Title:
FUSE CONSTRUCTION AND MOUNTING
Document Type and Number:
United States Patent 3803527
Abstract:
A temperature sensitive fuse assembly is disclosed for a thermal fire protection device. The fuse assembly is simply installed on said device using a snap connection, thereby minimizing the possibility of incorrect installation of the fuse assembly or damage to the fuse assembly during installation. This reduction of the possibility of fuse damage allows the use of a thinner heat collecting member on the fuse than was heretofore possible, increasing the rate of response of the fuse element to temperature changes which occur during a fire. Thermal insulation of the fuse from the mounting assembly is also disclosed, further enhancing the rate of response of the fuse element.
Inventors:
Gallagher, Edward L. (Capistrano Beach, CA)
Limacher, Robert W. (Corona Del Mar, CA)
House, Kenneth R. (Norwalk, CA)
Limacher, Robert W. (Corona Del Mar, CA)
House, Kenneth R. (Norwalk, CA)
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Application Number:
05/178250
Publication Date:
04/09/1974
Filing Date:
09/07/1971
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Export Citation:
Assignee:
A-T-O Inc. (Willoughby, OH)
Primary Class:
Other Classes:
337/407, 337/414
International Classes:
H01H37/76; H01H37/00; H01H37/76
Field of Search:
337/401,402,403,407,408,409,414 169/42 340/227.1
US Patent References:
Primary Examiner:
Gilheany, Bernard A.
Assistant Examiner:
Bell, Fred E.
Attorney, Agent or Firm:
Fowler, Knobbe & Martens
Claims:
1. A method of attaching a fuse assembly to the triggering mechanism of a temperature sensitive fire protection device, which triggering mechanism comprises a reciprocating trigger pin, comprising:
2. A method of attaching a fuse assembly to the triggering mechanism of a temperature sensitive fire protection device as defined in claim 1 wherein said snapping step includes the step of:
3. A method of attaching a fuse assembly including a socket which retains a resilient split ring to the triggering mechanism of a temperature sensitive fire protection device, which triggering mechanism comprises a spring-biased reciprocating trigger pin, and which device includes a stud member surrounding the triggering mechanism, said stud member having an enlarged outer extremity, comprising:
4. A temperature sensitive fire protection device comprising:
5. A fire protection device as defined in claim 4 wherein said interlocking
6. A fire protection device as defined in claim 5 wherein said means for snapping comprises a resilient ring attached to said temperature sensitive member, said resilient ring designed to expand as said temperature
7. A fuse assembly for a temperature sensitive fire protection device comprising:
8. A temperature sensitive fire protection device comprising:
9. A temperature sensitive fire protection device comprising:
10. A temperature sensitive fire protection device, comprising:
11. A temperature sensitive fire protection device comprising:
12. A temperature sensitive fire protection device, comprising:
13. A temperature sensitive fire protection device, comprising:
2. A method of attaching a fuse assembly to the triggering mechanism of a temperature sensitive fire protection device as defined in claim 1 wherein said snapping step includes the step of:
3. A method of attaching a fuse assembly including a socket which retains a resilient split ring to the triggering mechanism of a temperature sensitive fire protection device, which triggering mechanism comprises a spring-biased reciprocating trigger pin, and which device includes a stud member surrounding the triggering mechanism, said stud member having an enlarged outer extremity, comprising:
4. A temperature sensitive fire protection device comprising:
5. A fire protection device as defined in claim 4 wherein said interlocking
6. A fire protection device as defined in claim 5 wherein said means for snapping comprises a resilient ring attached to said temperature sensitive member, said resilient ring designed to expand as said temperature
7. A fuse assembly for a temperature sensitive fire protection device comprising:
8. A temperature sensitive fire protection device comprising:
9. A temperature sensitive fire protection device comprising:
10. A temperature sensitive fire protection device, comprising:
11. A temperature sensitive fire protection device comprising:
12. A temperature sensitive fire protection device, comprising:
13. A temperature sensitive fire protection device, comprising:
Description:
BACKGROUND OF THE INVENTION
The present invention pertains to temperature sensitive fire protection devices and, in particular, to fire devices which utilize a fusing element which is triggered at temperatures above the normal room teperature to activate an audible or visual alarm in response to a fire.
