GB2106077A

GB2106077A - Improvements in or relating to automated machines

Info

Publication number: GB2106077A
Application number: GB08226795A
Authority: GB
Inventors: John Graham Walker; Donald Bruce Athert Macmichael
Original assignee: Prutec Ltd
Current assignee: Prutec Ltd
Priority date: 1981-09-19
Filing date: 1982-09-20
Publication date: 1983-04-07
Also published as: GB2106077B

Abstract

An automated machine includes a movable arm which comprises an inner housing 1 and outer housing 2, the inner being load bearing while the surrounding outer house 2 is connected to the load bearing housing 1 by means of pressure sensitive pads 4. In the event of a collision, the pads detect a tendency for the outer housing 2 to move relative to the inner housing 1 and initiate an emergency procedure. In an alternative embodiment springs are used to mount the outer housing resiliently on the load bearing housing 1 and micro-switches are provided between the two housings. <IMAGE>

Description

SPECIFICATION Improvement in or relating to automated machines This invention relates to automated machines, particularly movable members therefor such as robot arms, and is concerned with constructions capable of sensing collisions with obstructions in order to prevent or reduce damage resulting from collisions between the moving parts of, say, a robot and obstructions such as fixed components, other moving parts or personnel in the vicinity of the robot.

Hitherto, for safety reasons, robots and like automated machines have normally only been used in isolated areas from which personnel are excluded, being, for example, housed within cages orfenced off from work spaces. Security devices, such as pressure sensitive floor panels, and also security guards have been used to detect improper access.

There is a considerable expense associated with ensuring that such a work space is adequately guarded. Furthermore, guards are notoriously unreliable.

It is accordingly an object of the present invention to provide a collision sensing mechanism for a movable member of an automated machine, such as a robot arm, to enable the machine to be used safely in less restricted circumstances than has hitherto been thought advisable.

According to one aspect of the present invention, there is provided a movable member for an automated machine, comprising first and second elements at least one of which constitutes at least part of an outer housing of the member; and means for sensing relative movement, or a tendency therefor, between the first and second elements and initiating an emergency procedure in response thereto.

When a member in accordance with the invention contacts an obstruction, the resulting force casues, or tends to cause, relative movement between the first and second elements and this is detected by the sensing means resulting in initiation of an emergency procedure, for example, an emergency stop, reversal, removal of power or other special procedure.

In this way, the risk of damage being caused by the movable member contacting an obstruction, such as other components or personnel, is eliminated, or at least substantially reduced, with the consequence that the machine may be safely used in less restricted conditions than was hitherto thought possible.

The first and second elements conveniently comprise inner and outer housings of the members, for example, an inner load-bearing housing and a surrounding outer housing.

The two elements may be resiliently mounted with respect to one another, for example via springs, sponges or the like, such that contact of the member with an obstruction will result in relative movement between the elements.

The sensing means may be in the form of one or more pads of pressure-sensitive material, for example a carbon-loaded polymer, such as the material known as Dynacon. A change in the pressure exerted on such material results in a change of its electrical resistance, and this change is used as a signal to initiate the emergency procedure. Alternatively, one or more switches may be incorporated between the elements to detect relative movement, or a tendency for this, between the elements and to initiate the emergency procedure in response to this.

By the use of a number of switches or pressuresensitive parts the direction of a collision could be determined and an emergency movement initiated to remove the member from the source of impact.

The initiation of the emergency procedure may be independent of the main control, e.g. computer control, of the machine, thus providing an added safeguard.

The invention is applicable to any automated machinery having movable members, including machine tools, and finds particular application in the case of robot arms, in the form of beams driven at one or both ends.

Hence, in a preferred aspect, the present invention provides a robot arm comprising inner and outer housings; and means for sensing relative movement, or a tendency therefor, between the housings and initiating an emergency procedure in response thereto.

The invention will now be described further, by way of example, with reference to the accompanying drawings, in which; Figure 1 is a schematic sectional view illustrating one embodiment of a robot arm in accordance with the present invention; and Figure2 is a schematic sectional view illustrating another embodiment of a robot arm in accordance with the present invention.

Referring to the drawings, Figure 1 illustrates a robot arm comprising inner and outer housings 1 & BR< 2, respectively. Power and instrument cables 3 are illustrated as passing along the arm. The housings 1 & 2 are held apart by two pads 4 of a pressure sensitive medium, for exapmle a carbon loaded polymer such as Dynacon. This material produces a change in resistance in response to changes in pressure, and this resistance change is used as a signal to initiate an emergency procedure, such as an emergency stop, reversal, removal of power or other special procedure.

The embodiment illustrated in Figure 2 is generally similar to that shown in Figure 1. However, in place of pads 4 the housings are linked by springs 5 with switches 6 being used to generates signals to initiate the emergency procedure.

1. A movable member for a automate machine, comprising first and second elements at least one of which constitutes at least part of an outer housing of the member and means for sensing relative movement, or a tendency therefor, between the first and second elements and initiating an emergency proce dure in response thereto.

