FIELD OF THE INVENTION

The present invention relates to a sensor device for measuring at least one property of a liquid in a pump or pump system. In particular, it relates to such a sensor device that can be integrated in a pump without a need for adding electric connections and changing the exterior of the pump. Furthermore, it relates to a pump comprising such a sensor device.

BACKGROUND OF THE INVENTION

The present invention has been developed in relation to pumps used for applications where it is needed to monitor the pressure in the liquid being pumped in order to quickly detect a possible leakage in the system. This will be relevant in many systems, such as in heating systems or in domestic hot water systems. However, the invention may find use in any application where it is relevant to measure a property of the liquid by a sensor.

The pressure or other property may be measured by sensors arranged in the pipes leading to or from the pump. Then the signals are to be transferred to a controller which may be provided inside the pump or as a separate unit, such as in a computer. The property may also be measured by a sensor arranged inside the pump housing. If the property being measured by the sensor is influenced by the operation of the pump, the measurements may need to be compensated for the pump influence by taking into account different pump parameters, such as rotational speed and power consumption. Alternatively, the relevant property of the liquid can be measured without the influence from the pump by shortly stopping the pump while performing the measurements. If the property of the liquid varies, there will typically be a delay in the measurements causing a lack of reaction that will be disadvantageous at least for some applications.

When the property is measured directly in the liquid being pumped, the fact that the sensor is in direct contact with the liquid results in a need for safety requirements of an isolation voltage typically in the order of above 1000V. Such components are typically costly.

Thus, there is a need for an improved way of measuring properties of a liquid in a pump.

OBJECT OF THE INVENTION

It is an object of the present invention to provide a sensor device for measuring at least one property of a liquid in a pump, which sensor device can be integrated in an existing pump without the need for adding extra electric connections.

It is another object of the present invention to provide such a sensor device which can be arranged in the limited free space inside an existing pump so that no redesigning of the mechanical and/or electrical parts of the control box of the pump is needed.

It is an object of at least some embodiments of the present invention to provide such a sensor device which can be arranged in a manner allowing for direct access thereto by removal of the control box of the pump.

It is a further object of a least some embodiments of the present invention to provide such a sensor device which has a high precision and reliability.

It is a further object of the present invention to provide an alternative to the prior art.

In particular, it may be seen as an object of the present invention to provide a sensor device that solves the above-mentioned problems of the prior art.

SUMMARY OF THE INVENTION

Thus, the above-described object and several other objects are intended to be obtained in a first aspect of the invention by providing a sensor device for measuring at least one property of a liquid in a pump, the sensor device comprising:

- at least one sensor,

- a wireless communication device configured to communicate a wireless signal, and

- an electric circuit unit having the at least one sensor electrically connected thereto at a first end and the wireless communication device electrically connected thereto at a second end, wherein the electric circuit unit is mounted in liquid-tight engagement with a first opening in a rotor can of the pump, and wherein the sensor device is configured so that during use:

- the at least one sensor measures the at least one property of the liquid,

- an output signal from the at least one sensor is transferred to the wireless communication device via the electric circuit unit, and

- the wireless communication device communicates the wireless signal representative of the output signal to a receiver at a distance therefrom.

What is referred to as "pump" throughout the text could also be referred to as "pump system".

In some embodiments of the invention, there is only one sensor and it may be configured to measure only one parameter, such as the pressure, or it may be configured to measure more parameters, such as the pressure and the temperature. The scope of protection also covers embodiments in which the sensor device comprises more than one sensor, such as a pressure sensor and a temperature sensor.

In presently preferred embodiments of the invention, the wireless communication device is a transceiver which is configured to both send and receive signals. Such an embodiment will be described in more details in relation to the figures. The electric circuit unit will typically be a printed circuit board, PCB, but other types may alternatively be used, such as flex print, thick film substrates, or wireframes.

By "electrically connected thereto" is preferably meant that the at least one sensor and the wireless communication device are mounted directly on the electric circuit board. However, the scope of protection also covers embodiments in which they are separate, electrically connected components.

By "liquid-tight engagement" is meant that it should be ensured that the liquid in the pump cannot flow through the first opening via the points of engagement. Hereby it is ensured that the liquid does not flow into other parts of the pump, such as into contact with a control unit thereof, or leak out of the pump.

The first opening in the rotor can may be an opening originally provided for the arrangement of a deblocking screw with which it is possible to release the rotor in case it has got stuck in a given position, e.g. after a period of no operation. Many pumps are provided with such a deblocking screw and by designing the sensor device for arrangement in the same opening, it is possible to provide a pump with a sensor device according to the present invention without having to change the design.

A sensor device according to the present invention makes it is possible to measure at least one property of a liquid in a pump without needing to add extra electric connections and at the same time utilizing the already available limited free space inside an existing pump.

