Can trimming apparatus

The apparatus includes a rotatable headstock trimmer unit including reciprocating spindles that are rotatable about a horizontal axis, one spindle having a first rotatable cutting element secured to one end thereof, the second spindle having a second rotatable cutting element disposed in the path of the first rotatable cutting element, the first and second rotatable cutting elements being adapted to engage the end portion of a can; and a rotatable tailstock unit including can supporting means that is rotatable about an axis coaxial with the horizontal axis of the second rotatable cutting element and which engages the lower end of the can. The spindles preferably move jointly relative to the tailstock assembly so that the rotatable cutting elements can engage the open upper end of the can and thereby cooperate to uniformly trim the end portion of the can.

TECHNICAL FIELD OF THE INVENTION 
The present invention generally relates to a can trimming apparatus and in 
particular to an apparatus for trimming the open upper end of a preformed 
can body. 
BACKGROUND OF THE INVENTION 
The use of metal cans in the beverage and food processing industries has 
increased dramatically over the past several decades and continues to 
increase. In an effort to reduce costs and preserve resources, it is 
desirable to manufacture metal cans with extremely thin side walls. Thus, 
the machines that form, trim and otherwise handle metal cans must be able 
to process cans in large volumes and at high speeds without damaging the 
relatively thin side walls. 
It is conventional practice to form an unfinished can having a cylindrical 
configuration with a closed bottom portion and a cylindrical side wall 
that is open at the top end. Unfinished cans may be formed by a variety of 
processes including impact extrusion and deep drawing processes whereby a 
generally circular flat metal plate or sheet is first passed through an 
impact extrusion or deep drawing press where it is formed into a 
relatively shallow cup. The cup is then passed through an ironing press 
which elongates the side walls and produces a can having the desired wall 
thickness. 
It is not possible, however, to produce a can by an extrusion or drawing 
process having the exact height required or having a side wall with a 
uniform upper edge. can bodies as initially formed are usually of 
non-uniform height and have irregular edges at the open top end. 
Subsequent to the formation of the unfinished container, it is necessary 
to trim the upper end of the cylinder to produce a can of a fixed height 
having a smooth upper edge. 
It is essential that the upper edge of a can be smooth and uniform. The 
operation employed in many devices of the prior art for trimming or 
forming the upper edge of the can to attach a can lid often produces an 
uneven or cracked perimeter which, of course, can result in an inadequate 
seal between the lid and the upper edge of the can. Any imperfections such 
as burrs or cracks will prevent a proper seal between the lid and the can 
in the upper edge area. 
Moreover, any metal slivers or shavings produced by an uneven 
circumferential cut about the can will render the can unsuitable for use 
in the beverage and food processing industries. Thus, the formation of a 
smooth upper edge is essential to efficient can making. 
As an additional matter, the scrap material trimmed from the can should be 
efficiently separated from the trimmed can during the cutting process to 
avoid jamming the machine. 
The elimination of such imperfections is a particularly troublesome matter 
in the can making industry. An apparatus is needed to avoid these problems 
by efficiently trimming the can with a uniform and even circumferential 
cut and discarding the scrap separate from the trimmed can. The irregular 
open edge of the can must be evenly trimmed without imperfections to 
produce identical mass-produced cans which can be efficiently sealed. 
SUMMARY OF THE INVENTION 
The present invention provides an apparatus for rapidly and accurately 
trimming the open upper end of a preformed can. By operation of the 
disclosed shearing arrangement, cans having smooth upper edges are formed, 
and cans are efficiently produced at high speed having a uniform length. 
The apparatus positions a can between a trimmer unit of a headstock 
assembly and can supporting means of a tailstock assembly to trim the 
excess material from the can and maintain the excess material separate 
from the can. The apparatus discards the excess material after trimming 
and ejects the trimmed can while the headstock and tailstock assemblies 
rotate at high speed in a continuous motion. 
