Self-adjusting Cut-off Knife

Abstract

A pair of cut-off knives for stripping the lower closure of a vertical stack of closures is floated on a spring shim to be able to ride between the curl portions of closures one of whose curl is so oversized as to otherwise cause the knives to interfere with the curl portion.

Parent Case Text

This application is a division of application Ser. No. 813,039 filed on Apr. 3, 1969, now U.S. Pat. No. 3,606,850.

Description

BACKGROUND OF THE INVENTION

This invention relates to container closure lining machinery, and particularly to an improvement in the device which picks the unlined closures from a vertical supply stack and advances them to a rotary chuck where the lining operation is performed.

In a slide feed lining machine closures are vertically stacked in anticipation of being transported individually to a lining station which consists basically of a rotary chuck and a nozzle. At the lining station a fluid gasketing or sealing compound is injected onto the closure as it rotates on the chuck. The closure is then transported away from the machine for subsequent operations such as curing of the compound. Closures are fed from the vertical stack by sliding the lowermost closure in the stack to the lining station.

This invention deals with the means by which the lowermost closure is separated from the vertical stack and slid to the lining station. The lowermost closure in the vertical stack of closures is stripped or cut off from the stack by cut-off knives, dropped to a slide table, and moved downstream to the rotary chuck. The device which performs this function is formed by two reciprocating parallel slides spaced apart a distance somewhat less than the diameter of the closure. The cut-off knives are mounted upon and above the slides for a coincident reciprocation. A vertical space is left between the slide and the knife suitable to receive the lower closure after the knives have cut it off from the stack. The stack rests on the slides until the knives cut off the lower closure at which time the stack rests on the knives, the lower closure dwelling in the space until it is dropped to the slide table, whereupon it is transferred to a rotary chuck for the lining operation.

The space between the slide and the knives must be of sufficient height to accept the "curl" of a can end or the "skirt" of other closures. In addition, the edge of the knives which cut off the lower closure must not be so high as to interfere with the curl of the second lowest closure nested in the lowest closure. It would be possible to set the height of the knives just right if the height of the curl of every closure were dependably consistent. However, a variation in closure dimensions must be anticipated due to the realities of their manufacture. Conventionally, the cut-off knives are set by a gauge to 0.002 of an inch over the maximum curl height expected. If a closure exceeds this dimension, a jam may occur. If the knife is set higher, it will not be able to work itself between the closures and will frequently damage the second lowermost closure.

The tolerances which are maintained by the closure industry are remarkably close. Some closure manufactures produce shells with a 0.002 inch tolerance, others however, keep only a 0.005 inch tolerance. Some closures have dimensions outside the specified tolerances. Therefore, among the billions of container closures which are made, some appear which cause difficulties in the feed mechanism and lead to jams.

The out-of-tolerance dimension which causes the greatest trouble is the vertical height of the curl. If that dimension exceeds by more than 0.002 of an inch the tolerance limit, the cut-off knives will smash against the closure and cause a machine jam which necessitates shut-down and clearing the machine. Freeing the jam can be a time-consuming operation. Consequently, any device which successfully passes on closures slightly out of tolerance (provided that tolerance is demanded solely because of the characteristics of the lining machine) is economically advantageous.

We have discovered that by mounting the cut-off knives on the slide so that they are free to float vertically through a small distance, and shaping the end of the knife so that it is tapered both longitudinally and transversely, the knife can be set as much as 0.007 inch above the curl height tolerance limit and still work its way between closure and closure, cause the supply stack to ride on the knife, and push the just-fed closure ahead towards the chuck. Closures which are as much as 0.005 of an inch over or below the present-day tolerance limits can now be successfully fed.

