Patent Application
20110065330
The present disclosure relates generally to electrical wiring and, in particular, to a convenient terminal wire block.
Terminal wire blocks are widely used to connect electrical wires to printed wiring boards (PWBs) or printed circuit boards (PCBs), to securely couple pairs of wires, and to otherwise provide reliable electrical contacts. In general, it is known to use either spring clamps or screw clamps as terminal wire blocks to secure electrical wires in a fixed position.
Spring wire clamps typically include a housing and a spring (or a similar elastic component) to which a force is manually applied as a wire is inserted into the clamp. Once released, the spring exerts a force on the wire to push the wire against one of the walls of the housing. It is also known to install an elastic element on the wire to interact with a clamp housing of a standard size. For example, a typical personal computer includes a cage terminal to receive an Ethernet cable that includes a flexible plastic strip, bent to define an acute angle, at one or both ends. The plastic strip and the cage terminal together define a push-in terminal that does not require screws, bolts, or other fasteners.
By contrast, screw clamps typically include a housing and an externally threaded fastener such as a screw operatively connected to the housing. A technician places a wire inside the housing and tightens the fastener to push the wire against one of the walls of the housing. Accordingly, screw clamps usually require the use of a tool such as a screwdriver.
Some technicians prefer spring clamps while others prefer screw clamps. In addition to personal preferences, certain applications make spring clamps preferable because spring clamps normally do not require special tools or room to maneuver such tools. Moreover, spring clamps typically are better suited for connecting wires on or adjacent to vibrating devices, as threaded connections (e.g., a screw and a nut) tend to loosen in response to vibration. On the other hand, spring clamps may include easily breakable components such as plastic strips, or may age faster as springs or similar flexible components lose rigidity or elasticity.
A terminal wire block includes two independently operable wire clamps for securing a wire in a fixed position. In at least some of the embodiments, the two independently operable wire clamps use different mechanisms, such as a spring mechanism and a screw mechanism, to hold the wire in place.
In an embodiment, the terminal wire block includes a screw clamp and a spring clamp positioned behind the screw clamp, so that an exposed end of the wire first passes through the screw clamp to reach the spring clamp. The spring clamp includes a cage and a flexible spring finger biased toward one of the walls of the cage, so that the spring finger must be bent to allow the wire to reach the inside of the cage. By contrast, the screw clamp includes a cage with a threaded opening and an externally threaded fastener to mate with the opening of the cage to define a narrower or wider opening in the direction of movement of the wire through the cage in response to tightening or loosening the externally threaded fastener, respectively.
To insert a wire into the spring clamp, a technician pushes an exposed end of the wire through the screw clamp to reach the flexible spring finger, and applies sufficient pressure to the wire to displace one end of the spring finger relative to its equilibrium position, and allow the wire to reach the inside of the cage of the spring clamp. When the technician stops applying pressure to the wire, the spring finger pushes the wire toward one of the walls of the cage and thereby secures the wire in a fixed position.
Optionally, the technician subsequently tightens the externally threaded fastener of the screw clamp to hold the wire more firmly in place and thus provide additional integrity to the corresponding electrical contact. As another option, the technician uses only the screw clamp. In this case, the technician pushes the wire inside the cage of the screw clamp but not far enough, or with a sufficient force, to displace the spring finger.
To remove the wire from the terminal wire block when only the screw clamp is engaged, the technician loosens the externally threaded fastener and pulls out the wire. To remove the wire from the terminal wire block when both the spring clamp and the screw clamp are engaged, the technician may also operate a push down button which applies pressure to the spring finger in the direction opposite to the bias of the spring finger, or reach the spring finger with a tool such as a screwdriver via a corresponding opening.