The wireless signal communicated by the wireless communication device may be a radio signal, a light signal, or an acoustical signal. A radio signal may be defined as an electromagnetic wireless signal with a frequency between 20 kHz and 300 GHz. This frequency range may also be referred to a Radio Frequency, RF. Correspondingly, a radio signal may be defined as an electromagnetic wave with a wavelength between 0.5 cm to 30,000 m. The at least one sensor may be configured to measure one or more of the following properties: pressure, temperature, sound, or concentration of a substance contained in the liquid. A substance contained in the liquid may e.g. be glycol added to the liquid if the pump is to be used in low temperature applications. However, the scope of protection covers any type of sensor as long as the use thereof is not in contradiction with the other features of the invention.

A sensor device according to the present invention may further comprise a sensor house housing the at least one sensor, the electric circuit unit, and the wireless communication device, wherein the sensor house:

- is configured to be mounted in engagement with the first opening in a rotor can of the pump,

- comprises an enclosure in which the electric circuit unit and the wireless communication device are arranged, and

- comprises a second opening or a membrane arranged to communicate with the first opening when the sensor house is mounted to the rotor can, and wherein the wireless communication device during operation communicates the wireless signal to the receiver being arranged outside the sensor house.

Such a sensor house will protect the electronic components from moisture and dirt possibly present within the pump. At least a part of the sensor house surrounding the wireless communication device is typically made from an electrically insulating material, such as a polymer or polymer-based material, as that will provide a more efficient and reliable communication of the wireless signal from the wireless communication device to the receiver. Furthermore, due to the protection provided by the sensor house, it is avoided to have to otherwise provide for galvanic isolation of the electronic components as the necessary protection is built into the design of the sensor house.

In the wording "the second opening or a membrane arranged to communicate with the first opening", the term "communicate" refers to the ability to transfer the value of the at least one parameter being measured. In the prototypes made during the development of the invention, there has been a second opening. However, provided that the membrane is thin enough to reliably and precisely transfer the information about the property being measured, such a membrane may be added e.g. to protect the sensor from possible particles present in the liquid.

In some embodiments comprising a sensor house, the sensor house comprises a sensor cup with an inner chamber surrounded by a sensor cup wall, the inner chamber being in liquid communication with the at least one sensor via the second opening or the membrane, and the sensor cup being dimensioned and shaped for extending in a liquid-tight manner through the first opening in the rotor can and into the liquid in the rotor can during use, and the sensor cup is provided with a third opening through which the liquid can flow into the inner chamber during use of the sensor device. The liquid-tight mounting of the sensor cup in the first opening may e.g. be obtained by welding or gluing. By such a design it is possible to arrange the at least one sensor in a region of the flow of liquid during operation of the pump. This may provide a more precise measurement of a value being representative of an average value for all the liquid flowing through the pump or being present in the pump when there is no flow.

In alternative embodiments to those having a sensor cup, the sensor house may have the second opening, and the at least one sensor may be in the form of a capacitive pressure sensor which is arranged at the second opening for measurement of the pressure in the liquid. The capacitive pressure sensor may e.g. be made from ceramic or silicon. The second opening in the sensor house may be flush with the first opening in the rotor can when in use so that the capacitive sensor measures the pressure in the fluid adjacent to the inner surface of the rotor can.

Examples of embodiments having a sensor cup and a capacitive pressure sensor, respectively, are shown in the figures and will be explained in more details in relation thereto.

In alternative embodiments to those having a capacitive pressure sensor, the at least one sensor may be a pressure sensor comprising at least one strain gauge, such as strain gauges forming a Wheatstone bridge. The technology of using strain gauges for pressure measurements will be well known to a person skilled in the art of pressure sensors.

In some embodiments of the invention, the output signal from the at least one sensor is an analogue signal that is converted to a digital signal by the electric circuit unit, the digital signal being transferred to the wireless communication device. However, the scope of protection also covers the use of sensors that provide digital outputs.

The wireless communication device may further be configured to wirelessly receive power from a power supply arranged outside the sensor device, the power being for powering components of the sensor device including the at least one sensor. Hereby the same component can be used for the transfer of both data and power so that no additional components or electrical connections are needed for the powering of the sensor device.

In presently preferred embodiments of the invention, the wireless communication device is based on Radio Frequency identification (RFID) communication technology, such as on Near Field Communication (NFC) technology. In general, RFID components are grouped into different frequency bands ranging from Low Frequency (LF) of 125 kHz - 134 kHz to Microwave Frequency (MF) of 2.45 GHz and 5.4 GHz and with several groups in-between.

