GB2241478A - Guide rail on a gantry loader - Google Patents

Abstract

A gantry loader includes a guide rail preferably comprising an aluminium extrusion (6) bolted to a portal (5) and having upper and lower bearing surfaces provided by steel rods (9, 11) retained respectively in longitudinal channels (8, 10) formed in the extrusion (6). The bearing surfaces are engaged by grooved rollers (12, 13) rotatably mounted on the handling module of the loader. The handling module is preferably moved along the portal by means of rodless cylinder (17) having drive member (18). The loader is easy and cheap to produce. <IMAGE>

Description

Gantry Loader This invention relates to gantry loaders of the type typically used for transporting items from one place to another, for example for transporting workpieces from one workstation to another on an automated production line.

The use of gantry loaders in automated production lines is known and in general such a loader comprises an overhead beam (or "portal") of appropriate length, typically several feet, which supports a handling device such as a pneumatically-operated jaw. The handling device depends from the portal and has means to move it along the portal whereby workpieces, for example, may be moved between workstations located beneath the loader.

When used in an automated production line such loaders, as well as many other functions of the line, will usually be operated electrically and/or pneumatically under the control of microprocessor sequence controllers.

In one known form of gantry loader, the handling device is mounted to one side of the portal and includes rollers that run on two discrete rails flushly embedded in, respectively, the lower and upper extremities of one side of the portal. In this arrangement, the portal in particular needs to be machined to close tolerances to receive the rails, which is an expensive operation.

In a more recent development, the portal has been comprised of a large, so-called, rodless cylinder, eg one of our LINTRA cylinders. The general nature of such a cylinder is known but briefly it comprises a longitudinally slotted cylinder containing a piston from which extends laterally, through the slot, a projection that is secured externally to a yoke slidably mounted in guides on the external surface of the cylinder. The slot is sealed by a sealing device so that the actuating fluid, usually compressed air, will be contained in the cylinder. During operation, the piston, and hence the yoke, move along the cylinder and in the present context the handling device is secured to, and depends from, the yoke and so moves with it.

Further details of such rodless cylinders may be found in, for example, European Patents Nos 69199 and 68088.

Large rodless cylinders are not only expensive, but more importantly in the present context they suffer from the disadvantage that the slot in the cylinder gives rise to an inherent mechanical weakness which limits the length of the cylinder that can be used; thus, an excessively long cylinder, when used as a portal, will tend to bow under its own weight, which of course would render it inoperative.

It is an object of the present invention to provide a precision gantry loader that can essentially be of any required length and that is considerably cheaper to produce than prior loaders.

According to the present invention, therefore, there is provided a gantry loader comprising: a) a portal, b) a guide rail projecting laterally from, and extending longitudinally of, the portal and having upwardly and downwardly facing, longitudinally extending bearing surfaces, c) a handling module having respective bearing means engaging said bearing surfaces of the guide rail so as to support the module on the guide rail; and d) driving means for moving the handling module along the guide rail.

The bearing means, which preferably each comprises one or more circumferentially recessed rollers, may alone serve to restrain the handling module against any significant movement relative to the portal (except, of course, for movement along the rail), for example lateral tilt. In a preferred embodiment, however, the portal includes a longitudinally extending surface adjacent to, and preferably located below, the guide rail and the handling module includes a further bearing means, for example a plain roller, that engages that surface. Such an arrangement serves to restrain unwanted movement of the handling module (eg lateral tilt) especially when the module is required to handle heavy loads.

The guide rail may be formed integrally with the portal. Preferably, however, it is a separately formed item and is rigidly secured to the portal; thus, the guide rail may, for example, be a standard extrusion eg of aluminium, retaining, for example, a pair of steel rods located respectively, in parallel relationship, in upper and lower longitudinal channels formed in the extrusion, the exposed surfaces of the rods affording, respectively, the upwardly and downwardly facing bearing surfaces.

The handling module may additionally be provided with a frictional braking device that, when desired, co-operates with an external surface of the portal to stop, or help stop, movement of the handling module along the guide rail.

The handling module may take a variety of different forms, depending on the intended application of the loader. By way of example, it may comprise a vertically disposed housing, at the upper end of which the said bearing means are securely mounted, and from the lower end of which a gripping device protrudes. Usually, the gripping device will be pneumatically operated and the necessary actuating means such as cylinders etc will be contained in the housing.

The driving means may be of any suitable type.

For example it may be in the form of a pneumatic cylinder, especially of the rodless type described earlier, or it may be an electric motor, for example of the servo-, stepping or brake-type.

A gantry loader of the invention may, of course, incorporate one or more of the optional items used in known gantry loaders, for example position sensors and so on.

An embodiment of the invention will now be described in more detail, by way of example only, with reference to the accompanying drawings of which: FIGURE 1 is a diagrammatic side elevation of a gantry loader of the invention; and FIGURE 2 is an enlarged view on the line II-II of Fig 1.

