Reusable intrinsically safe power module for field devices

Abstract

A reusable power module (110, 200) for a field device (100) is provided. The reusable power module (110, 200) includes a body (204) defining a chamber configured to receive a battery (206). A cover (202) is operably coupled to the body (204) and has a first configuration relative to the body (204) in which the body (204) opens to allow access to the battery (206). The cover (202) also has a second configuration in which access to the battery (206) is closed. When the cover (202) is in the second configuration, the reusable power module (110, 200) complies with intrinsic safety standards.

Description

Technical Field

[0001] The present invention generally relates to industrial process control and monitoring systems. More specifically, the present invention relates to wireless process field devices for use in such systems.

Background Art

[0002] In industrial settings, process control systems are used to monitor and control inventories and operations such as industrial and chemical processes. Typically, systems that perform those functions use field devices distributed at key locations in an industrial process, which are coupled to control circuits in a control room by process control loops. The term "field device" refers to a device that performs functions in a distributed control or process monitoring system, including all devices used in the measurement, control, and monitoring of industrial processes. Usually, such field devices can be installed outdoors in relatively harsh environments and have field-hardened enclosures so that they can withstand climatological extremes of temperature and humidity, vibration, and mechanical shock.

[0003] Typically, each field device also includes a communication circuit used to communicate with a process control device, other field devices, or other circuits via a process control loop. In some facilities, the process control loop is also used to apply regulated current and / or voltage to the field device to power it. The process control loop also carries data in analog or digital format.

[0004] In some facilities, wireless technology is now used for communication with field devices. Wireless operation simplifies the wiring and setup of field devices. Currently, field devices are used in wireless facilities that include local power supplies. However, power limitations can sometimes restrict the functionality of such wireless field devices.

[0005] Wireless field devices may use local intrinsically safe power supplies that can be replaced when the power supply's energy is depleted or falls below a selected threshold. Intrinsically safe is a term that refers to the ability of a field device to operate safely in a potentially explosive environment. For example, the environment in which a field operates can sometimes be explosive enough for irregular sparks or sufficiently high surface temperatures of electrical components to ignite the environment and cause an explosion. Intrinsically safe standards have been developed to ensure that such situations do not occur. Compliance with intrinsically safe requirements helps to ensure that the circuit or device itself will not ignite an explosive environment, even under fault conditions. One standard of intrinsically safe requirements is described in APPROVAL STANDARD INTRINSICALLY SAFE APPARATUS AND ASSOCIATED APPARATUS FOR USE IN CLASS I, II AND III, DIVISION 1 HAZARDOUS (CLASSIFIED) LOCATIONS, CLASS 3610, published by Factory Mutual Research in October 1998. Furthermore, compliance with additional industrial standards, such as those of the Canadian Standards Association (CSA) and the European Electrotechnical Standardization Committee, will be considered. [Overview of the project]

[0006] A reusable power module for field devices is provided. The reusable power module includes a body defining a chamber configured to house a battery. A cover operably coupled to the body has a first form in which the body opens to allow access to the battery. The cover also has a second form in which access to the battery is closed. When the cover is in the second form, the reusable power module conforms to intrinsic safety standards. [Brief explanation of the drawing]

[0007] [Figure 1] This is an exploded view of the upper part of a wireless measurement transmitter to which embodiments described herein are particularly applicable. [Figure 2] This is an exploded view of the lower part of a wireless measurement transmitter to which embodiments described herein are particularly applicable. [Figure 3] This is a cross-sectional view of a known replaceable power module according to prior art. [Figure 4] This is a diagram of a wireless measurement transmitter having interchangeable modules, to which embodiments of the present invention are particularly applicable. [Figure 5] This is a perspective view of a reusable, intrinsically safe D-cell battery power module according to an embodiment of the present invention. [Figure 6] This is a perspective view of a reusable, intrinsically safe D-cell battery power module according to an embodiment of the present invention. [Figure 7] This figure shows the internal features of a reusable single-cell battery power module according to an embodiment of the present invention. [Figure 8A] This figure shows the use of a pair of springs to provide polarity protection according to an embodiment of the present invention. [Figure 8B] This figure shows the use of a pair of springs to provide polarity protection according to an embodiment of the present invention. [Figure 9] This is a perspective view of a reusable single-cell battery power module according to another embodiment of the present invention. [Figure 10]This is a perspective view of a reusable single-cell battery power module according to another embodiment of the present invention. [Figure 11] This is a flowchart illustrating a method for using a non-intrinsically safe primary battery in a reusable power module to provide power to a field device located in a hazardous location, according to an embodiment of the present invention. [Modes for carrying out the invention]

