Adjustable-height support for rotary evaporators

The support has a base plate in which a rod is secured in a vertical position. A holder device can be moved up and down on the rod. An energy storage means in the form of a spring means, which is disposed beside the rod, is connected to a cable drum. A cable leads from the cable drum to the holder device by way of direction-changing rollers. Thus, force from the energy storage means is available for the upward movement of the holder device. The spring means in the energy storage means is put under tension again when the holder device is moved downwardly. The energy storage means has an adjusting means for prestressing the spring means. The energy storage means, being disposed outside the rod, makes it possible in a very simple manner to intervene in the force potential of the energy storage means with an additional drive means.

BACKGROUND OF INVENTION 
The invention relates to an adjustable-height support particularly for 
rotary evaporators, comprising a base plate and a holder device for 
securing a glass unit and a drive unit or the like, the holder device 
being displaceable along a substantially vertical rod and being lockable 
thereon by an arresting means. 
Supports of that kind, which are also referred to as quick-lift devices, 
can be used for example to hold an evaporator flask in a water bath. As 
the evaporation operation can only be stopped by rapidly lifting the flask 
out of the heating bath, it is desirable for the support to be quickly and 
easily adjusted. The support must also be capable of performing various 
pivotal movements in order on the one hand to be able to adjust the 
setting of the support to the respective dimensions of the glass unit and 
on the other hand to facilitate manipulation operation with the glass unit 
and the chemicals contained therein. Finally, besides a robust 
construction, it would also be desirable for the lifting and lowering 
movements of the support to be motorized as that permits automatic control 
of the evaporation operation by way of a timing circuit. 
DESCRIPTION OF PRIOR ART 
However, motorized drive for the support movement, with at the same time 
the option of manual operation, represent partly conflicting requirements 
which have not been satisfactorily resolved in the previously known 
supports. Thus for example most supports permit only manual operation, 
while generally adjustment in respect of height of the holder device 
cannot be performed with one hand as either the glass unit secured to the 
holder device is too heavy or the holder device has to be held with one 
hand while a fixing screw or the like is released with the other hand. In 
addition, the previously known supports do not take account of the 
different weights of the glass units which can be gripped on the holder 
device. Japanese utility model publication No. 145501/1982 discloses for 
example a support which is adjustable in respect of height by a motor 
drive, wherein an electric motor rotates a screwthreaded spindle which is 
disposed in the interior of the rod of the support. The rod itself is 
secured against rotary movement by means of a longitudinal guide so that 
the rod is raised or lowered, upon rotation of the screwthreaded spindle, 
depending on the direction of rotary movement thereof. However, that 
arrangement suffers from the disadvantage that there is no possibility 
whatever of manual operation. If for example in the event of a delay in 
boiling in the evaporator flask, immediate interruption in the supply of 
heat is required, the rod of the support must be raised by the motor 
drive, which however takes much too long by means of the screw threaded 
spindle, so that there is the danger of explosion. Another disadvantage is 
that for example in the event of a power failure, the holder device can no 
longer be moved at all and for example in an automatic operation the 
evaporator flask remains immersed in the heating bath which however cools 
down only very slowly. 
SUMMARY OF INVENTION 
An object of the present invention is therefore to provide a support of the 
kind set forth in the opening part of this specification, which is quick 
and easy to operate and wherein account can be taken of the different 
weights of the glass units to be secured to the support. 
A further object of the invention is to permit fully automatic control of 
the movements of the support, without detrimentally affecting the 
possibility of manual operation. 
Finally, the invention seeks to provide that the support also has maximum 
operating safety in emergency situations. 
In accordance with the invention, those objects are achieved by a support 
characterised in that the holder device is connected to a mechanical 
energy storage means in such a way that, when the arresting means is 
released the holder device is displaceable downwardly against the force of 
the energy storage means or can be raised with the assistance of the 
energy storage means, and that the energy storage means has an adjusting 
means for adjusting the potential energy that can be stored. The 
mechanical energy storage means provides, in a very simple manner, a force 
which lifts the holder device and thus raises the evaporator flask out of 
the heating bath. In order to produce such movement, it is only necessary 
to release the arresting means, and that can clearly be done by a single 
handle. Adjustment of the potential energy which can be stored in the 
energy storage means permits the force to be applied for lifting the 
holder device to be matched to the respective weight of the glass unit so 
that, when the arresting means is released, the holder device is always 
lifted approximately with the same amount of force. It will be appreciated 
that the adjusting device also makes it possible to provide for a 
condition of equilibrium between the weight of the glass unit and the 
force of the energy storage means. 
