An overload switch device for improving the firing rate of a small-angle fuse and its implementation method

Abstract

The present invention discloses an overload switch device for improving the firing rate of a small-angle fuze and its implementation method. The present invention arranges a plurality of elastic bodies symmetrically distributed around the inertial body to improve the utilization capacity of radial overload; the radial overload received is directly converted into the axial movement of the lower electric body by the elastic body, and has a higher radial overload utilization capacity in the small-angle overload environment. As the elastic body is unfolded, the elastic body pushes the lower electric body close to the upper electric body; when hitting the target, the overload signals along the radial and axial directions can be used as effective forces to drive the inertial body to move, making full use of the high radial overload in the small-angle situation; at the same time, the use of the axial spring mechanism also maintains the original axial overload perception ability; the threshold of the action environment of the present invention can be flexibly adjusted, and by adjusting the mass of the inertial body, the stiffness of the spring mechanism and the elastic body and the pre-compression amount, it can adapt to the application environment of different fuzes and adjust the sensitivity of the device to a suitable range.

Description

Technical Field

[0001] The invention relates to the technical field of ammunition fuzes, and in particular to an overload switch device for improving the firing rate of a small-angle fuze and a realization method thereof. Background Art

[0002] The inertial firing mechanism of the fuze uses the acceleration overload signal generated by the ammunition hitting the target to close the firing switch, thereby ensuring the realization of the fuze function. The inertial firing mechanism needs to reliably sense the terminal ballistic overload environment, and at the same time ensure that the collision with non-target objects avoids the occurrence of accidental firing.

[0003] With the diversified development of weapon application scenarios, it is common for weapons and ammunition to explode on the ground or touch the ground at other small angles on different ground and terrain. This makes the reliable and correct firing of fuzes at small angles particularly important both for the lethal effect on the battlefield and for the safety of personnel.

[0004] The angle between the axis of the projectile shaft and the target plane is called the drop angle, and a drop angle of no more than 15° is generally considered a small drop angle. Since the posture of the ammunition hitting the ground is very random, the traditional one-way overload sensing switch is difficult to sense the collision force in a large range. Especially in the case of small drop angles, compared with the axial overload, the radial overload is obviously stronger. How to make full use of the radial overload is the main problem faced by the current fuze inertial firing mechanism when firing at small drop angles. The current small drop angle overload switch device is insufficient in its ability to perceive and utilize radial overloads, which also leads to room for further improvement in the firing rate. Summary of the invention

[0005] In view of the above defects or deficiencies in the prior art, the present invention proposes an overload switch device and an implementation method thereof for improving the firing rate of small-angle fuzes, so as to meet the specific needs of reliable detonation of small-angle fuzes.

[0006] The fuze of the ammunition is located at the head of the projectile, and the fuze has a signal processing module and an ignition realization module built in the fuze, the signal processing module has an ignition circuit, and the ignition circuit is connected to the ignition realization module. The overload switch device for improving the ignition rate of the small-angle fuze of the present invention is located in the fuze of the ammunition.

[0007] An object of the present invention is to provide an overload switch device for improving the firing rate of a small-angle fuse.

