EP1378322B1 - Method and tumbling apparatus with two oscillating movements - Google Patents

Abstract

The method for polishing the surface of a part (2) with a polishing product (10) contained in a tank (1) consists of fixing the part to a support piece which holds it in contact with the polishing product. The support part is then given an oscillatory movement (A) so as to cause in the polishing product an induced circular movement which engenders its displacement in contact with the part. An Independent claim is included for a polishing device.

Description

The present invention relates to a method of polishing parts more particularly but not exclusively metal, and a polishing device adapted to implement this method, according to the preamble of claims 1 and 5 respectively. Document WO 0029171 describes a polishing method, as well as a polishing device according to the preamble of claims 1 and 5 respectively.

The standards concerning mechanical engineering, in particular the VSM standards (Vereins Schweizerischer Maschinen-Industieller), describe different degrees of surface state or roughness or polishing of a metal part. The VSM standards 10230 and 10231 define twelve degrees of roughness ranging from N1 to N12, the degree N1 corresponding to the finest polishing while N12 corresponds to a coarse surface state. Current polishing machines make it possible to reach the degree N4 or N3, the degrees N2 or N1 being currently obtainable only by covering the surface to be polished with a metal layer, for example by chromium plating. Such a method of lap polishing has several disadvantages. In particular after a mechanical polishing of the part, it is necessary to take this piece back by performing a subsequent soaking operation in a chromium plating bath. This way of proceeding increases the production costs and, moreover, the thickness of chromium as small as it is, modifies the mechanical dimensions of the part that is virtually impossible to retouch by machining.

It is known that the useful surfaces of molds intended for the injection of parts made of synthetic material must have a surface state that is as perfect as possible, the service life of the mold, and correspondingly the cost of the molded parts, being directly a function of this polishing state.

It may also be noted that for some molded parts of complex shape it is very difficult to obtain a uniformly satisfactory surface state, for example at the level of the recessed portions or the internal faces, on which it is moreover difficult to carry out a chroming.

A first object of the invention is therefore to propose a polishing process making it possible to obtain, by mechanical means, which can be automated, a high degree of polishing, for example at least the degree N1, this for a metal part of any shape, all polishing surfaces can be completed in the same degree of polishing and without the need to take the piece for a subsequent recovery operation such as a chromium recovery operation.

Another object of the invention is to propose a polishing device which makes it possible to carry out the preceding method, said device possibly comprising means allowing a fully automated operation of a polishing cycle.

For this purpose, the subject of the invention is a polishing method according to claims 1.

The invention also relates to a device for implementing the method according to claim 5.

• Figure 1 : vue de dessus, cuve de polissage d'un dispositif mettant en oeuvre le procédé de polissage de l'invention,
• Figure 2 : dispositif de polissage selon l'état de la technique.
• Figure 3 : une forme de réalisation préférentielle d'un dispositif de polissage selon l'invention

The invention will be better understood on reading the following description given by way of non-limiting example with reference to the appended drawing, which schematically represents:

• FIG. 1: top view, polishing tank of a device implementing the polishing method of the invention,
• Figure 2: polishing device according to the state of the art.
• Figure 3: a preferred embodiment of a polishing device according to the invention

As has been announced, the invention relates to a method of polishing at least one part 2 with a polishing product contained in a tank 1, at least one surface of the part 2 being exposed in contact with said product of polishing 10.

Although it does not appear in the drawings, the polishing product 10 comprises polishing particles and a liquid in which these particles bathe.

As the polishing product is not the subject of the invention, the composition of this product will not be detailed.

• on fixe chaque pièce 2 destinée à être polie à un support de pièce 1, 100 qui maintient cette pièce 2 au contact du produit de polissage 10, et
• on impose à au moins l'un des deux éléments que sont ledit support de pièce 1, 100 et ledit produit de polissage 10, au moins un premier mouvement oscillatoire A dont on choisit préalablement l'orientation, l'amplitude et la fréquence de manière à provoquer dans ledit produit de polissage 10 au moins un mouvement induit B, C qui engendre son déplacement au contact de la pièce 2.

Notably:

• each piece 2 intended to be polished is fixed to a workpiece support 1, 100 which holds this workpiece 2 in contact with the polishing product 10, and
• at least one of the two elements such as said workpiece support 1, 100 and said polishing product 10 is subjected to at least a first oscillatory movement A, the orientation, amplitude and frequency of which are previously chosen. in causing said polishing product 10 to induce at least one induced movement B, C which causes it to move in contact with the workpiece 2.

