Patent Description:
Factory areas such as automotive paint shops typically have multiple paint booths supplied from a single paint pump. Paint flow is maintained by a back pressure regulator (BPR) at each booth independently. Paint Flow can easily become unbalanced due to BPR drift or equipment changes (such as alteration in a hose length). Unbalanced paint flow in can cause issues such as:.

It is an object of the present invention to alleviate the aforementioned problems. <CIT>, XP055585244, discloses a trouble-free straight pipe sections designed for liquids, gases or light fibers. <CIT> discloses a paint circulation system.

According to a first aspect of the invention there is provided a paint circulating system suitable for providing paint to applicators in a product finishing facility, the system comprising:.

Herein, the term "means for indicating flow rate" may refer to a flow rate indicator. The term "control means for controlling the BPR" may refer to a BPR controller.

The conduit may be a pipe. The conduit may further refer to any passage through which fluid can flow and across which there is a measureable pressure drop. The conduit may have a circular cross-section.

The BPR may be a Back Pressure Regulator as disclosed in published European Patent Specification <CIT>. Such a back pressure regulator is remotely adjustable/controllable by varying a supply of pressurised fluid that applies pressure to a movable surface within the regulator thereby defining the constriction of a paint flow passage. Such an adjustable BPR may be referred to as a Pilot BPR.

Providing a means for indicating a flow rate of paint through a BPR helps with balance set-up and maintenance of the system. For example, variations in paint flow caused by the factors discussed in the Introduction above can be reduced by monitoring the paint flow and accordingly adjusting control settings of the BPR to ensure that the desired flow rate is maintained through parts of the system.

The paint circulation system may comprise two pressure sensors, one pressure sensor being located at each end of the section of the conduit.

The use of pressure sensors provide for the flow rate to be indicated non-restrictively by obtaining a value of the pressure drop that is directly proportional to the flow rate. Commercially available flowmeters usually involve some sort of restriction such as an orifice plate, or a moving/moveable component (e.g. a turbine meter). These are expensive and not suitable for use with paint because they give rise to high shear within the fluid which can damage the paint itself. The skilled person would appreciate the level of restriction or level of variation of the cross section of a conduit that would result in sufficiently high shear in a paint flow that would cause damage to paint.

The means for indicating the flow rate of paint may comprise means for calculating the flow rate based on the measured pressure drop, the dynamic viscosity of the paint, the length of the section of pipe, and a cross-sectional parameter of the conduit.

The section of the conduit may have a substantially constant diameter or a substantially constant hydraulic diameter. The term "constant hydraulic diameter" may refer to a cross-sectional shape of the conduit that remains unchanged along the section of the conduit that is not necessarily circular. The "constant diameter" may further refer to the length of any straight line passing from side to side through the centre of the conduit. The cross sectional parameter may be the constant diameter or constant hydraulic diameter.

The section of the conduit may have a variable cross section (i.e. varying across the length of the conduit) that does not vary significantly enough to cause degradation of paint due to paint sheer. The cross-sectional parameter may be derived from cross sectional dimensions of the section of the conduit.

In some embodiments of the invention, the flow rate does not need to be calculated. Instead, the measured pressure drop is considered as indicative of flow rate (i.e. as an indication of the flow rate). As such, whilst more complex geometry of the conduit section may render it difficult to provide a calculation of a flow rate value, embodiments may include such complex geometry whilst still providing the necessary indication of flow rate as determined by measuring the pressure drop.

The section of the conduit may be straight, but is not necessarily so.

The means for calculating the flow rate may be configured to be additionally based on a mass flow constant being <NUM>. This constant is based on the mass flow characteristics for a typical pipe/hose used for paint pipework installation.

The means for indicating the flow rate may be arranged to provide a flow rate signal to a paint system controller. The flow rate signal may comprise a pressure drop value.

The control means may be arranged to receive a control signal from the paint system controller based on the flow rate signal and accordingly control the BPR for maintaining the desired flow rate.

The paint system controller may comprise means for displaying any of the indicated flow rate or desired flow rate to an operator.

The paint circulating system may comprise a plurality of paint booths wherein one BPR is located downstream of each paint booth, and, corresponding means for indicating a corresponding flow rate through the corresponding paint booth are located either upstream or downstream of the corresponding paint booth.

The corresponding conduit section of the means for indicating flow rate of each BPR may comprise an equivalent geometric form. If each conduit has an equivalent geometry then a comparison of any pressure drop across each conduit section will provide for a comparison between the flow rate that occurs across each conduit section. The geometries of each conduit section may not be identical, for example they may be mirrored or inverse of eachother.

The paint system controller may be operable to compare the indicated flow rate corresponding to each paint booth and automatically control the BPRs to maintain the desired flow rate to each of the booths based on the comparison. In particular, the paint system controller may be operable to balance the paint booths so that the flow through each paint booth is the same. In some embodiments, the controller may be operable to balance the paint booth by controlling the BPRs to provide for the pressure drop determined by each means for indicating flow rate to be the same.

