Platen unit and printer

1. A platen unit of a printer configured to perform printing while nipping and feeding a linerless label using a thermal head and a platen roller, the platen unit comprising:

the platen roller;

a downstream-side wraparound prevention member disposed on a downstream side of a feeding direction of the linerless label with respect to the platen roller, the downstream-side wraparound prevention member being configured to prevent the linerless label from rolling up to the platen roller; and

an upstream-side wraparound prevention member disposed on an upstream side of the feeding direction of the linerless label with respect to the platen roller, the upstream-side wraparound prevention member being configured to prevent the linerless label from rolling up to the platen roller,

wherein the upstream-side wraparound prevention member and the downstream-side wraparound prevention member are rotatably assembled to a roller shaft of the platen roller independently from each other,

wherein the platen unit is configured to be attached to and detached from a support member of the printer, and

wherein the platen roller, the downstream-side wraparound prevention member, and the upstream-side wraparound prevention member are configured to be integrally detached from the printer when the platen unit is detached from the printer.

2. A printer comprising:

the platen unit according to claim 1 ; and

a fixing mechanism configured to receive the platen unit, the fixing mechanism including the support member.

3. The printer according to claim 2 , further comprising:

a downstream-side positioning mechanism configured to position the downstream-side wraparound prevention member; and

an upstream-side positioning mechanism configured to position the upstream-side wraparound prevention member.

4. The printer according to claim 3 , wherein the platen unit further comprises a fixing portion configured to rotatably support the roller shaft,

the downstream-side wraparound prevention member is assembled with the fixing portion fixedly in a rotational direction of the roller shaft, and

the downstream-side wraparound prevention member is positioned by the downstream-side positioning mechanism by inserting the fixing portion into a fixing concave portion formed in the support member in a predetermined direction and thereafter rotating the downstream-side wraparound prevention member and the fixing portion around the roller shaft.

5. The printer according to claim 3 , wherein the platen unit further comprises a fixing portion configured to rotatably support the roller shaft,

the upstream-side wraparound prevention member is positioned by the upstream-side positioning mechanism by inserting the fixing portion into a fixing concave portion formed in the support member while rotation of the upstream-side wraparound prevention member is restricted so as not to approach the downstream-side wraparound prevention member.

6. The printer according to claim 3 , wherein the platen unit further comprises a fixing portion configured to rotatably support the roller shaft,

the upstream-side wraparound prevention member is positioned in a predetermined position by the upstream-side positioning mechanism with assistance in rotation of the upstream-side wraparound prevention member to the predetermined position by inserting the fixing portion into a fixing concave portion formed in the support member while rotation of the upstream-side wraparound prevention member is restricted so as not to be apart from the downstream-side wraparound prevention member.

7. The printer according to claim 6 , further comprising an engagement portion provided with a slope surface, the slope surface being configured to rotate the upstream-side wraparound prevention member toward the predetermined position by abutting on the upstream-side wraparound prevention member when the fixing portion is inserted into the fixing concave portion.

8. The printer according to claim 7 , wherein the engagement portion includes a pair of engagement surfaces, the pair of engagement surfaces have different angles and position the upstream-side wraparound prevention member by engaging in different places of the upstream-side wraparound prevention member.

9. The printer according to claim 7 , wherein a portion of the upstream-side wraparound prevention member that abuts on the slope surface by inserting the fixing portion into the fixing concave portion is placed in the upstream side with respect to a center axis of the roller shaft.

10. The platen unit according to claim 1 , wherein the roller shaft is configured to be attached to and detached from the support member of the printer.

11. A printer comprising:

the platen unit and the support member according to claim 1 ; wherein

the support member is configured to support the roller shaft of the platen roller.

12. A platen unit of a printer configured to perform printing while nipping and feeding a linerless label using a thermal head and a platen roller, the platen unit comprising:

the platen roller;

a downstream-side wraparound prevention member disposed on a downstream side of a feeding direction of the linerless label with respect to the platen roller, the downstream-side wraparound prevention member being configured to prevent the linerless label from rolling up to the platen roller;

an upstream-side wraparound prevention member disposed on an upstream side of the feeding direction of the linerless label with respect to the platen roller, the upstream-side wraparound prevention member being configured to prevent the linerless label from rolling up to the platen roller; and

a restriction mechanism configured to restrict relative rotation of the downstream-side wraparound prevention member and the upstream-side wraparound prevention member,

wherein the upstream-side wraparound prevention member and the downstream-side wraparound prevention member are rotatably assembled to a roller shaft of the platen roller independently from each other.

13. A printer comprising:

the platen unit according to claim 12 ; and

a fixing mechanism configured to receive the platen unit.

14. The printer according to claim 13 , further comprising a downstream-side positioning mechanism configured to position the downstream-side wraparound prevention member.

15. The printer according to claim 14 , wherein the platen unit further has a fixing portion configured to rotatably support the roller shaft,

the downstream-side wraparound prevention member is assembled with the fixing portion fixedly in a rotational direction of the roller shaft,

the fixing mechanism has a support member configured to detachably support the fixing portion, and

the downstream-side wraparound prevention member is positioned by the downstream-side positioning mechanism by inserting the fixing portion into a fixing concave portion formed in the support member in a predetermined direction and thereafter rotating the downstream-side wraparound prevention member and the fixing portion around the roller shaft.

16. The printer according to claim 13 , further comprising an upstream-side positioning mechanism configured to position the upstream-side wraparound prevention member.

17. The printer according to claim 16 , wherein the platen unit further has a fixing portion configured to rotatably support the roller shaft,

the fixing mechanism has a support member configured to detachably support the fixing portion, and

the upstream-side wraparound prevention member is positioned by the upstream-side positioning mechanism by inserting the fixing portion into a fixing concave portion formed in the support member while rotation of the upstream-side wraparound prevention member is restricted by the restriction mechanism so as not to approach the downstream-side wraparound prevention member.

18. The printer according to claim 16 , wherein the platen unit further has a fixing portion configured to rotatably support the roller shaft,

the fixing mechanism has a support member configured to detachably support the fixing portion, and

the upstream-side wraparound prevention member is positioned in a predetermined position by the upstream-side positioning mechanism with assistance in rotation of the upstream-side wraparound prevention member to the predetermined position by inserting the fixing portion into a fixing concave portion formed in the support member while rotation of the upstream-side wraparound prevention member is restricted by the restriction mechanism so as not to be apart from the downstream-side wraparound prevention member.

19. The printer according to claim 18 , further comprising an engagement portion provided with a slope surface, the slope surface being configured to rotate the upstream-side wraparound prevention member toward the predetermined position by abutting on the upstream-side wraparound prevention member when the fixing portion is inserted into the fixing concave portion.

20. The printer according to claim 19 , wherein the engagement portion has a pair of engagement surfaces, the pair of engagement surfaces have different angles and position the upstream-side wraparound prevention member by engaging in different places of the upstream-side wraparound prevention member.

21. The printer according to claim 19 , wherein a portion of the upstream-side wraparound prevention member that abuts on the slope surface by inserting the fixing portion into the fixing concave portion is placed in the upstream side with respect to a center axis of the roller shaft.