LCD ultra-short-focus projector with self-circulation heat dissipation structure

Abstract

The invention relates to an LCD (liquid crystal display) ultra-short-focus projector with a self-circulation heat dissipation structure, which is characterized in that by adopting a newly added external cover as well as a heat carrying rod and an internal heat conduction square tube which are arranged in the external cover, when the projector is used, the heat carrying rod can be continuously expanded and contracted in the internal heat conduction square tube, so that the self-circulation heat dissipation of the projector body is realized; according to the projector, the heat transfer rods are arranged, so that the heat absorbed in the projector body can be continuously and directly carried out of the projector body when the heat transfer rods move back and forth, compared with natural heat dissipation, the heat dissipation efficiency can be greatly improved, and in addition, in cooperation with the arrangement of the heat exchange oil sheets, the heat transfer efficiency is improved in the continuous outward-extending and inward-retracting process of the heat transfer rods. And the heat conduction oil is continuously transferred in the oil gathering bag and the oil guiding sheet bag, so that the heat conduction oil is transferred inside and outside the external cover, and the self-circulation heat dissipation efficiency is further improved.

Description

Technical Field

[0001] The present invention relates to an LCD ultra-short-throw projector, and in particular to an LCD ultra-short-throw projector with a self-circulating heat dissipation structure applied in the field of projector heat dissipation. Background Art

[0002] The principle of LCD panel projector is: the optical system transforms strong light into three RGB beams through a beam splitter, which are transmitted through the RGB three-color liquid crystal panel respectively; the signal source is converted by AD, modulated and added to the liquid crystal panel, and the opening and closing of the liquid crystal unit are controlled to control the on and off of the light path. The RGB light is finally converged in the prism and projected on the screen by the projection lens to form a color image. The projector is prone to heat when it is working continuously. The existing technology achieves heat dissipation through heat dissipation holes and heat dissipation fins, but this method has limited heat dissipation and is difficult to meet the needs of continuous work, which has a certain impact on the stability of the projector.

[0003] In order to solve the problem of limited heat dissipation effect mentioned above, the specification of Chinese invention patent CN202121838388.4 discloses "LCD projector with better heat dissipation effect", which mainly accelerates heat dissipation by adding a fan inside to achieve heat dissipation by accelerating air circulation.

[0004] However, in the actual setting of the projector, the number of heat dissipation holes arranged in its outer shell is limited. The heat is dissipated by the fan, and the air flow of the internal hot air exhaust path is limited and constant, resulting in insufficient heat dissipation effect.

[0005] Application Contents

[0006] In view of the above-mentioned prior art, the technical problem to be solved by the present invention is the problem that the heat dissipation effect of the existing projector is insufficient.

[0007] To solve the above problems, the present invention provides an LCD ultra-short-throw projector with a self-circulating heat dissipation structure, comprising a projector body and a projection lens installed at the front end of the projector body, a chip is installed in the projector body, a plurality of evenly distributed heat dissipation fins are arranged at the outer end of the projector body, and evenly distributed heat dissipation holes are drilled at the position between two adjacent heat dissipation fins, an external cover is fixedly connected to the rear end of the projector body, the external cover is communicated with the interior of the projector body, heat dissipation ports are drilled at both left and right ends of the external cover, an inner heat-conducting square tube is fixedly connected between the two heat dissipation ports, the left and right ends of the inner heat-conducting square tube extend to the outside of the external cover, the front and rear end surfaces of the inner heat-conducting square tube are connected to heat transfer rods through electric slide rails, the slide rails are connected to chip signals, the heat transfer rod runs through one of the heat dissipation ports, the heat transfer rod comprises a guide inner rod and an embedded rod located outside the external cover and at one end facing the inside of the external cover, the guide inner rod is connected to the electric slide rail, and the embedded rod is movably embedded in the inner heat-conducting square tube.

[0008] In the above-mentioned LCD ultra-short-throw projector with a self-circulating heat dissipation structure, when the projector is in use, through the newly added external cover and the heat transfer rod and internal heat-conducting square tube inside the projector, the heat in the projector body can be continuously conducted outward by continuously expanding and contracting, thereby realizing self-circulating heat dissipation. At the same time, when it is expanded outward, the projector body is transparent inside and outside, which can greatly improve the heat dissipation efficiency.

