Piston assemblies and related components and systems

Abstract

A piston assembly includes a piston head. The piston assembly further comprises an upper connecting rod rotationally connected with the piston head. The piston assembly also includes a shoe between the upper connecting rod and the inner wall of the piston head.

Description

[0001] Priority claim

[0002] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 368,183, filed on July 12, 2022, and entitled “PISTOR ASSEMBLIES AND RELATED COMPONENTS, SYSTEMS AND METHODS,” under 35 U.S.C. 119(e), the disclosure of which is hereby incorporated by reference in its entirety. Technical Field

[0003] The present invention relates to an internal combustion engine, and more particularly to a piston assembly used in the engine and used to connect a piston head to a crankshaft of the engine. Background Art

[0004] The conventional type of internal combustion engine used in most vehicles today includes a plurality of pistons that are movably mounted in a plurality of cylinders formed in the engine block. Each piston is connected to a first end of a piston rod, and a second end of the piston rod is connected to a crankshaft. In addition, when a spark plug in the engine block is ignited to ignite the fuel mixture, the piston is driven downward to rotate the crankshaft, ultimately driving the entire vehicle. In a typical engine, a single connecting rod is used, the first end of which is connected to the corresponding piston and the second end is connected to the corresponding part of the crankshaft. The connection points between the two ends of each connecting rod and the corresponding piston and the corresponding crankshaft are located at the ends of the longitudinal center axis of the corresponding connecting rod. Summary of the invention

[0005] The embodiment of the present disclosure includes a piston assembly. The piston assembly includes a piston head. The piston assembly also includes an upper connecting rod rotatably connected to the piston head. The piston assembly also includes a boot portion located between the upper connecting rod and the inner wall of the piston head.

[0006] Another embodiment of the present disclosure includes an engine. The engine includes a cylinder, a crankshaft, and a piston assembly disposed in the cylinder. The piston assembly includes a piston head. The piston assembly also includes an upper connecting rod rotatably connected to the piston head. The piston assembly also includes a lower connecting rod connected between the upper connecting rod and the crankshaft. The piston assembly also includes a boot slidably connected between the upper connecting rod and the skirt of the piston head.

[0007] Another embodiment of the present disclosure includes an upper connecting rod of a piston assembly. The upper connecting rod includes a piston connection point. The upper connecting rod also includes a lower rod connection point. The upper connecting rod also includes a curved groove defined in an outer edge of the upper connecting rod. The curved groove is configured to accommodate an interface element between the upper connecting rod and the piston. The curved groove is located closer to the piston connection point than the lower rod connection point. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] While this specification particularly points out and distinctly claims the conclusions of the claims for embodiments of the present disclosure, advantages of embodiments of the present disclosure may be more readily ascertained from the following description of embodiments of the present disclosure when taken in conjunction with the accompanying drawings, in which:

[0009] Figure 1 is a schematic diagram of a piston assembly in an engine according to one or more embodiments of the present disclosure;

[0010] Figure 2-4 shows different views of a piston head assembly according to one or more embodiments of the present disclosure;

[0011] Figure 5 The present invention shows one or more embodiments of the present invention. Figure 2-4 A perspective view of the boot portion of the piston head assembly in FIG. 1 ; and

[0012] Figure 6 The present invention shows one or more embodiments of the present invention. Figure 2-4 Side view of the upper connecting rod of the piston head assembly in FIG. DETAILED DESCRIPTION

[0013] The drawings used herein are not actual views of any internal combustion engine system, piston assembly, or any components thereof, but are merely idealized representations used to describe embodiments of the present disclosure.

[0014] As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0015] As used herein, the term “may” in connection with materials, structures, features, or method actions indicates that these are considered for use in implementing the embodiments of the present disclosure, and this term takes precedence over the more restrictive term “are” to avoid any implication that other compatible materials, structures, features, and methods that may be used in combination therewith should or must be excluded.

[0016] As used herein, any relational terms, such as "first," "second," "top," "bottom," "upper," "lower," etc., are used to clearly and conveniently understand the present disclosure and the accompanying drawings, and do not represent or depend on any particular preference or order, unless the context clearly indicates otherwise. For example, these terms may refer to the orientation of a piston assembly or an engine element in a conventional direction. In addition, these terms may refer to the orientation of a piston assembly or an engine element as shown in the figure.

