Redrawing Apparatus

Abstract

An apparatus for redrawing cup-shaped blanks comprises an indexed rotary platform including members for receiving blanks and conveying them to a redrawing station comprising a redrawing die and a punch, said members each including a tubular cylindrical blank-clamping piece axially slidably mounted in the platform. The redrawing station includes a pusher unit disposed coaxially about said punch for axially pushing the blank-clamping piece of each member successively located at said redrawing station to a position in which a blank carried by said member is clamped against said die during redrawing.

Description

The invention relates to apparatus for redrawing cup-shaped blanks.

A known apparatus of this type described in U.S. Pat. No. 3,478,563 comprises an indexed conveying platform or turret for receiving blanks and conveying them to a redrawing station where the blanks are redrawn by means of a punch. The turret includes a plurality of blank carrying members, one for each indexed position of the turret, each including a redrawing die and a device for clamping a blank against the redrawing die. Each blank clamping device includes a centrally bored plate or flange mounted on two pistons associated with actuating cylinders. Clamping of the blanks against the dies is carried out at a dwell station located before a redraw or press station, and release of the clamping devices is carried out at a subsequent work station. The dies and clamping devices are relatively heavy compared to the weight of the remainder of the turret and the weight of the blanks, so that the overall moment of inertia of the turret is high, which impedes rapid movement of the turret to move the workpieces from one work station to the next, and therefore limits the working rate. Moreover, the provision of a plurality of dies with means for actuating an associated blank clamping device adds to the cost price of the apparatus.

An aim of the invention is to provide an apparatus for redrawing cup-shaped blanks, comprising an indexed conveying platform or turret whose mass (and moment of inertia) can be reduced compared to that of the known device referred to above, thereby enabling an increase in the working rate.

According to the invention, there is provided an apparatus for redrawing cup-shaped blanks, comprising a conveying turret for receiving blanks and conveying them with a step-by-step rotary movement to a redrawing station including a redrawing die and a punch between which the turret moves, said turret including a plurality of members for carrying blanks the number of which members is equal to the number of steps of the turret per rotation thereof, said members each including a tubular cylindrical blank-clamping piece axially slidably mounted in the turret, and said redrawing station including means disposed generally coaxially about said punch for axially pushing the blank-clamping piece of each member successively located at said redrawing station to a position in which a blank carried by said member is clamped against said die.

An embodiment of the invention and a variation thereof will now be particularly described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a plan view of an apparatus according to the invention, partially in cross-section taken along line I--I of FIG. 2;

FIG. 2 is a side elevational view of the apparatus, as seen along line II--II of FIG. 1;

FIG. 3 is a schematic end elevational view of part of the apparatus seen looking from the right of FIG. 2; and

FIG. 4 is a schematic cross-section of a part of a varied embodiment of apparatus.

The apparatus shown in FIGS. 1 and 2 comprises a frame upon which are mounted die means including a stationary redrawing die 2 including an interchangeable chafing ring 22, and a slidably mounted punch 1 able to pass through the central opening of die 2. The apparatus also includes a rotary conveying turret including a platform 3 whose hub 50 is keyed on a shaft 4 parallel to the axis of die 2 and punch 1. On shaft 4, which is rotatably mounted in a bearing 6' of the frame, is also keyed a disk 5 for transporting and unloading articles formed from blanks, disk 5 thus being coaxial with platform 3.

Facing and spaced apart from die 2 is a pusher unit composed of elements 13 to 19, including a central aperture disposed concentrically about the path of punch 1. This pusher unit includes a bored plate 13 having, on its face directed towards die 2, an annular recess 14 which is fluidtightly closed by an axially displaceable elastic membrane 15. To the outer face (i.e. the right hand face in FIG. 1) of a median portion of membrane 15 is stuck a rigid washer 16 provided with a central cylindrical sleeve 17 whose inner diameter is large enough to allow punch 1 to slide freely therein.

The outer and inner peripheral edges of membrane 15 are clamped to plate 13 by means of annular pieces 18 and 47 respectively, which are secured by any adequate means, such as by gluing, vulcanisation or by means of screws. Annular piece 18 has a radially inwardly directed flange 19 which serves as a stop to limit the movement of washer 16 and sleeve 17 which together form a push-piece. The annular chamber defined by recess 14 communicates via an inlet aperture 20 of plate 13 with a tube connected to means (not shown) for supplying compressed air.

