The invention relates to a closed loop fluid buffer for stabilizing an output pressure of a fluid supply system, in particular a bi-component mixing system. The invention further relates to a bi-component mixing system for use with a dispenser, a dispensing system comprising a bi-component mixing system, a bi-component mixing system mounted for movement with a dispenser and a method for dispensing a fluid.
Fluid supply systems, in particular bi-component mixing systems are widely used in industrial applications to dispense a fluid for example an adhesive on a substrate. Such substrates can include but are not limited to paper, cardboards, non-woven materials, electrical components and the like. In these applications it is often crucial to dispense a predetermined amount of fluid in an accurate way.
The objective of the invention is to provide a closed loop fluid buffer, a bi-component mixing system, a dispensing system and a method of the aforementioned types which are able to supply an improved fluid flow, in particular a stabilized fluid flow with stabilized output pressure and a bi-component mixing system mounted for movement with a dispenser.
According to a first aspect of the invention a closed loop fluid buffer for stabilizing an output pressure of a fluid supply system, in particular a bi-component mixing system is provided, comprising a fluid cavity having a fluid cavity volume and a fluid cavity wall, said fluid cavity having an inlet and an outlet, wherein said inlet is adapted to be in fluid communication with at least one fluid reservoir and said outlet is adapted to be in fluid communication with a dispensing applicator, wherein said fluid cavity wall comprises at least one flexible buffering portion to allow a volume change of the fluid cavity volume. Preferably the volume change of the fluid cavity volume acts to compensate fluctuations in an input pressure and/or flow through the buffer cavity. Further, the volume change of the fluid cavity volume acts preferably to provide a substantially constant output pressure at or immediately downstream of the outlet of the buffer cavity. The closed loop fluid buffer preferably is adapted to keep the output pressure constant, virtually independent of the flow.
In normal operation, the inlet and outlet flows to and from the fluid cavity should be equal. Also the pressure at the inlet and the outlet should be constant, aside from a normal pressure drop over the flow length of the fluid buffer cavity. However it may happen that fluctuations in an input flow to the fluid cavity occur for example due to an upstream mixing process of a two-component system. Further, also fluctuations in a consumption of a downstream dispensing applicator may occur based on variations in an application pattern. When for example an input flow at the inlet into the fluid cavity is higher than an output flow out of the outlet of the fluid cavity the flexible buffering portion allows the fluid cavity volume to increase accordingly. In the contrary case, where a fluid flow at the inlet into the fluid cavity is lower than an output flow out of the outlet of the fluid cavity, the flexible buffering portion allows the fluid cavity volume to decrease accordingly. This leads to an improved and stabilized output pressure and to a better dispensing and application quality.
The term bi-component is used herein to refer to plural component materials which are formed from two or more complements that are mixed together and when mixed are normally reactive to form a quick setting adhesive material or other type material. Thus, as described below, two pumps, each connected to a syringe of material to profits will be used to supply the two materials to a mixer which mixes the two materials together. If material were a three component material, for example, then three pumps would be used, with each connected to a syringe, or other source of the supply for the component material.
According to a first preferred embodiment the closed loop fluid buffer further comprises a rigid housing, said housing partially forming said fluid cavity wall, wherein said housing comprises a recess which cooperates with said flexible buffering portion such that said flexible buffering portion can expand into said recess in order to provide said volume change of the fluid cavity volume. Thus, the flexible buffering portion of the fluid cavity wall is arranged concurrent with the recess in the rigid housing, so that the recess provides a space allowing the flexible buffering portion to expand into this space. Therefore, when the fluid flow at the inlet increases and thus a pressure inside the fluid cavity increases, the flexible buffering portion expands into the recess of the housing thus increasing the fluid cavity volume and at the same time balancing the pressure inside the fluid cavity, while preventing an upstream dispenser or a nozzle from experiencing an excess pressure or fluid flow, which could cause damage such as compromising seals in the dispenser, for example.
According to a further preferred embodiment said recess is sealed from said fluid cavity by means of said flexible buffering portion so that said recess and said flexible buffering portion define a working chamber inside the housing. Thus, all the supplied fluid may be kept inside the fluid cavity and cannot escape into the recess or into the working chamber.
