US 2930121 A
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March 29, 1960 R. INMAN 2,930J21 POCKET KNIVES Fiied Dec. 10, 1958 37 Fig/A 57 'ff/9,55. ff/9.6.l f *L 44 A 44 M 47 4? 43 f 43 Inventor 45 ROGER INMHN :31% @msm SE MES l. Attorney 2,930,121 f POCKET KNIVES Roger Inman, Sheffield, England Application December 10, 1958, Serial No. 779,364
3 Claims. (Cl. 302-160) This invention relates to folding pocket knives of the type in which one end of a lengthwise spring urges a blade to open and shut positions by bearing on one side or other of the tang of the blade. l
In one form of knife, the spring is pinned between the side plates between which the blade is also pivoted,.the one springextending in both directions from the pinoften serving two blades. In another construction,1 a spring serving two blades has a projectionthat passes through and may be riveted into a hole in the back of a folded frame of U-section between which the blades are United States Patent O pivoted; and in a Vvariant of this construction, the back of l. the spring is formed to engage one or more notches in- Y side the backof the folded frame and is simply retained in position by the engagement with it of the tangs of the blades.
The formation and fitting of springs separate from the A frames in these known constructions add materially to the cost of pocket knives, and necessitate the application of considerable skill in nally shaping the tangs of the blades, which may have to `b e repeatedly inserted and removed before they are correctly positioned when open and shut.
According to the present invention, a folding pocket knife comprises a folded frame of U-section of spring steel between the sides of which a tanged blade is pivoted, and the back of the frame has two lengthwise slits with a cross cut between one end of the slits to form between the slits a lengthwise spring tongue that bears on one or other side of the tang to urge the blade to open or shut position.
The integral spring thus formed in the frame may be set inwardly of the line of the back, so as to remain within that line when it is deected by the usual rounded end of the tang as the blade is moved between open and shut positions. The end of the spring tongue near the position of contact with the tang is quite free, because of the cross cut between the lengthwise slits, the spring thus being a cantilever connected to the frame only at the other ends of the slits.
In a knife having two oppositely facing blades, two oppositely facing springs may be formed in the back of the frame, separated from each other by a length of the back that maintains a necessary rigidity in the U-section of the back.
The slits between the length of the spring and the body of the frame may be formed before the frame is bent into its U-section, and they may be relatively wide, so that the edges of the adjacent parts of the body lie clear of the edges of the spring after the frame is bent. The inner ends of the initial slits may be rounded, thus producing a dared root to the cantilever spring where it is connected to the frame.
The thickness of the spring being that of the sheet metal of the U-section frame, and the frame being subjected to the hardening and tempering treatment neces sary for the spring or springs, the frame is stiff and rigid, and admits of accurate location and maintenance 2,930,121 j PatentedMar. 29, 196,0
of the pair of pivot pin holes, for a blade in the sides of the frame, and this leads to the useful adoption of another important feature of construction made possible by the use of the rigid frame. Instead of the complete positioning of an open blade depending on accurate fitting of the end of a tongue spring against the back square at the junction of the tang withl the back of the blade, the spring end may lie clear of the back square, and the inside of a back bridge left between the sides of the frame just beyond the spring end forms a stop against which the back of the back square bears. The pivot pin holes can be positioned with great accuracy with respect to the inside of the bridge, and the pivot pin hole in the blade can `be positioned with similar accuracy with respect to the back of the back square, so that little or no fitting is necessary to ensure that the blade when it is pinned comes into correct open position. In the case of a two-bladed knife, the accurate assembly of the two blades to the frame with its two integral springs is very quickly effected.
The frame may be slender, and serve as a skeleton to carry an encasing handle. Thus, in a two-bladed knife, the frame sides may be just wide enough at their ends to receive the pivot pins, and then narrow to about half that width betweenk the ends, yet still retaining rigidity because of the gauge of the sheet metal in the shallow U-section now left beingrsuch as to provide the necessary thickness for the springs. The recessed sides allow the two blades to close with their edges clear of the frame. The skeleton frame may now be slid into ka one-piece handle, which may conveniently be formed of extruded metal or plastic, or may `be die-cast or moulded in metal or plastic. An extruded handle may be formed from a length of material of general U-section, with a slot wide enough to fit closely the sides of a frame pushed lengthwise into it, but with the inside edges of the mouth of the slot projecting inwards to embrace the edges of the sides of the frame at their ends. The mouth is then wide enough for the closed blades to enter, leaving the thumb nicks exposed. The frame may be a push fit in the handle. If necessary, it may be secured by cement.
