1. Field of Invention
The invention relates generally to the field of terminal blocks for printed circuit boards and, more specifically, to a terminal block with a housing arranged to enable the screw heads of the terminal block to be turned by a standard installer screwdriver.
2. Description of Related Art
Installers of electrical systems carry an industry standard flat blade screwdriver, also known as a pocket screwdriver. The blade width of this screwdriver is approximately ⅛ inch (3.175 mm). Electrical devices are electrically connected together with wires. These wires are connected to the circuit boards of electronic devices via terminal blocks. These terminal blocks contain screws which clamp down on the wires as the screws are tightened with these industry standard screw drivers. Electronic devices are getting smaller as the electronics industry advances. Miniature printed circuit board (PCB) mounted terminal blocks (3.5 mm centerline spacing) are being used more often in these smaller electronic devices. The industry standard screwdriver is too wide to be used with the small screws in the miniature terminal blocks. The screw head size in the current miniature terminal blocks can not be increased without interfering with the neighboring screw or increasing the length of the terminal block. The next size larger terminal block (5 mm centerline spacing) does accept the industry standard screw driver. However it is 43% longer, 10% wider and 18% taller. In many applications, the larger size terminal block can not be accommodated.
However, use of the smaller blade width screwdriver can result in inadequate torque and consequently in inadequate and poor quality electrical connections. As a result, use of the industry standard blade width screwdriver is strongly preferred by the installers.
What is needed is a smaller size terminal block to accommodate the trend to miniaturization of the electronic parts and which permits, at the same time, use of an industry standard blade width screwdriver to make the electrical connections.
To address the above and other issues, the present invention describes a technique for staggering the screw cavities of a miniature terminal block to decrease the size of PCBs while, at the same time, permits use of an industry standard installer's screwdriver for all styles or types of PCB mounting arrangements.
In a particular aspect of the invention, a printed circuit board (PCB) has a terminal block for coupling by screw-operated coupling means at least one conductor to the PCB, the terminal block comprising: a housing of insulating material, the housing having at least one transverse opening capable of receiving at least one contact member for coupling the at least one conductor to the PCB, and at least two cavities disposed within the housing. The cavities are for accepting the screw-operated coupling means. The housing has a length-wise direction along a reference line, and the at least two cavities each has a center point. The center point of at least one of the at least two cavities is disposed in an offset position from the reference line in the length-wise direction such that the at least two cavities are staggered with respect to each other.
Another aspect of the present invention is a printed circuit board (PCB) mountable terminal block for coupling by screw-operated coupling means at least one conductor to a PCB. The terminal block comprises a housing. At least two cavities within the housing are for accommodating a screw of the screw-operated coupling means; and at least one transverse opening within the housing is capable of accommodating a contact member, the at least one transverse opening being capable of disposing the contact member on an end surface of the PCB such that the at least one conductor can be coupled to the PCB from the end surface. The housing has a length-wise direction along a reference line, the at least two cavities each having a center point, and the center point of at least one of the at least two cavities is disposed in an offset position from the reference line in the length-wise direction such that the at least two cavities are staggered with respect to each other.
Another aspect of the present invention is a printed circuit board (PCB) mountable terminal block for coupling by screw-operated coupling means at least one conductor to a PCB. The terminal block comprises a housing. At least two cavities within the housing are for accommodating a screw of a screw-operated coupling means; and at least one transverse opening within the housing is capable of accommodating a contact member. The housing has a length-wise direction along a reference line. The at least two cavities each has a center point, the center point of at least one of the at least two cavities being disposed in an offset position from the reference line in the length-wise direction such that the at least two cavities are staggered with respect to each other. The housing of the terminal block has a height enabling orientation of a length-wise direction of the terminal block transversely with respect to a longitudinal centerline direction of a larger housing enclosing the terminal block and the PCB
Still another aspect of the present invention is a terminal block for coupling by screw-operated coupling means for coupling at least one conductor to a printed circuit board. The terminal block comprises a housing of insulating material. The housing has at least one transverse opening capable of receiving at least one contact member for coupling the at least one conductor to the PCB, and at least two cavities are disposed within the housing. The cavities are for accepting the screw-operated coupling means. The housing has a length-wise direction along a reference line. The at least two cavities each has a center point. The center point of at least one of the at least two cavities is disposed in an offset position from the reference line in the length-wise direction such that the at least two cavities are staggered with respect to each other.
In each of the foregoing aspects of the present invention, at least one of the at least two cavities has a diameter at least equal to the width of the blade of a standard installer screwdriver. A contact member can be disposed within at least one of the at least two cavities. The contact member comprises: an upper portion with a transverse opening, and a lower portion with a pin, and wherein the upper portion is threaded to accept a screw. The contact member can further comprise a screw with a head having a diameter at least equal to the width of the blade of a standard installer screwdriver.