The respect of these technical particularities makes it possible to significantly accentuate the polishing action of the polishing product 10, compared to a polishing technique which allows free movement of the workpiece 2 during carrying out any induced polishing motion that is imposed on the polishing product 10.

At least one induced movement B, C, of a substantially circular nature is caused.

When fixing the workpiece 2 on the workpiece support 1, 100, all the degrees of freedom of the workpiece 2 are eliminated with respect to said support 1, 100.

According to a variant, during the attachment of the part 2 to the part support 1, 100, all the degrees of freedom of the part 2 are eliminated with respect to said support 1, 100, with the exception of one degree of freedom in rotation about a predetermined orientation axis.

A polishing product is used which generates a mechanical action and a chemical action.

• un premier mouvement oscillatoire A réalisé dans un premier plan d'orientation déterminée par rapport à un plan horizontal et
• un deuxième mouvement oscillatoire D réalisé au moins dans une direction d'orientation déterminée par rapport audit premier plan.

At least one of the two elements such as said support 1, 100 and said polishing product 10 is imposed, two oscillatory movements of which:

• a first oscillatory movement A made in a first plane of orientation determined with respect to a horizontal plane and
• a second oscillatory movement D made at least in a direction of orientation determined relative to said first plane.

• D'une part, on choisit une cuve 1 de forme telle que, lorsqu'elle est en situation d'être utilisée pour le polissage, elle présente dans différents plans horizontaux, une section transversale de forme polygonale ou sensiblement circulaire et,
• d'autre part, on impose à au moins l'un des deux éléments que sont ledit support 1, 100 et ledit produit de polissage 10, au moins ledit premier mouvement oscillatoire A desdits premier et deuxième mouvements oscillatoires.

These technical features increase the polishing effect compared to a method in which only a movement in a plane is implemented.

• On the one hand, a tank 1 of a shape such that, when it is in a position to be used for polishing, it has, in different horizontal planes, a transverse section of polygonal or substantially circular shape and,
• on the other hand, at least one of the two elements, namely said support 1, 100 and said polishing product 10, is imposed on at least said first oscillatory movement A of said first and second oscillatory movements.

A vessel 1 having a substantially vertical side wall and a substantially flat and horizontal bottom is chosen.

The part support is constituted by using the wall of the vessel 1 in an area which is exposed in contact with the polishing product 10, and at least a first oscillatory movement A is imposed on said vessel 1 in such a way that the part 2 is displaced in the polishing product 10.

The part support is constituted by using a member 100 separate from the vessel 1 and it is to this member 100 that at least said first oscillatory movement A is imposed, while this member 100 keeps the part 2 in contact with said product. polishing 10.

• d'une part, on impose à la cuve 1 au moins un premier mouvement oscillatoire A et,
• d'autre part, on impose également à l'organe 100 qui constitue le support de pièce au moins un autre premier mouvement oscillatoire A choisi de manière telle que ce mouvement de l'organe 100 se combine au mouvement de la cuve 1, en vue de renforcer l'action de polissage.

According to the invention, the part support is constituted by using a member 100 distinct from the wall of the vessel 1 and,

• on the one hand, at least one first oscillatory movement A is imposed on the vessel 1 and,
• on the other hand, it also imposes on the member 100 which constitutes the workpiece support at least one other first oscillatory movement A chosen from such that this movement of the member 100 is combined with the movement of the vessel 1, to enhance the polishing action.

Hereinafter, it describes a method of construction of a polishing device 3 whose essential technical characteristics have just been defined.

Referring to the figures we see, a polishing tank 1 of at least one piece 2 by means of a fluid polishing product 10. The polishing tank 1 is subjected to the action of a displacement device 3, said polishing device 3. When the polishing device 3 operates, the tank is animated with movements intended to induce movements of the polishing product 10. In 1, to better illustrate the movements of the polishing product 10 inside the vessel 1, no mechanical part to be polished has been shown. The tank 1 is driven by a first oscillatory movement A carried out in a substantially horizontal plane. This first movement can be illustrated by the path of each of the constituent points of the vessel 1, for example the four corners, on a circle, in a direction represented by the arrows A, in a plane parallel to the plane of the drawing, a given face of the vessel remaining always parallel to itself during this movement. Another position of the vessel 1 during this first movement has been represented in 1A. This first oscillatory movement A is completed by a second movement made in a direction perpendicular to the horizontal, that is to say in a substantially vertical direction. The manner in which these movements are produced will be described later.

