US20070246618A1

US20070246618A1 - Display extension unit

Info

Publication number: US20070246618A1
Application number: US11/727,385
Authority: US
Inventors: Dong-Won Choi; Chil-Sung Lee; Kyoung-Shir Park; Jae-Kyung Kim
Original assignee: Samsung Electro Mechanics Co Ltd
Current assignee: Samsung Electro Mechanics Co Ltd
Priority date: 2006-03-27
Filing date: 2007-03-26
Publication date: 2007-10-25
Also published as: EP1840446A1; CN101047042A; KR100797444B1; JP2007264634A; KR20070096626A

Abstract

A display extension unit is disclosed. The present invention provides a display extension unit including a support, a link portion having one end coupled to a support, a driving part coupled to a joining point of the link portion, and a movable body coupled to the other end of the link portion, such that the movable body is separated from the support in accordance with the driving of the link portion.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korean Patent Application No. 10-2006-0027469 filed with the Korean Intellectual Property Office on Mar. 27, 2006, the disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND

1. Technical Field
The present invention relates to a display extension unit.
2. Description of the Related Art
The flat panel display, such as an LCD, PDP, or LED, applied to a TV set or monitor has the advantage of efficiently using a narrow space and is thus replacing the Braun tube TV or monitor, with demands for the flat panel display expected to continually increase in the future. In particular, the flat type LCD or the PDP-applied TV are referred to as a ‘wall mounted type TV’, and are used fixedly adhered to the wall. When viewing the wall mounted type TV adhered to the wall in this way, the screen is seen the widest when the TV is located in front of the viewers.
However, when the TV is fixed, a clear view of the TV may not be obtained when a viewer moves to a different position. The conventional wall-mounted-type TV has difficulty in changing directions, because it has little or only a narrow distance from the wall. Even if another material is applied to distance the TV from the wall, it still will not solve the problem of being unable to rotate to a certain orientation. Moreover, using another apparatus for maintaining a distance between the wall and the TV eliminates the advantage of small volume.

