EP0093372A1 - Reciprocating piston mechanism - Google Patents

Abstract

Reciprocating piston mechanism, which can be used as a motor, pump or, especially, a volumetric meter, having a cylindrical housing (H) in whose cylindrical space a piston (D) can be displaced back and forth, and whose cylindrical space is subdivided into two working chambers (V1, V2) constructed at the end face of the piston and whose two dead centre positions overlap one another, and having a sealable inlet opening (b) and a sealable outlet opening (k), which open into the cylindrical space and can each be connected alternately to one working chamber (V1) and the other working chamber (V2). The inlet opening (b) and the outlet opening (k) are arranged diametrically opposite one another on the circumference of the cylindrical space at its axial centre, where they are covered in each piston position by the piston (D). The piston (D) has channels (b1, b2, k1, k2) which open on the circumference of the piston offset with respect to one another and in the dead centre positions of piston (D) are sealed by the cylindrical housing (H) with respect to the inlet opening (b) and the outlet openings (k), and in the dead centre positions are situated in pairs on both sides of the inlet opening (b) or outlet opening (k). It is possible for the piston to be moved back and forth during the piston stroke by means of a control mechanism in such a way that in the piston positions between the dead centre positions the working chambers (V1, V2) are connected alternately via the assigned channels (b1, b2, k1, k2) in accordance with the respective direction of displacement of the piston (D) to the inlet opening (b) or the outlet opening (k) (Figs. 1a, 1b). <IMAGE> <IMAGE>

Description

The invention relates to a reciprocating piston mechanism which can be used as a motor, pump or in particular a volume counter and which works with a gaseous or preferably liquid working medium. The reciprocating piston mechanism has a cylinder housing, in the cylinder space of which a piston can be pushed back and forth, from which the cylinder space is divided into two working spaces formed on the end face of the piston, the two dead center positions of which overlap one another, and a lockable inlet opening and a lockable outlet opening, which in the Open cylinder space and are alternately connected to one work space and the other work space.

Piston mechanisms of this type (so-called volume displacement machines) are known in countless variations. These machines can be operated either as pumps or as motors. A specific type of reciprocating mechanism has become known through the volume displacement flow meter or volume counter. By means of these devices, the working medium flowing through is distributed to partial quantities determined in their volumes, and these partial quantities are then conveyed as such. The measuring method consists essentially of counting the subsets of a certain volume. In a suitable embodiment, these devices are also operated as pumps (in general, they are designed as metering pumps of lower output).

Depending on the operating mode of these devices (as is generally the case with piston machines) Outlet of the working medium flowing through into and out of the cylinder space in that the blocking and the opening of the inlet and outlet openings are carried out automatically in a controlled manner. A control is required for this, through which the inlet and outlet openings in the dead center positions of the piston are opened and closed in such a way that, in the operating mode as a volume counter, the piston is pressed into the opposite dead center position by the inflowing working medium and in the operating mode as a pump that through the piston in the working medium sucked in and the next subset of the working medium is sucked into the other working space.

In known embodiments, various sensing instruments and switches are used for this purpose.

Various electronic devices (for example HU-A-146 035) are also known, but they require auxiliary energy. If this auxiliary energy fails to appear, this disturbance not only interrupts the measuring process but also the flow of the working medium. However, this is not permitted in some cases. This problem can be practically eliminated by mechanical devices. If the piston is moved to its dead center position (mechanical position determination, changeover), a mechanism is actuated which indirectly or directly shuts off _or . Opening the inlet and outlet openings triggers. Such an embodiment is known from HU-A-171 771. Here, the piston is moved from the dead center position with the help of a speech memory.

A disadvantage of this mechanism is that the energy stored for the impulsartiγ function of the switch comes from the pressure energy of the working medium to be measured, whereby the pressure required for driving the working medium is increased.

