EP4219942A1 - Double-acting piston pump, and application system for applying a flowable medium to a substrate - Google Patents

Abstract

Double-acting piston pump for conveying a flowable medium to a dispensing device (5), the piston pump (1) having a piston (4) which can be moved between a first reversal point (24) and a second reversal point (25), for conveying the flowable medium, the The piston pump (1) has a control device for controlling the direction of movement of the piston (4), the control device being set up to reverse the direction of movement of the piston (4) when the respective reversal point (24, 25) is reached, the piston pump (1) having a Measuring device for measuring a piston speed, the control device being set up to reverse the direction of movement of the piston (4) when the measured piston speed falls below a certain speed value.

Description

The invention relates to a method for operating a double-acting, preferably pneumatically driven or drivable piston pump of an application system for applying a flowable medium, in particular a heated adhesive, to a substrate, the piston pump having a piston that can be moved between a first reversal point and a second reversal point for conveying the has flowable medium. When the respective reversal point is reached, the direction of movement of the piston is reversed. The application system has an output device for intermittently outputting the flowable medium conveyed to the output device by means of the piston pump. Furthermore, the invention relates to a double-acting piston pump for delivering a free-flowing medium to a dispensing device. Furthermore, the invention relates to an application system for applying a flowable medium to a substrate.

A piston pump for delivering a flowable medium is, for example, from EP 2 732 884 A2 known.

In the field of applying free-flowing media, in particular in the field of applying adhesives, there is a desire to obtain an application pattern that is as precise as possible. In this respect, there is particular interest in minimizing the effects of an adhesive delivery device, for example a double-acting piston pump, on the application pattern. When using double-acting piston pumps, in particular double-acting, pneumatically driven piston pumps, there is the problem that at the reversal points, when the direction of movement of the piston is reversed, there is a pressure drop in the flowable medium conveyed by the piston pump. This drop in pressure and its course over time are particularly dependent on the viscosity and the flow properties of the flowable medium, for example the heated adhesive being conveyed. Furthermore, the pressure drop and its course over time is highly dependent on the design and the design of some components of the piston pump. For example, the stroke direction of a pneumatically driven piston pump with a pneumatic piston is reversed via an electrically actuated pneumatic switchover valve. The switching process of this valve requires a certain amount of time. Likewise, when switching over, the reduction of air pressure on one side of the pneumatic piston and the build-up of air pressure on the other side of the pneumatic piston require a certain amount of time. In double-acting piston pumps, there are often two check valves, which usually do not have identical designs. The two non-return valves are usually designed in the form of movable balls which, when the piston is in the vertical operating direction, seal alternately at the top and bottom against a flow of the flowable medium to be pumped. During the switching process, the ball of one check valve moves from a sealed position to an open position and the ball of the other check valve moves from an open position to a sealed position and vice versa. This movement of the balls also takes some time. During the reversal process at the first reversal point and at the second reversal point of the piston, thus while the check valves are being actuated, there is a slight loss of volume flow of the free-flowing medium. This loss or pressure drop is typically of different magnitude in the two reversal points. With a double-acting piston pump, the problem arises that the pressure of the pumped, flowable medium drops for a limited time when the direction of movement of the piston is reversed, or it takes a certain amount of time before the pressure of the flowable medium assumes an approximately constant value again . The pressure drop at the reversal points has a negative effect on the quality of the flowable medium applied to the substrate or the application pattern. With a continuous application of the flowable medium to the substrate by means of the dispensing device, a reversal of the direction of movement of the piston and a pressure drop associated therewith leads to a temporarily reduced dispensing of flowable medium. Accordingly, in an application system with a double-acting piston pump, there is a reduced output of flowable medium at the reversal points of the piston pump, which has a negative effect on the application pattern. For example, when the flowable medium is continuously dispensed in the form of a strip, also referred to as an application bead or bead, there are significant constrictions in the cross section of the bead in the applied bead, which temporally correlate with the reversal points in the direction of movement of the piston of the adhesive pump. The so-called application pattern then shows clear, regular constrictions.

Various possibilities are known from the prior art for avoiding or reducing the pressure drop when reversing the direction of movement of the piston of the piston pump or for minimizing the effects of this pressure drop on the application pattern.

For example, the EP 2 107 241 A2 proposes a piston pump for this purpose, the piston pump having at least two piston-cylinder units for conveying the flowable medium. The two pumps are operated in such a way that a pressure drop during the delivery of the fluid from one pump is compensated for by the other pump. Furthermore, from the prior art ES 2 064 183 A2 the use of a pressure accumulator is known, with the pressure accumulator largely compensating for the falling pressure when the direction of movement of the piston of the piston pump is reversed. The disadvantage of this solution is that a pressure accumulator is optimally designed for only one operating state can be. Compensation for the falling pressure is satisfactory only for a specific pressure setting and only for a specific viscosity of the flowable medium. The larger the deviation from the optimal operating point, the worse the compensation of the pressure drop by the pressure accumulator works.

The object of the present invention is to specify a method for operating a double-acting piston pump of an application system for applying a flowable medium, in particular a heated adhesive, to a substrate, so that the effects of the pressure drop when reversing the direction of movement on the application pattern are avoided or at least reduced, in particular Constrictions of an application bead can be avoided or at least reduced. Furthermore, it is the object of the present invention to specify a double-acting piston pump for conveying a flowable medium to a dispensing device, with which constrictions in the application of the flowable medium can be avoided. Furthermore, it is the object of the present invention to specify an application system for applying a flowable medium that makes it possible to avoid or at least reduce constrictions in the application of the flowable medium.

These objects are achieved by a method having the features of patent claim 1, a double-acting piston pump having the features of patent claim 8, and an application system having the features of patent claim 15.

