WO2025087846A1

WO2025087846A1 - A sensing assembly for a hydraulic circuit

Info

Publication number: WO2025087846A1
Application number: PCT/EP2024/079687
Authority: WO
Inventors: Carsten Nielsen; Giuseppe DALLA COSTA; Martin Nøhr NIELSEN
Original assignee: Grundfos Holdings AS
Current assignee: Grundfos Holdings AS
Priority date: 2023-10-27
Filing date: 2024-10-21
Publication date: 2025-05-01
Anticipated expiration: 2026-04-27

Abstract

Sensing assembly for a hydraulic circuit, said sensing assembly comprising a sensor, a plug, a one-piece fitting, and fastening means arranged for detachably fastening the sensor to the one-piece fitting, said sensor comprising a sensing element, said plug comprising a cylindrical portion with an external thread, and said one-piece fitting comprising a cylindrical protrusion with an external thread, a first opening arranged to be in fluid communication with the sensing element of the sensor when the sensor is fastened to the one-piece fitting via the fastening means, a second opening comprising a hollow cylindrical portion with an internal thread suitable for engaging with the cylindrical portion of the plug, a third opening, and a fourth opening arranged passing through the cylindrical protrusion, said first, second, third and fourth openings being in fluid communication with each other, said second and third openings being arranged such that when the plug is inserted into the second opening, the plug can displace between two positions, a first position where the threaded plug prevents a fluid connection between the third opening and the fourth opening and a second position where a fluid connection is provided between the third and fourth openings. In this way a simple and flexible sensing assembly is provided.

Description

A sensing assembly for a hydraulic circuit

The current invention relates to a sensing assembly for a hydraulic circuit.

Description of related art

It is commonly desired to measure/observe a property of a liquid in a hydraulic circuit, such as the pressure, the flow, the temperature, a constituent concentration, the color, a vibration, or any other property of the liquid. For example, in the context of pressure sensing, to measure/observe the pressure, it is common to use a pressure gauge which shows a reading of the pressure directly to the viewer. Recently, sensors have become more frequently used. Sensors generally convert a measurement to an analogue electrical signal. The electrical signal can then be processed in different ways. Typically the electrical signal can be fed to an analogue circuit or to a converter which converts the analogue signal to a digital signal.

Typically, the processing of the analogue electrical signal is done remotely from the actual sensor. For example, a wire connects the sensor with a microcontroller located remotely from the sensor.

However, it has recently become more common to package electronic circuits which process the sensor signal together with the sensor itself. In this way, the sensor signal can be interpreted on site so that the sensor becomes smarter. Instead of sending a liquid property signal out of the sensor, an “interpreted” signal can be sent out of the sensor. For example, in the context of a pressure sensor, the on-board electronics can monitor the pressure and when the pressure exceeds a predefined value, the pressure sensor can send a warning signal. Hence, instead of having to implement external controllers to process the pressure signal, the pressure sensor itself can be programmed to generate the required signals to other components. Other options are possible. Some concrete examples are disclosed in applicant’s co-pending application filed in Denmark on 27-10-2023 and titled “APPARATUS AND METHOD FOR DETECTING A FAULT CONDITION OF A PUMP FOR PUMPING A FLUID” which is incorporated by reference in its entirety.

Pressure sensors are typically provided as a fitting with a male threaded connector which can be inserted into a fluid circuit via a threaded connection.

Summary of the invention

It is a first aspect of the current invention to provide a sensing assembly for a hydraulic circuit which minimize the component costs of the hydraulic circuit.

It is a second aspect of the current invention to provide a sensing assembly to minimize the complexity of the hydraulic circuit installation.

It is a third aspect of the current invention to provide a sensing assembly which reduces the total size of the components in a hydraulic circuit.

It is a fourth aspect of the current invention to provide a sensing assembly with more user friendliness to a hydraulic circuit comprising a pump.

These aspects are provided by a sensing assembly according to claim 1 . In this way, a simple, flexible and user friendly solution is provided which can also be reduced in size and cost compared to prior art installations.