Another disadvantage is the complicated structure of the mechanism and also that the components of the switch that come into contact with one another are exposed to intensive wear. A further disadvantage can be mentioned that, due to the pulsed actuation of the switching element, its movement period cannot be designed in such a way that a uniform partial flow is achieved during the movement period of the piston. The resolution capability is therefore limited by the stroke length _b or the stroke volume of the piston.

Fluidyne Instrumentation (Oakland, California) has developed a series of flow meters. With the 220 series, the disadvantages listed can be partially eliminated. The flow meters have four pistons offset by 90 °, which are operated in pairs. The pistons are connected via hinges to a crankshaft in the middle, from whose number of revolutions the quantity measured value is derived.

With this construction, the pistons not only carry out the position determination but also the switchover, since spaces are formed in the body surrounding the piston cylinders, as a result of which the inner space of any piston (in one of its dead center positions) with the outer space of the one following in the direction of rotation Piston, and the outer space of the piston preceding the direction of rotation are connected to the outlet opening by means of a groove provided on the jacket of the fourth piston. The four pistons have a common inner space into which the working medium to be measured enters.

This piston mechanism eliminates the aforementioned problems of previous mechanical switch designs. However, its structure is very complicated and requires very precise processing. The articulated arms connecting the pistons to the crankshaft must be provided with roller bearings at both ends and a composite cavity system must also be formed in the housing. Another disadvantage of this construction is that it must have at least three pistons if it is operated as a flow meter, or two pistons if it is operated as a pump. It is best to have three or more pistons to achieve a smooth gear.

The object of the invention is to solve the disadvantages mentioned and to design a piston mechanism with the features mentioned at the outset such that reliable operation can be achieved with a simple, low-wear construction, in particular when it is used as a volume meter.

For this purpose, a reciprocating piston mechanism is created by the invention, which can be used with a single piston as a pump and with two pistons as a volume counter with an approximately uniform flow rate. The reciprocating piston mechanism according to the invention retains the advantages of the known constructions without a changeover switch and without a mechanism determining the piston position. No special crank mechanism and no special connection space system in the housing is required. The device is simply constructed and can be easily manufactured and assembled. The reciprocating piston mechanism according to the invention is extremely reliable. According to the invention, it was recognized that if the piston is rotated back and forth around its own axis during its axial back and forth movement, both the position determination and the switchover can be brought about with the aid of channels worked out on the piston circumference. For this purpose, the drive mechanism for the piston is designed such that each point of the piston peripheral surface during the axial reciprocating movement between the two dead center positions is in a closed, returning path Moves, whereby through the channels in certain axial positions or angular positions of the piston corresponding connections from the work spaces to the inlet opening and the outlet opening can be created or the same can be interrupted.

The reciprocating piston mechanism according to the invention thus has at least one piston in the cylinder space of a cylinder housing. One or more inlet and outlet openings are formed on the cylinder space. The length of the piston is matched to the piston stroke in such a way that the two dead center positions of the piston overlap one another, i.e. that the piston stroke is smaller than the piston length. According to the invention, the outlet opening and the inlet opening are formed on the circumference of the cylinder space where they are covered by the piston in each piston position. The piston has at least two channels, each connected to one of the working spaces on the end face of the piston, which open out in relation to one another on the circumference of the piston and are blocked off from the cylinder housing against the inlet opening and the outlet opening in the dead center positions of the piston. The piston can be rotated back and forth by means of a control mechanism during the piston stroke in such a way that in the piston positions between the dead center positions, one channel is connected to the inlet opening and the other channel is connected to the outlet opening.

The piston preferably has four channels, which are arranged in pairs in their dead center positions on both sides of the inlet opening and the outlet opening. Here, one of the channels of each pair of channels is connected to one work area and the other to the other work area.