The method according to the invention is a method for operating a double-acting piston pump of an application system for applying a flowable medium. The flowable medium is in particular a heated adhesive and/or a viscous hot-melt adhesive. The piston pump is a double-acting piston pump, i.e. a piston pump that conveys the flowable medium in both stroke directions of the piston. The application system is used to apply the flowable medium to a substrate, which can be, for example, a sheet of paper, cardboard or a film. A substrate can consist of a large number of separate structures, For example, the substrate can be a large number of strip-like elements, for example strips of paper, strips of cardboard or strips of film, which are arranged at a distance and are successively guided past an application head which is used to dispense the medium.

The piston pump has a piston that can be moved between a first reversal point and a second reversal point for conveying the flowable medium, with the direction of movement of the piston being reversed when the respective reversal point is reached. The application system also has a dispensing device, for example one or more spray heads, for the intermittent dispensing of the flowable medium conveyed to the dispensing device by means of the piston pump. In the method according to the invention, it is provided that the flowable medium is dispensed by means of the dispensing device during periods of dispensing and that the dispensing of the flowable medium by means of the dispensing device is interrupted during periods of interruption. In the method according to the invention, the direction of movement of the piston is reversed during at least one interruption period of the interruption periods, with the piston being in an intermediate position between the first reversal point and the second reversal point during the at least one interruption period when the direction of movement is reversed.

Since the direction of movement of the piston is reversed during at least one interruption period of the interruption periods, at least this reversal of the direction of movement takes place during a period in which the reversal of the direction of movement of the piston and the associated pressure drop have little or no effect on the application pattern of the flowable medium the substrate is affected because the dispensing device is not dispensing the flowable medium during the pause period. In particular, the direction of movement of the piston is reversed during the at least one interruption period of the interruption periods in such a way that the time up to the dispensing period following the at least one interruption period is sufficient to build up a target value of the pressure again until the start of the subsequent dispensing period, insofar as this is the case at the beginning of the subsequent dispensing period, the reverse-induced, time-limited pressure drop is over.

In conventional piston pumps or methods for operating a piston pump, the direction of movement of the piston is reversed only when the respective reversal point is reached. Thus, with such methods or piston pumps, there is no temporal coordination of the reversal of the direction of movement of the piston and the interruption period or interruption periods. In contrast, in the solution according to the invention, the movement of the piston of the piston pump changes direction during the at least one interruption period of the interruption periods in an intermediate position, thus before the reversal point in the direction of movement is reached.

It is quite conceivable that the direction of movement of the piston of the piston pump is reversed during one interruption period of the interruption periods in an intermediate position between the two reversal points and the direction of movement of the piston of the piston pump is reversed during another interruption period of the interruption periods in another intermediate position between the two reversal points he follows.

It is quite conceivable that the piston also reaches the first and/or second reversal point during the movement.

It is also quite conceivable that during one or more other interruption periods the piston reaches the first reversal point or the second reversal point anyway, so that there is no earlier reversal of the direction of movement of the piston in an intermediate position.

The flowable medium is preferably dispensed intermittently in such a way that the intermittent dispensing results in a time-recurring pattern of dispensed flowable medium, in particular when a large number of substrates of the same type are provided with the flowable medium.

The piston pump preferably has a delivery area and a drive area. The piston is arranged in the conveying area and serves to convey the free-flowing medium. The components serving to drive the movement of the piston are arranged at least partially, preferably completely, in the drive area.

The piston pump is preferably a pneumatically drivable piston pump. The piston pump preferably has a pneumatic piston which is operatively connected to the piston which is used to convey the free-flowing medium and which is used to drive the movement of the piston. Preferably, for the stroke movement of the piston in the direction of the first reversal point or the second reversal point, compressed air is applied to a corresponding side of the pneumatic piston and the other side is vented. The direction of movement of the piston is preferably reversed via an electrically or magnetically actuable pneumatic switching valve.

In particular, the piston pump has a pneumatic part, also referred to as a pneumatic area, and a delivery area, with the pneumatic piston being arranged in the pneumatic part and the piston, which serves to deliver the free-flowing medium, being arranged in the delivery area.

Drives other than a pneumatic drive are also conceivable, which cause an alternating movement of the piston. For example, a hydraulic drive, in particular with a hydraulic piston, an electric drive, in particular in the form of a linear motor.

The first reversal point and the second reversal point are preferably not designed to be variable, so that the first reversal point and the second reversal point are fixed when the double-acting piston pump is operated. The two reversal points are preferably unchangeable, in particular due to the design.

The first reversal point and the second reversal point are preferably a bottom or top dead center of the piston.

It is considered to be particularly advantageous if the direction of movement of the piston is reversed exclusively or at least mostly during the interruption periods. As a result, the negative influences of the respective reversal of the direction of movement on the application pattern are particularly small. However, a reversal of the direction of movement of the piston does not necessarily occur during each pause period.

It is considered to be particularly preferred if a delivery quantity of the flowable medium delivered during the respective delivery period by means of the delivery device is smaller than a delivery quantity of the delivery device by means of the piston pump during a piston stroke of the piston pump from the first reversal point to the second reversal point and/or vice versa to the delivery device promoted medium. In such an embodiment, the flowable medium can be dispensed during the dispensing periods without reversing the direction of movement of the piston. This has a particularly advantageous effect on the quality of the application of the flowable medium to the substrate.

In the event that a delivery quantity of the flowable medium delivered by means of the delivery device during a delivery period of the delivery periods is greater than a medium delivered to the delivery device over a complete stroke length of the piston pump or when one of the reversal points is reached during a delivery period of the delivery periods, it is entirely conceivable to compensate for the pressure drop when reversing the direction of movement of the piston of the piston pump. For this purpose, it is conceivable to activate a pressure accumulator in a controlled manner so that the pressure drop during the switching process is compensated. A spring accumulator or a pressure accumulator with the principle of a single-acting, pneumatically actuated piston pump can be used as the pressure accumulator.

During operation of the piston pump, a number of reversals of the direction of movement that occur in intermediate positions of the piston between the first reversal point and the second reversal point is preferably greater than a number of reversals of the direction of movement that occur in the reversal points. Therewith the direction of movement is reversed predominantly in intermediate positions of the piston between the first reversal point and the second reversal point.