Comparing the flow rate in each paint booth and automatically adjusting the back pressure of each paint booth allows the correct flow rate per booth to be maintained. This data can be reported back to the relevant paint system controller and displayed to controllers/operators.

The paint system controller may be operable to balance the flow rate through each paint booth by controlling all of the BPRs of each of the plurality of paint booths to each maintain an equal proportion of a master flow rate based on the flow rate comparison, wherein the master flow rate is provided by a pumping station configured to pump paint to the plurality of paint booths.

According to a second aspect of the invention there is provided a method of operating a paint circulating system to provide paint to applicators in a product finishing facility comprising the steps of:.

The step of determining an indication of flow rate may comprise calculating the flow rate based on the measured pressure drop, the dynamic viscosity of the paint, the length of the section of the conduit, and the diameter of the conduit.

The method may further comprise the step of comparing the indication of flow rate (such as comparing the measured pressure drop) of paint through each of a plurality of paint booths each located upstream of one of a plurality of BPRs, and controlling each BPR to maintain a desired flow rate to each of the plurality of paint booths.

According to an example of this disclosure not claimed but presented as useful for understanding the invention defined in the claims, a paint flow measurement apparatus for use in a paint circulation system for providing paint to applicators in a product finishing facility. The assembly comprises:.

According to an example of this disclosure not claimed but presented as useful for understanding the invention defined in the claims, there is provided a paint circulating system suitable for providing paint to applicators in a product finishing facility, the system comprising:.

Referring to the drawings, a paint circulation system according to the invention is represented in <FIG>. Paint is pumped from a pumping station <NUM>, which feeds a supply line <NUM> that in turn, feeds paint booth supply lines <NUM> and <NUM>. The paint booth supply line <NUM> feeds paint booth <NUM>, and, the paint booth supply line <NUM> feeds paint booth <NUM>. Paint flows through applicators such as those referenced as 102a and 103a in the paint booths <NUM>, <NUM>. The applicators release some of the paint from the paint flow as spray that is applied to an object (not shown) situated within the paint booths <NUM>, <NUM>. Paint is returned from the paint booths via paint booth return lines <NUM> and <NUM> via a return pipe <NUM> to the pumping station <NUM>.

The embodiments described herein with respect to the drawings comprise pipes, however embodiments are not limited to the use of pipes as supply/return lines. For example, any conduit such as a hose, orifice, or channel that is cast or machined could be used in place of pipes. There may be a combination of different types of conduit within a paint circulation system of the invention.

Paint booth back pressure regulators (BPRs) <NUM> and <NUM> are remotely controllable and in series with the paint booth return lines <NUM> and <NUM> respectively. BPR flow measurement means <NUM> and <NUM> are each associated with one of the BPRs <NUM> and <NUM> respectively and are located upstream of each BPR <NUM>, <NUM>. The BPRs <NUM>, <NUM> are configured to maintain a pressure of paint flowing through the corresponding paint booth.

In the embodiment of <FIG>, the BPR flow measurement means <NUM> and <NUM> are located downstream of the paint booths <NUM>, <NUM>. However, in other embodiments the BPR flow measurement means could be located at other positions, such as upstream of the paint booths.

There is also a system BPR <NUM> in series with the return line <NUM>. System BPR <NUM> prevents fluid from continuing to flow out of return pipe <NUM> to pumping station <NUM> when pumping ceases.

It will be appreciated that a paint flow system according to the invention can include any number of paint booths having corresponding BPRs, and varying numbers of paint applicators within the paint booths without departing from the scope of the invention.

In use, paint flows around the system, as indicated by arrows <NUM>, and is applied to objects via the paint applicators 102a and 103a. In the example shown, the paint booth BPRs <NUM> and <NUM> are set at a desired pressure of <NUM> bar for each booth. In the shown embodiment, the supply and return lines <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are cylindrical and have mm diameters as indicated in <FIG>. In other embodiments, the supply and return lines may have diameters from <NUM> to <NUM>. The lines may comprise hoses, pipes, or other known means for transferring fluid at pressure. In embodiments, the diameter of the lines can vary from those indicated in <FIG>.

Due to BPR drift, or a change in the system configuration such as replacement of a hose, the paint flow between booths may become unbalanced. In other words, there can arise a variation of flow rate between the two booths <NUM> and <NUM>. It will therefore be necessary to adjust the pressure setting of the BPR in order to ensure that a constant flow rate of paint is maintained through each booth. In particular, it may be desired for the flow rate through each booth to be balanced (i.e. the same).