The outer peripheral edge of plate 13 has two cylindrical protuberances 11 and 12 diametrally opposed about the axis of punch 1 and serving as bearings for two square headed bored blocks 9 and 10 about which engage U-shaped ends 8a and 8b of a fork 8 pivotally mounted on an end of a lever 7. Lever 7 and fork 8 form part of a device for driving the pusher unit 13 to 19 with a reciprocating axial movement, the remainder of this device, for example including a cam or other known means acting on lever 7, not being shown in the drawings. A separate device, also not shown, is provided for axially reciprocating punch 1, the punch being held accurately along the axis of die 2 by means of a fixed guide bearing 21 (FIG. 2).

As is schematically indicated in FIG. 3, the turret has four identical members 24, 25, 26 and 27 disposed on the platform 3 at 90.degree. to one another about its central axis, these members being adapted to receive blanks 30, carry the blanks to the redrawing tation between punch 1 and die 2, and clamp the blanks during redrawing. Platform 3 also has a peripheral toothing meshing with a toothed wheel 33 (FIG. 1) of an indexing mechanism for driving the platform 3 with a step-by-step rotary motion, displacing platform 3 by an amount of 90.degree. each step. Each of members 24 to 27 is thus made to successively occupy four positions per rotation of platform 3: a loading position I, a dwell position II, a redrawing position III, and an unloading position IV.

Each of members 24 to 27 comprises, as is shown for member 26 in FIG. 1, a tubular cylindrical body 28 axially slidably mounted in a sleeve-like bearing 31 fixed to platform 3. The end of body 28 towards the pusher unit 13 to 19 has a radially inwardly directed shoulder in which a tubular cylindrical blank clamping piece or sleeve 32 is force fitted. Body 28 and sleeve 32 are thus solidly fixed together and define therebetween an annular chamber in which a blank 30 of suitable dimensions can be received, as is shown in FIG. 1. The axial displacement of members 24 to 27 relative to platform 3 is limited in one direction by a shoulder 48 of sleeve 32 which abuts against a shoulder of bearing 31 and in the other direction by a clip 29 fixed in a groove in the outer surface of body 28 and which abuts against an end face of bearing 31.

At the loading position I, blanks 30 are fed to platform 3 by a loading mechanism including a vertical supply channel, defined by a set of bars 35 to 40, in which blanks 30 are piled and are able to drop by gravity as indicated by the arrow in FIG. 3, and a pusher 41 reciprocated by means of a device including a fork 42 so as to push the lowermost blank 30 towards whichever of members 24 to 27 is at position I.

The generally cup-shaped blanks 30, which are formed for example in aluminium by a preliminary drawing operation, have an inner diameter greater than the outer diameter of sleeve 32 and an outer diameter less than the inner diameter of body 28, and a length such that the flat base of each blank 30 comes to bear against the outer edge of sleeve 32. When pusher 41 supplies a blank 30 to one of members 24 to 27 formed by a sleeve 32 and a body 28, the member is moved by the fed blank 30 to an initial position defined by the stop-forming shoulder 48.

The unloading disk 5 has at its periphery four cylindrical recesses 43 to 46 (best seen in FIG. 3) corresponding to respective members 24 to 27. Said recesses are of a complementary shape and size to a part of the outer cylindrical surfaces of articles 30' (shown in broken lines in FIGS. 1 and 3) formed from the blanks 30 by redrawing, and are disposed so as to successively receive articles 30' formed at the redrawing station. For example, FIG. 1 shows an article 3040 formed by pushing a blank 30 held by member 26 through die 2 by means of punch 1, and which engages in recess 45 at position III of disk 5. A stop 56 of frame 6 limits the axial displacement of article 30'. The cylindrical surfaces of recesses 43 to 46 have holes 49 (FIG. 1) communicating via bores in disk 5 with a vacuum source (not shown) by means of which articles 30' are held in the recesses when the punch 1 is withdrawn. A blocking device (not shown) cuts off the supply of vacuum to the recess arriving at position IV, where the articles 30' are thus freed and drop onto a conveyor belt 47 (FIG. 3).

The various driving mechanisms of the described apparatus are synchronized to operate as follows.

