DEVICE FOR STERILIZING PRODUCTS PACKED IN CYLINDRICAL CONTAINERS

Abstract: A device for sterilizing products packed in cylindri­ cal containers, comprises an elongate, essentially cylindri­ cal housing and an essentially cylindrical rotor located therein which can be driven via a central shaft. The circumferential wall of the housing is provided on the inside with a helically running, raised rib. The rotor is designed as a cage consisting of a number of rings placed behind each other, the centre line of which coincides with the axis of the rotor, and a number of raised ribs fastened to the circumference of the rings parallel to the axis of the rotor. The outer edge of the ribs on the rotor is located near the inner edge of the helically running rib on the inner wall of the housing so that spaces are formed between the ribs for receiving the cylindrical containers. Within the rotor between neighbouring rings bracing elements in the form of pipes are provided to reinforce the rotor.

Description: BACKGROUND OF THE INVENTION The invention relates to a device for sterilizing products packed in cylindrical containers, comprising an elongate, essentially cylindrical housing and an essentially cylindrical rotor located therein which can be driven via a central shaft, the circumferential wall of the housing being provided on the inside with a helically running, raised rib and the rotor being designed as a cage consisting of a number of rings placed behind each other, the centre line of which coincides with the axis of the rotor, and a number of raised ribs fastened to the circumference of the rings parallel to the axis of the rotor, the outer edge of which ribs is located near the inner edge of the helically running rib on the inner wall of the housing, so that spaces are formed between the ribs for receiving the cylindrical containers, and bracing elements which are at an angle relative to the rotor shaft being provided within the rotor between neighbouring rings to reinforce the rotor. A device as this type is known. In this known device, the containers present between the ribs are moved in circumferential direction by the rotation of the rotor and, because the housing is provided at the inside with a helical rib, are also moved on in the longitudinal direction of the rotor. In view of the fact that the distance between the outer edge of the ribs present on the rotor and the helically running rib arranged against the inside of the circumferential wall of the housing is relatively small, it is necessary for the sagging through of the rotor to be within very narrow limits. For this purpose, the rotor of the known device is reinforced by means of bracing element in the form of rods or wires which are fitted crosswise and under pretension between neighbouring rings of the rotor and together form a three-dimensional framework. However, a disadvantage of the known device is that in fact only half of the bracing elements contribute to the reinforcement of the rotor, since the rods or wires can be subjected only to tensile load and can absorb hardly any or no compressive forces. The relatively low flexural stiffness of such a rotor limits the usable length thereof, because the sag which occurs is limited in order to prevent excessive plays occuring in the guides for the containers. A rotor of this type has furthermore a limited torsional stiffness, as a result of which the rotor has to be driven at both ends. SUMMARY OF THE INVENTION It is the object of the invention to provide rotation with higher flexural and torsional stiffness. This object of achieved with a device of the above-named type, which is characterized in that the bracing elements consist of pipes. The pipes can absorb both tensile forces and compressive forces. It is possible as a result of this to achieve, with the same weight of the rotor, higher flexural stiffness as well as greater torsional stiffness than in the known construction. It is also possible, with the same maximum sag, to make the rotor longer, which increases the capacity of the device. Moreover, using the new construction it is sufficient to drive the rotor at one end, whereas in the known device the rotor had to be driven at both ends. Each pipe preferably consists of parts made of different materials, in a ratio such that the mean coefficient of expansion of the pipes is equal to the mean coefficient of expansion of the rings and the ribs of the rotor. This prevents temperature stresses from occuring in the rotor of the temperature increases, as was the case with the known device. In a practical embodiment of the device, the rings of the rotor are made of steel and the ribs are made of stainless steel, and each pipe consists partly of steel and partly of stainless steel. The invention also relates to a rotor intended for a device according to the invention for sterilizing products packed in cylindrical containers. The invention will now be explained in detail by means of the description of an exemplary embodiment and with reference to the drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a diagrammatic longitudinal section of a device according to the invention, and Fig. 2 is a cross section through the device of Fig. 1 along line II-II. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The device shown in the figures for sterilizing products packed in cylindrical containers comprises an elongate, essentially cylindrical housing 1 and an essentially cylindrical rotor 2 located therein which can be driven via a central shaft 3. The circumferential wall 4 of the housing 2 is provided on the inside with a helically running raised rib 5. In the embodiment described, the raised rib 5 is formed by the body of a T-shaped section, the flange 6 of which is arranged against the inside of the circumferential wall 4. The rotor 2 is designed as a cage consisting of a number of rings 7, 8, 8′, 8″, 9 arranged behind each other, the centre line of which coincides with the axis 10 of the rotor, and raised ribs 11 fastened on the circumference of the rings 7, 8, 8′, 8, 8″, 9 parallel to the axis 10 of the rotor. In the embodiment of the device described, each rib 11 is formed by a flange of an angled profile and fastened with the other flange 12 to the outer side of the rings 7, 8, 8′, 8″, 9. The outer edge 13 of the ribs 11 is located close to the inner edge 14 of the helically running ribs 5. Spaces in which the containers 15 to be sterilized can be received are formed between the ribs 11 and the helically running rib 5. A number of these containers are shown by broken lines in the figures. By rotating the rotor 2 about the axis 10 the containers are moved in the circumferential direction through a helical groove which is formed by the helically running rib 5. As a result, the containers are also transported in the longitudinal direction through the device. Bracing elements 16 which serve to increase the flexural and torsional stiffness of the rotor are fitted inside the rotor between neighbouring rings. The bracing elements 16 are arranged crosswise and together form a three-dimensional framework. In the embodiment shown in the figures, six bracing elements which extend from a particular point of one ring to a point on the other ring which is rotated through about 180°C about the axis 10 of the rotor relative to the first-named point are arranged between two neighbouring rings. Viewed in the direction of the axis 10 of the rotor, the bracing elements are at a mutual angle of 60°C. The bracing elements consist of pipes which are joined via flanges 17 to the rings 7, 8, 8′, 8″, 9. These pipes are suitable for absorbing both tensile and compressive forces. As a result of using pipes as bracing elements, a high flexural and torsional stiffness can be obtained for a given weight of the rotor. This makes it possible to use a longer rotor with maximum sag remaining the same, than in the case in which the bracing elements consist of rods or wires which are intended to absorb tensile forces and can absorb hardly any or no compressive forces. Thus, for example, it is possible to use a rotor having a length of about 12 metres and a diameter of about 1 metre, which rotor has a maximum sag of less than 2 mm. The rings of the rotor usually consist of steel and the angle sections of stainless steel. In order to prevent temperature stresses from occuring in the rotor on increasing the temperature as a consequence of differences in the coefficient of expansion between the rings and the angle sections of the rotor and the pipe-like bracing elements, the pipes consist of two parts, specifically a part 18 of stainless steel and a part 19 of steel, the lengths of the two parts being such that the mean coefficient of expansion of each pipe is equal to the mean coefficient of expansion of the rings 7, 8, 8′, 8″, 9 and the angle sections of the rotor. Thus, no additional tensions are introduced in the rotor in the event of temperature changes. Due to the greater torsional stiffness of the rotor it is sufficient to drive the rotor only at one end by means of the shaft 3. With the above-described construction of the rotor a greater dimensional stability is thus achieved both in relation to sagging and to torsion of the rotor both under mechanical loading and in the case of temperature variations.

