WO2026020007A1

WO2026020007A1 - Pyrofuse assemblies with pyrotechnically driven disconnection system

Info

Publication number: WO2026020007A1
Application number: PCT/US2025/038056
Authority: WO
Inventors: Robert A. F. Zwijze; Werner John Peter Kleissen
Original assignee: Sensata Technologies Inc
Current assignee: Sensata Technologies Inc
Priority date: 2024-07-17
Filing date: 2025-07-17
Publication date: 2026-01-22
Anticipated expiration: 2027-01-17

Abstract

Embodiments of the present disclosure describe fuse assemblies incorporating an improved pyrotechnically driven disconnection system. Each fuse assembly includes a housing that defines an axial bore, one or more conductive paths configured for coupling to external bus bars, and a pyrotechnic charge operable to initiate a mechanical disconnection sequence. Upon detection of an overcurrent or fault condition, the pyrotechnic charge actuates one or more movable elements—such as a piston, ignition slider, or bullet—disposed within the bore. These elements are configured to interrupt electrical continuity between conductor segments by displacing or destroying intermediate conductive structures, such as break tabs or detachable conductors. The disclosed assemblies are further configured to support interruption of multiple current paths within a compact footprint and may incorporate arc-suppressing features, including sealed bores, dielectric barriers, and coaxial alignment of moving components, to ensure rapid and reliable galvanic isolation.

Description

PYROFUSE ASSEMBLIES WITH PYROTECHNICALLY DRIVEN DISCONNECTION SYSTEM

BACKGROUND

[0001] Electrical systems — particularly those operating at high voltage or high current — commonly incorporate overcurrent protection devices to prevent damage caused by short circuits, sustained overloads, or electrical faults. Such protection mechanisms are essential to ensure system reliability, protect downstream components, and mitigate safety risks including thermal damage and electrical fires.

[0002] Fuses are a widely used form of overcurrent protection. In general, a fuse operates by interrupting the flow of current through a conductor when the current exceeds a defined threshold, typically through melting or mechanical separation of a conductive element. The disconnection is usually irreversible, requiring replacement or service to restore continuity. [0003] Various types of fuses have been developed to meet the increasing demands of modem electrical systems, particularly in applications such as electric vehicles (EVs), aerospace platforms, and high-power industrial equipment. These include electromechanical fuses and fuses incorporating pyrotechnic charges, which enable faster response times and more reliable disconnection under extreme fault conditions. Despite these advances, challenges remain in achieving compact, high-speed, multi-path disconnection while minimizing arcing, thermal propagation, and installation complexity.

SUMMARY

[0004] The following summary is meant to help one skilled in the art understand the various presently disclosed combinations of features. It is not meant to unduly limit the scope of any pending or future claims relating to the disclosure.

[0005] Embodiments of the present disclosure describe fuse assemblies incorporating an improved pyrotechnically driven disconnection system. Each fuse assembly includes a housing that defines an axial bore, one or more conductive paths configured for coupling to external bus bars, and a pyrotechnic charge operable to initiate a mechanical disconnection sequence. Upon detection of an overcurrent or fault condition, the pyrotechnic charge actuates one or more movable elements — such as a piston, ignition slider, or bullet — disposed within the bore. These elements are configured to interrupt electrical continuity between conductor segments by displacing or destroying intermediate conductive structures, such as break tabs or detachable conductors. The disclosed assemblies are further configured to support interruption of multiple current paths within a compact footprint and may incorporate arc-suppressing features, including sealed bores, dielectric barriers, and coaxial alignment of moving components, to ensure rapid and reliable galvanic isolation.

[0006] In an embodiment, a fuse assembly includes a fuse pipe having a first section and a second section. The fuse pipe is operable to cany⁷ current from a first bus bar to a second bus bar. In this embodiment, a pyrotechnic is disposed within the first section of the fuse pipe and a piston is disposed adjacent to the pyrotechnic within the first section of the fuse pipe. The assembly also includes a bullet disposed adjacent to the piston and between the first section and the second section of the fuse pipe. In this embodiment, a slider is disposed adjacent to the bullet and within the second section of the fuse pipe. The piston is operable to move in response to ignition of the pyrotechnic. Movement of the piston actuates the bullet to break a first break tab and a second break tab connecting the first section and the second section.

[0007] In another embodiment, a fuse assembly is disclosed that includes a housing having axially aligned segments. The fuse assembly also includes a first conductive bracket, a second conductive bracket, a third conductive bracket, and a fourth conductive bracket, each positioned between successive segments of the housing. In this embodiment, the fuse assembly includes a first bullet and a second bullet respectively disposed in different segments of the housing. The fuse assembly also includes a pyrotechnic charge configured, when activated, to drive each bullet axially so as to interrupt electrical continuity between a corresponding pair of the conductive brackets.

[0008] In another embodiment, a fuse assembly is disclosed that includes a housing that includes a plurality of shells joined end-to-end to define a common axial bore. The fuse assembly also includes an ignition slider positioned in the bore adjacent to a pyrotechnic charge within a first shell of the plurality of shells. In this embodiment, the fuse assembly also includes a first detachable conductor positioned in the bore and coupled to a first pair of conductors. The fuse assembly also includes a bullet having a first end and a second end, the first end of the bullet positioned in the bore adjacent to the first detachable conductor. The fuse assembly also includes a second detachable conductor coupled to a second pair of conductors. The second detachable conductor is positioned in the bore adjacent to the second end of the bullet. In this embodiment, activation of the pyrotechnic charge propels the ignition slider to sever the first detachable conductor from the first pair of conductors and drives the bullet to sever the second detachable conductor from the second pair of conductors, thereby interrupting electrical continuity across both the first pair of conductors and the second pair of conductors. [0009] The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular descriptions of exemplary embodiments of the invention as illustrated in the accompanying drawings wherein like reference numbers generally represent like parts of exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] One or more aspects of the present disclosure are discussed below with reference to the accompanying Figures. It will be appreciated that for simplicity and clarity of illustration, elements shown in the drawings have not necessarily been drawn accurately or to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity or several physical components may be included in one functional block or element. Further, where considered appropriate, reference numerals may be repeated among the drawings to indicate corresponding or analogous elements. For purposes of clarity, however, not every' component may be labeled in every drawing. The Figures are provided for the purposes of illustration and explanation and are not intended to be limiting. In the Figures:

[0011] FIG. 1 A is an example of a conventional fuse assembly of a known design. [0012] FIG. IB is a cross-section view of the fuse assembly of FIG. 1A.

