US3039811A - Lifting devices - Google Patents

Description

Ski-IKE?! I'IUUIV LIFTING DEVICES 5 Sheets-Sheet 1 Filed Nov. 12, 1959 FIG-I P I mm s x m A I l I I I I l l l I I I I I June 19, 1962 N. BRADLEY ETAL LIFTING DEVICES 5 Sheets-Sheet 2 Filed Nov. 12, 1959 24 INVENTORS NORMAN BRADLEY JACK JONES A A 672479 it! June 19, 1962 Filed NOV. 12, 1959 N. BRADLEY El AL LIFTING DEVICES T lo F|cs.4.

5 Sheets-Sheet 3 INVENTORS NORMAN BRADLEY JACK JONES June 19, 1962 N. BRADLEY ETAL 3,039,811

LIFTING DEVICES Filed Nov. 12, 1959 5 Sheets-Sheet 4 INVENT'ORS NORMAN BRADLEY JACK JONES June 19, 1962 N. BRADLEY ETAL 93,039,811

LIFTING DEVICES Filed Nov. 12, 1959 s Sheets-Sheet 5 INVENTORS NORMAN BRADLEY JACK JONES .trical system of control.

United States Patent 3,039,811 LIFIING DEVICES Norman Bradley, Culcheth, near Warrington, and Jack Jones, Manchester, England, assignors to United Kingdom Atomic Energy Authority, London, England Filed Nov. 12, 1959, Ser. No. 852,539 Claims priority, application Great Britain Nov. 20, 1958 3 Claims. (Cl. 294-83) This invention relates to lifting devices and is concerned with grabs for retrieving articles from places difficult of access such as the lower regions of long and narrow vertical holes.

One specific application of a grab according to the invention is in the retrieving of articles from vertical channels in the core of a nuclear reactor, necessitating the location and securing of articles, such as fuel elements, which may be disposed in the lower regions of a channel of a few inches in diameter. Grabs for similar purposes, which are either pneumatically or electrically operated, have already been proposed but each employs an elec- A device which includes electrical contacts is not suitable for use in some vaporous atmospheres, for example, a steam atmosphere such as would be encountered in a steam cooled nuclear reactor. Furthermore, electrical control necessitates providing the device with cables capable of being carried by a winding drum. The cables must therefore be flexible and also must be fluid impervious and their insulation be proof against long exposure to high temperature. These necessary properties are extremely difficult to realise in practice.

It is an object of the present invention to provide a I grab which, by virtue of elimination of electrical control,

is suitable for operation with a nuclear reactor cooled by vapour which is subsequently condensed.

According to the invention, a grab is piston operated and has the volume enclosed by the piston and its cylinder connectable via a control valve to evacuating means and also has the said volume in communication with ambient pressure via a bleed valve or orifice, means being provided for biasing the piston into a position in relation to the cylinder wherein the said volume is a maximum, the said position defining one of the operative positions of the grab, and the other operative position of the grab being defined by the position the piston occupies relative to the cylinder when the said volume becomes a minimum after establishing communication between the said volume and the evacuating means by opening of the said control valve.

The grab is preferably provided with means for operating remotely disposed indicating means serving to assist an operator in controlling the grab.

A grab according to the invention will now be particularly described with reference to the drawings accompanying the specification wherein:

FIGURE 1 is a side view in medial section of the grab showing it located on and engaged with a load,

FIGURE 2 is a plan view from beneath of the grab shown in FIGURE 1.

FIGURE 3 is an enlarged side view in section taken on line IIIIII of FIGURE 1 and illustrates a detail,

FIGURE 4 is a diagrammatic representation showing the operation of a location sensing device,

FIGURE 5 is a diagrammatic representation showing the operation of the grab arm sensing device, and

FIGURES 6, 7 and 8 are diagrammatic representations of the operating steps of the grab.

