DE4136267C1 - Linear bearing for industrial robot - has profiled guide for slide on which load carrying arm assembly is mounted - Google Patents

Abstract

The linear bearing consists of a profiled guide (1) on which a slide (2) with a load carrying arm (3) is mounted. A belt (4) for moving the slide, is moved by a NC drive (5). The drive belt (4) is made from, or incorporates, a metal. The metal in the belt forms an electric circuit which is insulated from the slide and the guide. When this electric circuit is broken, due to breaking of the drive belt, a control system operates a brake (12) which locks the slide in position. ADVANTAGE - The movement does not require a balance weight when used vertically.

Description

The invention relates to a vertically working, of an endless Traction devices, such as an endless toothed belt or an endless chain, driven NC linear axis for robot systems.

Robots of the type concerned are computer-controlled work machines for Handling techniques, for example for assembly, assembly and Sorting operations, and have transport and / or Gripping devices. The transport and / or gripping devices are carried by working arms, so-called axes, of the robot system and must reach from these axes or along these axes or object to be transported can be moved to and from it. Depending on the application, such a robot system has a reference to Cartesian coordinate system with the three spatial axes X, Y, Z (X- Spatial axis in the horizontal; Y-space axis perpendicular in the horizontal to the X-spatial axis; Z-spatial axis in the vertical) in X- and / or in Y- and / or robot individual axes arranged orthogonally in the Z direction.

The areas of application are varied and are always for a specific one Handling task designed such. B. for stacker cranes from automatic small parts warehouse.

For example, robot systems as storage and retrieval machines computer-controlled storage of loading units on a shelf or for Removal of the loading units from a shelf and to computer-controlled removal of, for example, an assortment of Small parts of different types from different loading units (Picking) usually work as Cartesian robots at least one robot axis each in the X, Y and Z directions, the Storage and retrieval machines can be moved along the front of the shelf in the X direction and the robot Z axis working vertically along the shelf front on the X-axis connected and into or out of the shelf depth robot Y axis working out can be adapted to the Z axis.  

They provide a constructive solution for such robot axes so-called NC linear axes (NC = numerically controlled), the The term linear axis (as opposed to a telescopic axis) is one Robot single axis referred to, one on a guide profile guided slide as a work slide straight, i.e. linear, is movable back and forth between fixed limits and a Tool, such as a gripper, carries or with a Load suspension devices, e.g. B. a carrying device for receiving Containers (loading units, pallets and the like) or another Payload is equipped. The guide profile is vertical (Z direction), one speaks of a mast.

For (computer-controlled) movement of the on the NC linear axis A carriage which is arranged along the robot axis and is movable along the means of transport driven by an electric motor. Such one Means of transport can be, for example, a spindle drive or a flexible or articulated traction device such as a movable back and forth endless toothed belt or an endless transport chain. For reasons of higher Transport speeds and, above all, lower manufacturing costs the flexible or articulated traction means become a spindle operation preferred.

Furthermore, according to Patent Abstracts of Japan 1991, Vol. 15 / No. 267, M-1133, known from JP 3-92 276 A2, for driving the load-carrying device Linear axis an endless steel flat ribbon of a high Elasticity coefficient to use to reduce the running noise faster movement of the load carriage and reduce the load carriage to accelerate quickly positive and negative.

In such, with an internal endless traction device such as one Toothed belt or a transport chain driven NC linear axes apply Special features for vertical operation (Z direction). To reduce the drive power for vertical movement are usually conventional counterweights on the mast as counterweights intended. These counterweights are transferred from the endless traction mechanism to the respective opposite direction to the direction of movement of the load handler or the moving material to be conveyed or the payload is moved and required own holding and management facilities. The mass of the counterweight is designed so that they the mass of the load handling device and all  other masses of the NC Linear axis construction compensated, including a mass that corresponds to approximately half of the mean nominal payload. In order to the drive and holding torque of the drive motor of the NC Linear axis while improving the Acceleration behavior.

