The present invention relates to a conveyor compris¬ ing an endless conveyor belt which along part of its length follows a path consisting of a number of helically extending turns laid upon each other, and a supporting in stallation consisting of two endless chains which are car ried by supports and support the lowermost of the helical ly extending belt turns by supporting the belt edge por- tions along said turn.

Conveyors of this type are disclosed in for example SE-C-7303179-1 and SE-C-8206760-4. The actual conveyor belt consists of link means which are mutually articulate and displaceable relative to each other. Each link means consists of a bottom part and spacing members fitted at the side edges of the bottom part and constituting the tw sides of the belt.

The supporting installation used in the conveyor can be of the type disclosed in SE-C-8206759-6. This support- ing installation can support a belt pile throughout a con tinuous revolution, since it is positioned substantially outside and, respectively, inside the circumferential sur faces of the belt pile and since each of its chains and the associated support rail are not higher than the heigh of the belt, i.e. the height of the spacing members. The described conveyor is conveniently used in a freezing plant, the belt pile being accommodated in a sub stantially closed container or the like which also holds refrigerating machine adapted to blow cooling air axially through the belt pile.

The freezing capacity of such a freezing plant is, o course, dependent on the cooling capacity of the refrige¬ rating machine, but the product of the maximum speed of the belt and its load capacity per unit of length sets an upper limit to the freezing capacity. This means that the freezing plant is poorly used when freezing easily frozen products, since the entire cooling capacity of the refri-

gerating machine then cannot be used efficiently. If the belt thus travels at ist maximum speed and the entire' cooling capacity of the refrigerating machine is used, th products will be frozen long before they have passed through the freezing plant. A conveyor belt of smaller length inside the container, for example fewer turns in the belt pile, would then be sufficient, but such a lower belt pile restricts the capacity when freezing products which are difficult to freeze. A first object of the present invention is to provid a conveyor of the type mentioned by way of introduction which renders it possible to fully utilise the capacity o the refrigerating machine in a freezing plant, indepen¬ dently of whether the products which are to be frozen, a easy or difficult to freeze;

A second object of the invention is to achieve such an improvement without necessitating an increased space for the freezing plant.

According to the present invention, these objects a achieved through the arrangement of a second endless con veyor belt which is of substantially the same shape as t first-mentioned conveyor belt and along part of its leng follows a path consisting of a number of helically ex¬ tending turns laid upon each other and alternating with the turns of the first-mentioned conveyor belt, each tur of one of the conveyor belts, except the lowermost turn the firs -mentioned conveyor belt, being supported by an underlying turn of the other conveyor belt, and vice versa, via spacing members arranged adjacent the belt edges, such that a self-supporting belt pile is formed o the helically extending turns of the two conveyor belts.

By arranging double conveyor belts in a self-suppor ing belt pile, which involves considerable difficulties, one obtains the advantage of a doubled freezing capacity for easily frozen products and a maintained freezing ca¬ pacity for products that are difficult to freeze.

To make the belt pile with double conveyor belts pos sible, the endless chains have, in their run along the lowermost of the helically extending turns of the first- mentioned conveyor belt, a rise corresponding to the tota height of the two conveyor belts, and moreover at least the inner chain supports the first-mentioned conveyor bel in the run of said chain up to the beginning of the lower most turn, with a second, bigger rise than along the same turn. According to the invention, there is further arrange a fixed supporting installation for carrying the second conveyor belt in the run thereof over the beginning of th lowermost turn of the first-mentioned conveyor belt, said fixed supporting installation giving the second conveyor belt a third rise which is smaller than the second rise. As a result, the second conveyor belt is supported by the first-mentioned conveyor belt not later than at the be¬ ginning of the lowermost turn thereof and from now on moves together with the first-mentioned conveyor belt as unit.

The fixed supporting installation preferably is self supporting at its end adjacent the beginning of the lower most turn of the first-mentioned conveyor belt and can conveniently comprise two parallel bars arranged at a distance from one another which is smaller than the dis¬ tance between the spacing members of the second conveyor belt.

