Patent Publication Number: US-11034575-B2

Title: Barrel pump having a follower plate with an adjustable sealing ring

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is the National Stage of PCT/EP2017/070672 filed on Aug. 15, 2017, which claims priority under 35 U.S.C. § 119 of German Application Nos. 10 2016 010 622.0 filed on Sep. 5, 2016 and 10 2017 100 712.1 filed on Jan. 16, 2017, the disclosures of which are incorporated by reference. The international application under PCT article 21(2) was not published in English. 
     The invention relates to a method for conveying viscous material, in accordance with the preamble of claim  1 . 
     In DE 10 2004 030 654 A1, an apparatus is described, which serves for conveying viscous material, in particular adhesives, sealants, insulation materials or heat-conduction pastes, from a barrel to a processing station. Such apparatuses are used, in particular, in the motor vehicle industry, when viscous material must be applied to car body parts. The follower plate, which is affixed to a frame, lies on the surface of the material situated in the container, configured as a barrel, and follows this surface as the material level drops. The material is removed from the barrel by means of a pump, wherein the follower plate is made to follow the material surface. In this regard, it is also possible that the follower plate additionally presses on the material surface, so that the material is pressed into the material outlet due to this pressure. In this regard, the wiper ring lies against the inner surface of the container wall, and for one thing seals the interior of the barrel off from the surroundings. For another thing, it wipes off material adhering to the inner surface of the barrel wall as the follower plate is lowered. Once the barrel has been emptied, it must be replaced with a new, full barrel. For this purpose, the follower plate must be moved upward out of the barrel. In order to be able to move the follower plate upward in the barrel, the interior of the barrel must be ventilated, since otherwise, a vacuum would be formed in the barrel, and this would prevent the follower plate from being moved out. This is achieved, in the case of previously known apparatuses, in that compressed air is introduced into the barrel through a ventilation opening in the follower plate. Since the follower plate has a large surface area, an excess pressure in the barrel exerts a great force on the follower plate. Therefore some effort is required for controlling the upward movement of the follower plate. 
     From DE 201 02 413 U1, a method of the type stated initially is known. In the case of a barrel melting apparatus, a piston acting as a follower plate is introduced into the cylinder space of the barrel and heated, so that it melts material to be conveyed that is situated in the barrel, so that this material can be conveyed out of the barrel. The piston is provided with sealing means that lie against a barrel wall, forming a seal. In order to be able to adapt the piston to barrels having different dimensions, the sealing means can be widened, in particular by means of the introduction of compressed gas. In this regard, it is provided that the sealing means are widened to the desired size before introduction of the piston into the barrel. The sealing means remains at this size until it needs to be adapted to a barrel having a different size. DE 201 02 413 U1 therefore cannot make any contribution to solving the problem that it is difficult to control the upward movement of the follower plate in an emptied barrel. Furthermore, the widened sealing means makes introduction of the follower plate into a new, filled barrel difficult. 
     It is therefore the task of the invention to further develop a method of the type stated initially in such a manner that the follower plate can be more easily removed from the container and/or can be introduced into the container more easily. 
     This task is accomplished, according to the invention, by means of a method having the characteristics of claim  1 . Advantageous further developments of the invention are the object of the dependent claims. 
     The invention is based on the idea of varying the sealing effect of the wiper ring in targeted manner, so as, on the one hand, to achieve a good sealing effect when the barrel or the container is filled with viscous material, at least in part, and to prevent penetration of air into the container, and, on the other hand, to cancel out the sealing effect, in whole or in part, when the follower plate is supposed to be removed from the emptied container or introduced into a new, full container. For this purpose, a contact part of the wiper ring, which projects radially outward and is intended for contact against the inner surface of the container wall, can have a variable press-down force applied to it for pressing it against the inner surface. The press-down force is variable in the sense that it can assume at least two different values, wherein a sealing effect is achieved with the one value, while no sealing effect or only a slight sealing effect is achieved with the other value. Between these extreme values, it is furthermore possible to change the press-down force discretely or continuously. It is not only the sealing effect of the wiper ring that can be varied by means of the variation of the press-down force, according to the invention, with which the contact part is pressed against the inner surface of the container wall. The friction force that occurs between the wiper ring and the container wall can be reduced, so as to remove the follower plate out of the container, by reducing the press-down force, and thereby removal of the follower plate out of the container is further facilitated. 
