US 3820761 A
Description (OCR text may contain errors)
United States Patent 1191 1111 3,820,761 Rigal 1451 June 2s, 1974  ROTATING AGITATOR FOR A 3,043,571 7/1962 swanhom 259/105 x CYLINDRICAL RECEPTACLE OF GREATl LENGTH Inventor: Jean Rigal, Saint-Etienne, France Assignee: CreusotLoire, Paris, France Filed: Mar. 23, 1972 Appl. 115.1231269 Foreign Application Priority Data Mar. 26, 1971 France 71.10816 U.S. Cl. 259/109, 416/227 Int. Cl ,B01f 7/02 Field of Search 259/9, l0, 25, 26, 45,
` References Cited UNITED STATES PATENTS 10/1960 Moultrie 259/105 Primary Examiner-Harvey C. Hornsby Assistant Examiner-Philip R. Coe
ABSTRACT 3 Claims, 2 Drawing Figures ROTATING AGITATOR FOR A CYLINDRICAL RECEPTACLE OF GREAT LENGTH This invention relates to a rotary agitator for a long cylindrical container. Thetagitator is particularly useful, for example, for a horizontal-axis chemical reactor for the production of certain basic polymers.
For efficient operation of such a reactor, and, in particular, to avoid accumulation of material on the reactor walls, the clearance between the agitator and the walls must b`e as small as possible. The minimisation of the radial clearance 'between the agitator blades and the inner surface of the container wall is limited both by the ordinary initial production tolerances and by deformation that the agitator undergoes in operation due 4to forces applied to it during agitation of the material in the container. The simplest and bestknown solution is therefore to make the agitator in the form of a robust and rigid central shaft with peripheral blades connected thereto by radiating arms. ln conventional constructions, the blades `are usually helical and are hollow, the central shaft of the agitator and the arms providing the connection between the shaft and the blades being also hollow; this arrangement allows fluid to flow inside the agitator elements` in order either to heat or cool the mixture being processed in the container.
Development in the plastics production industry has resulted in processing containers of ever-increasing volume being required. It has also been found lthat in order to obtain suitable homogeneity of the products the diameter of the container must be limited, the increased `volume required therefore being obtained by increasing the length of the containers. Consequently,
the central shaft of the agitator becomes increasingly longer and its diameter has to be increased to give it sufficient rigidity to ensure minimum clearances between the agitator blades and the container wall. This shaft diameter increase results in a reduction of the proportion of the volume of the container available for containing processing material and therefore a considerable increase in weight of the processing apparatus and hence a much higher cost price. The length of such a shaft is also limited because of the dimensional limitations of machines capable of machining the trunnion bearings. i
The object of the invention is to provide a rotary agitator having a much higher structural rigidity than known agitators made from a comparable amount of metal, so that longer chemical-reaction containers can be produced.
According to the invention there is provided a rotary agitator for a container comprising a plurality of bearing-members separated longitudinally of the agitator for cooperation with the bearings in the container, a plurality of helical blades each coupled directly and by at least one lattice rod to each of the bearing members, and coupled to each other by a plurality of said lattice rods.
In a preferred embodiment of the invention applied to cases in which the blades are hollow and carry a flow of fluid through the agitator trunnions, the lattice rods are hollow and the internal chambers of these rods communicate with the internal chambers of the blades.
The invention will now be described in greater detail with reference to a specific embodiment given by way of example and shown in the drawings, in which:`
FIG. 1 is a side view of an agitator according to the invention, showing the ends of the agitator and connection to the trunnions; and
FIG. v2 is an end view of the agitator.
The agitator is intended to be used in a generally cylindrical container l, the inside profile of which is shown in chain-dotted lines in the drawings. Both ends la of the container are of a conventional domed shape. At each end, the agitator rests via a trunnion 2 on a bearing 2a connected to the agitator body; these bearings are shown in the drawings and may be of any conventiona] type, for example,ysealed bearings if the container is to be operated under internal pressure.
The agitator operating members consist essentially of three helical blades 3, 4 and 5. In the specific case shown in the drawing, these blades consist of anglemembers so constructed that their angle is always directedtowards the axis of the container. Towards its inner end, the trunnion 2 bears three radial arms 7, 8 and 9, each provided at one endwith a support 10, 11 and 12 having an angled notch of the same profile as the angle-section forming each of the blades. Each support, 10, 11 or 12, is also connected to the trunnion 2 by a rod 13 acting as a strut.
Each blade, for example blade 3, is secured at l5 to the trunnion 2, and is then fitted into the `groove of the support 10 with a curvature very similar to the internal curvature of the tank end, and then continuesY in the form of a purely helical part over an outside coil diameter slightly less, to allow the necessary clearance, than the inside diameter of the container. In a series of transverse planes perpendicular to the axis of the apparatus and, for example, axially equidistant, each helical blade 3, 4 or 5 is connected to a support 1S, 16 and 17 respectively, in which they are each fitted. Eachoi` the supports of the same transverse plane is connected to the other two by a first set of rods 18 which form an equilateral triangle. Each support 15, 16 or 17 is also connected by a rod to a support of the preceding trans verse planeassociated with another blade, and to a sup port of the next transverse plane associated with the third blade. Thus the support 17' associated with the blade 5 is connected to the support 1l associated with the blade 4 and to a support 20 associated with the blade 3. Similarly, the support 16 associated with the blade 4 is connected to the support 10 associated with the blade 3 and to a support 22 associated with the blade S.
The agitator thus constructed according to the inven tion forms a three-dimensional lattice structure which allows the agitation blades to be used as the main frame members. The blades forming the frame members are remote from the central axis of the apparatus so that improved assembly rigidity is obtained for a smaller amount of metal used.
The elimination of the central shaft improves access to the interior of the container for maintenance and cleaning operations and for the normal sizes of such containers used as chemical processing containers, al lows man access to the interior of the apparatus.
This method of construction also means that it is possible to depart from the limited size of existing machines, because it is no longer necessary to mount the agitator on a lathe to machine the trunnions. This removes one of the limitations in the possible sizes of the containers and their agitators.
The blades of the agitator may be hollow as at 4a to allow fluid to flow through them for cooling or heating of the product being processed. This is already known in the case of conventional central-shaft agitators having radiating arms supporting the blades. In such cases the shaft 2 is hollow as at 2b and the same applies to the arms connecting it to the blades as at 9a. The agitator according to the invention also allows this fluid flow by the provision of tubular-section blades; since the supports to which the connecting arms are joined are also hollow as at 12a, as are the rods themselves, there is a complete interconnection of all the internal chambers of the agitator elements.
In the arrangement described above, each support forming a connecting rod junction comprises an even number of outlets, thus allowing an equal distribution of the fluid in the various blades.
l. A rotary agitator comprising a cylindrical container having a long horizontal axis, ends for said cylindrical container, a bearing in each of said ends, trunnions rotatably mounted in each of said bearings, three 1 helicoidal spaced blades in said container closely spaced to the internal wall of said container and each of said blades being connected to each of said trunnions and rotating about an axis coincident with the long axis of said container, means for connecting each of said blades at regular intervals to the other two of said blades including a bar disposed in a plane perpendicular to the long axis of said container and a bar oblique with respect to said plane, said two bars, relative to each of the other bars of said two other blades, being disposed on opposite sides of said perpendicular plane.
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