JP7733174B2 - Alarm bell - Google Patents

Description

This invention relates to an alarm bell that produces a bell sound when a motor-driven hammer strikes a gong.

An alarm bell includes a gong that produces a sound when struck, a striker that strikes the gong, a motor that drives the striker, and a housing that houses the motor. It rings to sound an alarm in the event of an emergency such as a fire (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 2000-235394

The main uses of this type of alarm bell are as local sounding devices in automatic fire alarm systems and emergency bells in emergency alarm systems (hereafter simply referred to as "emergency bells"). Standards for emergency bells are set in accordance with the Fire Service Act. One of these standards is sound pressure. Alarm bells used as emergency bells must meet the sound pressure standard.

Reducing the size of an alarm bell's gong can reduce manufacturing costs. However, simply reducing the size of the gong reduces the sound pressure, making it difficult to achieve the sound pressure required for use as an emergency bell.

In consideration of the above circumstances, this invention aims to provide an alarm bell that can increase the sound pressure of the bell sound produced by the gong.

This invention relates to an alarm bell comprising a gong that is circular in plan view and produces a bell sound when struck, a striker for striking the gong , and a motor for driving the striker. The gong has only two slits formed in the rim of its peripheral side , spaced equally apart in the circumferential direction , and has an antinode for the gong's vibration located within an angular interval of 35 to 55 degrees from one of the slits in the circumferential direction, and the striker strikes a position within this 35 to 55 degree angular interval.

The striking rod may strike positions at angular intervals of approximately 45 degrees in the circumferential direction from one of the slits, where the antinode of vibration of the gong is located.

Furthermore, the present invention may further include a housing that houses the motor, and the housing may have a plurality of curved wall portions that are bent in a V-shape in a planar view in the circumferential direction as part of its peripheral wall.

The curved wall portions may have substantially the same shape and may be arranged at substantially equal intervals in the circumferential direction. The housing may be Y-shaped or cross-shaped in plan view. The housing may have multiple branch spaces formed therein, and the motor and its power transmission unit that transmits power to the striking rod may be disposed and housed in these branch spaces.

The present invention can further include a mounting plate for mounting the alarm bell in an installation position, and the gong can have an outer diameter that, when mounted, exposes an insertion hole for a fixing member provided at the end of the mounting plate to the outside. The housing can also have an opening on its back side and a lid that closes the opening, with an insulating sheet provided between the opening and the lid to seal the opening.

According to this invention, the striking rod strikes a position within an angular range of 35 to 55 degrees circumferentially from the slit, where the antinode of the gong's vibration is located. This improves the efficiency of the gong's vibration caused by the strike, and increases the sound pressure of the chime produced by the gong.

1 shows an example of an embodiment of the alarm bell of the present invention, and is a rear view (with the back cover of the housing open) showing the inner side (rear side) of the alarm bell. FIG. 2 is a cross-sectional view taken along the line AA in FIG. 1. FIG. This shows an example of an installation form when the above alarm bell is installed as a rainproof type, and is a surface view showing the alarm bell, mounting plate, and the surface of the wall on which it is to be installed. 6 is a cross-sectional view of the alarm bell, the mounting plate, and the wall surface side of the installation target (wall surface, switch box, etc.), taken along the line E-E in FIG. 5. FIG. FIG. 2 is an exploded perspective view of the alarm bell, the mounting plate, and the wall-side portion of the installation target (wall, switch box, etc.).

An example of an embodiment of the alarm bell of this invention will be described with reference to the drawings. The alarm bell of this invention can be used, for example, as a district sounding device in an automatic fire alarm system or as an emergency bell in an acoustic device in an emergency alarm system.

<Basic configuration>
The alarm bell 1 comprises a gong 2 that produces a bell sound when struck, a striking rod 3 that strikes the gong 2, a motor 4 that drives the striking rod 3, a cam 5 that is fixed to the drive shaft 4a of the motor 4 and rotates together with the drive shaft 4a, a power transmission unit 6 that is connected to the striking rod 3 and the cam 5 and transmits the power of the motor 4 to the striking rod 3, and a housing 7 that houses the motor 4 and other components (see Figures 1 to 3).

