WO1998031079A1

WO1998031079A1 - Non-interrupt bypass switch for rf circuits

Info

Publication number: WO1998031079A1
Application number: PCT/US1998/000161
Authority: WO
Inventors: Stephen Charles Hancock; Arthur Sherman Morris, Iii; Daniel Barton Johnson; Steven Bryan O'steen; Andrew Davis Webb
Original assignee: Raychem Corporation
Priority date: 1997-01-10
Filing date: 1998-01-08
Publication date: 1998-07-16
Also published as: AU5732498A; TW379344B; AR011365A1; CO4810276A1

Abstract

A non-interrupt bypass switch for rf circuits has a pair of switch contacts (25) which are electrically connected to a pair of terminals (20). The terminals (20) are electrically engageable (21) by an auxiliary circuit component (16), which causes pushers (35) to disengage a switch blade (30) from the switch contacts (25). Pushers (35) engage the blade (30) inwardly from the blade ends (37) to deflect the blade ends with a leveraged deflection substantially greater than the corresponding movement of the pushers (35).

Description

NON-INTERRUPT BYPASS SWITCH FOR RF CIRCUITS

Background of the Invention

The present invention relates to a bypass switch for use in radio frequency (rf) circuit applications. More particularly, it relates to a switch for maintaining signal continuity in a signal tap, such as commonly used for example in CATV networks, when the tap face plate is removed for modifying the circuitry within the tap. This can be particularly important when the affected circuit is in service but the tap needs to be accessed for modification (e.g., upgrading internal features). In such a situation there should be no discontinuation of downstream service, and no interference with the downstream signal (e.g., no change in the impedance of the tap as seen by the CATV system) , and it should not require extra time for the installer/servicer to open and access the tap.

The prior art, for example as shown in U.S. Patent No. 3,895,318 (Ross, issued July 15, 1975), discloses a CATV distribution box with a bypass switch which bridges an rf blocking inductor when a tap plate is removed, and which is actuated by reinsertion of the tap plate to open the bridging or bypass switch. The actuating motions are co-linear and coupled such that movement of the tap plate into position causes an approximately equal movement of the contacts to open the bypass switch.

However, as increasing demands are placed on circuits and systems, especially in the CATV network environment, it is increasingly necessary to maintain continuous operation of the circuit in a manner which is essentially transparent or invisible both upstream and downstream. In particular, this means that the impedance of the circuit (for example, 75Ω) is maintained continuously, with at most but a momentary spike during insertion or removal of the auxiliary circuit (for example, as may be carried on such a tap plate) . Thus the switch should toggle quickly, efficiently, and simply between circuit impedance and essentially infinite impedance. At the same time, due to the very large volume of distribution boxes employed by the CATV industry, it is very important that the design and manufacturing cost of such a bypass switch be as uncomplicated and economical as possible.

Summary of the Invention Briefly, the present invention meets the above needs and purposes with a new and improved method and apparatus for maintaining circuit continuity upon removal of an auxiliary circuit component.

In the preferred embodiment, a bypass switch is disclosed which is particularly adapted for use in radio frequency (rf) circuit applications, such as in CATV distribution boxes or taps. Improved CATV tap configurations are now providing for circuit and service upgrades by means of removable and replaceable face plates which carry electrical and electronic capabilities appropriate to the desired upgrade or modification. A non- interrupt switch is necessary in such networks to provide continuous operation upstream and downstream during such service or upgrades, while the face plate has been removed. The switch provides automatic continuity between terminals in the circuitry within the tap when the auxiliary circuit component is thus disconnected from those terminals. Without the switch, the circuit through the component is lost and overall operation of the tap circuitry can be disrupted. The non- interrupt bypass switch of the present invention consists in part of dielectric supports and a symmetrical conducting spring member with contacts at both ends. The switch has two contacts directly at the terminals for the auxiliary component to minimize interference with the rf circuit when the switch is open and the auxiliary component is in the circuit . The switch employs the insertion action of the auxiliary component to actuate the opening of the switch, and the switch and component are designed such that the component makes electrical contact before the switch opens (make-before-break) , providing continuity of signal during the transition and minimizing the momentary slight rf performance degradation. The motion of the switch contacts is in the same direction as the component movement, and through a leveraging configuration provides large enough switch contact spacing at full component insertion to minimize undesirable interaction of the open switch with the rf operation of the auxiliary component .

