Interlocking fixed and ambulatory scrapers

Claim 1

FOR USE ON A SUCKER ROD TO BE RECIPROCATED IN WELL FLUIDS WITHIN A STRING OF TUBING AND THROUGH A PREDETERMINED STROKE, THE COMBINATION OF MORE THAN TWO PARAFFIN SCRAPERS OF TWO DIFFENT TYPES INCLUDING FIXED SCRAPERS CLAMPED TO THE ROD AND SPACED APART BY SUBSTANTIALLY THE LENGTH OF SAID STROKE AND ALTERNATING WITH AMBULATORY SCRAPERS SURROUNDING THE ROD AND FREELY SLIDABLE THEREON, SAID SCRAPERS EACH HAVING A HELICAL SCRAPING BLADE EXTENDING AROUNG THE ROD AND TERMINATING AT EACH END IN A SUBSTANTIALLY ANNULAR BOSS HAVING A TRANSVERSE END SURFACE, THE BOSSES ON ONE TYPE OF SCRAPER HAVING A PROJECTION OFFSET FROM THE SUCKER ROD AND EXTENDING BEYOND SAID TRANSVERSE SURFACE AND THE BOSSES ON THE OTHER TYPE OF SCRAPER BEING CUT AWAY ON ONE SIDE TO RECEIVE THE PROJECTION OF THE ADJACENT SCRAPER, WHEREBY THE SCRAPERS INTERLOCK TO PREVENT MUTUAL RELATIVE ROTATION WHEN THE TRANSVERSE SURFACES OF DIFFERENT TYPES OF SCRAPERS ARE BROUGHT TOGETHER.