SUMMARY

An aspect of the present invention is to provide a display extension unit, which allows a maximum viewing angle even when the location of a viewer is changed while maintaining the advantage of displays such as the wall mounted type TV of spacious use of indoor space.
One aspect of the present invention provides a display extension unit including a support, a link portion having one end coupled to a support, a driving part coupled to a joining point of the link portion, and a movable body coupled to the other end of the link portion such that the movable body is separated from the support in accordance with the driving of the link portion.
The link portion may include a first hinge member coupled to the support, a second hinge member coupled to the movable body, a first link element having one end rotatably coupled to the first hinge member, and a second link element having one end rotatably coupled to the second hinge member.
The driving part may include a motor unit and a rotary part coupled to a driving shaft of the motor unit, where the motor unit may be coupled to the first hinge member or the second hinge member, and the rotary part may be coupled to the first link element or the second link element to be in correspondence with the first link element or the second link element respectively.
The link portion may include a first guide member coupled to the support while separated from the first hinge member, and a second guide member coupled to the movable body while separated from the second hinge member, where the first link element and the second link element may intersect each other, with the other end of the first link element movably coupled to the second guide element, and the other end of the second link element movably coupled to the first guide element.
The driving part may include a motor unit and a driving part coupled to a driving shaft of the motor unit, where the motor unit may be coupled to the first link element or the second link element where the first link element and the second link element intersect, and the rotary part may be coupled to that one of the first link element or the second link element to which the motor unit is not coupled.
The driving part may includes a motor unit and an extend portion coupled to a driving shaft of the motor unit and configured to extend along the length direction of the driving shaft according to the rotation of the motor unit, with the motor unit coupled to the first guide member or the second guide member, and the extend portion coupled to one end of the second link element or the other end of the first link element to be in correspondence with the first guide member or the second guide member respectively.
The link portion may include a third hinge member coupled to the support while separated from the first hinge member, a fourth hinge member coupled to the movable body while separated from the second hinge member, a third link element having one end rotatably coupled to the other end of the first link element by way of an interposed fifth hinge member and having the other end rotatably coupled to the fourth hinge member, and a fourth link element having one end rotatably coupled to the other end of the second link element by way of an interposed sixth hinge member and having the other end rotatably coupled to the third hinge member.
The display extension unit may further include a worm gear member coupled with the fifth hinge member and the sixth hinge member for adjusting the distance between the sixth hinge member and the fifth hinge member while rotating with the axis in the longitudinal direction.
The driving part may include a motor unit and a rotary part coupled to a driving shaft of the motor unit, where the rotary part may be coupled to the worm gear member.
The worm gear member may include a first rod having a worm gear formed on one end with the worm gear coupled with the fifth hinge member, a second rod having a worm gear formed on one end with the worm gear coupled with the sixth hinge member, and a pipe having the other end of the first rod inserted in one end and having the other end of the second rod inserted in the other end, with a guide groove or a guide projection formed in the longitudinal direction along the inner perimeter of the pipe, and a hole formed at the other end of the first rod and the other end of the second rod in correspondence with the guide projection.
In one embodiment, the display extension unit may further include a first gear coupled to the outer perimeter of the first hinge member, and a second gear coupled to the first gear and the outer perimeter of the third hinge member.
The display extension unit may further include a first gear coupled to the outer perimeter of the second hinge member, and a second gear coupled to the first gear and the outer perimeter of the fourth hinge member.
The first gear and the second gear may be coupled by an even number of idle gears.
The driving part may include a motor unit and a rotary part coupled to a driving shaft of the motor unit, where the rotary part may be coupled to the first gear or the second gear.
The rotary part may include a clutch unit coupled to the driving shaft and a driven shaft positioned in contact with the clutch unit, with the driving force of the motor unit smaller than the frictional force between the driven shaft and the clutch unit.
The driving part may include a motor unit and a rotary part coupled to a driving shaft of the motor unit, where the motor unit may be coupled to the other end of the first link element or one end of the third link element, and the rotary part may be coupled to that one of the one end of the third link element or the other end of the third link element to which the motor unit is not coupled.
The driving part may include a motor unit and a rotary part coupled to a driving shaft of the motor unit, where the motor unit may be coupled to the other end of the second link element or one end of the fourth link element, and the rotary part may be coupled to that one of the one end of the fourth link element or the other end of the second link element to which the motor unit is not coupled.
The rotary part may include a clutch unit coupled to the driving shaft and a driven shaft positioned in contact with the clutch unit, with the driving force of the motor unit smaller than the frictional force between the driven shaft and the clutch unit.
The frictional force between the driven shaft and the clutch unit may be smaller than the cogging torque of the motor unit.
The display extension may further include one or more washers interposed between the clutch unit and the driven shaft.
Additional aspects and advantages of the present invention will become apparent and more readily appreciated from the following description, including the appended drawings and claims, or may be learned by practice of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a is a plan view of a display extension unit according to a first disclosed embodiment of the invention.

FIG. 1 b is an enlarged sectional view of the intersection in FIG. 1 a.

FIG. 1 c is an operation diagram of a display extension unit according to the first embodiment of the invention.

FIG. 2 a is a plan view of a display extension unit according to a second disclosed embodiment of the invention.

FIG. 2 b is an operation diagram of a display extension unit according to the second disclosed embodiment of the invention.

FIG. 3 a is a plan view of the display extension unit according to a third disclosed embodiment of the invention.

FIG. 3 b is an operation diagram of a display extension unit according to the third disclosed embodiment of the invention.

FIG. 4 a is a plan view of a display extension unit according to a fourth disclosed embodiment of the invention.

FIG. 4 b is an operation diagram of a display extension unit according to the fourth disclosed embodiment of the invention.

FIG. 5 a is a plan view of a display extension unit according to a fifth disclosed embodiment of the invention.

FIG. 5 b is a plan view of a display extension unit according to the fifth disclosed embodiment of the invention.

FIG. 5 c is a side view of a display extension unit adhered the display according to the fifth disclosed embodiment of the invention.

FIG. 6 is cross-sectional view of the rotary part a driving part according to a sixth disclosed embodiment of the invention.

