WO2012037598A1

WO2012037598A1 - Robotic support fixture

Info

Publication number: WO2012037598A1
Application number: PCT/AU2011/001201
Authority: WO
Inventors: Benn Mcgrath; Quong Yu
Original assignee: Anca Pty Ltd
Priority date: 2010-09-20
Filing date: 2011-09-20
Publication date: 2012-03-29

Abstract

A robotic arm support fixture (20) for supporting the end (18) of a robotic arm (13). The support fixture (20) includes a support (23) for supporting the end (18) and the support (23) provides height support and sideways movement support, so that the end (18) of the robotic arm (13) is supported against movement in at least two directions. The support (23) includes a U-shaped recess (32) into which the robotic arm end (18) can be inserted and supported.

Description

ROBOTIC SUPPORT FIXTURE

FIELD OF THE INVENTION

The present invention relates to a robotic arm support fixture and has been developed principally for improving the accuracy with which a robotic arm can position a workpiece for treatment such as grinding or milling.

BACKGROUND OF THE INVENTION

Robotic arms are used in many manufacturing environments for moving parts and components in a manufacturing facility. The parts can range from large parts, such as car panels, down to very small parts. The weight of the parts can vary widely also.

Different manufacturing facilities require different levels of accuracy in their robotic placement systems. Accordingly, in some facilities, relatively inaccurate positioning of parts can be tolerated, while in other facilities extreme accuracy is desirable.

The accuracy available to a robotic arm is influenced by several factors. Some robotic arms are fixed in length and simply swivel about an axis between a workpiece collection point and a workpiece delivery point. Other robotic arms are articulated so that their extension length can vary between collection and delivery points. In this latter form of arm, moment loads experienced by the robotic arm vary depending on the extension of the arm. This can affect the positioning accuracy of the arm particularly when the arm is at or near maximum extension where the greatest moment loads are experienced.

The accuracy of a robotic arm is also affected by the number of points at which the arm is articulated (and thus by the degrees of freedom), by the size of the arm, including weight and extension length, by the material it is made from and by the environment in which the arm operates.

The environment can have a significant effect on accuracy due to temperature and humidity fluctuations. This can be exacerbated where the robotic arm is manufactured from a different material to the machinery with which it is operating. For example, in order to reduce weight and thus the effects of moment loads, robotic arms are often manufactured from lightweight metals, such as aluminium alloys, while the machinery with which the arm operates often is made from steel, such as mild steel. Different metals such as these expand and contract at different rates with variation in temperature and humidity so that accuracy of arm movement established at a particular temperature and humidity may be lost if the temperature and/or humidity changes.

A further contributor to problems with accurate positioning of a workpiece by a robotic arm is the weight of the actual workpiece. If the weight varies (as it will normally do) the moment loads on the arm will also vary, thus affecting the position at which the arm will deliver the workpiece.

The above difficulties do not affect many manufacturing operations which do not demand extreme positioning accuracy. However, where the required accuracy is from 10 micron or below, accurate positioning becomes critical. This level of accuracy is required for example in:

loading a workpiece to a precision workholding with a less than 10 micron clearance in grinding, or

- placement of silicon cells within a 10 micron tolerance window in biomedical applications.

To date, the approach to providing extreme accuracy has been to provide ever more sophisticated and complex control mechanisms and/or to control the environment in which the robotic arm operates. These approaches can add significantly to the cost of the robotic arm and the installation in which the arm is employed, in terms of both the manufacturing cost and the ongoing operating cost.

The applicant has recognised the need for a less complex solution that nevertheless enables a robotic arm to accurately position a workpiece.

SUMMARY OF THE INVENTION

According to the present invention there is provided a robotic arm support fixture for supporting an end of a robotic arm, the support fixture including a mounting arrangement for mounting the fixture to a body, and a support extending from the mounting arrangement for supporting a robotic arm end, the support providing height support and sideways movement support so that the end of the robotic arm is supported against movement in at least two directions. The present invention also provides a robotic arm installation including a movable robotic arm and a support fixture for supporting an end of the robotic arm, the support fixture including a mounting arrangement for mounting the fixture to a part of the installation, and a support extending from the mounting arrangement for supporting a robotic arm end, the support providing height support and sideways movement support so that the end of the robotic arm is supported against movement in at least two directions.