According to a particular preferred embodiment the flexible buffering portion is formed by a flexible tube arranged in said housing and forming at least partially said fluid cavity wall. Preferably the flexible tube completely forms the fluid cavity wall. Preferably the flexible tube comprises an inlet and an outlet, said inlet and outlet of the flexible tube forming said inlet and outlet of the fluid cavity. Preferably, the flexible tube extends completely through said housing. This is a very simple arrangement wherein the flexible tube also may form a part of a fluid conduit system leading from a reservoir to a dispenser or the like. Alternatively, the flexible buffering portion is formed by a flexible membrane, said membrane being fixedly attached to said housing and covering said recess. Thus, according to this embodiment, the fluid cavity is defined by the rigid housing and the membrane. The membrane may be formed as a thin elastic layer, fixed along its circumferential edge to the edge of the recess
According to the above embodiment, it may further be provided that the flexible tube is fixedly attached to said housing, so that only the buffering portion may expand or contract to allow a volume change of the fluid cavity volume. Thus, the flexible tube may on its outer surface be fixedly attached to an inside surface of the rigid housing, only leaving a free portion concurrent with the recess in the housing, which forms the flexible buffering portion of the tube. Preferably the tube is fixed to the rigid housing, in particular by means of adhering the flexible tube to the housing. This provides that also when the fluid cavity volume decreases, only the flexible buffering portion of the tube may expand or contract in direction of the fluid cavity. Alternatively the tube may just be positioned in the housing, in particular in a tight manner, such as pressing. The tube is preferably positioned in the housing so that it can only expand in one direction, the recess.
In a further preferred embodiment of the closed loop fluid buffer the housing comprises a pressure inlet for supplying a pressurized fluid, in particular gas, into said working chamber. The pressure regulator preferably works to keep the pressure inside the working chamber substantially constant. Thus it can be ensured that the pressure at the outlet of the fluid buffer cavity can be kept substantially constant. Preferably the pressure regulator is adapted to supply a pressure to the working chamber which is substantially equal to the overall fluid pressure in the system, as e.g. the pressure the fluid is also pressurized with inside a reservoir or a syringe including the fluid.
Preferably the housing is at least partially transparent. The housing may be formed out of a transparent material such as a transparent polymer material. Further the housing may comprise a window or the like. Thus a person using the closed loop fluid buffer according to the invention is able to watch the fluid buffer working, i.e. expanding and contracting, and may determine if said buffer works correctly.
According to a further preferred embodiment the closed loop fluid buffer comprises a sensor for detecting a volume change of said fluid cavity volume. Such a sensor can be used to determine whether inside the cavity there is enough, too much or too less fluid and thus can be used to either increase or decrease a working speed of a supply pump supplying fluid to the cavity. Such a sensor can be formed as a proximity switch, a distance sensor, a pressure sensor or the like.
Particular preferred is that the sensor is adapted to measure a distance to said flexible buffer portion. Thus, the sensor is adapted to measure a distance between the sensor and/or a portion of the rigid housing to the flexible buffering portion. Since only the flexible buffering portion may expand or swell into the recess or into the direction of the fluid cavity, from a distance between the flexible buffering portion and a portion of the housing the volume of the fluid cavity can be determined and thus the amount of fluid inside the fluid cavity.
According to a preferred alternative said sensor comprises flow sensors arranged at the inlet and the outlet of said fluid buffer cavity. Instead of a flow sensor, a flow meter may be used. In the embodiment where a flow sensor, or flow meter, are positioned at the inlet and at the outlet of the fluid buffer, the difference value between these two sensors indicates the amount of fluid inside the fluid buffer. This difference value can be used for controlling the pumps and mixer, as will later be described.
In a second aspect of the invention, the above objective is solved by a bi-component mixing system for use with a dispenser, comprising a first pump for pumping a first component, said first pump having an inlet and an outlet, the inlet being in fluid communication with a reservoir of the first fluid component; a second pump for pumping a second component, said second pump having an inlet and an outlet, the inlet being in fluid communication with a reservoir of the second component; said outlets of said first and second pumps each being in fluid communication with a mixer for mixing said first and second components, and a closed loop fluid buffer in fluid communication with said mixer, wherein said closed loop fluid buffer is a fluid buffer according to one of the preceding described preferred embodiments of a closed loop fluid buffer.
