Claims:
We claim
1. A cooling bed for cooling billets, comprising:
2. A cooling bed as claimed in claim 1, wherein the means for moving the movable rack substantially vertically upwards and for moving the movable rack downwards moves the movable rack substantially vertically downwards.
3. A cooling bed as claimed in claim 1, wherein adjacent portions of the upstream and downstream flanks of adjacent teeth of the movable rack are inclined to one another at an angle of substantially 90° at the base of the flanks, at least the lower portion of the upstream flank extending parallel to the corresponding flank of a tooth of the fixed rack and at least the upper portion of the downstream flank, which upper portion terminates at the tip of the respective tooth, extending parallel to the corresponding flank of a tooth of the fixed rack.
4. A cooling bed as claimed in claim 1, and including means for moving the movable rack generally horizontally through a distance substantially equal to one tooth pitch of the fixed rack, prior to the next substantially vertical upwardly movement of the movable rack.
5. A cooling bed as claimed in claim 1, wherein adjacent portions of the upstream and downstream flanks of adjacent teeth of the movable rack are inclined to one another at an angle of substantially 90° at the base of the flanks, the upstream flank being divided into two portions, a lower portion extending parallel to the corresponding flank of a tooth of the fixed rack and an upper portion extending approximately vertically, which upper portion terminates at the tip of the respective tooth, and the downstream flank being divided into two portions, an upper portion, which terminates at the tip of the respective tooth, extending parallel to the corresponding flank of a tooth of the fixed rack, and a lower portion being inclined downwardly at a greater angle to the horizontal than the upper portion.
6. A cooling bed as claimed in claim 1, wherein the racks are formed such that the billets are displaced by vertical movement only of the movable rack.
Description:
The invention relates to a cooling bed for billets, the cooling bed comprising toothed racks for supporting and conveying billets. At least one of the racks is fixed and at least one of the racks is movable and arranged so that in conveying the billets rotate about their longitudinal axis which extends substantially perpendicular to the direction of conveying.
A previous cooling bed comprised two conveyor racks which were caused to move vertically relatively to each other; each of the racks had teeth provided with hollows or recesses adjacent the tips and the bases of the teeth to hold the slabs or billets. The edges of the billets are held in these recesses during transport, so that the center of gravity of the billets only undergoes a slight vertical movement. Each rack unit had to be provided with its own vertical drive system. Since each unit must be able to carry the billets alone, each must be provided with a necessary minimum number of racks. This all results in high construction costs.
Furthermore, a rack-type cooling bed having a fixed and a movable rack unit has been used; the movable rack unit is conveyed on a closed track. In order to prevent billets sliding on the surfaces of the teeth, and at the same time to cause them to carry out a partial rotation at each transfer movement, the teeth surfaces on the movable rack(s) are made steeper than those of the fixed rack(s). In this cooling bed too, the whole weight of the billets has from time to time to be borne by the moving racks, so that a number of racks has to be provided to ensure sufficient support. In order to cause the billet to rotate through 90°, the moving racks need to perform two lifting movements.
The terms "upstream" and "downstream" as used herein relate to the direction of travel of the billets on the cooling bed. Thus the upstream flank of a tooth is that flank facing towards the inlet end of the cooling bed and the downstream flank of a tooth is that flank facing towards the discharge end of the cooling bed; likewise an upstream tooth is nearer the inlet end of the cooling bed than a downstream tooth.
According to the present invention, there is provided a cooling bed for billets comprising a movable and a fixed rack, each rack having teeth for engaging a billet, the pitch of the teeth on the movable rack being not less than the pitch of the teeth on the fixed rack, and the movable rack being arranged to engage a billet supported on the fixed rack between first and second teeth of the fixed rack, and to displace the billet to cause the billet to pivot about the tip of the second tooth and move between the second tooth and a third tooth, the billet being at least partially supported by the fixed rack throughout the operation.
The invention can provide a rack-type cooling bed having fixed and movable supporting racks, in which a large proportion of the weight of the billets is continuously borne by the fixed racks. This can largely prevent billets sliding on the flanks or surfaces of the teeth.
The billets are thus tilted over the tips of the fixed racks and the movable racks can be designed to bear only a maximum of half the weight of the billets. This can reduce the number of movable racks required compared with a cooling bed in which the movable racks have to be able to withstand the full weight of the billets, even though only briefly. A further advantage of the invention can be that the movement of the billets in their longitudinal directions, which occurs in the case of a jolting rack conveyor, can be avoided.
Preferably, the pitch of the teeth in the movable rack is double the pitch of the teeth in the fixed rack.
The movable racks can be arranged so that the billets are displaced by vertical movement only of the movable rack.
