WO2023247382A1

WO2023247382A1 - Positioning device for a positioning system

Info

Publication number: WO2023247382A1
Application number: PCT/EP2023/066339
Authority: WO
Inventors: Erik Sundström
Original assignee: Zerofix Ab
Priority date: 2022-06-20
Filing date: 2023-06-17
Publication date: 2023-12-28

Abstract

Embodiments of the invention relates to a positioning device (100) for a positioning system (200) for positioning a first object (302) in relation to a second object (304) in a XY-reference system, the positioning device (100) comprising: a first XY-reference means (102) configured to be fixed to the first object (302), and a second XY-reference means (104) configured to be fixed to the second object (304); wherein the first XY-reference means (102) comprises a spring arrangement (130) configured to abut against the second XY-reference means (104) in operation for positioning the first object (302) in relation to the second object (304) in XY-directions, the spring arrangement (130) comprising at least one first spring portion (132) serially coupled to at least one second spring portion (134), and the first spring portion (132) is configured to deflect in a Z-direction (+Z, -Z) in operation and the second spring portion (134) is configured to deflect in the Z-direction (+Z, -Z) in operation to compensate for the deflection of the first spring portion (132) in the Z-direction (+Z, -Z).

Description

POSITIONING DEVICE FOR A POSITIONING SYSTEM

Technical Field

The invention relates to a positioning device for a positioning system for positioning a first object in relation to a second object. Furthermore, the invention also relates to a positioning system comprising such a positioning device.

Background

When placing two objects, e.g., a working table or a base plate on a milling machine table, it is important to be able to accurately position these two objects in relation to each other in order to be able to use e.g., a milling machine reference system for an object arranged on the working table. Before the 1960:s a majority of the machining and measuring within the engineering industry took place by making relative measurements using e.g. micrometer calipers, sliding calipers and templates for dimensional accuracy. Drawings were produced manually to fit these manufacturing methods. The precision depended more on the skill of the workers and operators of the machines than the stability and the lack of freedom of play of the machines. When numerically controlled machines for the production appeared on the market, the manufacturing methods began to be more and more automated and today the production is to a large extent more or less automated using e.g., CNC-controlled multioperation machines.

During the above development of the production processes, the manufacturers of the machines have also minimized the previous problems of the machines being able to turn the input instructions to corresponding output process steps without accuracy problems. This is also the case regarding problems with temperature stability, freedom of play and elastic deformation. The above enables for metalworking equipment to move to completely digitalized production by absolute coordinated originating from a given zero offset point using digital measurement and control systems and automated tool changing systems in the machines.

A reference system commonly used in e.g., machine shops is the Cartesian coordinate system having XYZ-directions. When talking about accurate positioning in machine shops and e.g., turning, milling and drilling, tolerances of 0.01 mm - 1 pm are considered “accurate”, whereas tolerances smaller than 1 pm are often difficult to use in production applications as such tolerances often are difficult to measure in real production. Whereas it is relatively easy to achieve and maintain high tolerances in a laboratory environment, temperature changes and pollution as well as wear are issues that have to be handled in real production equipment whether it is manually operated or automated. Summary

An objective of embodiments of the invention is to provide a solution which mitigates or solves the drawbacks and problems of conventional solutions.

Another objective of embodiments of the invention is to provide a solution with improved positing accuracy in the XY-plane of a first object in relation to a second object.

The above and further objectives are solved by the subject matter of the independent claims. Further advantageous embodiments of the invention can be found in the dependent claims.

According to a first aspect of the invention, the above mentioned and other objectives are achieved with a positioning device for a positioning system for positioning a first object in relation to a second object in a XY-reference system, the positioning device comprising: a first XY-reference means configured to be fixed to the first object, and a second XY-reference means configured to be fixed to the second object; wherein the first XY-reference means comprises a spring arrangement configured to abut against the second XY-reference means in operation for positioning the first object in relation to the second object in XY-directions, the spring arrangement comprising at least one first spring portion serially coupled to at least one second spring portion, and wherein the first spring portion is configured to deflect in a Z-direction in operation and the second spring portion is configured to deflect in the Z-direction in operation to compensate for the deflection of the first spring portion in the Z-direction.