According to a first preferred embodiment the bi-component mixing system the sensor provides a signal indicating a volume change of the cavity volume of the fluid buffer and the system further comprises a controller receiving the signal provided by said sensor and adapted to control said first and second pumps and/or said mixer based on said signal. Preferably the controller is adapted to control the first and second pumps and/or said mixer in order to keep a substantially constant fluid pressure at the outlet of said fluid buffer and therefore at an inlet of a dispensing applicator. The sensor is formed as described above with reference to a preferred embodiment of the closed loop fluid buffer.
Preferably said closed loop fluid buffer and said controller are adapted to define a flow request triggered fluid supply. The term “flow request triggered fluid supply” is herein understood to mean that the controller adjusts the pumps and/or the mixer based on the fluid request by a dispenser fed by the fluid buffer. For example, when starting the bi-component mixing system, the pumps are switched off after the fluid buffer cavity is filled with fluid to be supplied. At this time the dispenser is idle. When the dispenser starts to dispense e.g. by opening a nozzle, fluid flows out of the dispenser and thus out of the fluid buffer cavity. The sensor detects the decrease in the volume of fluid inside the fluid buffer cavity and provides a signal to the controller indicating this decrease in volume. The controller upon receiving said signal turns on the motors of the pumps and the mixer to supply fluid to the fluid buffer cavity and thus to the dispenser. Such a system is triggered by the flow request from the fluid buffer caused by the dispensing of material from the dispenser so that the fluid buffer together with the sensor and the controller work as a closed loop feedback system. In the preferred embodiment, the mixer is a dynamic mixer having a motor which rotates mixing blades, or helical mixing elements. Generally, as the speed of the motors driving the pumps is increased, the speed of the motor driving the mixer will be correspondingly increased. In another embodiment, the mixer is a static mixer and the mixing blades or helical mixing elements are fixed in position and do not rotate. If a static mixer is used, then the controller would only operate the motors of the pumps to supply materials and would not have any control over the mixer.
According to these embodiments it is preferred that the controller is adapted to control said first and second pumps and/or said mixer so that, when said signal provided by said sensor indicates that the amount of fluid in the fluid cavity is below a predetermined lower threshold, the fluid flow from said mixer to said fluid buffer is increased; and when said signal provided by said sensor indicates that the amount of fluid in the fluid cavity is above a predetermined upper threshold, the fluid flow from said mixer to a said fluid buffer is decreased. Preferably the fluid flow to the fluid buffer is ultimately determined by a downstream dispenser. The bi-component mixing system only has to follow the requested fluid flow.
Additionally, the controller preferably is adapted to stop the fluid flow from said mixer to said fluid buffer, when the signal provided by the sensor indicates that the amount of fluid in the fluid cavity exceeds a second predetermined upper threshold which is higher than the first predetermined upper threshold. This leads to an improvement of the bi-component mixing system, since an excess fluid flow is prevented. An excess fluid flow could occur, for example, if a tube or connection element would fail. Consequently, this function would prevent leakage or spilling of the liquid material being dispensed in that situation.
According a further preferred embodiment the fluid buffer is connectable or connected to a pressure regulator for supplying pressurized gas to the fluid buffer, in particular to the working chamber. The use of the pressurized gas is preferably adapted as described above with reference to the closed loop fluid buffer. The pressure regulator may preferably be part of a dispensing robot or the like. The pressure regulator preferably is also connected to a dispenser for use in such a system. Preferably the pressure regulator is connected to the reservoir of the first component and/or the reservoir of the second component. Thus, the pressure applied to the fluid in the system is constant throughout the active system. The controller may also adjust the pressure regulator. Alternately, the pressure regulator may be controlled by other control elements in the overall system.