According to this specification the term “one-piece fitting” refers to a fitting made from a single piece of material. This could for example be a fitting manufactured from a single piece of metal, for example formed via a casting operation. Or it could a moulded piece, or a 3D-printed element, either metal or plastic. These examples are not to be limiting for the scope of protection as other forms of manufacturing could be imagined. The term “one-piece fitting” is used to differentiate the current invention from a solution where multiple different fittings are joined together to form a complex assembly comprising multiple fittings.

In some embodiments, the sensing assembly is arranged for use in a hydraulic circuit where the fluid is water. In some embodiments, a centre axis of the first opening is parallel to a centre axis of the cylindrical protrusion. In some embodiments, a centre axis of the first opening is in-line with a centre axis of the cylindrical protrusion. In some embodiments, a centre axis of the first opening is parallel to a centre axis of the fourth opening. In some embodiments, a centre axis of the first opening is in line with a centre axis of the fourth opening. In some embodiments, the second and third openings are combined, such that the third opening is arranged alongside the second opening. In some embodiments, the third opening is a channel arranged along one side of the hollow cylindrical portion of the second opening. In some embodiments, the third opening is arranged perpendicular to a centre axis of the second opening. In some embodiments, the first opening is blocked when the sensor is fastened to the one-piece fitting.

In some embodiments, said fastening means are not provided by a threaded connection between the sensor and the one-piece fitting. In this way, it is easy to exchange the sensor. When using threaded connections, connecting and disconnecting the sensor will often times cause the one-piece fitting itself to turn, thereby increasing the risk of leakage. By providing a non-threaded connection between the sensor and the one-piece fitting, the sensor can easily be exchanged without any risk of leakage for the one-piece fitting itself. In some embodiments, the connection between the sensor and the one-piece fitting is a snap connection. In some embodiments, the fastening means comprise a fastening element which applies a force to the sensor holding the sensor in or against the first opening. In some embodiments, the force is applied along an axis which is parallel to a centre axis of the first opening. In some embodiments, the sensor comprises a cylindrical portion which is engaged in the first opening in a sealing manner. In some embodiments, the sealing manner is provided via a flexible annular sealing element arranged between the sensor and the first opening. In some embodiments, the sensor comprises a sealing surface which engages with a corresponding sealing surface on the one-piece fitting.

In some embodiments, the fastening element is held in place at least partially by a screw inserted into a fifth opening in the one-piece fitting. In some embodiments, a centre axis of the fifth opening is parallel to a centre axis of the first opening. In some embodiments, the centre axis of the fifth opening is offset to a centre axis of the first opening. In some embodiments, the fastening element is held in place on the one-piece fitting by a first fastener arranged on a first side of a plane comprising a centre axis of the first opening and a second fastener arranged on a second side of the plane opposite to the first fastener. In some embodiments, the first and/or second fasteners are screws. In some embodiments, the first and/or second fasteners are cooperating grooves/protrusions on the fastening element and/or the one-piece fitting.

In some embodiments, the fastening element comprise a fastening clip which may apply a force to the sensing assembly holding the sensor in or against the first opening. In some embodiments, the force may be applied axially to the center axis of the sensor, or the clip may hold the sensor in place by the force of friction. In some embodiments, the sensor comprises a cylindrical portion which is engaged in the first opening in a sealing manner. In some embodiments, the sealing manner is provided via a flexible annular sealing element arranged between the sensor and the first opening. In some embodiments, the sensor comprises a sealing surface which engages with a corresponding sealing surface on the one-piece fitting.

In some embodiments, the third opening is arranged above the sensing element of the sensor when the sensing assembly is engaged in a hydraulic circuit. In some embodiments, there is a passage connecting the fourth opening and the third opening which is blocked by the plug when the plug is in its first position. In some embodiments, the passage is the highest fluid containing point in the sensing assembly when the sensing assembly is installed in a hydraulic circuit. By fluid containing point, is meant a point which contains fluid of the hydraulic circuit. This will typically be a point which is in fluid communication with the fourth opening. In some embodiments, the third opening is arranged at the highest point in the passage.

