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Title:
IMPROVED PORT PLATE
Document Type and Number:
WIPO Patent Application WO/2019/211100
Kind Code:
A1
Abstract:
The invention relates to a port plate (1) for a fluid throughput regulating device, comprising at least one fluid blocking section, and at least one flu- id conduit means (7, 9, 10, 13, 14, 15, 17, 18, 19) that fluidly connects two surface parts (2, 3) of said port plate (1). Said fluid conduit means (7, 9, 10, 13, 14, 15, 17, 18, 19) comprises at least one fluid conduit (14) that is bent in a way that there is no line-of-sight axis between the surface parts (2, 3) that are connected by the respective fluid conduit (14).

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Inventors:
FIEBING, Anja (Danfoss Intellectual PropertyNordborgvej 81, 6430 Nordborg, 6430, DK)
FIEBING, Carsten (Danfoss Intellectual PropertyNordborgvej 81, 6430 Nordborg, 6430, DK)
Application Number:
EP2019/060108
Publication Date:
November 07, 2019
Filing Date:
April 18, 2019
Export Citation:
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Assignee:
DANFOSS POWER SOLUTIONS GMBH & CO OHG (Krokamp 35, Neumünster, 24531, DE)
International Classes:
F04B1/20; F03C1/06; F04B27/08; F04B39/10; F04B53/10
Foreign References:
JP2006207501A2006-08-10
JP2010174690A2010-08-12
KR20030034973A2003-05-09
JP2016075222A2016-05-12
Other References:
None
Attorney, Agent or Firm:
STEVENS, Brian et al. (Danfoss A/S, Intellectual PropertyL25-10, Nordborgvej 81 6430 Nordborg, 6430, DK)
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Claims:
C L A I M S

1. Port plate (1 ) for a fluid throughput regulating device, comprising at least one fluid blocking section, and at least one fluid conduit means (7, 9, 10,

13, 14, 15, 17, 18, 19) that fluidly connects two surface parts (2, 3) of said port plate (1 ), characterised in that said fluid conduit means (7, 9, 10, 13, 14, 15, 17, 18, 19) comprises at least one fluid conduit (14) that is bent in a way that there is no line-of-sight axis between the surface parts (2, 3) that are connected by the respective fluid conduit (14).

2. Port plate (1 ) according to claim 1 , characterised in that said at least one fluid conduit (14) comprises at least one fluid conduit section that is ar- ranged in a way that it cannot be reached by a line-of-sight axis from both of said two surface parts (2, 3) of said port plate (1 ).

3. Port plate (1 ) for a fluid throughput regulating device, comprising at least one fluid blocking section, in particular port plate (1 ) according to claim 1 or claim 2, characterized by at least one inset section (9, 10, 13, 15, 17, 18, 19) that is arranged within a recess section (7) of said at least one fluid blocking section of said port plate (1 ), wherein said at least one inset section (9, 10, 13, 15, 17, 18, 19) comprises at least one fluid conduit means (14) that fluidly connects two surface parts (2, 3) of said port plate (1 ).

4. Port plate (1 ) according to any of the preceding claims, characterised in that it is designed and arranged as a valve plate and/or as a bearing plate for a fluid working machine, preferably for a high-pressure fluid working machine, more preferred for a hydraulic fluid working machine, even more preferred for a high-pressure hydraulic fluid working machine.

5. Port plate (1 ) according to any preceding claims, characterised in that at least one of said fluid conduit means (7, 9, 10, 13, 14, 15, 17, 18, 19) comprises a fluid branching point (16), in particular an internal fluid branching point (16).

6. Port plate (1 ) according to any of the preceding claims, in particular ac- cording to claim 5, characterised in that for at least one fluid conduit means (9, 10, 13, 14, 16, 17, 18, 19) the number of fluid conduits (14) connecting to a first surface section (2) is different from the number of flu- id conduit, connecting to a second surface section (3) of said port plate (1 ).

7. Port plate (1 ) according to any of the preceding claims, characterised in that at least a section of at least one of said fluid conduit means (7, 9, 10, 13, 14, 16, 17, 18, 19) is arranged as a curved fluid conduit and/or runs along a direction deviating from the surface normal of said fluid blocking surface section of said port plate (1 ) and/or runs along a direction essen- tially parallel to the fluid blocking surface section of said port plate (1 ) and/or comprises a fluid conduit widening (16, 20) and/or a fluid conduit restriction.

8. Port plate (1 ) according to any of the preceding claims, in particular ac- cording to any of claim 3 to 7, characterised in that the surface sides (2, 3) of the port plate (1 ), in particular the surface of the port plate (1 ) across a fluid blocking surface section and an inset section (9, 10, 13, 14,

16, 17, 18, 19) is essentially homogeneous and/or smooth.

9. Port plate (1 ) according to any of the preceding claims, in particular port plate according to claim 8, characterised in that at least one of the sur- face sides (2, 3) of the port plate (1 ) is smoothened, ground and/or lapped in particular after insertion of at least one of the inset sections (9, 10, 13, 14, 16, 17, 18, 19).