[0017] As used herein, the term "substantially" refers to a given parameter, characteristic, or condition, and its meaning includes the degree to which a given parameter, characteristic, or condition is satisfied with a minor degree of variation as understood by those skilled in the art, such as within an acceptable manufacturing tolerance range. For example, depending on a particular parameter, characteristic, or condition that is substantially satisfied, the parameter, characteristic, or condition may be at least 90.0%, at least 95.0%, at least 99.0%, or even at least 99.9%.

[0018] As used herein, the term "about" when referring to a given parameter is inclusive of the stated value and has the meaning dictated by the context (eg, includes the degree of error associated with a given measurement).

[0019] Figure 1 A schematic diagram of a piston assembly 100 disposed within an engine 102 is shown. The piston assembly 100 may include a piston head 104, an upper connecting rod 106, a piston pin assembly 107 (e.g., two or more pin locks, needle sleeve bearings, and a piston pin (e.g., a wrist pin)), a lower connecting rod 108, and a connecting pin assembly 109. The engine 102 may include a cylinder 112, one or more valves 114 and exhaust ports 116 (e.g., intake valves and intake ports, and exhaust valves and exhaust ports), and a fuel injector 118. The one or more valves 114 and exhaust ports 116 of the engine 102 may be oriented in a conventional manner.

[0020] The piston head 104 of the piston assembly 100 may be disposed within a cylinder 112 of the engine 102 and may be configured to reciprocate back and forth during use (e.g., as Figure 1 The upper connecting rod 106 may be connected to the piston head 104 at a first longitudinal end of the upper connecting rod 106 by a piston pin assembly 107, and may be connected to the lower connecting rod 108 at a second opposite longitudinal end of the upper connecting rod 106. In some embodiments, the upper connecting rod 106 may be connected to the piston head 104 near or at the center of mass of the piston head 104. In one or more embodiments, the upper connecting rod 106 may be connected to the piston head 104 at a center point between the upper surface and the lower surface of the piston head 104, and intersect with the central longitudinal axis 122 of the piston head 104. In one or more embodiments, the longitudinal axis 120 of the piston pin assembly 107 may extend in a direction perpendicular to the longitudinal axis 122 of the piston head 104, and may intersect with the longitudinal axis 122 of the piston head 104. The upper connecting rod 106 may be configured not to rotate and / or translate relative to the piston head 104 during use.

[0021] The upper connecting rod 106 may extend axially (eg, in a direction parallel to the longitudinal axis 122 of the piston head 104) from the piston head 104 to an area below the piston head 104 (eg, Figure 1104). For example, the longitudinal length of the upper connecting rod 106 can be greater than the distance from the point where the upper connecting rod 106 is connected to the piston head 104 to the lowest surface of the piston head 104. In addition, the longitudinal axis of the upper connecting rod 106 can be parallel to the longitudinal axis 122 of the piston head 104. In view of the above, when the upper connecting rod 106 is connected to the piston head 104, the lower longitudinal end of the upper connecting rod 106 can be oriented below the piston head 104.

[0022] As described above, the upper connecting rod 106 may be coupled to the lower connecting rod 108 at the longitudinal end opposite to the piston head 104 (i.e., the lower longitudinal end of the upper connecting rod 106). In some embodiments, the upper connecting rod 106 may be connected to the lower connecting rod 108 via a connecting pin assembly 109. In one or more embodiments, the connecting pin assembly 109 may include any piston pin and / or wrist pin and related components known in the art.

[0023] The lower connecting rod 108 can rotate relative to the upper connecting rod 106. For example, the lower connecting rod 108 can be configured to pivot about the connecting pin assembly 109 and the upper connecting rod 106. For example, the connecting pin assembly 109 can be provided with a bearing about which the lower connecting rod 108 can pivot as the piston assembly 100 cycles through a stroke (as described below).