The arrangement according to the invention may be embodied in a 
particularly simple manner if the energy storage means is a spring means 
disposed beside the rod of the support. It is known that spring means are 
excellent energy storage means for such purposes, and can be installed in 
a relatively compact fashion. Arranging the spring means beside the 
support rod member permits on the one hand an advantageous structural 
configuration of the rod member and the holder device, such as in 
particular permitting the apparatus to be of low height. On the other hand 
however, that arrangement also permits the connection of the drive means 
which intervenes in the force potential of the energy storage means 
directly at said energy storage means, as will also be shown hereinafter. 
It will be appreciated that instead of the spring means, it would also be 
possible to use another mechanical energy storage means such as for 
example a pneumatic energy storage means or a counterweight. 
A particularly advantageous form of coupling between the holder device and 
the energy storage means can be achieved if the holder device is connected 
to the energy storage means by way of a cable. The cable is compact, 
inexpensive and can therefore be disposed in such a fashion as to be 
invisible from the outside, in a very simple manner. The direction of the 
force applied can be altered in a very simple manner by way of 
direction-changing rollers, in which respect only low frictional losses 
have to be tolerated. It will be appreciated that it would also be 
possible, instead of the cable, to use a linkage or a transmission 
arrangement for the transmission of forces. 
The construction may be further improved by the spring means being 
force-lockingly connected to a cable drum for winding on the cable. In 
itself, the cable movement could also be taken up by a lever arm of 
sufficient magnitude. However, a cable drum has the advantage that it 
takes up less space and that further accessories such as brakes, locking 
pawls, teeth etc. can be provided thereon. 
Depending on the desired force potential and the distance that the holder 
device must cover at the rod of the support, the spring mean may be either 
a spiral spring or a cylindrical coil spring with legs (leg spring). In 
both types of spring, the force may be transmitted to a spindle or shaft 
in a very simple manner. Springs with a suitable spring characteristic are 
already commercially available and only have to be installed in a suitable 
fashion. It will be appreciated however that, depending on the situation 
of use, other spring means would also be possible, such as for example 
straight bending springs, torsion springs, diaphragm springs and the like. 
The spring means may be adjusted in a particularly simple fashion if the 
spring means is disposed in a housing which at one end has a tooth 
arrangement and if the adjusting means is a spring plate which is provided 
with a corresponding tooth arrangement and which can be pressed against 
the tooth arrangement on the housing, by means of a setting device for 
adjusting the coil spring, in various positions. It will be seen that the 
spring means can be prestressed by means of the spring plate, while the 
weight of the glass unit secured to the holder device can be taken into 
consideration. A scale may be provided on the housing or on the spring 
plate, to facilitate adjustment of the spring means and to indicate the 
extent to which the spring means is prestressed. 
If the cable drum is connected to a disengageable drive means for motorized 
displacement of the holder device when the arresting means is in the 
released position, the support according to the invention may be operated 
in a very simple manner both manually and also automatically. When the 
drive means is connected in, it performs the same movement at the cable 
drum, as that which occurs in the manual mode of operation. In that 
connection, the drive means is relieved of load when the holder device is 
lifted by the spring means. In a particularly simple fashion, a tooth 
arrangement may be provided directly on the cable drum, the drive means or 
the transmission means thereof force-lockingly engaging into the tooth 
arrangement on the cable drum. It will be appreciated however that it 
would also be possible to provide a frictional force transmission effect 
by means of friction wheels or belts. 
