u . s . pat . no . 5 , 884 , 887 tided “ lock for slide adjustment of boat seat or table top ” describes an elevated slidably adjustable boat seat with a positive locking arrangement . the instant invention can be used in conjunction with the aforementioned invention so that the elevated boat seat is not only slidably adjustable and lockable fore and aft in the manner described in the &# 39 ; 87 patent but also can be rotatably or swivably adjusted and positively releasably locked facing in the desired direction . fig1 illustrates a typical installation in which the instant invention is utilized . conventionally and traditionally , a rigid circular hollow support post or column 10 extends vertically upward in a telescope arrangement from a tubular supporting pillar 9 which is attached at its base to the boat deck 7 . usually pillar 9 contains a suitable mechanism , not shown , for adjusting the height of column 10 to raise or lower the boat seat 6 , shown in dashed line , which is attached at the top end . in some cases the boat seat may be coupled directly to pillar 9 so the boat seat is at a fixed height or elevation . in either case , boat seat 6 is coupled to its support post by a spider or yoke generally identified by reference numeral 13 which is described in greater detail hereinafter . a lever arm 11 extends outward from the underside of the boat seat which can be operated by the user to unlock or disengage the boat seat to allow it to be rotatably or swivably adjusted and to lock the seat when facing in the desired adjusted position . a spider or yoke 13 is a metal casting , preferably of aluminum , and has a generally centered downwardly projecting section 14 with a centered hollow tubular section 16 for coupling to support post or column 10 and has an integrally cast horizontal upper plate 15 . as described in greater detail in the &# 39 ; 076 patent plate 15 has parallel side edges 15 a and 15 b which slidably engage in tracks , not shown , on the side edges of a plate member , not shown , attached to the underside of boat seat 6 for permitting the boat seat to be slidably adjusted fore and aft by the user . the teeth along side edge 15 b are for engaging a locking mechanism , not shown , on the boat seat plate for locking the seat in the desired adjusted forward or rearward position . the exterior surface of the vertical hollow support post or column 10 has a series of closely - spaced ridges and grooves generally designated by reference numeral 17 and its internal annular surface is smooth . a hollow plastic sleeve 18 is telescoped within support column or pedestal 10 at its upper end and has an overhang designated by reference numeral 19 which extends over the upper end of column 10 and overlaps to extend downward over the exterior of a portion at the top of column 10 . the inner surface of the overhang portion 19 designated by reference numeral 20 has a series of closely - spaced vertical grooves and ridges which mate with the corresponding grooves and ridges 17 on the outer surface of column 10 . this serves to prevent insert 18 from rotating with respect to the support column 10 , i . e ., the two are rotationally locked together . the outer surface of the overhang section 19 contains a series of circumferentially spaced vertical slots or grooves designated collectively by reference numeral 21 which , as will be described later , provide means for selectively locking the boat seat facing in the desired direction . yoke 13 is coupled to the support column 10 with hollow extension 16 telescoped within the interior of plastic sleeve 18 with the underside of the plate 15 effectively resting on top of the upper end of column 10 . yoke or spider 13 has a passageway generally designated by reference numeral 25 which extends radially outward in section 14 . a toothed locking plate 26 is slidably held in the opening 25 by an upper flange 26 a and is movable , as will be described later in greater detail , radially inward and outward as desired for its teeth 26 b to mesh with or disengage from the teeth 21 of the overhang section 19 of the plastic insert 18 . a bar or rod 27 extends radially outward from the back end of locking plate 26 and a coiled spring 28 in compression is wrapped around bar 27 with one end pressing against the back side or the untoothed side of locking plate 26 and the other end of the spring 28 resting against an upward extending stop 29 on spider or yoke 13 . in this fashion spring 28 is always in compression urging locking plate 26 radially inward to hold the teeth or grooves and ridges 26 b in mesh with the corresponding grooves and ridges 21 of the outer surface of the overhang 19 of the plastic insert 18 . lever 11 has an outer handle 30 and an inner leg 31 arranged at a general right angle and is pivotally engaged at 32 with yoke or spider 13 . extending radially outward from bar 27 is a cross pin 33 which rests in a cutout area on leg 31 . with the lever arm in the relaxed or locking position spring 28 acts on locking plate 26 to hold it firmly and securely with the teeth of locking plate 26 firmly in mesh with the corresponding ridges and slots 21 . this prevents the yoke and the attached seat from rotating with respect to the support column 10 . when the seat occupant grasps handle 30 to move lever arm 11 , in the illustrated embodiment , the handle is raised , the fulcrum action of the pivotally attached leg 31 acting on pin 33 pulls bar 27 radially outward and correspondingly locking plate 26 is moved radially outward against the force of compressed spring 28 far enough to disengage the teeth of locking plate 26 from the ridges and valleys 21 thereby permitting the yoke and the attached seat to be rotated with respect to the supporting pillar 10 . when the seat is facing in the desired direction the lever arm handle 30 is released and the spring compression takes over to move locking plate 26 radially inward against the ridges and valleys 21 . if the teeth 26 b do not mesh with the valleys or slots or grooves , the seat occupant merely shifts his or her weight enough to rotate the spider or yoke a small degree until the teeth 26 b snap into mesh to lock the yoke and seat in position . as a further feature , insert 18 has a downward extending tongue section 18 a which contains an outward extending button 18 b . button 18 b is engaged in a suitable aperture 10 a formed in column 10 as a security measure to prevent insert 18 from moving vertically with respect to column 10 . as illustrated in fig3 , spider or yoke 13 preferably is formed with a diametrically opposite area 25 a to accommodate the above - described locking mechanisms to make it convenient to provide either right - hand or left - hand lever arm control .
a boat seat is rotatably supported on a hollow , tubular , deck - mounted support post or column by a yoke or spider . a radially movable locking plate is biased by a spring member to rotatably lock the yoke in place and a lever arm can be operated to move the locking plate in opposition to the force of the spring member out of locking engagement to permit the seat to be rotatably adjusted .