142 results about "Sound Absorber" patented technology

The present invention relates to a broadband sound absorption device using area division, the device comprising: Helmholtz resonators including a neck portion and a cavity portion connected to the neck portion and having a predetermined area and thickness; and a unit sound absorber including at least one pair of the Helmholtz resonators, wherein a plurality of unit absorbers are arranged on a plane or curved surface, and the plurality of sound unit absorbers are formed to have cavity portions with different areas to minimize the thickness while enabling sound absorption for a wider band.

Cooling device (100) for cooling a position-sensitive component (M1-M6) of a lithography system (1), comprising: a liquid line (102) for transporting a coolant (104), and a silencer device (106) arranged on a section (108) of the liquid line (102) for damping a pressure fluctuation of the coolant (104), wherein the section (108) has an elastic wall (110), and the silencer device (106) has means (112) for changing a diameter (D1, D2) of the section (108) by applying a force (F2) to the elastic wall (110).

Each mixed main body of a plurality of mixed members is formed from a pulverized raw material of a steric shape, of a plurality of pulverized raw materials obtained by pulverizing a layered composite raw material into various shapes including the steric shape and a linear shape. Each mixed glass fiber portion of the plurality of mixed members is formed by a plurality of glass fibers extending by the pulverization from a portion of the mixed main body corresponding to a glass fiber layer. Each mixed glass fiber portion of the plurality of mixed members is located in a labyrinthine path formed between mixed main bodies facing each other among the plurality of mixed members in a stirred mixture body including the plurality of mixed members stirred and mixed in a binder and the binder.

The utility model discloses an adjustable sound absorber which comprises a cylindrical cavity shell, an inner cavity of the cylindrical cavity shell is provided with three partition plates, the partition plates divide the inner cavity of the cylindrical cavity shell into three fan-shaped resonant cavities, the sizes of the three resonant cavities are the same, the side wall of the cylindrical cavity shell is provided with three sound inlets, and the sound inlets are communicated with the three fan-shaped resonant cavities. The three sound inlets correspond to the three resonant cavities respectively, a fan-shaped shell is arranged in each resonant cavity, a first through hole is formed in the top of each fan-shaped shell, a sound wave absorption channel is defined by the side wall of each fan-shaped shell and the inner wall of the corresponding resonant cavity, the sound inlets are communicated with the sound wave absorption channels, and an impedance modulation interface is formed in a top plate of the cylindrical cavity shell. The impedance modulation interface is communicated with an inner cavity of the fan-shaped shell through the first through hole, a second through hole is further formed in the side wall of the fan-shaped shell, and the sound wave absorption channel is communicated with the inner cavity of the fan-shaped shell through the second through hole; and the shielding piece is provided with a shielding part, and the shielding part can rotate to the position of the impedance modulation interface in the horizontal direction. The adjustable sound absorber is good in ventilation effect, and the adjustable sound absorption frequency is large in low-frequency absorption coverage range.

The utility model discloses a sound barrier structure arranged back to a noise source, which comprises a T-shaped device body, the top end of the device body is provided with a sound absorber structure, the sound absorber structure comprises a plurality of tip sound absorbers which are arranged in sequence, each tip sound absorber is of an isosceles right triangle structure, and the tip sound absorbers are arranged at the top end of the T-shaped device body. The first right-angle side of each tip sound absorber serves as the bottom of the tip sound absorber and is connected with the top end of the T-shaped device body, the first right-angle sides and the inclined sides are arranged in the mode that the first right-angle sides and the inclined sides do not face a noise source, namely the second right-angle sides are opposite to the noise source, and the second right-angle side of each tip sound absorber serves as the height of the tip sound absorber and is right opposite to the noise source in a vertical mode. Compared with the prior art, the sound barrier structure has the highest insertion loss value within the center frequency range of 500 Hz to 1600 Hz, so that the sound wave absorption rate is highest, and the noise reduction effect is best.