     It is practical if the follower plate is first introduced into the container before the start of material conveying, and then the contact part is pressed against the inner surface. This facilitates introduction of the follower plate into the container. Preferably, the contact part is only pressed against the inner surface when the follower plate lies on the surface of the material, so that this plate can be moved in the interior of the container almost without friction, until the sealing effect is required. It is advantageous if the follower plate lying on the surface of the material can be detected by means of a sensor, so that the contact part is pressed against the inner surface by means of a control device, on the basis of a signal of the sensor. This allows automation of the introduction of the follower plate into the container, during which the sealing effect is automatically produced at the correct point in time. In this regard, it is possible that the follower plate is moved by means of a lifting device having a spindle drive, and that the sensor detects a change in the torque applied to the spindle of the spindle drive. When the torque increases, the sensor sends a signal to the control device, which device triggers pressing of the contact part against the inner surface. However, it is also possible that the follower plate is suspended on a lifting device and the sensor detects separation of the follower plate from the lifting device. The sensor is then a simple switch, which switches and passes its switching signal on to the control device when the lifting device continues to move downward, but because the follower plate lies on the material, the plate or a rod assembly firmly connected with it is mechanically separated from the lifting device at a contact point. Shutting the downward movement of the lifting device by triggering the switch is also possible. 
     In order to facilitate lifting the follower plate from the bottom of the emptied container, it is practical if compressed air is introduced into a region between the follower plate and the container bottom. This can be done before the sealing effect between the wiper ring and the container wall is cancelled out, so that the excess pressure that occurs in the container already lifts the follower plate somewhat. However, introduction of compressed air into the container can also take place simultaneously with cancellation of the sealing effect between the wiper ring and the container wall. 
     According to an advantageous further development of the invention, a detection device can be present, which detects the type of container and sets the press-down force of the contact part as a function of the type of container. In this way, the fact that different containers can have different stability can be taken into account, so that a great press-down force is not harmful for various containers, but can deform other containers, and this is not desirable. In contrast, it is advantageous to set the press-down force to be as great as possible, in order to achieve a good sealing effect. 
     In order to eliminate the friction force between the wiper ring and the container wall, it can be provided that the contact part can be retracted from the inner side of the container wall by reducing the press-down force. The press-down force is then at zero. The follower plate can then be removed from the container, wherein ideally, the wiper ring does not touch the container wall. 
     Variation of the press-down force can be implemented in different ways. However, it is preferred that the wiper ring is hollow and has an outer wall that encloses a cavity, which runs at least partially circumferentially. It is practical if the outer wall is thicker in the region of its contact part than in its other regions. It is furthermore advantageous to provide an aeration and ventilation device for the wiper ring, with which air can be introduced into the cavity or drained from it. If pressure is applied to the cavity, then the wiper ring expands, and the press-down force with which the contact part is pressed against the container wall is increased. If the outer wall is thicker in the region of the contact part, more material is available there, so that the sealing effect is improved. In a simple and effective embodiment, the contact part can be moved between a sealing position and a release position by means of the aeration and ventilation device, by applying two predetermined different pressures to the cavity. In the sealing position, it lies against the inner surface of the container wall, forming a seal, while in the release position, the sealing effect is cancelled out. 
     The follower plate can have a wiper ring. To improve the sealing and stripping effect, at least one further wiper ring can be provided, in advantageous manner, which ring has the same construction as the wiper ring and is disposed at a distance from and parallel to it. 
