Snow plow having obstacle compensating means on the forward edge of the blade

Claim 1

IN A CLEARING DEVICE FOR ATTACHMENT TO A STREET SNOW PLOW, THE COMBINATION WHICH COMPRISES: A MAIN SHARE HAVING A FRONT EDGE AND A FORWARDLY DIRECTED FRONT SURFACE; AN INTERMEDIATE LEDGE HAVING FRONT AND REAR EDGES; A LEADING SCRAPER HAVING FRONT AND REAR EDGES; MEANS PIVOTALLY CONNECTING SAID SCRAPER AT SAID REAR EDGE THEREOF TO SAID LEDGE AT SAID FRONT EDGE THEREOF; MEANS PIVOTALLY CONNECTING SAID LEDGE AT SAID REAR EDGE THEREOF TO SAID SHARE AT SAID FRONT EDGE THEREOF; SAID LEGE AND SCRAPER, IN OPERATIVE POSITION OF THE CLEARING DEVICE, FORMING A UNIT WHICH, AS A WH OLE, IS FORWARDLY INCLINED WITH RESPECT TO THE GROUND IN THE DIRECTION OF TRAVEL OF THE SNOW PLOW, SAID LEDGE HAVING, IN SID OPERATIVE POSITION OF THE CLEARING DEVICE, AN UPPER SURFACE WHICH FORMS A CONTINUATION OF SAID FRONT SURFACE OF SAID SHARE AND AN UNDERSURFACE WHICH IS GENERALLY DIRECTED TOWARD THE GROUND ALONG WHICH SAID FRONT EDGE OF SAID SCRAPER MOVES DURING PLOWING OPERATION;