10. Port plate (1 ) according to any of the preceding claims, in particular ac- cording to any of claims 3 to 9, characterised in that said part of said port plate (1 ), in particular at least one of said inset sections (9, 10, 13, 14, 16, 17, 18, 19) is manufactured by means of a technique, taken from the group comprising welding, laser welding, pressure welding, additive manufacturing techniques, 3D printing techniques, soldering, sintering techniques and pressing techniques, and preferably inserted into a pre- form of said port-plate (1 ).

11. Fluid valve unit, comprising at least two elements that can be moved relative to each other, in particular that can be rotated relative to each other, characterised in that at least one of said at least two elements is designed at least in part as a port plate (1 ) according to any of claims 1 to 10.

12. Fluid working device, comprising at least one fluid valve unit according to claim 11 and/or at least one port plate (1 ) according to any of claims 1 to 10.

13. Method for producing a port plate (1 ), characterised in that a raw work- piece is machined using material removing machining techniques (22), and the thus obtained pre-form is consequently machined using additive manufacturing techniques (23), in particular using 3D printing techniques.

14. Method according to claim 13, characterised in that it is used for manu- facturing a port plate (1 ) according to any of claims 1 to 10 and/or a fluid valve unit according to claim 11 and/or at least a part of a fluid working device according to claim 12.

Description:
IMPROVED PORT PLATE

The invention relates to a port plate for a fluid throughput regulating device, comprising at least one fluid blocking section, and at least one fluid conduit means that fluidly connects two surface parts of the port plate. The invention also relates to a fluid valve unit, comprising at least one port plate, the port plate comprising at least one fluid blocking section, and at least one fluid conduit means that fluidly connects two surface parts of the port plate. The invention further relates to a method for producing a port plate for a fluid throughput regulating device.

In hydraulics, it is standard that not only fluid connections are established between various components of a hydraulic system in a static way, but in- stead it is regularly required to establish or to cut such a fluid connection in dependence of certain conditions of the hydraulic system. These conditions can come from various considerations.

As an example, the question of whether the fluid connection has to be pre- sent or not (and possibly including the fluid throughput rate that is allowed through the fluid connection) might depend on an operator input. Just to give an example, an operator might command an upward or downward lift of the fork of a forklift truck (where usually not only the direction of the movement, but also the speed of the movement is controlled). Sometimes it is also required that the fluid connection is established or cut off / hindered in dependence of certain operational parameters of the system in an automated way, so that at least for the majority of the actuations to be performed no user input is necessary. An example for this is the operation of a fluid pump or a fluid motor of the piston-and-cylinder type. Here, a fluid in- put port and a fluid output port of the individual cylinders of the piston-and- cylinder pump has to be opened and closed depending on the phase of the actuation cycle the respective piston-cylinder-assembly is currently in. Such a controlled opening and closing of the fluid inlet and outlet ports has to be per- formed for all of the cylinder chambers individually. Usually, the actuation cycles are offset in phase so that a smoother fluid output flow and a smooth- er mechanical input requirement (hydraulic pump), or a smoother fluid intake flow and a smoother mechanical output behaviour (hydraulic motor) can be realised. Thus, the opening and closing behaviour of the individual cylinders has to be offseted in phase accordingly. One way of doing this is the use of actuated valves. The actuated valves can be actuated by use of a mechanical input command (typically using a me- chanical connection to the crankshaft) or an electrical actuation signal (which can bring forward additional advantages, like it is the case with the syntheti- cally commutated hydraulic fluid working machine design; also known as digi- tal displacement pump® or DDP®). This approach is well established in the art and has certain advantages that come along with this concept and which are clearly not deniable.

Sometimes, however, the advantages of the actuated valve design are not required (at least not to an extent that would justify the additional effort), so that the disadvantages of this approach will come to the fore, namely the more elaborate and costly design, as well as the increased requirement for building space. In these cases, the use of the so-called valve plate design is known and well established in the art, in particular when fluid working machines are used in which the cylinders are arranged circularly in some kind of a drum (the back- and-forth movement of the pistons is typically introduced by a rotation of the drum or of the swash plate, where the relative rotational movement between the swash plate and the drum is translated into the required back-and-forth movement of the pistons by means of a relative inclination between the sur- face of the swash plate and the axial direction of the drum). This design uses two so-called port plates, namely two plates that show a distinct pattern of orifices along their surfaces, and that are rotated relative to each other. The respective pattern of orifices is chosen in a way so that a fluid connection can be established or cut off during the appropriate phases of the working cycles of the individual cylinders. A fluid connection is established if two orifices in the respective port plates align with each other. A fluid connection is cut off if the respective orifices are out of line with each other.

The port plate concept shows a relatively simple design, has a high reliability and is comparatively cheap to produce. The disadvantage with the design, however, is that the resulting fluid flow pattern can hardly be influenced. In principle, so far a fluid connection is established by a direct fluid flow channel that runs parallel to the surface normal of the port plate. Therefore, a high velocity fluid jet will occur (considering the high differential pressures of typi- cally 300 bars and more that are around in hydraulic systems). This brings along a distinct fluid flow pattern in the various components. In particular, in the cylinder chambers of the fluid working machine huge amounts of vortices are generated (resulting in energy losses and heat up of the hydraulic fluid), and even increased wear of the components can occur due to cavitation ef- fects and fluid jets impinging on surface parts of the components.

