US3175720A

US3175720A - Fuel element handling device

Info

Publication number: US3175720A
Application number: US167612A
Authority: US
Inventors: Millot Jean; Mulot Pierre
Original assignee: Commissariat a lEnergie Atomique CEA
Current assignee: Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Priority date: 1961-02-03
Filing date: 1962-01-22
Publication date: 1965-03-30
Anticipated expiration: 1982-03-30
Also published as: BE613094A; LU41145A1; GB988283A; DE1220572B; FR1291575A; CH382866A

Description

SR CROSS REFERENCE SEARCH ROOM March 30, 1965 3,175,720

J. MILLOT ETAL FUEL ELEMENT HANDLING DEVICE Filed Jan. 22, 1962 2 Sheets-Sheet 1 March 30, 1965 J. MILLOT ETAL FUEL ELEMENT HANDLING DEVICE 2 Sheets-Sheet 2 Filed Jan. 22, 1962 FIG .3

United States Patent France Filed Jan. 22, 1962, Ser. No. 167,612 Claims priority, application France, Feb. 3, 1961,

51,614 4 Claims. (Cl. 214-658) The present invention relates to handling devices which operate to grip an object and, in particular to those used for loading or unloading fuel elements into or out of a nuclear reactor.

More particularly the invention relates to an improvement in handling devices having gripping jaws, of the kind intended to allow the opening or closing of the jaws only at the precise moment at which the device is located within a well defined working zone, that is to say in order to avoid any hasty movement of the jaws during the operation of placing or withdrawing an element in or from the heart of the reactor. Hereinafter, such handling devices will be referred to as handling tongs.

Handling tongs are already known which comprise a tubular body comprising, at its lower extremity, gripping jaws and including a push rod arranged within the body of the tongs, the axial displacement of which controls, by means of suitable cam surfaces, the opening or closing of the jaws. Tongs of the aforementioned type are known which also comprise control members capable of determining the exact nature of the objects grasped by the jaws (set of elements of fissile material, control rod sheaths, control rods themselves), as well as various security devices enabling in particular, the circulation of a neutral liquid around the object grasped in the jaws to be ensured so as to cool it when withdrawn from the reactor.

The invention has for a specific object to make the operation of such tongs completely safe by adding a control system for operating the movement of the gripping jaws, thereby making any false movement on the part of the operator during the transfer of the elements held by the tongs impossible.

According to the invention there is provided a handling device comprising a tubular body, the lower extremity of which carries gripping jaws and a control rod arranged within said body, the axial movements of which enable said jaws to be opened or closed and controlled by a gear reducing motor unit and a screw-bolt assembly, said unit and said assembly being connected by the gear train comprising a driving pinion and a driven pinion, wherein the drive of said driven pinion is carried out by a connecting pinion, the latter being able to move parallel to its rotation shaft by means of a mobile pin for decoupling said driving pinion from said driven pinion and preventing the movement of the jaws of the device.

In order that the invention may be more clearly understood, reference will now be made to the accompanying drawings which show one specific embodiment thereof by way of example and in which:

FIGURE 1 shows a diagrammatic view in vertical 3,175,720 Patented Mar. 30, 1965 section of an embodiment of handling tongs, provided with a security system, according to the invention,

FIGURE 2 is a detailed view showing the lower extremity of the tongs mechanism, grasping the head of an element of fissile material, and

FIGURE 3 shows a view on a larger scale of the seourity system itself.

As can be seen in FIGURE 1 of the drawings, a maneuvering carriage 1 is arranged inside a supporting framework 2. This carriage can be moved upwardly and downwardly by means of a gear reducing motor unit 3 having a torque limiter and electromagnetic gearing, via a transmission chain 4 for example, driven by a sprocket 5 and a pulley 6 respectively located on the base plate 7, which acts as a support for the framework 2, and on the upper part thereof. Two guide bars, such as 8, are integral with one of the lateral uprights of the framework and ensure that carriage 1 is kept in a suitable position during its displacement from bottom to top or vice versa. The chain 4 is connected to the carriage by rings 9 and passes through a bore 9a provided through the carriage itself when in movement. A counterweight 10 connected to carriage 1 by a cable 11 passes over pulley at 12 and is secured to a ring 13 thereby assuring the balancing of the assembly.

Within carriage 1 is located a mechanism comprising a gear reducing unit (not shown) and a pinion and worm arrangement 14 allowing a casing 15 to be rotated to any angle which can, for example, be of 60 in the embodiment describedand illustrated. The casing, moreover, extends into a housing 16 to which a tubular element 17 constituting the body of the tongs device is rigidly connected. The rotation of casing 15 is therefore directly transmitted to the body of the tongs 17 and can be carried out without any special difficulties on

ball bearings

18 and 19, diagrammatically shown in FIG- URE 1.

