Patent Publication Number: US-2016230750-A1

Title: Delivery device for discharging a fluid to a fluid line

Description:
The invention relates to a delivery device having a delivery piston displaceable in a pump chamber by means of an actuation device, which in one delivery direction removes fluid from a fluid line in a pressure-reducing manner and, in another, preferably opposite delivery direction, discharges fluid to another fluid line in a pressure-increasing manner. 
     Delivery devices of this type are prior art and are used in a wide variety of fields for the hydrostatic delivery of liquids. Such delivery devices, in the form of piston delivery pumps, which are actuatable by means of solenoids, are frequently used in electrically-controlled operating systems. In such applications, high demands will be placed on the operating behavior, in particular with respect to the tolerances of the delivery pressure, of the rapid response behavior with high repetition precision and with no hysteresis during periodic operation. 
     In view of this problem, the stated object of the invention is to provide a delivery device of the aforementioned kind, which is distinguished by a particularly favorable operating behavior. 
     This object is achieved according to the invention by a delivery device, which includes the features of claim  1  in its entirety. 
     Accordingly, a substantial distinctive feature of the invention, a valve device is introduced in each of the fluid lines allocated to the pump chamber, which valve device opens in the one delivery device during the pressure-reducing removal process and closes in the other delivery device and, in the opposite case, closes in the one delivery device and opens in the other delivery device. A high response precision and repetition precision can be achieved thereby, without hysteresis. 
     In preferred exemplary embodiments, the respective valve device is formed by check valves, the opening directions of which both point in a fluid delivery direction provided in the allocated fluid line. 
     The arrangement is obtained in a particularly advantageous manner, such that the respective fluid lines, calculated from the pump chamber to the respective check valve allocatable to said fluid line, have one and the same line segment with the same flow-through cross section. In this way, a particularly high repetition precision may be achieved without hysteresis. 
     The open cross section of the pump chamber in this case is advantageously the same as or smaller than the open cross section of the respectively connected line segments, relative to this connection area. Such a conformation of cross sectional sizes is advantageous with respect to repetition precision, in particular in the case of low delivery flows and high delivery pressure. 
     The arrangement may be obtained in a particularly advantageous manner, such that the respective fluid line is a component of a collective fluid delivery line system, into which the pump chamber with its integrated delivery piston is connected. 
     For high repetition precision during periodic operation and low delivery flows, the delivery piston has a needle-like extension, wherein the needle-like extension engages as a displacement element in the pump chamber, into which the free ends of the respective fluid lines open. 
     The actuation device is formed in a particularly advantageous manner by an energizable actuating magnet which, in its one currentless or other energized actuation state, moves the delivery piston into its pressure-reducing or pressure-increasing displaced position. 
     In particularly advantageous exemplary embodiments of the invention, the piston delivery pump, consisting of the delivery piston and the pump chamber, is provided with a pressure limiting device such that in the event of an undesired pressure increase in the fluid delivery line system, the pressure inside the pump chamber is limited to a predefinable maximum pressure value. The pressure limiting device integrated in the piston pump eliminates the necessity of providing other pressure limiting devices, such as pressure limiting valves. Furthermore, the disadvantages arising when attempting to limit the pressure by exploiting the lifting force characteristic of the magnetic actuation device are avoided. The resulting potential deviations in the intended electrical energy supply lead to disadvantages with respect to response precision, hysteresis and repetition precision. 
     To form the pressure limiting device, the delivery piston, assisted by an energy storage device, in particular in the form of a compression spring, may be advantageously movable into a resetting area which enlarges the holding volume of the pump chamber when the corresponding fluid pressure is present in the fluid delivery line system. 
     In particularly advantageous exemplary embodiments, an arrangement is advantageously obtained in this case, in which another energy storage device, in particular in the form of another compression spring, permanently acts on the delivery piston, which compression spring seeks to move the delivery piston into a delivery area that reduces the volume of the pump chamber. In this way, the pressure limiting is independent of the energy supply of the actuating magnet, and instead, is defined according to the characteristic of the two compression springs engaging the delivery piston. 
    
    
     
       The invention is explained in detail below with reference to an exemplary embodiment depicted in the drawings, in which: 
         FIG. 1  shows a schematic, highly simplified depiction in the form of a longitudinal section of an exemplary embodiment of the delivery device according to the invention; 
         FIG. 2  shows a longitudinal section of the exemplary embodiment, wherein the magnetic housing of the electromagnetic actuation device is omitted and the operating state of the currentless actuating magnet is depicted; 
         FIG. 3  shows a longitudinal section corresponding to  FIG. 2 , wherein the operating state of the energized actuating magnet is depicted, and 
         FIG. 4  shows a longitudinal section corresponding to  FIGS. 2 and 3 , wherein the operating state of the energized actuating magnet is depicted during active pressure limitation. 
     
