Reciprocating piston compressor, a retrofit kit for a reciprocating piston compressor and the use of a connecting rod in a reciprocating piston compressor

Abstract

A reciprocating piston compressor (100) includes a crank casing (10). The reciprocating piston compressor (100) includes a crankshaft (11), a piston rod (12) and a crosshead (13). The crosshead (13) and the piston (23) are actively connected to one another by way of a connecting rod (24). The connecting rod (24) is fixedly restrained on the crosshead (13) and on the piston (23).

Claims

1. A reciprocating piston compressor comprising: a crank casing; a crankshaft; at least one piston rod arranged on the crankshaft; a crosshead configured as a guide piston, the piston rod being actively connected to the crosshead; at least one cylinder; a piston movably arranged in the cylinder; a connecting rod, wherein the crosshead and the piston are actively connected to one another by way of the connecting rod, wherein the connecting rod is connected to the crosshead with a first fixed restraint and the connecting rod is connected to the piston with a second fixed restraint, the connecting rod being configured such the connecting rod permits alignment errors between the crosshead and the piston via one of deformation of the connecting rod and deflection of the connecting rod.

2. A reciprocating piston compressor according to claim 1, wherein at least one of the first and second fixed restraints is configured as a press fit.

3. A reciprocating piston compressor according to claim 1, wherein the connecting rod comprises a first connecting region for the crosshead and a second connecting region for the piston.

4. A reciprocating piston compressor according to claim 3, wherein the connecting rod between the first connecting region and the second connecting region comprises a section with a constant cross section.

5. A reciprocating piston compressor according to claim 3, wherein at least one of the connecting regions comprises a region with a reduced cross section for forming a solid joint.

6. A reciprocating piston compressor according to claim 1, wherein the connecting rod has a diameter and a length which are dimensioned such that a transverse force which results from a deviation of the axis of the first fixed restraint with respect to the axis of the second fixed restraint does not exceed a limit transverse force, wherein the deflection is maximally 3% of a piston diameter.

7. A reciprocating piston compressor according claim 6, wherein the limit transverse force does not exceed 20 N.

8. A reciprocating piston compressor according to claim 1, wherein the cylinder comprises a guide section and a compression section.

9. A reciprocating piston compressor according to claim 8, wherein the compression section is constructed with multiple parts comprising a cylinder head, a middle part and a cylinder base.

10. A reciprocating piston compressor according to claim 9, wherein the middle part is constructed with multiple parts and comprises a cylinder liner.

11. A reciprocating piston compressor according to claim 1, wherein the reciprocating piston compressor is air-cooled.

12. A reciprocating piston compressor according to claim 1, wherein the reciprocating piston compressor is water-cooled.

13. A reciprocating piston compressor according to claim 1, wherein the reciprocating piston compressor is dry-running.

14. A reciprocating piston compressor according claim 1, wherein the connecting rod has a diameter and a length which are dimensioned such that a transverse force which results from a deviation of the axis of the first fixed restraint with respect to the axis of the second fixed restraint does not exceed a limit transverse force, wherein the deflection does not exceed 0.5 mm when the limit transverse force is maximally 1/200 of a piston force F.

15. A reciprocating piston compressor according claim 14, wherein the limit transverse force does not exceed 20 N.

16. A retrofit kit for a reciprocating piston compressor comprising a piston rod, a crosshead, a piston and a connecting rod, wherein the crosshead and the piston can be brought into active connection with one another by way of the connecting rod, wherein the crosshead and the piston each comprise a receiver for a fixed restraining of the connecting rod, the connecting rod being configured such the connecting rod permits alignment errors between the crosshead and the piston via one of deformation of the connecting rod and deflection of the connecting rod.

17. A retrofit kit according to claim 16, further comprising a cylinder, wherein the cylinder preferably comprises a guide section and a compression section.

18. A reciprocating piston compressor comprising: a crank casing; a crankshaft; at least one piston rod arranged on the crankshaft; a crosshead configured as a guide piston, the piston rod being actively connected to the crosshead; at least one cylinder; a piston movably arranged in the cylinder; a one-piece integrally formed connecting rod, wherein the crosshead and the piston are actively connected to one another via the one-piece integrally formed connecting rod, wherein the connecting rod is connected to the crosshead with a first fixed restraint and the connecting rod is connected to the piston with a second fixed restraint, the one-piece integrally formed connecting rod comprising a one-piece integrally formed connecting rod extent extending between an end of the piston and an end of the crosshead, wherein only a portion of the at least one cylinder surrounds the one-piece integrally formed connecting rod extent, wherein no other structure is provided radially between the one-piece integrally formed connecting rod extent and an inner surface of the at least one cylinder with respect to a longitudinal axis of the at least one cylinder.