It is therefore an object of the present invention to provide new and improved methods and apparatus for maintaining circuit continuity upon removal of an auxiliary circuit component, the method and apparatus including a pair of terminals electrically engagable by such an auxiliary circuit component upon movement of the component in a first direction toward the terminals, a pair of switch contacts electrically connected respectively to the pair of terminals, a resilient switch blade positioned and dimensioned for electrically contacting and bridging the pair of contacts and oriented such that deflection of the blade in the first direction will break the contact of the blade with the contacts, and reverse deflection will restore the contact, and pushers interposed between such an auxiliary circuit component and the blade and positioned to contact the blade a substantial distance inwardly from the locations where the blade contacts the contacts, to cause the pushers to deflect the blade locations with a leveraged deflection movement which is substantially greater than the corresponding movement of the pushers; in which the pushers may be mounted on the auxiliary circuit component; in which the terminals, contacts, blade, and pushers may be configured to provide a make- before-break electrical switching action when such an auxiliary circuit component is moved in the first direction into engagement with the pair of terminals and the blade contact with the contacts is then broken; in which the switch blade may be symmetrical about a longitudinal axis thereof; in which the blade and pushers may be configured and dimensioned to yield a 75Ω impedance along the switch blade and contacts during the electrical contacting and bridging, and substantially no contribution to circuit impedance when deflected when such an auxiliary circuit component is fully engaged onto the pair of terminals; in which the blade may be supported such that at least the ends thereof are free to be so deflected; which may include a dielectric block having a channel therein configured and dimensioned for receiving and capturing the blade longitudinally, laterally, and rotationally therein; in which the pair of switch contacts may be positioned on a line opposite the channel in the dielectric block at a predetermined distance therefrom which sufficiently limits vertical movement of the blade with respect to the channel to keep the blade captured in the channel; and to accomplish the above objects and purposes in an inexpensive, uncomplicated, durable, versatile, and reliable method and apparatus, inexpensive to manufacture, and readily suited to the widest possible utilization. These and other objects and advantages of the invention will be apparent from the following description, the accompanying drawings, and the appended claims . Brief Description of the Drawings

Fig. 1 is a sectioned isometric illustration of a CATV tap, with portions omitted for clarity of illustration, which incorporates a non-interrupt switch for rf circuits according to the present invention; Fig. 2 is a view similar to Fig. 1 showing the tap face plate removed from the tap housing, and actuation thereby of the non-interrupt switch;

Fig. 3 is a front sectional view corresponding to Fig. 1; Fig. 4 is a front sectional view corresponding to Fig 2; and

Fig. 5 is an exploded isometric top/front view of the switch blade and blade block, the section of the block in Figs. 1-4 being taken on line 1-1 of Fig. 5.

Description of the Preferred Embodiment

With reference to the drawings, the new and improved non-interrupt switch for rf circuits, and the method therefor according to the present invention, will now be described. Fig. 1 shows a typical prior art CATV tap 10 (portions omitted for clarity of illustration) modified by incorporation therein of the present invention.

More specifically, tap 10 includes a base or housing 14 supporting a face plate 15 thereon. Face plate 15 includes circuitry 16 and a number of associated ports 17 for branching off the signal to provide local service from the main trunk cable connections 18. For this purpose, the main trunk cable connections 18 include terminals 20 (Fig. 2) which are engagable by metallic core terminal couplers 21 carried on the face plate 15 and forming part of the auxiliary circuit component 16 of the face plate. Fig. 4 shows the terminals 20 and terminal couplers 21 disconnected, the face plate and its associated auxiliary circuit component having been removed; Fig. 3 shows them coupled after movement of the face plate 15 in a direction toward the terminals 20.