[0013] FIG. 2A is an example fuse assembly with an improved pyrotechnically driven disconnection system in accordance with at least one embodiment of the present disclosure. [0014] FIG. 2B is a cross-section view of the fuse assembly of FIG. 2A.

[0015] FIG. 3 A illustrates a simulation showing temperature of the fuse assembly of FIG. 2A with example parameters in accordance with at least one embodiment of the present disclosure.

[0016] FIG. 3B illustrates a simulation showing current density of the fuse assembly of FIG. 2A with example parameters in accordance with at least one embodiment of the present disclosure.

[0017] FIG. 3C illustrates a simulation show ing voltage of the fuse assembly of FIG. 2A w ith example parameters in accordance with at least one embodiment of the present disclosure. [0018] FIG. 4 illustrates graphs showing changes in temperature, current density, and voltage over time in the fuse assembly of FIG. 2A with example parameters in accordance with at least one embodiment of the present disclosure.

[0019] FIG. 5 is a flow chart of an example method of operating a fuse assembly with a pyrotechnically’ driven disconnection system in accordance with at least one embodiment of the present disclosure. [0020] FIG. 6A is an isometric view of another example fuse assembly with a pyrotechnically driven disconnection system in accordance with at least one embodiment of the present disclosure.

[0021] FIG. 6B is a cross-section view of the fuse assembly of FIG. 6A in the non-triggered state.

[0022] FIG. 6C is a cross-section view of the fuse assembly of FIG. 6A in the triggered state.

[0023] FIG. 6D is an isometric view of a portion of the fuse assembly of FIG. 6A mounted on a thermal mat.

[0024] FIG. 6E is an isometric view of an ignition slider of the fuse assembly of FIG. 6A.

[0025] FIG. 6F is an isometric view of a bullet of the fuse assembly of FIG. 6A.

[0026] FIG. 6G is an isometric view of a non-conductive sleeve of the fuse assembly of FIG. 6A.

[0027] FIG. 6H is an isometric view of a housing segment of the fuse assembly of FIG. 6A.

[0028] FIG. 61 is an isometric view of a housing segment coupled to pair of conductive brackets of the fuse assembly of FIG. 6A.

[0029] FIG. 7 is a graph of the force and energy verses displacement for a known design of a pyrofuse and the fuse assembly of FIG. 6A.

[0030] FIG. 8A is an isometric view of another example fuse assembly with a pyrotechnically driven disconnection system in accordance with at least one embodiment of the present disclosure.

[0031] FIG. 8B is a bottom view of the fuse assembly of FIG. 8 A.

[0032] FIG. 8C is a cross-section view of the fuse assembly of FIG. 8A in the non-triggered state.

[0033] FIG. 8D is another cross-section view of the fuse assembly of FIG. 8A in the nontriggered state.

[0034] FIG. 8E is a cross-section view of the fuse assembly of FIG. 8 A in the triggered state.

[0035] FIG. 8F is an isometric view of a first detachable conductor coupled to a first pair of conductors of the fuse assembly of FIG. 8A.

[0036] FIG. 8G is an isometric view of the first housing shell of the fuse assembly of FIG.

8A.

[0037] FIG. 8H is an isometric view of the first housing shell of the fuse assembly of FIG.

8A coupled with the first pair of conductors.

[0038] FIG. 81 is an isometric view of a bullet of the fuse assembly of FIG. 8 A.

[0039] FIG. 8J is an isometric view of an ignition slider of the fuse assembly of FIG. 8A. DETAILED DESCRIPTION

[0040] The terminology used herein for the purpose of describing particular examples is not intended to be limiting for further examples. Whenever a singular form such as “a”, "an" and “the” is used and using only a single element is neither explicitly or implicitly defined as being mandatory, further examples may also use plural elements to implement the same functionality. Likewise, when a functionality is subsequently described as being implemented using multiple elements, further examples may implement the same functionality using a single element or processing entity. It will be further understood that the terms “comprises”, “comprising”, “includes” and/or “including”, when used, specify⁷ the presence of the stated features, integers, steps, operations, processes, acts, elements and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, processes, acts, elements, components and/or any group thereof. [0041] It will be understood that when an element is referred to as being “connected” or “coupled” to another element, the elements may be directly connected or coupled via one or more intervening elements. If two elements A and B are combined using an “or”, this is to be understood to disclose all possible combinations, i.e. only A, only B. as well as A and B. An alternative wording for the same combinations is “at least one of A and B”. The same applies for combinations of more than two elements.

[0042] Accordingly, while further examples are capable of various modifications and alternative forms, some particular examples thereof are shown in the figures and will subsequently be described in detail. However, this detailed description does not limit further examples to the particular forms described. Further examples may cover all modifications, equivalents, and alternatives falling within the scope of the disclosure. Like numbers refer to like or similar elements throughout the description of the figures, which may be implemented identically or in modified form when compared to one another while providing for the same or a similar functionality.

[0043] Described herein are various embodiments of fuse assemblies that incorporate components — individually or in combination — that are formed integrally or arranged to improve operational performance, reliability, and safety. The disclosed fuse assemblies include structural and functional innovations that enhance disconnection dynamics and thermal management while supporting higher power applications. In certain embodiments, the fuse assemblies are integrated into electrical switching devices such as contactors, and may be deployed in a wide range of electrical systems requiring rapid and reliable fault interruption. [0044] In electric vehicles, particularly in heavy-duty platforms, system voltages and continuous currents are increasing to enable extended range and faster charging. These elevated power levels create the need for fuses capable of carrying significantly higher current without overheating, while also safely interrupting high short-circuit currents. Conventional pyrotechnic fuses (or “pyrofuses”) are often limited to approximately 500 A of continuous current and breaking capacities around 850 V and 16 kA. To meet the evolving requirements of high-power electric vehicle applications, it is desirable to achieve currentcarrying capability up to 3000 A and interrupt ratings of 850 V and 40 kA — specifications beyond the capabilities of standard pyrofuse designs.

