Abstract:
A device ( 110, 10 ) dispenses dosages of a free-flowing substance from a source unit ( 70 ) containing the substance. The device has a base unit ( 120, 20 ) and a receiving unit ( 130, 30 ), so that the source unit can be set into, and removed from, the receiving unit. An actuator ( 150, 50 ) generates repeated bidirectional pivoting movements of the receiving unit about the base unit. A connector unit ( 140, 40 ), arranged between the base unit and the receiving unit, pivotally supports the receiving unit, providing rotational mobility about a pivoting axis. The connector unit is slidably supported with translatory mobility relative to the base unit. The actuator generates repeated bidirectional translatory movements of the base unit. In this way, the receiving unit is subjected to repeated bidirectional pivoting movements and, superimposed on the latter, repeated bidirectional translatory movements.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is entitled to benefit of a right of priority under 35 USC §119 from European patent application EP 11164771.5, which was filed on 4 May 2011, the content of which is incorporated by reference as if fully recited herein. 
     TECHNICAL FIELD 
     The disclosed embodiments relate to a dosage-dispensing device for dosage material in powder form, specifically a dosage-dispensing device that includes a holder device with the capability to loosen the dosage material which is contained in a dosage-dispensing unit. 
     BACKGROUND OF THE ART 
     Dosage-dispensing devices for material in powder form are used in particular to dispense small quantities of a substance into small target containers with a high degree of precision. In many cases, the target containers are placed on a balance in order to weigh the dosage material delivered by the dosage-dispensing device, so that it can subsequently be further processed according to a given purpose. 
     The dosage material to be dispensed is contained for example in a dosage-dispensing unit which includes a source container and a dispensing head. It is desirable to dispense the dosage material through a narrow discharge orifice of the dosage-dispensing unit, so that it can be filled in a targeted stream even into a container with a small opening diameter. 
     Ideally, dosage material in powder form flows, propelled by gravity, in a uniform stream out of a small discharge orifice, comparable to the sand flowing in an hourglass. In this ideal case, the flow of the dosage material could be controlled simply by varying the aperture cross-section of the discharge orifice with a suitable shutter device. Unfortunately, most of the materials used in practice don&#39;t behave according to the ideal case. Many of the particles that make up the dosage material are not conforming to an ideal flow behavior. It is often observed that particles clot together during the dispensing process, with the consequence that the dosage-dispensing unit becomes clogged up. Only by mechanical intervention can the clogging be removed, so that the dispensing process can be continued. 
     In addition, many powders are compressible, leading to the formation of clumps of compacted powder which can clog the discharge orifice partially or completely. A typical example is cornstarch, which exhibits a strong tendency of the powder particles to stick together. In addition, cornstarch is very compressible. In view of these properties, cornstarch is often used as a sample material to test the performance of dosage-dispensing devices. The problems which are caused by the sticking-together and the compressibility of a dosage material, also referred to as “stickiness” of a dosage material, have led to numerous proposals for a solution and for designs of dosage-dispensing devices, specifically their dispensing heads. There are dispensing heads, for example, which have conveyor screws designed to move the sticky dosage material from the source container to the discharge orifice of the dispensing head. The state of the art further includes stirring and scraping devices which scrape the dosage material from the interior walls of the source container and propel it towards the dispensing orifice. The stirring devices also have the purpose to prevent the formation of so-called bridges of the dosage material in the source container. Instead of, or in combination with, a stirring device, there are also tapping and vibrating devices among the known state-of-the-art solutions. 
     A possible way to solve the aforementioned problems is disclosed in US published application 2006/0011653 A1. A dosage-dispensing device designed to dispense dosage material in powder form in quantities from a few milligrams to a few grams with a weight tolerance of less than ±5% of the target weight includes a dosage-dispensing unit which is in essence composed of a source container and a dispensing head. From the part that connects to the source container, the inside wall of the dispensing head is conically tapered towards a discharge orifice. In the operating state, the discharge orifice is at the bottom of the dosage-dispensing unit and thus below the source container. Propelled by gravity, free-flowing dosage material inside the dosage-dispensing unit flows towards the discharge orifice. The latter is equipped with a shutter valve which serves to regulate the outflow of dosage material. The dosage-dispensing device includes means for vibrating and/or tapping the source container and can further include a stirrer device capable of rotary motion about, as well as linear motion along, its axis of rotation. 
