WELDABLE TOOL FOR REMOVING DENTS FROM SHEET METAL

Abstract: A weldable tool for removing dents from sheet metal includes a rod holding an electrode (E) electrically connected to the positive cable (CP) of a welding apparatus, so that it can be spot welded to the sheet metal, as well as a sliding hammer (H) to impart a traction along the longitudinal axis of the electrode-holding rod by means of an impact on a stop (P) so as to pull and straighten the sheet metal. The grounding connection of the sheet metal is achieved through a second hollow rod (R) enclosing the electrode-holding rod and carrying an end plate (C) electrically connected to the negative ground cable (CN) of the welding apparatus, the plate (C) being mobile along the hollow rod (R) with a movement controlled by a resilient contrast means. Once the straightening is over, the spot weld is easily broken by torsion and/or inclination of the tool which can be immediately used at another area of the sheet metal.

Description: "VvΕLDABLE TOOL FOR REMOVING DENTS FROM SHEET METAL" The present invention relates to tools used for removing dents from the sheet metal of vehicles and the like, and in particular it relates to a tool of the type achieving said removal by means of a temporary welding to the sheet metal to be repaired. It is known that for removing dents from sheet metal panels, typically of vehicles or the like, there exist various types of tools which differ mainly in the way the connection between the tool and the sheet metal is achieved. This connection allows to pull the sheet metal outwards in order to restore its planarity without requiring access to the sheet metal from the inner side, which usually requires dismounting the sheet metal. Some tools act on the sheet metal through a mechanical connection which generally requires making a hole in the sheet metal and/or access from both sides, with the obvious drawbacks stemming therefrom. Other tools operate in a non- invasive way through an electromagnetic pulling action directly on the sheet metal, which action is obtained by means of complicated apparatuses generating and controlling a strong electromagnetic field. Further tools achieve the connection to the sheet metal through a spot welding in the dented area, which weld can be easily broken at the end of the sheet metal straightening operation. The present application relates to a tool of this latter type, and in particular to a tool provided with a weight or hammer sliding along a rod which holds at its distal end the electrode to be welded to the sheet metal. Such a tool is disclosed in US patent no.4.376.385 (Davis), which the applicant deems to be the closest prior art, while similar weldable tools using mechanisms other than the sliding hammer to apply a force to the sheet metal are disclosed in US patents nos.5.333.486 (Ishihara) and 5.546.786 (Fugel) as well as in the European patent application no.0.868.950-Al . As mentioned above, all these tools have the common feature of including an electrode which is welded to the dented area and through which a pull is exerted on the sheet metal for the straightening thereof. This electrode is electrically connected to the positive voltage pole of a welding apparatus, whose negative ground pole must obviously be electrically connected to the sheet metal in order to effect the welding. In practice, the grounding connection of the sheet metal, which is permanent, is achieved first, then the electrode is placed into contact with the sheet metal to effect the welding at the desired position. The technical problem dealt with by the present invention is that of achieving in the simplest and most effective way a good grounding connection of the sheet metal so as to obtain a correct and satisfactory weld This connection is conventionally achieved through a clamp, located at the end of the ground cable, which must be clamped to a conductive area of the sheet metal to be repaired (see the above-mentioned Davis patent). In some cases it may be very difficult, when not impossible at all, to find a suitable area where to place the grounding clamp, particularly when you operate on a car In fact, the whole body of the vehicle is usually completely painted with multiple layers of paint which hinder the flow of current, therefore it may be necessary to remove the paint from an undamaged area (which will then have to be painted again) in order to obtain a suitable electrical connection Moreover even if some area of the vehicle is not painted it may possibly be too close to electric and/or electronic components of the car, or it may be too far from the welding area to achieve a good electrical connection through the various insulating elements connecting the car members such as gaskets, vibration- damping supports, hinge lubricants and the like Finally it may also happen that the grounding clamp comes away from the sheet metal due to a movement of the user, or to the shifting of the welding apparatus or because of the vibrations transmitted to the sheet metal by the hammer sliding on the rod when said hammer is used to straighten the sheet metal Therefore the object of the present invention is to