As will be described in more detail below one particularly important embodiment of the invention is the use of the fluid buffer described herein with a jetting valve. In that the fluid buffer is intended to provide constant pressure at its output, and at the input to the jetting valve, it is particularly advantageous when used with a jetting valve because maintaining a constant pressure in the fluid supplied to the jetting valve helps to ensure that consistently sized droplets are jetted from the jetting valve onto the substrate.
According to a third aspect of the invention, the objective stated in the introductory portion is further solved by a dispensing system comprising a x-y-mover, a dispenser mounted on said x-y-mover, and a bi-component mixing system according to one of the preferred embodiments of a bi-component mixing system, described herein above, wherein at least some of the components of said bi-component mixing system is mounted on said x-y-mover and connected to said dispenser so that said dispenser and components of said bi-component mixing system which are mounted on the x-y-mover are movable together as a unit by means of said x-y-mover.
In one preferred embodiment, only the mixer and fluid buffer are mounted for movement with the dispenser, and the controller, reservoirs, e.g. supply syringes and/or pumps are fixed in position. Preferably the dispenser comprises a jetting valve.
In a particularly preferred embodiment of the invention a bi-component mixing system is provided that can be mounted in close coupling to a jetting valve so that the bi-component mixing system and jetting valve can be moved together by an x-y mover over a substrate as the jetting valve dispenses droplets of two component materials, such as adhesives, onto the substrate for the attachment of electrical complements, for example, to the substrate by means of the adhesive.
For applying a fluid, in particular a two component or bi-component fluid on a substrate, the dispenser is moved along a predefined path to dispense a predefined pattern of fluid material, such as droplets of material, on the substrate. In that bi-component materials are generally reactive, meaning that the material will set up or harden very shortly after the components are mixed, it is important that the material be dispensed onto the substrate, or jetted out of the dispenser (for example through the jetting valve) onto the substrate, very quickly after it has been mixed. According to an aspect of this invention, by close coupling at least the mixer and fluid buffer parts of the bi-component mixing system to the dispenser, and moving them together over the substrate, the bi-component material can both be quickly dispensed after being mixed and can be provided to the dispenser, which is preferably a jetting valve, at a consistent pressure so that consistent droplets of the bi-component material can be jetted onto the substrate.
According to a fourth aspect of the invention, the objective stated in the introductory portion above is further solved by a method for dispensing fluid, in particular a bi-component fluid, comprising the steps: dispensing a specific amount of fluid from a dispenser; detecting a change of a fluid amount in a fluid buffer; providing a signal indicating said change of the fluid amount in the fluid buffer to a controller; controlling at least one pump and/or a fluid mixer based on said signal. Preferably the method is carried out by using a bi-component mixing system according to one of the preceding described preferred embodiments of a bi-component mixing system. Preferably the method is carried out by using a closed loop fluid buffer according to at least one of the preceding described preferred embodiments of a closed loop fluid buffer as the fluid buffer.
The method preferably further comprises the steps: controlling said at least one pump and/or said fluid mixer to supply an increased fluid flow when said signal indicates a decrease of the fluid amount in the fluid buffer; and controlling said at least one pump and/or said fluid mixer to supply a decreased fluid flow when said signal indicates an increase of the fluid amount in the fluid buffer. Preferably the steps above are carried out simultaneously and continuously. This method provides a flow request triggered closed loop system for supplying fluid from a reservoir to a dispenser. In the step “dispensing a specific amount of fluid from a dispenser”, the dispenser places the flow request and the pumps and/or the mixer follow the request by means of the closed loop fluid buffer and the controller. The sensor of the closed loop fluid buffer recognizes when the dispenser starts to dispense, since at that point in time the amount of fluid in the fluid buffer cavity decreases and in answer to this decrease the controller starts the at least one pump and/or the mixer in order to supply fluid. When the dispenser stops dispensing fluid, the amount of fluid inside the fluid cavity increases, which again is detected by the sensor. In answer to this detection, the controller decreases the working speed of the at least one pump and/or the mixer or stops the at least one pump and/or the mixer so that the fluid cavity of the fluid buffer is again filled to a normal level and the output pressure of the fluid buffer may be substantially constant.
