Bypass system for CATV signal tap

The present invention relates to cable television transmission components. More particularly, the invention relates to a bypass system which prevents interruption of the cable signal to downstream subscribers during servicing of a cable television tap.

Cable television (CATV) services are provided to subscribers through transmission networks that include taps, splitters, amplifiers and other equipment that distribute CATV service and ensure that the CATV signal quality is maintained. In particular, taps reside along the network to provide access outlets for localized subscribers. CATV network and service as used herein refers to all systems involving the transmission of television signals from the headend over a transmission medium, such as fiber optic cable or coaxial cable.

<b>Figure 1</b> is a block diagram of a CATV network <b>5</b>. The transmission line <b>34</b> provides cable signals from the headend <b>32</b> to subscribers <b>38, 39</b> at remote locations. The subscribers <b>38, 39</b> receive signals through taps <b>36, 37</b> placed along the transmission line <b>34</b>. The CATV signals are typically routed into the tap and through a printed circuit board attached to the tap cover which splits the signal and allows each tap <b>36, 37</b> to typically provide a connection to four or more subscribers.

Referring to <b>Figure 2</b>, a prior art CATV multiple tap <b>15</b> is shown. The multiple tap <b>15</b> generally includes a tap cover <b>10</b>, a printed circuit board <b>14</b>, a pair of terminal housings <b>40</b> and a main housing <b>26</b>. The tap cover <b>10</b> is provided with a plurality of tap outlets <b>12</b>, each of which provides CATV service to a different subscriber. The printed circuit board <b>14</b> is rigidly attached to the inside surface of the cover <b>10</b> and includes a pair of signal receptors <b>22, 23</b>. The signal receptors <b>22, 23</b> allow the signal to flow through the printed circuit board <b>14</b> and to be split among the subscribers fed from the tap outlets <b>12</b>. The signal also passes through the tap <b>15</b> to a downstream tap <b>37</b>. A detailed explanation of the function of the printed circuit board <b>14</b>, which is well known to those skilled in the art, is outside the scope of the present invention. A metal braid <b>11</b> surrounds the periphery of the printed circuit board <b>14</b> at the junction between the cover <b>10</b> and the main housing <b>26</b>. The metal braid <b>11</b> provides an EMI/RFI trap for the printed circuit board <b>14</b>.

The main housing <b>26</b> includes threaded signal ports <b>24</b>, <b>25</b> at opposing ends. The input signal port <b>24</b> is adapted to receive a signal input via a coaxial cable and a signal impact connector <b>50</b>. The output signal port <b>25</b> receives a signal output connector <b>51</b> for outputting the received signal to the downstream CATV network. The internal conductor <b>52, 53</b> of each coaxial cable <b>50, 51</b> is connected inside the tap <b>15</b> at a terminal housing <b>40</b>. A threaded plug port <b>27</b> is provided adjacent to each signal port <b>24, 25</b> to allow plugs <b>28</b> to be removed. Exposed terminal screws <b>46</b> aligned with the ports <b>27</b> are tightened onto the conductors <b>52, 53</b> to fix each to a contact terminal <b>42</b> positioned in the respective terminal housing <b>40</b> (see <b>Figure 5</b>). The components of the terminal housing <b>40</b> are shown in greater detail in <b>Figure 4</b>. Upon engagement of the cover <b>10</b>, the receptors <b>22, 23</b> on the printed circuit board <b>14</b> engage the contact terminals <b>42</b> to complete the circuit.

Referring to <b>Figure 3</b>, the uninterrupted signal path <b>16</b> for the CATV tap <b>15</b> is illustrated. When the cover <b>10</b> is installed, the signal, shown as line <b>16</b>, originates from the signal input connector <b>50</b>. The signal input conductor <b>52</b> contacts the contact terminal <b>42</b> within the first terminal housing <b>40</b> and the signal flows through the contact terminal <b>42</b> to the first signal receptor <b>22</b> on the printed circuit board <b>14</b>. The signal then flows through the printed circuit board <b>14</b> (and thus to each individual tap <b>12</b>) and to the second signal receptor <b>23</b>. The second signal receptor <b>23</b> is coupled to the second contact terminal <b>42</b> within the other terminal housing <b>40</b> which contacts the conductor <b>53</b> within signal output connector <b>51</b>.

