CN118788928A - Sand core, sand mold and method for making sand core - Google Patents

Abstract

The present disclosure relates to a sand core for casting a housing of an element for compressing or expanding gas, wherein the sand core (11, 21) comprises a partial core (12, 22) having a profile for completely or largely forming an inner surface or an inner space of the housing, characterized in that the partial core (12, 22) consists of an integral single-piece structure (13, 23).

Description

Sand core, sand mold and method for making sand core

Technical Field

The invention relates to a sand core, a sand mould, a method for producing a sand core and a method for casting a housing of an element for compressing or expanding gas.

An “element for compressing or expanding a gas” may denote, for example, a compressor element, a blower element, a vacuum pump element or an expander element.

More specifically, the invention relates to a sand core for casting a housing of an element for compressing or expanding gas, wherein the sand core comprises a partial core having a profile for completely or largely forming an inner surface or an inner space of the housing.

Here, "a contour for forming most of the inner surface or inner space of the shell" means that at least 50%, preferably at least 60%, more preferably at least 70%, even more preferably at least 80% and still more preferably at least 90% of the inner surface of the shell is formed by the contour of part of the core.

Background Art

Casting methods are known from the prior art in which molten casting material, usually grey cast iron or ductile iron, is poured via a runner into the interior of a sand mold.

When the cavity in the sand mold is filled with this molten casting material, the casting is at least partially formed by the surfaces of the cavity.

In this case, both the outer surface and the inner surface or the interior space of the casting may be formed at least partially by the surface of the cavity.

A housing of an element for compressing or expanding a gas as a casting has an inner surface which generally has a complex shape which is also reflected in a portion of a sand core positioned in a sand mould to form the inner surface.

Conventional tools used to make sand cores for the housing, such as patterns and molds, are expensive to make due to such complex shapes, and are also expensive to modify and store.

These traditional tools are also susceptible to wear and tear over time.

Some very complex shapes cannot even be achieved with traditional tools.

Due to the complex shape, a portion of a core must often be constructed from multiple components in order to fully or largely form the interior surface.

Therefore, these components must be designed to be compatible with each other, which may limit the design freedom of the components and ultimately also the sand core.

Furthermore, specific tooling is required to manufacture multiple of these parts.

Building this part of the core from multiple components also means

- Certain build time;

- Certain risk of damage to fragile parts;

- Certain risk of build errors;

- a certain dimensional inaccuracy due to tolerance stack-ups; and

- More waste is formed.

Sand cores and their various components are also typically solid, without internal cavities, which makes the core material expensive, heavy, and difficult to handle.

Summary of the invention

The present invention aims to address at least one of the above disadvantages and/or other disadvantages.

More specifically, the object of the present invention is to provide a sand core and a method for casting a housing of an element for compressing or expanding a gas,

The shell is cheaper and faster to manufacture, easier to handle and design, and dimensionally accurate than existing sand cores or methods for casting such shells.

Furthermore, the object of the invention is to provide a method for producing sand cores for casting housings of elements for compressing or expanding gases which is faster, cheaper, more flexible and more precise than existing methods for producing such housings.

For this purpose, the invention relates to a sand core for casting a housing of an element for compressing or expanding a gas,

wherein the sand core comprises a partial core having a contour for completely or mostly forming an inner surface or an inner space of the shell,

Characterized in that the partial core is composed of an integral single-piece structure.

In this context, "one unitary monolithic structure" means that the partial core is composed of a single continuous or cohesive piece of material. In other words, the material of the partial core is not broken into multiple separate pieces or components.

By designing the partial core as a unitary, monolithic structure, the partial core no longer needs to be constructed from multiple components.

Thus, the advantages of such a partial core consisting of one integral monolithic structure over a partial core consisting of multiple components include, among others:

- Shorter production time;

- Reduced risk of damaging the partial cores during handling, for example when transporting the partial cores or when assembling the sand cores;

- No risk of building errors;

- no tolerance stack-up caused by assembling the partial core from various components, and therefore higher dimensional accuracy; and

-Less waste formation.

Furthermore, it is no longer necessary to design the various components of the partial core to be compatible with each other, which increases the design freedom of the components and, ultimately, also the sand core. Furthermore, a large number of specific tools are not required to manufacture each component.

For example, by manufacturing the partial core using additive production techniques, it is possible to provide the integral monolithic structure of the partial core with complex geometries.

In a preferred embodiment of the sand core according to the invention, said integral monolithic structure comprises means for manipulating said integral monolithic structure.