The present invention is particularly useful for trimming the open ends of 
aluminum cans. However, the apparatus can also be used to trim the open 
end of any relatively thin-walled tubular member. As used herein, the term 
"can" means any hollow, elongated element having a generally circular 
cross-section. 
The apparatus of the present invention generally comprises first and second 
spindle means associated with a trimmer unit of a headstock assembly and 
can supporting means associated with a tailstock assembly which are 
rotated about a horizontal axis and are revolved about a second horizontal 
axis in a circular path. Secured to the end of the first spindle means is 
a first rotatable arcuate-shaped cutting element which cooperates in a 
shearing action with a second rotatable annular cutting element secured to 
the end of the second spindle means. Both the arcuate-shaped cutting 
element and the annular cutting element are driven. Means for jointly 
moving the first and second spindle means in a reciprocating motion 
relative to the tailstock assembly is provided so that the arcuate-shaped 
cutting element and the annular cutting element engage the can and 
cooperate to trim the open upper end of the can. 
In operation, a can is positioned between the second spindle means which 
supports the annular cutting element and the can supporting means which is 
secured to the end of a rotatable shaft associated with the can supporting 
means. The tailstock unit provides a vacuum to secure the bottom of the 
can to the can supporting means and thus maintain the can in a fixed 
position. The joint and simultaneous reciprocating motion of the first and 
second spindle means of the trimmer unit positions the upper edge of the 
can between the annular cutting element of the second spindle means and 
the arcuate-shaped cutting element of the first spindle means whereby the 
upper edge of the can is trimmed. The can remains secured to the 
supporting means while both spindle means are withdrawn, and the scrap or 
excess material which formed the uneven top of the can is removed from the 
second spindle means upon contacting a stripper plate. Shortly thereafter, 
the vacuum is released and the trimmed can is directed to a location 
separate from the scrap material. 
One advantage of the present apparatus is that cans having uniform 
circumferential cuts about the open upper end are produced efficiently at 
high speed. The apparatus can be adjusted to trim the can at any point 
along its length. 
Another advantage is that the scrap or excess material trimmed from the can 
is maintained separate from the trimmed can during the cutting process and 
is not allowed to fall between the various moving parts to jam the 
apparatus. 
Benefits which result from use of the present apparatus include the 
efficient, high speed production of cans having uniform and even trimmed 
edges without the various imperfections normally encountered in the mass 
production of trimmed cans.

DETAILED DESCRIPTION OF THE INVENTION 
Referring to FIG. 1, the can trimming apparatus of the present invention is 
indicated generally by the reference numeral 20. The apparatus 20 includes 
a frame 22 which comprises a support assembly 24 and a base platform 26. 
A first upright end frame 28 and a second upright end frame 30 are mounted 
on the base platform 26. Rotatably mounted in the upper periphery of the 
first and second upright end frames 28 and 30 is a horizontal main shaft 
32. Means for rotating the shaft is provided which, in a preferred 
embodiment, includes a drive unit that is mounted on the support assembly 
24 and is operatively connected to the main shaft 32 by means of a belt 
and pulley arrangement 36. 
Preferably secured to the first upright end frame 28 is a cam block 38 
which supports a raised cam 40. Associated with the cam block 38 is a 
stationary trimmer driving gear 42. Both the cam block 38 and the trimmer 
driving gear 42 include central apertures through which the main shaft 32 
rotatably extends. The trimmer driving gear 42 is ridden by a trimmer 
driven gear 44 as the main shaft 32 rotates. 
A support housing 46 which slidably supports a plurality of support shafts 
48 is secured to the second upright end frame 30. The support housing 46 
includes means for affixing the support shafts 48 to the housing 46 which 
in the described embodiment comprises bolts 50. 
In a preferred embodiment, a can base driving gear 52 is secured to the 
plurality of support shafts 48. Thus, the can base driving gear 52 is 
secured to the second upright end frame 30 by the plurality of support 
shafts 48 and the support housing 46. Both the can base driving gear 52 
and the support housing 46 include central apertures through which the 
main shaft 32 rotatably extends. 
