Method and apparatus for changing operating modules on a coordinate positioning machine

Abstract: A system is disclosed enabling the automated exchange of touch probes (34,38) on an articulating probe head 40. The touch probes are mounted to adaptors 32, and are housed in storage ports 20 of a magazine. An adaptor 32 is repeatably located upon the retaining module by the mutual engagement of kinematic support elements 50,52 on the probe head 40 and adaptor 32 respectively. The support elements 50,52 are urged into mutual engagement by a locking mechanism having a spigot 60 on the probe head 40 which engages a cam 62 on the adaptor 32; rotation of the cam 62 locks/unlocks the support elements into mutual engagement. During an exchange operation the cam 62 is rotated by a screwdriver 80 in the storage port. Rotation of the screwdriver 80 is caused by relative movement of the storage port and the support plate 14, which is part of the support structure of the magazine. This relative movement is powered by the motion of the arm of the machine (to which the probe head 40 is mounted) along a path B,C,D,E, during an exchange operation.

Description: The present invention relates to the exchange of operating modules on coordinate positioning machines, such as machine tools or coordinate measuring machines. Such machines comprise an arm and a table, movable relative to each other, typically with three linear degrees of freedom. In use, an operating module, such as a cutting tool or a touch probe, for example, may be mounted to the arm of the machine to enable the machine to perform a cutting or measuring operation upon a workpiece which is supported on the table. During operation of such a machine, it is frequently desirable to exchange one operating module for another. For example, in the case of a machine tool, after performing a cutting operation upon a workpiece, it may be desirable to exchange the cutting tool for a touch trigger probe, which will allow the machine to inspect the relative position and/or dimensions of the surfaces of the workpiece recently machined. In the case of a coordinate measuring machine, it may be desirable to exchange a touch trigger probe for an analogue probe, or a temperature sensing probe, for example. Alternatively, it may be desirable to exchange one stylus on a particular touch trigger or analogue probe, for another. Systems providing the automatic exchange of operating modules on coordinate measuring machines are known for example from EP 293036, US 4,637,119, EP 566719, US 4,349,946, EP 0 028 329 and WO89/05210. The prior art references disclose systems for exchanging operating modules in which the coupling and decoupling of an operating module to a retaining module supported on the arm of the machine is performed in a number of ways. In particular WO89/05210 shows a magazine for supporting stylus units for exchange. In use the stylus units are attached to a support unit and connection and disconnection of the stylus units to and from the support unit is undertaken by simple movements of the support unit, to pick-up and drop a stylus unit. According to a first aspect the invention provides a magazine for supporting an operating module, the magazine comprising: a storage port for mounting to the base structure which is able to support an operating module (30) for use with a coordinate positioning machine, the storage port including: a port member for housing an operating module having an actuating member for causing locking or unlocking of a module to or from the machine, the actuating member being movable between first and second positions; characterised in that the port member is mountable to the base structure in a manner enabling relative movement of the port member and the base structure and wherein the said relative movement is producable by movement of a movable part of the machine and causes the locking or unlocking movement of the actuating member between the first and second positions. According to a second aspect the present invention provides apparatus for providing exchange of operating modules on a coordinate positioning machine, the apparatus including a magazine according to the second aspect and a retaining module, each of which are located on relatively movable parts of the machine; at least one of the plurality of storage ports of the magazine housing an operating module; both the operating and retaining modules having support elements which are mutually engageable to locate an operating module repeatably on the retaining module; the apparatus also including a releasable locking mechanism including co-operable sub-mechanisms on the operating and retaining modules which act to hold the support elements in mutual engagement, locking and unlocking of the locking mechanism being performed by locking and unlocking movements of at least a part of one of the sub-mechanisms between two positions; the said locking/unlocking movements being actuable by the said movement of one of the storage ports relative to the base structure together with the retaining module relative to a part of the machine on which the magazine is located, while one of the retaining modules is docked with the said one of the storage ports to perform an exchange operation. In one embodiment of the present invention an actuating member is situated on the storage port, and