[0008] The overload switch device for improving the firing rate of a small-angle fuse of the present invention comprises: an external shell, an inertial body, an elastic body, a lower electrical contact, an upper electrical contact, a moving contact, a fixed contact and a spring mechanism; wherein the external shell is a tube having no upper bottom and a lower bottom, and has a cylindrical cavity inside, and the central axis of the cylindrical cavity is located at the elastic axis; an inertial body is placed in the external shell and at the center of the bottom, the inertial body is in the shape of a cylinder, the central axis of the cylinder is located at the elastic axis, and the diameter of the inertial body is smaller than the inner diameter of the external shell; a plurality of elastic bodies are arranged between the inner wall of the external shell and the side wall of the inertial body, the plurality of elastic bodies are centrally symmetrically distributed about the elastic axis, the elastic body stretches in a direction parallel to the elastic axis when subjected to radial force, and the distance between the two ends of the elastic body in a free state is equal to the height of the inertial body; a lower electrical contact is placed in the external shell and on the inertial body and the plurality of elastic bodies, the outer diameter of the lower electrical contact is not larger than the inner diameter of the external shell, and the lower electrical contact can move up and down along the elastic axis; the upper electrical contact is fixedly installed on the top of the external shell The electric body; spring grooves are respectively provided on the lower surface of the upper electric body and the upper surface of the lower electric body, the upper end and the lower end of the spring mechanism are respectively located in the spring grooves of the upper electric body and the lower electric body, the central axis of the spring mechanism is located on the elastic axis and the extension direction is parallel to the elastic axis, the distance between the surfaces of the spring grooves of the upper electric body and the lower electric body is less than the free length of the spring mechanism, the spring mechanism is in a compressed state, and the spring mechanism is insulated from the upper electric body and the lower electric body; a fixed contact connected to the upper electric body as a whole and electrically connected is provided on the surface of the spring groove of the upper electric body, the fixed contact exceeds the lower surface of the upper electric body, and a moving contact connected to the lower electric body as a whole and electrically connected is provided on the surface of the spring groove of the lower electric body, and the moving contact is higher than the upper surface of the lower electric body; before the ammunition hits the target, the fixed contact and the moving contact are located on the elastic axis and there is a distance between them, and the distance between them is less than the maximum elongation distance of the elastic body; the moving contact, the fixed contact, the upper electric body and the lower electric body are all made of conductive materials;

[0009] The upper electrical connection body and the lower electrical connection body are respectively connected to two ends of the firing circuit of the signal processing module of the fuze through a wire, and the firing circuit is turned on when the moving contact contacts the fixed contact;

[0010] During daily storage and service handling, the spring mechanism has rigidity, and the environmental force is not enough to compress the spring mechanism to cause the moving contact to contact with the fixed contact, and the firing circuit is open, which will not cause the fuze to detonate, ensuring the safety of daily storage and service handling of ammunition; when the ammunition moves to the terminal trajectory to hit the target after being fired, when the terminal trajectory is not a small drop angle, the axial overload is greater than the radial overload, and the inertial body mainly feels the axial overload. Under the action of the axial overload, the inertial body pushes the lower contact body to move along the direction of the axis of the bullet toward the direction of the fuze head, compressing the spring mechanism, and finally making the fixed contact connected to the upper contact body as a whole contact with the moving contact connected to the lower contact body as a whole, the firing circuit is closed, the detonation and firing realization module is detonated, and the fuze realizes the firing function; at the terminal trajectory When the falling angle is small, the radial overload is greater than the axial overload, and the inertial body mainly feels the radial overload. Under the action of the axial overload, the inertial body pushes the lower contact body to move along the axis of the projectile toward the head of the fuze, compressing the spring mechanism. At the same time, under the action of the radial overload, the inertial body squeezes the elastic body located in this radial direction, and the elastic body is expanded along the axis of the projectile under the action of the radial overload. Along with the expansion process of the elastic body, the lower contact body is pushed to move along the axis of the projectile toward the head of the fuze and close to the upper contact body, compressing the spring mechanism. The elastic body converts the radial overload it receives into the axial movement of the lower contact body, and finally makes the fixed contact connected to the upper contact body as a whole contact with the moving contact connected to the lower contact body as a whole; the ignition circuit is closed, the ignition realization module is initiated, and the fuze realizes the ignition function.

[0011] According to the specific situation, adjust the mass of the inertial body, the stiffness of the spring mechanism and the elastic body, and the pre-compression of the spring mechanism to adjust the end-point ignition sensitivity of the overload switch device to an appropriate range. Controlling the balance between the end-point ignition sensitivity of the overload switch device and the service handling insensitivity is the key to achieving reliable ignition. The greater the mass of the inertial body, the smaller the stiffness of the spring mechanism and the elastic body, the pre-compression of the spring mechanism is 2~6mm, and the higher the sensitivity of the acceleration switch device, and vice versa. The initial resistance of the spring mechanism is 0.2N~0.6N.

[0012] The outer surface of the outer shell is cylindrical in shape, with a diameter of 10~30mm and a height of 15~30mm. The material is aluminum, zinc or steel. The diameter of the cavity inside the outer shell is 7~24mm and the height is 12~26mm.

[0013] The inertial body is made of a material with high density, such as lead or steel; the diameter of the inertial body is 4~18mm; and the height is 5~15mm.

