Th e present i nvent ion rel ates to a n i m proved cl a m p for a key duplicating machine.

Key duplicating machines for flat keys with lateral bitting are known . They are usually provided with two clamps, one facing a mechanical feeler and intended to clamp the original key to be duplicated, and one facing the milling cutter and intended to clamp the blank key to be bitted. To achieve correct reproduction of the bitting pattern on the blank key, the original key and the blan k key, and hence the respective clam ps, must be precisely aligned longitudinally.

In particular, clamps are known with two superposed jaws of square plan and with their facing surfaces suitably shaped to be able to retain between them keys of different shapes. In particular, to securely retain a key, the clam p jaws present ribs designed to penetrate into the long itud i nal grooves generally present in the key shank.

To overcome the fact that keys present profiles of many shapes, all mutually different, the jaws are formed such as to present a different shape on each of its faces, such that by suitably choosing and positioning the two jaws facing the milling cutter and feeler, the same clamp can be adapted to several different key profiles.

In greater detail , according to the trad itional art, the clamp jaws are mounted on a vertical pin fixed to a support mounted on a structure movable in the mach ine d irections X and Y relative to its base, to which the mill ing cutter and feeler are fixed ; in particular, the jaws are mounted on said pin such as to enable each jaw to be rotated about the other and about their support. Correct positioning of the clamp lower jaw relative to its support is generally ach ieved by vertical pegs rigid with the support and engag ing in corresponding holes provided in the lower jaw. The drawback of this solution is that the jaw is rather laborious to construct and is difficult to engagement on the support pegs.

A solution has been proposed involving the presence of a rocker plate positioned on the face of the lower jaw opposite the clamping face and acting such as to u rge the jaw against the vertical pin , to wh ich it is connected together with the upper jaw. Th is sol ution enables inevitable slack and manufacturing tolerances to be elim inated and ensures that the jaws are d isposed with their surfaces always perfectly perpend icular to the mill ing cutter and feeler axes for any position into which they are rotated about their support. However, apart from the laborious construction of this solution, it requires the use of both hands to rotate the jaw, one hand being used to raise and reposition the jaws, while the other operates the rocker plate.

US 2282165 relates to a key duplicating machine in which the base of the lower jaw, of square plan, is provided with grooves which extend cross- shaped from a central hol e and are intended to come into contact with projections, also of cross-shape, defined on the upper surface of the clamp support. In particular, the lower jaw can be locked in each of the four angular operative positions by simply rotating the jaw such that its grooves engage different projections on the support.

An object of the invention is to eliminate these drawbacks by providing an improved clamp which ensures correct, qu ick and precise key clamping and positioning. Another object of the invention is to provide an improved clamp of simple and rapid construction at low production cost.

These and other objects wh ich will be apparent from the ensu ing description are attained, according to the invention, by an improved clamp in accordance with claim 1 .

The present invention is further clarified hereinafter with reference to the accompanying drawings, in which:

Figure 1 is a perspective view of an i m proved cla m p accord ing to the invention,

Figure 2 shows it in vertical section on the line ll-ll of Figure 5,

Figure 3 shows it in vertical section on the line I ll-Ill of Figure 5,

Figure 4 shows an enlarged detail of Figure 3,

Figure 5 shows a plan view of the support base of the clamp of Figure 1 , but without the two jaws.

As can be seen from the figures, the improved clamp 2 according to the invention comprises a support 4 with two superposed jaws 8, 1 0 mounted on a pin 6 fixed to said support.

The two jaws 8 , 1 0 are of sq ua re pl an with their facing surfaces differently shaped such as to be able to retain between them keys of different profiles.

More particularly, the facing surfaces of the two jaws 8, 10 are flat or are provided with ribs 1 2 complementary to the longitudinal grooves usually present in the shank of the key to be retained between the jaws. Suitably, the support 4 is also of sq uare plan with its sides su bstantial ly of the same dimensions as those of the jaws 8, 10. Advantageously, the u pper portion of the pi n 6 is th readed and engages in a corresponding thread provided in a knob, not represented, the purpose of which is to lock the two jaws 8, 10 to the support 4 by a single operation, against the reaction of a spring interposed therebetween.

The lower surface 14 of the lower jaw 8 is provided with four grooves 16 of essentially V-profile . These are paral lel to the jaw sides and are positioned at the same distance from them.

On the support 4, on opposite sides of the pin 6, two mutually parallel depressed seats 20 are defined housing two cyl indrical pegs 22. In greater detail, the pegs 22 project beyond the upper surface 24 of the support base 4 su ch as to cooperate with two oppos ing i nverted V-shaped grooves 16 provided in the lower jaw 8. As shown in Figure 4, the pegs 22 of the support 4 and the grooves 1 6 are shaped such that, on mutual cooperation, that part of the lower surface 14 of the lower jaw 8 not provided with said V-shaped grooves is raised from the opposing upper surface 24 of the support 4.

Evidently, when the angular position of the lower jaw 8 relative to the support base 4 varies, the two inverted V-shaped grooves 16 engaged by the two pegs 22 vary.

The operation of the improved clamp 2 accord ing to the invention is apparent from the description. In particular, when the user wishes to bring a certain pair of jaws to face the tool and the feeler, he firstly loosens their connection by operating the knob which retains them clamped, in this manner causing them to move apart, then ra ises them u ntil they d isengage the grooves 1 6 of the lower jaw 8 from the two pegs 22. He then rotates the two jaws 8, 1 0 about the support base 4 and about each other until the chosen pair faces the tool or feeler, then after placing the key between them , he clamps it in position by operating the knob. Correct and stable positioning of the lower jaw 8 relative to the support base 4 is ensured by the engagement of the two pegs 22 in the two grooves 1 6, which in th is position are located above the pegs 22 and which, by virtue of their shape, immediately ensure the precision of this engagement.

From the aforegoing it is apparent that the improved clamp according to the invention is much more advantageous than traditional clamps, in that:

- it is easier to construct,

- it renders the production, machining and inspection stages of the two jaws similar, enabling rationalization and simplification of the production process, with consequent cost saving,

- it enables easy, quick and precise jaw positioning,

- enables this positioning to be achieved with a single hand.