Transmission unit for industrial machines

A stepless speed variation transmission drive unit, comprising:

• at least a first input pinion;
• at least a first hydraulic motor connected to said first input pinion;
• an output shaft;
• and at least a second hydraulic motor, wherein the first hydraulic motor is connectable and disconnectable to/from said output shaft via a multi-disc clutch, and wherein the second hydraulic motor is always connected to said output shaft;
• a multi-disc brake device which blocks rotation of the first hydraulic motor when said first hydraulic motor is disconnected from the output shaft;
• and
• an intermediate shaft between said first input pinion and said output shaft, wherein the first input pinion is configured to transmit movement from the input pinion to the output shaft via said intermediate shaft, and wherein the intermediate shaft is connected and disconnected from said output shaft via said multi-disc clutch;
• wherein the multi-disc clutch comprises a pack of discs coated with friction material interposed to a pack of metal counter-discs, the pack of metal discs being operatively connected in rotation to the output shaft, the pack of metal counter-discs being integral with the intermediate shaft, or vice versa, and wherein said clutch is controlled by a clutch actuator operated to make the pack of discs integral with the pack of counter-discs;
• and
• wherein said clutch actuator is of the hydraulically or pneumatically-operated type.