AN APPARATUS FOR COOLING AND STRIPPING OBJECTS CAST IN SAND MOULDS

Abstract: In an apparatus for cooling and stripping of objects cast in and contained in sand moulds, said apparatus being of the kind comprising a drum (1) supported for rotation about a substantially horizontal axis (0) with at least two rolling surfaces or rolling surface members (2) shaped on or secured to the drum (1) bearing on at least four support wheels (3), of which at least one is adapted to be driven and thus make the drum (1) rotate, said support wheels (3) at least partially consisting of an elastomeric material, the new feature consists in that each support wheel (3) consists of a single substan­ tially circularly-cylindrical rim (56) of rigid material, such as steel, about which there are placed at least three rolling tyres (55) of elastomeric material, the axial width of which diminishes with increasing radius. This arrangement makes it possible to reduce maintenance costs and to achieve a highly desired sound and shock absorption using relatively low-costs means.

Description: The present invention relates to an apparatus for cooling and stripping cast objects, said apparatus being of the kind set forth in the preamble of claim 1. An apparatus of this kind is known from the European patent specifications No. 0 066 931. In this specification, it is not specified in detail how the support rollers are to be constructed in order to achieve the desired reduction in maintenance and the desired noise and shock absorption characteristics, but the specification does include the possibility of thermally insulating the annular rolling surfaces with respect to the drum jacket with a view to prolonging the lifetime of the synthetic resin rollers. On this background it is the object of the present invention to provide an apparatus of the kind referred to initially, with which the desired reduction in maintenance and the desired sound and shock absorption may be achieved with simple means without the necessity of providing a costly and in many cases highly inconvenient thermal insulation of the rolling surfaces, and this object is achieved in an apparatus also exhibiting the features set forth in the characterizing clause of claim 1. The construction of each support wheel in the form of a single, circular-cylindrical rim provides a simple and hence economical construction, and by equipping this rim with at least three rolling tyres with radially outward diminishing width in the axial direction, a uniform distribution of the support pressure between the rolling surface member and each support wheel is achieved, as a space is formed between adjacent rolling tyres, in which each tyre may expand in the axial direction when subjected to the support pressure from the rolling surface member. In the opposite case - i.e. if the resilient part of the support wheel were shaped in one piece - the material close to the center would experience a higher resistance against axial expansion than material close to the flanks, for which reason the support pressure per unit area would be greatest at the center of the support wheel. Due to the interspaces, the area of the rolling tyres is increased, which causes an improved cooling and hence a longer lifetime for the rolling tyres, normally consisting of organic material, such as synthetic rubber or an elastomeric synthetic resin, for which reason a thermal insulation of the rolling surfaces will normally be unnecessary. In the apparatus known from the above-mentioned European patent specification No. 0 066 931, each rolling surface member comprises a rolling track termed "rolling surface" secured to the outer periphery of two continuous and substantially plane annular plates, the inner periphery of which is secured to the drum, whereas their outer peripheral edges are secured to the edges of said rolling tracks. Seen in axial section, the rolling track in such an arrangement corresponds to a beam being resiliently secured at the ends, and which hence exhibits a not insignificant deflection under load. In large drums with wider rolling tracks, critical bending stresses with imminent danger of fatigue fracture may occur. With the embodiment set forth in claim 2, in which the rolling track corresponds to a beam supported at points distant from the ends, a not insubstantial reduction of both this deflection and the bending stresses is achieved, and hence also a more uniform distribution of the pressure between the rolling surface member and the support wheels, on which it rests and by which it is driven, so that the advantages referred to above that may be achieved with the new features according to claim 1 may be fully exploited. The invention will explained in more detail with reference to the drawing, in which Figure 1 is a perspective view of an exemplary embodiment of an apparatus according to the invention, Figure 2 is a section along the line II-II in Figure 1, Figure 3 is a section along the line III-III in Figure 1, and Figure 4 is a section along the line IV-IV in Figure 1. The apparatus shown in the drawing mainly comprises a drum 1, the forward part 1a of which is cylindrical and the rearward part 1b of which tapers towards the rear. Concentrically with the drum two rolling rings 2 are arranged, the construction of which is explained in more detail below. The rolling rings are bearing on support wheels 3, each being driven by a motor 4 with a gearbox 5. The drive is such that the drum rotates in the direction of the arrow P1. The support wheels 3 are journalled in foundation beams 6 bearing on a floor 7. The floor has a recess to accommodate a conveyor belt 8, the upper run of which moves in the direction of the arrow P2. At the forward end the drum 1 has an inlet opening 9, around which is disposed a suction box 10. Suction is caused by a suction device 11. Products P to be processed are fed from a conveyor belt 12, the upper run of which moves in the direction of the arrow P3. Placed at the outlet opening of the drum is a delivery conveyor 13, the upper run of which moves in the direction of the arrow P4. The end portion of the drum 1 is construction in the form of a sieve wall 14. Fig. 2 shows how the mass centre M of the load consisting of mould sand and castings is placed to the left of the vertical plane V-V. This placing of the mass centre M produces a turning moment about the axis of rotation O of the drum 1. This turning moment is taken up by the tangential forces from the support wheels 3. The sum of the tangential forces have a not insignificant horizontal component. The sum of the radial forces from the wheels have a horizontal component equal and opposite to the horizontal component from the tangential forces. Placing the left support wheels 3 further to the left of the axis O produces a load distribution on the wheels that reduces the wear on the support wheels 3, compared to what would have been the case with a symmetrical arrangement. As shown in Fig. 4 each support wheel 3 is composed of three rolling tyres 55 of resilient material, such as a synthetic resin, i.e. polyurethane, said tyres being placed around a circular-cylindrical rim 56 with a smooth cylindrical outer surface. The axial width of the three rolling tyres 55 diminishes slightly radially outward, for which reason they can carry radial compression forces in a substantially uniform manner, so that local load concentrations are avoided. As the load on each support wheel may become as high as 20 tons, it is important to avoid such load concentrations, as these could otherwise damage the rolling tyres. To the axle of each support wheel is fastened in a freely rotatable manner a gearbox 5 with a coupled motor 4. To the gearbox 5 is fastened a reaction arm 16 to the end of which is pivoted a buffer 17. The buffer 17 bears on the foundation beam 6. For axially locking the drum guide wheels 18 are rotatably supported in the foundation beam 6 on each side of the rolling ring 2. Fig. 3 shows a rolling ring 2 consisting of a relatively thick rolling track 57, which is secured to radially extending annular plates 58. The plates 58 are locally secured to the drum 1 at 33, vide Fig. 2. On the edges facing away from the drum 1 the plates 58 are connected to the rolling track 57 at distances 59 from the edges 60 of the rolling track 57 in such a manner that the ratio between each distance 59 and the axial width 61 of the rolling track 57 is approximately 1:6. This arrangement reduces the load stresses in the rolling track 57 to a minimum. Together with the use of the three (or more) rolling tyres 55 to cover the rims 56 of the support wheels, this makes it possible to produce the rolling track 57 from relatively low-cost material, i.e. conventional sheet steel. no special machining being required. Spray means 54 may be placed within the drum 1 for spraying the loose sand being produced when the sand moulds are tumbled in the drum 1 during its rotation. As may be seen from the Figs. 1 and 2, the two foundation beams 6 are constructed substantially in the same manner and each has two support wheels, each with its own drive motor 4 and associated gearbox 5. Hence in cases where it is found necessary to keep spare foundation beams ready for use, it is sufficient to have a single foundation beam as a spare. If also the drive assemblies each consisting of a support wheel 3, a drive motor 4 and a gearbox 5, are of uniform construction, it is sufficient to keep one single drive assembly as a spare.

