The invention relates to a clamping device for holding a threaded part.

Background of the invention

The problem of coupling of tools, or other objects, has been the subject of many patent publications. Screw thread is used in many instances for coupling objects or parts together. Screw thread provides a secure and stable coupling. A disadvantage of a screw thread coupling is that it often requires several rotations of at least one of the objects or parts.

DE102008043098 according to its abstract describes a screw that has a thread bolt including a screw part with a thread section. The part has connection elements that are joined with each other for relative displacement of the part in a direction running radial to an axis of the bolt up to in a usage position in which the sections lie against each other. The elements have guiding surfaces, which guide the part during displacing in the position in a rotational movement around a rotational axis running transverse to the axis of the bolt. The part is made of elastically deformable material e.g. steel.

DE102006005998 according to an abstract of a US counterpart describes a nut having an internal thread and at least two parts, wherein each of the parts has a section of the internal thread, and said section can be pushed onto an external thread in the radial direction, and wherein the parts have connecting elements which interact with one another and which permit a relative displacement of the parts in a direction running radially to the axis of the internal thread right into a position of use in which the internal thread of the nut encloses the external thread with slight play, wherein the connecting elements have guide surfaces which are inclined at an angle to the plane running radially to the axis of the internal thread and which guide the parts of the nut, during the displacement into the position of use,; in a rotational movement about an axis of rotation running transversely to the axis of the internal thread. The object of the invention is to provide a nut of the type mentioned at the beginning which is simple to produce and manipulate. This object is achieved by virtue of the fact that at least one part has at least one locking arm which has a guide surface only on one side, and this guide surface produces the rotational movement during the displacement of the parts and bears against a complementary guide surface of the other part.

EP454914 according to its abstract describes a divided nut comprising two divided nut parts made of plastics which provide engaging projection means and engaging step means so as to engage with each other in a state of fixed fittings. The divided nut parts are integrally connected to each other by means of belt-like connecting means where they are bent to fit each other.

WO87/02432 according to an abstract of its US counterpart describes a lock nut arrangement formed of a first and second generally C-shaped nut member which are joined together in a manner allowing limited axial movement and free rotation relative to one another about the axis were two members were initially threaded to central openings. The nut assembly may be radially installed on a threaded lock and locked thereon by rotating the nut members relative to one another. A lock nut is manufactured by first forming a first and second nut blanks, axially pressing the nut blanks together, clamping the nut blanks and threading the central bore, rotating the nut blanks relative to one another a predetermined distance and slotting the nut blanks.

Summary of the invention

The invention seeks to provide a device for coupling to, and holding or clamping, a threaded part. In particular, the invention seeks to provide a device for more efficient coupling and de-coupling providing a quick coupling, and/or a clamping device for coupling parts to a driving apparatus.

To that end, the invention provides a clamping device for coupling to a threaded part with an external thread having a major and a minor thread diameter and a longitudinal direction, said clamping device having:

- a first thread-engaging part extending in said longitudinal direction and having a first internal surface for in use engaging said external thread of said threaded part;

- a second thread-engaging part extending in said longitudinal direction and having a second internal surface for in use engaging said external thread of said threaded part;

said first and second thread-engaging parts with respect to one another having: - a first position in which said thread-engaging parts are clear from said threaded part for allowing removing said clamping device from said threaded part by displacing the clamping device in said longitudinal direction with respect to said thread of said threaded part, and

- a second, engaged position in which said thread-engaging parts engage said threaded part and block removal of said clamping device from said threaded part by displacing said clamping device in said longitudinal direction of said threaded part, wherein in said second, engaged position said first and second internal surfaces define at least part of a reference circle cylinder having a longitudinal axis, defining in said second, engaged position at least part of an engaging cylinder for an external thread, said thread-engaging parts mutually coupled to displace in functionally, in particular substantially, opposite radial direction with respect to said longitudinal axis, and said first and second thread-engaging parts are spring-biased for pulling said thread-engaging parts together to at least said second, engaged position for in operation allowing the first and second thread-engaging parts to hold the threaded part between them.

In this application, reference is made to longitudinal cylinder segments. In general, this relates to parts of a cylinder that are defined partly by a cylinder wall, and partly by one or more planes that run functionally or substantially parallel to a longitudinal axis of a cylinder. In fact, when referring to thread, the cylinder refers to a circle cylinder. A particular example is a cylinder segment that is defined as a "horizontal cylinder segment". Usually, this refers to a cylinder that is oriented with its longitudinal axis horizontally. A solid cut from such a horizontal cylinder by a single plane oriented parallel to the cylinder's axis of symmetry (longitudinal axis) is called a horizontal cylindrical segment.