     According to an advantageous further development of the invention, a transport device is provided for transporting the container. This transport device is used, in particular, when the lifting device is set up on a building wall, and the follower plate is mounted on a traverse that runs horizontally, by means of at least one holding rod that runs vertically, which traverse is mounted on a lifting device for raising and lowering the traverse, at or close to a first end, while its second end is free and the traverse extends away from the building wall in its longitudinal expanse that runs from the lifting device to the free end. Then it is possible that the transport device transports the container to the follower plate, parallel to the expanse of the building wall, and transports the emptied container away from the follower plate. According to a preferred embodiment, the transport device has a roller track on which the container is set up. Furthermore, it is possible to equip the conveyor apparatus according to the invention with a control device, with which the container is automatically positioned below the follower plate, with which the follower plate is automatically introduced into the container, with which the follower plate is automatically removed from the container after it has been emptied, and with which the emptied container is transported away automatically, by means of the transport device. 
     Most conveyor pumps have a conveyor cylinder and a conveyor piston that can be moved back and forth in the conveyor cylinder. In this regard, it was determined, at the facility of the applicant, that the speed of the conveyor piston during the conveying process can vary as a function of the material consistency. The applicant found, by means of experiments, that the speed of the conveyor piston is constant, at least within a tolerance range, during the conveying stroke, while the material consistency remains the same. If the conveyed material contains air bubbles, this leads to a significant change in the speed of the conveyor piston during the conveying stroke. Based on this recognition, it is proposed, according to an advantageous further development of the invention, to measure the speed of the conveyor piston during the conveying stroke by means of a measurement device, so that in the event of a change in the measured speed, it is possible to conclude that a change in material consistency has occurred, in particular that air bubbles are present, so that corresponding measures can be initiated. In particular, after the emptied container has been replaced with the filled container, material can be conveyed into a waste container by way of a waste line, by means of an automatic controller that can be integrated into the control device already mentioned above, or implemented by means of a separate control unit, until the measured speed of the conveyor piston lies in a predetermined tolerance range around a predetermined reference speed. Also during the further conveying process, the conveyed material can be checked for the presence of air bubbles by means of measuring the speed of the conveyor piston during the conveying stroke. 
    
    
     
       In the following, the invention will be explained in greater detail using an exemplary embodiment shown schematically in the drawing. This shows: 
         FIG. 1  an apparatus for conveying viscous material, having a follower plate, before its introduction into a container, in a schematic sectional view; 
         FIG. 2 a , 2 b    the apparatus according to  FIG. 1  with the follower plate introduced into the container, at the beginning and toward the end of the conveying process; 
         FIG. 3 a , 3 b    the apparatus according to  FIG. 1  with the follower plate situated in the container, in two different positions after the end of the conveying process, and 
         FIG. 4, 5  an apparatus for conveying viscous material in a front view and a top view. 
     
    
    
     The apparatus  10  shown schematically in the drawing serves for conveying viscous material such as adhesive, sealant or insulation material out of a barrel-like container  12 . In this regard, the conveyor apparatus  10  is not shown in all its details, but rather reduced to the components essential for understanding the invention. The container  12  has essentially a cylindrical shape, with a container bottom  14  and a container wall  18  that extends upward from the container bottom  14  up to a container top  16  and runs circumferentially. The container  12  is open to the container top  16 . 
     The conveyor apparatus  10  has a follower plate  20  that is introduced into the container  12  for conveying the material, and lies on the material surface there. The follower plate  20  is disposed on a frame, not shown in  FIG. 1 , and can be moved up and down by means of a lifting apparatus  50 . It has a mandrel  22  in the center, which extends upward from an underside  24  that lies on the material, and opens into a material outlet  26 . The material is conveyed out of the material outlet  26  to the location of use by means of a conveyor pump  40 , by way of a material line. 
