GB1279944A - Centrifuge indexing seal head assembly and method - Google Patents

Abstract

1279944 Centrifugal separators BECKMANN INSTRUMENTS Inc 19 April 1971 [26 Feb 1970] 21690/71 Heading B2P A multi-cell centrifuge rotor is loaded with sample to be investigated by spinning the rotor at a selected rotational speed and loading sample in one cell at a time while the rotor is spinning. As shown a zonal centrifuge rotor 11 has a number of equi-angularly spaced, sectorshaped cells 19 with transparent top and bottom walls 22, 23. Each cell is associated with a pair of radial passageways 31, 32 for carrying fluid to and from the cell. Fluid is fed to the pasageways 31, 32 by feed lines 91, 92 associated with conduits 100, 101 which are interconnected by way of a four-way valve 105 with either a conduit 102 and a pump 104 for density gradient solution or a conduit 103 which communicates via a valve 107 with either a sample pump 106, or a fraction collector (not shown), to collect and store the centrifuged sample. Instead of a sample pump a syringe may be used. The feed lines 91, 92 communicate with passageways 88, 89 formed in a stationary seal member 86 which is urged by a spring 97 against a rotary seal member 36 carried by the rotor 11 in a socket 28 lined with a seal 43. The seal 43 includes circumferentially spaced passageways 44, 46 (one pair for each rotor cell) which communicate with the passageways 31, 32. Two L-shaped passageways 41, 42 formed in the member 36 communicate with the passageways 88, 89 and terminate at the outer wall of the member 36 in openings 41a, 42a which can be selectively aligned with one set of the passageways 44, 46 to provide a pair of continuous paths to transmit fluid into and out of a respective rotor cell 19. In order to control the orientation of the member 36 relative to the rotor cells 19 an indexing head assembly is provided in the form of a rotary sleeve 12, a normally stationary sleeve member 13, a brake shoe 76 and an outer housing 14. The sleeve 12 is operatively connected to a hub 27 integral with the rotor 11 by means of a lug 47 carried by the hub and to the seal member 36 by a pin and slot arrangement 39, 38 which constrains the sleeve to rotate with and hence drive the seal member but allows relative axial movement between them. The lug 47 runs in a circumferentially extending castellated groove 48 formed in the outer surface of the sleeve 12 so that, by rotating the sleeve through successive segments of the groove relative to the lug, the openings 41a, 42a are brought into registry with successive rotor cells. To move the sleeve 12, it must first be moved up or down axially, depending whether the lug 47 is located in an upper or lower segment of the castellated groove 48, and then rotated with respect to the rotor. Axial motion is imparted to the sleeve 12 by manually pushing up or pulling down on the sleeve member 13 which acts on the sleeve 12 through a bearing 51. The sleeve member 13 is slidably and rotatably mounted within the housing 14 which is removably secured to the centrifuge housing and has side openings therein (not shown in Fig. 2) to facilitate access to the top of the sleeve member 13. A castellated groove 68 in the outer surface of the sleeve member 13 has a geometrical configuration identical to, and, when resting in a rotor cel position, corresponding in position with, that of the groove 48 in the sleeve 12. A ball 69 constrained between the sleeve member 13 and the housing 14 travels along the groove 68. The brake shoe 76 is semi-annular and made of semi-rigid material and, when compressed by diametrically opposed pushbutton assembles 81, cooperates with the upper surface of the sleeve 12 for momentarily retarding the rotation of the latter and hence of the seal member 36 relative to the rotor 11 thereby permitting the openings 41a, 42a to index to different cells in the rotor 11. The invention is also applicable to rotors of the swinging bucket or fixed angle type. The cells (the term includes tubes) may be stacked vertically as opposed to horizontally in the rotor.