Trimming apparatus and method

The excess covering material is trimmed from a workpiece using a blade assembly having side by side blade segments with cutting edges aligned with the contour to be cut. A rubber roller applies a longitudinal cutting force to the blade segments in sequential fashion by rolling across the blade segments ends opposite the cutting ends. The blade segments are returned to the noncutting position by a tension wire threaded through a notch in the shaft of each of the blade segments. Cutting pressure is adequate to cut through at least three layers of covering material without scoring the substrate. The rubber roller provides ceertain resiliency which helps control the cutting pressure.

BACKGROUND AND SUMMARY OF THE INVENTION 
The present invention relates generally to trim cutting. More particularly, 
the invention relates to an apparatus and method for trimming cloth, vinyl 
and plastic from around the periphery or along a contour of a workpiece 
such as vehicle interior quarter panels, headliners and the like. 
Present day automotive interiors are usually manufactured by vacuum forming 
a vinyl or plastic covering around a substrate of processed wood, 
cardboard or other natural or synthetic materials. The vacuum forming 
process involves wrapping the vinyl or plastic covering around the 
substrate, leaving a certain excess covering to be later trimmed. The 
vinyl or plastic is then heated and a vacuum is applied to cause the 
covering to conform closely to and adhere to the substrate. After the 
heated part has cooled, the edges of the covering must be trimmed so the 
end product will have a neat appearance. In many cases, the contour of the 
substrate, which corresponds generally to the contour of the end product, 
is an irregular or complex shaped owing to the physical dimensions of the 
vehicle interior. Because of this complex shape, the edges of the covering 
may be folded back upon themselves or pleated, meaning that in some places 
the trimming must be made through several layers of material, whereas in 
other places the trimming is only through a single layer. Also, in 
trimming away the excess or offall, care must be taken to avoid cutting 
into or scoring the substrate. A score in the substrate shows up as a 
blemish line in the end product and can also structurally weaken the part. 
Because of these difficulties, present day manufacturing processes still 
rely on hand trimming of vehicle interior parts. This adds considerably to 
the manufacturing time and cost of the vehicle. Punch presses have been 
used successfully to punch holes through the covering and substrate for 
mounting door handles, window handles and the like. These punches do not 
work satisfactorily in trimming operations, because it is difficult to 
predict where multiple folds in the covering will appear and because it is 
difficult to properly regulate the cutting force to trim the covering 
without damaging the substrate. 
The present invention overcomes the foregoing difficulties and provides an 
automated apparatus for trimming along a contour of a workpiece. The 
apparatus and method encompassed by the invention thus eliminate costly 
and time consuming hand trimming of vacuum formed vinyl interior parts. 
In accordance with the invention, a blade assembly is positionable at least 
partially along a line defined by the contour to be trimmed. The blade 
assembly comprises a plurality of blade segments arranged side by side and 
along the line defined by the contour. A means is provided for 
sequentially pressing the blade segments into cutting contact with the 
workpiece, thereby causing the blade segments to trim the workpiece. A 
means is also provided for urging the blade segments out of cutting 
contact with the workpiece after the trimming has been effected. 
The cutting blade assembly comprises a plurality of elongated blade 
segments, each segment having a longitudinally extending shaft and a 
cutting blade tip. The segments are substantially greater in length than 
width, the width being nominally 0.187 inches. The blades segments are 
positioned side by side in order to follow a contour to be trimmed and are 
individually moveable between a resting position and a longitudinally 
displaced cutting position. Each of the segments has an aperture therein. 
The apertures are generally aligned with one another when the segments are 
aligned in the resting position. A tension wire is threaded through the 
apertures to join the segments together. A spring is connected to the 
tension wire for placing the tension wire under tension and for thereby 
causing the segments to return to the resting position after being 
displaced to the cutting position. 