19. A reciprocating piston compressor according to claim 18, wherein the connecting rod is configured such the connecting rod permits alignment errors between the crosshead and the piston via one of deformation of the connecting rod and deflection of the connecting rod.

20. A reciprocating piston compressor according to claim 18, wherein the connecting rod has a diameter and a length which are dimensioned such that a transverse force which results from a deviation of the axis of the first fixed restraint with respect to the axis of the second fixed restraint does not exceed a limit transverse force, wherein the deflection of the connecting rod is maximally 3% of a piston diameter.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings:

(2) FIG. 1 is a partially sectional view of a reciprocating piston compressor according to the invention with four cylinders;

(3) FIG. 2 is a sectioned detail view from FIG. 1;

(4) FIG. 3a is a schematic view showing a detail of a connecting rod;

(5) FIG. 3b is a schematic view showing a detail of a connecting rod; and

(6) FIG. 4 is a schematic view showing a connecting rod.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(7) Referring to the drawings, FIG. 1 shows a reciprocating piston compressor 100. The reciprocating piston compressor 100 here comprises four cylinders 20, in which a piston is located in each case. The reciprocating piston compressor 100 is designed as a multi-stage piston compressor.

(8) FIG. 2 shows a detail of the reciprocating piston compressor 100 of FIG. 1. What is shown is a sectioned view through the high pressure stage of the reciprocating piston compressor 100 of FIG. 1.

(9) A crankshaft 11, on which a piston rod 12 is pivotally mounted is arranged in a crank casing 10. The piston rod 12 is connected to a crosshead 13. The connection between the piston rod 12 and crosshead 13 is configured as an articulated bolt connection. Suitable bearings are provided on the connection (not described in more detail here). The crosshead 13 is configured as a piston with a round cross section. An opening, in which a connecting rod 24 is retrained or clamped with a restraint A is located at the top on the crosshead 13. The connecting rod 24 is likewise fixedly retrained on a piston 23 with the restraint B. The piston 23 likewise comprises a suitable opening. Connecting regions 241 and 242 are provided on both sides of the connecting rod 24. The connecting regions 241 and 242 merge into a foot which is to say that they have a thickened cross section and a cross section which becomes thicker, in the region of the connection to the piston and to the crosshead respectively. Here, the restraint A and B are configured as press fits. The connecting rod comprises a middle section 243 between the restraint A and B, which is to say likewise between the connecting regions 241 and 242. This middle section 243 is reduced in diameter in comparison to the sections 241 and 242.

(10) The cylinder 20 is subdivided into a guide section 21 and into a compression section 22. The guide section 21 is configured as one piece. The crosshead 13 is located in this. The compression section 22 here is configured in a three-part manner. It comprises a cylinder head 221, a middle part 222 and a cylinder base 223. A cylinder liner 2221 which extends to into the cylinder base 223 is arranged within the middle part 222. The cylinder liner 2221 here is manufactured of high-alloy nickel steel. Carbide or a high-strength plastic can be used as an alternative. The materials preferably have a thermal coefficient of expansion of zero or approximately zero and are wear-resistant. The same materials are preferably applied for the piston 23. The cylinder head 221, the middle part 222 and the cylinder base 223 are restrained or tensioned to one another by way of screws. The middle part 222 comprises cooling ribs which serve for dissipating heat to the surroundings.

(11) The piston 23 runs up and down within the piston liner 2221 and comprises an antifriction layer for reducing the friction. The antifriction layer is of a high-strength, reinforced plastic, here PEEK. PTFE with carbon fibers could be used as an alternative. Here, the connecting rod 24 is configured in a manner such that given a loading of the position from the direction of the compression chamber, a buckling according to Euler 4 occurs. It consists of a high-strength Q&T steel, but titanium or titanium alloys would also be conceivable. The crosshead 13, the piston rod 12 and the guide section 21 here are manufactured of aluminum. Titanium and its alloys as well as steel can however be envisaged.