Several constructions embodying features of the inVention mentioned above will now be described with reference to the accompanying drawings, in which Figure 1 is a side elevation of a skeleton frame, before inserting its encasing handle, with two blades shown closed;
Figure 2 is an end elevation of the frame only of Figure 1;
Figure 3 is a view similar to that of Figure 1, showing both blades open;
Figure 4 is a side elevation of a knife in which a frame, with two blades, as in Figure 1, is inserted in a one-piece handle having the section shown in Figure 5;v and -Figure 6 is an alternative section of a one-piece handle.
In Figures 1 and 2, a U-section frame 25 of spring steel has its sides 26 of a width at the ends 27 of the frame just suiiicient to receive the pivot pins 28, but is reduced in width over a long central portion 29. Before the frame is bent to U-section, it has relatively wide slits 30 pressed out in parallel pairs to leave between each pair a spring tongue 31 that cantilevers from a central portion 32 of the back of the frame, with its free end just inside a back bridge 33 formed by a cross cut joining the outer ends of a pair of the slits 30. The edges of the' 3 rigidly the ends 27 where the pivot pins 28 carry the tangs 36 of the blades 37.
Each spring tongue 31 bears at two positions 38, 39 at opposite sides ofthe pivot pin 28 on one side of the tang 36 when a blade is shut. For convenience in inaking this two-position contact, each tongue 31 is kinked inwardly of the frame 2S, as shown at 40, between the inner end 34 of the slits 30 and the Vinner contact position 39. When a blade is open, the back 41 of its back square is brought by the urge of its springtongue 31 into contact with the outer side of the back bridge 33.
The skeleton frame 25, complete with blades 37 is slid endwise into a handle 42 (Figures 4 and 5) of general U-section, its lengthwise slot 43 fitting the sides 26 of the frame, with projecting inside edges 44 to engage the wider ends 27 at the ends f the trarne. The mouthft of the U-section handle is wide enough for the passage of the overlapping blades 37,l which project suliiciently from the handle to expose the thumb nicks 46 (one shown).
A handle with the section shown in figure is suit: able for production as an extrusion. Thus, it may be formed by extruding aluminium alloy, which may be anodised. The section 47 shown in Figure 6 is suitable for production in plastic material, e.g. by moulding. But the sections shown in these iigures are given by way or example only: either may be extruded or moulded, and the external form may be varied, provided the lengthwise slot 43 closely ts the overall cross-section of the skeleton frame. l
A mere push t may suce to secure the skeleton frame in the handle; but cement may be applied during assembly, or the ends of the handle may be lightly peened over the ends of the frame after assembly.
What I claim is:
1. A pocket knife comprising a handle of U-,section with edges projecting inwardly from the sides of the section to leave between them a slot narrower than the internal distance between said sides, a frame of U-section spring steel to fit lengthwise in the handle below Y 4 said projecting edges, at least one tanged blade pivoted in the U-s'ection frame, and 'a spring formed integrally from the back of the section of the U-section frame to engage the tang of the blade, said slot in the U-section handle being occupied by the blade in closed position and providing for pivoting of the blade to open position. 2. A pocket knife comprising a handle of U-section with edges projecting inwardly from the sides of the section to leave between them a slot narrower than the internal distance between said sides, a frame of U-section spring steel to vfit lengthwise in the handle below said projecting edges, at least one tanged blade pivoted in the U-sectin frame, the blade being wider than the frame and occupying in closed position said slot in the U-section handle, a thumb nick in the blade accessible beyond said slot in the closed position of the blade, and a spring formed integrally from the back of the section of the U-secton -frame to engage the tang Aof 4the blade. 3. A pocket knife comprising a ,u-section handle with open ends, allfsectilon frame of less width than the handle, at le'ast one tanged blade pivoted in the frame, a spring integral with the frame to engage the tang of the blade when the latter is moved to open and closed position, the blade inopen position extending through an open end of the handle, and inwardly projecting edges of the handle to o verlie the frame, lwhereby the frame and blade `assembly `may be slid lengthwise into the handle and retained by the projecting edges.
References Cited in the tile of this patent UNITED STATES PATENTS 254,404 Story Feb. 28, 1882 1,365,487 Hallvorson Jan. l1, 1921 1,667,462 Logan Apr. 24, 1928 2,779,098 Rocoski et al Jan. 29, 1957 2,798,290 Bassett July 9, 1957 j FOREIGN PATENTS 40,027 Germany Nov. 19, 1886