On the inner part of the tubular body 17, articulated at around its axis, are arranged three jaws 20, only one of which appears in the plane of the drawing. A push rod 21 located coaxially on the inside of body 17 comprises a member 22 at its lower extremity, provided with bevelled surfaces capable of forcing jaw 20 to open or to close when rod 21 is axially displaced. To this end the rod is fitted at its upper extremity with a threaded part 23 engaging with a bolt 23a. The latter is integral with a rod 24' terminating by a bevel gear 25 arranged on the inside of housing 16. This bevel gear is part of a gear train comprising a connecting crown wheel 26 and a control bevel gear 27. The latter is operated by a gear-reducing unit having a torque limiter 28 located on the inside of casing 15, and bearings 29 which facilitate the transmission of the movement through casing 15 and housing 16. The resultant rotation of bolt 23a produces a translatory displacement of the rod 21 by means of a lug 30 integral with the tongs body 17 and sliding in a groove 31 provided in one side of the rod.

The device also comprises a control member for determining the nature of the objects grasped by the jaws of the tongs. In fact the latter can, in particular in the special case considered, serve for the handling of various elements among which are included assemblies of fuel 3 elements of variable head lengths, control rods, control rod sleeves, various stoppers, etc.

It is thus considered necessary to be able to determine if the object to be grasped is firmly held or not in the jaws of the tongs and to be able to subsequently confirm if the object grasped is indeed the intended one.

In FIGURES l and 2, the mechanism which ensures this control is shown. The lower part of rod 21 is grooved in order to allow a pin 32 to slide within said rod. The pin 32 terminates in a small plate 33 which rests against the head of objects to be seized and makes it possible to assess the height in the manner to be subsequently described. The pin is also fitted with a probe or feeler 34 having three fingers, only one of which is shown. The central part of the pin is more particularly used when the gripping jaws work by drawing together and the three finger probe or feeler operates when the jaws are extended. Moreover, the upper part of pin 32 is connected to a small plate 35 located in a cavity 36 in rod 21. The small plate 35 has recesses or slots in which the actuating members of micro-switches 37 engage or not according to the vertical position of plate 35, that is to say as a result of pin 32 which is integral therewith. A flexible bellows 38 ensures an hermetic seal between cavity 36 and the passage of pin 32 within rod 21; in the same way a bellows 39 ensures a sealed connection between rod 21 and the tubular member 17. Finally, a tubular sleeve 41 which is able to freely slide around the body and which has an aperture 42, the purpose of which is subsequently defined, is retained by a flange provided on the outer part of body 17.

In FIGURE 1, the handling tongs are shown in the raised position, the carrier 1 being consequently in the upper part of the framework 2. The tubular body 17 passes through the base plate 17 into opening 43 provided in the centre thereof. A stopper 44 has a joint 45 on the inside which ensures hermetic sealing upon contact of the body 17 of the tongs when the tongs move in the translatory direction. This stopper is arranged on a support 46 and flange 47 on the body 17 abuts the stopper.

The entire device is, moreover, capable of being moved by means of a mechanism, not illustrated, so that the tongs proper can be brought up facing positions into which the various objects referred to above are to be placed or withdrawn in or from the reactor.

With reference to FIGURES 1 and 2, it will be seen that when the body of the tongs is correctly placed above the element to be gripped, for example a set of fuel elements, herein designated by reference letter A, the lowering of carriage 1 is controlled by motor 3 and the transmission chain 4. During this lowering the sleeve 41 abuts the top of the assembly and remains in this position while the tongs body continues its downward movement. During this operation, the sleeve 41 ensures an adequate seal between the body 17 and the upper part of the assembly; an inert gas is caused to circulate through said assembly, preferably from the bottom upwards, apertures 42 allowing the gas to discharge normally while continuing to cool the fuel elements during their withdrawal from the reactor. When the head of the assembly comes into contact with extremity 33 of pin 32, the latter is pushed backwards and operates one or more of the micro-switches 37 according to the height of the head itself. When the jaws of the tongs arrive at a suitable level, the upward movement of push rod 21 is begun moving member 22 upward which acts as a cam forcing the jaws of the tongs to close on the head of the assembly and grip them. The proper functioning of this latter operation is indicated by

microswitches

48 and 49 which are used to complete circuits to lights or the like at a control panel, none of which is shown.

It is also possible to operate the jaws not by tightening them but on the contrary by opening them out in order to grip, for instance, a control rod sheath. To this end the movement of the push rod 21 is reversed and it is the three pin probe or feeler 34 which then controls the correct functioning of the tongs.

Moreover, and according to the invention, the tongs are provided with certain ancillary security members for preventing the opening or closing of the jaws in positions that do not correspond to suitable predetermined working zones.

A shaft 50, the position of which is controlled by the position of the assembly control mechanism by means of a piston chamber for example, determines the drive of a group of gears 51 so as to assure the rotation of a second shaft 52 pivoting on the upper part of framework 2, in a bearing block 53. This shaft 52 comprises a certain number of slots 54 into which engages, according to the respective position of the carriage carrying the tongs, the extremity of a pin 55 fitted with a roller 56. The pin 55 is carried by a housing 16 and is permanently pushed towards shaft 52 by means of a spring 57 which rests, on the one hand, against a boss 58 integral with the pin and, on the other hand, on the housing itself. The pin is extended by a lug 59 in contact with the intermediate pinion 26 which in turn is pushed towards the teeth of

pinions

25 and 27 by spring 60 resting on a ball bearing 61. When the roller 56 is located at the back of a slot 54, the pinion 26 normally engages

pinions

25 and 27 thereby allowing the push rod 21 to be displaced under the control of motor 28. When the tongs are no longer at a predetermined height corresponding to the working position in which it should load or unload the element into or from the reactor, roller 56 withdraws from the slot of shaft 52 and pin 55, by means of lug 59 pushes back pinion 26 so as to prevent the movement of push rod 21 and consequently the jaws of the tongs.