[0045] To compensate for these limitations, existing systems often implement multiple fuses in parallel within the vehicle's charge or power distribution enclosure. However, this approach increases both component and system costs by requiring a larger housing, additional bus bars and wiring, and more complex assembly. Moreover, parallel fuse configurations introduce significant reliability concerns. In worst-case scenarios, the fuses may not actuate simultaneously, resulting in one fuse bearing the entire fault energy. This mismatch can cause rupture of the fuse housing or even explosion of the full system enclosure, creating a severe safety hazard. Accordingly, there is a need for an improved fuse architecture that enables higher current handling and coordinated high-power disconnection without relying on parallel fuse elements.

[0046] Turning to FIGs. 1 A and IB. a current pyrofuse design assembly 100 is shown with the following characteristics: a flat bus bar design; difficulty in connecting a cooling plate due to the position of the copper bar; 500 A and break short circuit currents of around 850 V/ 1 kA; and no full separation of the arc causing a longer short circuit due to ionized air. [0047] Embodiments in accordance with the present disclosure provide a fuse assembly featuring a pipe-shaped bus bar design capable of carrying 3000 A continuously and interrupting fault currents up to 850 V / 40 kA. The design enables complete separation of the positive pole from the piston-side circuitry following activation of the pyrotechnic charge. As the separation eliminates the presence of ionized air in the disconnection region, arcing is either prevented entirely or substantially minimized, allowing the high breaking capacity to be achieved through inherent structural features. The assembly further allows simplified integration with a cooling plate, supports a compact form factor in which a single fuse can replace two or more conventional units, and results in reduced fuse and overall system cost.

[0048] For further explanation, FIG. 2 shows an example fusing assembly 200 with an improved pyrotechnically driven disconnection system in accordance with at least one embodiment of the present disclosure. In this fuse design, the core element is a fuse pipe 203 that connects the positive pole 211 and negative 212 pole of the bus bar 210. The fuse pipe 203 is a conductor that carries the cunent. The fuse assembly 200 also includes a bullet 206 and two break tabs 221, 222 that connect the positive pole 211 and negative pole 212. During a short circuit event, the pyro 201 (i.e., pyrotechnic charge) is ignited and pressure is built up which pushes a piston 202 to the right in FIG. 2. The piston 202 may act as an isolator during a break event and may be formed of an insulating material. Once sufficient pressure builds up due to the ignited pyro 201, both break tabs 221, 222 will break and the current is interrupted/broken. In such an event, upon breaking of the tabs, an arc is present that should be extinguished. Elements of the fuse assembly 200 are supported by a fuse holder 204 that acts as an isolator and may be formed of an insulating material.

[0049] A fuse assembly in accordance with the present disclosure implements a number of features in order to improve breaking of the short circuit current. In some examples, a medium is provided around the break tabs to prevent ionization of the air and to facilitate cooling. This medium can also help lubricate the piston 202 and the slider 205 when these are moving. This medium can be. for example, oil or grease. To provide a similar advantage, anon-conducting medium is provided proximate to the bullet 206, such as oil, grease, sand, quartz, calk, dust, a combination of these and/or a sleeve 207 show n in FIG. 2B. All of these features help to reduce the chance of explosion. By filling the cavities with the medium/media, the amount of air is minimized and thus there is minimal air that could ionize. Thus, the risk of explosion is reduced.

[0050] In some examples, once the piston 202 is disconnected due to the explosion of the pyro 201 and has moved (e.g. to the right in FIG. 2B), an O-ring 231 or another radial spring element will seal off the positive and negative poles such that ionized air cannot connect these poles, which would cause the short circuit current to remain flowing. The circular design facilitates sealing off both sides as opposed to existing pyrofuses that are not fully circular designed. Additional O-rings 232, 233, 234 may be employed to ensure that no air enters the break area.

[0051] In some examples, the two break tabs 221. 222 by which the voltage drop is split over two connections, reduces the amount of arcing power per break tab. These breaking tabs may contain grooves or scores which make the breaking of these tabs easier. For example, break tab 221 increases the separation as the bullet is separated from the positive pole perpendicularly to its surface. Many classical pyrofuses shear off the connection, like break tab 222, which increases separation time and reduces the breaking capability. [0052] In some examples, the fuse pipe 203 is made from conducting materials such as copper or aluminum, which can be strengthened by increasing the wall thickness. In this way more pressure is permitted before the fuse will explode. In some examples, the fuse pipe 203 is cylindrical and may include a non-conducting cylindrical enclosure (not shown on figures) around it to improve the explosion resistance.

[0053] In some examples, the bullet 206 has a tapered cross section (parallel to moving direction), such that the non-conducting piston 202 is blocked after the explosion by the pole geometry on the opposite side (not shown on figures). As such, an arc or ionization of the air is prohibited due to the obstruction of the piston. This tapered shape may give more design freedom to the design of break tab 222, such as optimization for conductance, voltage drop, and cooling.

[0054] In some examples, in the case that the bullet 206 does not have a tapered cross section, the slider 205 is blocked by a feature 208 at the end of the fuse pipe 203 to prevent the bullet from exiting the fuse pipe after the explosion. This can be, for example, a tapered shape as shown in FIG. 2B.

[0055] In some examples, the fuse pipe 203 design has a cylindrical pipe cross section, though this is not required. Other fuse pipe shapes are contemplated.

