Distributor device for a filling shoe for compression moulding

#The present invention relates in one aspect to a filling shoe for filling a mould cavity of a powder compression die. More particularly, the present invention relates in one aspect to a distributor device for use in a filling shoe for filling a mould cavity of a powder compression die. According to a further aspect, the invention relates to a method of filling a mould cavity of a powder compression apparatus using a filling shoe.

#Powder forming processes, such as powder metallurgy, typically involve a compression moulding step, where a powder is filled into a die cavity and subsequently compacted under high pressure. The compression moulding step may be followed by a further heat treatment to produce the finished part. Such powder metallurgy processes may, for example, be used for producing magnetic core components for electrical machines, such as motors or generators and structural parts, such as for combustion engines. The finished components are usually subject to very high precision requirements regarding the tolerances for e.g. dimensions, planarity and density distribution within the finished component.

#An even filling of the die cavity with powder during the compression moulding step plays a critical role for achieving such a high precision. Besides for the precision of the geometric dimensions and for the density distribution, a uniform distribution of the powder in the mould die during the filling step is particularly important for the production of large thin parts in order to prevent warping deformation during the heat treatment of the compacted green part. When producing magnetic items, the magnetic properties of the finished part may also be affected by an inhomogeneous distribution of the powder in the mould during the filling step. Other problems arising from a non-uniform distribution of the powder in the mould, due to an uneven filling during the filling step may include an increased risk of mechanical damage to the powder compaction tool during the compression step.

#Preferred embodiments of the invention will be described in more detail in connection with the appended drawings, which show schematically in

#FIG. 1 a cross-sectional side view of a powder compression apparatus with a filling shoe including a distributor device according to one embodiment,

#FIGS. 2A-2C a distributor device according to a first embodiment in a top view (A), a side view (B), and an end view (C) as seen from the outlet end,

#FIG. 1 shows a powder compression apparatus for producing compressed green parts from a powder charge that is filled into a mould cavity of a compression die and subsequently compressed. The powder compression apparatus 1 has a powder compression die 2, and e.g. a bottom punch 3 and a core part 4 together defining a mould cavity 5 that delineates the shape of the green part to be formed. The apparatus is further equipped with a filling shoe including a distributor device 100 for filling the mould cavity 5 of the powder compression die 2 with a powder charge 99. The distributor device 100 has at a distal end an inlet portion 110, at a proximal end an outlet portion 120, and a distributor portion 130 arranged between the inlet and outlet portions 110, 120. An inlet 111 at the inlet portion 110 receives a powder flow 90 from a powder supply, such as a powder hopper (not shown) via a tube 9. A housing 101 of the distributor device 100 forms a conduit confining and directing the powder flow from the inlet 111 via the inlet portion 110 via the distributor portion 130 to the outlet portion 120, from where a powder charge 99 is delivered to the mould cavity 5 through an outlet opening 121 arranged at the proximal end of the outlet portion 120 so as to face an upper surface 6 of the powder compression die 2. The filling shoe with the distributor device 100 is adapted to perform a sliding to-and-fro movement along the upper surface 6 of the powder compression die 2 as indicated by the double block arrow. The to-and-fro movement covers the entire extension of the mould cavity 5 so as to ensure filling of all parts of the cavity 5, wherein the distributor portion 130 of the distributor device 100 at the interface between the outlet opening 121 and the upper surface 6 of the compression die 2 ensures a powder pressure that is uniformly distributed across the outlet opening 121. Thereby a uniformly distributed powder charge 99 filling the mould cavity 5 is obtained.

#FIGS. 2A, 2B, and 2C show three different views of a first embodiment of a distributor device 200: a top elevation (FIG. 2A); a side elevation (FIG. 2B); and an end elevation (FIG. 2C) as seen from a proximal end of the distributor device 200. The distributor device 200 has an inlet portion 210 with an inlet 211 at a distal end of the distributor device 200, an outlet portion 220 with an outlet opening 221 at a proximal end of the distributor device 200, and a distributor portion 230 arranged between the inlet portion 210 and the outlet portion 220. The inlet portion 210 of the distributor device 200 is connectable to a powder supply tube for receiving a powder flow through a single inlet 211. Under operation, the powder flow is passed from the inlet portion 210 through the distributor portion 230 to the outlet portion 220 from where it is discharged through outlet opening 221 for delivery to a mould cavity of a powder compression die. The distributor device 200 has a box-shaped housing 201 having in a vertical direction a top wall 201a, a bottom wall 201b opposite of the top wall 201a (best seen in FIGS. 2B and 2C), and, in a horizontal direction, a first side wall 201c and a second side wall 201d opposite of the first side wall 201c (best seen in FIGS. 2A and 2B). The top and bottom walls 201a, 201b are essentially parallel to each other, here spaced apart from each other with a height essentially matching the height of the inlet 211. The first and second side walls 201c, 201d are arranged at an angle with respect to each other so as to diverge in a direction from the inlet 211 to the outlet 221. The outlet opening 221 has a width which determines the width of a mould cavity that can reliable be filled by a filling shoe including the distributor device 200, i.e. the width of the outlet opening 221 matches or surpasses the width of a cavity to be filled.

#The distributor portion 230 has a plurality of guide elements 231, 232 forming distributor channels 240, 250, each distributor channel 240, 250 having an input 241, 251 with a corresponding input cross-sectional area and an output 242, 252 with a corresponding cross-sectional area. The top view of FIG. 2A best illustrates the arrangement of the guide elements 231, 232 in the distributor portion 230. The guide elements 231, 232 are arranged in a cascading arrangement of consecutive stages I, II with a first stage I of guide elements 231 forming first distributor channels 240 at an upstream end of the distributor portion 230, and a second stage II of guide elements 232 forming second distributor channels 242 downstream stream of the first stage I and extending to the downstream end of the distributor portion 230. Thereby, a uniform distribution of the powder flow across the entire width of the distributor device is achieved, which may then be passed on to the outlet portion 220.