(12) One end of the connecting rod 24 of FIG. 2 is shown in FIG. 3a. It comprises a region for the restraint A, a connecting region 241 and a middle section 243. The diameter of the connecting rod 24 is essentially constant in the middle section 243. This connecting rod in the connecting region 241 thickens into a foot, on which a pin the restraint A is subsequently provided. The cross section of the connecting region 241 constantly increases in the direction to the restraint A.

(13) In contrast to this and merely for comparison, the connecting rod of FIG. 3a is shown in FIG. 3b, wherein the connecting rod comprises a connecting region 241 with a cross-sectional narrowing 2411. This narrowing is configured in a peripheral manner and forms a solid joint. Here, the narrowing 2411 is located between the middle section 243 and the connecting region 241, and forms the termination of the connecting region 241 towards the middle section 243. The same embodiments likewise apply to the restraint B and the associated connecting region 242.

(14) FIG. 4 schematically shows a connecting rod 24, restrained in a piston 23 and a crosshead 13. An offset f which can arise for example on account of manufacturing tolerances is present between the central axes of the crosshead 13 and the piston 23. The offset f however can also set in over the course of time. For example, a guide portion at the crosshead can wear. This danger increases for example in the case of a dry-running, oil-free piston compressor.

(15) An exemplary computation of the connecting rod for different diameters and piston pressures (piston forces) is shown in the subsequent table. Herein, a material with a reverse bending strength of =420 N/mm.sup.2, a yield strength Re of 900 N/mm.sup.2, a modulus of elasticity of 210 kN/mm.sup.2 and a maximal possible offset f of 0.5 mm is assumed. A specific slenderness ratio limit can be computed for specific material constants. The slenderness ratio limit is 66 for the present material. The buckling according to Tetmajer, i.e. plastically must be computed below this slenderness ratio limit and according to Euler, i.e. elastically, above this slenderness ratio limit.

(16) The computations were effected for the Euler cases 3 and 4 amid the specification of a constant, maximally permissible transverse force, i.e. a transverse force which does not exceed an absolute valve. In a second step, the maximally permissible transverse force was computed on a percentage basis depending on the piston force and this value was taken a basis.

(17) Herein, the computations were carried out for piston forces F=4 kn, 8 kn and 12 kN. On the one hand the transverse force Q was limited to 20 N for all piston forces and on the other hand it was proportionally (F/200) included in the calculations.

(18) Herein, a safety of 4 of the _buckling to _compressive should not be fallen short of.

(19) The calculations could all be carried out according to Tetmajer. The following diameters D, lengths L and slenderness ratios X, could be iteratively determined.

(20) The stresses were computed in the following table, wherein both connecting regions of the connecting rod 24 according to FIG. 3a are specified.

(21) TABLE-US-00001 Euler 4 Euler 4 transverse force limited transverse force limited in an on a percentage basis absolute manner F 4000 8000 12000 [N] 4000 8000 12000 Q 20 40 60 [N] 20 20 20 L 160 192 215 [mm] 160 269 367 D 6 8.2 9.9 [mm] 6 8.9 11.2 53 47 43 [] 53 60 66 _buckling 559 601 622 [N/mm{circumflex over ()}2] 559 514 481 _compressive 141 151 156 [N/mm{circumflex over ()}2] 141 129 122 S 4 4 4 [] 4 4 4

(22) In the following table, the stresses have been computed under the assumption that the connecting rod 24 at one side comprises a connecting region according to FIG. 3a and at the other side a connecting region according to FIG. 3b (solid joint).

(23) TABLE-US-00002 Euler 3 Euler 3 transverse force limited transverse force limited in an on a percentage basis absolute manner F_piston 4000 8000 12000 [N] 4000 8000 12000 Q 20 40 60 [N] 20 20 20 L 95 117 130 [mm] 95 160 214 D 5.8 8 9.6 [mm] 5.8 8.5 10.6 46 41 38 [] 46 53 57 _buckling 607 638 658 [N/mm{circumflex over ()}2] 607 563 539 _compressive 151 159 166 [N/mm{circumflex over ()}2] 151 141 136 S 4 4 4 [] 4 4 4

(24) Given the selected values of L and D, a safety S of at least 4 resulted whilst taking into account the present stress _compressive and the critical buckling stress _buckling. The computations can of course also be calculated on the basis of a defined, demanded or desired safety value.

(25) While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.