US3391862A

US3391862A - Door mechanism for centrifuge vacuum chamber

Info

Publication number: US3391862A
Application number: US506492A
Authority: US
Inventors: Kenneth E Jacobson; Taylor John
Original assignee: Beckman Instruments Inc
Current assignee: Beckman Coulter Inc
Priority date: 1965-11-05
Filing date: 1965-11-05
Publication date: 1968-07-09
Anticipated expiration: 1985-07-09
Also published as: DE1532692A1; GB1120858A

Description

July 9, 1968 JACOBSON ET AL 3,391,862

DOOR MECHANISM FOR CENTRIFUGE VACUUM CHAMBER Filed Nov. 5, 1965 5 Sheets-Sheet 1 KENNETH E. JACOBSON JOHN TAYLOR INVENTORS ATTORNEY y 1968 K. E. JACOBSON ET AL 3,391,862

DOOR MECHANISM FOR CENTRIFUGE VACUUM CHAMBER Filed Noy 5, 1965 5 Sheets-Sheet 2 KENNETH E. JACOBSON JOHN TAYLOR NVENTORS ATTORNEY 1953 K. E. JACOBSON ET AL 3,391,862

DOOR MECHANISM FOR CENTRIFUGE VACUUM CHAMBER Filed Nov. 5, 1965 Y 5 Sheets-Sheet 3 KENNETH E. JACOBSON JOHN TAY LOR lM/ENTORS BY 2) ATTORNEY y 1968 K. E. JACOBSON T AL 3,391,862

DOOR MECHANISM FOR CENTRIFUGE VACUUM CHAMBER Filed Nov. 5, 1965 5 Sheets-Sheet 4 I24 20 I64 62 64 7O \szo' i f? IO 74 88 g 60 8 I is I d :ALB i N QLF I WW i n2 22 3o Fig. 4c

KENNETH E. JACOBSON JOHN TAYLOR -INVENTORS ATTORNEY July 9, 1968 JAcoBsoN ET AL 3,391,862

DOOR MECHANISM FOR CENTRIFUGE VACUUM CHAMBER Filed Nov. 5, 1965 5 SheetsSheet 5 Fig. 5b 82 Fig. 5c 82 KENNETH E. JACOBSON JOHN TAYLOR INVENTORS ATTORNEY United States Patent 3,391,862 DOOR MECHANISM FOR CENTRIFUGE VACUUM CHAMBER Kenneth E. Jacobson, Fremont, and John Taylor, Santa Clara, Calif., assignors to Beckman Instruments, Inc., a corporation of California Filed Nov. 5, 1965, Ser. No. 506,492 Claims. (Cl. 233-13) ABSTRACT OF THE DISCLOSURE A door mechanism for tightly sealing a vacuum chamber which houses a centrifuge rotor including a top plate having a chamber access hole secured over the top of the vacuum chamber and a sealing ring disposed about the access hole. A movable door overlies the top plate and is movable between a closed position in which the door covers the chamber access hole and an open position in which the access hole is completely uncovered by a pair of horizontally-movable transport elements located on either side of the movable door. Each transport element includes a cam surface which cooperates with a door support means projecting from each side of the door to displace the door in a vertical direction during initial movement of the transport elements as the door is moved from its closed position to its open position and during final movement of the transport elements as the door is moved from its open position to its closed position.

This invention relates in general to centrifuge apparatus utilizing a high speed rotor mounted inside a vacuum chamber, and in particular, to a door mechanism for the vacuum chamber.

High speed centrifuges, sometimes referred to as ultracentrifuges, may employ rotor speeds in the order of 65,000 r.p.m. and above. To obtain speeds of this magnitude and to reduce aerodynamic heating to a minimum, it is essential that the rotor be mounted in a chamber which can be evacuated. Since the chamber is a permanent part of the centrifuge structure, it is necessary to provide access to the interior of the chamber to permit insertion and removal of rotors. The chamber is therefor typically provided with an access hole in the top plate covering the chamber. A horizontally-movable door, which may be opened and closed either automatically or manually, is used to cover the access hole during centrifuge operation.

To provide an air-tight seal during centrifugation, a staling element, typically in the form of an O-ring, is mounted in the upper surface of the top plate about the chamber access hole. The door, as a result of the differential pressure across it when the chamber is evacuated, bears against the sealing element thereby effecting an excellent seal.

In door mechanisms of the prior art, the sealing element is subjected to excessive wear as a result of abrasion when the door is opened or closed. This is caused by horizontal movement of the door while it is in contact with the sealing element. It is therefore an object of the present invention to provide a door mechanism in which wearing of the sealing element by abrasion is minimized.