The trimming apparatus employs a roller disposed adjacent to the end of the 
blade segments opposite the cutting blade. Included is a means for moving 
the roller along the line of the contour, to cause the roller to 
sequentially contact the edges of the blade segments. A mechanical or 
fluid pressure means is provided for applying a force on the roller, to 
cause the roller to exert longitudinal pressure on the blade segments as 
the roller is moved along the line of the contour. This cause the roller 
to sequentially force the blade segments into cutting contact with the 
workpiece. 
The method of cutting is capable of trimming through at least three folds 
of vinyl, plastic or cloth covering without scoring or damaging the 
substrate beneath. The blade pressure is preferably on the order of 60 
pounds per 100/1,000th of linear width of the cutting blade. A urethane 
roller provides a resilient surface which takes up excess pressure. The 
invention can follow curved contours about flat workpieces and also about 
nonflat workpieces. The invention is thus well adapted for trimming vacuum 
formed vinyl vehicle interior parts.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring first to FIG. 1, an exemplary door panel workpiece is illustrated 
at 20. The workpiece comprises a substrate 22, which may have one or more 
cut out regions 24 to accommodate door handles, arm rests, ashtrays, 
mirror control knobs and the like. A cloth, plastic, vinyl or other 
covering material 26 is bonded to the substrate as by vacuum forming. The 
workpiece of FIG. 1 is shown in the untrimmed state. When trimmed, the 
workpiece would have the shape defined by the contour 28 of the substrate, 
with the free or unbonded covering material comprising the excess or 
offall. 
FIG. 1 is somewhat diagramatic in the sense that the substrate may not be a 
flat plane but might have a three dimensional contour. Also, during the 
vacuum forming or bonding process, the excess covering material may be 
puckered, folded or pleated in the vicinity of the curved portions of 
contour 28. This folding can often vary considerably from workpiece to 
workpiece, making automated trimming heretofore difficult to accomplish 
and unreliable. 
FIG. 2 illustrates workpiece 20 positioned in a first embodiment of the 
trim cutting apparatus 32. The workpiece 20 is seen in edge view, better 
showing the three dimensional contoured nature of the workpiece. 
Trim cutting apparatus 32 comprises a workpiece holding fixture 34 which 
includes lower supporting blocks 36 and pneumatically assisted upper 
clamping block 38. The pneumatic clamping devices are illustrated at 40. 
The invention employs a segmented blade assembly 42 which is also shown in 
FIGS. 3 and 4. As perhaps best shown in FIG. 4, the segmented blade 
assembly comprises a plurality of individual blade segments 44. The blade 
segments are arranged side by side and follow a line, curve or contour 
defined by the contour 28 of the workpiece to be trimmed. As illustrated, 
the blade segments are substantially narrower in width than in length. In 
the presently preferred embodiment, the blade segments are nominally 0.187 
inches in width and can be on the order of 11/2 to 2 inches long. Of 
course, the blades can be made in other lengths and widths to suit the 
particular application. 
With momentary reference to FIGS. 11 and 12, each blade segment comprises 
an elongated blade shaft 46 which is generally diamond-shaped or square in 
cross-section (see FIG. 12). A blade is formed at one end 48 generally as 
shown. Referring to FIG. 12, the blade extends across one diagonal of the 
diamond-shaped cross-section. The opposite end 50 is substantially flat. 
At an intermediate position, shaft 46 is provided with a notch or aperture 
52. 
Referring back now to FIG. 4, the blade segments 44 are aligned so that all 
notches 52 lie in the same plane when not in use. More specifically, when 
the blade segments are all positioned with blade ends in the noncutting or 
at rest position, apertures 52 line up with one another to receive tension 
wire 54. Tension wire 54 is pulled taut by a spring mechanism 56 which 
tends to hold the blades in the generally aligned, noncutting or resting 
position shown generally at A. As will be more fully explained, the blades 
are urged into a cutting position by force provided by a roller 58. Blades 
in the cutting position are shown generally at B. The presence of roller 
58 forces blade segments into the cutting position against the back 
tension provided by tension wire 42 and spring mechanism 56. As will be 
explained, the roller is rolled or urged in a transverse direction 
relative to the longitudinal dimension of the blade segments so that it 
sequentially contacts the opposite ends 50 of each of the blade segments. 
