SE542000C2

SE542000C2 - Pressing installation for finishing belt, and belt-finishing device

Info

Publication number: SE542000C2
Application number: SE1850047A
Authority: SE
Inventors: Marcel Bosch
Original assignee: Nagel Maschinen Und Werkzeugfabrik Gmbh
Priority date: 2017-01-24
Filing date: 2018-01-17
Publication date: 2020-02-11
Also published as: SE1850047A1; DE102017201120B3

Abstract

A pressing installation (150) for pressing a finishing belt onto a circumferential face of a rotationally symmetrical workpiece portion of a workpiece in belt finishing machining, wherein the finishing belt, by means of a flexurally elastic pressing belt, is pressed with a pressing force over a contact angle onto the circumferential face, comprises a pressing belt support installation (160), a first pressing belt (170-1) and a second pressing belt (170-2) which is disposed beside the first pressing belt (170-1). The belt widths of the first pressing belt (170-1) and of the second pressing belt (170-2) are adapted to the belt width of the finishing belt in such a manner that the finishing belt is capable of being pressed onto a first part-portion of the circumferential face and simultaneously capable of being pressed onto a second part-portion axially beside the first part-portion.

Description

Pressing installation for finishing belt, and beltfinishing device FIELD OF APPLICATION AND PRIOR ART

[0001] The invention relates to a pressing installation for pressing a finishing belt onto a circumferential face of a rotationally symmetrical workpiece portion of a workpiece in belt finishing machining, wherein the finishing belt, by means of a flexurally elastic pressing belt, is pressed with a pressing force over a contact angle onto the circumferential face, and to a belt-finishing device which has at least one pressing installation of this type.

[0002] Finishing is a fine-machining process by means of which the circumferential faces of rotationally symmetrical workpiece portions on workpieces such as crankshafts, camshafts, gear shafts, or other components for motor engines and work machines are machined in order to produce a desired surface finestructure. In the case of finishing, a machining tool that is fitted with a granular cutting means is pressed with a pressing force over a contact angle, by means of a pressing device, onto the circumferential face to be machined. In order to generate the cutting speed necessary for the removal of material, the workpiece is rotated about the workpiece axis thereof. At the same time, a relative movement between the workpiece and the machining tool bearing on the circumferential face is generated, said relative movement oscillating in a manner parallel with the workpiece axis. For this purpose, the workpiece can be set into an axial oscillating movement. Alternatively or additionally, it is also possible for the oscillating movement to be generated by the machining tool. The combination of the rotating movement of the tool and the superimposed oscillating movement enables a so-called cross-hatch pattern to be produced, as a result of which the machined workpiece circumferential faces are particularly suitable as running surfaces for plain bearings or roller bearings, for example, or the like. The workpiece portion to be machined can be, for example, a main bearing or pin bearing of a crankshaft, or a camshaft bearing.

[0003] In the case of so-called belt finishing, a finishing belt which with the aid of a pressing installation is pressed onto the workpiece surface is used as a machining tool. A finishing belt has a beltshaped flexible carrier in the case of which cutting grains are applied with the aid of a binding agent to the front side that is to face the workpiece. A tearresistant polyester film with low elongation often serves as the carrier material for the construction of grains and binding agent. Woven fabric belts are sometimes also used. The finishing belt that is used for machining can be advanced after or during a machining cycle so that a fresh cutting means is at all times available for subtracting material. Readily reproducible results can be achieved on account thereof.

[0004] In the case of one class of conventional beltfinishing devices, pressing installations having socalled finishing shoes are used for pressing a finishing belt onto the workpiece surface to be machined. A finishing shoe has a substantially C-shaped pressing portion, the curvature radius of the latter, while considering the thickness of the finishing belt, being adapted to the nominal diameter of the workpiece portion to be machined such that the finishing belt with the aid of the finishing shoe is pressed in a substantially planar manner onto the circumferential face of the workpiece portion during machining. The contour of the finishing tool can be imparted to the workpiece portion to be machined by way of such substantially rigid pressing elements such that a targeted setting of the macro-shape of the workpiece portion is possible. If a workpiece portion having another diameter is to be machined, the pressing element has to be replaced by a pressing element having a correspondingly different radius of the C-shaped portion.

[0005] The international patent application WO 2009/049868 A1 by the applicant discloses generic pressing installations which permit workpieces with workpiece portions of dissimilar diameters to be machined at a low complexity in terms of apparatuses, and to herein achieve a high surface quality independently of the diameter of the workpiece portions. The pressing installations have a flexurally elastic pressing belt which in the direction of the belt is substantially non-elastic and is mounted on two bearing faces of a pressing belt support installation that are mutually disposed at a spacing. On account thereof, the pressing installation is capable of adapting in a self-acting manner to workpiece portions of dissimilar diameters from a comparatively large diameter range. On account of this adaptability it is possible, for all diameters in a comparatively wide diameter range, for a machining engagement over a large area between the abrasive side of the finishing belt and the workpiece surface to be formed in the machining across the entire contact angle that is defined by the pressing installation, on account of which surfaces of high quality can be produced.

[0006] Documents DE 202013 005 504 U1, WO 2015/104372 A1, and WO 2016/005193 A1 disclose further variants of pressing installations having a flexurally elastic pressing belt.

