Locking device

Locking devices for locking two components that move relative to one another such as a housing and a cover are disclosed. The locking devices have two catches disposed on one component and opposite to one another and symmetrically with respect to a stop disposed on the second component and arranged in a plane of symmetry between the opposing catches. The catches have hook ends facing the plane of symmetry and the two catches are connected to a common shaft at the ends of the catches facing away from the hook ends. The common shaft is disposed in the plane of symmetry and is movable within the plane of symmetry toward and away from the stop. The shaft is arranged on a spindle disposed in the plane of symmetry or parallel to the plane of symmetry and engaged with a motor-driven gear to effect movement of the shaft. The catches have longitudinally-extending guide elements whose longitudinal axis does not run parallel to the plane of symmetry. The guide elements engage stationary guide pins disposed parallel and symmetrically with respect to the plane of symmetry. This arrangement provides the guidance of the catches when the shaft is moved toward and away from the stop. When the shaft is at rest in a position nearest to the stop, the hook ends of the catches are opposed across the plane of symmetry. When the shaft is moved downwardly away from the stop, the hook ends of the catches move into the plane of symmetry, without lateral forces, to close around the stop from two opposing sides. This ensures equal stress on the closed lock from all sides, even under high stress and, particularly, high lateral stresses placed upon the locked-together components.

BACKGROUND OF THE INVENTION 
1. The Field of the Invention 
The invention relates to a locking device for locking two components that 
move relative to one another such as a housing and a cover. In particular, 
the present invention relates to a locking device that operates by means 
of a catch disposed on one component and having at least one hook end that 
can extend around a stop disposed on the other component for the purpose 
of locking the components together. 
2. Related Applications 
Foreign priority benefits under Section 119 of Title 35 of the United 
States Code of German Utility Model Application No. 196 29 361.8, filed 
Jul. 20, 1996, incorporated herein by reference, are claimed for this 
application. 
3. The Relevant Technology 
Numerous types of locking devices for locking two components that move 
relative to one another by means of a catch disposed on one component that 
engages a stop disposed on the other component are known. For example, a 
cover-locking mechanism for a centrifuge is known from German patent 
application DE 28 16 395 A1 in which a catch extends around a stop that is 
held against the catch by a coil spring. In this lock design, lateral 
forces occur that can cause the components that are to be locked together 
to pull and detach from one another, particularly components subjected to 
high stress such as centrifuge components. The described lock is not 
positively guided to the stop without lateral force. The locking is 
dependent on the movability of the two interlocking parts; if one of the 
movable parts jam, the lock is not effective. Similar locks are known from 
EP 0 577 863 A1. A particularly costly locking achieved via linear 
movement of a closing cylinder is known from EP 470 428 B1. There is no 
lateral force-free positive guidance in the lock published herein. 
Additionally, manual locking mechanisms are generally known for centrifuges 
or other apparatuses in which a cover must be held securely to a housing. 
These types of locks are generally difficult to operate in mid-volume to 
high-volume centrifuges, and require relatively high sealing force. 
From DE 38 21 840 C1, a locking mechanism is known for a laboratory device 
in which an additional locking and opening element is attached to the 
locking mechanism embodied as the catch to achieve secure closure. DE 44 
07 912 A1 discloses a lock that is driven by an electric motor, in which 
the bolt is halted by two stops. The two stops lie opposite one another, 
are disposed symmetrically with respect to the axis of symmetry of the 
bolt, and have a common axis of rotation. 
SUMMARY AND OBJECTS OF THE INVENTION 
It is a primary object of the present invention to provide a lock for 
locking two components that move relative to one another by means of a 
catch disposed on one component that engages a stop disposed on the other 
component that ensures a high locking reliability, even when the 
components are subjected to high stress, and that is easily and securely 
locked with the application of low manual closing forces. 
These and other objects and features of the present invention will become 
more fully apparent from the following description and appended claims, or 
may be learned by the practice of the invention as set forth hereinafter. 
In accord with the present invention, the primary object is accomplished 
with a locking device having two catches disposed opposite to one another 
and symmetrically with respect to a stop arranged in a plane of symmetry 
between the opposing catches. The catches have hook ends facing the plane 
of symmetry and the two catches are connected to a common shaft at the 
ends of the catches facing away from the hook ends. The common shaft is 
disposed in the plane of symmetry and is movable within the plane of 
symmetry toward and away from the stop. The stop can usefully be designed 
as an extending hook having a closed end or as an extending hook having an 
end closed by a locking pin. The stop is disposed in the plane of symmetry 
such that the eye of the extending hook is disposed generally between the 
opposed catches and the closed end of the hook or the locking pin closing 
the end of the hook is disposed in the plane of symmetry parallel to the 
longitudinal axis of the shaft. 