    
    
     In  FIG. 1 , a pump housing is identified by “ 1 ” and an actuating magnet provided as an electric actuation device is identified by “ 3 ”. The pump housing  1  has a bore  5 , at the end of which, located to the right in  FIG. 1 , an inner thread  7  is formed. The actuating magnet  3  is attached to the pump housing  1  by securely screwing an extension  9  of its pole piece  11  with the inner thread  7  of the bore. The actuating magnet  3  includes a coil winding  15  inside its magnetic housing  13 , which surrounds parts of the pole piece  11  and a pole tube  17  in the manner customary in such actuating magnets  3 , in which a magnetic armature  19  is axially movable, to which an actuating plunger, coaxial to the longitudinal axis of the bore  5 , is securely attached. 
     The free end of the actuating plunger  21  abuts a pressure body  23 , on which one end of a compression spring  25  is supported, the other end of which abuts an actuating part  26  of the pump delivery piston  27 , the actuating part  26  of which is axially displaceable in the bore  5 . The end of the delivery piston  27  facing away from the actuating part  26  includes a needle-like extension  29 , which engages as the actual displacement part of the delivery piston  27  in a pump chamber  31 , which is formed in the housing  1  as a continuation, severely reduced in diameter, of the bore  5 . Another compression spring  33 , which surrounds the delivery piston  27  between the actuating part  26  and the step  28  formed in the bore  5  at the transition to the pump chamber  31 , is inserted between this step  28  and the actuating part  26 . 
     As indicated merely symbolically in  FIG. 1 , the pump chamber  31  is allocated fluid lines, of which a first fluid line, from which the delivery piston  27  removes fluid in a pressure-reducing manner during operation, is identified by the numeral  35 . A fluid line in which the delivery piston  27  discharges fluid in a pressure-increasing manner during operation, is identified in  FIG. 1  by the numeral  37 . The fluid lines  35 ,  37  are allocated a valve device, which is formed in each case by a check valve in the first fluid line  35  and in the second fluid line  37 , wherein the check valve of the first fluid line  35  is identified by the numeral  39  and opens during the pressure-reducing removal process. The check valve located in the second fluid line  37 , identified by the numeral  41  opens during the pressure-increasing discharge process. The fluid lines  35 ,  37  have a collective delivery line system, into which the pump chamber  31  is integrated, namely, a first line segment  43  extending from the check valve  39  of the first fluid line  35  to the pump chamber  31 , and a second line segment  45 , which extends from the pump chamber  31  to the check valve  41  of the second fluid line  37 . Both line segments  43 ,  45 , as segments of the collective delivery line system, have the same flow-through cross section and the same line length. 
       FIGS. 2 through 4 , in which the magnetic housing  13  and the winding  15  are omitted from the actuating magnet  3 , show further details of the structural configuration of the piston delivery pump.  FIG. 2  shows the operating state of the currentless actuating magnet  3 , in which the armature  19  of the actuating magnet  3 , formed as a so-called repelling magnet, is situated in its end position located below in  FIG. 2 . Absent magnetic force, the armature  19  assumes this end position due to the force exerted on the actuating plunger  31  by an energy storage device. This energy storage device is formed by the compression springs  33  and  25 , as previously explained with reference to  FIG. 1 . Of these, the compression spring  33  surrounding the delivery piston  27  as a coil spring tensions the delivery piston  27  in the displacement direction, which increases the volume of the pump chamber  31  and holds the actuating part  26  of the delivery piston  27  in abutment against a sleeve  47  slidable in the bore  5 , which forms a kind of spring housing for the other compression spring  25 . The return force exerted by the compression spring  33  on the sleeve  47  and, therefore, on the other compression spring  25 , acts on the plunger  21  via the compression body  23  and, therefore on the magnet armature  19 . In this currentless operating state, the needle-like extension  29  of the delivery piston  27  is situated in a position in which the volume of the pump chamber  31  is at its greatest, as shown in  FIG. 2 . 
       FIG. 3  shows the operating state when the actuating magnet  3  is energized with energized actuating magnet  3 , wherein the magnetic armature  19  has moved out of its end position (upward in  FIG. 3 ). This sliding movement, which the plunger  21  transfers to the compression body  23 , acts on the sleeve  47  via the compression spring  25  abutting the compression body  23  and, therefore, on the actuating part  26  of the delivery piston  27 . As a result of the displacement force exerted by the compression spring  25 , the delivery piston is pushed into the end position shown in  FIG. 3 , in which the delivery piston  27  is moved into the end position abutting the shoulder  28 , in which the extension  29  serving as a displacement part forces the fluid out of the pump chamber  31  into the line segments  43 ,  45  (in this piston position, the pump chamber  31  itself is no longer visible in  FIG. 3 , rather only the junction of the line segments  43 ,  45 ). This displacement movement of the delivery piston  27  takes place against the spring force of the compression spring  33 . 
       FIG. 4  shows an operating state, in which the actuating magnet  3  is again energized, so that the magnetic armature  19  has moved out of the retracted end position (upward in  FIG. 4 ). Unlike in  FIG. 3 , however, the delivery piston  27  is situated not in its end position, in which the volume of the pump chamber  31  is fully displaced, but rather, has returned to a pressure-relieving position as a result of the delivery pressure currently active at the junction  43 ,  45  of the pump chamber  31 , despite the magnetic piston  19  having moved from its end position. This equalizing movement, preventing a setpoint value of the delivery pressure from being exceeded, begins if the pressure force acting on the extension  29  in combination with the spring force of compression spring  33  exceeds the action of the other pressure spring  25 . In other words, the pressure threshold, at which the pressure-limiting return movement of the delivery piston  27  begins, is adjustable as a result of the spring characteristic of the compression springs  33 ,  25 . Since the pressure limitation is therefore mechanically determined and not a function of the magnetic force of the actuation device, it is possible to achieve a pressure-resistant delivery with high periodic repetition precision and with no hysteresis.