Suppose that initially the turret is empty, i.e. that members 24 to 27 carry no blanks. With the turret at rest, a blank 30 is pushed by pusher 41 into whichever of members 24 to 27 is at the loading position I, the loaded blank 30 pushing the sleeve 32/body 28 assembly to its extreme position defined by shoulder 48. Platform 3 is then made to undergo a rotation of a quarter of a turn in the clockwise direction (FIG. 3) which brings the loaded blank to dwell position II, and another blank is fed to the member at position I. Platform 3 is then rotated by a further quarter of a turn, which brings the first-loaded blank 30 to position III between the punch 1 and die 2 of the redrawing station.

During each period when the turret is stopped, the pusher unit 13 to 19 moves forwards, as shown in FIG. 1, with the push-piece forming sleeve 17 bearing against the blank-gripping piece or sleeve 32 located at position III. Flange 16 is pushed rearwardly, so that membrane 15 takes up play. The pressure of pusher unit 13 to 19 is transferred, as a function of the pressure of the compressed air in the chamber of recess 14, to sleeve 17 which pushes sleeve 32 and body 28 from its initial position to that shown in FIG. 1 in which sleeve 32 clamps the base of a blank 30 against the chafing ring 22 of die 2, and therefore holds the blank 30 in position against this die. Simultaneously, punch 1 advances, presses against the base of the blank 30, and redraws the blank through die 2 to form an elongated cylindrical article 30'. The pusher unit 13 to 19 and punch 1 are then withdrawn, freeing the sleeve 32 and body 28, and leaving the article 30' secured in a recess of disk 5. The platform 3 together with disk 5 then move by a further quarter of a turn bringing the article 30' to the unloading position IV where the article is freed from its recess, and drops onto conveyor belt 47.

The described sequence of operations is repeated cyclically.

It should be noted that the outward displacement of membrane 15 is limited by flange 19 of piece 18, which forms a stop for washer 16 fixed to membrane 15.

The redrawing die 2 is of a known type, the diameter of punch 1 being equal to the inner diameter of die 2 reduced by twice the thickness of the wall of a blank 30, in a case where the diameter of the blank has to be reduced without any substantial reduction of the wall thickness.

Since, apart from the mass of the blanks, the extra mass carried by platform 3 is simply the mass of the members 24 to 27 formed by sleeves 32 and bodies 28, and since disk 5 has a low moment of inertia, it is possible to impart large accelerations to the turret and to the blanks and formed articles carried thereby, which enables high working rates to be achieved.

FIG. 4, which shows a varied embodiment in which the mass of the turret is even further reduced, is a schematic cross-section through a part of a blank carrying member located at a redrawing station. In this variation, the blank carrying members are each formed simply by a blank-gripping piece in the form of a tubular cylindrical sleeve 52 slidably mounted in a circular hole 51 of platform 3, holes 51 each being provided with a chafing or bearing ring 55. Each sleeve 52 is urged away from the blank-clamping position and into an initial outer position by means of a compression spring 53 acting between a flange on sleeve 52 and the platform 3. A clip 54 engaged in a peripheral groove in sleeve 52 defines said initial position by abutment against platform 3. If the thickness of platform 3 is insufficient to ensure correct alignment of the sleeve 52, ring 55 could be replaced by a guide sleeve of greater length than the thickness of platform 3. As before, the cylindrical wall of a blank 30 fits about the sleeve 52, but in this variation the blanks are carried solely by sleeves 52.

Many variations to the described apparatus, for example modifications in the blank carrying members, in the pusher-unit, and in the blank supply and removal mechanisms, may be made without departing from the scope of the appended claims. It is possible to employ a single mechanism for driving platform 3 and disk 5 by means of the common shaft 4.

Claims

What is claimed is:

1. An apparatus for redrawing cup-shaped blanks, comprising a rotationally mounted conveying turret for receiving blanks and conveying them with a step-by-step rotary movement to a redrawing position, a redrawing station for redrawing a blank when same is in the redrawing position including a redrawing die and a punch disposed about the turret so that the turret moves therebetween, said turret including a plurality of tubular members for carrying blanks each having an inwardly directed shoulder, wherein the number of which members is equal to the number of steps of the turret per rotation thereof and wherein each member includes a tubular cylindrical blank-clamping piece axially slidably mounted in the turret and force-fitted in said inwardly directed shoulder of that member to define an annular blank receiving chamber between the tubular body of the members and the blank clamping piece, and wherein said redrawing station including means disposed generally coaxially about said punch for axially pushing the blank-clamping piece of each member successively located at said redrawing station to a position in which a blank carried by said member is clamped against said die.

