ITRE20100079A1 - HYDRAULIC PISTON MACHINE - Google Patents

Description

DESCRIPTION

of the Italian Patent for Industrial Invention entitled:

â € œPISTON HYDRAULIC MACHINEâ €

The present invention relates to a hydraulic piston machine, and in particular to a pump.

As is known, a piston pump comprises at least one reciprocating piston, which is slidably received inside a respective cylinder, so that a volume chamber remains defined between the piston crown and the cylinder head. variable. The chamber is in communication with an inlet and an outlet of the fluid to be pumped, respectively by means of a suction valve and a delivery valve.

The piston is driven by an external motor through a crankshaft and a connecting rod, in such a way as to alternatively perform an intake stroke, in which it moves away from the cylinder head, increasing the volume of the chamber, and a delivery stroke, in which it approaches the cylinder head again, decreasing the volume of the chamber.

During each suction stroke, the fluid to be pumped is drawn back into the chamber through the suction valve, so that during the subsequent discharge stroke, the fluid is first compressed and then made to escape from the discharge valve.

To ensure the hermetic closure of the chamber, it is known to use at least one annular sealing gasket, typically made of polymeric material, which is coaxially interposed between the cylinder and the piston.

As a rule, this annular sealing gasket is made axially integral with the cylinder, so as to remain stationary with respect to the sliding of the piston.

The annular sealing gasket generally comprises an internal lip adapted to stay in contact with the external skirt of the piston and an external lip adapted to remain in contact with the internal surface of the cylinder.

To improve the seal, the annular gasket can possibly be of the so-called energized type, that is comprising an annular core of metal, rubber or other material, conventionally called spring, which has an elastically yielding cross section and is coaxially received in a cavity interposed between the inner lip and the outer lip.

During assembly, the cross section of the core of the annular seal is compressed between the outer skirt of the piston and the inner surface of the cylinder, so that by elastic reaction it exerts a thrust suitable to move the inner lip away from the outer lip, pressing them respectively against the piston and the cylinder.

Due to the continuous rubbing with the piston, the possible chemical aggression of the treated fluid and / or the normal aging of the polymeric materials, the gasket is however subjected to a progressive wear process.

Beyond a certain wear limit, fluid leaks from the pump chamber may occur, so the sealing gasket must be replaced.

The operation of replacing the gasket is however a rather laborious and tiring operation, as it generally requires to empty the hydraulic system to which the pump is connected, to disconnect the pump from the system itself, to disassemble the piston from the relative cylinder and therefore to replace the gasket, before proceeding with the restoration.

For this reason, a requirement connected with piston pumps is to increase the useful life of the sealing ring as much as possible, in order to reduce the number of replacement operations to a minimum.

This need is particularly felt in high-pressure piston pumps which generally comprise a plurality of the aforementioned cylinder-piston groups, which are hydraulically connected to each other and are individually provided with at least one respective annular sealing gasket.

Furthermore, in these applications it often happens that the sealing gasket associated with one of the cylinder-piston groups wears out before those associated with the other groups, thus requiring their replacement when the other gaskets are still efficient.

When this occurs, it is economically advisable to replace all the pump seals, with the contraindication of not fully exploiting the seals that are still effective.

An object of the present invention is to increase the useful life of the sealing rings which are used in hydraulic piston machines such as pumps.

Another object of the present invention is to make better use of the useful life of all the sealing gaskets of machines having multiple cylinder-piston groups, so as to replace them only when they are worn.

A further object of the present invention is to achieve the aforementioned objective within the ambit of a simple, rational and low-cost solution.

These objects are achieved by the characteristics of the invention reported in independent claim 1. The dependent claims outline preferred and / or particularly advantageous aspects of the invention.

In particular, the invention makes available a hydraulic machine, for example a pump or a hydraulic motor, which comprises at least one cylinder, a piston sliding inside said cylinder, and an annular seal coaxially interposed between the cylinder and the piston, wherein said machine comprises means for compressing the annular gasket in the direction defined by the axis of the cylinder and means for adjusting the amount of said compression.

In this way, when the annular gasket reaches a level of wear whereby fluid leaks from the internal chamber of the cylinder are observed, it is advantageously possible to increase the axial compression of the gasket itself, so as to correspondingly increase the thrust that the lips exert against. the surfaces of the piston and cylinder, recovering any play and restoring the seal.

