GB2077220A - Load gripper with means to centralise the load - Google Patents

Abstract

An apparatus for engaging and lifting a cylindrical object disposed with its axis substantially vertical inside a substantially vertical tube, incorporates a circular array of radially movable and axially spring loaded jaws (1), said jaws being chamfered at their lower ends so that on being lowered on to a said object the weight of the apparatus causes the jaws to penetrate into the space between the object and the wall of the containing tube to centralise the object relative to the tube. A second circular array of jaws (4) is disposed coaxially above the first said array, said second array being arranged to engage the surface of a ridge or recess (16) of the object when the latter has been centralised so that lifting of the object is effected by the second array. <IMAGE>

Description

SPECIFICATION Apparatus for use in lifting cylindrical objects This invention relates to apparatus for use in - aligning and extracting substantially cylindrical ",objects from containers or other support structures. The invention is especially, but not exclusively, concerned with equipment for enabling nuclear fuel elements, more especially advanced gas-cooled reactor fuel elements, to be extracted from their containing tubes, and an object of the invention is to provide apparatus capable of lifting such elements from vertically disposed tubes, not only where the elements are stacked vertically, but also where they have toppled against the walls of the tubes, the apparatus being capable of righting an element prior to lifting.

However, the invention is not restricted to such a use, and may also be used to advantage for aligning and extracting other cylindrical objects in similar situations, not only where the objects and enclosures are disposed generally vertically, but also where they are inclined at a substantial angle thereto, even horizontally.

According to the invention an apparatus for enabling a substantially cylindrical object to be aligned about a given axis and extracted in the direction of said axis from a supporting enclosure, incorporates a support carrying a circular array of radially movable jaws which are capable of surrounding said object within said enclosure, the support and jaws being movable in the direction of the axis of the array to cause the jaws to approach an end of the object, the jaws being independently slidable relative to said support in a direction parallel to the axis of the array and being forwardly biased with respect to the support, and each jaw being chamfered at its forward end such that on movement into engagement with said end of the object the jaws can penetrate into the space between the object and the inside of the enclosure.

By arranging for the individual jaws to be independently biased forwardly, that is to say in the direction in which they are arranged to approach a said object, the jaws are enabled to penetrate into the space between the object and the wall of the enclosure, but in the event that one or more of the jaws abuts or abut against the end surface of the object, and so cannot immediately penetrate into said space, retraction against the associated biasing means, conveniently in the form of one or more springs, allows further movement of the remainder of the array, the jaws adjacent said one or more jaws are thus permitted to penetrate into the space between the object and the enclosure wall prising the object away from the wall and so providing a centralising action which can be completed, if necessary, by subsequent inward movement of the jaws.

After having been aligned, an appropriate surface of the object may be gripped or engaged by the jaws, enabling the object to be subsequently withdrawn from the supporting enclosure.

The inward movement of the jaws can be affected in any convenient manner. Preferably, however, each jaw is mounted for pivoting movement about an axis lying parallel to the axis of the array and displaced circumferentially with respect to the chamfered end of the jaw.

The chamfered surfaces of the array of jaws, which must, of course, be at a suitably acute angle, preferably have a curved shape so that they provide circumferentially spoked sections of a conical surface. Such shaping facilitates insertion of the jaws between the object and the wall of the tube.

Preferabiy a second circular array of jaws is disposed coaxially with but rearwardly of the first said array of jaws, said second array being arranged to engage the surface of a ridge or recess of the object when the latter has been centralised by the first array of jaws, so that withdrawal of the object is effected by the second array.

The invention has particular application to the lifting of cylindrical objects arranged with their axes generally vertical, that is to say either vertical or inclined at a small angle thereto.

The first array of jaws which will be the lower array in such a case may provide for safe operation of an apparatus in accordance with the invention.

Thus closure of said lower array beneath a cooperating part of the object serves to restrain the object in the event of failure of the second, or in this case upper, array of jaws to secure the object or in the event of collapse of the object under the pressure of the second array of jaws.

