Lee Valley & Veritas
Woodworking Newsletter
  Volume 8, Issue 2 - November 2013    
Featured Patents
Pli-Wrench Pliers
Over the last few years, any mention of the word espionage sends the press into a fury of activity over the practice used by government agencies under the guise of protecting sovereign interests. For the industrial world, it is a given that someone will always try to steal any fresh concept and market it for profit while maintaining much secrecy. In some cases, it is outright theft, and the perpetrator banks on the fact that there is a window of opportunity before the original manufacturer can or does mount a defense to stop this encroachment. As a companion piece to the "From the Collection" article, we offer up an "Interesting Patent" item that is very similar to but slightly different from the original and was outside any retaliation from the originator.

First the concept of a patent: Not wanting to arouse the ire of those who work in this field, we shall just state a very basic path. One thinks of a product, one makes a prototype (or not), one registers the idea with the appropriate country's patent agency, one manufactures the product and reaps the benefits (or not) of the new idea. It can be a long and arduous path. There are often fixed limits on how long a patent can be protected, and there are strong rules regarding replicating a patented item without making significant changes to an original concept. Protection has varied from 5, 12, 14 and 17 years. As of 2013, there is now a 20-year protection period internationally. Any litigation, however, is extremely costly and takes an inordinate amount of time. In some cases, the final costs can be more than the anticipated profits of selling the item.
Pli-Wrench Pliers   Pli-Wrench Pliers
Vise-grip pliers were the invention of William Peterson in 1921, with the locking-lever concept granted in 1924. By 1941, the original patent expired, and competitors started manufacturing their own concept of the locking pliers without violating the original Peterson patent. A subsequent patent in 1940 did nothing to stop the competition.

Ernest J. St. Laurence of Minneapolis, Minnesota, sought with patent #2,489,057, dated November 22, 1949, to improve the mechanical fixation for the jaws of locking pliers. With his design, he also allowed for a sliding movable lower jaw, thereby creating a better gripping action. St. Laurence's claim cites the earlier patent (#2,285,683), in which there were issues with the retaining pins in the insert jaws during usage. These pliers were manufactured under the name Pli-Rench, and the pictures show a sliding bottom jaw that maintained a parallel face throughout most of the tool's range.

A further word about copying: The Internet has done much to spread ideas and processes around the world. It is perfectly all right, I think, to replicate a product for one's personal use in a non-commercial venue. Making two, however, and selling one, or perhaps enabling others to copy it by publishing a version of a patented copy is a violation of the patent act.

D.S. Orr

D.S. Orr has been a collector, user and student of woodworking and metalworking tools and practices for more than 40 years. Recently retired, he has devoted even more time to these endeavors.

United States Patent Office



Ernest J. St. Laurence, Minneapolis, Minn.

Application September 20, 1945, Serial No. 617,646

Patented Nov. 22, 1949
My present invention relates to an improvement in hand-operated gripping tools such as pliers or wrenches of the type incorporating cooperating gripping jaws, one of which has a moveable gripping surface mounted for arcuate movements with respect to the cooperating gripping surface of the other jaw. In tools of this type the circumferentially shiftable gripping element of a gripping jaw is provided with segmental bearing surfaces that seat on corresponding segmental seats in the cooperating jaw and the shiftable gripping element is usually retained against accidental displacement by an arcuate slot and pin connection between the gripping jaw element and the cooperating jaw element, one such arrangement being shown in the Seashore Patent 2,285,683 of June 9, 1942.

In tools of the above described type, the retaining pin, referred to, is often accidentally sheared off by stresses placed thereon in service; and this invention is directed particularly to means for preventing this accidental shearing of the retaining pin when stresses applied to the tool tend to move the shiftable jaw element beyond the extreme limit permitted by engagement of one end of the slot with the cooperating retaining pin.

The above and other highly important objects and advantages of the invention will be made apparent from the following specification, claims, and appended drawings.

In the accompanying drawings, like characters indicate like parts throughout the several views.

Referring to the drawings:

Fig. 1 is a longitudinal sectional view through a tool incorporating the invention, with some parts on the sectional line shown in full;

Fig. 2 is an enlarged fragmentary view of the tool shown in Fig. 1, but showing a somewhat different position of the parts;

Fig. 3 is a front end view of the tool of Fig. 1 taken on the line 3-3 of Fig. 1; and

Fig. 4 is a transverse sectional view taken on the line 4-4 of Fig. 1.