It is quite conceivable that, during operation, the direction of movement is reversed only in intermediate positions, insofar as the reversal points are not reached. The reversal points would then only be reached if, for example due to a malfunction of the pump when executing the method or a controller for executing the method, the direction of movement in the intermediate position is not reversed unintentionally. Since the direction of movement is then reversed with regard to a movement of the piston in the direction of one of the reversal points at the latest when this reversal point is reached, damage to components of the piston pump is avoided.

It is considered to be particularly advantageous if, during the interruption periods, a piston speed, whereby piston speed is understood to mean the absolute value of the piston speed, of the piston is reduced compared to a piston speed during the dispensing periods, in particular the piston speed during the interruption periods is equal to zero. Accordingly, the piston velocity evolution over time is correlated to the dispense periods and the interrupt periods. Accordingly, by detecting the piston speed, it can be determined whether there is a dispensing period or an interruption period. Accordingly, it is not necessary to provide a higher-level control that detects whether the output device is outputting the medium or whether the output is interrupted, but the reversal of the direction of movement can be independent of the higher-level control or knowledge of the operating state of the output device (output or interruption of the output ) are carried out solely on the basis of the measured piston speed, so that the piston pump can be operated more or less independently, meaning that there is no need for a higher-level controller. Because the piston speed is correlated to the dispense periods and interrupt periods, a reversal of the direction of movement of the piston can be made dependent on the piston speed and from a knowledge of the piston speed a reversal of the Direction of movement take place during the at least one interruption period.

In the case of a recurring application pattern, the recurring application pattern can be recognized by measuring the piston speed. In this way, at the beginning of an interruption period, the expected stroke distance of the piston up to the beginning of the next interruption period can be determined. Alternatively, it is conceivable that the programmed or specified application pattern of a higher-level application control is used to determine the time course of the interruption periods for determining the piston positions to be expected with regard to the interruption periods. As a result, the operational reliability of the invention can be improved since unexpected changes in the application pattern can be taken into account.

It is considered to be particularly advantageous if the piston pump is subject to leakage with respect to the flowable medium to be delivered, so that during the interruption periods a piston speed of the piston is reduced compared to a piston speed in the dispensing periods. A piston pump prone to leaks is also to be regarded as advantageous with regard to minimizing wear, avoiding maintenance work and the longest possible service life of the piston pump. It is considered particularly advantageous if the leakage occurs between the piston and the cylinder. This leakage is primarily dependent on the viscosity and the flow behavior of the free-flowing medium, on the size of a gap around the piston and on the pressure that the piston pump builds up. In a leaking piston pump, piston speed during pause periods is reduced relative to piston speed during dispensing periods because during pause periods, resistance to piston movement is increased relative to resistance to piston movement when dispensing the flowable medium.

Preferably, the piston of the piston pump is non-sealing with respect to a cylinder and/or the piston pump has a non-sealing piston rod with respect to a guide.

The piston pump preferably has two check valves, one check valve being open and the other check valve being closed, depending on the direction of movement of the piston. The two non-return valves are usually designed in the form of movable balls which, when the piston is in the vertical operating direction, seal alternately at the top and bottom against a flow of the flowable medium to be pumped. During the switchover process, the ball of one check valve moves from a sealed position to an open position and the ball of the other check valve moves from an open position to a sealed position and vice versa during a subsequent switchover process.

In a preferred embodiment of the method, the piston speed is measured and the direction of movement of the piston is reversed outside the reversal points when the piston speed is equal to a certain value, in particular the certain value corresponds to the piston speed of the piston during the interruption periods. The aforementioned condition, namely that the piston speed is less than or equal to a specific value, is to be understood as a necessary condition but not a mandatory sufficient condition for reversing the direction of movement of the piston. However, it is quite conceivable that this is a sufficient condition for reversing the direction of movement of the piston.

In an advantageous development of the method, it is provided that a distance of the piston from the reversal point in the direction of movement of the piston is determined, with the direction of movement of the piston being reversed during the respective interruption period before the reversal point in the direction of movement of the piston is reached if the distance of the piston falls below a certain value from the reversal point in the direction of movement of the piston, and/or wherein a distance of the piston from the reversal point opposite to the direction of movement of the piston is determined, wherein a reversal of the direction of movement of the piston during the respective interruption period before reaching the in direction of movement of the piston reversal point occurs when the distance of the piston from the reversal point opposite to that in the direction of movement of the piston exceeds a certain value.

It is quite conceivable that the piston position is measured permanently.

The distance of the piston from the respective reversal point used for the comparison with the determined value is preferably determined at the beginning of the respective interruption period.

The determined value with regard to the reversal point in the direction of movement of the piston preferably corresponds to an expected stroke of the piston in the direction of movement of the piston until the beginning of the next interruption period.

The determined value with regard to the reversal point lying opposite to the direction of movement of the piston preferably corresponds to an expected stroke of the piston opposite to the direction of movement of the piston until the start of the next interruption period.

It is considered particularly advantageous if the piston speed is measured and a distance of the piston from the reversal point in the direction of movement of the piston is determined, with the direction of movement of the piston being reversed when the piston speed falls below a certain value and the distance of the piston from falls below a specific value at the reversal point in the direction of movement of the piston, and/or when the piston speed is measured and a distance of the piston from the reversal point opposite to the direction of movement of the piston is determined, with the direction of movement of the movable piston being reversed when the piston speed falls below a certain value and the distance of the piston from the reversal point opposite to the direction of movement of the piston exceeds a certain value.

The advantage of the aforementioned embodiment of the method is that the piston speed is a criterion for whether there is an interruption period. Since a reversal of the direction of movement of the piston is to occur during an interruption period, a reversal of the direction of movement of the piston is to occur only during a period of reduced piston speed. The reduced piston speed is therefore a first criterion for switching. The distance of the piston from the respective reversal point is used as a further criterion to decide whether the direction of movement should be reversed. This is against the background that if the distance between the piston and the reversal point opposite to the direction of movement of the piston is too small, there is a risk that when the direction of movement of the piston reverses, the piston will reach this reversal point in the subsequent dispensing period, resulting in a reversal of the direction of movement in occurs during this output period and a corresponding drop in pressure occurs during the output of the medium with the corresponding negative effects on the job image.

