EP2333336B1 - Reciprocating engine for use as a vacuum pump for medicinal purposes - Google Patents

Description

The invention relates to a piston engine having at least one cylinder and an opening of the cylinder occlusive cylinder head. Furthermore, the piston engine comprises an at least partially disposed within the cylinder piston, which is arranged by means of a connecting rod relative to the cylinder and relative to the cylinder head in its longitudinal direction movable.

A common type of piston guide is the so-called plunger guide, in which the piston is connected via the connecting rod directly to the crankshaft. The transverse forces exerted by the inclination of the connecting rod on the piston are absorbed by the cylinder wall through which the piston is guided. The transverse forces try to tilt the piston, which leads to a noise and on the other hand can lead to the clamping of the piston. Especially with vacuum pumps in medical use, such a noise can be perceived as very disturbing. In order to prevent jamming, the piston must be made relatively long compared to its diameter, resulting in a relatively large size of the cylinder and a high oscillating mass. On the other hand, the gap between the piston and the cylinder wall must be made so large that the piston can expand due to the evolution of heat during operation of the piston engine. This necessary large gap favors the noise, since the piston changes in an upper and a lower end position during its movement due to a load change in each case from one plant side to another plant side.

Another common type of piston guide is the so-called Kreuzkopfführung, in which the piston is connected via a piston rod with a guided on a plain bearing crosshead. The crosshead in turn is connected via the connecting rod with the crankshaft. About the plain bearing transmitted via the connecting rod of the crankshaft transverse forces are absorbed so that the piston experiences only forces in its longitudinal direction and no forces are transmitted from the piston to the cylinder wall. A disadvantage of the crosshead guide is that it requires a large space and has a high oscillating mass. Thus, the Kreuzkopfführung comes only for large machines with very low speeds in question.

From the document DE 2 001 921 A1 For example, a liquid dispensing pump is known in which a piston is slidably mounted on a valve stem.

From the document US 1 731 044 A is a compressor with two concentrically arranged compression chambers known. The oscillating piston is fixedly connected via a screw to an underlying part which serves for coupling to the crankshaft.

From the document DE 28 44 719 A1 is a two-piece pumping system is known, which has two concentrically arranged compression chambers. A first centrally located, fixed piston and the oscillating cylinder alone serve to form a compression space. They do not assume any managerial task regarding the implementation of a rotational movement into an oscillating motion.

From the document DE 76 23 119 A is a two-stage concentric pumping system is known, which is operated by a hand lever.

From the document EP 0 726 393 A1 is a two-stage pumping system known. As drive an electrically operated cam drive is disclosed.

It is an object of the invention to provide a piston engine which is compact and low noise and in which no or only small lateral forces are transmitted from the piston to the cylinder.

This object is achieved by a piston engine having the features of patent claim 1. Advantageous developments are specified in the dependent claims.

By providing a fixedly connected to the cylinder head guide element, of which at least a portion is disposed within a running in the longitudinal direction of the piston opening of the piston, it is achieved that the connecting rod exerted on the piston transverse forces are absorbed by the guide element and not, as z. B. in the plunger guide, are transferred to the cylinder wall. Because the size of the opening of the piston during heating of the piston by the operation the piston engine expands with the piston, the gap between the guide member and the piston can be made very small, so that a tilting of the piston is prevented or the piston can only slightly tilt. As a result, the noise is reduced during operation of the piston engine and prevents jamming of the piston in a simple way. By guiding the piston through the guide element is compared to the plunger guide, a favorable, ie as large as possible, achieved leadership ratio, wherein the guide ratio is the ratio of the length of the piston to the diameter of the element leading the Koben. Since no or only small forces are transmitted between the piston of the cylinder wall, the wear of the piston and / or the wear of the cylinder inner wall are reduced.

Through the opening in particular an inwardly directed sliding surface is formed. The piston preferably slides over this sliding surface on the guide element,

The longitudinal direction is the direction in which the longitudinal axis of the piston is directed, ie the direction in which the piston moves during reciprocation in the cylinder during operation of the piston engine. A tilting of the piston is understood to mean that the longitudinal axis of the piston pivots relative to the longitudinal axis of the cylinder and thus the longitudinal axis of the cylinder and the longitudinal axis of the piston no longer coincide. The cylinder and the cylinder head are preferably formed in one piece, whereby the stability of the piston engine is increased. It is also advantageous if the guide element and the cylinder head are integrally formed, whereby a secure attachment of the guide element is achieved on the cylinder head.