When zontal or continuous flow configuration is to be performed, the rotors utilized require an upper bearing and seal assembly having appropriate fluid inlet and outlet lines. This assembly may be removably mounted in the vacuum chamber door, as shown and described, for example, in US. Patent No. 3,168,474, issued on Feb. 2, 1965, and assigned to Beckman Instruments, Inc. To ensure the proper alignment between the rotor drive spindle and the upper bearing and seal assembly, the door, in its closed position, must be accurately located.

m 3,391,862 Ice Patented July 9, 1968 It is therefore a further object of the present invention to provide a door mechanism which ensures accurate location of the door with respect to the rotor drive spindle.

According to one specific, exemplary form of the invention shown and described herein, there is provided a door mechanism which, when actuated to open the door, initially lifts the door vertically until the lower surface of the door is well clear of the sealing element carried by the top plate of the vacuum chamber. As a result, there is no relative motion between the door and the sealing element in a direction which would cause wearing or abrasion of the sealing element. Following its initial elevation, the door is then transported horizontally to the open position. In this position, the hole in the top plate is completely uncovered thereby providing access to the interior of the vacuum chamber. The required vertical and horizontal motion of the door is controlled by two movable transport elements-one located on each side of the door-driven in unison by suitable manual or automatic drive means. Means projecting from the upper surface of the top plate serve to guide the door during its vertical displacement and to locate the door relative to the rotor drive spindle.

The novel features which are believed to be characteristic of the invention are set forth with particularity in the appended claims. The invention itself however, together with further objects and advantages thereof, can best be understood by reference to the following description taken in connection with the accompanying drawings in which:

FIG. 1 is a partially cut-away, exploded, perspective view of a door mechanism in accordance with one form of the present invention;

FIG. 2 is a top view of the door mechanism of FIG. 1 in place in a cetrifuge apparatus;

FIG. 3 is an end elevation view, in section, of the ap' paratus of FIG. 2 taken along the plane 33;

FIGS. 4a4d are schematic side views of the door mechanism illustrating the various stages of operation, and

FIGS. 512-50 are schematic top views, partially in section, showing the operational steps of a locking mechanism forming part of the present invention.

Turning now to the drawings, FIGS. 1-3 show a door mechanism in accordance with the present invention comprising generally a substantially square door 10,

side spacer blocks

12 and 14, rear spacer block 16 and

door transport elements

18 and 20. As best shown in FIGS. 2 and 3, the door mechanism is carried by a substantially square top plate 22 mounted atop a generally cylindrical vacuum chamber 24 defined by an outer wall 26 and a bottom plate 28. The top plate 22 is provided with a chamber access hole 30 large enough to permit the insertion and removal of any of the variety of rotors which may be used in the centrifuge. An annular groove 32, formed in the upper surface of the top plate 22 immediately adjacent the periphery of the hole 30, is dimensioned to receive a resilient O-ring 34 which serves to seal the chamber 24 when the door 10 is in the closed position. The O-ring 34 can be fabricated of a suitable synthetic rubber. In its expanded form, the resilient O-ring 34 extends above the upper surface of the top plate 22, as shown in FIG. 3. When the door 10 is in the closed position and with the chamber 24 evacuated, the O-ring 34 is compressed by the door 10 thereby completely filling the groove 32.

Suitable means are employed for establishing a good vacuum seal between the top plate 22 and the upper edge of the outer wall 26. Thus, an annular recess 36 is provided which serves to accommodate a resilient O-ring 38 made of a suitable material such as synthetic rubber. Normally, the O-ring 38 is slightly compressed whereby an effective vacuum seal is maintained.

To prevent injury or damage in the event of rotor failure during operation, a heavy guard ring 40 is placed inside the outer wall 26. Within the guard ring 40 is a light container or liner 42 which surrounds a rotor 44. The rotor 44 is supported and driven by a spindle 46 connected to a motor-transmission unit (not shown). The rotor 44 depicted in the drawings is of the fixedangle type commonly used in preparative centrifugation. Rotors for zonal or continuous flow centrifugation may also be used with the apparatus shown. Since the latter rotors require an upper bearing and seal assembly housing appropriate fluid inlet and outlet lines, mounting means are provided in the door to receive such an assembly. Suitable mounting means may take the form of a centrally located opening 48 in the door 10 which is provided with quick-release threading or other fastening means. See, for example, US. Patent No. 3,168,474, referenced above. When not in use, the opening 48 is closed off by a removable, disc-shaped plug 50 as shown in FIGS. 2 and 3. It will be evident that when an upper bearing and seal assembly is utilized, the alignment between that assembly and the drive spindle 38 must be accurately maintained. Means for locating the door 10 to achieve the required positioning accuracy will be described below.