The fact that the second conveyor belt is of substan tially the same shape as the first-mentioned conveyor bel means that the two conveyor belts are identical, possibly with the exception of the height of the spacing members.

Finally, the runs of the two conveyor belts up to th belt pile can preferably form an angle with each other in the horizontal plane. This facilitates the loading of pro ducts on to the two conveyor belts.

In the same manner, the runs of the two conveyor belts out of the belt pile suitably form an angle with each other in the horizontal plane, whereby a simple, separate unloading of products from the two conveyor belt is made possible.

The invention will now be described in detail with reference to the accompanying drawings in which:

Fig. 1 is a perspective view of a known conveyor having a single conveyor belt according to prior art technique;

Fig. 2 is a schematic perspective view of the sup¬ porting installation and the feeding of two conveyor belt to the lowermost turn in a belt pile according to the in¬ vention; Fig. 3 is a cross-sectional view along line III-III in Fig. 2;

Fig. 4 is a schematic top plan view of a conveyor a cording to the invention in a freezing plant;

Fig. 5 is a front view of the feeding side of the freezing plant in Fig. 4; and

Fig. 6 is a rear view of the discharge side of the freezing plant in Fig. 4.

The prior art conveyor shown in Fig. 1 comprises a conveyor belt 1 which is adapted to follow, along part o its length, a path consisting of a number of helically e tending turns laid above each other in a pile 2. The con veyor belt 1 is endless and extends from the upper end o the pile in a path 3 outside the pile 2 to the lower end thereof. However, the turning direction of the pile 2 is optional, and the belt can thus leave the pile 2 either the upper end or at the lower end.

To be able to move helically, as shown in Fig. 1, t belt 1 comprises, in per se known manner, a plurality of link means 4 (Fig. 3). The link means extend in the late ral direction of the belt 1 and are horizontally displac able relative to each other in the longitudinal directio of the belt, such that the belt is turnable in the later

direction. They are also vertically pivotable relative to each other about an axis parallel to the lateral direc¬ tion. Thus the belt can follow an endless path as shown i Fig. 1, i.e. with straight portions and with curved por- tions through vertical and horizontal curves. The actual piling is possible in that each link means 4 consists of staff-like members 5 (Fig. 3) which are included in the bottom part of the belt 1 and at the ends of which uprigh links 6 are fitted. The links 6 which form the sides of the belt 1, constitute spacing members which are adapted to bear with their upper edge portions 7 against the lowe edge portions of the spacing members of the overlying tur and thus carry the overlying belt turn (Fig. 1).

The pile 2 of the superposed, helically extending turns of the endless conveyor belt 1 is carried by a sup¬ porting installation. This comprises, as shown in Fig. 1, two endless chains 8 and 9 which are arranged under the lowermost turn of the belt pile 2, support the two side edge portions of the belt 1 and are themselves carried by supports. Each of the chains 8 and 9 is adapted to follow the belt 1 in the rise through at least one complete revo¬ lution. Then the chains 8 and 9 travel in a direction op¬ posite the rise of the conveyor belt 1 in a return run 10 and 11, respectively, beside the belt pile 2 so as to form an endless chain. The chain 8 follows the return run 10 which is narrower than the pile 2 and positioned outside the belt pile 2, while the chain 9 follows the return run 11 which is positioned inside the belt pile 2 and which is also narrower than the belt pile 2. At the beginning of the return run 10, the chain 8 is driven by a motor 12 and in turn drives the supported con¬ veyor belt 1. Also the chain 9 can be driven by a second motor 13.

