Patent Publication Number: US-RE40898-E

Title: Lubricating device for a plurality of lubricating stations

Description:
FIELD OF THE INVENTION 
     The invention relates to a lubricating device for a plurality of lubricating stations, especially for supplying lubricant, preferably oil, to lubricating stations of a knitting machine. 
     BACKGROUND OF THE INVENTION 
     In knitting machines, for instance, the needle drive requires constant lubrication, which is equally true for the needle guide in the needle bed or needle cylinder, and so forth. Yet satisfactory, regular lubrication is extremely important, precisely in modern high-speed knitting machines. The lubricating stations must be reliably supplied with oil. As a rule, failure of the lubrication leads to increased water and early failure of the knitting machine. On the other hand, the lubrication must be done in a thrifty way. It is counterproductive to supply too much oil to the lubricating stations. Such knitting machines are therefore often equipped with so-called pressure oilers or pressure oil lubricating systems, which feed oil under pressure from a central point to the individual lubricating stations via suitable lines. 
     A lubricating device for this purpose, known for instance from European Patent Disclosure EP 0 499 810 B1, permits reliable, metered lubrication of a plurality of lubricating stations. The lubricating device has a lubricant container in which a piston pump is accommodated. The output of the piston pump is connected to a motor-drive distributor valve, so that the pump outlet can be connected to one lubricant line at a time, selected from a group of lubricant lines. 
     It is an object of the invention to create a simplified lubricating device. It is another object of the invention to create an improved method of lubrication. 
     These and other objects are attained in accordance with one aspect of the invention directed to a lubricating device comprising a distributor device with which lubricant furnished by a pump is diverted to selected lines and can thus be delivered to selected lubricating stations. The distributor device and the pump device are combined into one unit. Combining the distributor device and the pump device into a unit makes for a considerably simpler design of the lubricating device. The triggering of the lubricating device can be simplified as well. 
     The pump device is embodied as a piston pump and has a piston that is axially displaceable in a cylinder. Together with the cylinder, this piston serves as a pumping element. The cylinder and the piston are also embodied as a control element. To that end, the piston is rotatably supported in the cylinder and is provided with control faces or conduits, with which control slots or outlets disposed in the cylinder are associated. The piston can be provided on its jacket face with at least one control conduit that is embodied in such a way that by suitable rotary positioning of the piston, it can be brought into coincidence with at least one of the outlet conduits at a time. If needed, the arrangement can also be made such that the control conduit can be switched into coincidence with a plurality of outlet conduits. The control conduit and the outlet conduits are disposed such that the work chamber, defined by the piston and the cylinder, communicates with whichever outlet conduit has been selected, over the entire stroke of the piston. In this way, all the oil volume positively displaced by the piston can be pumped into the outlet conduit. The piston pump embodied in this way is both a pump device and distributor device at one and the same time. 
     The pump device and the distributor device can be connected to a drive device that effects the rotation and displacement of the piston. This displacement motion is a pumping motion, so that the displacement drive forms a pump drive. If no displacement motion occurs, the rotary motion of the piston causes no change in volume in the cylinder, and as a result, only the blocking or uncovering of outlet conduits is controlled by the rotary motion. Thus the rotary drive is a distributor drive, and the piston is a control slide. The pumping and switchover can thus each be effected independently, by rotating and displacing the piston. This can be done by means of separate drive devices, or by a combined drive device that is capable of generating both a rotary and a displacement motion. 
     For rotating the piston, a stepping motor is preferably used, which generates a desired rotary positioning motion. Rotary positions to be taken for selecting an outlet conduit and thus for activating a lubricating station are simple to attain with a stepping motor. However, the displacement motion of the piston can be derived from this stepping motor as well. To that end, the piston is preferably connected to the stepping motor or other kind of control motor via a coupling, which initially allows a set or adjustable rotary play, and the relative rotation within the rotary play is converted by a gear means into the desired linear motion. 