This increases the ease of manipulation of the partial core, with the result that:

- the risk of inaccurate assembly or damage to the partial core when placing the partial core in the sand core and/or sand mould can be reduced;

- parts of the core can be cleaned more easily; and

- Visual inspection of partial cores is easier, thereby reducing the risk of quality problems in said partial cores.

In a subsequent preferred embodiment of the sand core according to the invention, the sand core comprises a second partial core having a second contour for at least partially forming the outer surface of the shell.

In this way, during the casting process of the shell, the outer surface of the shell can also be formed at least partially by the sand core.

Preferably, in this case, the integral monolithic structure and the second partial core are integrally connected to one another by means of at least one inter-core connection.

In this way, the integral monolithic structure and the second partial core together form an integral structure which is even larger than the integral monolithic structure itself.

Thus, on the one hand, the partial core consisting of the integral monolithic structure and on the other hand the second partial core can be positioned exactly relative to one another when assembling the sand core and can remain exactly positioned relative to one another when the sand core is placed in the sand mold and during casting of the shell.

In a subsequent preferred embodiment of the sand core according to the invention, the sand core comprises a hollow structure with a cavity which is configured such that during casting of the shell the cavity is not accessible by the casting material used to form the shell.

In this case, both the partial core composed of the integral monolithic structure and the second partial core or other partial cores of the sand core may be designed as hollow structures.

The advantages of designing sand cores with a hollow structure include, among others:

- Reduced weight of the sand core;

- Reduced material costs of sand cores; and

- Reduced gas formation and therefore reduced degassing required during casting of the shell.

Because the partial core consists of a potentially bulky, integral, monolithic structure, it is important to limit the weight of the partial core to optimize ease of handling of the partial core, particularly in the case of partial cores in sand cores for casting large shells.

In this case, designing the integral monolithic structure as a hollow structure therefore offers certain advantages with regard to the ease of handling of the partial core, in particular when the partial core is large and heavy.

The invention also relates to a sand mould for casting a housing of an element for compressing or expanding a gas, wherein the sand mould comprises a sand core according to any of the preceding embodiments.

It goes without saying that this sand mold has the same advantages as the above-described embodiment of the sand core according to the invention.

The invention also relates to a method for producing a sand core for casting a housing of an element for compressing or expanding a gas,

The invention is characterized in that the sand core is manufactured by means of additive manufacturing technology.

The advantages of manufacturing sand cores with additive production techniques over those with subtractive production techniques include, among others:

- no disposal of removed or cut material is required during the manufacture of the sand core;

- Reduced machining allowance due to optimal and repeated design or elimination of release angles, resulting in

- Reduced processing time;

- Reduced costs; and

- Reduced material and energy consumption;

- Eliminate the use of special tools and difficult to modify tools such as core boxes, templates and molds;

- For example, complex geometries for sand cores in a fast, flexible and dimensionally accurate manner with greater design freedom;

-Hollow geometry;

- a geometry having exhaust channels and/or holes along which the sand core can be cleaned of excess sand;

- a geometry for the housing which has an optimized flow behavior for the fluid through the cooling jacket and/or the oil channels in the housing;

- a geometry having features that allow easy and safe handling and transportation of the sand core; and/or

- A geometry having properties which facilitate the casting process and the machining process of the housing, for example due to stable clamping or elimination or reduction of tolerance stack-ups.

In terms of flexibility, additive manufacturing techniques allow the design of sand cores to be quickly and accurately adjusted and optimized in an iterative manner without the need to modify standard tools.

In this case, the sand core is preferably one of the above-described embodiments.

It goes without saying that the sand core manufactured using the method according to the present invention has the same advantages as the above-described embodiments of the sand core according to the present invention.

Finally, the invention relates to a method for casting a housing of an element for compressing or expanding a gas,

The method is characterized in that the method comprises the following steps:

- pouring molten casting material onto the surface of the sand core according to any of the above embodiments;

- Solidifying the casting material against the surface of the sand core to form the shell, wherein the inner surface or the inner space of the shell is completely or mostly formed by the contour of the integral monolithic structure.

It goes without saying that the advantages of the sand core according to any of the above-described embodiments also apply to the method according to the invention.

In this case, the outer surface of the housing is also preferably formed at least partially by the sand core.

In this way, during casting of the shell, both the inner surface or interior space of the shell and at least a portion of the outer surface of the shell may be formed by the same sand core.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to better illustrate the features of the invention, several preferred applications of the sand core and the method for casting the housing of an element for compressing or expanding gas according to the invention are described below by way of example and not limitation with reference to the accompanying drawings, in which:

FIG1 shows a first embodiment of a sand core according to the present invention;

FIG2 shows a second embodiment of a sand core according to the present invention; and

FIG. 3 is a bottom view of the sand core in FIG. 1 .

