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(11) | EP 0 449 189 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Honing process, particularly for the honing of loam cores used for casting metal bodies, and apparatus for carrying out said process |
(57) Honing process, particularly for honing loam cores comprising the steps of:
The honing apparatus for the continuous honing of loam cores comprises an openable hollow body (1) which is rotatable about its own horizontally arranged longitudinal axis (2). Perforated plate means (4,4a) are arranged inside the hollow body (1), and such plate means (4,4a) act, together with appropriate clamp means (6,6a), as support means for a loam core (5) to be honed. Honing means (3) are arrangeable in the hollow body. Deflection means (7,7a) are furthermore provided for improved honing. |
[0001] The present invention relates to a honing process, particularly for the honing of surfaces and cavities of loam cores to be used for the casting of metal bodies within dies.
[0002] A honing apparatus particularly suitable for carrying out said process is also within the scope of the present invention.
[0003] As is known, loam cores, suitable for being used in the die-casting of many metal bodies having a complicated structure, such as for example heads and other parts of engines and machines in general, are normally manufactured by casting molding sand, i.e. sand and various additives, under pressure within molds of the type which can be opened both in a vertical plane and in a horizontal plane.
[0004] The cores thus obtained are therefore formed bodies having various shapes and dimensions which, due to the particular nature of the material employed, are rather fragile and delicate: furthermore, since the molding is performed within openable metal molds, after the molds open said cores unavoidably have traces of burr and/or roughness both along the peripheral edges which correspond to the mating surfaces of the two half-molds and at the cavities, such as dead and through holes, undercuts and parts with a very small radius of curvature, as well as on the flat surfaces.
[0005] The presence of this burr or roughness on the core obviously does not allow to use said cores without honing them beforehand.
[0006] These small traces of burr are currently removed manually, using various tools which are caused to slide by friction at the burr and within the cavities of the core; this manual action, besides requiring considerable time and specialized personnel, entails constant care in order to avoid damaging the edges and surfaces of the core which, as already mentioned, is constituted by fragile and delicate material.
[0007] The manual removal of part of the material of the cores furthermore causes a dangerous contamination of the working environment, since said cores contain, together with the sand, synthetic resins which contain plasticizers and additives which are rather harmful to the health and which, if released into the air as a consequence of the rubbing of the walls of the cores, can cause serious harm to the personnel assigned to cleaning.
[0008] Finally, manual cleaning, as accurate as it may be, rarely allows a correct and complete removal of raised portions, especially in the innermost and deepest regions of the cores which as such are less easily accessible.
[0009] The aim of the present invention is therefore to provide a process for the mechanized and continuous removal of any burr and/or roughness present on molding-sand cores, conceived so as to totally obviate the disadvantages of the manual removal method and most of all capable of allowing a complete and uniform cleaning or honing of all the surfaces of the cores, even if they have a very complicated shape, with cavities of any size and shape, with no danger of damage to the cleaned surfaces.
[0010] Another object of the invention is to provide a mechanized cleaning process which allows to complete the treatment in a very short time, normally a few minutes, with extremely modest energy costs and with no emission of gases or fumes which are harmful to the operators.
[0011] A further object of the invention is to provide an apparatus which is particularly suitable for the practical execution of said honing-cleaning process which has a very simple structure, is highly reliable and uses, as abrasive means, materials which are practically wear-free, recoverable and reusable, with obvious advantages as regards the cost of the honing treatment.
[0012] This aim, these objects and others, which will become apparent from the following description, are achieved by a honing process for cleaning loam cores and the like, according to the present invention, which comprises the steps of:
- arranging, inside a rotating container which is tightly sealed, a mass of honing material with an incoherent structure, substantially a mass of metal balls, in such an amount as to fill substantially half of the internal volume of said container,
- positioning and retaining at least one core to be honed in the substantially central region of said container, with placement of said core in contact with said mass of metal balls,
- slowly rotating said container about its own barycentric axis with a preset rate, so as to allow the mass of balls to flow and thus affect, in succession, the various surface regions of the core, its lateral regions and its undercuts, as well as penetrate in the through cavities and in the dead ones, the value of the rotation rate being such as to allow said balls to affect and thus hone the parts of the core only by means of their own weight, and
- stopping said rotation, normally after a 360o turn of the containment body.
