Noise absorbing device

A noise absorbing device is adapted to prevent radiation noise or induction noise from a cable connected to an electronic apparatus. A pair of holder segments (11 and 12) receive core pieces (20) in receiving recesses and are coupled by hinge portions (19) so as to be brought into butt contact with each other so that the pair of core pieces (20) form a cylindrical body with a cable extending therethrough. Elastic pieces (31) are interposed between the pair of core pieces (20) and the pair of holder segments (11 and 12) in order to provide an elastic force to the core pieces (20) so that the core pieces are slightly protruded from opening edges of the holder segments (11 and 12). When the pair of holder segments (11 and 12) are brought into butt contact with each other, the pair of core pieces (20) are put into press contact with each other by the elastic force of the elastic pieces (60). An assembly of the core piece (20) and the elastic piece (31) engaged therewith is press fitted into the receiving recess to avoid drop-off from each of the holder segments (11 and 12).

TECHNICAL FIELD 
This invention relates to a noise absorbing device having a cylindrical 
magnetic core, for preventing radiation noise or induction noise from a 
cable connected to an electronic apparatus. 
BACKGROUND ART 
Generally, in order to prevent radiation noise or induction noise from a 
signal cable connected between electronic apparatuses and a power supply 
cable, noise absorbing devices each comprising a split-type cylindrical 
magnetic core and a core holder receiving the magnetic core therein are 
attached to such cables. The split-type cylindrical magnetic core 
comprises a pair of core pieces formed by dividing a cylindrical magnetic 
core into halves along a cylindrical center axis, the core being for 
receiving a cable to extend therethrough. The core holder has a structure 
such that the pair of core pieces are received therein and the pair of 
core pieces received therein are brought into tight contact with each 
other. The core holder is made of an insulating material having 
elasticity, such as nylon. 
FIG. 1 is an exploded perspective view of one example of a conventional 
noise absorbing device of the type described. Referring to FIG. 1, a core 
holder 10 comprises a pair of holder segments 11 and 12 with receiving 
recesses. The holder segments 11 and 12 receive a pair of core pieces 20 
(only one being illustrated in FIG. 1) with their inner concave surfaces 
21 of a semicircular section turned upward, respectively. The pair of core 
pieces 20 are formed by dividing a cylindrical magnetic core into halves 
along a cylindrical center axis. Each of the holder segments 11 and 12 has 
a configuration and a size such that the core piece 20 is received therein 
with its lip portions 23 outwardly exposed. Each holder segment has four 
opening edges two of which extend in parallel to the center axis of the 
magnetic core. At the respective opening edges 24, each of which is one of 
the above-mentioned two parallel opening edges, the holder segments 11 and 
12 are integrally coupled to each other by hinge portions 19 to be 
foldable. Semicircular notches 13 in conformity with the shape of the 
inner concave surface 21 of the core piece 20 are formed in the opening 
edges perpendicular to the center axis of the magnetic core. 
Two engaging projections 14 project from a side wall of the holder segment 
12. On the other hand, two engaging tabs 15 project from a side wall of 
the holder segment 11 in correspondence to the engaging projections 14. 
Protruding pieces 16 are formed on inner walls of the holder segments 11 
and 12 at positions slightly below the semicircular notches 13. The 
protruding pieces 16 have inclined surfaces. End faces of the core pieces 
20 slide along the inclined surfaces of the protruding pieces 16 to be 
easily received in the holder segments 11 and 12. Two cantilever springs 
17 (only one being illustrated in FIG. 1) having projections at their top 
ends are formed in a bottom of each of the holder segments 11 and 12. 
With the core pieces 20 received in the pair of holder segments 11 and 12, 
respectively, the core holder 10 of the above-mentioned structure is 
attached to a power supply cable (not shown) in the following manner. The 
signal cable or the power supply cable is extended on the inner concave 
surfaces 21 of the core pieces 20 and the semicircular notches 13, and 
opening faces of the holder segments 11 and 12 are butted against each 
other, then, the engaging tabs 15 being engaged with the engaging 
projections 14. 
FIG. 2 is a vertical sectional view of the core holder 10 after assembled. 
The signal cable or the power supply cable is not illustrated. Referring 
to FIG. 2, the core pieces 20 are fixed to the holder segments 11 and 12 
by bringing the protruding pieces 16 into contact with the end faces of 
the core pieces 20. In addition, the lip portions 23 of the pair of core 
pieces 20 are kept in tight contact with each other by cooperation of the 
four cantilever springs 17. 
In order to reliably fix the core pieces 20 by the protruding pieces 16 in 
the holder 10, it is necessary to realize the axial length of the core 
pieces 20 and the distance between the protruding pieces 16 opposite to 
each other with the high accuracy. However, it is difficult in 
mass-production to insure the high accuracy of these dimensions. 