In some embodiments, a terminal wire block with a small foot print includes a spring clamp having a spring and a screw clamp having a fastener operatively connected to the spring, so that the spring is deflected in response to pressure applied to the fastener. Once the spring clamp secures a wire in a fixed position, a technician may also engage the screw clamp by threading or otherwise tightening the fastener. In at least some of the embodiments in which the fastener is adapted to communicate pressure to the spring, the spring clamp and the screw clamp share a common cage. Further, the spring in some embodiments may have a first bias in a direction opposite to the direction in which the fastener is threaded, and a second bias approximately perpendicular to the first bias to better guide pressure applied to the fastener.
In some embodiments, multiple terminal wire blocks, each having a spring clamp and a screw clamp, are aligned on a circuit board to define a multiple-input connector or a connector array. In one such embodiment, multiple terminal wire blocks form several rows, with the back rows being progressively elevated relative to the front rows to provide convenient and secure access to each terminal wire block.
The terminal wire block 10 may include a terminal base 20 and an external cover 22. In general, the terminal base 20 may be mounted on a horizontal, vertical, or inclined surface. In some embodiments, the terminal base 20 may be soldered to a circuit board or another component. Alternatively, the terminal base 20 may include one or several pins (not shown) for mounting on the circuit board. The terminal base 20 may be manufactured from a rigid non-conductive material such as plastic, for example. However, the terminal base 20 in other embodiments may be made of metal or another conductive material. In addition to fulfilling the structural functions discussed in more detail below, a conductive terminal base 20 may serve as a conductive path between the wire 12 and another electrical contact such as a wire or a circuit board contact.
In the embodiment of
The spring finger 26 generally may be manufactured using a resilient material having a memory, so that the spring finger 26 has a tendency to return to its original shape once deformed. In an embodiment, the spring finger 26 is also conductive to provide an electric contact between the wire 12 and another wire or the cage 24, for example. To this end, the spring finger 26 may be made of a metal or alloy.
As best illustrated in
To release the wire 12 held by the spring clamp 14, a push button 34 is operated to apply pressure to the spring finger 26 via a pair of actuating levers or legs 36 in the direction opposite to D1. In other embodiments, the spring clamp 14 may not include the push button 34 at all, and a technician may apply pressure directly to the spring finger 26 using a screwdriver or another suitable tool, for example. Once the spring finger 26 is depressed, the wire 12 can be easily pulled out of the spring clamp 14. The cage 24 accordingly includes a pair of openings 38 to receive the respective legs 36.
The screw clamp 16 is disposed in front of the spring clamp 14 relative to the opening through which the wire 12 in inserted into the terminal wire block 10. In other words, the wire 12 passes through the screw clamp 16 to reach the spring clamp 14. In the embodiment illustrated in
If the fastener 50 is a screw, a bolt, or another type of a fastener with an external threaded surface, the internal surface of each of the openings 46 may include corresponding threads. The fastener 50 may thus couple the brackets 40 and 42 to each other, as well as serve as an actuating element of the screw clamp 16. Of course, it is also possible to provide the cage 44 as an integral element which, in turn, may also may be integral with other components of the terminal wire block 10.
To engage the screw clamp 16 when the wire 12 is inside the terminal wire block 10, a technician may tighten the fastener 50 to thereby reduce the distance between the work end 54 and the bottom wall of the cage 44. In this manner, the screw clamp 16 applies pressure to the wire 12 in the direction opposite to D1. To evenly distribute pressure applied to the wire 12, and to prevent damage to the threads of the wire 12, a plate 56 may be attached to the work end of the fastener 50. The technician may release the wire 12 from the screw clamp 16 by loosening the fastener 50 (i.e., by driving the work end 52 in the direction D1).
It will be noted that the spring clamp 14 may be operated independently of the screw clamp 16. In other words, a technician may push the wire 12 through the cage 44 to engage the push-in terminal of the spring clamp 14. Once engaged, the spring clamp 14 will hold the wire in place irrespective of the position of the fastener 50. Alternatively, the technician may choose not to push the wire 12 through to the spring clamp 14 and may engage only the screw clamp 16. As yet another alternative, the technician may engage both the spring clamp 14 and the screw clamp 16 if additional contact integrity or security is desired. In this case, the clamps 14 and 16 apply pressure to the wire 12 along the direction D1 and in the direction opposite to D1, respectively, thereby providing a tight and secure connection.
