Overload preventive device

An overload preventive device comprising:

• a hydraulic pump for supplying pressurized fluid of a specified pressure to a load detecting circuit when internal pressure of the load detecting circuit is below a preload pressure, and stopping supply of said pressurized fluid to the load detecting circuit when the internal pressure of the load detecting circuit is over the preload pressure;
• a relief valve for releasing the pressurized fluid in the load detecting circuit when the internal pressure of the load detecting circuit is over a specified value;
• a delay valve interposed between the hydraulic pump and the load detecting circuit so as to open when the internal pressure of the load detecting circuit is lower than the preload pressure continuously over a specified time;
• a valve case, said hydraulic pump, said relief valve, and said delay valve each being located within said valve case;
• a pressure chamber located within said valve case, a partition wall separating said pressure chamber into an upstream chamber and a downstream chamber, said delay valve being located between said downstream chamber and a discharge valve of said hydraulic pump;
• said delay valve including a movable delay valve element located within said upstream chamber, said delay valve element separating said upstream chamber into a front chamber and a rear chamber;
• said delay valve element including an orifice having a predetermined diameter, said orifice allowing fluid communication between said front chamber and said rear chamber;
• and
• a spring located within said rear chamber between said delay valve element and said partition wall for biasing said delay valve element away from said partition wall.