Ball Clamp

Abstract

The present invention relates to a ball clamp which is fixable to a machine bed for releasably clamping a workpiece, the shaft passing through which is kept connected to the workpiece via attachment means, while a clamping joint constituted by a ball socket and a ball clamp receiving the shaft can be selectively locked or unlocked, thereby allowing relative movement of the workpiece in the unlocked state and subsequent clamping thereof to allow fixing in a newly occupied position.

Description

[Technical field]

[0001] The present invention relates to a ball clamp for releasably clamping a workpiece. [Background technology]

[0002] It is often necessary to process a workpiece so that certain desired dimensions are observed, for which purpose it is often clamped, for example in a machine bed, by means of clamping means. In this case, residual stresses in the workpiece may arise as a result of processing, and it may then be attempted to deform the clamped workpiece in order to compensate for these residual stresses. This deformation occurs when the clamping means is released, and the deformed workpiece must be clamped again and reprocessed in order to process it to the desired dimensions. Re-clamping is very costly - especially if several clamping means are used in different areas of the workpiece - because, as a result of the deformation, the spatial positions of the application points of the clamping means on the workpiece usually change relative to one another and / or relative to a constant reference point. The clamping means must be adjusted accordingly. Summary of the Invention

[0003] The object of the present invention was therefore to provide a clamping means and a method for using the same, which simplifies and speeds up the (re)clamping of the workpiece and also takes into account deformations due to residual stresses during processing.

[0004] This problem is solved by a ball clamping device according to claim 1 or by a method according to claim 8. Further preferred embodiments emerge from the dependent claims.

[0005] The invention is based on the observation that the processing of the workpiece can generate residual stresses, which are not compensated for as long as the workpiece is still clamped after processing (clamping position). After the clamping means is released, the individual workpiece sections rotate and / or slide relative to the respective previous position until they assume a new position and position in space (compensating position) due to the reduction or compensation of the deformations and the associated stresses. The idea on which the invention is based is to carry out both such compensating movements from the clamping position to the compensation position when the clamping means are in the released state, so that the workpiece can be fixed again in the compensation position after the transition to the clamped state, thereby simplifying the clamping once again.

[0006] The clamping means according to the invention is a ball clamp as defined in claim 1. The ball clamp comprises a mounting means which can be coupled with the workpiece, so that it can be positioned and fixed relative to the ball clamp. The mounting means is linked with the other components of the ball clamp and moves relative to these components in the released state and is immobile therein in the clamped state. The ball clamp itself can be placed or clamped to the machine bed and remains there without changing position, even when the workpiece is deformed for the reduction of residual stresses and the mounting means perform this relative movement together.

[0007] To this end, the ball clamp of the invention comprises an axially configured shaft having an attachment means at one end to allow the clamping of the workpiece to be clamped. The ball clamp further comprises a ball clamp which abuts with its inner surface directly or via clamp jaws against a cylindrical section of the shaft. With its inner surface facing the shaft, the ball clamp can slide - preferably with a small radial clearance - along the cylindrical surface of the shaft. The outer surface of the ball clamp is spherically shaped, centered on an imaginary centre point located on the axis of the shaft.

[0008] The ball clamp is surrounded by a ball socket with its (preferably also spherical) inner surface abutting the spherical outer surface of the ball clamp, preferably also with a small radial clearance. The spherical inner surface of the ball socket and the spherical outer surface of the ball clamp preferably have the same centre of curvature M. The inner surface of the ball socket can slide polyaxially on the spherical outer surface of the ball clamp, thereby allowing any pivoting movement of the ball clamp relative to the ball socket.

[0009] According to the invention, the ball clamping device, in particular its ball socket, is movable from a clamped state along the clamping direction X or in the opposite direction to a released state and vice versa, thereby exerting or releasing a clamping force on the ball clamp and the shaft. In the released state, the shaft is slidable and preferably also rotatable relative to the ball clamp, and the ball clamp can pivot about a central point M relative to the ball socket. In the clamped state, on the other hand, the ball socket exerts a radial pressure force on the inner ball clamp, which in turn radially clamps the shaft. A relative movement of the ball socket, ball clamp and shaft is then no longer possible due to friction forces generated by the pressure force between the mutually clamped components.