So far, various suggestions have been made to avoid, or to at least reduce the problems that come along with the valve plate design. So far, however, the proposed solutions still show some deficiencies.

It is therefore the object of the present invention to suggest port plates that are improved over port plates that are known in the state of the art. Another object of the invention is to suggest a fluid valve unit, a fluid working device and a method for producing a port plate that is improved over fluid valve units, fluid working devices and methods for producing a port plate that are known in the state-of-the-art, respectively.

The presently proposed invention solves this object.

It is suggested to design a port plate for a fluid throughput regulating device that comprises at least one fluid blocking section and at least one fluid con- duit means that fluidly connects two surface parts of said port plate in a way that said fluid conduit means comprises at least one fluid conduit that is bent in a way that there is no line-of-sight axis between the surface parts that are connected by the respective fluid conduit. This way it is possible to avoid very fast fluid jets that could otherwise develop in case high pressure differences do occur across the fluid regulating device, the port plate is used for, when the respective orifices are aligned with each other, at least to a certain extent. This is because the bend(s) in the fluid conduit device will usually limit the occurring fluid speeds, at least to a certain extent. However, keeping the pur- pose of a port plate in mind, the fluid conduit device will still allow the throughput of a sufficiently high fluid flux, so that a hydraulic consumer can be supplied with hydraulic oil (or a hydraulic fluid source can deliver a suffi ciently high fluid flux). In particular, this should be the case without severe fluid flow hindrance, so that - as an example - a (severe) fluid throttling does not count as a fluid conduit device in the present sense. In the example of a hydraulic pump of the piston cylinder type, the fluid conduit device has to be able to allow for a fluid flux that is sufficiently high to supply the fluid needs of the respective piston-cylinder-combination. In case a plurality of fluid conduit devices is arranged in parallel, this applies mutatis mutandis to the plurality of fluid conduit devices.“Fluid conduit device” does relate to the situation that is present when the port plate is used in the machinery, it is intended for. If, for example, the port plate is intended to be used as a fluid valve device, a“fluid conduit device” relates to a situation, where the port plate is in mechanical sliding contact with a corresponding second port plate (where the second port plate may or may not have a similar design as the first port plate; usual- ly, however, the second port plate will show a different design, as compared to the first port plate). Quite often, the second port plate is referred to as a bearing plate. Therefore, as an example, a bore/recess/clearance/cavity that is foreseen for introducing another device later on, in particular a device that essentially (or at least significantly) blocks a fluid throughput through the bore/recess/clearance/cavity (for example a closing plug, a piston device, and so on), is not to be interpreted as a fluid conduit device in the present sense. The fluid conduit means can comprise one fluid conduit and/or several fluid conduits. In particular, it is also possible that a fluid conduit will "split up" or "be joined" along its fluid path, which will be elaborated in more detail later on. In particular, in case a single fluid conduit is used for the fluid conduit de- vice, the notion of a“fluid conduit" and a "fluid conduit device" might even be used interchangeably. Typically the port plate is of a plate-like shape (as the notion "plate" already suggests), meaning that its size in at least one, typical- ly in both directions of a plane (in the mathematical sense) shows a size that is usually significantly larger as opposed to a size in the direction of the sur- face normal of said plane (typically by a factor of at least 2, 5, 10, 20 or 50). The surfaces with the large(r) dimension will usually be addressed as“the surface" (in particular as the upper surface and the lower surface) of the re- spective port plate, albeit this is not true in a strict mathematical way. Math- ematically, the plate has of course a finite height, so that a circumferential wall / outer rim, showing a certain surface area, will be present as well. In case that orifices (like fluid conduits, fluid conduit devices and so on) are pre- sent, even here some rim-like surface area will be present. However, when talking about rim-like surface areas, this will normally be specifically men- tioned. Therefore, when simply talking about a "surface", typically (one of) the large surfaces of the plate are meant. Further, the at least one fluid conduit / fluid conduit means that fluidly connect the surfaces of the port plate are typi- cally arranged in a way that the "large" surfaces are fluidly connected. Alt- hough it is possible that the same“large” surface is meant (usually the upper surface and/or the lower surface; for example, the lower surface is connected to itself by a fluid conduit having a hollow half-ring design, starting from the lower surface and going back to the lower surface), typically the fluid conduit means / the fluid conduit will connect two opposing surfaces (or at least dif- ferent surfaces), i.e. typically the (large) upper surface with the (large) lower surface. Nevertheless, it is possible that a fluid conduit means / a fluid con- duit connects one or two of the large surfaces with one or more rim-surfaces and/or that a fluid conduit means / a fluid conduit connects two rim surfaces with each other (where it is possible that this encompasses the same rim sur- face and/or a different rim surface). A mixture of such fluid connection set- ups is possible as well, in particular in case fluid branches are present. In case that a plurality of fluid conduit means / fluid conduits are used, a mixing of the aforementioned (different) types is also possible. Further, the number of / percentage of the respective types that are used for the overall device may vary (therefore, it is possible that one, two or three fluid conduit means fluidly connect two opposing large surfaces, while a single one will fluidly connect one large surface with a rim surface. The numbers will scale appro- priately, in case a large number of fluid conduit means / fluid conduits is used. The fluid throughput regulating device will usually use a port plate valve arrangement. It is to be noted that one, two or more of the port plates that are used for the respective fluid throughput regulating device may be designed as an integral part of a certain (combined) device. As an example, the port plate can be a flange cap of the housing, the bottom of a pot-like housing, or the like. In case that several fluid conduits / fluid conduit devices are used, the respective fluid conduits / fluid conduit devices can (in part) show essentially the same cross-sectional shape and/or size and/or (in part) a different cross-sectional shape and/or size. While a single fluid conduit will usually show the same cross-sectional shape and/or size along its length, it is also possible that its cross-sectional shape and/or size varies along its length and/or between its different sections. In particular, a variation in cross- sectional shape and/or size that is limited to a certain upper limit of variation is possible. By a fluid blocking section, any arrangement is meant that blocks (or at least severely limits) a fluid throughput through the respective section. Therefore, some minor leakage fluid flows or so may still occur, despite of the presently chosen wording of a "fluid blocking section". Typically, the fluid blocking section is associated with a certain surface area part of the port plate. The simplest (and typically preferred) design for at least the majority of occurring fluid blocking sections is that a continuous surface is provided by a solid material block, in particular (but not necessarily) by a one-piece material block. For completeness, it should be mentioned that it is not ruled out that at least one (several of) said fluid conduit means / fluid conduits may show a line-of-sight connection (in particular when a special selection of certain sec- tions of the respective fluid conduit means / fluid conduit are considered). In effect, this might be even advantageous. When saying that a (single) fluid conduit (section) will usually show the same cross-sectional shape and/or size along its length (in particular a fluid conduit (section) without a line-of- sight connection may be meant), this may relate to a certain fraction of its respective (section) length. As an example, this may relate to up to 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80% or 90% of the respective length of the fluid conduit (section). For the remaining part, even larger variations may be allowed. Nevertheless, certain variations of the cross-sectional shape and/or size along (major parts of) the length may be permitted. As an example, vari- ations of up to 10%, 20%, 30%, 40% or 50% of the cross-sectional shape are not necessarily excluded. In particular, if larger variations occur (in particular along (major parts of) the length), the variation of the cross-sectional size may be limited, in particular limited to a factor of up to 1.5, 2, 2.5, 3, 4 or 5. Even more, in particular in case the variation in size and/or cross-sectional shape is limited to a comparatively short length of the fluid conduit (section), even larger variations may be allowed (as previously mentioned). In case a plurality of fluid conduit devices is used, the aforesaid may apply mutatis mu- tandis to the combined cross-sectional shape and/or size. A bending of the fluid conduit (device/section) may be limited to a range between 0°, 10°, 20°, 30°, 40 or 50° (lower limit) and 30°, 40°, 50°, 60°, 70°, 80°, 90° or 100°. This may relate to the surface normal of the connecting plate’s surface and/ or to an initial direction of the fluid conduit (device/section).