A particularly advantageous form of mounting and fixing the holder device 
on the rod of the support is achieved if, for arresting the holder device, 
a toothed rack is arranged in parallel relationship between the rod of the 
support, the holder device having a locking pawl which can engage into the 
rack. In that way, the mounting and the arresting of the holder device are 
separated from each other so that the holder device may be mounted on a 
precise, cylindrically ground rod by means of ball bearing bushes. That 
gives particularly advantageous qualities in regard to movement thereof, 
while the rack with the locking pawl engageable therewith ensures a 
reliable arresting action. That arrangement thus ensures sufficiently fine 
adjustability, depending on the number of teeth on the rack. The mounting 
structure may be further improved by a guide member being disposed in 
parallel relationship beside the rod of the support as a means for 
preventing rotary movement, the holder device being supported against the 
guide member to resist rotary moments about the axis of the rod. In 
comparison with a means for preventing rotary movement by longitudinal 
guide means on the rod itself, the above-indicated arrangement has the 
advantage that the friction which occurs when rotary moments are produced, 
at the guide means, can be reduced by the lever arm between the rod of the 
support and the guide rod. 
The guide and arresting elements can be protected from external influences 
and fouling in a particularly simple manner if the holder device has a 
casing which encloses the rod of the support, the toothed rack and the 
guide member, with a bellows or concertina-like member which is connected 
to the base plate being disposed at the lower edge of the casing. The 
bellows or concertina-like member bridges over the relative movement as 
between the casing and the base plate and also prevents objects being able 
to get into that region, which would block the holder device in the 
lowering movement. 
The casing also has the advantage that it can accommodate the cable which 
extends in the plane of the base plate, in such a way that the cable 
cannot be seen, and protects the cable from mechanical and chemical 
influences from the exterior. 
If the locking pawl on the holder device is connected to a switching means 
which switches off the drive means at the cable drum when the pawl is in 
the engaged condition, that arrangement reliably ensures that the drive 
means cannot be operated by mistake in the manual mode. If the locking 
pawl is disengageable with a release lever which is secured to a handle 
and if the release lever can be locked with a flap which pivots away when 
the release lever is gripped and which is so connected to a switching 
means that, when the flap member is pivoted away, the drive means is 
disconnected, the operator can intervene directly in the automatic mode of 
operation, without further actions. That is particularly advantageous if 
for example in an emergency, with the apparatus operating in the automatic 
mode, the evaporator flask has to be immediately lifted out of the bath. 
That can be done by means of the switching device on the flap member 
without the drive means having to be separately switched off or 
disconnected, before the lifting movement. 
It is also particularly advantageous in regard to emergency situations if 
the drive means at the cable drum is an electric motor which is so coupled 
to the cable drum that the cable drum is freely rotatable in the event of 
power failure. If by mistake anyone switches off the power in the 
automatic mode or if for example there is an interruption in power when 
the operator is absent, the cable drum can rotate freely as the arresting 
means is in the disengaged condition. By means of suitable adjustment at 
the spring means, that can provide that the evaporator flask can always be 
lifted out of the heating bath, in a situation of that nature, an 
electromagnetic clutch for example could be used as a suitable form of 
coupling means. 
The operating safety and controllability of the support may be further 
enhanced by an adjustable position switch being disposed between the 
casing and the base plate, which switch selectively switches off the drive 
means at the cable drum or reverses the direction of rotation thereof, 
when a lower and/or upper limit position of the casing or the holder 
device is reached. In that way, the limit positions can be set in a 
particularly simple fashion. On the other hand, in the automatic mode, 
that arrangement also permits a continuous upward and downward oscillating 
movement of the holder device, which may be desirable in certain 
situations. 
If the holder device is pivotal about an axis which extends transversely 
with respect to the rod of the support, it is also possible for small 
glass flasks to be dipped into the water bath to an adequate depth. Even 
if the support is used for purposes other than for rotary evaporators, 
universal displaceability is a desirable consideration.

DESCRIPTION OF PREFERRED FEATURES 
As shown in highly simplified diagrammatic form in FIG. 1, the support 1 
comprises a base plate 2 on which is disposed a support rod 3 which, in 
the illustrated embodiment, is not visible but is masked by a casing 28. A 
glass unit 4 and a drive unit 9 are secured to a holder device 10 which 
can be raised and lowered along the rod 3 in the direction indicated by 
the arrow X. The glass unit 4 comprises a flask 5 which is connected by 
way of a vapour carrier tube 8 to a cooler 6 of which only part is shown. 