Preferably, the angle between adjacent surfaces of adjacent teeth in the fixed rack is not less than 90°.
In one embodiment of the invention, when the pitch of the teeth in the movable rack is double that in the fixed rack, two movable racks can be used, the movable racks being 180° out of phase with each other i.e., shifted relatively to each other by the pitch of the fixed rack; billets are moved by alternating upward strokes of these two movable racks.
In another embodiment, the number of movable racks can be reduced, as all the movable racks are arranged in phase, and are connected to operating means such that the billets are advanced over one tooth of the fixed rack by one upward movement of the movable rack, and the movable racks are lowered and shifted horizontally through 180° (i.e., the pitch of the teeth in the fixed rack) so that a further upward movement of the movable racks further advances the billets.
The flanks of the teeth in the movable rack preferably meet at an angle of 90° at the bases of the teeth when billets of rectangular cross section are to be conveyed; preferably at least the lower portions of the flanks of the teeth arranged to receive the downstream sides of the billets (i.e., the lower portions of the upstream flanks of the teeth) extend parallel to the corresponding flanks of the teeth of the fixed rack, the upper portions of these flanks of the teeth of the movable racks preferably extending approximately vertically. At least the upper portions of the flanks of the teeth of the movable rack which face in the opposite direction (i.e., the upper portions of the downstream flanks) may extend parallel to the corresponding flanks of the teeth of the fixed rack. This arrangement can ensure that during the last phase of the lifting movement, the billets are tipped forward on to the next tooth, so that it is impossible for the billet to be tipped backwards when it is next gripped from below by the movable racks. The racks may be made suitable for use with billets of a different thickness by providing both the fixed and movable racks with a number of sets of teeth suitable for different billet widths which may be brought into working position as required. It is particularly advantageous for a number of sets of rack teeth to be arranged on a shaft associated with a pivot drive.
The invention will be further described, by way of example, with reference to the accompanying drawings, of which:
FIG. 1 is a cooling bed having a fixed and a movable rack unit;
FIG. 2 is a cross-sectional view of the cooling bed shown in FIG. 1; and
FIGS. 3 to 6 are various stages of the tipping or conveying process.
A cooling bed for billets 1 is composed of a system of fixed racks 2, which are connected to a base 5 of the bed by means of crossbeams 3 and vertical supports 4, and a system of movable racks 6. The movable racks are grouped in threes on longitudinal members 7 which abut on the base 5 through elbow levers 8a, 8b and 9a, 9b. The elbow levers 8a, 8b and 9a, 9b are connected together through joints 10, 11, distancing members 12 ensuring that they are held in a parallel position permanently. The joints 11 are connected by means of hydraulic cylinders 13 to pistons 14 and piston rods 15. Alternating actuation of the piston 14 may then produce a vertical movement of the racks 6.
The billets 1 are transferred from a chute 18 to the cooling bed by means of elbow levers 8b acting through rods 16 on offtake segments 17 and drop crossways on in the gaps between the teeth on the fixed racks. The flanks or teeth surfaces 19 of the teeth in the fixed racks 1 form an angle of more than 90°. The pitch of the teeth in the movable racks 6 is double that of the teeth in the fixed racks 1.
In order to cause the billets 1 to be tipped and conveyed forward, the pistons 14 of the cylinders 13 are actuated towards the outside, causing the elbow levers 8a, 8b and 9a, 9b to be straightened and the movable racks 6 to be raised. The teeth 20 of the movable racks 6 then grip below the lower edge of the billets 1 (FIG. 3) and tip it over the tips 21 of the teeth on the fixed racks (FIG. 4) into the next trough (FIG. 5).
In order to prevent the billet 1 being tipped backwards at the next movement of the movable racks 6, the downstream flanks 22 of the teeth on the movable racks 6 merge into a steeper lower portion 23 which forms an angle of 90° with the following (upstream) tooth flank 24. By further raising the movable racks, the billets are thus tipped forwards to the following tooth flank 25 of a tooth in the fixed rack, their center of gravity thus being shifted forward in the direction of transport (FIG. 6). The flanks 24 of the teeth on the movable racks 6 merge near the tip of the teeth into a vertically extending portion 26.
In order to further convey the billets, the movable racks 6 are designed to be able to slide horizontally in a lowered position for a distance equal to the pitch of the teeth of the fixed racks 2. This is made possible by the provision of a double-acting hydraulic cylinder 27, the piston rods 28 of which engage the upper point of articulation 29 of the levers 8a .
Offtake segments 31, actuated through rods 30 by the levers 8b , are provided at the output end of the cooling bed and serve to transfer the billets, which have cooled down uniformly, on to a conveyor 32.