The actual task of the counterweights is based on one Safety aspect and lies in the event of a break in the traction device (Endless chain, endless toothed belt or the like) of the Z linear axis too violent sinking of the load handler and the payload prevent. However, in conventional, with a balance weight equipped vertical NC linear axes in the event of a break in the traction mechanism always with damage to the axis itself, to the conveyed goods and to the peripheral ones Facilities (e.g. X-axis of a storage and retrieval machine; shelf).

Therefore, in certain application areas to avoid such Damages as vertical NC linear axes were previously only used for such axes practical use that with a versus a belt or Chain drive are equipped with much more expensive spindle drive, because the spindle drive due to failure of the motor drive self-locking effect prevents the load from dropping.

In contrast, according to DE 32 18 712 C2 with a biaxial, on two port columns stationary handling device, in which the load handler on the one hand on a horizontal, fixed rack back and forth movable and on the other hand on a vertical, fixed Rack by means of a drive torque and additionally one Air vane motor can be moved up and down, one on the drive unit of the air vane motor, but not described in detail, brake to be ventilated electrically in the event of a power failure for the air vane motor falls down along the load handler to prevent the vertical rack. This brake probably works on one of the vertical guide rods along which the Load suspension equipment is listed and removed.

In addition to the vertical NC linear axes with counterweight Advantages explained (in particular function as a safety device when the traction mechanism breaks) the arrangement of  Counterweights are particularly disadvantageous in that at one Horizontal travel (X direction) of the robot system, in particular one Storage and retrieval unit, the mass of the counterweight, the Small parts storage can be 100 kg or more, can also be accelerated must, so that additional forces and moments are generated and by the Construction must be included. In addition, because of the Accelerated mass of the counterweight uncontrolled Vibrations of the entire robot system arise, which are particularly rapid horizontal movements, but also with fast ones Vertical movements of the robot system to instabilities in the construction or the individual functional parts of the robot system. Such instabilities can then only be achieved through appropriate ones Switch off the stiffening of the construction or at least reduce it.

In contrast, it is the object of the invention, one for both Horizontal operation as well as for vertical operation, from one to provide endless traction-driven NC linear axes, which is not a balance weight for vertical operation Safety device required in the event of a break in the traction mechanism and thereby has the advantage of lower mass movements and the offers a much higher level of security that a break of the traction device a fall of the person, in particular, who is loaded Load suspension device is prevented.

Starting from a conventional one, using a toothed belt or a Chain or the like driven NC linear axis becomes the task solved according to the characterizing features of claim 1; special embodiments of the invention can be found in Subclaims 2 to 5 marked.

The invention is based on the consideration of the design principles of known, with a toothed belt or with a chain as endless Traction device for moving the load-bearing slide NC Maintain linear axes and if the traction mechanism breaks, the break itself as a triggering function for the spontaneous initiation of a mechanical brake device to act, which of the secures the broken slide no longer held.  

As a result, it was recognized according to the invention that the most sensitive Indicator for the breaking of the traction device with the breakage of the traction device occurred breakage of a current-carrying line can serve the Power interruption spontaneously to trigger a mechanical Brake device leads, which is carried by the carriage to be secured and, preferably as a friction brake, directly against the carriage leading guide profile of the NC linear axis acts.

For comparison, it should be noted that according to Patent Abstracts of Japan 1990, Vol. 14 / No. 52, M-928, for JP 1-2 79 152 A2 one for endless V-belts generally proposed warning device for advanced wear of the V-belt based on the following technical basis: The V-belt carries an electrically conductive rubber layer and runs over a pair of Deflection pulleys, between which the electrical resistance of the conductive Rubber layer is measured. If the V-belt wears out due to wear, its electrical resistance increases after reaching one predetermined maximum value triggers an alarm signal, which to replace the prompts worn belt before it breaks.

