Title:
Tool for removing dents from sheet metal
Kind Code:
A1


Abstract:
A tool for pulling a dent out of a sheet metal surface has a support post with a foot shaped to rest against a portion of the sheet metal surface adjacent the dent. The tool includes a hinged lever arm which is pivotally connected to this support post at a lever arm pivot point which is elevated above the foot and adjacent sheet metal region. The tool also includes a pulling rod for coupling, through a fastener or connecting means, to the dented portion of the surface which is to be drawn-out, the pulling rod being connected to the hinged lever arm through a pivoting joint. The pivoting joint of the pulling rod and the lever arm pivoting point are positionable through actuation of the lever arm able to lie in a common plane which is substantially parallel to the sheet metal surface into which the dent is to be drawn into alignment. The pulling rod is adjustable in its engagement with the lever arm to permit the lever arm to swing through a limited angular range. Coupling between the pulling rod and lever arm is either discrete or continuous. Fasting means connecting the tool to the sheet metal include a self-tapping, self-drilling screw or a bolt provided with a magnetic washer or magnetic head.



Inventors:
Knowles, Steven Michael (North Manchester, IN, US)
Application Number:
11/226458
Publication Date:
03/15/2007
Filing Date:
09/15/2005
Primary Class:
International Classes:
B21D1/12
View Patent Images:
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Primary Examiner:
TOLAN, EDWARD THOMAS
Attorney, Agent or Firm:
DOWELL & DOWELL, P.C. (ALEXANDRIA, VA, US)
Claims:
The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A tool for pulling a dent within a sheet metal surface into a plane which is generally in alignment with the surrounding sheet-metal surface, the tool including: a) a support post with a foot with a face surface which is shaped to rest against an adjacent generally planar area of a sheet metal surface lying laterally to the dent; b) a hinged lever arm which is pivotally connected to this support post at a lever arm pivot which is elevated above the foot; c) a pulling rod for coupling, through a connecting means, to a dented portion of the sheet-metal surface which is to be drawn-out, the pulling rod being connected to the hinged lever arm through a pulling rod pivoting joint, wherein the lever arm pivot and pulling rod pivoting joint are positionable during operation to lie in a common plane which is substantially parallel to the plane into which the sheet-metal of the dent is to be pulled.

2. A tool as in claim 1 in combination with a sheet metal surface to be worked wherein the lever arm pivot and pulling rod pivoting joint are positionable so as to be generally equally spaced above the sheet metal surface which is being worked.

3. A method for using the tool as in claim 1 wherein said lever arm is displaceable about the lever arm pivot by a range of movement of at least +10 degrees above said common plane.

4. A method for using the tool as in claim 1 wherein said lever arm is displaceable about the lever arm pivot by a range of movement of at least −10 degrees below said common plane.

5. A method for using the tool as in claim 1 wherein said lever arm is displaceable about the lever arm pivot by a range of movement of at least +/−10 degrees above and below said common plane.

6. A tool as in claim 1 wherein the pulling rod is provided with multiple apertures for engagement with the lever arm through the pulling rod pivoting joint, said pulling rod being positionable for alternate engagement by each of said apertures.

7. A tool as in claim 1 wherein the pulling rod comprises a ratchet means which allows it to engage with the lever arm at various degrees of extension below the lever arm.

8. A tool as in claim 7 wherein the pulling rod pivoting joint comprises a cylindrical seat and said ratchet means comprises an indented coupling edge which, is shaped to hook onto the cylindrical seat provided by the pulling rod pivoting joint, said indented coupling edge permitting the connection between the pulling rod and the lever arm to be progressively shifted upwards by one or more of the indentations after the lever arm is pulled through the range of a pulling stroke.

9. A tool as in claim 7 wherein said ratchet means comprises a continually adjustable coupling between the lever arm and the pulling rod.

10. A tool as in claim 9 wherein said continually adjustable coupling comprises: a) a pawl-means in the form of a canting plate that has a tight-fitting opening through which the pulling rod passes, whereby the canting plate will pass along said the pulling rod without an engagement with the pulling rod in one, first, direction when said plate is oriented transversely to the pulling rod, and will engage with the pulling rod at an angle when an attempt is made to advance the canting plate in the opposite, second direction.

11. A tool as in claim 10 comprising a resilient means that biases the canting plate to rotate into an angled orientation for engagement with the pulling rod when the canting plate is passed along said pulling rod in said second direction.

12. The tool of claim 1 in combination with a threaded sheet metal fastener having a central shaft comprising: a) a threaded portion; b) a seating shoulder to limit the penetration of the threaded portion of the post into sheet metal; c) a necked-in region on said shaft to provide an engagement surface on the side of the shoulder remote from the threaded portion; d) a larger terminating end connected to the necked-in region on the side remote from the threaded portion to provide an engagement shoulder for engaging the fastener, and e) a self-drilling tip at the end of the threaded portion.

13. The tool and threaded sheet metal fastener combination as in claim 12 wherein the larger terminating end of the faster is shaped in the form of a bolt head for engagement by a bolt-turning tool.