[0013] More particularly, said honing process provides means for slowing the movements of the mass of balls during rotation, in order to allow said balls to remain as much as possible always in contact with the surfaces of the core during the rotation of the containment body.
[0014] For the practical execution of said process, the present invention provides a particular honing apparatus, which comprises an openable substantially cylindrical containment body which can be rotated about its own horizontally arranged longitudinal axis and within which a plurality of metal balls with a smooth surface is loosely enclosed, the level of said balls being such as to not exceed the diametrical plane of the containment body. At least one core to be honed is arrangeable above said plurality of balls, said core being removably locked between a pair of perforated resting plates which are co-planar and rigidly associated, in a diametrically opposite position, with the internal wall of the container, so as to remain substantially in contact with the surface of said plurality of balls. Clamping means are furthermore provided, which act on the opposite part of the core and which are also rigidly associated with the container. Motor means are furthermore associated with the axis of said container, said motor means being suitable for imparting a slow rotation at an adjustable rate so as to allow the mass of balls to roll around the surfaces of the cores and within the cavities of the cores, to thereby perform honing only under the action of balls own weight.
[0015] More precisely, in order to allow the balls to remain constantly in contact with the surface of the core which is opposite to the initial base surface during the movement of said balls, deflection means are provided inside said containment body; said deflection means are substantially plate-shaped, are rigidly and protrudingly associated with the internal wall of the container, can be adjusted according to the dimensions of the core, and are suitable for deflecting the flow of balls onto the surface of the core when said core assumes inclined and/or vertical positions during rotation.
[0016] Further characteristics and advantages of the present invention will become apparent from the following detailed description of a preferred but not exclusive practical embodiment thereof, made with reference to the accompanying drawings and given only by way of non-limitative example, wherein:
figure 1 is a side elevation view of a cylindrical containment body according to the present invention;
figure 2 is a front elevation view of the cylindrical body of figure 1, and
figures 3 and 3a-g are views of the interior of the containment body of figure 1 showing a succession of positions which a core to be honed and cleaning balls assume, inside the containment body, upon rotation thereof.
[0017] With reference to the above figures, the apparatus according to the invention is substantially constituted by a hollow body or cylindrical hollow body 1 which can rotate about its longitudinal axis 2 by means of appropriate drive means such as a gearmotor or the like (not illustrated in the figures), preferably driven at a slow and programmable rate.
[0018] The cylindrical body 1 is openable; that is, it can be opened at one end, or opened alternatively by lifting a half-cylinder of the cylindrical body 1 and making it oscillate about hinges which are rigidly associated with the longitudinal edge of another half-cylinder of the cylindrical body 1.
[0019] Honing means such as metal balls 3 can be introduced inside the hollow cylindrical body and, when the cylinder is motionless as in figure 3, such introduced metal balls 3 fill the lower half of the cylindrical body 1 preferably up to a level 3a which is slightly lower than the horizontal diametrical plane 1a of said cylinder. Said metal balls have a smooth surface and a very small diameter, generally equal to a few millimeters.
[0020] Two opposite perforated rectangular plates 4-4a are positioned in contact with the level 3a of the balls, are rigidly (or removably) applied by means of appropriate connection means such as bracket and bolt means to the internal cylindrical wall of the lower half-cylinder and are arranged longitudinally with respect to said cylinder.
[0021] Said perforated plates 4-4a perform the function of support for a core 5 to be honed and at the same time allow the balls to pass through the perforations in said plates when the cylindrical body 1 is rotated, as will become apparent hereinafter.