[0007] Patent publication EP 2712 702 B1 also discloses a belt-finishing device having a pressing installation for pressing a finishing belt against a workpiece surface, wherein the pressing installation comprises a pressing belt which is mounted on two bearing faces that when viewed in the running direction of the finishing belt are disposed so as to be mutually spaced apart. The belt-finishing device is characterized in that at least one of the bearing faces and/or the pressing belt have/has a profile which in the width direction of the finishing belt deviates from a rectilinear profile. The intention is that the geometry of the workpiece surface to be machined is able to be influenced therewith. A curvature of the profile of the pressing face can be interpreted, for example, such that the machined workpiece surface is imparted an approximately cylindrical shape but optionally also a convex or concave shape.

OBJECT AND ACHIEVEMENT

[0008] It is an object of the invention to provide a pressing installation which is producible in a costeffective manner, is distinguished by a simple and robust construction and by a high service life, and which enables shape-preserving or shape-modifying belt finishing machining of rotationally symmetrical workpiece portions to be carried out such that the completely machined workpiece portion meets the requirements in terms of shape and surface with high accuracy.

[0009] In order for this object to be achieved, the invention provides a pressing installation having the features of Claim 1, and a belt-finishing device having the features of Claim 13. Advantageous refinements are set forth in the dependent claims. The content of all claims is incorporated in the description by way of reference.

[0010] The pressing installation utilizes the known technical advantages which are derived in that the finishing belt, by means of a flexurally elastic pressing belt, is pressed with a pressing force over a contact angle onto the circumferential face, and offers further advantages as compared to the prior art.

[0011] The pressing installation has a pressing belt support installation. A first pressing belt which is mounted on two first bearing faces of the pressing belt support installation that are mutually disposed at a spacing in the longitudinal direction of the first pressing belt is provided. Furthermore, a second pressing belt which in the width direction of the pressing belts is disposed beside the first pressing belt and is mounted on two second bearing faces of the pressing belt support installation that are mutually disposed at a spacing in the longitudinal direction of the second pressing belt is provided. The belt widths (measured in the width direction) of the first pressing belt and of the second pressing belt are adapted to the belt width of the finishing belt in such a manner that the finishing belt during the belt finishing machining by means of the first pressing belt is capable of being pressed onto a first part-portion of the circumferential face, and by means of the second pressing belt is simultaneously capable of being pressed onto a second part-portion of the circumferential face that lies axially beside the first part-portion. The term "axial" herein relates to the axis of symmetry of the rotationally symmetrical workpiece portion. The latter can have a substantially circular-cylindrical shape, for example, or else a "spherical" shape having the shape of a drum and a convex shell area, or a shape having a concave surface line shape, that is to say having a taper between two portions that in the diameter are thicker.

[0012] The pressing belts (first pressing belt and second pressing belt) are in each case substantially non-elastic in the longitudinal direction or the belt direction, respectively, such that the length of said belts is not substantially modified even under heavy tensile stress. On account thereof, it is possible for high machining forces to be transmitted by means of the pressing installation onto the finishing belt and thus onto the engagement region between the finishing belt and the workpiece surface, if required. A pressing belt can, for example, comprise at least one metal belt from a resilient-elastic metal, in particular from spring steel. It is possible herein for the pressing belt to be formed exclusively by such a metal belt and to not have any further elements.

[0013] The pressing belts can be fastened to the bearings or bearing portions that comprise the bearing faces at the associated bearing faces or in the proximity of the latter. It is also possible for end portions of the pressing belts to be fastened to other fastening locations of the pressing installation, in a manner spatially separate from the bearings or bearing portions, such that the bearing faces serve exclusively for mounting and fastening is implemented remotely therefrom at another location.

[0014] The pressing installation across the effective working width of the pressing installation (to be measured in the width direction of the pressing belts) has at least two pressing belts. Said two pressing belts, at least across the entire effective length of the pressing belts between the respective bearing faces, run in a mutually separate manner such that inter alia mutual play (or a mutual relative movement, respectively) is possible. A certain amount of free travel between the pressing belts is thus possible within the pressing belt assembly having the first and the second pressing belt. It has been demonstrated that an improved adaptability of the pressing installation in a direction that is parallel with the axis of the machined workpiece portion results on account thereof. As compared to pressing installations having only a single pressing belt, improved machining results can be achieved in the case of many machining tasks on account thereof.

[0015] The first and the second pressing belt can be disposed directly beside one another practically without any lateral spacing. For example, a relative mobility while enlarging the spacing in phases and/or dissimilar curvature profiles in the longitudinal direction are possible on account of the separation between the pressing belts in the region between the associated bearing faces. It is preferably provided that an intermediate space lies between the first and the second pressing belt. On account thereof, a mutual lateral play is possible both in conjunction with a reduction of the mutual spacing as well as with an increase of the mutual spacing. The mutual lateral spacing between the delimiting peripheries of the pressing belts, that is to say the local width of the intermediate space, can be uniform or non-uniform across the length of the intermediate space in the case of a non-stressed pressing installation. The width of the intermediate space (measured parallel with the width direction of the delimiting pressing belts) can be dimensioned such that mutual contact between the pressing belts that run beside one another is avoided in the case of all conceivable machining tasks such that each of the pressing belts can move laterally inter alia without being influenced by the other pressing belt that runs therebeside. The width of the intermediate space can be in the range between 5% and 20% of the mean belt width of the first and of the second pressing belt, for example, and/or be in the range from 0.5 mm to 4 mm. In order to avoid that nonmachined regions or only lightly machined regions are created on the machined workpiece portion, the gap width should be smaller than the amplitude of the axial oscillating movement.