The positioning device may also be denoted a zero-positioning device or a positioning device. The XY-reference system may also mean the XY-plane of a Cartesian coordinate system. The deflection of the first spring portion and the second spring portion may occur when forces are acting on the spring arrangement due to a press fit mounting. The deflection may also be understood as a deformation. The first XY-reference means may be denoted first XY- positioning means and the second XY-reference means may be denoted second XY- positioning means. The Z-direction may be the positive Z-direction or the negative Z-direction in a XYZ coordinate system also known as a Cartesian coordinate system in three dimensions.

The expression “in operation” may be understood as “when mounted and in operation” or “in use” or “when mounted and in use”. An advantage of the positioning device according to the first aspect is that the accuracy of the positioning of the first object in relation to the second object in the XY-plane is improved compared to conventional solutions.

In an implementation form of a positioning device according to the first aspect, the first spring portion extends conically in relation to a radial plane of the positioning device with a first angle; and the second spring portion extends conically in relation to the radial plane of the positioning device with a second angle.

The radial plane may be considered as a plane extending out from an axial axis, such as a center axial axis of the positioning device.

In an implementation form of a positioning device according to the first aspect, the first angle and the second angle are different angles.

This may be understood such that first spring portion and the second spring portion have different conicities.

In an implementation form of a positioning device according to the first aspect, the conicity of the first spring portion extends in an opposite direction in relation to the conicity of the second spring portion.

In an implementation form of a positioning device according to the first aspect, the conicity of the first spring portion is configured to increase and the conicity of the second spring portion is configured to decrease, or vice versa.

In an implementation form of a positioning device according to the first aspect, the first spring portion and the second spring portion form an angle larger than 90^e and smaller than 180^e at an intersection area of the first spring portion and the second spring portion.

In an implementation form of a positioning device according to the first aspect, the spring arrangement comprises a spring coupling portion configured to serially couple the first spring portion and the second spring portion.

In an implementation form of a positioning device according to the first aspect, the spring coupling portion is concentrically arranged around a center axial axis of the positioning device. This may also be understood such that the spring coupling portion comprises a radius that is symmetrically arranged around the center axial axis.

In an implementation form of a positioning device according to the first aspect, the spring coupling portion comprises a radius.

In an implementation form of a positioning device according to the first aspect, the radius of the spring coupling portion changes in relation to the center axial axis when an axial force in the positive Z-direction is applied at the spring arrangement.

In an implementation form of a positioning device according to the first aspect, the change of the radius of the spring coupling portion is dependent on the amount of the axial force.

In an implementation form of a positioning device according to the first aspect, the radial plane and the spring coupling portion intersect.

In an implementation form of a positioning device according to the first aspect, the spring coupling portion comprises a groove configured to serially couple the first spring portion and the second spring portion.

In an implementation form of a positioning device according to the first aspect, the groove is a punched groove.

In an implementation form of a positioning device according to the first aspect, the groove is circularly arranged with a constant radius around a center axis of the positioning device.

The constant radius means symmetry around the center axis.

In an implementation form of a positioning device according to the first aspect, the first spring portion is configured to deflect in the Z-direction with a first amount, and the second spring portion is configured to deflect in the Z-direction with a second amount different to the first amount.

In an implementation form of a positioning device according to the first aspect, the first XY- reference means has in a Z-direction conical inner surface, and the second XY-reference means has in a Z-direction conical outer surface. In an implementation form of a positioning device according to the first aspect, the spring arrangement has an annular disc shape, and the second XY-reference means comprises a taper.

In an implementation form of a positioning device according to the first aspect, the second XY- reference means is configured to be fixed to the second object via a spacer.

In an implementation form of a positioning device according to the first aspect, the spring arrangement comprises a rim portion serially coupled to the first spring portion and being configured to press against the taper of the second XY-reference means in operation.

In an implementation form of a positioning device according to the first aspect, the spring arrangement comprises a press fit guiding means serially coupled to the second spring portion and configured to press against the first object in operation.

In an implementation form of a positioning device according to the first aspect, the rim portion is arranged at an inner circumference of the spring arrangement, and the press fit guiding means is arranged at an outer circumference of the spring arrangement.

In an implementation form of a positioning device according to the first aspect, the spring arrangement is formed from a single sheet metal piece with constant thickness.