The mechanical braking device according to the invention is preferably a spring-loaded short-stroke cylinder, which can be pressurized with air Surface of the guide profile of steerable pistons in the non-braking Condition is kept tensioned against the spring by means of compressed air, whereby the compressed air requirement of the cylinder from a compressed air source is maintained. The compressed air supply to the cylinder is by means of an electromagnetically actuated 3/2-way valve is interrupted and the Cylinder spontaneously emptied when the electromagnetic 3/2-way valve is de-energized due to a break in the traction mechanism of the NC linear axis. To it is necessary that the electromagnetic 3/2-way valve on one Circuit is connected by the extension of the traction device of the NC linear axis. To conduct electricity through the traction mechanism (e.g. timing belt, chain) can be in a timing belt anyway conventionally contain metallic reinforcement inserts in  Form of, for example, strands can be used easily (Use of conventional toothed belts for NC linear axes according to the Invention), whereas conventionally provided metallic Endless chains as a traction device for moving the slide as a whole Conductors can function. In all cases, however be taken care that the current carrying line of the traction device against it driving or leading parts is electrically insulated.

The principle described according to the invention is described below a principle figure, which is only an embodiment represents, explained in more detail, according to which further configurations according to Invention, but without reference to figures.

The figure shows an NC linear axis according to the invention in vertical Position.

The NC linear axis shown is in terms of its construction as Robot axis conventional and has a braking or Safety device according to the invention on (essentially the right part of the illustration).

The conventional part of the NC linear axis according to the invention has a guide profile 1 or a mast and a carriage 2 movable along it, which in turn carries a load-carrying means 3 . The carriage 2 shown encompasses the guide profile 1 more or less and can conventionally also be designed such that it extends essentially only on one side of the guide profile 1 . An endless toothed belt 4 , which can be driven by an electric motor 5 as an NC drive via a toothed belt wheel 6 and is mounted on an opposite toothed belt wheel 7 , is used to move the carriage 2 up and down with the load suspension means 3 . The toothed belt 4 is made from a long piece by connection at its two ends by means of a clamping piece 8 and a clamping screw 9 , which is screwed into the carriage 2 , to form an endless belt. The clamp formed from the parts 2, 8, 9 serves not only for mounting the toothed belt 4 but also as a mechanical coupling of the toothed belt 4 with the slide 2 to be moved by it .

Further details of a complete NC linear axis according to the state of the art, such as belt tensioning device, belt cover, complicated mounting of the slide 2 , design of the guide profile 1 and the slide 2 with load-carrying means 3 , are not shown, since they are insignificant to explain the invention. Furthermore, the design features of an NC linear axis for adaptation to a multi-axis robot system are not shown. In this respect, the figure shows only a simplified representation of what is known.

In the event of a break in the toothed belt 4 (or an equivalent chain or the like), as a result of which the carriage 2 with the load suspension device 3 could no longer be held by the traction device 4 , a brake device on the carriage 2 , which is electrical, is used to secure the carriage 2 against falling indirectly or directly controlled, spontaneously comes into operation in synchronism with the breaking of the traction mechanism.

According to the solution shown in the figure, the braking device consists of a compression spring 10 , mounted on the carriage 2 , conventional short stroke cylinder 11 , the compression spring 10 of which can press a piston 12 with friction lining 13 so firmly against the outer surface of the guide profile 1 that the moving carriage 2 quickly comes to a standstill from its original functional movement (up or down). Further details are explained below. The cylinder 11 is fixedly mounted on the carriage 2 , for example flanged, via a passage in the carriage 2 for the passage of the piston 12 .

According to the figure, the piston 12 is shown in the normal (non-braking) operating state and is tensioned against the spring 10 by means of an air overpressure maintained in the cylinder chamber 14 . The air pressure in the chamber 14 is maintained by a compressed air source 15 which is connected via a 3/2-way valve 16 and a compressed air line 17 with the cylinder chamber fourteenth

The 3/2-way valve 16 is a conventional, electromagnetically operated pneumatic valve, the functional positions of which are controlled via the solenoid 18 of the valve 16 .

