EP0119177A2

EP0119177A2 - Method and apparatus for lubricating a forming cavity in a forging tool

Info

Publication number: EP0119177A2
Application number: EP84850045A
Authority: EP
Inventors: Mats Strömgren; Urban Björk
Original assignee: Hoganas AB
Current assignee: Hoganas AB
Priority date: 1983-03-14
Filing date: 1984-02-09
Publication date: 1984-09-19
Also published as: SE8301375D0; EP0119177A3; JPS59178145A; SE8301375L

Abstract

For the purpose of lubricating a cavity, particularly an annular cavity in a tool for forging blanks produced by powder metallurgy, a lubricant spray is directed towards a limited portion of the cavity surface and the nozzle is displaced such that impingement area of the spray against the cavity sweeps over the entire surface of the cavity. The impingement surface of the lubricant spray is adapted to cover the radial extension of the annular cavity, the nozzle being displaced along the periphery of the cavity. An apparatus for carrying out the method includes a carrier (10) with a mounting (11) for a swinging arm (12) carrying a spray nozzle (14). The carrier (10) is adapted for being positioned for mounting of the arm coaxial with the axis of the cavity, the arm (12,13) being arranged for positioning the nozzle (14) over a peripheral portion of the cavity. Means (31) are arranged for causing the nozzle (14) to circulate along the periphery of the cavity.

Description

TECHNICAL FIELD

The invention relates to a method and apparatus for lubricating a forming cavity in a forging tool. The lubricant is applied in the form of a spray on the surface of the cavity with the aid of a nozzle. The invention particularly relates to lubricating tools intended for forging blanks produced using powder metallurgy.

BACKGROUND

In forging mass-produced, generally annular details produced using powder metallurgy, forging is generally carried out in a so-called closed tool, the lower die of which has an annular cavity in which the blank produced by powder metallurgy is put. The upper die has an annular stamping surface insertable in the lower die cavity. To avoid defects in the forged details, and to enable forging a blank to the given tolerances for the avoidance of rejects, it is necessary to lubricate the tool on its surfaces facing towards the blank. In the prior art there has been inserted for this purpose an annular distribution box for the lubricant between the upper and lower dies of the tool, the box being disposed coaxially with the axis of the annular cavity. In such a case the box has had a plurality of individual nozzles separated along its periphery, through which the lubricant is sprayed towards the stamping surface of the upper die and the forming cavity of the lower die. The lubricant mist is established either by expelling the lubricant with the aid of compressed air through the nozzles or it is sprayed out under high pressure through the nozzles. If a large number of nozzles is arranged along the periphery of the distribution box, it has been found difficult to provide uniform flows through the nozzles, due to the difficulty of maintaining a uniform pressure in the distribution box, and the nozzles easily obtain different through-flow areas. If a smaller number of nozzles with greater spacing is used, there is an uneven distribution of the lubricant over the defining surfaces of the tool. According to one variation of the lubricating apparatus, the nozzles are formed by a plurality of small orifices evenly distributed over the curved surface of the distribution box, somewhat better distribution of the lubricant over the active surface of the tool thus being obtained. However, it has been found that lubrication will still be unsatisfactory in the forming cavity of the lower die, and especially at the lower defining surface of the cavity as well as the lower parts of the radially inner and outer limiting walls of the cavity.
In this connection it may be mentioned that forging machines for processing annular blanks produced by powder metallurgy, e.g., in the shape of a gear wheel, are made with a very high operating rate, a forging machine used at the present time having an operation start-to-finish time of about 4 seconds per detai. Accordingly, the lubricant must be applied rapidly, and it must not be applied in excess.
One object of the invention is to provide a technique enabling removal of the mentioned drawbacks with unsatisfactory lubrication of an annular cavity in a forging tool for forging details produced by powder metallurgy.