14. The tool and threaded sheet metal fastener of as in claim 12 wherein the threaded portion is a self-tapping threaded portion.

15. A method of pulling a dent within a sheet metal surface into a plane which is generally in alignment with the surrounding sheet-metal surface comprising engaging the sheet metal surface within the dent with a threaded sheet metal fastener having a central shaft and comprising: a) a threaded portion; b) a seating shoulder to limit the penetration of the threaded portion of the post into sheet metal; c) a necked-in region on said shaft to provide an engagement surface on the side of the shoulder remote from the threaded portion; d) a larger terminating end adjacent to the necked-in region on the side remote from the threaded portion to provide an engagement shoulder for engaging the fastener, and e) a self-drilling tip at the end of the threaded portion followed by the step of: i) positioning the tool of claim 1 with the foot against the adjacent sheet-metal surface and the pulling rod connected to the engagement shoulder on the larger terminating end of the sheet metal fastener, and ii) actuating the lever arm to apply a pulling force to the dent so as to pull it towards alignment with the surrounding sheet-metal surface.

16. A threaded sheet metal fastener having a central shaft comprising: a) a threaded portion; b) a seating shoulder to limit the penetration of the threaded portion of the post into sheet metal; c) a necked-in region on said shaft to provide an engagement surface on the side of the shoulder remote from the threaded portion; d) a larger terminating end connected to the necked-in region on the side remote from the threaded portion to provide an engagement shoulder for engaging the fastener, and e) a self-drilling tip at the end of the threaded portion.

17. A threaded sheet metal fastener as in claim 16 wherein the terminating end is shaped in the form of a bolt head for engagement by a bolt-turning tool.

18. A threaded sheet metal fastener as in claim 16 wherein the threaded portion is a self-tapping threaded portion.

19. A method of pulling a dent within a sheet metal surface into a plane which is generally in alignment with the surrounding sheet-metal surface comprising forming a hole within the dent and engaging the sheet metal surface through the hole within the dent with a fastener having a central shaft and comprising: a) an enlarged head portion having a seating shoulder to limit the penetration of the central shaft through the hole; b) a magnetized washer carried on said shaft adjacent said head portion; and c) tool engagement means positioned on the shaft remote from the head portion, followed by the steps of: i) extending the shaft of the fastener beyond the hole into the region of the dent; ii) positioning the tool of claim 1 with the foot against the adjacent sheet-metal surface and the pulling rod connected to the tool engagement means on the fastener shaft, and iii) actuating the lever arm to apply a pulling force to the dent so as to pull the dent towards alignment with the surrounding sheet-metal surface.

20. The method of claim 19 including the step of providing a further washer carried on said shaft on the side of the magnetized washer remote from the head portion wherein said further washer is larger than said magnetized washer.

21. A welding fastener means in the form of sheet-metal plate having an opening form therein for engagement by-hooked coupling mean, said sheet-metal comprising a lower edge for welding to the surface of sheet-metal.

22. A welding fastener as in claim 21 wherein the length of the edge is in the range of 5 to 10 mm.

23. A coupling means for engaging two or more welding pins for attachment by welding to sheet metal, said welding pins each having ends and said coupling means comprising: a) multiple openings to receive the ends of said two or more welding pins; and b) locking means for securing the ends of the welding pins into the coupling.

24. A coupling means as in claim 23 were in the locking means comprises set screws.

Description:

FIELD OF THE INVENTION

This invention relates to a tool for pulling dents, amongst other applications, from the sheet metal portions of an auto body in the process of auto-body repairing and refinishing. More particularly, the invention relates to a hand-operated pulling device with an improved system for connecting to and applying force to the surface which is to be pulled.

BACKGROUND TO THE INVENTION

Various devices have been proposed to allow an auto-body repairman to apply an outward force to an inwardly dented surface, restoring the surface to close to its original profile. One example is U.S. Pat. No. 2,749,795, dated Jun. 12, 1956 issued to Boykin, Jr. (FIG. 1 hereafter). This device provides a support post with a foot shaped to rest against an adjacent portion of a body panel on a vehicle. To this post is connected, at a height above the panel, a hinged lever arm with a handle which, in turn, carries a connecting rod for coupling to the dented portion of the surface which is to be drawn-out. This mechanism acts as a second-class lever. The pulling rod is fastened to a sheet metal screw which engages with the inwardly-dented sheet metal surface. The handle, lever arm and support post are depicted as being at 90° to each other at the commencement of the pulling process. In this configuration the pulling rod is initially parallel to the upright support post which extends vertically from the auto body surface. No provision is made for the pulling rod to swivel smoothly with respect to the lever arm once the arm is drawn upwardly.

A further similar device is depicted in U.S. Pat. No. 6,792,790 issued Sep. 21, 2004 to Ritter (FIG. 2 hereafter). In this device the lever arm handle rotates about a hinged joint positioned on the foot, a configuration discussed further below with respect to the next reference. This mechanism is also in the form of a second-class lever. Again, no provision is made for the pulling rod to swivel smoothly with respect to the lever arm once the arm is shifted upwardly.

