The present disclosure relates to a peristaltic pump.
Automated analyser systems for use in clinical diagnostics and life sciences are produced by a number of companies. For example, STRATEC® SE, Birkenfeld, Germany, produces a number of devices for specimen handling and detection for use in automated analyser systems and other laboratory instrumentation.
Different liquids are used during analytical assay in such analytical systems. Liquid waste results from the processing of samples with which have to be removed from the system, e.g. by pumps. Usually, the liquids are inhomogeneous and represent thus a potential risk for many pump technologies. As a result, the pumps wear out very quickly, which leads to increased maintenance effort and thus higher costs. In addition, potential leakage increases the risk of contamination in the unit.
Various pump technologies are commonly known from the prior art comprising gear pumps, diaphragm pumps, piston pumps, and peristaltic pumps. Many pump types are often unsatisfactory in terms of fault susceptibility.
Common faults are caused by deposits in the pump head and thus an insufficient delivery rate, pressure or lack of backflow resistance up to a complete failure of the pump. These faults can occur when pumping liquids that are corrosive, tend to precipitate or flocculate, contain particles or tend to deposit or stick together.
A backflow of liquid waste through the pump is a potential contamination risk for the patient sample and would negatively influence running assays so that they must be prevented at all costs.
Sticking or clogging of the valves by e.g. particles (blood, stool, etc. . . . ) in the liquid or by proteins or other sticky components from the patient samples and/or the reagents represent a risk for pump failure when using piston pumps or diaphragm pumps. Gearbox or gear pumps are basically very robust, but they have no backflow-proof.
In peristaltic pumps, the peristaltic hose is subject to increased wear due to the pump working principle and they must be replaced regularly as part of maintenance intervals. Since an incorrectly inserted hose can lead to a pump malfunction or loss of backflow resistance, this is a critical step. Therefore, hose replacement is reserved for a trained service technician. Nevertheless, errors can also occur here, which in the worst case can affect the running analysis.
The present invention is intended to prevent pump errors.
It is therefore the object of this invention to provide an improved peristaltic pump regarding durability and usability or misuse as well as modularity. The invention is intended to prevent errors when changing hoses and at the same time to simplify this step so that the hose can be changed by the standard or trained operator. Thus, a costly and time-consuming service call is eliminated.
The present invention provides a peristaltic pump, comprising a motor with a motor axis and a cassette with a rotor that is connected to the motor, wherein the rotor comprises a plurality of rollers, wherein at least one tube which surrounds the rotor partially is located between the plurality of rollers and a pressure plate which is mounted to a side wall, wherein a spring is located between pressure plate and a cover for applying a force to the pressure plate against the at least one tube, wherein the pressure plate comprises guiding ribs located on the inner surface of the pressure plate facing the at least one tube and the guiding ribs are located on both sides of the at least one tube, characterised in that the at least one tube is connected with a first end to a first vertical tube connector of a first external connector on one side of the rotor and with a second end to a second vertical tube connector of a second external connector on the opposite side of the rotor, wherein first and second vertical tube connector of the external connectors are connected to a connecting tube of a bridge providing at least one outlet, wherein the bridge comprises on their outer ends protrusions as connecting elements which engage into recesses of a side wall plate of the side wall.
Another aspect of a peristaltic pump according to the present disclosure relates to the cassette comprising a maximum of up to three tubes which are located next to each other and separated by the guiding ribs of the pressure plate.
In another embodiment of a peristaltic pump according to the present disclosure, each bridge is configured to engage into the side walls on both sides of the rotor.
It is further envisaged that the cover comprises a locking lever configured to engage with hooks arranged on top of each side wall by rotating the locking lever.
In an embodiment, the peristaltic pump comprises a locking lever which is configured in a manner that it can only be rotated in a closed position when the protrusions of the bridge correctly engage with the recesses of the side walls.
Another embodiment of a peristaltic pump provides a bridge with a grip which is arranged to extend from the bridge on the opposite side of the rotor.
The vertical tube connectors of the external connectors join in a horizontal collector tube in a peristaltic pump according to the present invention.
The peristaltic pump may comprise an external collector that comprises a maximum of three downwards projecting outlets.
The three cassettes of a peristaltic pump according to the present invention can be attached to another by bayonet couplings and the motor axis is extended, wherein the motor axis may comprise on its end cross-shaped couplings for their connection.
The peristaltic pump may further comprise at least two attached cassettes to the motor, wherein a gearing is arranged between the at least two cassettes.