[0056] In some examples, the fuse pipe 203 is composed of two or more pieces placed against each other, which facilitates manufacturing purposes. For reducing heat development caused by current carry, two design elements are incorporated: 1) The bullet 206 and break tabs 221 , 222 are relatively closely located to the busbars that are directly cooled. In existing pyrofuses, due to their construction, the current cartying element cannot be brought that close to the coolant. 2) The resistance across both break tabs 221, 222 and the bullet 206 is low (e.g., around 3 pQ). This resistance is much smaller than the typical value of 40 pQ of existing pyrofuses. In this example embodiment, this reduces heat development by a factor 40/3=13.3.

[0057] FIGS. 3A, 3B, and 3C illustrate a thermal-electric simulation of a fuse assembly that carries 3000 A. With a coolant temperature of 60°C, the maximum temperature is 75°C. which is an increase of only 15°C.

[0058] For further explanation, FIG. 4 illustrates graphs of simulation results. The simulation results include current carry simulations done in Ansys at 3000 A on a quarter symmetric model. Note that the effect of thermal gap filler and the box is not included. The maximum temperature rises to 75°C and stabilizes after around 120 seconds. Resistance (R) at 1=3000 A and V=2*14.286 mV is 2*14.826 mV/3000 A=9.88 pQ such that Power (P) equals P=1²R=89.0 W. The small resistance of 9.88 pQ explains the relatively limited temperature rise.

[0059] For further explanation, FIG. 5 sets forth a flow chart for an example method of operating a fuse assembly using a cylindrical disconnection system in accordance with at least one embodiment of the present disclosure. The method includes coupling 502 a fuse assembly to a positive pole and a negative pole of a bus bar, the fuse assembly including a fuse pipe having a first section and a second section, wherein the fuse pipe is operable to carry current from a first bus bar to a second bus bar; a pyrotechnic disposed within the first section of the fuse pipe; a piston disposed adjacent to the pyrotechnic within the first section of the fuse pipe; a bullet disposed adjacent to the piston and between the first section and the second section of the fuse pipe; and a slider disposed adjacent to the bullet and within the second section of the fuse pipe, wherein the piston is operable to move in response to ignition of the pyrotechnic, wherein movement of the piston actuates the bullet to break a first break tab and a second break tab connecting the first section and the second section. For example, the fuse assembly may be the fuse assembly 200 shown in FIG. 2.

[0060] The method of FIG. 5 also includes triggering 504, in response to an overcurrent event, the pyrotechnic. In some examples, the pyrotechnic is configured to explode in response to a threshold current being reached.

[0061] The method of FIG. 5 also includes actuating 506, by explosion of the pyrotechnic, the piston to move from a first location to a second location within the fuse pipe, wherein movement of the piston drives a bullet to break the break tabs, and wherein the piston, in the second location, prevents a flow of current between the first bus bar and the second bus bar. In some examples, actuating 506 the piston and breaking the break tabs is carried out as discussed above. The piston also prevents arcing.

[0062] For further explanation, FIG. 6A is an isometric view of an example fuse assembly 600 with a pyrotechnically driven disconnection system in accordance with at least one embodiment of the present disclosure. This view illustrates the outer construction of the fuse assembly, including its segmented cylindrical housing and connection points for external bus bars. FIG. 6B is a cross-sectional view of the fuse assembly 600 of FIG. 6A in a nontriggered (pre-actuation) state, showing the arrangement of internal components configured to conduct electrical current under normal conditions. FIG. 6C is a cross-sectional view of the fuse assembly 600 in a triggered state following actuation of the pyrotechnic, showing mechanical displacement of internal elements and disruption of current flow paths. FIG. 6D is an isometric view of a portion of the fuse assembly 600 mounted on a thermal mat 691, illustrating the assembly’s integration into a larger system and the thermal interface provided for heat dissipation. FIG. 6E is an isometric view of an ignition slider 670 of the fuse assembly, which is operable to translate in response to pyrotechnic detonation. FIG. 6F is an isometric view of a bullet 630 of the fuse assembly, showing the conductive and insulating structure of the component. FIG. 6G is an isometric view of a non-conductive sleeve 650 positioned between fuse segments, used to suppress arcing and prevent ionized gas propagation. FIG. 6H is an isometric view of a housing segment 602 with alignment features 655 for accurate assembly. FIG. 61 is an isometric view showing how a housing segment 604 is mechanically joined to a pair of conductive brackets 612, 614.

[0063] FIGS. 6A through 61 illustrate a distinct embodiment of a fuse assembly 600 in accordance with the present disclosure. This embodiment differs structurally and functionally from the fuse assembly 200 described in FIGs. 2A-2B, while incorporating similar principles of pyrotechnically actuated electrical disconnection. The assembly shown in FIGS. 6A-6I includes modified housing geometry, bullet engagement structures, and component alignment features, optimized for integration, manufacturability, or performance in alternative applications.

[0064] As illustrated in FIGS. 6A through 61, the fuse assembly 600 includes a generally cylindrical housing composed of five axially aligned and mechanically coupled housing segments: a first housing segment 602, a second housing segment 604, a third housing segment 606. a fourth housing segment 608. and a fifth housing segment 610. These housing segments may be individually manufactured and mechanically joined to form a rigid, modular structure that supports and aligns internal components. The housing segments may be made from electrically insulating and thermally stable materials. The housing segments are arranged end-to-end to define a continuous axial bore 699, as shown in FIG. 6B. The axial bore 699 houses internal electrical and mechanical components responsible for cunent conduction during normal operation and for mechanical disconnection during an overcurrent event. The modular cylindrical configuration allows for compact packaging and facilitates assembly and servicing.

[0065] Positioned between adjacent housing segments are conductive brackets that serve as primary current conduction paths and define points for mechanical disconnection during a fault event. A first conductive bracket 612 is disposed between the first and second housing segments 602 and 604. A second conductive bracket 614 is disposed between the second and third segments 604 and 606. A third conductive bracket 616 is disposed between the third and fourth segments 606 and 608. A fourth conductive bracket 618 is disposed between the fourth and fifth segments 608 and 610. These brackets are configured to form low-resistance electrical joints between adjacent segments and are designed to be severed during actuation to interrupt cunent flow. As shown in FIG. 6H, each housing segment may include alignment features 655 to aid precise positioning. FIG. 61 further illustrates how holes 657 in the conductive brackets engage with these alignment features to ensure mechanical stability and axial alignment during assembly.

