1. Sealing arrangement for internal tubesheet for tubular heat exchangers comprising,
a gasket fitted between shoulder and tubesheet, the gasket being made of spiral wound construction but without any metallic rings in the same and without any locating groove in the adjoining components;
on the outer side of the tubesheet, channel box being provided with its inner face resting on the shoulder provided on outer diameter of the tubesheet while the outer face of the channel box being reduced in diameter and arranged to align with the centerline of the push bolts; the outer face of the channel box resting against and attached to annular ring and push bolts being provided in the threaded holes that reach up to the outer face of the internal flange;
the push bolts when tightened loading the annular ring from its outer side in turn loading the gasketed joint through channel box and tubesheet; the reaction to this load in outward direction being taken by the split shear ring essentially by the action of shear stress and not bending stress; gussets being provided between channel box wall and the annular ring such that tightening of the set of push bolts load the annular ring through internal compression ring, diaphragm and internal sleeve and the load on annular ring is transmitted to channel box through the gussets and ultimately to the tubesheet to load the gasket; for small length (i.e. about 25 mm to 250 mm) inner diameter of channel provided with reduced clearance to achieve a close running fit with tubesheet followed by a conical portion, further portion being with a normal clearance.
2. Sealing arrangement for internal tubesheet for tubular heat exchangers as claimed in claim 1 wherein the gasket is of resilient characteristics such as spiral wound type without metallic ring, hollow metallic O ring type, hollow metallic C ring or the like.
3. Sealing arrangement for internal tubesheet for tubular heat exchangers as claimed in claim 1 wherein, the portion of the channel box, between the two end faces can assume any shape; conical shape being preferred for ease of manufacturing.
4. (canceled)
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A lead wire system for use with an active implantable medical device, the lead wire system comprising:
a) an implantable lead comprising at least one lead wire having a length extending to and meeting with a proximal lead end and a distal lead end;
b) a tank filter as a permanently passive circuit comprising a coiled conductor having parasitic capacitance between adjacent turns of the coiled conductor to provide a self-resonant inductor, wherein the tank filter is electrically connected in series with the lead wire somewhere along the length thereof;
c) wherein the inductor has an inductance and an inductor series resistance (RL) such that at frequencies of about 10 Hz to about 1 kHz an inductor reactance and the inductor series resistance permit passage of biological signals, and the parasitic capacitance has a capacitor series resistance (RC) such that at the frequencies of about 10 Hz to about 1 kHz a capacitor reactance and the capacitor series resistance substantially act as an open circuit to the same biological signals that the inductor permits to pass; and
d) wherein the inductor series resistance and the capacitor series resistance result in the tank filter having a Q wherein the resultant 3 db bandwidth is on the order of megahertz.
2. The lead wire system of claim 1 wherein an equivalent electrical circuit model of the tank filter results in an inductor in parallel with a capacitor.
3. The lead wire system of claim 1 wherein values of inductance and capacitance result in the tank filter having a resonant center frequency that is an MRI pulsed frequency.
4. The lead wire system of claim 1 wherein the frequency of the MRI RF pulse is substantially centered at either 64 MHz or 128 MHz.
5. The lead wire system of claim 1 wherein the 3 db bandwidth is permanently active across a plurality of MRI pulse frequencies.
6. The lead wire system of claim 1 wherein the tank filter circuit is disposed at or proximate to the distal end of the lead wire.
7. The lead wire system of claim 1 wherein the tank filter is integrated into an electrode.
8. The lead wire system of claim 6 wherein the electrode is selected from the group consisting of a TIP, a RING, and a PAD electrode.
9. The lead wire system of claim 1 wherein the inductance ranges from 1 and 100 nanohenries.
10. The lead wire system of claim 1 wherein the inductor comprises an air wound inductor.
11. The lead wire system of claim 1 wherein the parasitic capacitance ranges from 100 and 10,000 picofarads.
12. The lead wire system of claim 1 wherein the lead wire has a spiral wire structure.
13. The lead wire system of claim 1 wherein the lead wire has a bifilar wire structure.
14. The lead wire system of claim 1 being biocompatible.
15. The lead wire system of claim 1 wherein the tank filter has an insertion loss extending from and to points defining the 3 db bandwidth of greater than at least 10 db.