     The rotary angle of the rotary play can be utilized to generate a linear motion. To that end, the piston is preferably connected to a locking device, which keeps the piston nonrotatable in arbitrary or selected rotary positions, but without blocking its axial displacement. By way of example, this locking device can be formed by a locking wheel, which can be brought into and out of engagement with a locking member. This is preferably done by means of a suitable radial motion of the locking member, for instance by means of a pull magnet. If the piston is held in a manner fixed against relative rotation, then a rotation of the stepping motor within the context of the rotary play of the coupling device is possible. The displacement device is now preferably formed by a gear, which converts this relative rotation between the piston and the rotator device into a linear motion of the piston. 
     In an especially durable, simple embodiment, the locking wheel is embodied as a ratchet wheel. The locking element then acts as a pawl, which allows a rotation of the locking wheel in a selected direction. The pawl can also be releasable, for instance by a lifting magnet, to allow rotation of the locking wheel in the other direction. Such an arrangement allows normal operation of the lubricating device with only a very few actuations of the lifting magnet, used by way of example, for releasing and locking the paw. Even if simple, inexpensive lifting magnets are used, this makes a long service life possible. 
     The gear can be formed by two threaded elements meshing with one another. The pitch of the thread of the threaded elements is dimensioned such that by the relative rotation between the piston and the control motor, within the context of the rotary play of the coupling device, one complete piston stroke is executed. The piston can be moved back and forth by rotating the control motor forward and in reverse. 
     As needed, still other devices can serve as the gear means. For instance, it may be expedient to provide a cam drive, which enables a reciprocating motion of the piston upon rotation of the rotary drive in a single specified direction. Such a cam drive can be formed by an undulating annular groove provided in the wall of a bush, in which groove a radially extending pin or prong runs, driven by the control motor. 
     The gear that generates the linear motion is preferably prestressed. This can for instance be accomplished by means of a magnet that keeps flanks of the gear that slide past one another in contact with one another. This is advantageous particularly with a view to correct metering of the lubricant. If the drive reverses its rotary direction, for instance to change from a forward piston stroke to a reverse piston stroke, then the turning points are precisely defined, and incorrect metering is avoided. 
     The outlet conduits leading out of the cylinder and one inlet conduit are each preferably provided with check valves. The pump device thus makes do without further control means. The check valves are preferably automatic valves, controlled by the differential pressure applied. No other valve control arrangements are needed. 
     For monitoring proper operation of the lubricating device, a sensor device that detects and monitors the reciprocating motion of the piston can be advantageous. It may suffice to monitor whether the piston attains a certain stroke or not. For instance, if one lubricating conduit is stopped up, the piston is unable to pump any lubricant into this conduit and is accordingly blocked. It fails to reach the switching point of the sensor device, and the sensor device detects this and turns off the affected machine. 
     Another aspect of the invention is directed to a method for the lubrication of lubricating stations of a machine by means of at least one pump via lines. Lubricant is pumped discontinuously by the pump to the lubricating stations via the lines. For lubricant supply to one or more lubricating stations, the applicable line or lines are subjected by the pump to a pressure that fluctuates over time. Regardless of the specific design of the pump device and distributor devices in attached lines, and regardless of how many lubricating stations are connected, it is expedient for the pump pressure to be modulated during individual lubricating pulses. If a stepping motor is used to drive the pump, its individual steps can be converted into micropumping pulses, whose train forms a lubricating pulse. The intervals between individual micropumping pulses are expediently dimensioned such that the pressure in the lines does not drop below a minimum limit value. The minimum pressure is preferably somewhat less than the requisite injection pressure for the connected nozzles. It suffices to keep any resilience (elasticity) of the lines under initial stress. This makes it possible either to meter especially small quantities of lubricant, or to prolong the lubricating process. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows the lubricating device in a schematic perspective view; 