In general description and referring to FIGURE 1, the grab shown, which is wholly metallic, includes a cylindrically hollow body 1 formed with eight external guide lugs 2 and carrying internally a piston 3 limited in upward movement in the body 1 by a ring 4 attached to the body 1 by set screws 5. The piston 3 is fitted with two expanding sealing rings 6 and is spring loaded in an upward direction by a compression spring 7, which is end located by a groove 8 in the piston 3, and by a bush 9 co-axially located in the body 1. The grab is intended to be carried in a vertically suspended position by two co-axial flexible tubes 10 and 11 attached to the piston. The tubes 10, 11 are of such length as to enable a connection to be made with a steam condenser C and control valve 33 (see FIG- URES 6-8) remote from the grab. Three claws 12 having toes 36 are supported by fulcrum pins 13 carried in three equispaced pairs of lugs 14 located on a shaft 15 which is co-axially attached to piston 3 and is guided by bush 9. Three claw operating pins 16 are respectively carried in three equispaced pairs of lugs 17 formed integrally with the body 1, the pins 16 being respectively engaged in slots 16 provided in the claws 12 to accommodate sinusoidal displacement of the pins 16. A controlled-leakage orifice 18 is located in the cylindrical wall 3 of the piston 3. With the piston 3 located on the stop formed by the ring 4, a transverse passageway 19 leading from the outside surface of the body 1 registers with a second transverse passageway 20 connecting with a longitudinal passageway 21 formed co-axially and throughout the length of the shaft 15, to communicate with the flexible tube 10. The passageway 21 is adapted to contain at the end adjacent to the claws 12 and as shown particularly in FIGURE 3, a nozzle 22 which provides a tapering seat 23 for a probe 24, a valve guide 25 and a compression spring 26. As shown in FIGURES 1 and 2 a circlip 27 and a washer 28, located externally at the end of the shaft 15 retain a locating nose 29 fitted with a bush 30 and loaded with a compression spring 31.

The annulus 11 bounded by the tubes 10 and 11 is connected to the steam condenser C by way of a valve 33, see FIGURES 6, 7 and 8. A pressure indicating gauge 32 is connected into the annulus 11' downstream of the valve 33. The tube 10 is also connected to the condenser C through a control nozzle 35, see FIGURES 1, 4, 5, 6, 7 and 8. A pressure indicating gauge 34 is connected to the tube 10 at a point downstream of the nozzle 35.

The particular use of the grab described above to pick up an article or load, such as a fuel element, provided with a suitable lifting collar, from a long narrow vertical hole such as a fuel element channel in the core in a nuclear reactor, will now be described.

The grab is suspended by the flexible tubes 10 and 11 in a vertical channel 40 of the reactor, said channel conducting a flow of steam coolant at a pressure of the order of 800 p.s.i. The flexible tubes 10, 11 are windable on and off a winding drum W (FIGURES 6, 7 and 8) for raising and lowering the grab. On opening of the valve 33, the annulus 11' is connected to the condenser C thus serving to create a partial vacuum within the volume enclosed by the piston 3 and cylinder body 1 so that ambient steam pressure external to the body 1 and piston 3 causes the cylinder body 1 to move upwardly with respect to the piston 3 against the action of the spring 7. The lugs 17 and pins 16 thus move upwardly relative to the piston 3, shaft 15 and the lugs 14, rotating the claws 12 about the pins 13.

The grab is lowered, being guided in the channel 40 by the lugs 2, to make contact with an article or load 29. C0-axial alignment is achieved by the locating nose 29 having an internal taper engageable with a complementary external taper on the upper end of the article 29. On engagement of the respective tapers of the nose 29 and article 29', further lowering of the grab causes the locating nose 29 to slide vertically on the shaft 15, compressing the spring 31, until arrested by a shoulder 41 on the shaft 15. A warning signal indicating the engagement of the locating nose 29 with the article 29' i s i i is transmitted to the grab operator through the medium of a primary steam flow through the nozzle 22 (FIGURE 3) produced as a result of the probe 24 being forced off its seat by contact with a face 42 on the upper end of the article 29 (see FIGURE 1). The primary steam flow is conducted from the nozzle 22 by first the passageway 21 and then the flexible tube to the steam condenser C, its pressure being indicated on the pressure indicating gauge 34 which is local to the grab operator, such indication constituting the said warning signal. Referring to FIGURE 4, which shows diagrammatically the path of the said primary steam flow, the steam pressure thereof is first reduced over the nozzle 22 from 800 p.s.i. to 460 p.s.i. and then by pipe friction to approximately 400 p.s.i. at the gauge 34 which immediately precedes the control nozzle 35, after which the steam pressure falls off to the steam condenser pressure. The rate of the primary steam fiow is negligible.