In an embodiment of the peristaltic pump, the pressure plate comprises on both sides extension for engaging into vertical slots in each side wall for vertically aligning and guiding the pressure plate.
It is further envisaged for a peristaltic pump of the present disclosure, that each side wall comprises outer hooks for engaging into the openings of each one of the two circular guiding.
In a further embodiment of the peristaltic pump, the locking lever comprises two circular slits and the cover comprises two inner hooks for engaging into the two circular slits of the cover.
Still other aspects, features, and advantages of the present invention are readily apparent from the following detailed description, simply by illustrating preferable embodiments and implementations. The present invention is also capable of other and different embodiments and its several details can be modified in various obvious respects, all without departing from the spirit and scope of the present invention. Accordingly, the drawings and descriptions are to be regarded as illustrative in nature, and not as restrictive. Additional objects and advantages of the invention will be set forth in part in the description which follows and in part will be obvious from the description or may be learned by practice of the invention.
The invention will be described based on figures. It will be understood that the embodiments and aspects of the invention described in the figures are only examples and do not limit the protective scope of the claims in any way. The invention is defined by the claims and their equivalents. It will be understood that features of one aspect or embodiment of the invention can be combined with a feature of a different aspect or aspects of other embodiments of the invention, in which:
The technical problem is solved by the independent claims. The dependent claims cover further specific embodiments of the invention.
The terms tube and hose are used synonymously. The term fluid comprises liquids and gasses which may comprise solids.
The present invention is based on the use of a peristaltic pump for handling liquid waste as described above without causing damage or impairing performance of the system. One important element of the present invention is the peristaltic tube, which forms chambers by constrictions. These chambers are moved along the hose by peristalsis and thus generate the flow. The pump does not need any further flow-directing elements such as switch-over or non-return valves. The peristaltic hose, as a wearing element, can be replaced regularly.
In addition to the above-mentioned advantages, there are also some design-related disadvantages of the solutions from the prior art which are solved by the present invention in order to convey the problematic liquids occurring in analytical systems in a process-safe manner.
The peristaltic tube is subject to an increased wear in addition to the usual mechanical wear of a pump mechanism, caused by:
A device according to the present invention provides guiding ribs that at the surface of a pressure plate directed towards the tubes for preventing the peristaltic tubes from moving sideways and thus from touching neighbouring tubes. Thus, the tubes are properly positioned for preventing any collisions between neighbouring tubes. The pressure plate is spring-mounted. The contact pressure between pressure plate and hoses is configured for ensuring a safe, backflow-proof operation. At the same time, however, the contact pressure is configured that the hose is sufficiently squeezed by the rollers, so that the inner contour is just completely closed. The pressure has to be adjusted that it is not too low, so that the hose is not completely closed, and the pump performance deteriorates, and the pump is no longer backflow-proof. On the other hand, if the pressure is too high, the wear of the hose increases. In essence, the pressure is depending on the properties of the hose with respect to its diameter, material, the thickness of the walls etc. Thus, the pressure is adjusted to the minimal required contact pressure so that the rollers will close the hose completely during pressing it to the pressure plate.
A device according to the present disclosure does not comprise flow direction indicating elements such as change-over or non-return valves. A backflow resistance is solely generated by the sealing fit of the compressed peristaltic tube. This contact pressure is generated by a helical spring. The force is transmitted to an upper pressure plate which finally presses the peristaltic tubes onto the rotor or the pressure rollers, respectively, underneath.
In addition to reducing the wear, the spring-loaded upper pressure plate is related to further advantages: The nominal flow rate of a peristaltic pump is determined by the speed, the number of rotors and the internal cross-section of the peristaltic tube. The latter add up to the volume that can be pumped per revolution. The contact pressure has also an influence on the delivery rate. By using a helical spring as the element that causes the contact pressure, the contact pressure on the peristaltic tube can be kept constant by selecting a spring with a suitable spring characteristic curve, even if its dimensions vary within the usual production tolerances. It will also be possible to compensate manufacturing and assembly-related tolerances via this mechanism.
A device according to the present disclosure provides further a higher flexibility of the pump in analysis systems. Depending on the system, the number of required channels and the flow rates per channel may change. In principle, several channels or pumps can be combined in all common peristaltic pumps in order to multiply the flow rate. However, this increases the complexity of the peripheral tubing.
In the present invention, the number of channels of the pump can be configured arbitrarily between 1 to 9 channels with a maximum of three so-called cassettes with three tubes in each cassette. A single cassette can hold between 1 to 3 channels, i.e. peristaltic tubes. Thus, a maximum of three pumps (cassettes) are driven by one motor. The connection between the side walls of adjacent cassettes is made via a bayonet lock, which is additionally secured against rotation by means of a screw.