the actuating member is engageable with one of the sub-mechanisms to actuate the locking movement between two positions. Relative movement of the storage port and a support structure of the magazine upon which the storage port is mounted powers motion of the actuating member to achieve such actuation. In an alternative embodiment an actuating member on the retaining module interacts with a feature on the support structure during their relative movement to power the locking movement between the two positions. The sub-mechanisms of the locking mechanism may be single components, or may equally be more complex in nature and actuable by motion of one or more parts thereof. In a preferred embodiment both locking and unlocking of the operating and retaining modules takes place as a result of the movement of the storage port and retaining module relative to the machine. The nature of the operating module will be determined by the type of machine on which the apparatus is employed and may, for example, be any one of a touch probe or a stylus for such a probe, a non-contact inspection probe, an environmental sensor, a welding arm, or a cutting tool. The invention extends to a method of operating a coordinate positioning machine as claimed. An embodiment of the invention will now be described, by way of example, and with reference to the accompanying drawings in which: Fig 1 is a perspective view of a storage magazine in accordance with the present invention; Fig 2 is a perspective view of an operating module in position on a retaining module during an exchange operation; Fig 3 is a perspective view of a part of a retaining module during the exchange operation of Fig 2; Figs 4a and 4b are perspective views of a operating module; Fig 5 is a front perspective view of an individual storage port of the magazine of Fig 1; Fig 6 is a rear perspective view of the storage port of Fig 5; Figs 7a and 7b are front and rear perspective views of a sub-assembly of the storage port of Figs 5 and 6; Fig 8 is a rear elevation corresponding to the perspective view of Fig 6; Fig 9 is a rear perspective view of the operating module and retaining module shown in Fig 2; and Fig 10 is a rear perspective view (equivalent to that of Fig 6) of a modification to the storage port of Figs 1 to 9. Referring now to Fig 1, a magazine, retained within the working area of a coordinate measuring machine, includes a base structure provided by a square mounting plate 10 supporting an extruded pillar 12, and upon which a support plate 14 is mounted in a vertically adjustable position. A pair of storage ports 20 are mounted to the base structure at the support plate 14. Each of the storage ports retains an operating module 30. In the present example, the operating module 30A includes a mounting adaptor 32, upon which a touch trigger probe 34 is supported via an extension bar 36; the operating module 30B includes a mounting adaptor 32 to which an analogue probe 38 is connected. Referring now to Figs 2 and 9, each of the operating modules 30 is retained in a storage port 20 to enable a retaining module 40, supported on the arm of the coordinate measuring machine, to exchange one operating module for another. In this example, the retaining module 40 is a two-axis articulating probe head, having serially mounted rotary axis members 42,44, which provide orientation about rotary axes Q and R respectively. Referring now to Figs 3 and 4, an operating module 30 is repeatably located upon the retaining module 40 by the engagement of support elements, in the form of three balls 50 on the retaining module, with further support elements in the form of pairs of mutually convergent surfaces provided by three correspondingly positioned pairs of balls 52, located on the adaptor 32 of the operating module 30. Each operating module 30 is thus kinematically located upon the retaining module 40. Releasable retention of an operating module 30 upon the retaining module 40 is effected by a locking and unlocking mechanism having two sub-mechanisms: one on the retaining module and having the form of a ball-ended spigot 60; and one on the adaptor 32 having the form of a cam 62. Engagement of the ball-ended spigot 60 on the retaining module in the central slot of the rotatable cam 62 on the adaptor 32 of the operating module 30, and subsequent rotation of the cam 62 has the effect of applying a pulling force to the spigot 60, causing the balls 50,52 to come into engagement, thereby locking the operating module 30 to the retaining module 40. Alternatively, rotation of cam 62 in the reverse sense has the effect of releasing the aforementioned pulling force, and thereby unlocking the operating and retaining modules 30,40. Rotatable cam 62 is connected to a lever 70, and it is by rotation of this lever 70, either manually or automatically, that coupling and decoupling of the operating and retaining modules 30,40 occurs. Referring now additionally to Figs 5 and 6, the lever 70 includes a slot 72 which, when the operating module 30 is retained in a storage port 20, is engaged by an actuating member in the form of the blade of a screwdriver-type element 80, provided within the storage port 20. The screwdriver element 80 is connected at its rear end to a rotatable crank lever 82. Each storage port 20 is designed so that the crank lever 82 may be rotated to