A pair of switch contacts 25 is electrically connected one each to respective terminals 20, in the preferred embodiment on the opposite side thereof. Facing the switch contacts 25 is a resilient switch blade 30 which is positioned and dimensioned for electrically contacting and bridging the contacts 25. Blade 30, which in the preferred embodiment is symmetrical about its longitudinal axis, is oriented such that deflection of the blade 30 in the same direction by which the face plate 15 is moved into the closed position on housing 14 (illustrated by arrow 32 in Figs. 2 and 4) will break the contact of the switch blade 30 with the switch contacts 25. Similarly, reverse deflection, when the face plate 15 is removed from housing 14, will restore the contact between contacts 25 and blade 30. The movement of the ends of the switch blade toward and away from the switch contacts 25, in conjunction with parallel movement of face plate 15, is accomplished by means of pushers 35 which, in the preferred embodiment, are mounted on the auxiliary circuit component 16 or the face plate 15. The pushers

35 are positioned to contact blade 30 a substantial distance inwardly from the locations where the blade contacts the contacts 25. In this context, "inwardly" means closer to the location where blade 25 is supported and essentially thus immobilized on the housing base 14, thereby providing a leveraged deflection movement of the blade contact locations when moved or deflected by the pushers. This leveraged deflection motion will then be substantially greater than the corresponding movement of the pushers 35 and face plate 15. As illustrated, the ends 37 of the switch blades 30 are the preferred locations where the blade 30 contacts the contacts 25, blade ends 37 being freely moveable therefore in the direction of arrow 32 and opposite thereto. Pushers 35, in turn, contact blade 30 inwardly thereof from ends 37 and much closer to the immobilized center 38 thereof.

The center 38 of switch blade 30 is supported and immobilized by a dielectric block 40 having a channel 43 therein. Channel 43 is configured and dimensioned for receiving and capturing blade 30 longitudinally, laterally, and rotationally, and blade 30 is further held in channel 43 by the switch contacts

25 which are positioned on a line opposite channel 43 at a distance therefrom which limits vertical movement of blade 30 with respect to channel 43 such that it remains captured in the channel (as shown in Figs. 2 and 4) .

Finally, the leveraged or multiplied motion of the blade ends 37 due to the contact inwardly thereof by pushers 35 provides several important design and functional advantages for the present invention.

In particular, the pushers 35 can be sufficiently short that terminals 20 and 21 become fully electrically engaged before pushers 35 start to engage and move the switch blade 30 to open the electrical contact between the blade contacting locations 37 and the switch contacts 25. This make-before-break electrical switching action is very important for maintaining service continuity on the main trunk cable connections 18. Secondly, the leveraged blade motion multiplication, during the final stages of inserting the face plate 15 onto the housing 14, moves the blade ends 37 a significant distance away from the switch contacts 25. The distance is more than adequate to decouple the blade 30 from the active electrical circuitry at that point, within the housing and face plate, so that blade 30 makes substantially no contribution to circuit impedance. Conversely, when the auxiliary circuit component 16 and face plate 15 have been removed, the switch blade 30 is dimensioned and configured, in conjunction with the appropriate sizing of dielectric block 40 and taking into account the proximity of housing 14, which are well known design parameter options, to yield a 75Ω impedance along the switch blade 30 and contacts 25 during the electrical contacting and bridging action thereof.

As may be seen, therefore, the present invention provides numerous advantages. Principally, it provides inexpensive yet highly effective non-interrupt bypass switch operation and capabilities for high performance rf circuits for automatically maintaining circuit continuity during removal and replacement of an auxiliary circuit component. The removal and subsequent insertion of auxiliary circuit components are almost imperceptible both upstream and downstream from the tap itself. The non-interrupt bypass switch changes quickly from a 75Ω impedance continuity to making no contribution to circuit impedance, as appropriate and described. All switch motions are co-linear with the face plate motions, for uncomplicated and economical design, yet switch contact movement is actually enhanced (amplified or leveraged) without mechanical complication, for even further performance enhancement. Also, when the housing 14 is metallic, the blade 30 may be positioned very close to the bottom of the housing, as illustrated in the preferred embodiment, thus reducing the need for significant loading of dielectrics around the switch blade 30 to lower the impedance to 75Ω.

Of course, various modifications to the present invention will occur to those skilled in the art upon reading the present disclosure. For example, isolation of switch blade 30 from the circuit when face plate 15 is fully inserted can be enhanced in metallic housings 14 by causing the switch blade 30 to ground against the housing when deflected by pushers 35.