A robotic arm support fixture according to the invention provides a solution to the inaccurate positioning of the end of a robotic arm, in a much more simple and cheap manner than prior art solutions. In particular, there are fewer parts than in the prior art, and in some forms of the invention, no moving parts. In addition, while the robotic arm support of the invention secures the end of a robotic arm against movement in at least two directions, the arm can be arranged so that it can still pivot on the support for alignment purposes. The pivoting movement can be through a vertical plane or a horizontal plane or both.

While in the broadest form of the invention, the robotic arm support fixture provides support to the robotic arm against movement in two directions, in some forms of the invention, the support is arranged to support the end of a robotic arm in three directions or more. Those directions include providing height support and support against sideways movement in each of two opposite directions. The support could support the robotic arm end against pivoting movement in one or both of the vertical and horizontal directions, although as indicated above, the allowance of such pivoting movement can be desirable.

The support can also support the robotic arm end against movement transverse to or perpendicular to the sideways movement support it provides. That movement would be inwards or outwards movement of the robotic arm end and either of these movements or both of them could be the subject of support. In some forms of the invention, the support includes a base for height support and an upstanding arm for sideways movement support. Where the support is arranged to provide for support against movement in three directions, the support can include a base for height support and a pair of spaced apart upstanding arms for sideways movement support in each of two opposite directions. In this form of the support, the support can be formed in a substantially U-shape.

The above form of the support which includes a pair of upstanding arms can be formed in a different manner to provide the same support, whereby a U-shaped recess is formed in a member. In other forms of the invention, the support can comprise alternative arm arrangements or recesses, such as V-shaped arms or recesses or semi-circular recesses. Alternatively, the support can be formed at least partly by arms, the ends of which can engage the surface of the robotic arm end. For example, the support could comprise a base for height support and arms which extend to a position for sideways movement support. The arms could be adjustable if necessary. The arms form abutments for supporting the robotic arm end, although the abutments could be provided in different forms as suitable. These examples illustrate that the support of the robotic arm support fixture could take a variety of forms and still fall within the scope of the present invention.

The robotic arm installation can include a support according to any of the forms discussed above. In order to assist proper alignment of the end of the robotic arm in the support, a sleeve can be provided to extend about the end or an end portion of the robotic arm and which nests securely in the support. For example, where the support defines a U-shaped recess by a base and a pair of upstanding arms, the outside diameter of the sleeve can be such as to rest against the base of the recess and facing surfaces of the upstanding arms when the robotic arm is supported in the support fixture.

The mounting arrangement can take any suitable form and can be adjustable to provide for adjustment of the position of the support to likewise adjust the end resting position of the robotic arm end. The adjustment can provide vertical adjustment, or vertical and horizontal adjustment. The mounting arrangement can include a first bracket which can be fixed to a part of the machine to which the robotic arm support fixture is utilised, while a further bracket can extend from the first bracket for attachment to the support. The mounting bracket can be fixed in place while the second bracket can be adjustable. Alternatively, each of the first and second brackets can be adjustable, while the support can be adjustable on the second bracket. This maximises flexibility in setup and positioning of support. The support can be moved from a first inoperative position to a second operative position so that the support can be shifted out of the way of other parts of a machine that employs a robotic arm. For example, a robotic arm can be employed in grinding or milling machinery and the presence of an upstanding support might present interference with other parts of the machinery when the support is not being used to support the end of the robotic arm. In such circumstances, the support can be shifted to a position in which it is clear of interference or is at least in a position of less interference.

The support can be moved from the operative position to the inoperative position and back in any suitable manner including by rotation. The support can be manually rotated or can be rotated pneumatically or hydraulically for example. A 90 ° or 180 ° rotation might be all that is required although any amount of rotation can be provided.

The support can be a separate part to the mounting arrangement and attached to the mounting arrangement, or it can be formed integrally to the mounting arrangement. Where the support is formed separately to the mounting arrangement, the attachment can be by bolting or welding for example.

An advantage of the present arrangement is that the support and the mounting arrangement can be manufactured from the same metals as the machine in general and this will mean that differences in expansion and contraction of the robotic arm support fixture and the machine to which the fixture is fixed can be minimised or eliminated. A further advantage is that the robotic arm end can be firmly and accurately supported in place each time the arm end is supported by the robotic arm support fixture. In order that the invention may be more fully understood, some embodiments will now be described with reference to the figures in which:

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a view of a computer numeric controlled (CNC) machine utilising a robotic arm and a robotic arm support fixture according to the invention.

Figure 2 is a similar view to Figure 1 , but showing more detail in relation to the CNC machine of Figure 1 and showing a workpiece attached to the robotic arm. Figures 3A to 3D show the robotic arm support fixture in isolation, from perspective, plan, side and end views respectively.