Another reference is U.S. Pat. No. 4,930,335 issued Jun. 5, 1990 to Ishihara (FIG. 3 hereafter). FIGS. 5 and 6 of this reference depict a pulling device similar in the overall layout to the Boykin, Jr. device, with the added provision of a swiveling linkage 20 (20A in FIG. 3 hereafter) present in the pulling rod, positioned beneath the lever arm and above the connection to the sheet metal surface. In this reference, the lever arm and support post are joined at a rigid right-angle connection. Further, the support post and base are connected to each other through a hinged junction. The mechanism depicted in FIG. 5 of Ishihara is that of a second-class lever. The mechanism depicted in FIG. 6 is that of a first-class lever. The swiveling linkage in the pulling rod is located above the plane parallel to the sheet metal surface being worked. The hinged junction between the support post and base is located just above that plane. This pulling rod swivel is therefore located above the plane of the pivot connection between the base and the support post when the components are positioned for a pulling operation.

An object possibly not fully appreciated in the prior art is that it is desirable to apply a force to a dented portion of a sheet metal surface which will pull the dented portion directly outward, without applying any substantial lateral or angled force to the sheet metal as it is being displaced. This type of mechanical effect is desirable not only to maximize the prospects of restoring the dented surface as nearly as possible to its original configuration, but also to reduce the risk that the coupling device engaged to the sheet metal surface within the dent is not twisted. Any tendency to twist the coupling device will risk a breakage or its disconnection from the sheet metal surface.

In the Ishihara device, U.S. Pat. No. 4,930,335, because the pivot portion of the swivel linkage 20-20A is substantially above the hinged junction 20 (20B in FIG. 3 hereafter) between the support post in the base therefore, as the handle is drawn upwardly (FIG. 5) or downwardly (FIG. 6) to cause the support post to pivot about the lower hinged junction 20-20B, the upper portion of the pulling rod above the elevated swivel linkage 20-20A swings in an arc about the lower hinged junction 20-20B seated on the foot and is drawn sideways. The swivel linkage 20-20A in the pulling rod assembly does not adequately compensate for this sideways movement; it only serves to ensure that the upper pulling rod points directly to the swivel linkage 20-20A above the sheet metal connector. The consequence is that a degree of sidewards force (with respect to the general surface of the sheet metal of the body panel), or torque is applied to the connector coupled to the dented portion of the sheet metal surface.

Accordingly, neither the Boykin, Jr. nor Ishihara references addresses the object of applying a force to a dented portion of a sheet metal surface which will pull the dented portion directly outward, without applying any significant lateral or angled force to the sheet metal as it is being displaced. While the Ritter device may possibly momentarily act in such a manner when the swivel on the foot is in the same plane as the sheet metal connector, by reason of the fact that the pulling rod is not free to swivel, this desired mechanical effect does not persist. The present invention has the object of substantially obtaining such a mechanical effect and reducing the tendency for a torque or sideways force to be applied to the connector.

In drawing on the sheet metal, it is necessary to make a connection to such metal. Typically, this may be done by screwing-in a self tapping metal screw, or welding a connecting element, such as a washer, to the sheet metal. While it is known to provide for other purposes self tapping screws variously having a drilling point, a stopping shoulder, a narrowed neck and an enlarged head, cf U.S. Pat. Nos. 3,114,031 4,581,871; 5,011,354; 5,605,423; 5,755,542; 6,023,891; 6,077,096 6,112,491; the 6,363,679, and 6,875,947, such a fastening means has not been designed for use with respect to the repair of sheet metal surfaces. The present invention also has the object of addressing a fastener having characteristics suited to such application.

As an alternative to using a self-tapping screw, a bolt or equivalent may also be employed. In such cases, the bolt is inserted through a hole in the body panel from the interior. It would be desirable to provide a means to retain such a bolt in place while arrangements are made to engage it with a dent-pulling device. While examples of the use of magnetism in respect of screws exist, vis U.S. Pat. No. 6,111,491, the present invention intends to exploit use of magnetism in solving the different problem of positioning a bolt during the dent-pulling process.

The invention in its general form will first be described, and then its implementation in terms of specific embodiments will be detailed with reference to the drawings following hereafter. These embodiments are intended to demonstrate the principle of the invention, and the manner of its implementation. The invention in its broadest and more specific forms will then be further described, and defined, in each of the individual claims which conclude this Specification.

SUMMARY OF THE INVENTION

According to the present invention in one aspect, a tool is provided for pulling a dent out of a sheet metal surface into generally planar alignment with the surrounding sheet-metal surface portion. The tool includes a support post with a foot with a face surface which is shaped to rest against an adjacent portion of the sheet metal surface adjacent the dent. The tool includes a hinged lever arm which is pivotally connected to this support post at a lever arm pivot. The pivot point at which this connection occurs is elevated above the foot and sheet metal region surrounding the dented portion which is to be restored. The hinged lever arm in turn, carries a pulling rod for coupling, through a fastener or connecting means, to the dented portion of the surface which is to be drawn-out. The pulling rod may be fastened to the sheet metal surface in a variety of manners including by way of coupling to a connector that is welded to the sheet metal or by way of coupling to a screw or bolt which engages with the inwardly dented sheet metal surface.