[0024] The lower connecting rod 108 can be connected to the crankshaft 126 at the longitudinal end of the lower connecting rod 108 opposite to the upper connecting rod 106. The crankshaft 126 can include a conventional crankshaft. For example, the crankshaft 126 can convert the reciprocating motion of the piston head 104 into a rotary motion. As known in the art, the crankshaft includes a plurality of "cranks" or "crank pins" and a plurality of bearing surfaces (e.g., rod journals, connecting rod journals, etc.), and its axis deviates from the central longitudinal axis 128 of the crankshaft 126. The lower connecting rod 108 can be connected to the corresponding bearing surface of the crankshaft 126. In addition, the lower connecting rod 108 can be connected to the crankshaft 126 by any conventional bearing. In addition, it will be appreciated by those of ordinary skill in the art that the rotation axis 128 (i.e., the central longitudinal axis) of the crankshaft 126 can be parallel to the longitudinal axis 124 of the connecting pin assembly 109.

[0025] To describe the operation of the piston assembly 100, the hour position of a typical clock face (e.g., 12 o'clock, 3 o'clock, etc.) is used herein to indicate the position of the lower longitudinal end of the lower connecting rod 108 around the rotation axis 128 of the crankshaft 126. For example, the aforementioned position may refer to the center point of the lower longitudinal end of the lower connecting rod 108 and its position relative to the rotation axis 128 of the crankshaft 126, such as Figure 1 1 , wherein the piston head 104 associated with the lower connecting rod 108 is at top dead center at the 12 o'clock position and at bottom dead center at the 6 o'clock position, regardless of the orientation of the associated engine and / or cylinder.

[0026] In some embodiments, the engine 102 and the piston assembly 100 may include a four-stroke engine. For example, during use, the piston assembly 100 may complete four separate strokes while rotating the crankshaft 126. In other words, the engine 102 and the piston assembly 100 may cycle through a typical four-stroke cycle.

[0027] The piston assembly 100 may start a four-stroke cycle with an intake stroke (e.g., an intake or suction stroke). As is known in the art, the intake stroke begins with the piston head 104 at the top dead center and ends with the piston head 104 at the bottom dead center. During the intake stroke, the intake valve (e.g., valve 114) opens (due to the distribution cam lobes of the distribution cam, as is known in the art), and as the piston head 104 moves downward in the cylinder 112, a vacuum pressure is generated in the cylinder 112 by the downward movement of the piston head 104, and the piston head 104 draws an air mixture into the cylinder 112. In addition, the fuel injector 118 injects fuel into the air to form an air-fuel mixture. As described above, the piston assembly 100 of the present invention can reduce the force required to move the piston head 104 from the 12 o'clock position to the 6 o'clock position, thereby saving some of the energy required to perform the intake stroke (e.g., energy from other piston assemblies to rotate the crankshaft 126 during the power (i.e., combustion) stroke of other piston assemblies). Those skilled in the art will appreciate that reducing the energy required to perform the intake stroke allows more energy to be used for other operations of the engine 102 (e.g., operating a vehicle with the engine 102). Therefore, the piston assembly 100 of the present disclosure can provide a more efficient engine than conventional piston assemblies.

[0028] After the intake stroke, the piston assembly 100 begins a compression stroke. The compression stroke begins with the piston head 104 being at the bottom dead center and ends with the piston head 104 being at the top dead center. During the compression stroke, the piston head 104 compresses the air-fuel mixture in preparation for ignition during the power stroke (described below). In addition, during the compression stroke, the intake valve and the exhaust valve (e.g., valve 114) are closed. As described above, the piston assembly 100 of the present disclosure reduces the force required to move the piston head 104 from the 6 o'clock position to the 12 o'clock position, thereby saving some of the energy required during the compression stroke. Those of ordinary skill in the art will appreciate that reducing the energy required to perform the compression stroke will allow more energy to be used for other operations of the engine 102.

[0029] When the air-fuel mixture is compressed and reaches top dead center, the piston assembly 100 may begin a power (i.e., combustion or ignition) stroke. As the piston head 104 approaches top dead center, the air-fuel mixture is ignited by an igniter (e.g., a spark plug, a glow plug, etc.) or by heat generated by high compression (e.g., a diesel engine). Ignition of the air-fuel mixture causes an explosion that forces the piston head 104 back to bottom dead center. As is known in the art, the power stroke generates mechanical work from the engine 102 to rotate the crankshaft 126. For example, the power stroke may generate mechanical work by conventional methods involving a piston assembly and a crankshaft.

