Field of the Invention

This invention relates to trimming apparatus for trimming excess material from multi-dimensional

5 workpieces such as pre-formed films of paint, decorative or functional plastic or metal and the like as well as other non-film workpieces.

Background of the Invention

It is known in the art to provide preformed 1.0 paint films shaped to conform with the exterior configuration of a molded plastic part such as an automobile bumper, fender or the like. Such a film may be placed in a mold in which the finished part is to be formed so that, after completion of the molding process, 5 the bumper, or other part, has the pre-formed paint film integrated with and forming its exterior surface.

In order to fit properly in the mold, the pre¬ formed film must have its edges trimmed to remove any excess material remaining after formation of the film. 0 Various methods and devices have been used to perform the trimming operation, including hand trimming and fixture supported knife or laser cutting, sometimes performed by programmed robot machines.

The high labor costs of hand trimming and the 5 complexity and expense of programmed robot machines leave an opportunity for development of less complex and lower cost trimming apparatus incorporating simple fixtures and trimming mechanisms with a capability for accurate trimming of films and other workpieces.

Summary of the Invention

The present invention provides trimming apparatus and methods of relatively low cost and complexity employing novel mechanisms and methods for the automatic or semi-automatic trimming of the edges of films and other workpieces. Various features of the invention are usable alone and optionally combinable to provide some or all of the advantages of the apparatus and method. Among the features of the invention are that:

A steerable cutter is guided by dual followers engaging a first cam operative in a first plane to follow the prescribed edges of a workpiece as projected on the first plane. The cutter is preferably a circular rotary cutter wheel.

- A second cam operative in a second plane normal to the first plane guides the cutter and the first cam to follow the edges of the workpiece as projected on the second plane, thus providing for trimming of three dimensional workpiece edge configurations.

- A work holder supported on a base carries a workpiece optionally having edges requiring trimming and extending in three dimensional space. For film type workpieces, a perforated vacuum form is used as a nest to retain the film in position for trimming. Suitable clamping means are preferably provided for clamping excess material to be trimmed during the trimming operation.

- The base optionally supports first, second and third carriers respectively movable in lateral, longitudinal and vertical directions to provide three dimensional tool motion. A fourth carrier may also provide lateral motion to provide lateral cam controlled motion separate from a lateral clearance motion for loading and unloading workpieces.

- In a modified embodiment, cams are eliminated and the first, second and third carriers are actuated by servo motor driven screws or the like while the steerable cutter is rotatably controlled by a servo motor drive or the like.

These and other features and advantages of the invention will be more fully understood from the following description of certain exemplary embodiments of the invention taken together with the accompanying drawings.

Brief Description of the Drawings

In the drawings:

FIG. 1 is a partial transverse cross-sectional view of trimming apparatus according to the invention,-

FIG. 2 is a partial longitudinal cross- sectional view of the trimming apparatus of Fig. l showing the tool holder carriers;

FIG. 3 is a partial plan view of the apparatus of FIGS. 1 and 2 having portions broken away to further illustrate the invention;

FIG. 4 is an enlarged cross-sectional view of the tool holder follower and cutter construction,-

FIG. 5 is a view similar to FIG. 2 but showing an alternative embodiment utilizing servo motor drives for the carriers and tool holder,- and

FIG. 6 is a view similar to FIG. 4 but showing the servo motor driven tool holder of FIG. 5.

Detailed Description of the Invention

Referring now to the drawings in detail, numeral 10 generally indicates a trimming apparatus formed in accordance with the invention. Apparatus 10 includes a base 12 on which a positioning carrier 14, formed as a support plate, is supported for lateral motion on linear bearings 16 moveable along a pair of tracks 18, only one of which is shown. Suitable means, such as an air cylinder 20 acting between the base 12 and the carrier 14, are provided for moving the carrier between an operating position shown in the figures and a loading position, not shown, which will be subsequently more fully described.

Mounted upon the positioning carrier 14 is a lateral follower carrier 22 which is supported for lateral motion on linear bearings 24 laterally moveable upon tracks 26, only one of which is shown. A horizontal cam plate 28 is also fixed to the carrier 14 and includes an upwardly open closed-sided cam grove 30 lying in a horizontal plane and extending longitudinally and laterally across the cam plate for a purpose to be subsequently described.

Extending vertically upward from the lateral follower carrier 22 are a plurality of vertical supports 32 which are aligned longitudinally along the horizontal carrier 22 and are fixed in vertical and horizontal alignment by suitable means such as support webs 34 or other supporting means. Mounted on the supports 32, is

a vertical cam plate 36 in which is formed a laterally open closed-sided cam groove 38 extending in vertical and longitudinal directions along the cam plate 36.

Also mounted on the vertical supports 32 are a pair of vertically spaced horizontally extending cam tracks 40 mounted upon support spacers 42 secured to the vertical supports 32. The cam tracks 40 support vertically spaced horizontally moveable linear bearings 44 which in turn support a vertical member in the form of a post 46, a portion of which forms a vertical bearing track 48. A linear bearing 50 is moveable on the track 48 and carries a bracket 52 which in turn supports the housing 54 of a precision ball bearing set 56.