[0022] The molding-sand core 5 is furthermore locked on said perforated plates by appropriate clamp means such as rod-like clamp elements 6-6a, one end of which is anchored to the internal surface of the containment body 1; their opposite end is forced onto a planar (or substantially planar) region of the core 5.
[0023] Two laminae or plates 7-7a are furthermore arranged inside said cylindrical body 1. Such plates 7-7a are supported on appropriate support means so that they can slidably move radially toward one another, after the placement of the core 5, to be finally arranged at a small distance from the upper surface of the core, i.e. on the side opposite to the perforated supporting plates 4-4a; said small distance is such as to allow the balls (when the body 1 rotates) to be guided between the plates 7-7a and the upper surface of the core, so as to exert the honing action on said upper surface as well.
[0024] Without the plates 7-7a (which have the function of deflectors or guides), the balls would in fact tend to move away from the core without exerting any action thereon.
[0025] Finally, the diameter of the perforations or holes of the plates 4-4a and the distance between the deflectors 7-7a and the upper surface of the core 5 are such as to allow the free passage of the balls during the rotation of the cylindrical body 1, whereas the angular velocity of said body 1 must be chosen so as to prevent the balls from being subjected to centrifugal forces. This is done since it is indispensable that the balls may act only by means of their own weight in order to perform an effective honing action.
[0026] The action for honing the external surfaces of the core and its cavities and/or undercuts by means of said mass of balls is illustrated in figures 3 to 3g.
[0027] Initially, when the containment body is motionless as in figure 3, the core is placed on the outer edges of the perforated plates 4-4a and then locked by means of the clamps 6-6a; in this position, the balls are all motionless within the lower half-cylinder of the body 1.
[0028] By then slowly rotating the containment body 1 as indicated by the arrow F, it can be seen that the balls, after for example a 45o rotation (figure 3a), begin to pass beyond the perforated plate 4, to enter the holes 8-8a of the core and to affect the rear curved part of the core, while a small number of balls has passed through the opposite perforated plate 4a.
[0029] As the rotation according to the arrow F continues, when the rotation angle reaches 90o (figure 3b), the core is in vertical position and the balls have moved further beyond the perforated plate 4, affecting and cleaning the lower surface and the lateral surface of said core, whereas above the balls which have passed through the perforated plate 4a have mostly gathered between the deflector 7 and said core, and part of said balls have passed through the holes 8-8a.
[0030] A further 45o rotation, up to 135o (figure 3c), causes part of the balls to continue honing the bottom plane of the core; the portion of balls which has passed through the two perforated plates affects the opposite surface of the core, the end edges thereof and the holes 8-8a.
[0031] In the position of figure 3d, the core is overturned and almost all the balls have gathered in the other half-cylinder; in the position of figure 3e, the balls tend to pass through the perforated plates again until, in the position of figure 3g, almost all the balls have returned into the initial half-cylinder. By means of the last 45o rotation (figure 3), the core returns to the cleaning start position and the body 1 is stopped thereat.
[0033] In practice, it has been observed that the mass of balls is able to hone any part of the peripheral surface of the core, as well as its cavities and undercuts, normally by means of a single complete turn (360o) of the containment body 1.
[0034] For cores with a particular geometric shape and particular dimensions, it may be necessary to perform more than one complete turn; in practice, however, in any case the honing is completed with a very small number of turns and in a total time which does not exceed two to three minutes.
[0035] In practice, a plurality of cores arranged longitudinally side by side can obviously be inserted within a single rotating container when the dimensions of said cores allow to do so, in order to perform the simultaneous cleaning of a plurality of items; similarly, the deflection elements 7-7a can be provided so as to be adjustable both radially and along chords which are parallel to the diametrical plane of the body 1, in order to be able to process cores with mutually different dimensions. Finally, for series of cores with large dimensions and a particular shape, the containment body 1 and the related core locking means are given adequate dimensions.
[0036] Naturally, the mass of balls is periodically removed and cleaned from the residues removed from the honed cores.