In a preferred embodiment of this invention applicable to vertical cylindrical objects, the second array of jaws is actuated by the weight of the apparatus so that the jaws are closed when the apparatus is seated on a said cylindrical object, means preferably being provided for locking the second array jaws in the closed position.

For example when the apparatus is lifted there may be a small amount of free motion between the body of the apparatus and the second array of jaws, this differential motion causing the second array of jaws to be locked, with the result that an object held by these jaws cannot be released unless it is supported externally.

The invention may be better understood from the following description with reference to Figures 1 to 5 of the accompanying drawings of an apparatus in accordance with the invention for lifting fuel elements for an advanced gas-cooled nuclear reactor and including an upper and lower array of jaws.

Figure 1 shows a general perspective view of the apparatus looking at it from below, Figure 2 is a sectional illustration showing two of the upper array of jaws engaged with a fuel element, Figure 3 is a sectional illustration showing the two upper jaws released from the fuel element, Figure 4 is a sectional illustration of one of the lower array of jaws before lowering onto a fuel element, and Figure 5 is a sectional illustration of the lower jaw when closed beneath the fuel element to ensure safe transportation of the latter.

Referring first to Figure 1, the apparatus comprises an elongate hollow cylinder 2 which forms the main body of the apparatus. The lower jaws can be seen at 1 and the upper jaws are located within the body 2 at 3. The remaining features of the apparatus are described in relation to Figures 2 to 5.

Figure 2 is a sectional illustration of two of the upper array of jaws engaged with a fuel element 7.

There are eight of the upper jaws 4, radially disposed within the cylindrical body 2by which the apparatus may be raised and lowered. The upper jaws 4 pivot around pins 9 carried by a carrier in the form of a collar 8 which is mounted within the body 2, the pins being disposed along horizontal axes. The collar 8 bears a number of solenoid operated latches 10. An operating sleeve 5 surrounds the lower part of the collar 8 and is movable axially relatively to it, and in an upper position of the sleeve 5 relative to the collar 8, recesses in the sleeve may be engaged by the latches 10 which locks the sleeve to the collar 8.

When the latches 10 do not engage the operating sleeve 5, the latter is able to move downwards relative to the collar 8 and bear inwardly projecting extensions 4a on the upper jaws 4, the weight of the sleeve being such as to cause the jaws to open as shown in Figure 3. When the apparatus is lowered onto a fuel element 7 and is seated upon it, the weight of the operating sleeve 5 is supported by the fuel element 7 and, as the apparatus is lowered further, the sleeve 5 engages beneath the extensions 4a of the upper jaws 4.

Still further movement causes the jaws 4 to be pivoted into the closed positions and to be held closed by the weight of the apparatus. There is arranged to be approximately 1 cm of lost motion in an axial direction between the body 2 and the collar 8 carrying the upper jaws 4, so that when the apparatus is subsequently lifted lugs 11 on the body 2 move relative to the upper jaws 4 and prevent withdrawal of the latter from the fuel element 7 as shown by the broken lines in Figure 2.

Referring now to Figures 4 and 5 there are eight lower jaws 1 only one of which is shown.

These lower jaws 1 bear smoothly chamfered surfaces on their lower ends so that the aperture formed by the array of lower jaws 1 is widest at its lowest extent and the chamfered surfaces from circumferentially spaced sections of a common conical surface. The lowerjaws 1 are individually, slidably mounted for movement parallel to the axis of the lower array. A member 13 co-operates with the upper surface of each of the lower jaws 1. A spring 14 serves to restrain each member 1 3 and each lower jaw 1 from upward movement away from the lower extent of travel of the latter. A cam system 12 may be actuated to radially open or close the lower jaws, which can conveniently be supported for pivoting movement about individual vertical axes, the operative surfaces of the jaws being spaced circumferentially from the respective axes.

Operation of the apparatus is as follows. The apparatus is lowered into a tube containing a fuel element 7 until the lower jaws 1 engage the latter.