cause locking and unlocking of an operating and retaining module as a result of linear movement of the respective storage port 20 relative to the support plate 14 of the magazine upon which the storage port 20 is mounted. Such linear movement of the storage port 20 is driven by corresponding linear movement of the retaining module 40 (and thus the arm of the machine to which the retaining module is attached), once the retaining module 40 has docked with a storage port for the purpose of performing a locking or unlocking operation. Referring now to Figs 5-8, each storage port includes three relatively movable elements: a carriage 100, a box-shaped housing 110, and a sub-assembly (see specifically Figs 7a and 7b) consisting of a base member 120, and a U-shaped storage port member 122 fixedly mounted to the base member. A pivotable dust cover 124 prevents contamination of the support elements and locking/unlocking sub-mechanisms on the operating module 30 when it is housed in the magazine. Additionally, the sub-assembly includes a pair of elongate locating pins 126 which hold an operating module 30 in place, and the aforementioned screwdriver member 80. The carriage 100 and box-shaped housing 110 are movable relative to each other linearly in the direction of arrow z, by virtue of the mounting of the carriage 100 upon a pair of parallel runners 130, rigidly connected to the housing 110. These runners are engaged by three roller members upon the carriage 100 at the locations indicated by their retaining bolts 132. The sub-assembly is mounted to the box-shaped housing 110 via a parallel leaf spring arrangement, which includes a first pair of leaf springs 142 connected to the base member 120 of the sub-assembly, and a second pair of leaf springs 144, connected to a mounting block 150 which is rigid with the box-shaped housing 110, wherein the pairs of leaf springs 142,144 are interconnected by a pair of rigid parallel plates 152. The sub-assembly may, by virtue of leaf springs 142, 144, move linearly relative to the box-shaped housing in the direction of spacing of the parallel runners 130 upon which the carriage 100 is mounted. In use, the storage port 20 is mounted to the support plate 14 of the magazine via the carriage 100, i.e. the carriage 100 is effectively fixed to the rigid support plate 14 of the magazine. The carriage 100 comprises a pair of support pillars 160,162 to which a pair of cables 170,172 respectively, are anchored. The remote ends of cables 170,172 are connected, via springs 180,182 respectively, to anchorage bolts 190,192 provided on the rotatable crank lever 82. Linear movement of the box-shaped housing 110 and sub-assembly relative to the carriage 100 in the direction of arrow z, as permitted by the runners 130 and rollers will, by virtue of the connection of the cables 170,172 between the carriage 100 and the crank lever 82, thus cause rotation of the crank lever 82 (and therefore the screwdriver member 80). This linear movement is actuated by a corresponding linear movement of the retaining module 40 when the module 40 is docked with a storage port 20 during the course of an exchange operation (see for example Figs 2 and 9). During such linear movement, the retaining module bears against one of a pair of outwardly projecting, vertically spaced jaws 200, which are rigidly connected to the box-shaped housing 110. To prevent unwanted relative linear movement, a release mechanism is provided which latches the box-shaped housing and sub-assembly into one of two vertically displaced positions relative to the carriage 100; one of which corresponds to a rotational displacement of the crank lever 82 (and therefore screwdriver member 80) at which the operating module 30 is engaged with the retaining module 40, and the other at which the operating module 30 is disengaged from a retaining module 40. Referring now to Figs 6 and 8, a release mechanism which provides this latching includes a pair of vertically spaced locating lugs 220A,B, which are mounted to the rear face of base member 120 of the sub-assembly. In the upper latched position of the storage port (that is to say when the carriage 100 is in its lowest position relative thereto as shown in Fig 9), locating lug 220B seats in a recess 240B in the carriage 100; in the lower latched position of the storage port, locating lug 220A seats in the recess 240A in the carriage 100. Engagement and disengagement of the corresponding locating lugs 220 and recesses 240 is enabled by a small linear movement of the sub-assembly, as permitted by the parallel leaf spring arrangement 140, relative to the box-shaped housing 110. Once the respective lug 220A,B is disengaged from its corresponding recess 240A,B, the box-shaped housing 110 and sub-assembly are free to move together in a vertical direction relative to the carriage 100, thereby to effect locking and unlocking of a operating module 30 and retaining module 40. Referring now to Fig 2 and 3, the movement of the retaining module 40 during the course of a coupling operation is shown. Initially, the retaining module will approach the storage port in a direction parallel to the Q axis of the probe head which provides the retaining module, i.e. along a path AB in Fig 3. During movement of the retaining module along this path, the engagement of the retaining module with the dust