<Gong>
The gong 2 has a bottom 2b and a peripheral portion 2c, forming a shallow, circular, bowl-like shape in plan view. A space 2a is formed on the inner surface, surrounded by the peripheral portion 2c. The housing 7 is positioned within the space 2a so that the striking rod 3 strikes the inner surface of the peripheral portion 2c from the inside. Specifically, a fixing portion 2ba for fixing the housing is provided on the inner surface of the bottom 2b (see Figures 2 and 3), and the housing 7 is fixed to the fixing portion 2ba. The peripheral portion 2c has a slit 2e formed in its rim 2d. In the illustrated example, two slits 2e are formed, one at each 180-degree circumferential position around the peripheral portion 2c.

<Batter stick>
The striking rod 3 is positioned so that when it moves longitudinally forward (towards the gong 2 ), the striking portion 3 a at the tip strikes the inner surface of the peripheral portion 2 c of the gong 2 .

<Motor>
The motor 4 is disposed so that the drive shaft 4a is oriented at a substantially right angle to the longitudinal direction of the hitting rod 3. A cam 5 is provided around the drive shaft 4a, which rotates together with the drive shaft 4a.

<Power transmission section>
The power transmission unit 6 consists of a linear member whose tip end is connected to the striking rod 3 at a connection part 6a and whose rear end is connected to the cam 5 at a connection part 6b, and is arranged so that the power of the rotational movement of the motor 4 is converted into power of reciprocating movement via the cam 5 and transmitted to the striking rod 3, moving the striking rod 3 back and forth in the longitudinal direction.

<Housing>
Shape and Arrangement: The housing 7 has multiple curved wall portions 7aa that form part of its peripheral wall 7a and are bent in a V-shape in a plan view (widening toward the peripheral portion 2c of the gong 2). In the illustrated example, there are three curved wall portions 7aa, giving the housing 7 a Y-shape in a plan view. The multiple curved wall portions 7aa are substantially identical in shape and are evenly spaced in the circumferential direction. The housing 7 is arranged in such a shape, approximately centrally in a plan view, within the space 2a on the inner surface of the gong 2. Because the multiple curved wall portions 7aa are bent at an angle rather than a curve, the space 2a on the inner surface of the gong 2 can be enlarged and the direction in which the chime is reflected can be expanded.

The housing 7 also has multiple end walls 7ab that form part of the peripheral wall 7a and connect the curved wall portions 7aa. In the illustrated example, there are three end walls 7ab, corresponding to the number of curved wall portions 7aa. These multiple end walls 7ab are also of approximately the same shape and are arranged approximately evenly around the circumference. The housing 7 also has a bottom wall 7b. The bottom wall 7b has a protrusion 7ba on its outer surface (with a recess on its inner surface) that is fixed to the fixing portion 2ba on the gong 2. The housing 7 is arranged in the above-mentioned manner within the space 2a on the inner surface of the gong 2 by fastening the protrusion 7ba to the fixing portion 2ba on the gong 2 with screws 7bb.

The housing 7 also has a back cover 7g that closes the opening 7f on the back side, and in the illustrated example, an insulating sheet 7h is provided between the opening 7f and the back cover 7g (see Figure 3). The insulating sheet 7h seals the opening 7f to prevent corrosive gases and other contaminants from entering the interior 7c of the housing 7, thereby protecting the motor 4 and other components housed in the housing 7. The portion marked with a symbol on the outside of the back cover 7g is a hook 7i used to hang the alarm bell 1 on an object to which it is attached.

- Equalization of surrounding space Here, the peripheral wall 7a of the housing 7 has multiple curved wall portions 7aa that are V-shaped when viewed from above, and these curved wall portions 7aa are of approximately the same shape and are arranged in an approximately even circumferential direction.As a result, the space formed between these curved wall portions 7aa and the peripheral side portion 2c of the gong 2 in the space portion 2d on the inner surface of the gong 2 can also be formed in an approximately same shape and arranged in an approximately even circumferential direction.

