14 15 leading to the place of lubrication and to the oil tank respectively the pump is as an example operated by an angle gear with pinions 16 and 17 which have oblique teeth with a very small pitch therefore when the drive gear 16 rotates rapidly a large gear reduction takes place so that the piston 11 with the piston rod 18 and a helical spring 19 fitted on it rotates slowly during the rotation an oblique surface 20 of the piston slides towards the end of a lever 21 in the cylinder and from the force of the spring against the gear 17 the piston gets an axial movement of a length corresponding to the relative positions of the oblique surface as well as of the layer the movement is in one direction guided by the spring and in the other by the oblique surface the pumping effect is achieved by the axial movement mentioned and from the valve function caused by a bevel cutting 22 as well as by some ports 23 24 in the channels 14 15 of the pump housing 12 when the piston is fully pressed into the cylinder as shown on the figure the bevel cutting stands inclined upwards against the output channel 14 which then is open towards the cylinder twisted 180 u00b0 from there the bevel cutting stands towards the input channel 15 when the piston is somewhat retracted in the cylinder this type of oil pump is well known and used in chain saws the previously mentioned axial movement is made by the piston 39 s contact with the lever 21 which is swingably journalled on a pin 25 in the cylinder by means of different angular.