The present invention relates to an apparatus for preparing solutions
particularly for chemical analysis laboratories.
It is known that in all the analysis laboratories of every chemical
branch, one of the most common operation is the preparation of "known titre solutions".
This term refers to a mixture conisted of an amount measured in a very accurately
way of a component comprising one or more substances called solute (e.g. liquid
or solid salt), a volume, measured in the same accurate way, of one or more liquids
In fact, these solutions show a very accurate solid-liquid concentration
In order to obtaining the aforementioned solutions it is necessary
to weigh a sample (the solid can be generally found in a powder-like state) and
then to transfer it into a glass container (usually called "matress") provided
with an indentation located on the neck and provided for indicating a known volume
(e.g. 100 ml or 1 liter). Thanks to the shape of the matress, the solvent volume
cannot be modified and is an established parameter that fixes strictly the solute
amount. Accordingly, it is very important to be extremely accurate during the weighings
of the solute.
For example, if someone wishes to obtain a solution of one liter of
sodium chloride in water having a concentration of 1 gram/liter, it is absolutely
necessary to weigh one gram of salt. In order to obtained what has been just explained,
it is essential to use a sufficiently accurate scale, to pour the salt little by
little on a suitable sheet, whose tare has been measured, until the scale indicates
one grams. If this amount is exceeded, it is necessary to take away the excess
in order to obtain exactly one gram. At this time, it is necessary to pour carefully
the salt in the matress for not leaving it on the sheet. After that, the solvent
is added until the level gets to the measuring indentation on the matress neck.
Obviously, if the indentation is passed by mistake, it is necessary to repeat
all the process since it is not possible to know the effective volume of the solution
since the matress has just one reference indentation.
In view of what has just been described, it can be easily understood
that the actually used process systems for preparing solutions show several drawbacks.
For example, all the above described steps are carried out manually
by an operator who must weigh the small amounts of solute and transfer them into
the matress without loosing the solvent and pour it exactly to the matress indentation.
These steps require great attention and accuracy, for this reason
the operator is subjected to a particularly stressful work and, as the time goes
on, the possibility of doing mistakes increases considerably.
It has been also noted that every time the solvent amount is wrong,
it is necessary to weigh another time the solute having again all the problems
due to this operation, that is the operator has difficulties in obtaining an extremely
small amount of solute, he/she is not sure he will not disperd it and he/she will
have difficulty in pouring the solvent in order to reach precisely the indentation
of the matress. These steps are time consuming, especially if they must be repeated
For example it is known how it is extremely important the relation
between the solute and solvent amounts because accurate ratios are necessary.
From what said above it is clear how it is easy to do mistakes during the measuring
and the reading of the amounts. Moreover, during the known art process, all the
data are not automatically recorded so that, sometimes, there is the possibility
of altering the analysis results.
The object of the present invention is substantially to solve the
problems of the prior art, overcoming the above mentioned problems by an apparatus
for preparing solutions showing accurate features with reference to the meterings
of both the liquid and solid components.
Another object of the present invention is an embodiment of an apparatus
able to prepare solutions independently from the solvent volume, keeping at the
same time the required ratio between the solute and the solvent.
Another object of the present invention is an embodiment of an apparatus
which is able to eliminate the waiting times for carrying out a solutions as compared
with the prior art, wherein the set-ups were manually performed by an operator
who, in case of a mistake of every kind, had to repeat again the process.
Another object of the present invention is an embodiment of an apparatus
which can be easily produced and has a good operation independently of the characteristics
needed of the solutions.
The last but not least object of the present invention is an embodiment
which is able to record all the operations and store all the data of the solution
avoiding the possibility of altering the results and print it after the preparation
Further features and advantages will be more apparent from the detailed
description of an apparatus for preparing solutions according to the present invention
described as follows with reference to the accompanying drawings given only as
illustrative and therefore they are not intended to be limiting, wherein:
- figure 1 is a schematic view of an apparatus for preparing solutions that is
the object of the present invention;
- figure 2 is a schematic view of the operating and control means of the apparatus
of the invention;
- figure 3 is a schematic view the metering means of the apparatus of the invention;
Referring to the figures and particularly to figure 1, numeral 1
generally shows an apparatus for preparing solutions substantially comprising at
least a first component (solvent) and at least a second component (solute). The
apparatus 1 automatically prepares the meterings of the components independently
of the precision of the solute metering by an automatic metering of the solvent/s
in order to obtain an accurate and known ratio between the same components.