According to an embodiment of the invention, the means for compressing the annular gasket comprise a compression ring, which is placed coaxially in contact with the annular gasket and is received inside a seat in which it is movable in the direction defined by the cylinder axis.

In this case, the means for adjusting the amount of compression are adapted to adjust the axial position of said compression ring in the seat.

This solution has the advantage that the compression ring allows a uniform thrust to be exerted over the entire length of the annular gasket.

According to one aspect of this solution, the means for adjusting the amount of compression comprise at least one thrust body, which is placed in contact with the compression ring, on the opposite side with respect to the annular gasket, and is housed inside a guide seat in which it can slide in the direction defined by a longitudinal axis of the guide seat itself, and means for adjusting the axial position of said thrust body inside said guide seat.

This constructive solution has the advantage of being quite simple, economical and functional.

The longitudinal axis of the thrust body guide seat can be parallel to the cylinder axis, so that a displacement of the thrust body corresponds to an equal displacement of the compression ring, which allows to vary the compression of the annular seal very effectively.

Alternatively, the longitudinal axis of the thrust body guide seat can be transverse to the cylinder axis, provided that the contact between the thrust body and the compression ring occurs on an inclined surface. with respect to the longitudinal axis of the guide seat, so that an axial displacement of the thrust body in the guide seat still corresponds to a displacement of the compression ring in the direction of the cylinder axis.

This solution is advantageously applicable where it is not possible to realize, for example for reasons of space, a seat for the thrust body which has a longitudinal axis parallel to the cylinder axis.

According to a preferred aspect of the invention, the means for adjusting the amount of compression comprise a plurality of said thrust bodies, which are individually received in respective seats and are globally arranged circumferentially around the axis of the cylinder, preferably angularly equidistant from each other.

In this way, by suitably adjusting the position of the various thrust bodies in their respective seats, it is advantageously possible to prevent the compression ring from tilting and / or getting stuck in its respective seat, thus ensuring uniform compression of the annular gasket.

According to a preferred aspect of this embodiment, the means for adjusting the axial position of the thrust body in the respective guide seat are able to simultaneously adjust the axial position of the plurality of thrust bodies in the respective guide seats.

In this way, by means of a single adjustment action, it is advantageously possible to vary the position of all the thrust bodies, adjusting the compression of the annular gasket in a rapid and uniform way.

In particular, these means for adjusting the axial position of the plurality of thrust bodies can comprise a single actuation body, which is placed in contact with all the thrust bodies of the plurality, on the opposite side with respect to the compression ring , and is coupled to the machine by means of a threaded connection such that a rotation of the actuating body results in a displacement of the same in the direction defined by the axis of the cylinder.

In this way, the drive body is able to push all the thrust bodies against the compression ring at the same time, while the threaded connection prevents them from moving backwards.

According to one aspect of this solution, the hydraulic machine comprises means for signaling the extent of rotation of said actuation body.

These signaling means have the advantage of providing an operator with a clear indication of the amount of compression to which he subjects the annular seal by screwing / unscrewing the drive body.

According to an embodiment of the invention, the hydraulic machine can comprise two of said annular seals, of which one annular seal is closer to the cylinder head than the other.

In this case, the invention provides that the means for compressing the annular gasket and the means for adjusting the amount of said compression are associated with at least one of said annular gaskets, and preferably with the one placed at a greater distance from the head of the cylinder.

Nevertheless, it is also provided that respective means for compressing the annular gasket and means for adjusting the amount of said compression can be associated with each of said annular gaskets.

Further characteristics and advantages of the invention will become evident by reading the following description provided by way of non-limiting example, with the aid of the figures illustrated in the attached tables.

Figure 1 is a front view of a high pressure piston pump according to the present invention.

Figure 2 is a partially sectioned detail of Figure 1.

Figure 3 is the section III-III of Figure 1.

Figure 4 is the section IV-IV of figure 3.

Figure 5 is a detail of figure 4 shown on an enlarged scale. Figure 6 is a longitudinal section of a high pressure piston pump according to an alternative embodiment of the invention.

Figures 1 to 4 illustrate a high pressure piston pump 10, which is mainly intended for pumping rather dense fluids and generally containing solid particles, such as bentonite.