Periodically, the taps <b>36, 37</b> require servicing due to malfunctioning of the tap <b>36, 37</b> or to connect or disconnect subscribers <b>38, 39</b>. However, when the cover <b>10</b> is removed for servicing the tap <b>15</b>, the printed circuit board <b>14</b> is also removed and the signal path is open-circuited since the signal receptors 22, 23 no longer are connected to the contact terminals <b>42</b>. As a result, removal of the cover results in interruption of the cable signal over the transmission line <b>34</b> to subscribers downstream from that tap. For example, returning to <b>Figure 1</b>, servicing of the tap <b>36</b> not only results in interruption of service to the subscribers <b>38</b> who are fed from that tap <b>36</b>, but also subscribers <b>39</b> who access the CATV network <b>5</b> through the downstream tap <b>37</b>. Because of the increasing reliance upon the CATV system for lifesaving and other data critical applications, even a momentary signal interruption is undesirable. However, there is often no provision for maintaining uninterrupted service to downstream subscribers when the cover of the tap is removed for servicing.

In prior art systems, bypassing is generally accomplished by removing both of the plugs <b>28</b> and utilizing a jumper to bridge between the two contact terminals <b>42</b>. The jumper generally includes two prongs which are conductively interconnected. Each prong is placed into one of the open plug ports <b>27</b> and contacted with a respective terminal screw <b>46</b> to reroute the signal flow around the tap <b>15</b>. However, it is often difficult and time consuming to remove the plugs. Additionally, removal of the plugs exposes the internal components of the tap to environmental contamination.

Accordingly, it is an object of the invention to provide a bypass system which provides uninterrupted service to downstream subscribers during removal of the tap cover for servicing.

It is a further object of the invention to provide a cost efficient bypass which can be retrofitted to existing devices.

BRIEF DESCRIPTION OF DRAWINGS

<ul id="ul0001" list-style="none" compact="compact"><li><b>Figure 1</b> is an overall system block diagram of a typical cable television system;</li><li><b>Figure 2</b> is a perspective view of a prior art cable tap;</li><li><b>Figure 3</b> is a perspective view of the signal path through the prior art cable tap;</li><li><b>Figure 4</b> is a perspective view of a disassembled terminal housing;</li><li><b>Figure 5</b> is a plan view of the cables being connected in the tap;</li><li><b>Figure 6</b> is a section view of the preferred connection plug;</li><li><b>Figure 7</b> is a bottom plan view of a tap with the connection plugs inserted therein;</li><li><b>Figure 8</b> is a section view of the preferred jumper, with the sectioned jumper aligned with a tap;</li><li><b>Figure 9</b> is a section view of the jumper in engagement with a connection plug of the present invention;</li><li><b>Figure 10</b> is a perspective view of an unassembled alternative terminal housing.</li></ul>

The present invention relates to a system or kit for bypassing a signal tap. The tap includes a pair of plug ports which are aligned with a pair of contact terminals that connect the conductors to the tap. The system generally comprises a pair of contact plugs adapted to be inserted into the plug ports and a jumper. Each plug includes a hollow body and a plunger. The hollow body is open at a first end and terminates in a head surface, having an aperture therethrough, at a second end. Each plunger is positioned in the hollow body in alignment with the aperture. Each plunger is moveable between a non-contact position and a position where it extends from the open end and is in conductive contact with the terminal contact. The jumper includes at least two pins which are conductively interconnected and adapted to be aligned with the apertures. To allow a signal flowing through the tap to flow through the jumper, the pins are inserted into the apertures and move the plungers to the contact positions.

The preferred embodiment will be described with reference to drawing figures where the numerals represent like elements throughout.

As shown in <b>Figures 6-9</b>, the present bypass system generally comprises a contact plug <b>120</b> and a modified jumper <b>160</b>. The preferred bypass system <b>100</b> allows the tap <b>15</b> to be bypassed without removing the plugs <b>120</b>. The contacting plugs <b>120</b>, in conjunction with the modified jumper <b>160</b>, reduce the potential risk of environmental contamination in the tap <b>15</b> during bypassing. The preferred contact plug <b>120</b> is shown in <b>Figure 6</b>. The contact plug <b>120</b> includes a hollow bolt body <b>122</b>. The hollow body <b>122</b> has a configuration similar to prior art plugs <b>28</b> and generally comprises a threaded portion <b>124</b>, a washer portion <b>126</b> and a head <b>128</b>. The threaded portion <b>124</b> is configured to be threaded into the tap plug ports <b>27</b>. A washer <b>130</b> is positioned over the threaded portion <b>124</b> and provides an environmental barrier between the plug port <b>27</b> and the washer <b>126</b>. The head <b>128</b> has the same general configuration as a standard bolt with the exception of an aperture <b>132</b> extending through the terminal surface <b>131</b> of the head <b>128</b>. The aperture <b>132</b> is preferably centered in the terminal surface <b>131</b> (see <b>Figure 7</b>).

