure medium, for example an oil. The expansion sleeve is now shaped such that it deforms elastically in the radial direction when pressure is applied to the pressure medium and thus fixes the tool. A hydraulic expansion chuck has in particular the advantage that dampens vibrations and shocks that occur during operation. In this way, a particularly high surface quality and a long tool life are achieved during machining. From WO 03/095132 Al a hydraulic expansion mandrel of this nature is known. In the known hydraulic expansion mandrel, a pressure chamber is formed between a pressure bushing, formed in one piece with a basic body, and a tension ring screwed into the basic body. It is thus possible to reduce or increase the volume of the pressure chamber when screwing the tension ring and, therefore, to exert pressure, respectively to discharge, the pressure medium. In a different way, as in the previously described mandrel, a pressure generating unit, formed for example as a piston and cylinder unit, which is arranged axially displaced in the direction of the end of the tool with respect to the tool, is frequently provided in a hydraulic expansion mandrel. the pressure chamber and the pressure cap. Such an expansion mandrel is known, for example, from WO 98/39123 A1. For the transmission of the pressure of the pressure generating device to the pressure chamber, an oil duct system consisting of oil drilling is provided in this mandrel. fine connections, applied to the mandrel material. A mandrel inserted into a work shaft with an expansion bushing that expands both radially outwardly and radially inwardly is also known from DE 743 530 C. Particularly in the construction of molds and dies, very long mandrels are required. narrow. The usual expansion mandrels, however, can no longer be built in such long and narrow constructional forms without considerable complexity. For example, in a particularly narrow expansion mandrel it is not possible to place a mobile tension ring, as is known from WO 03/095132 Al, for reasons of space. It is also not possible to make a connection perforation, as is known from WO 98/39123 A1 for the transmission of pressure, due to the thin wall thickness of a narrow mandrel, or only with great difficulty. Furthermore, as the length of the mandrel increases, the technical difficulty of practicing a correspondingly longer connection perforation also increases drastically. Another problem arises from the fact that when applying the pressure, tensions are also introduced in the area of each connection hole in the material of the expansion mandrel that can cause a detectable doubling of the mandrel and with this a diminution of the rotational tranquility of the tool. The invention is based on the object of indicating a hydraulic expansion mandrel which can be embodied with relatively little complexity in a long and narrow construction and which is distinguished by advantageous application characteristics. This objective is achieved inventively by the features of claim 1. According to this, at the end of the mandrel where the tool is, an expansion bushing is provided for receiving and fixing a tool. In order to generate a pressure that hydraulically deforms this expansion bushing, the mandrel has a pressure generating unit that is arranged axially displaced relative to the expansion bushing and the surrounding pressure chamber. To transmit the applied pressure across the axial distance between the pressure chamber and the pressure generating unit, the mandrel contains a pressure conducting system which is inventively formed by a ring-shaped gap or closed channel and arranged concentrically with respect to to the axis of the mandrel. In this way, the pressure chamber is axially extended through the pressure-conducting system, in particular without transition, to the pressure-generating unit. Compared to a conventional perforation as a pressure conducting system, an annular gap has a substantially smaller radial expansion with a comparable cross-sectional area. An annular gap with suitable cross-sectional area for the pressure transfer can therefore be applied without requiring much space even in the case of an extremely narrow expansion mandrel. In addition, the stresses induced in the material of the mandrel in the area of the annular pressure conductor system under pressure are always rotationally symmetric with respect to the axis of the mandrel, so that no asymmetric deformation of the expansion mandrel can occur and therefore, the rotational tranquility of the expansion mandrel during operation is not affected. An annular and concentric pressure conductor system is particularly easy to materialize by a two-part construction of the expansion mandrel. This comprises, in a preferred embodiment of the invention, a central basic body carrying at its end near the tool the expansion bushing, and a tension bushing superimposed on this basic body. By means of an appropriate selection of the dimensions of the internal diameter of the tensioning bushing and the external diameter of the basic body, an annular gap is formed between the basic body and the tensioning bushing forming the pressure chamber and the pressure-conducting system axially contiguous. In order to achieve a simple and stable construction, it is preferably provided that the basic body and the tensioning bush are connected to each other rigidly and pressurized, in particular by brazing. An advantageous geometry of the expansion mandrel to save space is achieved by arranging the pressure generating unit in the tension bushing. Advantageous both for simple production and also for easy