Soundproof Construction in Printer Box

The present invention relates to a sound reducing construction for shielding sound generated upon operation of a machine such as a printer, and more particularly, to a type thereof adapted to be provided at a box which accommodates therein a printer for confining sound in the box.

As shown in FIG. 1, a printing machine such as a line printer P is accommodated in a box 100 consisting of a main body 102 and a cover 101 those being formed of metal plates. Within the main body 102, the printer P is accommodated, and the cover 101 is pivotally connected to the main body 102 at its rear portion 101R so as to cover a top surface portion of the printer P. During operation of the printer P, the rectangular lower open end face 101a of the cover 101 is brought into contact with a rectangular open end face 102a of the main body 102 by the pivotal motion of the cover 101, to thereby provide a confined space defined by the main body and the cover.

In order to avoid sound leakage from the box interior to outside, a sound reducing construction has been provided at an interface between the main body 102 and the cover 101. For this, one conventional sound reducing construction is shown in FIG. 2. FIG. 2 shows closed state of the cover 101 and the man body 102 as viewed in a direction indicated by an arrow A in FIG. 1, and left and right side margins of FIG. 2 designate box internal and external portions, respectively. According to the conventional sound reducing construction, a packing unit 103 is provided between the cover 101 and the main body 102. To be more specific, the packing unit 103 includes a resilient packing member 103a, a bolt 103b, packing holder plates 103c and a magnetic member 103d. Inner surfaces of the cover 101 and the main body 102 are provided with sound absorbing members 106, and the side end portion of the metal cover 101 is bent by a right angle to provide a packing attaching portion 101A. The packing member 103a formed of soft vinyl chloride has one end portion 103a' fixedly attached, through the packing holder plates 103c, to the packing attaching portion 101A by the bolt 103b. Another end portion 103a" of the packing member 103a is connected to the magnetic member 103d such as a rubber or plastic magnet which is in contact with a bent plate 102A of the main body 102.

Accordingly, the packing unit 103 seals the interface between the cover 101 and the main body 102 when the cover 101 is closed.

In the conventional sound reducing construction, attention should be drawn to "mass law of sound insulation". That is, the rule states that sound insulation for a single wall is determined almost wholly by its weight per unit area, and doubling the weight of the partition increases the insulation by 5 decibels. In this connection, the packing unit 103 provides a sound transmission loss lower than that of the metal plate portion, so that sufficient sound insulation or reducing effect may not be obtainable at the packing portion. Further, the thickness portion "t" of the packing member 103a merely serves as the partition defined in the law, and therefore, sound leakage may occur through the packing portion. Furthermore, according to the conventional structure, it would be rather difficult to conduct clamping work for securing the packing member 103a to the cover 101 by using the bolt 103b, since the packing member 103a must be held with being interposed between the packing holder 103c and the packing attaching portion 101A when the bolt 103b is rotationally advanced.

It is therefore, an object of the present invention to overcome the above-mentioned drawbacks and to provide an improved sound reducing construction for preventing sound generated from an operating machine from leaking through a machine accomodation box.

Another object of this invention is to provide such sound reducing construction capable of providing sufficient sound transmission loss, to thereby reduce leakage of the sound at minimum level.

Still another object of this invention is to provide such sound reducing construction which alleviates labor for attaching a sound reducing unit to the box.

These and other objects of this invention will be attained by a sound reducing construction provided between first and second components and sealingly maintained when the first component is rested on the second component. In this invention, there is provided a sound reducing construction for shielding sound in a confined box, the box including a first plate component formed with a first open end portion and a second plate component formed with a second open end portion and accommodating therein a machine which generates the sound, the first plate component being movable with respect to the second plate component. The sound reducing construction comprises: a packing unit having one end fixed to the first open end portion of the first component and having another end portion in contact with the second open end portion when the first component is rested on the second component; and, the first and second open end portions providing stepped portions in conformance with each other. The first and second open end portions define two horizontally extending gaps whose vertical heights are different from each other and a vertically extending gap. The packing unit is positioned in one of the horizontally extending gaps.

Since the vertically confronting walls of the cover and the main body serve to block noise or sound resulting in an increase in sound transmission loss. Further, the bent gap defined between the open end portions can attenuate the sound generated in the main body, to thus minimize leakage of sound out of the box confined by the packing unit.

In the drawings;

FIG. 1 is a perspective view showing a printer and a printer housing box which includes a main body and a cover;

FIG. 2 is a cross-sectional view showing a conventional sound reducing construction provided between the main body and a cover;

FIG. 3 is a cross-sectional view showing a sound reducing construction according to a first embodiment of this invention;

FIG. 4 is a cross-sectional view particularly showing a packing unit according to the present invention;

FIG. 5 is a cross-sectional view showing a sound reducing construction according to a second embodiment of this invention;

FIG. 6 is a cross-sectional view showing a sound reducing construction according to a third embodiment of this invention;

FIG. 7 is a cross-sectional view showing a sound reducing construction which is provided between a front end of a cover and a front end of a main body; and,

FIG. 8 is a cross-sectional view showing a sound reducing construction which is provided at a rear hinge portion of a box;

FIG. 9 is a cross-sectional view according to a fourth embodiment of this invention.