Temperature sensitive fire protection systems commonly utilize a fuse which is constructed using a metal alloy having a very low melting point, generally below 300° farenheit. Common construction techniques, for example, utilize this low melting point alloy as a soldering material to hold together in a fixed relationship the elements of a fuse. This assembly is then placed in the path of a spring-biased triggering mechanism so that, when the temperature of the fuse assembly exceeds the melting point of the alloy, the fuse becomes disasembled, allowing the trigger under the action of the spring bias to pass through the fuse thereby initiating an audible or visual alarm. It has likewise been common in the prior art to attach the fuse structure a heat collecting member which has a relatively small mass but which gathers heat over a substantial surface area. This heat collecting member is attached so that it is in good thermal contact with the fuse element so that heat gathered by the heat collecting member may be conducted to the fuse assembly. Such heat collecting members substantially increase the ratio of the exposed surface area to the volume of material to be heated, thereby increasing the rate at which the fuse element may change in temperature in response to changes in the temperature of the surrounding air.
Most prior art fire protection devices utilize interlocking tabs on the fuse assembly and the device to attach the heat collector and fuse assembly to the temperature sensitive protective device. Such fuse attachments usually require the bending of one or more of the tabs after final installation to lock the fuse assembly in its proper position. The mounting means are susceptible to incorrect fusing of the fire protection device by incorrect locking of the tabs or by improper placement of the fuse assembly. Such improper installation of the fuse assembly is not usually visible and, since the application of the fuse to the device requires awkward manipulation, it is possible to improperly fuse the apparatus without producing any obvious visual indications of this condition. The result of such improper fusing may be the triggering of the device due to vibration or contact with foreign objects, thus creating a false alarm. More dangerously, improper fusing can result in the inability of the temperature sensitive fire protection device to respond to temperatures above the melting point of the fusing alloy.
In addition, the fuse assemblies of prior art devices require relatively thick heat collecting members since these heat collecting members must absorb most of the force required in attaching the fuse assemblies. Since the ability of the heat collecting member to respond to atmospheric temperature changes varies in accordance with the thickness of the heat collecting member, the relatively thick prior art heat collecting members produced fuse assemblies which respond slowly to ambient air temperature changes. In addition, since the heat collecting members of the prior art fuses are generally attached directly to the temperature sensitive fire protection device, heat which is collected in th heat collecting member can be conducted to the body of the device as well as to the fuse assembly, thereby substantially lowering the rate of temperature change of the fuse element.
In addition, the interlocking connections used in the prior art typically result in a rigidly mounted fuse assembly which is particularly sensitive to accidental contact with foreign objects. This sensitivity can produce damaged fuse assemblies which are inoperative, but the damaged condition of which is not immediately apparent.
SUMMARY OF THE INVENTION
These and other disadvantages of the prior art fuse assemblies are alleviated by the fuse assembly of the present invention. This fuse assembly is designed to be applied to the temperature sensitive fire protection device by simple, snapping action which occurs along the direction of the axis of the fuse assembly. This snapping action assures that the fuse assembly is either fully engaged or not engaged at all, so that a partial application of the fuse assembly to the device is impossible. As a consequence, inaccurate placement of the fuse assembly on the device which could result in false alarms or the failure of the fire protection device to trigger on the occurrence of a fire is avoided.
This snap-action application of the fuse assembly likewise requires only a unidirectional application of force along the axis of the fuse assembly, so that no bending or twisting forces need be applied to the heat collection member as in the prior art devices. This heat collection member can therefore be made very thin so that the rate of change of temperature of the heat collection member will vary rapidly in response to increases in the ambient temperature.
In order to further enhance the speed of response of the fuse assembly to changes in the ambient temperature, the heat collection member and its associated fusing member are thermally insulated from the remainder of the fuse assembly so that the greatest possible percentage of the heat absorbed by the heat collection member will be transmitted to the fuse.
