US2645850A

US2645850A - Scissors pivot structure

Info

Publication number: US2645850A
Application number: US108496A
Authority: US
Inventors: Edmund L Sejman; Lorenzo Louis
Original assignee: Acme Shear Co
Current assignee: Acme Shear Co
Priority date: 1949-08-04
Filing date: 1949-08-04
Publication date: 1953-07-21
Anticipated expiration: 1970-07-21

Description

y 21, 3 E. L. SEJMAN arm. 2,645, 850

SCISSORS PIVOT STRUCTURE Filed Aug. 4, 1949 Fig.3. 1 :12.4.

Smaentors EDMUND L. BEA-IMAM AND LOUIE LURENZEI Gttorneg Patented July 21, 1953 SCISSORS PIVOT STRUCTURE Edmund L. Sejman, Devon, and Louis Lorenzo; Bridgeport, Conn., assignors to TheAcme Shear Company, Bridgeport, Conn, a corporation of Connecticut Application August 4, 1949, Serial No. 108,496

1 Claim. (01. 30-269) The present invention relates to an improved scissors pivot structure and has for an object pivot pin. v V g to provide a pivot structure by which uniformity Fig. 9 is a plan view of the spring washer cmof relative fit, tension and operation of the scisployed.

sors parts may be obtained through routine assembly methods, irrespective of variations of thickness that may exist in the blade partsas a result of grinding, finishing and similar operations; Such variation may result from any of the different methods of manufacturing scissor blades. For instance, in one method ofmanufacture the blade members' ,are first produced in relatively rough form by drop forgingor similar methods, and thereupon the cutting surfaces and other surfaces are ground or otherwise fin-.

ished. As the blade members mayvary in thickness, and the grinding operation may var in depth, non-uniformity in the thickness of the finished blade members is inevitable. Heretofore it has been necessary, in order to compensate for this variation and to produce properly working scissors, to individually fit and adjust each pivot pin, and as this operation depended upon the skill of the operator, variation in the scissors action was apt to result, the scissors in some'cases being too tight and in some cases too loose. .It is an object of the present invention to providea pivot structure in which an exact predetermined cooperative relation is obtained between the pivot pin and the blade members irrespective of variations in thickness of the blade members.

Fig. 8 is a side Fig. '10 is a side 'view thereof.

Referring to the drawings, the scissors comprises a thumb blade member In and a finger blade member H, these being of substantially conventional form having thumb and finger. engaging loops at one end of the respective blade portions. As seen in Fig. the thumb blade illustrated is in its unfinished form, that is, its surfaces have not been ground. As seen in Fig. 6

the inner cutting surface of the blade is ground,

as at l2, the ground surface being in the form of a helix, as shown clearly in Fig. 2, which terminates at its inner end in a heel or'ridge I3, the ground surface [4 between this heel orridge and the handle portion of the blade, which may be ground prior to the grinding of the surface 12, being at aslight downward angle, so thatwhen the two blades, which are similarly groundjare assembled and in the closed position, as seen in Figs. land 2, the heelportions l3 of the two blades contact each other at the side of the pivot pin toward the handle while the other ends of the bladescontact at the points. Obviouslythis With the above and other objects in view,'an

embodiment of the invention is shown in the ac companying drawings, and this embodiment will be hereinafter more fully described with reference thereto, and the invention will be finally pointed out in the claim.

In the drawings:

Fig. 1 is a plan view of scissors provided with a pivot structure, according to the illustrated exemplary embodiment of the invention.

Fig. 2 is a side view, as seen from the top in Fig. 1.

Fig. 3 is a longitudinal sectional view, taken along the line 3-3 of Fig. 1.

Fig. ,4 is a similar enlarged sectional view, showing the blades in a relatively open position. i

Fig. 5 is a plan view of the inner side of the thumb blade member prior to grinding and finishing.

ployed.

Fig. 6 is a similar view showing the blade memgrinding operation results in variations in the thickness of the blades between the inner cutting surfaces and the outer backing surfaces, particularly their pivot supporting portions, if it isassumed that under normal conditions the blanks from'which the blades are produced varyxin' thickness and the grinding operation varies in depth. m r I The pivot pin, presently to be more fully de-j scribed, is rigidly secured to one blade while the other blade freely pivots thereon, and, according to the invention, the pivot receiving hole l5 of the pivotal blade isdrilled after the grinding and finishing of the blade, this hole being provided at its outer end with an annular countersunk recess, it having a bearing surface I! at its base. The base surface I1 is produced by suitable precision methods, to provide a highly exact axial dimension between the ground surface |2 of the blade H! as a datum surface and the base surface [1 which is a precise predeter mined amount, so that irrespective of variations in the thickness of the finished blades in a pro duction run of scissors of a given size this dimension is uniform. -As the critical requirement is the exact dimension between the ground surface i 2 and the'bas'e I! of the recess, it is not important whether the hole [5 is producedlprior to or'after the grinding'operatio'n. tial, however, that the basesurface ll be cut'or elevation of a modified form of It is essenotherwise produced after the grinding and finishing operation, so that an exact predetermined dimension exists between it and the ground surface l2. The pivot receiving hole l8 of the other blade member II, in which the pivot pin is fixed, as will presently more fully appear, may be drilled either before or after the finishing operation, as it is not essential to the carrying out of the invention that its axial dimension be predetermined, as it will in fact vary in accord,- ance with variations in the blade thickness.