The distillate collecting flask is generally secured to a distillate 
outlet 7 of the cooler, although the distillate flask is not shown in the 
drawing. The drive unit 9 causes the glass unit 4 to rotate in known 
fashion. The drive unit 9 and the glass unit 4 are per se known components 
and are therefore not described in greater detail herein and are not shown 
in the other Figures of drawings. The flask 5 is immersed in a water bath 
11 which can be disposed on the base plate 2, as a separate structural 
unit. 
The holder device 10 has a casing 28 which surrounds the rod or bar 3. A 
control unit 12 which can be integrated into the holder device 10 monitors 
the function of the drive unit 9 for rotary movement of the glass unit 4. 
FIG. 2 shows an energy storage means 13 which is disposed beside the rod or 
bar 3. The energy storage means 13 is disposed in a housing 19 on the base 
plate 2. A cable drum 17 and a cable 16 which connects the energy storage 
means 13 to the holder device 10 or to the casing 28 thereof are 
indicated, being invisible beneath the base plate. Disposed directly 
behind the energy storage means 13, in the form of a separate component, 
is a drive means 24 which can be connected to the housing 2 for automatic 
operation of the support in a suitable manner. 
An arresting means 14 comprises a handle 34 and a locking pawl which cannot 
be seen in FIG. 2 but which will be described hereinafter. 
After the foregoing general review of the individual components, the 
precise mode of operation and construction will now be described, with 
reference to various particular views, as shown in particular in FIGS. 3 
and 4, the rod 3 is fixed to the base plate 2 in a vertical position. The 
rod 3 is surrounded by a case or sheath 36 which on the one hand carries 
the casing 28 and on the other hand accommodates ball bearing bushes 35 so 
that the case 36 together with the casing 28 and the entire holder device 
is displaceable with minimum friction along the rod 3. As will be seen 
from FIG. 5, the casing 28 is not rigidly connected to the case 36 but is 
tiltable about a tilting axis 37 so that the entire casing with the holder 
device may be disposed in an inclined position, with respect to the water 
bath. The casing 28 can be fixed within a given sector by means of 
arresting levers 38. 
Disposed at the lower edge 29 of the casing is a folding bellows or 
concertina-like member 30 which is connected to the base plate 2. In the 
illustrated embodiment, the lower edge 29 of the casing is formed by a 
projecting portion of the case 36 as in this case only the case 36 is 
always displaced with its axis in parallel relationship with respect to 
the rod 3. It will be seen that the member 30 closes off the space between 
the lower edge 29 and the base plate 2, in any relative position of the 
casing 28. 
Arranged directly beside the rod 3 and in parallel relationship thereto is 
a toothed rod or rack 25. The arresting means 14 comprising a locking pawl 
26, a handle 34 and a release lever 39 co-operate with the rack 25. A 
spring 40 urges the locking pawl 26 into the rack 25 so that the holder 
device is arrested when the release lever 39 is released. For the purposes 
of releasing the arresting means, the lever 39 must be operated at the 
handle 34 so that the locking pawl 26 is released from the teeth of the 
rack 25, against the force of the spring 40. The lever 39 may in turn be 
locked with a flap member 41 in such a way that the locking pawl 26 
remains out of engagement with the rack 25. It will be seen that that is a 
requirement for a motorized drive mode with the drive means 24. The flap 
member 41 is only secured by the force of the spring 40. When the lever 39 
is gripped, the flap member 41 pivots away for example due to spring force 
and actuates a switching means (not shown) which uncouples the drive means 
24. When the handle 34 is gripped therefore, the drive means is always 
uncoupled and cannot brake the cable drum. 
In order to ensure that the drive means 24 cannot be actuated when the 
locking pawl 26 is in the engaged condition, the locking pawl is provided 
with a switching means 32 which is shown in FIG. 5a. The switching means 
32 comprises a microswitch with a switching sensor 42 which interrupts the 
contact when the locking pawl 26 is in the engaged condition so that the 
drive means 24 cannot be activated. When the locking pawl 26 is retracted, 
the member 42 runs on a switching projection or cam 43 on the locking pawl 
and closes the contact at the switching means 32. 