[0030] As described above, the piston assembly 100 of the present invention reduces the force required to move the piston head 104 from the 6 o'clock position or the 12 o'clock position. Therefore, compared with conventional piston assemblies, the piston assembly of the present invention can ignite the air-fuel mixture closer to or at the 12 o'clock position. For example, the ignition position of a conventional piston assembly is generally located between the 10 o'clock and 12 o'clock positions to provide the necessary force to rotate through the 12 o'clock position. In addition, as will be understood by those of ordinary skill in the art, igniting the air-fuel mixture closer to or at the 12 o'clock position (rather than significantly earlier) may result in a greater pressure generated by the ignition acting on the piston assembly, thereby causing the piston assembly to move downward during the power stroke.

[0031] When reaching the bottom dead center, the piston assembly 100 starts the exhaust stroke. During the exhaust stroke, the piston head 104 of the piston assembly 100 returns from the bottom dead center to the top dead center again, and the exhaust valve (e.g., valve 114) opens. The action of the piston head 104 moving from the bottom dead center to the top dead center causes the combusted air-fuel mixture to exit the exhaust valve 114 and through the exhaust port 116. In addition, when reaching the top dead center, the piston assembly 100 can repeat the above four strokes.

[0032] During different strokes, the forces transmitted by the upper connecting rod 106 and the lower connecting rod 108 can introduce longitudinal forces in the direction of the central longitudinal axis 122 and transverse forces perpendicular to the central longitudinal axis 122. The longitudinal forces can act to move the piston head 104 along the central longitudinal axis 122 in the cylinder 112. Due to the moment arm generated by the upper connecting rod 106, the transverse force can generate a moment on the piston head 104. The piston head 104 may include a skirt 130, which is configured to substantially prevent the piston head 104 from tilting or rocking in the cylinder 112. However, the skirt 130 may contact the cylinder wall of the cylinder 112 and generate additional friction. Therefore, additional features configured to counteract the transverse forces and / or reduce the moment arm generated by the upper connecting rod 106 can reduce friction and improve the efficiency of the associated engine 102.

[0033] Figure 2-4Different views of the piston head 104 are shown, and the piston head 104 includes a boot 202 connected between the upper connecting rod 106 and the skirt 130 of the piston head 104. The boot 202 can be configured to change the moment arm of the upper connecting rod 106 relative to the piston head 104, and can reduce the lateral force transmitted to the piston head 104 by the upper connecting rod 106. For example, the boot 202 may include a skirt interface 204 and a rod interface 302. Each skirt interface 204 and rod interface 302 can be a sliding connection, so that the boot 202 can move relative to the skirt 130 and the upper connecting rod 106. The sliding connection can allow the upper connecting rod 106 to rotate slightly relative to the piston head 104. For example, the rod interface 302 can form a fulcrum around which the upper connecting rod 106 can rotate in small increments. The lateral force in the upper connecting rod 106 can be transmitted to the skirt 130 through the boot 202. Due to the fulcrum created by the rod interface 302 between the shoe 202 and the upper connecting rod 106, a second reverse force can be applied at the piston connection point 304. The lateral force in the shoe 202 and the lateral force at the piston connection point 304 can be applied to the piston head 104 at different positions on the same side of the piston head 104 relative to the rotation axis of the piston head 104. Therefore, the reverse lateral force can generate a reverse moment on the piston head 104 and can significantly reduce the moment on the piston head 104.

[0034] Figure 5 204. As shown, the width of the skirt interface 204 can be greater than the width of the rod interface 302. The larger width of the rod interface 302 can increase the surface area of ​​the rod interface 302 relative to the skirt interface 204. The larger relative surface area of ​​the skirt interface 204 can reduce the pressure generated by the lateral force, thereby reducing the skirt interface 204 on the skirt 130 ( Figure 2-4 ) on the skirt 130 ( Figure 2-4 ) can help form the skirt 130 with a thinner material, thereby reducing the weight of the piston head 104.

[0035] The radius of the skirt interface 204 may be the same as the radius of the associated skirt 130 ( Figure 2-4 ) substantially matches the inner surface radius of the boot 202. This radius can help the boot 202 distribute the lateral force substantially evenly on the associated skirt 130 ( Figure 2-4 ) on the skirt 130 ( Figure 2-4 ) local pressure on the inner surface, thereby facilitating the formation of skirt 130 with a thinner material similar to increasing the surface area of ​​skirt interface 204.