[0037] In any case, the rotation rate, the diameter of the balls and the surface thereof must in all instances and always be such as to allow the mass of balls to perform honing only by virtue of its own weight.
[0038] It is also obvious that the invention as described above is susceptible to further structurally and functionally equivalent modifications and variations without abandoning the scope of the protection of said invention.
[0039] Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the scope of each element identified by way of example by such reference signs.
1. Honing process, particularly for honing loam cores used for the casting of metal parts
and the like, characterized in that it comprises the steps of:
- arranging, inside a rotating container which is tightly sealed, a mass of honing material with incoherent structure, substantially a mass of metal balls, in such an amount as to fill substantially half of the internal volume of said container,
- positioning and retaining at least one core to be honed in the substantially central region of said container, with placement of said core in contact with said mass of metal balls,
- slowly rotating said container about its own barycentric axis with a preset rate so as to allow the mass of balls to roll and thus affect, in succession, the various surface regions of the core, the lateral regions and the undercuts, as well as to penetrate in the through cavities and in the dead ones, the rotation rate being such as to allow said balls to affect and thus hone the parts of the core only by means of their own weight, and
- stopping said rotation, normally after a 360o turn of the containment body.
2. Process according to claim 1, characterized in that it comprises the slow guidance
of said mass of balls during its movements consequent to the rotation of the containment
body, in order to allow said balls to remain in contact with the surfaces of the core
even during the rotation of the containment body.
3. Process according to claims 1 and 2, characterized in that said metallic balls preferably
have identical diameters and a smooth spherical surface.
4. Honing apparatus, particularly for continuously and automatically honing loam cores,
characterized in that it comprises a substantially cylindrical containment body (1)
which can be opened and can rotate about its own horizontally arranged longitudinal
axis (2), a plurality of metal balls (3) with a smooth surface being loosely enclosed
within said containment body (1), the level of said balls being such as to not exceed
the diametrical plane (1a) of the containment body, at least one core (5) to be honed
being arranged above said plurality of balls (3), said core (5) being removably locked
between a pair of perforated resting plates (4,4a) which are co-planar and rigidly
associated, in a diametrically opposite position, with the internal wall of the container
(1), so as to remain substantially in contact with the surface of said plurality of
balls (3), clamp means (6,6a) or the like being furthermore provided, said clamp means
acting on the opposite part of the core (5) and being also rigidly associated with
the container (1), motor means being furthermore associated with the axis (2) of said
container (1) and being suitable for imparting a slow rotation at an adjustable rate
so as to allow the mass of balls (3) to roll around the entire surface and within
the cavities of the core (5) and perform honing only under the action of its own weight.
5. Apparatus according to claim 4, characterized in that it has, inside said containment
body, deflection means (7,7a) which protrude radially from the internal surface of
said body (1) and which are adjustable in terms of the distance from said core (5)
to be honed, so as to deflect the flow of balls (3) onto the upper surface of the
core (5) every time said core (5) assumes inclined and/or vertical positions during
the rotation of the containment body (1).
6. Apparatus according to claims 4 and 5, characterized in that said containment body
(1) is driven by a gearmotor at a variable rate according to the type and size of
core (5) to be honed.
7. Honing process, particularly for honing loam cores used for casting metal bodies,
characterized in that it comprises the steps of:
- supporting at least one loam core in a containment body which is rotatable about a longitudinal axis defined thereof, said containment body being filled at least partially with honing means, and
- rotating said containment body about its longitudinal axis to thereby allow said honing means to affect the various surfaces of the loam core for honing thereof.
8. Honing apparatus, characterized in that it comprises a hollow body containment means
(1) rotatable about a longitudinal axis (2) defined thereof, support means (4,4a,6,6a)
for supporting inside said containment means at least one loam core (5) to be honed,
honing means (3) arranged in said containment means (1) and rotation means for rotating
said containment means (1) about said longitudinal axis (2).
9. Apparatus according to claim 8, characterized in that it further comprises deflection
means (7,7a) arranged in said containment means (1) for better honing.