Spacer blocks 12, 14 and 16 support a relatively heavy, generally square cover plate 52 having a chamber access opening 54 substantially coaxial with the hole 30 in the top plate 22. (For the sake of clarity, the cover plate 52 has been omitted from the perspective view of FIG. 1.) The assembly comprising the cover plate 52, the spacer blocks 12, 14 and 16, the top plate 22, the outer wall member 26 and the bottom plate 28 is securely fastened together, as shown in FIGS. 2 and 3, by means of eight clamping bolts 56, which are designed to withstand extremely high tensile loads. The entire vacuum chamber assembly described immediately above is suitably supported by a frame 58 shown in phantom in FIGS. 2 and 3.

The door 10 is moved between the open and closed positions by means of

transport elements

18 and 20 located on either side of the door 10.

Transport elements

18 and 20 may be conveniently constructed from commercially available racks, substantially square in cross section. The

racks

18 and 20 are positioned between the door 10 and the spacer blocks 12 and 14, respectively, appropriate clearance being allowed so that the racks may be freely slidable.

Formed in the upper surface of each of the

racks

18 and 20 are a pair of ca-m surfaces or ramps 60 which engage a pair of door support means during the operation of the door. The door support means may take the form of pins 62 projecting laterally from the door 10. The upper ends of the ramps 60 join horizontal seats 64 which serve to carry the support pins 62 during horizontal transport of the door 10. The rearmost end of the

racks

18 and 20 are forked to receive wheels 66 rotatably supported by axles 68. Plastic-tired ball bearings may be conveniently utilized to serve as the Wheels 66. Wheels 66 have a diameter which is slightly smaller than the height of the spacer blocks 12, 14 and 16 so that no binding or rolling resistance is encountered during rotation.

Means for guiding the door 10 during vertical travel and for locating the door relative to the rotor drive spindle will now be described. The door 10 is provided with a pair of holes 70, placed diagonally opposite one another, which are adapted to receive a pair of chamfered dowel pins 72 projecting upwardly from the upper surface of the top plate 22. Alignment between the dowels 72 and the holes 70, during descent of the door toward the closed position, is ensured by the chamfered portion of the dowels and the lower, straight portion of the dowels provides for the correct final door location.

Means are provided for locking together the rack 18 and the door 10 so that these members travel together during horizontal door movement. The locking means, according to the preferred embodiment as best shown in FIGS. 2 and 5a, may take the form of a pin 74 having a head 76 carried in a cylindrical recess 78 provided in the rack 18. A spring 80 biases the headed pin outwardly, that is, toward the spacer 12. A cam surface 82, having a straight section 84 and an inclined portion 86, is formed in the spacer block 12 in the side adjacent the rack 18. The locking pin 74 is actuated by the cam surface 82 in a manner to be described so that the pin will enter a vertical slot 88 formed in the door 10 in the side adjacent the rack 18.

Racks

18 and 20 are driven in unison by a pair of gears 90 mounted on a rotatable shaft 94 which is journaled in stationary support brackets (not shown) carried by the frame 58. The gears 90 mesh with the toothed, lower surface of the

racks

18 and 20. Any suitable means, automatic or manual, may be utilized to drive the gears. According to the preferred embodiment, a manual chain drive is provided which includes generally a drive sprocket 96 rotatably mounted on a bracket (not shown) aflixed to the frame 58, a driven sprocket 98 attached to one end of the shaft 94, and an endless chain 100 interconnecting the

sprockets

96 and 98. The chain drive may be actuated by turning a knob 102 mounted on a shaft 104 connected to the drive sprocket 96.