This causes a wave-like cutting motion to progress from blade segment to 
blade segment in the direction of roller movement. 
The trim cutting apparatus 32 illustrated in FIG. 2 has blade segments 
which are mounted on a pivoting blade fixture 60. The blade fixture 60 is 
shown in greater detail in FIG. 3. Blade fixture 60 holds the blades in 
one of two positions, an open, workpiece accessing position and a closed, 
cutting position. The cutting position is shown in FIG. 2. In FIG. 3, the 
cutting position is shown in solid lines and the open position in dashed 
lines. Actuator 62 (FIG. 2), which may be hydraulic, pneumatic, mechanical 
or electromechanical, moves the blade fixture between the two positions. 
In the open position, the workpiece may be readily inserted for trimming 
or removed after trimming. In the closed position the blades are oriented 
generally vertically for cutting. Rollers 58 are seen in FIG. 2 in contact 
with the blade segments. The rollers are pressed into contact with blade 
segments 42 by pneumatic or mechanical actuators 64, which apply pressure 
to the rollers. Preferably, the roller pressure is on the order of 60 
pounds per 100/1,000th of linear width of the cutting blade. The rollers 
are preferably made of a resilient material such as urethane rubber, 
preferably having a shore A, 40 durometer resilient rolling surface. By 
controlling the pressure on the blades and by providing a proper resilient 
rolling surface, adequate cutting pressure is delivered to the blades 
without generating too much pressure which would cut through or damage the 
substrate of the workpiece. 
As better seen in FIG. 3, the blade fixture 60 is connected to actuators 62 
through linkage 66 which is in turn coupled to coupling pin 68. The blade 
fixture has a body portion 70 which is pivoted for rotation about pivot 
pin 72. The holder supports the blade segments in a chuck 74 which has a 
recessed portion 76 to accept the end of the workpiece 20. When the blade 
fixture is in the closed or cutting position, the offall 30 of workpiece 
20 is folded inwardly by virtue of being captured in recess 76. After the 
blade assembly has made its cut entirely along the contour to be cut, the 
offall falls into the center of the workpiece where it may be readily 
removed as the workpiece is being removed. 
Another embodiment of the invention is illustrated in FIGS. 5, 6 and 7. 
Referring first to FIG. 5, the trim cutting apparatus is shown generally 
at 78. The workpiece is illustrated generally at 20. A base 80 supports 
both the cutting apparatus and the workpiece in the manufacturing 
environment. As illustrated, the cutting apparatus comprises a track 82 
which generally encloses the workpiece. The segmented blade assembly 42 is 
mounted inwardly of the track with the blades in a generally horizontal 
plane. Unlike the embodiment described above, the segmented blade assembly 
does its cutting in the horizontal position. The blade segments 44 are 
selected of an appropriate length to span the distance from the contour to 
be cut 28 to the track 82. As illustrated, the blade segments at the 
corners of the track and workpiece have angled cutting blade ends 48A. For 
the workpiece illustrated in FIG. 5, four separate blade assemblies 42A, 
42B, 42C and 42D would normally be employed. In this fashion, each blade 
assembly comprises a plurality of blade segments laid side by side and 
generally parallel to one another. Thus, it will be understood that blade 
assemblies 42A, 42B, 42C and 42D follow and circumscribe the full contour 
28 of the workpiece. 
Disposed in track 82 is one or more rollers 58 constructed preferably of 
urethane or another resilient material having the properties described 
above in connection with the embodiment of FIGS. 2-4. Roller 58 travels 
around track 82 by means of a chain drive mechanism described below. As 
the roller circumnavigates the track, it depresses the blade segments in 
sequence to effect the cutting operation. FIGS. 6 and 7 illustrate the 
roller and chain drive mechanism in greater detail. As seen in FIG. 6, 
workpiece 20 is held in place by means of supporting blocks 36 and 
clamping block 38. As shown, workpiece 20 comprises substrate 22 and 
covering material 26 with the excess portion or offall illustrated at 30. 