cover 124 causes the dust cover 124 to pivot out of the way, revealing the mating face of the operating module 30. The retaining module 40 is subsequently driven along a horizontal path, shown in Fig 3 as BC which is in the direction of the R axis of Fig 2. During movement the retaining module 40 along this path, the retaining module 40 comes into contact with the operating module 30; continued movement of the retaining module 40 along the path after such contact causes actuation of the release mechanism by disengaging the lug 220B from its corresponding slot 240B. As a result of this, the retaining module may then move vertically upward in the z direction along the path CD in Fig 3. Since the retaining module 40 is now docked within the storage port, and is in contact with the jaws 200, the box-shaped housing 110 and sub-assembly will also move relative to the carriage 100 and support plate 14 of the magazine along the path CD, as a result of which the crank lever 82 and screwdriver 80 will rotate, causing a corresponding rotation of the cam 62 on the operating module 30 and thereby locking of the operating module 30 and retaining module 40. The retaining module is then moved along the path DB, allowing engagement of the lug 220A and slot 240A, thus latching the storage port into its new vertical displacement. As the retaining module backs out of the storage port along EF, the pivotable dirt cover 124 closes. The locating lugs are mounted to the base member 120 of the sub-assembly via relatively flexible rods 250. This provides a small degree of compliance between the carriage 100, and the box-shaped housing 110 and sub-assembly when the lugs 220A,B are engaged in the slots 240A,B. Such compliance allows for a small tolerance in the path of the retaining module 40 (and thus the arm of the machine) during an exchange operation. A modified form of storage port is shown in Fig 10, and includes a modified profile of crank lever 382, to provide a more expedient application of torque to the screwdriver 80 for the purpose of rotating the cam 62 to lock modules together. This modification also provides a bias on the storage port to compensate for the effect of gravity: helical spring 400 is mounted to the storage port at a location concealed in Fig 10 by the carriage 410, and applies a translational biasing force to the carriage 410 via a fusee 420 and bias cable 440 (provided to create substantially constant biasing force with displacement of the carriage 410). The illustrated embodiments of the present invention all possess mechanical locking mechanisms which pull the support elements into mutual engagement. Alternative mechanisms are possible. For example a solenoid on the operating module may be energised to provide locking of the operating and retaining modules by the switching of electrical power to a pair of electrical terminals on the retaining module; the switching being actuated by movement of the storage port and/or retaining module relative to the support structure of the magazine. Alternatively permanently magnetised structures on the operating and retaining modules may be oriented to attract or repel each other (thereby locking and unlocking support elements into engagement) by means of such relative movement.

Claims: A magazine for supporting an operating module, the magazine comprising: a storage port (20) for mounting to the base structure (10,12,14) which is able to support an operating module (30) for use with a coordinate positioning machine, the storage port including: a port member (122) for housing an operating module (30) having an actuating member (80) for causing locking or unlocking of a module to or from the machine, the actuating member (80) being movable between first and second positions; characterised in that the port member (122) is mountable to the base structure (10,12,14) in a manner enabling relative movement of the port member (122) and the base structure (10,12,14) and wherein the said relative movement is producable by movement of a movable part of the machine (40) and causes the locking or unlocking movement of the actuating member (80) between the first and second positions. A magazine as claimed in claim 1 wherein the port member is movable linearly relative to the base structure. A magazine as claimed in claim 1 or 2 wherein the locking or unlocking movement of the actuating member is rotation between the first and second positions. A magazine as claimed in any one of claims 1-3 having a plurality of storage ports (20) which may each house an operating module (30). A magazine according to claim 4 further comprising a release mechanism (142,144,152,220,240) which operates to permit and prevent the relative movement of the storage port and base structure which moves the actuating member. A magazine according to claim 5 wherein the release mechanism is actuable to permit the relative movement of the port and base structure which moves the actuating member by means of a further and distinct release movement of at least a part of the storage port relative to the base structure. A magazine according to claim 6 wherein the relative movement of the storage port and base structure which moves the actuating member is a linear movement along a first direction, and the release movement is a movement along a second direction, transverse to the first