In the embodiment illustrated in
In an embodiment, the head 52 of the fastener 50 may be shaped so as to retain the cage 44 in a fixed position within the terminal wire block 10 without rigidly securing one or both of the brackets 40 and 42 to the terminal 20. As best illustrated in
It is also possible to provide a single component (e.g., an extended terminal base) in which the terminal base 20 is integral with the cage 44. Further, if such an extended terminal base is manufactured from a conductive material, and if the spring finger 26 is soldered to the extended terminal base, the cage 44 may be at the same electric potential as the contact point 28. In this manner, the terminal wire block 10 may electrically connect the wire 12 to an electrical wire connected at the contact point 28 even if only the screw clamp 16 is engaged. Alternatively, an electrical wire may be connected to the screw clamp 14 at the top of the cage 44.
Generally speaking, some or all of the components of the terminal wire block 10 may be manufactured using metal extrusion, injection molding of plastic, cutting and bending of sheet metal, or any other suitable techniques. The selection of suitable material for some of these components may depend on the desired electrical connections within the terminal wire block 10. For example, it may be necessary to manufacture the terminal base 20 from a metal or metal alloy if the terminal base 20 serves as a conductive path between the wire 12 and another wire or the PWB.
In one embodiment, the terminal wire block 10 is compatible with a 0.2″ terminal pitch, and the wire 12 is in the range between the No. 24 American Wire Gauge (AWG) stranded (i.e., measured along the cross-sectional area of the conductive strands) wire to 12 AWG solid core wire. As best illustrated in
It will be appreciated that the terminal wire block 10 is discussed above by way of example only. Several additional features and alternatives to the embodiment of
In one aspect, it is not necessary for the fastener 50 to apply pressure to the wire 12 in the direction opposite to D1. As one alternative, the screw clamp 16 may push the wire 12 in the direction D1 when the technician tightens the fastener 50. In another alternative, the screw clamp 16 may be positioned so as to direct the pressure from the fastener 50 perpendicularly to both D1 and D2. Other orientations of the screw clamp 16 and/or the fastener 50 are also possible.
Further, the spring clamp 14 may include a biasing element other than the spring finger 26. For example, the biasing element may be a spring, a coil, or another flexible element. Also, the biasing element may be biased in any direction other than D1 that results in the wire 12 being pressed against a wall of the corresponding cage and thereby being held in place.
Still further, the fastener 50 in another embodiment may be combined with the push button 34 to reduce the foot print of the terminal wire block 10. The spring clamp 14 and the screw clamp 16 may accordingly share a cage to hold the wire 12. However, the respective mechanisms of the clamps 14 and 16 are preferably independently operable. For example, the head 52 of the push button 34 may include an aperture, and the push button 34 may include an internal threaded surface, to receive and mate with the external threads of the fastener 50 along the direction D1.
In yet another aspect, a terminal wire block similar to the terminal wire block 10 may include more than two wire clamps implementing different wire clamping techniques, with at least two of the wire clamps being independently operable.
Also, the spring clamp 14 in some embodiments may be disposed in front of the screw clamp 16 relative to the opening through which the wire 12 in inserted into the terminal wire block 10. To reach the cage 44 of the screw clamp 16, the wire 12 may be pushed against and past the spring finger 26 of the spring clamp 14. Thus, in this embodiment, the spring clamp 14 may be engaged automatically when the wire 12 is secured using the screw clamp 16.
Referring to
With continued reference to
As best illustrated in
Similar to the spring finger 26 discussed with reference to
Once the spring clamp 152 secures the wire in a fixed position, the technician sometime may wish to also engage the screw clamp 156 to provide additional integrity and security to the contact. In this embodiment, the spring 154 includes an internally threaded opening 190 in the portion corresponding to the upper tail of the letter “G” with which the fastener 159 may mate. A sleeve or guide 192 may be rigidly secured to the spring 154 at the opening 190 to properly guide the fastener 159. In another aspect, the sleeve 192 may help to distribute the pressure applied to the spring 154 via the fastener 159 when the spring clamp 152 is being engaged.
