Flat key

Details Flat key Flat key

2000-12-06

2001-11-13

Barrett, Suzanne Dino (Department: 3627)

Locks

Parts, attachments, accessories and adjuncts

For key-operated mechanism

C070S408000

Reexamination Certificate

active

06314775

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to a flat key having a grip element and a key bit, the grip element including a casing and the key bit being arranged in a manner enabling it to be moved into and out of the grip element casing and to be fixed in its respective extreme position.
Flat keys of this type have the advantage that they take up relatively little space and that when being carried, for example in a jacket or trouser pocket, there is less risk of injury than is the case with flat keys having a key bit that is rigidly fixed on the grip element.
DESCRIPTION OF THE PRIOR ART
Normally in the case of the conventional flat keys of the prior art, the key bit is folded out from the grip element casing via a rotary spring, and swivelled into the grip element casing against the pressure of the rotary spring. The key bit is secured in the respective extreme position by means of a push-button arranged on the grip element.
The drawbacks of these known flat keys include the fact that as a rule it is necessary to use two hands to fold down the key bit. In addition, the key bit requires a relatively large swivel radius when swivelling it in and out, which means that problems can frequently arise if the key bit is swivelled out by inadvertently operating the push-button whilst the key is in the jacket or trouser pocket, etc. It is also easy for fingers to become jammed when swivelling in the key bit.
From German Patent Application No. 199 12 749. 2, which is not a prior publication, a flat key is already known on which the key bit is mounted in the grip element casing in an axially displaceable manner. The key bit is displaced on the one hand with the aid of a gearwheel disposed on a head element of the key bit, which gearwheel engages in teeth integral with the casing and extending in the direction of the key's longitudinal axis, and on the other hand with the help of a spring which pushes the key bit into its withdrawn extreme position and which is pretensioned by pushing the key bit into the grip element casing.
The primary disadvantage of this flat key is the fact that the drive consisting of the gearwheel, the teeth and the spring is relatively expensive to make and takes up a lot of space.
SUMMARY OF THE INVENTION
It is the object of the invention to provide a flat key having an axially displaceable key bit which has an inexpensively manufactured drive and relatively small dimensions.
In accordance with the invention this object is achieved by the features of claim
1
. The subsidiary claims disclose additional, particularly advantageous embodiments of the invention.
The invention is essentially based on the concept of arranging, as the drive in the grip element casing, a spring whose two end zones are each wound spirally onto two holders (cores) disposed at the side of the key bit. The central zone of the spring rests on a support on the end of the key bit that is situated inside the grip element casing, with the result that when the key bit is inserted into the grip element casing the spring is uncoiled from the cores and is thus tensioned.
The spring may be a flat coil spring, the ends of which are respectively joined to the cores. However, in practice it has proved more advantageous to use scroll springs rather than standard flat coil springs, the ends of the scroll springs not being gripped (i.e. not rigidly joined to the barrel core). Springs of this type allow relatively flat spring load deflection curves to be achieved, with the result that even where the key bit has a long displacement path a uniform force operates thereon.
It has also proved to be advantageous if the cores are in the form of rollers against which the key bit rests laterally and is thus guided in its movement into and out of the grip element casing, since if the flat key is configured in this manner only minor friction forces occur between the key bit and the grip element casing. The rollers should be made of rubber or plastic, at least in those zones in which the key bit rests against them.
In one embodiment of the invention the support for the key bit consists of a peg-shaped element about which the central zone of the scroll spring is externally guided. The peg-shaped element engages positively by its end remote from the key bit into a slot-shaped recess extending longitudinally down the key, with the result that the key bit is guided axially in a corresponding fashion during its displacement.
To secure the key bit in its two extreme positions, the peg-shaped element incorporates a recess in which is mounted a displaceably arranged, spring-loaded pin which in the two extreme positions of the key bit engages positively in a corresponding recess in the grip element casing. To release the fixing of the key bit, at least one actuating element adapted to be pressed from outside is arranged on the grip element, said actuating element operating on the pin in such a way that when pressure is exerted on the actuating element the pin is pushed out of the respective recess in the grip element casing and into the recess in the peg-shaped element and thus the key bit can subsequently be displaced axially.


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patent: 3672192 (1972-06-01), Dontas
patent: 3696649 (1972-10-01), Chow et al.
patent: 4281458 (1981-08-01), Okada
patent: 4660397 (1987-04-01), Girimont
patent: 5460022 (1995-10-01), Parsons

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