To actuate the megnet coil 18 is a direct current source 19 , which keeps the compressed air source 15 connected to the cylinder chamber 14 when the circuit is intact and in the de-energized state opens the compressed air line 17 to the outside and at the same time closes the compressed air source 15 , so that the air pressure in the cylinder chamber 14 closes degrades spontaneously and the now dominant spring force of the tensioned compression spring 10 allows the piston 12 with the friction surface 13 to protrude against the surface of the guide profile 1 .

To serve to the power source 19 to be connected to the circuit according to the figure of a hand, the incorporated in the insulating plastic material of the toothed belt 4 the metallic reinforcing inserts, or (optionally specially recessed) metal strands 20 and the other hand with the strands 20 connected to electrical leads 21 (for clarity in the figure shown in dashed lines), which can be carried together with the flexible compressed air line 17 in a cable drag channel 22 with the movement of the carriage 2 . Either a single strand 20 (as shown in the figure) or a plurality of strands 20 connected in series are used for the power line in the toothed belt 4 .

Obviously, a breakage of the traction means 4 will have an effect on the carriage 2 in such a way that with the synchronous breakage of the or one of the current-carrying strands 20, the magnet coil 18 excited up to that point becomes currentless and thereby closes the compressed air source 15 to the cylinder chamber 14 , at the same time the cylinder chamber 14 opens to the atmosphere and thus allows the piston 12 to protrude spontaneously against the guide profile 1 .

In the embodiment shown in the figure embodiment, a friction brake in which a friction lining 13 acts against the surface of the guide profile 1 is used to dimension or laying down of the carriage 2 at Führungsfprofil. 1 Depending on the choice of the force of the spring 10 and the type of friction lining 13 , a more or less strong braking effect can be set for a slide 2 of a predetermined mass of the slide 2 and its superstructures including the payload.

Preferred is a braking effect which does not bring the moving carriage 2 to a sudden stop, but rather brings it to a standstill in a delayed manner in order to avoid excessive acceleration forces acting on the overall system.

For example, in robot systems as storage and retrieval machines for small parts warehouses, in which mast heights (heights of the guide profile 1 ) of 12 m and more and payloads of up to 200 N are common, by means of a short-stroke cylinder 11 with a force of the spring 10 of 1000 N, fall braking distances of the carriage 2 from set one or less than one meter, the normal, smooth surface of the metal mast 1 serving as the braking surface for the friction lining 13 (for example the technically untreated surface structure of an extruded guide profile obtained in the aluminum extrusion process) and the material of the friction lining consisting for example of profiled hard rubber.

Assuming that the sled 2 has a braking distance of 1 m, it will not be fully braked only when going down and when the braking force is below 1 m above its working low (Z = 0), which in view of the short fall and the intended buffer (not shown) made of rubber, however, is harmless.

With a force of the spring 10 of 1000 N, with a corresponding design of the pressure surface of the piston 12 delimiting the cylinder chamber 14, a pressure of the compressed air source 15 of, for example, 6 bar is completely sufficient to keep the piston 12 tensioned against the force of the spring 14 .

The direct current source 19 which supplies the strands 20 and the magnetic coil 18 can have a voltage of 24 V, for example.

Within the scope of the invention and patent claim 1 are further Embodiments of an NC linear axis possible according to the invention.

If, for example, a spontaneous braking of the carriage 2 is desired, the arrangement shown in the figure can be modified in such a way that the piston 12 instead of a friction lining 13 has a bar-like end piece, for example in the form of a mandrel, which in corresponding recesses or against projections of the guide profile 1 , for example in a toothed strip, engages and thus locks the carriage in a form-fitting manner.

In such a case, it would then also suffice to use instead of a short-stroke cylinder 11 with an associated compressed air supply 15, 17 only a bolt or mandrel held back by a magnet coil, which is moved against the guide profile 1 by spring force when the magnet coil is de-energized due to breakage of the traction means 4 .

