Folding mechanism of folding rotary cultivator

Abstract

The utility model discloses a folding mechanism of a folding rotary cultivator, which comprises a pair of first support frames, a pair of second support frames and a pair of third support frames, the bottoms of the second supporting frames are fixedly arranged on the front side and the rear side of the suspension beam of the rotary cultivator respectively; one end of the sleeve is rotatably supported at the top of the first support frame on the rear side of the cross beam and the top of the second support frame on the rear side of the suspension beam, and the other end is rotatably supported at the top of the first support frame on the front side of the cross beam and the top of the second support frame on the front side of the suspension beam; the supporting shaft rotatably penetrates through the sleeve; one end of the connecting rod is rotatably connected to the supporting shaft in a sleeving manner; the connecting rod pin shaft rotatably penetrates through the other end of the connecting rod, and the connecting rod pin shaft and the supporting shaft are arranged in parallel; a cylinder barrel of the first hydraulic cylinder is hinged to the cross beam; the piston rod is hinged with the connecting rod pin shaft and can rotate around the connecting rod pin shaft; a cylinder barrel of the second hydraulic cylinder is hinged to the suspension beam; the piston rod is hinged to the connecting rod pin shaft and can rotate around the connecting rod pin shaft.

Description

Technical Field

[0001] This utility model belongs to the technical field of tillage machinery and devices, and specifically relates to a folding mechanism for a folding rotary tiller. Background Technology

[0002] Currently, most rotary tillers on the market use a through-shaft or intermediate gearbox to drive the left and right half-shafts to achieve rotary tillage, which results in a small working area and low working efficiency. Furthermore, rotary tillers based on through-shaft or intermediate gearbox drives lack versatility and cannot effectively increase the working area per cycle.

[0003] Increasing the length or number of rotary tillers can increase the working area per pass. Increasing the number of rotary tillers requires installing cantilever beams at both ends of the crossbeam. However, since installing cantilever beams would cause the rotary tiller to exceed road transport size requirements, it is necessary to install a folding mechanism to fold the rotary tiller's cantilever beams during road transport.

[0004] Existing folding mechanisms suffer from complex structures and large space requirements. Utility Model Content

[0005] The purpose of this invention is to provide a folding mechanism for a folding rotary tiller, which has a simple structure, occupies little space, and can maintain the stability of the rotary tiller shaft in both the unfolded and folded states.

[0006] The technical solution provided by this utility model is as follows:

[0007] A folding mechanism for a folding rotary tiller includes:

[0008] A pair of first support frames, the bottoms of which are fixedly installed on the front and rear sides of the rotary tiller's crossbeam, respectively;

[0009] A pair of second support frames, the bottoms of which are fixedly installed on the front and rear sides of the rotary tiller's suspension beam, respectively;

[0010] The sleeve has one end rotatably supported on the top of the first support frame behind the crossbeam and the top of the second support frame behind the cantilever beam, and the other end rotatably supported on the top of the first support frame in front of the crossbeam and the top of the second support frame in front of the cantilever beam.

[0011] A support shaft, which is rotatably inserted through the sleeve, with both ends of the support shaft extending to the outside of the sleeve;

[0012] A connecting rod, one end of which is rotatably sleeved on the support shaft;

[0013] A connecting rod pin, which rotatably passes through the other end of the connecting rod, is arranged parallel to the support shaft;

[0014] The first hydraulic cylinder has its cylinder barrel hinged to the crossbeam; the piston rod is hinged to the connecting rod pin and can rotate around the connecting rod pin.

[0015] The second hydraulic cylinder has its cylinder barrel hinged to the suspension beam; the piston rod is hinged to the connecting rod pin and can rotate around the connecting rod pin.

[0016] Preferably, a first support seat is fixedly provided on the front side of the crossbeam, and the end of the cylinder of the first hydraulic cylinder is connected to the first support seat through a first support pin.

[0017] The first support pin is arranged parallel to the support shaft.

[0018] Preferably, a second support seat is fixedly provided on the front side of the suspension beam, and the end of the cylinder of the second hydraulic cylinder is connected to the second support seat through a second support pin.

[0019] The second support pin is arranged parallel to the support shaft.

[0020] Preferably, both ends of the sleeve are supported in the first support frame and the second support frame by bearings, respectively.

[0021] Preferably, the link includes:

[0022] Two plate-shaped connecting rods are arranged in parallel and opposite directions;

[0023] The first sleeve is fixedly installed at one end of both plate-shaped connecting rods, and the first sleeve is rotatably sleeved on the support shaft.

[0024] Two second sleeves are fixedly installed at the other end of the two plate-shaped connecting rods, one to one. The two second sleeves are coaxially arranged and parallel to the first sleeve.

[0025] The two second sleeves are rotatably mounted on the connecting rod pin.