DETAILED DESCRIPTION

Embodiments of the display extension unit based on the invention will be described below in more detail with reference to the accompanying drawings. In the description with reference to the accompanying drawings, those components are rendered the same reference number that are the same or are in correspondence, regardless of the figure number, and redundant explanations are omitted.
FIG. 1 a is a plan view of a display extension unit according to a first disclosed embodiment of the invention, FIG. 1 b is an enlarged sectional view of the intersection in FIG. 1 a, and FIG. 1 c is an operation diagram of the display extension unit according to the first embodiment of the invention. Referring to FIGS. 1 a to 1 c, a link portion 10, support 11, movable body 12, first hinge member 13 a, second hinge member 13 b, first guide member 14 a, second guide member 14 b, first link element 15 a, second link element 15 b, intersection 16, universal joint 17, display 18, driving part 19, motor unit 19 a, and rotary part 19 b are illustrated.
The support 11 is coupled with the link portion 10, and supports the movable body 12 joined to the link portions 10. While the support 11 is illustrated to have a particular form in the detailed description and figures, it may include any form of medium used in coupling the link portion 10 to the wall, etc., such as an anchor bolt, bracket, braces, and plates. The support 11 may be strong enough to bear the weight of the link portion 10, movable body 12, and display 18.
The link portion 10 includes a first hinge member 13 a, second hinge member 13 b, first guide member 14 a, second guide member 14 b, first link element 15 a, second link element 15 b, and intersection 16.
The first hinge member 13 a is coupled with the support 11 and is hinge-coupled with one end of first link element 15 a. A part of the support 11 at a point separated from first hinge member 13 a by a particular distance is coupled with the first guide member 14 a. A hole 140 a is formed in the first guide member 14 a such that allows linear motion after one end of the second link element 15 b is joined to the hole 140 a.
Also, the second link element 15 b joins the first link element 15 a at the intersection 16. The intersection 16 may be at the central part of the second link element 15 b and first link element 15 a. Moreover, the driving part 19 may be coupled with the intersection 16 such that the first and second link elements 15 a, 15 b are rotatable.
The other end of the first link element 15 a is coupled with the hole 140 b of the second guide member 14 b to move rectilinearly, and the other end of the second link element 15 b is hinge-coupled with the movable body 12.
As shown in FIG. 1 a, the second guide member 14 b may be coupled with the movable body 12 as one body or as separate bodies. As shown in the figure, the universal joint 17 may be coupled to the movable body 12, and the display 18 may be coupled to the universal joint 17 for movement.
FIG. 1 b is an enlarged sectional view of the intersection in FIG. 1 a. At the intersection 16, the rotary part 19 b of the driving part 19 is coupled with the first link element 15 a, and the motor unit 19 a of the driving part 19 is coupled with the second link element 15 b. Thus, when the rotary part 19 b is rotated, the first link element 15 a and second link element 15 b rotate together about the intersection 16. Consequently, as in FIG. 1 c, the movable body 12 adhered to the link portion 10 becomes either closer or farther from the support 11. Meanwhile, the motor unit 19 a may be coupled with the first link element 15 a, and the rotary part 19 b may be coupled with the second link element 15 b.
FIG. 2 a is a plan view of a display extension unit according to a second disclosed embodiment of the invention, and FIG. 2 b is an operation diagram of a display extension unit according to the second disclosed embodiment of the invention. The second embodiment is similar to the first embodiment with the exception of the driving part 29. The difference will be described below.
The driving part 29 in this embodiment includes a motor unit 29 a, and an expansion portion 29 c coupled with the driving shaft 29 b of the motor unit 29 a. The extend portion 29 c extends or contracts in the longitudinal direction according to the rotation of the driving shaft 29 b. As shown in the figure, the motor unit 29 is joined with the first guide member 24 a, and is coupled with one end of the second link element 25 b. Therefore, when the driving shaft 29 b is rotated, one end of the second link element 25 b is moved rectilinearly, whereby the whole link portion 20 is moved. This motor unit 29 may be coupled with the second guide member 24 b. FIG. 2 b shows the link portion 20 in an extended position.