Flow indication means <NUM> and <NUM> indicate the flow rate without obstructing the paint flow in a manner as will be detailed below. Flow indication means provide a flow rate signal to a controller (not shown). This value is used to adjust the BPRs <NUM> and <NUM> in order that the desired flow rate is maintained through the paint booths. The BPRs <NUM> and <NUM> may (but not necessarily) be pilot-operated BPRs as mentioned in the Summary section above. For example, the BPRs may be air-operated and remotely controllable by varying the pressure of a fluid that applies pressure to a movable surface within the BPR thereby adjusting the size of a variable restriction in the paint flow passage. Therefore, the BPRs are remotely controllable using signals provided by the controller (not shown). The BPRs are automatically controlled by the controller to maintain the desired flow rate. In embodiments, the flow rate through each paint booth can be reported to the relevant paint system controller and displayed to operators using a computer terminal (not shown). In the embodiment of <FIG>, the flow rate downstream of the paint booths <NUM> and <NUM> is indicated. However in other embodiments, the flow rate upstream of the paint booths may be indicated and used to provide the flow rate signal.

In some embodiments, the indication of flow rate is a pressure drop measurement. As will be discussed below, measurement of a pressure drop provides an indication of flow rate that can be used for comparing the flow rate between different booths. Therefore, a controller can be configured to ensure that flow rate through each booth <NUM>, <NUM> is substantially the same by adjusting the BPRs <NUM>, <NUM> so that the pressure drop measurement indicated by flow indication means is the same.

<FIG> is a schematic representation of a flow measurement means according to the invention.

Pressure sensors 203a and 203b are positioned to measure the change in pressure of paint within the section of line <NUM> of the length indicated by arrow <NUM> that is between the pressure sensors. Pressure sensors 203a, 203b are static pressure sensors that are unobtrusive and do not restrict the paint flow. Paint flows in the direction as indicated by the arrow <NUM>, and there will be a pressure drop from pressure sensor 203a to 203b. The pressure drop value is measured by sensors 203a and 203b that are positioned in the section of line <NUM> that is upstream of the BPR <NUM>, and downstream of paint booth <NUM>. The section of line <NUM> is shown as a cylindrical pipe having a known constant diameter, however this is not the case in all embodiments. The section of line <NUM> is shown as being straight, however in embodiments this section is not necessarily straight, for example the section may be curved. The pressure drop is indicative of the flow rate of paint within the line <NUM>. This flow rate is indicative of the flow rate of paint through the paint booth <NUM>.

Whilst the calculation of flow rate from the measured pressure drop discussed below is implemented in some embodiments, in other embodiments this explanations serves to provide an illustration of how the measured pressure drop value is indicative of the flow rate. In the latter embodiments, the flow rate is not calculated and merely the measured pressure drop is used by the controller. As long as the geometry of each section of line for the flow measurement means of each paint booth <NUM> are substantially equivalent, then the relative flow rate between each paint booth can be compared. The controller can be configured to adjust the BPR so that the flow rate through each paint booth is the same by ensuring that the measured pressure drop for each section of line <NUM> corresponding to each paint booth is the same.

In the embodiment shown, the flow rate from the pumping station <NUM> (of <FIG>) is known and an operator can configure the controller to provide a particular flow rate ratio expressed as a percentage to each booth. For example, <NUM>%/<NUM>%.

The flow rate can be determined using the pressure drop formula: <MAT> Where:.

In some embodiments, where a non-tubular conduit is used instead of a pipe, the hydraulic diameter can be used to calculate the pipe factor, the hydraulic diameter is determined by the formula <NUM>*(cross-sectional area of section)/perimeter of section.

In an exemplary embodiment, a controller (not shown) calculates the flow rate of paint based on the measured pressure drop using sensors 203a, 203b and the remaining known factors as per the pressure drop formula. As discussed above, the flow rate is used to adjust the setting of the BPR <NUM> to ensure that the desired flow rate is maintained.

Line <NUM> transfers the paint to downstream components of the paint circulating system such as a pump (not shown).

Claim 1:
A paint circulating system suitable for providing paint to applicators in a product finishing facility, the system comprising:
a pump (<NUM>) for pumping paint around the system;
an automatically adjustable back-pressure regulator, BPR, (<NUM>, <NUM>, <NUM>) to reduce pressure fluctuations of paint upstream of the BPR (<NUM>, <NUM>, <NUM>);
means for indicating a flow rate of paint through a conduit (<NUM>) upstream of the BPR (<NUM>, <NUM>, <NUM>) comprising means for measuring a pressure drop in the paint flow along a length of a section of the conduit (<NUM>) without restricting the paint flow, wherein the means for measuring a pressure drop in the paint comprises pressure sensors (203a, 203b) configured to measure a starting pressure of paint at the start of the section of the conduit (<NUM>), and an ending pressure of paint at the end of the section of the conduit (<NUM>);
control means for adjusting a setting of the BPR (<NUM>, <NUM>, <NUM>) to maintain a desired flow rate based on the indicated flow rate.