Steam at ambient pressure also flows from the channel 40 through the controlled-leakage orifice 18, which functions as a continuous bleed, and is evacuated to the condenser C via the annulus 11' bounded by tubes 10 and 11 and the open control valve 33 shown diagrammatically in FIGURES 6, 7 and 8. Closure of the claws 12 on to the article 29' (see FIGURE 1) is achieved by closing 'the valve 33 to isolate the steam condenser C and allow the steam pressure internal the body to build up by inleakage through orifice 18 and ultimately balance the external pressure whereupon the spring 7 effects downward movement of the cylinder body 1 relative to the piston 3. This downward movement contrarotates the claws 12 about the pins 13 and closes them on the upper end of article 29. A warning signal indicating closure of the claws 12 onto the article 29 is then transmitted to the grab operator through the medium of a secondary steam flow. The secondary steam flow takes place from the channel 40 through passageway 19 which coincides with passageway 20 when the piston 3 is at rest on the stop ring 4, through passageway 21, through the flexible tube 10 and to the steam condenser C, its pressure being indicated on the gauge 34, such indication constituting the warning signal.

Referring to FIGURE 5, which is a diagrammatic representation of the secondary steam flow, the steam pressure is reduced by pipe friction from 800 p.s.i. to approximately 750 p.s.i. at the gauge 34 and to condenser pressure over the control nozzle 35. The rate of secondary steam flow is approximately 20-lb./hr.

Engagement of the claws 12 is effected on upward movement of the locating nose 29 against the spring 31, the toes 36 of the claws 12 sliding into engagement with an annular recess 37 formed on the underside of the nose upper end of the article 29. This provides a safety factor in that the claws 12 cannot open again unless and until the load constituted by the article 29' is removed, by upward movement of the locating nose 29 against the action of its spring 31.

The grab and the article 29' can then be lifted vertically by rotation of the winding drum W.

It will be appreciated that the grab is effective with coolants other than steam, a condenser being usefully employable for effecting evacuation and grab operation where the coolant is condensible vapour, a vacuum pump being employed where the coolant is not condensible within the relevant temperature range.

We claim:

1. A grab comprising a body member defining a piston chamber, a piston movable in the piston chamber, means providing unrestricted access to ambient pressure on one side of the piston, means providing restricted access to ambient pressure on the other side of the piston, a piston chamber evacuating connection on the said other side of the piston, a shaft connected to the piston and passing axially through the piston chamber to extend beyond the piston chamber, a plurality of claw members disposed radially about the portion of the shaft external the piston chamber, means pivotally supporting the claw members on the body member and means linking the claw members with the shaft so that they are moved radially about their supports by axial movement of the shaft.

2. A grab as claimed in claim 1 in combination with a pressure operated indicator disposed remote from the grab, a valve device disposed adjacent the grab members, said valve device comprising a valve chamber, means defining access for ambient pressure to within the chamber, a valve member within the valve chamber for closing said access, means urging the valve member into a closing position, a valve opening member extending into the space between the grab members and a conduit connection between the valve chamber and the pressure operated indicator.

3. A grab as claimed in claim 1 in combination with a pressure operated indicator disposed remote from the grab, wherein the body member defines a first internal passageway having one end open to ambient pressure and the shaft defines a second internal passageway, the first and second passageways being arranged so that the other end of the first passageway is in communication with the second passageway when the piston connected to the shaft is at one end of its travel in the piston chamber, and a conduit connection between the second passageway and the pressure operated indicator.

References Cited in the file of this patent UNITED STATES PATENTS 2,118,991 Turecheck et al. May 31, 1938 2,457,834 Ricketson Jan. 4, 1949 2,494,124 Hegy Jan. 10, 1950 2.863.287 Berkman Dec. 9. 1958

Images