         FIG. 2  shows the lubricating device of  FIG. 1 , in a sectional view of a detail and on a different scale; 
         FIG. 3  is a horizontal section taken at line III—III of the cylinder body  8  of  FIG. 7 , but with piston  21  assembled thereinto; 
         FIG. 4  is a horizontal section taken at line IV—IV of the lubricating device of  FIG. 2 ; 
         FIG. 5  is a plan view of a locking wheel belonging to the drive device of  FIG. 4 ; 
         FIG. 6  is a horizontal section through coupling device  39 , taken at line VI—VI in  FIG. 7 , but with pin  42  assembled thereinto; 
         FIG. 7  shows a pump device, belonging to the lubricating device of  FIG. 2 , with an associated coupling device, an associated locking wheel, and a threaded element for generating a linear motion; 
         FIG. 8  is a graph showing the course over time of the injection pressure of the oil stream flowing to an injection nozzle and the oil stream output by the injection nozzle; 
         FIG. 9  is a schematic plan view of a modified embodiment of a locking device with a locking wheel embodied as a ratchet; and 
         FIG. 10  is a schematic plan view of a further modified embodiment of a locking device with a locking wheel embodied as a ratchet. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In  FIG. 1 , a lubricating device  1  is shown, which includes a supply container  2 , for lubricant, such as oil. A distributor and pump unit  3  is inserted into the supply container  2  and dispenses predetermined portions of lubricant at predetermined times to a group  4  of lubricant lines  5 a through  5 e that lead away from it. 
     The pump and distributor unit  3  schematically shown in  FIG. 1  is shown separately in  FIG. 2. A  piston pump  7 , which is both a pump device  7 a and a distributor device  7 b simultaneously is used for pumping and allocating the lubricant. The piston pump  7 , as seen particularly from  FIGS. 3 and 7 , includes a cylinder body  8  with a cylindrical through bore  9 . The through bore  9  is embodied on its lower end in terms of  FIGS. 2 and 7  as a stepped bore, because it has one portion  10  of increased diameter. This portion serves to receive a check valve  12 , whose valve body  14  is screwed for instance into a corresponding thread in the portion  10 . 
     The valve body  14  is provided with a through conduit  15  for receiving a valve closure member  16 . The head of the valve closure member  16  points toward the inner chamber, defined by the through bore  9 , of the cylinder body  8 . If needed, a spring, not shown, can brace the valve closure member against a valve seat embodied on the valve body  14 . 
     The valve  cylinder body  14    8  is provided with a plurality of radial bores  17 , in the present example  12  of them ( 17 a- 17 l; FIG.  3 ), which are all disposed in the same plane  18  to which the through bore  9  is perpendicular. The radial bores  17 a- 17 l FIG.  3 ), which are disposed in the same plane  18  to which the through bore  9  is perpendicular.  The radial bores  17 a- 17 l are disposed at equal angular spacings from one another, while the spacing between the radial bore  17 l and the radial bore  17 a is somewhat greater than the otherwise uniform spacings among the radial bores  17 a through  17 l. Check valves, not identified by reference numeral, are inserted into the radial bores  17  (the reference numeral without a letter following it stands equally for all the radial bores  17 a through  17 l), and these check valves allow a fluid flow in the radial direction outward, that is, from the bore  9  outward through the outlet conduit formed by the respective radial bore  17 , but not back again. 
     The lubricant lines  5 a through  5 e are connected to the outlet valves and lead to the lubricating stations. The check valves can be provided as needed also on an end of the respective line  5 a through  5 e remote from the distributor device  7 b, in which case only connection nipples are screwed into the radial bores  17 . 
     A piston  21  is inserted into the through bore  9 , and its outer diameter substantially matches the inside diameter of the through bore  9 , so that while the piston is seated axially displaceably and rotatably in the through bore  9 , it also together with the through bore defines a work chamber  22  relatively tightly (FIG.  2 ). Along with its cylindrical jacket face  23 , the piston  21  also has a substantially plane end face  24 . A control groove  25  extends over the jacket face, beginning at the end face  24 , parallel to the center axis  26  of the piston. The length of the control groove  25  is preferably equal to or somewhat greater than the spacing of the plane  18  from a “top” dead center  27  of the piston; this point is represented by a dashed line in FIG.  2 . 