[0014] The material of the spring mechanism is one of carbon spring steel, low manganese spring steel, silicon manganese spring steel and chrome vanadium steel; it is a cylindrical helical spring or a conical helical spring, and the stiffness is controlled to be 0.2N / mm~0.8N / mm. Insulating sheets are respectively arranged at both ends of the spring mechanism, so that the two ends of the spring mechanism are insulated from the upper electrical connection body and the lower electrical connection body respectively. The elastic body adopts a reed, and the material is copper or steel. The number of multiple elastic bodies is 4~12.

[0015] The top inner wall surface of the external shell is provided with an internal thread, and the side wall of the upper electrical contact has an external thread, and the two are fixedly connected by threads.

[0016] The side wall of the lower contact has a distance of less than 2 mm from the inner wall of the outer shell, or the contact surface of the two is smooth, so that the lower contact can move freely up and down along the elastic axis. The moving contact, the fixed contact, the upper contact and the lower contact are made of aluminum or steel.

[0017] Another object of the present invention is to provide a method for realizing an overload switch device for improving the firing rate of a small-angle fuse.

[0018] The method for realizing an overload switch device for improving the firing rate of a small-angle fuse of the present invention comprises the following steps:

[0019] 1) The upper contact and the lower contact are connected to the two ends of the firing circuit of the signal processing module of the fuze through a wire respectively, and the firing circuit is turned on when the moving contact contacts the fixed contact;

[0020] 2) During daily storage and service handling, the spring mechanism has rigidity, and the environmental force is not enough to compress the spring mechanism to cause the moving contact to contact the fixed contact, and the firing circuit is open, so that the fuse will not be detonated, ensuring the safety of daily storage and service handling of ammunition;

[0021] 3) When the ammunition moves to the final trajectory and hits the target, it is divided into non-small angle and small angle:

[0022] a) When the terminal trajectory is not at a small drop angle, the axial overload is greater than the radial overload, and the inertial body mainly feels the axial overload. Under the action of the axial overload, the inertial body pushes the lower contact body to move along the direction of the missile axis toward the direction of the fuze head, compressing the spring mechanism, and finally making the fixed contact connected to the upper contact body contact with the moving contact connected to the lower contact body, the ignition circuit is closed, the ignition realization module is detonated, and the fuze realizes the ignition function;

[0023] b) When the terminal trajectory is at a small drop angle, the radial overload is greater than the axial overload, and the inertial body mainly feels the radial overload. Under the action of the axial overload, the inertial body pushes the lower contact to move along the axis of the projectile toward the fuze head, compressing the spring mechanism. At the same time, under the action of the radial overload, the inertial body squeezes the elastic body located in this radial direction, and the elastic body expands along the axis of the projectile under the action of the radial overload. Along with the expansion process of the elastic body, the lower contact is pushed to move along the axis of the projectile toward the fuze head and close to the upper contact, compressing the spring mechanism. The elastic body converts the radial overload it receives into the axial movement of the lower contact, and finally makes the fixed contact connected to the upper contact as a whole contact with the moving contact connected to the lower contact as a whole; the ignition circuit is closed, the ignition realization module is initiated, and the fuze realizes the ignition function.

[0024] Advantages of the present invention:

[0025] The present invention arranges a plurality of elastic bodies symmetrically distributed around the inertial body, which greatly improves the ability to utilize radial overload. In the past, small-angle overload sensing devices mostly use the combined force of radial force and axial force as a drive, which loses part of the overload signal to a certain extent. The present invention directly converts the radial overload suffered by the inertial body into the axial movement of the lower electric body through the elastic body, and has a higher radial overload utilization ability in the small-angle overload environment. With the expansion process of the elastic body, the elastic body pushes the lower electric body to approach the upper electric body. When the target is hit, the overload signals in the radial and axial directions can be used as effective forces to drive the inertial body to move, and the high radial overload in the small-angle situation can be utilized to a greater extent. At the same time, the use of the spring mechanism along the axial direction also maintains the original axial overload sensing ability. The threshold of the action environment of the present invention can be flexibly adjusted, and a combination of a spring mechanism and a plurality of elastic bodies is used to control the contact state of the switch. By adjusting the mass of the inertial body, the stiffness of the spring mechanism and the elastic body and the pre-compression amount, it adapts to the application environment of different fuzes, and adjusts the sensitivity of the device to a suitable range according to the specific situation. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A cross-sectional view along the axial direction of an embodiment of an overload switch device for improving the firing rate of a small-angle fuse according to the present invention;