It is quite conceivable that the piston position for determining the distance value of the piston from the respective reversal point or the distance value of the piston from the respective reversal point is determined when the piston speed falls below a specific value. In this respect, it is first checked whether the first criterion, namely that the piston speed falls below a specific speed value, is present. Only when the first criterion is present is the second criterion, namely the distance, checked. This reduces the measurement and evaluation effort.

It is considered particularly advantageous if the piston pump has sensors for measuring a piston position and/or a distance of the piston from the first reversal point or the second reversal point and/or for measuring the direction of movement of the piston and/or for measuring the speed of the piston. It is considered particularly advantageous if the sensor is designed as a Hall sensor. In connection with a Hall sensor, it is considered to be particularly advantageous if the piston pump has a magnet, preferably a ring magnet, the magnet together with the Piston is movable. It is entirely conceivable that the piston pump has a plurality of Hall sensors, preferably at least four Hall sensors, in particular exactly four Hall sensors.

The term "distance" is to be understood broadly in the aforementioned contexts. For example, it is conceivable that the distance of the piston from one reversal point to the other reversal point is divided into at least two sections, with "distance" then meaning that section in which the piston is located. For example, the route can be divided into a first section and a second section, with the first section containing the first reversal point and the second section containing the second reversal point. The section in which the piston is currently located can then be used as the distance criterion or distance. Thus, the distance of the piston from the first reversal point is less when the piston is in the first section than when the piston is in the second section. Knowing which section the piston is in can therefore be used as a criterion for falling below or exceeding a distance value.

In principle, it is conceivable in an application system with two double-acting piston pumps to control the reversal of the direction of movement of the piston of the respective piston pump in a similar manner in such a way that the direction of movement of the pistons of the two piston pumps is not reversed at the same time, but the direction of movement of the piston of the change a piston pump prematurely if it is foreseeable that a reversal of the direction of movement of one piston pump at the first or second reversal point would coincide with a reversal of the direction of movement of the piston of the other pump at the first reversal point or the second reversal point.

The double-acting piston pump according to the invention serves to convey a free-flowing medium to a dispensing device. In particular, the double-acting piston pump is used to convey a heated adhesive, in particular a viscous hot-melt adhesive, to a dispensing device. The dispensing device can in particular be a spray head. The piston pump has a reversal point between a first and a second Reversal point movable piston, which is used to convey the flowable medium. Furthermore, the piston pump has a control device for controlling the direction of movement of the piston, the control device being set up to reverse the direction of movement of the piston when the respective reversal point is reached. Furthermore, the piston pump has a measuring device for measuring a piston speed, the control device being set up to reverse the direction of movement of the piston when the measured piston speed falls below a certain speed value.

Since the speed of the piston is usually dependent on whether flowable medium is being dispensed from the dispenser or not, the piston speed is a measure of whether flowable medium is being dispensed from the dispenser or the dispensing of flowable medium by the dispenser is interrupted. The double-acting piston pump is therefore suitable for carrying out the method according to the invention, with the corresponding advantages.

It is considered to be particularly advantageous if the piston pump is subject to leakage with respect to the flowable medium to be conveyed. In this context, it is considered to be particularly advantageous if the piston is not designed to be sealing with respect to a cylinder and/or the piston pump has a piston rod that is not designed to be sealing in a guide. A piston pump prone to leaks has the advantage that wear on the piston pump is reduced and also, with regard to the method, the advantage that the speed of the piston during the interruption periods is reduced compared to the speed of the piston during the dispensing periods.

The piston pump preferably has two check valves, one check valve being open and the other check valve being closed, depending on the direction of movement of the piston, and in particular the check valves being designed differently. The two check valves are assigned to that part of the piston pump in which the free-flowing medium is conveyed, ie the conveying region.

The double-acting piston pump is preferably designed as a pneumatically drivable piston pump. In particular, the piston pump has a pneumatic part, also referred to as a pneumatic area, and a delivery area, with the pneumatic piston being arranged in the pneumatic part and the piston, which serves to deliver the free-flowing medium, being arranged in the delivery area.

The piston pump preferably has a measuring device for measuring a distance between the piston position of the piston and the reversal point in the direction of movement of the piston, with the control device being set up to change the direction of movement of the reversing the piston, or the piston pump has a measuring device for measuring a distance between the piston position of the piston and the reversal point opposite to the direction of movement of the piston, wherein the control device is set up, when the measured piston speed falls below a certain speed value and the measured piston speed exceeds a certain distance value distance to reverse the direction of movement of the piston.

The piston pump preferably has a magnet or a plurality of magnets, preferably one or more ring magnets, the magnet being movable together with the piston or the magnets being movable together with the piston, the measuring device for measuring the piston speed having at least one Hall sensor and/or or the measuring device for measuring the distance has at least one Hall sensor. The piston pump preferably has at least three Hall sensors, in particular at least four Hall sensors. If there are several Hall sensors, the piston pump preferably also has several magnets. In particular, each Hall sensor is assigned a magnet. The control device preferably has an evaluation device for evaluating the magnetic flux density measured by means of the one or more Hall sensors, the evaluation device being set up in particular to determine the first and the second derivation of the measured magnetic flux density. From the measured magnetic flux density, the first derivative of the flux density and the second derivative of the flux density draw conclusions about the piston position, the piston speed and the piston acceleration.

The piston pump preferably has at least two Hall sensors, with a distance traveled by the piston from one reversal point to the other reversal point being divided into at least two sections with regard to the measurement of the piston speed and/or a measurement of the piston position, with the respective section being one of the at least two sensors is assignable. In particular, the distribution of the distance and the assignment of the Hall sensors is such that for the Hall sensor that can be assigned to the respective section, there is an almost linear relationship between the magnetic flux density detected by this Hall sensor and the piston position of the piston when the piston is in the section assigned to this Hall sensor located.

