Rotary piston machine for liquids
United States Patent [1 1 Giversen 1 1 ROTARY PISTON MACHINE FOR LIQUIDS [75] Inventor: Svend Giversen, Sonderborg.  
 Denmark [73] Assignee: Danfoss A/S, Nordborg, Denmark [22] Filed: July 30, 1973 [21] Appl. N0.: 383,891  
 :30} Foreign Application Priority Data Aug, 18. 1972 Germany 2240632 52] U.S.Cl. ..4l8/6l B;4l8/186 51] lnt. Cl F04c 17/18; F04c 29/08 58] Field of Search i. 418/61 R, 61 B, 186, 188, 418/171 56] References Cited UNITED STATES PATENTS 2.985.110 5/1961 Burt et al. 7. 418/188 X 2.989951 6/1961 Charlsonw r. 418/61 B 1.233.524 2/1966 Charlsonm 418/61 B 1.698.841 10/1972 Lusziig .4 418/188 X FOREIGN PATENTS OR APPLICATIONS 9,359 6/1915 United Kingdom t. 418/61 B 61,871 8/1923 Sweden l. 418/61 8 Primary Examiner-C. J. Husar Assistant Examiner-Leonard E. Smith [57] ABSTRACT The invention relates to a fluid pressure operated motor or pump of the type having a gerotor displacement mechanism. Such devices normally have a separate valve member for directing pressurized fluid from the casing inlet to the expanding chambers of the gerotor and exhaust fluid from collapsing chambers to the casing outlet. In this invention there is no separate valve member and a unique valve passage ar rangcment is provided in a stationary casing port wherein a centrally located port is surrounded by a ring of ports. The centrally located port may be the inlet or outlet port and the ring of ports is the opposite thereof.  
 1 Claim, 3 Drawing Figures ROTARY PISTON MACHINE FOR LIQUIDS The invention relates to a rotary piston machine for liquids having a toothed wheel and a toothed ring which surrounds the toothed wheel. Said toothed ring having one more tooth than the wheel and forming displacement chambers with the wheel, a distributor valve comprising two parts one of which is coupled to one of the toothed elements and has first control openings which overlap second control openings in the other valve part and connecting ducts which lead from the second control openings to the displacement chambers.  
  The object of the present invention is to provide a rotary piston machine, the distributor valve of which is of very simple, space saving construction and is particularly suitable for small machines.  
  According to the invention, this object is achieved by a rotary piston machine having two sets of control openings. One of said sets is connected to the supply line and the other to the discharge line. The difference in the positioning of the two sets relative to the eccentricity of the movement of one of the toothed elements provides a commutator type fluid feeding and exhausting arrangement.  
  The advantage ofa machine of this kind resides in the fact that the two parts of the distributor valve are firmly connected to the toothed wheel and to the toothed ring or can even be formed directly on one of these toothed elements. A disadvantage, on the other hand, is that the distributor valve gives a poorer control performance than distributor valves having two parts arranged concentrically with each other. In particular, during transition from one set of the first control openings to the other, the second control openings are completely covered over a greater angle of rotation of the associated toothed element.  
  When, however, this distributor valve is used as a primary distributor valve in conjunction with a secondary distributor valve, 21 machine of simple construction and having an accurate control function is obtained. In a preferred arrangement, one set is formed by a central bore and the other set is in surrounding relation thereto.  
  In particular the above arrangement enables very small rotary piston machines to be produced which have for example a toothed wheel with four teeth and a toothed ring with five teeth.  
  It is advisable for reasons of construction for the toothed wheel to have a central cavity in which is fitted an insert incorporating the second control openings. The portions of the connecting duct formed in the insert and in the toothed wheel being at an angle to each other. This results in the control opening being connected to a displacement chamber offset through 90; the connecting duct however does not interfere with the adjacent control opening.  
  Manufacture is rendered easier if the insert consists of two parts, one of which incorporates the portions of the connecting duct, and the other the second control openings.  
  The invention will now be described in greater detail by reference to a preferred embodiment illustrated in the drawing in which:  
  FIG. 1 is a longitudinal section through a motor in accordance with the invention,  
  FIG. 2 is a side view, on a greater scale, of the toothed elements and the control openings, one displacement chamber being seen at its maximum size, and  
  FIG. 3 is an illustration similar to that of FIG. 2 showing one displacement chamber at its minimum size.  
  The rotary piston machine has a casing l to one end face of which a cover plate 3 is secured by means of screw bolts 2, while at its other end face an intermediate plate S, a toothed ring 6, an intermediate plate 7 and a connection plate 8 are secured by means ofscrew bolts 4. A main shaft 9 is mounted in the casing 1. This shaft is connected to a toothed wheel 11 through a universal joint shaft 10.  
  The toothed wheel 11 has four teeth 12, and the toothed ring 6 has five teeth I3 in the form of cylindrical rollers. Displacement chambers 14 are formed between these teeth and the intermediate plates 5 and 7. The displacement chambers 14 are connected through a valving arrangement in the correct working manner to two ports 15 and 16 in the plate 8 associated with the supply and discharge lines.  