In view of the above, an approach has been tried to reliably fix the core 
pieces 20 without requiring such a high dimensional accuracy as mentioned 
above. For example, as depicted by a dash-and-dot line in FIG. 1, the 
holder segments 11 and 12 are provided with vertical grooves 18 formed at 
both sides of each of the protruding pieces 16. Those portions including 
the protruding pieces 16 are rendered movable so that a freedom is given 
to the distance between the protruding pieces 16 opposite to each other. 
There is another approach with respect to the core piece 20 where engaging 
recesses 22 are formed at opposite ends of the inner concave surface 21 of 
each core piece 20 for insertion of the top ends of the protruding pieces 
16 as depicted by a dash-and-dot line in FIG. 1. 
The size of the protruding pieces 16 must be selected small so that a 
clamping force required to clamp the core pieces 20 is smaller than a 
pressing force of the cantilever springs 17 and that the core pieces 20 
are easily loaded into the holder segments 11 and 12. As a consequence, 
when the core pieces 20 are inserted into the holder segments 11 and 12, 
the protruding pieces 16 can not bear the pressing force during insertion 
and is damaged. Because of a complicated structure including the 
protruding pieces 16 and the cantilever springs 17, injection molding of 
the holder 10 often suffers from molding failure such as short mold. 
It is therefore a technical object of this invention to provide a noise 
absorbing device having a holder of a strong structure free from damage 
during assembly or use. 
It is another technical object of this invention to provide a noise 
absorbing device having a holder of a simple structure. 
DISCLOSURE OF THE INVENTION 
According to this invention, there is provided a noise absorbing device 
comprising a pair of core pieces formed by dividing a cylindrical magnetic 
core into halves along a cylindrical center axis, the core being for 
receiving therethrough an extension of a cable connected to an electronic 
apparatus, and a pair of holder segments receiving the pair of core pieces 
in receiving recesses thereof, respectively, and coupled to enable butt 
contact with each other so that the pair of core pieces form a cylindrical 
body with the cable extending therethrough, wherein elastic pieces are 
interposed between the pair of core pieces and the pair of holder segments 
receiving the core pieces, respectively, the elastic pieces being for 
applying an elastic force to the core pieces so that the core pieces are 
slightly protruded from opening edges of the holder segments, the pair of 
core pieces being brought into press contact with each other by the 
elastic force of the elastic pieces when the pair of holder segments are 
brought into butt contact, assemblies of the core pieces and the elastic 
pieces being press fitted in the receiving recesses so as to avoid release 
from the holder segments. 
According to this invention, there is also provided a noise absorbing 
device comprising a pair of core pieces formed by dividing a cylindrical 
magnetic core into halves along a cylindrical center axis, the core being 
for receiving therethrough an extension of a cable connected to an 
electronic apparatus, and a pair of holder segments receiving the pair of 
core pieces in receiving recesses thereof, respectively, and coupled to 
enable butt contact with each other so that the pair of core pieces form a 
cylindrical body with the cable extending therethrough, wherein elastic 
pieces are interposed between the pair of core pieces and the pair of 
holder segments receiving the core pieces, respectively, the elastic 
pieces being adapted for applying an elastic force to the core pieces so 
that the core pieces are slightly protruded from opening edges of the 
holder segments, the pair of core pieces being brought into press contact 
with each other by the elastic force of the elastic pieces when the pair 
of holder segments are brought into butt contact, assemblies of the core 
pieces and the elastic pieces being engaged with engaging holes formed at 
opposite ends perpendicular to the center axis so as to avoid release from 
the holder segments.

MODE FOR EMBODYING THE INVENTION 
Now, description will be made as regards embodiments of this invention with 
reference to the drawing. In FIGS. 3 through 12 hereafter referred to in 
connection with this invention, the same or similar parts corresponding to 
the conventional example are designated by like reference numerals as 
shown in in FIGS. 1 and 2. 
Referring to FIG. 3, a core holder 10 according to this embodiment 
comprises a pair of holder segments 11 and 12 made of insulating resin and 
having receiving recesses 111 and 121, like the conventional device 
illustrated in FIG. 1. The holder segments 11 and 12 receive a pair of 
core pieces 20 (only one being illustrated in FIG. 3) with their inner 
concave surfaces 21 of the semicircular section turned upward, 
respectively. The pair of core pieces 20 are formed by dividing a 
cylindrical magnetic core into halves along a cylindrical center axis. 
