Combination current sensor and relay

A combination current sensor and relay has an improved housing. In one aspect, the housing includes light emitting diodes on an upper surface that indicate open circuit and short circuit conditions. In another aspect, the housing includes a securement structure for a circuit board that includes the transformer and switches for device operation, together with aligned openings therein for routing wires to external devices. In another aspect, a multiple position switch is included on the upper surface that indicates multiple modes of operation of the device. In another aspect, the housing may be assembled in multiple parts by affixing a first portion to a support, a circuit board to the first potion, and a second portion to the first portion. In another aspect, the housing is suitable for engagement to alternatively a junction box and a duplex box. In another aspect, the configuration of the upper surface provides usability advantages.

BACKGROUND OF THE INVENTION

The present invention relates to a housing for a combination current sensor and relay.

One of the trends in many industrial environments is to use an ever increasing number of electrical devices that include small motors, such as motors incorporated with fans. Typically such small motors only draw a limited amount of current, such as 1-10 amps. To provide fault detection for electrical devices having limited current requirements, a current sensor is electrically interconnected with the power cable to the electrical device to sense the electrical load current. The current sensor may include an electrical interconnection to a remotely located control panel to provide a signal to the control panel representative of the current within the power cable. It is desirable to locate such a current sensor within a housing, such as a starter housing within a substation. The current sensor or an associated relay may be interconnected to a separate starter, if desired. A relay is typically electrically interconnected between the remotely located control panel and the electrical device to receive a control signal from the control panel and in response selectively enable or disable power to the electrical device. Like the current sensor, such a relay may be located within the starter housing. In addition, the relay may function as the starter if the power rating of the relay is appropriate. Because of decreasing starter housing sizing, the relay and current sensor may be enclosed within a single unitary housing. Such a device is disclosed in U.S. Pat. No. 5,808,846, incorporated by reference herein.

Referring toFIG. 1, Functional Devices, Inc. of Russiaville, Ind., manufacturers a Model RIBXLSA combination current sensor and relay10. Referring toFIG. 1, the device10includes a start/stop relay12that is energized or otherwise controlled by the digital output of a controller14. Power from a power source16is provided by a wire18which is interconnected to the start/stop relay12of the device10. The start/stop relay12is likewise interconnected to an internal sensor20by a wire22, namely, a current sensor in the form of a transformer. The output of the internal sensor20is interconnected to a load24by a wire26. The load24is interconnected to the source16by a wire28. Accordingly, a loop for current flow is provided by wire18, the start/stop relay12, the wire22, the internal sensor20, the wire26, and the wire28. When the start/stop relay12is open, as a result of the controller14, the power to the load24is interrupted (open circuit). Likewise, when the start/stop relay12is closed, as a result of the controller14, power is provided to the load24(short circuit). Accordingly, the controller14may control power to the load24by energizing and de-energizing the start/stop relay12. The device10may include a closed/open/auto switch21for enabling the operation of the start/stop relay12. Other applications of the device10, are illustrated inFIGS. 2 and 3. A solid state switch21measures the current level to the load24and provides an open/closed signal to the controller14based on the current level.

Referring toFIG. 4, the combination current sensor and relay10Model RIBXLSA from Functional Devices, Inc. is packaged in a rectangular housing40with a threaded opening42on the lower portion though which are passed a pair of wires18and26. The wires18and26are connected in series with the power cable to the load as shown inFIGS. 1-3. Internal to the housing40are a set of four wire connectors110to which the control wires to the controller14are attached. To access the four wire connectors110the rear panel44is removed. The control wires may be passed through an opening46in the upper left hand side, an opening48in the upper right hand side, or both, as desired. The textual and graphical indication for which connectors correspond to the solid state switch21and to the relay12are provided on the back panel of the device. A set of three light-emitting-diodes50,52and54are provided on the top of the housing40. The right hand diode54provides an indication as to whether the relay is energized. The left hand pair of diodes50and52provides assistance in adjusting the set point for the current level of the solid state switch21. When the central diode54is activated the current is over the trip point. When the leftt hand diode50is activated the current is under the tri point. A potentiometer that is accessed within the housing40when the back44is removed adjusts the set point for the switch21. The switch21includes some hysteresis. To adjust the device10, the potentiometer is decreased (turned counterclockwise) until the central diode52turns on (may already be on). The potentiometer is then increased (turned clockwise) until the left hand diode50turns on. Then the potentiometer is decreased (turned counterclockwise) until the central diode52turns on. This properly adjusts the current level. The instructions for adjusting and the meaning for the light emitting diodes are provided within the housing40. A closed/open/auto switch56is provided on the left hand panel of the housing40. Likewise, the instructions for the settings of the switch56are provided on the back panel of the housing40. The entire housing40is secured to a wall by a set of four screws at the corners thereof.