A first embodiment of this invention will be described with reference to FIGS. 3 and 4. FIG. 3 is viewed in a direction indicated by arrow A in FIG. 1, so that the left and right side margins in FIG. 3 designate internal and external portions with respect to a box B. The sound reducing structure B includes a main body 2 (referred to as a second component in claims) and a cover 1 (referred to as a first component in claims), each being provided with sound absorbing members 6 in their inner surfaces, and the confronting surfaces between the cover 1 and the main body 2 are stepped to define a pair of horizontal portions and a vertical riser portion That is, the cover 1 has a lower open end 1a (referred to as a first open end in claims) confronting an upper open end 2a (referred to as a second open end in claims) of the main body 2, and the lower open end portion 1a of the cover 1 is not flat but steppingly arranged which stepped shape is in conformance with a stepped shape of the upper open end 2a of the main body 2. In other words, metal plates of the cover and the main body are bent three times to provide the aforementioned horizontal and riser portions

In the confronting portion, there are two horizontally confronting portions and a vertically confronting portion directed in a direction perpendicular to the horizontally confronting portions. The two horizontally confronting portions have vertical heights different from each other because of the bending arrangement. Further, gaps G.sub.2 and G.sub.3 are defined at the horizontally confronting portions, and gap G.sub.1 is defined at the vertically confronting portion. It goes without saying that these gaps are minimumly provided for ensuring sound reducing effect. Here, a length L defined by vertical confrontation between the vertical portions of the cover member 1 and the main body 2 is larger than the thicknesses thereof (t.sub.1 plus t.sub.2). If large length L can be provided, sound reducing effect will be enhanced. Because of the vertically confronting walls, numbers of the sound insulation wall is increased to enhance sound insulation effect.

Further, in one of the horizontally confronting portions (in the gap G.sub.3) positioned near the distal side face of the cover or main body, a packing unit 3 is provided.

Referring to FIG. 4, the packing unit 3 includes a flexible packing member 3a formed of soft vinyl chloride whose one end portion 3a' is secured to the cover 1 by an adhesive member 5 such as a double-faced adhesive tape. Within the packing member 3a at end portion 3a" thereof, a magnetic member 4 such as a rubber magnet or plastic magnet is disposed as best shown in FIG. 4. The packing member 3a is in a form of flat barrel shape as shown when the cover is closed. The barrel portion is slightly stretched in an axial direction of the packing member 3a when the cover 1 is opened. The rubber or plastic magnet is well known, in which magnetic particles are dispersed in a rubber or plastic material to obtain flexible magnetic member. The magnetic member 4 is in close contact with the main body end face 2a at the gap G.sub.3. Because of the magnetic force of the magnetic member 4, the cover 1 is not jumped up from the upper end face 2a of the main body 2 due to minute vibration caused during printing operation.

A sound reducing structure B' according to a second embodiment of this invention is shown in FIG. 5 wherein the stepping orientation is opposite to that in the first embodiment. With this structure, excellent sound reducing effect is obtainable similar to the first embodiment.

A sound reducing structure B" according to a third embodiment of this invention is shown in FIG. 6, wherein two packing units 3 and 3 are provided at the horizontally confronting portions (at portions corresponding to gaps G.sub.2 and G.sub.3) so as to enhance sound shielding effect. However, in the third embodiment, attention should be drawn to the gap G.sub.2 which is greatly larger than the gap G.sub.2 in the foregoing embodiments. Due to the increase in the gap, the overlapping length L becomes short. Therefore, even in the third embodiment, the length L should be larger than the lengths t.sub.1 plus t.sub.2.

According to the foregoing embodiments, the packing units are provided at the side wall portions of the cover 1 and the main body 2 (see 101S and 102S in FIG. 1). However, the packing unit can be provided between the front walls of the cover and the main body (see 101F and 102F) as shown in FIG. 7, or can be provided between the rear walls thereof (see 101R and 102R) as shown in FIG. 8. In the latter case, a hinge member H is fixed to the walls 101R and 102R for pivotally moving the cover 1.

In view of the foregoing, according to the sound reducing construction of this invention, the packing unit is attached to the printer box by adhesive, additional mechanical component for securing the unit to the box can be eliminated. Further, the open end portions of the cover and the main body are bent at three times to provide stepped faces, so that these portions provide excellent mechanical strength or rigidity. Furthermore, since the packing unit is attached without using the packing holder and screw, the gap space in which the packing unit is provided can be minimized, to thus further enhance sound reducing effect.

While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent for those skilled in the art that various changes and modifications can be made therein without departing from spirit and scope of the invention.