Although the channels can be designed as bores, which open on the one hand on the relevant end face of the piston and on the other hand on its peripheral surface, it is preferred in a development of the invention to design the channels as axial grooves on the piston peripheral surface, the one end of the groove being closed. The A the inlet opening and the outlet opening are preferably diametrically opposite the piston and in the axial center of the cylinder space opposite one another. Since in the preferred solution each of these openings is assigned two channels, which are arranged in the dead center positions of the piston on both sides of the inlet opening or outlet opening so that they are not connected to this opening, the distance of the two channels measured along the circumference of the piston is the each channel pair associated with the openings is larger than the dimension of the associated opening measured along the circumference of the piston. The distances between the channels measured on the piston circumference are preferably the same at least in pairs.

The control mechanism by which the piston rotations are controlled preferably has a drive wheel in which a seat is formed in the form of a bore for a pin projecting radially from the piston on its circumferential surface, the drive wheel running tangentially to the piston circumference. Since the pin is inclined relative to the bore during the rotary drive movement, the diameter of the bore is correspondingly larger than the diameter of the pin.

If, in a more preferred solution, a second piston is arranged in a separate cylinder space, which runs parallel to the first cylinder space, the pistons are controlled for the operating mode as a volume counter by means of the control mechanism, both in terms of their stroke movement and in terms of their rotational movement, with their inlet openings on the one hand and their outlet openings on the other hand communicate with each other so that the throughput of the working medium flowing through the device is smoothed at the outlet of the device and therefore the flow of the working medium through the piston mechanism is disturbed as little as possible. This can be further refined if a third or fourth piston and all pistons are provided of the reciprocating piston mechanism are controlled out of phase with respect to both their rotary movement and their stroke movement. For this purpose, the drive wheels of the pistons are designed as meshing gears.

• Fig. la den Hubkolbenmechanismus schematisch im Längsschnitt, wobei sich der einzige Kolben in seiner einen Totpunktlage befindet,
• Fig. lb den Hubkolbenmechanismus im Querschnitt entlang der Schnittlinie B-B aus Fig. la,
• Fig. 2a den Längsschnitt, wobei sich der Kolben in seiner Mittellage befindet,
• Fig. 2b den Schnitt entlang der Schnittlinie B-B aus Fig. 2a,
• Fig. 3a den Längsschnitt mit dem Kolben in dessen anderen Totpunktlage,
• Fig. 3b den Schnitt entlang der Schnittlinie B-B aus Fig. 3a,
• Fig. 4a den Längsschnitt mit dem Kolben in dessen Mittellage auf seinem Rückweg in die erste Totpunktlage,
• Fig. 4b den Schnitt entlang der Schnittlinie B-B aus Fig. 4a,
• Fig. 5 ein Diagramm, welches den Durchsatz des Arbeitsmediums in Abhängigkeit von der Drehlage des Kolbens darstellt,
• Fig. 6 ein Ausführungsbeispiel mit zwei Kolben im Querschnitt entsprechend der Schnittlinie VI-VI aus Fig. 7,
• Fig. 7 den Längsschnitt des Hubkolbenmechanismus aus Fig. 6 entlang der Schnittlinie VII-VII,
• Fig. 8 den Längsschnitt des Hubkolbenmechanismus aus Fig. 6 entlang der Schnittlinie VIII-VIII und
• Fig. 9 den Längsschnitt des Hubkolbenmechanismus aus Fig. 6 entlang der Schnittlinie IX-IX.

The invention is explained with reference to the drawing, from which a preferred embodiment of the reciprocating piston mechanism according to the invention can be seen. The drawing shows:

• La schematically shows the reciprocating piston mechanism in longitudinal section, the only piston being in its one dead center position,
• Lb the reciprocating piston mechanism in cross section along the section line BB from Fig. La,
• 2a shows the longitudinal section, the piston being in its central position,
• 2b shows the section along the section line BB from Fig. 2a,
• 3a shows the longitudinal section with the piston in its other dead center position,
• 3b shows the section along the section line BB from Fig. 3a,
• 4a shows the longitudinal section with the piston in its central position on its way back to the first dead center position,
• 4b shows the section along the section line BB from FIG. 4a,
• Fig. 5 is a diagram showing the throughput of the work medium depending on the rotational position of the piston,
• 6 shows an embodiment with two pistons in cross section corresponding to section line VI-VI from FIG. 7,
• 7 shows the longitudinal section of the reciprocating piston mechanism from FIG. 6 along the section line VII-VII,
• Fig. 8 shows the longitudinal section of the reciprocating piston mechanism of Fig. 6 along the section line VIII-VIII and
• FIG. 9 shows the longitudinal section of the reciprocating piston mechanism from FIG. 6 along the section line IX-IX.

The reciprocating piston mechanism according to the invention can be seen schematically from FIGS. 1-4, the excellent piston positions being shown during one working cycle of the mechanism.

The reciprocating piston mechanism has a cylinder housing H, in the cylinder space of which a piston D is guided, through which the cylinder space is divided into two working spaces V1 and V2, which are formed on the two end faces of the piston D. The length of the piston is greater than the piston stroke, so that the two dead center positions, which can be seen from FIGS. 1a and 3a, overlap one another in the axial center of the cylinder space. Within this overlap area, an inlet opening b and an outlet opening k are formed in the axial center of the cylinder space, which are diametrically opposite to the piston D, so that they are covered by the peripheral surface of the piston in each piston position.

On the circumferential surface of the piston D, four channels bl, b2 and kl, k2 designed as axial grooves are worked out, of which the channels bl and b2 of the inlet opening b, and the channels kl, k2 are assigned to the outlet opening k. The two channels bl, b2 and kl, k2 assigned to each of the openings b, k open at opposite end faces of the piston D into the working space V1 or V2, whereas their other groove end is closed. Furthermore, the channels bl, k2 and b2, kl opposite each other diametrically to the piston also open at different end faces of the piston D in such a way that when the piston moves between its dead center positions, that of the working spaces V1, V2, the volume of which has just increased, via one of the Channels bl, b2 with the inlet opening b, and that of the working spaces V1, V2, the volume of which has just been reduced, are connected to the outlet opening k via one of the channels kl, k2.

The channels bl, b2 and kl, k2 are arranged offset from one another along the circumference of the piston at equal angular intervals. The distance measured on the piston circumference of the two channels bl, b2 and kl, k2 assigned to each of the openings b, k is greater than the dimension of the openings b, k measured on the piston circumference, so that in the two perpendicular positions of the piston (FIG and 3b) the channels bl, b2 are arranged on both sides of the inlet opening b, and the channels k1, k2 are arranged on both sides of the outlet opening k and the opening b, k between them is completely blocked off by the circumferential surface of the piston D. The length of the channels b1, b2 and k1, k2 is chosen such that the channels in each piston position overlap axially with at least one part of the openings b, k.

The piston D is controlled by a drive mechanism so that it operates in the pump mode. In addition to its reciprocating stroke movement, the piston D executes a reciprocating rotary movement about its piston axis in such a way that the points A, which lie on that surface line of the piston, lie in the middle between the channels b1, b2 and . k1, k2 runs, describe a self-contained path by the superimposition of the stroke movement and the rotary movement of the piston, which is a circular path p when projected onto the tangential plane of the piston containing this surface line. Each axial position of the piston D is therefore assigned a precisely determined angular position of the piston. If, for example, it is assumed that the one dead center position of the piston D according to FIG. 1 a is its angular position ϕ = 0, one can use the angle ϕ to describe the position of the point A on the circular path during the piston movements. 5 shows the throughput of the working fluid flowing through the reciprocating piston mechanism above this angular position ϕ with the solid line.