SUMMARY OF THE INVENTION

The present invention overcomes the aforementioned drawbacks of the prior art by providing a combination current sensor and relay with an improved housing. The housing has several aspects which result in improved functionality. In one aspect, the housing includes light emitting diodes on an upper surface that indicate open circuit and short circuit conditions. In another aspect, the housing includes a securement structure for a circuit board that includes the transformer and switches for device operation, together with aligned openings therein for routing wires to external devices. In another aspect, a multiple position switch is included on the upper surface that indicates multiple modes of operation of the device. In another aspect, the housing may be assembled in multiple parts by affixing a first portion to a support, a circuit board to the first portion, and a second portion to the first portion. In another aspect, the housing is suitable for engagement to alternatively a junction box and a duplex box. In another aspect, the configuration of the upper surface provides usability advantages.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present inventors came to the realization that while the housing for the aforementioned combination current sensor and relay RIBXLSA is functional, it has limitations that become important when the device is mounted in a small enclosure, such as a starter housing within a substation.

First, the three status light emitting diodes are on the top surface of the housing making them difficult to observe if the device is mounted deep within a starter housing at any level other than the user's eye level. For example, when mounted in a starter housing near the floor, the user will need to excessively bend down to observe the light emitting diodes on the top of the housing. Also, when mounted in a starter housing near the ceiling, the light emitting diodes on the top surface may be obscured by the upper portion of the front panel. In addition, the textual and graphical indications for the meaning of each diode are provided on the back panel of the housing, which is not observable when mounted in the starter housing. Accordingly, the user must memorize the meaning of each of the diodes or carry an extra device to read the textual and graphical indications therefrom.

Second, the closed/open/auto switch is located on and independently secured to the side of the housing making it difficult to operate when the housing is mounted adjacent an upright left hand wall of the starter enclosure or another device. Also, the switch is difficult to observe if the user is not directly aligned with the left side of the housing. In addition, the textual and graphical indication for the meaning of the three settings of the switch is provided on the back panel of the housing, which is not observable when mounted in the starter housing. Accordingly, the user must memorize the meaning of each of the positions or carry an extra device to read the textual and graphical indications therefrom.

Third, the rear panel of the housing must be removed in order for the control wires to be installed. This necessarily requires the device not be mounted within the starter housing because when mounted the rear panel is secured to the wall of the starter housing. Unfortunately, it is cumbersome to install the control wires when the device is unmounted and thereafter mount the housing to the wall of the starter housing with the control wires attached. In addition, if the user is not careful the control wires may end up being to short to mount the device where intended. Further, the textual and graphical indication for the function of each of the connections for the control wires is provided on the back panel of the housing.

Fourth, the housing is installed on a flat surface, such as the back wall of a starter housing through a set of four openings provided therein. In addition, the present inventors came to the realization that such a combination current sensor and relay would be more versatile if mountable on a duplex box, a junction box, and a surface, and electrically connected thereto.

Referring toFIGS. 5 and 6, the improved housing70for a combination current sensor and relay of the present invention includes two separate portions, namely a base portion72and a top portion74. Referring also toFIG. 7, the base portion72includes a pair of supports74aand74band a central set of fingers76which supports an enclosed circuit board73(see FIG.8). A pair of resilient members78aand78bflexibly bend and engage the circuit board with protrusions to secure it in place within the housing70on the supports. To remove the circuit board73, the flexible resilient members78aand78bare pulled away from the circuit board73thereby releasing the circuit board73(see FIG.9). This provides an easy way of removing the circuit board73from the housing70if it needs to be replaced, thereby alleviating the need to replace the entire device. In addition, a pair of openings80aand80bare provided in the back of the base portion72in front of the resilient members78aand78b(directly under the protrusions) so that the members may be pulled away from the circuit board73by prying with a suitable device, such as a small screwdriver, from the back of the device thereby releasing the circuit board73.