In some embodiments, the sensor comprises electrical signal processing means to process the measurement. In some embodiments, the electrical signal processing means comprises digital computing means arranged to process the measurement property and output a signal which is different from the sensor signal. In some embodiments, said signal is not a signal expressing a property of the liquid, but a signal that is calculated based on the liquid property signal. In some embodiments, the sensor outputs multiple signals, where one of said signals is a liquid property signal and another signal provides other information.

In some embodiments, the first opening comprises a centre axis A and the second opening comprises a centre axis B and in that the angle (6) between the axis A and the axis B is less than 90 degrees. In this way, the sensing assembly provides a more space efficient design whereby it is easier to access both the bleed function and the sensor. In some embodiments, the angle is less than 80 degrees, less than 70 degrees or less than 65 degrees. In some embodiments, the fourth opening comprises an elongated hollow portion having a cross section which is formed to allow a torque applying tool to be inserted into the elongated hollow portion and apply torque to the one- piece fitting. In some embodiments, the elongated hollow portion is suitable for positive engagement with an Allen key. In some embodiments, said cross section of the elongated hollow portion is arranged inside a cross section of the first opening when viewing the one-piece fitting along an axis which is parallel to a centre axis of the first and/or fourth openings.

In some embodiments, the sensor may be any sensor configured to measure one or more properties of a liquid, such as a pressure-, temperature-, colour-, flow-, optical-, capacitive-, or a constituent concentration-sensor or a combination thereof. Various embodiments of the assembly disclosed herein are particularly useful for sensors that require contact with, or at least close proximity to, the liquid whose property is to be measured. However, it will be appreciated that various embodiments of the assembly disclosed herein may also be used for other types of sensors. In one embodiment, the sensor is or includes a pressure sensor.

The current specification also discloses a pump comprising an opening with an internal threaded portion and a sensing assembly as described above inserted in said opening where the cylindrical protrusion of the one-piece fitting is engaged with the internal threaded portion of the opening of the pump.

In some embodiments of the pump, the opening and the sensing assembly are arranged in fluid communication with an outlet of the pump and located at a location which is at the highest point in the fluid circuit of the pump. In this way, the sensing assembly allows easier air venting and sensing in one and the same one-piece fitting. In some embodiments, the pump is a vertical multistage pump and the one-piece fitting of the sensing assembly is arranged in an opening in the housing of the pump at the top of the pump. It should be noted that the current specification also discloses a second invention which could form the basis of a divisional application. The second invention relates to the elongated hollow portion on the inside of the one-piece fitting described above which is shaped to be suitable for positive engagement with a torque applying tool. In the current embodiment, the elongated hollow portion is provided in a one-piece fitting for a sensing assembly, however the same inventive concept could be applied to other fittings for other purposes and other types of fluid power circuits. For example, valve fittings could be provide with such an internal elongated hollow portion to allow the valve fittings to be more easily screwed into a circuit.

A potential claim directed to this second invention could be formulated as follows:

A fitting for a fluid power circuit, said fitting comprising a first opening, a cylindrical protrusion with an external thread, said cylindrical protrusion being in line with the first opening, said first opening comprising an elongated hollow portion formed inside the first opening, a cross section of said elongated hollow portion being formed to be suitable for positive engagement with a torque applying tool. In some embodiments, the torque applying tool is an Allen key (or hex key) and the elongated hollow portion is formed for positive engagement with an Allen key (or hex key).

In some embodiments, the fluid power circuit is a hydraulic or a pneumatic circuit.

In some embodiments, a centre axis of the first opening is parallel to a centre axis of the cylindrical protrusion. In some embodiments, the centre axis of the first opening is in-line with the centre axis of the cylindrical protrusion. In some embodiments, the cross section of the elongated hollow portion is arranged inside the cross section of the first opening when viewing the fitting along an axis which is parallel to the centre axis of the first opening. In some embodiments, a centre axis of the elongated hollow portion and a centre axis of the first opening are parallel. In some embodiments, the centre axis of the elongated hollow portion is in line with the centre axis of the first opening. In some embodiments, at least a portion of the elongated hollow portion is arranged inside at least a portion of the cylindrical protrusion.