Roller 58 is journaled for rotation as at 84. Roller 58 is driven around 
track 82 by drive linkage coupler 86 which is connected to chain drive 88. 
FIG. 7 shows the chain drive mechanism in greater detail. The chain drive 
mechanism includes chain drive 88 which is driven by sprocket 90 (also 
shown in FIG. 5). Sprocket 90 is coupled through a drive shaft 92 to a 
conventional motor (not shown). 
Yet another embodiment of the invention is illustrated in FIGS. 8, 9 and 
10. This embodiment uses an alternate drive mechanism. Instead of the 
track and chain drive mechanism, the invention may be practiced using a 
pulley driven carriage illustrated in FIGS. 8 and 9. The carriage 94 
carries roller 58 which is positioned to supply pressure to the blade 
segments 44. Roller 58 may be fabricated from urethane rubber or another 
resilient material having the characteristics described above. Roller 58 
is journaled about axle 96 which is positioned in a yoke 98. Springs 100 
apply a force on axle 96 in the longitudinal direction of the blade 
segments. The springs provide the proper pressure for cutting the covering 
material, preferably on the order of 60 pounds of force per 100/1,000th of 
blade. FIG. 10 illustrates a blade segment 44 in contact with roller 58. 
Note the tension wire 54, shown in cross-section. 
The carriage 94 is connected to a pair of cables or chains 102 which are in 
turn wrapped around pulleys 104. A motor drive unit 106 is provided for 
driving the pulleys which in turn cause the carriage to travel along the 
contour to be cut. 
The embodiments described above are well calculated to effect efficient 
automated trimming of a workpiece without damaging the underlying 
substrate. In accordance with the inventive method, the trimming apparatus 
operates as follows. First the workpiece to be cut is positioned in the 
trimming apparatus and clamped in place. In the embodiment shown in FIGS. 
2 and 3, the segmented blade assembly is then moved into position using 
actuators 62. Once the workpiece is properly in position, the blade ends 
48 of the blade segments are positioned adjacent the contour to be cut 28. 
Because the blade segments are quite narrow and because of the flexibility 
afforded by the tension wire structure, the blade assembly can be made to 
follow virtually any curved or irregular contour. 
Next, the roller 58 is caused to roll across the segmented blades creating 
a wave-like cutting action which cuts into the covering material, severing 
it. By controlling the force applied to the roller and because of the 
resiliency of the roller, the cutting pressure delivered through the blade 
segments is closely controlled, sufficient to cut through at least three 
layers or folds of covering material, but insufficient to score the 
substrate beneath. This is particularly advantageous for some workpieces 
which by their nature have puckered or folded edges due to tight corners 
or complex curves. 
As the roller moves along the contour to be cut, the blade segments spring 
back into their resting position after cutting, due to the return force 
provided by tension wire 54. When the roller or rollers have made a 
complete traverse of the contour to be cut, the workpiece can be extracted 
from the apparatus and the offall removed. In the case of the embodiment 
illustrated in FIGS. 2 and 3, removal of the workpiece is effected by 
first returning the blade assemblies to the open position prior to 
removal. 
From time to time it may be necessary to replace one or more blade segments 
as they become dull. This is quite easily done by pulling the tension wire 
laterally outwardly from the aperture 52 so as to free the blade from the 
assembly. The blade may then be lifted upwardly from the blade fixture and 
a new blade inserted. The new blade is then held in place with its 
aperture 52 in line with the apertures of adjacent blades and the tension 
wire is then released, so that it snaps back in place and engages the 
aperture of the new blade, holding it in place. 
From the foregoing it will be seen that the present invention provides an 
apparatus and method for trimming along a contour of the workpiece. While 
the presently preferred embodiments are well calculated to fulfill the 
requirements of an automated trimming apparatus, it will be understood 
that the invention is susceptible to certain modification and change 
without the parting from the spirit of the invention as set forth in the 
appended claims.