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EP-4737030-A1 - APPARATUS AND METHOD FOR PRESSING METAL POWDERS TO MAKE HELICAL GEARS

EP4737030A1EP 4737030 A1EP4737030 A1EP 4737030A1EP-4737030-A1

Abstract

An apparatus (1) for pressing metal powders to make helical gears (2) comprises: a mould (10) comprising an active zone which is operatively in contact with the metal powders and which defines a cavity for forming the gear (2); a support structure (50), including a frame (51), a mould holding ring (52), connected to the frame (51) by a ring bearing (53) to rotate about a longitudinal axis (X) and configured to receive the mould (10) removably so that the mould (10) is interchangeable with other moulds (10) to make gears (2) of different kinds, and an actuator (61) for rotating the mould holding ring (52) relative to the frame (51); an encoder (41), including a reference ring (41r) connected to the mould holding ring (52), and a sensor (41s) connected to the frame (51) and cooperating with the reference ring (41r) to detect an angular position of the reference ring (41r) around the longitudinal axis (X).

Inventors

  • FOSCHI, DAVIDE
  • MEZZETTI, Mirco
  • STOCCO, Marco
  • ALBONETTI, Pietro

Assignees

  • SACMI COOPERATIVA MECCANICI IMOLA SOCIETA' COOPERATIVA

Dates

Publication Date
20260506
Application Date
20251021

Claims (13)

  1. An apparatus (1) for pressing metal powders to make helical gears (2), comprising: - a mould (10) comprising an active zone which is operatively in contact with the metal powders and which defines a cavity for forming the gear (2); - a support structure (50), including a frame (51), a mould holding ring (52), connected to the frame (51) by a ring bearing (53) to rotate about a longitudinal axis (X) and configured to receive the mould (10) removably so that the mould (10) is interchangeable with other moulds (10) to make gears (2) of different kinds, and an actuator (61) for rotating the mould holding ring (52) relative to the frame (51); - an encoder (41), including a reference ring (41r), connected to the mould holding ring (52), and a sensor (41s) connected to the frame (51) and cooperating with the reference ring (41r) to detect an angular position of the reference ring (41r) around the longitudinal axis (X).
  2. The apparatus (1) according to claim 1, wherein the mould holding ring (52) comprises an annular seat (520) for the reference ring (51r) which, relative to a longitudinal direction, is located between the active zone of the mould (10) and the bearing (53).
  3. The apparatus (1) according to claim 2, wherein the annular seat (520), which is made in the mould holding ring (52), faces the frame (51) of the support structure (50).
  4. The apparatus (1) according to claim 2 or 3, wherein the annular seat (520) is accessible from the outside of the apparatus (1).
  5. The apparatus (1) according to any one of the preceding claims, wherein the detecting ring (41r) is fastened to the mould holding ring (52) by screwing.
  6. The apparatus (1) according to any one of the preceding claims, wherein the mould (10) comprises: - an upper punch (11) and a lower punch (12), aligned along the longitudinal axis (X), and - a die block (13) located between the upper punch (11) and the lower punch (12), wherein the upper punch (11) and the lower punch (12) are mutually movable along the longitudinal axis (X) between a spaced position and a pressing position, where they cooperate to compact the metal powders inside the forming cavity, wherein at least one between the upper punch (11), the lower punch (12) and the die block (13) is movable in rotation about the longitudinal axis (X), and the mould holding ring (52) is configured to support the die block (13) and/or the lower punch (12).
  7. The apparatus (1) according to any one of the preceding claims, wherein the bearing (53) is an axial-radial bearing.
  8. The apparatus (1) according to claim 7, wherein the bearing (53) comprises a radial race (53r) configured to support the frame (51) and the mould holding ring (52) radially, and two axial races (53a) configured to support the frame (51) and the mould holding ring (52) axially.
  9. The apparatus (1) according to any one of the preceding claims, wherein the frame (51) comprises a seat (510) for housing the sensor (41s), the seat (510) being accessible from the outside of the apparatus (1).
  10. A method for pressing metal powders to make helical gears (2) comprising the following steps: - providing a mould (10), comprising an active zone which is operatively in contact with the metal powders and which defines a cavity for forming the gear (2); - providing a support structure (50), including a frame (51), a mould holding ring (52), connected to the frame (51) by a ring bearing (53) to rotate about a longitudinal axis (X) and configured to receive the mould (10) removably so that the mould (10) is interchangeable with other moulds (10) to make gears (2) of different kinds, and an actuator (61) for rotating the mould holding ring (52) relative to the frame (51); - providing an encoder (41), including a reference ring (41r) connected to the mould holding ring (52), and a sensor (41s) connected to the frame (51); - via the sensor (41s), detecting an angular position of the reference ring (41r) around the longitudinal axis (X); - forming the gear (2) in the forming cavity.
  11. The method according to claim 10, wherein the mould holding ring (52) comprises an annular seat (520) for the reference ring (41r) which, relative to a longitudinal direction, is located between the active zone of the mould (10) and the bearing (53).
  12. The method according to claim 10 or 11, wherein providing the mould (10) comprises providing an upper punch (11) and a lower punch (12) aligned along the longitudinal axis (X), and a die block (13) located between the upper punch (11) and the lower punch (12), wherein the mould holding ring (52) is configured to support the die block (13) and/or the lower punch (12), the method comprising the following steps: - mutually moving the upper punch (11) and the lower punch (12) away from each other along the longitudinal axis (X); - mutually moving the upper punch (11) and the lower punch (12) towards each other along the longitudinal axis (X); - mutually rotating at least one between the die block (13) and the upper punch (11) and/or the lower punch (12) about the longitudinal axis (X); - pressing the metal powders with the upper punch (11) and the lower punch (12) and compacting the metal powders inside the forming cavity.
  13. The method according to any one of claims 10 to 12, wherein the bearing (53) is an axial-radial bearing and comprises a radial race (53r) for supporting the frame (51) and the mould holding ring (52) radially, and two axial races (53a) for supporting the frame (51) and the mould holding ring (52) axially.