[0010] As a result, when in the released state, the shaft can slide along its axis and pivot about its axis, and in addition can pivot arbitrarily about the central point M. The invention makes use of this property to enable a compensation movement of the workpiece from the clamping position to the compensation position, during which the workpiece remains connected to the ball clamp via the attachment means. As will be seen later, after assuming the compensation position, the shaft together with the workpiece to be carried thereby can be simply and quickly fixed again by renewed generation of the clamping force.

[0011] The ball clamp must be designed in such a way that the clamping force exerted on it by the ball socket can be transferred to the shaft located inside, so that each section of the ball clamp must have a minimal but constant radial movement in order to be able to clamp the shaft securely. In a particularly simple case, the ball clamp can be designed to have a substantially ball-shaped body with a central through-hole for receiving the shaft, which has at least one circumferential slit that allows elastic deformation of the body in the circumferential and therefore radial directions when it is pressed with a pressure force on its outer surface.

[0012] Alternatively, the ball clamp preferably comprises a plurality of ball clamping members, which are partially or completely separated from one another and are preferably arranged evenly around the shaft in the circumferential direction, each of which has on its inner surface a cylindrical surface for abutting against the shaft, which can also be configured by or with the clamping jaws in order to obtain a particularly good clamping action. On its outer surface, each ball clamping member is provided with a spherical surface area which can slide along the inner surface of the ball socket and in so doing pivot about a central point M. The individual ball clamping members, which are separated from one another or separable, can be easily replaced, for example for maintenance purposes, and allow easy access to the inner clamping jaws, if any.

[0013] The ball socket is also preferably formed by a number of ball socket members which are partially or completely separated from one another and which are arranged around the ball clamp in the circumferential direction, each of which has a spherically shaped inner surface for abutting against the ball clamp or against its respective ball clamp member and, optionally, is configured with clamping jaws for a particularly reliable force transmission.The respective ball socket members are preferably provided on their outer surface with connecting means for receiving the clamping forces introduced therein.

[0014] The clamping force can be applied to the ball socket or its ball socket member, for example, via pneumatically, hydraulically or electromechanically operated clamping means. In principle, it may be sufficient to bias the ball socket with a clamping force in only one direction to generate the desired clamping effect between the ball socket, the ball clamp and the shaft, the clamping force then preferably pointing towards the shaft axis or centre point M.

[0015] A particularly effective alternative thereto provides for the clamping force to be exerted on the ball socket from all sides in the radial direction along the circumference, so that it is pressed radially inwards over its entire circumference, thus achieving a uniform clamping action and avoiding lateral displacement of the shaft, in particular when biased on one side only. In addition, the ball socket can also be designed for biasing the ball clamp simultaneously above and below the equatorial plane, so that a biasing or deformation of the ball socket (and correspondingly of the ball clamp) in an overall three-dimensional manner occurs radially inwards towards the shaft. The largest possible contact surface between the ball socket, the ball clamp and the shaft results in a particularly secure locking of these components relative to one another under an appropriate amount of clamping force.

[0016] A particularly preferred embodiment of the ball clamping device comprises a clamping means in the form of one, preferably several, for example hydraulically, but preferably pneumatically operable radial springs for generating the clamping force. To this end, the ball clamping device comprises a housing, which is preferably configured substantially rotationally symmetrically about a central axis Z0. The housing is configured for mounting on a machine bed for machining the workpiece held by the ball clamping device. In the housing, radial springs are arranged around the housing axis. They each comprise a chamber surrounded by a spring element, which can be energized by a fluid, in particular by compressed air. Under pressure energization, the chambers expand in a direction parallel to the housing axis, while at the same time their extension perpendicular thereto, i.e. radially, is reduced. Such extension takes place against the spring force inherent in the radial spring, which then tries to deform the spring back to its initial position of radial extension. Thus, when the pressure is reduced, the radial spring expands again - according to its spring force - in the radial direction. If a radial spring is supported along its outer circumference against the inner wall of the housing, its inner circumference will move toward or away from the central housing axis by a distance dependent on the pressure bias. Depending on the configuration of the radial spring and its spring force, high radial forces can be generated at the inner circumference.