[0016] In principle, it is possible for the pressing installation to have more than two pressing belts that run beside one another, for example three or four pressing belts. In preferred embodiments, the pressing installation does not have any further pressing belt apart from the first and the second pressing belts, such that exactly two pressing belts are provided. A good compromise between a sufficiently large individual width of the individual pressing belts (resulting in a contact pressure of the finishing belts over a large area) and an achievable flexibility by splitting the working width across (at least) two pressing belts can be achieved on account thereof.

[0017] On account of providing at least two pressing belts that run beside one another, new degrees of freedom in terms of the geometry of the overall pressing face that is defined by the pressing belts are achieved. This can be achieved without the individual pressing belts being provided in any way with a profile in the width direction. The first pressing belt and the second pressing belt are in each case preferably a nonprofiled flat belt which in the section perpendicular to the longitudinal direction has a substantially flat rectangular cross section. By dispensing with profiling in the width direction, such pressing belts are producible in a simple and cost-effective manner, for example as the result of a rolling process. Avoiding profiling in the transverse direction moreover contributes towards the long-term mechanical stability of the pressing belts.

[0018] While it is possible for the first pressing belt and the second pressing belt to differ, for example, in terms of the belt width and/or the belt thickness, it is preferably provided that the first pressing belt and the second pressing belt have identical belt widths. The first pressing belt and the second pressing belt in the context of the manufacturing tolerances can preferably be of identical shape, that is to say not only have the same belt width, but also the same length, and optionally the same curvature or curvature profile, respectively, etc. On account thereof, symmetrical arrangements of the first and of the second pressing belts are possible by way of the working width of the pressing installation.

[0019] In the case of many embodiments, the first bearing faces (on which as signed portions of the first pressing belt are mounted) and the second bearing faces (on which assigned portions of the second pressing belt are mounted) in the longitudinal direction of the respectively assigned pressing belt are at least in portions curved in a continuously convex manner, and in the curved portion in the width direction of the pressing belt have a straight surface line. In the curved portion, these are thus bearing faces having a curvature in one direction about an axis that runs parallel with the width direction, such that no profile is provided in the width direction. On account thereof, a stress on the pressing belts that bends in the width direction can be avoided in the curved region of the bearing faces, this having a favourable effect on the service life of the pressing installation. By way of the continuous convex curvature of a bearing face in the longitudinal direction of the pressing belt it can be achieved that the pressing belt in the region of the bearing face bears across a large area, this likewise having a favourable effect on the service life of the pressing installation. Planar portions of the bearing faces can terminate at a curved portion on one side or on both sides.

[0020] The first pressing belt and the second pressing belt can run parallel with one another in the sense that said belts define a common pressing face (overall pressing face) for the finishing belt that is curved in one direction. To this end, it can be provided that the surface lines of the bearing faces run so as to be mutually parallel. For example, an already substantially circular-cylindrical circumferential face can be machined by belt finishing by way of a pressing installation of this type while preserving the circular-cylindrical shape. By way of an arrangement of this type it would also be possible for a spherical shape that optionally results from prior machining to be transformed into a shape of reduced sphericity or into a substantially circular-cylindrical shape by way of a comparatively large subtraction of material in the central portion of the workpiece portion. Homogenizing a concave shape of the workpiece portion is also optionally possible.

[0021] However, pressing installations according to the concept of the invention can also be conceived such that a potential sphericity of the workpiece portion that results from prior machining is largely preserved, that an existing sphericity is amplified by finishing, or a spherical shape of the workpiece portion is generated from a non-spherical, for example circularcylindrical, initial shape. This can be achieved by way of embodiments of pressing installations in which the first bearing faces and the second bearing faces are mutually aligned or alignable in such an oblique manner that pressing faces of the first and of the second pressing belt that are provided for contacting the finishing belt enclose an angle of less than 180°. On account thereof, the overall arrangement of the first pressing belt and of the second pressing belt, when viewed in the longitudinal direction of the pressing belts, can assume a slight V-shape.

[0022] Conversely, it is also possible for the first bearing faces and the second bearing faces to be mutually aligned or alignable in such an oblique manner that the pressing faces of the first and of the second pressing belt that are provided for contacting the finishing belt enclose an angle of more than 180°. On account thereof, the overall arrangement of the first pressing belt and of the second pressing belt, when viewed in the longitudinal direction of the pressing belts, can assume a slight roof shape. On account thereof, concave shapes can be produced by finishing, for example.

[0023] There are numerous possibilities for implementing embodiments of the pressing installation. In the case of one variant, the pressing belt support installation has a support element which has two bearing portions that are mutually disposed at a fixed spacing, wherein the first and the second bearing faces (for mounting the first and the second pressing belt) are configured beside one another on the bearing portions. A single support element can thus potentially support both pressing belts (or two or more pressing belts, respectively) . Embodiments of this type are cost-effective in production and extremely robust in operation.

[0024] It is also possible for the pressing belt support installation to have a first support element and a separate second support element that is disposed beside the first support element, wherein the first support element comprises the two first bearing portions that are mutually disposed at a fixed spacing, and the second support element comprises the two second bearing portions that are mutually disposed at a fixed spacing. The first and the second support element can be of identical design, on account of which manufacturing is simplified. Said first and second support elements can be fixedly interconnected, for example by means of screws.

[0025] In the case of other embodiments, the first support element, for example by way of a pivot joint, is coupled to the second support element so as to be tiltable relative to the latter. On account thereof, relative tilting between the first support element and the second support element is enabled in that dissimilar angles can be set between the mutually adjacent bearing faces for the first and for the second pressing belt, or that dissimilar angles can arise, respectively.

