The present invention relates to a scoring tool for trimming sheet metal or vinyl sheet stock in a bending brake.
In construction and building trades, aluminum trim installation applications use aluminum sheet metal or vinyl for trimming out soffit, fascia, corners and edges of siding sections and window and door frames. Sheet metal or vinyl from coil stock is cut, shaped or bent by workmen on-site using sheet metal bending brakes, saw tables and coil slitters. The sheet metal or vinyl is held by the bending brake during forming operations. Common bends created include simple flanges, brick molding, and J channel shapes. The stock material is also held by the bending brake for cutting to size.
Roller cutters having opposed rollers have long been used in Europe and were recently introduced in the United States to cut material longitudinally along the length of the brake. A problem with the use of opposed rollers to cut thin sheet stock is that the roller cutters may leave a wavy edge that is referred to as xe2x80x9crippling.xe2x80x9d This is an inherent problem due to the need for roller cutters to cut different thicknesses of material. In particular, roller cutters are most effective when there is an overlap of the opposed rollers equal to approximately 7% of material thickness. If there is any variance from this optimum overlap, rippling will result.
Other problems with roller cutters can cause rippling. If the roller cutter knives separate laterally the knives will tend to tear the material rather than cut the material causing rippling. Also, if the tool becomes misaligned on the top clamping bar, this may be referred to as being xe2x80x9ctoed-inxe2x80x9d or xe2x80x9ctoed-out,xe2x80x9d the tool may make irregular cuts causing rippling.
Sheet stock having a thickness of 0.019xe2x80x3 to 0.040xe2x80x3 is commonly cut with roller cutters and formed with portable sheet metal bending brakes. The rollers can be set to cut thicker sections of material with a 7% overlap, but when thinner sections of material are subsequently cut, they may ripple due to excessive overlap. If the rollers are set to provide a 7% overlap to cut thin material then cutting quality problems may arise when thicker stock is cut. Rippling and inaccurate cutting can also result if there is a slight variance in the tool geometry or location of the cutting rollers.
As a piece of material is cut off from a main section by a roller cutter, the piece cut-off is generally unsupported and drops to the ground. Since the tools are intended to be used at a job-site the material cut-off may be damaged when it falls to the ground.
Roller cutters also suffer from the disadvantage of being difficult to precisely align the location of a cut since there is no quick reference provided on the roller cutter or brake for the location of the cut made by the roller cutter. Once the tool is aligned, the roller cutter may tend to ride up and off the track formed on the top clamping bar.
Another approach used in the prior art is to score a section of sheet metal or vinyl with a utility knife that is guided xe2x80x9cfreehandxe2x80x9d by following a lip of an upper clamping member of the sheet metal bending brake. The lip of the upper clamping member is generally located directly above a piano-type hinge that is used to connect a lower bending bar to clamping jaws of the sheet metal bending brake. Generally, a worker will score the coil stock by moving the utility knife along the lip of the upper clamp to score the material. A worker pulls up on the handle of the bending bar causing the bending anvil to work the material at the point where it has been scored by closing the score line. Generally this is insufficient to break the sheet metal which must then be bent up and down repeatedly until the metal breaks at the score line. This process may leave a rough edge on the material because the material is bent back and forth. This method also can result in the score line having curves or deviations especially if the worker is not experienced or careless in scoring the coil stock. Furthermore, the hinge and other parts of the brake can be nicked or scraped by a utility knife if the utility knife is pushed beyond the end of the sheet stock.
These and other problems and disadvantages associated with the prior art devices for trimming sheet metal are resolved by Applicant""s invention as will be summarized below.
According to the present invention, a trim stock scoring tool is provided that includes a knife blade mounted on a carriage. Vinyl or aluminum sheet stock is held in a bending brake, slitter, saw table, or coil holder that is provided with a track on which the carriage is designed to be moved to score the sheet stock.
According to another aspect of the invention, the carriage holds the knife so that it contacts the section of coil stock to be trimmed immediately outboard of the bending bar of the bending brake so that the knife blade does not come in contact with the hinge or any other part of the brake if it is moved past the edge of the coil stock. The outboard location of the score line facilitates breaking off the piece of coil stock by bending the coil stock downwardly against the outboard edge of the bending bar, causing the score line to be expanded as the metal or vinyl is bent downwardly. If an appropriate depth of cut has been achieved, a single downward bend of the portion of the stock to be trimmed off should be sufficient to break the stock. In some instances, a single downward bend may cause the material to fracture and a single upward bend, back to level, will sever the material.
The carriage preferably is provided with concave rollers that follow a complimentary convex track that assures that the score line is formed in a straight line.
In practice, the invention may use common utility knife blades that are mounted on a knife retainer that is in turn pivotally supported in a knife retainer housing. The knife retainer is pivotally supported to allow adjustment of the height of the knife blade so that as it is pushed (or pulled) across the coil stock it causes the coil stock to be scored. The knife retainer preferably retracts into a knife retainer housing that shields the knife blade during storage.
The outer edge of the bending bar is preferably located approximately xc2xexe2x80x3 outboard of the upper clamp bending edge. This corresponds to the most common segment of length for hemming or for forming brick molding and J channel shapes. By locating the cut xc2xexe2x80x3 from where a bend will be formed, the brake may be clamped on a section of sheet stock, trimmed with the trim stock scoring tool and then the xc2xexe2x80x3 bend may be formed without having to reposition and reclamp the material.
Layout of cut locations is simplified using the trim stock scoring tool of the present invention since the cut is always formed at the outer edge of the bending bar. Workmen may simply visually line up marks located on the sheet stock for cut locations with the outer edge of the bending bar, thereby eliminating the need to make additional measurements that are required with roller cutters.
The knife retainer housing of an alternative embodiment of the invention may include an adjustable mounting mechanism for mounting the knife retainer within the knife retainer housing so that the knife blade is at the proper height for scoring. The adjustment mechanism may include a spring that exerts a biasing force downwardly on the knife retainer causing the knife blade to be resiliently secured within the knife retainer housing. This resiliency provides some degree of tolerance in adjusting the height of the knife so that adequate scoring is provided without overscoring that can lead to excessive knife wear. The force applied to the knife may be controlled by the strength of the spring used.
An alternative method of securing the knife retainer within the knife retainer housing is to provide an arcuate slot and screw lock connection between the knife holder and the retainer housing.
A preferred embodiment of the invention may include a handle for the knife retainer that is pressed by a worker""s hand to apply the appropriate degree of force for scoring the sheet stock.
The knife retainer housing may be removed from the carriage to permit other tools such as a roll forming tool to be attached to the carriage.
These and other advantages of the invention will be better understood in view of the attached drawings and detailed description of the invention below.