Figure 4 is a view of part of a computer numeric controlled (CNC) machine utilising a robotic arm and a robotic arm support fixture according to another embodiment of the invention.

Figure 5 is a view of part of the computer numeric controlled (CNC) machine of Figure 4 showing a robotic arm supported in the robotic arm support fixture of Figure 4. DETAILED DESCRIPTION OF THE DRAWINGS

With reference to Figures 1 and 2, a CNC machine 10 is illustrated. The Figure 1 illustration shows just the housing of the machine 10, while in Figure 2, the spindle 1 1 is illustrated and it is into the spindle 1 1 that a workpiece 12 is to be inserted. Figures 1 and 2 also illustrate a robotic arm 13 which is employed to move the workpiece 12 from a position adjacent to the machine 10 to the position shown in Figure 2. In that position, the workpiece 12 can be received within the spindle 1 1 and the robotic arm 13 can release the workpiece 12 and return for supply of a further workpiece. The robotic arm 1 3 includes several moveable sections. The base section 14 is a fixed or stationary section which would be bolted to a portion of the machine 10, or to an adjacent fixture. For that reason, the portion to which the base section 14 is bolted is not illustrated. Attached to the base section 14 is a first intermediate section 15 which can swivel or rotate through a horizontal plane relative to the base section 14. A second intermediate section 16 extends from the first intermediate section 15 and can pivot about a horizontal axis relative to the intermediate section 15. A further section 17 extends from the intermediate section 16 and can rotate clockwise or anticlockwise relative to the intermediate section 16. A section 1 8 extends from the section 17 and is pivotable through a horizontal axis relative to the section 17. The section 18 includes a gripper which comprises a pair of jaws 19 (see Figure 2) in which the workpiece 12 is shown as being gripped.

A robotic arm support fixture 20 is shown in each of Figures 1 and 2 and comprises a mounting bracket 21 , a bracket arm 22 and a support 23.

The support fixture 20 is shown in more detail in Figures 3A to 3D and reference will now be made to those figures. Figures 3A to 3D illustrate the mounting bracket 21 which comprises a base section 24 which includes openings through which four screw fasteners 25 extend for fixing the fixture 20 to the upright portion 26 of the machine 10 (see Figure 1 ).

The bracket arm 22 is fabricated to form a mounting section 27, through which a plurality of screw fasteners 28 extend for fastening the bracket arm 22 to the mounting bracket 21 . As shown in Figure 3B, the mounting section 27 includes a lengthwise projection 29 for receipt within a recess 30 formed in an upper section 31 of the mounting bracket 21 . The bottom end of the recess 30 is shown in Figure 3C.

The bracket arm 22 defines a recess 32 into which the support 23 can be fixed. The support 23 is fixed to the bracket arm 22 by screw fasteners 33.

It can be seen from Figures 3A to 3D that the screw fasteners 25 and 28 extend through openings which are elongate and which thus provide adjustment in placement of the mounting bracket 21 on the upright portion 26 of the machine 1 0, and the bracket arm 22 on the mounting bracket 22. No adjustment is provided in respect of fixing the support 23 to the bracket arm 22, but adjustment could be provided if required. The support 23 defines a U-shaped recess 34 and thus includes a base 35 and a pair of upright arms 36. The recess 34 is dimensioned to snugly receive the sleeve 37 which is illustrated in Figure 3A and in Figures 1 and 2.

The sleeve 37 is fixed about an end portion of the robotic arm 13 and once received within the recess 34 of the support 23, is supported at a particular height and against sideways movement in each of two opposite directions. However, the support 23 does not preclude pivoting movement of the sleeve 37 through a vertical plane (up and down pivoting for example) as may be required. Pivoting movement of the sleeve 37 through a horizontal plane (side to side pivoting for example) is also possible in relation to the support 23.

The support fixture 20 supports the robotic arm 13 against movement or deflection which is due to flexibility within the robotic arm 13 or in other words, which is due to the lack of rigidity in a robotic arm 13. This is particularly important in relation to the Figure 2 illustration, in which the spindle 1 1 moves towards the workpiece 12 and unless there is accurate alignment of the workpiece 12 for receipt within the spindle 1 1 , the spindle 1 1 may abut the workpiece 12 or may frictionally engage the workpiece 12. Upon either of those engagements occurring, a load will be placed on the robotic arm 13 causing it to deflect and in general, causing the loading operation to fail.