For a given amplitude and for a determined speed of the first movement of the vessel 1, the mixture 10 that it contains is animated with induced movements of substantially circular nature as shown in FIG. 1. A main displacement B, substantially central, is distinguished. , and secondary displacements C, substantially peripheral.

The principle of the method therefore consists in imposing a compound oscillatory movement on the vessel 1 such that displacements are created in the polishing product 10. It is understood that if a metal part 2 is fixed in the vessel 1, - see FIG. it is covered with the polishing product 10 and that the movement described further to the tank is printed, it will create a plurality of displacements around the part 2, these displacements coming from the movement imposed on the vessel 1 in cooperation with the irregularities of shape of the piece facing irregularities of shape of the vessel. Preferably the part 2 will not be disposed in the center of the tank, first to create an unbalance, thereby increasing the amplitude of the translational movement in rotation, and then to increase the substantially circular effect. Displacements B and C shown in Figure 1 correspond to movements produced when the tank does not contain the part 2 to be polished; it can be seen that when one or more pieces are arranged in the tank, there are still other displacements as well as displacements along axes different from those represented, resulting from the irregularities of shape of the pieces as well as the movement of oscillation perpendicular to the plane of the figure mentioned above.

The polishing product 10 effecting the polishing under the action of the displacements described can be any known polishing product, in liquid or pasty form.

A device enabling the polishing tank to be set in motion according to the substantially circular induced movements that have been mentioned is described below and is shown in FIG. 2. The polishing device 3 consists of a frame 30 resting on shock absorbers known to the art on the ground, this in order to limit the transmission of vibrations to the environment. A motor 32, preferably an electric motor, rotates a vertical axis 33, via two pulleys and a belt according to the embodiment shown. The vertical axis 33 is composed of two portions, a lower portion 33A and an upper portion 33B, the lower portion 33A rotating the upper portion 33B, but the upper portion being axially slidable relative to the lower portion 33A. For example, the upper part of the lower portion 33A consists of a tube, in which the lower part of the upper portion 33B is slidably engaged, a key ensuring the transmission of the rotational movement between the two axis portions. without preventing the axial relative sliding of the two axis portions. The lower portion of the lower portion 33A of the shaft 33 is held by a first bearing 34 whose outer cage is held rigidly by a support fixed to the frame 30. The upper portion of the upper portion 33B of the shaft 33 projects out of frame 30 by an opening of its upper face and is held in a second bearing 35, the outer cage is maintained on a swash plate 36. The swash plate 36 is fixed to the frame 30 by means of spring means, for example a plurality of relatively rigid coil springs 37, arranged on the periphery of the swash plate 36, so as to keep it in a substantially horizontal plane. An unbalance flyweight 38 is attached to the upper portion of axis 33B. The tank 1 is fixed to the upper face of the swash plate 36 by detachable fixing means 11.

The axis of rotation 33, rotated as indicated by the motor 32, pivots between the two bearings 34 and 35. Since only one of these bearings, and precisely that of the bottom referenced 34 is fixed to the frame and that the other, that referenced 35 is fixed to the swash plate 36, in turn connected only by the springs 37 to the frame 30, the axis 33 will tend to take a rotational movement oscillating around the vertical direction, the oscillation component being transmitted said swash plate 36. The presence of the weight 38 near the upper end of the axis 33 tends to increase this oscillation movement. The period of rotation of the translation movement in rotation corresponds to the speed of rotation of the axis 33 while its amplitude depends on the moving masses and in particular the unbalance they represent with respect to the vertical axis. The springs 37 are chosen with sufficient rigidity to limit the range of motion. The rotation of the device as described above, thus imposing the translation movement in rotation along a substantially horizontal plane described above, imposes constraints on the springs 37 which then impose, in addition to the first oscillatory movement A in a substantially horizontal plane. , a second oscillatory movement D in a substantially vertical direction such as a slight oscillation movement as indicated in D. The frequency and amplitude of this second oscillatory movement D depend essentially on the moving masses, the characteristics of the springs, as well as the amplitude and frequency of the first oscillatory movement A of the tank. The relative sliding of the two axis portions 33A and 33B is intended to absorb the second movement oscillatory D as well as to compensate for the bending of the springs 37 when the swash plate 36 is loaded with the vessel 1 containing the parts to be polished as well as the polishing product 10.