Referring now to FIGS. 4a-4d and Sa-Sc, the operating cycle of the door, from the closed position to the open position, will now be described. Clockwise rotation of the knob 102, which results in a similar rotation of the driven sprocket 98, causes the

racks

18 and 20 to begin horizontal movement forwardly or toward the open position. Since a slight clearance is provided between the pins 62 and the lowest extremity of the ramps 60, a small initial movement of the

racks

18 and 20 is required before the ramps 60 engage the pins 62 (FIG. 4a). As the movement of the racks continues, the ramps 60, acting on the pins 62, displace the door .10 upwardly. The door is now carried by the

racks

18 and 20 which in turn are supported solely by the wheels 66 and the gears 90. Finally, a point is reached, as shown in FIG. 4b, at which the lower surface of the door 10 just clears the tops of the dowel pins 72. At this point, the pins 62 have not quite reached the top of the ramps 60. During the small vertical displacement of the door which remains until the pins 62 reach the seats 64, horizontal movement of the door is precluded by restraining means comprising a spring clip 106, secured to the rear edge of the door 10, and an adjustable post 108 which is releasably engaged by the clip 106. The post 108 is mounted on the top plate 22 by means of a threaded bolt 110 which is securely held in a longitudinal slot 112 and projects upwardly therefrom. A nut 114 may be used to hold the bolt 110 in place. It will be noted that the spring clip 106 and the post 108 are shaped so as to permit relative vertical motion between them while engaged. As best shown in FIG. 2, the post 108 is shaped so that the engaging resistance encountered by clip 106 is less than the disengaging resistance. This is accomplished by providing the forward end of the post 108 with a gradual taper 116 and the rear end with a steep taper 118. To help prevent the post 108 from shifting rearwardly as a result of impact by the door 10, a backing screw 120 is provided. The screw 120 is conveniently carried by the rear spacer 116 which is provided with an appropriately threaded hole 122. A knob 124, aflixed to the end of the screw 120 projecting rearwardly from the spacer 16, is utilized to rotate the screw.

With the door mechanism in the positions as illustrated in FIGS. 4a and 4b, the locking device assumes the positions illustrated in FIGS. 5a and 5b, respectively. It will be seen that during the initial movement of the rack 18, the pin 74 moves along the straight section 84 of the cam surface 82. Further horizontal movement of the

racks

18 and 20 causes the door pins 62 to climb up on the horizontal seats 64 and the pin head 76 to engage the inclined portion 86 of the cam surface 82 thereby driving the pin 74 into the slot 88, the latter two elements now being in alignment (FIGS. 40 and 50). This action locks together the

racks

18 and 20 with the door so that further horizontal movement of the racks will cause the clip.106 and the post 108 to disengage as shown in FIG. 4d. With the door 10 resting on the seats 64 and the locking pin 74 in the slot 88, horizontal movement toward the open position begins. During the initial horizontal travel of the door v10, the wheels 66 are in contact with the upper surface of the top plate 22. When the center of gravity of the door mechanism passes beyond the gear shaft 94, the mechanism rotates slightly in a clockwise direction about the shaft 94 thereby causing the wheels 66 to raise off the top plate 22 and come into contact with the lower surface of the cover plate 52. Rotation of the knob 102 is continued by the operator until the door 10 is in the fully open position thereby providing access to the interior of the vacuum chamber 24.

To close the door, the operation just described is essen tially reversed, the operator moving the knob 102 in the counterclockwise direction. The door reaches the end of its rearward travel when the clip 106 engages the post 108. The position of the post 108 is adjusted before the machine is put into service so that when the door reaches the end of its horizontal travel in the closing direction, the locating holes 70 in the door 10 will be in alignment with the dowels 72. The final movement of the racks 18 and causes the pin head 76 to move into contact with the cam surface 82, thereby disengaging the pin 74 and the slot 88 and also causes the door 10 to descend vertically until contact is made with the sealing O-ring 34. In the final position of the racks, the door 10 is supported solely by the sealing O-ring 34. Sufiicient clearance is provided between the pins 62 and the lowest point on the ramps 60 so that when the chamber is evacuated, and door 10 comes down toward the top plate 22, the pins 62 will not bottom out on the ramps. The differential pressure across the door resulting from chamber evacuation, brings the door into metal-to-metal contact with the upper surface of the top plate 22, thereby deforming the O-ring and compressing it within the confines of the groove 32 to effect a substantially air-tight seal. It will be seen that since the door movement has no horizontal component when the lower surface of the door contacts the O-ring, no abrasion and resulting wear the O-ring takes place.

Other advantages inhere in the structural features of the present invention. For example, the simplicity of construction provides for ease of assembly and adjustment of the door mechanism. In addition, since the door simply rests on the

racks

18 and 20, its removal for maintenance or replacement is an easy matter.