[0009] As a further improvement of the present application, the inner heat-conducting square tube, the guiding inner rod and the embedded rod are all made of heat-conducting materials, so that when the three are in the external cover, they can effectively absorb and gather the heat generated when the projector body is working. When they are extended outward, this part of the heat can be directly carried from the inside of the projector body to the outside of the projector body. Compared with natural heat dissipation, the heat dissipation efficiency is greatly improved, and the outer surface of the embedded rod is in close contact with the inner wall of the inner heat-conducting square tube, so that it is not easy to have a gap between the two, which is convenient for fully absorbing the heat inside the projector body.

[0010] As a further improvement of the present application, a plurality of evenly distributed ventilation holes are drilled at the front and rear ends of the inner heat-conducting square tube, and the plurality of ventilation holes are located in the external cover. The ventilation holes connect the inner heat-conducting square tube with the interior of the projector body, and when the heat-transferring rod is extended outward to separate the embedded rod from the inner heat-conducting square tube, the mouth of the inner heat-conducting square tube is exposed. At this time, this place can be directly connected with the interior of the projector body. With the blowing of the fan, the discharge of internal hot air can be greatly increased, thereby effectively accelerating the heat dissipation.

[0011] As a further improvement of the present application, the length of the embedded rod is 1 / 3-1 / 2 of the length of the inner heat-conducting square tube, which effectively ensures that the guiding inner rod does not need to be moved outward too much, and the embedded rod can be detached from the inner heat-conducting square tube, effectively ensuring the stability of the heat-conducting rod when it moves outward, and is not prone to imbalance due to excessive outward movement. When the heat-conducting rod is not moved outward, the two ends of the inner heat-conducting square tube respectively conflict with each other, so that when the projector body is not in use, the two ends of the inner heat-conducting square tube can be blocked, making it difficult for external dust or rats and ants to enter the projector body.

[0012] As a further improvement of the present application, the cross-sectional projections of the two heat dissipation ports overlap, and the width of the inner heat-conducting square tube is smaller than the width of the heat dissipation ports. The inner heat-conducting square tube is located at the overlapped position of the two ports, and the two heat transfer rods are respectively located at the staggered portions of the two ports, so that the heat dissipation ports are just blocked by the heat transfer rods and the inner heat-conducting square tube, and are not easily exposed directly, making it difficult for external dust, rats, ants, etc. to enter the projector body.

[0013] As another improvement of the present application, the internal heat-transmitting square tube includes side square tubes fixedly connected to two heat dissipating ports respectively and four connecting strips fixedly connected between the upper and lower front and rear end surfaces of the two side square tubes. The two electric slide rails are respectively installed at the ends of the two connecting strips that are away from each other. Compared with the setting of the vents, the two connecting strips make the inside and outside of the internal heat-transmitting square tube and the projector body more permeable. When the heat transfer rod moves outward, it is easier for the hot air in the projector body to overflow.

[0014] As another improvement of the present application, a heat exchange oil plate is provided between the two embedded rods, and the heat exchange oil plate includes an oil collecting bag located between the two embedded rods and an oil guide plate bag located on the two embedded rods respectively. A plurality of oil guide pipes are also fixedly connected between the oil collecting bag and the oil guide plate bag. The oil guide pipes are fixedly embedded in the embedded rods, and the oil collecting bag is an elastic sealing structure.

[0015] As another improvement supplement to the present application, the oil-collecting bag and the oil-guiding sheet bag are saturated with heat-conducting oil. When the two heat-conducting rods are not moved out of the external cover, the two guiding inner rods are closest to each other at this time. At this time, due to the squeezing of the inner heat-conducting square tube, most of the heat-conducting oil is concentrated in the oil-collecting bag. At this time, the oil-collecting bag is in an expanded state. When the heat-conducting rod moves outward, the oil-guiding sheet bag gradually loses the squeezing of the inner heat-conducting square tube and bulges outward to reset, generating an adsorption force on the heat-conducting oil in the oil-collecting bag that has absorbed more heat, so that part of the heat-conducting oil returns to the oil-guiding sheet bag along the oil guiding tube, thereby effectively dissipating the heat carried by this part of the heat-conducting oil directly into the air. During the process of the heat-conducting rod shrinking and expanding, the heat-conducting oil also continuously changes position back and forth, thereby further improving the efficiency of self-circulating heat dissipation.