Referring to the drawings, the gantry loader comprises a pair of legs 1, 2 provided with respective feet 3, 4. The legs support a rigid portal 5, eg of aluminium, which is of hollow, rectangular cross-section. A vertical face (the face visible in Fig 1) of the portal 5 has a guide rail, in the form of a solid, elongate aluminium extrusion 6, secured to it by bolts 7. The extrustion 6 has a longitudinal channel 8 formed in its upwardly facing surface which retains a hardened steel rod 9. Similarly, the downwardly facing surface of the extrusion 6 has a longitudinal channel 10 which retains a hardened steel rod 11. The exposed surfaces of the rods 9 and 11 provide bearing surfaces.

Those bearing surfaces are engaged by, respectively, upper and lower pairs of circumferentially grooved steel rollers 12, 12' and 13, 13' that are rotatably mounted on a yoke 14. The yoke 14 is rigidly secured to a downwardly vertically extending handling module 15 that houses pneumatic actuating equipment for operating a grabbing device 16.

Secured on top of the portal 5 is a double acting "rodless" cylinder 17 (of the type previously referred to), the drive member 18 of which is secured to the yoke 14. The cylinder 17 is operated by compressed air via inlet/exhaust ports 19, 20 in known manner.

Referring specifically to Fig 2 (from which the handling module 15 has been omitted), it can be seen that the circumferentially grooved rollers, of which only two, namely 12', 13, are visible, engage the bearing surfaces afforded by the steel rods 9, 11 in such a manner that the yoke 14 will be restrained against any substantial sideways tilting movement, whilst of course permitting the yoke to be moved freely along the guide rail by the cylinder 17. In order to be able to optimise the engagement between the rollers and the bearing surfaces, at least one of each pair of rollers is preferably adjustable.

However, any tilting tendency of the yoke 14, which may occur if the module 15 is to handle heavy items, is further restrained by providing a plain roller 21, eg of nylon, rotatatably mounted on a lower section 22 of the yoke 14 and which abuts the side face of the portal 5 whereby any unduly high tilting moment will be counteracted. The lower section 22 of the yoke 14 also carries a pneumatically-operated braking device 23 whereby, if necessary, movement of the yoke 14 and the handling module 15 may rapidly be stopped.

In operation of the gantry loader, the cylinder 17 will move the handling module 15 between pre-determined positions along the portal 5 corresponding to workpiece etc pick-up and deposit positions situated beneath the loader. For example, at one location, the loader may be required to pick up a workpiece; the module 15 would thus be moved to a position above the location of the workpiece and the grabbing device 16 would then be automatically lowered (as indicated by the lower arrow in Fig 1) and its claws actuated to engage the workpiece.

The grabbing device 16 would then be raised (as indicated by the upper arrow in Fig 1) and the module 15 would then be moved to a second location where the workpiece would be deposited, again after lowering of the grabbing device 16. The cycle may then be repeated again and again.

As will be appreciated, all operations of a gantry loader according to the invention may be fully automated using, for example, microprocessor controlled pneumatic and electropneumatic devices.

Because the relatively simple guidance arrangement incorporated in a gantry loader of the invention can readily be made from commonly available stock items without the need for any machining, both small and, especially, large loaders may be bui-lt at significantly reduced cost whilst not in any way detracting from precision of operation and quality.

Claims (7)

CLAIMS:

1. A gantry loader comprising: a) a portal, b) a guide rail projecting laterally from, and extending longitudinally of, the portal and having upwardly and downwardly facing, longitudinally extending bearing surfaces, c) a handling module having respective bearing means engaging said bearing surfaces of the guide rail so as to support the module on the guide rail; and d) driving means for moving the handling module along the guide rail.

2. A gantry loader according to claim 1 wherein the guide rail is a separately formed component and is rigidly secured to the portal.

3. A gantry loader according to claim 1 or claim 2 wherein the guide rail comprises an aluminium extrusion retaining at least a pair of steel rods located, respectively, in parallel relationship, in upper and lower longitudinal channels formed in the extrustion, exposed longitudinal surfaces of the rods affording, respectively, the upwardly and downwardly facing bearing surfaces.

4. A gantry loader according to any one of claims 1 to 3 wherein the bearing means each comprises one or more circumferentially grooved rollers.

5. A gantry loader according to any one of claims 1 to 4 wherein the portal includes a longitudinally extending surface adjacent to, and preferably located below, the guide rail and the handling module includes a further bearing means that engages said surface so as to help restrain lateral tilt of the handling module.

6. A gantry loader according to claim 5 wherein said further bearing means comprises at least one plain roller.

7. A gantry loader substantially as hereinbefore described with reference to, and as illustrated in,the accompanying drawings.