It will be obvious to those skilled in the art that various modifications may be made to the specific exemplary embodiment of the invention described. While a particular embodiment has been discussed, it will be understood that the invention is not limited thereto and that it is contemplated to cover in the appended claims any modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. A door mechanism for a vacuum chamber which houses a centrifuge rotor mounted on a drive spindle, comprising a horizontal top plate secured over the top of said vacuum chamber, said plate having a chamber access hole;

sealing means carried by said top plate, said sealing means being disposed about said access hole;

a horizontal door disposed to overlie said top plate, said door being movable between a closed position in which said door sealingly covers said chamber access hole and an open position in which said access hole is completely uncovered, said door having substantially parallel sides and door support means projecting from each said side, said door including means for mounting an upper bearing and seal assembly;

spacer means having a height greater than the height of said movable door aflixed to said top plate adjacent each said side of said door;

a horizontal cover plate supported by said spacer means over said top plate, said cover plate having a chamber access opening aligned with said access hole in said top plate;

a horizontally-movable transport element disposed between each said side of said door and said adjacent spacer for transporting said door between said open and closed positions, said transport elements including cam means for engaging said door support means and displacing said door vertically during initial movement of said transport elements when said door is moved from said closed position to said open position and during final movement of said transport elements when said door is moved from said open position to said closed position, sealing means for carrying said door support means and locking means for engaging and holding said door during horizontal movement of said door;

means for guiding and locating said door aflixed to said top plate for guiding said door during vertical movement and locating said door in the closed position relative to said spindle;

door restraining means for releasingly holding said door until horizontal movement of said door commences; and

means for driving said transport elements in a horizontal direction.

2. A mechanism as defined in claim 1 in which said sealing means comprises an O-ring; and

the upper surface of said top plate has a groove disposed about said chamber access hole for receiving said O-ring, the thickness of said O-ring being greater than the depth of said groove whereby said O-ring is compressed 'by said door until said door comes into metal-to-metal contact with said top plate upon evacuation of said chamber.

3. A mechanism as defined in claim 2 in which said door support means comprises a pair of pins projecting outwardly from each said side of said door.

4. A mechanism as defined in claim 3 in which said transport element comprises a rack having an upper surface and a lower, toothed surface and said cam means comprises a pair of ramps extending downwardly from said upper surface of said rack and in which said seating means includes horizontal surfaces extending rearwardly from the upper extremity of said ramps.

5. A mechanism as defined in claim 4 in which said locking means comprises a pin mounted on one of said racks, said pin being movable toward and away from the corresponding side of said door, said pin being spring-biased away from said side;

and which includes a slot in said side of said door for receiving said locking pin; and

a cam surface in the spacer adjacent said rack whereby said pin is driven into said slot as said rack is moved in the horizontal direction toward said open position.

6. A mechanism as defined in claim 5 in which said door guiding and locating means includes at least one dowel extending upwardly from the upper surface of said top plate; and

said door includes at least one hole for receiving said dowel, the height of said dowel above said upper surface of said top plate being such that the lower surface of said door clears said dowel just before said door support pins reach the upper extremity of 7 said ramps when said racks are moved toward the open position.

.7. A mechanism as defined in claim 6 in which said door restraining means includes a post adjustably secured to said top plate and a spring clip attached to said door for engaging said post.

8. A mechanism as defined in claim 7 in which said means for driving said racks includes a gear in mesh with each of said racks, said gears being mounted on a common, transverse shaft;

and which includes a wheel rotatably mounted on the rearmost end of each of said racks, said wheels and said gears supporting the assembly comprising said door and said rack during movement of said assembly, said wheels being in contact with the upper surface of said top plate when the center of gravity of said assembly is rearward of said gear shaft and in contact with the lower surface of said cover plate when said center of gravity is forward of said gear shaft.

9. A door mechanism for tightly sealing a vacuum chamber which houses a centrifuge rotor comprising:

a plate having a chamber access hole secured over the top of the vacuum chamber;

sealing means carried by said plate and disposed about said access hole;

a door having at least two substantially parallel sides disposed to overlie said top plate, said door being movable between a closed position in which the door covers the chamber access hole and an open position in which the access hole is completely uncovered;

said door having door support means associated with each of said parallel sides;

a pair of horizontally-movable transport elements disposed on either side of said door, each of said transport elements including cam means for engaging said door support means to displace said door in a vertical direction during initial movement of the transport elements as the door is moved from its closed position to its open position and during final movement-of References Cited UNITED STATES PATENTS 3,168,474 2/1965 Stallman et a1. 23333 3,216,694 11/1965 Perazone 251204 XR 3,347,453 10/1967 Goergen 233.11 982,036 1/ 1911 Collar 251-326 HENRY T. KLINKSIEK, Primary Examiner.