In an implementation form of a positioning device according to the first aspect, the second object is configured to support the first object in the positive Z-direction in operation.

According to a second aspect of the invention, the above mentioned and other objectives are achieved with a positioning system for positioning a first object in relation to a second object in a XY-reference system, the positioning system comprising at least one positioning device according to any one of the preceding claims.

Further applications and advantages of the embodiments of the invention will be apparent from the following detailed description. Brief Description of the Drawings

The appended drawings are intended to clarify and explain different embodiments of the invention, in which:

- Fig. 1 shows in a cross sectional view a positioning system according to an embodiment of the invention;

- Fig. 2 shows in a cross sectional view a positioning device according to an embodiment of the invention;

- Fig. 3a and 3b show a spring arrangement according to an embodiment of the invention in a cross sectional view and in a view from above, respectively;

- Fig. 4 shows in a cross sectional view a section of a spring arrangement according to an embodiment of the invention;

- Fig. 5 shows the spring arrangement more in detail; and

- Fig. 6 illustrates exemplary measurements of an exemplary spring arrangement.

Detailed Description

Fig. 1 shows in a cross sectional view a positioning system 200 according to an embodiment of the invention. The positioning system 200 may comprise any number of positioning devices 100 and in the exemplary case of Fig. 1 two positioning devices 100 are shown in their mounted operating position. Each positioning device 100 may act as a zero-reference in the system 200 for high accuracy. Further, the system 200 also comprises a first object 302 and a second object 304 to be positioned in relation to each other in the XY-reference system or the XY- plane. The positive Z-direction “+Z” and the negative Z-direction “-Z” are also illustrated hence a Cartesian coordinate system in three dimensions is illustrated in Fig. 1. It is naturally noted the positive Z-direction and the negative Z-direction are opposite directions in relation to each other, i.e., the positive Z-direction is the opposite direction to the negative Z-direction. However, in embodiments of the invention when cylindrical symmetry is at hand cylindrical coordinates may also be used with an axis A extending axially and a radius R extending radially as also illustrated in the Figs.

Furthermore, the first object 302 may e.g., be a working table, a base plate, a fixture, a pallet, a tool, etc., and the second object 304 may e.g., be a machine table, a machine base, etc. but are not limited thereto. The first object 302 may comprise a downward directed cavity in which cavity the first XY-reference means 102 may be fixed to against the side walls of the cavity as shown in Fig. 1. Therefore, the first XY-reference means 102 may be arranged to be fixed against an inner wall of the cavity by a press-fit arrangement, e.g., if the first XY-reference means 102 comprises a spring arrangement, and may be mounted non-removably therein, e.g., by pressing it therein using a mandrel or any other suitable device. The second XY- reference means 104 may be configured to be fixed to the second object 304 with or without a spacer 1 10. The second XY-reference means 104 may be made of a hard metal in order to withstand wear. In embodiments of the invention, the second object 304 is configured to support the first object 302 in the positive Z-direction in operation as shown in Fig. 1 .

Fig. 2 shows in a cross sectional view a positioning device 100 according to an embodiment of the invention. The positioning device 100 comprises a first XY-reference means 102 configured to be fixed to the first object 302, and a second XY-reference means 104 configured to be fixed to the second object 304. The first XY-reference means 102 comprises a spring arrangement 130 configured to abut or press against the second XY-reference means 104 in operation for positioning the first object 302 in relation to the second object 304 in XY-directions or equivalently in the XY-plane. Further, the spring arrangement 130 comprises at least one first spring portion 132 which is serially coupled to at least one second spring portion 134. In operation, the first spring portion 132 is configured to deflect or deform in a Z-direction +Z, -Z and the second spring portion 134 is configured to deflect or deform in the same Z-direction +Z, -Z so as to compensating for the deflection or the deformation of the first spring portion 132 in the same Z-direction. The Z-direction may be the positive Z-direction +Z or the negative Z-direction -Z.

In embodiments of the invention, the first spring portion 132 is configured to deflect in the Z- direction with a first amount, and the second spring portion 134 is configured to deflect in the Z-direction with a second amount. The first amount is different to the second amount for balancing the deflection of the first spring portion 132 and the second spring portion, respectively, for controlled total deflection of the spring arrangement 130 of the positioning device 100.