[0036] Figure 6A side view of the upper connecting rod 106 is shown. The upper connecting rod 106 includes a piston connection point 304 and a lower rod connection point 604. The upper connecting rod 106 may also include a groove 602, which is configured to connect to the rod interface 302 of the associated boot 202. The groove 602 may have a curved surface complementary to the rod interface 302 of the associated boot 202. The curved surface of the groove 602 may define an arc having an angle greater than about 60 degrees, for example, an angle greater than about 90 degrees, or an arc having an angle greater than about 100 degrees. In some embodiments, the groove 602 may include a bearing material or an insert configured to reduce the friction between the rod interface 302 of the boot 202 and the groove 602. Compared to the lower rod connection point 604, the groove 602 may be located closer to the piston connection point 304. Positioning the groove 602 near the piston connection point 304 may make the moments and forces in the components and areas near the groove 602 and the piston connection point 304 similar, thereby substantially preventing the piston head 104 ( Figure 1-4 ) in cylinder 112( Figure 1 ) in a tilt or sway.

[0037] Non-limiting example embodiments of the present disclosure include:

[0038] Embodiment 1: A piston assembly comprises: a piston head; an upper connecting rod rotatably connected to the piston head; and a boot portion located between the upper connecting rod and the inner wall of the piston head.

[0039] Embodiment 2: The piston assembly according to embodiment 1, wherein the shoe comprises a piston interface surface in sliding contact with an inner wall of the piston head.

[0040] Embodiment 3: The piston assembly according to embodiment 1 or embodiment 2, wherein the inner wall of the piston head comprises the inner wall of the piston skirt.

[0041] Embodiment 4: The piston assembly of Embodiment 3, wherein the shoe is configured to distribute lateral forces on an inner wall of the piston skirt.

[0042] Embodiment 5: The piston assembly of any one of Embodiments 1 to 4, wherein the shoe includes a rod interface surface in sliding contact with the upper connecting rod.

[0043] Embodiment 6: A piston assembly according to Embodiment 5, wherein the upper connecting rod includes a complementary groove that is in sliding contact with the rod interface surface of the boot.

[0044] Embodiment 7: The piston assembly of Embodiment 6, wherein the complementary groove comprises a curved surface.

[0045] Embodiment 8: The piston assembly according to any one of embodiments 1 to 7, wherein the boot has a first width proximate to the upper connecting rod and a second width proximate to the inner wall of the piston head, and wherein the second width is greater than the first width.

[0046] Embodiment 9: An engine comprises: a cylinder; a crankshaft; and a piston assembly arranged in the cylinder, the piston assembly comprising: a piston head; an upper connecting rod rotatably connected to the piston head; a lower connecting rod connected between the upper connecting rod and the crankshaft; and a boot portion slidably connected between the upper connecting rod and the skirt of the piston head.

[0047] Embodiment 10: The engine of Embodiment 9, wherein the shoe comprises a skirt interface surface slidably connected to the skirt of the piston head.

[0048] Embodiment 11: The engine of embodiment 10, wherein the radius of the skirt interface surface substantially matches the radius of the inner surface of the skirt of the piston head.

[0049] Embodiment 12: An engine according to any one of embodiments 9 to 11, wherein the upper connecting rod includes a groove slidably connected to the shoe.

[0050] Embodiment 13: An engine according to Embodiment 12, wherein the groove includes a curved surface complementary to the rod interface surface of the shoe.

[0051] Embodiment 14: An engine according to embodiment 12 or embodiment 13, wherein the groove also includes bearing material.

[0052] Embodiment 15: An engine according to any one of Embodiments 12 to 14, wherein the groove is located closer to the piston connection between the upper connecting rod and the piston head than to the lower rod connection between the upper connecting rod and the lower connecting rod.

[0053] Example 16: An upper connecting rod of a piston assembly, comprising: a piston connection point; a lower rod connection point; and a bending groove defined in the outer edge of the upper connecting rod, the bending groove being configured to accommodate an interface element between the upper connecting rod and the piston, the bending groove being positioned closer to the piston connection point than to the lower rod connection point.

[0054] Embodiment 17: An upper connecting rod according to Embodiment 16, wherein the piston connection point includes a piston pin assembly.

[0055] Embodiment 18: An upper connecting rod according to embodiment 17, wherein the lower rod connection point includes a connecting pin assembly.