The diameter of the at least one of the at least two cavities is at least equal to 0.125 inches (3.175 mm). The head of the screw has a diameter at least equal to 0.125 inches (3.175 mm). The contact member can further comprise a wire guard for guarding a conductor wire. The lower portion with a pin can be disposed to permit through hole mounting to a printed circuit board (PCB). The terminal block can comprise solder pads permitting surface mounting to a printed circuit board (PCB). The terminal block can be for coupling by screw-operated conductor-clamping terminal coupling means for coupling at least one conductor to a printed circuit board. Alternatively, the terminal block is for coupling by screw-operated insulation displacement terminal coupling means for coupling at least one conductor to a printed circuit board. The housing can comprise at least four transverse openings that can be disposed on an end surface of the PCB, the openings each capable of accommodating at least one contact member for coupling a conductor to the PCB.
When the housing of the terminal block has a height enabling orientation of a length-wise direction of said terminal block transversely with respect to a longitudinal centerline direction of a larger housing enclosing the terminal block and the PCB, the larger housing can have an inner diameter of 1 inch (25.4 mm).
These and other features, benefits and advantages of the present invention will become apparent by reference to the following text and figures, with like reference numbers referring to like structures across the views, wherein:
The present invention describes a terminal block structure in which by alternately shifting each screw fore or aft (staggering), larger screw head diameters can be accommodated without increasing the length of the terminal block. The screw heads can be enlarged sufficiently to accept at least the ⅛″ (3.175 mm) wide industry standard screwdriver or greater. The front face of the wire receptacle is recessed within the nonconductive housing to prevent the exposed uninsulated portions of neighboring wires from contacting each other. By staggering the screws and associated wire receptacles, the same effect is achieved without increasing the width of the miniature terminal block. Therefore, within the same PCB foot-print used by a current miniature PCB mountable terminal block, this invention provides the installer a terminal block which will accept the industry standard screwdriver, and so result in high quality electrical connections even with reduced size terminal blocks.
This invention can be used in any application that currently employs a miniature PCB mountable terminal block and will provide the benefit of working with a larger range of screwdrivers. Although the embodiment of this invention shown in the attached illustrations contains pins for a “through hole” PCB attachment, an alternate embodiment can be made in a surface mount (SMD) configuration.
In addition, when a sensor package is mounted and recessed into a cavity in a wall, an end mounted terminal block provides much greater advantages to the installer since the wires can be inserted from the end of the PCB rather than from the side. In the present invention, four terminals are possible in an end mounted configuration, and less depth of the recess cavity is required as compared to the prior art.
In the present invention, due to the removal of the recessed screw retention features at the top of the screw cavities 203, Z2 typically is only 0.261 inches (6.6 mm). The spacing interval X3 or pitch p between the contact pins 110 can remain the same as in the prior art, and is typically 0.138 inches (3.5 mm).
In a terminal block embodiment of the present invention, which contains typical screw retention features, the height Z2 would remain the same as the prior art, i.e., Z1=Z2. These retention features typically take the form of deeper counterbores in the housing which have a slight interference fit with the screw heads. These counterbores are typically of sufficient length to maintain interference with the screw heads when the screws threads are completely disengaged from the contacts, thereby preventing the screws from being removed inadvertently.
By removing the screw retention features, the terminal block 200 affords a lower profile, as exemplified by dimension Z2, as compared to dimension Z1 of the terminal block 100, i.e., 0.261 in. (6.6 mm) as compared to 0.335 in. (8.5 mm). The lower profile affords additional degrees of freedom in orienting the terminal block 200 with respect to the nonconductive housing 108. This is exemplified in
The prior art terminal block 100 in
The typical dimensions of a terminal block both the prior art and of the present invention are shown in the table which follows below.
Those skilled in the art recognize that the dimensions of X2, Y2, Z2 and offsets represented by Y3 (=d) are not limited and can be varied as desired. Similarly, the spacing interval or pitch X3 (=p) can also be varied as desired.
Although the contacts 116 described in FIGS. 1B through 5B-3 for the present invention include pins 110 for a “through hole” PCB attachment, an alternate embodiment can be configured for a surface mount (SMD) configuration. In such a case, terminal block 200 includes solder pads (not shown) permitting surface mounting to a printed circuit board (PCB).
Those skilled in the art recognize that the screw-operated coupling means for clamping a conductor as discussed for
The invention has been described herein with reference to particular exemplary embodiments. Certain alterations and modifications may be apparent to those skilled in the art, without departing from the scope of the invention. The exemplary embodiments are meant to be illustrative, not limiting of the scope of the invention, which is defined by the appended claims.