The transverse forces are all those forces that do not act in the longitudinal direction of the piston. The transverse forces acting on the piston come about, in particular, through the rotation of a crankshaft connected to the piston via the connecting rod. About the crankshaft and the connecting rod, the reciprocation of the piston is effected within the cylinder.

The play between the piston and the guide element is in particular so small that the passage of a medium between the piston and the guide element is prevented or the extent of the passage of the medium between the piston and the guide element is so small that it during operation of the Is negligible piston engine. This ensures that it is possible to dispense with a sealing element for sealing the gap between the piston and the guide element. Furthermore, tilting of the piston is prevented by the small clearance and a secure guidance of the piston from the guide element is achieved. The medium is in particular a gas, a liquid or a mixture of a gas and a liquid.

The opening of the piston and the guide element are preferably each cylindrical, so that a secure guidance of the piston is achieved on the guide member and tilting of the piston is prevented. Alternatively, the guide element and the opening may also have any non-cylindrical cross-section.

It is advantageous if the opening is a bore and if the radius of the guide element has a value between 98% and 99.9% of the radius of the bore. This ensures that it is possible to dispense with a sealing element between the piston and guide element and tilting of the piston and thus noise is avoided.

During a movement in the longitudinal direction, the piston preferably slides on the guide element, so that the piston is guided over the guide element at all times and tilting is prevented.

It is advantageous if, during operation of the piston engine, at least a partial region of the guide element is arranged within the opening in all operating states. This ensures that the piston is guided in all operating states by the guide element and in all operating states, the transverse forces acting on the piston are absorbed by the guide member.

Further, it is advantageous if the longitudinal axis of the opening and the longitudinal axis of the piston coincide, so that the opening is arranged centrally in the piston. In this way it is achieved that the distance of the guide element to the inner surface of the cylinder in all directions is the same and thus no tilting moment is created by different pressures on the end faces of the piston.

The opening is in particular a through-bore, so that the piston is also guided by a relatively large distance in the longitudinal direction of the piston through the passing through the through hole guide member when reciprocating the piston. The guide element is in particular designed so long that it completely penetrates the through hole in each operating state of the piston engine.

In an alternative embodiment of the invention, in particular in piston engines, in which the piston is moved only by short distances, the opening may also be formed as a blind bore. In this case is the length over which the guide element projects into the bore varies depending on the position of the piston.

In an alternative embodiment of the invention, the piston may comprise a sealing element projecting into the bore, which reduces, preferably prevents, the passage of the medium through the guide element into the piston. In this way, a seal of the working space of the piston engine is achieved and thus increases the effectiveness of the piston engine.

The cylinder, the guide element and the piston are in particular dimensioned such that even at the maximum permissible operating temperature of the piston engine, the piston does not contact the inner surface of the cylinder when moving in the longitudinal direction. By preventing the contact between the piston and the inner surface of the cylinder, on the one hand the clamping of the piston and the wear on the piston and cylinder is prevented. On the other hand, noises are avoided, which are caused in known plunger engines by the change of the contact side of the piston on the inner surface of the cylinder.

It is advantageous if the piston comprises a sealing element which is fixedly connected to the piston, which contacts the inner surface of the cylinder and which reduces the passage of the medium between the inner surface of the cylinder and the piston. It is particularly advantageous if the sealing element completely prevents the passage of the medium. As a result, the effectiveness of the piston engine is increased.

The piston engine is in particular a piston working machine, preferably a piston pump. By the reciprocation of the piston is Pumped the pumped medium from one location to another. The piston pump is in particular a vacuum pump for the medical sector or a fluid pump. The piston working machine may also be a compressor. Alternatively, the described piston guide can also be used for piston engines. In particular, the piston guide can be used in internal combustion engines, hydraulic and gas drives.

In a preferred embodiment of the invention, the piston engine comprises at least two cylinders, in each of which a longitudinally extending bore having a piston is arranged, which is movable relative to the cylinder. The pistons are each guided via a guide element which is fixedly connected to a cylinder head of the respective cylinder and which is arranged at least partially within the bore of the respective piston. By providing several cylinders, the performance of the piston engine is increased. In one pump, the provision of several cylinders increases the pump power.

Further features and advantages of the invention will become apparent from the following description, the invention with reference to exemplary embodiments explained in more detail in conjunction with the accompanying figures.

Figur 1

eine schematische perspektivische teilgeschnittene Darstellung einer Kolbenpumpe gemäß einer ersten Ausführungsform der Erfindung; und

Figur 2

eine schematische perspektivische teilgeschnittene Darstellung einer Kolbenpumpe gemäß einer zweiten Ausführungsform der Erfindung.