[0016] As another improvement supplement of the present application, the oil deflector bag includes an outer spring piece and two edge sealing pieces respectively fixedly connected between the upper and lower ends of the outer spring piece and the embedded rod, and the upper and lower edges of the outer spring piece respectively extend to the outside of the connection between the two edge sealing pieces and the outer spring piece, and an inner shrinkage arc groove is opened on the end surface opposite to the inner rod and the oil deflector bag, and the connection between the outer spring piece and the edge sealing piece and the embedded rod are all located in the inner shrinkage arc groove, so that the edge sealing piece is on the inner side of the outer spring piece, and when squeezed by the inner heat-conducting square tube, both of them can be retracted into the inner shrinkage arc groove, thereby not easily affecting the back and forth movement of the embedded rod in the inner heat-conducting square tube.

[0017] In summary, on the basis of the heat dissipation of fans, heat dissipation holes and heat dissipation fins in the prior art, an external cover and a heat transfer rod and an internal heat-conducting square tube are added. When the projector is in use, the heat transfer rod can continuously expand and contract in the internal heat-conducting square tube to achieve self-circulating heat dissipation of the projector body, so that the heat transfer rod can directly carry the heat adsorbed in the projector body to the outside of the projector body when moving back and forth. Compared with natural heat dissipation, the heat dissipation efficiency can be greatly improved. In addition, with the setting of the heat exchange oil sheet, during the process of continuous expansion and contraction of the heat transfer rod, the heat transfer oil continuously transfers its position in the oil gathering bag and the oil guide sheet bag, that is, the position transfer of the heat transfer oil inside and outside the external cover is achieved, further improving the efficiency of self-circulating heat dissipation. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a front perspective view of the first embodiment of the present application;

[0019] Figure 2 This is a rear perspective view of the first embodiment of the present application;

[0020] Figure 3 A front perspective view of an additional cover according to a first embodiment of the present application;

[0021] Figure 4 A front perspective view of the heat transfer rod with an external cover when it is extended in the first embodiment of the present application;

[0022] Figure 5 A rear perspective view of the heat transfer rod of the first embodiment of the present application with the cover extended;

[0023] Figure 6 This is a three-dimensional diagram of an inner heat-conducting square tube according to a first embodiment of the present application;

[0024] Figure 7 This is a schematic diagram of the self-circulating heat dissipation of the first embodiment of the present application;

[0025] Figure 8 This is a three-dimensional diagram of an inner heat-conducting square tube according to a second embodiment of the present application;

[0026] Fig. 9 This is a three-dimensional diagram of a heat exchange oil sheet according to a third embodiment of the present application;

[0027] Fig.10 A three-dimensional diagram of the oil guide piece bag portion of the third embodiment of the present application;

[0028] Fig.11 This is a cross-sectional view of the oil guide piece bag portion of the third embodiment of the present application.

[0029] Description of the numbers in the figure:

[0030] 1 projector body, 2 projection lens, 3 external cover, 4 heat transfer rod, 41 guide inner rod, 42 embedded rod, 5 inner heat square tube, 51 edge square tube, 52 connecting strip, 501 vent hole, 61 oil collecting bag, 62 oil guide piece bag, 621 outer spring piece, 622 edge sealing piece, 63 oil guide pipe. DETAILED DESCRIPTION

[0031] Three implementation modes of the present application are described in detail below with reference to the accompanying drawings.

[0032] The first implementation method:

[0033] An LCD ultra-short-throw projector with a self-circulating heat dissipation structure, see Figure 1-2 , including a projector body 1 and a projection lens 2 installed at the front end of the projector body 1, a chip is installed in the projector body 1, a plurality of evenly distributed heat dissipation fins are arranged at the outer end of the projector body 1, and evenly distributed heat dissipation holes are drilled in the area between two adjacent heat dissipation fins, an external cover 3 is fixedly connected to the rear end of the projector body 1, the external cover 3 is communicated with the inside of the projector body 1, and heat dissipation ports are drilled at both left and right ends of the external cover 3.