A gland <b>134</b> is provided on the inside of the terminal surface <b>131</b> to completely seal off the aperture <b>132</b>. The gland <b>134</b> will be punctured upon penetration of a jumper pin as will be described hereinafter. Alternatively, the gland <b>134</b> may be provided with an initial passage (not shown) to allow penetration. A plunger <b>140</b> is positioned in the hollow body <b>122</b>, preferably coaxial with the aperture <b>132</b>. The plunger <b>140</b> includes a main shaft <b>142</b> which is preferably slightly greater in length than the hollow body <b>122</b>. The main shaft <b>142</b> terminates at one end in a collar <b>144</b> and at the other end in a configured tip <b>146</b>. The shaft <b>142</b> extends through an aperture in a retaining collar <b>136</b> positioned in the bolt head <b>128</b> adjacent to the washer <b>126</b>. The retaining collar <b>136</b> is preferably made from a nonconductive material and maintains the plunger <b>140</b> in its axial alignment. The retaining collar <b>136</b> also provides a seal between the head <b>128</b> and threaded portion <b>124</b> to prevent contamination from entering the tap <b>15</b> upon insertion of a jumper pin <b>170</b> into the bolt head <b>128</b>.

The plunger is movable between a retracted position where the collar <b>144</b> is adjacent to the gland <b>134</b> and a contact position adjacent the returning collar <b>136</b>. The plunger <b>140</b> is urged toward the retracted position by a spring <b>150</b> positioned between the retaining collar <b>136</b> and the plunger collar <b>144</b>. The plunger collar <b>144</b> includes a detent <b>148</b> for receiving a jumper pin, as will be described hereinafter.

Insulation <b>137, 138</b> is provided about the plunger <b>140</b> in the head <b>128</b> and threaded portion <b>124</b>. The insulation <b>137, 138</b> helps prevent grounding of the plunger <b>140</b> against the internal surfaces of the contact plug <b>120</b>.

The preferred modified jumper <b>160</b> is shown in <b>Figure 8</b>. The jumper <b>160</b> includes an insulated body <b>161</b> with a pair of connection ports <b>162</b> extending therefrom. A pair of partitions <b>166</b> generally close the body <b>161</b> from the open ports <b>162</b>. A conductive jumper pin <b>170</b> extends through each partition <b>166</b> into a respective open port <b>162</b> and preferably terminates prior to the sealing ring <b>164</b>. The pair of jumper pins <b>170</b> are conductively interconnected inside of the jumper body <b>161</b> by conductor means <b>172</b>.

The connection ports <b>162</b> are spaced to align with the plug ports <b>27</b> on the tap <b>15</b>. Each connection port <b>162</b> is sized to extend over a respective plug port <b>27</b> and includes a sealing ring <b>164</b> which contacts the exterior surface of the plug port <b>27</b> as the jumper <b>160</b> is moved into engagement with the tap <b>15</b>. The sealing ring <b>164</b> provides a seal against contamination and also maintains proper alignment of the jumper pin <b>170</b> as it is inserted into the contact plug <b>120</b>. Each pin <b>170</b> is centered in the extension <b>162</b> whereby it is in alignment with the plug aperture <b>132</b> upon engagement with the tap <b>15</b>. Since each pin <b>170</b> is set back in the port <b>162</b> and maintained in alignment by the sealing ring <b>164</b>, the risk of the pin <b>170</b> contacting the surface of the a plug <b>120</b> is reduced.

In operation, the contact plugs <b>120</b> are screwed into the plug ports <b>27</b>. The contact plugs <b>120</b> can be provided to new taps <b>15</b> and can also be placed in existing taps <b>15</b> without disrupting signal flow. Since retrofitting only requires removal of the old plugs <b>28</b> and insertion of the contact plugs <b>120</b>, signal flow is not disturbed during retrofitting of existing taps <b>15</b>. Since each plunger <b>140</b> is maintained in its retracted position, it does not contact the terminal screws <b>46</b> and the signal flow through the tap <b>15</b> is essentially unaffected when plugs <b>120</b> are retrofitted.