SUMMARY OF THE INVENTION

The cut-off knives of a strip feed lining machine are floated in a controlled manner and may have edges which are tapered both longitudinally and transversely in order to permit cut off of the lowermost closure of the stack without jamming.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be better understood from the specification and from the drawing in which:

FIG. 1 is a perspective view of the slide-feed lining machine on which the invention is used;

FIG. 2 is a plan view of the left- and right-hand cut-off knives;

FIG. 3 is a cross-section on line 3--3 of FIG. 2 of one arm of the feed slide;

FIG. 4 is a plan view of the cut-off knives;

FIG. 5 is a cross-section on line 5--5 of the cut-off knife of FIG. 4;

FIG. 6 is a plan view of the self-adjusting spring shim;

FIG. 7 is a side view of the self-adjusting spring shim;

FIG. 8 is a side view of an alternative configuration for floating the knives;

FIG. 9 is a perspective view of another embodiment of the cut-off knives.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In FIG. 1 is shown the slide-feed lining device of which the cut-off knives of the present invention are a part. Closures are supplied from a stack 1 to be delivered to a lining station 2 from whence they are subsequently transported to a take-away apparatus shown as a conveyor 3. The device is shown with feed bars 4 and 5 at the end of their forward or downstream stroke having delivered an unlined closure 6 to the lining station 2 and at the same time a lined closure 7 to the conveyor, which latter closure had been at the lining station. On their return or upstream stroke the feed bars 4 and 5 will separate the lowermost closure from stack 1 and drop it to the slide table 8. Upon the forward stroke, the closure will be slid along the slide table 8 to the lining station 2. The stack 1 is located by a block assembly 9 fixed by a means not shown, to the slide table 8. The right hand feed bar 4 and the left-hand feed bar 5 is thus reciprocally driven in unison, by a means not shown, along the path of closure movement.

The present invention deals with the means by which the lowermost closure is separated from the stack for subsequent delivery to the lining station, 2, an embodiment comprised of the right-hand cut-off knife 10 and the left-hand cut-off knife 12 which are attached to the feed bars 4 and 5 respectively. The invention also deals with the means by which the knives 10 and 12 are mounted. The cut-off knives 10 and 12 serve to separate or cut off the lowermost closure from the stack 1 for subsequent delivery to the lining station 2.

The closures shown and described in the following description and No. 2 can ends, and the dimensions indicated are representative particularly of those exiting with No. 2 can ends.

Referring to FIG. 2, the feed bars 4 and 5 straddle the can ends of stack 1 and have slide shelves 14 which extend inwardly to present a space somewhat smaller than the diameter of the can ends. The slide shelves 14 terminate upstream in an inclined edge 16. When the feed bars 4 and 5 are at the downstream extreme of their stroke as shown in FIG. 2, the stack 1 rests upon the slide shelves 14. The cut-off knives 10 and 12 are mounted on the feed bars 4 and 5 and spaced above the slide shelves 14.

FIG. 3 taken in cross section along the line 3--3 of FIG. 2 shows the mounting of the cut-off knife 10 above the slide shelf 14. By way of example, the knife 10 is held in position by a NYLOK socket head cap screw 18. The knife 10 is not secured against the feed bar 4 but rather is resiliently floated or raised upwardly against the screw head by a spring shim 20. Thus there is a vertical space between the slide shelf 14 and the knife 10 which may be varied by adjusting the screw 18.

A spring shim 20 which provides this easy vertical adjustment is shown in FIGS. 6 and 7 as a strip of spring steel which may, e.g., be three-eighths of an inch wide and bent as shown with 1/8 inch offsets, approximately 11/2 inches from base to base. Spring steel 0.020 inch in thickness floats the knives nicely. A wide variety of compressible and/or resilient materials may be utilized to float the knives. Additional materials found suitable are laminated brass shim stock one-sixteenth inch thick consisting of 0.002 inch laminations or an elastomeric material such as neoprene rubber.

The knives 10 and 12 are shown in greater detail in FIGS. 2 and 4. The leading edge 22 of the knives are ground into a particular and peculiar double tapered shape. FIG. 4 shows one such shape which works on No. 2 can ends in which the knives 10 and 12 have a radius of 11/2 inches struck three-eighths of an inch offset from the center line 24 of the two knives when mounted in position. The taper is finished in an arc ground three-eighths of an inch above the center line 24 on a radius of 21/4 inches and one-half inch to the left of the 11/2 inches arc. FIG. 5 is a cross-section through line 5--5 of FIG. 4 showing the tapered portion of the knife edge.

In describing the cyclical operation of the device, it will be assumed to commence from the extreme downstream position shown in FIG. 2. The feed bars 4 and 5 are driven upstream (to the right in FIG. 2) by a means not shown.