A turret-like headstock assembly 54 and a turret-like tailstock assembly 56 
are mounted on the main shaft 32. The headstock assembly 54 includes a 
main shaft mounted central hub 58 to which are secured three 
circumferentially-spaced trimmer units 60. The tailstock assembly 56 
includes a main shaft mounted tailstock plate 62 in which is carried three 
circumferentially-spaced can supporting means 64. 
Since the three trimmer units 60 and the three can supporting means 64 are 
identical in construction and operation, only one trimmer unit 60 and one 
can supporting means 64 will be described in detail. Preferably, the 
apparatus 20 includes three, five or six circumferentially spaced trimmer 
units 60 and a corresponding number of can supporting means 64. 
Referring now to FIG. 2, the headstock assembly 54 is shown in greater 
detail. The trimmer unit 60 preferably includes first spindle means 66 
which is rotatably and slidably disposed within the central hub 58. 
Mounted on the first spindle means 66 is the trimmer driven gear 44 which 
is positioned to ride the trimmer driving gear 42 as the main shaft 32 
rotates the central hub 58. In particular, as the main shaft 32 rotates 
about the central hub 58, the gear assembly causes the first spindle means 
66 to spin about its own axis within the central hub 58. 
Attached to the first spindle means 66 opposite the trimmer driven gear 44 
is a first trimmer head 68 which includes a first rotatable cutting 
element 70. Preferably, the first rotatable cutting element 70 is 
generally arcuate-shaped. In particular, the first rotatable cutting 
element 70 includes a cutting portion which comprises a generally 
arcuate-shaped edge 71 and a non-cutting portion defined by a cutaway 
section along the arcuate-shaped edge of the cutting portion. In one 
embodiment, the non-cutting portion can comprise a generally flat portion 
72 (as shown in FIG. 7). 
Disposed along the first spindle means 66 opposite the first trimmer head 
68 is a first spindle gear 74 which is secured to the first spindle means 
66 with a retaining member 76 and is supported by a gear hub 78. The first 
spindle gear 74 engages the stationary trimmer driving gear 42 to rotate 
the first spindle means on its axis as the main shaft 32 is rotated. 
Also disposed along the first spindle means 66 is a second gear 80 which is 
secured to the first spindle means 66 with a key 82. Spacer sleeves 84 and 
a plurality of radial bearing assemblies 86 are positioned along the 
length of the first spindle means 66 to provide for smooth and efficient 
rotation of the first spindle means. An additional retaining member 88 can 
be provided at the end of the first spindle means 66 adjacent the first 
trimmer head 68 to hold the bearing assemblies in position and to 
rotatably mount the first spindle means within the headstock assembly. 
The second gear 80 of the first spindle means 66 engages a gear 90 which is 
secured to a second spindle means 92 by a key 94. The second spindle means 
92 is likewise rotatably mounted within the headstock assembly by radial 
bearing assemblies 96, spacer sleeves 98 and retaining members 100. 
Attached to one end of the trimmer unit 60 by means of a linear bearing 102 
is cam follower means 104. The linear bearing 102 maintains horizontal 
attachment between the trimmer unit 60 and the cam follower 104. The cam 
follower means 104 includes a frame member 106 which is secured to the 
linear bearing 102 and on which is secured a pair of cam followers 108. 
The cam followers 108 engage the sides of the raised cam 40 as the main 
shaft 32 rotates the central hub 58 thereby imparting a horizontal 
reciprocal sliding motion to the trimmer unit 60. The first spindle driven 
gear 74 and the stationary trimmer driving gear 42 are of sufficient width 
to maintain working contact as the trimmer unit 60 reciprocates. 
In an alternative (but less preferred) embodiment, the raised cam 40 and 
the cam follower means 104 can be incorporated into the tailstock assembly 
56 to provide reciprocal motion for the can supporting means 64. 