The pulling rod of the invention is connected to the hinged lever arm through a pulling rod pivoting joint. The lever arm pivot and pulling rod pivoting joint are preferably positionable during use, or virtually so, in a common plane which is substantially parallel to the plane into which the material of the dent is to be pulled. Thus according to the device of the invention, both pivots are preferably positionable during use so that they may be generally equally spaced above the sheet metal surface which is being worked.

In operation, the lever arm is displaced about the pivoting point on the support post by only a limiting range of movement, preferably moving the link carrying the pulling rod pivot joint only +/−10 degrees above or below the common plane referenced above. With this arrangement the movement of the pulling rod and its pivoting joint during use remains virtually vertical, minimizing any sidewards force to be applied to the sheet metal connector. Within the range +/−10 degrees these elements are displaced only very slightly sideways. Beyond this range there develops an increasingly sideways motion and a sideways twisting force. The pivoting joint in the pulling rod helps compensate for even this minute movement by minimizing the application of shear forces to the sheet metal connector.

In order for the pulling rod pivoting joint and the pivoting point on the support post to both lie in a plane which is substantially parallel to the sheet metal surface from which the dent is to be removed, the lever arm handle need not straight. It may be shaped to include a dogleg shaped portion that allows that the two pivots to both lie substantially in the same plane as stipulated while placing the handgrip at a convenient location.

According to another feature of the invention, provision is made to facilitate limiting motion of the lever arm handle to a range which is basically within the +/−10 degrees as referenced above. To achieve this result, the pulling rod may be provided with an adjustable engagement with the lever arm handle. This may include a ratchet means which allows the pulling rod to engage with the lever arm at various degrees of extension below the lever arm. Thus the pulling rod may be provided with a undulating or indented coupling edge which, conveniently, hooks on to a cylindrical seat surrounding the pivoting joint. As the lever arm is progressively pulled up through its preferred range of +/−10 degrees, the connection between the pulling rod and the lever arm may be progressively shifted downwards by one or more of the undulations or notches. Thus, as the lever arm is pulled to the upper limit of its preferred pulling stroke, it may then be lowered to the bottom end of its permitted range of travel and the engagement between the lever arm and pulling rod adjusted to shorten the extension of the pulling rod before commencing the next pulling stroke.

While this ratcheting effect is very desirable in terms of maximizing the lever advantage of the tool and minimizing the application of sidewards force to the sheet metal coupling, the use of a undulating or indented coupling edge on the pulling rod “granularizes” the adjustment that is available to be made between each stroke. As a further feature of the invention, a continually adjustable coupling between the lever arm and the pulling rod may be provided.

Such a continually adjustable coupling can be in the form of a pawl-like catch in the form of a canting plate that has a tight-fitting opening through which the pulling rod passes. This canting plate acts as a clutch to engage with the side surface of the pulling rod when it is angled—“canted”—during a pulling stroke. On the return stroke the plate slides on the pulling rod. Thus engagement occurs progressively with consecutive portions of the surface of the pulling rod. Such a clutching mechanism is able to provide an infinite degree of adjustments in respect to the position at which the pulling rod is grasped. An example of this type of clutch is a vehicle jack sold in the past in connection with Volvo-brand automobiles. This type of clutching mechanism is also typically used on screen door closure cylinders to prop open the screen door.

A resilient means, such as a spring biases the canting plate to rotate into engagement with the pulling rod. On the downward stroke of the lever arm, the canting plate is carried downward, rotating against the direction of the force supplied by the resilient means to align the hole with the pulling rod. Consequently, the canting plate tends to slide on the pulling rod. On the upward stroke, the canting plate is driven upwardly, rotating in the direction of the force applied by the resilient means. Consequently, the canting plate tends to bite-into the surface of the pulling rod, engaging therewith and transmitting the force applied at the lever arm to the pulling rod. Once engagement occurs, the locking effect increases with the applied force. Thus a convenient automatic engagement and re-engagement clutch mechanism is provided which allows the lever arm to be swung repeatedly through a narrow arc, preferably of no more than +/−10 degrees.

Irrespective of the mechanical structure of the pulling mechanism, the pulling rod must be coupled to the dented portion of the sheet metal. A known method of doing so has been to use a sheet metal screw. However, such a screw of normal shape is apt, when engaged with the hooked-end on the pulling rod, to tend to twist in its seat within the sheet metal. In order to minimize such a twisting tendency, by a further feature of the invention a threaded engagement post is provided that includes a seating shoulder to limit the penetration of the threaded portion of the post into the sheet metal and to provide resistance to twisting forces. Above this seating shoulder, the post is provided with a necked-in region surmounted by a larger terminating end. This terminating end is dimensioned to be engaged by the hook-and on the pulling rod. Preferably, this terminating engagement end is shaped in the form of a bolt head or other coupling interface for engagement by a bolt-turning or other corresponding tool.