[0017] According to the invention, at least one radial spring is operatively connected with the ball socket by its inner circumference or by a section thereof. In the clamped state, the radial spring generates a clamping force directed radially inwards on the ball socket, so that the ball clamp, which is then acted upon by the ball socket, further clamps the shaft enclosed by the ball clamp. The frictional forces generated by the clamping force between the ball socket, the ball clamp and the shaft then ensure that the shaft is clamped against relative movement with respect to the housing not only with respect to rotational movements about the shaft axis, but also with respect to pivotal movements about a central point and with respect to sliding movements in the direction of the shaft axis. Its position and orientation in space are then fixed. When pressure is applied against it, and the clamping force is released by the radial contraction of the radial spring as a result (released state), the shaft can be moved freely in each of the above-mentioned directions and realigned.

[0018] According to the invention, it is ensured that the shaft is held without any clearance in the clamped state. In particular, even slight movement possibilities or clearances along the shaft axis are prevented. Since the ball clamp or its individual parts, like the ball socket or its individual ball socket parts, are (slightly) pressed radially inwards towards the shaft when clamped and may be slightly deformed in the process, it is ensured that as little as possible of an axial clearance of the ball clamp and ball socket relative to the housing results from this radial inward movement or deformation. If such a clearance occurs, then the shaft itself - even when clamped - will likewise have a small clearance. According to the invention, it is intended that the ball socket acting on the ball clamp is guided along at least one stop surface when moving between the clamped and released states, so that the ball socket cannot deviate perpendicularly to this direction of movement (clamping direction X). Such a guide - especially if it is provided above and below the ball socket - prevents, on the one hand, a deflection (clearance) of the ball socket (including ball clamp and shaft) perpendicular to the clamping direction, and, on the other hand, prevents the ball socket from expanding perpendicular to the clamping direction or from flattening in the clamping direction, if the ball socket is supported and geometrically held by a stop surface at least on one side.

[0019] The ball socket or socket member has a spherical inner surface into which the ball clamp or member engages with its respective outer surfaces (preferably complementary), so that in the clamped state, the ball clamp is also fixed without clearance by the guidance of the clamp socket or socket member along the stop surface, and as a result, the shaft itself has no axial clearance.

[0020] In terms of design, for such guidance, according to the invention, at least one stop surface H is provided, along which the ball socket or the individual ball-socket components slide or are guided in the clamping direction X. The stop surface runs along the clamping direction X, preferably in a plane perpendicular to the housing axis Z0. It can be configured as a stop surface on the inside or on the surface of the housing of the ball clamping tool. The stop surface can be configured as a step or a step surrounding the housing axis Z0 on a housing that is configured essentially rotationally symmetrical (if there are several ball-socket components arranged around the housing axis Z0, each component is assigned its own clamping direction X that runs radially inwards).

[0021] Preferably, two axially facing stop surfaces, in particular planar and parallel to one another, are provided between which the ball socket or its individual ball socket parts are guided radially without any clearance. Ball socket parts which are positioned one above the other in the direction of the housing axis Z0 can likewise form stop surfaces H' between each other and axially support or stabilize one another.

[0022] The mounting means arranged on the shaft preferably comprises a bearing for accommodating the pivoting movement of the workpiece when passing from the clamped position to the compensation position relative to the shaft. This is preferably a purely pivoting bearing that does not allow sliding. In particular, this may be a ball joint or a (metal) bellows acting similarly. One area of ​​the joint is connected to the shaft, whereas the area that can be pivoted relative to the shaft is designed for attachment to the workpiece, for example in the form of a fixing pin that can be screwed or otherwise connected to the workpiece.

[0023] Such a swivel bearing in combination with a second bearing consisting of a ball socket, a ball clamp and a shaft slidable therein allows, in the released state, a completely free movement of the workpiece from the clamping position to the compensation position, including subsequent easy fixation. The advantage is that the laborious and expensive re-clamping of the machined workpiece after deformation, known from the prior art, in which a large number of individual clamping members are often aligned and operated, can thus be accelerated and automated. This will become particularly clear from the following description of the method according to the invention, which utilizes at least one ball clamp according to the invention.

