Patent Application
20160158819
This is an original U.S. patent application.
The invention relates to auto body repair. More specifically, the invention relates to pneumatically-operated impact tools for repairing dented body panels.
Vehicle body panels were once formed by hand, with craftsmen beating or planishing metal sheets over solid forms to create desired surfaces. Manufacturing techniques have advanced significantly over the decades, and most contemporary metal body panels are formed by stamping, hydroforming or even higher-tech processes.
However, vehicles often become involved in mishaps that result in damage to these carefully-formed, complexly-curved panels. This damage cannot generally be repaired by removing the panel and re-pressing it in the original forms—the panel will already have been finished with paint or other coatings, and may have been permanently fixed to the vehicle (e.g., by adhesive or welding). Thus, in-place and by-hand repair is usually the most economical, and often the only way to restore a creased, dented or crumpled panel.
Tools to repair body panels typically comprise mechanisms to apply sharp impacts to a panel through a shaped tool head. Tools are often pneumatically operated, although electrical and manual alternatives are also in use. When the tools are too large or unwieldy to position behind a damaged panel, the repair person must often work from the outside of the dent, for example by welding a stud to the panel and then using a tool such as a slide hammer to create tension (pulling) impacts rather than the more common compression (pushing) impacts. Repairs from the outside of a dent thus require additional work to remove the stud and re-finish the panel.
Small, easily manipulated impact tools are known in the art (for example, U.S. Pat. No. 3,813,993 by Smith describes a hand-held pneumatic impact tool that is small enough to operate in confined spaces behind dented panels). Similarly, proposals to adapt impact tools for other applications to use in body repair have been made. For example, U.S. Patent Application Publication No. 2007/0057009 by Thorne and Preacher describes planishing attachments for a “palm nailer”—a small pneumatic device designed to drive nails in places where a hammer cannot easily be used.
The present applicant's long experience in vehicle body repair suggests that these prior art devices are not well known, not commonly used, and have never achieved commercial success. System improvements and methods of use that can turn these known devices into practical, useful tools may be of significant value.
Embodiments of the invention are systems comprising a hand-held pneumatic hammer with an interchangeable tool head and a pneumatic pressure regulator to provide fine control of impact force.
c show views of another embodiment of the invention.
Prior-art standard pneumatic planishing hammers are too large to use in many vehicle body repair situations (for example, in repairing dents to door panels, the hammer may not fit between the exterior panel and the door's supporting structure, or the structure may prevent the application of impacts from the hammer to a part of the dent). Small prior-art hammers may fit in the space available, but they do not offer good control over the impact force, so they may over-strike the dent, causing a convex bulge in the exterior panel that must also be repaired.
Internally, many embodiments use a monostable, short-stroke, pneumatically-driven piston to produce the impact action. One suitable mechanism is shown and described in substantial detail in U.S. Pat. No. 3,813,993 to Smith. The entire disclosure of that patent is incorporated by reference here. Other embodiments may use an electrically-driven solenoid to produce the impact action.
Turning to
A tool according to an embodiment is a monostable reciprocating device—that is, it does not automatically begin hammering as soon as pressurized air is applied. Instead, the toolhead assumes a fixed, stable position until the tool can be maneuvered into place. Then, a single strike or a sequence of strikes can be initiated by a trigger mechanism. In a preferred embodiment, hammering is initiated by pressing the toolhead firmly against the surface to be planished. When the user's pressing force exceeds a predetermined trigger force (set, e.g., by the locations of intake and exhaust ports in a pneumatic reciprocating mechanism and by the applied air pressure) the tool performs a striking cycle. If the user continues to press the tool against the panel with a force exceeding the trigger force, repetitive strikes will be made. Preferably, the stroke of each cycle will be between about 1 cm and 2 cm, although shorter- and longer-stroke tools may have applications in some specialty situations (e.g., operation in extremely constrained areas or on softer or stiffer malleable panels).
In another embodiment, a mechanical trigger (actuated, e.g., by the user's thumb) may initiate striking action. Such a mechanical trigger is shown in
It should be noted that the striking frequency or repetition rate of a tool according to an embodiment depends partly on the reciprocating mass, and partly on the motive pressure supplied by the pneumatic connection. To alter the striking frequency and the inertia of the toolhead that can be transferred to the dented panel, an embodiment may comprise interchangeable toolheads of varying mass—from small, lightweight anvils for rapid, low-inertia hammering, to larger, heavier anvils for slower and more energetic hammering. An embodiment may provide interchangeable extension shafts of varying weight, permitting any particular anvil to be operated at faster or slower hammering rates. See, for example, the toolhead assortment shown in
Varying the air pressure of the system can change the striking frequency, but it also varies the striking force. In fact, Applicant has determined that air pressure control is a critical feature of the inventive system. Without pressure control, a hand-held pneumatic hammer device cannot provide the lighter impacts necessary to finish a repair without over-hammering and out-denting the panel. Thus, an embodiment comprises a pressure regulator, which may be placed at the compressor or air storage tank; inline between the compressor and the tool, or on the body of the tool itself. (On-tool placement is shown in
The embodiments shown in the foregoing figures have a single air supply line and exhaust to the atmosphere. However, an embodiment provided with an air-return line may operate in a closed loop fashion. This may reduce the operational noise emitted by the tool (although the noise of hammering a panel is inevitably significant). With a closed-loop system, motive power may be provided by pressurized liquid (i.e., hydraulically) instead of by pressurized gas.
The applications of the present invention have been described largely by reference to figures showing specific exemplary embodiments, with alternate implementations and operational details as discussed. However, those of skill in the art will recognize that small, hand-held pneumatic or hydraulic impact tools can also be constructed of components shaped or configured differently than herein described. Such variations and alternate configurations are understood to be captured according to the following claims.