Additionally, this improved threaded engagement post may be provided with a drilling tip that initiates penetration of the threaded portion of the post into engagement with the sheet metal. A self-tapping thread is positioned on the engagement post directly behind the drilling tip. Formation of an initial opening in the sheet metal by the drilling tip facilitates subsequent engagement of the self-tapping thread in the hole formed in the sheet metal.

As an alternate fastener for pulling on a body panel, a bolt and washer arrangement can be employed wherein either the bolt has a magnetized head or a magnetized washer is provided. In use, the bolt, either with a magnetized head or with a magnetized washer positioned directly under the bolt head, is passed through a hole drilled through the dented portion of the sheet metal from the back side. An assortment of various widths of steel washers may be placed against the backside of the panel to spread the pulling force and prevent dimpling. Additional washers need not be magnetized if they allow adequate penetration of the magnetic field of the magnetized washer or bolt head into the sheet metal.

Because of the presence of the magnetized metal, the bolt and washer(s) are held in place providing a protruding shaft for engagement by the dent pulling tool. This tool may engage a nut threaded onto the protruding bolt shaft, or the bolt shaft may be notched as an alternate coupling means for engagement by the dent pulling tool. This, therefore, is an additional fastening system to the self-threading screw by which the dent pulling tool may be fastened to the sheet metal.

A further fastening system is based upon the use of a welding tab having an opening in the tab which may be engaged by a, preferably, single-hooked coupling mean. This welding tab may be in the form of a preferably flat plate of metal which may be stamped to form an opening and provide a short, straight, lower edge. The edge is for welding to the sheet metal which is to be straightened. Because it is an edge with a definite length, e.g. 5 to 10 mm, it may more easily be welded to the sheet of steel than the standard pins that are used in the industry. Further, a stronger bond with the sheet metal is created by the length of this weld.

As an alternative to using the welding tab of the invention, above, two or more welding pins may be welded in the known manner to the sheet metal. These pins are engaged by a multiple pin coupling which has openings to receive the weld pins. Set screws lock the ends of the welding pins into the multiple pin coupling. By using a multiple pin coupling, the traditional system of relying on welding pins may be employed while increasing the amount of force that may be applied to the sheet metal through the pulling tool.

Individually, the various features of the invention constitute useful advances in the art of tools used in the bodywork industry. By the combination of these features a new and superior tool is provided to permit the easy and accurate removal of dented portions from the sheet metal surfaces.

The foregoing summarizes the principal features of the invention and some of its optional aspects. The invention may be further understood by the description of the preferred embodiments, in conjunction with the drawings, which now follow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of the metal panel repair tool of FIG. 1 in prior art U.S. Pat. No. 2,749,795 to Boykin, Jr.

FIG. 2 is a pictorial side view of the sheet metal repair tool of FIG. 1 in prior art U.S. Pat. No. 6,792,790 to Ritter.

FIG. 3 is a side view of the sheet metal repair tool of FIG. 6 in prior art U.S. Pat. No. 4,930,335 to Ishihara. The pivot points in this figure have been renumbered respectively as 20A and 20B in place of the number 20 as used for both pivots in the original figure.

FIG. 4 is a pictorial side view of the sheet metal tool of the invention with a simplified pulling rod pivot shown in a simplified second-class lever format.

FIGS. 4A and 4B are respectively side and perspective views of a slotted, adjustable pulling rod for substitution for the pulling rod depicted in FIG. 4.

FIGS. 4C and 4D are pictorial depictions of assemblies for engaging with various types of fastener that can be attached to the sheet metal surface.

FIG. 5 is a pictorial side view of the sheet metal tool of the invention with a combined pivot and adjustable grip for engaging the mounted pulling rod with the handle at the lower end of the 20° preferred range of rotation. The canting plate locking mechanism for grasping the pulling rod is shown in this figure as being engaged with the pulling rod.

FIG. 6 is a side view of the dent-pulling tool of the invention of FIG. 5 with the handle at the upper end of the 20° preferred range of rotation. The canting plate locking mechanism for grasping the pulling rod is showing in its position during recovery when it slides on the pulling rod.

FIG. 6A is a further pictorial depiction of the sheet metal tool of FIGS. 5 and 6.

FIGS. 6B, 6C, and 6D are pictorial depictions of further assemblies for engaging with various types of fastener that can be attached to the sheet metal surface.

FIG. 7 is a side view of a preferred form of self-tapping fastener for engagement with the sheet metal.

FIG. 8 is a pictorial view of the fastener of FIG. 7.

FIG. 9 is a side view of a bolt with magnetized washer positioned within a hole formed in a dented sheet-metal surface with the pulling tool positioned for engagement with a nut mounted on the bolt.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows the prior art metal panel repair tool U.S. Pat. No. 2,749,795, dated Jun. 12, 1956 issued to Boykin, Jr. This device provides a support post 20 with a base 18 shaped to rest against an adjacent portion of an outer body panel 10 overlying an inner body panel 8 on a vehicle. To this post 20 is connected a hinged lever arm 24 with an extending handle portion which, in turn, carries a connecting or pulling rod 36 for coupling to the dented portion 12 of the surface 10 which is to be drawn-out. This mechanism acts as a second lever.