In general, embodiments of the clamping device can be designed for clamping an internal thread and embodiments of the clamping device can be designed an external thread. Some general features can be used for both embodiments. In the current description, clamping of both internal and external thread will be described when indicated. In the description of embodiments, various embodiments will be illustrated. Clamping internal thread and external thread can have different requirements.

In an embodiment, the clamping device is adapted for clamping a threaded part that is provided with an external thread. In such an embodiment for clamping an external thread, thread-engaging parts have a first respectively a second surface that define a cylinder surface. In such an embodiment, the surfaces are concave and correspond to the curvature of the external thread to be clamped and engaged. In an embodiment, the surfaces of the thread- engaging parts together define a cylinder wall. In an embodiment, the thread-engaging parts together in the thread-engaging position define a complete cylinder wall. The combined cylinder wall may have an internal thread matching the external thread of a part to be clamped.

First, several embodiments for clamping an external thread will be discussed. In an embodiment, said spring-biasing force is adapted for providing a biasing force at said second, engaged position, pulling said first and second thread-engaging parts in said second position together and in operation onto said external thread.

In an embodiment, said thread-engaging parts together in said second, engaged position define a circle cylinder wall, with each thread-engaging part defining half of a circumference of said circle cylinder wall.

thread-engaging parts on said first and second internal surface are provided with internal thread which with said thread parts in said second, engaged position define an internal thread matching said external thread.

In an embodiment, said first and second thread-engaging parts in said first position are spaced apart further than in said second position, wherein said further spacing is at least a difference between a major thread diameter and a minor thread diameter of said internal thread of said thread-engaging parts in said second, engaged position.

In an embodiment, said first and second surfaces of said thread-engaging parts in said first, disengaged position providing a first circumference and in said second or engaged position provide a second circumference that is smaller than the first circumference, in use in said first position said first and second internal surfaces not engaging said external thread, and in use in said second position said first and second internal surfaces engaging said external thread fittingly like a bolt and a matching nut.

In an embodiment, said first and second thread-engaging parts are spring-biased with respect to one another in radial direction, for allowing the first and second thread- engaging parts to engage the threaded part under said spring-biasing force. In an embodiment, said thread-engaging parts together in said second, engaged position define said engaging circle cylinder wall, with each thread-engaging part defining between 40 and 20 % of a circumference of said circle cylinder wall.

In an embodiment, said thread-engaging parts are circle cylinder segments.

In an embodiment, said thread-engaging parts are mounted on a mounting part or with respect to one another for displacing along a line when moving between said first and second position, said line intersecting said longitudinal line, in particular intersecting said longitudinal line functionally perpendicularly.

In an embodiment, the clamping device comprises at least one spring element having two opposite ends each coupled to a thread-engaging part and having its non- spring-biased state or a pulling spring-biased state with the thread-engaging parts in the second position, in particular comprising two substantially parallel spring elements each having one end coupled to one thread-engaging part and the opposite ends coupled to an opposite thread-engaging part.

In an embodiment, said clamping device has two thread-engaging parts.

In an embodiment, said first and second thread-engaging parts form part of a threaded end with an internal thread, said thread-engaging parts in an embodiment forming horizontal circle cylinder segments, and for displacing between said first and second position, said thread-engaging parts displace in a radial direction of said circle cylinder.

In an embodiment, the clamping device is adapted for clamping a threaded part that is provided with an internal thread.

In an embodiment for clamping an internal thread, the thread-engaging parts are longitudinal cylinder segments that have a spacing such that the thread-engaging pasts can be brought together in such a way that they can be removed from a hole with an internal thread. In particular, these thread-engaging parts can be opposite horizontal cylinder segments, i.e., each having a plane substantially or functionally parallel to the longitudinal axis of the cylinder. In particular, at least one of these planes is at a distance from the longitudinal axis. More in particular, both these planes are parallel to one another and at a distance from the longitudinal axis. A design that is relatively easy to make has planes at a distance from the longitudinal axis of the cylinder.

In an embodiment, one of the walls of the thread-engaging parts is part of a cylinder wall. This wall is for engaging the internal thread of the hole. This surface may for instance de of a polymer material of have a metal surface and may be provided with a ribbed or profiled structure in order to better engage the internal thread. In an embodiment, the thread-engaging surface is provided with thread that matches the internal thread of the hole. In this way, a good engagement can be provided. In fact, if the thread-engaging parts are blocked at their second or engaging position, the clamping part is mounted inside the thread almost as good as a threaded end would be. Such a blocking coupled for instance be accomplished by inserting a blocking like a wedge or pin between the thread-engaging parts.

