US3427850A

US3427850A - Sheet metal stretching tool

Info

Publication number: US3427850A
Application number: US525398A
Authority: US
Inventors: Jacob Anton
Original assignee: Individual
Current assignee: Individual
Priority date: 1966-02-07
Filing date: 1966-02-07
Publication date: 1969-02-18
Anticipated expiration: 1986-02-18

Description

Feb. 18, 1969 T N 3,427,850

SHEET METAL STRETCHING 001;

Filed Feb. 7. 1966 INVENJ'QA JACOB ANTONv Me me vs United States Patent 5 Claims Int. Cl. B2111 11/02, 1/04, 41/02 ABSTRACT OF THE DISCLOSURE A sheet metal stretching tool having a pair of clamps, each of which has a movable jaw element and a fixed jaw element, mounted on a rigid guide, at least one of the clamps being movable longitudinally of the latter. An extensible jack positioned between the movable jaw elements simultaneously moves the latter into a gripping position relative to the fixed jaw elements and moves the clamps apart.

This invention relates to tools for stretching sheet metal, particularly to the stretching of automotive door and trunk panels to aid in the removal of dents and other deformations therefrom.

The art of straightening sheet metal panels is one that is highly developed and, consequently, there have been developed numerous tools whereby the work may be accomplished with a minimum of effort. One of the tools necesary in this work is a stretcher which may be applied to opposite edges of a sheet metal panel in order that the latter may be stretched to facilitate the removal of dents or other deformations therefrom. These stretching devices all take the form of a pair of clamps which may be afiixed in one manner or another to opposite edges of a sheet steel panel to be stretched, and means to push the clamps apart so as to stretch the metal extending therebetween. These stretching tools of prior art have in the main employed clamps which must be tightened down upon so as to grip the metal to be stretched and, consequently, if they are not tightened down sufiiciently, they tend to slip and gouge the metal when it is necessary to employ extremely heavy jacking forces to move them apart.

It is appreciated that stretching tools having automatically operated clamps have been ,devised wherein the means required to move them apart has also been utilized for tightening the grip of the clamps upon the metal to be stretched. However, these last-mentioned devices or tools have been of unduly complicated construction which are costly to manufacture and are relatively difficult to operate.

The present invention relates to the last-mentioned type of stretching tool which is of relatively simple construction, being easy to affix to the metal to be stretched and to operate, which is readily adjustable to panels of varied sizes and thicknesses, yet which is relatively inexpensive to manufacture and maintain.

The present invention comprises an elongated guide member, a pair of clamps mounted on the guide member for engagement with opposite edges of a panel to be stretched, at least one of said clamps being movable longitudinally thereof, said clamps each having a stationary jaw element and a movable jaw element pivotally mounted thereto for movement between open and gripping positions, and an extensible jack extending between the movable jaw elements for simultaneously moving the latter into their gripping position and pushing the clamps apart.

Referring to the drawings which illustrate the invention,

FIGURE 1 is a side view of the invention,

3,427,850 Patented Feb. 18, 1969 FIGURE 2 is an enlarged end view of the invention taken in the direction 2-2 of FIGURE 1, and

FIGURE 3 is a top plan view of the invention.

Referring to the drawings, the stretching tool therein illustrated comprises in general a pair of clamps 10 and 11 slidably mounted on an elongated cylindrical guide rod 12 for movement in a direction away from and towards each other and arranged to grip

opposite edges

15 and 16 respectively of a sheet metal panel 18, such as an automobile door or the like, said clamps being arranged to be pushed apart by means of an extensible jack 20 so as to stretch the metallic panel and thereby facilitate the removal of dents or other deformations therein.

The clamps 10 and 11 are of substantially but counterposed identical construction, accordingly, the same numerals will be used to identify identical components in each. Each clamp comprises a pair of

jaw elements

23 and 24 which are pivotally interconnected and which may be pivotally moved between open and gripping positions. Jaw element 23 which, for the purposes of the specification and claims following, shall be termed the stationary jaw, is of L-shaped construction and forms a pair of arms 26 and 27, arm 26 being elongated and having secured at its free end 28 an elongated cylindrical sleeve 30, whereas the free end of arm 27 is provided with a gripping element 32 having a serrated face 33. Jaw element 24 is also of L-shape

configuration having arms

35 and 36, arm 35 having at its free end 38, a gripping element 39, also having a serrated face 40 which extends when the jaws are moved to their gripping position as illustrated in FIGURE 1 in planar parallelism with the face 33 of the element 32. The arm 36 is elongated and is provided with a forwardly extending hooked element 43 at its free end 44. Both the

jaw elements

23 and 24 are pivotally mounted on the shank 46 of a rivet 47 located substantially at the juncture of the arms with each of said jaws, the latter being spaced apart by means of a thick washer over the shank 46.

The clamps are normally urged to their gripping position by the provision of elongated helical tension springs 50 connected between the hooked elements 43 of the arms 36 and engaged through suitable apertures in arms 26.

The guide rod 12 is preferably formed of a length of cylindrical tubular pipe into one end 52 of which is threadedly inserted a plug 53 having a radially extending annular flange 53 of larger outside diameter than the outside diameter of the guide 12.

The outside diameter of the guide 12 is suflicient to permit it to be slidably and rotatably inserted through the sleeves 30 of both of the clamps so that the clamps may depend freely therefrom, both clamps being arranged so that the

jaw elements

23 and 24 of one extend towards the corresponding jaw elements of the other with the sleeve 30 of clamp 11 abutting the flange 54 of plug 53.