     The follower plate  20  has a wiper ring  28  composed of elastically expandable material, in the present case of rubber, which ring runs circumferentially, is configured in tubular manner, with an outer wall  32  enclosing a ring-shaped cavity  30 . The outer wall  32  is thickened in its region that faces outward radially and projects outward, forming a contact part  34 , which is intended for contact against an inner surface  36  of the container wall  18 , forming a seal. If compressed air is applied to the cavity  30  by means of an aeration and ventilation device, not shown, the wiper ring  28  expands and the contact part  34  moves radially outward. If the follower plate  20  is introduced into the container  12 , the contact part  34  is moved into a sealing position in which it is pressed against the inner surface  36  by the force exerted by the compressed air in the cavity  30 , as shown in  FIG. 2 a , 2 b   , and seals the container interior  38 , which is situated below the follower plate  20 , off from the surroundings. 
     Before the start of a conveying process, first a container  12  filled with material is made available. The follower plate  20  is introduced into the container interior  38  from above, through the open container top  16 , wherein the cavity  30  is ventilated, so that the diameter of the wiper ring  28  is smaller than the inside diameter of the container  12  (see  FIG. 1 ). The follower plate  20  is moved downward, until its underside  24  lies on a surface of the material contained in the container  12 . This contact is detected by a sensor that sends a signal to a control device, which triggers introduction of compressed air into the cavity  30 . The wiper ring  28  increases its diameter, so that the contact part  34  is moved into the sealing position. 
     At the start of a conveying process, the follower plate  20  is in the position shown in  FIG. 2 a   , in which its underside  24  lies on the surface of the material in the filled container  12 . The contact part  34  is situated in its sealing position, so that the wiper ring  28  seals the container interior  38  off from the surroundings. If material is conveyed out of the container  12 , the material level drops and the follower plate  20  is moved downward in the container  12 , following the material level, by means of the lifting apparatus, wherein the contact part  34  slides over the inner surface  36 , overcoming a friction force, and wipes off material adhering to this surface. Once the container has been emptied completely, the follower plate  20  is situated on the container bottom  14 , as shown in  FIG. 2 b   , wherein possibly a thin material film is still present between the follower plate  20  and the container bottom  14 . After the container  12  has been emptied, compressed air is introduced into the mandrel  22 , so that the follower plate  20  is lifted off the container bottom  14 . At the same time with introduction of compressed air into the mandrel  22 , or a short time afterward, the force that presses the contact part  34  against the inner surface  36  is taken away by discharging compressed air out of the cavity  30 , so that the contact part  34  withdraws from the inner surface  36 . The contact part  34  is then in a release position, in which the sealing effect between the container interior  38  and the surroundings is cancelled out. The follower plate  20  is then lifted out of the container  12  by means of the lifting apparatus  50 , until it is back in the position shown in  FIG. 1 . The empty container  12  can then be replaced by a new, full container, and the conveying process can begin once again. 
     A conveyor pump  40  firmly connected with the follower plate  20  is connected with the material outlet  26  of the follower plate  20 , which pump serves to convey material out of the container  12  into a conveying line  42  that leads to a processing station, by way of the material outlet  26 . The conveyor pump  40  has a conveyor cylinder  44 , firmly mounted on the follower plate  20 , as well as a conveyor piston, not shown in the drawing, which can move back and forth in the conveyor cylinder  44 , the linear movement of which piston in the conveyor cylinder  44  draws material into the conveyor cylinder  44  through the material outlet  26  and presses the material out of the conveyor cylinder  44  into the conveying line  42 . 
     Since the follower plate  20  can be introduced into the container  12  almost without contact and without exertion of force, due to the variable diameter of the wiper ring  28 , in the event of a container change, a lifting device  50  is provided in the case of the conveyor apparatus  10  according to the invention, on which device a traverse  52  that runs horizontally, in the form of a metal plate is mounted with its first end  54 , while its second end  56  is free. Two holding rods  58  run vertically downward from the traverse  52 , which rods carry the follower plate  20 . The lifting device  50  has a spindle drive, not shown in any detail, which is driven by means of an electric motor, for raising and lowering the traverse  52 . 