With regard to a measurement of the piston position and/or piston speed based on the magnetic flux density by the Hall sensors, it is considered advantageous to carry out a calibration process, in particular to compensate for manufacturing tolerances of the individual parts. It is possible to carry out this calibration process automatically when the piston pump is started up. To do this, the piston can be moved at low speed for several cycles without adhesive. The reference values of the flux densities can be taught in.

The alignment process also makes it possible to determine the polarity of the magnet during the alignment process. The reference values can be adjusted automatically, in particular digital electronics for evaluating the Hall sensors can be programmed according to the installation position of the magnet. It is therefore not necessary to adhere to a specific alignment of the magnet during assembly. Dismantling to correct an incorrect installation position of the magnet is therefore not necessary.

By determining the speed and/or an acceleration of the piston, it is possible to measure an oscillating behavior or a vibration from the piston. This vibration behavior can be used as an indication of wear and tear possible early failure of components of the piston pump. This can be used for preventive maintenance or replacement of components. This means that production downtime, which is expensive for the customer, can be avoided.

It is considered to be particularly advantageous if the piston pump is designed as a pneumatically drivable piston pump with a pneumatic piston that is operatively connected to the piston, the control device having an actuatable valve or an actuatable valve arrangement, with actuation of the valve or the valve arrangement in a direction in which pressure is applied to the pneumatic piston changes. By actuating the valve or the valve arrangement, the direction of movement of the piston can thus be reversed in a simple manner.

The application system according to the invention for applying a flowable medium, in particular a heated adhesive, to a substrate has the above-described double-acting piston pump or one of the above-described embodiments of the double-acting piston pump and a dispensing device for intermittently dispensing the flowable medium conveyed to the dispensing device by means of the double-acting piston pump.

Aspects of the invention:

• Aspect 1: Method for operating a double-acting piston pump of an application system for applying a flowable medium, in particular a heated adhesive, to a substrate, wherein the piston pump has a piston that can be moved between a first reversal point and a second reversal point, for conveying the flowable medium, wherein at When the respective reversal point is reached, the direction of movement of the piston is reversed, with the application system having an output device for intermittently outputting the flowable medium conveyed to the output device by the piston pump, with the flowable medium being output by means of the output device during output periods and the flowable medium by means of the dispensing device is interrupted, with the direction of movement of the piston being reversed during at least one interruption period of the interruption periods, with the piston being in an intermediate position between the first reversal point and the second reversal point during the at least one interruption period when the direction of movement is reversed.
• Aspect 2: Method according to aspect 1, wherein a reversal of the direction of movement of the piston takes place mainly during the interruption periods, in particular exclusively during the interruption periods.
• Aspect 3: The method according to aspect 1 or 2, wherein a number of reversals of the direction of movement that occur in intermediate positions of the piston between the first turning point and the second turning point is greater than a number of reversals of the direction of movement that occur in the turning points.
• Aspect 4: Method according to one of aspects 1 to 3, wherein during the interruption periods a piston speed of the piston is reduced compared to a piston speed during the dispensing periods, in particular the piston pump is leaky with respect to the flowable medium to be delivered, so that a piston speed of the piston is reduced during the interruption periods is versus piston speed during dispensing periods.
• Aspect 5: Method according to aspect 1-4, wherein the piston speed is measured and the direction of movement of the piston is reversed if the piston speed is less than or equal to a certain value, in particular the certain value corresponds to the piston speed of the piston during the interruption periods.
• Aspect 6: Method according to one of aspects 1 to 5, wherein a distance of the piston from the reversal point in the direction of movement of the piston is determined, with a reversal of the direction of movement of the piston takes place during the respective interruption period before the reversal point in the direction of movement of the piston is reached if the distance between the piston and the reversal point in the direction of movement of the piston falls below a certain value,
  and or
  wherein a distance of the piston from the reversal point opposite to the direction of movement of the piston is determined, wherein a reversal of the direction of movement of the piston takes place during the respective interruption period before reaching the reversal point lying in the direction of movement of the piston if the distance of the piston from the point opposite to the direction of movement of the Piston lying reversal point exceeds a certain value.
• Aspect 7: Method according to one of aspects 1 to 6, wherein the piston speed is measured and a distance of the piston from the reversal point in the direction of movement of the piston is determined, with the direction of movement of the piston being reversed if the piston speed falls below a certain value and the distance of the piston from the reversal point in the direction of movement of the piston falls below a certain value,
  and or
  wherein the piston speed is measured and a distance of the piston from the reversal point opposite to the direction of movement of the piston is determined, the direction of movement of the piston being reversed when the piston speed falls below a certain value and the distance of the piston from the point opposite to the direction of movement of the piston lying reversal point exceeds a certain value.
• Aspect 8: Double-acting piston pump for delivering a flowable medium to a dispensing device, wherein the piston pump has a piston that can be moved between a first reversal point and a second reversal point, for delivering the flowable medium, the piston pump having a control device for controlling the direction of movement of the piston, wherein the control device is set up to reverse the direction of movement of the piston when the respective reversal point is reached, the piston pump having a measuring device for measuring a piston speed, the control device being set up to reverse the direction of movement of the piston when the measured piston speed falls below a certain speed value.
• Aspect 9: Double-acting piston pump according to aspect 8, wherein the piston pump is subject to leakage with respect to the flowable medium to be delivered, preferably the piston is not designed to be sealing with respect to a cylinder, and/or the piston pump has a piston rod that is not designed to be sealing with respect to a guide.
• Aspect 10: Double-acting piston pump according to aspect 8 or 9, wherein the piston pump has two check valves, depending on the direction of movement of the piston, one check valve of the check valves is open and the other check valve of the check valves is closed, in particular the check valves are designed differently.
• Aspect 11: Double-acting piston pump according to one of aspects 8 to 10, wherein the piston pump has a measuring device for measuring a distance of the piston position of the piston from the reversal point in the direction of movement of the piston, wherein the control device is set up to fall below a certain speed value of the measured Piston speed and falling below a certain distance value of the measured distance to reverse the direction of movement of the piston,
  and/or wherein the piston pump has a measuring device for measuring a distance of the piston position of the piston from the reversal point opposite to the direction of movement of the piston, wherein the control device is set up, when the measured piston speed falls below a specific speed value and the measured distance exceeds a specific distance value reverse the direction of movement of the piston.
• Aspect 12: Double-acting piston pump according to one of aspects 8 to 11, wherein the piston pump has a magnet or a plurality of magnets, preferably one or more ring magnets, the magnet or the magnets being or are movable together with the piston, the measuring device for measuring the piston speed has at least one Hall sensor and/or the measuring device for measuring the distance between the piston position of the piston and the reversal point in the direction of movement of the piston has at least one Hall sensor and/or the measuring device for measuring the distance between the piston position of the piston and the opposite direction of movement of the piston lying reversal point has at least one Hall sensor.
• Aspect 13: Double-acting piston pump according to aspect 12, wherein the piston pump has at least two Hall sensors, preferably four Hall sensors, with a distance of the piston from one reversal point to the other reversal point with regard to the measurement of the piston speed and/or a measurement of the piston position in at least two divided into sections, with one of the at least two sensors being assignable to the respective section, in particular for the Hall sensor which can be assigned to the respective section, there is an almost linear relationship between the magnetic flux density detected by this Hall sensor and the piston position of the piston when the piston is in this Hall sensor associated section is located.
• Aspect 14: Double-acting piston pump according to one of aspects 8 to 13, wherein the piston pump is designed as a pneumatically drivable piston pump, wherein the control device has an actuatable valve or an actuatable valve arrangement, wherein when the valve or the valve arrangement is actuated, the direction of pressurization of a pneumatic piston changes , wherein the pneumatic piston is operatively connected to the piston.
• Aspect 15: Application system for applying a flowable medium, in particular a heated adhesive, to a substrate, having a double-acting piston pump according to one of aspects 8 to 14 and having a dispensing device for intermittently dispensing the flowable medium conveyed to the dispensing device by means of the double-acting piston pump.