In addition, because the support 23 accurately locates the sleeve 37 and thus the gripper 18 which extends out of the sleeve 37, it has been possible through testing to automatically load and unload a workpiece to a less than 0.01 mm clearance precision workholding system.

In addition, by providing height support to the sleeve 37, deflection of the robotic arm 13 due to the weight of a workpiece is substantially or entirely eliminated. The support 23 can be of any suitable material but in some forms is 4140 high tensile steel, nitrocarburised to 50-52 HRc. The sleeve 37 can also be of any suitable material such as EN36a case hardening steel, case hardened to 55-58 HRc. These parts come in contact with each other when the sleeve 37 slides into the recess 34 of the support 23 so that the hardening treatment on the respective parts helps resist wear of those parts. It is intended that of the two parts, the support 23 should wear preferentially to the sleeve 37.

It will be easily appreciated, that the U-shaped recess 34 of the support 23 allows the section 17 of the robotic arm 13 to be lifted out of the support 23 vertically, and for the robotic arm 13 then to function as normal to return to a supply of workpieces 1 2 and to grip a further workpiece and then return to the position shown in Figures 1 and 2.

It will be appreciated that some very simple variations of the invention illustrated in figures can be made. For example, the separate construction of the mounting bracket 21 , the bracket arm 22 and the support 23 could be replaced by a single unitary component in which those three separate components are fixed together. Alternatively, two of the components could be formed integrally with a third component separately connected thereto.

Moreover, the provision of a sleeve is considered to be advantageous as providing an accurate resting surface within the recess 34 of the support 23 for the end of the robotic arm. The end of the robotic arm might not otherwise have a construction which is easily supported by the support 23, so that the provision of the sleeve can provide this. The sleeve 37 and the support 23 can be customised to suit each other for proper support of the robotic arm. However, a suitably configured section 1 7 could be provided so as to eliminate the need for the sleeve 37. Alternatively, the shape of the support 23, in particular the recess 34 could be altered to accommodate the section 17.

It will further be appreciated that the form of the invention illustrated in the figures discussed above is very simple. It comprises three parts which are bolted together and which are easily machined or fabricated. The positioning of the parts is critical, however once that position has been fixed and established, there is certainty in the position of the robotic arm 13 with respect to components such as a spindle 1 1 for feeding workpieces. That certainty of position is not provided in current robotic arm arrangements, unless significantly costly and complex control arrangements are adopted.

A modification of the arrangement illustrated in Figures 1 to 3 is illustrated in Figures 4 and 5. With reference to Figures 4 and 5, the base of a CNC machine 40 is illustrated and includes a robotic arm support fixture 41 . The fixture 41 comprises a base 42 which is bolted to a support portion 43 of the CNC base 40. A post 44 extends upwardly from the base 42 and a mounting bracket 45 is connected to the post 44. The bracket 45 is fixed to the post 44 by a plurality of bolts.

A rotatable bracket 46 is fixed to the mounting bracket 45 for rotation between the non-operational position shown in Figure 4 to the operational position shown in figure 5. The rotational difference between the non-operational and operational positions is approximately 90 °.

It has been discussed above as to why a rotational connection of the bracket 46 to the mounting bracket 45 is desirable. The major reason is to displace the support 47 to a position in which it does not interfere with other working components of the CNC machine. In the position shown in Figure 4, the support 47 is shown in a position in which it does not interfere with other working components of the CNC machine, whereas in the position shown in Figure 5, interference may result. Thus, in the arrangement of Figures 4 and 5, the support 47 can be rotated to the operational position of Figure 5 when support for the robotic arm end 48 is required and from Figure 5, it can be seen that the same arrangement is employed as has been employed in the earlier figures, whereby a sleeve 49 is supported within a U-shaped support 47. Rotational movement of the bracket 46 can be accomplished in any suitable manner, but in the preferred manner, rotation is by pneumatic activation. Electric or hydraulic activation could alternatively be employed, or manual rotation could be employed. In all other respects, the arrangement of Figure 4 and 5 operates in a manner which is similar to the arrangement illustrated in Figure 1 to 3. Thus, the arm end 48 is securely located by location of the sleeve 49 within the support 47 and each of height and sideways movement is eliminated when the sleeve is located within the recess of the support 47.

The invention described herein is susceptible to variations, modifications and/or additions other than those specifically described and it is to be understood that the invention includes all such variations, modifications and/or additions which fall within the spirit and scope of the present disclosure.

Throughout the description of this specification the word "comprise" and variations of that word, such as "comprises" and "comprising", are not intended to exclude other additives or components or integers.

