# US 6,091,315 A · Switch having a safety element > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 6,091,315 A - Document ID: US6091315A - Status: Granted - Kind: A - Application number: 08/924,783 - Filed: 1997-09-05 - Granted: 2000-07-18 - Earliest claimed: 1996-09-10 - Inventors: Marcel Hofsass - Web page: https://patentgrep.com/patent/US6091315A ## CPC - H01H 37/002: {combined with protective means} - H01H 37/323: {making use of shape memory materials (in thermal relays H01H61/0107; release mechanism H01H71/145; treatment of SMF alloys C22F1/006; for control of temperature G05D23/024)} - H01H 37/52: actuated due to deflection of bimetallic element - H01H 2061/0115: {Shape memory alloy [SMA] actuator formed by coil spring} - H01H: ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES (contact cables H01B7/10; electrolytic self-interrupters H01G9/18; emergency protective circuit arrangements H02H; switching by electronic means without contact-making H03K17/00) ## Abstract A switch has a switching mechanism, which switches at a response temperature, for opening and closing a circuit that can be connected to external terminals of the switch. In this context, the switching mechanism has a movable contact, electrically connected to one external terminal, which as a function of the temperature of a bimetallic part is in contact with a fixed contact that is electrically connected to the other external terminal. The switching mechanism further has a safety element that changes its shape into a high-temperature shape if its temperature reaches a transformation temperature which is above the response temperature. The movable contact is in contact with the fixed contact as a function of the temperature of the safety element. ## Claims ### Claim 1 A switch, comprising: two external terminals for connection to a circuit, a temperature-dependent switching mechanism that above a response temperature interrupts and closes, respectively, said circuit when connected, said switching mechanism comprising: a fixed contact electrically connected to one of said two external terminals, and a moving contact electrically connected to the other of said two external terminals, a bimetallic part acting on said movable contact such that the latter is in contact with the fixed contact depending on the temperature of the bimetallic part, and a safety element produced from a shape-memory alloy that changes its shape into a high-temperature shape if its temperature reaches a transformation temperature which is above the response temperature, the safety element, in its high-temperature shape, holding the movable contact in a safety position which it retains even if the temperature of the safety element again drops below the transformation temperature, wherein the safety element is a compression spring. ### Claim 2 A switch, comprising: two external terminals for connection to a circuit, a temperature-dependent switching mechanism that above a response temperature interrupts and closes, respectively, said circuit when connected, said switching mechanism comprising: a fixed contact electrically connected to one of said two external terminals, and a moving contact electrically connected to the other of said two external terminals, a bimetallic part acting on said movable contact such that the latter is in contact with the fixed contact depending on the temperature of the bimetallic part, and a safety element produced from a shape-memory alloy that changes its shape into a high-temperature shape if its temperature reaches a transformation temperature which is above the response temperature, the safety element, in its high-temperature shape, holding the movable contact in a safety position which it retains even if the temperature of the safety element again drops below the transformation temperature, wherein the safety element is a tension spring. ### Claim 3 A switch, comprising: two external terminals for connection to a circuit, a temperature-dependent switching mechanism that above a response temperature interrupts and closes, respectively, said circuit when connected, said switching mechanism comprising: a fixed contact electrically connected to one of said two external terminals, and a moving contact electrically connected to the other of said two external terminals, a bimetallic part acting on said movable contact such that the latter is in contact with the fixed contact depending on the temperature of the bimetallic part, and a safety element that changes its shape into a high-temperature shape if its temperature reaches a transformation temperature which is above the response temperature, wherein the switching mechanism comprises a spring element, clamped at one end, at whose free end the movable contact is arranged; and the safety element, in its high-temperature shape acts on the spring element. ### Claim 4 A switch, comprising: two external terminals for connection to a circuit, a temperature-dependent switching mechanism that above a response temperature interrupts and closes, respectively, said circuit when connected, said switching mechanism comprising: a fixed contact electrically connected to one of said two external terminals, and a moving contact electrically connected to the other of said two external terminals, a bimetallic part acting on said movable contact such that the latter is in contact with the fixed contact depending on the temperature of the bimetallic part, and a safety element that changes its shape into a high-temperature shape if its temperature reaches a transformation temperature which is above the response temperature, wherein the switching mechanism comprises a spring snap disk which carries the movable contact approximately centeredly, and is braced peripherally against a housing part by means of which it is electrically connected to the external terminal; and the safety element acts on the spring snap disk. ### Claim 5 (depends on 4) The switch of claim 4, wherein associated with the spring snap disk is a bimetallic snap disk which is slipped over the movable contact and which, above the response temperature, is braced peripherally against a housing part. ### Claim 6 (depends on 4) The switch of claim 4, wherein the safety element is a disk which is slipped over the movable contact and is braced, at least in its high-temperature shape, against a housing part. ### Claim 7 (depends on 6) The switch of claim 6, wherein the disk is retained peripherally on a housing part. ### Claim 8 (depends on 7) The switch of claim 7, wherein the disk is held peripherally on a shoulder between a lower housing part and a cover part.