Attached to the second spindle means 92 opposite cam follower means 104 is 
a second trimmer head 110 which includes a second rotatable cutting 
element 112 having a diameter slightly less than the inside diameter of 
the can. The second rotatable cutting element 112 is preferably annular. 
Attached to the second rotatable cutting element 112 is pilot means 114 
which is adapted to extend into the inside of the can during the trimming 
operation. The pilot means 114 can include a plurality of biased 
extensions along its periphery for contacting the inner surface of the 
can. When the trimmer unit 60 is extended away from the first upright end 
frame 28 by the cam follower means 104, the second rotatable cutting 
element 112 cooperates in a shearing action with a first rotatable cutting 
element 70. 
In particular, the non-cutting portion (represented by the generally flat 
portion 72 in FIG. 7) of the first rotatable cutting element 70 and the 
second rotatable cutting element 112 cooperate to allow joint reciprocal 
movement of the cutting elements as the trimmer unit 60 is moved relative 
to the tailstock assembly. As the first and second spindle means are moved 
towards the can, the rotation of the cutting elements is geared so that 
the sidewall of the can is positioned between the non-cutting portion of 
the first cutting element 70 and the second cutting element 112. As the 
cutting elements continue to rotate, the cutting portion of the first 
cutting element engages the sidewall of the can to start the trimming 
operation. 
The cutting elements are secured to the respective spindle means in the 
following manner. The first trimmer head 68 receives and supports the 
first rotatable cutting element 70 which is securely mounted thereon with 
a cover plate 115 and a plurality of bolts 116 or the like. The first 
trimmer head 68 in turn is secured to the first spindle means 66 with 
means which can include a lock screw and cotter pin assembly 118. Spacer 
means 120 can be provided to adjust the position of the cutting element 
70. 
The second trimmer head 110 receives and supports the second rotatable 
cutting element 112 in a similar manner. In particular, a cover plate 122 
and a plurality of bolts 124 securely mount the second rotatable cutting 
element 112 onto the second trimmer head 110 which is in turn secured to 
the second spindle means 92. Spacer means in the form of a slip ring 126 
mounted on a corresponding hub 128 can be provided to adjust the position 
of the cutting element 112. 
The relative positions of the first and second cutting elements in FIG. 2 
provide a slight burr (if any burr is formed) on the inner surface of the 
trimmed edge of the can. As is known in the art, a burr can be formed if 
the cutting elements are slightly out of alignment due to the wearing of 
parts after prolonged use. One of the benefits of the present apparatus, 
of course, is that any burrs that may be formed are minimal or virtually 
nonexistent. 
FIG. 3 illustrates a reversal in the relative positions of the first and 
second cutting elements which is accomplished by changing the position of 
the spacer means associated with each cutting element. This orientation of 
the first and second cutting elements provides a slight burr (if any burr 
is formed) on the outer surface of the trimmed edge of the can. 
Any preference for the location of any burr (even though it may be minimal) 
depends on the intended use of the can. Cans used in the beverage or food 
processing industry may be acceptable if a slight burr is formed on the 
outer surface of the trimmed edge. Burrs on the inner surface, however, 
must be avoided. On the other hand, burrs on the inner or the outer 
surface of the trimmed edge are generally considered suitable for use in 
the processing of pet food and the like. 
Thus, one advantage of this apparatus is that when positioned by cam 
follower means 104, the second rotatable cutting element 112 and the first 
rotatable cutting element 70 trim the upper end of the can to produce a 
smooth edge that is both even and uniform. Cans may be either aluminum or 
steel with a wall thickness, for example, of between 0.0035 to 0.060 
inches (0.089 to 1.53 mm). For satisfactory shearing action, the radial 
planes of the adjacent edges of the cutting elements may overlap about 
0.002 inches (0.051 mm) and the radii of curvature of the adjacent edges 
of the cutting elements may have a clearance of about 0.0005 to 0.001 
inches (0.0127 to 0.0254 mm). 