The pulling rod 36 is fastened to a sheet metal screw 45 which engages with the inwardly-dented sheet metal surface 10. The lever arm 24 and support post 20 are depicted as being at 90° to each other at the commencement of the pulling process. In this configuration the pulling rod 36 is parallel to the upright support post 20 which extends vertically from the auto body surface 10. No provision is made for the pulling rod 36 to swivel freely with respect to the lever arm 24 once the arm 24 is drawn upwardly. As the lever arm 24 pivots about a joint 30, a sidewise force is applied to the fastener 45.

FIG. 2 shows the tool depicted in FIG. 1 U.S. Pat. No. 6,792,790 issued Sep. 21, 2004 to Ritter. In this device the lever arm handle 6 rotates about a hinged joint 4 positioned on the foot 3, a configuration discussed further below with respect to the next reference. This mechanism is also in the form of a second-class lever. Again, no provision is made for the pulling rod 8 to swivel freely with respect to the lever arm 5 once the arm 5 is shifted upwardly.

FIG. 3 shows the tool depicted in FIG. 6 of U.S. Pat. No. 4,930,335 issued Jun. 5, 1990 to Ishihara. FIG. 6 of this reference depicts a pulling device tool in first class lever format having a lever arm 62, a foot 40 and a support post 60. The pulling rod function is provided by the combined components 46, 64 joined by a swiveling linkage 20A, positioned beneath the lever arm 62 and above the connection to the sheet metal surface. In this reference, the lever arm 62 and support post 60 are joined at a rigid right-angle connection 34 and the support post 60 and base 40 are connected to each other at a hinged junction 20B. The swiveling linkage 20A in the pulling rod assembly 46, 64 is therefore located above the hinged junction 20B which is positioned adjacent to the base 40, of the bottom end of the support post 60. This pulling rod swivel 20A therefore tends to swing in an arc about the hinged junction 20B between the support post 60 and base 40. This gives rise to a sideways pull on the pulling rod component 46 irrespective that such force is applied through swivel 20A.

In FIG. 4 a dent pulling tool according to the invention are shown as having a foot 11, a support post 12 standing upright from the foot 11, a support post hinge point or pivot 13, a lever arm 14 and a pulling rod 15. The pulling rod 15 is connected to the lever arm 14 through a pulling rod pivot pin 16. At the end of the pulling rod 15 is a coupling means 17 for engagement with a self tapping fastener 19 connected to the sheet metal to be repaired (not shown in this figure).

The foot 11 should be large enough to ensure that it can support the tool without imposing its own dent in the sheet metal surface. Optionally, a portion of the foot may extend towards the pulling rod 15 to provide a solid face which blocks the extent to which the sheet metal of the dent may be drawn outwardly.

It is to be noted in FIG. 4 that the support post pivot 13 and pulling rod pivot pin 16 are located at substantially equal heights above the general surface of the sheet metal underlying the foot 11. That is, by displacement of the lever arm it may be arranged for both pivots 13, 16 to lie in a common plane which is substantially parallel to the plane of this sheet metal surface; or, equivalently, both pivots 13, 16 are positionable so that they are generally equally spaced above the sheet metal surface which is being worked.

Consequently in this orientation, rotation of the lever arm 14 from such position applies a fully upward force to the pulling rod 15 with virtually no sideways components. For small amounts of displacement from this orientation, the departure of such force from the true vertical is small, minimizing any sidewards forced to be applied to the sheet metal connector. Thus, little departure from the application of a vertical force arises when the lever arm 14 is displaced either upwardly by 10° or downwardly by 10° from the common plane referenced above. In use, it is preferred to limit the range of motion of the lever arm 14 within such boundaries.

The lever arm 14 may also have a handle portion which is provided with a dog-leg or is “cranked” so as to place the gripping surface or handle end at a more convenient elevation above the sheet-metal surface. In particular, the handle end may be located at a height above the sheet-metal surface that is higher than the common plane. Further, the end of the lever arm 14 may either meet directly with the support post pivot 13 as shown in FIG. 4, or may curve downwardly to make the connection, as shown in FIG. 5. This shape doesn't matter so long as, by displacement of the lever arm 14 it may be arranged for both pivots 13, 16 during a drawing stroke to momentarily lie in a common plane which is substantially parallel to the plane of this sheet metal surface. Special shapes for the handle or lever arm 14 may be provided to allow clearance for grasping the handle end.

The pulling rod 15 in FIG. 4 is provided with multiple apertures 18 allowing the engagement between the pivot pin 16 and pulling rod 15 to be adjusted. Thus, by such adjustment, it becomes possible to draw the sheet metal through a substantial displacement while limiting the motion of the lever arm within the preferred +10° to −10° range. Optionally, this range may be from 0° to +10°; or from 0° to −10°, or portions thereof.

