Abstract:
A medium pump for a motor includes a pump case with a pump cylinder and a pump piston positioned displacaebly in the pump cylinder in the direction of a pump axle. The pump piston rotates about the pump axle by running off an oblique control surface and realizes axial pump movements against the pressure of a first spring. A pump lift adjusting device is removably positioned in a guide placed transversely to the pump axle and fixedly connected with the pump case.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is entitled to the benefit of and incorporates by reference essential subject matter disclosed in International Application No. PCT/EP01/04045 filed on Apr. 9, 2001 and German Patent Application No. 200 06 638.2 filed on Apr. 11, 2000. 
   FIELD OF THE INVENTION 
   This invention relates to the field of pump technique. It concerns a medium pump according to the preamble of claim  1 . Such a medium pump is known, for example, from the U.S. Pat. No. 4,797,073. 
   BACKGROUND OF THE INVENTION 
   Medium pumps for displacing liquid media have been known for a long time, in particular in form of lubricating oil pumps for motor chain saws or the like (see for example DE-A1-41 07 110 or the DE-A137 21 643 or the DE-A1-34 47 091 or the DE-Cl-1 95 29 368). Such lubricating oil pumps in chain saws are complex structural components which are assembled by the manufacturer and which can be maintained by the user only by means of “special tools”. Since the displaced oils tend to gum, it is necessary from time to time to disassemble the pump and to make it free from the gum accumulations. For the pumps known at present, this is only possible with the aid of special tools. Since the user of the chain saw does not have such special tools or since he does not have them continuously on him, this can mean a nonworking time. 
   SUMMARY OF THE INVENTION 
   Thus, the aim of this invention is to create a medium pump which can be simply disassembled, cleaned, put together again and which can be built-in again practically without any tool. 
   This aim is achieved by all the characteristics of claim  1 . The core of the invention consists in the fixing of the pump piston in the pump cylinder only by the pump lift adjusting device and to configure the pump lift adjusting device itself removable from its guide without any tool. In this way, the pump as a whole can be easily dismantled, cleaned and put together again by simply removing the pump lift adjusting device. 
   A preferred embodiment of the medium pump according to the invention is characterized in that the pump lift adjusting device is positioned displaceable along a guiding axle in the guide associated to the pump case, that the guide is limited on its side turned to the pump piston axle by a setting surface placed transversely to the guiding axle and provided with snap-in deepenings, that the pump lift adjusting device is supported, when in the built-in condition, against the pressure of a spring by means of laterally projecting trunnions on the setting surface and that axially running grooves are provided in the guide, grooves in which the trunnions are guided when the pump lift adjusting device after twisting into a predetermined angular position is withdrawn from the guide. In this embodiment, for dismantling the pump, the pump lift adjusting device is first displaced axially against the spring pressure as far as the laterally projecting trunnions of the adjusting device are above the grooves placed laterally from the guide. The alignment of the trunnions and of the grooves is achieved with a subsequent torsion of the adjusting device. The pump lift adjusting device can then be withdrawn from the guide by releasing the spring, whereby the trunnions in the grooves can glide out in direction of the guiding axle. The assembly takes place in the reverse order. 
   Preferably, the pump lift is adjustable by a displacement of the pump lift adjusting device in direction of the guiding axle and the setting surface provided with snap-in surfaces for adjusting the pump lift adjusting device is graded in height. By correspondingly twisting the pump lift adjusting device about the guiding axle, the trunnions supported on the setting surface are brought to different height levels which correspond to an axial displacement of the pump hub adjusting device. The oil pump piston which is placed orthogonally to the adjusting device, pressed with its oblique control surface by resilience to the control head of the adjusting device, describes a lift movement by rotation. The axial displacement of the adjusting device causes a variation of the distance between the control head of the adjusting device and the center axle of the pump piston which causes the variation of the lift movement of the piston and likewise of the lift capacity. 
   The adjustment and dismounting or mounting of the medium pump ist particularly simple when, according to a preferred further development, the pump lift adjusting device projects at its end opposite the control head with an adjusting head out of the guide, by means of which it can be twisted about the guiding axle, the adjusting head is slit in the manner of a screw head and the second spring is supported with the one end on the guide and with the other end on the adjusting head. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be explained in detail below by means of embodiments with reference to the attached drawings. 
       FIG. 1  shows a perspective view of a preferred embodiment of a medium pump according to the invention in assembled condition. 
       FIG. 2  shows the pump case of the medium pump according to  FIG. 1 . 
       FIG. 3  shows a section of a topview on the guide of the adjusting device of the medium pump according to  FIG. 1  with its setting surface. 