Also, the pushers 35 could alternatively be carried on the arms of blade 30 facing upwardly toward the face plate 15.

Claim dependencies have been drafted to comply with PCT Rule 6.4, but it will be understood that, at least by virtue of this paragraph, any appropriate combination of the features disclosed and/or claimed herein is in itself an embodiment of the invention, and it is intended to use multiple dependent claims in the national phase where permitted.

Therefore, while the methods and forms of apparatus herein described constitute preferred embodiments of this invention, it is to be understood that the invention is not limited to these precise methods and forms of apparatus, and that changes may be made therein without departing from the scope of the invention.

Claims

THAT WHICH IS CLAIMED IS:

1. A non-interrupt bypass switch for rf circuits for automatically maintaining circuit continuity upon removal of an auxiliary circuit component, comprising: a) a pair of terminals electrically engagable by such an auxiliary circuit component upon movement of the component in a first direction toward said terminals, b) a pair of switch contacts electrically connected respectively to said pair of terminals, c) a resilient switch blade positioned and dimensioned for electrically contacting and bridging said pair of contacts and oriented such that deflection of said blade in said first direction will break the contact of said blade with said contacts, and reverse deflection will restore said contact, and d) pushers interposed between such an auxiliary circuit component and said blade and positioned to contact said blade a substantial distance inwardly from the locations where said blade contacts said contacts, to cause said pushers to deflect said blade locations with a leveraged deflection movement which is substantially greater than the corresponding movement of said pushers.

2. The non-interrupt bypass switch of claim 1 wherein said pushers are mounted on the auxiliary circuit component.

3. The non-interrupt bypass switch of claim 1 wherein said terminals, contacts, blade, and pushers are configured to provide a make-before-break electrical switching action when such an auxiliary circuit component is moved in said first direction into engagement with said pair of terminals and said blade contact with said contacts is then broken.

4. The non-interrupt bypass switch of claim 1 wherein said switch blade is symmetrical about a longitudinal axis thereof .

5. The non-interrupt bypass switch of claim 1 wherein said blade and pushers are configured and dimensioned to yield a 75╬⌐ impedance along said switch blade and contacts during said electrical contacting and bridging, and substantially no contribution to circuit impedance when deflected when such an auxiliary circuit component is fully engaged onto said pair of terminals.

6. The non-interrupt bypass switch of claim 1 wherein said blade is supported such that at least the ends thereof are free to be so deflected.

7. The non-interrupt bypass switch of claim 1 further comprising a dielectric block having a channel therein configured and dimensioned for receiving and capturing said blade longitudinally, laterally, and rotationally therein.

8. The non-interrupt bypass switch of claim 7 wherein said pair of switch contacts is positioned on a line opposite said channel in said dielectric block at a predetermined distance therefrom which sufficiently limits vertical movement of said blade with respect to said channel to keep said blade captured in said channel .

9. A non-interrupt bypass switch for rf circuits for automatically maintaining circuit continuity upon removal of an auxiliary circuit component, comprising: a) a pair of terminals electrically engagable by such an auxiliary circuit component upon movement of the component in a first direction toward said terminals, b) a pair of switch contacts directly at and electrically connected respectively to said pair of terminals , c) a resilient switch blade positioned and dimensioned for electrically contacting and bridging said pair of contacts and oriented such that deflection of said blade in said first direction will break the contact of said blade with said contacts, and reverse deflection will restore said contact, said switch blade being symmetrical about a longitudinal axis thereof, d) pushers mounted on such an auxiliary circuit component and interposed between it and said blade and positioned to contact said blade a substantial distance inwardly from the locations where said blade contacts said contacts, to cause said pushers to deflect said blade locations with a leveraged deflection movement which is substantially greater than the corresponding movement of said pushers, e) a dielectric block having a channel therein configured and dimensioned for receiving and capturing said blade longitudinally, laterally, and rotationally therein, and supporting said blade centrally thereof such that at least the ends thereof are free to be so deflected, and said pair of switch contacts being positioned on a line opposite said channel at a predetermined distance therefrom which sufficiently limits vertical movement of said blade with respect to said channel to keep said blade captured in said channel, f) said terminals, contacts, blade, and pushers being configured to provide a make-before-break electrical switching action when such an auxiliary circuit component is moved in said first direction into engagement with said pair of terminals and said blade contact with said contacts is then broken, and g) said blade and pushers being configured and dimensioned to yield a 75╬⌐ impedance along said switch blade and contacts during said electrical contacting and bridging, and substantially no contribution to circuit impedance when deflected when such an auxiliary circuit component is fully engaged onto said pair of terminals.