When the technician threads or otherwise tightens the fastener 159, the loop section of the spring 154 contracts, thereby increasing the pressure the spring 154 exerts on the wire in the direction D1, and thus improving the integrity and security of the contact. To release the wire, the technician may loosen the fastener 159 to first disengage the screw clamp 156, and then apply pressure to the fastener 159 to align the openings 180 and 164 until the wire can be released.
It is noted that some technicians may inadvertently release the wire held by the spring clamp 152 when operating the screw clamp 156. In particular, the technician must apply little pressure to the fastener 159 in the direction opposite to D1 when tightening the fastener 159, e.g., by threading the work end of the fastener 159 in the clockwise direction if the fastener 159 is a screw, a bolt, or another type of an externally threaded fastener.
Now referring to
In the example embodiment illustrated in
With continued reference to
To engage the spring clamp 202, a technician applies pressure to the fastener 232 to align the opening 214 with the opening 218, and pushes an end of a wire into the cage 216. Because of the shape of the spring 210, some of the pressure the fastener 232 communicates to the spring 210 at the opening 236 is directed at the inclined wall 212. As a result, the technician must exert greater pressure to align the openings 214 as 218 as compared to the embodiment of
To also engage the screw clamp 204, the technician may thread the fastener 232 which may be a screw, for example. The screw clamp 204 may clamp the wire between a work end 240 of the fastener 232 and the upper section of the bracket 220. In at least some of the embodiments, the tail of the spring 210 may also bend toward the upper section of the bracket 220 if the technician continues to thread the fastener 232 after the work end 240 reaches the upper section of the bracket 220. Although the use of the screw clamp 204 is optional, the terminal wire block 200 may provide a secure and reliable wire contact by clamping the wire with both the spring clamp 202 and the wire clamp 204. Similar to the terminal wire block 150, the terminal wire block 200 releases the wire if the fastener 232 is loosened, and sufficient pressure is applied to the fastener 232 in the direction opposite to D1.
In some embodiments, the base 206 may be soldered to a circuit board. If desired, one or several contacts 244 may extend or be soldered to the lower portion of the bracket 220 to provide an easily detachable connection to a wiring board.
In an embodiment suitable for use with wires that carry 4-20 mA signals in a process control environment, for example, the spring 210 may be made of beryllium copper and have a thickness of approximately 0.457 mm (26 gauge). Further, the maximum stress of the spring 210 may be approximately 90% of yield. The initial preload at 1 mm nominal deflection may be 1.5 lbs, and the maximum load at full screw deflection may be 6.5 lbs. In other embodiments, it is also contemplated that stainless steel may be used to manufacture the spring 210. Further, the composition and thickness of the spring 154 (illustrated in
Now referring to
From the foregoing, it will be appreciated that the terminal wire block 10, 150, or 200, as well as the multiple-input connector 100 or 300, addresses individual preferences of technicians by providing independently operable wire clamps implementing different wire clamping techniques. When using the terminal wire block 10 or the multiple-input connector 100, for example, a technician need not necessarily use a screwdriver or another tool or, conversely, the technician may choose not to engage the push-in contact of the spring clamp 14 if the push button 34 is hard to reach, for example. Moreover, the technician may also choose to provide additional contact integrity by securing the wire 12 using both the spring clamp 14 and the screw clamp 16. On the other hand, the terminal wire block 150 or 200 allows a technician to engage the spring clamp 152 or 202 alone, or together with the corresponding screw clamp 156, using a single tool such as a screwdriver.
While the present system and methods have been described with reference to specific examples, which are intended to be illustrative only and not to be limiting of the disclosure, it will be apparent to those of ordinary skill in the art that changes, additions and/or deletions may be made to the disclosed embodiments without departing from the spirit and scope of the disclosure.