In the case of NC linear axes which, instead of a belt drive with an integrated current conducting path, has a metallic chain, a metallic drawstring or the like, the invention can, as far as described, be practiced in the same way, with the only requirement being that the current-carrying metallic conductors are opposite theirs Environment are electrically isolated. This is possible in a simple manner by building the means which drive or store the traction means 4 and lead from electrically non-conductive material. Such active ingredients are known and gears, bearings and the like made therefrom are generally available.

The direct current source 19 can have an independent power supply or, preferably, be fed from the power supply for the NC drive motor 5 . In the latter case, the braking device according to the invention then automatically secures the carriage 2 from falling down on the mast 1 , provided the drive current for the drive motor 5 fails or - with the appropriate electrical circuit - the drive motor 5 fails or is switched off normally. Thanks to the present invention, the drive motor 5 needs for the preferred case that the motor 5 and the DC power source are supplied from the same power supply system 19 to have no integrated engine brake, since the carriage 2 is then always automatically kept braked energized state of the engine. 5

When operating a robot system with a vertically operating NC linear axis according to the invention, it must be ensured that the compressed air supply for the short-stroke cylinder 11 is ensured. This is controlled either by compressed air monitors, which monitor the pressure in the compressed air system 14, 17 , or by position sensors on the piston 12 , with these devices switching off the drive motor 5 and the braking device for the slide 2 in when the operating pressure of the air pressure holding the spring 14 falls Gear is set. For the function and circuits of such compressed air monitors and position sensors, reference is made to the relevant prior art.

Claims (7)

1. NC linear axis for robot systems, comprising a guide profile (1), one on the guide profile (1) along the movable carriage (2) as a carrying device for a load receiving means (3), integrated in the guide profile (1), designed as a flexible endless construction, reciprocable, NC motor-driven ( 5 ) traction means ( 4 ) for moving the carriage ( 2 ) mechanically coupled to the traction means ( 4 ), the traction means ( 4 ) being made of or using metal, characterized in that that the metallic portion of the traction means (4) completely or partially part of an over which the traction means (4) moving or leading means is electrically isolated circuit which at its interruption, in particular by rupture of the traction means (4), a in the circuit located control device causes a mechanical device mounted on the slide ( 2 ) spontaneously in braking contact with the outer surface of the guide letting profile ( 1 ) step and to bring a movement sequence of the slide ( 2 ) to a standstill. 2. NC linear axis according to claim 1, characterized by a short-stroke cylinder ( 11 ) with spring-actuated ( 10 ) piston ( 12 ) with friction lining ( 13 ) as a mechanical braking device, the piston ( 12 ) by means of compressed air from a compressed air source ( 15 ) against the The force of the spring ( 10 ) is kept under tension as long as a magnetic coil ( 18 ) located in the circuit of a direct current source ( 19 ) is energized as a control device for an electromagnetic 3/2-way valve ( 16 ) regulating the air flow from the compressed air source ( 15 ). 3. NC linear axis according to claim 1, characterized by a located in the circuit, from a direct current source ( 19 ) fed solenoid with an assigned bolt or mandrel as a control device and at the same time mechanical braking device, with an interruption of the current flow the solenoid its bolt or mandrel in recesses or can protrude against projections of the guide profile ( 1 ). 4. NC linear axis according to claim 2, characterized by a compressed air monitor or by a position sensor on the piston ( 12 ) for checking the air pressure for the short-stroke cylinder ( 11 ) and optionally for switching off the drive motor ( 5 ). 5. NC linear axis according to one of claims 1 to 4, characterized by a with a metallic reinforcing insert or with metal strands ( 20 ) equipped as part of the circuit toothed belt ( 4 ) as a traction means for the carriage ( 2 ). 6. NC linear axis according to one of claims 1 to 4, characterized by a metallic chain or a metal strip or the like as part of the circuit and as a traction means for the carriage ( 2 ). 7. NC linear axis according to one of claims 1 to 6, characterized in that the current source ( 19 ) from the power supply for the NC drive motor ( 5 ) is fed.