handling of the expansion mandrel is a pressure generating unit comprising a piston and cylinder system. It comprises a pressure piston that is guided in a cylinder bore or a bushing that is optionally inserted in such a bore. A simple filling of the pressure chamber, the pressure-conducting system and the pressure-generating unit with the pressure medium is achieved by a filling hole at an angle of the cylinder bore, which connects the cylinder bore with the borehole. pressure driver system. In a particularly simple and effective embodiment, the pressure piston can be driven by a tensioning screw. In a construction form of the expansion mandrel which is particularly advantageous for the construction of molds and dies, the tensioning bushing fades at the end where the tool is located in an elongated and thin neck area whose axial length is at least four times its diameter external. The length of the neck area in particular amounts to at least 100 mm. A particular advantage of the expansion mandrel is that it can be achieved, with relatively little complexity, a very narrow tool housing, which is determined by the internal diameter of the expansion bushing. The internal diameter of the expansion sleeve is preferably 12 mm, but it is possible to select it substantially smaller or larger. In conventional expansion mandrels, a reduction element that can be inserted into the mandrel housing for fastening such slender tools is often required. This can have an unfavorable effect on the rotational tranquility of the tool. To achieve an efficient tensing effect of the mandrel, it is found advantageous if the total volume of the entire pressure system, ie the pressure chamber, the pressure-conducting system and the pressure generating device, is kept as small as possible. This is achieved in an advantageous refinement of the invention by very small selection of the radial extent of the annular gap forming the pressure-conducting system and the pressure chamber. The radial extension of the annular gap conveniently ascends to a maximum of 0.2 mm, preferably 0.1 mm. This extremely thin configuration of the annular gap also saves space and is therefore advantageous in particularly slender construction forms of the expansion mandrel. The ring-shaped materialization of the pressure-conducting system creates space in the central region of the expansion mandrel that can advantageously be used for other purposes. It is thus provided in an advantageous embodiment of the invention to provide the basic body with a central passage which can be used, for example, as a cooling medium channel. In another advantageous embodiment of the invention, an axial adjustment unit for the tool is provided, which is preferably also arranged in the central region of the expansion mandrel. In a suitable arrangement, this axial adjustment device comprises an axially adjustable adjusting pin relative to the basic body which serves as an axial stop for the tool to be fixed and which is preferably guided in a central bore of the basic body. In a variant which is particularly advantageous in terms of ease of handling, the adjustment pivot can be adjusted by means of a radially accessible adjusting screw, so that the adjustment device can also be operated when the tool is already in place. The adjusting screw, which is preferably guided in the basic body, is provided at its inner end with a helical thread which engages an axial-linear toothing of the adjusting pin. In the following, exemplary embodiments of the invention are explained in more detail by means of a drawing. In this show: Fig. 1 in perspective representation a hydraulic expansion mandrel to fix a tool, Fig. 2 a side elevational view of the expansion mandrel according to Fig. 1, Fig. 3 in a longitudinal section III-III the expansion mandrel according to Fig. 2, Fig. 4 in a longitudinal section IV-IV the mandrel of expansion according to Fig. 2, Fig. 5 in a representation of longitudinal section turned by the axis of the mandrel with respect to Fig. 3, the expansion mandrel according to Fig. 2 and Fig. 6 in a representation according to Fig. .5, the expansion mandrel with an alternating axial adjustment unit for the tool to be fixed. Components and dimensions that correspond to each other are provided in all figures always with the same reference symbol. The hydraulic expansion mandrel (hereinafter referred to briefly as an expansion mandrel 1) shown in FIGS. 1 to 4, in different representations, serves to fix a tool (not shown) rotationally driven, in particular of a drill bit. or a milling cutter, in the driving spindle of a machine tool (also not shown). The expansion mandrel 1 essentially has a figure of rotational symmetry with mandrel axis 2 relation forming the rotary axis and comprises, viewed in the direction of this mandrel shaft 2, an end 3 on the tool side and an end 4 on the side of the machine. Near the end 3 on the side of the tool, the expansion mandrel 1 is elongated to form an elongated and slender neck area 5 comprising a housing 6 for the tool at its free end. The length L of the neck area 5 here amounts to four to five times the external diameter D. In a preferred selection of dimensions, the length L amounts to 100 mm in the case of an external diameter of 20 mm and an internal diameter d of the housing 6 of 12 mm. However, it is also possible to realize an even longer and / or slender construction of the expansion mandrel 1 or even a smaller internal diameter d. The end 4 on the side of the machine is provided with a clamping cone 7, made for example in the manner of an arrow HSK, as a connection of the expansion