The apparatus 1 comprises at least a metering device 2 comprising
a substantially known scale having a precision at least equal to the requested
precision which is necessary for performing the weighings of both the solid and
Alternatively, the measuring device can be a pH measuring element.
The apparatus 1 is provided with at least one container 3 arranged
for receiving the components for the preparation of the solutions and connected
with the measuring device 2. Moreover, the apparatus 1 comprises means 5 for metering
the solvent located above the container 3. In particular, as clearly shown in figure
3, the metering means 5 substantially comprises a moving electromechanical system
formed by an electromagnet 50 having a return element 51 either mechanical, such
as a spring, or electromagnetic, for moving a stem 53 connected at one end to a
pin 54 arranged to move in a containing body 52. The containing body 52 shows an
inlet 56 communicating with drawing means 7.
The chamber 55 of the body 52 is filled with solvent/s and, thanks
to the moving of the pin 54 from a stand-by position, wherein the pin adheres
against the chamber 55 walls shaped in order to be complementary with the outline
of the same pin to an operative position wherein the pin 54 raises allowing the
solvent/s to escape to the container 3, it is performed the transferring of said
According to the present form of embodiment, it is provided at least
one vessel 6 arranged to contain at least one solvent.
Moreover, the apparatus 1 comprises drawing solvent means 7 communicating
with the vessel 6 and the metering device 5, respectively through one or more hydraulic
lines 5a and 7a provided for transferring the solvent from the container 6 to said
metering means 5. Such drawing means are basically formed by a pump.
The apparatus comprises also operating and control means 4 connected
to the measuring device 2, the drawing means 7 and the metering means 5. Even more
particularly stated, the operating an control means 4 comprises central control
unit 10 provided for operating all the procedures and data relating to the solutions
to be prepared, a plurality of memory units 13, 14, 15 and 16 and each memory
unit is connected to the central control unit 10, a display 11 provided for showing
the instructions and the data operated by the central control unit 10 and the readings
of parameters and information both exiting or entering. The display 11 is connected
with the central control unit 10.
Moreover, the operating and control means 4 comprises a keyboard 12,
to digitize data and parameters relating to the solutions and the instructions
to be input in the central control unit 10 connected to the keyboard. The keyboard
comprises function keys arranged to qualify a plurality of functions, such the
cleaning, the tare, the aid function, the tables, the introduction of solution
data or the callback of memory data, repetition, the metering, the print and the
The keyboard is washable and comprises also a plurality of keys having
alphanumeric characters to input data.
In addition, the plurality of memory unit comprises in particular
a first memory unit 13 used as an intermediate memory, a second memory unit 14
used as an operating memory, a third memory unit 15 used only as a table file,
conversion data of either from density to volume or form volume to density, and
a fourth memory unit 16 provided as file of the prepared solutions.
Moreover. the central control unit 10 is provided with devices for
adpating the signal from an electrical standpoint in order to allow a connection
17 to the metering means 5, a connection 18 to the drawing means 7, a connection
19 to the printing means 8 and a connection to the 20 to the measuring device 2.
The apparatus comprises also a plurality of control elements 17a,
18a, 19a and 20a provided for the operation of the metering means 5, of the drawing
means 7, of the printing means 8 and of the measuring device 2.
Moreover, the apparatus of the present invention comprises printing
means 8 arranged for carrying out labels and tables having the component data
and the characteristics of the solution obtained. The printing means 8 comprises
a printer connected to the operating and control means 4.
Moreover, according to the present invention, the apparatus 1 comprises
operating and actuating means for cleaning the hydraulic lines 5a and 7a and a
device for controlling the operative errors.
At last, the apparatus comprises a connection to the electrical feeding
source 21 which is the electrical network.
The operation of the apparatus is as follows.
When the apparatus 1 is used before any other steps, an operator
must carry out a step for cleaning the hydraulic lines of the solvent used before.