Description

This invention relates to an apparatus for pressing metal powders to make helical gears. This invention also relates to a method for pressing metal powders to make helical gears. Traditionally, prior art apparatuses for pressing metal powders to make helical gears comprise an upper working unit, including an upper punch, and a lower working unit, including a lower punch and a die block; these components act in conjunction to compact the metal powders inside a forming cavity. To make helical profile gears (internal or external), at least one between the upper punch, the lower punch and the die block rotates relative to the others, and at least two of these components have helical surfaces to form the corresponding helical profile of the gear, internally or externally. Thus, during pressing of the powders, the upper punch and the lower punch move towards each other in translation along an axis while at least one of the components rotates so as form the helical profile. Usually, once the metal powders have been compacted, the punches move apart and the lower punch can move in rotation and upwards in translation relative to the die block so as to extract the compacted product, which is thus removed from the cavity. In another configuration, the lower punch remains fixed and the die block can move in rotation and downwards in translation to perform the same function of extracting the compacted product from the cavity. The pressing apparatuses comprise an axial movement system for moving the upper punch, the lower punch and the die block in translation relative to each other, and a rotational movement system for moving the upper punch, the lower punch and the die block in rotation relative to each other. Examples of apparatuses for pressing metal powders to make helical gears are described in patent documents US5906837 and US6440357. Document US5906837 uses a servo-controlled movement system to actuate the axial and rotation movements of the components. Such an apparatus, however, is nevertheless unable to meet market requirements. Documents EP0773846B1, US6440357B1 and EP3466665A1 also describe examples of apparatuses for pressing metal powders; however, neither those documents are able to satisfy the market's needs. This disclosure has for an aim to provide an apparatus and a method to overcome the above mentioned drawbacks of the prior art. In particular, the aim of this disclosure is to provide a pressing apparatus capable of precisely controlling the relative movements between the components of the apparatus. Another aim of this disclosure is to propose a pressing apparatus capable of reducing component wear as much as possible. This aim is fully achieved by the apparatus and method of this disclosure as characterized in the appended claims. In particular, the apparatus for pressing metal powders to make helical gears comprises a mould. In an embodiment, the mould includes an upper punch. In an embodiment, the mould includes a lower punch. The upper punch is aligned with the lower punch along a longitudinal axis. In an embodiment, the mould includes a die block. The die block is located between the upper punch and the lower punch along the longitudinal axis. The upper punch defines an upper working unit; the lower punch defines a lower working unit. The lower punch, the upper punch and the die block extend longitudinally. The lower punch, the upper punch and the die block comprise a thread defining a helical profile corresponding to the profile of the gear to be made. The upper punch and the lower punch are mutually movable in translation along the longitudinal axis. It is noted that the expression "mutually movable" may apply to the case where only one between the upper punch and the lower punch moves along the longitudinal axis, as well as to the case where both the upper punch and the lower punch move along the longitudinal axis. Preferably, the upper punch and the lower punch are each movable in translation along the longitudinal axis. The upper punch and the lower punch are movable between a spaced position away from the die block, an engagement position, where the punch (upper and/or lower) is in contact with the die block so that corresponding ends of their threads engage each other, and a pressing position, where it is inserted in the die block and cooperates therewith to define a forming cavity and to compact the metal powders. The apparatus comprises a sensor system. The sensors of the sensor system are configured to detect a torsion signal. The torsion signal is representative of torsional stress which at least one between the upper punch and the lower punch is subjected to during pressing (or in any case during contact with the metal powders). The apparatus comprises a control unit. The control unit is connected to the sensor system to receive the torsion signal detected by the sensor system. The apparatus may comprise an actuator system, comprising actuators configured to impart relative movemen