mandrel 1 with the drive spindle. The expansion mandrel 1 has essentially a two-part construction and comprises a central base body 8 in whose area on the side of the tool a bell-shaped tension bushing 9 is located. The basic body 8 and the tensioning bush 9 are welded together by brazing, both on the tool side and on the machine side, and therefore rigidly joined and pressure-proof. In the area of the housing 6, the basic body 8 is configured as a hollow cylinder with a thin wall. This thin-walled region of the basic body 8 is designated as expansion bushing 10. The expansion sleeve 10 is preferably formed in one piece with the basic body 8, but can also be formed from a separate component. An annular gap 11 is formed in the neck area 5 between the inner wall of the tensioning sleeve 9 and the external wall of the opposite basic body 8. This annular gap 11 has only one extension. Radial extremely reduced radius of preferably 0.1 mm (equivalent to about one tenth of the wall thickness of the expansion bushing 10) and is therefore seen as such, for reasons of resolution, only in Fig. 4 increased and especially in the detailed A representation, once again increased. In Fig. 3 the annular gap 11 is seen only in a hinted form as a widened black line. The annular gap 11 extends axially over most of the length of the tensioning bushing 9 and forms, in the area of the housing 6, a pressure chamber 12 in which a liquid pressure medium F is housed, in particular a oil. The region of the annular gap 11 which extends beyond the pressure chamber 12 towards the end 4 on the machine side, forms a pressure-conducting system 13 which hydraulically connects the pressure chamber 12 to a generating unit 14 of pressure axially displaced relative to the pressure chamber 12 and thus allowing a pressure transfer of the pressure generating device 14 to the pressure chamber 12. The radial extension R is, in the free pressure state, the same over the entire length of the annular gap 11, so that the camera 12 pressure becomes without interruption in the system 13 pressure conductor. As seen in particular from FIG. 4, the pressure generating unit 14 comprises a cylinder bore 15 in which a pressure plunger 16 is disposed. The pressure piston 16 is guided in adjustable form directly in the cylinder bore 15 or - as shown in Fig. 4 - in a bushing 17 inserted in the bore 15 of the cylinder. The pressure piston 16 can be actuated by a tensioning screw 16. The inner end of the pressure plunger 16 carries a packing 19 of an elastic material, in particular a rubber elastomer. The pressure generating device 14 further comprises a filling bore 20 and is therefore connected hydraulically to the cylinder bore 15 and simultaneously - through a connection groove 21 - to the annular gap 11. The filling bore 20 is closed against the ambient pressure by a spherical seal 22. Before beginning the operation with the expansion mandrel 1, the common volume of the pressure cylinder 15, the filling bore 20 and the annular gap 11 through the open filling bore 20 with the medium are first completely filled. F of liquid pressure. To avoid the presence of air bubbles in the pressure system, this operation is carried out under vacuum. After filling, the pressure-proof filling bore is closed by the spherical seal 22. To fix a tool placed in the housing 6, the tensioning screw 18 can now be adjusted by means of a screwdriver, and with this the pressure piston 16 in the cylinder bore 15 and thus the volume of the cylinder bore 15 filled with medium can be reduced. F pressure. Thus a hydrostatic pressure can be applied on the pressure medium F of typically up to 1000 bar. This pressure is transmitted through the annular gap 11 as the pressure-carrying system 13 to the area of the pressure chamber 12. Here, the hydrostatic pressure causes a deformation, oriented radially inwardly to the axis 2 of the mandrel, of the thin wall expansion bushing 10, which holds the tool placed in the housing 6. Due to the comparatively large wall thickness, in front of this, of the tensor cap 9 delimiting the pressure chamber 12 towards the outside, there is no significant deformation due to the effect of the pressure on the outer periphery of the expansion mandrel 1. To remove the tool from the expansion mandrel 1, the pressure piston 16 is returned again by a few revolutions of the tensioning screw 18, which discharges the pressure medium F. The elastically deformed expansion sleeve 10 thus assumes its original shape again, so that the tool can be retracted. The expansion mandrel 1 further comprises an axial adjustment unit 23 for the tool which can be seen particularly well in the longitudinal section representation according to FIG. 5, which is rotated in relation to FIG. 3. The axial adjustment 23 comprises an adjustment pivot 24 having the approximate shape of a hollow cylinder and being guided in a sliding manner in a central bore 25 of the basic body 8. The end 26 on the tool side of the adjustment pivot 24 projects into the housing 6 and thus forms an axial stop for the tool to be inserted into the housing 6. To be able to adjust the adjustment pivot 24 in the direction axially, and with this the stop for the tool, the adjustment pivot 24 is provided near its end 27 on the machine side with an axial-linear toothing 28. This toothing 28 engages in a helical thread 29 which is applied to the end of an adjusting screw 30, guided essentially radially in the basic body with respect to the mandrel axis 2. The advantage of this construction is that the radial adjustment screw 30 is accessible even when a tool is inserted in the housing 