As examples of articles sterilised in the manner indicated above in autoclaves utilising circulating hot water may be mentioned plastic bags containing nutrient solutions, plasma and other liquids given to hospital patients via intravenous drip. The plastic bags are placed in a number of rows on each shelf of the assembly, whereafter the entire shelf assembly is moved into an autoclave, which is then closed. It has been found, however, that the arrangement involving spraying the hot water from the top of the shelf assembly downwards through the shelves causes the water to be distributed unevenly, i. e. the plastic packages placed on the uppermost shelf receive the largest amount of water whereas the plastic packages placed on the shelves underneath are showered with progressively smaller amounts of water, since from the uppermost shelf part of the water flows laterally of or in between the packages on the lower shelves. This phenomenon occurs even though the shelves are perforated.

The above-mentioned phenomenon is highly unfavour- able. By necessity, the autoclaving process has to continue for too long in order to ensure that also the packages on the lowermost shelves are sterilised. Owing to the nature of the package contents mentioned above,

they are temperature-sensitive, one serious consequence of which may be that the packages on the upper shelves run the risk of being spoiled due to having been exposed to the sterilisation process for too long.

One prior attempt to solve the problem of obtaining even distribution of the hot water that is sprinkled over the plastic packages involves changing the pattern in which the packages are placed on the shelves, by arrang- ing them in a staggered manner such that a package on. one shelf is positioned between two packages on the shelf immediately above and two packages on the shelf imme- diately below, and so on, with corresponding staggered package distribution upwards and downwards. An advantage with this manner of positioning the packages is that the water flowing downwards, in-between two packages falls down onto the middle of the package positioned between said packages on the shelf below.

At the same time this arrangment suffers from several serious drawbacks. The capacity of the shelf assembly, for instance, is poorly utilised, with the result that a larger number of autoclaves may be required than would have been necessary, had each shelf been allowed to support a maximum number of packages. This is bad economy.

Another disadvantage has bearing on the step of loading the packages into the shelf assembly prior to the autoclaving process proper. Usually the loading step is effected by means of a robot which, when placing the packages on the shelves, follows a certain, comparatively simple pattern of movements. This pattern of movements becomes complicated, should it be necessary to place the packages in one shelf in a pattern that differs from that of the following shelf.

It is likewise possible to provide nozzles on either side of the shelf assembly inside the autoclave. However, this is not either a satisfactory solution to the steri- lisation problem and it is particularly disadvantageous

for the reason that such laterally positioned nozzles obstruct the path of movement of the shelf assemblies as the latter are moved into or out of the autoclave and thus, in the case of impacts, they may easily be damaged or may themselves cause damage to packages in the shelf assembly.

The present invention provides a shelf assembly by means of which the sterilisation process may be optimised because it allows the best possible distribution of the hot water uniformly across each and every package, also when the shelf assembly contains the maximum number of packages. The characteristic features of the invention appear from the appended claims.

The invention will be described in more detail in the following with reference to the accompanying drawings, wherein Fig 1 is a perspective view of one shelf unit of a shelf assembly with parts broken away, and Fig 2 is a vertical sectional view through an auto- clave and a shelf assembly supporting packages, during the progress of a sterilisation process.

The shelf assembly in accordance with the invention is constructed from shelves 1,2,3 and so one, usually in the number of 15-20 shelves. The primary characteris- tic feature of the invention is the subdivision of each one of said shelves into two shelf layers, one upper layer la, 2a, 3a and so on, and one lower layer lb, 2b, 3b, and so on. The shelves 1,2,3 are stacked one on top of the other and they are maintained in their spaced- apart relationship by means of insert spacer pins 4, said pins also preventing relative lateral movements of the shelves. Each upper layer la, 2a and 3a, and so on consists of a plate formed with perforated zones 5 and with openings 6 positioned between said perforated zones.

Packages 7 to be sterilised are intended to be placed on top of the perforated zones 5.

In a corresponding manner each lower layer lb, 2b, 3b, and so on, consists of a plate formed with perforated zones 8, which are positioned below their respective perforated zones 5 in the upper shelf layer la, 2a, 3a, and so on. The lower layers lb, 2b, 3b, and so on are <BR> <BR> <BR> <BR> formed with impervious zones 9, which are located between the perforated zones 8 and below and vertically aligned with the openings 6 formed in the respective upper layers la, 2a, 3a, and so on.

Along one of its sides, or as shown in Fig 1 along two opposite sides, each lower layer lb, 2b, 3b, and so on merges with a wall 10 in which is formed a number of drainage holes 11 serving as a spillway means.

Fig 2 illustrates the shelf assembly in accordance with the invention when positioned inside an autoclave 12 during a sterilising process. Hot water passes through a perforated sheet-metal plate 13 positioned underneath the cover of the autoclave and further downwards onto the packages 7 positioned on the uppermost shelf layer la.

The water flows off the packages 7 and downwards through the openings 6 on either side of the packages. The holes in the perforated zones 5 are comparatively small and are intended primarily to prevent the formation of air pockets underneath the packages 7. The water flows further downwards onto and across the lower shelf layer lb, across which it spreads and trickles through the holes formed in the perforated zones 8 of the lower shelf layer lb, onto the packages 7 positioned on the shelf layer 2a immediately below. The impervious zones 9 prevent the water from flowing linearly downwards, between and past the latter packages 7. The process is repeated from one shelf to the next, with the result that all layers of packages 7 will be showered by essentially identical amounts of hot water. In this manner, the sterilising process will be effected to the same extent simultaneously throughout the entire shelf assembly, and consequently the process may be performed in the shortest

possible time while at the same time ensuring that no package contents will be exposed to prolonged steri- lisation that may cause them to be spoiled.

The purpose of the drainage apertures 11 is to handle water that for some reason or other has collected on top of the lower layer lb, 2b, 3b, and so on, for example on account of too large amounts of water passing through the plate 13 or because of clogging of the holes in the perforated zones 8.

The invention is not limited to the features shown and described herein but may be varied in several ways within the scope of the appended claims. This is true for example both with respect to the spacing between two layers and to the spacing between two shelves of the shelf assembly.

It should be emphasised that the shelf assembly is well suited for its intended purpose also when it comes to the cooling process that succeeds the sterilising process, during which instead of hot water cooling water is made to pass through the plate 13 downwards onto the packages 7, from one shelf to the next of the shelf assembly.