The present invention relates to a method for verifying tool integrity in automatic m u lti-tool key duplicating machines, and a mach i n e fo r implementing the method.

Three-axis electronic machines are known for duplicating dimple keys and laser keys. As these require considerable operational accuracy, it is necessary to be able to precisely determine the distance between the surface on which the key blank to be bitted rests and the tip of the particular tool mounted on the spindle, as this distance is critical in calculating the depth of the individual dimpling indentations by the machine software

In these known duplicating machines, the different operations on the keys to be bitted require frequent tool substitution, which is done manually. This involves inevitable problems related both to the different length of the individual tools and to their greater or lesser extent of insertion into the machine spindle, with consequent possible uncertainties in the level of the tip of the tool mounted in the machine spindle and possible inaccuracies in determining the depth of the dimples.

To overcome this drawback, which would compromise the operational accuracy of the machine, particular clamps have been long proposed provided w ith refe re n ce p l u g s fo r d ete rm i n i n g th e ze ro l eve l of th e too l ti p , independently of the tool length and of the extent of its insertion into the machine spindle. With these tool clamps, after each tool substitution, the tool is rested with its tip on the reference peg provided i n them , such as to establish an electrical contact between the two, and enable the mach ine software to calculate from the corresponding signal the level difference between the tool tip and the clam p surface on which the key blank to be duplicated rests.

The level of the tool tip constitutes zero level, relative to which the machine software relates the commands for moving the tool holder spindle along the Z axis.

The clamp calibration, i.e. the determ ination of the level difference between the plug and the clam p surface, on which the key blank rests, is effected once and for all, using a particular sized tool (feeler).

For duplicating dimple keys and laser keys, industrial electronic machines have been recently used provided with several tools which can be substituted automatically. These machines are loaded with large quantities of key blanks to undergo different operations with different tools, and carry out all the operations required for their bitting by means of automatic cycles.

In these automatic multi-tool machines, the zero level for each tool is determ ined differently once and for all, by m illing a key blank placed on the m ach i n e c l a m p a n d then measuring the depth of the cut obtained. Consequently in these known automatic multi-tool machines no reference plug is provided in the clamp, as it would be superfluous given the different manner of determining the zero level of the tool tip, and there is also no facility for using this plug, as manual substitution of the tool does not take place at each operation but only if it undergoes breakage, or is program med for manual substitution after a predetermined very large number of operations.

Hence as manual tool substitution is infrequent, it is not possible to visually check its integrity, and it can happen that a possible breakage is identified only after a large number of keys have been cut, they then having to be discarded. The object of the present invention is to elim inate this drawback by solving the problem of verifying tool integrity in autom atic m ulti-tool key duplicating machines.

Th is and other objects wh ich wi l l be apparent from the ensu ing description are attained, according to the invention, by a method for verifying tool integrity in automatic multi-tool key duplicating machines as described in claim 1 .

The autom at ic m u lti-tool machine presents the characteristics indicated in claim 4.

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

Figure 1 is an exploded perspective schematic view of a clamp of the automatic multi-tool key duplicating machine of the invention and the relative tool holder unit,

Figure 2 is a perspective view of just the clamp of said machine showing a tool undergoing integrity verification, and

Figure 3 shows it in the same view, with a key blank undergoing bitting.

As can be seen from the figures, the method of the invention is used in automatic multi-tool key duplicating machines. One of these machines, or rather its tool holder unit 2 and the support clamp 4 for a key blank to be bitted, are shown in Figure 1 . This figure shows two different m illers 8, 8' mounted on the tool holder unit 2 and each provided with an upper cone 10 for fixing to a tool holder spindle (not shown), with which the machine is provided.

In the illustrated example the clamp 4 is of pneumatic type with two jaws 12, 12', between which the key blank 6 can be clamped while milling its shank. A plug 14 is applied to the clamp 4, in an manner sim ilar to that which occurs in most of the clam ps of electronic machines for duplicating dim ple keys and laser keys with manual tool substitution, even though said plug is used for a totally different purpose, as will be apparent hereinafter.

U n der no rm a l o perati ng cond itio ns , an autom ati c m echan i sm withdraws a key 6 to be bitted from a key blank store (not shown) and positions it within the clamp 4, between the jaws 12, 12', which lock it in the working position. A com mand is then given to the tool holder spindle (not shown), which withdraws from the tool holder unit 2 a tool 8, 8' suitable for the particular operation to be carried out on the key blank 6, and performs that operation therewith.

It then returns the tool into the tool holder unit 2, from which it withdraws a different tool to carry out a new operation on the key 6, and so on until the key bitting has been completed.

Within the scope of this traditional operation of an automatic multi-tool key duplicating machine, according to the invention the machine provides for positioning the tool holder spindle at a certain periodicity rate such that the tip of the tool 8, 8' rests on a fixed point of the machine structure. As the clamp 4 is generally of the type used in electronic duplicating machines with manual substitution of the different tools, it is already provided with a reference peg 14 used in the traditional machine for determining the tool zero level along the Z axis.

This enables that reference peg 14 to be used as the fixed point of the machine structure, although for the purposes of the present invention any other fixed point on the machine structure would be usable. I ndependently of the chosen fixed point, the electrical contact is generated when the tip of the tool 8, 8' touches the reference peg 1 4, to determ ine a signal which the machine operative logic associates with the position of the tool holder spindle along the Z axis and memorizes it.

When that tool is again brought into contact with the reference peg 14 at the predetermined periodicity rate, the machine senses the new position of the tool holder spindle along the Z axis, memorizes it and com pares it with that previously memorized.

If this comparison shows substantial identity between the two positions, or at most a difference less than a predetermined value, this signifies substantial tool integrity; in contrast, the existence of a difference exceeding that predeterm ined value signifies loss of tool integrity, either because of abnormal wear or because of breakage, causing a tool substitution signal to be emitted.

As stated, the method of the invention requires the use of a reference point which is fixed relative to the machine structure, the purpose of this fixed point being to sense any differences in the position of the tool holder spindle along the Z axis due to the loss of tool integrity. This fixed point can consist of any point on the machine structure, even if in the described exam ple it consists of the reference peg usually provided in the tool holder clam p of trad itional electron ic mach ines with manual tool substitution , g iven the frequent substitution of these latter and the facility for visually verifying their state by the operator.

In contrast, in the case of automatic multi-tool machines, as it is not possible to visual ly verify the tool state at each manual tool substitution, periodic automatic operations must necessarily be carried out, for which the reference peg mounted on the clam p or on any other fixed m ach ine part enables a new function to be performed, which is not provided in, and in any event superfluous in, traditional machines with manual tool substitution.