Dispensing – With discharge assistant – Plural
Reexamination Certificate
1999-02-22
2001-01-16
Jacyna, J. Casimer (Department: 3751)
Dispensing
With discharge assistant
Plural
C222S383300
Reexamination Certificate
active
06173867
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to an installation for conveying a liquid from a container to a dispensing head via a conduit system consisting of two parallel conduit branches, each one of which has a conveying pump. The invention further relates to the use of the installation.
BACKGROUND OF THE INVENTION
Within the scope of this specification, liquids are understood to be low- and high-viscosity liquids of all types, and in particular also liquids whose viscosity is a function of the temperature to a high degree.
Installations of the type mentioned at the outset, by means of which liquids can be conveyed from a container to one or several dispensing stations, are for example employed in machines for the application of adhesives. Adhesives, as well as other pastes, such a dyes, products used in the food industry and materials processed in the chemical industry, which have comparatively high viscosities, are often processed at temperatures which differ from the ambient temperature. They are conveyed via conduit systems with rigid and/or flexible conduits, which can be cooled or heated, to dispensing heads and are dispensed by the latter to a carrier material at the dispensing stations.
For example, in many cases it is necessary to dispense continuous ribbons of liquid to the carrier material, which is in an endless form or in the form of directly successive material sections and is conducted past the dispensing heads. In other cases there is the requirement of providing several application locations of the same carrier material with the same liquid wherein, depending on the occasion, either continuous liquid ribbons or liquid beads limited in length are to be created.
To generate pressure in the conduit systems it is possible to employ intermittently operating pumps, such as piston pumps, or continuously operating, or respectively rotating, pumps, such as gear pumps.
Gear pumps convey in a volumetric manner and are therefore mainly suitable for the chronologically constant dispensation of liquids, for example of continuous liquid ribbons on carrier materials. If a carrier material is to be provided with a liquid only in sections, the associated dispensing head must release the liquid intermittently, so that the dispensed liquid forms a plurality of liquid beads, which are spaced apart and whose length is limited, instead of an endless ribbon of liquid. An increased amount of liquid is dispensed at the start of each dispensation period because of the sluggishness of the installations and of the properties of the gear pumps, which results in that the liquid beads being generated have an excess of liquid at the start, which is unwanted in many cases.
In contrast to volumetrically conveying gear pumps, double-acting reversible piston pumps are purely pressure-generating systems. In the course of dispensing a liquid, the piston moves in such a way that the pressure drop occurring because of the dispensation of liquid is always compensated. As long as the associated installation does not dispense liquid, the piston does not move and the piston pump does not convey liquid. It is obvious that piston pumps are particularly suited to the intermittent dispensing of liquids, because they always dispense chronologically limited amounts of liquid during the respective dispensing periods, so that the liquid beads being created in the process do not have increased starting sections, but instead are even over their lengths. Neither the length of the dispensing periods nor their chronological spacing have any effects on this behavior. On the other hand, because of their intermittent operation, installations with a piston pump are not suitable for creating continuous ribbons of liquids.
OBJECT AND SUMMARY OF THE INVENTION
It is the object of the invention to
create an installation of the type mentioned at the outset, by means of which it is possible either to dispense an even, continuous liquid ribbon at a dispensing station, or a series of liquid beads, which are limited in length, at a first dispensing station and, at a second dispensing station, a continuous liquid ribbon or a further series of liquid beads, which are limited in length, and
propose a use for this installation.
Thus, the installation in accordance with the invention always has two conveying pumps, wherein at least one of these two conveying pumps is a piston pump, while the other one of the two conveying pumps can be of any arbitrary type of construction. A dispensing head is assigned to each conveying pump, through which the liquid to be dispensed is dispensed to the carrier material. The dispensing head assigned to the piston pump dispenses the liquid in the form of a series of faultless, length-limited liquid beads. It is therefore possible to employ two different pumps with different characteristics in an installation with only one container, because of which the possibility of solving a plurality of problems in the area of the conveyance and dispensation of liquid is obtained with a small outlay of apparatus.
An installation in accordance with the invention, wherein the second pump is a gear pump, is suitable for dispensing faultless, length-limited liquid beads or intermittent spraying at a first dispensing station by means of the dispensing head assigned to the piston pump, and of even continuous ribbons of liquid or continuous spraying at a second dispensing station by means of the dispensing head assigned to the gear pump.
Installations of this type with a piston pump and a gear pump are employed, for example, in the packaging industry and in the graphic industry, where it is required, for example, to provide a carrier material continuously with a liquid in the form of an adhesive, wherein it is necessary to create two lateral ribbons of liquid and, in addition, intermittently length-limited liquid beads. The latter need not be absolutely elongated, but can also be very short, for example in the shape of circles.
In the health-care industry it is possible by means of installations comprising a piston pump and a gear pump, to perform the intermittent dispensation of liquid beads of an adhesive for the lateral strip fixation, and the continuous dispensation of liquid ribbons for the fixation of cellulose on a carrier material made of polyethylene.
The insulation industry is a further example of the use of installations with a piston pump and a gear pump. A fine, continuously sprayed application of a liquid consisting of an adhesive is made by means of a dispensing head, which is connected to a branch conduit with a gear pump. At the same time an intermittent dispensation of length-limited liquid beads of an adhesive to the edge foil, which must not be continuously provided with an adhesive, takes place from a dispensing head connected to a branch conduit with a piston pump.
In connection with many applications it is useful to employ installations with two piston pumps. It is possible by means of such installations to create an almost continuous ribbon of liquid by a suitable, or respectively chronologically offset, reversal of the piston pumps. The two piston pumps are locked in relation to each other, preferably electronically. In this case it is possible to combine the portion of the conduit system arranged downstream of the piston pumps into a collecting conduit, to which a single dispensing head is connected or wherein, if desired, a further dispensing head is connected via a second conduit branch. An installation, wherein the reversing of the piston pumps does not result in a pressure drop, is obtained when using two piston pumps with the same gear ratio and the same conveying characteristics.
However, in an installation containing two piston pumps and separate conduit branches or a collecting conduit, it is also possible to dispense respectively one series of length-limited liquid beads at two dispensing stations. The piston pumps used for this can be designed and controlled in the same way or differently If a collecting conduit is provided, a conduit for a further dispensing head needs to be branche
Browdy and Neimark
Jacyna J. Casimer
Robatech AG
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