Each of the holder segments 11 and 12 has a configuration and a size such 
that the core piece 20 is received with its lip portions 23 outwardly 
exposed. Holder segments 11 and 12 have opening edges and are integrally 
coupled by hinge portions 19 at their opening edges 24 extending in 
parallel to the center axis of the magnetic core, adapted to be placed 
into butt contact with each other. Semicircular notches 13 in conformity 
with the shape of the inner concave surface 21 of the core piece 20 are 
formed in the opening edges perpendicular to the center axis of the 
magnetic core. Two engaging projections 14 project from a side wall of the 
holder segment 12. On the other hand, two engaging tabs 15 corresponding 
to the engaging projections 14 project from a side wall of the holder 
segment 11. The above-mentioned structure is similar to that of the 
conventional example (FIGS. 1 and 2). 
An elastic piece or resilient element 31 made of plastic, rubber, elastic 
metal, a foaming material, or the like is attached to each core piece 20. 
The elastic piece or element 31 comprises an arcuately shaped strip body 
32 and engaging portions formed at opposite ends thereof. Each engaging 
portion comprises an upwardly extending portion and an engaging portion 33 
angularly extending inwardly therefrom. The strip body 32 has a length 
equal to or slightly greater than the axial length of the core piece 20 
and is arcuately curved upwards to provide elasticity. Thus, it serves as 
an elastically deformable spring plate. 
The elastic piece 31 is attached so that the engaging portions at the 
opposite ends thereof are engaged with opposite end portions of the core 
piece 20. In this state, the engaging 33 are lockingly engaged with 
engaging recesses 22 formed at the inner peripheries of the opposite end 
portions of the core piece 20. Thus, the core piece 20 is clamped, at 
inner and outer peripheral surfaces thereof, by the engaging portions at 
the opposite ends of elastic piece 31. 
An assembly of the core piece 20 and the elastic piece 31 attached thereto 
is press fitted into each of the receiving recesses 111 and 121 (that is, 
the recesses shown in FIG. 1) of the holder segments 11 and 12. 
Thus, the elastic piece 31 exerts an elastic force such that the core piece 
20 is pushed up by the strip body 32 outwardly from each of the holder 
segments 11 and 12. In other words, the core piece 20 is subjected to the 
elastic force to slightly protrude from the opening edges of each of the 
holder segments 11 and 12. When one of the holder segments 11 and 12 
receiving the core pieces 20 is rotated around the hinge portions 19 to 
bring the holder segments 11 and 12 into butt contact with each other, the 
lip portions 23 of the pair of core pieces 20 are pressed in abutting 
contact with each other. 
As is obvious from FIG. 3, the engaging portions at the opposite ends of 
the elastic piece 31 are outwardly expanded as they extend upwardly from 
the strip body 32. This structure serves to give a spring property to the 
engaging portions also. 
As illustrated in FIG. 5, the core piece 20 is manufactured to be smaller 
than each of the receiving recesses 111 and 121 of the holder segments 11 
and 12. It is assumed here that, during an assembling process, the elastic 
piece 31 in the assembly of the core piece 20 and the elastic piece 31 
attached thereto is not press fitted into each of the receiving recesses 
111 and 121 of the holder segments 11 and 12. In this instance, the 
assembly is dropped when the holder segment is turned upside down. On the 
contrary, the engaging portions at the opposite ends of the elastic piece 
31 in the assembly are outwardly expanded within each of the receiving 
recesses 111 and 121 to be brought into press contact with the internal 
walls of each of the receiving recesses 111 and 121. As a consequence, 
when the holder segments 11 and 12 are turned upside down during the 
assembling process, the assemblies are prevented from dropping out from 
the receiving recesses 111 and 121. The assembly of the core piece 20 and 
the elastic piece 31 attached thereto is fixed, by press fit, to each of 
the receiving recesses 111 and 121 of the holder segments 11 and 12. If 
such press fit is slightly tightened, the engaging portions at the 
opposite ends of the elastic piece 31 may be formed perpendicular to the 
strip body 32. 
FIG. 4 is a vertical sectional view of the assembly of the core piece 20 
and the elastic piece 31 attached thereto which is fixedly press fitted 
into the holder segment 11 (the holder segment 12 being omitted). FIG. 5 
is a transverse sectional view of the noise absorbing device according to 
this invention in an assembled state. Referring to FIG. 4, the core piece 
20 is held by the elastically deformable piece 31 within each of the 
holder segments 11 and 12 and slightly projects from the opening edges of 
each of the holder segments 11 and 12. As illustrated in FIG. 5, the 
holder segments 11 and 12 are closed by rotation around the hinge portions 
19. When the engaging projections 14 are engaged with the engaging tabs 
15, the core pieces 20 forced by elastic elements 31 to slightly project 
are pushed down against the elastic force of the elastic pieces 31. The 
pair of core pieces 20 are brought into pressing contact with each other 
by the elastic force exerted by strip body 32 of elastic element 31. 