The invention is explained in more detail in the following figures using an exemplary embodiment, without being restricted thereto.

Fig. 1

ein Auftragssystem zum Auftragen eines fließfähigen Mediums aufweisend eine doppeltwirkende Kolbenpumpe und aufweisend eine Ausgabevorrichtung,

Fig. 2

die Kolbenpumpe gemäß Fig. 1 mit einem Kolben in einem ersten Umkehrpunkt,

Fig. 3

die Kolbenpumpe gemäß Fig. 1 mit dem Kolben in einer Zwischenposition,

Fig. 4

die Kolbenpumpe gemäß Fig. 1 mit dem Kolben in einem zweiten Umkehrpunkt,

Fig. 5

ein Diagramm zur Veranschaulichung eines zeitlichen Verlaufs einer Kolbenposition einer Kolbenpumpe, einer Ausgabemenge des fließfähigen Mediums pro Zeiteinheit sowie eine schematische Darstellung der daraus resultierenden Auftragsraupe, einer Kolbenpumpe bzw. eines Verfahrens zum Betreiben der Kolbenpumpe bei der/dem eine Umkehr der Bewegungsrichtung des Kolbens ausschließ in fixen Umkehrpunkten erfolgt,

Fig. 6

ein Diagramm zur Veranschaulichung des zeitlichen Verlaufs der Kolbenposition, der Ausgabemenge des fließfähigen Mediums pro Zeiteinheit sowie eine schematische Darstellung der daraus resultierenden Auftragsraupe, bei einer erfindungsgemäßen Kolbenpumpe bzw. erfindungsgemäßen Verfahren zum Betreiben einer Kolbenpumpe.

Show it:

1

an application system for applying a flowable medium, having a double-acting piston pump and having an output device,

2

the piston pump according to 1 with a piston in a first reversal point,

3

the piston pump according to 1 with the piston in an intermediate position,

4

the piston pump according to 1 with the piston in a second reversal point,

figure 5

a diagram to illustrate a time course of a piston position of a piston pump, an output quantity of the flowable medium per unit of time and a schematic representation of the resulting bead of application, a piston pump or a method for operating the piston pump in which a reversal of the direction of movement of the piston excludes in fixed reversal points,

6

a diagram to illustrate the time course of the piston position, the output quantity of the flowable medium per unit of time and a schematic representation of the resulting application bead, in a piston pump according to the invention or inventive method for operating a piston pump.

The 1 shows an application system 2 for applying a flowable medium, in this case a heated adhesive, to a substrate 3. The substrate 3 can be, for example, sheets of paper or cardboard. The application system 2 has a double-acting piston pump 1 . Since it is a double-acting piston pump 1, the piston pump 1 is effective in both stroke directions of the piston 4. The flowable medium is conveyed by means of the piston pump 1 from a storage container (not shown) that can be connected to the piston pump 1 to a dispensing device 5 . The dispensing device 5 is in fluid communication with the piston pump 1, namely a cylinder bore 12 of the piston pump, by means of a heating hose 11. During the operation of the piston pump, the adhesive gets from the storage container into a suction chamber 13 for adhesive. From there, the adhesive is sucked into the cylinder bore 12 and conveyed under pressure to the dispensing device 5 via a pressure connection 14 to which the heating hose 11 is connected.

The dispensing device 5 is presently suitable for intermittently dispensing the adhesive conveyed to the dispensing device 5, so that the adhesive is dispensed by the dispensing device 5 during dispensing periods and the dispensing of the adhesive by the dispensing device 5 is interrupted during interruption periods. This is For example, an advantage if, as in the 1 shown schematically, the adhesive is to be applied to substrates 3, which are arranged at a distance from one another on a conveyor belt 15 and are moved past the dispensing device 5, in particular continuously, by means of this conveyor belt 15 in the direction of arrow 16, with the dispensing device 5 each having a bead of adhesive 17 applies to the respective substrate 3. In order to ensure a clean application of adhesive to the substrates 3, it makes sense to temporarily interrupt the dispensing of the adhesive by means of the dispensing device 5, particularly at times when no substrate 3 is arranged below the dispensing device 5.