When the first XY-reference means 102 is mounted, e.g., by press fit in which a high radial force Fr will act on the first XY-reference means 102, the first XY-reference means 102 may deform in a non-controlled manner so that the positioning of the first object in relation to the second object is not accurate enough for precision applications. However, by having a spring arrangement 130 according to embodiments of the invention the deformation or deflection of the spring arrangement 130 may be controlled. This means improved accuracy and higher precision.

Furthermore, the positioning device 100 may comprise means for attach ing/fasteni ng the positioning device 100 to the first object 302 and the second object 304, respectively. In the disclosed embodiment, the positioning device 100 comprises first attachment means 120 for attaching to the first object 302 and second attachment means 118 for attaching to the second object 306. The first attachment means 120 and the second attachment means 1 18 may e.g., be first hi and second h2 through holes of different diameters arranged inside a body 106 of the position device 100, the body 106 having an axial extension and e.g., having a cylindrical symmetry and further comprise a section that is encircled by a taper of the second XY- reference means 104. The body 106 may be made of a suitable material such as a metal. The first hi and second h2 through holes may comprise inner threads configured to receive outer threads of bolts (not shown in the Figs.) of the first 302 and second objects 304, respectively, for fixing the first 302 and second objects 304. Thereby, a secure attachment or fastening of the positioning device 100 to the first 302 and second objects 304, respectively, is achieved.

As also illustrated herein with reference to Fig. 2, the positioning device 100 may comprises a clearance 116 also in the form of a through hole h3 having a diameter larger than the diameter of the through holes of the first 120 and second 118 attachment means. Thereby, the risk of the positioning device 100 being misaligned due to radial forces acting on the positioning device 100 so as to distort the positioning accuracy in the XY-plane is minimized or at least reduced. This is especially the case when the positioning device 100 is to be mounted in the positioning system 200.

As further disclosed in Fig. 2, the first XY-reference means 102 may have a in a Z-direction conical inner surface which in operation abuts or presses against a in a Z-direction conical outer surface of the second XY-reference means 104. Moreover, in embodiments of the invention, the spring arrangement 130 has an annular disc shape and the second XY-reference means 104 comprises a taper. Therefore, in such cases, the disc may comprise the conical inner surface whilst the taper comprises the conical outer surface abutting against each other as shown in Fig. 2. It may also be noted that the second XY-reference means 104 may be configured to be fixed to the second object 304 via a spacer 110, also known as a spacing device or a distance peace, as shown in Fig. 1 and 2. The spacer 1 10 supports the first object in the Z-direction and depending on application the thickness and shape of the spacer 1 10 may vary.

Fig. 3a and 3b show a spring arrangement 130 according to an embodiment of the invention in a cross-sectional view and in a view from above, respectively. Furthermore, Fig. 4 shows a section of the spring arrangement 130 in a cross-sectional view. With reference to mentioned Fig. 3a, 3b and 4 more details and aspects of the herein disclosed spring arrangement 130 will now be described. As shown, in embodiments of the invention, the spring arrangement 130 comprises a rim portion 136 which is serially coupled to the first spring portion 132. The rim portion 136 may be of the type stiff rim and being configured to press against the taper of the second XY- reference means 104 in operation as shown in Fig. 2. Further, the spring arrangement 130 may comprise a press fit guiding means 138 serially coupled to the second spring portion 134. The press fit guiding means 138 is configured to press or abut against the first object 302 in operation as also shown in Fig. 2. The press fit guiding means 138 may in this respect comprise a beak portion 138' so as to lock and secure the spring arrangement 130 against the first object 302 in operation at mounting. In embodiments of the invention, the rim portion 136 is arranged at an inner circumference of the spring arrangement 130, whilst the press fit guiding means 138 is arranged at an outer circumference of the spring arrangement 130.

As previously mentioned, the first spring portion 132 is serially coupled to the second spring portion 134, or vice versa. This may be achieved by the use of a spring coupling portion 140 that is configured to serially couple the first spring portion 132 and the second spring portion 134 to each other. The spring coupling portion 140 may be considered as a spring hinge mechanically coupling independent springs serially to each other, but also demark or define different spring portions from each other. It is noted that the spring arrangement 130 herein may comprise any number of spring coupling portions coupling any number of first 132 and second 134 spring portions which means that embodiments of the invention is not limited to a single spring coupling portion coupling a single first spring portion and a single second spring portion.