CHARACTERIZATION OF THE INVENTION

The invention is based on a method of lubricating a forming cavity in a forging tool, a lubricant being applied in the form of a spray against the surface of the cavity with the aid of a nozzle, and is essentially distinguished in that the nozzle is adapted to give a lubricant spray, the impingement area of which against the cavity constitutes a fraction of the surface thereof, and in that the nozzle is displaced relative the cavity such that the impingement area of the spray sweeps over the entire surface of the cavity. For lubricating an annular cavity in the forging tool, the nozzle may be adapted to give a lubricant spray, the impingement area of which against the cavity covers the cavity's radial extension along a limited part of the periphery of the cavity, the nozzle being displaced in the peripheral direction of the cavity.
An inventive apparatus for lubricating a forming cavity in a forging tool includes a nozzle adapted to apply a spray of lubricant on the surface of the cavity and is essentially distinguished in that the nozzle is adapted to give a lubricant spray, the impingement area of which against the cavity constitutes a fraction of the cavity surface, and that means are arranged for displacing the nozzle relative the cavity, such that the entire surface of the cavity is swept over by the impingement area of the lubricant spray. For lubricating an annular cavity, the nozzle can be adapted to give a spray, the impingement area of which against the cavity covers the radial extension of the cavity along a limited part of its periphery, the means being adapted to displace the nozzle in the peripheral direction of the cavity.
These means may include a carrier supporting the nozzle, the carrier being adapted such as to enable its displacement from and to a position above the cavity, and in the position above the cavity to displace the nozzle in a path along the periphery thereof.
Alternatively, the means can include an arm, one end of which carries the nozzle, its other end being mounted on a carrier, as well as means for displacing the carrier to and from a position wherein its mounting axis is coaxial with the cavity axis, the arm being adapted to support the nozzle in a position for spraying lubricant on a peripheral section of the cavity and for swinging the arm around its mouting axis.
The method and apparatus in accordance with the invention has been found to circumvent the disadvantages associated with the previously known technique. A possible explanation of the disadvantages occurring with the previously known technique may be that for spray containing a flow of air, irrespective of whether the spray is formed by compressed air or the like or not, there is created a return air flow in the bottom portions of the cavity which is so large that this counterflow restricts the possibility of depositing the lubricant drops on the bottom portions of the cavity and particularly in corner areas in the cavity. In such a case, the effect gained with the aid of the invention would depend on the return flow from the spray being able to depart from the cavity to one side of the spray jet coming from the nozzle towards the surface of the cavity.
The nozzle is preferably kept in one plane with the aid of suitable means, and at a substantially constant distance from the bottom of the cavity during its displacement.
The invention is particularly suitable in conjunction with forming cavities having sharp corners in the bottom area of the cavity, e.g. when the cavity has a substantially right-angular configuration. The invention is particularly utilizable with annular cavities, especially cavities adapted for forging gear wheels or the like from blanks produced by powder metallurgy.
The invention will now be described in the form of an example with reference to the appended drawing.

DRAWING

Fig. 1 illustrates perspectively an apparatus in accordance with the invention in its working position in a forging tool.
Fig. 2 illustrates a detail in an axial section through a lower die of the tool.