The radial bearing assemblies 86 and 96 maintain a coaxial orientation of 
the first and second spindle means 66 and 92 and a precise alignment of 
the first rotatable cutting element 70 and the second rotatable cutting 
element 112. Thus, the apparatus 20 can be operated for extended periods 
of time without servicing or replacing the spindle means due to wear of 
the shafts or the associated sleeves 84 and 98. 
In an alternative embodiment, the first and second spindle means can 
include a spline shaft and ball spline to provide a ball spline assembly. 
In this embodiment, the shaft of each spindle means is slidably mounted in 
a spline sleeve by a plurality of ball bearing which are supported in rows 
by cages as disclosed in U.S. Pat. No. 4,914,990 which issued to the 
present inventor on Apr. 10, 1990. It is estimated that if the apparatus 
20 includes the foregoing ball spline assembly instead of a conventional 
ball bearing assembly, the apparatus can be operated up to twenty times 
longer without servicing or replacing the spindle means and the associated 
bearing assemblies. 
When the trimmer unit 60 is retracted inwardly towards the first upright 
end frame 28 by the cam follower means 104, stripper means comprising a 
stationary plate 130 associated with the trimmer unit 60 about the spindle 
means 92 engages the trimmed material for disposal after shearing. 
With particular reference to FIG. 4, the stationary plate 150 of the 
stripper means is shown. The stationary plate is secured to the headstock 
assembly and defines an opening 132 through which the pilot means 114 and 
the second trimmer head 110 can extend and a cutaway portion 134 through 
which the first trimmer head 68 can extend. The opening 132 is preferably 
offset relative to the axis of the pilot means. 
As described above, the pilot means 114 and the first and second spindle 
means 66 and 92 are adapted for joint and simultaneous reciprocal movement 
relative to the stripper means. The pilot means is advanced for insertion 
within the can. After the can is trimmed by the shearing action of the 
cutting elements 70 and 112, the spindle means and the pilot means retract 
with the trimmed scrap material remaining disposed about the pilot means. 
As the trimmed scrap material engages the stationary plate, the scrap 
material is slid off the pilot means for disposal. The length of travel of 
the pilot means is preferably less than about 2-3 inches, and more 
preferably about 1 inch. 
Referring now to FIG. 5, the tailstock assembly 56 is shown in greater 
detail. Contained in the tailstock plate 62 are the can supporting means 
64. The can supporting means 64 include a can base shaft 136 which is 
rotatably disposed in base pad housing 138 which is secured to the 
tailstock plate 62. While the can base shaft 136 is also capable of 
horizontally reciprocal movement, in the preferred embodiment no 
reciprocating action is imparted. 
At one end, a can base pad 139 is attached to the can base shaft 136 by a 
biasing means which in the described embodiment is a spring 140. The can 
supporting means 64 thus freely rotates with the can base shaft 136 while 
maintaining a bias in its horizontal orientation. 
Mounted on the can supporting means 64 is a can base driven gear 142. The 
can base driven gear 142 rides the stationary can base driving gear 52 as 
the main shaft 32 rotates the tailstock plate 62 thus causing the can base 
shaft 136 to spin on its own axis in the base pad housing 138. 
The can base driven gear 142 is also locked horizontally onto the 
stationary can base driving gear 52 by a locking ring 144. Thus, when the 
stationary can base driving gear 52 can be adjusted horizontally by 
loosening the bolts 50 of the support housing 46 and sliding the support 
shafts 48. The can base shaft 136 is also adjusted accordingly thereby 
allowing for cans of different heights. The tailstock plate 62 is thus 
moved along the main shaft 32 during this adjustment. To maintain the 
driving relationship between the tailstock plate 62 and the main shaft 32, 
a raised ridge 146 is provided on the main shaft 32 which is keyed into a 
groove provided on the tailstock plate 62. 
The can base shaft 136 includes a central aperture 147 defined in the 
center of the shaft 136 which opens to the can supporting means 64. 
