Zipper chain

1. A zipper chain comprising a plurality of chain portions arranged to face each other and configured to engage with each other at one point in time while making linear movements,

wherein each chain portion comprises:

a plurality of upper plates connected to each other;

a plurality of lower plates arranged to respectively face the upper plates, respectively spaced apart from the upper plates, and connected to each other;

a plurality of connecting portions each connecting one of the upper plates to a corresponding one of the lower plates and connecting adjacent upper plates among the plurality of upper plates or adjacent lower plates among the plurality of lower plates; and

a plurality of protrusions respectively protruding from the plurality of connecting portions,

wherein the plurality of chain portions comprises:

a first chain portion; and

a second chain portion arranged to face the first chain portion, and

wherein a protrusion, from among the plurality of protrusions of the first chain portion, is inserted in a space that is directly between an upper plate and a lower plate of the second chain portion and directly between centers of two adjacent connecting portions from among the plurality of connecting portions of the second chain portion, and a protrusion, from among the plurality of protrusions of the second chain portion, is inserted in a space that is directly between an upper plate and a lower plate of the first chain portion and directly between two adjacent connecting portions from among the plurality of connecting portions of the first chain portion,

wherein each protrusion of the plurality of protrusions of the first chain portion and the plurality of protrusions of the second chain portion comprises a first side surface and a second side surface, opposite of the first side surface, that are obliquely formed towards an end of the protrusion,

wherein the first side surface of the protrusion from among the plurality of protrusions of the first chain portion faces the first side surface of the protrusion from among the plurality of protrusions of the second chain portion, such that the protrusion from among the plurality of protrusions of the first chain portion and the protrusion from among the plurality of protrusions of the second chain portion are configured to guide insertion of each other into the first chain portion and the second chain portion, respectively,

wherein one of the upper plates or one of the lower plates of the first chain portion comprises a receiving portion that is a groove recessed inwardly in a first direction, between two inner walls of the one of the upper plates or of the one of the lower plates that face each other in a second direction, and extends within the one of the upper plates or the one of the lower plates in a third direction,

wherein the first direction, the second direction, and the third direction are perpendicular to each other,

wherein a distance between the two inner walls in the second direction is constant along the first direction,

wherein the second direction is perpendicular to an extending direction of the first chain portion and extends towards the one of the upper plates of the first chain portion from the one of the lower plates of the first chain portion, and

wherein one of the upper plates or one of the lower plates of the second chain portion comprises an inserted portion protruding outward and that is inserted in the receiving portion of the first chain portion.

2. The zipper chain of claim 1 , wherein the end of each of the protrusions is round.

3. The zipper chain of claim 2 , wherein an upper plate from among the plurality of upper plates of the first chain portion and an upper plate from among the plurality of upper plates of the second chain portion are arranged to alternate with each other.

4. The zipper chain of claim 2 , wherein the protrusion from among the plurality of protrusions of the first chain portion is inserted in a space between adjacent protrusions from among the plurality of protrusions of the second chain portion.

5. The zipper chain of claim 2 , wherein the protrusion from among the plurality of protrusions of the second chain portion is inserted in a space between adjacent protrusions from among the plurality of protrusions of the first chain portion.

6. The zipper chain of claim 1 , wherein the protrusions are inserted in the chain portions facing each other.

7. A zipper chain comprising a plurality of chain portions arranged to face each other and configured to engage with each other at one point in time while making linear movements,

wherein each chain portion comprises:

a plurality of upper plates connected to each other;

a plurality of lower plates arranged to respectively face the upper plates, respectively spaced apart from the upper plates, and connected to each other;

a plurality of connecting portions each connecting one of the upper plates to a corresponding one of the lower plates and connecting adjacent upper plates among the plurality of upper plates or adjacent lower plates among the plurality of lower plates; and

a plurality of protrusions respectively protruding from the plurality of connecting portions,

wherein one of the upper plates or one of the lower plates of one of the chain portions comprises an inserted portion protruding outward,

wherein one of the upper plates or one of the lower plates of another one of the chain portions, adjacent to the one of the chain portions, comprises a receiving portion that is a groove recessed inwardly in a first direction, between two inner walls of the one of the upper plates or of the one of the lower plates that face each other in a second direction, and extends within the one of the upper plates or the one of the lower plates in a third direction,

wherein the inserted portion of the one of the chain portions is inserted in the receiving portion of the another one of the chain portions,

wherein the first direction, the second direction, and the third direction are perpendicular to each other,

wherein a distance between the two inner walls in the second direction is constant along the first direction, and

wherein the second direction is perpendicular to an extending direction of the another one of the chain portions and extends towards the one of the upper plates from the one of the lower plates.

8. A zipper chain comprising a plurality of chain portions arranged to face each other and configured to engage with each other at one point in time while making linear movements,

wherein each chain portion comprises:

a plurality of upper plates connected to each other;

a plurality of lower plates arranged to respectively face the upper plates, respectively spaced apart from the upper plates, and connected to each other;

a plurality of connecting portions each connecting one of the upper plates to a corresponding one of the lower plates and connecting adjacent upper plates among the plurality of upper plates or adjacent lower plates among the plurality of lower plates; and

a plurality of protrusions respectively protruding from the plurality of connecting portions,

wherein at least two inserted portions protruding outward are each provided in a respective one of the upper plates or the lower plates of one of the chain portions,

wherein one of the upper plates or one of the lower plates of another one of the chain portions, adjacent to the one of the chain portions, comprises a receiving portion that is a groove recessed inwardly in a first direction, between two inner walls of the one of the upper plates or of the one of the lower plates that face each other in a second direction, and extends within the one of the upper plates or the one of the lower plates in a third direction,

wherein the at least two inserted portions of the one of the chain portions face the receiving portion of the another one of the chain portions,

wherein the first direction, the second direction, and the third direction are perpendicular to each other,

wherein a distance between the two inner walls in the second direction is constant along the first direction, and

wherein the second direction is perpendicular to an extending direction of the another one of the chain portions and extends towards the one of the upper plates from the one of the lower plates.