[0026] Preferably, the first sleeve is mounted on the support shaft via a needle roller bearing; the second sleeve is mounted on the connecting rod pin via a needle roller bearing.

[0027] Preferably, the piston rods of the first hydraulic cylinder and the second hydraulic cylinder are respectively connected to circular support rings at their tops, and are respectively rotatably sleeved on the connecting rod pins through the circular support rings.

[0028] Preferably, the circular support ring of the first hydraulic cylinder is disposed between the two second sleeves, and the circular support ring of the second hydraulic cylinder is disposed near the rear end of the connecting rod pin.

[0029] The beneficial effects of this utility model are:

[0030] The folding mechanism provided by this utility model has a simple structure, occupies little space, and can maintain the stability of the rotary tiller shaft in both the unfolded and folded states. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the overall structure of the folding rotary tiller described in this utility model.

[0032] Figure 2 This is a schematic diagram of the main and auxiliary reduction gearboxes and transmission mechanism described in this utility model.

[0033] Figure 3 This is a schematic diagram of the transmission mechanism described in this utility model.

[0034] Figure 4 This is a structural diagram of the main reduction gearbox and the first rotary tiller shaft transmission of the present invention.

[0035] Figure 5 This is a schematic diagram of the first (second) rotary tillage blade shaft structure described in this utility model.

[0036] Figure 6 This is a structural diagram of the connector described in this utility model.

[0037] Figure 7 This is a schematic diagram of the unfolded structure of the connector described in this utility model.

[0038] Figure 8 This is a schematic diagram of the folding mechanism of the rotary tiller described in this utility model.

[0039] Figure 9 This is a schematic diagram of the connecting rod described in this utility model.

[0040] Figure 10 This is a schematic diagram of the folding mechanism described in this utility model.

[0041] Figure 11 This is a schematic diagram of the folding rotary tiller of this utility model in its folded state. Detailed Implementation

[0042] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0043] This utility model provides a folding mechanism for a folding rotary tiller, used to fold the tiller's suspension beam and the rotary blade shaft mounted on the suspension beam.

[0044] like Figure 1-5As shown, in this embodiment, the folding rotary tiller using the folding mechanism mainly includes: a suspension lifting system 101, a main drive shaft 102, a driving bevel gear 103, a driven bevel gear 103a, a main reduction gearbox 104, a rotary tiller crossbeam 105, two suspension beams 105a, two auxiliary reduction gearboxes 106, two drive shafts 107, two first rotary tiller blade shafts 108, two second rotary tiller blade shafts 109, and two folding mechanisms 110.

[0045] The folding rotary tiller is supported at the rear of the tractor by a suspension lifting system 101, and its ground clearance can be automatically adjusted according to the needs of driving or tilling the land. The engine output power is connected to the main drive shaft 102 via the gearbox output shaft using a ten-way fork structure, ensuring the rotary tiller's spatial power input requirements.

[0046] The crossbeam 105 is a frame structure, horizontally positioned. The main reduction gearbox 104 is fixedly supported in the middle of the crossbeam 105 by bolts, and the crossbeam 105 is arranged symmetrically on both sides. A driving bevel gear 103 is installed at the tail end of the main drive shaft 102, and a driven bevel gear 103a is fixed to a horizontal shaft 1041 inside the main reduction gearbox 104. The horizontal shaft 1041 is positioned along the length (transverse direction) of the crossbeam 105, and both ends of the horizontal shaft 1041 are supported by bearings passing through and attached to the upper part of the housing of the main reduction gearbox 104. The main drive shaft 102 drives the driven bevel gear 103a inside the main reduction gearbox 104 to rotate via the driving bevel gear 103 installed at its tail end. This driving and driven bevel gear structure not only reduces speed and increases torque but also changes the power transmission direction by 90 degrees. The first cylindrical gear 1042 is fixed on the horizontal shaft 1041, and the first cylindrical gear 1042 meshes with the second cylindrical gear 1043 for transmission. The second cylindrical gear 1043 is assembled on the pin 1043a through a bearing structure. The two ends of the pin 1043a are fixed at the middle position on both sides of the housing of the main gearbox 104. The second cylindrical gear 1043 then meshes with the third cylindrical gear 1044 for transmission.

[0047] The third cylindrical gear 1044 is connected via an internal spline structure to the spline shaft at the left end of the first rotary tiller shaft 108 located on its right and the spline shaft at the right end of the first rotary tiller shaft 108 located on its left, respectively, so that the two first rotary tiller shafts 108 rotate synchronously. The other ends of the two first rotary tiller shafts 108 are supported on two first tiller shaft brackets 108a via bearing structures; wherein the two first tiller shaft brackets 108a are respectively fixed to both ends of the crossbeam 105 by bolts.