Claims

THE CLAIMS DEFIN ING THE INVENTION ARE AS FOLLOWS:

1 . A robotic arm support fixture for supporting an end of a robotic arm, the support fixture including a mounting arrangement for mounting the fixture to a body, and a support extending from the mounting arrangement for supporting a robotic arm end, the support providing height support and sideways movement support so that the end of the robotic arm is supported against movement in at least two directions.

2. A robotic arm support fixture according to claim 1 , the support providing sideways movement support in each of two opposite directions so that the end of the robotic arm is supported against movement in three directions.

3. A robotic arm support fixture to claim 1 or 2, the support permitting pivoting movement of the end of the robotic arm through a vertical plane relative to the support.

4. A robotic arm support fixture according to any one of claims 1 to 3, the support including a base for height support and an upstanding arm for sideways movement support.

5. A robotic arm support fixture according to claim 4, the support including a pair of upstanding arms for sideways movement support in each of two opposite directions.

6. A robotic arm support fixture according to claim 5, the support being formed in a substantially U shape.

7. A robotic arm support fixture according to any one of claims 1 to 3, the support including a pair of upstanding arms which diverge at an angle to each the arms providing height support and sideways movement support in each of two opposite directions.

8. A robotic arm support fixture according to claim 7, the pair of upstanding arms being formed in a substantially V shape.

9. A robotic arm support fixture according to any one of claims 1 to 8, the mounting arrangement including a mounting bracket that is mountable to a body and a support bracket that is mounted to the mounting bracket, the support being attached to the support bracket.

10. A robotic arm support fixture according to claim 9, the mounting bracket being adjustably mounted to a body.

1 1 . A robotic arm support fixture according to claim 9 or 10, the support bracket being adjustably mounted to the mounting bracket.

12. A robotic arm support fixture according to any one of claims 9 to 1 1 , the support being adjustably mounted to the support bracket.

13. A robotic arm support fixture according to claim 9, the mounting bracket and the support bracket being formed as a unitary structure.

14. A robotic arm support fixture according to claim 9 or 13, the support bracket and the support being formed as a unitary structure.

15. A robotic arm support fixture according to any one of claims 1 to 14, the support being rotatable between a non-operational position and an operational position, the operational position being a position in which the support can support a robotic arm end.

16. A robotic arm support fixture according to claim 1 , the mounting arrangement including a mounting bracket that is mountable to a body and a support bracket that is mounted to the mounting bracket, the support being attached to the support bracket, the support bracket being rotatably mounted to the mounting bracket to permit rotation of the support between a non-operational position and an operational position, the operational position being a position in which the support can support a robotic arm end.

17. A robotic arm installation including a movable robotic arm and a support fixture for supporting an end of the robotic arm, the support fixture including a mounting arrangement for mounting the fixture to a part of the installation, and a support extending from the mounting arrangement for supporting a robotic arm end, the support providing height support and sideways movement support so that the end of the robotic arm is supported against movement in at least two directions.

18. A robotic arm installation according to claim 17, the end of the robotic arm being in resting engagement with the support when the end of the robotic arm is supported by the support fixture.

19. A robotic arm installation according to claim 17, a sleeve being applied to the end of the robotic arm and the sleeve being in resting engagement with the support when the end of the robotic arm is supported by the support fixture.

20. A robotic arm installation according to claim 1 9, the sleeve being cylindrical.

21 . A robotic arm installation according to any one of claims 17 to 20, the robotic arm being pivotable through a vertical plane on the support.

22. A robotic arm installation according to any one of claims 17 to 21 , the support including a base for height support and an upstanding arm for sideways movement support.

23. A robotic arm installation according to claim 22, the support including a pair of upstanding arms for sideways movement support in each of two opposite directions.

24. A robotic arm installation according to claim 23, the support being formed in a substantially U shape.

25. A robotic arm installation according to any one of claims 17 to 24, and including a robotic arm support fixture according to any one of claims 1 to 16, the whereby the body of the support fixture of claims 1 to 16 is a portion of the installation.

26. Machinery including a robotic arm installation according to any one of claims 17 to 25.

27. A method of operating a robotic arm, including employing a robotic arm support fixture, the method including picking up a workpiece by the robotic arm, moving the robotic arm to a position for release of the workpiece and at that position supporting an end of the robotic arm by the support fixture, the support fixture providing height support and sideways movement support so that the end of the robotic arm is supported against movement in at least two directions, releasing the workpiece and returning the robotic arm to a position for picking up a further workpiece.