[0024] In this case, the workpiece to be processed is clamped by the ball clamp, which is further supported by the machine bed or tension-fixed therewith. The attachment means of the ball clamp to the shaft are connected to the workpiece and are fixed relative to the machine bed when the ball clamp is in the clamped position (it is assumed that the workpiece is supported at least at one other point of application on the machine bed by at least one other ball clamp or other clamping means, so that a pivoting movement of the workpiece about the attachment means of the ball clamp to the shaft, which is configured as a swivel bearing, is also prevented. In this position, the workpiece can first be clamped and processed without stress, which can lead to residual stresses that would deform the workpiece if the workpiece was not tension-fixed to the ball clamp in the clamped position. The residual stresses then act on the ball clamp in addition to any clamping forces that may have occurred.

[0025] The first method step a) according to the invention is intended to transfer the ball clamp from the clamped state to the released state, so that the workpiece or the workpiece area can automatically deform or move from the clamping position given in the clamped state to a compensation position relative to the corresponding ball clamp, thereby reducing or eliminating the stresses that arise between the workpiece and the ball clamp. The clamped state can be released, for example, by pressure on one or more radial springs, which in the clamped state eliminate the clamping force generated on the ball socket, the ball clamp and the shaft by radial contraction. In this state, the shaft, together with the part of the mounting means fixedly connected to it, can be freely pivoted and slidable relative to the machine bed. In this way, the part of the mounting means connected to the workpiece, for example a fixing pin that is not slidable but pivotable relative to the shaft, can carry out the compensation movement of the workpiece from the clamped position to the compensation position together with any rotational position and position in space. The shaft, which is pivotably and slidably supported in the ball clamp in the released state, can move relative to the housing of the ball clamp or relative to the machine bed - according to the movement of the workpiece or the attachment means - to a new position and pivoting position together, so as to automatically perform the realignment of the clamping means, which in the prior art was carried out manually and at considerable time expense, in order to be able to clamp the deformed workpiece again.

[0026] Such limitations on the compensating movements are at most imposed by design constraints, such as the maximum possible swivel angle of the mounting means or the ball clamp, or the maximum sliding movement of the shaft along the ball clamp, etc. However, such limitations are rather theoretical, since residual stresses can be reduced by compensating movements that are usually of the order of a few millimeters or tenths of a millimeter - depending on the size of the workpiece.

[0027] According to the invention, the compensation movement can be performed without completely releasing the workpiece from the ball clamp or ball clamps. In particular, no access to the machine bed or other manual costs are required to enable the deformation of the workpiece into the compensation position. Instead, this can be performed only by the corresponding ball clamps moving into the release state, which can be caused, for example, by a pressure bias on a radial spring, which is as automated as possible. This considerably simplifies and speeds up the processing method.

[0028] The method according to the invention can be further expanded by an additional method step b) following the transfer of the workpiece into the compensation position, in which at least one of the previously released ball clamps transfers back into the clamped state and again fixes the workpiece in the newly occupied compensation position relative to the machine bed. This can also be particularly easily automated with the ball clamps according to the invention, for example by removing the pre-pressure on the radial springs, which deform radially towards the shaft and thereby fix the shaft again through the clamping force acting between the ball socket, the ball clamp and the shaft. (This also applies if, instead of radial springs, a different clamping mechanism is used and controlled, which is operated hydraulically, electromechanically or in another way, non-manually, to selectively clamp or release the ball socket against the ball clamp and the shaft.)

[0029] According to a further embodiment of the method according to the invention, the additional method step c) consists in machining the workpiece after it has been clamped again in the compensation position, which serves in particular to correct any deformations present when moving to the compensation position and / or to machine the deformed workpiece to the set dimensions.

[0030] Method steps a) to c) can be repeated multiple times if necessary in order to also reduce residual stresses which are again induced in the workpiece by subsequent processing.

[0031] A particularly preferred embodiment of the method provides that at least one area of ​​the workpiece is continuously connected to the machine bed through the stationary clamping means during method steps a) to c). Such at least one area, which is kept substantially stationary throughout the method, can serve as a reference point for the subsequent processing steps to be performed on the workpiece after the compensation position is assumed. Meanwhile, other areas of the workpiece can be releasably tension-fixed to the machine bed through the ball clamp according to the invention. When transitioning to the release state, the area of ​​the workpiece, which is respectively supported by the ball clamp, moves relative to at least one stationary clamped area, which does not change in position.