[0026] The arrangement can be such that the angular position between the first and the second support element is not fixedly predefined such that an optimal angular position can arise in a self-acting manner under the effect of the pressing forces during machining. On account thereof, the pressing installation can adapt, for example, to a workpiece surface that has already been machined in a spherical manner, so as to avoid undesirable contact pressure peaks and thus an undesirable non-uniform subtraction of material. A pressing installation of this type can be referred to as being "passively adaptive". Said pressing installation can primarily act in a shapepreserving manner.

[0027] In the case of another variant having a tilting installation (a pivot joint, for example) between the first and the second support element, a setting installation for setting a relative orientation between the first support element and the second support element is provided. On account thereof, a potentially desired angular position between the support elements can be fixedly predefined. Embodiments of this type are particularly suitable for carrying out a shapemodifying machining by means of belt finishing, for example in order for a workpiece portion having an axial contour, for example a drum-shaped or spherical workpiece portion, respectively, or a workpiece portion having a tailored waist in the central region (concave surface line), to be machined from a substantially circular-cylindrical initial shape at the end of prior machining.

[0028] The invention also relates to a generic beltfinishing device for finishing, which has at least one pressing installation which is configured according to the claimed invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Further advantages and aspects of the invention are derived from the claims and from the description hereunder of preferred exemplary embodiments of the invention which are explained hereunder by means of the figures, in which:

[0030] Fig. 1 shows a belt-finishing unit for a beltfinishing device, wherein the belt-finishing unit supports a replaceable pressing installation according to one exemplary embodiment;

[0031] Fig. 2 shows a partial detailed view of a pressing installation from Fig. 1;

[0032] Fig. 3 shows the machining of a bearing portion of a crankshaft by means of belt finishing with the aid of a pressing installation having two parallel pressing belts;

[0033] Fig. 4 in 4A, 4B and 4C shows a further embodiment of a pressing installation in various views;

[0034] Fig. 5 in 5A, 5B and 5C shows a passively adaptive embodiment of a pressing installation in various views; and

[0035] Fig. 6 in 6A, 6B and 6C shows an adjustable embodiment of a pressing installation in various views.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0036] An exemplary embodiment of a belt-finishing unit 100 for a belt-finishing device (not illustrated in more detail) is shown schematically in Fig. 1. The belt-finishing device, or the belt-finishing unit, respectively, is specified for machining a workpiece 110 in the form of a crankshaft. The workpiece is rotated about the main axis of said workpiece (workpiece axis) 112 by a rotating installation (not shown) and by way of an oscillating installation (not shown) is simultaneously set in an oscillating motion with short axial strokes, said strokes being in the magnitude of a few millimetres and parallel with the workpiece axis 112.

[0037] The belt-finishing device has a plurality of belt-finishing units that are disposed beside one another and are disposed on a common machine frame. The belt-finishing units are in each case very narrow so as to simultaneously machine workpiece portions lying beside one another. The belt-finishing machine has a plurality of belt-finishing units for machining main bearings and interdisposed belt-finishing units for machining connecting-rod bearings of the crankshaft.

[0038] The belt-finishing unit 100 substantially has the shape of a machining jaw and is provided for machining the rotationally symmetrical, for example substantially cylindrical, circumferential face 114 of the workpiece portion 116 that in Fig. 1 is visible in a section, said workpiece portion 116 being a main bearing of the crankshaft. In the case of corresponding incorporation of the belt-finishing unit, pin bearings can also be machined. To this end, belt-finishing units which can follow the eccentric movement of the pin bearings in the rotation of the workpiece about the workpiece axis 112 thereof are provided.

[0039] The belt-finishing unit 100 has a base element 120 having installations for fitting the base element to a frame part of a belt-finishing device. The base element is pivotable about a pivot axis 122 in relation to the frame part. Two pressure arms 130-1, 130-2 of the belt-finishing unit are fastened to the base element. The pressure arm 130-1 that is visible on the left is fixedly fitted to the base element 120 and in the state shown protrudes downward in a substantially perpendicular manner. The pressure arm 130-2 that is shown on the right in the region of a bearing portion 132 is mounted so as to be movable on the base element 120. For example, the pressure arm 130-1 is mounted on the base element 120 so as to be pivotable, to which end a rotary bearing installation which enables the pressure arm 130-1 to pivot about a pivot axis 135 in the direction towards the other pressure arm 130-2 (for closing the machining jaw) or in the opposite direction (for opening the machining jaw) is provided. A pivotably mounted hydraulic cylinder 136, the piston rod thereof by way of the free end of said piston rod being articulated on an upper end portion of the pressure arm 130-1 so as to be spaced apart from the pivot axis 135, is provided in the base element 120 for opening and closing the pivotable pressure arm 130-1. The hydraulic power generator enables the pivotable pressure arm 130-1 to be pushed inwardly with a predetermined force against the workpiece 110.

[0040] A fitting portion 138 for fastening a replaceable pressing installation 150 to the pressure arm or to the fitting portion, respectively, is located at the lower free end of the pivotable pressure arm 130-1, so as to be remote from the bearing portion 132. Fig. 2 shows a partial detailed view of the pressing installation 150. The fitting portion, in the case of a closed machining jaw during finishing, extends so as to be substantially parallel with the other pressure arm 130-2. The pressing installation 150 is fitted to the internal side of the fitting portion 138 that faces the workpiece 110, or the other pressure arm 130-2, respectively, on a planar fitting face.

