Balanced pneumatic manipulator

The manipulator comprises a supporting device (11) having an assembly (13) rotatable about a vertical axis and an articulated parallelogram (21) with a swing arm (24). A pneumatic linear actuator (22), acts between the rotatable assembly (13) and the articulated parallelogram (21), for causing the arm (24) to rotate about a horizontal axis of oscillation. A slide (23) is connected to the actuator (22) and slidably mounted on the rotatable assembly (13) by means of a first vertical guide (30). The slide has a second horizontal guide (31) in which is engaged an element (32, 33) mounted on the swing arm (24).

The present invention relates to a balanced pneumatic manipulator.

Manipulators of this type are widely used in manufacturing industry for supporting and moving, in a balanced condition, various tools and devices, typically including gripping devices, welding machines, screwdrivers and others, which require a minimum of manual effort by the user.

Over the years, technological progress has resulted in a continuous improvement in the sensitivity of these types of manipulator, which have been subject to problems of non-constant balancing when faced with increasing demands in terms of the loads to be handled.

To assist the understanding of the prior art and its inherent problems, a balanced pneumatic manipulator of the conventional type will be at first described, with reference toFIGS. 1 to 3. A balanced pneumatic manipulator10comprises a support device which includes an assembly13rotatable about a vertical axis z and an articulated parallelogram mechanism21, including a swing arm24pivoted on the rotatable assembly13about a horizontal axis of oscillation. The balancing action is provided by a pneumatic linear actuator22which includes a cylinder22apivoted on the rotatable assembly13and a rod22bpivoted on the swing arm24. A rotatable horizontal arm36, supporting a tool such as a screwdriver, a welding machine, a gripping device, or other tool, is mounted on the articulated parallelogram mechanism.

The aforesaid configuration suffers from a drawback in that the different inclinations assumed by the actuator in its different operating positions cause the transmission of forces having a horizontal component which increases with the deviation a of the line of action of the actuator with respect to a vertical axis. Very small angular deviations, of the order of a few sexagesimal degrees, have negative repercussions on balancing, and require a manual effort for movement which increases with the extent of the angular deviation of the actuator from the vertical. The manual effort required thus increases from an optimal value of the order of 20-30 N to 100-150 N or more, when the angular deviation from the vertical is maximal. In these conditions, the supported load becomes unstable and fatiguing to handle, with adverse effects on the safety and accuracy of movement.

The object of the present invention is to provide a balanced pneumatic manipulator which can overcome the aforesaid problems. In particular, it is desirable to provide a manipulator requiring a constant minimal manual effort, independently of the extension of the pneumatic actuator.

This and other objects and advantages, which will be made clearer below, are achieved according to the invention by a balanced pneumatic manipulator having the features defined in claim1. Preferred embodiments are defined in the dependent claims.

Features and advantages of the invention will become clear from the following detailed description which is given purely by way of non-limiting example with reference to the attached drawings, in which:

With reference toFIG. 4, a manipulator indicated as a whole by numeral10comprises a support device11on which a balancing device20is mounted. The support device11defines a vertical geometric axis z, and, in this example, comprises a fixed lower vertical column12and an upper assembly13which is rotatable about the vertical axis z. The lower column12may be integral with a base (not shown) which can be fastened to a floor or to a movable support surface (not shown). In other applications, the support device may form part of a suspended structure, for example a structure suspended from a carriage which can run along tracks. In these other applications, the rotatable assembly13is placed below an upper non-rotatable part. In the following text, terms and expressions indicating positions and orientations such as “upper” and “lower” are to be construed with reference to the illustrated example, but are not to be considered as limiting.

In the embodiment shown inFIG. 4, the rotatable assembly13has a pair of vertical uprights15(only one of which is visible), which are parallel and equally spaced about the vertical axis z.

The balancing device20is mounted on the rotatable assembly13and comprises an articulated parallelogram mechanism21, a pneumatic linear actuator22and a slide23mounted slidably on the rotatable assembly13of the support device.

In the upper part of the uprights15, an upper swing arm24forming part of the articulated parallelogram mechanism21is pivoted about a horizontal axis of oscillation x (also indicated inFIGS. 6 and 7). The pneumatic actuator acts between a lower connecting axis a, integral with the rotatable assembly13, and an upper connecting axis b defined by the slide23. Preferably, the actuator22is a single-acting pneumatic actuator with a cylinder22a, in a lower position in this example, and an upper extensible rod22b. More particularly, in the illustrated embodiment, the cylinder of the actuator is connected to the lower connecting axis, while the rod22bis connected to the upper connecting axis b. The letter c indicates (FIGS. 6 and 7) the line of action of the actuator, which in this example is substantially vertical and parallel to the axis z. InFIGS. 4 and 5, numeral29indicates a spindle fixed to the head of the rod22band pivoted on the slide23about the horizontal axis b.

At the opposite end of the swing arm24and of the articulated parallelogram21there is mounted, in a known way, a vertical spindle25about which a horizontal arm36can rotate.

This arm may serve to support various devices, such as gripping tools, screwdrivers, welding machines, and others.