In the following the invention is described in more detail with reference to the accompanying drawings:
According to
The housing 2 further includes a recess 16 which is formed as an upper opening (seen with respect to
As further shown in
The flexible buffering portion 18 seals the recess 16 against the fluid cavity 10 and thus defines together with the housing and also the upper shell 20 a working chamber 22. The upper shell 20, which is part of the housing 2, comprises a pressure inlet 24 formed as a bore. As the arrow 25 indicates pressure can be supplied through the pressure inlet 24 into the working chamber 22. The pressure inlet 24 can be provided with a pressure inlet connector (not shown) so that a pressure regulator may be connected to the pressure inlet.
With further reference to
One preferred cantilevered mechanical assembly is shown in
The working principle of the closed loop fluid buffer 1 is shown in greater detail in
In
Contrary to this state with increased volume (
The schematic drawings of the fluid buffer 1 show the movement of the flexible buffering portion 18 quite clearly. However in practice the movement (with respect to h1 and h2) preferably is in the range of h2 lower than 4 mm, 3 mm, 2.5 mm, 2 mm, 1.5 mm in particular 1 mm or 0.5 mm.
In an alternative to the normal position of the flexible buffering portion shown in
A bi-component mixing system 100 (see
The system 100 further comprises a mixer 126, the mixer 126 comprising first and second inlets 128, 129 and one outlet 130. The first inlet 128 is connected via a line 132 to the outlet 110 of the first pump and the second inlet 129 of the mixer 126 is connected via a line 134 to the outlet 114 of the second pump 106.
According to the embodiment of
The bi-component mixing system 100 additionally comprises a controller 146. The controller 146 is electrically connected to the pump 104, the pump 106, the mixer 126 and the closed loop fluid buffer 136, as indicated by the ghost lines 147, 148, 149, 150. Via the connection 150 the controller 146 is connected to a not shown sensor of the closed loop fluid buffer 146. The sensor of the closed loop fluid buffer 146 preferably is the sensor 26 according to
According to the embodiment shown in
At the time point T0 the dispenser is idle (see graph 200) the fluid buffer cavity is filled to a certain degree (cf. normal degree) (see graph 300) and the pumps are stopped (see graph 400). At a time T1 the dispenser opens 202 and thus fluid flows out of the dispenser. Therefore at 301 the amount of fluid in the fluid buffer decreases 302. At the same time when the level of fluid in the buffer cavity decreases 302 the sensor of the fluid buffer 1 (see
At point T3 the dispenser is closed again 204 and in an idle state 206. Thus, since the pumps still supply fluid 404 in the fluid level of the fluid buffer start to rise 304 and increase 305 until it reaches a state 306. The increase 305 of the amount of fluid in the fluid buffer is again detected by the sensor and the pumps are controlled accordingly, thus decreasing 405 the working speed until again a balanced state at point T4 is reached; the fluid buffer is filled 306 and the pumps are stopped 406.
After a certain time at point T5 the dispenser again turns from idle 208 to open 210 and dispenses a fluid flow 210. Again the amount of fluid in the fluid buffer decreases 308 from normal 307 to a specific lower level 309 where in the same time the pumps increase their speed from 407 to 408. Until T7 the amount of fluid in the fluid buffer and the operation speed of the pumps are in the balanced state from 309 to 310 and 408 to 409. At time point T7 the dispenser again turns to idle 212 which again leads to an increase 311 of the amount of fluid in the fluid buffer and on the same time a decrease of the operation speed of the pumps until the pumps are stopped 410 at point T8. The level of fluid in the fluid buffer then is constant from 312 to 313.
At time points T9 and T11 two shorter dispensing cycles of the dispenser start. Thus at T9 and also T11 the dispenser is switched from idle 214, 220 to open 216, 222. At time point T9 thus the amount of fluid in the fluid buffer decreases 314 and on the same time the pumps start to operate and increase the operation speed until time point T10 when the pumps reach the full speed at 412. However, at the same time the dispenser is switched to idle 218 thus the amount of fluid immediately increases 316 again until it reaches point 317 which falls together with time point T11 at which the dispenser again is switched from idle 220 to open 222 thus the amount of fluid decreases 318 again and on the same time the pumps start to operate until 414 when also the dispenser is switched to idle. Subsequently the amount of fluid increases 320 to reach a normal level at 321 when the pumps are stopped 415.