[0032] The processing of the workpiece may in particular include machining, or, supplementary or alternatively, the processing may include welding, gluing, soldering, bending, stamping, punching, hammering, or roll forming.

[0033] The fixed clamping means for permanently tensioning the workpiece to the machine bed in one embodiment can also be a ball clamp according to the invention, which continuously maintains the clamped state during the individual method steps. Alternatively, it can be another clamping means known to the person skilled in the art. Preferably, a clamping pot, as described in DE 10 2005 033 468 A1, which is already known from the prior art, comes into consideration.

[0034] It is preferred, but not essential, that the ball socket and the ball clamp each have a spherical surface for the mutual clamping contact. Alternatively, it may be sufficient if only the ball clamp or only the ball socket has a spherical contact surface. In comparison, the other component can slide along it with a corresponding contact surface and at the same time pivot about the central point M. For example, instead of a spherical inner surface, the ball socket can have one or more radially deformable annular members, preferably with slits, which closely surround the ball clamp. The ball clamp with its spherical surface can also penetrate into a circular opening in the inner surface of the ball socket, which opening has a smaller diameter than the spherical surface. Then, in the clamped state, the opening is pressed with its edge against the ball clamp and clamped.

[0035] The method can also be carried out with multiple ball clamps holding the workpiece at different areas, which may be necessary, especially when the workpiece is relatively large. Individual or all of the ball clamps can be selectively moved simultaneously or individually into a clamped or released state, thereby allowing the respective workpiece area to deform into the compensation position.

[0036] An embodiment of the ball clamping device according to the invention and the implementation of the method according to the invention will now be described in more detail with reference to the example of the drawing, which shows: [Brief description of the drawings]

[0037] [Figure 1] FIG. 2 is a perspective cross-sectional view showing a ball clamping device according to the present invention. [Diagram 2] FIG. 2 is a cutaway side view showing the ball clamping device of FIG. [Diagram 3] 1 shows the progression of the method according to the invention with the aid of a simplified side view of the machine bed. [Figure 4]1 shows the progression of the method according to the invention with the aid of a simplified side view of the machine bed. [Diagram 5] 1 shows the progression of the method according to the invention with the aid of a simplified side view of the machine bed. [Figure 6] 1 shows the progression of the method according to the invention with the aid of a simplified side view of the machine bed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0038] The ball clamping device T shown in Figures 1 and 2 comprises a housing G which is arranged substantially rotationally symmetrically about a housing axis Z0. Via clamping means not shown in more detail, the housing G can be clamped onto a machine bed E, as can be seen, for example, in Figures 3 to 6.

[0039] Inside the housing G, two radial springs F are arranged around the housing axis Z0, one above the other, whose chambers N can be energized by compressed air via a connection not shown in detail. The radial springs F are supported on their outer circumference radially inwards against the inner wall I of the housing G. On their inner circumference, the radial springs F are supported by a number of individual ball-socket members P arranged circumferentially around the housing axis. a ,P b .... The radial spring has a maximum radial extension in the unclamped state (without pressure on the chamber N) and exerts a clamping force on the radial inner surface of the ball-socket member P towards the housing axis Z0. a ,P b ... (clamped condition). When pressure is applied to the chamber N, the radial spring F expands parallel to the housing axis Z0 and simultaneously contracts radially, thereby reducing or eliminating the clamping force on the ball-socket member (released condition).

[0040] Ball socket component P a ,Pb ... forms with its inner surface facing towards the housing axis Z0 a spherical surface for bearing against the ball clamp K, which in turn is formed by individual ball clamping members K1, K2... with spherical outer surfaces arranged around the housing axis. The centre of curvature of the spherical inner surface of the ball socket P and the outer surface of the ball clamp K which bears closely against it is the centre point M, which is illustrated in a simplified manner in FIG. 2. The ball socket P and the ball clamp K jointly form a ball joint, such that the ball clamp K can be pivoted relative to the ball socket P and the housing G, as long as no clamping forces are transmitted between the ball socket and the ball clamp, which creates a blocking static friction, between these two components. The ball socket member P a ,P b ... and the ball clamping members K1, K2... are each separated from one another in the circumferential direction by a slit, so that when biased radially by a radial spring, they can each slide slightly toward the center toward the housing axis Z0.