In the piston position according to FIG. 1 a with ϕ = 0, there is no connection between the channels kl, k2 or bl, b2 and the outlet opening k or the inlet opening b, and thus between these and the working spaces V1, V2, so that the throughput Is zero. In the piston position according to FIG. 2a, where the piston is in the middle position between its plumb point positions and ϕ = 90 ° after the piston has been rotated 45 ° to the left, the inlet opening b is connected to the working space V1 via the channel bl , whereas the outlet opening k is connected to the working space V2 via the channel k2 and the flow rate reaches a maximum. The working fluid leaves the working space V2 through the channel k2 and the outlet opening k, while flowing into the working space V1 through the inlet opening b and through the channel bl.

3a is ϕ = 180 °, the piston D being in its other dead center position, in which the connection between the channels bl, b2 or k1, k2 with the inlet opening or the outlet opening is interrupted after the piston D from the rotational position according to fig. 2h has returned to the starting rotational position by 45 °. The flow rate is zero again in this piston position. After that the piston D is rotated in the other direction of rotation until after a rotation of 45 ° it reaches the rotational position according to FIG. 4b, in which ϕ = 270 ° and the piston is again in its axial central position according to FIG. 4a. Here, the working space is connected to the outlet opening k via the channel kl, while the working space V2 is connected to the inlet opening b via the channel b2 and the flow rate of the working fluid again reaches a maximum. The piston then returns to its first dead center position according to FIG. 1 a, so that point A then moves back through 90 ° along the circular path p to its starting position.

The flow rate therefore varies according to the solid line in FIG. 5 during the movement of the piston between its dead center positions between zero and a maximum. When using the reciprocating piston mechanism according to the invention as a volume counter, two or more pistons are therefore preferably used, the control movements of which are phase-shifted both with regard to their rotational positions and with regard to their axial positions. From Fig. 5, the flow rate v is plotted over the angular position ϕ of the point A of the second piston with a dashed line. Therefore, if the inlet openings b of the two cylinder spaces on the one hand and the outlet openings k of the two cylinder spaces on the other hand are connected to one another, then the flow throughput of the working fluid is equalized according to the dash-dotted line in FIG. 5, which represents the resulting throughput.

An exemplary embodiment of such a reciprocating piston mechanism with two pistons which are shifted in phase can be seen from FIGS. 6-9. The axes of the two pistons 2, 3 run parallel and are guided in separate cylinder spaces 20, 21 within their common cylinder housing 1. The pistons 2, 3 are in accordance with the construction of FIGS. 1-4 with the outlet channels kll, k21, k22, kl2 and provided with the inlet channels bll, b21, b22, b12. In the cylinder housing 1, the inlet openings 22 and 23 are formed below the pistons 2, 3, which are connected to an inlet channel 19 common to them, whereas the outlet openings 26, 27 formed above the pistons 2, 3 in the cylinder housing 1 to an outlet channel 28 common to them are connected.

The cylinder spaces 20, 21 are divided by the pistons 2, 3 into the working spaces Vll, V21 and V12, V22. The pistons 2, 3 are controlled out of phase with respect to the angular positions ϕ of the piston points A1, A2. Therefore, when the piston 2 is in its axially central position, the second piston 3 is in one of its axial end positions (cf. FIG. 7). The two piston points A1, A2 describe a self-contained path during the piston movement, which are identical circular paths p1 and p2 in the vertical projection onto the cutting plane VII-VII from FIG. 6 containing the two piston axes.

The control mechanism for the pistons 2, 3 consists of two meshing gears 9, 10, which are arranged on the outlet side of the cylinder housing 1 such that their axis intersects the axis of the associated piston 2, 3 perpendicularly. The pistons 2, 3 each have, on the piston surface line, which runs in the middle between the piston channels kll, k21 and k22, k2, a pin 4, 5 projecting radially to the piston, which in a seat 24, 25 in the form of a bore engages, which is formed in a control disc 7, 8 on the underside of the drive wheels 9, 10 parallel to the axes thereof. The bore diameter is larger than the pin diameter in accordance with the largest angle that the pin axis includes with the axes of the drive wheels 9, 10 (see pin 4 in the left half of FIG. 6). The seats 24, 25 are each eccentric to the axis of the drive wheels 9, 10 arranged and offset from each other in accordance with the phase shift of 90 ^u .

