WO2003078839A2

WO2003078839A2 - Hydraulic pump

Info

Publication number: WO2003078839A2
Application number: PCT/GB2003/001039
Authority: WO
Inventors: Alan Rodney Henderson; Paul Wakefield
Original assignee: Salamander Pumped Shower Systems Limited
Priority date: 2002-03-15
Filing date: 2003-03-11
Publication date: 2003-09-25
Also published as: GB0419566D0; WO2003078839A3; AU2003209499A1; GB2402444B; GB2402444A; GB0206110D0

Abstract

A hydraulic pump comprises one or more outlets, one or more pressure sensors and/or one or more flow sensors linked to or incorporated in a pump's control means which is adapted to compare the or each measurement obtained from the or each pressure sensor and/or the or each flow sensor with one or more pre-set pressure or flow values stored in the memory of said control means, wherein said control means is adapted to switch off the pump once or repeatedly for a period if the or each measurement from the or each pressure sensor and/or flow sensor is outside a range of pre-set pressure or flow values, such period being sufficient for air to escape from the pump through the or each outlet or the or each pump chamber to be flooded.

Description

HYDRAULIC PUMP

Field of the Invention

The invention relates to hydraulic pumps, particularly of the centrifugal type which are destined for domestic use and which are equipped with control means to optimise the running of the pump. The invention also relates to the method of installing these pumps.

Review of Art Known to the Applicant

The closest prior art known to the applicant is constituted by its own pumps available in the marketplace under the brand name RIGHT PUMP manufactured by Salamander Pumped Shower Systems Limited.

The person skilled in the art will easily be able to identify which of the previously manufactured pumps is most applicable to the various aspects of the present invention. One of the problems of conventional pumps is that of pump breakdown arising from unexpected or unforeseen system conditions.

The most common causes of pump breakdown are:

• Water starvation

• Chronic aeration

• Airlock in the pump or the system into which the pump is installed.

• Elevated temperature of the stored Hot water of the system in which the pump operates.

When the pump is in an airlock condition such that for example a significant percentage of air is trapped in the chambers of the impellers, the short-term consequence of this is a drop in pump performance.

The long-term consequence of this condition is damage to the pump because when air is trapped in the chambers, the cooling of the various parts of the pump is not efficiently carried out. In this condition, the pump may also not be sufficiently lubricated which can seriously damage the pump. Furthermore, this malfunction can damage the pump as the water circulating through the pump tends to contain an increased level of grit, dirt or debris.

The damage caused by these latter particles can be particularly serious at the mechanical shaft seal area whose failure can cause the premature breakdown of the pump.

The seal may also deform due to the elevated temperature in the chambers, which in turn can lead to leakage from the chambers to the driving means and consequently damage these driving means. Another detrimental consequence of airlock is the change in differential pressure associated with this condition. It is the differential pressure which usually keeps the moving parts away from the static parts, therefore when the differential pressure is modified damage to the pump may result.

In order to correct the malfunctions mentioned above, the traditional method may require the intervention of a service engineer which is a reactive measure taken by the user of the pump in an attempt to put right the damage which has already occurred. The intervention of a service engineer is of course also expensive.

Another drawback of some traditional pumps is their absence of an automatic calibrating system. The installation engineer is therefore required to accurately determine the head of pressure of each individual domestic system and then manually calibrate the pump. There is therefore a risk of incorrectly calibrating the pump which would have serious consequences such as the pump failing to identify abnormalities (airlock, water starvation and low performance) or shutting down under normal operating conditions. This in turn could result in expensive and unnecessary maintenance costs.

Conventionally, pumps that operate under negative head conditions are either negative head specific pumps or positive head specific pumps to which are added negative head control modules, usually one at each pump end chamber. These conventional systems fail to incorporate both a negative and a positive head system and means for switching from one to another. These may also require a careful study of the system into which the pump is installed to make sure that the pump is provided with the appropriate negative or positive head means.

Most negative head specific pumps available in the market are significantly more expensive than their positive head alternative (approximately 60-80 % more), occupy an uncomfortably large area and therefore can be difficult to install. Some of these may even require re-calibration to match a specific pump to the static head of a particular system.

An additional drawback of systems which require the addition of negative head control modules lies in the fact that a number of components have to be plumbed and wired by the installer of the pump. Since the installer is usually a plumber, he may require the services of an electrician. This possible two-stage process is not only very labour-intensive but can lead to problems and frustrations as these busy professions attempt to co-ordinate their activities.