Show it:

FIG. 1

a schematic partial perspective view of a piston pump according to a first embodiment of the invention; and

FIG. 2

a schematic perspective partially sectioned view of a piston pump according to a second embodiment of the invention.

In FIG. 1 is a schematic perspective partially sectioned view of a piston pump 10 according to a first embodiment of the invention shown. The piston pump 10 comprises two cylinders 12a, 12b, which are formed integrated into a housing 14 of a crankshaft 16. Each of the cylinders 12a, 12b has two openings, of which each of the crankshaft 16 facing away from the opening by means of a cylinder head 18a, 18b is closed.

The crankshaft 16 facing openings of the cylinder 12a, 12b are not closed. The cylinder heads 18a, 18b are fastened to the housing 14 in particular via a plurality of screws. For this purpose, the cylinder heads 18a, 18b each have a plurality of holes, one of which in FIG. 1 is denoted by the reference numeral 20 by way of example. In an alternative embodiment of the invention, the cylinders 12a, 12b and the cylinder heads 18a, 18b may also be integrally formed.

Furthermore, the piston pump 10 comprises two pistons 22a, 22b, of which one is arranged at least partially within one of the cylinders 12a, 12b. The pistons 22a, 22b are articulated via two bolts 24a to 24d, each with a connecting rod 28a, 28b. The bolts 24a to 24d are secured by means of retaining rings 26a, 26b against accidental slipping out. In an alternative embodiment of the invention, the connecting rod 28a, 28b may also be connected to the respective piston 22a, 22b only via a securing bolt 24a to 24d or more than two securing bolts 24a to 24d.

The piston 22a, 22b facing away from the ends of the connecting rods 28a, 28b are connected to the crankshaft 16. The crankshaft 16 is using a in FIG. 1 not shown engine rotated. As a result of the rotational movement of the crankshaft 16, the connecting rods 28a, 28b are set in motion, which in turn reciprocates the pistons 22a, 22b connected to the connecting rods 28a, 28b within the cylinders 12a, 12b in the longitudinal direction. The longitudinal direction is the direction in which the axial center axis of the pistons 22a, 22b and thus the longitudinal axis of the cylinders 12a, 12b extends. As the pistons 22a, 22b reciprocate through the connecting rods 28a, 28b, the connecting rods 28a, 28b produce both longitudinal forces which are responsible for reciprocating the pistons 22a, 22b and transverse to the longitudinal direction acting forces transmitted to the pistons 22a, 22b.

The pistons 22a, 22b each have a longitudinal through-bore, the central axis of the through-hole and the longitudinal axis of the pistons 22a, 22b respectively coinciding. The pistons 22a, 22b are each guided in their reciprocating motion by a guide element 30a, 30b designed to be complementary to the bores of the pistons 22a, 22b. The guide elements 30a, 30b are each fixedly connected to the respective cylinder head 18a, 18b. The guide elements 30a, 30b are arranged such that, irrespective of the operating position in which the respective piston 22a, 22b is arranged, at least a portion of the respective guide element 30a, 30b is disposed within the throughbore of the respective piston 22a, 22b. At the in FIG. 1 In the embodiment shown, the guide elements 30a, 30b are designed as a rod with a cylindrical cross-section, for which reason the guide elements 30a, 30b are also referred to as guide rods.

In an alternative embodiment of the invention, the guide elements 30a, 30b and the openings of the pistons 22a, 22b, in which the guide elements 30a, 30b are arranged, also each have a rectangular cross section. Likewise, any other cross-sectional shapes are conceivable.

The forces directed by the connecting rods 28a, 28b on the pistons 22a, 22b transversely to the longitudinal directions are transmitted by the pistons 22a, 22b to the respective guide element 30a, 30b, so that the forces acting transversely to the longitudinal direction do not flow from the piston 22a, 22b to the respective inner wall of the respective cylinder 12a, 12b must be transmitted. The play between the piston 22a, 22b and the respective inner wall of the respective cylinder 12a, 12b can therefore be so large that the piston 22a, 22b, even at the maximum operating temperature of the piston pump 10 and thus the maximum thermal expansion, the inner wall of the cylinder 12a, 12b not contacted. As a result, wear of the piston 22a, 22b and / or the inner wall is prevented. The necessary seal between the piston 22a, 22b and the inner wall of the cylinder 12a, 12b, which is required to prevent passage of the medium to be pumped between the piston 22a, 22b and the inner wall of the cylinder 12a, 12b, is provided by a sealing member 32a, 32b achieved. The sealing elements 32a, 32b are made of an elastic material and, in particular, so elastic that they are independent of the play between the piston 22a, 22b and the inner wall of the cylinder 12a, which changes due to the thermal expansion of the pistons 22a, 22b and the cylinders 12a, 12b , 12b ensure a secure seal and thus prevent the passage of the medium to be pumped. The sealing elements 32a, 32b are in particular fixedly connected to the respective piston 22a, 22b and, when the pistons 22a, 22b are reciprocated, respectively contact the inner wall of the cylinders 12a, 12b. The sealing elements 32a, 32b may also be formed as piston rings.