In the use of the tool, the panel 18 is located between the clamps 10 and 11 as illustrated in FIGURE 1, the tension springs serving to impart an initial grip of the jaw elements with the opposite edges of the panels. The extensible jack 20 which, in this particular case is illustrated as a hydraulic type having a piston rod 55 and cylinder 56, is extended between the arms 36 of both clamps and hydraulic fluid emitted into the cylinder 56 via the conduits 57. This tends to cause rotation of the jaw elements 24 about their pivotal axes, tighening the grip of the clamps upon the panel 18 and at the same time exerting suflicient pressure so as to move clamp 10 away from clamp 11, thereby stretching the panel extending therebetween. With the construction of the tool as hereinbefore described, it will be seen that the gripping force of the jaw elements upon the panel is a direct function of the force required to move the clamps apart, the proportionate length of

arms

35 and 36 of the jaw element 24 being arranged so that the gripping force imposed upon the panel is never excessive, being sufficient only to hold the jaws in place against the force necessary to spread the clamps apart.

Occasionally, in order to properly repair the damaged panel, it is necessary to remove the jack in order to provide Working room over the damaged area, In order, therefore, to maintain the panel in stretched condition, clamp is fitted with a locking device 60 which is arranged so as to be inoperable when the jack is operated to spread the clamps apart and which will automatically grip the guide rod 12 and prevent movement of the clamp 10 in the reverse direction.

This locking device comprises an annular plate 61 having a pair of diametrically opposed radially extending

arms

62 and 63, the internal diameter of the plate being slightly larger than the exterior diameter of the guide rod so as to permit lateral deflection of the plate thereon. The device is positioned adjacent the outer end of sleeve 30 of clamp 10, one arm 62 extending downwardly through a longitudinally extending slot 64 formed in an extending piece 65 secured to the arm 26 of jaw element 23 of the clamp 11 so as to be slidably movable therein. The other arm 63 extends above the sleeve 30 of the lastmentioned clamp and is secured to one end 66 of a tension spring 67, the other end 68 of the spring 67 being secured to the last-mentioned sleeve. The spring 67 normally pivots the annular plate 61 about the sleeve into a laterally deflected position, as shown in FIGURE 1, in which position the plate is urged into binding engagement with the guide rod. It will be seen that any movement of clamp 10 towards clamp 11 will tend to result in greater lateral deflection of the plate 61 with respect to the guide rod, thereby increasing the binding effect. Conversely, the locking device 60 will not hinder the movement of clamp 10 in a direction away from clamp 11 as movement in this direction will result in movement of plate 61 to a less laterally deflected position with a consequent decrease in the latters binding effect on the guide rod.

The binding effect of the locking device 60 may of course be overcome by simply moving the arm. 63 by hand against the action of the spring 67 to a less laterally defiected position so as to permit free movement of the clamp 10 in any direction.

What I claim as my invention is:

1. Sheet metal panel stretching apparatus comprising an elongated rigid guide member, a pair of clamps mounted on the guide member for engagement with opposite edges of a panel to be stretched, at least one of said clamps being movable longitudinally of the guide member, said clamps each having a stationary jaw element and a movable jaw element pivotally mounted thereto for movement between open and gripping positions, and an extensible jack extending between the movable jaw elements for simultaneously moving the latter into their gripping position and continued extension of said jack pushing the clamps apart along said guide member.

2. Sheet metal panel stretching apparatus comprising an elongated rigid guide member, a pair of clamps mounted on the guide member for engagement with opposite edges of a panel to be stretched, at least one of said clamps being movable longitudinally of said guide member, said clamps each having a stationary jaw element and a movable jaw element pivotally mounted thereto for movement between open and gripping positions, a lever extending from each of the movable jaw elements for pivotally moving the latter, and an extensible jack extending between the levers for simultaneously moving the jaws to their gripping position and continued extension of said jack pushing the clamps apart along said guide member.

3. Sheet metal panel stretching apparatus comprising an elongated cylindrical shaft, 21 pair of clamps mounted on the shaft for engagement with opposite edges of a panel to be stretched, at least one of said clamps being slida-bly and pivotally connected to the shaft for longitudinal and radial movement relative thereto, said clamps each having a stationary jaw element and a movable jaw element pivotally mounted thereto for movement between open and gripping positions, a lever extending from each of the movable jaw elements for pivotally moving the latter, and an extensible jack extending between the levers for simultaneously moving the jaws to their gripping position and continued extension of said jack pushing the clamps apart along said shaft.

4. Sheet metal panel stretching apparatus as claimed in claim 3 including resilient means connected to each of the movable jaw elements normally urging the latter into their gripping position so as to provide initial gripping engagement of the clamps with the panel to be stretched.

5. Sheet metal panel stretching apparaus as claimed in claim 3 in which the jaw elements are each provided with serrated gripping surfaces.

References Cited UNITED STATES PATENTS 2,606,467 8/1952 Desjarlais et al. 72302 2,845,983 8/1958 Hanson 72302 X 2,855,972 10/ 1958 Greider 72-302 2,858,872 11/1958 Hougen 72392 X 2,956,458 10/1960 Hougen 72302 3,015,353 1/1962 Brown 72302 3,051,217 8/1962 Hill et al. 72302 3,111,159 11/1963 Jenkins 72302 1,353,632 9/1920 Coons 269-254 X 756,723 4/1904 Skoog 269-254 X CHARLES W. LANHAM, Primary Examiner.

E. SUTTON, Assistant Examiner.

US. Cl. X.R.