The device 3 is completed with an electronic part 39A, possibly programmable, controlling the motor 32, as well as a control panel 39B schematically with a keyboard and two push buttons.

The tank 1 can be closed by a cover (not shown in the figure).

• un organe 100 qui, distinct de la cuve 1, constitue le support de pièce, et,
• un premier moyen fonctionnel 50 pour imposer à la cuve 1 au moins le premier mouvement oscillatoire A et,
• un deuxième moyen fonctionnel 60 pour imposer à l'organe 100 qui constitue le support de pièce au moins un autre premier mouvement oscillatoire A choisi de manière telle que ce mouvement de l'organe 100 se combine au mouvement de la cuve 1, en vue de renforcer l'action de polissage.

According to the invention, the polishing device comprises:

• an element 100 which, distinct from the tank 1, constitutes the part support, and,
• first functional means 50 for imposing on the vessel 1 at least the first oscillatory movement A and,
• a second functional means 60 for imposing on the member 100 which constitutes the workpiece support at least one other oscillatory first movement A chosen in such a way that this movement of the member 100 is combined with the movement of the vessel 1, in order to strengthen the polishing action.

The second functional means 60 for imposing at least the first oscillating movement on the arm 100 is advantageously of the same nature as the first functional means 50.

Advantageously, but without limitation, the polishing device comprises two independent motors 32.

Remarkably, the polishing device 3 comprises a means 101 controlled for multi-directional movement of at least the part of the arm 100 which supports at least one piece 2, so as to constitute a means of handling at least one such room 2.

This technical feature allows the mechanical manipulation of at least one part 2 for its loading and unloading in the tank 1, namely, at the beginning and end of the cycle.

Also, the existence of such a means 101 of manipulation makes it easier to perform a control during the polishing cycle.

This mechanization of loading and unloading can advantageously be automated.

Hereinafter is described a complete polishing cycle which does not form part of the invention, comprising a step of preparation of the tank 1. In an empty tank 1, one or more pieces to be polished 2 are placed so that they are not directly in contact with each other or with the walls of the tank. The parts are fixed inside the tank, by any suitable means 12, so that they are fixed rigidly and that their attachment is not destroyed under the effect of vibration. Preferably the fasteners will support the parts to be polished by surfaces of said parts that do not require polishing; if this would not be possible, it will be appropriate later, after having polished a first part of the part, to disassemble the assembly, to modify the fixation of this part so that it presses on a portion already polished and to take again the polishing to polish the surface portions previously masked by the fastener. When one or more portions of surfaces should not be polished, it is possible to protect them by covering them with a protective wax or even more simply an adhesive tape. When the parts 2 are firmly fixed in the tank 1, the tank is filled with the polishing product 10 so as to cover the parts to be polished. The tank 1 is then disposed on the swash plate 36, which is fixed thereto by the fastening means 11, and then the polishing cycle is controlled via the control panel 39B. This control panel 39B can be very simple, controlling only the start or stop of the motor and its speed and direction of rotation. Other parameters can also be introduced by this control panel or by other means, for example taking into account the mass of the parts to be polished and the initial surface state, it is possible to determine the duration of the cycle of polishing and control one or more changes of direction of rotation and speed of the motor during the cycle.

At the end of the polishing cycle, the tank 1 is removed from the plate 36, the polishing product is removed from the tank, the polished pieces are also removed from the tank and are then thoroughly washed. The liquid components of the polishing product are removed from the mixture and are then regenerated or destroyed if they can not be recovered. The particles are also washed and recovered for future use.

With a polishing method, and a polishing device as described above, it is possible to obtain a polishing corresponding to a degree of roughness at least equal to N1 of metal parts of all shapes, this by relatively mechanical means. simple that can be automated.