EMBODIMENT

The forging tool for forging annular blanks produced by powder metallurgy is illustrated in Fig. 1. The lower die portion of the tool includes an annular matrix 1, a core 2 arranged therein, and a lower die 3 (see Fig. 2), these forming an annular cavity for the blank which is to be processed. The too] further includes an annular upper die 4. The tool parts are mutually displaceable in a manner known per se. When the tool is open in the manner illustrated in Fig. 1, a lubricating device may be inserted between the upper die 4 and the matrix 1. The device includes a carrier 10 which is displaceable, with the aid of some conventional drive means 32, to and from the illustrated position. The carrier 10 has two arms 12,22 mounted for turning about mountings 11,21 which are kept coaxial with the forging tool by the carrier 10. At their free ends, each arm 12,22 carries a nozzle tube 13,23 which is terminated by a spray nozzle 14,24, adapted for directing a spray towards the side walls and bottom of the forming cavity, and to the lower surface of the upper die 4, respectively. Means 31 are arranged for swinging the arms 22,12 about their mountings. The carrier 10, mountings 11,21 and arms 12,22 may all be hollow to allow the supply of a lubricant via the carrier to the nozzles 14. The lubricant spray 15,25 departing from the nozzles 14,24 can either be formed directly by ejecting the lubricant at a relatively high pressure, or by ejecting the lubricant with the aid of compressed air. The bearings 11,21 may be of the swivelling type.
In the open state of the forging tool, the nozzles 14,24 are preferably disposed for having their orifices at a small distance above the upper surface of the matrix 1, and under the lower surface of the upper die 4, respectively. On the drawing, the nozzles 14,24 are illustrated as directing a spray 15,25 in a direction parallel to the axis of the cavity, but it should be quite clear that the direction of the nozzles can deviate from this direction, and then preferably in the tangential direction of the annular cavity.
The invention has been described above in conjunction with one nozzle, but it should be clear that instead of a single nozzle, a nozzle unit comprising a plurality of jets may be utilized. The impingement area of the spray is, for the mentioned reason, a fraction of the cavity area, and in the case of the annular cavity the fraction being for example the relationship between the radial width and the periphery of the cavity.
Lubrication of the upper die is normally not critical, but can be carried out with conventional means. In the embodiment the inventive apparatus has been illustrated also for the upper die, but then substantially solely for the sake of uniformity.
If so desired, the nozzle may also be lowered into the cavity with the aid of suitable means.
The implementation of the nozzle may be adjusted to suit the configuration of the cavity, such as to give a spray depositing a uniform lubricant coating over the cavity, particularly transverse its longitudinal direction.

Claims

1. Method of lubricating a forming cavity in a forging tool, a lubricant being applied in the form of a spray (15) against the surface of the cavity with the aid of a nozzle (14), characterized in that the nozzle (14) is adapted to give a lubricant spray, the impingement area of which against the cavity constitutes a fraction of the cavity surface, and that the nozzle 14 is displaced relative the cavity such that the impingement area of the spray sweeps over the entire surface of the cavity.

2. Method as claimed in claim 1 for lubricating an annular cavity in the forging tool, characterized in that the nozzle (14) is adapted to give a lubricant spray, the impingement area of which against the cavity covers the radial extension of the cavity along a limited portion of its periphery, and in that the nozzle is displaced along the periphery of the cavity.

3. Apparatus for lubricating a forming cavity in a forging tool, including a nozzle (14) adapted for applying a spray of lubricant to the cavity surface, characterized in that the nozzle 14 is adapted to give a lubricant spray, the impingement area of which against the cavity constitutes a fraction of the cavity surface, and in that means (31,10,11,12,13) are arranged for displacing the nozzle (14) relative the cavity, such that the entire surface of the cavity is swept over by the impingement area of the lubricant spray.

4. Apparatus as claimed in claim 3, for lubricating an annular cavity in the forging tool, characterized in that the nozzle is adapted to give a spray, the impingement area of which against the cavity covers the radial extension thereof along a limited portion of its periphery, and in that the means (31,10-13) are arranged to displace the nozzle along the periphery of the cavity.

5. Apparatus as claimed in claim 4, characterized in that the means includes an arm (12) carrying the nozzle (14), and in that members (10,11,31,32) are arranged for enabling displacement of the nozzle from and to a position above the cavity, as well as in a path along the periphery of the cavity when the nozzle (14) is in the position above the cavity.

6. Apparatus as claimed in claim 4, characterized in that the means includes an arm (12,13), one end of which carries the nozzle (14), its other end being connected to a carrier (10) by a mounting (11); means (32) for displacing the carrier (10) from and to a position in which the axis of the mounting (11) is coaxial with the axis of the cavity, and in which the orifice of the nozzle (14) is in a position for directing the spray (15) towards the cavity; and a member (31) for swinging the arm (12,13) about its mounting (11).

7. Apparatus as claimed in any of claims 4-6, characterized in that a lubricant duct extends from the nozzle (14) through the arm (12,13) carrying the nozzle.