[0008] Detailed description of exemplary embodiments Currently, power modules for wireless field devices are relatively expensive and can only be used once. Therefore, if a power module needs to be replaced, the entire power module must be removed and disposed of according to local recycling regulations. In addition to the primary battery (generally a lithium-based primary battery), the plastic surrounding the battery and the circuitry of the power module are also discarded. The various embodiments described below generally use a new, reusable power module that can be opened to remove and replace the depleted primary lithium battery. Furthermore, the embodiments generally utilize off-the-shelf primary lithium batteries rather than custom-made batteries. These types of lithium batteries are common and available from several wholesalers. The ability of the end user to replace the battery and reuse the power module offers a significant advantage over current commercially available products. The lithium primary battery itself is not an intrinsically safe device. Embodiments provided herein provide a power module that can receive a commercially available off-the-shelf lithium primary battery, and also provide an enclosure that can be opened to receive the battery and then closed to provide an intrinsically safe power module (which can then be transported to the field device site and replaced with the depleted power module even in explosive environments).

[0009] Figure 1 is an exploded view of the upper part of a wireless measurement transmitter to which embodiments described herein are particularly applicable. The wireless measurement transmitter 100 includes a housing assembly formed by upper and lower housing components 102, 104, respectively. The housing assembly generally has a housing body including a cavity 106. The lower housing 104 includes a second chamber 108 that is sized and molded to receive a replaceable power module 110.

[0010] Figure 2 is an exploded view of the lower part of a wireless measurement transmitter to which embodiments described herein are particularly applicable. As shown in Figure 2, the replaceable power module 110 is enclosed within the chamber 104 by engagement of the housing 104 and the end cap 112 by screwing the housing and the end cap together. The use of two covers (102 and 112) and two cavities (106 and 108) allows service work (e.g., primary battery replacement, setting adjustment) to be performed by removing the second cover 112, without exposing the electronic components located in the first cavity 106 to contamination from the surrounding industrial environment, and without exposing the first cavity 106 to the atmosphere of the surrounding industrial environment. As shown in Figure 2, the wireless measurement transmitter 100 may include a measurement sensor 120 that can be coupled to the electronic components in the cavity 106 by electrical contacts 122. Examples of measurement sensors include temperature sensors, pressure sensors, gas sensors, humidity sensors, and the like.

[0011] Figure 3 is a cross-sectional view of a portion of a wireless measurement transmitter showing a replaceable power module located within a chamber 108 according to prior art. The replaceable power module 110 is installed in the cavity 108, which is closed by a cover 112. When this occurs, a spring 124 is compressed between the cover 112 and the thrust surface 126 of the outer shell 128 of the replaceable module 110. As shown in Figure 3, the replaceable module 110 generally includes a contact 130 that engages with a corresponding contact 132 in the cavity 108. The replaceable module 110 includes a primary battery 134 and a service communication connector 136 that protrudes beyond the edge 138 of the cavity 108 when the cover 112 is removed. Thus, the wireless measurement transmitter is powered solely by energy from the primary battery 134.

[0012] Figure 4 shows a wireless measurement transmitter connected to a measurement sensor, to which an embodiment of the present invention is particularly applicable. As shown in Figure 4, the transmitter 100 is coupled to a measurement and temperature sensor 150, which is on the other hand coupled to an industrial process 152. The measurement and temperature sensor 150 is coupled to a measurement circuit 154 of the wireless transmitter 100. The measurement circuit 154 receives an electrical output from the measurement sensor 130 representing process variables sensed from the industrial process 152. In one example, the measurement sensor 150 measures temperature, and the measurement circuit 154 can determine the process state as a function of that temperature. The measurement circuit 154 provides an output representing the process state to a control device 156.