The present invention aims to overcome the drawbacks of the traditional pumps.

One of the objects of the invention is to provide a control unit which is an integral part of the pump which does not require an electrician to install and has no external connections apart from the power lead.

Another object of the present invention is to provide a pump with control means capable of identifying abnormalities such as airlock, water starvation, hunting conditions and even inappropriately controlled domestic water temperature.

More particularly, the object of this invention is to provide means to correct these abnormalities.

It is also an object of the invention to provide a pump which is equipped with a self-calibrating system.

A further object of the invention is to provide a pump which incorporates means to operate with a negative or a positive head of pressure and means to switch between negative head and positive head settings and by so doing significantly reduce the cost of manufacturing when compared to the negative head specific pumps, arrange the pump in such a way as it occupies the same area as would a comparable positive head pump.

An additional object is to provide a user friendly control system for a domestic pump.

Summary of the Invention

In a first broad independent aspect, the invention presents a hydraulic pump comprising:

One or more outlets, one or more pressure sensors and/or one or more flow sensors linked to or incorporated in the pump's control means which is adapted to compare the or each measurement obtained from the or each pressure sensor and/or the or each flow sensor with one or more preset pressure or flow values stored in the memory of said control means, wherein said control means is adapted to switch off the pump once or repeatedly for a period if the or each measurement from the or each pressure sensor and/or flow sensor is outside a range of preset pressure or flow values, such period being sufficient for air to escape from the pump through the or each outlet or for the or each pump chamber to be flooded.

These features are particularly advantageous because these can permit the identification of a water starvation or an airlock condition and the separation of the air from the liquid and its displacement from the chambers to the outlet. This is particularly advantageous because most of the air trapped in the chambers escapes the pump and the likely ensuing damage is avoided.

This system is also advantageous because it improves the pump's performance. In a subsidiary aspect of the first broad encapsulation of the present invention, the control means is adapted to repeat up to 10 times the switching off of the pump for a period and then to shut down the pump.

Repeating up to 10 times the switching off of the pump for a period is sufficient to clear almost the entirety of the air trapped within the pump or the system into which the pump is installed and therefore to solve the problem of an airlock or water starvation in most circumstances. The control means is also adapted if the problem persists to shut down the pump after these repetitions in order to safeguard the pump from long-term damage and to enable the intervention of a servicing engineer in the rare occasion when he would be required.

In a subsidiary aspect of this encapsulation of the present invention, the control means is adapted to repeat 5 times the switching off of the pump for a period and then to shut down the pump.

Switching the pump off 5 times for a period is particularly advantageous because it allows sufficient air to escape while preventing any inconvenience due to the fact that the pump is momentarily switched off.

According to a further aspect of the present invention with reference to its first encapsulation, the or each period is of 5 seconds or more.

5 seconds or more is the advantageous period of time during which sufficient air separates from the water into which it was locked and escapes to enable the pump to return to normal operating conditions.

According to an additional aspect of the present invention with reference to its first independent aspect, the or each period is of 10s. 10s is the preferred period of time to solve airlock or water starvation problems. In a second broad independent aspect, the invention presents a hydraulic pump comprising:

One or more pressure sensors linked to or incorporated in the pump's control means, wherein after a period following the end of the or each work cycle, the control means compares the or each measurement obtained from the or each pressure sensor with one or more preset pressure values stored in the memory of the control means to determine the actual head of pressure and then calibrates the pump for the actual head of pressure of the system in which the pump is operating.

This combination of features is particularly advantageous because the pump can be inserted into any domestic water delivery system irrespective of its actual head of pressure and without requiring the installation engineer to determine the specific head of pressure of the system.

In a further independent aspect, the invention provides a method of installing a pump comprising the steps of:

calibrating the pump for operation at a specific head of pressure prior to knowing the actual head of pressure of the system in which it is destined to operate,

connecting the pump to the system in which it is destined to operate,

- working the pump for one or more cycles.

This method is advantageous because it is carried out by three simple steps. The operator installing the pump will only have to connect the pump to the system in which it is destined to operate. He may therefore not require the services of an electrician and may not have to calculate separately the actual head of pressure of the system. This system saves both costs and labour.