However, the present invention can be advantageously applied also to other piston pumps and / or pumps suitable for treating different types of fluids.

As illustrated in Figure 4, the pump 10 comprises a head 11, which is generally provided with two parallel and opposite flat faces, of which a front face 110 and a rear face 111.

Three through cavities 12 are obtained in the head 11, which cross the entire thickness of the head 11, from the front face 110 to the rear face 111.

Each through cavity 12 substantially houses an extractable body 13, typically cylindrical in shape, which can be inserted and removed from the respective cavity 12.

The removable bodies 13 are fixed to the head 11 by means of a cover 14, which is fixed to each removable body 13 by means of a single screw 140 and is further fixed to the front face 110 of the head 11 by means of a plurality of screws 141 ( see for example figure 3).

Each extractable body 13 has a cylindrical coaxial cavity 15, usually simply called a cylinder, which has an open end facing the part of the rear face 111 of the head 11, and an opposite closed end facing the part of the front face 110 .

The closed end of the cylindrical cavity 15 defines the so-called cylinder head, in correspondence with which the screw 140 connecting the cover 14 is screwed.

The extractable bodies 13 are arranged so that the longitudinal axes X of the respective cylindrical cavities 15 lie parallel and aligned on the same plane.

As shown in Figure 5, at the open end, each cylindrical cavity 15 has a coaxial cylindrical portion 150 with an increased diameter, which defines a shoulder 151 and acts as a housing for the sealing means which will be described below. .

Inside each cylindrical cavity 15 is received, coaxially and substantially to size, a piston 16, also cylindrical in shape, which is able to slide inside the relative cylindrical cavity 15 in the direction defined by the longitudinal axis X of the latter.

In this way, a variable volume chamber 152 is defined between the cylinder head and the piston crown 16, which is in communication with an inlet 153 and with an outlet (not visible) for the fluid to be treated.

Associated with said inlet 153 and said outlet are respectively an intake valve and a delivery valve (not visible in the figures), which are known per se and are therefore not described in detail.

As illustrated in figure 4, each piston 16 is rigidly fixed to a piston 17, by means of the further interposition of a spacer 18.

Each piston 17 is slidably received substantially to size in a cylindrical seat 19, coaxial with the cylindrical cavity 15 of the relative piston 16.

Said cylindrical seat 19 is obtained in a casing 20, which is fixed to the rear face 111 of the head 11 by means of the interposition of a hollow spacer body 21 which houses the spacers 18.

The crankcase 20 contains and supports, by means of suitable bearings, a crankshaft 22 having a rotation axis Y orthogonal to the longitudinal axis X of the cylindrical cavities 15, which is driven by an external motor (not shown).

The crankshaft 22 is connected to each piston 17 by means of a respective connecting rod 23, so that the rotation of the crankshaft 22 results in an alternative movement of the pistons 17 and therefore of the pistons 16.

In particular, each piston 16 is able to alternately perform an intake stroke, in which it moves away from the cylinder head, increasing the volume of the chamber 152, and a compression and delivery stroke, in which it approaches the cylinder head again. , decreasing the volume of chamber 152.

During each suction stroke, the fluid to be pumped enters the chamber 152 through the suction valve and the inlet 153, so that during the subsequent compression and delivery stroke, the fluid is first compressed and then made to escape from the discharge valve .

As illustrated in Figure 5, the hermetic seal of each chamber 152 is obtained by means of a respective annular gasket 30, which is received in the enlarged portion 150 of the cylindrical cavity 15, so as to be coaxially interposed between the internal lateral surface of the cavity cylindrical 15 and the outer lateral surface of the piston 16.

In the example shown here, the annular seal 30 is of the so-called energized type.

In practice, the annular gasket 30 comprises a rubber jacket, for example made of polymeric material, which has an internal lip able to stay in contact with the external surface of the piston 16 and an external lip able to stay in contact with the surface. of the cylindrical cavity 15, and an annular metal core, of rubber or other material, conventionally called spring, which is coaxially received in a cavity interposed between the inner lip and the outer lip of the liner and has an elastically cross section yielding, in this case having a substantially circular shape.

The diameter of the enlarged portion 150 is chosen in such a way that, during assembly, the cross section of the seal core 30 is compressed between the outer surface of the piston 16 and the inner surface of the cylindrical cavity 15, so that it exerts by elastic reaction a thrust suitable to move the inner lip away from the outer lip, pressing them against the respective surfaces of the piston 16 of the cylindrical cavity 15.