FIG. 3 a is a plan view of the display extension unit according to a third disclosed embodiment of the invention, and FIG. 3 b is an operation diagram of a display extension unit according to the third disclosed embodiment of the invention. In FIGS. 3 a and 3 b, a link portion 30, support 31, movable body 32, first hinge part 34 a, second hinge part 34 b, third hinge part 34 c, fourth hinge part 34 d, first link element 35 a, second link element 35 b, universal joint 37, display 38, and driving part 39 are illustrated.
In the third disclosed embodiment, the first link element 35 a and second link element 35 b are respectively hinge-coupled with the movable body 32 and the support 31. The movable body 32 is capable of swinging, because the link elements 35 a, 35 b rotate about the hinge parts 34 a˜34 d.
Meanwhile, the driving part 39 is coupled with one of the hinge parts 34 a˜34 d. As shown in FIG. 1 b, the driving part 39 includes the motor unit 19 a and the rotary part 19 b. The first link element 35 a and second link element 35 b are rotated together by the torque of the rotary part. While this embodiment illustrates the mode of coupling the driving part 39 with the first hinge member 34 a, other modes, such as uniting the driving part 39 with other hinge members 34 b˜34 d may also be acceptable.
FIG. 3 b shows the first and second link elements 35 a, 35 b extended by swinging. The rest of the elements of this embodiment function the same as the elements illustrated in the first embodiment.
FIG. 4 a is a plan view of a display extension unit according to a fourth disclosed embodiment of the invention, and FIG. 4 b is an operation diagram of a display extension unit according to the fourth disclosed embodiment of the invention. In FIGS. 4 a and 4 b, a link portion 40, support 41, movable body 42, first link element 45 a, second link element 45 b, third link element 45 c, fourth link element 45 d, fifth link element 45 e, sixth link element 45 f, universal joint 47, display 48, driving part 49, motor unit 49 a, and worm gear member 49 c are illustrated.
In this embodiment, the first and second hinge members 43 a, 43 b are respectively coupled to the support 41. The first link element 45 a is coupled with the first hinge member 43 a, and the second link element 45 b is coupled with the second hinge member 43 b. Therefore, rotation is possible with a constant angle. The other hinge members 45 c˜45 d are also hinge-coupled.
In the present embodiment, the driving part 49 includes the motor unit 49 a, rotary part (non illustration), and worm gear member 49 c. The motor unit 49 a is attached and fixed to the fourth link element 45 d, and the worm gear member 49 c penetrates and is screw-coupled with the third link element 45 c. Thus, the third link element 45 c comes either closer or further apart from the fourth link element 45 d depending on the rotational direction of the worm gear member 49 c. Consequently, the link portion 40 is contracted or extended. FIG. 4 b shows the driving part 49 in its extended state as the third link element 45 c and fourth link element 45 d come closer together. The same function is possible in the case where the motor unit 49 a is fixed to the third link element 45 c and the worm gear member 49 c is joined to the fourth link element 45 d. Detailed descriptions will not be provided on the remaining elements, as they are substantially the same as the elements in the first disclosed embodiment.
While six link elements are coupled in this embodiment, a structure having four link elements may be used, with the four link elements hinge-coupled in a rhombus shape, where the link elements facing each other may be joined with a driving part 49 that includes the worm gear member 49 c shown in FIG. 4 a.
FIG. 5 a is a plan view of a display extension unit according to a fifth disclosed embodiment of the invention, FIG. 5 b is a plan view of a display extension unit according to the fifth disclosed embodiment of the invention, and FIG. 5 c is a side view of a display extension unit adhered the display according to the fifth disclosed embodiment of the invention. In FIGS. 5 a, 5 b, and 5 c, a link portion 50, a support 51, a movable body 52, a first hinge member 54 a, a second hinge member 54 b, a third hinge member 54 c, a fourth hinge member 54 d, a fifth hinge member 54 e, a sixth hinge member 54 f, a first link element 55 a, a second link element 55 b, a third link element 55 c, a fourth link element 55 d, a universal joint 57, a display 58, idle gears 59 c, and a display extension unit 500 are illustrated.