[0056] Embodiment 19: The upper connecting rod according to any one of Embodiments 16 to 18, wherein the curved groove includes an arc of at least 60 degrees.

[0057] Embodiment 20: The upper connecting rod of any one of Embodiments 16 to 19, wherein the curved groove comprises an arc of at least 90 degrees.

[0058] Embodiments of the present disclosure can substantially prevent or reduce the tilting or rocking of the piston head in the engine cylinder. Reducing or preventing the tilting or rocking of the piston head can significantly reduce the contact and associated friction between the piston head and the cylinder wall. Reducing the contact between the piston head and the cylinder wall can improve the efficiency of the engine and reduce the wear of the piston head and the cylinder wall. The embodiments of the present disclosure described above and shown in the accompanying drawings do not limit the scope of the present invention, because these embodiments are merely examples of embodiments of the present invention, and the scope of the present invention is defined by the attached claims and their legal equivalents. Any equivalent embodiments should be included within the scope of the present disclosure. In fact, in addition to the modifications shown and described herein, various modifications of the present disclosure, such as useful combinations of substitutions of the elements, are obvious to those skilled in the art based on this specification. Such modifications and embodiments are also intended to fall within the scope of the attached claims and their legal equivalents.

Claims

1. A piston assembly, comprising: Piston head; an upper connecting rod rotatably connected to the piston head; as well as A boot is located between the upper connecting rod and the inner wall of the piston head.

2. The piston assembly according to claim 1, wherein: The shoe includes a piston interface surface in sliding contact with the inner wall of the piston head.

3. The piston assembly according to claim 1, wherein: The inner wall of the piston head includes an inner wall of a piston skirt.

4. The piston assembly according to claim 3, wherein: The shoe is configured to distribute lateral forces on an inner wall of the piston skirt.

5. The piston assembly according to any one of claims 1 to 4, wherein: The shoe includes a rod interface surface that is in sliding contact with the upper connecting rod.

6. The piston assembly according to claim 5, wherein: The upper connecting rod includes a complementary groove that slidingly contacts the rod interface surface of the shoe.

7. The piston assembly according to claim 6, wherein: The complementary groove comprises a curved surface.

8. The piston assembly according to any one of claims 1 to 4, wherein: The shoe has a first width proximate to the upper connecting rod and a second width proximate to the inner wall of the piston head, and wherein the second width is greater than the first width.

9. An engine, comprising: cylinder; Crankshaft; as well as A piston assembly is arranged in the cylinder, and the piston assembly comprises: Piston head; an upper connecting rod rotatably connected to the piston head; a lower connecting rod connected between the upper connecting rod and the crankshaft; and A shoe is slidably connected between the upper connecting rod and the skirt of the piston head.

10. The engine according to claim 9, wherein: The shoe includes a skirt interface surface slidably connected to the skirt of the piston head.

11. The engine according to claim 10, wherein: The skirt interface surface has a radius that substantially matches a radius of an inner surface of the skirt of the piston head.

12. An engine according to any one of claims 9 to 11, wherein: The upper connecting rod includes a groove slidably connected to the shoe.

13. The engine according to claim 12, wherein: The groove includes a curved surface that is complementary to the rod interface surface of the shoe.

14. The engine according to claim 12, wherein: The groove also includes bearing material.

15. The engine according to claim 12, wherein: The groove is located closer to the piston connection between the upper connecting rod and the piston head than to the lower rod connection between the upper connecting rod and the lower connecting rod.

16. An upper connecting rod of a piston assembly, the upper connecting rod comprising: Piston connection point; Lower rod connection point; as well as A flex groove is defined in an outer edge of the upper connecting rod, the flex groove being configured to accommodate an interface element between the upper connecting rod and a piston, the flex groove being located closer to the piston connection point than to the lower rod connection point.

17. The upper connecting rod according to claim 16, wherein: The piston connection point includes a piston pin assembly.

18. The upper connecting rod according to claim 17, wherein: The lower rod connection point includes a connecting pin assembly.

19. The upper connecting rod according to any one of claims 16 to 18, wherein: The curved groove includes an arc of at least 60 degrees.

20. The upper connecting rod according to any one of claims 16 to 18, wherein: The curved groove includes an arc of at least 90 degrees.

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