The mounting apparatus of the present invention additionally allows a limited degree of freedom of motion of the fuse assembly once it is installed on the temperature sensitive fire protection device. The fuse assembly may therefore move to some extent in response to accidental contact by tools and the like. This motion allows the fuse assembly to absorb some of the energy of the blow and to move from the path of the interfering object to avoid fuse or heat collector damage.
These and other advantages of the present invention are best understood in reference to the drawings in which:
FIG. 1 is an elevation view of the temperature sensitive fire protection device of the present invention installed on a wall in a room to be protected, the fuse assembly of the present invention installed upon the device; and
FIG. 2 is a sectional view of that portion of the temperature sensitive protective device in the vicinity of the fuse assembly of the present invention, taken along lines 2--2 of FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The fuse assembly 10 of the present invention is shown attached to a temperature sensitive fire protection device 12. This fire protection device 12, in the preferred embodiment, includes a base member 14 to which the various components of the alarm system are attached. One such component is a bell 16 which is utilized to generate an audible alarm signal when the fuse assembly 10 responds to high ambient temperatures from a fire.
A trigger pin 18 is reciprocally mounted on the base member 14 and includes an enlarged flange 20 which is free to reciprocate within an opening 22 in the base member 14. An annular flange 24 in the base member 14 serves as a lower support for a spring 26 which engages the flange 20 and thereby biases the trigger pin 18 in an upward direction as viewed in FIG. 2. The upper extremity of the trigger pin 18 is in contact with the fuse assembly 10 and will penetrate and pass through the fuse assembly 10 when the fuse assembly 10 reaches an elevated temperature, as explained below. This vertical movement of the trigger pin 18 through the fuse assembly 10 will trigger the fire protection apparatus to sound the bell 16 and thereby produce an audible warning of a fire.
A pair of screws 28 act in conjunction with a retaining ring 30 to hold the various elements of the fire protection device 12 together. A thin washer 32 may be used to hide the screws 28 from view when the fuse assembly 10 is removed from the fire protection device 12.
The retaining ring 30 includes a central frustoconical element 34 which includes an internal annular ridge 36 surrounding a central bore through which the trigger pin 18 may freely reciprocate.
Through the use of an eyelet or rivet 38 the annular ridge 36 mounts a hollow vertical protruding stud or pin member 40 which is circular and includes an enlarged, protruding ridge 42 near its outer extremity and inwardly extending valley 44 adjacent the retaining ring 30. The eyelet 38 is inserted through the retaining ring 30 and the stud or pin member 40 and swaged in that position to hold the stud or pin member 40 in position on the retaining ring 30.
The fuse assembly 10 includes a circular heat collecting member 46 which is generally convex in shape in order to strengthen this member 46 as much as possible and to thereby allow it to be made extremely thin. This thinness of the heat collecting member 46 allows the collection of heat from the ambient air over a large surface area while maintaining the mass of the heat collecting member 46 low, thereby allowing rapid temperature change in response to changes in the temperature of the surrounding air. The center of the heat collecting member 46 includes a bore through which the trigger pin 18 may freely pass, this bore being surrounded by an outwardly and downwardly extending flange 48.
Soldered to the heat collecting member 46 at the shoulder surrounding the upper extremity of the flange 48 is a fuse element 50 which blocks the bore through the center of the heat collecting member 46 and maintains the trigger pin 18 in the position shown in FIG. 2. The solder 52 which is used to connect the fuse member 50 to the heat collecting member 46 is made from a eutectic alloy which has a melting point temperature in the range which is achieved during the early stages of a fire in a building or structure. This alloy solder 52 will therefore melt in response to increased temperatures caused by a fire and will allow the fuse member 50 to be pushed from the central bore of the heat collecting member 46 by the trigger pin 18 under the action of the spring 26, thereby triggering the fire protection device 12. The cover member 54 maybe attached to the fuse element 50 in order to hide a warning label 56. This label 56 makes the fact that the fuse element 50 is no longer in place on the heat collecting member 46 visually apparent. Since the heat collecting member 46 is connected to the fuse element 50 by use of the eutectic alloy solder 52, there is good thermal contact between the heat collecting member 46 and the fuse member 50. Therefore, heat which is collected by the heat collecting member 46 may readily be conducted to raise the temperature of the fuse element 50 and the solder 52 which holds it in place.
