Method and apparatus for producing one or more hollow sand cores suitable for casting moulds

A method for producing one or more hollow sand cores suitable for casting moulds by means of a bipartite core box (A, B) defining a mould cavity having an interior with bottom and side surfaces into which sand, binder, and catalyst or a curing agent are introduced comprising the steps of:

• (1) establishing a pressure gradient which decreases from the interior to the exterior of a non-heated core box (A, B) of porous material, at least a portion of the porous material being coarse so that the pressure gradient is readily transmitted through walls of the core box,
• (2) introducing sand, binder, and a catalyst or a curing agent into the mould cavity defined by said non-heated core box (A, B),
• (3) directing the introduced sand, binder, and catalyst or curing agent against the side surfaces of the interior of the non-heated core box (A, B) which step of directing, at least in part, is obtained by the pressure gradient established between the interior and exterior of the non-heated core box (A, B), the introducing and the directing of the introduced sand including positioning a pipe in the mould cavity with its bottom close to the bottom of the mould cavity, progressively removing the pipe from the mould cavity while the sand is being directed from the bottom of the pipe against the interior surface of the mould cavity, the introducing and the directing of the introduced catalyst or curing agent including progressively reintroducing the pipe into the mould cavity while the catalyst or curing agent is being directed from the bottom of the pipe against the sand positioned on the interior surface of the mould cavity, and
• (4) using the pressure gradient to hold the introduced sand, binder, and catalyst or curing agent against the side surfaces of the interior while they solidify to form the hollow sand core.

An apparatus for producing one or more hollow sand cores suitable for casting moulds by means of a bipartite core box (A, B) defining a mould cavity having an interior with bottom and side surfaces into which sand, binder, and a catalyst or a curing agent are introduced comprising:

• (1) means for establishing a pressure gradient which decreases from the interior to the exterior of a non-heated core box (A, B) of porous material,
• (2) means for introducing sand, binder, and a catalyst or a curing agent into the mould cavity defined by said non-heated core box (A, B), said means for introducing comprising a sand supply pipe arranged to be inserted into the mould cavity, said sand supply pipe being porous and closed at the end to be inserted into the mould cavity, and said apparatus includes a source of vacuum and a source of compressed air which are selectively connectable to the pipe in such manner that vacuum holds sand on the pipe when it is inserted into the mould cavity and compressed air replaces the vacuum after the pipe has been introduced into the mould cavity, and
• (3) means for directing the introduced sand, binder, and catalyst or curing agent against the side surfaces of the interior of the non-heated core box (A, B) which step of directing, at least in part, is obtained by the pressure gradient established between the interior and exterior of the non-heated core box (A, B), the pressure gradient holding the introduced sand, binder, and a catalyst or a curing agent while they solidify to form the hollow sand core.

An apparatus for producing one or more hollow sand cores suitable for casting moulds by means of a bipartite core box (A, B) defining a mould cavity into which sand, binder, and a catalyst or a curing agent are introduced comprising:

• (1) means for establishing a pressure gradient that decreases from the interior to the exterior of a non-heated core box (A, B) of porous material,
• (2) means for introducing a mixture of sand and a cold curing binder into the mould cavity defined by said non-heated core box (A, B), and for directing said mixture against the interior surface of the non-heated core box (A, B),
• (3) means for directing the introduced mixture against the interior surface of the non-heated core box (A, B) on which surface the mixture is held at least partly by means of the pressure gradient established between the interior and exterior of the non-heated core box (A, B), said means for introducing comprising a sand supply pipe arranged to be inserted into the mould cavity, said sand supply pipe being porous and closed at the end to be inserted into the mould cavity and said apparatus includes a source of vacuum and a source of compressed air which are selectively connectable to the pipe in such manner that vacuum holds sand on the pipe when it is inserted into the mould cavity and compressed air replaces the vacuum after the pipe has been introduced into the mould cavity, and
• (4) means for introducing a catalyst or a curing agent into said mould cavity.