FR2782791A1 - COUPLER IN THE FORM OF A FLAT BELT - Google Patents

Abstract

This coupler (200) comprises: a strip-shaped portion (424); and a plurality of flexible members (420, 421, 425, 426) connected to the strip-shaped portion (424). In particular applicable to a three-dimensional coordinate measuring machine, to compensate for an alignment deviation between the movable element and the measuring transducer used for the transmission of the rotational movement to the rotational measuring transducers used in each coupler of the measuring machine. coordinate measurement.

Description

Context of the invention Field of the invention The present invention

  generally relates to three-dimensional coordinate measuring machines. More particularly, the present invention relates to a new and improved coupler which compensates for an alignment difference between the mobile element and the measurement transducer used for the transmission of the rotational movement to the rotation measurement transducers used in each coupler of the machine. coordinate measurement. Without these couplers, forces

  significant error would appear in the transducer measurements.

  PRIOR ART It should be noted that, in the physical world, everything occupies volume or space. A position in a space can be defined by the length, the width and the height which, in engineering terms, are often called coordinates X, Y, Z. The numbers X, Y, Z represent the dimensions of the length, width and height, three dimensions. Three-dimensional objects are described in terms of position and orientation; in other words, not only where an object is, but in which direction it is oriented. The orientation of an object in space can be defined by the position of three points on this object. The orientation can also be described by the angles of alignment of the object in space. The X, Y and Z coordinates can be measured most simply by three linear scales. In other words, if you put a ladder along the length, width and height of a space,

  we can measure the position of a point in space.

  Currently, coordinate measuring machines measure objects in space using three linear scales. FARO Technologies Inc., Lake Mary, Florida (owner of the present invention)

  has successfully produced a series of electronic type scanning devices

  goniometer for the fields of medicine and industry. Electro-goniometer-type devices of the type used for skeleton analysis and surgery are described in U.S. Patent Nos. 4,670,851, 5,251,127 and 5,305,203, all of which are attributed to the holder of this document and used here by means reference. Portable coordinate measuring machines are now used for three-dimensional measurement of objects for reverse engineering, inspection, etc. An example of such a portable coordinate measurement system is described in U.S. Patent No. 5,402,582, which is

  attributed to the holder of this deposit and reproduced here by reference.

  As shown in FIG. 1, the three-dimensional measurement system of the prior art generally comprises a coordinate measurement machine composed of a multi-articulated arm 12 actuated manually and of a support or upright base 14, a controller or serial box 16 and a host computer 18. It should be noted that the coordinate measuring machine 10 communicates electronically with the serial box 16 which, in turn, communicates electronically with the host computer 18. It should be noted that the number of transfer boxes depends the number of degrees of freedom that are required to perform the desired measurements with the

coordinate measuring machine.

  As will be explained in more detail below, the coordinate measuring machine 10 comprises transducers (for example one transducer for each degree of freedom) which collects information on the position of rotation and transmit this basic data to the serial box 16. The prior art coordinate measuring machine 10 includes a base connected to a measuring arm which includes a plurality of transfer cases. With regard to these transfer cases, it should be noted that the transmission of the rotational movement to a rotational measurement transducer requires the use of a coupler to compensate for deviations in alignment between the movable element and the transducer. measured. Referring to Figures 2 and 3, the transducer 80 of the prior art is mounted on a universal mounting plate 82 to be mounted in the transfer case 64. High precision rotation measurements using coders require that '' there is no load on the encoders and the movement of the transfer case can be precisely transmitted to the encoder despite small deviations

  for aligning the axis of the transfer case and the axis of the encoder.

  Referring now to Figures 2 to 4 of the prior art, both

  diaphragm couplers are designated by the reference 84 in the figures.

  The arrows marked with "A" in FIG. 3 further underline the space occupied by the coupler 84 of the prior art assembled in the arm 12. It should be noted that the transmission of the rotational movement to a transducer for measuring rotation requires the use of a coupler to compensate for differences in alignment between the movable element and the measurement transducer. As shown in Figures 2 and 3, the transducer 80 is mounted on a universal mounting plate 82 to mount in the transfer case 64. The extension shaft 86 is used to finally connect the encoder 80 to the transfer case . The shaft 86 is fixed to a coupler 84 and to the end of the support 62 at the level of the screwing 74 using socket-head screws 88, 90. High precision rotation measurements using encoders 80 require that no load is applied to the encoders and that the movement of the transfer case can be accurately transmitted to the encoder despite small misalignments of the axis of the case

transfer and encoder axis.