The flange 48 on the heat collecting member 46 is formed through a swaging operation which also serves to connect the heat collecting member 46 to a socket or receiver 58. This receiver 58 acts as an interconnecting member with the stud or pin member 40 so that this pair of interconnecting members 40 and 58 are used to removably attach the fuse assembly 10 to the fire protection device 12. The receiver 58 is insulated from the flange 48 of the heat collecting member 46 through the use of an insulating spacer 60, typically formed of material having a low thermal conduction properties, such as a plastic. The flange 48 is swaged over the insulating spacer 60 and the receiver 58 so that a rigid assembly is formed between the heat collection member 46 and receiver 58 while maintaining thermal isolation between these elements. This thermal isolation insures that the greatest possible percentage of the heat which is collected in the heat collected member 46 is conducted to raise the temperature of the fuse element 50 rather than that of the receiver 58.
The receiver or socket 58 includes a circular retaining portion 61 which supports a circular resilient split ring 62. This split ring 62, in its relaxed position, is smaller than the largest inside diameter of the circular retaining portion 61, but is not small enough to pass below a lower flange 64 of the retaining portion 61 and is therefore confined to rest within the retaining portion 61. The split ring 62 can expand within the retaining portion 61 to a sufficient degree to pass over the enlarged ridge 42 of the stud or pin member 40. In its relaxed condition the split ring 62 is slightly smaller than the undercut or valley portion 44 of the stud or pin member 40, so that it will grip the valley portion 44 snugly when the fuse assembly 10 is in position, as shown in FIG. 2. The force required to remove the split ring 62 from the stud or pin member 40 is greater than that which is produced by the spring 26 on the trigger pin 18, so that once the fuse assembly 10 is positioned on the fire protection system 16, the split ring 62 acting against the enlarged ridge 42 will maintain the fuse assembly 10 in position.
It can be seen from FIG. 2 that the application of the fuse assembly 10 to the fire protection device 16 requires only a unidirectional application of force through the center of the fuse assembly 10 and along the axis of the fuse assembly 10 in order to fuse the split ring 62 past the enlarged ridge 42 of the stud or pin member 40. This application of the fuse assembly 10 occurs with a snapping action as the split ring 62 passes over the ridge 42. During this assembly, no force need be applied to the heat collection member 46 other than at its center where it is reinforced with the fuse member 50. The heat collection member 46 may, therefore, be made very thin, since it does not have to absorb the forces which are applied during application. The snap-action of the split ring 62 over the enlarged ridge 42 makes it impossible to install the fuse assembly 10 to a sufficient degree to hold it in place on the fire protection device 12 without properly fusing the fire protection device 12.
It will be recognized that the application of the fuse assembly 10 to the fire protection device 16 simultaneously depresses the trigger pin 18, and that the axis of the fuse assembly 10 is placed directly over the trigger pin 18 so that the same force which is used to apply the socket 58 to the stud or pin member 40 may be used to depress the trigger pin 18. The unidirectional force therefore occurs along the axis of both the fire protection system 12 and the fuse assembly 10 and creates a snapping interconnection which assures proper fusing of the fire protection system 12 without application of stress to the heat collection member 46.
As shown in FIG. 2, the inwardly extending valley 44 of the stud or pin member 40 is sufficiently long in the direction of the axis of the pin member 40 to allow the split ring 62 a limited degree of freedom to move toward the trigger pin 18, or to cant about the upper extremity of the trigger pin 18, without becoming dislodged from the pin member 40. This freedom allows the fuse assembly 10 to absorb the force of accidental blows from foreign objects without damage thereto, thus increasing the reliability of the fuse assembly 10.