[0041] A finishing belt conveying installation (not illustrated in detail) provides a finishing belt 190 which is drawn off a supply roll (not shown) in the direction of an entry side of the belt-finishing unit and after use (that is to say after machining of the workpiece) is guided from an exit side of the beltfinishing unit to a wound roll for spent finishing belt (see arrows). In the exemplary case, the finishing belt comprises a largely non-compressible polyester film with low elongation, said polyester film on the front side 191 thereof that is to face the workpiece being fitted with a granular cutting means.

[0042] A replaceable pressing installation 150, 180 is fastened to each of the pressure arms 130-1, 130-2 in the region of the free end that protrudes downwards on that side that faces the workpiece, said replaceable pressing installation 150, 180 in each case being conceived for pressing the finishing belt 190 that is fitted with a cutting means onto the circumferential face 114 of the workpiece portion such that the finishing belt is pressed over a wrapping angle or contact angle, respectively, with a pressing force that is provided for the machining procedure onto the circumferential face. The contact angle can be in the range of, for example, from 10° to 120°, and in the exemplary case is approximately 90°.

[0043] In the exemplary case, machining regions of the rotating workpiece portion that are mutually diametrically opposite are machined with the aid of the pressing installations. The finishing belt 190 during machining herein is stationary such that the cutting speed that is required for the subtraction of material is generated exclusively by the rotating movement of the workpiece 110 in combination with the superimposed axial oscillating movement, so as to generate a crosshatch pattern on the workpiece surface that is advantageous for the use as a friction bearing face.

[0044] The replaceable pressing installation 180 that is fastened to the rigid pressure arm 130-2 has two pressing elements 181, 182 that are mutually disposed at a circumferential spacing and are from a relatively strong, slightly resilient plastics material, said two pressing elements 181, 182 pressing the finishing belt onto the circumferential face in two relatively narrow pressing regions which are mutually circumferentially offset. The replaceable pressing installation 150 that is disposed on the pivotable pressure arm 130-1 (cf. also Fig. 2) is constructed according to an embodiment of the claimed invention and will be described in more detail hereunder.

[0045] The replaceable pressing installation 150 (cf. also Fig. 2) has a rigid pressing belt support installation 160 which in the operationally ready fitted state illustrated is fastened to the fitting portion 138 by means of fastening screws. The pressing installation 150 is removable from the fitting portion by releasing the screws, the former thus being replaceable.

[0046] The pressing belt support installation 160 has a solid plate-shaped support element 162 from tool steel. The longitudinal direction (x direction) of the pressing belt support installation 160, that lies in the plane of the plate, in the fitted state runs substantially parallel with the plane in which the finishing belt is guided. The width direction (y direction) that runs perpendicularly thereto runs perpendicularly to the longitudinal direction of the finishing belt. The depth direction (z direction) runs parallel with or at an acute angle to that direction in which the pressing force is applied to the finishing belt in operation.

[0047] The support element 162 on that side thereof that faces away from the pressure arm 130-1 or is to face the workpiece portion, respectively, has a substantially trapezoidal or C-shaped or V-shaped recess 163 which (when viewed in the longitudinal direction) is laterally delimited on both sides by bearing portions 164-1, 164-2.

[0048] The bearing portions serve as bearings for two pressing belts that run so as to be mutually parallel (first pressing belt 170-1 and second pressing belt 170-2) of a pressing belt arrangement 170. The bearing portions or bearings, respectively, (when viewed in the longitudinal direction of the base element or of the pressing belts, respectively) lie at a mutual fixed spacing. Each bearing portion on that free end side thereof that faces away from the pressure arm has a continuously curved, partially cylindrical external contour which serves as a cylindrically curved contact face or bearing face, respectively, 166-1, 166-2 for a cylindrically curved portion of the pressing belts 170-1, 170-2 to be fastened. Surface portions, which are in each case externally planar and into which in each case one lateral threaded bore for receiving a fastening screw 169 is incorporated for each pressing belt, adjoin the partially cylindrical bearing faces.

[0049] The pressing belt support installation 160 on that side thereof that faces away from the fitting face or is to face the workpiece, respectively, supports the two pressing belts 170-1, 170-2 of identical design. The free length of each of the pressing belts between the bearings is larger than the free spacing of the bearings measured in the longitudinal direction, such that a curvature that is directed into the interior of the support element (into the recess 163) is configured on the non-stressed pressing belts in such a manner that each of the non-stressed pressing belts has a largely cylindrically curved, concave pressing face that is to face the workpiece.

[0050] Each of the pressing belts 170-1, 170-2 in the exemplary case is a flat belt from spring steel having a typical thickness in the range from 0.1 mm to 3 mm and having a constant width measured transversely to the belt direction (longitudinal direction of the pressing belt), said width corresponding to less than half the width of the finishing belt 190 (and also to less than half the width of the support element 162). The pressing belt width can be in the range from, for example, 5 mm to 40 mm. A small intermediate space 175 of uniform width (for example in the range from 0.5 mm to 4 mm) remains between the pressing belts, such that the pressing belts at least in the non-stressed state do not contact one another across the entire free length between the bearings.

[0051] The spacing measured in the width direction (y direction) between the external edges of the first pressing belt 170-1 and of the second pressing belt 170-2 that face away from one another is referred to here as the effective working width 172 of the pressing belt arrangement 170, or of the pressing installation, respectively. The effective working width corresponds substantially to the sum of the individual widths of the individual pressing belts, plus the width of the intermediate space 175.

