IL22136A - Lifting mechanism - Google Patents

Description

The present invention relates to a lifting mechanism which is especially intended for use in a nuclear reactor facility for the purpose of lifting covers of tanks or leak-tight vessels.

In nuclear research laboratories, radioactive materials are manipulated within leak-tight and shielded vessels and in order to transfer the radioactive materials or products from one vessel to the other, use is made of totally enclosed conveyors for connecting said vessels to each other. When one of said vessels is removed, it is necessary to ensure that the vessel and conveyor both remain leak-tight ; it is therefore necessary to close the openings which provide a communication between the vessel and the conveyor by means of covers with liquefiable seals, for example.

Such covers are normally closed, and when it is desired to transfer an object from a vessel into the conveyor or conversely, it is of. course necessary to remove said covers.

In the case in which said covers are fitted with, liquefiable seals, it is necessary to lift the covers to a height such that the seal is broken and to leave said covers suspended above the seal for a certain period of time prior to removing then in order to allow then to drip and thus prevent the liquid of the seal from being dispersed either within the vessel or within the conveyor .

The present invention is directed to the design of a lifting mechanism wherein the upward travel of the cover is broken down into two stages ; in the first stage, the cover is lifted ^vertically while remaining parallel to second stage, the cover is removed so as to free the opening.

The lifting mechanism according to the invention comprises an articulated parallelogram formed "by two parallel arms which are pivotally mounted on a base-plate so as to rotate about pivot pins which are in alignment on a vertical line, there being pivotally attached to the ends of said arms a vertical yoke which is fi ed on the cover, said base-plate being mounted to rotate freely about a driving shaft to which is attached a c ank- rm, said crank-arm being coupled to one of the arms cf the articulated parallelogram and provided with a nose which is adapted to come into contact with a stationary abutment of said base-plate so as to drive said b.ase-plate in rotation about the axis of said driving shaft, said nose being located at a distance away from said abutment when the cover is closed, so that the ro ational movement of the driving shaft first produces the deformation of the parallelogram and consequently the vertical displacement of the cover and then, when the nose of the crank-arm is in contact with said abutment, produces the rotational motion of the combined assembly consisting of base-plate, arm, yoke and cover about the axis of the driving shaft.

The invention also consists of other arrangements which can usefully be employed in conjunction with the foregoing arrangement but whic can also be employed independently thereof. All of these arrangements will become apparent from a perusal of the following description of one mode of practical application of the invention as given by way of illustrative example The description relates to the accompanying drawings, wherein .

- Fig. 1 is a partial sectional view of an installation in which the lifting mechanism of the invention is employed ; - Fig. 2 is another partial view of the same installation ; - Fig. 3 is a sectional view of the cover-lifting mechanism which is employed in this installation; and - Fig. h is a sectional view along the line h-h of Fig. 3· The lifting mechanism A in accordance with the invention is x^laced within the interior of a leak-tight tank or vessel 12 housed within a cell which is designed to contain a number of similar tanks and a conveyor ih which is also leak-tight and which provides a communication between said tanks. This type of installation is employed in particular in the nuclear energy industry. As can be seen from Fig. 1, the conveyor Ih is placed beneath the tanl: 12 and openings 16 and 18 which are formed in the base of the tank and the conveyor shaft respectively permit the possibility of transferring objects from the conveyor into the tank or conversely. The opening 16 of the tanl: is normally sealed off by a cover 20 and leak-tightne s between the cover and the base of the tank is ensured by means of a liquefiable seal formed of a material having a melting temperature which is slightly higher than room temperature such as pitch, said seal being placed within an annular trough 22 which is formed around the opening The annular trough 22 also extends within an annular trough ore channel 25 which has a larger cross-section and which surrounds the edge of the opening 18 formed in the conveyor shaft. The said trough 25 is filled with liquefiable material in the same manner as the trough 22 .

The opening 18 is normally sealed by a cover 26 which rests on the annular trough 25 and which is provided with a flange extending within said trough. It is thus possible to separate the tank 12 from the conveyor Ik while nevertheless retaining leak-tightness of the tank and of the conveyor and, in addition, when the tank is in position above the conveyor, both covers 20 and 26 can be removed without impairing leak-tightness of the assembly as a whole. The tank cover 20 is provided with, magnetic suckers 28 which normally couple the conveyor cover 26 to the tank cover 20. Provision is made for a device which makes said suckers inoperative when it is desired to separate the tank from the conveyor.