     In tests with cornstarch, severe difficulties were encountered in the attempts to dispense the material out of differently designed dosage-dispensing units. The free-flow ability of this kind of dosage material depends directly on how loosely it is aggregated, i.e. by its bulk density. In some tests it was found that the dosage material was compacted, instead of loosened up, by the use of a stirrer device and/or a vibrating means. This had the result that, even with the discharge orifice fully opened, no dosage material could be moved out of the dosage-dispensing unit. 
     A solution for this problem is disclosed in EP 1959244 A1. The dosage-dispensing device disclosed there includes a holder device and at least one receiving device. The receiving device is designed so that at least one dosage-dispensing unit can be removably seated in it. The dosage-dispensing device further includes at least one actuator to agitate the receiving device. The receiving device is pivotally supported on the holder device, so that the actuator can impart oscillating swivel movements to the receiving device. The actuator performs this function by directing a short sequence of several tapping strikes at the receiving device, causing the latter to swing like a pendulum. The pendulum frequency of the receiving device is preferably out of step with the impact frequency of the actuator. This has the effect that the shock waves or mechanical pulses generated by the strikes are propagating in different directions. This counteracts the tendency of the dosage material to clump together. Nevertheless, there may still be some clumping of the dosage material in isolated instances. The known state of the art includes moving components, for example stirrers or scrapers, which are arranged in the dosage-dispensing unit and serve to counteract the clotting of the dosage material. These movable components require a complex mechanism and are prone to wear out. In addition, the additional movable parts can cause damage in particular to delicate dosage materials. 
     It is therefore an objective to provide a dosage-dispensing device which has the capability to condition the dosage material in the dosage-dispensing unit prior to the dispensing process and for the dispensing process, specifically to loosen up the dosage material and to thereby counteract the clogging of the dosage-dispensing unit, but wherein no movable parts are arranged in the interior of the dosage-dispensing unit. 
     SUMMARY 
     This task is solved with a dosage-dispensing device having the features set forth in the independent patent claim. 
     The dosage-dispensing device, which serves to dispense measured quantities of free-flowing substances, includes a base unit, at least one receiving unit and at least one actuator. The receiving unit is designed so that at least one dosage-dispensing unit can be set into, as well as removed from, the receiving unit. The actuator acts on the at least one receiving unit, which is pivotally mounted with rotational mobility relative to the base unit, wherein the actuator has the capability to generate repeated bidirectional pivoting movements of the receiving unit. The arrangement includes at least one connector unit between the base unit and the receiving unit, wherein the receiving unit is pivotally supported on the connector unit with rotational mobility about a pivoting axis, wherein the connector unit is slidably supported with translatory mobility relative to the base unit, and wherein the actuator has the capability to generate repeated bidirectional translatory movements of the connector unit, whereby the receiving unit can be subjected to repeated bidirectional pivoting movements and, superimposed on the latter, repeated bidirectional translatory movements. 
     The free-flowing substances that are to be dispensed normally come in the form powders and granular bulk solids. However, the dosage-dispensing device can also be used to dispense pastes or other substances that are capable of moving in a flow. In particular, this includes materials with complex rheological properties that are prone to clog up in the dispensing process. 
     The superposition of a pivoting movement and a translatory movement agitates the structure of the dosage material with a composite oscillatory movement, whereby the dosage material is propelled towards the dispensing orifice. The flow behavior can be controlled through the intensity of the pulses and the frequency of the pivoting movement and/or the translatory movement. 
     In a preferred embodiment, the oscillating pivoting movements of the receiving unit and the oscillating translatory movements can be generated by means of the same actuator. This embodiment has the advantage that both the translatory movement and the pivoting movement can be generated with only one actuator and thus with only one motor. 