It should be emphasized that the term "comprises/comprising/comprised of" when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

Brief description of the drawings

In the following, the invention will be described in greater detail with reference to embodiments shown by the enclosed figures. It should be emphasized that the embodiments shown are used for example purposes only and should not be used to limit the scope of the invention. Various aspects disclosed herein will be described in the context of a pressure sensor. However, it will be appreciated that the various aspects may also be implemented with another type of sensor

Figure 1 shows a perspective top view of a sensing assembly according to the current invention.

Figure 2 shows a perspective bottom view of the one-piece fitting of the sensing assembly of figure 1 .

Figure 3 shows a top view of the one-piece fitting of figure 2. Figure 4 shows a perspective top exploded view of the sensing assembly of figure 1.

Figure 5 shows a front view of the sensing assembly of figure 1 .

Figure 6 shows a cross section view of the sensing assembly of figure 1 according to the line VI-VI defined in figure 1 .

Figure 7 shows an exploded cross section view of the sensing assembly of figure 4 according to the line VII-VII defined in figure 4.

Figure 8 shows a perspective view of a vertical multistage pump with a one- piece fitting of a sensing assembly according to the current invention inserted into the pump at the top of the fluid section of the pump.

Detailed description of the embodiments

Figures 1 to 7 show different views of a first embodiment 1 of a sensing assembly for a hydraulic fluid power circuit according to the current invention. In particular, the sensing assembly may be a pressure sensing assembly.

The sensing assembly 1 comprises a one-piece fitting 2, a first opening 4 for a sensor 6, a second opening 8 for a plug 10, a third opening 12 functioning as an air bleed opening and an cylindrical protrusion 14 with an external thread suitable for inserting the one-piece fitting into an opening with an internal thread of a hydraulic component in a hydraulic circuit. A fourth opening 15 is arranged in the one-piece fitting, passing through the cylindrical protrusion. The first, second, third and fourth openings are all in fluid connection with each other (see for example figure 7) when the sensor is not inserted into the fitting. When the sensor is inserted into the first opening, the sensor blocks the first opening. After this, the second, third and fourth openings are in fluid communication. For the sake of simplifying the drawings, the threads are not shown in the drawings. The sensor 6 may be a pressure sensor or another type of sensor.

An internal thread 16 is provided in the second opening and a complementary external thread 18 is formed on the plug 10. A first end of the plug is provided with a tapered portion 20 and the opposite end of the plug is provided with a hexagonal head 22. The plug is inserted into the second opening with the tapered portion first. The user can then displace the plug in the second opening via the hexagonal head 22. As can be seen from the cross section view in figure 7, the second opening and the fourth opening are connected by a channel 24. Likewise, the third opening 12 is also in fluid communication with the channel. When the plug 10 is inserted into the second opening and screwed into its bottom position (figure 6), the plug blocks the third opening. When the plug is screwed at least partially out of the second opening, the third opening comes into fluid communication with the channel. Fluid in the channel, typically coming from the hydraulic circuit via the fourth opening can then escape the hydraulic circuit via the third opening. This is used to bleed air out of the fluid circuit. Bleeding air out of a hydraulic circuit is well known in the art.

It should be noted that in the current embodiment, the third opening is provided as a hole through the one-piece fitting and arranged perpendicular to the centre axis of the second opening. However, other options for providing the same air bleed functionality can be provided instead. For example, in one embodiment, the third opening could be arranged as a channel parallel to the centre axis of the second opening. The channel could extend only partially along the second opening. When the plug is in the bottom position, the channel is blocked, but when the plug is withdrawn, the channel is unblocked and fluid can escape through the third opening. The sensing assembly further comprises fastening means 26 which are arranged to hold the sensor 6 in place in the first opening. The fastening means comprise a fastening bracket (or fastening element) 26 which is in the shape of a bent metal plate element. A first portion 28 of the fastening bracket is arranged to engage with a groove 30 in the one-piece fitting of the sensing assembly. A second portion 32 of the fastening bracket is arranged to wrap over the sensor and a third portion 34 of the fastening bracket is provided with a hole 36 whereby the bracket can be held in place with a screw 38 which engages with a fifth opening 40 in the one-piece fitting.