The annular gasket 30 is axially blocked between the shoulder 151 and a Seeger ring 31 received in an internal groove of the cylindrical cavity 15, so as to remain stationary during the sliding of the piston 16.

In particular, a further rigid ring 32 is coaxially interposed between the annular gasket 30 and the Seeger ring 31 which also acts as a guide for the sliding of the piston 16, while between the annular gasket 30 and the shoulder 151 is coaxially interposed a compression ring 33.

The compression ring 33 has a substantially trapezoidal cross section, with the major base facing the shoulder 151 and the minor base placed in contact with the core of the annular gasket 30, and is free to slide inside the section enlarged 150 of the cylindrical cavity 15 in the direction defined by the X axis of the latter.

The compression ring 33 is axially pressed against the annular gasket 30 by three thrust rods 34 (of which only one per ring is visible in figure 5), each of which is inserted in a respective guide hole 35 , so as to be able to slide in the direction defined by the longitudinal axis Z of the hole itself.

In this example, the guide holes 35 have a longitudinal axis Z parallel to the X axis of the respective cylindrical cavity 15 and are globally arranged circumferentially around the aforementioned longitudinal axis X, angularly equidistant from each other or separated by an angle of 120 degrees.

The guide holes 35 are obtained in the extractable body 13 at a radial distance from the X axis equal to the average radius of the compression ring 33, extending through the shoulder 151 of the cylindrical cavity 15 up to the surface of the extractable body 13 facing the lid 14.

In this way, the thrust rods 34 are individually aligned with a respective portion of the respective compression ring 33.

Going into more detail, the thrust rods 34 associated with each compression ring 33 have one end in direct contact with the compression ring 33 and an opposite end that protrudes from the extractable body 13 and slips into a corresponding hole in the cover 14, to be in direct contact with a single drive ring 36.

The operating ring 36 is housed in a cavity of the cover 14, and is screwed to a threaded head 142 which protrudes from the bottom of said cavity, in such a way that it is screwed / unscrewed by rotating on itself around the X axis of the cavity cylindrical 15.

In this way, each screwing / unscrewing of the operating ring 36 corresponds to a movement thereof in the direction of the X axis.

Thanks to this axial displacement, by rotating the operating ring 36 it is advantageously possible to move the three thrust rods 34 at the same time by the same amount towards the compression ring 33, which in turn is forced to slide in the widened section 150 of the cylindrical cavity 15, compressing the annular gasket 30 more against the rigid ring 32 and the Seeger ring 31.

In particular, the compression ring 33 acts against the core of the annular gasket 30, causing an axial crushing thereof and a corresponding radial expansion which increases the thrust exerted by the lips against the external lateral surface of the piston 16 and the internal lateral surface of the cylindrical cavity 15.

In this way, should the wear of the annular gasket 30 cause fluid leaks from the chamber 152, it is advantageously possible to recover any play and restore the seal.

The axial stroke of the actuating ring nut 36 is limited, in one direction, by the bottom of the seat in which it is received and, in the other direction, by a limit switch plate 143 screwed to the cover 14.

It should also be noted that, between the operating ring 36 and the bottom of the relative cavity, some compression springs 144 are interposed (of which only one per ring is visible in figure 5), arranged angularly equidistant around the X axis of the cylindrical cavity 15, whose function is to create friction between the threads of the threaded connection, which prevents accidental unscrewing of the drive ring nut 36, as well as to recover any play in the coupling.

As shown in the cross section of Figure 2, means are finally associated with each actuating ring 36 to signal to the user, during the adjustment, the amount of rotation to which the actuating ring 36 is subjecting.

In the example illustrated here, said signaling means comprise a steel ball 37, which is inserted into a guide hole 38 obtained in the thickness of the cover 14, which has an axis orthogonal to the rotation axis of the ring nut. drive 36 and faces the cylindrical side surface of the drive ring 36 itself.

The ball 37 is pressed against the lateral surface of the operating ring 36 by a spring 39, which is pre-compressed inside the guide hole 38 by a threaded dowel 40 screwed into the same hole.