・Improved sound pressure (due to the housing shape, surrounding space, etc.)
In the alarm bell 1 of this invention, the housing 7 has multiple curved wall portions 7aa that are V-shaped in plan view and form part of the peripheral wall 7a. This allows the multiple curved wall portions 7aa to function as acoustic walls, improving the resonance effect within the space 2a inside the gong 2. Furthermore, by providing the multiple curved wall portions 7aa with substantially the same shape and uniformly spaced circumferentially, the spaces formed between the curved wall portions 7aa and the peripheral portion 2c of the gong 2 in the space 2d inside the gong 2 can also be formed with substantially the same shape and uniformly spaced circumferentially, as described above. This also improves the resonance effect within the space 2a inside the gong 2. Furthermore, using a housing 7 with a Y-shape in plan view, as shown in the example shown, can increase the sound pressure of the chime generated by the gong 2, as shown in the sound pressure measurement experiment results described below.

・Sound pressure measurement experiment (compared to a case using an L-shaped housing in plan view)
The inventors conducted an experiment to measure the sound pressure of an alarm bell using a Y-shaped housing as in the present invention to house the motor and power transmission unit, and an alarm bell using an L-shaped housing as in the present invention. The results of the experiment showed that the sound pressure was higher in the alarm bell using a Y-shaped housing as in the present invention than in the alarm bell using an L-shaped housing as in the present invention. This result is believed to be due to the fact that, as mentioned above, in the alarm bell using a Y-shaped housing as in the present invention, the multiple curved walls function as acoustic walls, and the multiple curved walls are generally the same shape and are arranged in a generally uniform manner, and the spaces formed between the curved walls and the circumferential sides of the gong are also generally the same shape and are generally uniformly distributed in the circumferential direction, thereby improving the resonance effect in the space on the inner surface of the gong.

The inventors also used a simulation program to analyze the sound pressure distribution of the alarm bells used in the above-mentioned measurement experiments. The analysis revealed that, within the space on the inside of the gong, when a housing with an L-shape in plan view was used, high-pressure areas were unevenly distributed, whereas when a Y-shape was used, high-pressure areas were distributed approximately evenly radially. Furthermore, on the outside of the gong, when a housing with an L-shape in plan view was used, high-pressure areas were distributed circumferentially to the sides of the gong and were also distributed in front of the gong, away from the front. However, when a Y-shape in plan view was used, high-pressure areas were distributed in a continuous ring shape to the sides of the gong and were concentrated in front of the gong. These results demonstrate that using a Y-shape in plan view, as in this invention, can improve the resonance effect within the space on the inside of the gong, thereby increasing the sound pressure of the gong sound.

Branch Spaces: The interior 7c of the housing 7 is formed with multiple branch spaces 7cb-7cd, corresponding to the case shape. In the illustrated example, three branch spaces 7cb-7cd are formed branching off from the central space 7ca, corresponding to the Y-shaped case shape in plan view. The shape of each of the branch spaces 7cb-7cd toward the tip end (the side toward the circumferential portion 2c of the gong 2) is generally rectangular in plan view.

Of the branch spaces 7cb-7cd, the striking rod 3 penetrates the end wall 7ab of branch space 7cb, with the connection portion 3b with the power transmission unit 6 at the rear end located inside branch space 7cb and the striking portion 3a at the front end located outside branch space 7cb. Branch space 7cb, where the striking rod 3 is located, is connected to the adjacent branch space 7cc via the central space 7ca, forming a continuous V-shaped space together with these spaces in a plan view. The motor 4 and power transmission unit 6 are housed within this V-shaped space. Specifically, the motor 4 is housed in an arrangement where the main body side is located within the branch space 7cc and the drive shaft 4a side is located within the central space 7ca, while the power transmission unit 6 is housed in an arrangement where the connection part 6b with the cam 5 is located within the central space 7ca and the connection part 6a with the bat 3 is located within the branch space 7cb, extending approximately perpendicular to the drive shaft 4a. Furthermore, a support member such as a collar 7d is provided at the end wall 7ab of the branch space 7cb where the bat 3 passes through, allowing the bat 3 to move back and forth in the longitudinal direction.

