In some known shaving units, the shaving geometry, i.e., the spatial relationships between the blade and rigid portions of the razor head are fixed.  U.S. Pat.  No.  3,786,563, issued Jan. 22, 1974 to Francis W. Dorion, et al.  is illustrative of this type of razor unit.  In a second known category of shaving units, the shaving geometry is adjustable in that one or more of the portions of the unit may be re-positioned relative to the others, by the user, and remain in their new positions until selectively re-adjusted. 
It has also been proposed to construct a shaving system with a cap member fixed relative to a handle and with blade and guard members made fast with each other and spring biased to a position of maximum blade exposure, the blade and guard members being adapted to retract against the spring bias upon encountering undue resistance during shaving.  An arrangement of this sort is described in U.S. Pat.  No.  4,063,354, issued Dec. 20, 1977 to Harry Pentney et al. 
Several arrangements of shaving units permitting dynamic movement of various portions thereof during a shaving operation have been devised; examples of such contrivances are illustrated in U.S. Pat.  Nos.  1,935,452 issued Nov. 14, 1933 to M. R. Kondolf; 2,313,818 issued Mar. 16, 1943 to H. J. Gaisman; 2,327,967 issued Aug. 24, 1943 to P. N. Peters; 2,915,817 issued Dec. 8, 1959 to E. Peck; 3,500,539 issued Mar. 17, 1970 to J. P. Muros; 3,657,810 issued Apr. 25, 1972 to W. I. Nissen; 3,685,150 issued Aug. 22, 1972 to F. L. Risher; and 3,740,841 issued Jun. 26, 1973 to F. L. Risher, as well as U.S. Pat.  Nos.  3,880,284, 4,026,016, 4,168,571, 4,170,821, 4,270,268, 4,379,219, 4,492,024, 4,498,235, 4,551,916, 4,573,266, 4,586,255, 4,621,424 and 4,742,909, all of which are incorporated by reference.