GB2157646A - A vacuum gripper - Google Patents

Abstract

A remotely controllable gripper for picking up and setting down objects of various shapes and sizes, and of varying degrees of cleanliness, comprising a flexible skirt (10) flaccidly pendent from a lifting head (1) provided with a fluid extraction means. An upper portion of the skirt is stiffened by longitudinal ribs (13) which maintain it in circumferential extension when engaged with an enveloped object. In use, air is drawn upwardly through the skirt by the extraction means and ejected from vents 2 causing the lower, flaccid portion of the skirt circumjacent the object to collapse inwardly against the object to form a partial seal, thereby imparting a negative pressure to the whole plan area of the object which permits lifting of the combined gripper and object by means of a lifting eye 5. <IMAGE>

Description

SPECIFICATION A vacuum gripper This invention relates to a remotely controllable gripping device capable of picking up and setting down objects of various shapes and sizes without damaging them.

A wide variety of vacuum grippers are known for remote handling without causing damage, i.e. soft handling, the majority of which are capable of handling only objects of unique handling characteristcs e.g. dimension, shape and weight, to which the gripper design can be specifically directed. In all cases a good airtight seal between the gripper and the object is essential for effective operation.

Most commonly used for lifting purposes are suction cups which can be held in contact with an upper surface of the object by negative pressure.

These are effective only if the surface engaged is even and clean, otherwise sealing is poor and a good grip cannot be obtained.

The present invention seeks to provide a vacuum gripper capable of soft handling and lifting objects of various shapes and sizes having irregular and possibly dirty surfaces.

In accordance with the present invention, a vacuum gripper includes: a lifting head; a flexible skirt coaxially sealed to the lifting head so as to extend axially thereform; and a fluid extraction means operative to draw fluid inwardly through the skirt and outwardly through the lifting head.

The gripper is suspended in use with the skirt hanging flaccidly pendant from the lifting head, the head being conveniently provided with suspension means located in axial opposition to the skirt, for attachment to conventional lifting apparatus such a crane or robotic arm.

The fluid extraction means may conveniently comprise an impeller and drive motor mounted within the head. Alternatively the head may be coupled via a flexible fluid transfer line to a fluid extraction means, such as a compressor, located separately from the head.

Preferably a circumferential zone of the skirt adjacent the lifting head is provided with stiffening members for maintaining the zone in a circumferentially extended condition when fluid is being drawn upwardly through the skirt by the extraction means. The stiffening members may conveniently comprise a porous support frame located within the skirt so as to fill the cross-section of the zone and attached to the lifting head. Alternatively, the stiffening members may comprise ribs attached to the skirt itself, which ribs preferably extend longi tudinaliy through the zone to react with any object that may be encompassed by the skirt.

An embodiment of the invention will now be described by way of example only with reference to the accompanying drawings, of which Figures 1 and 2 are perspective views of a vacuum gripper having in-built fluid extraction means, respectively drawn in an open and closed condition, and Figure 3 is an axial part-section of the same gripper.

The vacuum gripper illustrated in all three figures comprises a hollow cylindrical lifting head 1 having four radial air vents 2, an open lower end 3 and a closed upper end 4 to which is attached a lifting eye 5.

Secured within the head 1 is an electrically operated motor 6 having impeller blades 7 disposed and angled to direct air inwardly through the open end 3 and outwardly through the air vents 2. A perforated barrier plate 8 extends across the open end 3 to present entry of solid objects into the impeller blades 7, a sponge rubber ring 9 being provided adjacent the plate 8 to cushion the impact of such objects against the plate 8 and head 1.

A frusto-conical flexible skirt 10 of a plastics material, eg polythene, is sealed at its narrow end 11 to the head 1 by means of a clamping ring 12 circumjacent the open end 3. Eight longitudinal stiffening ribs 13 are attached to the upper half of the skirt 10, which arms act both to assist in spreading the skirt open when the gripper is being lowered over an object 14 (Figure 1) and also to prevent the skirt from being drawn in above the object 14 when the impeller blades 7 are actuated (Figure 2).

The material of the skirt 10 is desirably translucent in order that an operator can observe the position of the object within the skirt. The stiffening ribs 13 may be semi-flexible throughout or substantially rigid with short flexible end portions (not shown).

In use, the gripper is lowered onto an object of interest by means of a robotic arm (not shown) so as to envelop the object within the skirt 10. When the object has been encompassed as far as possible, the impeller blades 7 are actuated, causing the air pressure within the skirt to be reduced below atmospheric pressure. The lower, unstiffened zone of the skirt 10 then collapses inwards under the external air pressure, to fold itself against the object thereby to provide a partial seal. A negative pressure is then imparted over the whole plan area of the object, which pressure is sufficient to permit lifting of the object with the flexible skirt. If insufficient negative pressure develops for effective lifting, the negative pressure can be released and the skirt relocated on the object to seek a more effective sealing disposition.As soon as sufficient negative pressure has been imparted, the object and the gripper may be lifted by the robotic arm and moved and lowered to any desired location at which the negative pressure is finally released.

The relatively large lift area, ie the whole plan area of the object, made available by this embodiment permits the use of low powered impellers for lifting comparatively heavy objects. For example, an impeller of 120mm diameter, typically drawing 200 its at 2,000 Elm2, used with a skirt of approximately 500mm diameter at mid-length, has been found capable of lifting any encompassable object of weight up to 35kg.

It will be apparent that various alternative arrangements are possible. In one particularly advantageous example, the stiffening ribs may comprise flexible tubes which are longitudinally compressed in use into rigid struts by the operation of a drawstring, as described in our co-pending application number 8407306. In such arrangement the ribs preferably extend throughout the full length of the skirt so that an encompassed object is doubly supported both by the negative pressure of the vacuum gripper and by the draw-string.

Claims (5)

1. A vacuum gripper including: a lifting head; a flexible skirt coaxially sealed to the lifting head so as to extend axially therefrom; and a fluid extraction means operative to draw fluid inwardly through the skirt and outwardly through the lifting head.

2. A vacuum gripper as claimed in Claim 1 wherein the skirt has a circumferential zone adjacent the lifting head provided with a stiffening means.

3. A vacuum gripper as claimed in either of the preceding claims wherein the fluid extraction means is located within the lifting head.

New claims or amendments filed on 7 February 1985 New or amended claims:

4. A vacuum gripper as claimed in Claim 2 wherein the stiffening means comprise ribs attached to the skirt so as to extend longitudinally through the said zone.

5. A vacuum gripper substantially as hereinbefore described with reference to the accompanying drawings.