The motor axis is connected via a cross-shaped coupling which is male on one side and female on the other side. Within a cassette, this axle is only supported on the output side (away from the motor), the input side support is provided by the output side support of the previous cassette, or in the case of the first cassette, by the motor.
To reduce the complexity of the peripheral tubing and to save installation space, it is possible to combine all channels per cassette. Conversely, it is also possible to distribute from one common channel to three channels. Thus, for example, up to nine individual channels can be extracted. Only three channels must be discharged on the pressure side. It is also possible to combine the channels on the suction and pressure sides. This means that three channels can be used in parallel, which also triples the volume flow.
If only one tube is used in a cassette, a lower contact pressure is necessary, which is the reason for adjusting or reducing the spring force of the contact plate in this case. The cassettes of this alternative (cover, tube kit, cassette side wall) are color-coded for a better differentiation and thus for reducing assembly errors (for instance: green=cassette for one tube, black =cassette for two and three tubes).
Furthermore, the speed of the following cassettes can be reduced by a ratio of 1:3 via a gear stage between two cassettes. Using a suitable channel configuration, ratios between 1:1 and 1:10 can be achieved. This means that the pump is also capable of producing mixing ratios beyond its pure application as a suction pump.
The device according to the present disclosure is not only directed to merely solve technical disadvantages but for solving disadvantages of known devices regarding the user interface. The present invention is intended to enable a trained user to independently replace the peristaltic tube as a wearing element within the scope of the usual maintenance intervals.
Currently available peristaltic pumps are related to the following discussed faults that can occur due to incorrect operation.
A problem may result from a peristaltic hose which is not correctly installed when it is replaced. This leads to an undefined contact pressure between the roller and the hose and thus to an undefined delivery volume and a pump that may not be resistant to backflow. It is possible that the pump still functions normally directly after the hose package has been replaced and only loses its function afterwards.
The present invention solves this first problem by having latching elements formed by a protrusion which engages into a recess at both attachment points (external connector) for the tube assembly, which initially provide haptic feedback for a correct installation of the tube.
A further problem in devices known from the prior art may result from a cover that is not correctly mounted or closed. As a result, the correct contact pressure will not be generated on the peristaltic tubes and the pump does thus not work correctly and/or is no longer non-refluxing. In this case, it is also conceivable that the pump still functions correctly initially and only gradually loses its function.
The pump according to the present disclosure has a central locking element, a locking lever, for avoiding this condition. Such a locking lever allows basically only two states, open and closed. If the cover is closed, the locking lever is in a perceivable closed position and full pressure is applied to the peristaltic tubes and the pump works correctly. If the locking lever is in a perceivable open position, the pump does not deliver any liquid at all. Closed and open position of the locking lever can be distinguished by its angle with respect to the side walls of the housing. A loss in pressure can additionally be detected more easily by a downstream sensor system as an incorrect flow rate. The locking lever of the bayonet lock of a device according to the present disclosure has roughened grip surfaces and pictograms (open and closed lock) for a simple and more intuitive operation.
In addition to the purely mechanical issues mentioned above, there are also solutions in the field of electronics or embedded software which will be discussed below.
The peristaltic pump is driven by a stepper motor. The drive torque can be adjusted via the current intensity. The revolutions are monitored via a home sensor. This results in the following advantages:
Turning to
The housing of cassette 50 comprises two side walls 53. Outer hooks 18a are arranged on the upper end of side walls 53 as part of the bayonet coupling for cover 12. The embodiment in
Thus, the required connection between the connecting elements 123 and recesses 16 can be regarded as safety features for a correct assembly of a cassette with the external connectors, because the correct interaction between the protrusions of connecting elements 123 and the recesses are a prerequisite for the possibility to fix the cover in gaps 54 of side walls 53.
Locking lever 4 of cover 12 is missing in
The advantages of a device according to the present invention can be summarised as follows:
The foregoing description of the preferred embodiment of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible considering the above teachings or may be acquired from practice of the invention. The embodiment was chosen and described to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto, and their equivalents. The entirety of each of the aforementioned documents is incorporated by reference herein.
Number | Date | Country | Kind |
---|---|---|---|
103064 | Jan 2023 | LU | national |
The present invention claims priority to national Luxembourg patent application No. LU 103064 filed on Jan. 20, 2023. The aforementioned application is incorporated herein by reference.