In an embodiment for clamping both an internal as well as an external thread, the thread-engaging parts are biased, in particular spring-biased for engaging the thread to be clamped. In an embodiment, the biasing force has a component in a radial direction of the thread to be clamped.

The engaging of the thread-engaging parts may also be accomplished in an embodiment for clamping an internal thread by biasing the thread-engaging parts away from one another. One or more of the thread-engaging pasts may for instance be spring-biased away from the longitudinal cylinder axis, in particular in a radial direction. The direction in an embodiment has a radial component. Thus, in fact the spring force thus can be equivalent to a clamping force of the clamping device. For clamping an external thread, the thread-engaging parts are in an embodiment biased towards the longitudinal axis. In an embodiment a force having a component directed towards the longitudinal axis can be applied. To effect a biasing force, spring elements like coil springs or alternative spring elements can be used.

In an embodiment, the threaded part has a hole provided with an internal thread as said thread, and wherein:

- said first thread-engaging part having a first external surface for in use engaging the internal thread;

- said second thread-engaging part having a second external surface for in use engaging the internal thread;

said first and second thread-engaging parts having a first or disengaged position providing a first circumference and a second position having a second circumference that is larger that the first circumference, in use in said first position said first and second external surfaces not engaging said internal thread, and in use in said second position said first and second external surfaces engaging said internal thread. In an embodiment for clamping an internal thread, the first and second thread- engaging parts are spaced apart in said second, engaged position, wherein in particular said spacing providing a clearance that measures at least a difference between a major thread diameter and a minor thread diameter of a given thread which said clamping device is designed to clamp.

In an embodiment for clamping an external thread, in the engagement position the thread-engaging parts form an engagement cylinder that has a circumference. In an embodiment, the cross sectional area of one thread-engaging parts differs from the cross sectional area of another thread-engaging part.

In an embodiment for clamping an internal or an external thread, the thread- engaging parts each have less than 40% of the engagement cylinder circumference. In an embodiment, a larger thread-engaging part has between 30-40% of the engagement cylinder circumference. In an embodiment a smaller thread-engaging part has between 20-30% of the engagement cylinder circumference.

In an embodiment for clamping an internal thread, a hole provided with the internal thread has a major diameter D5 of the internal thread, and a the minor diameter Dm of the internal thread of the hole. In the first position the thread-engaging parts have an engaging diameter D2. In order to be able to remove the clamping device from the centred hole with an internal thread ('pull it out of the centred hole, parallel to a longitudinal direction L), this engaging diameter D2 should be smaller than the minor diameter Dm of the internal thread. In that way, a quick-release coupling can be provided.

In an embodiment for clamping both internal and external thread, thread- engaging parts are provided on a sledge mounted on a mounting part. In an embodiment, the mounting part and sledge parts have a provision for providing a linear motion (i.e., along a straight line) when the first and second thread-engaging parts move between the first and second positions. In this embodiment, the mounting part has a slotted hole for each thread-engaging part. The thread-engaging parts in turn each have an extended part that is provided for running in one of the respective slotted holes. The pin and slotted hole may also be reversed, providing the mounting part with pins and the sledge parts with a slotted hole. In an alternative embodiment, one or more rails and corresponding runners may be provided on one of the mounting part and the tread-engaging parts for providing the linear motion.

In an embodiment, the linear motion is in a radial direction of a thread to be clamped, or defined alternatively, radially with respect to the cylinder defined by the thread-engaging parts.

The sledge or sledges may de mounded for moving at an angle with respect to a radial plane that is normal to the longitudinal direction. In an embodiment such an angle is between 3 and 7 degrees.

In an embodiment for clamping an internal or external thread, in order to prevent a possible rotation of a clamped part with respect to the clamping device, the clamping device is provided with a rotation-blocking that engages the clamped part. In an embodiment, the clamping device may be provided with one or more rotation-blocking members. The one or more rotation-blocking members may comprise one or more pins mounted on the mounting part that is provided to engage a hole in a clamped part. In an embodiment, such one or more pins extend functionally parallel to the first and second thread-engaging parts.

In an embodiment for clamping an internal of external thread, the first and second thread-engaging parts are biased with respect to one another in radial direction, for allowing the first and second thread-engaging parts to engage the threaded part under said or a biasing force. In particular, said parts are spring-biased. In an embodiment, the biased force has a working component along or parallel to the linear motion of the thread-engaging part or parts.