The number and shape of the branch spaces within the housing 7 can be changed by changing the angle, number, and arrangement of the bends in the V-shaped curved wall portion 7aa in plan view, and by changing the shape of the housing 7.

Bending angle of the V-shaped curved wall portion in plan view In the illustrated example, the bending angle of the curved wall portion 7aa is approximately 120 degrees. The reason for setting this bending angle to approximately 120 degrees is that the shape of the branch spaces 7cb to 7cd toward their tip ends can be made approximately square in plan view. Note that this bending angle can be changed by changing the number of curved wall portions 7aa and the shape of the housing 7.

Shape of the Portion Through which the Batting Rod Passes While the multiple curved wall portions 7aa and end walls 7ab have been described as having substantially the same shape, in the illustrated example, some of the shapes are slightly different. That is, only the end wall 7ab through which the batting rod 3 passes and the curved wall portion 7aa connected to that end wall 7ab have a slightly different shape from the others. Specifically, the end wall 7ab through which the batting rod 3 passes is slightly bent so that the portion through which the batting rod 3 passes is oriented substantially perpendicular to the length of the batting rod 3 (the direction of movement of the batting rod 3). Furthermore, the curved wall portion 7aa connected to that end wall 7ab is slightly shorter in length due to the inward bending of the end wall 7ab. The part of the end wall 7ab through which the striking rod 3 passes is oriented approximately perpendicular to the longitudinal direction of the striking rod 3 because the amplitude direction of the vibration of the gong 2 is perpendicular to the striking position, making it easier for the striking force to propagate as vibration.

<Gong striking position>
Vibration Antinodes and Angular Spacing from the Slits: The gong 2 can have vibration antinodes located at angular intervals of 35 to 55 degrees circumferentially from the slit 2e in the circumferential side 2c (angular intervals from the circumferential midpoint of the slit; the same applies below). The striking rod 3 can be positioned to strike positions within this angular interval. In the illustrated example, the gong 2 has vibration antinodes located at angular intervals θ of approximately 45 degrees circumferentially from the slit 2e in the circumferential side 2c, and the striking rod 3 is positioned to strike positions at these angular intervals θ.

-Improved sound pressure (due to the gong striking position)
In the alarm bell 1 of this invention, the vibration efficiency of the gong 2 can be improved by striking positions within an angular range of 35 to 55 degrees circumferentially from the slit 2e in the circumferential side 2c, where the antinodes of the vibration of the gong 2 are located. Furthermore, by striking positions within this angular range at angular intervals of approximately 45 degrees, as in the illustrated example, the sound pressure of the gong 2 can be increased, as will be shown in the results of a sound measurement experiment described below.

- Sound pressure measurement experiment (compared to hitting positions spaced approximately 90 degrees apart)
The inventors conducted an experiment to measure the sound pressure of the gong sound produced by striking the gong with the striker at a position on the gong's vibration antinode, approximately 45 degrees apart from the slit on the periphery of the gong, as in the present invention, and at a position approximately 90 degrees apart in the same direction.The results of the experiment showed that the sound pressure of the gong struck at a position approximately 45 degrees apart from the slit was higher than that of the gong struck at a position approximately 90 degrees apart from the slit.This result is believed to be due to the fact that striking a position closer to the slit, which is on the gong's vibration antinode, improves the vibration efficiency of the gong when struck, as mentioned above.