16. The lead wire system of claim 1 wherein the inductor does not comprise a ferritic material or a material with a magnetic dipole.
17. The lead wire system of claim 1 wherein the inductor is comprised of at least two series discrete inductors.
18. The lead wire system of claim 1 wherein the parasitic capacitance is the sum of the turn-to-turn parasitic capacitance between adjacent turns of the coiled conductor.
19. The lead wire system of claim 1 wherein the parasitic capacitance ranges from a few tens of picofarads to 10,000 picofarads.
20. A lead wire system for use with an active implantable medical device, the lead wire system comprising:
a) an implantable lead comprising at least one lead wire having a length extending to and meeting with a proximal lead end and a distal lead end;
b) a tank filter as a permanently passive circuit comprising a coiled conductor having parasitic capacitance between adjacent turns of the coiled conductor to provide a self-resonant inductor, wherein the tank filter is electrically connected in series with the lead wire somewhere along the length thereof;
c) wherein the inductor has an inductance and an inductor series resistance (RL) such that at frequencies of about 10 Hz to about 1 kHz an inductor reactance and the inductor series resistance permit passage of biological signals, and the parasitic capacitance has a capacitor series resistance (RC) such that at the frequencies of about 10 Hz to about 1 kHz a capacitor reactance and the capacitor series resistance substantially act as an open circuit to the same biological signals that the inductor permits to pass; and
d) wherein an equivalent electrical circuit model of the tank filter results in an inductor in parallel with a capacitor having a Q wherein the resultant 3 db bandwidth is on the order of megahertz.
21. An active implantable medical device lead wire system, which comprises:
a) an implantable lead comprising at least one lead wire having a length extending to and meeting with a proximal lead end and a distal lead end;
b) a tank filter as a permanently passive circuit comprising a coiled conductor having parasitic capacitance between adjacent turns of the coiled conductor to provide a self-resonant inductor, wherein the tank filter is electrically connected in series with the lead wire somewhere along the length thereof;
c) wherein the inductor has an inductance and an inductor series resistance (RL) such that at low frequencies of about 10 Hz to about 1 kHz an inductor reactance and the inductor series resistance permit passage of biological signals, and the parasitic capacitance has a capacitor series resistance (RC) such that at the low frequencies of about 10 Hz to about 1 kHz a capacitor reactance and the capacitor series resistance substantially act as an open circuit to the same biological signals that the inductor segment permits to pass;
d) wherein the inductor series resistance and the capacitor series resistance result in the tank filter having a Q wherein the resultant 3 db bandwidth is on the order of megahertz; and
e) wherein the tank filter is electrically conductively connected between the distal end of the lead wire and an electrode, or is electrically conductively connected to the proximal end of the lead wire and electrically connectable to an external portion of a terminal pin of a hermetic seal.
22. A lead wire system for use with an active implantable medical device, the lead wire system comprising:
a) an implantable lead comprising at least one lead wire having a length extending to and meeting with a proximal lead end and a distal lead end;
b) a tank filter as a permanently passive circuit comprising a coiled conductor having parasitic capacitance between adjacent turns of the coiled conductor to provide a self-resonant inductor, wherein the tank filter is electrically connected in series with the lead wire somewhere along the length thereof;
c) wherein the inductor has an inductance and an inductor series resistance (RL) such that at low frequencies of about 10 Hz to about 1 kHz an inductor reactance and the inductor series resistance permit passage of biological signals, and the capacitor has a capacitance and a capacitor series resistance (RC) such that at the low frequencies of about 10 Hz to about 1 kHz a capacitor reactance and the capacitor series resistance substantially act as an open circuit to the same biological signals that the inductor permits to pass; and
d) wherein the inductor series resistance and the capacitor series resistance result in the tank filter being tuned to a resonant center frequency and having a 3 db bandwidth in the megahertz frequency range.
23. The lead wire system of claim 22 wherein the resonant center frequency is an MRI pulsed RF frequency.