The invention discloses an underwater sound absorber with low-frequency broadband sound absorption and high pressure bearing performance and a design method of the underwater sound absorber. The sound absorber comprises a plurality of hexagonal honeycomb units which are spliced in sequence. Each honeycomb unit is composed of a hexagonal metal honeycomb framework, a rubber coating, a special-shaped embedded neck part and a cavity. The hexagonal honeycomb framework forms a hexagonal cylindrical cavity, the side wall and the bottom plate of the honeycomb framework are coated with the rubber coating, the acoustic impedance of the rubber coating is matched with the underwater acoustic impedance, and sound wave energy can be effectively absorbed. The special-shaped embedded neck part is embedded into the cavity of the honeycomb framework, and the neck part structure protrudes inwards, so that the vibration velocity and the hot sticking loss of sound waves are remarkably improved. The cavity is formed by a honeycomb framework and a rubber coating and used for storing sound energy and providing a resonance space. Multi-path dissipation and broadband sound absorption of sound energy are achieved through viscoelastic dissipation of the rubber coating and hot viscous loss of the special-shaped embedded neck part, and the composite material has remarkable potential application value in the field of underwater low-frequency noise control.

The invention discloses an ultra-wide-band noise reduction and bearing function integrated metamaterial structure sound barrier. The ultra-wide-band noise reduction and bearing function integrated metamaterial structure sound barrier comprises a multifunctional integrated screen body and a porous metamaterial sound absorber. The multifunctional integrated screen body comprises a composite non-uniform hollowed-out plate and a cavity, the composite non-uniform hollowed-out plate is arranged at the open end of the cavity, and partition plates are arranged in the cavity to divide the cavity into a plurality of sub-cavities; the porous super-structure sound absorber comprises a plurality of high-porosity sound absorption media arranged in the corresponding sub-cavities, and sound wave regulation and control channels are formed in the high-porosity sound absorption media. The metamaterial structure sound barrier is applied to the field of acoustic noise reduction, the metamaterial structure sound barrier can obtain low-frequency and ultra-wide-band efficient sound absorption performance, the overall rigidity of the sound barrier is improved, the longitudinal supporting area of the sound barrier is increased, the ultra-wide-band sound insulation performance of the sound barrier is greatly improved, meanwhile, the bearing capacity of a sound barrier body is greatly improved, and the noise reduction effect is good. The integration of the ultra-wideband efficient noise reduction performance and the high bearing function of the sound barrier with the metamaterial structure is realized.

The invention provides a production method of a light-transmitting sound-absorbing module suitable for an air film structure, and belongs to the technical field of building sound absorption and noise reduction. Then borate flame retardant treatment is carried out; forming a plate-shaped sound absorber by adopting a hot press molding process; then micro-pore distribution parameters are calculated, and the transparent micro-pore polymer film is compounded with the sound absorber through ultrasonic welding; performing waterproof and mildew-proof treatment on a fluorocarbon water repellent and a quaternary ammonium salt mildew preventive; after accurate drying, the acoustic performance of the composite material is analyzed by applying a pre-trained neural network model, a cutting scheme is optimized, and hot edge sealing treatment is carried out; and finally, testing the sound absorption performance of the product at the frequency band of 100Hz to 5000Hz by using an acoustic impedance tube, and screening qualified products meeting the standard, thereby solving the technical problem that a gas film structure building in the prior art cannot realize high light transmittance and high sound absorption performance at the same time.

The invention discloses a bent channel-Helmholtz composite low-frequency broadband sound absorber and a design method thereof. The sound absorber is formed by connecting a plurality of bent channel metamaterial sound absorption units around a Helmholtz resonator unit in parallel in a coupling mode. By controlling the impedance of the Helmholtz neck and the impedance of the bending channel, each unit is in an under-loss state, and then the overall critical coupling is realized by utilizing the area coupling effect, so that the sound absorber has the sound absorption coefficient of more than or equal to 0.5 in the frequency band of 267-382Hz under the thickness of 35mm. According to the sound absorber, broadband efficient sound absorption is achieved through impedance coupling of the Helmholtz resonators and the bent channels, the problems that a traditional structure is narrow in frequency band, difficult to regulate and control and the like are solved, and theoretical and technical supports are provided for low-frequency noise control.

The present application relates to a sound absorber (1) for acoustic shielding, comprising a planar base body in which several strip-shaped sections (2a) are formed parallel to one another, each of the strip-shaped sections (2a) having two opposite edges and at least one recess (4) extending along the strip-shaped section (2a), which projects from the planar base body and through which an opening (5) with side edges (6a, 6b) is formed at each of the opposite edges. The recess (4) has an edge (4a) extending transversely to the strip-shaped section (2a) and is subdivided by the edge (4a) along the strip-shaped section (2a) into a first recess area (4b) with first side edges (6a) and a second recess area (4c) with second side edges (6b). The first side edges (6a) are curved differently than the second side edges (6b).