The wireless communication device may operate at a frequency of above 5 MHz, such as above 10 MHz, such as between 10 and 100 MHz, such as between 13 and 14 MHz. Such frequencies are significantly higher than other frequencies present in or near the pump, such as from the motor running the pump. Thus, by operating the wireless communication device at such higher frequencies, it is possible to avoid noise in the signals, such as Electro Magnetic Interference (EMI) noise generated from a Variable Frequency Controller of the pump motor. Such noise could otherwise result in errors or lack of precision in the measurements being performed. The frequency of the wireless communication device may be 13.56 MHz which is referred to as High Frequency. This is the frequency typically used by an NFC component, and it is the type used during the development of the present invention. It is a well-known technology utilizing the open ISM band without the need for specific approval of the electronics before a new product is put on the market. The ISM radio bands are portions of the radio spectrum reserved internationally for industrial, scientific and medical purposes, excluding applications in telecommunications. If one of the alternative frequency bands of RFID components were chosen, when operating at 860MHz - 960MHz (Ultra High Frequency) it is necessary be robust towards GSM noise, and at 2,4Ghz and 5GHz (Microwave Frequency) there is a risk of experiencing noise from possible Wi-Fi Access points possibly present near the pump. These potential error sources can be avoided by choosing NFC technology operating at 13.56 MHz.

In some embodiments of the invention, the calibration parameters are stored in the sensor device and are configured to be read at initialization during a first use of the sensor device. This is advantageous when a sensor device is mounted in an existing pump or when the sensor device is replaced by another one. In both cases, the first powering will automatically transfer the calibration parameters for that specific sensor to the power unit so that it is ready for use without the need for any further calibration or tests to be performed.

In some embodiments of the invention, the sensor device is configured for communication directly with the sensor via a smart phone. This may e.g. be possible via the use of an NFC component as the wireless communication device, such as by use of NFC technology operating at 13.56 MHz. Hereby an easy access and communication is obtained which may be relevant e.g. during maintenance.

In a second aspect, the present invention relates to a pump comprising:

- a sensor device according to any of the embodiments mentioned above,

- a motor driving the pump,

- a rotor can housing a rotor of the motor,

- at least one control unit comprising the receiver for receiving the wireless signal communicated from the wireless communication device. In such a pump, the at least one control unit may be provided in a control box which is releasably mounted on the pump, and wherein removal of the control box provides direct access to the sensor device. Hereby it will be easy to inspect the sensor device and to replace it if necessary.

The first and second aspects of the present invention may each be combined. These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE FIGURES

The sensor device and the pump comprising such a sensor device according to the invention will now be described in more detail with regard to the accompanying figures. The figures show one way of implementing the present invention and is not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.

Figure 1 schematically shows an exploded view of an example of a prior art pump.

Figure 2 schematically shows an example of how a sensor device according to the present invention can be arranged in relation to a rotor can of a pump.

Figure 3 schematically shows a cross-sectional view through a pump with a sensor device according to the present invention.

Figure 4 schematically shows an embodiment of a sensor device according to the present invention, the sensor device comprising a sensor house with a sensor cup.

Figure 5 schematically shows the sensor device of figure 4 arranged in a pump.

Figure 6 schematically shows an example of the communication between the sensor and an external receiver.

Figure 7 schematically shows another embodiment of a sensor device comprising a capacitive pressure sensor. DETAILED DESCRIPTION OF AN EMBODIMENT

Figure 1 schematically shows an exploded view of an example of a prior art pump 1. The different components of which it is composed will be well known to a person skilled in the art. The figure shows the location of the stator 2 of the motor driving the pump and the rotor can 3 housing the rotor 4 of the motor. It also shows a printed circuit board 5 which may, in a similar pump according to the present invention, comprise the receiver for receiving signals from a sensor device of the present invention as will be described in the following. This printed circuit board is arranged in a control box 6 which is releasably mounted on the pump. Removal of the control box 6 will provide direct access to the upper part of the rotor can 3.

Figure 2 schematically shows an example of how a sensor device 7 according to the present invention can be arranged in relation to a rotor can 3 of a pump, so that it can be used for measuring at least one property of a liquid present in the pump. As explained above, the sensor device 7 may be configured to measure one or more of the following properties: pressure, temperature, sound, or concentration of a substance contained in the liquid. In the embodiments illustrated in the figures, there is only one sensor 8. However, as described above, the scope of protection also covers sensor devices comprising more than one sensor; e.g. a pressure sensor and a temperature sensor. When the sensor is a pressure sensor, it may be of the type comprising at least one strain gauge, such as strain gauges forming a Wheatstone bridge. The functioning of such a type of sensor will be well known for a skilled person working within the field of pressure sensors.