[0066] A pyrotechnic charge 634 is positioned within the axial bore of the first housing segment 602. This charge is configured to detonate in response to an overcurrent condition or similar fault signal. Upon activation, the charge rapidly generates high-pressure gas, initiating the mechanical disconnection sequence. Immediately adjacent to the pyrotechnic is the ignition slider 670. shown in FIG. 6E. The ignition slider translates axially in response to the expanding gases and transmits mechanical energy to a first bullet 630. The ignition slider 670 includes a circumferential gas seal 671 to prevent gas migration during actuation, and an alignment feature 673 configured to engage with the central cavity⁷ 631 of the first bullet 630 for accurate coupling and energy transfer.

[0067] The first bullet 630 is disposed in the second housing segment 604 and is mechanically connected to both the first and second conductive brackets 612 and 614. FIGS. 6F and 61 show that the bullet serves as a conductive bridge between these brackets under normal operating conditions. A second bullet 632 is similarly positioned in the fourth housing segment 608 and connects the third and fourth conductive brackets 616 and 618. During a fault event, both bullets are displaced along the bore, breaking their respective electrical connections by shearing or separating from the welded joints at the brackets. This dual-break mechanism enables simultaneous or sequential interruption of two independent current paths using a single actuation event.

[0068] Each bullet is an internal, axially movable component configured to establish electrical continuity during normal operation and to interrupt current flow upon actuation. Structurally, each bullet includes two conductive end portions separated by a non-conductive central portion. The first bullet 630 includes a first conductive end portion 640 and a second conductive end portion 642 that are mechanically and electrically coupled, with a non- conductive center 648 positioned over the junction between them. Similarly, the second bullet 632 includes conductive end portions 644 and 646 joined by an insulating center 649. The conductive end portions, typically formed from high-conductivity metals such as copper or aluminum, are welded to corresponding conductive brackets to form a continuous current path. During normal operation, electrical current flows through the conductive end portions of the bullets and into the adjacent brackets. Upon axial displacement of the bullet caused by actuation of the pyrotechnic mechanism, the non-conductive central portion aligns with the brackets, thereby severing electrical continuity and interrupting the circuit.

[0069] The non-conductive central portions 648 and 649 serve as dielectric barriers following actuation, maintaining galvanic isolation between conductive elements and preventing arc reformation or re-strike. These central portions may be fabricated from high-strength, electrically insulating materials such as ceramics or engineered polymers selected for their thermal stability and dielectric strength. Their geometry and material properties contribute to the safety and reliability of the fuse assembly in post-disconnection conditions.

[0070] A non-conductive sleeve 650 is disposed within the axial bore between the second and fourth housing segments 604 and 608 and is positioned between the two bullets. As shown in FIG. 6G, the sleeve includes circumferential seals 652 and 654 configured to inhibit the spread of ionized gas or plasma during the disconnection event, thereby enhancing arc suppression. The sleeve also serves to reduce the internal air volume within the bore, which further mitigates the risk of sustained arcing. Alignment features 651 are integrated into the sleeve to interface mechanically with adjacent components, such as the central cavities of the bullets, and help maintain coaxial alignment during axial displacement. The sleeve may be formed from high-dielectric, thermally stable insulating materials — such as reinforced engineering polymers or ceramic composites — selected to withstand high-voltage environments and the mechanical forces associated with pyrotechnic actuation.

[0071] As illustrated in FIG. 6D, the fuse assembly 600 is designed for integration into larger systems, such as vehicle battery packs or industrial power nodes. The fuse is mounted to a thermal mat 691, which serves to absorb and dissipate heat generated during normal operation and fault events. In the depicted configuration, the first conductive bracket 612 connects to a first bus bar 660, the second bracket 614 to a second bus bar 662, the third bracket 616 again to the first bus bar 660, and the fourth bracket 618 to a third bus bar 690. This configuration allows for branching or looping of the pow er path and supports bidirectional or multiphase system topologies.

[0072] Each housing segment includes a set of aligned through-holes 620 (shown in FIG. 6B) that permit mechanical coupling of adjacent segments via fasteners 622. Screws 624 are inserted from one side and secured using nuts 626 threaded onto the opposite side, clamping the segments together. This modular approach ensures both axial alignment and robust structural integrity while facilitating straightforward assembly and disassembly for manufacturing or maintenance purposes. [0073] During a fault event, the pyrotechnic charge 634 is ignited, rapidly releasing high- pressure gas that propels the ignition slider 670 forward within the bore. The slider impacts the first bullet 630, causing it to displace axially. FIG. 6B shows the fuse assembly in its nontriggered state, with the first bullet 630 bridging the first and second conductive brackets 612 and 614. Upon actuation, as shown in FIG. 6C, the first bullet slides forward, bringing its insulating central region 648 into alignment with the second conductive bracket 614. This motion severs electrical continuity between the first and second conductive brackets.

[0074] The displacement of the first bullet 630 simultaneously pushes the adjacent non- conductive sleeve 650 forward. The sleeve, in turn, transmits this motion to the second bullet 632 in the fourth housing segment 608. As a result, the second bullet 632 slides into an empty portion 680 of the bore, and its non-conductive region 649 becomes positioned between the fourth conductive bracket 618, thereby breaking this second current path between the third and fourth conductive brackets. A single pyrotechnic actuation event thus triggers two independent electrical disconnections in series, allowing for high-reliability isolation of both upstream and downstream circuit segments.

[0075] The fuse assembly 600 as shown in FIGS. 6A through 61 presents several significant advantages over traditional pyrofuses and electromechanical interrupt devices. The modular cylindrical housing offers high current-carry ing capacity⁷ in a compact format. The dual-break mechanism enhances fault tolerance and permits simultaneous or staged disconnection of parallel paths. Dielectric barriers such as the bullet centers, ignition slider, and non- conductive sleeve suppress arc formation and prevent plasma bridging. Thermal management is improved via direct bus bar interfaces and the use of a thermal mat. In contrast to conventional designs that require multiple fuses or risk catastrophic failure under high fault currents, this design provides galvanic isolation in a single actuation with improved safety, reliability, and manufacturability for modem high-power systems.