     The piston  21  reaches top dead center  27  with its end face  24  when the work chamber  23  is smallest, or in other words, in terms of  FIG. 2 , when the piston  21  is in its bottommost position. 
     The control groove  25 , as  FIG. 3  shows, is relatively narrow and extends in the circumferential direction along the jacket face  23  over a circumferential region that is approximately equivalent to the diameter of the radial bores  17  at the wall of the through bore  9 . The depth of the control groove  25  is dimensioned such that the flow resistance in the control groove  25  is not substantially greater than in the radial bores  17 . 
     On its end protruding out of the cylinder element  8 , the piston  21  is mounted in a connection cuff  29  and pinned to it (pin  30 ). The connection cuff  29  is also connected via a further pin  31  to an actuating rod  32  that leads to a drive device  33 . The actuating rod  32  is connected in a manner fixed against relative rotation and solidly in the axial direction to a coupling half  34 , which has two ribs  35  and  36  extending axially and disposed parallel to and spaced apart from one another. Between these ribs, windows  37 ,  38  are formed, which can be seen particularly in FIG.  6 . 
     The coupling half  34  belongs to a coupling device  39 , whose other coupling half  40  is formed by a radial pin  42  driven by a shaft  41 . This pin with both ends engages the windows  37 ,  38 , and after each execution of a certain rotary play, here defined at 90°, it can come into contact with one flank of each of the ribs  35 ,  36 . 
     The shaft  41  also has a bush  43 , which can be seen from FIG.  7  and establishes the connection to the radial pin  42  and is provided on its outside with a threaded element  44 . This threaded element has a male thread with multiple turns. Its pitch is dimensioned such that over 90° of the circumference of the threaded element  44 , a distance is traversed in the axial direction that corresponds to the complete piston stroke of the piston  21 . 
     During operation, the threaded element  44  is in communication with a threaded element  45 , which is seen in FIG.  5  and is embodied in an annular element or portion that is supported by the ribs  35 ,  36  of the coupling half  34 . Thus when the rotary play of the coupling  39  is executed, the coupling half  34  changes its axial position relative to the coupling half  40 . 
     The portion of the coupling half  34  provided with the female thread (threaded element  45 ) is embodied, on its outside, as a locking wheel  46 . This locking wheel has axially extending teeth  47  of approximately trapezoidal cross section, which serve to lock the coupling half  34  in a manner fixed against relative rotation but axially displaceably. This can be seen from  FIG. 4. A  locking bar  48  is displaceably supported radially to the locking wheel  46 . The locking bar  48  is prestressed by a compression spring  49  toward its radially outer position, in which it is not in engagement with the locking wheel  46 . A lifting magnet  51  serves with its armature  52 , via a corresponding rod  53 , to put the locking bar  48  into engagement with the locking wheel  46 , so that the rotation of the locking wheel is blocked in discrete positions specified by the teeth  47 . These blocking or locking positions each correspond to rotary positions in which the control groove  25  ( FIG. 3 ) is aligned with one of the radial bores  17 . Accordingly, 13 interstices between teeth are present, 12 of which correspond to the positions of the radial bores  17 , and the 13th of which corresponds to the larger interstice between the radial bores  17 l and  17 a. The size of the interstices between teeth corresponds to the size of the spacings of the radial bores  17 . 
     The coupling half  40  is connected in a manner fixed against relative rotation to the shaft  41 , which forms the power takeoff shaft of a stepping motor  55 . This motor is oriented coaxially to the actuating rod  32  and is supported by a corresponding mount  56 . The mount  56 , which is embodied in multiple parts, also carries the lifting magnet  51  and has a tubular, tapering extension  57 , which is disposed coaxially to the actuating rod  32  and carries the pump unit  7  on its lower free end. There, it has a flange-like extension  58 , on which the lubricant lines  5  can be retained and which moreover has a microporous sieve  58 . This sieve is embodied in cup-like shape and encloses the lower end of the extension  57 . The lubricant flowing to the inlet valve  12  must accordingly pass through the microporous sieve  59  and is thus filtered. 
