GB2559743A

GB2559743A - Safety device for a multi-axis manuipulator

Info

Publication number: GB2559743A
Application number: GB1702454.8A
Authority: GB
Inventors: Daniel De-Gol Gino
Original assignee: Robocoaster Ltd
Current assignee: Robocoaster Ltd
Priority date: 2017-02-15
Filing date: 2017-02-15
Publication date: 2018-08-22
Anticipated expiration: 2037-02-15
Also published as: GB201702454D0; GB2559743B

Abstract

A shock absorbing witness block 10 for a single or multi-axis manipulator comprises a base 12 and a plunger arrangement 14 movably supported within the base 12, the plunger arrangement 14 has a first end which projects from the base 12 in a first direction and second end which projects from the base 12 in a direction opposite to the first direction, wherein a movable portion 18 of the plunger arrangement 14 is movable relative to the base 12 in the second direction by the application of a force greater than a predetermined value to the first end of the plunger arrangement 14. A first indicator or end cap 20 may be formed from plastic and may deform or bear a witness mark from a force less than the predetermined value. A second indicator or knurled head 22 may be rotatable relative to movable portion 18 following the application of a force greater than a predetermined value to the first end of the plunger arrangement 14. Movable portion 18 may be a tubular member carried as an interference fit within a sleeve 16.

Description

(71) Applicant(s):

RoboCoaster Limited (Incorporated in the United Kingdom)

Second Avenue, The Pensnett Estate, Kingswinford, West Midlands, DY6 7UL, United Kingdom

1702454.8 ₍₅₁₎ |_{NT CL}B25J 19/06 (2006.01) A63G 31/16 (2006.01) 15.02.2017 F16F 7/08 (2006.01)

(56) Documents Cited: GB 1360290 A	US 4901829 A
(58) Field of Search: INT CL B25J, F16F Other: WPI, EPODOC

(72) Inventor(s):

Gino Daniel De-Gol (74) Agent and/or Address for Service:

Withers & Rogers LLP

More London Riverside, LONDON, SE1 2AU, United Kingdom (54) Title of the Invention: Safety device for a multi-axis manuipulator

Abstract Title: Shock absorbing witness block for a single or multi-axis manipulator (57) A shock absorbing witness block 10 for a single or multi-axis manipulator comprises a base 12 and a plunger arrangement 14 movably supported within the base 12, the plunger arrangement 14 has a first end which projects from the base 12 in a first direction and second end which projects from the base 12 in a direction opposite to the first direction, wherein a movable portion 18 of the plunger arrangement 14 is movable relative to the base 12 in the second direction by the application of a force greater than a predetermined value to the first end of the plunger arrangement 14. A first indicator or end cap 20 may be formed from plastic and may deform or bear a witness mark from a force less than the predetermined value. A second indicator or knurled head 22 may be rotatable relative to movable portion 18 following the application of a force greater than a predetermined value to the first end of the plunger arrangement 14. Movable portion 18 may be a tubular member carried as an interference fit within a sleeve 16.

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Safety Device for a Multi-Axis Manuipulator

TECHNICAL FIELD

This invention relates particularly, though not exclusively, to a safety device for a multi-axis payload manipulator, for example a computer controlled robotic arm. The invention is of use in the industrial sector in which safety critical overhead loading operations are of concern, in passenger carrying medical applications, and has application in a fairground or amusement park ride.

BACKGROUND TO THE INVENTION

Multi-axis manipulators are well-known in industry, and typically comprise multi-axis manipulators or robotic arms capable of being programmed to perform repetitive tasks. Such arms have many degrees of freedom, and may be fitted with tools of many different kinds to perform, for example, handling, welding, painting and so on. Such arms may also be used in or above environments within which, for example, humans, machinery and fluid service conduits may be located.

Known manipulators of this kind are generally driven electrically, hydraulically or pneumatically, and are computer controlled.

Adjacent manipulator elements, for example at a major waist axis, elbow or wrist, are relatively movable about an axis of rotation, and suitable rolling element bearings are provided to resist axial and cantilever loads; such loads may be high in view of the potential reach of a manipulator and the forces capable of being exerted at the tool.

It has been proposed to use multi-axis manipulators in safety critical applications, in this case by way of example, for fairground and amusement park machinery, and in this application the manipulator carries a passenger carrying module or chair for one or more riders in place of a tool. Such machinery can offer far more flexibility as compared with bespoke fairground ride solutions, and moreover may offer a significantly enhanced degree of automation and integration with other amusement devices with increased reliability due to the use of standardized components. A multi-axis manipulator of this kind can also be programmed to give precisely controlled and variable motion dynamics within a defined envelope, and the ride may be changed on demand by use of a different program.

It will be understood that safety requirements for fairground and amusement park machinery are somewhat complex, and present the greatest challenge, and an absolute prerequisite is that riders are safe at all times. Accordingly the modes of potential machinery failure must be considered in detail, and to an extent which may not be necessary for an industrial device or robotic arm utilising conventional driveline components, bearings and structure whilst working in an environment from which humans are excluded.