The catches have longitudinally-extending guide elements whose longitudinal 
axis does not run parallel to the plane of symmetry. The guide elements 
engage stationary guide pins disposed parallel and symmetrically with 
respect to the plane of symmetry. This arrangement provides the guidance 
of the catches when the shaft connecting the catches to one another is 
moved toward and away from the stop. When the shaft is at rest in a 
position nearest to the stop, the hook ends of the catches are opposed 
across the plane of symmetry. When the shaft is moved downwardly away from 
the stop, the hook ends of the catches move into the plane of symmetry, 
without lateral forces, to enter the extending hook and close around the 
closed end of the hook (or the locking pin closing the end of the hook) on 
the stop from two opposing sides. This ensures equal stress on the closed 
lock from all sides, even under high stress and, particularly, high 
lateral stresses placed upon the locked-together components. 
In a preferred embodiment, the shaft is arranged on a spindle disposed in 
the plane of symmetry or parallel to the plane of symmetry, with the help 
of which spindle the shaft can be moved toward and away from the stop to 
thereby effect opening and closing, respectively, of the locking device. 
In addition, the spindle preferably engages a gear connected to a motor, 
which gear effects movement of the spindle. To move the shaft with the aid 
of the spindle, the spindle can either be connected permanently to the 
shaft and be movable in the direction of the spindle axis, for example by 
means of a worm pinion in the gear, e.g., by a rotating spindle nut seated 
in the gear, or the spindle can move about its spindle axis and engage a 
thread of the shaft. In the latter variation, only the spindle rotates, 
that the spindle is screwed into or out of the shaft, thus causing the 
shaft to move. 
It is preferred to configure the catches to be essentially plate-shaped and 
disposed perpendicular to the plane of symmetry. It is also preferred to 
configure the guide elements as slots that are disposed in the catches in 
curved form with respect to the plane of symmetry. In a preferred 
embodiment, the hook ends of the catches are disposed in planes one behind 
the other with respect to the longitudinal axis of the shaft within the 
plane of symmetry so that the hook ends do not meet each other in the 
plane of symmetry but, rather, each hook end can be extended through the 
plane of symmetry, one behind the other, when entering the extending hook 
and closing around the stop from two opposing sides, without lateral 
force, thereby increasing the reliability of the lock. It is also 
preferable that the hook ends rest in frictional connection against the 
stop when the lock is in a closed state, with the stop being acted upon by 
a force in the direction of the shaft. This means that the spindle causes 
the shaft to move away from the stop not only far enough to cause the two 
catches to extend around the stop, but even farther so that the hook ends 
draw the stop in the direction of the self-locking spindle. In this 
manner, the component that the stop is mounted upon is pulled toward the 
component having the catches mounted thereon. This ensures not only a 
secure, but also a tight, closure between the two components, for example 
a housing and a cover. 
In addition, in a preferred embodiment of the present invention, the gear 
is in a housing that is seated to be movable in the direction of the 
spindle axis, and a lever connected to the gear housing is disposed 
approximately perpendicular to the plane of symmetry and is engaged with a 
detent pawl, which is disposed to be movable with respect to the lever 
and, with the lever, stops the gear housing. When detaching the detent 
pawl from the lever, it is possible to move the gear manually with the 
spindle so that the lock can be released manually. If the motor operating 
the spindle loses power, for example, it is thus possible to open the lock 
manually. To this end, it is preferred that the detent pawl be rotatably 
seated and provided with a release cord so that the pawl can be pulled 
away from the lever by pulling the release cord. 
In an exemplary embodiment of the present invention, the catches are 
disposed on a centrifuge housing and the stop is disposed on a centrifuge 
cover. The locking device of the present invention provides reliable and 
secure locking of a centrifuge even under the high stresses commonly 
generated during centrifuge use. Although the locking device of the 
present invention is very well suited for use with a centrifuge, the 
description of the locking device in connection with a centrifuge is 
illustrative only and not to be construed as limiting.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The drawings illustrate vertical cross-sections of a preferred embodiment 
of the locking device of the present invention with respect to a cover 1 
for a housing 2. Cover 1 and housing 2 can be, for example, components of 
a laboratory centrifuge. The locking device of the present invention 
provides reliable and secure locking of a centrifuge even under the high 
stresses commonly generated during centrifuge use. Although the locking 
device of the present invention is very well suited for use with a 
centrifuge, the description of the locking device in connection with a 
centrifuge is illustrative only and not to be construed as limiting. 
