EP0050576A1 - Tool for manufacturing sintered articles with helically formed surfaces - Google Patents

Abstract

1. Equipment for producing sintered components having helicoidal surfaces (2) by means of a press (P) provided with two plates (21) comprising a die (1) having a helicoidal internal surface (2) mounted in a ring (3) which is fixed with respect to the press (P), and upper and lower punch members (4, 4') which are provided at their ends with helicoidal surfaces (5) which engage into the helicoidal surfaces (2) of the die (1) with a small clearance, said punch members (4, 4') being driven in rotation when they are displaced along the axis of the helicoidal surface (2), characterised in that the head or heads (8) of a punch member or members (4, 4') is or are supported on the plate or plates of the press (21) by way of a hydraulic axial abutment or abutments (B) permitting free rotation thereof, rotation of the punch member or members (4, 4') then being provided only by the guiding action of said helicoidal surfaces (2, 5).

Description

The invention relates to a tool for producing parts with helical surfaces, made of sintered materials.

It is known that the compression of pulverulent materials in a matrix, and the subsequent sintering of the compressed part, make it possible to produce objects of complex shape, the manufacture of which was difficult, expensive or even impossible by casting, hot or cold deformation and / or machining.

The compression of such parts is generally carried out using mechanical or hydraulic presses, in a matrix of hardened steel, or tungsten carbide, with finely polished walls, by means of punches, also polished, penetrating into the matrix. with little play.

In the case of obtaining parts with helical surfaces, the punch (s) moves (s) along the helix axis while undergoing around this axis, a rotation proportional to their advance, depending on the not the propeller considered.

In previous embodiments, such as that described in French patent 1,416,918 and which relates to the compression of powders to obtain helical pinions, the punches are controlled in rotation as a function of their advance, positively, by two long kinematic, complex and bulky chains. These include, among others, many helical pinions (F / F '), (11-12), (12-3), (27-30), (29-25), intended to impose a predetermined pitch during advance of the punch (s).

• 1°) En raison du grand nombre de pignons, de leur jeu relatif ou de leurs usures respectives, il arrive que, au bout d'un certain nombre d'opérations, le poinçon ne reprenne pas sa position géométriquement exacte devant la matrice ; il peut en résulter notamment des bris d'outillage, lors de l'opération suivante.
• 2°) Il faut évidemment autant de jeux d'engrenages différents que de pas d'hélice à réaliser, d'où un investissement très lourd. De plus, cela implique leur montage et démontage sur la presse entre chaque série de pièces, d'où des pertes de temps et de productivité.
• 3°) La transmission des efforts axiaux, très importants (jusqu'à plusieurs dizaines de tonnes) par l'intermédiaire de butées à bille font que celles-ci sont volumineuses et encombrantes ; malgré leurs dimensions, elles peuvent même subir des détériorations locales (écaillages) qui empêchent leur bon fonctionnement conduisant aussi à des dégradations ou ruptures d'outillages de la presse proprement dite ; da plus, en raison du nombre élevé d'organes mobiles en rotation, elles sont également très nombreuses, ce qui accroît les risques de pannes.

However, this type of device has the following major drawbacks:

• 1) Due to the large number of pinions, their relative play or their respective wear, it sometimes happens that, after a certain number of operations, the punch does not resume its geometrically exact position in front of the die; this can in particular result in breakage of tools, during the following operation.
• 2 °) Obviously, as many different sets of gears are needed as there is no propeller to make, hence a very heavy investment. In addition, this involves their assembly and disassembly on the press between each series of parts, resulting in loss of time and productivity.
• 3 °) The transmission of very large axial forces (up to several tens of tonnes) via ball bearings means that these are bulky and bulky; in spite of their dimensions, they can even undergo local deterioration (flaking) which prevents their proper functioning leading also to degradations or ruptures of tools of the press itself; da more, because of the high number of mobile moving parts, they are also very numerous, which increases the risks of breakdowns.

The Applicant's invention eliminates all of these drawbacks. It provides an elegant solution to the problem of mass production of a large number of parts (for example \ 10,000), with a helical surface, with high reliability, low cost price and high productivity.