In a fourth broad independent aspect, the invention presents a hydraulic pump comprising: a control means whose memory incorporates preset operating instructions for operation in negative head conditions and positive head conditions and means to switch between negative head and positive head settings.

The applicant believes this combination to be new and also inventive as it has not been brought forward in any single document in the public domain.

This type of pump is advantageous because it can operate in either negative or positive head conditions.

The arrangement of this equipment is also advantageous because it does not occupy a greater space than the equipment of a comparable positive head specific pump. The means to switch can be a manually operated switch selecting between the negative head equipment and the positive head equipment.

In a subsidiary according to the fourth broad independent aspect of the invention, there is provided:

One or more flow sensors and/or one or more pressure sensors linked to or incorporated in the pump's control means, wherein said control means is adapted to determine whether there is a negative or a positive head of pressure by comparing one or more pressure or flow measurements with one or more preset pressure or flow values stored in the memory of the control means, and means to switch between negative head and positive head settings. These latter features are advantageous because they can permit the automatic selection between negative head and positive head operation.

Embodiments of the Present Invention

As mentioned in the section reviewing the art known by the applicant, the closest prior art known to the applicant is constituted by its own pumps. It is therefore not necessary to describe in detail how these known pumps operate.

In a preferred embodiment of the present invention, pressure sensors are arranged on the pump to obtain pressure measurements in the outlet port. A pressure transducer produces a change in voltage or current when the internal pressure changes state. The analogue reading of the pressure transducer is then fed into an analogue to digital converter. The digital signal produced by the analogue to digital converter is then fed into the processor of the control means.

The control means also incorporate a memory and a comparator enabling the comparison of the programme's memory range of preset pressure values and the digital actual pressure measurements. Depending on the outcome of this comparison, the control means will communicate its result by displaying an appropriate combination of lit up LEDs. The control means will also directly control the operation of the pump in a pre-programmed manner.

The entire circuitry of the control means is placed within an appropriately sized casing which can be incorporated within the existing dimensions of the pump. The casing of the control means is affixed to the junction box. The LED indicators protrude from the casing to be readily visible to the operator of the pump.

Holes are provided at the upper sections of the pump's diameters between each stage of the pump. The diameter of the holes is currently 1mm. When the pump is stationary, the air which can become trapped in the water circulated through the pump can accumulate at the top of each chamber at each stage of the pump. The lmm holes provide a channel for the air to escape out of each chamber as the static head pressure pushes the air through these holes. A lmm diameter hole is sufficient to clear the air from the pump while preventing too much pressure loss during its operation. The hole size is however not limited to lmm. A 2mm hole size has also been envisaged because it allows airlock to be cleared more rapidly than a lmm hole while the loss of pressure remains minimal.

The pressure sensors are set to obtain pressure measurements at the end of each work cycle, preferably after 4 - 6 seconds of override. When the pressure falls below 75% of the open discharge pressure of the pump, the control means switch off the pump once or repeatedly for a period. A period of 10 seconds between pulses of work of 5s by the pump is usually sufficient time for 80 - 90% of the air locked in the water to escape the pump. The air trapped in the pump escapes through the various holes of the pump's stages and is expelled at the system outlets.

Repeating the procedure of switching off the pump several times is usually sufficient to solve most air lock situations. After repeating 5 times the switching off operation, the pump is adapted to shut down completely.

The control means described above can be used to self-calibrate the pump. This is achieved by obtaining pressure measurements at the end of the first work cycle after allowing the pump to override for 4 - 6 seconds. The measured closed head pressure will then be compared with the factory settings inputed to the programme's memory. This comparison will be used to calibrate the system so that it can correctly identify functional abnormalities such as air locking and water starvation.

The pump is also equipped with the means necessary for operation under positive head settings and negative head settings. These means are arranged within the dimensions of the comparable positive head specific pump. In one embodiment, the control means has stored in its memory a set of operating instructions applicable to a positive head system and a set of operating instructions applicable to a negative head system. The operator of the pump will determine whether the head of pressure is negative or positive and will appropriately position the manual switch protruding from the control means casing in its negative head position or in its positive head position.

In a further embodiment, at the end of the first cycle of work, the pressure measurements will be obtained and compared to the factory settings stored in the memory of the control means to determine whether the system is a negative head system or a positive head system. The control means will display a particular combination of LEDs to inform the installer of the outcome of the comparison. The operator will then be able to select between a positive head and a negative head operation.