This embodiment illustrates a display extension unit using two pairs of link members. The first link element 55 a and second link element 55 b are respectively hinge-coupled with the first and second hinge members 54 a, 54 b. The first and second hinge members 54 a, 54 b are coupled with the support 51. The first link element 55 a is coupled with the third link element 55 c, and the second link element 55 b is coupled with the fourth link element 55 d.
While the driving part 59 may be joined with the hinge members 54 a˜54 f, in the present embodiment, an even number of idle gears 59 c are coupled between the first gear 541 a and the second gear 541 b formed respectively on the first hinge member 54 a and second hinge member 54 b, and the driving part is coupled with one of the first gear 541 a, second gear 541 b, and idle gears 59 c, to supply power thereto. The even number of idle gears 59 c make the second gear 541 b and first gear 541 a rotate in opposite directions, so that the link elements operate smoothly without a high load concentrated on any one link element.
In the present embodiment, the first gear 541 a and second gear 541 b are respectively coupled with the first hinge member 54 a and second hinge member 54 b, and the even number of idle gears 59 c and the driving part 59 are coupled between the first hinge member 54 a and second hinge member 54 b. However, the even number of idle gear 59 c and the driving part 59 may be coupled between the fifth hinge member 54 e and sixth hinge member 54 f in a similar fashion. Meanwhile, the link elements may be driven without the idle gears 59 c in cases where the first gear 541 a is directly coupled with the second gear 541 b. FIGS. 5 b and 5 c show a plan view and a side view of the display extension unit joined with the display 58.
Detailed descriptions will not be provided on the rest of the elements, because the operation principles of the rest of the elements of this embodiment are substantially the same as those of the first embodiment.
The embodiments described above relate to the automatic mode of using a remote controller. However, a display extension unit may be manually extended, at which the rotor of the motor may be damaged by the forced rotating. Now, the structure of the rotary part for preventing damage will be illustrated.
FIG. 6 is cross-sectional view of the rotary part a driving part according to a sixth disclosed embodiment of the invention. Referring to FIG. 6, a rotary part 60, driving shaft 61, clutch unit 61 a, and driven shaft 62 are illustrated.
This embodiment describes a mode which may be applied to the rotary part of the driving part used in the first to fifth embodiments. The driving shaft 61 of FIG. 6 is coupled with the motor unit 19 a of the driving part 10 in FIG. 1 b, where the driving shaft 61 may be the rotary shaft of the motor. The driving shaft 61 is coupled with the driven shaft 62 at the clutch unit 61 a. As shown in FIG. 6, the clutch unit 61 b for controlling the frictional force may be coupled with the driving shaft 61 as one body. Moreover, the clutch unit 61 b may be coupled with the driven shaft 62. A washer 61 b is interposed between the clutch unit 61 b and the driven shaft 62, to maintain a constant frictional force.
With regard the operating method of the rotary part 60, the driving force of the motor running the link portion in the first to fifth embodiments is smaller than the frictional force of the clutch unit 61 b, such that there is no slipping at the clutch unit 61 b and the driven shaft 62. However, when the driven shaft 62 is rotated by forced moving of the link portion, the friction force of the clutch unit 61 b is smaller than the cogging torque of the motor, such that there is slipping. Consequently, the possibility is decreased of forced rotation of the motor by external force.
According to certain aspects of the present invention set forth as above, the display can be extended from the support such to attain a desired rotation angle of the display. This extending and rotating operation can be performed manually or automatically. The durability of the apparatus can be increased even with manual rotating.
While the above description has pointed out novel features of the invention as applied to various embodiments, the skilled person will understand that various omissions, substitutions, and changes in the form and details of the device or process illustrated may be made without departing from the scope of the invention. Therefore, the scope of the invention is defined by the appended claims rather than by the foregoing description. All variations coming within the meaning and range of equivalency of the claims are embraced within their scope