In an embodiment, the first and second thread-engaging parts form part of a threaded end with an external thread, said thread-engaging parts in an embodiment forming circle cylinder segments having a clearance allowing the thread-engaging parts to be displaced between the first and second position. In particular, said thread- engaging parts in said second position forming part of a circle cylinder, and for displacing between said first and second position, said thread-engaging parts displace in functionally a radial direction of said circle cylinder. In an embodiment, said thread- engaging parts displace in substantially a radial direction of said circle cylinder. In embodiment, said thread-engaging parts displace exactly in a radial direction of said circle cylinder. In an embodiment, the first and second thread-engaging parts form part of a threaded end with an external thread, said thread-engaging parts in an embodiment forming horizontal circle cylinder segments having a clearance allowing the thread- engaging parts to be displaced between the first and second position, in particular said thread-engaging parts in said second position forming part of a circle cylinder, and for displacing between said first and second position, said thread-engaging parts displace in a radial direction of said circle cylinder.

In an embodiment, the clamping device is adapted for engaging a threaded part provided with an internal thread, said clamping device comprising:

- said first thread-engaging part extending in a longitudinal direction and having a first external surface for in use engaging the internal thread;

- said second thread-engaging part extending in a longitudinal direction and having a second external surface for in use engaging the internal thread;

said first and second thread-engaging parts having a first or disengaged position providing a first circumference and a second position having a second circumference that is larger than the first circumference, in use in said first position said first and second external surfaces not engaging said internal thread, and in use in said second position said first and second external surfaces engaging said internal thread.

In an embodiment, the first and second thread-engaging parts are spaced apart in said second position, wherein in particular said spacing providing a clearance that measures at least a difference between an major internal thread diameter and a minor internal thread diameter of a given internal thread into which said clamping device is designed to clamp. In particular, the space can be up to a fifth, a fourth or a third of the major diameter. This enables quick and secure assembly. In particular, the space should be dimensioned in such a way as to enable the parts to be released quickly and safely without any of the parts being too weakened in their cross-section.

In an embodiment for clamping an internal thread, the first and second thread- engaging parts are biased away from one another at least to said second position, for allowing the first and second thread to be brought into said first position under elevation of said biasing force.

In an embodiment, the first and second thread-engaging parts form part of a threaded end with an external thread, said thread-engaging parts in an embodiment forming horizontal circle cylinder segments having a clearance allowing the thread- engaging parts to be displaced between the first and second position, in particular said thread-engaging parts in said second position forming part of a circle cylinder, and for displacing between said first and second position, said thread-engaging parts displace in a radial direction of said circle cylinder.

In an embodiment for clamping internal or external thread, thread-engaging parts move between said first and second position in a radial direction with respect to said thread or said cylinder. In an embodiment, two thread-engaging parts move along a line, linearly. Two thread-engaging parts move is such an embodiment in an opposite direction. A mounding part and thread-engaging parts moveable with respect to the mounting part may be provided. In an embodiment, the mounting part and the thread- engaging parts comprise linear-motion guiding for guiding said linear motion. In an embodiment, one of the mounting part and the thread-engaging parts comprises a linear guiding rail and the other one or ones of the mounting part and the thread-engaging parts comprises a linear guiding rail engaging end. In an embodiment, one of the thread-engaging parts and the mounting part comprises a slotted hole, and the other comprises a pin running in said slotted hole. In an embodiment, blocking means are provided for blocking the thread-engaging parts at the first and second positions. In an embodiment, the thread-engaging parts comprise a sledge that is radially displaceable on a mounting part.

In an embodiment, a thread-engaging part comprises a rail and another thread- engaging part comprises a guide for running on the rail. In such an embodiment, the relative motion of thread-engaging parts with respect to one another is defined.

The invention further relates to a clamping device for coupling to or engaging or clamping a threaded part with a thread having a major and a minor thread diameter and a longitudinal direction, said clamping device having:

- a first thread-engaging part extending in said longitudinal direction and having a first surface for in use engaging said thread of said threaded part;

- a second thread-engaging part extending in said longitudinal direction and having a second surface for in use engaging said thread of said threaded part;

said first and second thread-engaging parts with respect to one another having:

- a first position in which said thread-engaging parts are clear from said threaded part for allowing removing said clamping device from said threaded part by displacing the clamping device in said longitudinal direction with respect to said thread of said threaded part, and

- a second position in which said thread-engaging parts engage said threaded part and block removal of said clamping device from said threaded part by displacing said clamping device in said longitudinal direction of said threaded part.

This clamping device in embodiments can have all the elements and features described in this application, or a combination of the features.

The person skilled in the art will understand the term "substantially" in this application, such as in "substantially encloses" or in "substantially extends up to". The term "substantially" may also include embodiments with "entirely", "completely", "all", etc. Hence, in embodiments the adjective substantially may also be removed. Where applicable, the term "substantially" may also relate to 90% or higher, such as 95% or higher, especially 99% or higher, even more especially 99.5% or higher, including 100%. The term "comprise" includes also embodiments wherein the term "comprises" means "consists of .

