Sheet metal forming tool

Details Sheet metal forming tool Sheet metal forming tool

2002-08-22

2004-05-25

Larson, Lowell A. (Department: 3725)

Metal deforming

Tool and/or tool holder

Including flexible or yieldable tool or support

C072S705000

Reexamination Certificate

active

06739173

ABSTRACT:

TECHNICAL FIELD
This invention relates generally to sheet metal forming and more particularly to repairing dents and dings in body panels of vehicles.
BACKGROUND
Historically, dents in the sheet metal body panels of vehicles have been repaired by various manual pulling, filling, and repainting techniques. Unfortunately, these old techniques are time consuming, expensive, require substantial skill and experience, and often produce less than desirable results. More recently, dent repair tools and techniques have been developed that eliminate many of these problems. In general, these new techniques involve adhering a small specially shaped plastic puller to the central portion of a dent with a high strength adhesive and applying a pulling force to the puller, preferably with a pneumatic or hydraulic pulling tool, to pull the dent back to a flush configuration.
Inevitably, an impacting object that causes a depression or dent in the sheet metal of a vehicle body also, at the time of impact, causes the sheet metal to raise a small amount around a portion of the indented area. This impact forms an arched raised lip or rim around part of the dent, which is known in the industry as an “eyebrow.” Prior to pulling a dent out of a body panel, a dent removal technician first must treat the surrounding eyebrow by carefully hammering it down until it is flush with the surrounding sheet metal. Otherwise, the eyebrow will remain visible as a small arched raised bump where the repair was made.
Currently, techniques for treating eyebrows are difficult to learn and require substantial skill and experience to master. These techniques involve the use of a hard plastic punch-like device that is placed over the eyebrow and carefully tapped repeatedly with a sheet metal hammer until the eyebrow is hammered back to a flush configuration. In many instances, and particularly when a technician is not experienced or is in a hurry, this technique can result in the raised sheet metal of the eyebrow being over or under stretched and, more often than not, causes tiny dents, kinks, or other collateral damage that cannot be repaired without sanding and repainting the entire area of the original dent.
Accordingly, a need exists for a methodology and a tool for treating eyebrows when repairing dents in vehicles that tends to be more reliable, accurate, and as fast as existing methods and tools; that reduces the risk of over stretching the metal beyond a flush configuration; that reduces the risk of collateral damage to the indented area; and that does not require a high level of skill and experience of a dent removal technician. More broadly, a need exists for a sheet metal forming tool and technique for removing small raised areas in the sheet metal. It is to the provision of such a tool and methodology that the present invention is primarily directed.
SUMMARY OF THE INVENTION
Briefly described, the present invention encompasses a sheet metal forming tool specifically designed to treat a raised eyebrow surrounding a dent in a body panel of a vehicle before the dent is pulled out. More specifically, the tool is designed to remove an eyebrow by progressively hammering it back down to a configuration flush with the surrounding surface while avoiding the risk of over depressing the eyebrow beyond flush or causing collateral damage to the sheet metal. The tool comprises a hammer driver operably connected to a metal forming attachment for treating an eyebrow. The hammer driver may be a hand-held pneumatic type driver. The attachment comprises a hammer, a base, and a hammer pad aligned to engage the hammer when the hammer is actuated. The hammer is contained within a housing coupled to the hammer driver and extending to a distal end. A head defining the base and the hammer pad is mounted to the distal end of the housing. The head, hammer pad and base may be formed of a suitable polymeric material, such as polyurethane or machined rubber that tends to be both substantially rigid and non-marring. The head is molded, machined, or otherwise formed to define a generally flat ring-shaped support base, which surrounds the convex or dome-shaped structure referred to herein as the hammer pad. The inside surface of the hammer pad within the housing may be formed with a concave shape. Thus, when viewed in cross-section, the hammer pad portion of the plastic base resembles a section of a sphere.
An elongated hammer is reciprocally and axially mounted within the housing and has a proximal end coupled to the piston of the hammer driver and a distal end located adjacent the inside surface of the hammer pad. The distal end of the hammer is formed with a convex or dome shape that is sized to complement and to nest within the concave inside surface of the hammer pad when the hammer is driven into engagement with the pad. When the hammer is driven toward the inside surface of the hammer pad by the hammer driver, its convex distal end impacts and nestles or nests within the concave inside surface of the hammer pad. This impact, in turn, causes the plastic material of the head to stretch slightly such that the hammer pad moves or flexes slightly outwardly with respect to the plane of the surrounding support base. After the impact, the hammer pad returns to its rest position with respect to the support base. In use, the hammer is repeatedly driven against the inside surface of the hammer pad by the pneumatic hammer with a frequency, for example, in the range of between 2000 and 5000 impacts per minute.
The present invention also encompasses a method for forming sheet metal that generally comprises placing a metal sheet forming tool as described above over the section of the sheet metal containing an a raised portion such that the hammer pad of the tool defined in the head overlies the raised portion and the base of the tool rests upon the surface of the sheet metal adjacent the raised portion. The hammer of the tool is activated to engage the hammer pad, thereby causing the pad to reciprocally flex outward. The head of the tool may be moved back and forth along the raised portion to smooth out the defect.
More specifically, when using the tool to carry out the method of the invention, a dent repair technician places the head of the tool over an eyebrow to be treated with the support base resting on the undamaged surface of the sheet metal surrounding the eyebrow and with the dome-shaped hammer pad overlying the eyebrow. The pneumatic hammer is then actuated to drive the internal hammer repeatedly against the inside surface of the hammer pad. With each impact, the hammer pad moves outwardly a slight distance with respect to the plane of the surrounding support base. The air pressure to the hammer may be adjusted such that the center portion of the hammer pad moves outwardly to a position substantially in the plane of the support base. Since the support base rests on the undamaged sheet metal surface adjacent the damaged area, the plane of the support base lies in and is co-extensive with the original plane of the surface prior to being damaged. Therefore, because the eyebrow is raised relative to this original plane, the outwardly flexing hammer pad impacts the eyebrow with substantial force, causing the metal in the region of the eyebrow to be bent back toward a flush configuration.
Repeated impacts by the hammer pad at the aformentioned frequency of between 2000 and 5000 per minute gradually and gently hammer the eyebrow down until it is again flush with the surrounding surface of the sheet metal. In practice, it has been found that slowly moving the tool around and along the eyebrow during operation gradually massages the eyebrow down to its flush configuration along its entire length without causing the kinking and other small difficult-to-repair collateral damage common with prior art manual techniques. The elimination of such collateral damage is due, at least in part, to the smoothly contoured hammer pad and the non-marring plastic construction of the head.
Further, since the center portion of the hammer pad moves outwardly to the pla

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