As the feed bars 4 and 5 move upstream, the slide shelves 14 slide beneath the stack 1 which is held steady by the block 9. Leading edges 22 of the cut-off knives 10 and 12 work themselves between a lowermost can end 26 and a second lowermost can end 28 as shown in FIG. 3. The can end 28 with the stack 1 above it is thus lifted slightly to ride on the upper face 30 of the cut-off knife 10. The can end 26 remains on the slide shelf 14.

The feed bars 4 and 5 continue to move upstream until the inclined edges 16 of the slide shelves 14 pass beyond the can end 26. The can end 26 then drops to the slide table 8. At this point the feed bars 4 and 5 begin the forward of downstream stroke (to the left in FIG. 2) in which the can end 26 is engaged by the inclined edges 16 and is slid to the lining station 2. The lined can end which was at the lining station is then pushed to the conveyor 3. During the downstream stroke the can end 28 and the stack 1 above it drop to the slide shelf 14 as the knives 10 and 12 are withdrawn.

With reference to FIG. 3, in the past the distance between the knife 10 and the slide shelf 14 was fixed at the most 0.002 inch over the maximum tolerance of the height of the curl 32. The knives could not be set any higher because they could then crush the can end 28. Jams therefore occurred if the curl portion 32 of the can end 26 was higher than the space between the knife 10 and the slide shelf 14. By floating the knives in the manner shown, it is possible to handle can ends where the curl height varies as much as 0.005 inch over the tolerance limit. In this case the knives 10 and 12 are set as much as 0.007 inch above the expected maximum curl height. As the leading edges 22 of the knives hit the can end 28, they are pushed downward against the force of the spring shim 20 to enter between the can ends 26 and 28. The resistance of the spring shim 20 may be chosen and adjusted by a skilled mechanic sufficiently to keep the knives floated upward, but still allow them to move downward upon contacting the can end 28.

In FIG. 8 is shown a further development of the concept in which a knife 10 is spaced above a shim 34 which may comprise any of the materials or shapes mentioned but which is cut back behind the tapered portion 36 of the knife 10 so that the resilience of the knife 10 itself may in whole or in part provide the desired floating effect.

Floating the cut-off knives in the manner described has made a remarkable improvement in reducing jams. Only very rarely will a can end come through with dimensions outside the operating limits of this spring-floated cut-off knife, providing much more constant operation of machines so equipped.

FIG. 9 shows a further embodiment in the double tapered knife edge having the advantage of lower cost and superior performance. The embodiment of FIG. 9 is especially characterized by having no compound surfaces, a smaller angle of entry between the closures, and entry at a point of greater closure strength.

Thus the knife 38 shown has a longitudinal ramp 40 which is at an angle to the upper surface 42 of about 1.degree.-5.degree., about 2.degree. 12' being preferred. It also has a transverse camming surface 44 which is struck downward from line 46 at an angle of about 20.degree.-25.degree. degrees. Finally, the leading edge 48 extends rearward at an angle of from about 10.degree.-20.degree. to the longitudinal axis of the knife 38 having a preferred angle of about 12.degree.. By this configuration the leading edges 48 enter between the can ends 26 and 28 at points more nearly diametrically opposed and upon a line more nearly tangent to the periphery of the ends at the point of entry.

Claims

What we claim is:

1. The method of cutting off and feeding can ends of a given nominal curl height in a can end lining machine comprising; stacking the can ends in a vertical stack; supporting the stack on slide shelves of spaced apart reciprocating feed bars where the slide shelves terminate at a point where they will pass beyond the stack upon the upstream stroke of their reciprocation; mounting and resiliently biasing upward upon the feed bars, cut-off knives, where the upward biasing is limited to a point above the slide shelf up to about 0.007 inch above the maximum curl height of the can end; moving the feed bars in an upstream direction and the cut-off knives carried thereon to cut off the lowermost can end by the cut-off knife contacting the second lowermost can end and biasing downward to enter between the said two can ends; supporting the stack on the cut-off knives and the cut-off can end on the slide shelf until the termination of the shelf permits the can end to drop off it; moving the feed bars in the downstream direction until the cut-off knives pass out from under the stack which then drops onto the slide shelf.