[0041] The individual ball clamping members, with their inner faces facing towards the housing axis Z0, jointly form a substantially cylindrical abutment surface which rotates in intimate abutment against a shaft arranged around the shaft axis Z through the centre of the housing G. When in the released state, the ball clamping members do not exert a relative clamping force against the cylindrical surface of the shaft W, which is thereby able to slide in the direction of the shaft axis Z relative to the ball clamping members. Pivotal movement of the shaft W relative to the housing G (or to the machine bed E carrying the housing) is also readily possible in the released state. When in the clamped state relative to it, the ball-socket member P a ,P b... are pressed radially (clamping direction X) inwards against the ball clamping members K1, K2... which in turn exert a clamping force on the shaft W, thereby fixing it against rotation or sliding relative to the housing G. The clamping direction X is shown in FIG. 2 by the ball-socket member P a Of course, each ball-socket member has its own clamping direction towards the housing axis Z0.

[0042] Ball socket component P a ,P b In order to guide the ball-socket member P without any clearance, two parallel stop surfaces H (see in particular FIG. 2) are provided in the housing G, between which the ball-socket member P a ,P b ... are radially guided and axially supported in contact with each other. Both stop surfaces H are formed by rotationally symmetric supports of the housing which run around the housing axis Z0. The stop surfaces H allow the ball-socket component P a ,P b ... does not deviate perpendicularly to the clamping direction X, and the ball-socket member P under the pressure applied during clamping a ,P b ... is also prevented by the guiding on both sides. As a result, the ball-socket part P a ,P b ... are pressed form-stable and clearance-free against the ball clamp K. The outer surfaces of the ball clamping members K1, K2..., which are shaped complementarily or form-fittingly thereto, seat against the spherical inner surface of the ball-socket member, so that the ball clamping members K1, K2 are also indirectly guided and supported by the stop surface H. The shaft W, which is clamped by the ball clamping members K1, K2, is thus likewise fixed clearance-free in the direction of the shaft axis Z or the housing axis Z0.

[0043] Ball-socket members P positioned vertically in the direction of the housing axis Z0 a and P b , likewise form a stop surface H' between them, thereby supporting or stabilizing them in the axial direction.

[0044] At the upper end of the shaft W, mounting means S in the form of a ball joint B are arranged. A lower section of the ball joint B is (preferably removably) connected to the shaft W. The upper section of the ball joint B carries a fixing bolt R with a thread and a spanner face. The fixing bolt R is connected to the shaft W in a positionally fixed but pivotable manner through the ball joint B. A sliding of the fixing bolt relative to the shaft W is therefore not possible, but a pivoting movement therewith is. As shown in particular in figures 3 to 6, the fixing bolt R serves for connecting the workpiece U with the shaft W, for example by being screwed into a thread of the workpiece U for which the fixing bolt R is intended.

[0045] In Fig. 1 the ball clamp T is shown in the released state. The chamber N of the radial spring F is pressure-biased and expanded, so that no centrally directed clamping force is generated. The shaft W can accordingly rotate about the shaft axis Z relative to the housing G, slide along the shaft axis Z and pivot freely about the central point M, which is illustrated by the double arrow. The shaft axis Z can therefore also extend at an angle relative to the housing G and does not have to coincide with the housing axis Z0, although both axes intersect at the central point M.

[0046] 2, on the other hand, shows the ball clamp T in the clamped state. Due to the clamping force realized on the centrally guided shaft W, the degree of freedom illustrated by the double arrow in FIG. 1 is eliminated, instead the shaft W is rigidly connected with the housing and the machine bed.

[0047] The processing method with the aid of the ball clamp according to the invention is shown in a simplified manner in figures 3 to 6. In figure 3, a workpiece U is intended for processing and for this purpose is stress-connected in one area to the machine bed E via a fixed clamping means L. Such clamping is maintained continuously during the method and serves as a reference or datum point for the individual processing steps.