[0052] The pressing belts (flat belts) that are not profiled in the width direction are pre-bent in the production thereof to the M-shape or ?-shape, respectively, illustrated. Concavely curved portions in which the finishing belt is later pressed against the workpiece with the aid of the pressing belts are located in each case in the central region. Each of the pressing belts herein presses only part (somewhat less than half) of the finishing belt (cf. Fig. 3). Less intensely curved or optionally portions which in portions are planar adjoin on both sides (when viewed in the longitudinal direction), said portions in the region of the end portions of the pressing belts then transitioning into portions that in relation to the central portion are curved in the opposite direction, the latter being adjoined by rectilinear portions that are directed rearwards. The curved end portions match the convexly curved bearing faces 166-1, 166-2 of the base element 162 with an exact fit. Fastening holes which align with threaded bores of the support element when the pre-shaped pressing belts are placed beside one another onto the support element 162 at the correct lateral spacing are provided in the planar end portions of the pressing belts. Fastening screws 169 are screwed through these holes into the base element.

[0053] In order for the pressing belts 170-1 and 170-2 to be fastened to the support element 162, a fastening installation 180-1 for fastening the two associated end portions to the respective bearing portion 164-1, 164-2 is provided for each of the bearing portions. Each fastening installation has a fastening element 182-1 that is separate from the support element 162 and serves as clamping jaw in order for the assigned end portions of the pressing belts to be fixedly clamped to the respective bearing portion. Each of the fastening elements has a through bore for passing through a fastening screw 169. An inwardly curved claw-shaped portion is provided at that end of each fastening element that is to face the pressing belts, the internal side of said portion being adapted to the shape of the curved bearing face 166-1, 166-2 of the associated bearing portion in such a manner that the correspondingly shaped pressing belts 170-1, 170-2 by way of the fastening element 182-1 are conjointly pressed across a large area onto the bearing face of the bearing portion in the region of the curved contact face or bearing face, respectively, and can be fixedly clamped to the bearing portion.

[0054] The bearing faces 166-1 and 166-2 on the bearing portions 164-1, 164-2 that in each case are curved in one direction (only about one curvature axis that runs in the width direction) are in each case continuously convexly curved in the longitudinal direction of the pressing belts and in the width direction of the pressing belts accordingly have a straight surface line 167-1. Those parts of the bearing faces in which the first pressing belt 170-1 bears function as first bearing faces for the end portions of the first pressing belt 170-1. The portions that in the width direction lie therebeside and in which the second pressing belt 170-2 bears accordingly function as second bearing faces.

[0055] The surface lines of the first and of the second bearing faces of a bearing portion are in mutual alignment. In the case of this arrangement, the in each case curved pressing belts 170-1 and 170-2 run so as to be nominally mutually parallel such that said pressing belts 170-1 and 170-2 define a common pressing face or overall pressing face, respectively, that is concavely curved in one direction for the finishing belt.

[0056] As is schematically illustrated in Fig. 3, a more or less cylindrical bearing portion 116 of a workpiece can thus be machined across a large area and without any substantial modification of the cylindrical macro-shape in order for the surface to be improved, for example. In as far as the bearing portion prior to starting the finishing displays comparatively large deviations from the circular-cylindrical shape, said deviations by virtue of the mutually parallel profile of the two pressing belts can at least be partially equalized.

[0057] It can be seen in Fig. 3 that the belt widths of the first pressing belt 170-1 and of the second pressing belt 170-2 are adapted to the belt width of the finishing belt 190 in such a manner that the finishing belt during the belt finishing machining by means of the first pressing belt 170-1 can be pressed onto a first part-portion 114-1 of the circumferential face 114, and by means of the second pressing belt 170-2 can simultaneously be pressed onto a second partportion 114-2 of the circumferential face that lies axially beside the first part-portion.

[0058] The pressing belt arrangement 170 having the two mutually parallel pressing belts 170-1, 170-2 can also be described as a pressing belt which on the complete length between the two bearings is split along the length. By virtue of being split in the longitudinal direction and of the intermediate space 175 between the pressing belts, the latter during machining can be moved relative to one another (see double arrows), for example while increasing or decreasing in size the width of the intermediate space, for instance in the central concave portion and/or in directions that are perpendicular to the belt face. It has been demonstrated that this possibility of equalization movements and of some degree of free travel in certain operating situations can offer an improvement in terms of the adaptability as compared to a single continuous pressing belt. On account thereof, improved machining results can be obtained in many machining tasks.

[0059] A further embodiment of a pressing installation 450 having a pressing belt support installation 460 and two pressing belts is shown in Fig. 4. Fig. 4A shows the pressing installation 450 in a lateral view in the width direction (y direction); Fig. 4B shows a plan view in the depth direction (z direction), and Fig. 4C shows a view parallel with the longitudinal direction (x direction). In a manner similar to that of the exemplary embodiment of Figs. 2 and 3, the pressing belt arrangement has precisely two identical pressing belts 470-1, 470-2 which are in each case mounted separately on and fastened separately to opposite bearing portions of the pressing belt support installation. On account of the separation of the pressing belt arrangement across the entire length, an intermediate space 475 which is wider than in the exemplary embodiment of Fig. 2 is created in a centrical manner between the pressing belts. The intermediate space can have a width which is between 50% and 100% of the width of the laterally delimiting pressing belts.

[0060] As can be seen in Figs. 4B and 4C, this pressing installation can be utilized for machining spherical bearing portions, that is to say rotationally symmetrical workpiece portions 416 which in a manner parallel with the workpiece axis (rotation axis) have a convexly curved surface line shape. On account of the separation of the pressing belts across the entire length, an improved adaption to the spherical shape is achievable. The line shape in the axial direction of the bearing point can be readily preserved during the improvement of the surface quality by finishing.