  This valving arrangement is represented by a distributor valve 17 in which a first stationary port is the plate 7, and a second movable port is the wheel 11 and inserts 27 and 28 fastened thereto so as to be integral therewith. Plate 7 constitutes a valve plate with a central bore I8 which is directly connected to the port 15, and five openings 19 along a circle concentric with port I5 which openings 19 are connected to the port 16 by way of an annular channel 20 in the connection plate 8. The bore 18 and the circle of control openings I9 are disposed concentrically with the central axis of the toothed ring 6. Four openings 21 are provided in inserts of the toothed wheel, and these openings are disposed along a circle around the central axis of the toothed wheel 11.  
  The control openings I9 extend in the peripheral direction. Their inwardly directed limiting edge 22 runs tangentially to a circle concentric with the bore 18. The lines 23, 24, 25 and 26 defining the control openings 21 are so selected that, in the position illustrated in FIG. 2 in which one displacement chamber 14 is at its maximum volume, said lines extend parallel to the limiting line 22 of the control openings 19 and thus lie between the bore 18 and these control openings 19.  
  The second control openings 21 are provided in a first insert part 27, which part, together with a second insert part 28, is accommodated in a cavity 29 in the toothed wheel 11. In the second insert part 28 there are provided first connecting duct portions 30 which take the form of channels and are covered by the first insert part 27. Provided in the toothed wheel 11 are second connecting duct portions 31 and these extend from the periphery of the cavity 29 to the base of the gap between two consecutive teeth. The two connecting duct portions 30 and 31 are at an angle to each other.  
  Auxiliary ducts 32 are also provided on the toothed wheel 11. They take the form of channels at the two end faces of the toothed wheel and are disposed on the flanks of each tooth. They extend over a distance such that they each enable a connection between adjacent displacement chambers 14 to be established, this connection however being interrupted by the remaining tooth configuration bearing on the tooth of the toothed ring 6 in the zone of the line of symmetry S.  
  This arrangement results in the following operating cycle. If it is assumed that pressurized fluid is supplied through the port 15, and that the union 16 is connected to the return line, then the upper control opening 21 seen in FIG 2 receives pressurized fluid over the hatched portion of its area, whereas the lower control opening 21 is connected to the return line over the cross hatched area. lf, proceeding in the clockwise direction, the displacement chambers 14 are designated by the letters a, b, c, a and e, then the chamber a is at maximum volume and is sealed off at the two sides. The chamber e is under supply pressure; the same also applies as regards chamber d which is connected to chamber e through auxiliary ducts 32. Conversely, the chambers b and c are under return pressure The toothed wheel 11 and consequently the main shaft 9 are therefore turned in the clockwise direction. After a distance corresponding to a half tooth pitch, the toothed wheel occupies the position shown in FIG. 3 in which the chamber a is at its minimum size. In this position too the auxiliary ducts 32 each connect adjacent chambers b and c, and d and 0, but this connection is cut off in the zone of the line S of symmetry of the toothed ring. When the toothed ring turns from the position shown in FIGv 2, the return pressure should be communicated to the chamber a as rapidly as possible. This is achieved by connecting the chamber a to the chamber b through an auxiliary duct 32. No importance therefore attaches to the size of the angle through which the toothed wheel must turn before the right hand control opening 21 associated with the chamber a at this moment moves into contact with the control opening 19.  
  The same applies as regards the position seen in FIG. 3, where the chamber a, after turning through a small angle, is connected through an auxiliary duct 32 to the chamber b which is under supply pressure, even if a very considerable rotary movement is required before an associated connecting duct receives pressure.  
  Instead of the illustrated auxiliary ducts 32 in the flanks of the teeth of the toothed wheel, there are other types of auxiliary ducts which may be utilized.  
 I claim:  
  1. A fluid pressure motor comprising an internally toothed ring gear having an axis, a cooperating externally toothed star gear having fewer teeth than said ring gear disposed eccentrically relative to said ring gear axis, said star gear having rotational movement about its own axis and orbital movement about the axis of said ring gear with the teeth of said gears intermeshing in sealing engagement to form expanding chambers on one side of a rotating line of symmetry and contracting chambers on the other side of said line during relative movement between said gears, an end wall fixedly attached to said ring gear and forming fixed wall means for said chambers, valve means comprising a first valve part formed by said end wall and a second movable valve part integral with said star gear, a first set of inlet and outlet fluid ports in said first valve part comprising a centrally located port surrounded by a ring of ports, said centrally located port being one of said ports and said ring of ports being the remaining ones of said ports, said second valve part having a single set of ports arranged in a circle between said centrally located port and said ring of ports which alternately communicates with said inlet and outlet ports and have sequential fluid communication with (1) said centrally located port and with (2) said ring of ports, to continuously route fluid to said expanding chambers and away from said contracting chambers, and passage means in said second valve part providing fluid communication between said single set of ports and said chambers.