6. In the variant of the axial adjustment unit 23 shown in F.ig. 6, simplified in its construction, the adjustment pivot 24 is provided with an external thread 31 which is complementary to an internal thread 32 of the bore 25. According to this embodiment, the adjustment pin 24 can be adjusted by means of a screwdriver which is introduced into the housing 6. Along the mandrel axis 2, in both described embodiments of the expansion mandrel 1, a passage 34 is formed by the bore 25 and a bore 33 aligned therewith of the adjusting pin 24, which is It can be used as a cooling medium channel, through which a coolant can be introduced from the machine tool into the area of the housing 6 during the operation, and with this to the area of the tool. Also on the periphery of the basic body 8 is an inertia area 35, that is to say a milling of an area deliberately calculated as a function of the axial symmetry of the basic body 8, which makes it possible to precisely compensate for the imbalance caused by the generator unit 14. asymmetric pressure. In this way, operation of the expansion mandrel 1 is achieved even at comparatively high rpm with high-precision operation, which is particularly important in view of the long and slender design. Instead of a milled inertia area 35, it is also possible to provide a screw of inertia screwed with the basic body 8, one or more inertial discs or other millings or perforations. List of reference symbols Expansion mandrel 31 external thread (hydraulics) 2 mandrel shaft 32 internal thread 3 end (side of the 33 drilling tool) end (side of the 34 machine step) 5 area of the neck 35 inertia area 6 housing 7 clamping cone L length 8 basic body D external diameter 9 tension bushing d internal diameter 10 expansion bushing R radial extension 11 annular gap F pressure medium 12 pressure chamber A detail display 13"pressure-conducting system 14 pressure-generating unit 15 cylinder bore 16 pressure piston 17 bushing 18 tension screw 19 gasket 20 filling hole 21 connection groove 22 ball seal 23 axial adjustment unit 24 adjustment pin 25 hole 26 end (tool side) 27 end (machine side) 28 serrated 29 helical thread 30 adjusting screw

Claims (16)

1. Hydraulic expansion mandrel comprising, arranged at its end on the side of the tool, surrounded by a pressure chamber, an expansion bushing that can deform radially under the effect of a pressure medium housed in the pressure chamber to fix a tool , comprising a pressure generating unit axially spaced from the expansion bushing relative to a mandrel shaft and a pressure conducting system for the pressure transmission of the pressure generating unit to the pressure chamber, characterized in that the pressure conducting system It is formed by an annular gap concentric with respect to the axis of the mandrel. Expansion mandrel according to claim 1, characterized by a central basic body with respect to the axis of the mandrel carrying the expansion bushing and a tension bushing that concentrically surrounds it, being that the pressure chamber and the pressure-conducting system they are formed between the basic body and the tensioning bushing. Expansion mandrel according to claim 1 or 2, characterized in that the basic body and the tension sleeve are connected to each other in a rigid and pressure-proof manner. Expansion mandrel according to one of claims 1 to 3, characterized in that the pressure-generating unit is arranged in the tension bushing. Expansion mandrel according to one of claims 1 to 4, characterized in that the pressure generating unit comprises a cylinder bore with a pressure piston arranged in it in an adjustable manner, as well as a filling bore connecting the bore of the cylinder with the pressure driver system. Expansion mandrel according to claim 5, characterized in that the pressure piston is adjustable by means of an adjusting screw. Expansion mandrel according to one of claims 1 to 6, characterized in that the tension sleeve has on the side of the tool an elongated, slender neck area, the axial length of which is at least four times its outer diameter. Expansion mandrel according to claim 7, characterized in that the axial length of the neck area is at least 100 mm. Expansion mandrel according to one of claims 1 to 8, characterized in that the radial extension of the annular gap amounts to a maximum of 0.2 mm. Expansion mandrel according to one of claims 1 to 9, characterized in that the basic body comprises a central passage. Expansion mandrel according to one of claims 1 to 10, characterized by an axial adjustment unit for the tool. Expansion mandrel according to claim 11, characterized in that the axial adjustment unit comprises an adjustment pivot which is axially adjustable relative to the basic body and which forms a stop for the tool. 13. Expansion mandrel according to claim 12, characterized in that the adjustment pivot is guided in a central bore of the basic body. Expansion mandrel according to claim 13, characterized in that the adjustment pivot is provided with an external thread which cooperates with an internal thread of the bore for axial adjustment of the adjusting pin. Expansion mandrel according to claim 13, characterized in that the adjustment pivot has an axial-linear toothing which acts together with the helical thread of a screw. adjustment, guided essentially radially in relation to the axis of the mandrel, for the axial adjustment of the adjustment pin. Expansion mandrel according to one of claims 1 to 15, characterized by an area of inertia, milled in a region of the circumference, to compensate for an imbalance caused by the pressure generating unit.