[0061] Fig. 5 shows illustrations of a pressing installation 550 according to a further embodiment, having exactly two pressing belts 570-1, 570-2. The views in Figs. 5A, 5B and 5C are analogous to the views in Figs. 4A, 4B and 4C. A peculiarity in the case of this pressing installation lies in that the pressing belt support installation 560 is inherently movable. Said pressing belt support installation 560 has a first support element 562-1 and a separate second support element 562-2. The support elements are of identical construction and are disposed beside one another at a mutual spacing in the width direction. The first support element 562-1 by way of a pivot joint 563 is coupled to the second support element 562-2. In the case of a fitted pressing installation, the pivot joint is fixedly connected to the supporting pressure arm.

The pivot joint 563 enables a relative tilting of the two support elements about a pivot axis 564 that runs parallel with the longitudinal direction (x direction). The pivot angles are delimited by detents. Maximum pivot angles from the zero position (parallel with the x-z plane) are in the range of a few degrees, for example 10° or less. Each support element can rotationally move about the pivot axis 564 independently of the other support element within the mechanically permissible pivot angle ranges.

[0062] Each of the support elements made from tool steel, for example, is planar in a plate-shaped manner, and in terms of the basic shape thereof by way of the recess that faces the workpiece and of the limiting bearing portions is designed in a manner similar or identical to the support element 162 from Fig. 2. However, the support elements in the width direction (y direction) are significantly narrower, specifically less than half as wide as the effective working width of the pressing installation. The first support element 562-1 supports the first pressing belt 570-1, the second support element 562-2 in a corresponding manner supports the second pressing belt 570-2. An intermediate space 575 in the width direction between the pressing belts of this embodiment results by virtue of the lateral spacing of the support elements. Said intermediate space 575, by virtue of the tilting ability of the support elements relative to one another, has a variable width but in terms of said width is dimensioned such that a lateral spacing remains between the pressing belts in the case of any tilting of the support elements relative to one another that is possible in terms of construction, said support elements thus not contacting one another.

[0063] On account of being split into two support elements that are pivotable relative to one another, and on account of the thus movable pressing belts, the effective pressing geometry of the pressing installation 550 can adapt in a particularly flexible manner and, by way of an additional degree of freedom (pivoting about the pivot axis 564), particularly well to many different axial contour profiles of the tool portion to be machined. The curved bearing faces for the pressing belts that are configured on the support elements are set so as to be mutually oblique when required, such that the surface lines thereof no longer are in mutual alignment but enclose angles of significantly more than or significantly less than 180°.

[0064] Fig. 5C shows a machining situation in which a spherical tool portion 516 is machined during rotation about the workpiece axis 512. Herein, tilting of the two support elements relative to one another arises under the influence of the pressing force that is introduced radially in relation to the workpiece axis. The first pressing belt 570-1 that is supported by the first support element 562-1 herein presses onto the circumferential face of a first workpiece portion 515-1 that is located on one side of the axial centre 517 of the machined workpiece portion, while the second pressing belt 170-2 at the opposite side of the centre 517 presses the finishing belt onto the circumference of a second workpiece portion 515-2.

[0065] The oblique positions of the two support elements 562-1, 562-2 are in each case set automatically or self-actingly, respectively, in such a manner that on each of the pressing belts the angle between the pressing force that is caused on the finishing belt by the pressing belt and the surface normals on the workpiece surface in the region of the finishing belt pressed thereon becomes smaller than in the case of a rigid arrangement of the pressing installation in which the pressing force would be directed so as to be substantially radial to the workpiece axis 512. On account of the additional degree of freedom in the axial direction (provided by the pivot joint 563), the pressing installation can bear in a substantially unlimited manner both on a convex surface line shape (as shown) as well as on a concave surface line shape of the machined workpiece portion, so as to achieve an optimized alignment of the pressing forces relative to the profile of the surface to be machined.

[0066] Fig. 6 shows an embodiment of a pressing installation 650 in various views in analogous manner to the illustration of Fig. 5. This variant, in terms of the construction having the separate support elements 662-1, 662-2 of the pressing belt support installation 660 and the coupling pivot joint 663 can be of similar or identical construction as the exemplary embodiment of Fig. 5. A setting installation 690 by way of which the relative orientation between the first support element 662-1 and the second support element 662-2 can be fixedly predefined is additionally provided. The setting installation 690 in the exemplary case has a set screw 692 which is routed through a thread in the first support element 662-1 and by way of a protruding portion is supported on the lateral face of the second support element. The tilting angle between the first support element 662-1 and the second support element 662-2 can be precisely set by rotating the set screw 692. The pressing geometry of the pressing installation, in particular the tilting angle between the support elements, is fixedly set prior to starting finishing and is then not modified any more during machining. On account thereof, within certain limits, every shape of an axial profile of the surface line (for example convex shapes, or sphericity, respectively, or concave shapes) can be set in a targeted manner by finishing by means of an axially non-uniform subtraction of material.

[0067] In the case of all embodiments, the portions of the pressing belts that in the width direction are in each case non-profiled and bear on the bearing faces contact a bearing face that is curved in only one direction. The bearing faces have in each case straight surface lines in the width direction. In the case of the exemplary embodiments of Figs. 2 to 4, the surface lines of the bearing faces that lie beside one another for the first pressing belt and the second pressing belt run so as to be mutually coaxial. In the case of the exemplary embodiment of Fig. 5, an oblique position between the support elements can be set such that also the surface lines of the bearing faces that are in each case curved in one direction (first bearing faces and second bearing faces that lie therebeside) can mutually run at an angle that significantly deviates from 180°.