The term "functionally", when used for instance in "functionally coupled" will be understood by, and be clear to, a person skilled in the art. Where applicable, the term "functionally" may also relate to 90% or higher, such as 95% or higher, especially 99% or higher, even more especially 99.5% or higher, including 100%). In fact, "functionally" is used to indicate that features relate to one another in such a way that deviations from the exact relation are possible as long as the functioning is present. When for instance computer devices are "functionally coupled", this means that they may be coupled via a wired connection, a wireless connection, and the like.

Furthermore, the terms first, second, third and the like if used in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

The device and elements herein are amongst others described during operation.

As will be clear to the person skilled in the art, the invention is not limited to methods of operation or devices in operation. It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb "to comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the device or apparatus claims enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

The invention further pertains to a method or process comprising one or more of the characterising features described in the description and/or shown in the attached drawings.

The various aspects discussed in this patent can be combined in order to provide additional advantages. Furthermore, some of the features can form the basis for one or more divisional applications.

Brief description of the drawings

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawing in which corresponding reference symbols indicate corresponding parts, showing in:

figure 1 shows in cross section an application of the clamping device on a part having an internal thread;

figure 2 shows the device of figure 1 in an exploded view in cross section;

figure 3 shows the embodiment of figure 1, in cross section in the first or released position;

Figure 4 shows the embodiment of figures 1-3 with the clamping device in its second or releasing position; Figure 5 shows an embodiment of an alternative clamping device for clamping a piece or part that has an external thread, with the clamping device in its second or clamping position;

Figure 6 shows the alternative clamping device of figure 5 with the clamping device in its first or releasing position;

Figures 7 A and 7B show a working principle of an embodiment of the clamping device, with figure 7 A the first or releasing position, and figure 7B the second or clamping position;

Figures 8 - 11 show a further embodiment of the clamping device for clamping an internal thread, in which figure 8 shows a perspective view, figure 9 a top view indication the cross sections of figure 10 and 11.

The drawings are not necessarily on scale.

Description of preferred embodiment

The drawings show features that may be combined as described.

In figure 1, in cross section an embodiment of the clamping device 1 for clamping a part 5 with an internal thread is shown, showing an application of the clamping device 1 for holding a clamped part or piece 5 that has an internal thread. Figure 2 shows figure 1 with the clamping device in perspective, exploded view and the clamped part in cross section.

When the clamping device 1 also needs to drive piece 5 in rotation about a longitudinal axis L, additional driving parts may be provided to engage the piece 5, and or to lock or block torsion force on the clamping device 1. Drive pins and drive holes are an example of a torque engagement part that in use also block (further) rotation of the clamping device and the piece 5 with respect to one another.

The clamped piece 5 here has a centred hole 10 that has an internal screw thread or, shortly, an internal thread 11. The internal thread 11 has a thread form, a pitch between the crests of adjacent threads, and a lead, usually equal to the pitch. Furthermore, the internal thread 11 has a major diameter, a minor diameter, and a pitch diameter.

The major diameter of the internal thread 11 is the larger of two extreme diameters delimiting the height of a thread profile, as a cross-sectional view is taken in a plane containing the axis of the thread. The minor diameter is the lower extreme diameter of the internal thread 11. Major diameter minus minor diameter, divided by two, equals a height of the thread. The minor diameter of the internal thread 11 is its inside diameter.

The pitch diameter of the internal thread 11 is the diameter of a cylindrical surface that is axially concentric to the internal thread. The cylindrical surface intersects thread flanks at equidistant points, when viewed in a cross-sectional plane containing the axis of the thread. The distance between these points is exactly one half the pitch distance. Equivalently, a line running parallel to the axis and a distance away from it, slices the sharp-V form of the thread at exactly 50% of its height, assuming that the flanks have the proper shape, angle, and pitch for a specified thread standard. The pitch diameter is generally unrelated to the major and minor diameters, especially if the crest and root truncations of the sharp-V form at these diameters are unknown.

Figures 3 and 4 show the embodiment of the clamping device of figures 1 and 2 in cross section, showing in figure 3 the clamping device 1 in its first or disengaged position, and in figure 4 showing the clamping device 1 in the second or engaged position.

