Sliding device

A sliding device comprising:

• a first rail member of which one side surface is open;
• a second rail member which slidably moves on the first rail member and of which one side surface is open;
• and
• ball members disposed between the first rail member and the second rail member and including at least three said ball members provided on a cross section of the sliding device,
• wherein the first rail member and the second rail member are engaged with each other through the open one side surfaces,
• wherein:
• the first rail member includes a first upper portion, a first side portion connected to the first upper portion, a first lower portion connected to the first side portion, and a first insertion part which is inserted into the second rail member, and is formed at an end of the first upper portion;
• the second rail member includes a second upper portion, a second side portion connected to the second upper portion, a second lower portion connected to the second side portion, and a second insertion part which is inserted into the first rail member, and is formed at an end of the second lower portion;
• the first upper portion is positioned between the second upper portion and the second lower portion;
• and
• the second lower portion is positioned between the first upper portion and the first lower portion,
• wherein a first said ball member is disposed between the first upper portion and the second upper portion, and a second said ball member is disposed between the first lower portion and the second lower portion,
• wherein a third said ball member is disposed between the second lower portion and the first insertion part, and a fourth said ball member is disposed between the first upper portion and the second insertion part,
• wherein an acute angle is formed between a line connecting a center of the first ball member and a center of the fourth ball member and the first side portion, and an acute angle is formed between a line connecting a center of the second ball member and a center of the third ball member and the second side portion, and
• wherein when viewed in the cross section, a center of the first ball member and a center of the second ball member are disposed between a center of the third ball member and a center of the fourth ball member in a direction parallel to the first lower portion or the second upper portion.