Pilot Construction For Necking Die Assembly

Abstract

An annular die member and internal pilot for forming a reduced-diameter cylindrical neck on the end of a cylindrical can body having a side lap, wherein no orientation of the lap relative to the die assembly is required. The pilot is longitudinally segmented and the segments are each resiliently biased outwardly so that the segment or segments adjacent the lap may yield inwardly to accommodate the lap while the other segments provide a full circumferential support to the can body end. The pilot is axially movable relative to the annular die member as a can body end is inserted into the die assembly so that there is no relative movement between the pilot segments and can body as would otherwise cause scratching of the interior of the can body.

Description

BACKGROUND OF THE INVENTION

This invention relates to the formation of a reduced-diameter neck on a "three-piece" metal can, i.e., cans having a can body made from a rectangular piece of metal rolled into a cylinder with the edges being joined at a soldered lap extending the length of the cylinder, the two end pieces being therafter secured to the can body by rolling operations.

It is well known that the end of a cylindrical body can be reduced in diameter by forcing the can end into a die set comprising a ring die having an annular inwardly facing die surface of a diameter to produce the desired size neck, and an inner cylindrical pilot, and an inner pilot, there being a clearance between the ring and pilot to enable the can end to be received therebetween. It is also known that the amount of clearance between the ring and pilot is quite critical. Obviously, the clearance must be sufficient to allow the can body to be inserted therebetween. However, if the clearance is too great, then the can body end will not be properly supported during the necking operation and undesirable wrinkling of the necked portion will occur.

With deep drawn aluminum cans having no side laps, i.e., a uniform wall thickness at all points around the can end, a ring die and pilot assembly can be made easily with proper clearance. With lapped can bodies, the problem is considerably greater. A fixed ring die and pilot assembly could be made with a uniform spacing therebetween equal to the wall thickness of the can and with a large clearance at one point therebetween to accommodate the thicker can lap. However, such a die assembly would require orientation of the can body to the die assembly before the can body is inserted thereinto. Such orientation is slow and expensive and unsuitable for commercial operations.

One approach to the problem of providing a can necking die assembly for lapped cans is that shown in U. S. Pat. No. 3,600,927 wherein a floating pilot is disposed within the ring die, with the clearance therebetween averaging half the combined thickness of the can wall and the can lap. With this arrangement, no orientation of the lap of the can body is required. This approach, however, requires that the can bodies operated thereon by made to very close tolerances. If the lap thickness is greater than that for which the ring and pilot are designed, the can body cannot be inserted into the die set. If the lap thickness is appreciably less, then the can body end may not be suitably supported during the necking operation, and wrinkling of the can end may result.

The floating pilot approach also has an inherent drawback resulting from the fact that the ring and pilot members are both circular in cross section. At the point wherein the can lap is between the members the gap therebetween must obviously be at least equal to the thickness of the lap. The gap between the members gradually diminishes around the die, in either direction from the lap, with the least amount of gap, approximately the thickness of the can body wall, being at the point diametrically opposite to the can lap. As a result the gap on either side of the can lap and for a substantial distance therefrom will be only slightly less than the thickness of the lap. If the can lap is made by a process wherein the lap thickness is substantially less than twice the thickness of the can wall, the gap between the ring and pilot created by the lap will not be too detrimental. However, if the can lap is formed in a conventional manner, wherein the edges of the can body are simply lapped one over the other and soldered together, the finished lap will be as much as four times the thickness of the can wall. As a consequence, if this type can body is necked with a floating pilot, the gap between the die members for a substantial distance on either side of the lap will be four times the thickness of the can wall therebetween, and the can wall will not be properly supported so as to prevent wrinkling thereof during the necking process.

The floating pilot approach also has an inherent drawback in that as the can body end is forced into the die assembly the can body end will slide along the surface of the pilot. If the can body has a protective inner coating, such relative movement of the pilot and can body can often cause detrimental scratching of this coating.

SUMMARY OF THE INVENTION

The present invention utilizes an annular die member to reduce the diameter of a can body pushed thereinto. In place of a solid internal pilot, a segmented pilot is used, the pilot having its cylindrical support surface formed by a plurality of longitudinally extending segments, all of which are resiliently biased outwardly, and each of which is capable of inward yielding relative to the adjacent segments. Thus, as a can body is pushed into the die assembly, the pilot segment or segments adjacent the can body lap will yield inwardly to enable the can body end to be inserted between the two die members. The remaining pilot segments will be undisturbed and will provide a full circumferential support for the can body end. With this arrangement no orientation of the can body lap is required and considerable variation in lap thickness of the can body can be accommodated.