The present invention pertains to temperature sensitive fire protection devices and, in particular, to fire devices which utilize a fusing element which is triggered at temperatures above the normal room teperature to activate an audible or visual alarm in response to a fire.
Temperature sensitive fire protection systems commonly utilize a fuse which is constructed using a metal alloy having a very low melting point, generally below 300° farenheit. Common construction techniques, for example, utilize this low melting point alloy as a soldering material to hold together in a fixed relationship the elements of a fuse. This assembly is then placed in the path of a spring-biased triggering mechanism so that, when the temperature of the fuse assembly exceeds the melting point of the alloy, the fuse becomes disasembled, allowing the trigger under the action of the spring bias to pass through the fuse thereby initiating an audible or visual alarm. It has likewise been common in the prior art to attach the fuse structure a heat collecting member which has a relatively small mass but which gathers heat over a substantial surface area. This heat collecting member is attached so that it is in good thermal contact with the fuse element so that heat gathered by the heat collecting member may be conducted to the fuse assembly. Such heat collecting members substantially increase the ratio of the exposed surface area to the volume of material to be heated, thereby increasing the rate at which the fuse element may change in temperature in response to changes in the temperature of the surrounding air.
Most prior art fire protection devices utilize interlocking tabs on the fuse assembly and the device to attach the heat collector and fuse assembly to the temperature sensitive protective device. Such fuse attachments usually require the bending of one or more of the tabs after final installation to lock the fuse assembly in its proper position. The mounting means are susceptible to incorrect fusing of the fire protection device by incorrect locking of the tabs or by improper placement of the fuse assembly. Such improper installation of the fuse assembly is not usually visible and, since the application of the fuse to the device requires awkward manipulation, it is possible to improperly fuse the apparatus without producing any obvious visual indications of this condition. The result of such improper fusing may be the triggering of the device due to vibration or contact with foreign objects, thus creating a false alarm. More dangerously, improper fusing can result in the inability of the temperature sensitive fire protection device to respond to temperatures above the melting point of the fusing alloy.
In addition, the fuse assemblies of prior art devices require relatively thick heat collecting members since these heat collecting members must absorb most of the force required in attaching the fuse assemblies. Since the ability of the heat collecting member to respond to atmospheric temperature changes varies in accordance with the thickness of the heat collecting member, the relatively thick prior art heat collecting members produced fuse assemblies which respond slowly to ambient air temperature changes. In addition, since the heat collecting members of the prior art fuses are generally attached directly to the temperature sensitive fire protection device, heat which is collected in th heat collecting member can be conducted to the body of the device as well as to the fuse assembly, thereby substantially lowering the rate of temperature change of the fuse element.
In addition, the interlocking connections used in the prior art typically result in a rigidly mounted fuse assembly which is particularly sensitive to accidental contact with foreign objects. This sensitivity can produce damaged fuse assemblies which are inoperative, but the damaged condition of which is not immediately apparent.
SUMMARY OF THE INVENTION
These and other disadvantages of the prior art fuse assemblies are alleviated by the fuse assembly of the present invention. This fuse assembly is designed to be applied to the temperature sensitive fire protection device by simple, snapping action which occurs along the direction of the axis of the fuse assembly. This snapping action assures that the fuse assembly is either fully engaged or not engaged at all, so that a partial application of the fuse assembly to the device is impossible. As a consequence, inaccurate placement of the fuse assembly on the device which could result in false alarms or the failure of the fire protection device to trigger on the occurrence of a fire is avoided.
This snap-action application of the fuse assembly likewise requires only a unidirectional application of force along the axis of the fuse assembly, so that no bending or twisting forces need be applied to the heat collection member as in the prior art devices. This heat collection member can therefore be made very thin so that the rate of change of temperature of the heat collection member will vary rapidly in response to increases in the ambient temperature.
In order to further enhance the speed of response of the fuse assembly to changes in the ambient temperature, the heat collection member and its associated fusing member are thermally insulated from the remainder of the fuse assembly so that the greatest possible percentage of the heat absorbed by the heat collection member will be transmitted to the fuse.