Bearing 56 rotatably supports a follower shaft

58 on which are mounted a pair of diametrically spaced roller cam followers 60. The cam followers 60 are positioned so that they extend into and engage the cam groove 38. An outwardly opening hollow portion of the follower shaft 58 receives a shaft portion 62 of a tool holder 64. The shaft portion 62 includes a hollow center 66 in which a spring 68 is mounted compressed between the shaft portion 62 and the follower shaft 58 to bias the tool holder 64 outward, away from the cam followers. A support 70 at the outer end of the tool holder 64 carries a circular cutter wheel 72 which is mounted for rotation on a screw 74 with a washer spring 76 or equivalent urging the sharpened edge of the cutter wheel against a support surface 78 which intersects the axis of rotation of the tool holder 64 within the bearing 56.

At its lower end, the vertical post 46 carries a bracket 80 on which a single roller cam follower 82 is mounted extending downwardly into the cam groove 30 of the horizontal cam plate 28 for a purpose to be

subsequently described. Suitable linear drive means, such as a ball screw 84 or, optionally, a rodless air cylinder or other linear actuating means, is mounted upon the vertical supports 32 and connects with the vertical post 46 for moving the post 46 and the associated tool holder horizontally on bearings 44 along the bearing tracks 40.

Also mounted upon the base 12, in a manner not shown, is a work holder 86 in the form of a nest comprising a porous filler material 88 surrounded or enclosed by an outer cover 90 formed of relatively stiff material such as fiberglass and having a plurality of perforations or vacuum holes spaced along the surface. The cover 90 is mounted upon a support 92 which includes a vacuum connector tube 94 for connecting the porous interior of the work holder nest with a source of vacuum, not shown.

The outer surface of the cover 90 is configured to an identical shape to that of the exterior of a component, such as an automobile bumper, on which a film, such as a preformed paint film 96, is to be applied. The film 96 is preformed in other suitable equipment, not shown, to the desired shape and is then installed upon the nest with its inner surface directly engaging the outer surface of the cover 90 as shown. A vacuum applied to the nest interior through the connector tube 94 is utilized to hold the paint film in place on the cover 90 of the work holder. Additionally, if desired, one or more spring loaded plungers 98 may be mounted on one or more of the vertical supports 32 so as to engage the paint film 96 during operation and assist in holding it in position. Such a plunger type clamping means would, however, preferably be used with other types of films which are not so likely to be damaged or have their finish marred as would the described paint film.

Excess material 100, formed as part of the paint film 96 and located below the cutting line of the cutter wheel 72 to be trimmed off during the trimming operation, is preferably held in place on the nest cover 90 by a clamp 102 extending horizontally along the length of the nest and actuated by one or more cylinders 104 or other suitable devices. The work holder 86 is positioned such that when the carrier 14 is advanced to the operating position shown in the figures, the cutter wheel 72 is forced into engagement with the paint film 96, partially collapsing the spring 68 and exerting a controlled force on the cutter which pierces the paint film and engages the backing surface of the work holder 86. This surface may be formed of any suitable material; however, nylon is preferred since it has good resistance to being damaged by a cutter such as the cutter wheel. Preferably, as shown, a groove 106 is formed in the fiberglass surface of the cover 90 in which a backing strip 108 of nylon is formed. The nylon backing strip and the associated groove are formed behind the edge of the paint film to be trimmed at the upper edge of the excess material 100 so that the backing strip is engaged by the cutter wheel during its full travel from one end to the other of the portion of the paint film to be trimmed by the apparatus 10.

In operation, the air cylinder 20 is released, or actuated, to move the positioning carrier 14 laterally away from the work holder 86 so that the cutter wheel 72 and the optional plunger clamp 98, if used, are retracted by moving them away from the surface of the cover 90 and the associated paint film 96, or other workpiece if used. The previously trimmed paint film may then be removed and a new film 96 is positioned on the cover 90 for trimming. Vacuum is then applied to hold the film in place and the clamp 102 is actuated to the clamping position shown in the drawings to hold the excess material 100 in position during trimming.

Air cylinder 20 is then actuated to move the positioning carrier 14 into the operating position shown in the drawings wherein the tool holder is advanced toward the work holder until the cutter wheel 72 is pushed against the paint film and spring 68 is partially compressed to force the wheel through the paint film and against the backing strip 108. At this point, the tool holder 64 and the associated vertical post 46 are preferably located at one edge or end of their longitudinal travel.