The motion profile of a multi-axis manipulator is programmed to ensure that it does not contact fixed elements of its surroundings in an uncontrolled manner. Such contact may result in unanticipated extreme deceleration and/or shock loading of the whole or part of the manipulator. While such deceleration and/or shock loading may not lead to immediate damage to the manipulator, it may lead to premature wear of drive components and cracking of structural components, for example. It is therefore important that the occurrence of an unanticipated extreme deceleration and/or shock loading of the manipulator be immediately recognised such that appropriate inspection of the manipulator can take place.

According to the present invention there is provided a shock absorbing witness block for a single or multi-axis manipulator, the witness block comprising a base and a plunger arrangement movably supported within the base, wherein the plunger arrangement has a first end which projects from the base in a first direction and second end which projects from the base in a direction opposite to the first direction, wherein a movable portion of the plunger arrangement is movable relative to the base in the second direction by the application of a force greater than a predetermined value to the first end of the plunger arrangement.

The shock absorbing feature of the of the present invention permits the deceleration to rest of a manipulator which has, for example, exceeded its intended motion envelope and contact a solid interface. The witness feature allows an inspector or engineer to be informed that a manipulator has briefly or slightly exceeded its motion envelope.

The movable portion of the plunger arrangement may include a tubular member having a through bore which is movable relative to the base in the second direction.

The tubular member may be provided at with a first indicator at the first end, which first indicator is configured so as indicate the application of a force to plunger arrangement which is less than the predetermined value. The first indicator may be configured so as to deform and or bear a witness mark as the result of the application of a force which is less than the predetermined value. The first indicator may take the form of an end cap of the tubular member. The end cap may be formed from a plastics material. The end cap may be retained to the tubular member by a threaded connection. The end cap may be provided with a threaded projection which is receivable by a complementarily threaded region of the through bore.

The tubular member may be provided with a further indicator at the second end, which further indicator is configured so as indicate the application of a force to the plunger arrangement which is greater than the predetermined value. The further indicator may be movable relative to tubular member after the application of a force to the plunger arrangement which is greater than the predetermined value. The further indicator may be rotatable relative to the tubular member after the application of a force to the plunger arrangement which is greater than the predetermined value.

The plunger arrangement may include a sleeve within which the tubular member is supported. The tubular member is preferably a press fit within the sleeve.

An embodiment of the present invention will now be described with reference to the accompanying figures in which:

Figure 1 shows a perspective view of a witness block according to the present invention in an initial pre-strike position;

Figure 2 shows a partially sectioned perspective view of the witness block of figure 1; and

Figure 3 shows a partially sectioned perspective view of the witness block in a post-strike position.

Referring to the figures there is shown a shock absorbing witness block generally designated 10. As will be described in greater detail below, the witness block 10 is intended to be mounted upon a single or multi-axis manipulator. The witness block 10 is configured so as to indicate to an observer whether or not there has been contact between the multi-axis manipulator and a feature present within the movement envelope of the multi-axis manipulator. The witness block 10 can further act as shock absorber to decelerate to rest a manipulator that has exceeded its motion envelope and struck an solid interface. The deceleration afforded by the witness block 10 can be configured so as to be within certain acceptable design limits for the manipulator.

The witness block 10 comprises a base 12 and a plunger arrangement generally designated 14. The plunger arrangement 14 includes a cylindrical sleeve 16, a tubular member 18, an end cap 20, a knurled head 22 and a connecting bolt 24.

The base 12 is of unitary construction and is machined from a single block of material. The base 12 is provided with a plurality of attachment apertures 26 which, in use, enable the witness block 10 to be mounted at a desired location on a multi-axis manipulator. Mounting of the witness block 10 may be effected by the use of appropriately sized and configured threaded fasteners. The base 12 comprises a cuboid portion 28 and a flange portion 30. Each portion 28,30 is provided with attachment apertures 26. It will be understood that the configuration of the base 12 shown in the figures is illustrative of one of a number of base configurations.

The base 12 is further provided with a through aperture 28 which is configured to receive and support the plunger arrangement 14, in use. The through aperture 28 is provided about an axis which is substantially perpendicular to the axes of the attachment apertures

26. The through aperture 28 is stepped and comprises a first portion 30 and a second portion 32 where the diameter of the first portion 30 is greater than that of the second portion 32. The axial length of the first portion 30 is greater than the axial length of the second portion 32. At the transition between first and second portions 30,32 there is provided an annular step 34. The step 34, in use, is utilised as an abutment surface for the sleeve 16.

Referring now to the plunger arrangement 14, the tubular member 18 is provided with a through bore 36. Opposing ends of the through bore 36 are threaded. A first end of the through bore 36 is threaded to receive a complementarily threaded projection 38 of the end cap 20. The opposite end of the through bore 36 is threaded to receive the connecting bolt 24.

The tubular member 18 is carried by the cylindrical sleeve 16. The cylindrical sleeve 16 is in turn located within the first portion 30 of the base through aperture 28. An end of the cylindrical sleeve abuts the step 34 defined between the first and second portions 30,32 of the through aperture 28.