An additional threaded dowel 42 is screwed into the guide hole 38 so as to act as a lock nut and prevent accidental unscrewing of the threaded dowel 40.

The signaling means also comprise six cavities 41, which are formed on the lateral surface of the drive ring 36, angularly equidistant from each other, and are adapted to snap-in the ball 37 pushed by the spring 39.

In this way, every time the operator makes the drive ring 36 perform a rotation equal to 60 degrees, the snap engagement of the ball 37 in a cavity 41 generates a metallic noise perceptible by the operator, commonly called click.

By counting the number of these clicks, the operator is therefore able to quantify the amount of overall rotation of the drive nut 36 and therefore the amount of additional compression that is applied to the O-ring 30.

Figure 6 illustrates a piston pump 10A of the same type as the one described above, whereby the common elements are indicated here with the same numerical reference.

Ultimately, the pump 10A differs from the previous one in that each cylindrical cavity 15 is obtained directly in the body of the head 11.

Figure 6 also shows the intake valve 50 and the delivery valve 51 which are in communication with the variable volume chamber 152 defined by the piston 16 inside the cylindrical cavity 15.

The pump 10A also differs from the previous one in that the hermetic seal of each chamber 152 is obtained by means of two annular gaskets coaxially interposed between the external lateral surface of the piston 16 and the internal lateral surface of the cylindrical cavity 15.

In particular, the seal is obtained by a first annular gasket 300, called high pressure, located closer to the cylinder head, and by a second annular gasket 301, called low pressure, located at a greater distance.

The first annular gasket 300 is received in the widened portion 150 of the cylindrical cavity 15, interposed between two coaxial rigid rings, respectively 302 and 303, of which the ring 303 also acts as a guiding element for the piston 16.

The rings 302, 303 and the first annular gasket 300 are axially blocked against the shoulder 151, by means of a further coaxial ring 304, which is received in a further widened section of the cylindrical cavity 15, where it is in turn blocked axially from the crankcase 20.

In this case, there is in fact no spacer body between crankcase 20 and head 11.

This further ring 304 defines with the external lateral surface of the piston 16 a narrow gap, in which the second annular gasket 301 is received, which is of the energized type.

Going into more detail, the annular gasket 301 is axially clamped between a shoulder 305 of the ring 304 and a compression ring 306, which is coaxially received in the same gap defined by the ring 304, where it is free to slide along the direction of the X axis of the cylindrical cavity 15.

The compression ring 306 is pushed against the annular gasket 301 by two push rods 340, each of which is received in a respective guide hole 350 obtained in the ring 304, so that it can slide in the defined direction from the longitudinal axis Zâ € ™ of the hole itself.

In this case, the guide holes 350 have a longitudinal axis Zâ € ™ orthogonal to the X axis of the respective cylindrical cavity 15 and are arranged on diametrically opposite sides with respect to said longitudinal axis X.

The guide holes 350 pass through the thickness of the ring 304 and individually face a rear threaded hole 351 obtained directly in the head 11.

The push rods 340 have one end in direct contact with the compression ring 306 and an opposite front end which is in contact with a threaded dowel 352 started in the threaded hole 351.

In this way, by screwing the threaded dowels 352 deeper into the respective holes 351, a displacement of the thrust rods 340 towards the X axis of the cylindrical cavity 15 is obtained.

The contact surfaces between each thrust pin 340 and the compression ring 306 are inclined both with respect to the Z axes of the guide holes 350 and with respect to the X axis of the cylindrical cavity 15, so that a displacement of the thrust pin 340 towards the X axis corresponds to a displacement of the compression ring 306 towards the annular seal 301.

Thanks to this axial displacement, the compression ring 306 compresses the O-ring 301 more against the shoulder 305 of the ring 304.

Also in this case, the compression ring 306 acts especially against the core of the annular gasket 301, causing an axial crushing and a corresponding radial expansion aimed at increasing the thrust that the lips exert against the external lateral surface of the piston 16 and the inner lateral surface of the ring 304.

In this way, when the wear of the annular gasket 300 and of the gasket 301 should cause fluid leaks from the chamber 152, it is advantageously possible to recover any play and restore the seal at least in correspondence with the low pressure gasket 301.

After making the adjustment, a further threaded dowel 353 is screwed into the hole 351 so as to act as a lock nut and avoid accidental unscrewing of the threaded dowel 352.