The device according to the invention also comprises a manual emergency control which makes it possible to cancel the preceding requirement. If it be arranged that, as a result of unforseen circumstances, it is necessary very rapidly to withdraw any member such, for example, as an assembly of fuel elements in which the sheath has broken or any other dangerous incident has taken place; for this purpose shaft 52 is provided with a bevel gear 62 capable of engaging with a gear 63 which can be operated by hand crank 63' but normally situated slightly above gear 62. A lever 64, articulated on shaft 65 integral with a rest 66, can be operated by a jack 67 for example, so as to raise the shaft 52 and to put the gear 62 in mesh with gear 63. From this moment shaft 52 is made to turn at a suitable angle, a flattened part 68 is arranged opposite rollers 56 along its entire length, thus enabling gear 26 to engage, what ever may be the position of carriage 1 and of the tongs.

What we claim is:

l. A handling device comprising a supporting framework, a carriage movable in said framework, a tubular body mounted on said carriage, gripping jaws mounted on the lower extremity of said body, a control rod mounted for axial movement in said body for opening and closing said jaws, a gear reducing motor unit, a screw bolt assembly connected to said rod, means for connecting said assembly to said unit comprising a driving pinion, a driven pinion and a connecting pinion, resilient means urging said connecting pinion into engagement with said driving and driven pinions, a movable pin engaging and moving said connecting pinion out of engagement with said driving and driven pinions, resilient means opposing movement of said pin toward said connecting pinion, a cam shaft rotatably mounted in said framework parallel to said tubular body engaging said pin, rotation of said cam shaft moving said pin to disconnect said connecting pinion and said driving and driven pinions, and a plurality of spaced slots in said cam shaft for receiving said pin whereby said connecting pinion engages said driving and driven pinions only when said pin is in one of said slots, said slots being disposed at predetermined positions of said carriage and said tubular body.

2. A device as described in claim 1, said slots being disposed axially along said shaft whereby said jaws are operable at predetermined closely located work positions.

3. A device as described in claim 1, including a flattened surface extending along said shaft and rotated with said shaft into engagement with said pin for disengaging said connecting pinion and said driving and driven pinions.

4. A device as described in claim 3, including manual means normally disengaged from said shaft for rotating said shaft and manual means for moving said shaft axially for engagement with said manual rotating means whereby said shaft may be rotated manually to engage said flattened surface and said pin.

References Cited by the Examiner UNITED STATES PATENTS FOREIGN PATENTS 7/13 France.

HUGO O. SCHULZ, Primary Examiner.

MORRIS TEMIN, Examiner.

Claims

1. A HANDLING DEVICE COMPRISING A SUPPORTING FRAMEWORK, A CARRIAGE MOVABLE IN SAID FRAMEWORK, A TUBULAR BODY MOUNTED ON SAID CARRIAGE, GRIPPING JAWS MOUNTED ON THE LOWER EXTREMITY OF SAID BODY, A CONTROL ROD MOUNTED FOR AXIAL MOVEMENT IN SAID BODY FOR OPENING AND CLOSING SAID JAWS, A GEAR REDUCING MOTOR UNIT, A SCREW BOLT ASSEMBLY CONNECTED TO SAID ROD, MEANS FOR CONNECTING SAID ASSEMBLY TO SAID UNIT COMPRISING A DRIVING PINION, A DRIVEN PINION AND A CONNECTING PINION RESILIENT MEANS URGING SAID CONNECTING PINION INTO ENGAGEMENT WITH SAID DRIVING AND DRIVEN PINIONS, A MOVABLE PIN ENGAGING AND MOVING SAID CONNECTING PINION OUT OF ENGAGEMENT WITH SAID DRIVING AND DRIVEN PINIONS, RESILIENT MEANS OPPOSING MOVEMENT OF SAID PIN TOWARD SAID CONNECTING PINION, A CAM SHAFT ROTATABLY MOUNTED IN SAID FRAMEWORK PARALLEL TO SAID TUBULAR BODY ENGAGING SAID PIN, ROTATION OF SAID CAM SHAFT MOVING SAID PIN TO DISCONNECT SAID CONNECTING PINION AND SAID DRIVING AND DRIVEN PINIONS, AND A PLURALITYOF SPACED SLOTS IN SAID CAM SHAFT FOR RECEIVING SAID PIN WHEREBY SAID CONNECTING PINION ENGAGES SAID DRIVING AND DRIVEN PINIONS ONLY WHEN SAID PIN IS IN ONE OF SAID SLOTS, SAID SLOTS BEING DISPOSED AT PREDETERMINED POSITIONS OF SAID CARRIAGE AND SAID TUBULAR BODY.