     On its side toward the actuating rod  32 , the coupling half  34  is provided with a hub  60 , which has a male thread  61 . On the hub  60 , an annular, axially polarized permanent magnet  62 , shown separately in  FIG. 7 , is retained with the aid of a nut  63 , for which nut the male thread  61  is intended. By means of its magnetic field, the permanent magnet  62  generates a force that keeps the threaded element  44  in engagement with the thread  45  without play. This serves to prevent an undesired idle motion in the gear at the reversal of the rotary direction of the stepping motor  55 ; the gear is formed by the threaded element  44  and the female thread  45  and serves to convert a rotary motion into a linear motion. 
     The actuating rod  32  is supported on the extension  57  in a bush  65 , which is disposed adjacent the connecting cuff  29  in a corresponding partition of the extension  57 . The bush  65  allows both a rotary and an axial motion of the actuating rod  32 . 
     For monitoring the motion of the piston  21 , a magnetic sensor, for instance a Hall sensor  66 , is disposed on the inside of the extension  57 , adjacent to the permanent magnet  62 ; it detects the position of the permanent magnet  62  and distinguishes between at least overshooting and undershooting a switching position. If needed, a further Hall sensor or other kind of position sensor  67  may be provided in the vicinity of the transverse pin  42 , in order to detect the position of this pin. Both the Hall sensors as well as the stepping motor  55  and the lifting magnet  51  are all connected to a control device, which controls the lubricating device  1  as follows: 
     For describing proper operation, it will be assumed that the piston  21  is initially in the position shown in  FIG. 3 , and the locking bar  48 , as a consequence of triggering of the pull magnet  51 , is in engagement with the locking wheel  46  (FIG.  4 ). If the thread of the threaded element  44  is a right-handed thread, then the stepping motor  55 , at least if the transverse pin  42  is not yet in the position represented by heavy lines in  FIG. 6 , is now rotated in such a way that the transverse pin  42  is pivoted clockwise. For example, it is moved out of the position shown in dashed lines in  FIG. 6  to the position shown in heavy lines. On traversing this course, the axially fixed element  44  lifts the coupling half  34  in the axial direction in such a way that the piston  21  executes one complete intake motion. The work chamber  22  becomes larger, and lubricant, such as oil, flows into the work chamber  22  via the inlet valve  12 . 
     The locking wheel  46  is held in a manner fixed against relative rotation. At the latest when the transverse pin  42  runs up against the ribs  35 ,  36 , the stepping motor  55  stops. The pull magnet  51  is now deexcited, and as a result the locking wheel  46  is released. The stepping motor  55 , which until now has served to impart a reciprocating motion to the piston  21 , now positions the now freely rotatable locking wheel  46  onward by one tooth. In the process, the transverse pin  42  carries the ribs  35 ,  36  and thus the coupling half  34  along with it. The control groove  25  is thereby moved into coincidence with the radial bore  17 a. Once this position is reached, the pull magnet  51  is triggered again and as a result presses the locking bar  48  into the corresponding interstice between teeth of the locking wheel  46 . As a result, this locking wheel is once again retained in a manner fixed against relative rotation. 
     For dispensing a desired portion of lubricant to the lubricant line  5 a, the stepping motor  55  is now triggered counter clockwise. Because of the size of the windows  37 ,  38 , the rotary motion is limited here to a one-quarter rotation. If the stepping motor  55  traverses this course, this rotary motion is converted, by interaction of the threaded element  44  with the female thread  45 , into an axial motion of the coupling half  34  that is oriented downward, in terms of FIG.  2 . Via the actuating rod  32 , the piston  21  is moved, without rotating, downward in the direction of its top dead center  27 . The positively displaced oil is correspondingly dispensed at the lubricant line  5 a. There is no need for the entire course available to be traversed. The stepping motor  55  can also be stopped before it has executed a one-quarter rotation. A lesser quantity of oil is then correspondingly dispensed. As a result, fine metering of the oil portions to be dispensed is attainable. 