Returning to the Figures, a stop 3 is disposed on cover 1, the stop having 
an extending hook 4 (only one side of extending hook is visible in 
vertical cross-section view) that projects downward into the housing 2 
when the cover 1 is closed upon the housing 2. The extending hook can be 
closed at the bottom end or, preferably, as shown in the Figures, has a 
bottom end closed by a locking pin 5 (seen in cross-section). An apron 6 
is disposed within the housing 2 for mounting of various components of the 
locking device. Stop 3, comprising extending hook 4 and locking pin 5, 
lies upon a plane of symmetry that extends perpendicular to apron 6. 
Extending outward from apron 6, shaft 7 stands in this plane of symmetry 
below locking pin 5 such that the longitudinal axis of shaft 7 is parallel 
to locking pin 5. Shaft 7 is supported on spindle 12 to be movable in the 
plane of symmetry up and down, i.e., toward and away from locking pin 5, 
as described in detail below. 
Two catches 8, disposed on opposite sides of the plane of symmetry, are 
connected to shaft 7 and disposed to be movable symmetrically with respect 
to the plane of symmetry. The stop 3 is disposed in the plane of symmetry 
such that the eye of the extending hook 4 is disposed generally between 
the opposed catches 8 when the cover 1 is closed upon the housing 2. 
Catches 8 are preferably plate-shaped and have hook ends 11 at the ends 
opposite to the shaft 7. Each catch 8 has a guide slot 9 that is angled 
with respect to the plane of symmetry. 
As seen in FIG. 1, when the lock is closed, the angle of each guide slot is 
preferably about 45.degree. with respect to the plane of symmetry when an 
extension of the longitudinal axis of each slot intersects the center of 
shaft 7. Stationary guide pins 10 are rigidly connected to extend from 
apron 6 to engage guide slots 9. It is preferred to configure the catches 
to be essentially plate-shaped and disposed perpendicular to the plane of 
symmetry. It is also preferred to configure the guide elements as slots 
that are disposed in the catches in curved form with respect to the plane 
of symmetry and to arrange the guide pins parallel and symmetrically with 
respect to the plane of symmetry. This arrangement provides the guidance 
of the catches when the shaft connecting the catches to one another is 
moved toward and away from the stop. When the shaft is at rest in a 
position nearest to the stop (FIG. 2), the hook ends of the catches are 
opposed across the plane of symmetry. When the shaft is moved downwardly 
away from the stop (FIG. 1), the hook ends of the catches move into the 
plane of symmetry, without lateral forces, to enter the extending hook and 
close around the locking pin from two opposing sides. This ensures equal 
stress on the closed lock from all sides, even under high stress and, 
particularly, high lateral stresses placed upon the locked-together 
components. 
As seen in FIG. 1, when the locking device is closed, the hook ends 11 of 
the catches 8 are positioned within the plane of symmetry to enter 
extending hook 4 and rest on locking pin 5. In a preferred embodiment, the 
hook ends of the catches are disposed in planes one behind the other with 
respect to the longitudinal axis of the shaft 7 in the plane of symmetry 
so that the hook ends do not meet each other in the plane of symmetry but, 
rather, each hook end 11 can be extended through the plane of symmetry, 
one behind the other, when entering the extending hook 4 and closing 
around the stop 3 from two opposing sides, without lateral force, thereby 
increasing the reliability of the lock. It is also preferable that the 
hook ends 11 rest in frictional connection against the locking pin 5 when 
the lock is in a closed state such that the stop is being acted upon by a 
force in the direction of the shaft. A downward force acting upon locking 
pin 5 causes the cover 1 to be pulled tightly down onto housing 2. The 
downward pulling force is effected by spindle 12 that is pulled downward 
by a gear 13 by means of a motor 14. 
In a preferred embodiment, the shaft is arranged on a spindle disposed in 
the plane of symmetry or parallel to the plane of symmetry, with the help 
of which spindle the shaft can be moved toward and away from the stop to 
thereby effect opening and closing, respectively, of the locking device. 
To move the shaft with the aid of the spindle, the spindle can either be 
connected permanently to the shaft and be movable in the direction of the 
spindle axis, for example by means of a worm pinion in the gear, e.g., by 
a rotating spindle nut seated in the gear, or the spindle can move about 
its spindle axis and engage a thread of the shaft. In the latter 
variation, only the spindle rotates, so that the spindle is screwed into 
or out of the shaft, thus causing the shaft to move. 
As described above, when motor 14 rotates, spindle 12 is moved upward or 
downward by gear 13 so that the lock is opened or closed. When moving 
downward, i.e., when closing the lock, the spindle 12 is not merely moved 
downward far enough so that the hook ends 11 rest against locking pin 5 
but, instead, the movement progresses slightly further a few millimeters 
so that cover 1 is drawn tightly and securely onto housing 2 by catches 8. 