     An arrangement in which the pivoting movement and the translatory movement are generated simultaneously is realized advantageously with a concept wherein the oscillating or repeated bidirectional pivoting movement of the receiving unit can be generated by the actuator, and wherein the oscillating or repeated bidirectional translatory movement of the connector unit can be generated by means of the oscillating or repeated bidirectional pivoting movement of the receiving unit. 
     As an alternative, the dosage-dispensing device could also have more than one actuator, in particular two actuators, wherein the pivoting movement of the receiving unit can be generated by means of a first actuator, and the translatory movement of the connector unit can be generated by a second actuator. 
     A preferred embodiment includes the capability to synchronize the frequency of the repeated bidirectional pivoting movements of the receiving unit with the frequency of the repeated bidirectional translatory movements of the connector unit. There are different ways to achieve this synchronization. One possibility is to mechanically couple the participating components. In such an arrangement, the bidirectional pivoting movement of the receiving unit and the repeated bidirectional translatory movement of the connector unit are, for example, driven simultaneously by a single actuator. It is also possible to couple the bidirectional pivoting movement of the receiving unit to the repeated bidirectional translatory movement of the connector unit. 
     If more than one actuator is used, the synchronization of the bidirectional pivoting movement of the receiving unit with the bidirectional translatory movement of the connector unit can be achieved by means of an electronic control device. However, it is also possible to operate the actuators asynchronously. The superposition of asynchronous frequencies produces a beat frequency oscillation which, depending on the properties of the dosage material, counteracts the clotting tendency of the dosage material. 
     In the operating position of the dosage-dispensing device, the connector unit is preferably supported with vertical mobility relative to the base unit. To satisfy this condition, it can also be sufficient if the direction of movement of the connector unit relative to the operating position of the dosage-dispensing device has a horizontal as well as a vertical component. Ideally in this case, the vertical component is larger than the horizontal component of the movement vector. This ensures that the receiving unit is subjected to an up- and down movement, whereby the dosage material contained in the dosage-dispensing unit is likewise subjected to an up- and down movement and, as a result, the dosage material is loosened up and separated from the walls. 
     Preferably, when the dosage-dispensing device is in its operating position, the orientation of the pivot axis is essentially horizontal. Ideally, with the dosage-dispensing device in operating position, the outlet orifice of the dosage-dispensing unit moves in an arc of primarily constant radius about the pivot axis. This imparts a swiveling movement to the dosage material approaching the outlet opening, whereby the flow movement is improved. 
     Ideally, the base unit is connected to the receiving unit by means of an articulated joint, for example a rotary bearing or a ball joint. 
     Preferably, the connector unit is connected to the base unit by means of at least one linear bearing. 
     In the operating position of the dosage-dispensing device, the base unit is in essence rigidly connected. Thus, the base unit provides a stable support for the connector unit. 
     Ideally, the receiving unit and the connector unit are coupled to each other by means of a pre-tensioned spring element. This allows a movement of the receiving unit to be passed on to the connector unit. The spring element can further exert a damping effect in the transfer of the movement. 
     In a preferred embodiment, the actuator includes a hammer mass designed to be propelled by an impact spring, wherein the latter can be cocked with a tensioning mechanism and instantaneously released, so that the hammer mass is accelerated by the impact spring and the impact of the hammer mass on the receiving unit and/or on parts connected to the receiving unit and/or on the connector unit and/or on parts connected to the connector unit generates a shock wave in the receiving device. The resultant shock waves counteract the clotting tendency of the dosage material. 
     Of course, it is also possible to use other actuators such as for example piezo- or ultrasonic actuators. 
     With a suitable choice of the spring elements and impact springs, the time sequence and velocity of the movements can be influenced, whereby the flow of the dosage material towards the dispensing orifice can be optimized. 
     All of the guide elements can include rolling elements. They can further include elastomeric materials and/or elastically flexible elements such as for example leaf springs, or flexure elements consisting of a metal and/or a polymer. 