     Once the downward motion of the piston  21  has ended, the stepping motor  55  is actuated clockwise again, until the traverse pin  42  again meets the ribs  35 ,  36 . The pull magnet  51  is now released, and as a result the compression spring  49  moves the locking bar  48  radially outward and releases the locking wheel  46 . The stepping motor can now rotate onward by one tooth (or as needed a plurality of teeth), carrying the coupling half  34  and thus the piston  21  by rotation along with it, in order to approach the next lubricating position. For instance, the control groove  25  is now made to coincide with the radial bore  17 b. The process described in conjunction with the radial bore  17 a now begins over again. As described, all the radial bores  17  can thus be approached in succession, and thus all the lubricant lines  5  can be supplied separately with suitable portions of oil. 
     The dispensing of an oil portion can be done in pulsed fashion, as illustrated by  FIG. 8 ; the injection pressure p built up by the pump device  7 a is modulated within a lubricating interval t 1  t 2 . To that end, the stepping motor  55  is triggered and moved incrementally, so that the piston  21  is likewise moved incrementally. In each of the brief resting periods, the pressure p can drop somewhat below a pressure limit value p 1 . The connected nozzles begin to inject at the pressure limit value p 1 . If the pressure meanwhile drops below this value, for instance to a somewhat lesser valve p 0 , then the nozzles inject intermittently. The incoming flow V 1*  to the nozzles fluctuates as a result and over time,  oil injection through the nozzles is interrupted. As a result, the incoming flow V 1   * to the nozzles fluctuates over time and  as a consequence of the elasticity of the lines. The nozzles inject the oil stream V 2 * droplet by droplet in the form of micropulses, so that the oil stream between individual droplets, because of the brief pressure drops, is zero. In this way, even small oil quantities can be dispensed over a prolonged time in the injection stream, using relatively large nozzles that are not likely to become stopped up. 
     When the lubricating device  1  is put into operation, venting of the pump device  7 a may initially be needed. To that end, the piston  21  is rotated into a venting position, in which its control groove  25  coincides with a radial bore  17 l that is open to the outside and in which no check valve is disposed. One or more complete piston strokes now cause the expulsion of air and the filling of the pump volume with oil. Proper operation can then be begun. 
     A modified embodiment of the locking mechanism is shown in FIG.  9 . Here the locking wheel  46  is embodied as a ratchet wheel. The locking bar  48  is embodied as a pawl. This makes it unnecessary to trigger the pull magnet each time the locking wheel  46  is to be indexed onward. The locking bar  48  is spring-loaded toward the locking wheel  46 . It enables a rotation of the ratchet wheel  46  in the clockwise direction (arrow  70 ) for rotating the piston  21  and thus actuating the distributor. In the opposite direction (arrow  71 ), however, any rotation is blocked, so that the pumping operation can be performed. It is now necessary to actuate the lifting magnet  51  only in a very few exceptional cases. 
     A further modified embodiment is shown in FIG.  10 . The toothing of the locking wheel  46  has teeth  47  with a relatively slight flank pitch. The locking bar  48  is embodied as a radially resilient pawl. The control of the rotary motion of the piston  21  in this embodiment is effected in that the stepping motor  55 , once the play of the coupling device  39  has been traversed, overcomes the detent moment of the locking bar by rotating clockwise or counterclockwise. 
     In a lubricating device for a plurality of lubricating stations, especially for supplying lubricant to knitting machines, a pump device  7 a is provided that acts at the same time as distributor device  7 b. To that end, the pump and distributor unit  7  has a piston  25 , which is provided with a control groove  25 . The corresponding pump cylinder has one inlet and a plurality of outlets that are distributed over the cylinder wall. Depending on which of the outlets the control groove  25  of the piston  21  is made to coincide with, a corresponding lubricating station is selected. The pump device  7  is thus at the same time a distributor device.