According to the invention, the punch (s) is (are) supported on the plate (s) of the press by means of hydraulic stop (s) which allow the rotation of this (s) punch (s) around their axis, which is also the axis of the helical surfaces of the parts concerned; this rotation is practically free, that is to say that it has only a negligible resistive torque. The friction and wear are therefore reduced considerably, which ensures at the same time a lower energy consumption, a long service life of the device and a great precision of the relative positioning of the moving parts.

The punches are obviously provided at their end with helical surfaces which engage in the conjugate helical surfaces of the matrix. The rotation of the punch (s) under the effect of their displacement is only ensured by guiding said helical surfaces.

The correct positioning of the punch and of the die, when these come into contact, is ensured by an adjustable stop integral with the press frame.

The invention will be better understood using the following example, relating to the manufacture of helical pinions whose axis is assumed to be in the vertical position.

• Figure 1 : coupe axiale schématique du dispositif,
• Figure 2 : coupe axiale de la butée hydraulique,
• Figure 3 : vue de dessous de la butée hydraulique (supérieure).

The figures represent:

• Figure 1: schematic axial section of the device,
• Figure 2: axial section of the hydraulic stop,
• Figure 3: bottom view of the hydraulic stop (upper).

The die (1) whose internal profile (2) is helical, is mounted in a hoop (3) integral with the press (P). The matrix is closed at its lower part by the top of the punch (4), whose helical external profile (5) corresponds to that of the matrix (2). The lower punch (4) is also provided with a core (6) to form the bore of the pinion. The powder to be compressed (7) is placed in the annular space between the core and the matrix.

The lower punch is attached to the lower hydraulic stop.

The upper punch (4 '), similar in structure to the lower punch, is fixed to the upper hydraulic stop.

• - un cylindre (10) fermé par un piston (11) solidaire du poinçon (4 ou 4'), lequel est muni de joints haute pression (12) connus en eux-mêmes. L'espace (13) entre le cylindre et le piston est complètement rempli par un fluide hydraulique approprié tel que de l'huile;

The hydraulic stops include:

• - A cylinder (10) closed by a piston (11) secured to the punch (4 or 4 '), which is provided with high pressure seals (12) known in themselves. The space (13) between the cylinder and the piston is completely filled with a suitable hydraulic fluid such as oil;

The cylinder (10) rests on one of the plates (21), mobile or fixed, of the press (P).

The upper piston (4) is, in addition, secured, by means of screws (20) of two positioning arms (14), which are supported, under the action of a small cylinder (not shown) exerting force F, on an adjustable mechanical stop (15), consisting of a screw (16) and a lock nut (17). The purpose of this is to allow the upper punch (4 ') to be positioned exactly for its precise engagement in the matrix (1) when they come into contact, without any risk of deterioration.

The cylinder (10) is closed by a cover (18) which rests on the piston (11) by means of a ball bearing (19).

The punch head (8) (whose diameters are variable) is centered in the recess (22) of the piston (11) using appropriate annular spacers (9).

During the manufacture of the parts, the device is used either for the compression of the powders before sintering, or for the cold calibration of the parts after sintering (in the case of ductile materials), or for both operations.

One of the punches, in general the lower punch, is also used as an ejector at the end of the compression cycle by means of a relative (upward) movement relative to the die.

One of the main uses of this device is the manufacture of simple helical pinions. However, the device can also be used for the manufacture of parts comprising two distinct helical surfaces such as chevron gears, the axes and the helical pitches of each of the surfaces possibly being different; this requires, however, a known adaptation of the matrix (in two parts).

Claims (6)

1 ⁰ ) Tools for the production of parts with helical surfaces (2) made of sintered materials, characterized in that the punch head (s) (8) (4, 4 ′) is supported ( nt) on the plate (s) of the press (21) by means of an axial hydraulic stop allowing their free rotation. 2 °) Tooling according to claim 1, characterized in that the hydraulic axial stop essentially comprises a cylinder (10) and a piston (11) delimiting between them a space completely filled with a liquid (13). 3 °) Tooling according to claim 2, characterized in that the liquid is an oil. 4 °) Tooling according to one of claims 1 to 3, characterized in that the axes of movement of the punches are different. 5 °) Tooling according to one of claims 1 to 4, characterized in that the pitches of the helical surfaces (2) are different. 6 °) Tooling according to one of claims 1 to 5, characterized in that the (or) punch (s) (4) is (are) integral (s) with at least one adjustment stop (15) of its (their) initial angular position around the axis.

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