[0013] The control device 156 can be a suitable circuit or combination of circuits that executes program steps to generate process variables based on signals received from the measurement circuit 154. In one example, the control device 156 is a microprocessor. The control device 156 is also coupled to a communication circuit 158, which can receive process variable output information from the control device 156 and provide wireless industrial standard process communication signals based on it. Preferably, the communication circuit 158 ​​enables bidirectional wireless communication using a wireless antenna 160. As shown in the figure in reference no. 162, this bidirectional wireless communication generally communicates with an industrial process control system 164. An example of a suitable wireless process communication protocol is described in IEC 62591. However, other examples may also be considered instead of or in addition to IEC 62591.

[0014] Figure 5 is a perspective view of a reusable, intrinsically safe D-cell power module for a field device according to an embodiment of the present invention. In Figure 5, the power module 200 is shown in its open configuration, with the upper part 202 pivoting away from the body to allow access to a commercially available, off-the-shelf D-cell primary battery 206. Preferably, the D-cell is a primary battery using lithium-ion chemistry. The access provided by the power module 200 facilitates the removal of a depleted D-cell and the placement of a new D-cell. Once a new battery has been placed in the body 204, the upper part 202 is pivoted back into its original position and the enclosure is closed. This closed configuration is shown in Figure 6.

[0015] In its closed configuration, the module 200 preferably has substantially the same form factor as a prior art replaceable power module. Thus, such a reusable power module can operate with legacy systems designed for prior art modules. In one embodiment, the power module enclosure comprises four injection-molded parts, two of which are external and two are internal. The external parts (shown in Figures 5 and 6) form an enclosure that can be opened and closed by an end user releasing or engaging snaps between two positions 202, 204. These snaps are indicated by reference numerals 208 and 210 in Figure 5. Snaps 208, 210 engage with corresponding slots 212 in the body 204. In addition, recesses 214 allow the snaps to be released from the slots 212 by the user's fingers. The detachable enclosure allows an end user to easily remove and replace the battery. As mentioned above, the form factor of the reusable power module is preferably consistent with currently available disposable power modules, and it is possible to use it in legacy field devices using the same external electrical connections.

[0016] Internal polymer components may include a protective enclosure (not shown) to protect the electronic circuit board (printed circuit board) from user contact and damage during battery replacement. When the battery is placed inside the enclosure and the enclosure is closed, the entire assembly becomes intrinsically safe and can be installed in field devices in hazardous locations. However, lithium batteries must be removed from and / or installed inside the enclosure in a non-hazardous area. This is because exposed D-cell primary batteries are not intrinsically safe outside of the enclosure. To obtain intrinsically safe ratings, the device must meet the requirements described above or other applicable international standards deemed appropriate by the approval body. This includes mechanical and electrical design requirements, such as wire / conductor insulation thickness, enclosure material properties, and mechanical testing.

[0017] To form a robust internal connection to the battery, preferably, a pair of conical coil springs are used on the negative terminal of the battery. The purpose of this pair of conical coil springs is also mechanical in nature in that they hold the positive terminal of the battery against one of the internal enclosing plates, thereby securing it both in the event of a drop and in response to strong vibrations. Also preferably, there is a set of additional spring push pins that contact the positive terminal of the battery to complete a circuit for providing power to the field device. There are three wires (power, common, and HART COMM) that connect two printed circuit boards within the enclosure. Preferably, the field communicator connection (COMM clip 216 shown in FIG. 6) is located at the end of the power module. The field communicator connection enables easy wired access to the field device by a handheld maintenance device so that a technician can interact with the field device during maintenance and / or commissioning.