  Although the coupler 84 used in the coordinate measurement systems of the prior art is well suited for its intended use, there is still a need to increase the precision and reduce the costs of these couplers used in coordinate measurement machines . We therefore feel the need to develop more precise couplers and / or

  less expensive used in coordinate measurement systems.

Summary of the invention

  The drawbacks and deficiencies of the prior art presented above

  above, as well as others, are surmounted or resolved by the coupler in the form of a flat strip for machines for measuring coordinates of the

present invention.

  According to one aspect of the invention, this coupler in the form of a flat strip comprises: a part in the form of a strip; and

  a plurality of flexible elements connected to the strip-like part.

  According to another aspect of the invention, this coupler in the form of a flat strip connects a rotary element to a measuring device, and comprises: a strip-shaped part a first pair of flexible elements connected to the strip-shaped part , and connected to the rotary element; and a second pair of flexible elements connected to the shaped part

  tape, and connected to the measuring device.

  According to another aspect of the invention, this coupler in the form of a flat strip is intended to be used in a multi-articulated arm transmitting a rotational movement from a rotary element to a measuring device, and comprises: a strip-shaped part a first pair of flexible elements connected to the strip-shaped part and connected to the rotary element; and a second pair of flexible elements connected to the shaped part

  tape and connected to the measuring device.

  As mentioned, the coupler of the prior art of US Pat. No. 5,402,582 is compensated for the misalignments between the movable member and the movable transducer. Without these couplers, large forces are produced, which induce errors in the measurement of the transducer. The prior art used a coupler with two diaphragms to transmit the rotational movement between the pin of the housing.

transfer and transducer.

  According to the present invention, the transducer is mounted instead on a coupler composed of a relatively thin flat strip and is connected directly to the mobile transducer. The coupler in the form of a flat strip therefore provides a flexible mount to take account of the alignment difference between the encoder and the transfer case while delivering precise transmission of the rotational movement between the parts. The coupler in the form of an unlubricated flexible strip consists of wear-free parts to directly connect the transfer case to the measuring element, establishing a clearly more reliable connection which compensates for an alignment deviation while reducing shock loads. In addition, this design also reduces the axial length of the combination of the transfer case coupler and the encoder by employing the coupler in the form of a relatively thin strip of the present invention in conjunction with the coupler element of the prior art. This allows the overall length of the arms of the coordinate measuring machine to be

significantly more compact.

  According to a possible characteristic of the invention, the coupler under

  flat strip shape is generally planar.

  According to another possible characteristic of the invention, the flexible elements are composed of parts forming a spring arranged in

circuit trajectories.

  According to another possible characteristic of the invention, the elements

  hoses include mounting holes in them.

  According to another possible characteristic of the invention, the coupler in the form of a flat strip is composed of a metallic material, of a

  plastic or a fiber-reinforced composite material.

  According to another possible characteristic of the invention according to its second or third aspect, the second pair of flexible elements

  is connected to the strip-like part by a pair of links.

  According to another possible characteristic of the invention according to its second or third aspect, the second pair of flexible elements

  is attached to a mounting plate.

  According to another possible characteristic of the invention according to its second or third aspect, the rotary element is a coupling of

transfer of a multi-articulated arm.

  According to another possible characteristic of the invention according to its second or third aspect, the measuring device is an encoder

of a multi-articulated arm.

  The features and advantages of the present invention presented above, as well as others, will be appreciated and understood by those with ordinary skill in the art from the

  detailed discussion that follows and sketches.

Brief description of the sketches:

  Referring now to the sketches, in which identical elements are numbered in the same way in the various figures: FIG. 1 is a schematic front view showing a typical three-dimensional measuring machine of the prior art comprising a coordinate measuring machine , a controller box and a host computer; Figure 2 is an exploded side elevation view of a transfer case used in the prior art coordinate measuring machine of Figure 1; Figure 3 is a sectional view of two assembled transfer cases, oriented transversely, of the coordinate measuring machine of the prior art of Figure 1; Figure 4 is a view taken along line 4-4 of Figure 2 Figure 5 is a plan view of a coupler in the form of a flat strip according to the present invention; Figure 6 is a side view of the coupler in the form of a flat strip according to the present invention; Figure 7 is a schematic sectional view of a coupler in the form of a flat strip showing a transfer case and an encoder; Figure 8 is a view taken along line 8-8 of Figure 7 showing a coupler in the form of a flat strip and a universal mounting plate; and Figure 9 is a plan view of an alternative embodiment

  a coupler in the form of a flat strip.