The clamping device in this embodiment has a first thread-engaging part 12 and a second thread-engaging part 13. Both thread-engaging parts 12, 13 extend in longitudinal direction L. At their outer surfaces, the thread-engaging parts 12, 13 have sections of external thread 14 that match the internal thread 11 of the centred hole 11. The first and second thread-engaging parts 12, 13 can move with respect to one another, in this current embodiment in radial direction Ra. In the currently discussed embodiment, the first thread-engaging part 12 is stationary with respect to the further clamping device 1, and the second thread-engaging part 13 can move in the radial direction Ra with respect to the first thread-engaging part 12. This construction of two thread-engaging parts 12, 13, and one stationary with respect to the rest of the clamping device 1, is relatively simple in construction. Other embodiments, with more than two thread-engaging parts can be engineered. Other directions of movement may also be possible, although often an radial component of motion will be involved.

In the embodiment illustrated in figures 1-4, the second thread-engaging part 13 is mounted on, or here integrally formed as one piece with, a sledge part 15. The first thread-engaging part is here mounted on, or here integrally formed as one piece with, a mounting part 16. Mounting part 16 may comprise a slide provision (not shown here). The sledge part 15 can be mounted into the slide provision to allow the sledge part 15 to slide back and forth in radial direction Ra on the mounting part 16. The sledge part 15 with the second thread-engaging part 13 can displace with respect to the longitudinal axis L.

The sledge part 15 and thus the second thread-engaging part 13 is in this embodiment further biased, here spring-biased, via spring 18. The second thread- engaging part 13 is in this way biased away from the longitudinal direction L. The mounting part 16 provides a first abutment for the sledge part 15 with the second thread-engaging part 13 in the first position in which the first and second thread- engaging parts 12, 13 can be inserted in the centred hole 10, in insertion direction I. The mounting part 16 furthermore in this embodiment has a second abutment for the sledge part 15 in which the second thread-engaging part 13 is at least at the second position. Note that the second abutment may also block the second thread-engaging part 13 at a position in which the second thread-engaging part 13 is further removed from the longitudinal axis L than in the second position. In this way, the external surface of the second thread-engaging part will be spring biased against the internal thread of the hole 10.

The outer surface of the thread-engaging parts 12, 13 here has an external thread that matches the internal thread 11. In this way, the first and second thread-engaging parts 12, 13 can simply and securely engage the internal thread 11 of centred hole 10. There may, however, also be other external surfaces that allow the thread-engaging parts 12, 13 to engage with the internal thread 11 in such a way that the first and second thread-engaging parts can work together to hold and clamp the part 15. In particular, hold and clamp the piece 5 in such a way that it will not fall off the clamping device 1. An external thread 14 matching the internal thread 11 is a secure and safe choice for the thread-engaging surfaces.

In the embodiment of figures 1-4, it is illustrated that in the first position of figure 4, the circumference of the thread-engaging parts 12, 13 is such that they can be inserted in the insertion direction I. Any diameter of the circumference of the thread- engaging parts 12, 13 is smaller that the minor diameter of the internal thread 11 of the centred hole 10, allowing easy insertion of the thread-engaging parts 12, 13 into the centred hole 10. With the first and second thread-engaging portions 12, 13 in the second position, the first and second thread-engaging portions are here spaced apart.

In figures 5 and 6, an alternative embodiment of a clamping device 1 is illustrated. In this embodiment, the threaded piece is now a threaded end 5' with external thread I V . In this embodiment, the thread-engagement parts 12 and 13 have an engagement surface (concave) that is here provided with internal thread 14. Again, the thread-engagement parts 12, 13 have the first (mutual) position and the second (mutual) position. In figure 5, the thread-engaging parts 12, 13 are in the second or engaging position, and in figure 6 the thread-engaging parts 12, 13 are in the first or disengaging position. The thread-engaging part 13 in this embodiment is also biased in radial direction Ra, but here the spring force F (figure 5) is in opposite direction having a component towards the longitudinal axis L, forcing the thread-engaging part 13 against the external thread 1 1 ' of the threaded end 5' . A force P (figure 6) pulling the threaded part 13 via sledge 15 away from the threaded end 5' in this embodiment has to be applied in order to bring the threaded parts 12, 13 in the first or clear or disengaged position.

Again, a blocking provision (not indicated in the drawings) may be added to block or lock the threaded parts 12, 13 in the second, engaged position.

Figures 7A and 7B show a working principle of an embodiment of the clamping device of figures 1-4, with figure 7 A the first or releasing or engaging position, and figure 7B the second or clamping or disengaging position. In the clamping position, the thread-engaging parts 12, 13 form part of a cylinder, here with an external thread 14. These thread-engaging parts 12, 13 can engage with an internal thread 1 1 of the internal hole 10. A spacing between thread-engaging parts 12, 13 can be selected such that that it allows displacing these parts 12, 13 from their first position to their second position and vice versa.