Thereafter, the linear drive means, such as ball screw 84, is actuated to traverse the vertical post 46 from an initial position adjacent one end of the trimming apparatus longitudinally along the bearing tracks 40 to the other end of the apparatus. This causes travel of the cutter wheel along the edge of the portion of the paint film 96, or other film to be trimmed, from one end to the other. During this travel, the dual followers 60 in the cam groove 38 steer the cutter wheel to maintain it parallel with and guide it along the path formed by the cam groove 38. Groove 38 conforms in shape to a projection on the vertical cam plate of the corresponding shape of the edge of the paint film to be trimmed. If desired, an auxiliary spring or air cylinder 110 may be provided to bias the tool holder 64 and its supporting bearing 56 upwardly so that the cam followers may more easily follow portions of the cam groove 38 which extend in a direction approaching vertical while being driven solely by the horizontally actuated ball screw 84.

During the longitudinal travel of the vertical post 46 and its associated tool holder 64, the cam follower 82 riding in the cam groove 30 of the horizontal cam plate 28 causes the cutter wheel 72 and the post 46 to be moved laterally as required to follow the lateral undulations of the edge of the paint film

being trimmed. For this purpose, the cam groove 30 is shaped or configured as a vertical projection on the horizontal cam plate of the shape of the edge of the paint film being trimmed. The lateral motion of the post 46 causes a like motion of the follower carrier 22 to which the post is connected by bearings 44 so that the cam plate 36 is moved with the tool holder 64. Thus, the roller followers 60 are maintained within the cam groove 38 of vertical cam plate 36 for steering and vertically guiding the cutter wheel 72 while lateral motion thereof is being controlled by motion of the cam follower 82 in the cam groove 30 of the horizontal cam plate 28.

When the vertical post 46 and the associated cutter wheel reach the opposite end of their travel so that the portion of the edge of the paint film to be trimmed has been traversed, the air cylinder 20 is again released, or actuated, so that cutter wheel 72 and positioning carrier 14 are retracted away from the paint film. At this point, further trimming if needed may be accomplished by advancing a second trimming apparatus, similar to that just described, to undertake the additional trimming function. However, if the trimming operation has been completed, the clamping devices are released and the vacuum shut off so that the paint film may be removed from the cover 90 of the work holder 86.

Referring now to FIGS. 5 and 6, there is shown an alternative embodiment of trimming apparatus according to the invention generally indicated by numeral 120. Trimming apparatus 120 is fundamentally similar to the apparatus 10 shown in FIGS. 1-4, so that like numerals are used to indicate like parts. Apparatus 120 differs primarily in that the cam plates 28, 36, roller cam followers 60, 82, lateral follower carrier 22 and air cylinder 110 are deleted and their functions are replaced by other means to be described.

These means include servo driven mechanisms which are controlled by a programmable controller not shown.

As is shown in FIG. 6, the shaft portion 62 of tool holder 64 is connected with a rotatable shaft 122 supported by the bearing set 56 and carrying a worm wheel 124. The worm wheel is engaged by a worm gear 126 that is driven by a servo motor 128 supported by a bracket 130 from the linear bearing 50.

As seen in FIG.5, a vertical ball screw drive 132 is driveably connected with the front of the bracket

52 that is connected with the bearing 50. The ball screw 132 is driven by a servo motor 134 supported by a bracket 136 carried by the post 46. The ball screw 84 that is driveably connected with the post 46 is also driven by a servo motor, not shown, at the other end of the trimming apparatus. A laterally extending ball screw 138, also driven by a servo motor not shown, is driveably connected between the base 12 and the positioning carrier 14 which, in this embodiment, is the only lateral carrier required and on which the vertical supports 32 are mounted. Other features and functions of the apparatus 120 are essentially unchanged from that of the trimming apparatus 10.

In operation of trimming apparatus 120, movement of the circular cutter wheel 72, or other cutting tool, is controlled by actuating the various servo motors of the longitudinal ball screw 84, vertical ball screw 132 and the lateral ball screw 138 as directed by the programmable controller, not shown, to move the cutting tool along the edge of the workpiece being trimmed. The attitude of the cutting tool is controlled by the servo motor 128 acting through the worm gear and wheel 126, 124 to maintain the cutting tool parallel with the direction of motion, thereby

steering the cutting tool as required to maintain a clean cut.

Terms such as longitudinal, lateral, vertical, depth, length, height, and the like as used herein are relative only and not intended to limit the application of the claimed apparatus to use in the positions described. In FIGS. 1-3 of the drawings, double dashed phantom lines are used to indicate some of the alternative positions of movable components shown in full lines in the drawings.

The linear bearings 16, 24, 44 and 50 may be of any suitable type with sufficient accuracy of movement,- however, recirculating ball bearings such as Thompson Accuglide Bearings are presently preferred. Other suitable biasing, actuating and clamping means may be substituted for the cylinders 20 and 110, ball screw 84, spring 66 and clamps 98 and 102. Similarly other forms of cams and structural components of the apparatus may be used as may be appropriate to accomplish the intended purposes. Where appropriate, a knife blade or other type cutter may be substituted for the rotary circular cutter wheel 72. Finally, if desired, apparatus according to the invention may be adapted for trimming flash and other excess material from plastic components or the like in addition to or instead of film materials.

Thus, while the invention has been described by reference to a various specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiments, but that it have the full scope defined by the language of the following claims.