A laser chamber according to an aspect of the present disclosure includes a container, a first electrode, a second electrode, and a sound absorber. The container is filled with a laser gas. The first electrode is disposed in the container. The second electrode is disposed in the container and faces the first electrode. The sound absorber is disposed on at least one of an upstream side and a downstream side of the laser gas from the first electrode. The sound absorber is configured to cause a propagation speed of an acoustic wave generated in a discharge space between the first electrode and the second electrode to decrease as a distance from the discharge space increases.

The invention discloses a firmly-connected assembly type noise reduction floor, and belongs to the technical field of assembly floors, the firmly-connected assembly type noise reduction floor comprises a vibration reduction panel and a sound absorption base, the vibration reduction panel is mounted at the top of the sound absorption base, the sound absorption base comprises a sound insulation supporting box, and a plurality of first sound absorbers and a plurality of second sound absorbers are arranged in the sound insulation supporting box; the first sound absorbers and the second sound absorbers are evenly distributed in an array mode, sound conducted from bottom to top is absorbed through the first sound absorbers, sound conducted from top to bottom is absorbed through the second sound absorbers, and the vibration reduction panel comprises a first vibration reduction plate. A second vibration reduction plate, a third vibration reduction plate, a fourth vibration reduction plate and a sound insulation supporting plate are sequentially arranged on the lower portion of the first vibration reduction plate from top to bottom, the sound insulation supporting plate and a sound insulation supporting box are mutually clamped and fixed, various scratching and scraping damages in the external environment are borne, various liquid pollutants and solid pollutants are blocked, overall damage and pollution are avoided, and the sound insulation effect is good. And a user can conveniently take care.

The utility model provides a noise reduction structure, a fresh air module and an air conditioner. The noise reduction structure comprises an air inlet shell with an air inlet cavity and a noise reduction assembly arranged in the air inlet cavity. The noise reduction assembly comprises at least one medium-high frequency sound absorber and at least one low-frequency sound absorber. The medium-high frequency sound absorber and the low-frequency sound absorber are arranged in the airflow direction, a first air layer is arranged between the medium-high frequency sound absorber and the bottom wall of the air inlet cavity, and a second air layer is arranged between the medium-high frequency sound absorber and the low-frequency sound absorber. And / or, the medium-high frequency sound absorber and the low-frequency sound absorber are arranged in the direction perpendicular to the airflow direction, a third air layer is arranged between the medium-high frequency sound absorber and the bottom wall of the air inlet cavity, and a fourth air layer is arranged between the low-frequency sound absorber and the bottom wall of the air inlet cavity. According to the noise reduction structure, the noise reduction frequency band can be widened, the multiple noise reduction effect is achieved, and therefore the operation quality of the fresh air module is effectively improved, and the user experience is improved.

The invention belongs to the technical field of noise reduction, and particularly relates to an impedance composite type low-frequency broadband superstructure sound absorber and an impedance transfer matching composite design method thereof.The impedance composite type low-frequency broadband superstructure sound absorber comprises a mounting side plate, an end face perforated plate, a metal wire mesh, a perforated material domain and a bottom plate; the end face perforated plate and the bottom plate are arranged at the axial end part of the mounting side plate to form a cavity with a hole in one end; the metal wire mesh is arranged in the cavity, and a surface cavity is formed between the end face perforated plate and the metal wire mesh; the perforated material area is arranged between the metal wire mesh and the bottom plate, and a back cavity is formed between the bottom and the bottom plate; the perforated material domain comprises at least one perforated material layer; the perforated material layer is of an acoustic impedance matching structure. Compared with the prior art, the problem that the cost is increased due to the complex structure of the acoustic superstructure in the prior art is solved. According to the impedance composite type low-frequency broadband superstructure sound absorber, low-frequency and broadband noise control is achieved, meanwhile, the structure is simple, and the design and production efficiency is high.