2. An apparatus as claimed in claim 1, comprising stop means for limiting the axial sliding movement of said blank-clamping pieces.

3. An apparatus as claimed in claim 1, comprising a mechanism for feeding to said members cup-shaped blanks the inner diameter of which is greater than the outer diameter of said blankclamping pieces, and a stop defining an initial position wherein each of said pieces are movable by a fed blank to the initial position defined by the stop.

4. An apparatus as claimed in claim 3, in which said blank feeding mechanism comprises a supply channel in which blanks can be piled and drop by gravity, and a pusher for pushing the lowermost blank in said channel towards a member in a loading position.

5. An apparatus according to claim 1, in which said pushing means of said redrawing station comprises means defining an annular enclosure, an axially displaceable elastic membrane fluidtightly closing the enclosure, means for communicating said chamber with a source of compressed air, a rigid part connected to said membrane, and means for axially reciprocating said enclosure to make said rigid part bear against said blank-clamping piece.

6. An apparatus according to claim 1, in which each blank-clamping piece is urged by a spring away from the blank clamping position.

7. An apparatus according to claim 1, comprising an unloading disk mounted coaxially for rotation with said turret, said disk having at its periphery a plurality of cylindrical recesses each corresponding to one of said members, said recesses being of complementary shape and size to part of the outer cylindrical surfaces of articles formed from said blanks and being disposed so as to successively receive articles formed at said redrawing station, said disk including means for holding formed articles in said recesses.

8. An apparatus for redrawing cup-shaped blanks received therein during use comprising: rotatable means receptive of a cup-shaped blank during use for moving same from a loading position to a redrawing position including means defining a plurality of axially slidable cylindrical blank-receiving chambers mounted on the means for moving and rotatable therewith and each having a cylindrical slot at one end portion thereof receptive of the open end portion of a blank; and means for redrawing a blank when same is in the redrawing position comprising die means disposed at the receiving end side of the means for moving and means for punching disposed on the other side of the means for moving and including means fixedly mounted with respect to the rotational movement of said blank-receiving chambers for pushing said blank-receiving chamber towards said die means to clamp the blank between said one end portion of said blank-receiving chamber and said die means.

9. An apparatus according to claim 8, wherein said means defining each blank-receiving chamber comprises an outer cylindrical member having a diameter greater than that of the blank and an inner cylindrical member disposed coaxially within said outer cylindrical member and having a diameter less than that of the blank whereby the circumferential wall of the blank is received between the inner and outer cylindrical members, and means mounting said inner and outer cylindrical members together for axially slidable movement, and wherein said means for pushing includes means for engaging with said inner cylindrical member to push said blank-receiving chamber towards said die means thereby clamping the blank between one end portion of said inner cylindrical member and said die means.

10. An apparatus as claimed in claim 9, further comprising stop means for limiting the axial sliding movement of each inner cylindrical member.

11. An apparatus as claimed in claim 9, further comprising means for feeding cup-shaped blanks into the blank-receiving chamber when said is in the loading position.

12. An apparatus as claimed in claim 11, in which said means for feeding comprises a supply channel in which blanks can be piled and drop by gravity, and a pusher for pushing the lowermost blank in said channel towards said blank-receiving chamber when same is in loading position.

13. An apparatus according to claim 9, in which the pushing means comprises means defining an annular enclosure, an axially displaceable elastic membrane fluidtightly closing the enclosure, a source of compressed air, means for providing communication between said chamber and said source of compressed air, a rigid member connected to said membrane, and means for axially reciprocating said enclosure to make said rigid member bear against said inner cylindrical member.

14. An apparatus according to claim 9, further comprising a spring for urging said blank-receiving chamber away from die means.

15. An apparatus according to claim 9, further comprising an unloading disk mounted coaxially for rotation with said means for moving and having at its periphery a plurality of cylindrical recesses each corresponding to one of said blank-receiving chambers and each of said recesses being of complementary shape and size to part of the outer cylindrical surfaces of a redrawn blank disposed so as to successively receive same after redrawing, said disk including means for holding said redrawn blanks in said recesses.