Claims

1. A display extension unit comprising:

a support;

a link portion having one end coupled to the support;

a driving part coupled to a joining point of the link portion; and

a movable body coupled to the other end of the link portion, such that the movable body is separated from the support in accordance with the driving of the link portion.

2. The display extension unit of claim 1, wherein the link portion comprises:

a first hinge member coupled to the support;

a second hinge member coupled to the movable body;

a first link element having one end rotatably coupled to the first hinge member; and

a second link element having one end rotatably coupled to the second hinge member.

3. The display extension unit of claim 2, wherein the driving part comprises:

a motor unit; and

a rotary part coupled to a driving shaft of the motor unit,

and the motor unit is coupled to the first hinge member or the second hinge member,

and the rotary part is coupled to the first link element or the second link element to be in correspondence with the first link element or the second link element respectively.

4. The display extension unit of claim 2, wherein the link portion comprises:

a first guide member coupled to the support while separated from the first hinge member; and

a second guide member coupled to the movable body while separated from the second hinge member,

and wherein the first link element and the second link element intersect each other,

and the other end of the first link element is movably coupled to the second guide element, and the other end of the second link element is movably coupled to the first guide element.

5. The display extension unit of claim 4, wherein the driving part comprises:

a motor unit; and

a driving part coupled to a driving shaft of the motor unit;

and wherein the motor unit is coupled to the first link element or the second link element where the first link element and the second link element intersect, and the rotary part is coupled to that one of the first link element or the second link element to which the motor unit is not coupled.

6. The display extension unit of claim 4, wherein the driving part comprises:

a motor unit; and

an extend portion coupled to a driving shaft of the motor unit and configured to extend along the length direction of the driving shaft according to the rotation of the motor unit,

and wherein the motor unit is coupled to the first guide member or the second guide member, the extend portion is coupled to one end of the second link element or the other end of the first link element to be in correspondence with the first guide member or the second guide member respectively.

7. The display extension unit of claim 2, wherein the link portion comprises:

a third hinge member coupled to the support while separated from the first hinge member;

a fourth hinge member coupled to the movable body while separated from the second hinge member;

a third link element having one end rotatably coupled to the other end of the first link element by way of an interposed fifth hinge member and having the other end rotatably coupled to the fourth hinge member; and

a fourth link element having one end rotatably coupled to the other end of the second link element by way of an interposed sixth hinge member and having the other end rotatably coupled to the third hinge member.

8. The display extension unit of claim 7, further comprising a worm gear member, coupled with the fifth hinge member and the sixth hinge member, for adjusting the distance between the sixth hinge member and the fifth hinge member while rotating with the axis in the longitudinal direction.

9. The display extension unit of claim 8, wherein the driving part comprises:

a motor unit; and

a rotary part coupled to a driving shaft of the motor unit,

and wherein the rotary part is coupled to the worm gear member.

10. The display extension unit of claim 8, wherein the worm gear member comprises:

a first rod having a worm gear coupled with the fifth hinge member formed on one end;

a second rod having a worm gear coupled with the sixth hinge member formed on one end; and

a pipe having the other end of the first rod inserted in one end thereof and having the other end of the second rod inserted in the other end thereof,

and wherein a guide groove or a guide projection is formed in the longitudinal direction along the inner perimeter of the pipe, and a hole is formed at the other end of the first rod and the other end of the second rod in correspondence with the guide projection.

11. The display extension unit of claim 7, further comprising a first gear coupled to the outer perimeter of the first hinge member, and a second gear coupled to the first gear and the outer perimeter of the third hinge member.

12. The display extension unit of claim 7, wherein the display extension unit further comprises a first gear coupled to the outer perimeter of the second hinge member, and a second gear coupled to the first gear and the outer perimeter of the fourth hinge member.

13. The display extension unit of claim 12, wherein the first gear and the second gear are coupled by an even number of idle gears.

14. The display extension unit of claim 12, wherein the driving part comprises:

a motor unit; and

a rotary part coupled to a driving shaft of the motor unit,

and wherein the rotary part is coupled to the first gear or the second gear.

15. The display extension unit of claim 14, wherein the rotary part comprises:

a clutch unit coupled to the driving shaft; and

a driven shaft positioned in contact with the clutch unit,

and wherein the driving force of the motor unit is smaller than the frictional force between the driven shaft and the clutch unit.

16. The display extension unit of claim 12, wherein the driving part comprises:

a motor unit; and

a rotary part coupled to a driving shaft of the motor unit,

and wherein the motor unit is coupled to the other end of the first link element or one end of the third link element,

and the rotary part is coupled to that one of the one end of the third link element or the other end of the third link element to which the motor unit is not coupled.

17. The display extension unit of claim 12, wherein the driving part comprises:

a motor unit; and

a rotary part coupled to a driving shaft of the motor unit,

and wherein the motor unit is coupled to the other end of the second link element or one end of the fourth link element,

and the rotary part is coupled to that one of the one end of the fourth link element or the other end of the second link element to which the motor unit is not coupled.

18. The display extension unit of claim 9, wherein the rotary part comprises:

a clutch unit coupled to the driving shaft; and

a driven shaft positioned in contact with the clutch unit,

19. The display extension unit of claim 18, wherein the frictional force between the driven shaft and the clutch unit is smaller than the cogging torque of the motor unit.

20. The display extension unit of claim 18, further comprising one or more washers interposed between the clutch unit and the driven shaft.