The illustrated sensor device 7 comprises a sensor 8, a wireless communication device 9 configured to communicate a wireless signal, and an electric circuit unit 10 having the at least one sensor 8 electrically connected thereto at a first end and the wireless communication device electrically connected thereto at a second end. The output signal from the sensor 8 is typically an analogue signal that is converted to a digital signal by the electric circuit unit 10, and the digital signal is then transferred to the wireless communication device 9. The electric circuit unit 10 is mounted in liquid-tight engagement with a first opening Il in a rotor can 3 of the pump so that it is ensured that liquid does not flow via the first opening 11 and into other parts of the pump, such as into the control unit, or leak out of the pump 1. An output signal from the sensor 8 is transferred to the wireless communication device 9 via the electric circuit unit 10, and the wireless communication device 9 communicates the wireless signal representative of the output signal to a receiver 12 at a distance therefrom. As described in more details above, the wireless signal communicated by the wireless communication device 9 is typically a radio signal.

Figure 3 schematically shows a cross-sectional view through a pump 1 with a sensor device 7 according to the present invention. The sensor device 7 will be described in more details in the following. As seen from the figure, the space where the sensor device 7 is arranged is quite limited. As mentioned above, the first opening in the rotor can 3 may be an opening originally provided for the arrangement of a deblocking screw with which it is possible to release the rotor in case it has got stuck in a given position e.g. after a period of no operation. Many pumps are designed to be provided with such a deblocking screw and by designing the sensor device for arrangement in the same opening, it is easy to provide a pump with a sensor device according to the present invention by using the same space as was originally prepared for a deblocking screw which may not be needed for that pump.

Figure 4 schematically shows an embodiment of the invention comprising a sensor house housing 13 the at least one sensor 8, the electric circuit unit 10, and the wireless communication device 9. The sensor house 13 is illustrated as mounted in engagement with the first opening Il in a rotor can 3 of the pump as described in relation to the previous figures. The sensor house 13 comprises an enclosure 14 in which the electric circuit unit 10 and the wireless communication device 9 are arranged. The sensor house 13 in figure 4 comprises a sensor cup 15 with an inner chamber 16 surrounded by a sensor cup wall 17, and the inner chamber 16 is in liquid communication with the sensor 8 via a second opening 18. The sensor cup 15 is dimensioned and shaped for extending in a liquid-tight manner through the first opening 11 in the rotor can 3 and into the liquid 19 in the rotor can 3 during use as shown in the figures. The sensor cup 15 is provided with a third opening 20 through which the liquid 19 can flow into the inner chamber 16 during use of the sensor device 7. Hereby the sensor 8 will be in more direct contact with the liquid which may provide a more precise measurement of a value being representative of an average value for all the liquid flowing through the pump or being present in the pump when there is no flow. Even though the sensor device 7 has been illustrated with a sensor cup 15 extending through the first opening 11 in the rotor can 3, in other embodiments the sensor house 13 is arranged without doing so.

Figure 5 schematically shows the sensor device 7 of figure 4 arranged in a control box 6 of a pump. The figure also shows the pump having a main printed circuit board 5, PCB, used for the control of the pump. This PCB 5 is where the receiver for receiving the wireless signal from sensor device 7 is typically placed.

Figure 6 schematically shows an example of the communication between the sensor 8 and an external receiver 12. An output signal from the sensor 8 is sent to the wireless communication device 9 via the electric circuit unit 10, which in the illustrated embodiment is an NFC or other RFID component. It communicates with an NFC/RFID reader 12 typically mounted on the primary PCB 5 of the pump. This NFC/RFID reader 12 then transfers the received data to a control unit 21 of the pump. In addition to the transfer of data between the two NFC/RFID components 9,12, the NFC/RFID component 9 may also be provided with energy for the powering of the sensor device 7. The powering is typically done via an electromagnetic field as shown schematically in the figure. For some technologies, it will also be possible to use light, such as an infrared LED, for the transmission of data and or power.

Figure 7 schematically shows a partial view of another embodiment of a sensor device according to the invention. In this embodiment, the sensor house 13 has the second opening 18 which is flush with the first opening 11 in the rotor can 3 when in use, and the at least one sensor 8 is in the form of a capacitive pressure sensor which is arranged at the second opening 18 for measurement of the pressure in the liquid. The figure only includes the region around the sensor 8, but the not included parts, such as the electric unit, may e.g. look like in previous figures. The pressure signal measured by the capacitive pressure sensor 8 is then transferred to the wireless communication device 9 via an electric unit 10 in the same manner as described for the previous embodiments. Although the present invention has been described in connection with the specified embodiments, it should not be construed as being in any way limited to the presented examples. The scope of the present invention is set out by the accompanying claim set. In the context of the claims, the terms "comprising" or "comprises" do not exclude other possible elements or steps. The mentioning of references such as "a" or "an" etc. should not be construed as excluding a plurality. The use of reference signs in the claims with respect to elements indicated in the figures shall also not be construed as limiting the scope of the invention. Furthermore, individual features mentioned in different claims, may possibly be advantageously combined, and the mentioning of these features in different claims does not exclude that a combination of features is not possible and advantageous.