FIG. 6 shows an elastic piece according to another embodiment. Referring to 
FIG. 6, an elastic piece 31' is shown having a strip body 32' of a 
corrugated shape. This shape provides a spring property greater than that 
of the arcuate shape in FIG. 3. 
FIG. 7 shows a modification of the elastic piece 31 illustrated in FIG. 3. 
Referring to FIG. 7, the modification of the elastic piece 31 has a 
protrusion 34 formed at an intermediate portion of the strip body 32. In 
this case, it will be understood that a hole adapted for insertion of the 
protrusion 34 is formed at the outer periphery of the core piece 20. 
FIG. 8 shows an elastic piece according to still another embodiment. 
Referring to FIG. 8, the elastic piece has, at one end of the strip body 
35 alone, an engaging portion to be engaged with the core piece 20. In 
this embodiment, a corrugated projection 36 is formed on the outer surface 
of the engaging portion. An engaging piece 37 has a length longer than 
that of the engaging piece 33 illustrated in FIG. 3. 
FIGS. 9, 10, and 11 are an exploded perspective view, a partial vertical 
sectional view, and an axial side view of a noise absorbing device 
according to another embodiment of this invention, respectively. In these 
figures, same or similar parts as those of the foregoing embodiment are 
designated by like reference numerals in FIGS. 3 through 5 and description 
thereof will be omitted. 
Referring to FIGS. 9 through 11, in the noise absorbing device, notches 13' 
of a semi-elliptical shape slightly smaller than the inner concave surface 
21 of the core piece 20 are formed at longitudinal opposite ends of each 
of the holder segments 11 and 12. By provision of such notches in the 
holder segments 11 and 12, a cable having a nonuniform diameter can be 
reliably clamped by the holder segments 11 and 12. 
At the longitudinal opposite ends of the holder segments 11 and 12, 
engaging holes 51 are formed to be engaged with end portions 62 of elastic 
pieces 60 which will be described below. 
Each elastic piece 60 made of a material similar to that of the elastic 
piece 31 mentioned above comprises a strip body 61, opposite end portions 
62, and engaging portions upwardly extending from end portions 62 and 
comprising engaging elements 63 extending inwardly from the upwardly 
extending portions. 
The end portions 62 of the elastic pieces 60 are engaged with the engaging 
holes 51 of the holder segments 11 and 12. This prevents drop-off of the 
assembly of the core piece 20 and the elastic piece 60 from each of the 
holder segments 11 and 12 and dislocation of contact surfaces of the pair 
of core pieces 20. In order to remove the assembly from each of the holder 
segments 11 and 12, disassembling is easily carried out by inserting a 
penpoint or the like into each engaging hole 51 of the pair of holder 
segments 11 and 12 in an opened state. 
Each engaging hole 51 may have any shape engageable with the end portion 62 
of the elastic piece 60, for example, a depression or indent instead of a 
through hole. 
FIG. 12 is another example of an elastic piece used in the noise absorbing 
device illustrated in FIGS. 9 through 11. Referring to FIG. 12, an elastic 
piece 60' has a strip body 61' of a convex shape. Accordingly, a spring 
property is greater than that of the elastic piece 60 of an arcuate shape 
illustrated in FIG. 9. 
EFFECT OF THE INVENTION 
A noise absorbing device according to this invention has a structure in 
which the elastic piece or element is interposed between the core piece of 
the magnetic core and the holder segment. Because the holder segment 
itself has no complicated structure such as the protruding piece and the 
cantilever spring, it is possible to avoid a manufacturing failure and a 
damage of the holder during assembly and use. 
Furthermore, the holder segment may be provided with the engaging holes 
formed at the opposite ends perpendicular to the center axis of the 
magnetic core. The opposite end portions of the elastic piece clamping the 
core by clamping portions are engaged with the engaging holes. With this 
structure, the following effect is obtained. 
Since the engagement by the above-mentioned engaging structure is strong, 
the core piece is free from possibility of dropping out of the holder 
segment. The condition of the contact surfaces of the pair of core pieces 
is kept constant so that dislocation of the core pieces is avoided. It is 
therefore possible to prevent deterioration of the characteristic of the 
core that is important as the noise absorbing device. Although the 
engagement of engaged parts is strong, it is possible to easily remove the 
core piece by pressing the elastic piece through the engaging hole by the 
use of a pen or the like. Thus, handling is easy. 
The notches having a semi-elliptical shape smaller than the inner concave 
surface or the inner cylindrical surface of the core piece may be formed 
at the opening edges of the holder segment that are perpendicular to the 
center axis of the magnetic core. With this structure, it is possible for 
the holder segment to reliably hold a cable having various diameters. 
INDUSTRIAL APPLICABILITY 
The noise absorbing device according to this invention is adapted to 
prevent radiation noise or induction noise from a cable connected to an 
electronic apparatus.