The diameter of the guide elements 30a, 30b is only slightly smaller than the diameter of the respective bores of the respective piston 22a, 22b. This ensures that between the guide member 30a, 30b and the piston 22a, 22b only a slight clearance is present. This causes on the one hand that can be dispensed with a sealing element between the piston 22a, 22b and the guide elements 30a, 30b, since due to the small clearance and the large length of the bore passage of the medium to be pumped between the guide member 30a, 30b and the Piston 22a, 22b is prevented or the amount of medium passing through is so small that it moves in an acceptable for the operation of the piston pump frame. On the other hand is achieved by the small clearance between the guide member 30a, 30b and the piston 22a, 22b, that the piston 22a, 22b is not tilted when moving back and forth by the transverse forces acting transversely to the longitudinal direction or only minimally based on its longitudinal axis , This in turn ensures that clamping of the piston 22a, 22b within the cylinder 12a, 12b avoided and the noise of the piston pump 10 is reduced. Especially in the medical field, for example in vacuum pumps, the noise of the piston pump 10 may be disturbing, so that such a reduction of noise brings a significant advantage.

The play between the piston 22a, 22b and the guide member 30a, 30b is particularly so small that the piston 22a, 22b slides on the guide member 30a, 30b during reciprocation in the longitudinal direction, whereby a secure guidance of the respective piston 22a, 22b is reached. Since the radius of the bore of the pistons 22a, 22b at a heating of the Pistons 22a, 22b increased during operation of the piston pump 10, the clearance between the piston 22a, 22b and the guide member 30a, 30b may be made particularly low, since a jamming during operation by the expansion of the game is avoided.

In an alternative embodiment of the invention may be arranged between the guide member 30a, 30b and the respective piston 22a, 22b, respectively, a sealing element that prevents or reduces the passage of the medium to be pumped between the pistons 22a, 22b and the guide member 30a, 30b , The sealing element is preferably in each case fixedly connected to the piston 22a, 22b, but may alternatively also be fixedly connected to the respective guide element 30a, 30b.

The cylinder heads 18a, 18b each include a diaphragm 34a, 34b each having two tabs 36a, 36b, 38a. When the pistons 22a, 22b are moved in the direction of the crankshaft 16, the first lug 36a, 36b of the respective cylinder head 18a, 18b is opened in the direction of the cylinder 12a, 12b so that the medium to be pumped into the working space of the cylinder 12a through the opened opening , 12b can flow in. When moving a piston 22a, 22b away from the crankshaft 16, the first tab 36a, 36b is closed and the second tab 38a is opened, so that the medium to be pumped through the closable by the second tab 38a outlet channel from the working space of the cylinder 12a, 12b is pumped.

In an alternative embodiment of the invention, instead of a piston pump, the device 10 may also be a piston engine, in particular an internal combustion engine or a Stirling engine. In this case, the principle of operation of the device is reversed, so that the crankshaft 16 is not driven by a motor, but the crankshaft 16 by the The reciprocating movement of the pistons 22a, 22b via the connecting rods 28a, 28b is set in rotation.

In FIG. 2 are shown a schematic perspective partially cutaway view of a piston pump 40 according to a second embodiment of the invention and a schematic perspective view of a motor 42. Elements with the same structure or the same function have the same reference numerals. The motor 42 is flanged to the piston pump 40 and serves to drive the crankshaft 16.

Unlike the in FIG. 1 shown first embodiment, the two cylinders 12a, 12b are not arranged in a row but offset by 90 ° t. In an alternative embodiment of the invention, more than two cylinders 12a, 12b or only one cylinder 12a, 12b may be provided. Likewise, alternatively, a plurality of cylinders may be arranged in a row and additionally one or more cylinders may be arranged offset by an angle.