Claims: 1. A device for sterilizing products packed in cylindrical containers, comprising an elongate, essentially cylindrical housing (1) and an essentially cylindrical rotor (2) located therein which can be driven via a central shaft (3), the circumferential wall (4) of the housing (2) being provided on the inside with a helically running, raised rib (5) and the rotor (3) being designed as a cage consisting of a number of rings (7, 8, 8′, 8″, 9) placed behind each other, the centre line of which coincides with the axis (10) of the rotor, and a number of raised ribs (11) fastened to the circumference of the rings (7, 8, 8′, 8″, 9) parallel to the axis (10) of the rotor, the outer edge (13) of which ribs is located near the inner edge (14) of the helically running rib (5) on the inner wall of the housing (1) so that spaces are formed between the ribs for receiving the cylindrical containers (15), and bracing elements (16) which are at an angle relative to the rotor shaft (3) being provided within the rotor (2) between neighbouring rings to reinforce the rotor, characterized in that the bracing elements (16) consist of pipes. 2. A device as claimed in Claim 1, characterized in that each pipe (16) consists of parts (18, 19) made of different materials, in a ratio such that the mean coefficient of expansion of the pipes (16) is equal to the mean coefficient of expansion of the rings and the ribs of the rotor (2). 3. A device as claimed in Claim 2, characterized in that the rings (7, 8, 8′, 8″, 9) of the rotor (2) consist of steel and the ribs of stainless steel, and that each pipe (16) consists partly of steel and partly of stainless steel. 4. A rotor for a device as claimed in any one of the Claims 1-3.

Inventors: MOELLENKAMP, DANIEL LAMBERTUS, Möllenkamp, Daniel Lambertus
Applicants: STORK AMSTERDAM B.V.
Application year: 1988
Main classification: A23L3
IPC codes: A23L3, A61L2