10. A non-interrupt bypass method for rf circuits for automatically maintaining circuit continuity upon removal of an auxiliary circuit component, comprising: a) moving such an auxiliary circuit component in a first direction toward a pair of terminals to engage the terminals electrically, b) with a resilient switch blade, electrically contacting and bridging a pair of switch contacts which are electrically connected respectively to the pair of terminals, the pair of contacts being oriented such that deflection of the blade in the first direction will break the contact of the blade with the contacts, and reverse deflection will restore the contact, and c) with pushers interposed between such an auxiliary circuit component and the blade and positioned to contact the blade a substantial distance inwardly from the locations where the blade contacts the contacts, deflecting the blade locations with a leveraged deflection movement which is substantially greater than the corresponding movement of the pushers.

11. The non-interrupt bypass method of claim 10 wherein the pushers are mounted on the auxiliary circuit component.

12. The non-interrupt bypass method of claim 10 wherein the terminals, contacts, blade, and pushers are configured to provide a make-before-break electrical switching action when such an auxiliary circuit component is moved in the first direction into engagement with the pair of terminals and the blade contact with the contacts is then broken.

13. The non-interrupt bypass method of claim 10 wherein the switch blade is symmetrical about a longitudinal axis thereof.

14. The non-interrupt bypass method of claim 10 wherein the blade and pushers are configured and dimensioned to yield a 75╬⌐ impedance along the switch blade and contacts during the electrical contacting and bridging, and substantially no contribution to circuit impedance when deflected when such an auxiliary circuit component is fully engaged onto the pair of terminals.

15. The non-interrupt bypass method of claim 10 further comprising supporting the blade such that at least the ends thereof are free to be so deflected.

16. The non-interrupt bypass method of claim 10 further comprising receiving and capturing the blade longitudinally, laterally, and rotationally in a dielectric block having a channel therein configured and dimensioned therefor.

17. The non-interrupt bypass method of claim 16 further comprising, by means of the pair of switch contacts, sufficiently limiting vertical movement of the blade with respect to the channel to keep the blade captured in the channel.

18. A non-interrupt bypass method for rf circuits for automatically maintaining circuit continuity upon removal of an auxiliary circuit component, comprising: a) moving such an auxiliary circuit component in a first direction toward a pair of terminals to engage the terminals electrically, b) with a resilient switch blade, electrically contacting and bridging a pair of switch contacts which are directly at and electrically connected respectively to the pair of terminals, the pair of contacts being oriented such that deflection of the blade in the first direction will break the contact of the blade with the contacts, and reverse deflection will restore the contact, the switch blade being symmetrical about a longitudinal axis thereof, c) with pushers mounted on such an auxiliary circuit component and positioned to contact the blade a substantial distance inwardly from the locations where the blade contacts the contacts, deflecting the blade locations with a leveraged deflection movement which is substantially greater than the corresponding movement of the pushers, d) receiving and capturing the blade longitudinally, laterally, and rotationally in a dielectric block having a channel therein configured and dimensioned therefor, e) with the pair of switch contacts, sufficiently limiting vertical movement of the blade with respect to the channel to keep the blade captured in the channel, f) supporting the blade centrally thereof such that at least the ends thereof are free to be so deflected, g) configuring the terminals, contacts, blade, and pushers to provide a make-before-break electrical switching action when such an auxiliary circuit component is moved in the first direction into engagement with the pair of terminals and the blade contact with the contacts is then broken, and h) configuring and dimensioning the blade and pushers to yield a 75╬⌐ impedance along the switch blade and contacts during the electrical contacting and bridging, and substantially no contribution to circuit impedance when deflected when such an auxiliary circuit component is fully engaged onto the pair of terminals.