The tool illustrated, and in connection with which a preferred form of the invention is herein illustrated, is of the general character shown in the said Seashore Patent 2,285,683 and comprises a relatively fixed handle element 5, formed integrally with a relatively fixed or rather relatively stationary gripping jaw 6, a cooperating relatively moveable gripping jaw 7, that is pivotally anchored to the fixed jaw 6 at 8, an operating lever 9 pivoted to the movable jaw 7 at 10, and a toggle link 11 pivoted at one end to the lever 9 at 12 and having its other end slidable in the handle 5. The rear end of the toggle link 11 works slidably in a slot 13 and the handle 5 is retained against accidental displacement therefrom by a head acting pin 14, and reacts against a screw threaded adjustment screw 15. The toggle link 11 at its intermediate portion is provided with a depending stop lug 16 that engages the lever 9 when the toggle link 11 is moved just past dead center in a jaw closing direction. The jaw 7 is biased to move pivotally in a jaw opening position by means of a coil tension spring 17. The fixed jaw 6 is provided with a fixed gripping element in the nature of a toothed gripping plate 61 that may be assumed to be welded or otherwise rigidly secured thereto.

Preferably and as illustrated herein the movable jaw element 7 is formed of a cooperating pair of sheet metal plates 18 that are riveted or otherwise rigidly secured as at 19. These jaw plates 18 are spread apart beyond their intermediate portions to provide a pair of laterally spaced jaw flanges 20. In accordance with the invention the upper surfaces of these jaw flanges 20 are formed to provide concave seats 21 to receive convex bearing surfaces on shoulders 22 of a shiftable or movable toothed gripping element 23 for the jaw 7. The shiftable gripping element 23 is provided, intermediate the convex bearing surfaces 22, with a downwardly projecting guide flange 24 that works between the laterally spaced jaw flanges 20. The moveable jaw element 23 is held against accidental displacement from the cooperating jaw 7 by slot and pin connection comprising a segmental slot 25 in the guide flange 24 and a cooperating guide pin 26 extending through the spaced jaw flanges 20 and the slot 25.

Circumferential or arcuate movements of the shiftable jaw element 23 are limited in one direction by engagement thereof with the fixed jaw 6, as shown in Fig. 1, or by coincidental engagement of the pin 26 with the outer end of the segmental slot 25.

In prior art, tools having sliding jaws of the type described, outward circumferential or arcuate movements of the sliding jaw have been limited solely by engagement of the guide pin with the opposite or inner end of the arcuate slot and tend, under conditions such as shown in Fig. 2, to shear off the guide pin. In Fig. 2, the tool is shown as gripping a pipe A between the inner portions of its gripping surfaces, which tends to force the shiftable jaw element 23 beyond the normal limit permitted by engagement of the pin 26 with the end of the slot 25 and, of course, this tendency is greatly increased when the tool is turned in a counter-clockwise direction with respect to Fig. 2. In the present tool, however, this tendency is eliminated or greatly reduced by provision on the guide flange 24 of a stop lug or projection 27 with a cooperating stop pin 28 extending through and between the jaw flanges 20. The pin 28 is so oriented as to be engaged by the stop lug 27 either just prior to or coincidentally with engagement of the pin 26 with the inner end of slot 25. The pin 28 can be heavier and stronger than is normally used for cooperation in the slot 25.

What I claim is:
In a gripping tool having cooperating jaws mounted for relative movement, one of said jaws having a relatively fixed gripping surface and the other jaw being provided with an arcuately shiftable gripping element for cooperation with the relatively fixed gripping surface of the first named jaw, said second named jaw comprising laterally spaced parallel flanges provided with concave seats, said shiftable gripping element having a plane guide flange projecting therefrom and freely extending into the space between said jaw flanges and said gripping element having convex shoulders on opposite sides of the guide flange seated on said concave seats, an arcuate slot and pin connection between the guide flange and the jaw flanges for maintaining said convex shoulders in seating engagement with said concave seats and for limiting movement of the gripping element in an outward direction, said guide flange being provided with a stop lug projecting therefrom in a direction away from said griping element, and a stop pin carried by the jaw flanges and extending across the space therebetween, said pin being disposed beneath said guide flange and in the path of movement of said stop lug for engagement thereby substantially coincidentally with the engagement of the first named pin with an end of its cooperating arcuate slot upon movement of said gripping element in an outward direction, whereby to prevent shearing of the first named pin.
The following references are of record in the file of this patent:
Number Name Date
949,557 Whetzel Feb. 15, 1910
1,048,380 Youngquist Dec. 24, 1912
1,750,817 Root Mar. 18, 1930
2,285,683 Seashore June 9, 1942
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