Claims: 1. An apparatus for cooling and stripping of objects cast in and contained in sand moulds, said apparatus being of the kind comprising a drum (1) supported for rotation about a substantially horizontal axis (O) with at least two rolling surfaces or rolling surface members (2) shaped on or secured to the drum (1) bearing on at least four support wheels (3), of which at least one is adapted to be driven and thus make the drum (1) rotate, said support wheels (3) at least partially consisting of an elastomeric material, characterized in that each support wheel (3) consists of a single substantially circularly-cylindrical rim ( 56) of rigid material, such as steel, about which there are placed at least three rolling tyres (55) of elastomeric material, the axial width of which diminishes with increasing radius. 2. An apparatus according to claim 1 and of the kind in which each rolling surface member (2) comprises a rolling track (57) secured to the outer periphery of two continuous and substantially plane support rings (58), the inner peripheries of which are secured to the drum (1), characterized in that the support rings (58) are secured to the radially inward facing surfaces of the rolling tracks (57) at a distance (59) from the edges (60) of the rolling tracks, said distance corresponding to approximately 1/6 of the axial width (61) of the rolling tracks (57).

Inventors: CHRISTIANSEN, HANS CHRISTIAN
Applicants: DANSK INDUSTRI SYNDIKAT A/S
Application year: 1989
Main classification: B22C5
IPC codes: B22C5, B22D31