[0076] For further explanation, FIG. 7 is a graph 700 illustrating a comparison of force and energy versus displacement for a conventional pyrotechnic fuse (fuse assembly 100 of FIG.

1) and the fuse assembly 600 described herein. The horizontal axis represents displacement in millimeters (mm), while the vertical axes represent force in newtons (N) and energy in joules (J), respectively. The graph includes two force curves and two energy curves. One force curve corresponds to the known pyrotechnic fuse design of assembly 100, and the other corresponds to the fuse assembly 600. Similarly, one energy⁷ curve corresponds to the known design, and the other represents the disclosed fuse assembly 600. [0077] The graph demonstrates that the fuse assembly 600 requires a lower peak force to actuate compared to the known design, indicating reduced mechanical resistance and improved response efficiency. Additionally, the energy curve for the disclosed fuse assembly 600 shows lower energy transfer over displacement, signifying a more stable and predictable actuation process. The lower force and energy curve highlight the mechanical advantage of the assembly 600, which enables reliable disconnection while minimizing stress on internal components. These characteristics contribute to increased safety, reduced risk of structural damage, and enhanced performance under high-current fault conditions.

[0078] For further explanation, FIG. 8A is an isometric view of another example fuse assembly 800 with a pyrotechnically driven disconnection system in accordance with at least one embodiment of the present disclosure. FIG. 8B is a bottom view of an example fuse assembly in accordance with at least one embodiment of the present disclosure. FIG. 8C is a cross-section view of the fuse assembly of FIG. 8A in the non-triggered state. FIG. 8D is another cross-section view of the fuse assembly of FIG. 8 A in the non-triggered state. FIG. 8E is a cross-section view of the fuse assembly of FIG. 8A in the triggered state. FIG. 8F is an isometric view of a first detachable conductor 834 positioned in the bore and coupled to a first pair of conductors 830, 832 of the fuse assembly of FIG. 8A. FIG. 8G is an isometric view of the first housing shell 804 of the fuse assembly of FIG. 8A. FIG. 8H is an isometric view of the first housing shell of the fuse assembly of FIG. 8 A coupled with the first pair of conductors 830, 832. FIG. 81 is an isometric view of a bullet 820 of the fuse assembly of FIG. 8A. FIG. 8J is an isometric view' of an ignition slider 813 of the fuse assembly of FIG. 8A. [0079] FIGS. 8A through 8J illustrate a distinct embodiment of a fuse assembly 800 in accordance with the present disclosure. This embodiment differs structurally and functionally from the fuse assembly 200 described in FIGs. 2A-2B and the fuse assembly 600 described in FIGs. 6A through 61, while incorporating similar principles of pyrotechnically actuated electrical disconnection. The assembly shown in FIGS. 8A-8J includes modified housing geometry, bullet engagement structures, and component alignment features, optimized for integration, manufacturability, or performance in alternative applications.

[0080] Referring to FIG. 8A, the fuse assembly 800 includes a housing 802 formed from a series of interlocking cylindrical shells, including a first housing shell 804, a second housing shell 806, and a third housing shell 808. These shells are arranged end-to-end along a common axis and collectively define a continuous axial bore 810. The shells may be formed from electrically insulating materials depending on system requirements. The shells may be made from molded polymeric materials to balance electrical insulation and structural integrity. The shells are mechanically secured using fasteners 880 that pass through aligned through-holes, as seen in FIGS. 8A and 8B, and are retained by corresponding nuts 882 to clamp the structure together. The axial bore 810 houses the active internal components of the fuse assembly 800, including conductive elements and movable disconnection components. [0081] As shown in FIGS. 8C and 8D, which both illustrate the non-triggered state, the fuse assembly 800 includes an ignition slider 813, a pyrotechnic charge 812, a first detachable conductor 834. a second detachable conductor 839, and a bullet 820. The ignition slider 813 is positioned w ithin the axial bore of the first housing shell 804, adjacent to the pyrotechnic charge 812. The first detachable conductor 834 is located within the second housing shell 806 and electrically couples a first pair of conductors 830 and 832. The second detachable conductor 839 is positioned within the third housing shell 808 and electrically connects a second pair of conductors 836 and 838. The first pair of conductors 830, 832 and the second pair of conductors 836, 838 are configured for external coupling to bus bars. As shown in FIG. 8B, the first pair of conductors 830, 832 are coupled to bus bars 850 and 854, and the second pair of conductors 836. 838 are coupled to bus bars 852 and 856.

[0082] The bullet 820 is an internal, axially movable component configured to translate within the bore during actuation and mechanically interact with the detachable conductors. It is positioned between the first and second detachable conductors and is configured to facilitate or directly cause electrical disconnection upon movement. The bullet may include circumferential sealing features and may be fabricated from a mechanically robust, electrically insulating material — such as a high-strength polymer or composite — suitable for withstanding pressure loads and providing dielectric separation between conductor segments during fault isolation

[0083] In the non-triggered state, both detachable conductors 834 and 839 are intact with their corresponding pair of conductors, and electrical continuity is maintained across each respective pair of conductors. The bullet 820, also located within the bore, is aligned between the tw o detachable conductors. In a particular embodiment, a first end 840 of the bullet is positioned in the bore adjacent to the first detachable conductor 834 and a second end 842 of the bullet is positioned in the bore adjacent to the second detachable conductor 839.

[0084] Upon detection of an overcurrent or fault condition, the pyrotechnic charge 812 is triggered and rapidly expands, generating pressure that propels the ignition slider 813 axially along the bore. The ignition slider 813 is configured to first impact and sever the first detachable conductor 834 from the first pair of conductors 830 and 832. The forward motion of the ignition slider 813 also drives the bullet 820 axially forward. The bullet then impacts and severs the second detachable conductor 839 from the second pair of conductors 836 and 838. FIG. 8E shows the fuse assembly 800 in this triggered state, where the detachable conductors have been separated from the pairs of conductors. As a result, current flow is interrupted across both conductor paths, and galvanic isolation is achieved.