[0048] The area of ​​the workpiece U that is remote from the clamping means L is screwed in by means of a fastening bolt R, which is furthermore pivotally connected to the shaft W of the ball clamping device T according to the invention. The ball clamping device is clamped to the machine bed E, and its radial spring can be energized by compressed air via a lead-in line, not shown in more detail, to selectively move the ball clamping device T from the clamped state to the released state and vice versa. In the illustrated example, the shaft axis Z coincides for the time being with the housing axis Z0 in order to clearly show the subsequent transition from the clamping position to the compensation position. The chamber N is relieved, and the ball clamping device T can be moved into the clamped state by utilizing the spring prestress generated by the radial spring, so that the area of ​​the workpiece U carried by the ball clamping device T is stably clamped and is ready for processing.

[0049] In FIG. 4 it can be seen how the workpiece U is machined by a cutting method on the surface of the machining area D. This machining generates residual stresses which subsequently try to deform the workpiece U. However, due to the clamping via the ball clamp T, this deformation is prevented.

[0050] 5 shows the position of the workpiece U after the ball clamp T has been moved into the release state according to the invention. The shaft W is thereby unclamped and the clamping action of the ball clamp T on the workpiece U is temporarily removed. The workpiece U can then be deformed - according to the residual stresses that have developed - from the previous clamping position into a compensation position, as evidenced by a slight upward curvature of the machining area D. Through the fastening bolt R, this movement is transferred via the ball joint B to the shaft W and is thereby carried out together, so that the shaft W can assume a new position and orientation relative to the housing G. The shaft axis Z and the housing axis Z0 no longer coincide.

[0051] In this new compensation position, the machining no longer corresponds to the target dimensions and remachining is necessary. For this purpose, the workpiece must be clamped again in a fixed manner in the compensation position so that it can be machined again in the machining area D. According to the invention, this can be achieved in a simple manner by the ball clamp T moving again from the release position to the clamping position, so that the shaft W together with the workpiece area carried by it is automatically and fixedly fixed in its new position and orientation relative to the housing G or the machine bed E. The advantage is that no manual intervention is necessary to clamp the workpiece again in the changed position.

[0052] In this clamped state, as shown in FIG. 6, the workpiece can then be reliably machined again, with the reworking in the machining area D achieving the desired dimension. Provided that this reworking no longer generates additional residual stresses, the workpiece can subsequently be released from the fixed clamping means L and the ball clamp T, without any further deformations occurring and the desired dimension being maintained. Alternatively, it is also conceivable to first only release the clamping in the ball clamp T (transition to the released state) and in the meantime check the workpiece U for possible further deformations or relative movements. If this does occur again, the above-mentioned method steps can be repeated until the desired dimension is within the defined tolerance range even in the unclamped state. [Explanation of symbols]

[0053] A Outer surface of ball clamp B. Ball joint D Machining area E Machine Bed F Radial spring G Housing H Stopper surface I Housing inner wall K Ball Clamp K1, K2... Ball clamp parts L Fixed fastening means M Center point of the spherically curved ball clamp outer surface N Radial spring chamber P Ball Socket Pa,Pb... Ball socket parts R Fixing pin S Mounting means T-Ball Clamp U workpiece W Shaft X Clamp Direction Z shaft (W) axis Z0 housing axis

Claims

1. A ball clamp (T) for removably clamping a workpiece (U), the ball clamp (T) having a central axis Z ０ The housing has a center structure including: a) a shaft (W) configured about an axis (Z) having a mounting means (S) at a first end for mounting to a workpiece (U); b) a ball clamp (K) which bears against the cylindrical section of the shaft (W) with its inner surface either directly or through clamping jaws, and whose outer surface (A) facing away from the inner surface is spherically shaped about a central point (M) located on the axis (Z); c) a clamp mechanism is provided having a ball socket (P) whose inner surface abuts against the spherical outer surface (A) of the ball clamp (K); d) the ball socket (P) is movable in a clamping direction (X) or in the opposite direction from a clamped state in which the ball socket (P) is biased with a clamping force against the spherical outer surface (A) of the ball clamp (K) to a released state in which the clamping force is reduced or eliminated; In the ball clamping device, e) when the shaft (W) is in a released state different from when it is in a clamped state, i) axially (Z) slidable and / or rotatable about an axis (Z) relative to the ball socket (P); and, ii) capable of pivoting about said central point (M); f) the ball socket has a spherically shaped inner surface which abuts against the spherical outer surface of the ball clamp (K); g) the ball socket (P) extends along a clamping direction (X) during the transition between the clamped and released states, preferably along a central axis Z ０ and sliding along a stopper surface (H) formed perpendicular to the stopper surface (H), thereby fixing the ball clamp (K) clamped by the ball socket (P) when in a clamped state, and the shaft (W) therewith, without any clearance, so as not to move perpendicular to the stopper surface (H). A ball clamping device characterized by:

2. The ball clamp (T) according to claim 1, characterized in that the ball clamp (K) includes a plurality of ball clamping members (K1, K2...) partially or completely separated from one another and circumferentially arranged around the shaft.

3. 3. The ball clamping device (T) according to claim 1 or 2, characterized in that the ball socket (P) can be biased in a direction towards the axis (Z) or towards the centre point (M) by a clamping means operable pneumatically or hydraulically to generate a clamping force.

4. A ball clamping device (T) according to any one of the preceding claims, characterized in that the ball socket (P) is constituted by a plurality of ball socket members (Pa, Pb...) which are partially or completely separated from one another and arranged circumferentially around the ball clamp.

5. a housing (G) for placement on the machine bed; a) in said housing (G), a fluid-biasable and thereby deformable fastening means is provided in the form of at least one radial spring (F) attached to said housing axis (Z ０ ) around the b) said radial spring (F) is operatively connected with said ball sockets (P, Pa, Pb...) with its radially inner area and supported with its radially outer end against the housing wall; c) the radial spring (F) generates a clamping force directed radially inwards against the ball sockets (P, Pa, Pb...) in the clamped state, thereby causing the ball clamps (K, K) which are then biased by the ball sockets (P, Pa, Pb...) １ , K ２ . . .) clamps the shaft (W) surrounded by the ball clamp, A rotational movement about the shaft axis (Z), and A pivoting motion about the central point (M), and Sliding in the direction of the shaft axis (Z) relative to the housing (G); 13. A ball clamping device (T) according to any one of the preceding claims, for fixing the ball against deformation.

6. 10. A ball clamping device (T) according to claim 9, characterized in that the shaft (W) maintains the position and attitude it occupies in the release state when passing to the clamped state.

7. A ball clamp (T) according to any one of the preceding claims, characterized in that the mounting means (S) of the shaft (W) comprise a ball joint or a metal bellows having a fixing pin (R) rotatable relative to the shaft (W), the fixing pin (R) being configured for a detachable connection with the workpiece to be fixed.

8. A method for machining a workpiece (U), the workpiece (U) being fixable by at least one ball clamp (T) through its mounting means (S) arranged on a shaft (W) relative to a machine bed (E) carrying said ball clamp (T), said method comprising the steps of: a) transferring at least one ball clamp (T) from a clamped state to a released state, thereby automatically enabling the workpiece or a workpiece area to move, starting from the clamping position it occupies in the clamped state, into a compensation position relative to the corresponding ball clamp (T), thereby reducing or eliminating the stresses occurring between the workpiece and said ball clamp (T) in the clamping position; A method comprising:

9. After said method step a), the following step b) transferring at least one ball clamp (T) released in step a) back into the clamped state in order to again fix the workpiece relative to the machine bed in the compensation position it now occupies; The method according to the preceding claims, wherein:

10. The following configuration requirements: c) the workpiece is processed while at least one said ball clamp (T) is in the clamped state, said processing may include cutting, welding, gluing, soldering, bending, stamping, punching, hammering, roll forming.

11. 10. The method according to claim 1, wherein at least one area of ​​the workpiece is kept fixed to the machine bed through a stationary clamping means (L), while at least one said ball clamp (T) is released and re-clamped according to said method steps a) and b).

12. 12. The method according to claim 10 or 11, wherein the method steps a), b) and c) are performed several times in succession before the workpiece is removed from the machine bed.

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