As seen in FIG. 1, in its lower, final position, spindle 12 preferably 
activates a final-position switch 15 which terminates the closing 
procedure via control electronics of motor 14. Additionally, if desired, 
final-position switch 15 can also perform an emergency-release function 
through a mechanical coupling (not shown) to detent pawl 19, described in 
more detail below. In a preferred embodiment, the state of the lock (open 
or closed) is indicated by switches 16 and 22 or, indirectly, by 
final-position switch 15 in connection with switches 16 and 22. Switch 22 
switches motor 14 on and off via control electronics of a known type. In a 
preferred embodiment, a final-position switch is disposed below the 
spindle axis for detecting the spindle position. This final-position 
switch can be used to indicate the lock status. The switch can be used to 
signal the motor to stop when the spindle is in the final-position. 
Furthermore, a position indicator is preferably provided to indicate the 
position of the catches. 
As seen in FIG. 2, the locking device is opened by driving spindle 12 
upward using motor 14 and gear 13. In this manner, shaft 7 is pushed 
upward and, in turn, shaft 7 moves catches 8. The catches 8 do not move 
directly vertically but, due to positive guidance provided by guide slots 
9 moving along stationary guide pins 10, move away from the plane of 
symmetry causing the hook ends 11 to be angled upwardly and guided out of 
the extending hook 4 such that the stop 3 is released and cover 1 can be 
opened. 
It is, of course, conceivable to exchange positions of the catches and 
stops with one another, in which case, for example, instead of the stop, a 
catch having two hook ends is disposed in the plane of symmetry, and two 
stops that are movable about the shaft are shifted into and out of 
engagement with the catch hook ends due to the positive guidance when the 
shaft is moved relative to the catch. Here, too, the symmetrical movement 
ensures equal distribution of forces and thus secure closing. Likewise, it 
is possible to exchange the positions of the longitudinally-extending 
guide elements with the guide pins (pins in the catch engaged with 
stationary guide elements). 
In addition, in a preferred embodiment of the present invention, the unit 
comprising gear 13 and motor 14 is seated to be movable with respect to 
the apron 6 in the direction of the spindle axis. Normally, the unit 
comprising gear 13 and motor 14 is stopped from moving with respect to 
apron 6 by a lever 17 rotatably seated on apron 6 adjacent to gear 13 and 
disposed approximately perpendicular to the plane of symmetry. Lever 17 is 
drawn downward by means of a spring 18 and latched in a recess of detent 
pawl 19. When lever 17 is detached from the detent pawl 19, it is possible 
to manually move the gear with the spindle so that the lock can be 
released manually. The lock must be able to be opened, if necessary, even 
in a powerless state preventing spindle 12 from being driven upward by 
motor 14. To this end, it is preferred that the detent pawl 19 be 
rotatably seated and held in the operating position by spring 20. Release 
cord 21 is attached to detent pawl 19 such that a counter force to spring 
20 is produced by pulling on release cord 21. Lever 17 is not permanently 
connected to the motor-gear unit. Thus, release of detent pawl 19, in 
turn, unlatches lever 17 so that the unit comprising the motor 14, gear 
13, spindle 12 and shaft 7 is no longer stopped by lever 17. If desired, 
the position query for detent pawl 19 can be effected by an additional 
switch (not shown) as well as through a mechanical coupling (not shown) to 
final-position switch 15. 
During emergency unlatching, a relative movement occurs between lever 17 
and motor 14 and gear 13. Cover 1 can be manually raised causing shaft 7 
and, with it, spindle 12, gear 13, and motor 14, to raise relative to 
apron 6. Movement of the shaft, in turn, moves hook ends 11, positively 
guided by guide slots 9 and stationary guide pins 10, out of the extending 
hook 4 permitting the cover 1 to be opened. To return the lock to the 
functional position for automatic operation following the manual unlocking 
procedure, spindle 12 is driven upward by motor 14 and gear 13. Because 
the guide slots 9 are supported on stationary guide pins 10, gear 13, 
along with motor 14, is pressed downward. Since lever 17 is biased 
downwardly by spring 18, the lever 17 is also pulled downward to latch in 
detent pawl 19 thereby effecting a return to operating condition of the 
locking device. 
The present invention may be embodied in other specific forms without 
departing from its spirit or essential characteristics. The described 
embodiments are to be considered in all respects only as illustrative and 
not restrictive. The scope of the invention is, therefore, indicated by 
the appended claims rather than by the foregoing description. All changes 
which come within the meaning and range of equivalency of the claims are 
to be embraced within their scope.