     The conveyor apparatus  10  furthermore has a transport device  80 , which has a roller track  82 , with which the container  12  can be transported in a direction perpendicular to the longitudinal expanse of the traverse  52 . In this manner, emptied containers  12  can be transported away from the follower plate  20 , and full containers  12  can be transported under the follower plate  20 . Furthermore, a housing  84  is provided, which encloses the container  12  and the follower plate  20  all around during introduction of the follower plate  20  into the container  12  and during conveying of the material. The housing  84  has two transparent sliding doors  86 ,  88  that are disposed one on top of the other and enclose an interior all around, in each instance, which doors enclose the container  12 , the follower plate  20 , and the conveyor pump  40  during operation, all around, to minimize the risk of injury to operating personnel. In order to have access to the conveyor pump  40 , the upper sliding door  86  can be moved downward, while the lower sliding door  88  can be moved upward, so as to allow a change of container. Furthermore, a control device is provided, with which a filled container  12  is positioned under the follower plate  20  fully automatically, by means of advancement on the roller track  82 , with which device the follower plate  20  is automatically introduced into the container  12 , with which device the follower plate  20  is automatically removed from the container  12  after it is emptied, and with which device the emptied container  12  is automatically transported away by means of the transport device  80 . A sensor  98  detects the correct positioning of the container  12  under the follower plate  20 . 
     The conveyor apparatus  10  furthermore has a measurement device  90 , with which the speed of the conveyor piston during the conveying stroke can be measured. The measurement device  90  has a path measurement unit in the form of an absolute value transducer  92 , the housing of which is mounted in the lifting device  50 . A piston rod  94  firmly connected with the conveyor piston is passed out of the conveyor cylinder  44  upward, and rigidly connected with a movable element of the absolute value transducer  92  by means of connecting rods  96 . The path measurement device  90  furthermore has a control unit, not shown in any detail, which controls conveying of the viscous material as a function of the measured speed of the conveyor piston. The control unit detects when the measured speed of the conveyor piston lies outside of a tolerance range about a predetermined reference speed, which indicates that the consistency of the conveyed material has changed to such an extent that its usability is doubtful. In this case, the control unit switches a valve  100 , so that the conveyed material is conveyed not to the processing station but rather to a waste line  102  that branches off from the conveying line  42  and leads to a waste container  104 . If the control unit detects that the speed of the conveyor piston lies in the tolerance range again, it switches the valve  100  once again, and the viscous material is conveyed to the processing station once again, by way of the conveying line  42 . The measurement device  90  is particularly supposed to prevent material containing air bubbles from being conveyed. It can particularly be used when the follower plate  20  was introduced into a full container  12 , so as to convey material into the waste container  104 , in an automated process, until it no longer contains any air bubbles. However, it can also be used during the conveying process and detect the air bubbles present in the material, and convey the material containing air bubbles into the waste container  104  instead of to the processing station. In  FIG. 5 , the representation of the measurement device  90 , the valve  100 , the waste line  102 , and the waste container  104  was left out for the sake of clarity. 
     In summary, the following should be stated: The invention relates to an apparatus  10  for conveying viscous material out of a barrel-like container  12 , having a container bottom  14  and a circumferential container wall  18  that extends from the container bottom  14  to a container top  16 , which container is open toward the container top  16 , having a follower plate  20  that has a material outlet  26  connected with a conveyor pump, for closing off the container  12 , wherein the follower plate  20  has a wiper ring  28  that runs circumferentially around, and wherein the wiper ring  28  has a contact part  34  that projects radially outward, for contact with an inner surface  36  of the container wall  18 , which surface faces the follower plate  20 . According to the invention, it is provided that the contact part  34  can have a variable contact force applied to it, to press it against the inner surface  36  of the container wall  18 .