The sensor 6 is provided with a cylindrical portion 42 which is inserted into the first opening. A pliable cylindrical sleeve 44 arranged on the cylindrical portion forms a sealed connection between the sensor and the one-piece fitting when the sensor is pressed into the first opening. The sensor also comprises a sensing element 45 near a lower portion of the cylindrical portion 42. The sensing element is arranged inside the chamber connected to the fourth opening. The sensor also comprises a computing element arranged inside a housing 46 arranged on top of the cylindrical sensing portion. The housing also comprises a connector 48 suitable for connecting an electrical wire with a cooperating plug (not shown).

In this embodiment, the fourth opening 15, the channel 24, the second opening 8 and the third opening 12 are arranged such that the channel is connected to the upper-most portion of the fourth opening when the fitting is installed in a hydraulic circuit. As can be seen from the cross section of figure 6, when the sensor is inserted into the fitting, the pliable cylindrical sleeve 44 has an upper portion which seals the fitting at the top, ensuring that any air in the fitting will collect in the channel. Likewise, the third opening is arranged at the upper end of the channel. In this way, when the plug is put into its second position, any air in the fitting will move upwards and out of the third opening. In particular it should be noted that the third opening, and the channel, are arranged above the sensing element of the sensor. In this way, any air collected in the fitting, will be able to leave the fitting and the sensing element will be arranged in the fluid to be measured, rather than in air.

It should also be noted (see especially figures 2+3) that the fourth opening 15 of the one-piece fitting is formed with an elongated hollow portion 50 with a cross section formed such that an Allen key can be inserted into the one-piece fitting via the first opening and engaged in a positive fit with the elongated portion. The one-piece fitting can then be turned in an easy way via the Allen key to screw the one-piece fitting into an opening in another component of a hydraulic circuit. In this way, the one-piece fitting can easily be inserted into and attached to a hydraulic circuit after which the sensor can be engaged with the one-piece fitting. This is a big improvement over prior art fittings which need to be grasped with external tools, such as wrenches, when inserting them into hydraulic circuits. This can damage the fittings. Furthermore, it is often difficult to hold and turn the fittings effectively with the prior art tools which engage the external surface of the fitting. It should be noted that this concept can be applied to other types of fittings and could be the subject matter of a divisional application.

Figure 8 shows a vertical multistage pump 200 of the kind which is known in the art. The pump itself will therefore not be described in detail in this specification. The pump comprises a pump portion 202 with an inlet 204, an outlet 206 and an electric motor 208 which drives the pump via a coupling (hidden inside the cover element 210). A one-piece fitting 212 according to the current invention is inserted into an opening at the top 21 of the pump portion 202. As described above, the one-piece fitting has a first opening 216 suitable for receiving a sensor, in particular a pressure sensor, and a second opening 218 suitable for receiving a plug. As will be known to the person skilled in the art of vertical multistage pumps, the fluid will enter the pump via the inlet and then be pressed upwardly through the housing via one or more pump stages until it reaches the top 214 of the pump. The fluid will then be pushed downwardly through channels (hidden inside the pump) to reach the outlet. There is very little flow resistance through these channels, hence, the pressure at the top of the pump and the pressure at the outlet will be essentially the same. Hence, measuring the pressure at the top of the pump is a good indication of the pressure output of the pump. In prior art systems, pressure sensors are typically placed in the fluid circuit downstream of the pump. However, according to the current invention, there are numerous advantages to placing the sensor near the top of the pump. In addition to measuring the pressure of the fluid, the pressure sensor itself can be used to bleed air from the system due to the novel construction of the one- piece fitting. Furthermore, by placing the sensor near the top of the pump, it has been found that different characteristics of the pump can be measured by the pressure sensor, in addition to the pressure of the output fluid. This is described in more detail in applicant’s co-pending international patent application PCT/EP2024/079656 filed on 21-10-2024 and titled “APPARATUS AND METHOD FOR DETECTING A FAULT CONDITION OF A PUMP FOR PUMPING A FLUID” which is hereby incorporated by reference in its entirety.