provide a weldable tool for removing dents which is free from the above-mentioned drawbacks This object is achieved by means of a tool wherein the grounding connection of the sheet metal is achieved through a contact plate located at the tool tip as better defined in the first claim. Other advantageous features of the present tool are disclosed in the subsequent claims. A first fundamental advantage of the tool according to the present invention is that the grounding connection of the sheet metal is achieved at the welding area without requiring to damage other areas, with a very small distance between the poles which assures a perfect electrical connection and in a practically automatic way since it does not require a separate clamping operation of the grounding clamp A further advantage of the present tool comes from the absolute guarantee that the grounding connection will hold since it is provided by the weld itself Further advantages and characteristics of the tool according to the present invention will be clear to those skilled in the art from the following detailed description of two embodiments thereof, with reference to the annexed drawings wherein: Fig. la is a diagrammatic side view of a first embodiment of the tool; Fig. lb is a top p.lan view of the distal portion of said tool; Fig.2 is a perspective enlarged view of the members which achieve the grounding connection; Figs.3, 4 and 5 are side views showing some of the positions which may be taken by the contact plate illustrated in the preceding figures; and Fig.6 is a partial view similar to fig. la, showing a second embodiment of the tool. Referring to figs. la, lb and 2 there is seen that a first embodiment of the present tool includes a hollow rod R, on which a weight or hammer H is slidably slipped, which is provided at its proximal end with a stop P and is mounted on a handle M. Within the latter there arrive the cables for the connection to the welding apparatus, namely the positive cable CP, the negative cable CN and a cable CS for the remote control of said apparatus through a switch S located on the handle. The positive cable CP is connected to a second rod (not visible in the figures) internal to rod R and ending with an electrode-holding tip D, wherein an interchangeable electrode E is secured by means of locking bolts U. The negative cable CN is connected to the external rod R so as to achieve the grounding connection of a sleeve F carrying two supports G on which an end plate C is mounted. The electrical insulation between the two poles is guaranteed by an internal insulator (not visible) and by an external insulator T (fig.3). Sleeve F is slidably mounted on rod R, its movement being controlled by a resilient contrast means (typically a spring located between the sleeve and the rod) which biases it towards the distal end of the rod. The group of elements F, G, C for the grounding connection is sized and positioned so that in the rest position the plate C is slightly forward of electrode E. With particular reference to figs.2-5, there is seen that supports G are fixed to sleeve F through screws VG and plate C is in turn fixed to supports G through relevant screws VC. Plate C has a frontal U-shaped profile (fig.2) to allow the central passage of electrode E mounted along the longitudinal axis of rod R. Plate C also has a substantially U-shaped top plan profile (fig. lb) and it is mounted externally at the tips of supports G through a single screw VC on each side, whereby it can rotate with respect thereto around an axis orthogonal to the axis of rod R, as indicated by the arrows in figs 2-4 In particular, the end portion of supports G is shaped with notches X which allow plate C to move from the normal operative position (figs.2, 3) to a position rotated through 180° (fig 4) It is clear that plate C can also be locked by screws VC at any intermediate angular position, such as the position of fig.5 corresponding to a rotation of about 55° with respect to fig 3 The simple operation of the tool according to the present invention results clear from the description above it is sufficient to lean the tool on the sheet metal at the dented area so that plate C achieves the grounding connection of the sheet metal, thereafter, a slight push overcomes the contrast of the spring of sleeve F which slides back along rod R until electrode E comes into contact with the sheet metal, and finally the spot welding is effected by pressing switch S At this moment the stability of the grounding connection is guaranteed by the weld itself and by the action of the biasing spring, and the dent can be removed by acting on the sliding hammer H Once the sheet metal has been straightened it is easy to break the weld by means of a torsion and/or inclination of the tool and proceed to another welding at another dented area The rotational capacity of plate C also allows to adapt the tool to different operative arrangements according to the type of dent to be repaired In the normal operative position of figs 2, 3 the contact occurs through the extended front surface Ca, said position being most suitable for usual small substantially circular dents In the