Operating the lever arm by displacing it about the pivoting point on the support post by only a limiting range of movement, preferably only +/−10 degrees above or below the common plane referenced above, not only minimizes sideways motion, but provides for maximum force to be applied to the sheet metal for a given pull on the handle. Staying within the +/−10 degree range ensures the greatest mechanical advantage for any given pull on the handle. If this range is increased much beyond 10 degrees the mechanical advantage is reduced.

By reason of the preferred limit on the range of motion of the lever arm 14, an alternate form of hooked pulling rod 21 is shown in FIGS. 4A, 4B. In this variant the alternate pulling rod 21 has multiple engagement hooks 22 formed along the side of the rod 21. These hooks 22 are dimensioned to engage with pulling rod pivot pin 16. By reason of their staggered locations, such hooks 22 may be consecutively engaged in a ratchet-like manner while the lever arm 14 is moved back and forth through its permissible 20° range of motion. As the lever arm 14 is progressively pulled up through its preferred range of +/−10 degrees, the connection between the pulling rod and the lever arm may be progressively shifted downwards by one or more of the hooks 22. This ensures that there is little departure from the vertical in terms of the direction of a force applied to this hooked pulling rod 21.

Allowing that while operating within the range +/−10 degrees, the direction of the force applied to the pulling rod 15, 21 departs only slightly from the vertical and very little sideways or twisting force is applied to the fastener 19, the presence of the pivoting pulling rod joint 16 helps compensate for even such minute tendencies as may occur.

As an alternative to the hooked pulling rod 21 of FIGS. 4A and 4B, FIGS. 5 and 6 depict the tool of the invention with a combined pivot and adjustable grip for engaging a straight-shafted pulling rod 23 by means of a continually adjustable coupling. The canting plate locking mechanism for grasping the pulling rod 23 includes a plate 25 having a hole form therein which is substantially the same shape as the transverse cross-section of the rod 23. When transversely oriented to the rod 23, the plate 25 slides thereon with a close sliding fit. When angled, the plate 25 jams.

As shown in FIGS. 5 and 6, the plate 25 is carried in a cage 26 which is pivotally mounted through cage pivot pin 27 to a frame 28 which can be adjustably positioned along the lever arm 14. Adjustment of the frame 28 along the lever arm 14 is effected by the use of seating pins 29 which engage with seating holes 31 formed in the lever arm 14. In the absence of the seating pins 29, the frame 28 would slide along the lever arm 14 unless limited by other means, such as a high friction or saw tooth interface between the frame 28 and lever arm 14.

Again, as with the embodiment of FIG. 4, the support post pivot 13 and cage pivot pin 27 are able, during use, to share a common plane which is generally parallel to the surface of the sheet metal to be worked when the lever arm 14 is in the middle of its preferred range of rotation.

The canting plate 25 acts as a clutch to engage with the side surface of the straight-shafted pulling rod 23. This engagement occurs progressively along consecutive portions of the surface of the pulling rod 23. Such a clutching mechanism is able to provide a virtually infinite degree of adjustments in respect to the position at which the pulling rod 23 is grasped.

A resilient means, such as a spring 32 carried within the cage 26 biases the canting plate 25 to rotate into engagement with the straight-shafted pulling rod 23. On the downward stroke of the lever arm 14 (FIG. 6), the canting plate 25 is carried downward, rotating against the direction of the force supplied by the resilient means 32. Consequently, the canting plate 25 tends to slide on the pulling rod 23. On the upward stroke (FIG. 5), the canting plate 25 is carried upwardly, rotating in the direction of the force applied by the resilient means 32. Consequently, the canting plate 25 tends to bite-into the surface of the pulling rod 23, engaging therewith, and transmitting the force applied at the lever arm 14 to the pulling rod 23.

FIGS. 7 and 8 depict a preferred form of fastener 19 in the form of a self-drilling, self-tapping, shouldered sheet metal screw 19 for engagement with the sheet metal. This fastener 19 is formed around a central shaft having a self-tapping spiral thread 33 that terminates at a seating shoulder 34 to limit the penetration of the threaded portion of the fastener 19 into the sheet metal. As the threads 33 draw the fastener 19 into the sheet metal, the seating shoulder 34 eventually abuts against the metal. A slight further tightening of the fastener 19 at this point will lock the fastener 19 in place. The shoulder 34 also gives the screw 19, when it is fully seated, improved strength to resist twisting.

Above this seating shoulder 34, the post is provided with a necked-in region 35 surmounted by a larger terminating end 36 which respectively provide an engagement surface and engagement shoulder. This necked-in region may then be engaged by the hooked, two-fingered coupling means 17 on the pulling rod 15, 21, 23. The enlarged terminating end 36 provides the engagement shoulder and ensures secure engagement with the hooked coupling means 17. The terminating end 36 is preferably shaped in the form of a bolt head for engagement by a bolt-turning tool. The terminating end 36 may also include an annular rim 37 to prevent over-advancement of an engagement tool, such as a socket, when engaging the bolt head.