     With the installation of additional features in the source container, the clotting tendency of the dosage material can be reduced further. Installations at the access to the dispensing orifice have been found to be particularly advantageous. These installed features can have the most diverse shapes. The underlying idea for the use of these installed features is to make the pressure distribution in the dosage material upstream of the dispensing orifice as uniform as possible, because a clumping-together of the dosage-material is to be expected especially in those regions where the material is subjected to large pressure- and/or velocity gradients. The installation can have the shape of simple sheet-metal elements. It is also conceivable to use more complex shapes. An installation of conical elements proved to be effective against the clogging of the dosage material. In operating position, the apex of the cone is directed in essence against the flow direction of the dosage material. The dosage material streams over the cone, more specifically its lateral surface, from the apex. After flowing around the cone or its lateral surface, the stream of dosage material closes up again. The measure of directing the flow around the cone, more specifically its lateral surface, is very effective in reducing large pressure- and/or velocity gradients, whereby a more uniform pressure- and or velocity distribution is achieved. 
     Likewise, displacement bodies with streamlined shapes of the kind that are used for example in silos are an effective means to achieve a more uniform pressure- and/or velocity distribution. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The dosage-dispensing unit is hereinafter explained through examples and with references to the drawings, wherein: 
         FIG. 1  is a sectional view of a first embodiment dosage-dispensing device in neutral position with one actuator; and 
         FIG. 2  is a sectional view of a second embodiment dosage-dispensing device in neutral position with two actuators. 
     
    
    
     DETAILED DESCRIPTION 
     In  FIG. 1 , a first dosage-dispensing device  10  with an actuator  50  is shown in neutral position in a sectional view. A second dosage-dispensing device  110  in neutral position with two actuators  150 ,  160  is shown in a sectional view in  FIG. 2 . 
     Each of the two dosage-dispensing devices  10 ,  110  has a base unit  20 ,  120 , a receiving unit  30 ,  130 , and a connector unit  40 ,  140 . The base unit  20 ,  120  serves to fasten and to support the further units. The base unit  20 ,  120  is in most cases immovably mounted and essentially rigid. The base unit  20 ,  120  can be, for example, rigidly connected to the housing or to the ground below. It is also possible that the base unit  20 ,  120  is part of the housing. The receiving unit  30 ,  130  serves to hold a source unit  70 . The source unit  70  includes a source container  72  and a dispensing head  71 . The source container  72  serves to hold the dosage material. In the operating position of the dosage-dispensing device  10 ,  110 , the dosage material is located above the dispensing head  71 . The dispensing head  71  is designed to open and close and serves to control the outflow of dosage material from the source container  72 . The opening and closing of the dispensing head  71  is controlled by means of a controller (not shown in the drawing). When the dispensing head  71  is open the dosage material flows out of the source container  72  under the force of gravity. The source unit  70  can be set into, and taken out of, the receiving unit  30 ,  130 . Normally, the source container  72  is essentially cylindrical, and the receiving unit  30 ,  130  has a round opening as a seat for the source container  72 . Of course, one could also choose any other shape as long as it provides a compatible seat for the source container  72  in the receiving unit  30 ,  130 . In particular, it would also be possible to arrange intermediate elements between the receiving unit  30 ,  130  and the source unit  70 . 
     The source unit  70  is held in place in the receiving unit  30 ,  130  by means of a holder  80 ,  180 . The holder  80 ,  180  is resiliently attached to a holder base  90 ,  190  by means of a pre-tensioned spring element  23 ,  123  and by way of two hinges  82 ,  83 ,  182 ,  183 . A centering pin  94 ,  194  of the holder base  90 ,  190  cooperating with a perforation  81 ,  181  of the holder  80 ,  180  allows the latter to be held in a defined position relative to the holder base  90 ,  190 . The elastic force of the spring element  23 ,  123  pushes the source container  70  into the receiving unit  30 ,  130  against the force of gravity. The holder base  90 ,  190  is secured to the base unit  20 ,  120 . The holder base  90 ,  190  can take at least two positions. In the operating position, the holder  80 ,  180  which is fastened to the holder base  90 ,  190  retains the source unit  70  in the receiving unit  30 ,  130 . In the loading position, the holder  80 ,  180  is moved away from the receiving unit  30 ,  130  to clear the space so that the source unit  70  can be set into, or removed from, the receiving unit  30 ,  130 . In the operating position of the dosage-dispensing device, the holder  80 ,  180  has a substantially horizontal orientation. 
