Tape Lock Mechanism

This invention relates to steel measuring tapes of the type which are coiled in a casing around a reel with the reel enclosing a coil spring which rewinds the tape after it has been withdrawn from the casing. The casing is of a known type with parallel side walls and a slot at the bottom of the front wall of the casing and a locking mechanism which is operative to clamp the tape from movement to or from the casing. The locking mechanism is capable of holding the tape firmly, is easily operative, and compact and sturdy. The locking mechanism is operative by moving a slide up and down the front wall of the casing and is operable by the thumb when the casing is held in the hand. It is an object of the present invention to provide an improved locking mechanism of that general type.

Referring to the drawings:

FIG. 1 is a side view of one embodiment of the invention with the left-hand portion of the casing cut away;

FIG. 2 is a view similar to the left-hand portion of FIG. 1 but showing the locking mechanism engaging the tape when the tape is partially withdrawn from the casing;

FIGS. 3 and 4 are views respectively on the lines 3--3 of FIG. 1 and 4--4 of FIG. 2;

FIGS. 5 and 6 are similar to FIGS. 1 and 2, but show another embodiment of the invention; and,

FIGS. 7 and 8 are sectional views respectively on the lines 7--7 of FIG. 5 and 8--8 of FIG. 6.

Referring to FIG. 1 of the drawings, a rigid plastic casing 2 encloses a tape 4 which is wound onto a reel (not shown) having an axis 6 and enclosing a rewind spring (not shown). Attached to the end of tape 4 is a tape hook 8 which is held against the casing wall by the coil spring when the tape is fully wound, and which is engaged to withdraw the tape from the casing. As the tape moves to and from the casing it slides along the top surface of the bottom casing wall 12.

A tape-locking mechanism 14 is provided having a thumb actuated slide 15 mounted on the front wall of the casing with limited sliding movement up and down the casing wall. This mechanism includes a locking assembly (see FIG. 3) formed of two flat plastic members comprising a locking member 16 and an operating member 18, lying in the same plane in a channel 17 formed in the housing with their side edges guided for sliding movement by the sidewalls of channel 17.

Locking member 16 has a rectangular body portion 20 with a pair of downwardly extending feet 22 which are adapted to engage and lock the tape. In addition, member 16 has two inwardly extending angle arms 24.

The plastic of which members 16 and 18 are formed permits arms 24 to flex from the relaxed position out of engagement with the casing sidewalls 49, but they return to that normal position when not engaged by operating member 18. Each of the angle arms has two portions of equal length and extends upwardly from body portion 20 with the two lower arm portions extending toward each other, and the upper portions extending away from each other to near engagement with the sidewalls of the casing.

Operating member 18 has a main rectangular body portion 30 and a downwardly projecting operating portion 32 which projects between arms 24. When the mechanism is positioned as shown in FIG. 3, the tape is not locked. A pair of cam surfaces 34 of operating portion 32 are parallel respectively with the top surfaces 36 of the upper portions of arms 24, and surfaces 38 on the bottom of operating portion 32 are respectively parallel to surfaces 40 of the lower portions respectively of arms 24. Referring to FIGS. 1 and 2, the movement of slide 15 is limited by a stop 41 which projects into a slot 42 in the casing wall. Mounted rigidly in slide 14 is an operating pin 43 which has a free end that projects through a hole 44 in operating member 18. Hence, when slide 15 is slid down, it moves operating member 18 from the position of FIG. 1 in which the tape is not locked to the position of FIG. 2 in which the tape is locked. During that movement, surfaces 34 engage surfaces 36 of the upper portions of arms 24 of locking member 16 as shown in FIG. 3, and upon further movement of the operating member, surfaces 34 engage the angle portions 35 of arms 24, and then the parallel side surfaces 37 engage angle portions 35. The bottom surface 45 of the operating member is also moved into engagement with the top surface 46 of the body portion 20 of locking member 16, and the locking member is pushed downwardly to the position of FIG. 4 in which the tape is locked. Simultaneously, arms 24 are pushed in opposite directions against the casing sidewalls, and the top ends of the arms are pushed outwardly below ledges 48 in the casing sidewalls 49. The ends 50 are tapered so as to provide secure engagement with ledges 48. The engagement of arms 24 with ledges 48 holds the locking member in the locking position as long as arms 24 are held apart by surfaces 37. The movement of slide 15 back to the position of FIG. 1 permits arms 24 to move back to their normal position of FIG. 3 so that they no longer hold the locking member in the position of FIG. 4. Surfaces 38 on the lower portion of operating portion 32 also engage surfaces 40 and lift the locking member 16 upwardly so that the locking member no longer engages the tape.

The embodiment of FIGS. 5 to 8 is similar in many respects to that of the embodiment of FIGS. 1 to 4 and the identical components are numbered the same.

Referring to FIGS. 5, 7 and 8, a slide 80 has two pins 82 which are positioned adjacent to the sidewalls of casing 84 and which extend through a slot 83 in the front wall of the casing. A locking member 86 has a bottom locking portion 88, a top portion 90 and a central expandable portion 92. An integral cylindrical anchor 94 is snugly received at its ends in pockets 96 formed in the sidewalls of the casing. The front wall of the casing is a segment of a cylinder, and locking member 86 is formed and positioned to extend along the front wall from its anchor portion 90 to its bottom locking portion 88. The central portion 92 has two angle arms 95 which form a "diamond" shape with the maximum width being at the angle portions 97 of the two arms. When the tape is unlocked, slide 80 is in its upper position, and it is slid downwardly to lock the tape. The movement of slide 80 is limited by an integral portion or tongue 81 which projects into a slot 83 in the front wall of the casing.

In the unlocked position, pins 82 are positioned (FIG. 7) directly above the upper angle portions of arms 95, and when the slide 80 is pushed downwardly the pins move to and slightly beyond the joint or angle portions 97 of the arms. During that movement, the vertical dimension of angle arms 95 and therefore of locking member 86 is increased sufficiently to push feet 22 on locking portion 88 into engagement with the tape and to lock the tape against the bottom wall 12. The fact that pins 82 are below the center of angle portions 97 insures that slide 80 will remain in that position, and the tape remains locked until the slide is moved back up to the position shown in FIG. 5. That return movement of the slide moves pins 82 from the position of FIG. 8 to that of FIG. 7 so that arms 95 return to their normal position and the locking member moves out of engagement with the tape.

Each of the constructions which are disclosed operates in an efficient manner to lock and unlock the tape. The combination of the pair of angular arms with the cam operation reduces the operating force required. That produces a "leverage" effect which multiplies the force required to move the slide to the greater force which is required to lock the tape against the casing wall and hold the slide in its locked position.

In FIGS. 1 to 4, the angle arms are secured in their elongated "tape-locking" positions by the parallel side edges 37 pressing transversely against the angle portions 35 of arms 24. A similar result is provided in FIGS. 5 to 8 by moving pins 82 slightly past the center of the angle portions of the angular arms. The ledges 48 in FIGS. 1 to 4 provide an "anchor" for the angular arms, but the arms are still free to move upwardly when they move toward each other to their rest positions.

It is understood that modifications can be made in the illustrative embodiments of the invention and that the various aspects thereof can be used separately or together all within the scope of the claims.