[0085] As show n in FIG. 8F, the first detachable conductor 834 may be formed from a high- conductivity material such as copper or aluminum. It is positioned within the bore to establish a physical and electrical bridge between the first pair of conductors 830 and 832 during normal operation. The design allows the conductor to be sheared or displaced upon actuation without damaging surrounding components. FIG. 8G shows the first housing shell 804 as a standalone component, highlighting structural features such as alignment cylinders 891 for inserting into the second housing shell. The first housing shell 804 also includes a central cylinder opening 894 for positioning of the first detachable conductor 834 and cavities 892, 893 for positioning of the first pair of conductors 832, 830. FIG. 8H illustrates the first housing shell 804 assembled with the first pair of conductors 830 and 832, showing their positioning relative to the housing and the detachable conductor 834.

[0086] FIG. 81 shows an isometric view of the bullet 820. which is configured to move with or guide the motion of internal components during actuation. The bullet may include circumferential seals 862 and 864 to provide gas sealing between adjacent bore sections. FIG. 8J shows the ignition slider 813 with at least one circumferential seal 860. These circumferential seals may be implemented using O-rings or similar radial sealing elements and are configured to inhibit ionized gas migration across compartments within the bore. These sealing features contribute to arc suppression and containment, improving the safety and performance of the fuse assembly 800.

[0087] The fuse assembly 800 illustrated in FIGS. 8A-8J provides several practical and technical advantages over conventional pyrotechnic disconnection systems. By integrating a modular shell-based housing design with detachable conductors and an internal ignition slider, this embodiment supports efficient manufacturing, simplified assembly, and precise disconnection dynamics. The axial layout enables both mechanical and electrical separation across multiple conductor paths using a single pyrotechnic event, reducing system complexity and cost. The use of a sealed bullet and sealed ignition slider minimizes air gaps and suppresses arc formation, which is critical for high-voltage or high-current environments. Additionally, the mechanical interfaces between the housing shells and conductors allow for reconfiguration or replacement. Compared to prior art devices that rely on bulky, parallel fuses or exposed arc zones, the fuse assembly 800 offers a compact, enclosed, and safer solution capable of isolating multiple circuit paths rapidly and reliably. This makes it particularly well suited for electric vehicle battery systems, industrial power distribution, and other safety-critical applications requiring fast and complete electrical isolation.

[0088] Advantages and features of the present disclosure can be further described by the following statements:

[0089] 1. A fuse assembly comprising: a fuse pipe comprising a first section and a second section, wherein the fuse pipe is operable to carry current from a first bus bar to a second bus bar; a pyrotechnic disposed within the first section of the fuse pipe; a piston disposed adjacent to the pyrotechnic within the first section of the fuse pipe; a bullet disposed adjacent to the piston and between the first section and the second section of the fuse pipe; and a slider disposed adjacent to the bullet and within the second section of the fuse pipe, wherein the piston is operable to move in response to ignition of the pyrotechnic, wherein movement of the piston actuates the bullet to break a first break tab and a second break tab connecting the first section and the second section.

[0090] 2. The fuse assembly of statement 1, wherein the fuse pipe forms a cylindrical enclosure in which the pyrotechnic, piston, bullet, and slider are disposed, and wherein the piston, bullet, and slider move along an axis of the cylindrical enclosure.

[0091] 3. The fuse assembly of any of statements 1-2, wherein the piston includes one or more O-rings that prevent air from entering the interior of the fuse pipe and ionizing.

[0092] 4. The fuse assembly of any of statements 1-3. wherein the slider includes one or more O-rings that prevent air from entering the interior of the fuse pipe and ionizing.

[0093] 5. The fuse assembly of any of statements 1-4, wherein the first section and second section of the fuse pipe are separated by an insulating sleeve that surrounds the bullet.

[0094] 6. The fuse assembly of any of statements 1-5. wherein the piston is an insulator.

[0095] 7. A fuse assembly comprising: a housing having axially aligned segments; a first conductive bracket, a second conductive bracket, a third conductive bracket, and a fourth conductive bracket, each positioned between successive segments of the housing; a first bullet and a second bullet respectively disposed in different segments of the housing; and a pyrotechnic charge configured, when activated, to drive each bullet axially so as to interrupt electrical continuity between a corresponding pair of the conductive brackets.

[0096] 8. The fuse assembly of statement 7, wherein the first bullet is located in a second housing segment and the second bullet is located in a fourth housing segment.

[0097] 9. The fuse assembly of any of statements 7-8. wherein each bullet comprises conductive end portions and a non-conductive central portion. [0098] 10. The fuse assembly of any of statements 7-9, wherein the conductive end portions of each bullet are welded to adjacent conductive brackets.

[0099] 11. The fuse assembly of any of statements 7-10, further comprising a non-conductive sleeve disposed within a housing segment between the first bullet and the second bullet.

[00100] 12. The fuse assembly of any of statements 7-11, wherein axial displacement of the first bullet interrupts electrical continuity between the first and second brackets, and axial displacement of the second bullet interrupts electrical continuity between the third and fourth brackets.

[00101] 13. The fuse assembly of any of statements 7-12, wherein each conductive bracket is configured for connection to a bus bar.

[00102] 14. The fuse assembly of any of statements 7-13. wherein each housing segment includes a plurality of aligned through-holes, and a fastener passes through each set of aligned through-holes, the fastener comprising a screw inserted from one side of the housing and a nut threaded onto the screw on an opposite side to clamp the segments together.

[00103] 15. The fuse assembly of any of statements 7-14. further comprising an ignition slider positioned between the pyrotechnic charge and the first bullet.