In particular, it is possible to design the port plate in a way that said at least one fluid conduit comprises at least one fluid conduit section that is arranged in a way that it cannot be reached by a line-of-sight axis from both of said two surface parts of said port plate. This way, the flexibility with respect to a fluid speed limiting effect can be even larger. Nevertheless, as already mentioned, a sufficient fluid flux must be possible through the fluid conduit (usually ex- cluding a fluid throttle, an insertion of fluid throughput restriction means, a plug, a piston, or the like) Furthermore, the resulting fluid flow pattern of fluid entering or leaving the respective fluid conduit means / fluid conduit can show more flexibility as well (both inside the respective fluid conduit means and/or the connecting devices, like cylinders). It is to be noted that technolog- ically the presently proposed feature includes the previously discussed de- sign effectively. Therefore, it shall be possible to use the present definition as a "fresh start" without referring to the previous definition (including the possi- bility to combine the present definition with other features, without referring to the previous definition). Admittedly, the presently proposed port plate is somewhat difficult to manufacture, since the fluid conduit cannot be produced by two straight bores that are drilled from two opposing surface sides of the port plate, where the bores are arranged at an angle with each other (the bores being dead-end bores, when seen as an individual bore), at least in general. Nevertheless, production of such a design is still possible. Just to name a few possibilities, a bore can be introduced from a rim and/or from a rim-surface side. The respective bore can possibly be (partially) filled by some kind of a plug later on, if necessary. The arrangement can also be manufactured by using two plates showing appropriately placed bores and trenches, where the plates will be arranged as some kind of stacked layers later on. This proposal can be used for a complete port plate. Also, it is pos- sible to use this manufacturing technique for an inset that will later on be placed in and attached in a sufficiently large recess of the port plate (which will be described in more detail later on). Furthermore, it is possible to limit the thickness of the port plate in a certain area and to introduce an inset later on in this area to bring the thickness of the port plate in this area“back to normal”. Therefore, in the respective area, a stacked layer of plates will be created effectively (some kind of a "half inset" or filling). Furthermore, addi- tive manufacturing techniques can be used as well, where this/these additive manufacturing technique(s) can be used for the complete plate, for an inset or for a“half-inset” (as previously described). In particular an additive manu- facturing technique is usually the way of choice in case that (partially) a one- piece plate (inset) has to be generated. The various possibilities with respect to fluidly connecting surfaces / rims that were previously discussed, do apply to the present proposal as well.