The pivot pin, indicated generally as [9, comprises a stud portion 20, the axial dimension of which is a highly exact predetermined dimension for a given size of scissors, calculated relatively to the predetermined dimension established for the dimension between the surfaces l2 and ll of the blade member 0. The diameter of the stud portion 20 is slightly less than that of the hole l5, so that in the assembled relation the blade may have a slight tilting movement with respect to the pivot pin. At its upper end the stud portion is provided with a circular head 2| which engages in the countersunk recess l6, and at its lower end is provided with a reduced diameter shank portion 22 which is engaged in the hole [8 of the blade member H, with the shoulder 23 at the lower end of the stud portion engaging the ground surface !2 at the inner side of the blade ll, while the lower end the shank portion is headed over, as at 24, upon the outer surface to thus rigidly secure the pivot pin to the blade.

As the shoulder 23 is fixedly engaged with the flat annular abutment surface immediately surrounding the inner end of the hole [8, this abutment surface constitutes a datum surface with respect to which the critical axial length of the stud portion 20 is determined.

A spring washer 25, formed of suitable material such as spring steel, is engaged in the recess [6 between the under surface of the head 2| and the base surface l1, and is in the form of a circular ring of undulating form providing three point bearings at each side. In the assembled relation this spring is under tension and exerts pressure to force the blades toward each other, being compressed to its greatest extent in the closed position of the blades, as seen in Figs. 1 to 3, with the heel portions l3 and the points of the blades in contact, and being expanded in the open position of the blade, as seen in Fig. 4, to bring the ground surfaces together at the pivot area. It will be understood that the washer 25 will be of a predetermined dimension and tension related to the predetermined dimensions of the hole l5 and the stud portion 20 of the pivot pin, so that in a production run of scissors where the predetermined dimensions of these three factors are maintained, the cutting action, tension, and other operating characteristics of the scissors will be uniform, irrespective of variations in blade thickness.

In Fig. 8 there is illustrated a modified form of pivot pin l9a comprising a stud portion 20a having a head 2 Id at its upper end provided with a slot 26, and having a threaded shank 22a at its lower end, there being an annular shoulder 23a at the lower end of the stud portion for engagement with the ground surface of the blade. The threaded shank may be screwed into a threaded hole in the blade or it may be engaged in a plain hole and secured by a nut.

While the inner surfaces 12 are shown as ground surfaces, it will be understood that these '4 surfaces may be produced by any other desired method.

We have illustrated and described a preferred and satisfactory embodiment of the invention, but it will be understood that changes may be made therein, within the spirit and scope thereof, as defined in the appended claim.

What is claimed is:

In a pair of scissors: a first blade member including a blade part and a handle part, said blade part having an inner cutting surface and an outer backing surface and being provided at its end portion adjacent the handle part with a cylindrical pivot bearing hole extending through it to its inner surface, there being an annular bearing surface extending laterally from and surrounding the outer end of a said hole; a second blade member consisting of a blade part and a handle part, said blade part having an inner cutting surface and an outer backing surface and being provided at its end portion adjacent the handle part with a pivot mounting hole extending through it to its inner surface, there being a fiat annular abutment surface upon the inner surface of said second blade part extending laterally from and surrounding the inner end of said pivot mounting hole; a pivot pin including a cylindrical stud portion pivotally engaged in said bearing hole of said first blade part, a head at the outer end of said stud portion having an annular laterally projecting rim including an annular 'under surface axially facing said annular bearing surface to retain said first blade part in assembled relation with said second blade member, a flat annular shoulder at the inner end of said stud portion extending laterally inwardly from its periphery and fixedly seated upon said annular abutment surface of said second blade part, and said pivot having a shank portion tightly secured in said mounting hole of said second blade part; and a spring member engaged under tension between the annular under surface of said head and said annular bearing surface; said stud portion between said under surface of said head and said annular shoulder being of a highly exact axial length; said annular bearing surface being axially spaced a highly exact distance from the inner cutting surface of said first blade part, and said spring member being of a dimension and tension predetermined relative to the axial length of said stud portion and the axial spacing between said annular bearing surface and said inner cutting surface of said first blade part, and there being a ridge on the cutting face of each blade member spaced each the same distance rearwardly of said pivot as the other; whereby the cutting and tension relation between the inner cutting surfaces of said blade members are predetermined with high exactitude irrespective of an inexact thickness dimension between the inner and outer surfaces of said first blade part.

EDMUND L. SEJMAN. LOUIS LORENZO.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,287,442 McLean June 23, 1942 FOREIGN PATENTS Number Country Date 22,712 Great Britain Apr. 28, 1904 747,025 France June 9, 1933