The inventors also conducted sound pressure measurements when striking a position approximately 8 degrees circumferentially (approximately 53 degrees from the slit) away from a position approximately 45 degrees from the slit (the position of the vibration antinode). The sound pressure obtained was comparable to that obtained when striking a position approximately 45 degrees apart. From this, it can be concluded that, while the most preferable striking position for the gong 2 with the striker 3 is the antinode of the gong 2's vibration, even if the striking position is shifted from this position, as long as the shift is within a circumferential range of approximately ±10 degrees, a similar improvement in sound pressure can be expected. Of course, it can also be concluded that a similar improvement in sound pressure can be expected as long as the shift is within a circumferential range of approximately ±5 degrees. That is, for example, if the antinode of the vibration of the gong 2 is located approximately 45 degrees circumferentially from the slit 2e as in the example shown, then even if the striking position is shifted from that position, as long as the striking position is within an angular range of 35 to 55 degrees circumferentially from the slit 2e, it can be expected that the same degree of improvement in sound pressure can be achieved. Of course, if the striking position is within an angular range of 40 to 50 degrees circumferentially from the slit 2e, it can be expected that the same degree of improvement in sound pressure can be achieved.

<Example of housing shape change>
The shape of the housing 7 can be modified as appropriate as long as it has portions corresponding to the plurality of V-shaped curved wall portions 7aa in plan view. For example, the bending angles of the V-shaped curved wall portions 7aa in plan view may be set to approximately right angles, the number of the V-shaped curved wall portions 7aa may be set to four, and the housing 7 may have a cross shape in plan view.

<Other parts that contribute to improving sound pressure>
Thinning the Gong's Bottom Near the Center: In the illustrated example, the gong 2 has a continuous annular groove 2bb around the fixing portion 2ba, which is located approximately in the center of the gong's bottom surface in a plan view. The groove 2bb reduces the thickness of the gong 2 near the center of the bottom surface in a plan view. When the sound pressure of the gong 2 was measured with and without the thinning, the sound pressure was higher with the thinned portion than without the thinned portion. This suggests that the sound pressure of the gong 2 can be increased by providing the groove 2bb and thinning the bottom surface of the gong 2 near the center of the bottom surface in a plan view.

<Benefits of improved sound pressure>
As mentioned above, the alarm bell 1 of this invention can increase the sound pressure of the bell. This allows the gong 2 to be made smaller, but still meet the sound pressure standards required by the Fire Service Act when used as an emergency bell.

・Sound pressure measurement experiment (sound pressure when the gong is made smaller)
The outer diameter of a gong in a conventional emergency bell is typically 150 mm. The inventors prepared a prototype alarm bell with a smaller gong diameter of 130 mm, and conducted experiments measuring the sound pressure of the bell sound. The results showed that the prototype achieved a sound pressure of 90 dB or more, the standard required by the Fire Service Act. This result is believed to be due in particular to the fact that the prototype's housing is Y-shaped in plan view, as in the housing 7 shown in the figure, and that the striking position of the bat, as in the striking position of the bat 3 shown in the figure, is located at the antinode of the gong's vibration and is spaced approximately 45 degrees circumferentially from the slit on the periphery of the gong.

In other words, in the alarm bell 1 of this invention, as shown in the example, the housing 7 has a Y-shape in plan view, and the striking position of the gong 2 with the striking rod 3 is at the antinode of the gong 2's vibration, and is located approximately 45 degrees circumferentially from the slit 2e in the peripheral side portion 2c of the gong 2. Therefore, even if the outer diameter of the gong 2 is reduced to, for example, 130 mm, it will still be able to meet the sound pressure standards required by the Fire Service Act when used as an emergency bell.

In addition, in Figures 1 to 3, as well as Figures 4 to 6, which will be referred to later in the explanation of how to make the alarm bell 1 weatherproof, the dimensional ratios of each part are shown assuming that the outer diameter of the gong 2 is 130 mm.

<Advantages of a smaller gong>
Reduction of manufacturing costs As described above, the alarm bell 1 of the present invention allows the gong 2 to be made smaller, thereby reducing manufacturing costs.