It is to be noted that the figures and the above description have shown the example embodiments in a simple and schematic manner. Many of the specific mechanical details have not been shown since the person skilled in the art should be familiar with these details and they would just unnecessarily complicate this description. For example, the specific materials used and the specific manufacturing procedures have not been described in detail since it is maintained that the person skilled in the art would be able to find suitable materials and suitable processes to manufacture the sensing assembly according to the current invention.

Claims

1. Sensing assembly (1) for a hydraulic circuit, said sensing assembly comprising a sensor (6), a plug (10), a one-piece fitting (2), and fastening means (26) arranged for detachably fastening the sensor to the one-piece fitting, said sensor comprising a sensing element (45), said plug comprising a cylindrical portion (18) with an external thread, and said one-piece fitting comprising a cylindrical protrusion (14) with an external thread, a first opening (4) arranged to be in fluid communication with the sensing element of the sensor when the sensor is fastened to the one-piece fitting via the fastening means, a second opening (8) comprising a hollow cylindrical portion (18) with an internal thread suitable for engaging with the cylindrical portion of the plug, a third opening (12), and a fourth opening (15) arranged passing through the cylindrical protrusion, said first, second, third and fourth openings being in fluid communication with each other, said second and third openings being arranged such that when the plug is inserted into the second opening, the plug can displace between two positions, a first position where the threaded plug prevents a fluid connection between the third opening and the fourth opening and a second position where a fluid connection is provided between the third and fourth openings.

2. Sensing assembly (1 ) according to claim 1 , characterized in that said fastening means (26) are not provided by a threaded connection between the sensor (6) and the one-piece fitting (2).

3. Sensing assembly (1 ) according to claim 1 or 2, characterized in that the fastening means (26) comprise a fastening element (32) which applies a force to the sensor (6) holding the sensor in or against the first opening (4).

4. Sensing assembly (1) according to claim 3, characterized in that the fastening element (32) is held in place at least partially by a screw (38) inserted into a fifth opening (40) in the one-piece fitting (2).

5. Sensing assembly (1 ) according to any one of claims 1 to 4, characterized in that the third opening (12) is arranged above the sensing element (45) of the sensor (6) when the sensing assembly is engaged in a hydraulic circuit.

6. Sensing assembly (1) according to any one of claims 1 to 5 characterized in that the sensor (6) comprises electrical signal processing means to process a measurement.

7. Sensing assembly (1 ) according to any one of claims 1 to 6, characterized in that first opening (4) comprises a centre axis A and the second opening (8) comprises a centre axis B and in that the angle (0) between the axis A and the axis B is less than 90 degrees.

8. Sensing assembly (1 ) according to any one of claims 1 to 7, characterized in that the fourth opening (15) comprises an elongated hollow portion (50) having a cross section which is formed to allow a torque applying tool to be inserted into the elongated hollow portion and apply torque to the one-piece fitting (2).

9. Sensing assembly (1 ) according to any one of claims 1 to 8, characterized in that the sensor is any one of a pressure-, flow-, temperature-, constituent-, concentration-, vibration-, optical-, color-, or infrared-sensor.

10. Pump (200) comprising an opening with an internal threaded portion and a sensing assembly (1 ) according to any one of claims 1 to 9 inserted in said opening where the cylindrical protrusion (14) of the one-piece fitting (2) is engaged with the internal threaded portion of the opening of the pump.

11 . Pump (200) according to claim 10, characterized in that the opening and the sensing assembly (1 ) are arranged in fluid communication with an outlet (206) of the pump and are located at a location which is at the highest point in the fluid circuit of the pump.