Additionally or alternatively, it is suggested to design a port plate for a fluid throughput regulating device, the port plate comprising at least one fluid blocking section, in a way that at least one inset section that is arranged with- in a recess section of said at least one fluid blocking section of said port plate, wherein said at least one inset section comprises at least one fluid conduit means that fluidly connects two surface parts of said port plate. While a large-sized fluid blocking section and/or a large-sized plate area (a plate- like member) is usually comparatively simple and cheap to manufacture, the manufacture of a fluid conduit means / fluid conduit might prove to be some- what more problematic (and costly), in particular in case that certain specially shaped fluid conduits are to be provided (more particular a bent fluid conduit without line-of-sight axis and/or a fluid conduit with a conduit section that is not accessible by a line-of-sight connection from both of the surfaces of the afore described types). When following the proposal of an inset section (that can be manufactured separately and/or in a separate manufacturing step), one can achieve a greater flexibility for manufacturing while the "majority" of the port plate can still be produced using cheap and well established stand- ard manufacturing techniques. As an example, in case an additive manufac- turing technique, in particular a 3D printing technique, is used for the inset, the rather slow 3D printing process can be limited to a small surface area of the port plate, so that the manufacturing process of the port plate as a whole can be significantly accelerated, resulting in significant cost advantages. The inset section can be manufactured in a way that a one-piece workpiece with the surrounding port plate can be realised (in particular when using additive manufacturing techniques) or in a way that the surrounding port plate and the inset section are two separate pieces that will be attached to each other us- ing appropriate connection techniques (for example glueing, welding, form-fit connections, soldering or a combination thereof). In particular, in case that a plurality of inset sections is present, a mixture of various inset types is possi- ble as well, in particular of the aforementioned types.

According to a preferred embodiment, the port plate is designed and ar- ranged as a valve plate and/or as a bearing plate for a fluid working machine, preferably for a high-pressure fluid working machine, more preferred for a hydraulic fluid working machine, even more preferred for a high-pressure hy- draulic fluid working machine. If the presently proposed port plate is used in this way, it can show its intrinsic features and advantages particularly well. In particular, the functionality of a controlled fluid flow pattern and/or fluid flow speed can be particularly advantageous in this context.

Further, it is proposed to design the port plate in a way that at least one of said fluid conduit means comprises a fluid branching point, in particular an internal fluid branching point. This way, it is possible to provide a different number of fluid orifices on both opposing surface sides of the port plate. Ad- ditionally or alternatively, it is possible to fluidly connect both opposing sur- face sides of the port plate, while providing a fluid connection to a rim surface (outer rim surface/inner rim surface, as required). Even if the same number of fluid orifices on both opposing surface sides is provided, this proposal can still be advantageous in that the branching point can provide for a cross mix- ing effect and/or for providing a special fluid flow throughput behaviour in light of the stream pattern and vortices generated in and in the vicinity of the fluid branching point. While typically one fluid branching point per fluid conduit means is sufficient, it is also possible to provide a plurality of fluid branching points. It is to be noted that it is possible that when using a certain selection of fluid channel sections, a line-of-sight connection can be realised for this particular selection of fluid channel sections. Nevertheless, when using an- other selection of fluid channel sections, a non-line-of-sight connection will be present, at least for some of the fluid conduit means. The combined cross- sectional shape and/or a size of the fluid conduit means before and after the internal fluid branching point may be (essentially) the same; a variation thereof may be present and/or a variation thereof may be limited. With re- spect to explicit numbers, reference is made to the previously mentioned numbers in the context of single fluid conduit devices in analogy. Further- more, the previous discussion about same or different cross-sectional shapes and/or sizes may apply to a/the individual fluid conduit section(s), like a fluid conduit section leading from a first surface towards an internal fluid branching point and/or a fluid conduit section leading from an internal fluid branching point towards a second surface and/or a fluid conduit section leading from a first internal fluid branching point towards a second internal fluid branching point.

It is further suggested that for the port plate for at least one fluid conduit means the number of fluid conduits connecting to a first surface section is different from the number of fluid conduits, connecting to a second surface section of the port plate. As already mentioned, by this a particularly advan- tageous fluid flow pattern can be achieved, not only within the fluid conduit means, but particularly in the connecting fluid manifold, piston chamber and so on. According to a special embodiment, it is possible that in said port plate at least a section of at least one of said fluid conduit means is arranged as a curved fluid conduit and/or runs along a direction deviating from the surface normal of said fluid blocking surface section of said port plate and/or runs along a direction essentially parallel to the fluid blocking surface section of said port plate and/or comprises a fluid conduit widening and/or comprises a fluid conduit restriction. As already previously mentioned, a fluid conduit re- striction has to be somewhat limited with respect to the amount of restriction, so that a sufficient fluid flow through the fluid flow restriction is still possible. For example, a sufficient fluid flux to support filling/emptying of the cavity of a piston/cylinder arrangement of a fluid pump of the piston and cylinder type has to be maintained. Using one or several of these features including, but not limited to a combination of all the aforesaid features, a fluid flow behav- iour of the port plate can be realised that is particularly well suited for the de- vice, the port plate is used for. It is of course possible to use a different em- bodiment of the present invention instead of the mentioned features and/or in addition to the mentioned features.