[0034] See also Figure 3 , in the figure, a indicates that an inner heat-conducting square tube 5 is fixedly connected between the two heat dissipation ports of the electric slide rail, and the left and right ends of the inner heat-conducting square tube 5 are extended to the outside of the outer cover 3. The front and rear end surfaces of the inner heat-conducting square tube 5 are connected to heat-conveying rods 4 through the electric slide rail. The slide rail is connected to the chip signal. When the projector body 1 is working, the electric slide rail can be controlled to work synchronously, so that the heat-conveying rod 4 continuously cycles the process of expansion-contraction. The heat-conveying rod 4 runs through one of the heat dissipation ports. The cross-sectional projections of the two heat dissipation ports overlap, and the width of the inner heat-conducting square tube 5 is smaller than the width of the heat dissipation port. The inner heat-conducting square tube 5 is located at the overlap of the two, and the two heat-conveying rods 4 are respectively located at the dislocation parts of the two, so that the heat dissipation port is just blocked by the heat-conveying rod 4 and the inner heat-conducting square tube 5, and is not easy to be directly exposed, so that it is difficult for external dust, rats, ants, etc. to enter the projector body 1.

[0035] See also Figure 4-5 The heat transfer rod 4 includes a 43 located outside the external cover 3, a guide inner rod 41 and an embedded rod 42 with one end of 43 facing the inner side of the external cover 3, the guide inner rod 41 is connected to the electric slide rail, and the embedded rod 42 is movably embedded in the inner heat-conducting square tube 5. The inner heat-conducting square tube 5, the guide inner rod 41 and the embedded rod 42 are all made of heat-conducting materials, so that when the three are in the external cover 3, they can effectively absorb and gather the heat generated when the projector body 1 is working. When they are extended outward, they can directly carry this part of the heat from the projector body 1 to the outside of the projector body 1. Compared with natural heat dissipation, the heat dissipation efficiency is greatly improved, and the outer surface of the embedded rod 42 is in close contact with the inner wall of the inner heat-conducting square tube 5, so that it is not easy to have a gap between the two, which is convenient for fully absorbing the heat in the projector body 1.

[0036] like Figure 6 A plurality of evenly distributed ventilation holes 501 are drilled at the front and rear ends of the inner heat-conducting square tube 5, and the plurality of ventilation holes 501 are located in the external cover 3. The ventilation holes 501 enable the inner heat-conducting square tube 5 to communicate with the interior of the projector body 1, and when the heat-conducting rod 4 is extended outward to separate the embedded rod 42 from the inner heat-conducting square tube 5, the mouth of the inner heat-conducting square tube 5 is exposed, and at this time, the place can be directly communicated with the interior of the projector body 1. With the blowing of the fan, the external discharge of the internal hot air can be greatly increased, and the heat dissipation can be effectively accelerated.

[0037] The length of the embedded rod 42 is 1 / 3-1 / 2 of the length of the inner heat-conducting square tube 5, which effectively ensures that the guiding inner rod 41 does not need to move outward too much, and the embedded rod 42 can be separated from the inner heat-conducting square tube 5, effectively ensuring the stability of the heat-conducting rod 4 when it moves outward, and it is not easy to cause imbalance due to excessive outward movement. When the heat-conducting rod 4 is not moved outward, the two ends of the inner heat-conducting square tube 5 respectively conflict with the two 43, so that when the projector body 1 is not in use, 43 can block the two ends of the inner heat-conducting square tube 5, making it difficult for external dust or rats and ants to enter the projector body 1.

[0038] The second implementation method:

[0039] This embodiment is different from the first embodiment only in the arrangement of the inner heat-conducting square tube 5, and the rest is consistent with the first embodiment. The specific differences are as follows:

[0040] See also Figure 8 The inner heat-conducting square tube 5 includes side square tubes 51 respectively fixedly connected to the two heat dissipation ports and four connecting strips 52 fixedly connected between the upper and lower front and rear end surfaces of the two side square tubes 51. The two electric slide rails are respectively installed at the ends of the two connecting strips 52 that are away from each other. Compared with the setting of the vent holes 501, the two connecting strips 52 make the inside and outside of the inner heat-conducting square tube 5 and the inside of the projector body 1 more permeable. When the heat transfer rod 4 moves outward, it is easier for the hot air in the projector body 1 to overflow.

[0041] The third implementation method:

[0042] This embodiment adds the following technical contents on the basis of the first implementation or the second implementation, and the rest is consistent with the first implementation or the second implementation.