In the example shown here, the axial compression of the low pressure O-ring 300 cannot be adjusted. Nevertheless, it is possible to apply the solution used to adjust the compression of the annular seal 30 of the pump 10 described initially, to adjust the compression of the annular seal 300 of this second pump 10A, thus obtaining a pump in which the axial compression of both seals can be adjusted.

Obviously, a person skilled in the art can make numerous modifications of a technical-applicative nature to the pumps described above, without thereby departing from the scope of the invention as claimed below.

Claims (13)

CLAIMS 1. Hydraulic machine (10, 10A) comprising at least one cylinder (15), a piston (16) sliding inside the cylinder (15), and an annular gasket (30, 301) coaxially interposed between the cylinder (15) and the piston (16), characterized in that it comprises means (33, 306) for compressing the annular gasket (30, 301) in the direction defined by the axis (X) of the cylinder (15) and means (34, 36, 340, 352) to adjust the amount of said compression. 2. Machine (10, 10A) according to claim 1, characterized in that said means for compressing the annular gasket (30) comprise a compression ring (33, 306), which is placed coaxially in contact with the annular gasket (30, 301) and is housed inside a seat (150) in which it is movable in the direction defined by the axis (X) of the cylinder (15), the means (34, 36, 340, 352 ) to adjust the amount of compression being able to adjust the axial position of said compression ring (33, 306) in the seat (150). 3. Machine (10, 10A) according to claim 2, characterized in that said means for adjusting the amount of compression comprise at least one thrust body (34, 340), which is placed in contact with the ring compression (33, 306), on the opposite side with respect to the annular gasket (30, 301), and is housed inside a guide seat (35, 350) in which it can slide in the direction defined by a longitudinal axis (Z, Zâ € ™) of the guide seat (35, 350) itself, and means (36, 352) for adjusting the axial position of said thrust body (34, 340) inside said guide seat ( 35, 350). 4. Machine (10) according to claim 3, characterized in that the longitudinal axis (Z) of the guide seat (35) of the thrust body (34) is parallel to the axis (X) of the cylinder ( 15). 5. Machine (10A) according to claim 3, characterized in that the longitudinal axis (Zâ € ™) of the guide seat (350) of the thrust body (340) is transverse to the axis (X) of the cylinder (15), the contact between the thrust body (340) and the compression ring (306) occurs on a surface inclined with respect to the longitudinal axis (Zâ € ™) of the guide seat (350). 6. Machine (10, 10A) according to any one of claims 3 to 5, characterized in that the means for adjusting the amount of compression comprise a plurality of said thrust bodies (34, 340), which are individually received in respective guide seats (35, 350) and are arranged circumferentially around the axis (X) of the cylinder (15). 7. Machine (10, 10A) according to claim 6, characterized in that said thrust bodies (34, 340) are angularly equidistant from each other with respect to the axis (X) of the cylinder (15). 8. Machine (10) according to claim 6, characterized in that the means (36) for adjusting the axial position of the thrust body (34) in the respective guide seat (35) are adapted to simultaneously adjust the axial position of the plurality of the thrust bodies (34) in their respective guide seats (35). Machine (10) according to claim 8, characterized in that said means for adjusting the axial position of the plurality of thrust bodies (34) comprise an actuation body (36), which is placed in contact with all the thrust bodies (34) of the plurality, on the opposite side with respect to the compression ring (33), and is coupled to the machine (10) by means of a threaded connection such that a rotation of the drive body (36) involves a displacement of the same in the direction defined by the axis (X) of the cylinder (15). 10. Machine (10) according to claim 9, characterized in that it comprises means (37-41) for signaling the extent of rotation of said drive body (36). 11. Machine (10A) according to claim 1, characterized in that it comprises two (300, 301) of said annular gaskets, and in that said means (306) for compressing the gasket and means (340, 352) for adjusting the The amount of said compression are associated with at least one (301) of said annular gaskets (300, 301). Machine (10A) according to claim 11, characterized in that said at least one annular gasket (301) is placed at a greater distance from the cylinder head (15) than the other annular gasket (300). Machine (10A) according to claim 12, characterized in that each of said annular gaskets (300, 301) is associated with respective means (33, 306) for compressing the annular gasket and means (34, 36, 340, 352) to adjust this compression.