SPECIFICATION
Rotating cylinder piston pump The invention concerns a rotary cylinder piston pump, particularly a lubricating pump, having a cylindrical body journalled in a pump housing for rotation about a rotational axis that is stationary with respect to the housing, which cylindrical body is driven by a drive-shaft extending parallel to its axis of rotation and in which there is a working chamber or space in which a piston is guided perpendicularly to its axis of rotation, the piston being journalled on a bolt extending parallel to the rotational axis of the cylindrical body, which bolt extends eccentrically with respect to the axis of the drive shaft and on rotation of the cylinder in the working chamber the piston is reciprocatingly displaceably driven.
Such a roatary cylinder piston pump is known from DE-PS 421,648. In this known pump, the drive shaft is arranged eccentrically of the rotational axis of the cylindrical body and drives a disc at which two diametrically oppositely lying bolts sit, of which one bolt rotatably engages in a cylindrical bore of the piston, the piston being displaceably guided in a first guide groove that constitutes the working chamber or space of the pump and extends diametrically over one end face of the cylindrical body. In contrast, the other bolt engages a second guide groove which crosses perpendicularly the first guide groove, the second bolt being slidable in the same end face of the cylindrical body.Thus, here, on the one hand the cylindrical body and on the other hand the piston are always driven by one or other of the two bolts, the bolts rotating about an axis which is eccentric to the rotational axis of the cylindrical body and coinciding with the axis of the drive shaft.
However, by such a drive not only the mass of the piston but also the relatively much greater mass of the cylindrical body are alternately accelerated and decelerated in each rotation of the cylindrical body so that the varyingly large and non-uniformly changing forces arising' thereby cause a relatively large unbalanced rotating mass for the drive disc and the drive shaft to be present. To this should be added that the sliding movement of the second bolt in its guide groove in the cylindrical body is also non-uniform and that both the second bolt as well as the piston must pass through at the intersection position of the guide grooves between the corners present at the flanks of the guidegrooves intersecting there. All in all, this known pump is subject to very great wear and its highest possible r.p.m. is limited.
The invention seeks to provide a rotary cylinder piston pump which in comparison with the above described known pump is subject to lower wear, and with a compact constructional embodiment can be driven at a higher r.p.m. This is sought to be achieved according to the invention for a rotary cylinder piston pump having the abovedescribed characteristics in that the cylindrical body and the drive shaft are rigidly and coaxially connected with each other and the bolt is arranged in the pump housing in a stationary manner, and engages in an elongated slot in the piston extending transversely to the axis of the piston and to the axis of the bolt, the bolt extending in the slot from the end of the cylindrical body opposite to the drive shaft.
In this way, the rotary cylinder piston pump according to the invention can be constructed with smaller dimensions and a more compact method of assembly. Essentially over its whole peripheral surface the cylindrical body can be clearly supported and journalled in a correspondingly formed internal space of the pump housing and its rotating mass is balanced relative to the smaller rotating mass of the piston relative to the drive shaft. Apart from the piston which uses a translatory motion, the other parts utilised are either stationary or move exclusively in rotation, whereby the invention is realised with only a minimum number of parts that move against each other. In this way the rotary cylinder piston pump according to the invention is exposed to wear to a very small extent, runs relatively quietly and can be driven equally well even at high r.p.m.
The working chamber for guiding the reciprocating movement of the piston may be formed, as in the above mentioned known solution as with the solution according to the invention, as an open groove at one end face of the cylindrical body, the groove being closed at the open side thereof by a stationary cover plate of the housing.
Since however here the translatory movements of the piston are superimposed on its circular movement and in this way at this location there is an increased risk of wear, and since in addition by such a form of construction additional sealing surfaces with relatively narrow tolerances must be present at the plane of separation between the stationary cover plate and the rotary cylindrical body, an embodiment of the invention is preferred wherein the entire periphery of the working chamber is surrounded by the cylindrical body and the bolt passes through a bore formed concentrically with the rotational axis of the cylindrical body.
Thus in this embodiment the piston is fully enclosed in the interior of the cylindrical body and is guided in pure translatory movement along its whole periphery. In addition, in this way both pump chambers are well sealed at both sides over the peripheral surfaces of the cylindrical body as well as the journal surfaces of the housing cooperating therewith. Furthermore, in this way the piston and the complementary piston guiding working chamber may be formed cylindrically which is cheaper in manufacture than other crosssectional surfaces which are in themselves also possible.