Opposite the can supporting means 64, the central aperture is attached to 
a rotary union 148. 
The rotary union 148 includes main housing 150, a male elbow 152, and a 
rotating shaft 154 having a central passage. The rotary union 148 allows 
free rotation of the rotating shaft 154 while maintaining gaseous 
communication between the rotating shaft 154, central passageway and the 
male elbow 152. The central aperture of the can supporting means 64 is 
specifically connected to the rotary union 148 thus establishing gaseous 
communication from the can supporting means 64 to the male elbow 152. 
The male elbow 152 is attached via a flexible hose 156 to a second male 
elbow 158 attached to a vacuum plate 160. The vacuum plate 160 is attached 
to the main shaft 32. The vacuum plate 160 is also attached to a source of 
vacuum (not shown) in conventional manner and thus supplies the can 
supporting means 64 with suction as explained in greater detail below. 
In particular, according to the present invention, can edges are trimmed by 
the cooperative shearing action of the first, and second rotatable cutting 
elements. This action provides the clean cut that is necessary to form a 
smooth edge as long as the can is properly positioned between the cutting 
elements. But imperfections in the edge can occur as a result of the wear 
associated with movement of the trimmer unit 58 as it reciprocates towards 
and away from the shearing position. Because of the precision required to 
form a clean cut, even the smallest deviation (for example, 0.0001 inch) 
from the coaxial orientation of the shaft as a result of wear can produce 
imperfections in the edges of the trimmed can. 
As untrimmed cans are fed into the can trimming apparatus, the cans are 
held against the can supporting means 64 by the applied vacuum. During the 
trimming cycle, pilot means 114 holds the trimmed annular edge away from 
the can as the pilot means is retracted. After trimming, the trimmed 
annular edge is separated from the pilot means upon contact with the 
stripper means and is discharged in a first discharge chute while the can 
is held on the can supporting means 64. The main shaft 32 continues to 
rotate so the trimmed can is discharged into a separate discharge chute. 
Referring to FIGS. 6 and 7, the sequence of operation according to a 
preferred embodiment of the present apparatus is presented. Initially, 
cans having an open upper end are fed into the can trimming apparatus 20 
by means such as an infeed spiral in conjunction with a starwheel or other 
can feeding means well known in the art. The cans are positioned on and 
adhere to the can supporting means 64 as a result of the vacuum. 
Individual cans are positioned between the retracted trimmer unit 60 and 
the can supporting means 64. 
The apparatus is geared so that the non-cutting portion (for example, the 
generally flat portion 72) of the first rotatable cutting element 70 is 
positioned to allow the second rotatable cutting element 112 and the pilot 
means to easily be inserted in the open end of the can. The edge of each 
can is then individually trimmed as the second rotatable cutting element 
112 and the first rotatable cutting element 70 are brought into a shearing 
position by rotation. After trimming, the trimmer unit 60 is retracted and 
the trimmed material is fed by gravity into a scrap chute while the 
trimmed can remains adhered to the can supporting means by the vacuum. 
After the can has rotated past the scrap chute, the vacuum is released and 
the can separates from the can base pad. Thereafter, the can is fed by 
gravity into the can discharge chute. As the can is discharged, a second 
can has just been trimmed while a third has just been fed into the 
trimming device. Thus, in each complete rotation of the main shaft, three 
(or more) cans are trimmed (depending on the number of trimmer units 
employed). 
As described above, the apparatus can also be constructed with at least 
one, but preferably three, five or six, circumferentially spaced trimmer 
units and a corresponding number of associated can supporting means. An 
apparatus with three trimmer units can trim at least about 300 cans per 
minute, and an apparatus with five trimmer units 58 can trim at least 
about 500 cans per minute. 
It should be understood that various modifications, changes and variations 
in addition to those herein discussed may be made in the arrangement, 
operation and details of construction of the elements disclosed herein 
without departing from the spirit and scope of the invention.