The present invention relates to a key-controlled locking device suitable for pneumatic or hydraulic systems, and particularly to a locking device provided with an oil leakage system able to operate every time a breaking of the device is attempted.

The locking devices of pneumatic or hydraulic systems are adopted in order to prevent an unauthorized access to the system they are applied to. The prior art locking systems can be in most of the cases described as on-off valves interposed between a pneumatic or hydraulic supply unit and a given machine or mechanism supplied by said unit. In such cases the shut-off member within the above valve is controlled by a key such that the authorized personnel by turning the key can operate the supply unit thus allowing the machine or mechanism to be started. The various known locking devices are then different in terms of construction solutions selected for the particular adopted shut-off member and in terms of operative functions achieved by the valve inner hydraulic circuit which, in any case, is in communication with both inlet port and outlet port of said devices.

The locking devices are generally constituted by a main body, in which the abovementioned inner hydraulic circuit is housed together with the corresponding shut-off member, and a protrusion of said main body in which a key lock operatively connected with control member of said shut-off member is in turn housed.

Therefore all the prior art locking devices leave the opportunity to shear such protrusion with every suitable tool for everyone intendeds to tamper the locking device, so as to freely and directly access the shut-off member or, alternatively, control member thereof in order to cause the working fluid to flow and, consequently, the machine or the mechanism to operate. This drawback of the prior art devices can be partially overcome by providing the key lock protrusion with an armour consisting of, for example, hardened steel or other materials or performing a surface treatment of the same protrusion: however, in such manner, the only advantage is to increase time required to shear the protrusion and, very rarely, to affect the desired final result, that is removal of the key lock.

Main object of the locking device suitable for hydraulic or pneumatic systems according to the present invention is therefore to provide an improved arrangement of the valve inner hydraulic circuit such that, even if a removal of the key lock from its protrusion occurs regardless of how it has been carried out, it causes leakage of the working fluid which irreversibly compromises its flow from inlet channel to outlet channel of the locking device.

The advantages and features of the locking device suitable for hydraulic and pneumatic systems according to the present invention will be clear from the following detailed description of a preferred embodiment thereof taken in conjunction with the annexed drawings in which:

fig. 1 is a perspective view of a preferred embodiment of the locking device according to the present invention showing the inner hydraulic circuit of said device in phantom, and

fig. 2 is a partial cross sectional view of the device in fig. 1 showing the device in its open position (on the right hand side) and in its closed position (on the left hand side), respectively.

With reference now to fig. 1 a locking device 10 suitable for pneumatic or T/IB2011/001115

3

hydraulic systems is shown constituted by a main body 1 and a cylindrical slot 2 integrally formed into said body 1. Within the body 1 the various channels constituting the inner hydraulic circuit of the device 10 and connecting an inlet channel 3 with an outlet channel 4 of the working fluid can be recognized. Arrangement of the connecting inner channels can be any of the prior art locking devices as the one shown in fig. 1 , in which particularly a shut-off member (not shown) is displaced into the indicated position 7' so as to stop the working fluid flow from said inlet channel 3 to said outlet channel 4. The cylindrical slot 2 is internally hollow and in communication with the inner hydraulic circuit such that control member of said shut-off member and key lock coupled therewith can be housed.

Turning now to fig. 2, the above said shut-off member 7 and its control member 8 together with a security key 9 are shown. Turning of said key 9 causes, through corresponding key lock, the control member 8 to bias downwardly the shut-off member 7 thus allowing flow of the working fluid and normal start of the machine the device 10 is applied to. It is therefore clear that shear of the slot 2, and therefore control member 8 and/or the key lock, will allow removal thereof and permit to freely access the shut-off member and manually move it.

In order to avoid even this tampering approach, which is known as the most effective since it allows access to inner hydraulic circuit in almost all prior art locking devices, the present invention provides addition to said inner hydraulic circuit of a blind channel 6 communicating, for example, with the outlet channel 4 of the working fluid and vertically extending within said main body 1 and specifically into almost the whole cylindrical wall of the hollow of said slot 2. Therefore a shear of the key lock cannot occur without also involving a shear of said blind channel 6 which, consequently, will be no more blind but opened exactly at the shear position. Oil or any other working fluid adopted contained upstream the channel 6 - and obviously portion of the external hydraulic circuit - will be free to leak under the pressure being in that portion of the hydraulic circuit. A subsequent attempt of shut-off member opening or tampering of like mechanism having been provided in the locking device for a flow control unavoidably leads to a continuous oil leakage from channel 6 and subsequent pressure drop into the outlet channel 4 and the downstream hydraulic circuit portion, thus resulting in the impossibility to start machine. In order to discourage any attempt to shear the key lock of said device 10 an armour 5 constituted, for example, by hardened steel can be further provided around the slot cylindrical wall.

As previously said in the just provided detailed description the improved locking device 10 according to the present invention can be fit to any arrangement of the inner hydraulic circuit including even those circuits of the state of the art and any control member and mechanism of the shut-off member of said circuits.