In order to prevent the casing 28 from rotating about the centre line of 
the rod 3, a guide member 27 is disposed in parallel relationship beside 
the rod 3. That form of lateral guide arrangement is substantially more 
advantageous than providing a guidance action at the rod itself. On the 
one hand, if a longitudinal guide means were to be provided at the rod 
itself, relatively high forces would occur due to the small lever arm 
involved, while on the other hand the form of mounting on the rod 3 would 
be considerably more difficult as the rod 3 would have to be provided with 
at least one longitudinal groove. A relatively long lever arm is formed 
between the centre line of the guide member 27 and that of the rod 3 so 
that rotary moments can only exert low forces at the guide rod. The 
guidance action at the guide member 27 is provided by means of adjustable 
guide sleeves or bushes 44 of plastics material, which have a flat front 
face so that there is a low degree of friction in regard to contact with 
the guide member. The bushes or sleeves 44 are shown in FIG. 6. 
FIGS. 6 and 7 show an adjustable position switch 33 with which the lower 
limit position of the casing can be defined. The position switch 33 
comprises a limiting pin 45, the relative position of which with respect 
to the housing 2 can be adjusted with an adjusting wheel 46. In the manual 
mode of operation, with the casing 28 in the lower limit position, an 
abutment 47 bears against the pin 45. If the support is actuated by the 
motor means, a microswitch 48 interrupts the drive when the lower limit 
position is reached. In a similar manner, the upper limit position may be 
defined by means of a microswitch, in which respect it is possible for 
both functions to be combined in the position switch 33. 
The mode of operation of the energy storage means 13 will now be described 
with reference to FIG. 8. A coil spring 18 is disposed in an upwardly 
closed, substantially cylindrical housing 19. The coil spring 18 is a 
leg-type spring, one leg being fixedly clamped to an adjusting means 15 
and the other leg being connected to the cable drum 17. The cable drum 17 
is mounted in the base plate 2 by a ball bearing assembly 49. The 
adjusting means 15 for prestressing the coil spring 18 comprises a spring 
plate 22. The spring plate 22 is urged against the teeth or serrations 20 
on the inside of the housing, by a control means 23 in the form of a 
compression spring. The spring plate 22 in turn has a corresponding tooth 
or serration arrangement 21. When the control means 23 is tensioned, the 
spring plate 22 cannot therefore rotate relative to the housing. For the 
purposes of prestressing the coil spring 18, the control means 23 must be 
urged downwardly until the two tooth arrangements 20 and 21 come out of 
engagement with each other. The spring plate 22 can then be rotated so 
that the prestressing of the coil spring can be altered. 
The choice of the appropriate form of coil spring with the desired spring 
characteristic is an aspect which is known to the man skilled in the art 
and is therefore not described in greater detail herein. In a similar 
manner as with regard to the coil spring, the cable drum could also be 
connected to a spiral spring. At any event, the springs must be of such 
sizes that the spring force and spring travel are sufficient to move the 
largest glass unit which can be held at the holder device from the 
lowermost limit position into the uppermost limit position. In addition, 
consideration must also be given to the time in which that movement must 
take place. 
The cable 16 is wound on the cable drum 17. Depending on the periphery of 
the cable drum, two or three turns are sufficient for the cable to be 
wound on when the holder device is in the fully raised position. The cable 
drum is provided with a toothed rim portion as indicated at 50 which 
co-operates with the drive means 24 or the transmission means thereof, as 
shown by way of indication in FIG. 2. 
The run of the cable 16 is shown in FIG. 5. Although it cannot be seen from 
the outside, the cable goes from the cable drum in the interior of the 
base plate and in the plane thereof, firstly to a first direction-changing 
roller 51 beneath the casing 28. From there the cable runs inside the 
concertina member 30 and within the casing 28 upwardly to a second 
direction-changing roller 31 which is disposed in the upper region of the 
rack 25. From the roller 31, the cable runs down again where it is secured 
to the case 36 at a clamping location 52. The cable ensures precise and 
reliable transmission of force from the energy storage means to the holder 
device. As the cable is a flexible member, an additional advantage is 
that, if necessary, even when the drive means 24 is in the operatively 
coupled condition, the holder device can be moved upwardly by hand. In 
addition, that also excludes the danger of an accident occurring during 
the downward movement of the holder device as it is only the weight of the 
holder device itself which acts in the direction of downward movement. 