[0027] Figure 2 A schematic diagram of the arrangement of multiple elastic bodies perpendicular to the axial direction in one embodiment of an overload switch device for improving the firing rate of a small-angle fuse according to the present invention;

[0028] Figure 3 The present invention is a cross-sectional view of the elastic body along the axial direction of an embodiment of the overload switch device for improving the firing rate of a small-angle fuse of the present invention. DETAILED DESCRIPTION

[0029] The present invention will be further described below through specific embodiments in conjunction with the accompanying drawings.

[0030] like Figure 1 As shown, the overload switch device for improving the firing rate of a small-angle fuse in this embodiment comprises: an outer shell 1, an inertial body 4, an elastic body 6, a lower electrical contact 3, an upper electrical contact 5, a moving contact 7, a fixed contact 8 and a spring mechanism 2; wherein the outer shell 1 is a tube having no upper bottom and a lower bottom, and has a cylindrical cavity inside, and the central axis of the cylindrical cavity is located at the elastic axis; the inertial body 4 is placed inside the outer shell 1 and at the bottom, and the shape of the inertial body 4 is a cylinder, and the diameter of the inertial body 4 is smaller than the inner diameter of the outer shell 1; as shown in FIG. Figure 2 and 3 As shown, a plurality of elastic bodies 6 are arranged between the inner wall of the outer shell 1 and the side wall of the inertial body 4, and the plurality of elastic bodies 6 are centrally symmetrically distributed about the elastic axis. When subjected to radial force, the elastic bodies 6 extend in a direction parallel to the elastic axis, and in a free state, the distance between the two ends of the elastic body 6 is equal to the height of the inertial body 4; a lower electrical connection body 3 is placed inside the outer shell 1 and on the inertial body 4 and the plurality of elastic bodies 6, and the outer diameter of the lower electrical connection body 3 is 1 mm smaller than the inner diameter of the outer shell 1, so that the lower electrical connection body 3 can freely move up and down along the elastic axis; an upper electrical connection body 5 is fixedly installed on the top of the outer shell 1; spring grooves are respectively provided on the lower surface of the upper electrical connection body 5 and the upper surface of the lower electrical connection body 3, and the upper end and the lower end of the spring mechanism 2 are respectively located on the upper electrical connection body 5 and the lower electrical connection body 3. In the spring groove of the body 3, the central axis of the spring mechanism 2 is located at the elastic axis and the extension direction is parallel to the elastic axis. The distance between the surfaces of the spring grooves of the upper electrical body 5 and the lower electrical body 3 is the free length of the spring mechanism 2, and the spring mechanism 2 is insulated from the upper electrical body 5 and the lower electrical body 3; a fixed contact 8 connected to the upper electrical body 5 as a whole and electrically connected is arranged on the surface of the spring groove of the upper electrical body 5, and the fixed contact 8 exceeds the lower surface of the upper electrical body 5; a moving contact 7 connected to the lower electrical body 3 as a whole and electrically connected is arranged on the surface of the spring groove of the lower electrical body 3, and the moving contact 7 is higher than the upper surface of the lower electrical body 3; there is a distance between the fixed contact 8 and the moving contact 7, and the distance between the two is less than the maximum value of the elastomer 6.

[0031] In this embodiment, the ammunition is a single-soldier rocket; the outer surface of the outer shell 1 is cylindrical, with a diameter of 20 mm, a height of 20 mm, and a material of steel; the inertial body 4 is made of lead; the spring mechanism 2 is a cylindrical helical spring, and the stiffness is controlled to be 0.2N / mm~0.8N / mm; insulating sheets are respectively provided at both ends of the spring mechanism 2, so that the two ends of the spring mechanism 2 are insulated from the upper power connection body 5 and the lower power connection body 3 respectively; the elastic body 6 is a spring sheet, and the material is copper; the number of elastic bodies 6 is 8. The top inner wall surface of the outer shell 1 is provided with an internal thread, and the side wall of the upper power connection body 5 has an external thread, and the two are fixedly connected by threads.