The last two dispensing cycles are even shorter than the dispensing cycles at T9 and T11. At T13 the dispenser again turns from idle 226 to an open state 228. The amount of fluid in the fluid buffer subsequently used to decrease until point 323 (T14) when the dispenser is switched to idle 230 again. Since the time period between T13 and T14 is very short the level at 323 of fluid in the fluid buffer is in an intermediate point from the levels before. Even though the pumps start to speed up from 416 to 417 they do not reach their top speed. This shows that the pumps may be driven continuously and also may be driven at intermediate speeds. The pumps stop then again at point T15, 418 when the fluid amount inside the buffer is at the top level 324. This state is balanced until the dispenser turns from idle 232 to open 234 again when the amount of fluid in the fluid buffer decreases subsequently from 325 to 326 when at the same time the pumps start to supply fluid from 419 to 420 until the dispenser turns to idle 236 again and the fluid amount rises from 326 to 327 and the pumps are stopped from 420 to 421. At time T18 the system is again in a balanced state.
The bi-component mixing system comprises to reservoirs 118, 122, which are both formed as syringes according to this embodiment. The reservoirs 118, 122 are connected to two pumps 104, 106, which are connected to a mixer 126. The mixer 126 is connected to a fluid buffer 136. The fluid buffer 136 is formed as a closed loop fluid buffer as above described with reference to
In one preferred embodiment, the whole bi-component mixing system 100 is mounted via a mounting means 180, which according to this embodiment is formed as a metal retainer, to the x-y-mover 500 for movement with the jetting valve 102. More specifically the bi-component mixing system 100 is mounted to a hoist 502, which is movably mounted on a gantry 504 of the x-y-mover 500. The gantry 504 is movable into an x-direction indicated by the arrow 506. The hoist is movable into a y-direction indicated by arrow 508 relative to the gantry 504. Thus the whole bi-component mixing system 100 is movable as a single unit by means of the x-y-mover 500 into an x- and y-direction.
In another preferred embodiment, only the mixer 126 and fluid buffer 136 of the bi-component mixing system 100 are mounted on the X-Y mover 500 for movement with the jetting valve 102, and some or all of the remaining components of the bi-component mixing system 100 could be fixed in position. For example, the syringes (or other material supplies) as well as the pumps connected to the syringes, could be fixed in position with fluid lines connecting them to the mixer which is moving with the jetting valve. Likewise, the controller could be fixed in position and connected by electrical conductors to the sensor (or flow meters) of the fluid buffer, with the fluid buffer moving with the jetting valve.
For measuring the volume of the buffer the sensor 26 is arranged as already described above with reference to
According to this specific and preferred embodiment the sensor 26 cooperates with a cantilever arrangement 800 which helps the sensor 26 to measure the movement of the flexible buffering portion 18. The cantilever arrangement 800 in general comprises a ferromagnetic part 802 and a contactor 804. Both parts 802, 804 are fixed together. The contactor 804 is in permanent contact with the flexible buffering portion 18 and is moved up and down when the buffer is being filled or emptied. The ferromagnetic part 802 moves in accordance with the contactor and thus travels forth and back in the direction of the sensing portion 27 of the sensor 26. As may be seen from comparing
The functioning principle of the sensor 26 and the cantilever arrangement 800 can be described as follows: As volume of the tube 8 increases, the ferromagnetic part 802 and the contactor 804 are pivoted upwardly and moved closer to the sensor 26. As the ferromagnetic part 802 moves towards and away from the sensor 26, the sensor 26 produces a signal that indicates the distance of the ferromagnetic part 802 and thus the contactor 804 from the sensor 26, and thereby, the expansion of the fluid buffer 1, 136.
Number | Date | Country | Kind |
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13192371.6-1802 | Nov 2013 | EP | regional |
Filing Document | Filing Date | Country | Kind |
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PCT/IB2014/065529 | 10/22/2014 | WO | 00 |