The base portion72includes a pair of openings82and84at the opposite corners thereof spaced at an appropriate location for securing the base portion72to a standard junction box, such as a 4S junction box86as shown in FIG.10. The openings82and84are slightly oblong to permit a little movement of the base portion to make alignment of the openings82and84with the junction box86easier. The base portion72also includes a pair of openings88and90therein at the bottom and top of the central portion spaced at an appropriate location for securing the base portion72to a standard duplex box92as shown in FIG.11. The top opening90is slightly oblong to permit a little movement of the base to make alignment of the openings88and90with the duplex box94easier. In addition, a central opening96is provided in the central portion of the base portion72to permit the routing of the power wires18and26therethrough for connection within the junction box86or duplex box94. Without the central opening96in the base portion72, the device would need to be mounted to an adjacent surface with the power wires routed therefrom into the junction box or duplex box, which is inconvenient. Further, with multiple openings in the base portion72, the same base portion72may be installed on multiple boxes, such as the duplex and junction boxes. This reduces the necessary inventory for users and increases the flexibility of the different uses for the device. In addition, with the wires routed through one or more of the openings in the sides thereof, the device may be mounted on a surface, such as a flat surface of a starter housing, as shown in FIG.12.

The fingers76surrounding (in a circumferential relationship) the opening96are spaced to engage the protrusions of a threaded metal member98as shown in FIG.13. The threaded metal member98is placed within the fingers76and thereby prevented from rotating or substantial rotation. The engagement of a threaded member98to a pipe is normally performed by pressing engagement of the pipe thereon while turning the pipe. In addition, with the circuit board73supported by the fingers76, the threaded member98will not become disengaged by raising above the fingers76when a pipe is rotatably pressingly engaged therewith.

The control and power wires may be routed through the openings in the sides, as necessary. The openings defined by both the top portion74and the base portion72include one or more ribs100which engage a protrusion of the threaded member98when supported therein. In addition, the ribs100are sufficiently recessed so that the face of the threaded member98is also in at least in partial face to face opposing relationship with the side. Accordingly, when the top portion74and base portion72are engaged with one another the threaded member98is prevented from significant rotational movement and also prevented from significant lateral movement. Thus the sufficiently threaded member98is retained in place to secure a threaded member thereto.

The base portion72includes a pair of threaded posts104and106to which a pair of screws are secured through the top portion74when engaged therewith. By securing the top portion74to the base portion72, while the base portion74is secured to the supporting device, such as a surface or a box, the top portion74may be removed to allow access to the circuit board73therein without removal of the entire housing70from the supporting device or surface. Accordingly, the base portion72may be attached to a supporting surface. Then the circuit board73is detached to permit easier assess the central opening96in the base portion73, if necessary. The power wires18and26are routed through the appropriate opening and the control wires are attached to the connectors100(see FIG.8). Textual indications indicating the function of each connector110are provided on the circuit board73adjacent the connector, such as relay (+) (−) and status. Thus, when a user installs the control wires and power wires, the device may be previously secured in the desired location, so that the length of the controls wires and power wires may be accurately determined. Also, the textual and/or graphical indications of the function of the control wires is provided next to the connectors so that it is less likely that the user will install the control wires improperly. In addition, without the need to search for the textual and/or graphical indications for the functions of the connectors110the user will likely install the connectors faster.

A relay120, a transformer122, a potentiometer132, three light emitting diodes124,126,128, the connectors110, and a switch130are supported by the circuit board73. Accordingly, when any of the electrical or mechanical devices fail, the entire circuit board73may be easily replaced as a single unit. This alleviates the need to troubleshoot individual components connected to different portions of the housing. The relay may be any type of switching circuit, as desired. The transformer may be directly connected in series or at least partially encircle the power cable. The relay and switch may be designed to sense any type of signal, such as a voltage, current, short circuit, and open circuit. The controller is preferably a programmable logic device.

Referring again toFIG. 6, the top portion74is secured to the base portion72with a pair of screws. The switch130is provided through an opening136in the top portion74. Locating the switch130on the frontal surface permits easy access to the switch130and easy identification of the state of the switch. Textual and/or graphical indications134for the operation of the switch130are provided on the top member. The textual and/or graphical indications134of the operation of the switch130being provided on the front surface make it easy for the user to recall the operations of the switch, without the need to look at other uninstalled devices, a manual, or rely on the user's memory. In addition, the switch130is recessed from the upper surface138of the top portion74which reduces the overall height of the device while simultaneously locating the switch130at a location less likely to become inadvertently bumped thereby interrupting or unintentionally providing power to the load. The upper upright surface140above the left hand upright surface142partially surrounding the switch130provides a stop for a user's finger to hold the finger in position above the switch130so that the switch130may be more easily operated, especially when the user is wearing gloves. In addition, such upright surfaces140and142stop and maintain the finger of a user in position above the switch130while testing the electrical load even when the housing70is in an awkward location, such as the back of a starter housing.