[0032] The implementation method of the overload switch device for improving the firing rate of a small-angle fuse in this embodiment includes the following steps:

[0033] 1) The upper electrical connection body 5 and the lower electrical connection body 3 are respectively connected to the two ends of the firing circuit of the signal processing module of the fuze through a wire, and the firing circuit is turned on when the moving contact 7 contacts the fixed contact 8;

[0034] 2) During daily storage and service handling, the spring mechanism 2 has rigidity, and the environmental force is insufficient to compress the spring mechanism 2 to cause the moving contact 7 to contact the fixed contact 8, and the firing circuit is open, so that the fuse will not be detonated, ensuring the safety of the daily storage and service handling of ammunition;

[0035] 3) When the ammunition moves to the final trajectory and hits the target, it is divided into non-small angle and small angle:

[0036] c) When the terminal trajectory is not a small drop angle, the axial overload is greater than the radial overload, and the inertial body 4 mainly feels the axial overload. Under the action of the axial overload, the inertial body 4 pushes the lower contact body 3 to move along the direction of the bullet axis toward the direction of the fuze head, compressing the spring mechanism 2, and finally making the fixed contact 8 connected to the upper contact body 5 as a whole contact with the moving contact 7 connected to the lower contact body 3 as a whole, the ignition circuit is closed, the ignition realization module is detonated, and the fuze realizes the ignition function;

[0037] d) When the terminal trajectory is a small drop angle, the radial overload is greater than the axial overload, and the inertial body 4 mainly feels the radial overload. Under the action of the axial overload, the inertial body 4 pushes the lower contact 3 to move along the axis of the projectile toward the fuze head, compressing the spring mechanism 2. At the same time, under the action of the radial overload, the inertial body 4 squeezes the elastic body 6 located in this radial direction. The elastic body 6 is expanded along the axis of the projectile under the action of the radial overload. Along with the expansion process of the elastic body 6, the lower contact 3 is pushed to move along the axis of the projectile toward the fuze head and close to the upper contact 5, compressing the spring mechanism 2. The elastic body 6 converts the radial overload it receives into the axial movement of the lower contact 3, and finally makes the fixed contact 8 connected to the upper contact 5 as a whole contact with the moving contact 7 connected to the lower contact 3 as a whole; the ignition circuit is closed, the ignition realization module is initiated, and the fuze realizes the ignition function.

[0038] Finally, it should be noted that the purpose of publishing the embodiments is to help further understand the present invention, but those skilled in the art can understand that various substitutions and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the present invention should not be limited to the contents disclosed in the embodiments, and the scope of protection claimed by the present invention shall be subject to the scope defined in the claims.

Claims

1. An overload switch device for improving the firing rate of a small-angle fuze, wherein the overload switch device is located in the fuze of ammunition, the fuze of the ammunition is located at the head of the projectile, the fuze has a built-in signal processing module and a firing realization module, the signal processing module has a firing circuit, the firing circuit is connected to the firing realization module, and is characterized in that: The overload switch device comprises: an external shell, an inertial body, an elastic body, a lower electrical body, an upper electrical body, a moving contact, a fixed contact and a spring mechanism; wherein the external shell is a tube having no upper bottom and a lower bottom, and has a cylindrical cavity inside, the central axis of the cylindrical cavity is located at the elastic axis; an inertial body is placed in the external shell and at the center of the bottom, the shape of the inertial body is a cylinder, the central axis of the cylinder is located at the elastic axis, and the diameter of the inertial body is smaller than the inner diameter of the external shell; a plurality of elastic bodies are arranged between the inner wall of the external shell and the side wall of the inertial body, the plurality of elastic bodies are centrally symmetrically distributed about the elastic axis, the elastic body stretches in a direction parallel to the elastic axis when subjected to radial force, and the distance between the two ends of the elastic body in a free state is equal to the height of the inertial body; a lower electrical body is placed in the external shell and on the inertial body and the plurality of elastic bodies, the outer diameter of the lower electrical body is not greater than the inner diameter of the external shell, and the lower electrical body can move up and down along the elastic axis; an upper electrical body is fixedly installed on the top of the external shell; The lower surface of the body and the upper surface of the lower contact body are respectively provided with spring grooves, the upper end and the lower end of the spring mechanism are respectively located in the spring grooves of the upper contact body and the lower contact body, the central axis of the spring mechanism is located at the elastic axis and the extension direction is parallel to the elastic axis, the distance between the surfaces of the spring grooves of the upper contact body and the lower contact body is less than the free length of the spring mechanism, the spring mechanism is in a compressed state, and the spring mechanism is insulated from the upper contact body and the lower contact body; a fixed contact connected to the upper contact body as a whole and electrically connected is arranged on the surface of the spring groove of the upper contact body, the fixed contact protrudes from the lower surface of the upper contact body, and a moving contact connected to the lower contact body as a whole and electrically connected is arranged on the surface of the spring groove of the lower contact body, the moving contact is higher than the upper surface of the lower contact body; before the ammunition hits the target, the fixed contact and the moving contact are located on the elastic axis and there is a distance between them, and the distance between them is less than the maximum elongation distance of the elastic body; the moving contact, the fixed contact, the upper contact body and the lower contact body are all made of conductive materials; The upper power contact and the lower power contact are respectively connected to the two ends of the firing circuit of the signal processing module of the fuze through a wire, and the firing circuit is turned on when the moving contact contacts the fixed contact.