In addition, the pilot is axially yieldable so that as the can body end is inserted into the annular die member and engages the pilot, the pilot will then move axially with the can body end during the remainder of the necking operation. This movement together of the pilot and can body end eliminates the scratching of the inner surface of the can body as it is being necked.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings forming a part of this application and in which like parts are designated by like reference numerals throughout the same,

FIG. 1 is a sectional view taken along the axis of the die assembly, illustrating the position of the ring die and pilot members prior to the insertion of a can body end thereinto;

FIG. 2 is a view similar to FIG. 1, illustrating the position of the die members upon full insertion of a can body end thereinto;

FIG. 3 is an enlarged sectional view, taken along the axis thereof, of the pilot member;

FIG. 4 is a transverse sectional view of the pilot member, taken along line 4--4 of FIG. 3;

FIG. 5 is a transverse sectional detail, on an enlarged scale, illustrating the manner in which the pilot segments yield inwardly to accommodate the can body lap.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The can necking machine, generally indicated by the reference numeral 10, comprises a base plate 11 to which the cup-shaped adapter plate 12 is secured by mounting screw 13. Locking nut 14 is threaded into the adapter plate 12, nut 14 having an inwardly projecting flange 15 to engage ring die member 16 and hold the die member and annular die shoe 17 securely in place against the end of adapter plate 12.

The ring die member 16 has a die surface facing inwardly towards the axis of the die member, the die surface comprising an annular cylindrical portion 18 substantially equal to the normal outside diameter of the can body to be necked, an inwardly tapered surface 19 and an annular cylindrical portion 20 of reduced diameter substantially equal to the desired outer diameter of the neck to be formed on the can body.

The pilot member 21, axially disposed within the ring die 16, includes a cylindrical guide 22 disposed within adapter plate 12 for axial movement, between a first position (FIG. 1) wherein one end of guide 22 engages shoulder 23 of die shoe 17 and a second position (FIG. 2) wherein the other end of guide 22 engages shoulder 24 of adapter plate 12. Compression spring 25 resiliently biases guide 22 to its first position.

Pilot 21 further includes a cylindrical core 26 and retainer plate 27, these elements being firmly secured to guide 22 by screw 28. A plurality of longitudinally extending support segments 30 are radially disposed around the core, the segments 30 having outwardly facing shoulders 31 and 32 which engage inwardly facing surfaces on the retainer plate 27 and guide 22 to limit outward movement of the segments.

Each pilot segment 30 has an outwardly extending shoulder 33 thereon and an outwardly facing surface 34 which extends from the inner edge of shoulder 33 to the outer end of the segment. As seen in FIG. 4, the individual surfaces 34 of the segments form an outwardly facing annular cylindrical surface 34' and the individual shoulders 33 form an annular shoulder 33' circumferentially of the pilot. The annular shoulder 33' is adjacent the outer and inner ends of the reduced-diameter die surface 19 when the pilot is in its first and second positions respectively.

A flexible, fluid-impervious sleeve 35 is disposed within the pilot 21, around core 26, and with its outer surface 36 being in engagement with the inner surfaces 37 of all of the pilot segments 30. A fluid path from the interior of the sleeve 35 to the exterior of the assembly is provided by the lateral passages 38 through core 26, the axial passage 39 through screw 28 and the axial passage 40 through mounting screw 13 and the axial stub 41 thereof. A conduit 41 extends from passage 39 to two-way valve 43, this valve being operable to supply fluid under pressure from a suitable source S to the interior of sleeve 35, or to exhaust pressure therefrom. Stub 41 of mounting screw 13 is sealed to guide 22 by O-ring 44.

The outer cylindrical surface 45 of retainer plate 27 is slightly less in diameter than the diameter of the surface 34' when the segments 30 are in their farthest radially outward position.

Adapter plate 12 is provided with a passage 46 therethrough so that the interior of the adapter plate is substantially at ambient pressure regardless of the movement of guide 22 therein.