     The holder base  90 ,  190  is connected to the base unit  20 ,  120  by way of a linear bearing  26 ,  126 . The axis of the linear bearing  26 ,  126  has a substantially vertical orientation. By means of a first indent  91 ,  191  of the holder base  90 ,  190  cooperating with a pin  93 ,  193 , the holder base  90 ,  190  can be secured in the operating position. A second indent  92 ,  192  of the holder base  90 ,  190  cooperating with the pin  93 ,  193  allows the holder base  90 ,  190  to be secured in the loading position. Of course, the holder base  90 ,  190  could also be secured in some other way. For example, the holder base  90 ,  190  could be held in place on the base unit by means of a spring detent. 
     The holder base  90 ,  190  does not necessarily have to be connected to the base unit  20 ,  120 . The holder base  90 ,  190  could also be fastened in some other way that allows the holder  90 ,  190  to be switched between an operating position and a loading position. 
     The connector unit  40 ,  140  is attached to the base unit  20 ,  120 . Interposed between the connector unit  40 ,  140  and the base unit  20 ,  120  is a linear bearing  24 ,  124  which allows a vertical displacement of the connector unit  40 ,  140  relative to the base unit  20 ,  120  which is mounted in an essentially fixed position. The range of vertical movement of the connector unit  40 ,  140  is delimited by a recess  25 ,  125  of the base unit  20 ,  120  cooperating with a projection  43 ,  143  of the connector unit  40 ,  140  to form an end stop. Relative to the operating position of the dosage-dispensing device  10 ,  110 , the projection  43 ,  143  has an essentially horizontal orientation. Damper elements  44 ,  144  can be arranged between the projection  43 ,  143  and the end stop recess  25 ,  125 . The damper elements  44 ,  144  can be made of a flexible material such as for example rubber or a polymer. 
     Of course, it is also possible to limit the range of vertical movement in some other way. In particular, there could be an end stop recess arranged in the connector unit  40 ,  140  which would cooperate with a projection of the base unit  20 ,  120 . In principle, any kind of suitable end stop could be chosen. 
     A first spring element  21 ,  121  which is arranged between the base unit  20 ,  120  and the connector unit  40 ,  140  holds the connector unit  40 ,  140  in a predefined neutral position. The first spring element  21 ,  121 , in its predefined neutral position, is pre-tensioned to pull the connector unit  40 ,  140  in the vertical direction, relative to the operating position of the dosage-dispensing device  10 ,  110 , against the flank of the end stop recess  25 ,  125 . 
     The connector unit  40 ,  140  is connected to the receiving unit  30 ,  130 . The connector unit  40 ,  140  and the receiving unit  30 ,  130  are linked together by a pivoting joint  41 ,  141  which allows a pivoting movement of the receiving unit  30 ,  130  relative to the connector unit  40 ,  140 , while the latter is capable of linear movement in an essentially vertical direction. There are also alternative choices for the connector elements that allow the pivoting movement between receiving unit  30 ,  130  and the connector unit  40 ,  140  to take place. The possibilities include in particular radial bearings and crossed flexure pivots. 
     The range of the pivoting movement of the receiving unit  30 ,  130  is delimited by a recess  42 ,  142  of the connector unit  40 ,  140  cooperating with a projection  31 ,  131  of the receiving unit  30 ,  130  to form an end stop. Relative to the operating position of the dosage-dispensing device  10 ,  110 , the projection  31 ,  131  has an essentially horizontal orientation. Damper elements  32 ,  132  can be arranged between the projection  31 ,  131  and the end stop recess  42 ,  142 . 
     Of course, it is also possible to limit the range of the pivoting movement in some other way. In particular, there could be a projection arranged on the connector unit  40 ,  140  which would cooperate with an end stop recess of the receiving unit  30 ,  130 . In principle, any kind of suitable end stop could be chosen. 