The mounting apparatus of the present invention additionally allows a limited degree of freedom of motion of the fuse assembly once it is installed on the temperature sensitive fire protection device. The fuse assembly may therefore move to some extent in response to accidental contact by tools and the like. This motion allows the fuse assembly to absorb some of the energy of the blow and to move from the path of the interfering object to avoid fuse or heat collector damage.
These and other advantages of the present invention are best understood in reference to the drawings in which:
FIG. 1 is an elevation view of the temperature sensitive fire protection device of the present invention installed on a wall in a room to be protected, the fuse assembly of the present invention installed upon the device; and
FIG. 2 is a sectional view of that portion of the temperature sensitive protective device in the vicinity of the fuse assembly of the present invention, taken along lines 2--2 of FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The fuse assembly 10 of the present invention is shown attached to a temperature sensitive fire protection device 12. This fire protection device 12, in the preferred embodiment, includes a base member 14 to which the various components of the alarm system are attached. One such component is a bell 16 which is utilized to generate an audible alarm signal when the fuse assembly 10 responds to high ambient temperatures from a fire.
A trigger pin 18 is reciprocally mounted on the base member 14 and includes an enlarged flange 20 which is free to reciprocate within an opening 22 in the base member 14. An annular flange 24 in the base member 14 serves as a lower support for a spring 26 which engages the flange 20 and thereby biases the trigger pin 18 in an upward direction as viewed in FIG. 2. The upper extremity of the trigger pin 18 is in contact with the fuse assembly 10 and will penetrate and pass through the fuse assembly 10 when the fuse assembly 10 reaches an elevated temperature, as explained below. This vertical movement of the trigger pin 18 through the fuse assembly 10 will trigger the fire protection apparatus to sound the bell 16 and thereby produce an audible warning of a fire.
A pair of screws 28 act in conjunction with a retaining ring 30 to hold the various elements of the fire protection device 12 together. A thin washer 32 may be used to hide the screws 28 from view when the fuse assembly 10 is removed from the fire protection device 12.
The retaining ring 30 includes a central frustoconical element 34 which includes an internal annular ridge 36 surrounding a central bore through which the trigger pin 18 may freely reciprocate.
Through the use of an eyelet or rivet 38 the annular ridge 36 mounts a hollow vertical protruding stud or pin member 40 which is circular and includes an enlarged, protruding ridge 42 near its outer extremity and inwardly extending valley 44 adjacent the retaining ring 30. The eyelet 38 is inserted through the retaining ring 30 and the stud or pin member 40 and swaged in that position to hold the stud or pin member 40 in position on the retaining ring 30.
The fuse assembly 10 includes a circular heat collecting member 46 which is generally convex in shape in order to strengthen this member 46 as much as possible and to thereby allow it to be made extremely thin. This thinness of the heat collecting member 46 allows the collection of heat from the ambient air over a large surface area while maintaining the mass of the heat collecting member 46 low, thereby allowing rapid temperature change in response to changes in the temperature of the surrounding air. The center of the heat collecting member 46 includes a bore through which the trigger pin 18 may freely pass, this bore being surrounded by an outwardly and downwardly extending flange 48.
Soldered to the heat collecting member 46 at the shoulder surrounding the upper extremity of the flange 48 is a fuse element 50 which blocks the bore through the center of the heat collecting member 46 and maintains the trigger pin 18 in the position shown in FIG. 2. The solder 52 which is used to connect the fuse member 50 to the heat collecting member 46 is made from a eutectic alloy which has a melting point temperature in the range which is achieved during the early stages of a fire in a building or structure. This alloy solder 52 will therefore melt in response to increased temperatures caused by a fire and will allow the fuse member 50 to be pushed from the central bore of the heat collecting member 46 by the trigger pin 18 under the action of the spring 26, thereby triggering the fire protection device 12. The cover member 54 maybe attached to the fuse element 50 in order to hide a warning label 56. This label 56 makes the fact that the fuse element 50 is no longer in place on the heat collecting member 46 visually apparent. Since the heat collecting member 46 is connected to the fuse element 50 by use of the eutectic alloy solder 52, there is good thermal contact between the heat collecting member 46 and the fuse member 50. Therefore, heat which is collected by the heat collecting member 46 may readily be conducted to raise the temperature of the fuse element 50 and the solder 52 which holds it in place.