[0018] In the embodiments shown in FIGS. 5 and 6, each of the upper housing and the lower housing preferably includes its own respective printed circuit board. Each of these printed circuit boards is electrically coupled to each other via a connection at the hinge portion 218 (shown in FIG. 5). The upper housing assembly houses a printed circuit board that includes connectors for connecting to a communication device such as the above-described handheld field maintenance device and a connector for connecting to the battery cathode 220. The lower housing assembly 204 houses another printed circuit board and a spring for contacting the battery anode. In addition, the lower housing assembly houses connectors for providing power and communication to the field device. The printed circuit board of the lower housing is electrically coupled to the printed circuit board of the upper housing via a connector that passes through the hinge portion 218. This connection not only provides power from the opposite end of the battery but also carries communication signals when the COMM clip 216 is used.

[0019] Figure 7 is a diagram of the internal features of a single rechargeable battery power module according to an embodiment of the present invention. The power module 200 includes a pair of circuit boards 222, 224 coupled to each other by conductors 226. When the cover 202 is closed, one of the conductors 226 connects to the positive terminal 220 (shown in FIG. 5) of the battery 206. Additional conductors 226 couple the COMM clip 216 to pin 132 for communicating with the electronics of the transmitter 100. Each of the circuit boards 222, 224 is securely attached within the polymer of the power module. FIG. 7 also shows a pair of springs 228 disposed on either side of the center of the circuit board 222. In the illustrated example, the springs 228 are conical coil springs. It is preferable to use a pair of springs 228 to apply a significant force to the negative side of the single battery so that a robust electrical contact is maintained even under vibration. In addition, the use of a pair of springs disposed on either side of the center of the circuit board 222 provides passive polarity protection. The manner in which this protection is provided will be described below with reference to FIGS. 8A and 8B.

[0020] FIGS. 8A and 8B are diagrams showing the use of a pair of springs to provide polarity protection according to an embodiment of the present invention. FIG. 8A shows a single battery 206 inserted into the power module with incorrect polarity. In this arrangement, the positive terminal 206 is inserted first and comes to rest between the springs 228. When this occurs, no electrical contact occurs between the springs 228 and 220, eliminating the risk of reverse polarity operation without relying on additional polarity protection circuitry. This provides a significant passive protection function without adding additional cost beyond the cost of the additional springs. As shown in FIG. 8B, when the negative terminal 230 is inserted into the power module, the negative terminal rides on both springs 228, thereby providing a robust mechanical and electrical contact.

[0021] The embodiments described thus far generally provide embodiments in which the upper portion of the enclosure pivots away from the lower portion to allow access to the primary battery, but other mechanical techniques can equally well be used.

[0022] Figure 9 illustrates a reusable power module using a "coffin" design in which electronic components are permanently held. The electronic components may also be held by ultrasonically welded or heat-screwed polymer components. The power module may include a door 250 that pivots away from the body 252 to allow access to the primary battery 206. As shown in Figure 9, the door 250 preferably includes a latch 254 that engages with a slot 256 to seal the primary battery within the power module. In this way, once the door 250 is closed, the power module complies with intrinsic safety standards, thereby allowing the power module to be installed in wireless field devices in hazardous environments. It will be understood that further types of connections may be utilized without departing from the spirit and scope of the invention.

[0023] Figure 10 shows yet another reusable power module according to another embodiment of the present invention. As shown in Figure 10, the power module 280 includes a body 282 and a sliding door 284, the door having components 286, 288 edges that engage with corresponding slots 290 of the body 282, allowing the door 284 to slide back and forth in the direction indicated by arrow 292. As shown in Figure 8, the door slides open to allow access to the primary battery 206.

[0024] In yet another design, a replaceable power module similar to those shown in Figures 5 and 6 is provided, but the engagement between the upper part and the body is via a screw connection, rather than the upper part latching and pivoting away. In yet another embodiment, the engagement may be via a quarter-turn rotational engagement, in which a feature of the first part engages with a feature of the second part during the quarter-turn, which provides a locked configuration at the end of the quarter-turn.

