Hydraulic preheating apparatus for hydraulic oil coolers in a large hydraulic excavator

Abstract

An apparatus for preheating hydraulic oil which is located at low temperatures in at least one air-cooled hydraulic oil cooler, wherein at least one hydraulic oil cooler is arranged outside an engine compartment, in particular of a large hydraulic excavator, characterized in that the oil, in particular hot oil, coming from a tank is fed to the inlet box of the hydraulic oil cooler and is passed on via connecting lines and an interposed pressure relief valve or a non-return valve to the outlet box of at least one hydraulic oil cooler, wherein the outlet box and the cold oil located therein can be heated and fed to the tank.

1 . A device for preheating hydraulic oil in a large hydraulic excavator at low temperatures comprising:
 at least one hydraulic oil cooler is arranged outside an engine compartment;   a tank configured to direct hot oil to an inlet box of the hydraulic oil cooler;   connecting lines and an interposed pressure-limiting valve or a check valve configured to conduct the hot oil to the outlet box of the at least one hydraulic oil cooler, wherein the cold oil situated in the outlet box can be heated and supplied to the tank.   
     
     
         2 . The device as claimed in  claim 1 , wherein the oil flowing from the inlet box of the hydraulic oil cooler to the pressure-limiting valve, or the check valve, and from there to the outlet box of the hydraulic oil cooler is raised from a low temperature level to a higher temperature level before it passes into the outlet box of the hydraulic oil cooler. 
     
     
         3 . The device as claimed in  claim 1 , wherein the pressure-limiting valve opens the line to the outlet box of the hydraulic oil cooler when a preset response pressure is reached, wherein the preset response pressure lies below the admissible operating pressure of the hydraulic oil cooler. 
     
     
         4 . The device as claimed in  claim 3 , wherein, when the response pressure preset at the pressure-limiting valve is undershot, the line to the outlet box of the hydraulic oil cooler is closed. 
     
     
         5 . The device as claimed in  claim 1 , wherein a spring-preloaded check valve can be used instead of the pressure-limiting valve. 
     
     
         6 . A device for preheating hydraulic oil in a large hydraulic excavator, comprising:
 at least one hydraulic oil cooler having an inlet box and outlet box, and arranged outside an engine compartment and having hydraulic oil at a cold temperature disposed therein;   a tank having hydraulic oil at a hot temperature;   a pump configured to direct hydraulic oil at the hot temperature to the inlet box   a first connecting line having a first end coupled to the inlet box and a second end coupled to a valve;   a second connecting line having a first end coupled to the valve and a second end coupled to the outlet box;   wherein the first connecting line, the valve, and the second connecting line are configured to conduct hydraulic oil at the hot temperature from the inlet box to the outlet box, so that hydraulic oil at the cold temperature disposed in the outlet box can be heated and returned to the tank.   
     
     
         7 . The device as claimed in  claim 6 , wherein the hydraulic oil flowing from the inlet box to the valve, and from the valve to the outlet box of the hydraulic oil cooler is raised from a low temperature level to a higher temperature level before passing into the outlet box of the hydraulic oil cooler. 
     
     
         8 . The device as claimed in  claim 7 , wherein the valve comprises one of a pressure-limiting valve or a check valve, and permits passage of hydraulic oil to the outlet box of the hydraulic oil cooler when a predetermined response pressure is reached, and wherein the predetermined response pressure lies below an admissible operating pressure of the hydraulic oil cooler. 
     
     
         9 . The device as claimed in  claim 8 , wherein, when a pressure of hydraulic oil in the first line is less than the predetermined response pressure at the valve, the valve is closed. 
     
     
         10 . The device as claimed in  claim 9 , wherein the valve comprises a spring-preloaded check valve.