[0068] In the example of Fig. 5C, the support elements under the effect of the pressing force align themselves such that the pressing faces of the first and of the second pressing belt that are provided for contacting the finishing belt enclose an angle of less than 180°. The pressing belts thus form a flat roof shape. When machining a convex tool portion, the support elements can also mutually tilt such that the spacing of said support elements in the region of the pivot joint is larger than at a distance therefrom, such that an angle of more than 180° is set between the surface lines of the first and of the second bearing faces, on account of which the pressing faces of the first and of the second pressing belt that are provided for contacting the finishing belt would also enclose an angle of more than 180°.

[0069] The angular setting for the machining of a spherical bearing face is fixedly predefined in the case of the exemplary embodiment of Fig. 6

Claims

1. Patent Claims Image available on "Original document" Pressing installation (150, 450, 550, 650) for pressing a finishing belt (190) onto a circumferential face (114) of a rotationally symmetrical workpiece portion (116) of a workpiece (110) in belt finishing machining, wherein the finishing belt, by means of a flexurally elastic pressing belt (170-1, 170-2), is pressed with a pressing force over a contact angle onto the circumferential face, comprising: a pressing belt support installation (160); a first pressing belt (170-1) which is mounted on two first bearing faces (166-1, 166-2) of the pressing belt support installation (160) that are mutually disposed at a spacing; a second pressing belt (170-2) which is disposed beside the first pressing belt (170-1) and is mounted on two second bearing faces of the pressing belt support installation (160, 460, 560, 660) that are mutually disposed at a spacing; wherein belt widths of the first pressing belt (170-1) and of the second pressing belt (170-2) are adapted to the belt width of the finishing belt (190) in such a manner that the finishing belt during the belt finishing machining by means of the first pressing belt (170-1) is capable of being pressed onto a first part-portion (114-1) of the circumferential face, and by means of the second pressing belt (170-2) is simultaneously capable of being pressed onto a second partportion (114-2) of the circumferential face that lies axially beside the first part-portion.

2. Pressing installation according to claim 1, characterized in that an intermediate space (175) lies between the first pressing belt (170-1) and the second pressing belt (170-2).

3. Image available on "Original document" Pressing installation according to claim 2, characterized in that the intermediate space (175) has a width that is in the range between 5% and 20% of the mean belt width of the first and of the second pressing belt (170-1, 170-2) and/or is in the range from 0.5 mm to 4 mm.

4. Image available on "Original document" Pressing installation according to one of the preceding claims, characterized in that the pressing installation (150, 450, 550, 650) does not have any further pressing belt apart from the first pressing belt (170-1) and the second pressing belt (170-2).

5. Image available on "Original document" Pressing installation according to one of the preceding claims, characterized in that the first pressing belt (170-1) and the second pressing belt (170-2) are a non-profiled flat belt.

6. Image available on "Original document" Pressing installation according to one of the preceding claims, characterized in that the first pressing belt (170-1) and the second pressing belt (170-2) have identical belt widths, wherein the first pressing belt and the second pressing belt preferably are of identical shape.

7. Image available on "Original document" Pressing installation according to one of the preceding claims, characterized in that the first bearing faces (166-1, 166-2) and the second bearing faces in the longitudinal direction of the pressing belt (170-1, 170-2) are curved in a continuously convex manner, and in the width direction of the pressing belt have a straight surface line (167-1).

8. Pressing installation according to one of the preceding claims, characterized in that the first bearing faces (166-1, 166-2) and the second bearing faces are mutually aligned or alignable in such an oblique manner that pressing faces of the first pressing belt (170-1) and of the second pressing belt (170-2) that are provided for contacting the finishing belt (190) enclose an angle of less than 180° or more than 180°.

9. Pressing installation according to one of the preceding claims, characterized in that the pressing belt support installation (160, 460) has a support element (162) which has two bearing portions (164-1, 164-2) that are mutually disposed at a fixed spacing, wherein the first and the second bearing faces (166-1, 166-2) are configured beside one another on the bearing portions.

10. Pressing installation according to one of claims 1 to 8, characterized in that the pressing belt support installation (560, 660) has a first support element (562-1, 662-1) and a separate second support element (562-2, 662-2) that is disposed beside the first support element, wherein the first support element comprises the two first bearing portions that are mutually disposed at a fixed spacing, and the second support element comprises the two second bearing portions that are mutually disposed at a fixed spacing.

11. Pressing installation according to claim 10, characterized in that the first support element (562-1, 662-1) by way of a pivot joint (563, 663) is coupled to the second support element (562-2, 662-2).

12. Pressing installation according to either of claims 10 and 11, characterized by a setting installation (690) for setting a relative orientation between the first support element (562-1, 662-1) and the second support element (562-2, 662-2).

13. Belt-finishing device for finishing circumferential faces of rotationally symmetrical workpiece portions on workpieces, having: a rotating installation for generating a rotating movement of the workpiece (110) about a workpiece axis (112); an oscillating installation for generating a oscillating relative movement, aligned so as to be parallel with the workpiece axis (112), between the workpiece and at least one pressing installation (150, 450, 550, 650) for pressing finishing belt (190) onto the circumferential face (114) in such a manner that the finishing belt is pressed with a pressing force over a contact angle onto the circumferential face; wherein the pressing installation (150, 450, 550, 650) is conceived according to one of the preceding claims.