The control means can be adapted to automatically select between negative head and positive head settings. The pump can be initially set to default to positive head settings. The control system would then obtain pressure drop measurement on the system and if the pressure measurements correspond to positive head pressure measurements, the control system will instruct the operation of the flow switches. In the case where there is a negative head on the system, the flow switches would not operate and the control system would reset the pump to the negative head conditions.

In order to provide for the situation where the pump is changed from a negative head situation to a positive head situation, or from a positive head situation to a negative head situation, there would be means provided to reset the control system every time the power is interrupted. The pump can also be equipped with commissioning means. These are particularly beneficial in the case of twin pumps which are prone to premature damage when there is only flow through one side of the pump while the other side runs under dry conditions. In order to avoid the potential damages that this disproportionate flow can cause, the pump can be equipped with flow sensors which measure whether there is simultaneous flow for a period of 5 seconds. If the control means identifies that there has been a simultaneous flow for 5 seconds, the pump is commissioned. If a simultaneous flow condition is not detected in the first 20 seconds of run, the control means shuts down the pump. The operator will then have to identify the problem causing the non-proportional flow and then switch off the power of the pump for 10 seconds to facilitate the resetting of the pump.

The pumps of the various embodiments above may also be equipped with temperature sensors coupled with the control means so that the control means can instruct the shut-down of the pump when the temperature exceeds a predetermined value.

Claims

1. A hydraulic pump comprising:

one or more outlets, one or more pressure sensors and/or one or more flow sensors linked to or incorporated in the pump's control means which is adapted to compare the or each measurement obtained from the or each pressure sensor and/or the or each flow sensor with one or more preset pressure or flow values stored in the memory of said control means,

wherein said control means is adapted to switch off the pump once or repeatedly for a period if the or each measurement from the or each pressure sensor and/or flow sensor is outside a range of preset pressure or flow values, such period being sufficient for air to escape from the pump through the or each outlet or for the or each pump chamber to be flooded.

2. A pump according to claim 1, characterised by the feature that the control means is adapted to repeat up to 10 times the switching off of the pump for a period and then to shut down the pump.

3. A pump according to claim 2, characterised by the feature that the control means is adapted to repeat five times the switching off of the pump for a period and then to shut down the pump.

4. A pump according to any preceding claim, wherein the or each period is of 5 s or more.

5. A pump according to any preceding claim, wherein the or each period is of 10 s.

6. A hydraulic pump substantially as hereinbefore described with reference to and/or illustrated in any appropriate combination of the accompanying text and drawings and in accordance with claim 1.

7. A hydraulic pump comprising:

one or more pressure sensors linked to or incorporated in the pump's control means,

wherein after a period following the end of the or each work cycle, the control means compares the or each measurement obtained from the or each pressure sensor with one or more preset pressure values stored in the memory of the control means to determine the actual head of pressure and then calibrates the pump for the actual head of pressure of the system in which the pump is operating.

8. A hydraulic pump substantially as hereinbefore described with reference to and/or illustrated in any appropriate combination of the accompanying text and drawings and in accordance with claim 7.

9. Method of installing a pump in accordance with claim 6 or claim 7, comprising the steps of:

- calibrating the pump for operation at a specific head of pressure prior to knowing the actual head of pressure of the system in which it is destined to operate, connecting the pump to the system in which it is destined to operate, working the pump for one or more cycles.

10. Method for installing a pump substantially as hereinbefore described with reference to and/or illustrated in any appropriate combination of the accompanying text and drawings and in accordance with claim 9.

11. A hydraulic pump comprising:

a control means whose memory incorporates preset operating instructions for operation in negative head conditions and positive head conditions and means to switch between negative head and positive head settings.

12. A hydraulic pump according to claim 11, comprising:

one or more flow sensors and/or one or more pressure sensors linked to or incorporated in the pump's control means, wherein said control means is adapted to determine whether there is a negative or a positive head of pressure by comparing one or more pressure or flow measurements with one or more preset pressure or flow values stored in the memory of the control means, and means to switch between negative head and positive head settings.

13. A hydraulic pump substantially as hereinbefore described with reference to and/or illustrated in any appropriate combination of the accompanying text and drawings and in accordance with claim 11.