When it is necessary to bypass the tap <b>15</b>, the modified jumper connection ports <b>162</b> are aligned with the respective tap plug ports <b>27</b>. The jumper <b>160</b> is then engaged with the tap <b>15</b> with the sealing rings <b>164</b> contacting the plug ports <b>27</b> and maintaining proper alignment during engagement. As the jumper <b>160</b> engages the tap <b>15</b>, each jumper pin <b>170</b> penetrates the gland <b>134</b> and mates with a respective plunger detent <b>148</b>. In the preferred embodiment, the jumper pin <b>170</b> punctures the gland <b>134</b> as it penetrates. In the alternate embodiment described above, the jumper pin <b>170</b> penetrates through the small passage provided in the gland <b>134</b>.

As shown in <b>Figure 9</b>, each jumper pin <b>170</b> pushes a respective plunger <b>140</b> towards its contact position. As it moves toward the contact position, the plunger tip <b>146</b> extends beyond the plug <b>120</b> and contacts the terminal screw <b>46</b>. The signal is then able to flow from the incoming conductor <b>52</b> through the terminal screw <b>46</b>, through the plunger <b>140</b>, and through the jumper <b>160</b> to the other terminal screw and the outgoing conductor <b>53</b> (not shown). The tap cover <b>10</b> can be removed without interrupting downstream signal flows.

Once the tap cover <b>10</b> is replaced, the jumper <b>160</b> can be removed. In the preferred gland <b>134</b> embodiment, the jumper pin <b>170</b> leaves a small hole in the gland <b>134</b> and in the alternate embodiment, the pin <b>170</b> exits the provided passage. In any event, the gland <b>134</b> is preferably made from a resilient material such that the gland is substantially closed upon removal of the jumper pin <b>170</b>.

An LED indicator <b>180</b>, internally connected to the conductor means <b>172</b>, may be provided on the jumper <b>160</b> to indicate when the signal is properly flowing through the jumper <b>160</b>. Additionally, the LED indicator <b>180</b> may also be configured to provide a voltage reading upon activation of button <b>182</b>. This allows the jumper <b>160</b> to not only be used as a bypass, but also as a trouble shooting tool.

While it is preferred to use the modified jumper <b>160</b> to provide an efficient, safer bypass, it will be understood that any jumper can be inserted into the contact plugs <b>120</b> to bypass the tap <b>15</b>.

The present invention can also be used with taps <b>15</b> that utilize retaining terminal housings <b>240</b> similar to that shown in <b>Figure 10</b>. The retaining terminal housings <b>240</b> are similar to the above described terminal housings, but instead of using a terminal screw, the terminal contact <b>242</b> is in contact with retaining clasps <b>90</b> that maintain the conductors <b>52, 53</b> in position. The retaining clasps <b>90</b> are preferably formed by opposed collets <b>91</b> which include a plurality of receiving arms <b>92</b> which extend outwardly from central openings <b>96</b>. The collets <b>91</b> are constructed of a flexible, electrically conductive material. The ends of arms <b>92</b> are molded into generally semi-circular shaped portions <b>93</b>. The arms <b>92</b> are angled outward and away from the central openings <b>96</b>. When the terminal housing <b>40</b> is riveted together, the arms <b>92</b> of the collets <b>90</b> are compressed by the inner walls of the housing cover to form expandable couplers <b>94, 95</b>. The couplers <b>94</b> are generally aligned for receiving input and output conductors <b>52, 53</b> and the couplers <b>95</b> are aligned with the tap plug ports <b>27</b>. Upon insertion of the signal-input and output conductors <b>52</b>, <b>53</b>, the couplers <b>94</b> are forced slightly apart as the arms <b>92</b> of the collets <b>90</b> separate to accommodate the conductors. The couplers <b>94</b> clamp the conductors to limit movement and provide a secure signal contact. When the jumper <b>160</b> is connected, the plungers <b>140</b> are moved into contact with the couplers <b>95</b> to bypass the tap <b>15</b>.

While the present invention has been described in terms of the preferred embodiment, other variations which are within the scope of the invention as defined in the claims will be apparent to those skilled in the art.