  Description of the preferred embodiment

  Referring first to Figure 5, a flat strip coupler 200 for use in coordinate measuring machines according to the present invention will be presented in detail in the following. As can be seen in FIG. 5, a coupler in the form of a flat strip 200 is basically of square configuration (preferably a little more than a square inch), symmetrical with respect to the two axes of the plane defined by the median lines 412, 414. The coupler in the form of a flat strip 200 comprises flexible elements 420, 421 joined by connections 422, 423 to a central strip 424 and which are placed on each side of the center line 414, and further comprises flexible elements 425 , 426 placed on each side of the central line 412. The flexible elements include spring parts 427 composed of narrow strips of material formed in circuit paths. The inside radius at the end of the spring portions 427 is preferably 0.020 inch, as typically shown at point 429, and the outside radius, typically shown at point 430, is preferably 0.060 inch. Other radii and groove lengths are considered suitable as long as the stress is reduced

  and to retain the flexibility of the coupler in the form of a flat strip 200.

  The clearance 431 in the center of the coupler in the form of a flat strip 200 is preferably 0.500 inch in diameter in order to provide sufficient play for the extension shaft 222 (FIG. 7). The flexible elements maximize the faculty of the coupler in the form of a flat strip 200 to deform in and out of the plane defined by the center lines 412, 414 while precisely transferring the torque and the rotational movement, as will be explained in more detail below. It should also be noted that the above dimensions can be easily modified as required

  without in any way departing from the spirit and the scope of the invention.

  Reducing the length of the coupling is of particular importance for the present invention, and as shown in Figure 6, the thickness shown by the arrows 428 of the coupler as a flat strip in the embodiment shown is preferably 0.020 inch. It is partly this relatively thin section thickness which allows the reduction of the space occupied by the coupler 84 of the prior art once assembled to the arm 12 (FIG. 13). The preferred material of the embodiment is cold worked stainless steel 301 or 302, which

  delivers extraordinary resistance for such a low thickness 428.

  Naturally, any other suitable material can be chosen instead, if it satisfies the resistance and deformation parameters which are necessary to obtain satisfactory performances of the coupler in the form of a strip 200, like other metals with high resistance, as well than

  certain plastic materials and fiber-reinforced composites.

  The coupler in the form of a flat strip 200 shown in FIG. 5 is then shown mounted on an encoder 280 in FIG. 7, via an attachment to the universal mounting plate 201, as shown in FIG. 8. In the embodiment shown , blind screw receptacles 400, 402 are preferably spaced on a center line 414 of 1.024 inch from each other and mount the coupler in the form of a flat strip on the encoder 280 via socket head screws 90. mounting tabs 404, 406, which have screw mounting holes 408, 410, are preferably spaced apart on the center line 412 at 1.63 inches apart from each other to engage the coupler as flat band with the universal mounting plate 201 via socket head screws 204 and nuts 205. In turn, the universal mounting plate 201 fixes the encoder 280 to the transfer case 264 via the coupler in the form of a flat strip 200 using socket head screws 28 7 by means of mounting holes 288. In this way, any misalignment between the axis of the transfer case 264 and the axis of the encoder 280 is easily compensated for by deformation of the spring parts 427, while a rotational movement is precisely transmitted between the transfer case and the encoder. Referring now to Figure 9, an alternative embodiment

  of the coupler in the form of a flat strip is generally indicated by 250.

  In this embodiment, a coupler in the form of a flat strip similar to the embodiment described above is combined with a universal mounting plate. The advantage of this particular embodiment is that the mounting lugs 404, 406 and the blind screws 204 are eliminated and replaced by parts of lugs 251, 252 which connect the

  spring portions 427 to mounting plate portion 253.

  Referring to FIGS. 3 and 7, it can easily be seen how a large space is saved by substituting the coupler in the form of a flat strip 200 according to the present invention, represented by the arrow "B" (FIG. 7), for the coupling of the prior art 84 (Figure 3), represented by the arrow "A". These space savings reduce the movement and total mass of the individual transfer case, thereby producing inherent cost savings, a reduction in mass, as well as a reduction in the forces transmitted to the encoders. The result is an increase in the precision of the transfer of the rotational movement between the transfer case 264 and the encoder 280 by using a new coupler in the form of a flat strip 200 instead of the coupling 84 of the prior art, while retaining the ability to correct misalignments between the two elements. While preferred embodiments have been illustrated and described, various modifications and substitutions can be made without departing from the scope and spirit of the invention. Consequently, it goes without saying that the present invention has been described by way of illustration, not by limitation.