DETAILED DESCRIPTION

FIG. 1 shows a sand core 11 according to the invention for casting a housing for an element for compressing or expanding a gas.

The sand core comprises a partial core 12 having a profile for completely or largely forming an inner surface or an inner space of a shell during casting of the shell.

The partial core 12 consists of an integral monolithic structure 13 .

FIG. 2 shows a second embodiment of a sand core 21 according to the invention, in which an alternative integral monolithic structure 23 is used as a partial core 22 .

In this second embodiment according to the invention, the sand core 21 is provided with means 24 for manipulating the integral monolithic structure 23 .

The device 24 may take a variety of forms:

- firstly, at least one recess or opening, in this case a groove for example, in the integral monolithic structure 23; and/or

- Secondly, at least one protrusion of the integral monolithic structure 23 , such as a handle protruding from the integral monolithic structure 23 .

It is not excluded within the scope of the invention that the device 24 is located at a different position of the integral monolithic structure 23 .

FIG. 3 is a bottom view of the sand core 11 in FIG. 1 .

In this bottom view, it can be seen that the integral monolithic structure 13 is a hollow structure having a cavity 15 .

The hollow structure is constructed in such a way that during casting of the housing, the casting material used to form the housing cannot enter the cavity 15 .

It is not excluded within the scope of the invention that the sand core comprises other partial cores besides the partial core consisting of a one-piece monolithic structure.

In this way, the sand core can include a second core portion having a second contour for at least partially forming the outer surface of the shell.

The second partial core may be integrally connected to the unitary monolithic structure by means of at least one inter-core connection.

An example of a method according to the invention for casting a housing of an element for compressing or expanding a gas is described below.

In a first step of the method according to the invention, molten casting material is poured onto the surface of the sand core according to the invention.

The casting material then solidifies against the surface of the sand core to form a shell, wherein at least one inner surface or inner space of the shell is completely or mostly formed by the contour of the integral monolithic structure of the partial core of the sand core.

Within the scope of the invention, at least a portion of the outer surface of the shell can also be formed during solidification of the casting material against the surface of the sand core.

According to the invention, it is not excluded that the sand core is pretreated before the molten casting material is poured onto the sand core. For example, the surface of the sand core can be at least partially provided with a coating to prevent the burning of the sand and reduce or even eliminate the rough areas on the surface of the formed shell.

The invention is in no way limited to the sand cores and the method described by way of example and shown in the drawings, but the sand cores according to the invention can be realized in various forms and sizes and the method according to the invention can be realized in various forms without exceeding the scope of protection of the invention as defined in the claims.

Claims (11)

1. A sand core for casting a housing for an element for compressing or expanding gas, The sand core (11, 21) comprises a partial core (12, 22), wherein the partial core has a profile for completely or mostly forming the inner surface or the inner space of the shell. It is characterized in that The partial core (12, 22) consists of an integral monolithic structure (13, 23). 2. A sand core according to claim 1, wherein the integral monolithic structure (13, 23) comprises means (24) for manipulating the integral monolithic structure (13, 23). 3. The sand core according to claim 1 or 2, wherein the sand core (11, 21) comprises a second partial core having a second contour for at least partially forming the outer surface of the shell. 4. The sand core according to claim 3, wherein the integral monolithic structure (13, 23) and the second core section are integrally connected to each other by means of at least one inter-core connection. 5. The sand core according to claim 1 or 2, wherein the sand core (11, 21) comprises a hollow structure having a cavity (15), the hollow structure being configured such that casting material for forming the shell cannot enter the cavity (15) during casting of the shell. 6. The sand core according to claim 5, wherein the integral monolithic structure (13, 23) is a hollow structure. 7. A sand mould for casting a housing of an element for compressing or expanding gas, wherein the sand mould comprises a sand core (11, 21) according to any one of claims 1 to 6. 8. A method for producing a sand core for casting a housing of an element for compressing or expanding a gas, Features The sand cores (11, 21) are manufactured by means of additive manufacturing technology. 9. The method according to claim 8, wherein the sand core (11, 21) is a sand core according to any one of claims 1 to 6. 10. A method for casting a housing for an element for compressing or expanding a gas, Features: The method comprises the following steps: - pouring molten casting material onto the surface of the sand core (11, 21) according to any one of claims 1 to 6; - Solidifying the casting material against the surface of the sand core (11, 21) to form the shell, wherein the inner surface or the inner space of the shell is completely or mostly formed by the contour of the integral monolithic structure (13, 23). 11. Method according to claim 10, wherein the outer surface of the housing is also at least partially formed by the sand core (11, 21).