In particular, the port plate can be designed in a way that the surface sides of the port plate, in particular the surface of the port plate across a fluid blocking surface section and an inset section is essentially homogeneous and/or smooth. This way, the port plate is particularly suited for mechanical contact with another device, in particular with a second plate. This way, a relative rotational movement between two port plates can be easily achieved without major mechanical problems occurring.

Even more, it is possible to design the port plate in a way that at least one of the surface sides of the port plate is smoothened, ground and/or lapped, in particular after insertion of at least one of the inset sections. This way a par- ticularly high surface smoothness can be realised, which is particularly suita- ble if the port plate is to be moved relative to another workpiece, the port plate is in mechanical contact with (for example another port plate).

In particular, it is suggested that at least part of said port plate, in particular at least one of said inset sections is manufactured by means of a technique, taken from the group comprising welding, laser welding, pressure welding, additive manufacturing techniques, 3D printing techniques, soldering, sinter- ing techniques and pressing techniques, and preferably in a way that an inset section is inserted into a pre-form of said port plate. This way, a combination of a fast and cost-efficient manufacturing of the port plate can be realised in combination with a particularly large degree of freedom with respect to its design, in particular its internal design, more particular of the design and rout- ing of fluid conduits.

Further, a fluid valve unit is suggested that comprises at least two elements that can be moved relative to each other, in particular comprising at least two elements that can be rotated relative to each other, wherein at least one of said at least two elements is designed at least in part as a port plate accord- ing to the previous suggestions. The at least two elements are usually in a sliding mechanical contact with each other. This way, the resulting fluid valve unit can show its intrinsic advantages and characteristics particularly pro- found, at least in analogy. Of course, it is also possible to modify the resulting fluid valve unit in the above-described sense, at least in analogy.

Quite often, for such fluid valve units an arrangement of (at least two) port plates is used, where the port plates are in a sliding mechanical contact with each other (which refers particularly to two adjacent large sized surfaces). Sometimes, the second port plate is referred to as a“bearing plate” as well. Albeit the port plates may be (essentially) of the same, or at least of a similar design, usually the port plates are somewhat different. This relates particular- ly to the size, number, arrangement and/or shape of any openings that are used for the fluid flow throughput (in particular for the major/main fluid flow throughput). In the case of a hydraulic fluid pump of the piston-and-cylinder type that is controlled by a fluid valve unit, this relates to the fluid fluxes that are directed to/come from the cavities of the piston-cylinder arrangements. Just to give an example of a“non-major fluid flow throughput”: those may be any auxiliary fluid flows that are used for controlling purposes, for example fluid orifices that are used for repositioning pistons that are used for control- ling the distance between the two port plates. Just for the sake of complete- ness: the diameters, the material and/or the thickness of the respective port plates may be (essentially/somewhat) similar or even (essentially) the same. Irrespective of the detailed design of the two port plates, a fluid throughput between the two outermost sides of the two (or possibly more) port plates will be established at certain relative angular positions between the two port plates, while the fluid throughput will be inhibited (essentially zero) at other relative angular positions. Usually, there will be intermediate positions with a fluid flux that lies between (essentially) zero and the maximum possible fluid flux.

Furthermore, a fluid working machine is suggested that comprises at least one fluid valve unit according to the previous description and/or at least one port plate according to the previous description. Again, the resulting fluid working machine can show the already mentioned advantages and charac- teristics, at least in analogy. Further, the fluid working machine can be modi- fied in the above-described sense as well, at least in analogy.

Furthermore, a method for producing a port plate is suggested, wherein a raw workpiece is machined using material removing machining techniques, and the thus obtained pre-form is consequently machined using additive manufacturing techniques, in particular using 3D printing techniques. This way, it is on one hand possible to realise a particularly high degree of free- dom for otherwise difficult to produce parts of the port plate, while, at the same time, it is possible to provide a fast and efficient method of producing a port plate for those areas, that do not show a complicated to produce design. Using additive manufacturing techniques, a particularly tight contact between the two areas of the resulting port plate can be realised, in particular if mate- rials are used that bond together particularly well. This way, a particularly high strength of the resulting port plate can be realised.

In particular, it is suggested to use the presently suggested method for manu- facturing a port plate and/or a fluid valve unit and/or at least a part of a fluid working device that is designed according to the previous description. This is, because the presently proposed manufacturing method is particularly well suited for such units.

Further advantages, features, and objects of the invention will be apparent from the following detailed description of the invention in conjunction with the associated drawings, wherein the drawings show:

Fig. 1 : a port plate disc in a top view;

Fig. 2: a first possible embodiment of an inset in a cross-sectional view, a top view, and a bottom view, respectively;

Fig. 3: a second possible embodiment of an inset in a cross-sectional view, a top view, and a bottom view, respectively;

Fig. 4: a third possible embodiment of an inset in a cross-sectional view, a top view, and a bottom view, respectively;

Fig. 5: a fourth possible embodiment of an inset in a cross-sectional view, a top view, and a bottom view, respectively;

Fig. 6: a fifth possible embodiment of an inset in a cross-sectional view, a top view, and a bottom view, respectively.