Claims (23)

  1. Coupler (200) in the form of a flat strip comprising a portion (424) in the form of a strip; and a plurality of flexible elements (420, 421, 425, 426) connected to the strip-shaped part (424).   2. Coupler in the form of a flat strip according to claim 1, in   wherein the coupler (200) in the form of a flat strip is generally planar.   3. Coupler in the form of a flat strip according to claim 1, in which the flexible elements (420, 421, 425, 426) are composed of   spring parts (427) arranged in circuit paths.   4. Coupler in the form of a flat strip according to claim 1, in which the flexible elements (420, 421, 425, 426) comprise holes.   mounting (400, 402, 408, 410) in them.   5. Coupler in the form of a flat strip according to claim 1, in which the coupler (200) in the form of a flat strip is composed of a metallic material, of a plastic material or of a composite material. fiber reinforced.   6. Coupler in the form of a flat strip connecting a rotary element to a measuring device, the coupler (200) in the form of a flat strip comprising: a part (424) in the form of a strip a first pair of flexible elements (425, 425 ) connected to the strip-like part, and connected to the rotary member; and a second pair of flexible elements (420, 421) connected to the part   in the form of a strip, and connected to the measuring device.   7. Coupler in the form of a flat strip according to claim 6, in   which the coupler in the form of a flat strip is generally planar.   8. Coupler in the form of a flat strip according to claim 6, in which the flexible elements (420, 421, 425, 426) are composed of   spring parts (427) arranged in circuit paths.   9. Coupler in the form of a flat strip according to claim 6, in which the flexible elements (420, 421, 425, 426) comprise holes.   mounting (400, 402, 408, 410) in them.   10. Flat strip coupler according to claim 6, wherein the flat strip coupler is made of a metallic material, a plastic material or a composite material. fiber reinforced.   11. A coupler in the form of a flat strip according to claim 6, in which the second pair of flexible elements (420, 421) is connected to the part (424) in the form of a strip by a pair of connections (422, 423). 12. Coupler in the form of a flat strip according to claim 6, in which the second pair of flexible elements (420, 421, 425, 426)   is attached to a mounting plate.   13. Coupler in the form of a flat strip according to claim 6, in which the rotary element is a transfer coupling of an arm. multi-articulated (12).   14. Coupler in the form of a flat strip according to claim 6, in which the measuring device is an encoder (80) of one arm. multi-articulated (12).   15. Coupler in the form of a flat strip intended for use in a multi-articulated arm (12) transmitting a rotational movement from a rotary element to a measuring device, the coupler in the form of a flat strip comprising: a part (424) in forming a first pair of flexible elements (425, 426) connected to the band-shaped part (424) and connected to the rotary element; and a second pair of flexible elements (420, 421) connected to the part   (424) in the form of a strip and connected to the measuring device.   16. Coupler in the form of a flat strip according to claim 15,   in which the coupler in the form of a flat strip is generally planar.   17. A flat band coupler according to claim 15, wherein the first pair and the second pair of flexible members (420, 421, 425, 426) are composed of spring portions (427)   arranged in circuit paths.   18. A coupler in the form of a flat strip according to claim 15, in which the first pair and the second pair of flexible elements (420, 421, 425, 426) comprise mounting holes (400, 402, 408, 410) in them.   19. A flat strip coupler according to claim 15, wherein the flat strip coupler is composed of a metallic material, a plastic material or a composite material. fiber reinforced.   20. Coupler in the form of a flat strip according to claim 1 5, in which the second pair of flexible elements (420, 421) is connected to   the part (424) in the form of a strip by a pair of links (422, 423).   21. A flat band coupler according to claim 15, wherein the second pair of flexible members (420, 421) is attached to a mounting plate (201).   22. Coupler in the form of a flat band according to claim 1 5, in which the rotary element is a transfer coupling of an arm. io multi-articulated (12).   23. Coupler in the form of a flat strip according to claim 1 5, in which the measuring device is an encoder (80) of an arm multi-articulated (12).