       FIG. 4  shows the pump lift adjusting device of the medium pump according to  FIG. 1  in disassembled condition. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   In  FIG. 1 , a preferred embodiment of a medium pump according to the invention in assembled condition is represented in a perspective view. The medium pump  100 , which is configured in the represented example as a lubricating oil pump for a motor chain saw, comprises a pump case  1  with a pump cylinder  14  and with a (hollow cylindrical) guide  11  which are connected with each other by a connecting piece  13  in such a way that their axles  18  and  19  cross at a right angle (see also  FIG. 2 ). A pump piston  6  is positioned displaceable in the pump cylinder  14  in direction of the pump axle  19 . The pump piston  6  projects with one end out from the pump cylinder  14  and is provided with an coaxially placed pinion which is in mesh with a driving worm  5  (represented only schematically) driven by the motor of the chain saw. The free end of the pump piston  6  is terminated on the front side by an oblique control surface  7  which is in contact with a fixed control head  16 . The spring  4  presses the pump piston  6  with its oblique control surface against the control head  16  of the adjusting device  8 , whereby the spring  4  is supported on one side on the pump cylinder  14  and at the other end on the pinion. The pump piston  6  is set rotating about the pump axle  19  during the motor operation over the driving worm  5  and the pinion. Due to this rotation, the control surface  7  runs off on the control head  16  and thus sets the pump piston  6  in periodical axial pump movements. The pumped medium then enters (during the suction stroke of the pump piston) the pump cylinder  14  by a suction opening  2  and is exhausted again by a pressure opening  3  (during the pressure stroke of the pump piston). 
   The control head  16  is a part of a pump lift adjusting device  8  (represented separately in  FIG. 4 ). The control head  16  is placed at the one end of a shaft  15  of the pump lift adjusting device  8 . At the other end of the shaft  15  there is an adjusting head  20  which is provided with a slot in the manner of a screw head. A (spiral) spring  10  is pushed over the shaft  15 , this spring being supported with its one end on the adjusting head  20 . Two laterally projecting opposite trunnions  9 , preferably formed by a dowel pin, are placed below the control head  16 . When in built-in condition ( FIG. 1 ), the pump lift adjusting device  8  is positioned displaceable in the guide  1  in direction of the axle  18 , whereby the bore hole of the guiding  11  is adapted to the outer diameter of the shaft  15 . The pump lift adjusting device  8  is then supported against the pressure of the spring  10  by means of the trunnions  9  on the setting surface  12  of the guide ( FIG. 3 ). An automatic torsion of the pump lift adjusting device  8  is avoided by the fact that snap-in deepenings, in which the trunnions  9  snap in due to the pressure of the spring  10 , are provided in the setting surface for determined angular positions. Different snap-in positions are at different height levels of the setting surface  12  so that a change of the snap-in position (by torsion of the pump lift adjusting device) causes a displacement of the pump lift adjusting device  8  in direction of the axle  18  and thus (due to the cooperation of control head and control surface  7 ) a variation of the pump lift. 
   The mounting and dismounting of the pump lift adjusting device  8  into or out of the guide  11  is made possible in a simple manner in that corresponding grooves  17  ( FIG. 3 ) are provided in the guide, grooves in which the trunnions  9  of the pump lift adjusting device  8  can glide in axial direction when in an appropriate angular position. For the dismounting of the mounted medium pump  100  ( FIG. 1 ), by actuating the adjusting head  20 , the pump lift adjusting device  8  is first lifted against the pressure of the spring  10  in axial direction until the trunnions  9  on the setting surface  12  are unlocked. The pump lift adjusting device  8  is then twisted until the trunnions  9  are aligned with the grooves  17  and the pump lift adjusting device  8  can be withdrawn out of the guide  11  downwards. When the pump lift adjusting device  8  is withdrawn out of the guide  11 , the pump piston  6  can be easily removed out of the pump cylinder  14  so that all the parts of the medium pump  100  are accessible and can be cleaned. After cleaning, the mounting takes place in the reverse order. 
   The characteristics and advantages of the solution according to the invention can be summarized as follows. 
   Due to the arrangement of the components (pump piston  6  and pump lift adjusting device  8 ) to each other, the pump case  1  can be configured in such a way that the fitting of the pump lift adjusting device  8  fixes the pump piston  6  in its position. 
   Due to the special configuration of the pump case  1  in the area of the guide  11  with its setting surface  12  as well as of the pump lift adjusting device  8 , the pump lift adjusting device  8  can be completely pre-assembled according to  FIG. 4  and, after having connected the pump case  1  and the pump piston  6 , can be inserted through the pump case  1  by means of the grooves  17  and locked by a “tool-free” torsion in its setting range so as not to slip. 
   The medium pump  100  can then be installed in the chain saw as a completely pre-assembled unit. Should it come to problems with the pump during the operation of the chain saw, the user can dismantle the pump, disassemble it “tool-free” in single parts, put it together and install it again “tool-free”. 
   LIST OF NUMERALS 
   
       
         1  Pump case 
         2  Suction opening 
         3  Pressure opening 
         4  Spring 
         5  Driving worm 
         6  Pump piston 
         7  Control surface 
         8  Pump lift adjusting device 
         9  Trunnion 
         10  Spring 
         11  Guide 
         12  Setting surface 
         13  Connecting piece 
         14  Pump cylinder 
         15  Shaft (pump lift adjusting device) 
         16  Control head (pump head adjusting device) 
         17  Groove 
         18  Guiding axle (pump head adjusting device) 
         19  Pump axle 
         20  Adjusting head (slit) 
         100  Medium pump