direction. Apparatus for providing exchange of operating modules (30) on a coordinate positioning machine, the apparatus including a magazine as claimed in claim 4 and a retaining module (40), each of which are located on relatively movable parts of the machine; at least one of the plurality of storage ports of the magazine (20) housing an operating module (30); both the operating and retaining modules (30,40) having support elements (50,52) which are mutually engageable to locate an operating module repeatably on the retaining module; the apparatus also including a releasable locking mechanism including co-operable sub-mechanisms (60,62) on the operating and retaining modules which act to hold the support elements in mutual engagement, locking and unlocking of the locking mechanism being performed by locking and unlocking movements of at least a part (62) of one of the sub-mechanisms between two positions; the said locking/unlocking movements being actuable by the said movement of one of the storage ports (20) relative to the base structure together with the retaining module (40) relative to a part of the machine on which the magazine (10,12,14,20) is located, while one of the retaining modules is docked with the said one of the storage ports to perform an exchange operation. Apparatus according to claim 8 wherein movement of the actuating member is powered by movement of the retaining module and/or the storage port relative to the part of the machine on which the magazine is mounted, and wherein during the relative movement, the actuating member is engageable with said one of the sub-mechanisms to cause the locking movement between the two positions. Apparatus according to claim 8 or claim 9 wherein part of the one sub-mechanism (62) is movable between the two positions to actuate a mechanical interaction of the sub-mechanisms, and thereby to lock the support elements into mutual engagement. Apparatus according to claim 8 or 9 wherein the part of the one sub-mechanism is movable between the two positions to actuate an electrical, electromagnetic, or magnetic interaction of the sub-mechanisms, thereby locking the support elements into mutual engagement. Apparatus according to any one of claims 8 to 11 wherein the magazine has a base structure (10,12,14) mounted on the machine, and the storage port (20) is movably mounted to the base structure. Apparatus according to claim 12 wherein the storage port is linearly movable relative to the base structure. Apparatus according to any one of claims 8 to 13 further including a release mechanism (142,144,152,220,240) which operates to permit and prevent the relative movement which powers the actuating member to lock and or unlock the operating and retaining modules. Apparatus according to claim 14 as dependent upon claim 10 or claim 11 wherein the release mechanism is actuable by means of a further and distinct release movement (B,C;D,E) of at least a part (120) of the storage port relative to the base structure. Apparatus according to claim 15 wherein the relative movement which powers the actuating member takes place along a first direction (C,D), and the release movement which actuates the release mechanism takes place along a second direction (B,C;D,E) transverse to the first direction. A method of operating a coordinate positioning machine which includes apparatus comprising a retaining module (40) and a magazine supported on relatively movable parts of the machine, the magazine having a plurality of storage ports (20) each for housing an operating module (30), the method comprising the steps of: operating the machine to dock the retaining module (40) with a storage port (20); operating the machine to move the storage port (20) and retaining module (40) simultaneously relative to the part of the machine upon which the magazine is located to lock the retaining module (40) and operating module (30) together; and with the operating and retaining modules locked together, operating the machine to undock the retaining module (40) from the storage port (20); characterised by : using the movement of the storage port (20) and the retaining module (40) relative to the part of the machine upon which the magazine is located to actuate a mechanism which locks the operating module (30) and retaining module (40) together. A method according to claim 17 wherein the simultaneous movement of the retaining module (40) or storage port (20) and support structure includes: a simultaneous release movement in a first direction, which then enables a subsequent simultaneous actuating movement in a second direction, which is in turn followed by a simultaneous movement in a direction opposite to the first direction to prevent further unwanted actuating movement. A method according to claim 17 wherein the operating and retaining modules are mechanically locked together. A method according to claim 17 wherein the operating and retaining modules are electrically, magnetically, or electromagnetically locked together. A method according to claim 17 wherein relative movement of the storage port and the part of the machine upon which the magazine is located actuates the locking of the operating and retaining modules.

Inventors: HAJDUKIEWICZ PETER, HAJDUKIEWICZ, PETER
Applicants: RENISHAW PLC
Application year: 1998
Main classification: B23Q3
IPC codes: G01B5, G01B21, B23Q3