The articulated parallelogram mechanism21comprises, in addition to the upper swing arm24, a second, lower swing arm or lever26, which is parallel to the upper arm24and has its ends (not shown) hinged on the uprights15. Two vertical connecting plates27a,27b, which are parallel to each other, are hinged on the reaction end of the mechanism where the vertical spindle is mounted. Two further intermediate connecting links28a,28bare hinged on the upper and lower swing arms in a known way. The parallelogram mechanism does not differ appreciably from the known type, and therefore will not be described in greater detail herein.

As explained above, the linear actuator22acts between the rotatable assembly13and the parallelogram mechanism21, for causing the arm24to rotate about the horizontal axis of oscillation x, in order to raise and lower, in rotary translational movements, the vertical spindle25supported at the end of the parallelogram mechanism opposite the end near which the actuator22is mounted. The actuator22does not act directly on the arm24, but acts via the slide23.

The slide23is slidable along a first linear guide which is indicated schematically by30inFIGS. 6 and 7, and which is integral with the rotatable assembly13and parallel to the line of action c of the actuator22. To improve the balance and load distribution, the first guide30preferably includes a pair of parallel linear guides (or “support” guides) which extend parallel to the line of action c of the actuator.

The slide23has a second linear guide31, preferably composed of a second pair of parallel rectilinear guides31a,31bwhich are orientated perpendicularly to the first support guide or pair of support guides30. A movable element32mounted on the end of the upper swing arm24nearer the actuator22is engaged along the second pair of guides31a,31b. Preferably, the second guides31a,31bof the slide take the form of a pair of parallel slots, and the movable element32comprises a cylindrical roller33which is mounted in a free-running way about a horizontal axis (shown in broken lines and indicated by35in FIG.7) fixed in the position34at the end of the upper swing arm24. In this embodiment, the cylindrical roller33is mounted by means of a pair of rolling bearings (not shown in detail) spaced apart along the horizontal axis37, each composed of a respective outer fixed ring fastened to the arm24and a respective inner rotatable ring locked at one of the two opposite ends of the roller33.

The cylindrical roller33is preferably housed with a predetermined minimal vertical clearance in the second guide31(or in the parallel second guides31a,31b). A clearance of the order of a few tenths of a millimeter allows the cylindrical roller to roll along the second guides31a,31bwhen the actuator22is extended or retracted in its movement between the alternative positions shown schematically inFIGS. 6 and 7. The rolling contact between the movable element32and the second guides31a,31bminimizes the friction between the slide and the actuator.

In an alternative embodiment (not shown), the movable engagement element32may comprise a block which is engaged in a sliding manner, instead of a rolling manner, in the second guide or guides31provided in the slide23. For this purpose, the guide (or guides)31may have a shape different from that of one or two slots, depending on the shape of the block (or blocks). The choice of the slotted shape is advantageous in that it provides an optimal exchange of forces between the slide23and the arm24, and produces a reliable coupling between these two members, making use of the structural strength provided by two openings formed in the arm24.

As shown schematically inFIG. 7, the end of the swing arm24may be double, providing two parallel vertical plate formations24a,24b, thus making it possible to obtain an effective mounting of the movable engagement element32. The slide23, in the embodiment illustrated inFIG. 7, also includes a pair of parallel metal plates23a,23b, spaced apart in a horizontal direction, in each of which one of the two second guides for the cylindrical roller33(or for a slidable block) is formed. According to an embodiment, which optimizes the available space and the connections between the actuator and the upper assembly, each of the plates of the slide is substantially L-shaped, a straight or longer portion of this L-shape being coupled to the first linear guide30, while a shorter portion of the L-shape has the slot or second guide31. For the production of the first linear guide30, the use of a recirculating ball slide is particularly preferable.

FIGS. 6 and 7show schematically two opposite alternative positions assumed by the manipulator. The extension of the actuator results in a movement from the position ofFIG. 6to that ofFIG. 7, causing the movement of the slide23along the first guide30and the simultaneous movement of the movable engagement element32along the second guide31of the slide.

Because of the slide, interposed between the actuator and the swing arm, and the mutual perpendicularity of the guides30and31, the actuator transmits an exclusively vertical force, in other words a force without horizontal components, to the parallelogram mechanism. This ensures the constant balancing of the manipulator in all the ranges of excursion of the actuator, requiring the operator to use constant minimal manual effort during the operation, thus favouring the accurate use of the tool combined with the manipulator. Furthermore, the manipulator has particularly stable behaviour, enabling the operator to temporarily remove both hands from the manipulator, which remains stationary in the position that it has reached, which is advantageous in terms of safety and ease of use.

It is to be understood that the invention is not limited to the embodiments described and illustrated herein, which are to be considered as examples of embodiment of the manipulator; in fact, the invention can be modified in respect of the shape and arrangements of parts and details of its construction and operation. For example, as shown inFIGS. 8 and 9, in another embodiment of the manipulator, the line of action c of the actuator22can be inclined with respect to the vertical, for example at an angle of 45°. Consequently, the first guide30is inclined parallel to the line c, and the second guide31is perpendicular to the latter. Furthermore, the manipulator may be provided with two pneumatic actuators instead of a single actuator. For example, two pneumatic linear actuators can be mounted parallel to each other, one beside the other, with the respective cylinders mounted on the rotatable assembly13along the axis a and the respective rods integral with the spindle29or with extensions of the latter on the two opposite sides of the oscillating arm24.