[0043] See also Fig. 9A heat exchange oil sheet is provided between the two embedded rods 42, and the heat exchange oil sheet includes an oil collection bag 61 located between the two embedded rods 42 and an oil guide piece bag 62 respectively located on the two embedded rods 42. A plurality of oil guide pipes 63 are fixedly connected between the oil collection bag 61 and the oil guide piece bag 62. The oil guide pipe 63 is fixedly embedded in the embedded rods 42, and the oil collection bag 61 is an elastic sealing structure; the oil collection bag 61 and the oil guide piece bag 62 are saturated with heat transfer oil. When the two heat transfer rods 4 are not removed from the external cover 3, the distance between the two guide inner rods 41 is the shortest at this time. At this time, due to the internal heat transfer direction Due to the squeezing of the tube 5, most of the heat-conducting oil is concentrated in the oil-collecting capsule 61. At this time, the oil-collecting capsule 61 is in an expanded state. When the heat-conducting rod 4 moves outward, the oil-guiding sheet capsule 62 gradually loses the squeezing of the inner heat-conducting square tube 5 and bulges outward to reset, generating an adsorption force on the heat-conducting oil in the oil-collecting capsule 61 that has absorbed more heat, so that part of the heat-conducting oil returns to the oil-guiding sheet capsule 62 along the oil-conducting tube 63, thereby effectively dissipating the heat carried by this part of the heat-conducting oil directly into the air. During the process of the heat-conducting rod 4 shrinking and expanding, the heat-conducting oil also continuously changes position back and forth, further improving the efficiency of self-circulating heat dissipation.

[0044] like Fig.10 The oil guide piece bag 62 includes an outer spring piece 621 and two edge sealing pieces 622 respectively fixedly connected between the upper and lower ends of the outer spring piece 621 and the embedded rod 42, and the upper and lower edges of the outer spring piece 621 respectively extend to the outside of the connection between the two edge sealing pieces 622 and the outer spring piece 621. Fig.11 In the figure, b represents the inner shrinkage arc groove. An inner shrinkage arc groove is cut on the end surface of the embedded rod 42 opposite to the oil guide plate bag 62, and the connection between the outer spring piece 621 and the edge sealing piece 622 and the embedded rod 42 are all located in the inner shrinkage arc groove, so that the edge sealing piece 622 is on the inner side of the outer spring piece 621. When squeezed by the inner heat-conducting square tube 5, both of them can be retracted into the inner shrinkage arc groove, so that it is not easy to affect the back and forth movement of the embedded rod 42 in the inner heat-conducting square tube 5.

[0045] In summary, on the basis of the heat dissipation of the fan, the heat dissipation holes and the heat dissipation fins in the prior art, an additional cover 3 and its internal heat transfer rod 4 and inner heat square tube 5 are added, such as Figure 7 When the projector is in use, the heat transfer rod 4 can continuously expand and contract in the inner heat-conducting square tube 5 to realize the self-circulating heat dissipation of the projector body 1, so that the heat transfer rod 4 can continuously and directly carry the heat absorbed in the projector body 1 to the outside of the projector body 1 when moving back and forth. Compared with natural heat dissipation, the heat dissipation efficiency can be greatly improved. In addition, with the setting of the heat exchange oil sheet, during the process of continuous expansion and contraction of the heat transfer rod 4, the heat transfer oil is continuously transferred in the oil collection bag 61 and the oil guide bag 62, that is, the position transfer of the heat transfer oil inside and outside the external cover 3 is realized, and the efficiency of self-circulating heat dissipation is further improved.

[0046] In view of current practical needs, the above-mentioned implementation mode adopted in this application is not limited to the scope of protection. Various changes made within the knowledge scope of technical personnel in this field without departing from the concept of this application still fall within the scope of protection of the present invention.