One or more of the jaws 1 will usually engage against the top surface of the element if this is not centrally disposed within the tube, in which case they will be forced upwards against its spring 14.

However other jaws will penetrate between the element 7 and the tube 15, those adjacent the upwardly forced jaws gradually urging the top of the element away from the tube wall, allowing the remaining element or elements to penetrate between them. This centralises the element and allows the apparatus to be lowered around the element until the top of the latter contacts the operating sleeve 5. The upper jaws automatically close into a co-operating groove 1 6 in the element as previously described. The solenoid latches are then actuated to lock the collar 8 to the operating sleeve 5. Before the element is lifted by the aDparatus the weight of the element is supported by lifting the body 2, whereupon the lost motion between the body and the jaws 4 is taken up further locking the jaws 4 in the closed position.

The element is then raised to lift it clear of the component beneath, after which the lower jaws are closed to bring them underneath the end of the element ensuring its safe transportation.

The latches 10 instead of being operated by solenoids may alternatively be actuated by other means, for example mech3nically, by the use of cams or other suitable devices.

Claims (10)

1. Apparatus for enabling a cylindrical object to be aligned about a given axis and extracted in the direction of said axis from a supporting enclosure, incorporating a support carrying a circular array of radially movable jaws which are capable of surrounding said object within the enclosure, the support and jaws being movable in the direction of the axis of the array to cause the jaws to approach an end of the object, the jaws being independently slidable relative to said support in a direction parallel to the axis of the array and being forwardly biased with respect to the support, and each jaw being chamfered at its forward end such that on being moved into engagement with said end of the object the jaws can penetrate into the space between the object and the surrounding wall of the enclosure.

2. Apparatus according to Claim 1 wherein the forward biasing of each jaw is effected by one or more springs.

3. Apparatus according to Claim 1 or 2 wherein each jaw is mounted for pivoting movement about an axis lying parallel to the axis of the array and displaced circumferentially with respect to the chamfered end of the jaw.

4. An apparatus according to Claim 1, 2 or 3 in which the chamfered surfaces of the array of jaws have a curved shape such that they provide circumferentially spoked sections of a conical surface.

5. Apparatus according to any preceding claim wherein a second circular array of jaws is disposed coaxially with and rearwardly of the first said array of jaws, the jaws of the second array being movable radially to engage the surface of a ridge or recess of said substantially vertical cylindrical object after penetration of the first array of jaws for a predetermined distance between the object and the wall of the surrounding enclosure.

6. An apparatus according to Claim 5 for use in lifting a said cylindrical object arranged with its axis generally vertical, the apparatus being arranged to be lowered on to said object, and in which the second array of jaws is actuated by the weight of said apparatus so that the second array of jaws is closed when the apparatus is seated on a said substantially cylindrical object.

7. An apparatus according to Claim 6 incorporating means for locking the second array of jaws in the closed position.

8. An apparatus according to any preceding claim in which the first array of jaws is arranged to close beneath a co-operating part of the said object.

9. Apparatus according to Claim 6 or 7 including a carrier member to which each of the jaws of the second array is pivoted about a respective horizontal axis, and an actuator movable with respect to the carrier and depending downwards therefrom so as to be engaged and arrested by a said object as the apparatus is lowered on to it, and such that relative movement between the carrier and the actuator on further lowering of the apparatus, after the arrest of the actuator, produces a pivoting movement of the jaws which causes them to close on to said surface of the ridge or recess of the object.

10. Apparatus according to Claim 9 including means for locking the actuator to the carrier on closure of the second array of jaws, which locks the jaws in the closed position.

1 Apparatus according to Claim 9 or 10 wherein there is a degree of free motion between the support and the carrier such that raising of the support after closure of the second array of jaws causes parts of the support to move to positions in which they prevent withdrawal of the jaws from the closed position.

1 2. An apparatus substantially as described hereinbefore with reference to the accompanying drawings.