The flange 48 on the heat collecting member 46 is formed through a swaging operation which also serves to connect the heat collecting member 46 to a socket or receiver 58. This receiver 58 acts as an interconnecting member with the stud or pin member 40 so that this pair of interconnecting members 40 and 58 are used to removably attach the fuse assembly 10 to the fire protection device 12. The receiver 58 is insulated from the flange 48 of the heat collecting member 46 through the use of an insulating spacer 60, typically formed of material having a low thermal conduction properties, such as a plastic. The flange 48 is swaged over the insulating spacer 60 and the receiver 58 so that a rigid assembly is formed between the heat collection member 46 and receiver 58 while maintaining thermal isolation between these elements. This thermal isolation insures that the greatest possible percentage of the heat which is collected in the heat collected member 46 is conducted to raise the temperature of the fuse element 50 rather than that of the receiver 58.
The receiver or socket 58 includes a circular retaining portion 61 which supports a circular resilient split ring 62. This split ring 62, in its relaxed position, is smaller than the largest inside diameter of the circular retaining portion 61, but is not small enough to pass below a lower flange 64 of the retaining portion 61 and is therefore confined to rest within the retaining portion 61. The split ring 62 can expand within the retaining portion 61 to a sufficient degree to pass over the enlarged ridge 42 of the stud or pin member 40. In its relaxed condition the split ring 62 is slightly smaller than the undercut or valley portion 44 of the stud or pin member 40, so that it will grip the valley portion 44 snugly when the fuse assembly 10 is in position, as shown in FIG. 2. The force required to remove the split ring 62 from the stud or pin member 40 is greater than that which is produced by the spring 26 on the trigger pin 18, so that once the fuse assembly 10 is positioned on the fire protection system 16, the split ring 62 acting against the enlarged ridge 42 will maintain the fuse assembly 10 in position.
It can be seen from FIG. 2 that the application of the fuse assembly 10 to the fire protection device 16 requires only a unidirectional application of force through the center of the fuse assembly 10 and along the axis of the fuse assembly 10 in order to fuse the split ring 62 past the enlarged ridge 42 of the stud or pin member 40. This application of the fuse assembly 10 occurs with a snapping action as the split ring 62 passes over the ridge 42. During this assembly, no force need be applied to the heat collection member 46 other than at its center where it is reinforced with the fuse member 50. The heat collection member 46 may, therefore, be made very thin, since it does not have to absorb the forces which are applied during application. The snap-action of the split ring 62 over the enlarged ridge 42 makes it impossible to install the fuse assembly 10 to a sufficient degree to hold it in place on the fire protection device 12 without properly fusing the fire protection device 12.
It will be recognized that the application of the fuse assembly 10 to the fire protection device 16 simultaneously depresses the trigger pin 18, and that the axis of the fuse assembly 10 is placed directly over the trigger pin 18 so that the same force which is used to apply the socket 58 to the stud or pin member 40 may be used to depress the trigger pin 18. The unidirectional force therefore occurs along the axis of both the fire protection system 12 and the fuse assembly 10 and creates a snapping interconnection which assures proper fusing of the fire protection system 12 without application of stress to the heat collection member 46.
As shown in FIG. 2, the inwardly extending valley 44 of the stud or pin member 40 is sufficiently long in the direction of the axis of the pin member 40 to allow the split ring 62 a limited degree of freedom to move toward the trigger pin 18, or to cant about the upper extremity of the trigger pin 18, without becoming dislodged from the pin member 40. This freedom allows the fuse assembly 10 to absorb the force of accidental blows from foreign objects without damage thereto, thus increasing the reliability of the fuse assembly 10.