In the drawings 7 A and 7B, diameter D5 is the major diameter of the internal thread 1 1, diameter Dm is the minor diameter of an internal thread 1 1 of a hole 10. Diameter D2 is the largest diameter of the thread-engaging parts in their first position. In order to be able to remove the clamping device 1 from the centred hole 10 ('pull it out of the centred hole 10', parallel to the longitudinal direction L), diameter D2 should be smaller than diameter Dm. In that way, a quick-release coupling can be provided. The radius of curvature of the thread-engaging parts corresponds here to the radius of curvature of the hole 10. In case the hole 10 is provided with an internal thread 11 and the thread-engaging parts 12, 13 are provided with (parts of) external thread 14, the radii of curvature of the threads correspond, see figure 7B, where the dotted lines almost overlap. In a definition, both the internal thread and the external thread have a pitch diameter. For matching threads, these pitch diameters will substantially match.

In the embodiment shown in figure 7A and 7B, the first and second thread- engaging parts 12, 13 are horizontal cylinder segments as explained earlier. These thread-engaging parts 12, 13 have parallel longitudinal faces.

In this shown embodiment, part of the thread-engagement parts have been clipped off in order to reduce the maximum diameter D2 of the thread-engaging parts 12, 13. When two horizontal cylinder segments are used as thread-engagement parts 12, 13 in case of an internal thread of the clamped piece 5, there are several options for making the thread-engaging parts 12, 13 such that their external surface is disengaged from the thread of the clamped piece 5. The options below are not limiting, but illustrate some options available.

One option is to make one (the largest) thread engaging part 12 a half cylinder. The other thread-engaging part 13 should then have a longitudinal face at least 2x(D5— Dm) removed from the longitudinal axis L. Furthermore, a part of the largest thread-engaging part 12 should be clipped as is shown in figures 7 A and 7B in order to obtain a largest diameter D2 that is smaller than Dm. The clipping at both ends should reduce the diameter D2 to less than Dm.

Another option is to select both thread-engaging parts 12, 13 with a longitudinal face at a distance from the longitudinal axis. This is done in the embodiment of figures 7A and 7B. The space D4' between both thread-engaging parts 12, 13 in their second or engaged position (or between their longitudinal faces) then is larger than 2x(D5— Dm). In this embodiment, the space D4' is less than a third of diameter D5. Again, when that spacing D4' is close to 2x(D5— Dm), additionally, one or both thread- engaging parts should be clipped as shown in the figures 7A and 7B, in such a way that again the largest diameter D2 is smaller than Dm. The different options presented above, combinations thereof, and other options that are possible make it difficult to provide a general mathematical equation for all possible options.

When for instance the thread-engaging part, for instance part 12, has a longitudinal face, i.e., is cut along a straight line parallel (solid line) to, but at a distance from, the longitudinal axis L, creating in fact a longitudinal cylinder segment, then largest diameter D2 can be calculated via:

D2 = 2-V(R ² -d ² ) , or

D2 = 2-R-sin(½ q>).

In any way, D2 is smaller than Dm.

The clamping part may comprise more than two thread-engaging parts, although this may increase complexity. In order to make production easy, the thread-engaging parts can be horizontal cylinder segments, but other cylinder types parts or segments may also be devised.

In an embodiment, as shown in figures 1-4 and 7A-7B, the thread-engaging parts

12, 13 are horizontal cylinder sections that have the external thread 14. These cylinder sections are part of an engagement cylinder.

The engagement cylinder has a circumference. Usually, the thread-engaging parts each have less than 40% of the engagement cylinder circumference. In the embodiment shown in the drawings, the thread-engaging part indicated with reference number 12 is stationary. The thread-engaging part with reference number 13 in this embodiment defines a smaller part of the engagement cylinder circumference that the thread- engagement part 12. It in figures 1-5 is placed on the sledge part 15 and in use moves here in radial direction. In an embodiment, the larger thread-engaging part 12 has between 30-40% of the engagement cylinder circumference. The smaller thread- engaging part 13 in an embodiment has between 20-30% of the engagement cylinder circumference.

In the embodiment of figures 1-4, the thread-engaging part 13, or in fact the sledge part 15, is spring-biased in radial outward direction. Usually, the sledge-part 15 has a thread-engaging parts blocking, not indicated. Such a thread-engaging parts blocking can block or fix or lock the position of the thread-engaging parts 12, 13 with respect to one another at or beyond the second or engaging position. In particular, the thread-engaging parts blocking fixes the thread-engaging parts 12, 13 with respect to one another in the second or engaging position. In this way, the clamping device provides the same or almost the same fixing as a regular set of threaded parts with an internal and external thread, respectively, like a bolt and nut.