The piston 4 of the piston pump 1 can be moved between a first reversal point 24 and a second reversal point 25 . When the respective reversal point 24, 25 is reached, the direction of movement of the piston 4 is reversed. When the direction of movement of the piston 4 is reversed, there is a temporary drop in the pressure of the adhesive being conveyed. If during this limited period of time adhesive is dispensed by means of the dispensing device 5, this drop in pressure has a negative effect on the quantity of adhesive dispensed and thus on the so-called application pattern. During the switching process of the piston pump 1 and thus during the drop in adhesive pressure, there is a significantly lower application of adhesive than during a continuous movement of the piston 4 of the piston pump 1. A clear constriction 18 is then visible in the applied adhesive bead 17. The effects of the switching operations of the piston pump 4 on the output quantity of adhesive per unit time 23 and the adhesive image or the adhesive beads 17 are from FIG figure 5 evident.

Usually, the direction of movement of the piston 4 is changed in piston pumps 1 or in methods for operating a piston pump 1, as are known from the prior art, always and exclusively at fixed positions, namely at the two fixed reversal points 24, 25, which typically coincide with the dead centers of the piston pump 1: After a complete stroke of the piston 4 has taken place, the switchover process is initiated and then a complete stroke takes place in the opposite direction up to the respective other reversal point of the reversal points 24, 25. Usually the Actuation of the switching process thus reversing the direction of movement of the piston 4, purely mechanically or by actuating an electrical or electronic switch. There is no temporal coordination of the switching process of the direction of movement of the piston 4 of the piston pump 1 and the delivery periods and interruption periods of the adhesive application.

At the in the figure 6 The exemplary embodiment according to the invention shown in the illustration provides that the direction of movement of the piston 4 is reversed only during the interruption periods. The development over time of the piston position 26 and the quantity of adhesive dispensed per unit of time 23 are shown schematically in FIG 6 shown. As from a comparison of Figures 5 and 6 becomes apparent, it comes at the 6 does not result in a drop in the amount of adhesive dispensed per unit time 23 during the dispensing periods, since reversal of the direction of movement of the piston 4 occurs only during the pause periods. Accordingly, the 6 Beads of adhesive 17 shown in contrast to those in FIG figure 5 shown adhesive beads 17 no constrictions 18 on.

As also from the 6 As can be seen, when the direction of movement is reversed, the piston 4 is in an intermediate position between the first reversal point 24 and the second reversal point 25, the intermediate positions being different.

How from the 6 can also be seen that a delivery quantity of the adhesive delivered during the respective delivery period by means of the delivery device 5 is smaller than a delivery quantity of the adhesive delivered by means of the piston pump 1 during a piston stroke of the piston 4 from one reversal point 24, 25 to the other reversal point 24, 25 to the delivery device 5 funded medium.

At the in the Figures 1 to 4 Piston pump 1 shown is a piston pump 1 which is subject to leakage with respect to the adhesive to be delivered, so that during the interruption periods a piston speed of the piston 4 is reduced compared to a piston speed during the dispensing periods. This is also evident from the development of the piston position over time 26 of the piston 4 can be seen, as in the Figures 5 and 6 is shown. The leakage is realized in that the piston 4 is not designed to seal with respect to a cylinder bore 12 , the cylinder bore 12 being introduced into a housing 19 of the piston pump 1 .

The piston pump 1 has an upper pneumatic part with a pneumatic piston 20 for the drive. The pneumatic piston 20 is firmly connected to a piston rod 6, which in turn is connected to the piston 4, which serves to convey the adhesive. In the pneumatic area of the piston pump 1, a ring magnet 9 is also connected to the pneumatic piston 20 and thus to the piston rod 6. An electronic circuit board 21 is also formed adjacent to the pneumatic piston 20 or the ring magnet 9 , with three Hall sensors 10 being connected to the electronic circuit board 21 . The Hall sensors 10 are designed in such a way that they measure the magnetic flux density in the horizontal direction. With a stroke of the pneumatic piston 20 or the piston 4, which are connected to each other by means of the piston rod 6, the ring magnet 9 moves according to the movement of the piston rod 6, so that due to the change in the position of the ring magnet 9, the position of the respective Hall sensor 10 detected magnetic flux density changes. The piston position 26 and the piston speed can then be determined by means of the output signals of the Hall sensors 10 . Furthermore, the direction of movement of the piston 4 or of the pneumatic piston 20 can also be determined.

In principle, both the piston position 26, the piston speed and the direction of movement of the piston 4 can be determined using a single Hall sensor 10. However, at least three Hall sensors 10 are preferably used, since this increases the accuracy on the one hand and increases the redundancy on the other hand, as a result of which the failure, functional and operational reliability of the piston pump 1 is increased.

Outside the pneumatic part of the piston pump 1, ie in the adhesive delivery area of the piston pump 1, this has an extension in the area of the end of the piston rod 6 facing away from the pneumatic piston 20, which forms the double-acting piston 4.

The piston 4 is provided with an axial passage, in the area of which a check valve 7 with associated valve seat is arranged. The piston 4 is guided in the cylinder bore 12 formed in the housing 19 in a non-sealing manner. A second check valve 8 is formed in the cylinder bore 12 . The check valve 8 is associated with the suction chamber 13, so that adhesive can enter from the suction chamber 13 into the adhesive delivery chamber of the piston pump 1 when the check valve 8 is in a defined position. If the non-return valve 7 is in a defined position, adhesive can reach the pressure connection 14 and from there via the heating hose 11 to the dispensing device 5 .

A dynamic seal 22 without differential pressure is provided between the pneumatic part and the adhesive-delivering part of the piston pump 1 .