The drive means 24 is preferably disposed in a structural unit which can be 
connected to the housing 2 with a small number of operations. The user can 
thus selectively connect the drive means to the support, or not. Manual 
operation of the support is possible even when the drive means 24 is 
connected thereto, by the position of the flap member 41 on the handle 34 
being sensed by means of a switch. If the flap member 41 is in the engaged 
condition and the blocking pawl is constantly in the released position, a 
coupling means between the drive means 24 and the cable drum can be 
automatically actuated. If on the other hand the handle 34 is gripped and 
the release lever 39 is pressed entirely inwardly at the handle 34, the 
flap member 41 swings out due to spring force and actuates a switch which 
automatically uncouples the drive means 24. In that way, it is possible at 
any time to intervene manually in the motorized operation of the support, 
without the drive means on the cable drum blocking manual operation. The 
available switching functions are summarized in the Table set out below: 
______________________________________ 
Manual Mode Motorized Mode 
______________________________________ 
Locking pawl 26 
disengaged, drive 
disengaged, drive 
means can be means can be 
switched on switched on 
Release lever 39 
actuated but not 
actuated and 
arrested arrested with the 
flap member 
Flap member 41 
pivoted out pivoted in for 
arresting the 
release lever 
Drive means 24 
uncoupled coupled 
______________________________________ 
The support according to the invention also includes an electronic control 
device having various parameters, which can control not only the stroke 
movement of the support but also the rotary movement of the drive unit and 
the supply of heat in the heating bath. In that way, entire operating 
procedures can be controlled for a fully automatic mode of operation, by 
the evaporator flask for example being immersed in the heating bath at a 
given temperature for a given time at a given speed of rotation and 
automatically lifted out of the heating bath after the expiry of the 
above-indicated period of time, whereafter all drive devices are 
automatically shut down. 
The apparatus is extremely simple to handle and there is virtually no 
possibility of errors and defects in operating the apparatus. After the 
filled glass set has been fitted into the holder device 10, the required 
force potential is set at the energy storage means 13 by the adjusting 
means 15. In that connection, care is advantageously taken to ensure that 
the energy storage means is capable of lifting the evaporator flask 
entirely out of the heating bath when the arresting means 14 is released. 
The holder device is then lowered either by hand or by operation of the 
motor means so that the evaporator flask dips into the heating bath. 
During the downward movement, the cable 16 is unwound from the cable drum 
17 and the spring means which is used as the energy storage means is put 
under tension. For the manual mode of operation, the handle 34 must be 
gripped and the release lever 39 actuated so that the locking pawl 26 
comes out of engagement with the rod 25. When the arrangement is in the 
desired position, the handle 34 is released so that the lever 39 moves 
back into the rest position due to the spring force at the locking pawl, 
and the locking pawl moves into its position of engagement. For motorized 
operation, the release lever 39 must be secured by means of the flap 
member 41 so that the locking pawl remains in a disengaged position when 
the handle 34 is released. Motorized operation of the holder device 10 is 
then effected by pressing a suitable button or key on the control 
apparatus (not shown) which operates the drive means 24. At any time, it 
is possible to switch over automatically from the motorized mode to the 
manual mode by gripping the handle 34 and pressing the release lever 
entirely against the handle once again. When that is done, the flap member 
41 automatically pivots outwardly so that the drive means 24 is uncoupled. 
If an unintentional interruption in power occurs while the apparatus is in 
the automatic mode, the drive means is also uncoupled so that the 
potential energy stored in the energy storage means 13 moves the holder 
device with the evaporator flask upwardly. The energy storage means also 
assists the upward movement of the holder device with glass unit and drive 
unit, in the manual mode of operation. In spite of the spring means being 
simultaneously put under tension in the energy storage means, downward 
movement of the holder device does not require a large amount of force to 
be applied, as the weight of the holder device assists in tensioning the 
spring means.