Claims

1. An LCD ultra-short-throw projector with a self-circulating heat dissipation structure, characterized in that: The projector comprises a projector body (1) and a projection lens (2) installed at the front end of the projector body (1), wherein a chip is installed in the projector body (1), a plurality of evenly distributed heat dissipation fins are arranged at the outer end of the projector body (1), evenly distributed heat dissipation holes are drilled at the position between two adjacent heat dissipation fins, an external cover (3) is fixedly connected to the rear end of the projector body (1), the external cover (3) is communicated with the inside of the projector body (1), heat dissipation ports are drilled at both left and right ends of the external cover (3), and an internal heat-conducting square tube (5) is fixedly connected between the two heat dissipation ports. The left and right ends of the inner heat-transmitting square tube (5) are extended to the outside of the outer cover (3); the front and rear end surfaces of the inner heat-transmitting square tube (5) are connected to heat transfer rods (4) through electric slide rails; the slide rails are connected to chip signals; the heat transfer rod (4) passes through one of the heat dissipation ports; the heat transfer rod (4) comprises a guide inner rod (41) and an embedded rod (42) located outside the outer cover (3) and facing one end of the outer cover (3) with the guide inner rod (41) and the electric slide rail; the embedded rod (42) is movably embedded in the inner heat-transmitting square tube (5).

2. The LCD ultra-short-throw projector with a self-circulating heat dissipation structure according to claim 1, characterized in that: The inner heat-conducting square tube (5), the guiding inner rod (41) and the embedded rod (42) are all made of heat-conducting materials, and the outer surface of the embedded rod (42) is in close contact with the inner wall of the inner heat-conducting square tube (5).

3. The LCD ultra-short-throw projector with a self-circulating heat dissipation structure according to claim 2, characterized in that: The inner heat-conducting square tube (5) is provided with a plurality of evenly distributed ventilation holes (501) at the front and rear ends, and the plurality of ventilation holes (501) are located inside the outer cover (3).

4. The LCD ultra-short-throw projector with a self-circulating heat dissipation structure according to claim 2, characterized in that: The inner heat-conducting square tube (5) comprises side square tubes (51) respectively fixedly connected to two heat dissipation ports and four connecting strips (52) fixedly connected between upper and lower front and rear end surfaces of the two side square tubes (51); and two electric slide rails are respectively mounted at ends of the two connecting strips (52) that are away from each other.

5. The LCD ultra-short-throw projector with a self-circulating heat dissipation structure according to claim 2, characterized in that: The length of the embedded rod (42) is 1 / 3-1 / 2 of the length of the inner heat-conducting square tube (5), and when the heat-conducting rod (4) is not moved outward, the two ends of the inner heat-conducting square tube (5) respectively contact the two (43).

6. The LCD ultra-short-throw projector with a self-circulating heat dissipation structure according to claim 1, characterized in that: The cross-sectional projections of the two heat dissipation ports overlap, and the width of the inner heat-conducting square tube (5) is smaller than the width of the heat dissipation port. The inner heat-conducting square tube (5) is located at the overlapped portion of the two ports, and the two heat transfer rods (4) are respectively located at the offset portions of the two ports.

7. The LCD ultra-short-throw projector with a self-circulating heat dissipation structure according to claim 1, characterized in that: A heat exchange oil sheet is provided between the two embedded rods (42), and the heat exchange oil sheet comprises an oil collecting bag (61) located between the two embedded rods (42) and oil guide bag (62) respectively located on the two embedded rods (42). A plurality of oil guide pipes (63) are fixedly connected between the oil collecting bag (61) and the oil guide bag (62), and the oil guide pipes (63) are fixedly embedded in the embedded rods (42), and the oil collecting bag (61) is an elastic sealing structure.

8. The LCD ultra-short-throw projector with a self-circulating heat dissipation structure according to claim 7, characterized in that: The oil collecting bag (61) is an elastic sealing structure, and the oil collecting bag (61) and the oil guide piece bag (62) are saturated with heat transfer oil.

9. The LCD ultra-short-throw projector with a self-circulating heat dissipation structure according to claim 8, characterized in that: The oil deflector bag (62) comprises an outer spring piece (621) and two edge sealing pieces (622) respectively fixedly connected between the upper and lower ends of the outer spring piece (621) and the embedded rod (42), and the upper and lower edges of the outer spring piece (621) respectively extend to the outside of the connection between the two edge sealing pieces (622) and the outer spring piece (621).

10. The LCD ultra-short-throw projector with a self-circulating heat dissipation structure according to claim 9, characterized in that: An inwardly contracted arc groove is cut on the end surface of the embedded rod (42) opposite to the oil guide plate bag (62), and the connection points between the outer spring piece (621) and the edge sealing piece (622) and the embedded rod (42) are all located in the inwardly contracted arc groove.

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