During a stroke of the piston rod 6 from the first reversal point 24 in the direction of the second reversal point 25 , adhesive is simultaneously conveyed to the dispensing device 5 and adhesive is sucked into the suction chamber 13 from the storage container (not shown). Leakage losses between the piston rod 6 and the housing 19 and between the piston 4 and the housing 19 occur. When the piston rod 6 is moved in the opposite direction, i.e. when the piston rod 6 is moved from the second reversal point 25 in the direction of the first reversal point 24, no adhesive is sucked in, but only adhesive is conveyed to the dispensing device 5.

The piston pump 1 also has a control device, not shown, for controlling the direction of movement of the piston 4, the control device being set up to reverse the direction of movement of the piston 4 when the respective reversal point 24, 25 is reached. The piston pump 1 also has a measuring device for measuring the piston speed, the control device being set up to reverse the direction of movement of the piston 4 when the measured piston speed falls below a certain speed value. Furthermore, the piston pump 1 has a measuring device for measuring a distance of the piston position 26 of the piston 4 from the reversal point lying in the direction of movement of the piston 4 on. The Hall sensors 10 form part of the measuring device for measuring the piston speed, the piston position 26 or the distance and the direction of movement of the piston 4. The control device is set up to fall below a certain speed value of the measured piston speed and falls below a certain distance value of the measured Distance to reverse the direction of movement of the piston 4. Such a design of the piston pump 1 has the advantage that the switching process of the direction of movement of the piston 4 takes place solely on the basis of the knowledge of internal measurement data or measurement variables of the piston pump 1 . It is therefore not necessary to record data about the status of the dispensing device 5 and to transmit it to the control device of the piston pump 1 . The piston pump 1 can thus be used completely independently of the dispensing device 5 actually used and can carry out the method described above. Thus, the piston pump 1 can be used universally. In particular, existing application systems 2 can be converted by replacing the piston pump 1 in such a way that these application systems 2 can carry out the method described above.

Reference List

1

piston pump

2

order system

3

substrate

4

Pistons

5

dispenser

6

piston rod

7

check valve

8th

check valve

9

ring magnet

10

Hall sensors

11

heating hose

12

cylinder bore

13

suction chamber

14

pressure connection

15

conveyor belt

16

Arrow

17

glue bead

18

constriction

19

Housing

20

pneumatic piston

21

electronics print

22

dynamic seal

23

Output quantity per time unit

24

first turning point

25

second reversal point

26

piston position

Claims (8)

Double-acting piston pump for conveying a flowable medium to a dispensing device (5), the piston pump (1) having a piston (4) which can be moved between a first reversal point (24) and a second reversal point (25), for conveying the flowable medium, the Piston pump (1) has a control device for controlling the direction of movement of the piston (4), the control device being set up to reverse the direction of movement of the piston (4) when the respective reversal point (24, 25) is reached, the piston pump (1) having a Measuring device for measuring a piston speed, the control device being set up to reverse the direction of movement of the piston (4) when the measured piston speed falls below a certain speed value. Double-acting piston pump according to claim 1, wherein the piston pump (1) is subject to leakage with respect to the flowable medium to be conveyed, preferably the piston (4) is not designed to be sealing with respect to a cylinder, and/or the piston pump (1) is designed to be non-sealing with respect to a guide Has piston rod (6). Double-acting piston pump according to claim 1 or 2, wherein the piston pump (1) has two check valves (7, 8), depending on the direction of movement of the piston (4), one of the check valves (7, 8) being open and the other check valve of the check valves ( 7, 8) is closed, in particular the check valves (7, 8) are designed differently. Double-acting piston pump according to one of claims 1 to 3, wherein the piston pump (1) has a measuring device for measuring a distance of the piston position (26) of the piston (4) from the reversal point (24, 25) in the direction of movement of the piston (4), where the Control device is set up to reverse the direction of movement of the piston (4) when the measured piston speed falls below a certain speed value and the measured distance falls below a certain distance value,
and or
wherein the piston pump (1) has a measuring device for measuring a distance between the piston position (26) of the piston (4) and the reversal point (24, 25) lying opposite to the direction of movement of the piston (4), the control device being set up for this purpose if the value falls below this a specific speed value of the measured piston speed and exceeding a specific distance value of the measured distance to reverse the direction of movement of the piston (4). Double-acting piston pump according to one of Claims 1 to 4, in which the piston pump (1) has a magnet or a plurality of magnets, preferably one or more ring magnets (9), the magnet or the magnets being or can be moved together with the piston (4). where the measuring device for measuring the piston speed has at least one Hall sensor (10) and/or the measuring device for measuring the distance between the piston position (26) of the piston (4) and the reversal point (24, 25) in the direction of movement of the piston (4). ) has at least one Hall sensor (10) and/or the measuring device for measuring the distance between the piston position (26) of the piston (4) and the reversal point (24, 25) opposite to the direction of movement of the piston (4) has at least one Hall sensor (10) having. Double-acting piston pump according to Claim 5, in which the piston pump (1) has at least two Hall sensors (10), preferably four Hall sensors (10), a distance of the piston (4) from the one reversal point (24, 25) to the other reversal point ( 24, 25) regarding the measurement of the piston speed and / or a measurement of Piston position (26) is divided into at least two sections, one of the at least two sensors (10) being assignable to the respective section, in particular for the Hall sensor (10) which can be assigned to the respective section between the magnetic flux density detected by this Hall sensor (10). and the piston position (26) of the piston (4) there is an almost linear relationship when the piston (4) is in the section associated with this Hall sensor (10). Double-acting piston pump according to one of claims 1 to 6, wherein the piston pump (1) is designed as a pneumatically drivable piston pump (1), the control device having an actuatable valve or an actuatable valve arrangement, wherein when the valve or the valve arrangement is actuated, a direction in which pressure is applied of a pneumatic piston (20), the pneumatic piston (20) being operatively connected to the piston (4). Application system for applying a free-flowing medium, in particular a heated adhesive, to a substrate (3), having a double-acting piston pump (1) according to one of Claims 1 to 7 and having a dispensing device (5) for intermittently discharging by means of the double-acting piston pump (1 ) to the dispensing device (5) funded flowable medium.

Images