The shaft 12 of the one drive wheel 10 is guided out of the cylinder housing cover via a ball bearing 14 and carries a magnet 13 arranged under the cover 11, which serves as a volume counter as a speed counter in the operating mode of the piston mechanism. The shaft 16 of the second drive wheel 9 is mounted as a drive shaft in the ball bearing 18 and is guided out of the cylinder housing cover in a sealed manner by means of the seal 17. While in the operating mode of the piston mechanism as a volume counter the pistons are driven by the pressure of the flowing working medium, they are driven in the operating mode as a pump via the drive shaft 16, which also in the operating mode of the piston mechanism as a motor which is driven by the flowing medium, can serve as an output shaft. The phase-shifted arrangement of the pistons 2, 3 contributes to overcoming the perpendicular positions of the pistons in the operating modes of the reciprocating piston mechanism, in which its pistons are driven by the flowing medium. The operation of the reciprocating piston mechanism from FIGS. 6-9 corresponds to that which was explained with reference to FIGS. 1-4.

Claims (8)

1. reciprocating piston mechanism, which can be used as a motor, pump or in particular a volume meter, with a cylinder housing (H), in the cylinder space of which a piston (D) can be pushed back and forth, from which the cylinder space can be moved into two working spaces (VI, VI, V2) is divided, the two dead center positions overlap each other, and with a lockable inlet opening (b) and a lockable outlet opening (k), which open into the cylinder space and can be connected alternately to one work space (VI) and the other work space (V2) are characterized in that the inlet opening (b) and the outlet opening (k) are arranged on the circumference of the cylinder space at those locations at which they are covered by the piston (D) in each piston position such that the piston (D) has at least two each with one of the working spaces (V1, V2) connected channels (bl, b2, kl, k2), which open offset against each other at the piston circumference and in the dead center positions of the piston (D) are blocked off from the cylinder housing (H) against the inlet opening (b) and the outlet opening (k), and that the piston (D) can be rotated back and forth during the piston stroke by means of a control mechanism (6) such that in the Piston positions between the dead center positions one channel (bl, b2) is connected to the inlet opening (h) and the other channel (kl, k2) to the outlet opening (k). 2. Reciprocating mechanism according to claim 1, characterized in that the piston (D) has four channels (bl, b2, kl, k2), which are in pairs in the dead center positions of the piston (D) on both sides of the finlassschluß (b) or Outlet opening (k) are arranged, of the channels (bl, b2 and kl, k2) of each pair of channels, one being connected to one working space (V1) and the other to the other working space (V2). 3. Reciprocating piston mechanism according to claim 1 or 2, characterized in that the channels (bl, h2, kl, k2) on the peripheral surface of the piston (D) are grooves, the one end of which is closed. 4. Reciprocating mechanism according to claim 2, characterized in that the distances between the channels (bl, b2, kl, k2) measured on the piston circumference are at least in pairs the same. 5. Reciprocating mechanism according to one of claims 1-4, characterized in that the inlet opening (b) and the outlet opening (k) face each other diametrically to the cylinder space in the axial center thereof. 6. Reciprocating mechanism according to one of claims 1-5, characterized in that the control mechanism (6) has a drive wheel (9, 10) in which a seat (24, 25) for a radial to the piston (2, 3) on the latter Peripheral surface projecting pin (5) is formed. 7. Reciprocating mechanism according to one of claims 1-6, characterized in that a second piston is arranged in a separate cylinder space and the pistons (2, 3) by means of the control mechanism (6) are controlled both in terms of their stroke movement and in terms of their rotational movement out of phase . 8. Reciprocating mechanism according to claim 7, characterized in that the pistons (2, 3) are coupled via two meshing drive wheels (9, 10).

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