The present invention discloses a subwavelength ventilated asymmetric sound absorber, which is composed of one or more absorption cells. The absorption cell includes a metamaterial resonator and a backing impedance boundary. The backing impedance boundary includes a rear panel, a top panel, a bottom panel, a long plate and a short plate, which together form an L-shaped structure; a flow port is provided on the upper portion of the rear panel to facilitate airflow; the bottom of the metamaterial resonator is placed on the short plate of the backing impedance boundary, and a channel is left between it and the bottom plate of the backing impedance boundary; the back of the metamaterial resonator is fixedly connected to the side of the long plate of the backing impedance boundary, and a channel is left between it and the rear panel of the backing impedance boundary. The deep subwavelength absorber of the present invention can almost perfectly absorb the sound energy incident from the loss end and almost perfectly reflect the sound energy incident from the opposite end, has a good suppressive effect on broadband noise, and can achieve ventilation and heat dissipation functions while controlling noise.

The invention relates to a vehicle pneumatic tire comprising at least one sound absorber adhesively attached to an internal surface opposite the tread inside the tire, wherein the at least one sound absorber is adhered to an adhesive, and to an adhesive composition for fixing at least one sound absorber to the surface of a vehicle pneumatic tire. The adhesive contains at least the following ingredients: - from 10% to 80% by weight of at least one rubber, and - from 11% to 80% by weight of at least one polyolefin, and - from 2% to 20% by weight of at least one hydrocarbon resin. The adhesive has optimized flow characteristics and optimized tackiness.

The utility model discloses a composite absorption device for enhancing low frequency sound absorption, which belongs to the technical field of pipeline acoustics black holes, and comprises a sound tube, a plurality of micro-perforated plates and a Helmholtz sound absorber, the micro-perforated plates are distributed at equal intervals along the axial direction of the inlet end of the sound tube and are arranged from large to small according to the perforated distribution area, and the Helmholtz sound absorber is arranged on the sound tube. Micro-pores are uniformly distributed in each micro-perforated plate; every two adjacent micro-perforated plates are connected through a separation ring; the Helmholtz sound absorbers are distributed at equal intervals in the axial direction of the outlet end of the sound tube, the diameters of the gradually-changed embedded necks are gradually reduced, the center of each Helmholtz sound absorber is provided with a gradually-changed embedded neck, and the inner diameter of each gradually-changed embedded neck is gradually reduced from the inlet end to the outlet end; every two adjacent Helmholtz sound absorbers are connected through a sound absorber cavity. According to the utility model, through the combination of the composite gradually-changed micro-perforated plate and the gradually-changed cascaded Helmholtz sound absorbers which are embedded in the neck part, low-frequency sound absorption and medium-high frequency broadband sound absorption are realized under the sub-wavelength length.

The utility model relates to a fast splicing sound absorber, which comprises an enclosing plate and two end plates, the enclosing plate is provided with a plurality of creases along the vertical direction, the enclosing plate can form a three-dimensional structure after being bent along the creases, and the two end plates are arranged at the two ends of the three-dimensional structure and seal the three-dimensional structure. Sawtooth structures are arranged on the periphery of the enclosing plate, sawtooth structures are also arranged on the peripheries of the two end plates, and the two end plates are matched through the sawtooth structures in the enclosing process. According to the sound absorber, the sawtooth-shaped splicing structure is adopted, connection between the plates is achieved, an original glue connection mode is replaced, the degumming phenomenon does not exist, and the using effect of the sound absorber is guaranteed. And the plates can be transported to a site to be quickly spliced, so that the transportation space is not occupied. And the environmental protection problem caused by the use of glue is avoided.

The application discloses a low-frequency broadband sound absorber, which comprises a resonator, the outer part of the resonator is covered with a porous material layer, one side of the porous material layer is connected with a rigid backing, and the side opposite to the rigid backing is an incident surface; the resonator comprises an inner shell and an outer shell, the inner shell is located inside the outer shell; a first opening is arranged at the center of one side of the outer shell close to the sound wave incident surface, a second opening is arranged at the center of one side of the inner shell close to the rigid backing, and the first opening and the second opening are oppositely arranged. The application can efficiently absorb sound waves in a wide band range of low-frequency waves, and the high-efficiency absorption effect is hardly affected by the sound wave incident angle.

The present invention provides a micro-perforated panel sound absorber with an axially periodically rough surface annular micropore, which includes a micro-perforated panel, a rigid backing, and a cavity between the micro-perforated panel and the rigid backing. An annular sound absorption through-hole is provided on the micro-perforated panel, and the opening directions of the annular sound absorption through-holes are all perpendicular to the micro-perforated panel. The axially periodically rough surface morphology of the annular sound absorption through-holes provided on the micro-perforated panel is controlled by a function. The structure of the present invention is simple, light in weight, and has a high sound absorption coefficient in the mid-low frequency band. Through reasonable design of the structure, the sound absorption frequency band can be flexibly and effectively adjusted, and the sound absorption performance in the corresponding frequency band can be improved, having a wide range of engineering application prospects.