In operation, the interior of the flexible sleeve 35 is pressurized from source S, which may be a source of compressed air. Merely for purposes of illustration, the pressure may be in the order of 300-425 p.s.i.g. As a cylindrical can body 50 is forced axially into the ring die 16, the can body end 51 first slides along the die surface portion 18 without deformation. As the end of the can is forced into engagement with and moves along the tapered die surface 19, the diameter of the can body end will be reduced thereby. Further movement of the can body end will then cause the extreme leading edge of the can to be guided by surface 19 into engagement with shoulder 33' on the pilot. Continued movement of the can body will then force the pilot to move axially against the bias of spring 25. The air pressure within the sleeve acts radially outwardly on all of the pilot segments 30, causing these segments to press outwardly on the can end to form a constant diameter neck on the end of the can as the can end passes along the die surface 20 of the ring die 16.

At the same time, since the pilot segments 30 are each capable of inward translatory movement against the bias of the pressurized sleeve 35, those segments contacted by the thicker lap portion 52 of the can body will yield inwardly so that the lap can be received between the pilot and the die surface portion 20 of the ring die member 16, as seen in FIG. 5. Although the pilot segments 30 are wider at their outer surface than at their inner surface, very little total radial clearance is necessary between the segments to provide for the relatively small amount of inward movement of the segment or segments engaged by the can body lap. All of the segments are capable of inward radial movement relative to the segments on either side thereof, and thus no orientation of the can body lap to the die assembly is required. Since the segments are mounted on the pilot for individual translatory movement towards the axis of the pilot, the outer surface 34 of the segment or segments engaged by the can lap will remain parallel to the axis of the pilot and parallel to the die surface 20 of the ring die to provide proper support of the can body.

Many can bodies are provided with a very thin protective coating on the inner surface thereof to prevent contact of the subsequent can contents with the can body wall. It will be noted that as the can body end is pushed into the ring die and as it engages and moves the pilot axially, there is no relative movement of the pilot segments 30 longitudinally or circumferentially relative to the interior of the can body end. As a consequence, with no such relative movement, there is an elimination of the scratching of the internal coating on the can body as would otherwise occur if the can body end were forced onto a fixed pilot.

The necking operation will be completed when the can body end has pushed the pilot to its second position, i.e., when guide 22 bottoms against surface 24 of the adapter plate 12, FIG. 2.

The can body is now pulled axially from the die assembly. During initial withdrawal, spring 25 forces the pilot to return with the can body end until the pilot reaches its first position, again with no relative movement between the pilot and can body taking place during such travel. Shortly in advance of the pilot reaching its initial position, valve 43 is operated to release the pressure from the interior of sleeve 35. With the pressure relieved, there is little outward force on the pilot segments and the can body end may then be pulled therefrom without scratching of the inner protective coating of the can body.

After the can body has been stripped from the die assembly, valve 43 is actuated to repressure the sleeve 35 in readiness for the next can body.

As may be seen from the foregoing, the described pilot construction has three significant advantages. First, no orientation of the can body lap is required. Second, the outer surfaces 34 of all of the pilot segments are in contact with the can body so that a full circumferential support is provided to the interior of the can body end as the cylindrical neck is formed thereon. Third, during the necking operation scratching of the inner surface of the can body is eliminated since there is no relative movement between the pilot segments and the can body.

For a typical can body formed from tin plate having a thickness of .006 inch the pilot segments should be formed to provide a clearance of .007 between the outer cylindrical pilot surface 34' and the reduced-diameter die surface 19 on the ring die. The thickness of the can body at the lap 52 will be twice the thickness of the tin plate plus the thickness of the solder 53 between the lapped surfaces. The solder thickness may vary between minimum and maximum acceptable limits of .004 to .013 inch. Thus, with a wall thickness of .006 inch, the lap may vary from .016 to .025 inch in thickness. However, the segmented pilot described herein can easily accommodate such variations and still provide a firm circumferential support to the entire periphery of the can body, including the lap and the portions of the can body immediately on either side of the lap. The outer surface 45 of the retainer plate 27 on the end of the pilot should have a diameter sufficiently less than the expanded diameter of the pilot surface 34' so that the necked-in lap of the can body can be easily stripped off the pilot.