The tubular member 18 is a press fit to the cylindrical sleeve 16. The provision of a press fit between the tubular member 18 and the sleeve 16 means that movement of the tubular member 18 relative to the sleeve 16 is achieved only after the application a force to the end cap 20 that is greater than predetermined minimum. The force required to move the tubular member 18 relative to the sleeve is dependent upon a number of factors including, for example, the press fit dimensions, the frictional coefficient between the respective materials of the tubular member 18 and sleeve 16, and the maximum permitted deceleration of a multi-axis manipulator.

It will be appreciated that the resistive force applied to movement of the tubular member 18 through the sleeve 16 by the press fit interaction therebetween can, in use, act to decelerate a manipulator in a strike event.

Figures 1 and 2 show the witness block 10 in an initial position, i.e. before the application of a force to the end cap 20 that is sufficient to move the tubular member 18 relative to the cylindrical sleeve 16. In this initial position the knurled head 22 is pressed against the base 12 and thus is unable to rotate relative to the connecting bolt

24.

Figure 3 shows the witness block in a post-strike position, i.e. after the application of a force to the end cap 20 that is sufficient to move the tubular member 18 relative to the cylindrical sleeve 16. In this post-strike position the knurled head 22 is no longer pressed against the base 12 and thus is able to rotate relative to the connecting bolt

24.

The witness block 10 is further configured so as to show the contact of a multi-axis manipulator with a surface where the force applied was insufficient to move the tubular member 18 relative to the cylindrical sleeve 16. The end cap 20 may be formed from a relatively soft plastic material that is deformed and/or marked when contacted.

In use, witness blocks 10 in accordance with the present invention are mounted at predetermined locations on a multi-axis manipulator. The locations are chosen so as to have easy inspection access. Strike blocks, which are intended to contact the end caps 20 of the witness blocks 10, may be provided upon structures within then movement envelope of the multi-axis manipulator. Each of the witness blocks 10 is initially provided in the above described initial position, i.e. with no marking or deformation of the end cap 20, and the knurled head 22 held in a non-rotatable manner against the base 12.

Periodic inspection of the witness blocks 10 is undertaken during operation of the multi-axis manipulator. In the event that one or more of the witness block 10 is found to have marking and/or deformation of the end cap, and/or movement of the tubular member 18 such that the knurled head 22 is rotatable, then the manipulator can be withdrawn from service for inspection and/or repair.

In the event of a heavy strike, it will be appreciated that movement of the tubular member 18 through the sleeve 16 provides a resistive force which acts to decelerate the manipulator.

The shock absorbing witness block of the present invention may be used in conjunction with single and multi-axis manipulators that are used in a number of fields including, but not limited to, entertainment, medical, industrial, subsea, and space. The block of the present invention may also be used with other types of machinery where there is a need to identify instances of movement outside of a pre-determined movement envelope or to decelerate a component to rest in an emergency or non-standard operating condition.

Claims

1. A shock absorbing witness block for a single or multi-axis manipulator, the witness block comprising a base and a plunger arrangement movably supported within the base, wherein the plunger arrangement has a first end which projects from the base in a first direction and second end which projects from the base in a direction opposite to the first direction, wherein a movable portion of the plunger arrangement is movable relative to the base in the second direction by the application of a force greater than a predetermined value to the first end of the plunger arrangement.

2. A witness block as claimed in claim 1, wherein the movable portion of the plunger arrangement includes a tubular member having a through bore which is movable relative to the base in the second direction.

3. A witness block as claimed in claim 1 or claim 2, wherein the tubular member is provided at with a first indicator at the first end, which first indicator is configured so as indicate the application of a force to plunger arrangement which is less than the predetermined value.

4. A witness block as claimed in claim 3, wherein the first indicator is configured so as to deform and/or bear a witness mark as the result of the application of a force which is less than the predetermined value.

5. A witness block as claimed in claim 2 or claim 3, wherein the first indicator takes the form of an end cap of the tubular member.

6. A witness block as claimed in claim 5, wherein the end cap is formed from a plastics material.

7. A witness block as claimed in claim 5 or claim 6, wherein the end cap is retained to the tubular member by a threaded connection.

8. A witness block as claimed in claim 7, wherein the end cap is provided with a threaded projection which is receivable by a complementarily threaded region of the through bore.

9. A witness block as claimed in any preceding claim wherein the tubular member is provided with a further indicator at the second end, which further indicator is configured so as indicate the application of a force to the plunger arrangement which is greater than the predetermined value.

10. A witness block as claimed in claim 9, whereon the further indicator is movable relative to tubular member after the application of a force to the plunger arrangement which is greater than the predetermined value.

11. A witness block as claimed in claim 10, wherein the further indicator is rotatable relative to the tubular member after the application of a force to the plunger arrangement which is greater than the predetermined value.

12. A witness block as claimed in any preceding claim, wherein the plunger arrangements include a sleeve within which the tubular member is supported.

13. A witness block as claimed in claim 12, wherein the tubular member is a press fit within the sleeve.

Intellectual

Property

Office

Application No: GB1702454.8 Examiner: Mr Karl Whitfield