In Fig. 1 a possible and somewhat typical design of a circular port plate 1 is shown. Port plates 1 of the type shown in the figure are known in the state of the art as such, as well as their functional abilities. In particular, in combina- tion with a second port plate, they are used for appropriately opening and closing the inlet and outlet ports of the cyclical pumping chambers of a pis- ton-and-cylinder type hydraulic motor / piston-and-cylinder type hydraulic pump. Such pumps are also well known in the state-of-the-art as such.

Albeit the circular port plate 1 and the second port plate may be of the same or an (essentially/somewhat) similar design in principle, typically circular port plate 1 and second port plate are different with respect to the arrangement, size and/or shape of the fluid throughput orifices. At the same time, however, typically the material, diameter and/or thickness of the circular port plate 1 and the second port plate are similar or (essentially) the same.

Irrespective of the detailed design of the two port plates (circular port plate 1 and second port plate), a fluid throughput between the two outermost sides of the two (or possibly more) port plates will be established at certain relative angular positions between the two port plates, while the fluid throughput will be inhibited (essentially to zero) at other relative angular positions. Usually, there will be intermediate positions with a fluid flux that lies between zero and the maximum possible fluid flux.

The principal design of a port plate 1 comprises a disc-like shape with a di- ameter of typically some 10 cm to 30 cm. The height (thickness) of the port plate 1 is typically in the order of 2 or 3 mm. Therefore, the top surface 2 (that is visible in Fig. 1 ) shows a significantly larger surface area, as compared to the cylinder surface area that limits the outer rim 4 of the port plate 1. Only for completeness, it should be mentioned that different shapes of the port plate 1 are also possible, albeit a circular design is by way the most frequent- ly used design that is employed for port plates 1. In the middle of the port plate 1 a driving hole 5 is located. The driving hole 5 is of an essentially circular design in the present case, as well. However, in the presently shown example, two recesses 6 are arranged along the circum- ference of the driving hole 5 (the exact number of recesses may vary, of course). For either driving the port plate 1 or for holding the port plate 1 firmly in place (so that it cannot rotate inadvertently under the torque that is intro- duced by the opposing port plate, for example), a shaft with protrusions that correspond to the recesses 6 is introduced into the driving hole 5 (the shaft is not shown), so that a form-fit and torque-proof connection is established be- tween the shaft and the port plate 1. Only for completeness, it should be mentioned that of course different shapes of the driving hole 5 are possible as well. In particular, a triangular, a ellipsoidal, a rectangular, a hexagonal or a torx-like shape is possible as well, just to name some possible designs.

In the presently shown design, a plurality of holes 7 is arranged in a suitable pattern along a circular path 8 around the center of the port plate 1. The cir cular path 8 is typically not indicated or otherwise visible on a "real" port plate 1 , but presently shown as a dashed line for illustrative purposes.

In the standard design of port plates 1 , only holes 7 that do fully penetrate the thickness of the port plate 1 are typically employed. It should be noted that the holes 7 can have a shape that is different from the designs shown. Apart from circular holes or somewhat elongated slits, shapes with a varying width along their length are possible as well. Furthermore, (a series of) holes 7 can also be arranged along several circular paths 8 with varying radii and/or with variable distance from the center of the port plate 1 along a circular walk around the surface 2, 3 of the port plate 1.

In the presently shown embodiment, however, four of the holes 7 (to be ex- act: holes 7a through 7h), namely holes 7b, 7c, 7f and 7g are filled with an inset 9, 10. In particular, in the presently shown embodiment, opposing holes 7b, 7f and 7c, 7g are filled with a different inset 9, 10, respectively. However, the exact arrangement, the exact types of insets, and so on, can vary from the presently shown embodiment.

In Fig. 1 , the insets 9, 10 are highlighted by a hatching. In practice, however, the insets 9, 10 will usually be hardly visible, due to the manufacturing tech- nique chosen (as further explained later on). In typical embodiments, the large surfaces (i.e. top surface 2 and bottom surface 3) are smoothened and typically somewhat polished, so that an essentially fluid proof seal is estab- lished between two port plates 1 , when they are arranged in a way that their large surfaces 2, 3 face each other. Certainly, a certain type of fluid leakage can never be avoided; however, this is not contrary to the notion of a fluid- tight connection for practical purposes.

In the presently shown example, first insets 9 show two fluid orifices 11 on the top surface 2 of port plate 1 , while second insets 10 only show a single orifice 11 on the top surface 2 of port plate 1. However, this can be complete- ly different as well.

Some exemplary examples for insets are shown in Figs. 2 to 6. Each of Figs.