Claims (12)

1. Method of polishing at least one piece (2) with a polishing product (10) contained in a tank (1), at least one surface of the piece (2) being exposed to the contact of said polishing product (10), according to which

   - each piece (2) intended to be polished is fixed to a piece support (1, 100) which holds this piece (2) in contact with the polishing product (10);

   - imparted to at least one of the two elements, which are said piece support (1, 100) and said polishing product (10), is at least a first oscillatory movement (A) of which the orientation, the amplitude and the frequency is selected beforehand in such a way as to bring about in said polishing product (10) at least one induced movement (B, C) which engenders its displacement in contact with the piece (2);

   - the piece support is formed by using an element (100) separate from the wall of the tank (1);

   - on the one hand, at least a first oscillatory movement (A) is imparted to the tank (1);

   this method being characterised in that

   - on the other hand, likewise imparted to the element (100) which constitutes the piece support is at least one other first oscillatory movement (A) selected such that this movement of the element (100) combines with the movement of the tank (1), with a view to reinforcing the action of polishing.
2. Polishing method according to claim 1, characterised in that imparted to at least one of the two elements, which are said support (1, 100) and said polishing product (10), are two oscillatory movements, being:

   - a first oscillatory movement (A) achieved in a first plane of predetermined orientation with respect to a horizontal plane, and

   - a second oscillatory movement (D) achieved at least in a predetermined direction of orientation with respect to said first plane.
3. Polishing method according to one of the claims 1 or 2, characterised in that:

   - a tank (1) is selected of shape such that when it is in position to be used for the polishing, it has in different horizontal planes a cross section of polygonal or substantially circular shape.
4. Polishing method according to claim 3, characterised in that a tank (1) is selected having a substantially vertical lateral wall and a substantially flat and horizontal bottom.
5. Device for implementing the method according to any one of the claims 1 to 4, comprising a tank (1) containing a polishing product (10) and a first functional means (50) for imparting to the tank (1) at least a first oscillatory movement (A), and

   - an element (100) which, separate from the tank (1), constitutes the piece support; and characterised in that it comprises

   - a second functional means (60) for imparting to the element (100) which constitutes the piece support at least one other first oscillatory movement (A) selected such that this movement of the element (100) combines itself with the movement of the tank (1), with a view to reinforcing the action of polishing.
6. Polishing device according to claim 5 characterised in that it comprises a first functional means (50) for imparting to at least one of two elements which are said support and the polishing product, two oscillatory movements, being:

   - a first oscillatory movement (A) achieved in a first plane of predetermined orientation with respect to a horizontal plane,

   - a second oscillatory movement (D) achieved at least in a direction of predetermined orientation with respect to said first plane, and

   the amplitudes and frequencies of these first and second movements being predetermined in such a way as to bring about in said polishing product (10) at least one induced movement (B, C) which engenders its displacement in contact with the piece (2).
7. Polishing device according to claim 5 or 6, characterised in that it comprises a frame (30) and at least one of said first and second functional means (50, 60), at least one of these functional means (50, 60) including means of driving in rotation (32) a substantially vertical shaft (33), an end portion (33A) of said shaft being held by a first rolling device (34) whose outer cage is fixed to the frame (30), the other end (33B) of said shaft protruding through an opening in the upper face of the frame and supporting an oscillating plate (36), disposed horizontally, through the agency of a second rolling device (35) whose outer cage is fixed to said plate, said plate being, on the other hand, connected to the frame by spring means (37) and being provided with a means of fixing a piece support (2) such as the tank (1) or the support element (100).
8. Polishing device according to claim 7, characterised in that the substantially vertical shaft (33) comprises an imbalance weight (38) disposed in proximity to its upper end (33B).
9. Polishing device according to one of the claims 7 or 8, characterised in that the substantially vertical shaft (33) is made up of two shaft portions (33A, 33B), in prolongation one of the other, and being able to slide, one with respect to the other, in the axial direction.
10. Polishing device according to one of the claims 7 to 9 characterised in that the motorised means (32) are able to drive the shaft (33), or respectively the oscillating plate (36) and the polishing tank (1) in two directions of rotation.
11. Polishing device according to one of the claims 6 to 10, characterised in that it further comprises means of automatic control (39A, 39B) of polishing cycles.
12. Polishing device according to one of the claims 6 to 11, characterised in that it comprises a controlled means (101) of multi-directional displacement of at least the part of the arm (100) which supports at least one piece (2), so as to constitute a means of manipulation of at least one such piece (2) and to permit the mechanical manipulation of at least one piece (2) with a view to its loading and unloading in the tank (1), i.e. in particular at the beginning and at the end of the polishing cycle, as well as during the cycle with a view to achieving a control in the course of said cycle.

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