This invention discloses a broadband duct silencing structure combining perforated tubes and cavities. The structure uses a galvanized housing as its main body, with perforated tubes coaxially arranged inside. A perforated partition divides the structure into front and rear silencing chambers. The front silencing chamber contains a first sound absorber and an air layer, forming a Helmholtz resonant cavity to efficiently eliminate low-frequency fan noise. The rear silencing chamber is filled with a second sound absorber and is equipped with perforated tubes, micro-perforated tubes, and micro-perforated inserts with progressively smaller apertures, forming a gradient microporous structure to achieve broadband absorption of mid-to-high frequency noise. The structure utilizes the airflow in the duct to drive the impeller to rotate, which in turn drives a bidirectional reciprocating screw via bevel gear transmission. This drives a delivery rod and a one-way valve to form a directional airflow circulation. The sound absorber is automatically purged through the air duct and comb-shaped air duct to remove fiber dust, preventing secondary pollution and stabilizing acoustic performance. This invention combines the advantages of low-frequency resonance silencing and mid-to-high frequency gradient microporous sound absorption, featuring a compact structure, wide silencing bandwidth, and stable and reliable operation.

The invention relates to a curable and preferably polymer composition that is useful as a sealant, an adhesive (e.g., structural adhesive), a reinforcement, a dampener, a sound absorber or any combination thereof. The composition preferably comprises one or more ethylene polymers, tackifier, curing agent, and rheology modifier. The invention also relates to extrusion of the composition onto an article surface, e.g. through a robotically mounted extrusion die, and subsequent activation for curing by an external stimulus.

A weightlifting implement configured to be lifted from the ground surface includes: a first portion made of a high-hardness material; a second portion made of an elastomeric material having a hardness lower than that of the first portion; and a handle for gripping the weightlifting implement and lifting the implement from the ground surface, wherein the second portion includes spaced-apart holes within the elastomeric material, the spaced-apart holes being configured to absorb noise generated when the weightlifting implement is placed on the ground surface. Alternatively, a weightlifting implement configured to be lifted from the ground is disclosed, the weightlifting implement including at least one elastomeric material layer having spaced-apart holes therein, the spaced-apart holes being configured to absorb noise generated when the weightlifting implement is placed on the ground surface, and an opening configured to receive a handle. A slip deformation for mounting a sound absorber to an existing weightlifting device is disclosed. In an alternative example, a sound absorber can be used to fabricate a pill, an Atlas stone, or a similar weightlifting device to improve the experience.

The utility model relates to a mounting structure of an array type silencer, which comprises a shell, an accommodating space is arranged in the shell, the front end and the rear end of the accommodating space are respectively provided with an opening, and a fixing frame is arranged on the outer side of the shell in a surrounding manner; the silencer assembly is arranged in the shell and comprises sound absorbers and flow guide covers, the flow guide covers are fixedly arranged at the two ends of the sound absorbers, the sound absorbers are arranged in the containing space in an array mode, and the flow guide covers are fixedly connected with the shell; the longitudinal section of the sound absorber is wave-shaped; the supporting rod is arranged in the shell, a through hole penetrating through the upper end face and the lower end face is formed in the flow guide cover, the supporting rod penetrates through the through hole and is connected with the fixing frame, and the supporting rod is fixedly connected to the flow guide cover. By adopting the structure, the effective length of the sound absorber is increased, so that the silencing effect of the silencer is effectively improved.

The present technology relates to an information processing apparatus, method, and program that enable sound field control having a higher degree of freedom. The information processing method of the present invention involves an information processing apparatus performing the following: identifying a parameter relating to the complex acoustic impedance of a resonator, or a sound absorber that uses the resonator, installed on a surface forming a target space, said parameter being identified on the basis of a target sound pressure frequency characteristic at an evaluation point in the target space and an acoustic analysis model for obtaining the sound pressure frequency characteristic at any point in the target space; and identifying the shape of the sound absorber on the basis of the parameter. The present technology can be applied to an acoustic metamaterial.