[00104] 16. A fuse assembly comprising: a housing that includes a plurality of shells joined end-to-end to define a common axial bore; an ignition slider positioned in the bore adj acent to a pyrotechnic charge within a first shell of the plurality of shells; a first detachable conductor positioned in the bore and coupled to a first pair of conductors; a bullet having a first end and a second end, the first end of the bullet positioned in the bore adjacent to the first detachable conductor; and a second detachable conductor coupled to a second pair of conductors, the second detachable conductor positioned in the bore adjacent to the second end of the bullet; wherein activation of the pyrotechnic charge propels the ignition slider to sever the first detachable conductor from the first pair of conductors and drives the bullet to sever the second detachable conductor from the second pair of conductors, thereby interrupting electrical continuity across both the first pair of conductors and the second pair of conductors.

[00105] 17. The fuse assembly of statement 16. wherein the plurality of shells further includes a second shell and a third shell that cooperate to form with the first shell, the common axial bore, wherein adjacent shells being secured by complementary alignment features that maintain coaxial positioning of the bore.

[00106] 18. The fuse assembly of any of statements 16-17, further comprising bus-bar terminals respectively coupled to the conductors. [00107] 19. The fuse assembly of any of statements 16-18, wherein the ignition slider carries at least one circumferential seal configured to impede migration of ionized gases.

[00108] 20. The fuse assembly of any of statements 16-19, wherein each shell includes a plurality of aligned through-holes, and a fastener passes through each set of aligned through- holes, the fastener comprising a screw inserted from one side of the housing and a nut threaded onto the screw on an opposite side to clamp the shells together.

[00109] It will be understood from the foregoing description that modifications and changes may be made in various embodiments of the present disclosure w ithout departing from its true spirit. The descriptions in this specification are for purposes of illustration only and are not to be construed in a limiting sense. The scope of the present disclosure is limited only by the language of the following claims.

Claims

CLAIMS What is claimed is:

1. A fuse assembly comprising: a fuse pipe comprising a first section and a second section, wherein the fuse pipe is operable to carry current from a first bus bar to a second bus bar; a pyrotechnic disposed within the first section of the fuse pipe; a piston disposed adjacent to the pyrotechnic within the first section of the fuse pipe; a bullet disposed adjacent to the piston and between the first section and the second section of the fuse pipe; and a slider disposed adjacent to the bullet and within the second section of the fuse pipe, wherein the piston is operable to move in response to ignition of the pyrotechnic, wherein movement of the piston actuates the bullet to break a first break tab and a second break tab connecting the first section and the second section.

2. The fuse assembly of claim 1, wherein the fuse pipe forms a cylindrical enclosure in which the pyrotechnic, piston, bullet, and slider are disposed, and wherein the piston, bullet, and slider move along an axis of the cylindrical enclosure.

3. The fuse assembly of claim 1, wherein the piston includes one or more O-rings that prevent air from entering the interior of the fuse pipe and ionizing.

4. The fuse assembly of claim 1, wherein the slider includes one or more O-rings that prevent air from entering the interior of the fuse pipe and ionizing.

5. The fuse assembly of claim 1, wherein the first section and second section of the fuse pipe are separated by an insulating sleeve that surrounds the bullet.

6. The fuse assembly of claim 1, wherein the piston is an insulator.

7. A fuse assembly comprising: a housing having axially aligned segments; a first conductive bracket, a second conductive bracket, a third conductive bracket, and a fourth conductive bracket, each positioned between successive segments of the housing; a first bullet and a second bullet respectively disposed in different segments of the housing; and a pyrotechnic charge configured, when activated, to drive each bullet axially so as to interrupt electrical continuity between a corresponding pair of the conductive brackets.

8. The fuse assembly of claim 7, wherein the first bullet is located in a second housing segment and the second bullet is located in a fourth housing segment.

9. The fuse assembly of claim 7, wherein each bullet comprises conductive end portions and a non-conductive central portion.

10. The fuse assembly of claim 9, wherein the conductive end portions of each bullet are welded to adjacent conductive brackets.

11. The fuse assembly of claim 7, further comprising a non-conductive sleeve disposed within a housing segment between the first bullet and the second bullet.

12. The fuse assembly of claim 7, wherein axial displacement of the first bullet intermpts electrical continuity between the first and second brackets, and axial displacement of the second bullet intermpts electrical continuity between the third and fourth brackets.

13. The fuse assembly of claim 7, wherein each conductive bracket is configured for connection to a bus bar.

14. The fuse assembly of claim 7, wherein each housing segment includes a plurality of aligned through-holes, and a fastener passes through each set of aligned through- holes, the fastener comprising a screw inserted from one side of the housing and a nut threaded onto the screw on an opposite side to clamp the segments together.

15. The fuse assembly of claim 7, further comprising an ignition slider positioned between the pyrotechnic charge and the first bullet.

16. A fuse assembly comprising: a housing that includes a plurality of shells joined end-to-end to define a common axial bore; an ignition slider positioned in the bore adjacent to a pyrotechnic charge within a first shell of the plurality of shells; a first detachable conductor positioned in the bore and coupled to a first pair of conductors; a bullet having a first end and a second end, the first end of the bullet positioned in the bore adjacent to the first detachable conductor; and a second detachable conductor coupled to a second pair of conductors, the second detachable conductor positioned in the bore adj acent to the second end of the bullet; wherein activation of the pyrotechnic charge propels the ignition slider to sever the first detachable conductor from the first pair of conductors and drives the bullet to sever the second detachable conductor from the second pair of conductors, thereby interrupting electrical continuity across both the first pair of conductors and the second pair of conductors.

17. The fuse assembly of claim 16, wherein the plurality of shells further includes a second shell and a third shell that cooperate to form with the first shell, the common axial bore, wherein adjacent shells being secured by complementary alignment features that maintain coaxial positioning of the bore.

18. The fuse assembly of claim 16, further comprising bus-bar terminals respectively coupled to the conductors.

19. The fuse assembly of claim 16, wherein the ignition slider carries at least one circumferential seal configured to impede migration of ionized gases.

20. The fuse assembly of claim 16, wherein each shell includes a plurality of aligned through-holes, and a fastener passes through each set of aligned through-holes, the fastener comprising a screw inserted from one side of the housing and a nut threaded onto the screw on an opposite side to clamp the shells together.