By constructing the bolt guiding the reciprocating movement of the piston, as a part which is stationary in operation of the pump, it is additionally possible in a simple manner to make the piston stroke adjustable. To this end in a further advantageous embodiment of the invention it is proposed that the bolt should be seated at an adjustable sliding member perpendicular to the rotational axis of the cylindrical body which member may for example be guided in a corresponding guiding groove of the pump housing and which can be adjusted with a screw spindle preferably provided with a fine thread.
A preferred embodiment of the invention is described purely by way of example with reference to the accompanying drawing, in which: Figure 1 is an axial cross-section of a rotary cylinder piston pump according to the invention, and Figure 2 is a section taken along the section lines in Figure 1.
In a pump housing 1 there is an essentially cylindrical interior cavity 2 closed at one end face by a housing cover 5 which cavity journals a cylindrical body 4 in a rotatable manner. The cylindrical body 4 is traversed by a cylindrical bore serving as a working chamber 6 for a cylindrical piston 7 which is reciprocatingly guided in the working space 6. On the side opposite to the housing cover 5 a drive shaft 8 projects out of the pump housing 1, the drive shaft being coaxial with the cylindrical body 4 and is made of one piece with the latter to operate as a shaft pin.A bolt 9 sits at the inner side of the housing cover 5 and extends parallel to the axis of rotation of the cylindrical body but is offset or eccentric relative to it by an amount e; the bolt 9 projects through a bore 10 which is coaxial with the axis of roatation of the cylindrical body 4 at that end of the cylindrical body 4 which faces the cylinder cover 5, the bolt 9 projecting diametrically through the working space 6 in the cylindrical body 4. The piston 7 is journalled on this bolt 9 which for this end passes through an elongated slot 11 in the piston 7 which extends perpendicular to the axis of the bolt and the axis of the piston, and slidingly bears against the longer sides of the longitudinal slot 11.As can be seen from Figure 2, the internal cavity 2 of the housing 1 and at mutually diametrically oppositely lying locations, a sickleshaped entry chamber and discharge or exit chamber 20 are formed, the width of which measured perpendicular to the plane of the drawing in Figure 2 can correspond to the diameter of the piston 7 and into which a respective threaded bore 12 opens in which screw nipples for the supply and removal of the pressure medium delivered by the pump can be screwed.
By rotation of the drive shaft 8 both the cylindrical body 4 and the piston 7 in it are set into rotation but the piston is held by the stationary bolt 9 so that it is forced to reciprocate by virtue of the eccentricity relative to the axis of rotation of the cylindrical body within the working space or chamber 6 of the cylindrical body 4; each time when the piston with one or other of its end faces runs over the entry chamber, the pressure medium is sucked in and when it runs over the exit or discharge chamber 20, the pressure medium is pressed out.
In a non-illustrated embodiment the bolt 9 sits at a slider which is adjustably guided in a corresponding or suitable groove of the housing cover 5 perpendicular to the axis of rotation of the cylindrical body 4.
A threaded spindle engages in the threading of a tapped bore in the pusher and the screw spindle is rotatable in a slitted plate stationarily secured outside the housing 1 but journalled against axial movement so that by means of the actuation head of the screw spindle the slider and thus the bolt 9 sitting in it can be finely adjusted to adjust the eccentricity e and thus the stroke of the piston, in a stepless manner. In other respects this embodiment corresponds to that of Figures 1 and 2.
The positions where the apices of the sickleshaped inlet and outlet chambers 3, 20 lie and where the threaded bores 12 open for the inlet and outlet ducts, are diametrically opposite the cylindrical internal space 2 of the housing 1 in a plane which contains the axis of the cylindrical body 7 and extends perpendicularly to the plane containing the axes of the cylindrical body 7 and the bolt 9. By changing the direction of rotation of the drive shaft 8, the inlet chamber and the outlet chamber are functionally reversed in role. The same possibility is also present in the said nonillustrated embodiment in that the bolt 9 is displaced from one axial side of the cylindrical body 4 via the axis of the latter to the other axial side of the cylindrical body 4.
The greatest length of the longitudinal slot 11 corresponds to double the maximum eccentricity e increased by the diameter of the part of the bolt 9 which engages in the longitudinal slot 11. The diameter of the cylindrical bore 10 corresponds to at least twice the value of the maximum possible eccentricity e increased by the diameter of the part of the bolt 9 which passes through the bore 10.
If in the embodiment according to Figure 1 it is not desired that the bolt 9 should be adjustable then to shorten the non-supported projecting length of the bolt 9 the shaft portion thereof which projects through the bore 10 can be constructed so as to be concentric with the cylinder shaft arranged on the cylindrical body 7 the diameter of the shaft corresponding to that of the bore 10 so that the cylinder shaft is rotatably supported in the bore 10 (not shown).