Although a spring 25 is shown to provide a bias force for the pilot, it is to be appreciated that the guide 22 has a surface equal to the cross-sectional area sealed by the stub O-ring 44 upon which the pressure fluid acts in a direction to return the pilot to its first position of FIG. 1. As a consequence, with a proper sizing of this area, the fluid pressure alone may provide sufficient bias force so that spring 25 can be eliminated if desired.

In the apparatus described above, the necking operation has been performed by moving a can body axially into and out of a stationary annular die member. If desired, the very same results would be obtained by holding a can body against axial movement and by forcing the die assembly axially onto and off the can body end.

Claims

Having thus described my invention, I claim:

1. Can necking apparatus comprising:

a ring die having a die surface facing inwardly towards the axis of said die, said die surface including an annular portion of a diameter substantially equal to the diameter of the can body to be necked, an inwardly tapered surface and an annular portion of reduced diameter,

a pilot disposed within and coaxial to said ring die, said pilot having an outwardly facing surface thereon extending longitudinally therealong opposite to said annular portion of reduced diameter of said ring die and having a clearance therewith to receive a can body therebetween,

said pilot including a plurality of longitudinally extending segments radially disposed around said pilot, the outer surfaces of said segments together forming said outwardly facing surface of said pilot,

means mounting said segments on said pilot for individual translatory movement of said segments towards and away from the axis of said pilot to enable any of said segments to be moved towards the axis of said pilot by the lap of a can body inserted into said clearance,

means yieldably biasing each of said segments away from the axis of said pilot and exerting a substantially equal outward force on each segment even though a segment has been moved towards the axis of said pilot by the lap of a can body inserted into said clearance.

2. Can necking apparatus comprising:

a ring die having a die surface facing inwardly towards the axis of said die, said die surface including an annular portion of a diameter substantially equal to the diameter of the can body to be necked, an inwardly tapered surface and an annular portion of reduced diameter,

a pilot disposed within and coaxial to said ring die, said pilot having an outwardly facing surface thereon extending longitudinally therealong opposite to said annular portion of reduced diameter of said ring die and having a clearance therewith to receive a can body therebetween,

said pilot including a plurality of longitudinally extending segments radially disposed around said pilot, the outer surfaces of said segments together forming said outwardly facing surface of said pilot,

means mounting said segments on said pilot for individual translatory movement of said segments towards and away from the axis of said pilot,

a sleeve inside said pilot, said sleeve having the outer surface thereof engaging the inner surface of all of said segments, said sleeve being filled with a pressure-transmitting fluid.

3. Can necking apparatus as set forth in claim 2, and further including means for pressurizing the fluid in the interior of said sleeve and for relieving pressure from the interior of said sleeve, and means on said pilot for positively limiting movement of said segments away from the axis of said pilot.

4. Can necking apparatus as set forth in claim 3 and further including means for moving said pilot axially between first and second positions relative to said ring die, said pilot having an outwardly extending shoulder thereon at one end of said outwardly facing pilot surface, said shoulder being adjacent one end of said annular portion of reduced diameter when said pilot is in its first position and said shoulder being adjacent the other end of said annular portion of reduced diameter when said pilot is in its second position.

5. Can necking apparatus comprising:

a ring die having a die surface facing inwardly towards the axis of said die, said die surface including an annular portion of a diameter substantially equal to the diameter of the can body to be necked, an inwardly tapered surface and an annular portion of reduced diameter,

a pilot disposed within and coaxial to said ring die, said pilot having an outwardly facing surface thereon extending longitudinally therealong opposite to said annular portion of reduced diameter of said ring die and having a clearance therewith to receive a can body therebetween,

said pilot including a plurality of longitudinally extending segments radially disposed around said pilot, the outer surfaces of said segments together forming said outwardly facing surface of said pilot,

means mounting said segments on said pilot for individual translatory movement of said segments towards and away from the axis of said pilot,

means for yieldably biasing each of said segments away from the axis of said pilot and for releasing said bias to allow a necked can body to be stripped from said pilot.

6. Can necking apparatus as set forth in claim 5 and further including means for moving said pilot axially between first and second positions relative to said ring die, said pilot having an outwardly extending shoulder thereon at one end of said outwardly facing pilot surface, said shoulder being adjacent one end of said annular portion of reduced diameter when said pilot is in its first position and said shoulder being adjacent the other end of said annular portion of reduced diameter when said pilot is in its second position.