Example implementations relate to a method and system of cooling a computing system, while simultaneously absorbing airborne noise in the computing system. The computing system includes a chassis having a base and a pair of walls coupled to a peripheral side of the base, and a plurality of rotational drives disposed in the chassis. The computing system includes a frame having a plurality of first openings, and a first acoustic absorber having a plurality of second openings, coupled to the frame to form an acoustic absorber frame. The acoustic absorber frame extends along a lateral direction, disposed downstream relative to the plurality of rotational drives, and coupled to the pair of walls. Each second opening is concentrically aligned to a respective first opening. The computing system includes a plurality of fans coupled to frame and disposed downstream relative to the frame, and aligned to the respective first opening.

According to the complex closed space global low-frequency noise reduction method based on the active micro-perforated plate sound absorber, an active control technology is introduced into a small-size MPPA, the low-frequency acoustic reactance of a cavity of the MPPA is reduced by offsetting the sound field of the cavity of the MPPA, and the sound energy dissipation performance of the MPP is improved by breaking the waveform matching of the sound fields on the two sides of the MPP; the noise of the whole complex closed space is reduced in an active sound absorption mode, and meanwhile the problem that the noise reduction performance of some medium-high frequency resonance frequency points is weak due to coupling of a closed space sound field and an MPPA cavity sound field can be solved. The invested active control measure is low in cost, and the low-frequency noise reduction performance of the complex closed space is remarkable, so that the method has important engineering application value.

The present invention relates to the field of noise control and specifically provides a composite broadband noise reduction superstructure, comprising a mid-high frequency noise reduction body and a low-frequency broadband noise reduction body; the mid-high frequency noise reduction body comprises an incident perforated plate and a second sound absorber; the low-frequency broadband noise reduction body comprises a plurality of parallel sound absorbing units, each comprising a top perforated plate, a back closed plate, a side closed plate, and a closed partition; at least one internal perforated plate is disposed within the cavity of the sound absorbing unit, the top perforated plate being connected to the second sound absorber of the mid-high frequency noise reduction body; the internal perforated plate divides the sound absorbing unit into two or more series-connected sound absorbing chambers, each of which is provided with a first sound absorber; the sound absorbing chambers comprise a rearmost sound absorbing chamber and a front sound absorbing chamber, into which sound waves enter via the incident perforated plate, the second sound absorber, and the top perforated plate. This solution is applicable to broadband noise sources of various frequency domains or multi-order harmonic noise sources, can reduce the effective sound absorption frequency, and achieve full-band noise reduction through the composite mid-high frequency noise reduction body and low-frequency broadband noise reduction body superstructure.

The utility model relates to a ventilation equipment technical field especially a noise reduction type fan box device. The device includes the fan cabinet and sets up in its fan assembly, the inner wall of fan cabinet is attached with composite sound absorption cotton board to constitute primary sound absorption structure, the air outlet of fan assembly is connected with sound absorption assembly through hose joint, the sound absorption assembly includes the sound absorber and several character shape flow channel sound absorption box connected in proper order, constitutes secondary sound absorption and tertiary sound absorption structure. The utility model through in the inner wall, air outlet and export flow channel carry out multistage, compound type sound absorption and damping design, effectively widened the noise reduction frequency band, especially significantly reduced low frequency noise, guaranteed good ventilation performance simultaneously, compact structure, maintenance is convenient, effectively solved the problem that the frequency band is limited, the volume is heavy and the durability is poor in the existing fan box noise reduction technology.

To construct a sound absorber with excellent designability capable of easily changing an indoor sound environment, and improve comfort of a room using the sound absorber.SOLUTION: A sound absorber 10 comprises: a self-supporting rectangular frame body 11 with a part of an outside surface serving as a bottom part; a first membrane body 12 closing a first opening 11a on one end side of the frame body 11; a second membrane body 13 closing a second opening 11b on the other end side of the frame body 11; and a sound absorption material 14 made of a porous material, which is arranged inside the frame body 11. The first membrane body 12 and the second membrane body 13 are made of different materials. The first and second membrane bodies 12, 13, together with the first and second openings 11a, 11b, integrally cover front end surfaces 15a, 16a and outside surfaces 15b, 16b of first and second frame members 15, 16, and their peripheral edge parts extend to inside surfaces 15d, 16d of the first and second frame members 15, 16, and are fixed to the inside surfaces 15d, 16d.SELECTED DRAWING: Figure 2