LIST OF REFERENCE NUMBERS

10, 40

piston pump

12a, 12b

cylinder

16

crankshaft

18a, 18b

cylinder head

20

drilling

22a, 22b

piston

24a to 24d

bolt

26a, 26b

circlip

28a, 28b

pleuel

30a, 30b

guide element

32a, 32b

sealing

34a, 34b

membrane

36a, 36b, 38a

flap

42

engine

Claims (14)

1. A piston machine, comprising
   at least one cylinder (12a, 12b),
   a cylinder head (18a, 18b) closing an opening of the cylinder (12a, 12b), and
   a piston (22a, 22b) arranged at least in part within the cylinder (12a, 12b),
   the piston (22a, 22b) having an opening extending in its longitudinal direction, and
   wherein at least a partial area of a guiding element (30a, 30b) firmly connected to the cylinder head (18a, 18b) is arranged within the opening of the piston (22a, 22b),
   characterized in that the piston (22a, 22b) is arranged movably in its longitudinal direction relative to the cylinder (12a, 12b) and to the cylinder head (18a, 18b) by means of a connecting rod (28a, 28b), and
   in that the opening is a through bore.
2. The piston machine (10, 40) according to claim 1, characterized in that an inwardly directed sliding surface is formed by the opening.
3. The piston machine (10, 40) according to one of the preceding claims, characterized in that the guiding element (30a, 30b) absorbs at least a part, preferably all of the forces acting on the piston (22a, 22b) transversely to the longitudinal direction of the piston (22a, 22b) during the movement of the piston (22a, 22b) in longitudinal direction.
4. The piston machine (10, 40) according to one of the preceding claims, characterized in that the play between the piston (22a, 22b) and the guiding element (30a, 30b) is so little that the passage of a medium between the piston (22a, 22b) and the guiding element (30a, 30b) is prevented.
5. The piston machine (10, 40) according to one of the preceding claims, characterized in that the guiding element (30a, 30b) is cylindrical.
6. The piston machine (10, 40) according to one of the preceding claims, characterized in that the piston (22a, 22b), when moved in longitudinal direction, slides on the guiding element (30a, 30b).
7. The piston machine (10, 40) according to one of the preceding claims, characterized in that in all operating states during the operation of the piston machine (10, 40) at least a partial area of the guiding element (30a, 30b) is arranged within the opening each time.
8. The piston machine (10, 40) according to one of the preceding claims, characterized in that the longitudinal axis of the opening and the longitudinal axis of the piston (22a, 22b) coincide.
9. The piston machine (10, 40) according to one of the preceding claims, characterized in that the piston (22a, 22b) comprises a sealing element projecting into the bore and reducing, preferably preventing the passage of a medium between the guiding element (30a, 30b) and the piston (22a, 22b).
10. The piston machine (10, 40) according to one of the preceding claims, characterized in that the cylinder (12a, 12b), the guiding element (30a, 30b) and the piston (22a, 22b) are dimensioned such that even given a maximum allowable operating temperature of the piston machine (10, 40) the piston does not contact the inside surface of the cylinder (12a, 12b) when the piston (22a, 22b) is moved in longitudinal direction.
11. The piston machine (10, 40) according to one of the preceding claims, characterized in that the piston (22a, 22b) comprises a sealing element (32a, 32b) which contacts the inside surface of the cylinder (12a, 12b) and reduces, preferably prevents the passage of a medium between the inside surface of the cylinder (12a, 12b) and the piston (22a, 22b).
12. The piston machine (10, 40) according to one of the preceding claims, characterized in that the piston machine (10, 40) is a piston work machine, preferably a piston pump, in particular a vacuum pump.
13. The piston machine (10, 40) according to one of the preceding claims, characterized in that the piston (22a, 22b) is connected via the connecting rod (28a, 28b) to a crankshaft (16).
14. The piston machine (10, 40) according to one of the preceding claims, characterized in that at least a further cylinder (12a, 12b), a further cylinder head (18a, 18b) closing an opening of the further cylinder (12a, 12b) and a further piston (22a, 22b) are provided, which piston is arranged at least in part within the further cylinder (12a, 12b) and is arranged movably in its longitudinal direction relative to the further cylinder (12a, 12b) and relative to the further cylinder head (18a, 18b) by means of a further connecting rod (28a, 28b), in that the further piston (22a, 22b) has an opening extending in its longitudinal direction, and in that at least a partial area of a further guiding element (30a, 30b) firmly connected to the further cylinder head (18a, 18b) is arranged within the opening of the further piston (22a, 22b).

Images