In further embodiments of the invention, the spring coupling portion 140 comprises of a groove which may be circularly arranged with a constant radius around a center axial axis A of the positioning device 100 as shown in 3a, 3b and 4. It has been noted that a groove works well in acting as a spring coupling portion 140 for many applications. However, the spring coupling portion 140 may be realized with other means having the same function as previously described.

When the spring coupling portion 140 comprises of a groove, economic advantages is achievable when manufacturing the spring arrangement 130 herein. For example, the groove may be a punched groove which is inexpensive to produce. In embodiments of the invention, the spring arrangement 130 may be formed from a single sheet metal piece with constant thickness, and the single sheet metal piece may be punched or stamped in a single manufacturing step using a dedicated tool so as to produce the spring arrangement 130. In this way both high accuracy in positioning and low cost at production of the positioning device 100 is possible.

With reference to Fig. 4 and 5 yet further details and aspects of the invention is presented. It may be noted that the first spring portion 132 extends conically in relation to a radial plane P of the positioning device 100 with a first angle cd , and that the second spring portion 134 extends conically in relation to the radial plane P of the positioning device 100 with a second angle a2. Hence, the spring portions have conicity in relation to the radial plane P which may be seen as a plane extending radially out from the center axial axis of the positioning device as illustrated in the Figs. The radial plane P may therefore be a horizontal plane parallel with the XY-plane of a Cartesian reference system.

In embodiments of the invention, the first angle cd and the second angle a2 are different angles thus giving the first 132 and second 134 spring portions different conicities. This also implies that the first 132 and second 134 spring portions will have different spring constants. The conicities of the first 132 and second 134 spring portions are in embodiments of the invention arranged to extend in opposite directions.

The first spring portion 132 and the second spring portion 134 may together form an angle p that is obtuse, i.e., larger than 90^e and smaller than 180^e at an intersection area of the first spring portion 132 and the second spring portion 134. The intersection area may in embodiments of the invention overlap with the mentioned spring coupling portion 140 which is configured to serially couple the first spring portion 132 and the second spring portion 134. The spring coupling portion 140 may be concentrically arranged around a center axial axis A of the positioning device 100. This may be understood such that the spring coupling portion 140 is symmetrically arranged around center axial axis A, i.e., having a constant radius around the center axial axis A. The radial plane P and the spring coupling portion 140 will intersect with each other according to embodiments of the invention.

When the spring arrangement 130 is mounted in the positioning device 100 and a locking/securing device is used for locking the different parts of the positioning device 100 together two different forces, i.e., a radial force “Fr” and a force in the positive Z-direction “Fz”, will act in the positioning device 100 so that some of the accuracy of the zero point may be lost. However, due to the present spring arrangement 130, the first spring portion 132 is arranged to deflect from angle a1 to a1 ' while the second spring portion 124 is configured to deflect from angle a2 to a2', i.e., the conicity of the first spring portion 132 is configured to increase while the conicity of the second spring portion 124 is configured to decrease so as to balance or compensation for the deflection of the first spring portion 132. A direct result of such deflection is that a radius “r” of the spring coupling portion 140 will change in relation to the center axial axis A when the axial force Fz in the positive Z-direction is applied at the spring arrangement 130. Thereby, the change of conicities of the first 132 and second 134 spring portions will balance each other so as to retain the zero point of the reference system without any so called positioning distortion i.e., without losing accuracy of the zero point. The accuracy in the XY-plane of the present solution will outperform that of conventional positioning systems.

It is to be understood that depending on the design the first 132 and the second 134 spring portions may deflect in the positive Z-direction or in the negative Z-direction. However, the general principles and aspects herein disclosed will apply. Further, when designing the radius r of the spring arrangement 130, the spring constants of respective spring portion should be considered for a properly functioning position device 100.

For providing even deeper understanding of embodiments of the invention in respect of the spring arrangement 130, some numbers are given which are exemplary only and are dependent on the application of the positioning device 100 and positioning system 200. With reference to Fig. 6, the spring arrangement 130 may have a symmetrical disc shape with a smaller outer diameter d2 of 36mm, a larger outer diameter d1 of 36.12mm, and an inner diameter d3 at the stiffed rim of 17.50mm. The thickness of such a disc may e.g., be formed from a 0.9mm thick sheet metal with a punched groove acting as the spring coupling portion 140. Generally, the different parts of the positioning device 100 may be made from any suitable material having the properties needed for its functioning such as different types of metal, plastics, etc.