・Improved workability (when used as a rainproof type)
4 and 5 show how the rainproof alarm bell 1 is mounted in a wall W with a flush-mounted switch box 50 embedded therein. The switch box 50 is embedded in the wall W together with a front paint cover 40, and a rainproof mounting bracket 30 (a three-layer structure with waterproof packing on the front and back of the bracket) is exposed on the surface of the wall W and attached to the paint cover 40 with screws. The rainproof alarm bell 1 has a rainproof mounting plate 7j (which has an internal space and may be referred to as a case, box, etc.) on the back side of the housing 7 in place of the back cover 7g (or may have this in addition to the back cover 7g and insulating sheet 7h). When the switch box 50 is mounted in the wall W, the mounting plate 7j is fastened to the mounting bracket 30 on the switch box 50 side with screws 7jb (an example of a fastening member)

Here, the mounting bracket 30 on the switch box 50 side is a general-purpose part, and the screw holes 30a into which the alarm bell 1 is screwed are located at positions determined by standards. The screw holes 7ja (an example of a through-hole for a fixing member) on the mounting plate 7j on the alarm bell 1 side are located at positions corresponding to the screw holes 30a on the mounting bracket 30 on the switch box 50 side. In the illustrated example, the screw holes 7ja are provided at each corner (an example of an end) of the mounting plate 7j. If the gong 2 has a large outer diameter of 150 mm, as in conventional products, the screw holes 7ja would be hidden behind the gong 2 in a plan view. In this case, when the mounting plate 7j is attached to the gong 2 together with the housing 7, it is not possible to insert the screws 7jb into the screw holes 7ja and screw them into the screw holes 30a on the mounting bracket 30 on the switch box 50 side. Therefore, once the gong 2 and housing 7 are assembled, they must be removed, the mounting plate 7j screwed to the mounting bracket 30 on the switch box, and then the gong 2 and housing 7 must be reassembled. However, if the gong 2 is small, with an outer diameter of, for example, 130 mm, as in the present invention, even when the housing 7 is attached to the gong 2, the screw holes 7ja in the mounting plate 7j are located on the outside of the gong 2 and are exposed to the outside, so the screws 7jb can be used to screw the gong 2 into the mounting bracket 30 on the switch box 50.

In other words, the alarm bell 1 of this invention allows for the gong 2 to be made smaller, which improves ease of installation when installing it as a weatherproof type.

<Example of configuration change>
In the alarm bell 1 of the present invention, the configuration can be changed, for example, as follows.

For example, the outer diameter of the gong 2 is not necessarily limited to 130 mm, and may be larger or smaller. Even if the outer diameter is increased or decreased in this way, it is possible to improve the sound pressure of the gong sound by configuring the shape of the housing 7 and the striking position of the mallet 3 as described above.

1: Alarm bell 2: Gong 2a: Space 2b: Bottom 2ba: Fixing part 2bb: Groove 2c: Peripheral side 2d: Rim 2e: Slit 3: Mallet 3a: Striking part 3b: Connection part 4: Motor 4a: Drive shaft 5: Cam 6: Power transmission part 6a: Connection part (mallet side)
6b: Connection part (cam side) 7: Housing 7a: Peripheral wall 7aa: Curved wall part 7ab: End wall 7b: Bottom wall 7ba: Convex part 7bb: Screw 7c: Inside 7ca: Central space part
7cb to 7cd: Branch space 7d: Collar 7f: Opening 7g: Back cover 7h: Insulation sheet 7i: Hook 7j: Mounting plate 7ja: Screw hole 7jb: Screw 30: Mounting bracket 40: Paint margin cover 50: Switch box W: Wall surface

Claims (2)

An alarm bell comprising: a gong that is circular in plan view and produces a bell sound when struck; a striking rod that strikes the gong; and a motor that drives the striking rod ,
The gong has only two slits formed in the rim of its peripheral side at equal angular intervals in the circumferential direction , and has antinodes of vibration of the gong at angular intervals of 35 to 55 degrees from one of the slits in the circumferential direction,
The alarm bell is characterized in that the striking rod strikes a position within the range of the angular interval. 2. The alarm bell according to claim 1, wherein the striking rod strikes a position at an angular interval of approximately 45 degrees in the circumferential direction from one of the slits, where the antinode of vibration of the gong is located.