position rotated through 180° illustrated in fig 4, the contact occurs only through the rear points Cb, said position being suitable for narrower dents extending along the line connecting said points Finally, in the intermediate position of fig.5 the contact occurs along a thin arc Cd located above electrode E, said position being preferable to operate along the edges of a larger dent The tool according to the present invention can also be made so as to use an existing welding apparatus, as shown by the second embodiment illustrated in fig 6 This figure shows the handle M' of a conventional welding apparatus with interchangeable electrode which is provided with a quick-mount socket A for mounting the electrode Handle M' is connected to the current generator through the positive cable CP and the control cable CS for operation through switch S, as explained above In this case the tool is provided with a tail K for the mounting in socket A, whereas the grounding connection is achieved through cable CN which is connected to stop P' also acting as a connector. Once tail K is introduced and locked into socket A there is obtained a tool absolutely similar to the first embodiment illustrated above, the only difference being that the negative cable CN is connected to rod R not through handle M' but rather through stop P'. It is clear that the above-described and illustrated embodiments of the tool according to the invention are just examples susceptible of various modifications. In particular, the shapes of supports G and contact plate C may be freely changed according to specific needs of the user, same as the shapes of hammer H, stop P, P', handle M, M' and so on. Furthermore, though both the external rod R and the internal rod are preferably made of metallic material (e.g. brass), it could also be possible to use other types of material even non-conductive (e.g. fiberglass, plastic) as long as electrode E and plate C are electrically connected to the respective poles, for example through sheets, wires or the like. Finally, it is obvious that the resilient member biasing sleeve F may be of any kind, same as the elements suitable to electrically insulate the positive pole from the negative pole.

Claims: CLAIMS 1. A weldable tool for removing dents from sheet metal, for use in conjunction with an electrical welding apparatus, including a rod holding an electrode (E) electrically connected to the positive cable (CP) of said apparatus, as well as a sliding hammer (H) suitable to impart a traction along the longitudinal axis of said electrode-holding rod by means of an impact on a stop (P) located at the proximal end of the rod, characterized in that said hammer (H) slides along a second hollow rod (R) enclosing the electrode-holding rod and carrying at its distal end a plate (C) electrically connected to the negative ground cable (CN) of the welding apparatus, said plate (C) being mobile along the longitudinal axis of said hollow rod (R) with a movement controlled by a resilient contrast means biasing it towards the distal end of the rod (R), means for electrical insulation being also provided to insulate the members achieving the grounding connection from those achieving the connection to the positive pole. 2. A tool according to claim 1, characterized in that the plate (C) can be rotated around an axis orthogonal to the axis of the rod (R). 3. A tool according to claim 1 or 2, characterized in that the plate (C) is mounted on two supports (G) which are in turn mounted on a sleeve (F) slidably slipped on the rod (R), the resilient contrast means being interposed between said sleeve (F) and the rod (R). 4. A tool according to claim 3, characterized in that the supports (G) of the plate (C) are shaped with notches (X) in their end portion so as to allow a rotation of the plate (C) through 180°. 5. A tool according to one or more of the preceding claims, characterized in that the plate (C) has a frontal U-shaped profile suitable to allow the central passage of the electrode (E). 6. A tool according to one or more of the preceding claims, characterized in that the plate (C) has a substantially U-shaped top plan profile with pointed ends (Cb). 7. A tool according to one or more of the preceding claims, characterized in that the internal electrode-holding rod and/or the external hollow rod (R) are made of conductive material. 8. A tool according to one or more of the preceding claims, characterized in that it includes a handle (M) in which there arrive the positive cable (CP) and the negative cable (CN) as well as a cable (CS) for the remote control of the welding apparatus through a switch (S) located on said handle (M). 9. A tool according to one or more of claims 1 to 7, characterized in that it is provided at its proximal end with a tail (K) suitable to allow its mounting in the socket (A) of the handle (M') of a welding apparatus with interchangeable electrode, the proximal stop (P') acting as a connector for the connection to the negative cable (CN).

Inventors: KUZMANOVIC SASA, KUZMANOVIC, SASA
Applicants: KUZMANOVIC SASA, KUZMANOVIC, SASA
Application year: 2000
Main classification: B21D1
IPC codes: B21D1, B23K9