2. A movable member as claimed in Claim 1, wherein the first and second elements comprise inner and outer housing of the member, the inner

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improvement in or relating to automated machines This invention relates to automated machines, particularly movable members therefor such as robot arms, and is concerned with constructions capable of sensing collisions with obstructions in order to prevent or reduce damage resulting from collisions between the moving parts of, say, a robot and obstructions such as fixed components, other moving parts or personnel in the vicinity of the robot. Hitherto, for safety reasons, robots and like automated machines have normally only been used in isolated areas from which personnel are excluded, being, for example, housed within cages orfenced off from work spaces. Security devices, such as pressure sensitive floor panels, and also security guards have been used to detect improper access. There is a considerable expense associated with ensuring that such a work space is adequately guarded. Furthermore, guards are notoriously unreliable. It is accordingly an object of the present invention to provide a collision sensing mechanism for a movable member of an automated machine, such as a robot arm, to enable the machine to be used safely in less restricted circumstances than has hitherto been thought advisable. According to one aspect of the present invention, there is provided a movable member for an automated machine, comprising first and second elements at least one of which constitutes at least part of an outer housing of the member; and means for sensing relative movement, or a tendency therefor, between the first and second elements and initiating an emergency procedure in response thereto. When a member in accordance with the invention contacts an obstruction, the resulting force casues, or tends to cause, relative movement between the first and second elements and this is detected by the sensing means resulting in initiation of an emergency procedure, for example, an emergency stop, reversal, removal of power or other special procedure. In this way, the risk of damage being caused by the movable member contacting an obstruction, such as other components or personnel, is eliminated, or at least substantially reduced, with the consequence that the machine may be safely used in less restricted conditions than was hitherto thought possible. The first and second elements conveniently comprise inner and outer housings of the members, for example, an inner load-bearing housing and a surrounding outer housing. The two elements may be resiliently mounted with respect to one another, for example via springs, sponges or the like, such that contact of the member with an obstruction will result in relative movement between the elements. The sensing means may be in the form of one or more pads of pressure-sensitive material, for example a carbon-loaded polymer, such as the material known as Dynacon. A change in the pressure exerted on such material results in a change of its electrical resistance, and this change is used as a signal to initiate the emergency procedure. Alternatively, one or more switches may be incorporated between the elements to detect relative movement, or a tendency for this, between the elements and to initiate the emergency procedure in response to this. By the use of a number of switches or pressuresensitive parts the direction of a collision could be determined and an emergency movement initiated to remove the member from the source of impact. The initiation of the emergency procedure may be independent of the main control, e.g. computer control, of the machine, thus providing an added safeguard. The invention is applicable to any automated machinery having movable members, including machine tools, and finds particular application in the case of robot arms, in the form of beams driven at one or both ends. Hence, in a preferred aspect, the present invention provides a robot arm comprising inner and outer housings; and means for sensing relative movement, or a tendency therefor, between the housings and initiating an emergency procedure in response thereto. The invention will now be described further, by way of example, with reference to the accompanying drawings, in which; Figure 1 is a schematic sectional view illustrating one embodiment of a robot arm in accordance with the present invention; and Figure2 is a schematic sectional view illustrating another embodiment of a robot arm in accordance with the present invention. Referring to the drawings, Figure 1 illustrates a robot arm comprising inner and outer housings 1 & BR< 2, respectively. Power and instrument cables 3 are illustrated as passing along the arm. The housings 1 & 2 are held apart by two pads 4 of a pressure sensitive medium, for exapmle a carbon loaded polymer such as Dynacon. This material produces a change in resistance in response to changes in pressure, and this resistance change is used as a signal to initiate an emergency procedure, such as an emergency stop, reversal, removal of power or other special procedure. The embodiment illustrated in Figure 2 is generally similar to that shown in Figure 1. However, in place of pads 4 the housings are linked by springs 5 with switches 6 being used to generates signals to initiate the emergency procedure. CLAIMS

2. A movable member as claimed in Claim 1, wherein the first and second elements comprise inner and outer housing of the member, the inner housing being load bearing and being surrounded by the outer housing.

3. A movable member as claimed in Claim 2, wherein the two elements are resiliently mounted with respect to one another.

4. A movable member as claimed in Claim 3, in which the resilient mounting is effected by means of springs.

5. A movable member as claimed in Claim 3, in which the resilient mounting is effected by means of sponges.

6. A movable member as claimed in any preceding claims, wherein the sensing means comprises one or more pads of pressure sensitive material.

7. A movable member as claimed in Claim 6, wherein the pressure sensitive material is a carbon loaded polymer.

8. A movable member as claimed in any one of Claim 1 to 6, in which the sensing means comprises one or more switches.

9. A robot arm comprising inner and outer housings, and means for sensing relative movement, or a tendency therefor, between the housings and initiating an emergency procedure in response thereto.

10. A movable member for an automated machine constructed substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.