[0025] Figure 11 is a flowchart of a method for providing power to a field device located in a hazardous location using a non-intrinsically safe primary battery in a reusable power module, according to an embodiment of the present invention. Method 300 begins in block 302, which provides a reusable power module. In one example, the reusable power module is shown in Figure 5. Next, in block 304, a non-intrinsically safe D-cell battery is obtained. In one example, this is a commercially available D-cell battery. Preferably, the commercially available D-cell battery is a lithium battery. In block 306, the reusable power module is opened as shown in Figure 5. With the reusable power module open, the D-cell battery is inserted into the power module. Next, in block 308, the cover of the reusable power module is closed, thereby bringing the reusable power module into compliance with intrinsically safe requirements. As such, in block 310, the reusable power module can be taken to the location of a deployed field device (i.e., located in the "field") that may be in a hazardous or potentially explosive environment.

[0026] In block 312, the field device cover is opened to expose the depleted power module. This may be a legacy power module or simply another reusable power module that houses the depleted D-cell battery. In block 314, the depleted power module is removed from the field device. In block 316, a reusable power module housing a new or new battery is inserted into the field device. In block 318, the field device cover is replaced. In this way, an intrinsically safe power module can be provided by placing a non-intrinsically safe D-cell battery inside a reusable power module. The entire power module assembly can then be used to power a field device located in a hazardous or potentially explosive location without moving the field device from its location (i.e., without bringing the field device to a non-hazardous location to replace the power module).

Claims

1. A reusable power module for field devices, A body defining a chamber configured to house a primary battery; A cover operably coupled to the main body, having a first form in which the main body opens, allowing access to the primary battery, and a second form in which access to the primary battery is closed. A plurality of field communicator clips, wherein at least a portion of each of the plurality of field communicator clips is a plurality of field communicator clips extending outward around the cover when the cover is in the second form, A first circuit board attached to the main body, A second circuit board attached to the cover, the second circuit board housing the plurality of field communicator clips, At least three conductors connecting the first circuit board to the second circuit board, the at least three conductors including a conductor for power, a conductor for common, and a conductor for communication, The first circuit board comprises a pair of springs spaced apart from the center of the first circuit board, configured to make electrical contact only with the flat side of the primary battery, A reusable power module that conforms to intrinsically safe standards when the cover is in the second form.

2. The reusable power module according to claim 1, wherein the cover is pivotably connected to the main body.

3. The reusable power module according to claim 1, wherein the cover is slidably coupled to the main body.

4. The reusable power module according to claim 1, wherein the cover includes at least one feature that engages with a corresponding feature of the body to hold the cover in the second form.

5. The reusable power module according to claim 4, wherein at least one of the features includes a snap.

6. The reusable power module according to claim 1, wherein the chamber is configured to house a single cell.

7. The reusable power module according to claim 6, further comprising a D-cell primary battery disposed within the main body.

8. The reusable power module according to claim 7, wherein the single primary battery is a lithium battery.

9. The reusable power module according to claim 1, wherein the pair of springs provides passive polarity protection.

10. A measuring circuit operably coupled to at least one process variable sensor and configured to provide a digital indication of the electrical characteristics of the at least one process variable sensor; A control device coupled to the measurement circuit and configured to generate process variable information based on the digital reading; A process communication circuit coupled to the control device, configured to generate a process variable output based on the process variable information provided by the control device; and A reusable power supply module operably coupled to the measurement circuit, the control device, and the process communication circuit, The main body that defines the chamber; A cylindrical primary battery arranged in the chamber, the cylindrical primary battery having a first side with a positive terminal and a second side with a negative terminal; A cover operably coupled to the main body, having a first form in which the main body opens, allowing access to the primary battery, and a second form in which access to the primary battery is closed; A first circuit board attached to the main body; A second circuit board attached to the cover, the second circuit board housing a plurality of field communicator clips; At least three conductors connecting the first circuit board and the second circuit board, the at least three conductors including a power conductor, a common conductor, and a communication conductor; A pair of springs spaced apart from the center of the first circuit board, configured to electrically contact only the negative terminal of the primary battery, Reusable power modules, including Field devices including...

11. The field device according to claim 10, wherein the primary battery is a lithium-ion primary battery.

12. The field device according to claim 10, wherein the process communication circuit is a wireless process communication circuit.

13. The field device according to claim 10, wherein the cover is pivotably connected to the main body.

14. The field device according to claim 10, wherein the cover is slidably coupled to the main body.

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