2 to 6 show a possible embodiment of an inset in three views, namely a cross-sectional view in sub-figure a), a top view in sub-figure b) and a bottom view in sub-figure c), respectively. The cross-sectional view a) is cut along a plane, where one axis of the plane is parallel to the surface normal of the port plate 1 , while the second axis of the plane is parallel to a circular path 8 (when seen locally). The top view (sub-figure b) ) resembles the sight when looking on the top surface 2 of port plate 1 , while the bottom view (sub-figure c) ) resembles the sight that can be seen when looking at the bottom surface

3 of the port plate 1. It is to be noted that presently the cross sections and the top / bottom view of the insets are shown with the shape of a rectangle; how- ever, the respective shape can vary widely. In Fig. 2, the inset 13 shows a fluid conduit 12 with two sections 14a, 14b, that are arranged at an angle with each other. Therefore, there is no line-of- sight connection between the top surface 2 and the bottom surface 3 of the inset 13. Further, in the presently shown embodiment of an inset 13, the two sections 14a, 14b do show a different cross-section, namely a circular cross- section for the first section 14a and an elongated slit-shaped cross-section for the second section 14b. This can also be seen by the different shapes of the orifices 11 on the top surface 2 and bottom surface 3, as visible in sub- figures b) and c).

In Fig. 3, a different possible embodiment of an inset 15 is shown. Presently, the fluid conduit 12 shows altogether four sections 14a, 14b, 14c, 14d that are connected via a branching point 16. Presently, three of the four sections 14a, 14b, 14c of the fluid conduit are connecting to the top surface 2, while only a single section 14d connects to the bottom surface 3. This can be seen from the top view b) and the bottom view c) as well. Presently, the cross sec- tions of all sections 14a to 14d show the same diameter and shape. Flowev- er, it is also possible that particularly the "single section 14d" shows a larger cross-section, as compared to sections 14a, 14b and 14c, to compensate for the larger number of sections in the upper half of the inset 15.

As a remark, one can see from Fig. 3 that indeed a line-of-sight connection between top surface 2 and bottom surface 3 is effectuated via sections 14b and 14d. Nevertheless, the fluid connection between top surface 2 and bot- tom surface 3 via sections 14a and 14d on the one hand, and sections 14c and 14d on the other hand, and similarly the fluid connection between any two / all three of the sections 14a, 14b and 14c (connecting top surface 2 with itself) are not of a line-of-sight type. In Fig. 4, yet another possible embodiment of an inset 17 is shown. Here, the fluid conduit 12 is arranged in a way that the two orifices 11 of the fluid con- duit connect to the same surface side 2, 3, namely presently to the top sur- face side 2 of the port plate 1.

In Fig. 5, yet another possible embodiment of an inset 18 is shown. In the presently shown embodiment of an inset 18, the fluid conduit 12 shows alto- gether three sections 14a, 14b, 14c, two of which (sections 14a, 14b) con- nect to the top surface 2, while the third section 14c connects to the bottom surface 3. Furthermore, the branching point 16 is designed as an enlarged void inside of inset 18. Presently, the void of the branching point 16 has a diameter of approximately 2 to 3 times the diameter of an individual section 14a, 14b, 14c of the fluid conduit 12.

Yet another possible embodiment of inset 19 is shown in Fig. 6. Here, the fluid conduit shows two sections 14a, 14b that both connect to the top sur- face 2 (similar to the embodiment of an inset 17, as shown in Fig. 4). Pres- ently, however, along the fluid conduit 12 (approximately in the middle) an inner void 20 is arranged. The void 20 is approximately ball-shaped with a diameter of approximately 2 to 3 times the diameter of the sections 14a, 14b of the fluid conduit 12.

In Fig. 7, a possible flow chart for the manufacturing process of a port plate, in particular of a port plate 1 of the design as shown in Fig. 1 , is shown.

In the beginning, a circular plate (without recesses) is provided (step 21 ).

In the following step 22, the plurality of holes 7 and the driving hole 5 (and/or similar openings) are manufactured using standard material removing tech- niques. As an example, drills, saws, laser cutting tools, milling tools or the like can be used. Following this, in another step 23 additive manufacturing techniques, in par- ticular 3D printing techniques are used to fill some of the holes 7 (possibly the majority or even all of the holes 7) with insets 9, 10 (or likewise). In par- ticular, the examples of insets 13, 16, 17, 18, 19, as shown in Figs. 2 to 6 can be used for this.

After the additive manufacturing technique step 23, the top surface 2 and the bottom surface 3 of the port plate 1 is flattened, for example by grinding and polishing techniques, as they are known in the state-of-the-art, as such (step 24).

Of course, some variations are possible as well. As an example, the 3D print- ing step 23 might be performed independently from the“main part” of the port plate 1 , initially (steps 21 and 22). Afterwards, the independently manufac- tured insets can be placed within the respective holes 7 and attached in the holes 7 of the pre-prepared port plate 1 , using appropriate fixation methods. Just to name some possible examples, welding techniques, soldering tech- niques, gluing, form locking attachment techniques or the like can be used, possibly even by combining two or more of such (and other types of) bonding techniques.

As yet another possible method of manufacturing a port plate 1 , the complete port plate 1 can be manufactured, using additive manufacturing techniques (3D printing processes, for example). Reference list

1 . port plate 15 13. inset

2. top surface 14. channel section 3. bottom surface 15. inset

4. outer rim 16. branching point

5. driving hole 17. inset

6. recesses 20 18. inset

7. holes 19. inset

8. circular path 20. void

9. first inset 21. providing circular plate

10 second inset 22. providing holes

1 1 orifice 25 23.3D printing step

12 fluid conduit 24. flattening step