The mechanism A which is employed for the purpose of lifting the covers 20 and 26 is shown in detail in Figs. 3 and h . Said mechanism comprises two yokes 30, one extremity of each yoke being attached to the cover 20 close to one edge of this latter, ISach yoke is pivotally mounted on the extremities of two arms 32 and 3 which are placed in parallel relation to each other and pivotally mounted on a base-plate 36 . The pivot-pins on which the yoke 30 is pivoted to t e arms 32 and >h are in alignment on a vertical line whilst the fulcrum-pins of the arms are in alignment on another vertical line and the spacing of said fulcrum-pins is equal to that of said pivot-pins, with the result that the yoke 30 , the arms 32 parallelogram, the deformation of which produces the vertical displacement of the oke and consequently of the cover. T e base-plate 36 is supported on a driving shaft 38 and is freely rotatable on said shaft. A crank-arm hO is secured to the ..shaft 38 by means of a locking-pin h2 and is coupled to the arm 32 by means of a connecting-arm hh which is pivotally attached to the arm 32 at a point which is distant from the fulcrum of the arm. The crank-arn hO is provided with a nose h6 which, when the cover 20 is in position, is located at a distance away from a stub shaft^which is secured to the base-plate 36 as shown in Fig. 3 but is intended to come into contact with said stub shaft when the crank-arm hO is caused to rotate. The entire mechanical assembly which has been described above is enclosed within a casing 50 which is secured to the base-plate 36, and the two mechanisms whic are associated with the two yokes 30 are mounted on the shaft 38 on each side of a frame 52 which is secured to the base of the tank and which carries an electric motor and the speed-reduction gear for driving the shaft 38.

When the cover 20 is in position, the casings 50 are supported on brackets 53 which are fixed on the frame 52 and which serve as a support for the base-plates 3G during the first stage of the lifting movement of the covers. The yokes 30 traverse the bases of the casings 50 through openings which are formed for this purpose and rubber protection sleeves 5k which surround the bottom portion of each yoke 30 are clamped aromid annular flanges provided on the cover 20 and on the casings 50.

V/hen the covers 20 and 26 are closed, the components of the mechanism A are located in the desired to lift the covers, the first step consists in heating the material contained within the annular troughs 22 and 25 by means of electric heating resistors placed within said troughs, with a view to liquefying said material. The second step consists in starting-up the motor which drives the shaft 38 on which the crank-arns hO are mounted. In a first time-interval, the crank-arms ho cause the arms 3 to swing about their pivotal axes, thereby producing the deformation of the articulated parallelograms which are formed by the yokes 30, the arms 3 and > and the base-plates 36 5 "the covers 20 and 2b which are coupled together by me ns of the magnetic suckers 28 are then lifted vertically while remaining horizontal, with the result that, during this first time-interval, the cover flanges which had been immersed in the liquefied material of the sealing joint are able to drip into the troughs 22 and 25. When the shaft 38 has rotated through a certain angle, the noses he of the crank-arms hO accordingly come into abutting contact with the stub shafts 8 which are secured to the respective base-plates ; and, starting from t is moment, the rotation of the crank-arms initiates the movement of the base-plates 36 and the assembly consisting of arms 32 and 3^ > yokes 30 and covers 20 and 26 , said assembly being thus displaced as ; single unit together with the base-plates 36 inasmuch as the arms 32 and h can no longer pivot about their axes. Cams which are integral with the shaft 38 control contactors for the purpose of interrupting the circuit which supplies current to the motor when the covers have been lifted to a sufficient extent ; an interlocking In order to replace the covers in position, said covers are allowed to fall back under the action of their own weiglitj provision being nevertheless made to brake their falling motion. During this movement, the base-plates 36 are brought back so as to bear on the brackets 53 a d the crank-arms hO as well as the arms 32 and !+ are returned to their initial positions.

As will be apparent, the invention is not limited to the single form of construction which has been described and illustrated and it must be understood that the scope of this patent extends to any alternative forms of the arrangements hereinbefore described which remain within the definition of equivalent mechanical means.

Claims (2)

HAVING NOW PARTICULARLY DESCRIBED AND ASCERTAINED THE NATURE OF OUR SAIO INVENTION AND IN WHAT MAN. ER THE SAME 16 TO BE PERFORMED, WE OECLARE, THAT WHAT WE CLAIM 18.- V/iiat we claim is :

1. Lifting mechanism comprising an articulated parallelogram formed by two parallel arms which are pivotally mounted on a base-plate so as to rotate about pivot-pins which are in alignment on a vertical line, there being pivotally attached to the ends of said arms a vertical yoke whic is fixed on the element to be lifted, said base-plate being mounted to rotate freely about a driving shaft to which is attached a crank-arm* said crank-arm being. coupled to one of the arms of the articulated parallelogram and provided with a nose which is adapted to come into contact with an. abutment fixed -on said base-plate so as to drive said base-plate in rotation about the axis of said driving shaft, said nose being located at a distance away from said abutment when the element to be lifted is in position, with the result that the rotational movement of the driving shaft first produces the deformation of the Oarallelogram and consequently the vertical displacement of said element until the nose of the crank-arm comes into contact with said abutment, and then produces the rotational motion of the combined assembly consisting of base-plate, arm, yoke and element about the axis of the driving shaft.

2. Lifting mechanism in accordance with Claim 1, cooprising a base-plate which is brought to bear on a stationary bracket when the parallelogram is deformed as a result of the rotational movement of the driving shaft. bracket when the element to be lifted is located in the initial osition thereof. h . Lifting meclianism, su stantially as hereinbefore described with, reference to and as illustrated in tiie accompanying drawings. DATED THI S 22ND SEPTEMBER f 1964 3 1C31-3