The light emitting diodes124,126and128and set point adjustment132(potentiometer) are provided through a set of openings144in the top portion74. Locating the light emitting diodes on the front (upper) surface permits easy reading of the status and adjustment of the set point from the front of the housing70. Textual and/or graphical indications146for the function of the set point and light emitting diodes are provided on the top portion74. The textual and/or graphical indications146of the operation of the diodes and set point being provided on the front surface148make it easy for the user to recall the operation of the diodes and set point, without the need to look at other devices nor open the device to adjust the set point. In addition, the set point and light emitting diodes are proximate the switch and recessed from the upper surface138of the top portion74and further recessed from the surface137with the switch130. When the user is adjusting the switch130his finger will likely partially obscure from view the surface148proximate the light emitting diodes and set point. However, by further recessing the surface148proximate the light emitting diodes the user will be more likely to observe the status of the light emitting diodes by observing the diodes at an angle thereof under the finger. It is unlikely that the finger of a user on the switch will totally obscure the surface148further recessed therefrom.

Referring toFIG. 14, an exemplary circuit (similar in functionality toFIGS. 1-3) includes a start/stop relay, an internal current sensor, and a switch circuit. The power cables are interconnected to a terminal block. The terminal block is interconnected to a switch circuit that provides an on-off-on functionality. With the switch in the upper position, referred to as the hand mode, the terminal block is electrically connected across a transformer with the start/stop relay effectively removed from the circuit. Any power from the source to the load is provided without interference by the combination current sensor and relay device. With the switch in the central position, referred to as the off mode, the terminal block is open circuited. Any power from the source to the load is open circuited. With the switch in the lower position, referred to as the auto mode, the electronics are enabled. Any power from the source to the load is provided dependant on the status provided to the relay coil contacts from the controller.

For the auto mode the connection of the contact jumper provides either a normally closed or normally open functionality. Interconnecting pins1and2provides a normally closed condition to the relay, while interconnecting pins2and3provides a normally open condition to the relay. The power from the controller is preferably 24 volts, either AC or DC. If the input signal is AC then diode D1rectifies the signal and provides a DC voltage between the capacitor and the resistor. Light emitting diode D2provides a status indication to the user that the relay is energized. Energizing or de-energizing the relay changes its state and hence whether the circuit to the load is open or short circuited.

The primary of a transformer, generally referred to herein as an internal current sensor, is electrically interconnected between the switch and the terminal block. The secondary of the transformer provides a current (or voltage) signal representative of the current flowing between the terminals of the terminal block, and hence to the load. A pair of diodes provides alternating current clipping at 6.3 volts to protect the remaining portions of the circuit and also provide a reference voltage at the upper terminal of the secondary of the transformer. A scaling resistor and potentiometer provides a scaled voltage at the base of the diode. The diode and capacitor provide a ½ wave rectifier functionality. A diode clamps the voltage to a maximum of 9.1 volts. A positive voltage detector, such as a 4.1 volt detector, interconnects VDD to the output when the difference across its terminals is greater than approximately 4.1 volts. The positive voltage detector interconnects VSS to the output when the difference across its terminals is less than approximately 4.1 volts. The PDD has some built in hysteresis to avoid repetitively switching near the switching point, such as 4.1 volts. When the output of the PDD is high then transistor Q5is activated with diode D4indicating an over current situation. When the output of the PDD is low then transistor Q5is not activated and diode D5is activated indicating an under current situation. By adjustment of the potentiometer in combination with the diode indications, the suitable current level may be obtained.

When the output of the PDD is high then transistors Q4A and Q4B are activated thereby shorting the status terminals together. This permits DC or AC current to flow between the contacts. A pair of diodes provides excess voltage protection, such as 47 volts. When the output of the PDD is low then Q4A and Q4B are not activated thereby providing an open circuit between the terminals.

Referring toFIGS. 15A and 15B, an alternative circuit provides an additional set of contacts. Preferably the upper PDD and associated circuit provides an over current indication, such as a locked rotor. Preferably the lower PDD and associated circuit provides an under current indication, such as a belt loss. Accordingly, the output terminals provide both an over current and an under current indication. It is noted that the field effect transistors are provided for a normally open circuit and alternatively the npn bipolar transistors are provided for normally closed circuit. Both are not typically simultaneously included, or otherwise electrically interconnected, in an actual circuit.