As shown in Fig. 3, each chain 8, 9 consists of links 14 and 15 overlapping each other. The links 14 are outer links and overlap the links 15 which are inner links. The links 14, 15 are interconnected by spindles 16 on which

further a link roller 17 is rotatably mounted between the links 14, 15 and a lower chain bar 18 of substantially th same length as the inner link 15. Each inner link 15 ex¬ tends along a support rail 19 and has a downwardly de- fleeted edge portion .20 with a bending radius which sub¬ stantially conforms to the radius of balls 21 which serve as rolling elements between the rail 19 and the chain 8 and 9, respectively. The rail 19 has a roll race 22 which extends opposite the downwardly deflected side edge por- tion 20 of the inner link 15 and on which the balls 21 roll, while transferring the load of the belt pile 2 to the support 19. The rail 19 is supported by brackets 23 o cross bars 24 which are fixedly mounted in uprights 25. The supporting installation is described in detail in SE- A-8603202-6.

According to the present invention, the belt pile 2 is formed of the conveyor belt 1 and of a second conveyor belt 1' , as shown in detail in Figs. 2 and 3. The convey belt 1 has in its run towards the lowermost turn in the belt pile 2 a first portion la which follows a substan¬ tially horizontal path, and a second portion lb which fol lows a path having a rise which is bigger than the rise the chains 8, 9 along the lowermost turn of the belt 1 i the belt pile 2. The latter rise corresponds to the tota height of the two conveyor belts 1, 1'. The portion lb o the conveyor belt 1 is at its inner edge carried by the chain 9, while the outer edge of the portion lb is car¬ ried by a fixed support which is not shown.

In its run towards the belt pile, the second convey belt 1' has an outer portion 1'a which follows a substan tially horizontal path, and an inner portion l'b having rise which is smaller than the rise of the portion lb of the conveyor belt 1. As a result, the conveyor belt 1' rests against the conveyor belt 1 so as to be supported the links 6 thereof, as shown in the upper part of Fig.

The second conveyor belt 1 ' rests against the con¬ veyor belt 1 at a point before a radius 26 in the lower¬ most belt turn. From the radius 26, the conveyor belt is carried by the chains 8 and 9 through at least one turn. For carrying the second conveyor belt 1 ' up to the point where it is carried by the conveyor belt 1, there is ar¬ ranged a fixed supporting installation which thus support the second conveyor belt 1 ' along the portions 1 'a and l'b. This supporting installation consists more precisely of two parallel bars 27, 28 whose top face has a coating of a material with a low friction coefficient and which are supported by cross bars 29 fixedly mounted in the up¬ rights 25. The bars 27, 28 are, however, self-supporting at their ends adjacent the beginning of the lowermost tur of the conveyor belt 1, i.e. the position in. which the se cond conveyor belt 1 ' comes into engagement with the con¬ veyor belt 1.

As shown in Fig. 2, the conveyor belt 1 and the con¬ veyor belt 1' are supplied at different angles towards th belt pile 2. As a result, the loading stations of the con veyor belts 1, 1', which are positioned in the extension of the portions la, l'a, are separated, which of course facilitates the loading of products.

The use of the inventive conveyor in a freezing plan is shown schematically in Figs. 4-6. As appears from

Fig. 4, the belt pile 2 is accommodated in a container 30 whose short sides is provided with doors 31 for entering the interior of the container 30, and openings for intro¬ ducing the belts 1, 1' from loading stations 32, 32' into the container 30 and for discharging the belts 1, 1' to emptying stations 33, 33'. The container ^' 30 holds a re¬ frigerating machine (not shown) which is adapted to blow cooling air axially through the belt pile 2. As shown in Fig. 4, the runs of the two conveyor belts 1, 1' up to th belt pile 2 form an angle with each other in the horizon¬ tal plane. This also applies to the runs of the conveyor

belts 1, 1' out of the belt pile 2 to the emptying sta¬ tions 33, 33 ' .

In the embodiment shown in Figs. 4-6, the loading stations 32, 32' are positioned on different levels, and this also applies to the emptying stations 33, 33'.

A variety of modifications of the conveyor described above are possible within the scope of the invention as defined in the appended claims.