In order to carrying out this, the apparatus is provided with a cleaning function
key that, by sending a signal to the central control unit, allows the opening of
a valve which remain opened until the operator keeps the same key down or at least
for a predetermined minimum time.
After this step that is obtained by flowing new solvent, the apparatus
is ready to operate and asks the operator if he/she desires to store a new procedure
or if he/she wants to use a procedure that is already in the memory. In the former
event, the operator must input a series of parameters through the keyboard of
the operating and control means and in the latter event it is just necessary to
retrieve the storing procedure by a call back function key.
More specifically stated, for example, in the former event, the operator
must digitize the following parameters:
- date, hour and name of the operator.
- name of the salt to be solubilized (e.g. NaCl).
- pureness of the salt used (e.g. 99,8%).
- total volume required (e.g. 1 liter).
- number of solvents (e.g. one).
- name of the solvent used (e.g. H&sub2;O).
- solvent density and in case also the temperature.
- final strength required (e.g. 1 g/l).
Once the data have been input, the operator put the solution container
on the scale and read the tare, as soon as the scale has been zeroed, the central
control unit, by means of the display, asks the operator to add on the scalepan
the solute according to the limits showed on the same display. Such limits are
a range of the weights calculated by the central control unit in view of the data
contained in the operative memory depending from the solution to be obtained,
the operator must stay within that range (in former event, for example 0,9 - 1,1
g of NaCl). The above mentioned limits are displayed graphically on the display.
A bar having a length proportional to the weight will also show the weight obtained
during the weighing.
When the weight is within the limits assigned by the working memory,
the latter asks the operator to stop adding solute and allows the metering by
a suitable metering function key.
In the case the operator exceeds the upper limit off the weighing
allowed, the operative memory inform the operator and inhibits the metering steps
until the wirghing is again within the limits allowed either by removing part of
the solute or by repeating all the weighing steps.
At this time, the central control unit commands the addition of the
solvent/s by actuating a valve the valve/s which form the metering means, until
has been obtained a weight that has a right ratio with respect to the solute weighted
(1 g/l) after it has calculated the weight of the solvent required depneding on
the density, the final strength required, the solute pureness and the weighing
made by the operator.
After the above described procedure has ended, the central control
unit commands the printing of a sheet or a label containing all the information
relating to what has been really produced, for example:
- date and hour,
- operator's name,
- strength of the solution required and obtained,
- name, type, ratio and density of the solvent,
- name/formula of the solute used,
- solute pureness,
- approximate volume of the solution,
Once the just described steps have been performed, the central control
unit communicates, through an acoustic signal, that the metering has ended and
that the operator can remove the container and can perform a new operation.
In the same way, when the measuring device 2 is a pH measuring element,
the apparatus 1, performing the automatic solvent metering step, allows any solution
to reach a desidered pH value.
With this condition, the operator puts the pH measuring device in
the solution and by the keyboard of the operating and control means digitizes
the desidered pH parameters. At this time, the control central unit starts the
metering of the predetermined amount of the basic or acidic solvent for obtaining
the desidered pH value.
Therefore, the present invention meets the objects cited above.
For example, thanks to the present apparatus it is possible to carry
out meterings with extremely accurate characteristics, and however known at the
end of the procedure, such as the solute and solvent ratio or the pH value, since
all the operations are automatically performed. In this way, it is possible to
avoid costly time losses, the necessity to have trained personnel, the fact that
the success of the operation depends on the operator ability and mostly the probability
Moreover, the apparatus is provided for recording, storing and printing
all the operations and both the starting and final parameters, preventing in this
way the danger of exchanging data, errors and variations of the results as it occurs
in the prior art. It has been also noticed that the apparatus is extremely flexible
and therefore it is very easy to be used.
Advantageously, the automatized procedure allows the preparation of
solutions repeatedly, quickly and accurately, instead of relying on the operator
In addition to what has been described until now, the solute is certainly
pour in the container, differently from what occurred in the prior art wherein
did not exist checking instruments.
Moreover, thanks to the apparatus of the present invention for preparing
solvent amounts, it is possible to be independent of liquid volume, this is also
due to the fact that this volume is measured using the weight by taking into account
the density, the temperature, etc..
Obviuosly, one can add to the present invention several modifications
and variations which are considered within the scope of the inventive step that