Figures 8 and 9 show a further embodiment of a clamping device for clamping an internal thread. Here, the thread-engaging parts 12, 13 again define a central hole 10 that continues through the mounting part 16. This allows the clamping device to be fixed to a further tool or to a shaft. In this embodiment, the first and second thread- engaging part 12, 13 are both moveable. When providing the internal surface of the thread-engaging parts 12, 13 (i.e., the central hole 10) with an internal thread, it allows a design for clamping an external thread. The first and second thread-engaging parts 12, 13 are biased away from one another, here spring-biased via (two) springs 18. Upon applying pressure, the first and second thread-engaging parts 12, 13 can be pressed towards one another. When pressed together, the thread-engaging parts 12, 13 beyond the first position for allowing a threaded part with internal thread to be removed or passed onto the clamping part. When released, the thread-engaging parts 12, 13 move away from one another. When moving away from one another, the thread-engaging parts 12, 13 move to or even passed the second position. In this embodiment, both thread-engaging parts are provided on a sledge part 15 that allows the thread-engaging parts to slide in the mounting part 16. In this embodiment, the thread-engaging parts displace in a substantially and/or functionally parallel, opposite direction. Furthermore, the thread-engaging parts displace while remaining functionally parallel. In this embodiment, the thread-engaging parts 12, 13 can be identical, making the clamping device 1 easier to produce.

In an embodiment, shown in figures 8 - 11, the mounting part 16 and sledge parts 15 have a provision 17 for providing a linear motion (i.e., along a straight line) when the first and second thread-engaging parts 12, 13 move between the first and second positions. In this embodiment, the sledges 15 have a slotted hole at reference number 17 for each thread-engaging part 12, 13. The mounting part holds pins 8 provided for running in one of the respective slotted holes. The pins and slotted holes may also be reversed, providing the mounting part 16 with slotted holes and the sledge parts 15 with pins. The slotted holed here are straight and define a straight, radial direction of motion. In the current embodiment, an end of the slotted holes near the longitudinal axis L define the second or engaged position and an end of the slotted holes remote from the longitudinal axis L define the first of cleared position.

In an alternative embodiment, one or more rails and corresponding runners may be provided on the mounting part 16 and the tread-engaging parts 15, respectively, for providing the linear motion.

In the embodiment of figures 8 and 9, the sledge parts 15 have a lower surface that slide over an upper surface of the mounting part 16 when the sledge parts 15 slide between the first and second positions. In the current embodiment, in order to make the thread of the first and second thread-engaging parts 12, 13 come into engagement with the thread of the part-to-be-engaged 11, 11 ', the sledge parts 15 further displace under an angle with respect to a radial plane (normal to the longitudinal axis L). In particular, that angle can be between 3 and 8 degrees. In the current embodiment, the angle is about 5 degrees.

In order to prevent a possible rotation of a clamped part 5 with respect to the clamping device 1, the clamping device 1 may additionally be provided with a rotation- blocking that engages the clamped part 5. This in fact for any possible embodiment. In an embodiment that is not further indicated in the drawings, the clamping device 1 may be provided with one or more rotation-blocking members. The one or more rotation- blocking members may comprise one or more pins mounted on the mounting part 16 that is provided to engage a hole in a clamped part 15. In an embodiment, such one or more pins 8 extend functionally parallel to the first and second thread-engaging parts 12, 13.

In the embodiment of figures 8-11, a holding plate 21 is mounted on the mounting part 16 to hold the sledges 15 and thus the thread-engaging parts 12, 13 on the mounting part 16. Here a (radial) length of the slotted hole in each sledge 15 limits the radial motion of the sledges The holding plate 21 holds the sledges on the mounting part 16, allowing them to slide radially or substantially radially.

It will also be clear that the above description and drawings are included to illustrate some embodiments of the invention, and not to limit the scope of protection. Starting from this disclosure, many more embodiments will be evident to a skilled person. These embodiments are within the scope of protection and the essence of this invention and are obvious combinations of prior art techniques and the disclosure of this patent. List of reference numbers

I clamping device

5 clamped part

10 hole

I I internal thread

12 first thread-engaging part

13 second thread-engaging part

14 external thread

15 sledge part

16 mounting part

18 spring for application of a spring-biased force

21 holding plate

22 central hole in mounting part

Ra Radial direction

P direction of applied force to overcome biasing force

I insert direction of thread engagement parts into hole

L longitudinal direction

F direction of (spring) biasing force

Dl smallest minor diameter of the external thread of the clamping device

D2 largest major diameter of the external thread of the thread-engaging part in the first or disengaged position

D3 largest minor diameter of the external thread of the clamping device

D4' maximum clearance between the first and second thread-engaging parts 12,

13

D5 major diameter of the internal thread 11

Dm minor diameter of the internal thread 11.