     A second spring element  22 ,  122  which is arranged between the connector unit  40 ,  140  and the receiving unit  30 ,  130  holds the receiving unit  30 ,  130  in a predefined neutral position. The second spring element  22 ,  122 , in its predefined neutral position, is pre-tensioned to pull the receiving unit  30 ,  130  in the vertical direction, relative to the operating position of the dosage-dispensing device  10 ,  110 , against the flank of the end stop recess  42 ,  142 . 
     Due to the rotational mobility of the receiving unit  30 ,  130 , the source unit  70 ,  170  which is seated in the receiving unit  30 ,  130  can be subjected to a pivoting movement which promotes the flow of the dosage material in the dispensing head. 
     Due to the axial mobility of the connector unit  40 ,  140 , the source unit  70 ,  170  which is seated in the receiving unit  30 ,  130  can be subjected to an up- and down movement which promotes the flow of the dosage material in the dispensing head. 
     As has been found, a combination of pivoting movements and up/down movements promotes the flow of the dosage material in the dispensing head. 
     The pivoting movements and the up/down movements are generated by suitable actuators  50 ,  150 ,  160 . It has been found that pulse-shaped impacts are most effective in counteracting the clogging of the dosage material. In the dosage-dispensing device  10  of  FIG. 1 , a single actuator  50  is employed to generate the pivoting movement and the up/down movement. The actuator  50  serves to deliver shock impacts to the receiving unit  30 . These impacts cause a pivoting movement of the receiving unit  30 . The pivoting movements of the receiving unit  30 , in turn, cause an up- and down movement of the connector unit  40 . 
     In the dosage-dispensing device  110  of  FIG. 2 , two actuators  150 ,  160  are employed to generate the pivoting movement and the up/down movement. The actuator  150  serves to deliver shock impacts to the receiving unit  130 . These impacts cause a pivoting movement of the receiving unit  130 . The additional actuator  160  serves to deliver shock impacts to the connector unit  140 . These impacts cause an up- and down movement of the connector unit  140 . 
     Each of the actuators  50 ,  150 ,  160  of the two embodiments includes a drive unit  51 ,  151 ,  161 . The drive unit  51 ,  151 ,  161  can for example be an electric motor. The drive unit  51 ,  151 ,  161  drives a translatory-motion mechanism  54 ,  154 ,  164  which converts the rotary movement of the motor into a linear movement. The translatory-motion mechanism  54 ,  154 ,  164  can include for example an eccentric, a cam shaft, a crown gear and/or a curve follower mechanism. Good results were achieved with a cam shaft with ramp-shaped cams, which showed the capability to produce rapid pulse impacts. The translatory-motion mechanism  54 ,  154 ,  164  serves to propel a hammer mass  52 ,  152 ,  162  in a linear movement. The hammer mass  52 ,  152 ,  162  is supported with linear mobility. A bumper  53 ,  153 ,  163  is formed on the hammer mass  52 ,  152 ,  162  in the form of a projection through which a strike can be directed at the receiving unit  30 ,  130  and/or at the connector unit  40 ,  140 . In order to impart a pivoting movement to the receiving unit  30 ,  130 , the strike has to occur in the axial direction relative to the pivoting joint  41 ,  141 . The larger the distance of the strike from the pivoting joint  41 ,  141 , the stronger will be the lever effect. The impact pulse can be made even stronger with the addition of an impact spring  55 ,  155 ,  165 . The impact spring  55 ,  155 ,  165  can be cocked with a tensioning mechanism and instantaneously released. After it has been released, the hammer mass  52 ,  152 ,  162  is accelerated by the impact spring  55 ,  155 ,  165  and the impact of the hammer mass  52 ,  152 ,  162  on the receiving unit  30 ,  130  and/or on the connector unit  40 ,  140  generates a shock wave in the receiving device. This shock wave counteracts the clotting tendency of the dosage material in the source unit  70 . 
     While the invention has been described through the presentation of a specific embodiment, it is considered self-evident that numerous further variant embodiments could be created based on the teachings of the present invention.