2. The overload switch device according to claim 1, characterized in that: It also includes insulating sheets, which are respectively arranged at two ends of the spring mechanism, so that the two ends of the spring mechanism are respectively insulated from the upper electrical contact and the lower electrical contact.

3. The overload switch device according to claim 1, characterized in that: The inertial body is made of lead or steel.

4. The overload switch device according to claim 1, characterized in that: The material of the spring mechanism is one of carbon spring steel, low manganese spring steel, silicon manganese spring steel and chrome vanadium steel; the spring mechanism is a cylindrical helical spring or a conical helical spring.

5. The overload switch device according to claim 1, characterized in that: The outer surface of the outer shell is in the shape of a cylinder with a diameter of 10 to 30 mm and a height of 15 to 30 mm.

6. The overload switch device according to claim 1, characterized in that: The inertial body has a diameter of 4 to 18 mm and a height of 5 to 15 mm.

7. The overload switch device according to claim 1, characterized in that: The top inner wall surface of the external shell is provided with an internal thread, and the side wall of the upper electrical contact has an external thread, and the two are fixedly connected by threads.

8. A method for realizing an overload switch device for improving the firing rate of a small-angle fuse as claimed in claim 1, characterized in that: The implementation method comprises the following steps: 1) The upper electrical contact and the lower electrical contact are connected to the two ends of the firing circuit of the signal processing module of the fuze through a wire respectively, and the firing circuit is turned on when the moving contact contacts the fixed contact; 2) During daily storage and service handling, the spring mechanism has rigidity, and the environmental force is not enough to compress the spring mechanism to cause the moving contact to contact the fixed contact, and the firing circuit is open, so that the fuse will not be detonated, ensuring the safety of daily storage and service handling of ammunition; 3) When the ammunition moves to the end point and hits the target, it is divided into non-small angle and small angle: a) When the terminal trajectory is not at a small drop angle, the axial overload is greater than the radial overload, and the inertial body mainly feels the axial overload. Under the action of the axial overload, the inertial body pushes the lower contact body to move along the direction of the bullet axis toward the direction of the fuze head, compressing the spring mechanism, and finally making the fixed contact connected to the upper contact body as a whole contact with the moving contact connected to the lower contact body as a whole, the ignition circuit is closed, the ignition realization module is detonated, and the fuze realizes the ignition function; b) When the terminal trajectory is at a small drop angle, the radial overload is greater than the axial overload, and the inertial body mainly feels the radial overload. Under the action of the axial overload, the inertial body pushes the lower contact body to move along the axis of the projectile toward the direction of the fuze head, compressing the spring mechanism. At the same time, under the action of the radial overload, the inertial body squeezes the elastic body located in this radial direction, and the elastic body expands along the axis of the projectile under the action of the radial overload. Along with the expansion process of the elastic body, the lower contact body is pushed to move along the axis of the projectile toward the direction of the fuze head and close to the upper contact body, compressing the spring mechanism. The elastic body converts the radial overload it receives into the axial movement of the lower contact body, and finally makes the fixed contact connected to the upper contact body contact with the moving contact connected to the lower contact body; the ignition circuit is closed, the ignition realization module is initiated, and the fuze realizes the ignition function.

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