In FIG. 9 an alternate fastener combination for pulling on a body panel 43 is depicted in the form of a bolt 40 and washer 41. The bolt has a shaft portion 40 and enlarged head 42 which provides a seating surface for resting against sheet metal. Either the bolt 40 has a magnetized head 42 or a magnetized washer 41 is provided, or both may be used. As an example, the magnetized washer 41 is positioned directly under the bolt head 42 and the shaft portion of the bolt 40 is passed through a hole drilled through the dented portion of the sheet metal 43 from the back side. Various widths of additional steel washers 44 may optionally but preferably be placed against the backside of the panel 43 to spread the pulling force and prevent dimpling. This is a particular advantage of this configuration. The additional washers 44 need not be magnetized if they allow adequate penetration of the magnetic field of the magnetized washer 41 or bolt head 42 into the sheet metal.

The magnetized washer 41 holds the bolt 40 and washer(s) 44 in place providing a protruding shaft 45 for engagement by the dent pulling tool 23. This tool 23 may engage a nut 46 threaded onto the protruding bolt shaft 45, or the bolt shaft 45 may be notched for engagement by the dent pulling tool 23 as an alternate form of tool engagement means. The bolt shaft 45 in FIG. 9 is shown with an exaggerated degree of extension; in use, the presence of the magnetic coupling permits a much shorter bolt 40 to be employed, particularly where the hole in the sheet metal number 43 is oversized. This provides an alternate fastening system to the sheet metal screw 19 whereby the dent pulling tool 23 may apply force to the sheet metal 43.

FIG. 4C depicts the engagement between the hooked coupling means 17 and the bolt head 42 carried by bolt 40. The hooked coupling means 17 is threaded onto the pulling rod 15. Allowing for sufficiently excess threading, coupling means 17 may swivel around at the end of the pulling rod 15 so that it to be fitted into engagement with the fastening means by swinging in an arc beneath the handle.

FIG. 4D depicts an alternate, single-hooked coupling means 50 which may be threaded onto the pulling rod 15. In this case, the single hook 50 engages with the opening 52 in a tab 51 which has a short straight lower edge 53. The tab 51 is a flat plate of metal which is preferably stamped to form the opening 52 and lower edge 53. This edge 53 is welded to the sheet metal which is to be straightened, forming a stronger weld than would occur with a simple pin. By providing excess threading, the single hook 50 may be rotated on the pulling rod 15 to align with the opening 52.

FIG. 6B depicts the engagement between the hooked coupling means 17 and a self tapping, threaded faster 19. The hooked coupling means 17 is threaded onto the pulling rod 15. Again, the hooked coupling means 17 may swivel at the end of the pulling rod 15 for engagement with the fastener 19.

FIG. 6C shows the most common, established method for attaching a pulling tool to sheet metal through use of a weld pin 54. In this case, a modified coupling means 55 has a knurled wheel 56 rotationally mounted within a slot that opens into the hollow interior of the cylindrical sleeve 57 of the coupling means 55. This modified coupling means 55 is threaded onto the end of the pulling rod 15.

The knurled wheel 56 is of a conventional type used with normal slide hammers to grip long weld pins. The wheel does not rotate on its center, but rather has an offset pivot. The welding pin 54 slides up into the hollow interior of the cylindrical sleeve 57 until it is positioned behind the wheel 56. Then the wheel 56 is rotated so that, due to its eccentric dimensions, it pushes against the pin 54 holding the pin 54 in place, As force is applied to withdraw the pin 54, the wheel 56 wedges the pin 54 between itself and the back of the hollow interior of the sleeve 57 and locks the pin 54 in place. A small handle 59 extending from the wheel 56 permits release of the pin 54 by rotating the wheel 56 in the opposite direction.

FIG. 6D depicts a double weld pin coupling means 61 which grabs two weld pins 54 at the same time. Two pins 54 are welded to the damaged surface of the sheet metal at locations spaced apart by approximately 2 cm (¾ inch). The double pin coupling means 61 is then slid over the ends of both pins 54 and held in place by setscrews 62 or equivalent which can be tightened with an Allen wrench 63. Optionally, the double weld pin coupling means 61 can be modified to engage three or more pins, if desired, by adding further openings and set screws 62.

The tool of the invention may be combined with one or several of the classes of fasteners as described to form a kit which will conveniently enable shop workers to address the repair of dents in sheet metal surfaces.

On this basis, a new and useful tool for removing dents from sheet metal has been described, together with new and useful accessories.

CONCLUSION

The foregoing has constituted a description of specific embodiments showing how the invention may be applied and put into use. These embodiments are only exemplary. The invention in its broadest, and more specific aspects, is further described and defined in the claims which now follow.

These claims, and the language used therein, are to be understood in terms of the variants of the invention which have been described. They are not to be restricted to such variants, but are to be read as covering the full scope of the invention as is implicit within the invention and the disclosure that has been provided herein.





 
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