Finally, it should be understood that the invention is not limited to the embodiments described above, but also relates to and incorporates all embodiments within the scope of the appended independent claims.

Claims

1 . A positioning device (100) for a positioning system (200) for positioning a first object (302) in relation to a second object (304), the positioning device (100) comprising: a first XY-reference means (102) configured to be fixed to the first object (302), and a second XY-reference means (104) configured to be fixed to the second object (304); wherein the first XY-reference means (102) comprises a spring arrangement (130) configured to abut against the second XY-reference means (104) in operation for positioning the first object (302) in relation to the second object (304) in XY-directions, the spring arrangement (130) comprising at least one first spring portion (132) serially coupled to at least one second spring portion (134), and wherein the first spring portion (132) is configured to deflect in a Z-direction (+Z, -Z) in operation and the second spring portion (134) is configured to deflect in the Z-direction (+Z, -Z) in operation to compensate for the deflection of the first spring portion (132) in the Z-direction (₊Z, -Z).

2. The positioning device (100) according to claim 1 , wherein the first spring portion (132) extends conically in relation to a radial plane (P) of the positioning device (100) with a first angle (cd ); and the second spring portion (134) extends conically in relation to the radial plane (P) of the positioning device (100) with a second angle (a2).

3. The positioning device (100) according to claim 2, wherein the first angle (cd ) and the second angle (a2) are different angles.

4. The positioning device (100) according to claim 2 or 3, wherein the conicity of the first spring portion (132) extends in an opposite direction in relation to the conicity of the second spring portion (134).

5. The positioning device (100) according to claim 4, wherein the conicity of the first spring portion (132) is configured to increase and the conicity of the second spring portion (134) is configured to decrease, or vice versa.

6. The positioning device (100) according to any one of claims 2 to 5, wherein the first spring portion (132) and the second spring portion (134) form an angle (P) larger than 90^e and smaller than 180^e at an intersection area of the first spring portion (132) and the second spring portion (134).

7. The positioning device (100) according to any one of the preceding claims, wherein the spring arrangement (130) comprises a spring coupling portion (140) configured to serially couple the first spring portion (132) and the second spring portion (134).

8. The positioning device (100) according to claim 7, wherein the spring coupling portion (140) is concentrically arranged around a center axial axis (A) of the positioning device (100).

9. The positioning device (100) according to claim 8, wherein the spring coupling portion (140) comprises a radius (r).

10. The positioning device (100) according to claim 9, wherein the radius (r) of the spring coupling portion (140) changes in relation to the center axial axis (A) when an axial force (Fz) in the positive Z-direction is applied at the spring arrangement (130).

1 1 . The positioning device (100) according to claim 10, wherein the change of the radius (r) of the spring coupling portion (140) is dependent on the amount of the axial force (Fz).

12. The positioning device (100) according to any one of claims 7 to 11 when dependent on any one of claims 2 to 5, wherein the radial plane (P) and the spring coupling portion (140) intersect.

13. The positioning device (100) according to any one of claims 7 to 12, wherein the spring coupling portion (140) comprises a groove configured to serially couple the first spring portion (132) and the second spring portion (134).

14. The positioning device (100) according to any one of the preceding claims, wherein the first spring portion (132) is configured to deflect in the Z-direction (+Z, -Z) with a first amount, and the second spring portion (134) is configured to deflect in the Z-direction (+Z, -Z) with a second amount different to the first amount.

15. The positioning device (100) according to any one of the preceding claims, wherein the first XY-reference means (102) has in a Z-direction conical inner surface, and the second XY- reference means (104) has in a Z-direction conical outer surface.

16. The positioning device (100) according to any one of the preceding claims, wherein the spring arrangement (130) has an annular disc shape, and the second XY-reference means (104) comprises a taper. 17. A positioning system (200) for positioning a first object (302) in relation to a second object

(304) in a XY-reference system, the positioning system (200) comprising at least one positioning device (100) according to any one of the preceding claims.