[0048] When the driving bevel gear 103 drives the driven bevel gear 103a to rotate, it drives the coaxial first cylindrical gear 1042 to rotate, and then through the transmission of the second cylindrical gear 1043 and the third cylindrical gear 1044, it finally drives the two first rotary tillage blade shafts 108 to rotate synchronously.

[0049] like Figure 1-3 As shown, two suspension beams 105a are respectively set at both ends of the crossbeam 105, and two auxiliary reduction gearboxes 106 are respectively fixed and supported at the inner ends (near the end of the crossbeam 105) of the two suspension beams 105a by bolt structure.

[0050] The two ends of the horizontal shaft 1041 inside the main reduction gearbox 104 are respectively connected to the inner ends of the two drive shafts 107 via a ten-way fork 1071 structure. For example... Figure 3 As shown, the outer end of the drive shaft 107 is connected to the connecting shaft 202. The connecting shaft 202 passes through the support plate 201 via the bearing support 203. The support plate 201 is longitudinally fixed to the crossbeam 105 of the rotary tiller, ensuring stable support for the drive shaft 107 and the connecting shaft 202 during power transmission. The drive shaft 107, support plate 201, connecting shaft 202, and bearing support 203 together form the transmission mechanism. The outer end of the connecting shaft 202 is a connector 204, and the outer end of the connector 204 is connected to the spline shaft 205. Both ends of the spline shaft 205 are supported by bearing structures inside the upper part of the auxiliary reduction gearbox 106. The first cylindrical gear 1061 of the auxiliary reduction gearbox is fixed on the splined shaft 205 and meshes with the second cylindrical gear 1062 of the auxiliary reduction gearbox for transmission. The second cylindrical gear 1062 of the auxiliary reduction gearbox is assembled on the pin 1062a by setting a bearing structure. The two ends of the pin 1062a are fixed at the middle position of the two sides of the auxiliary reduction gearbox 106. The second cylindrical gear 1062 of the auxiliary reduction gearbox then meshes with the third cylindrical gear 1063 of the auxiliary reduction gearbox for transmission.

[0051] The third cylindrical gear 1063 of the auxiliary reduction gearbox is connected to the splined shaft at the inner end of the second rotary tiller shaft 109 via an internal spline structure, driving the second rotary tiller shaft 109 to rotate. The outer end of the second rotary tiller shaft 109 is supported on the second blade shaft bracket 109a via a bearing structure, and the second blade shaft bracket 109a is fixed to the outer end of the cantilever beam 105a by bolts.

[0052] When the driving bevel gear 103 drives the driven bevel gear 103a to rotate, it drives the horizontal shaft 1041 to rotate. The power is transmitted through the ten-way fork 1071, drive shaft 107, connecting shaft 202, connector 204, and spline shaft 205 to drive the first cylindrical gear 1061 of the auxiliary reduction gearbox 106 to rotate. Then, through the second cylindrical gear 1062 and the third cylindrical gear 1063 of the auxiliary reduction gearbox, it finally drives the second rotary tiller shaft 109 to rotate. The rotary tiller shaft structure is as follows: Figure 5 As shown.

[0053] Because the rotary tiller has a symmetrical structure, the power is transmitted through the two drive shafts 107 to the lower gear in the auxiliary reduction gearbox 106 via the same path, ultimately driving the two second rotary tiller shafts 109 to rotate synchronously.

[0054] The rotary tiller adopts a dual-shaft transmission scheme, which can improve the power and stability of the two second rotary tillage blade shafts 109 located outside the crossbeam 105 when tilling the land, avoiding problems such as insufficient power and poor balance at the end of the rotary tillage blade shaft that occur when the single-shaft power transmission is used.

[0055] Two folding mechanisms 110 are correspondingly arranged with two suspension beams 105a, used to connect the corresponding suspension beams 105a and crossbeams 105. When the rotary tiller is in operation, the two folding mechanisms 110 are unfolded, and the connector 204 connects, connecting the transmission mechanism to the input end of the auxiliary reduction gearbox 106, causing the two first rotary tiller shafts 108 and two second rotary tiller shafts 109 to rotate synchronously. When the rotary tiller is not in operation, the folding mechanisms 110 are folded, the transmission mechanism is disconnected from the input end of the auxiliary reduction gearbox 106, and the two suspension beams 105a, along with the second rotary tiller shafts 109 and the auxiliary reduction gearbox 106, are flipped above the crossbeams 105. By setting the folding mechanisms 110, the dimensional requirements of the rotary tiller's suspension during normal road operation can be met.

[0056] In one embodiment, the connector 204 is structured as follows: Figure 6 and 7 As shown, connector 204 consists of a first connecting plate 2041 and a second connecting plate 2042 connected by a plurality of mushroom-shaped pins 206 (evenly arranged circumferentially on the plate) fixed on the circumference of the first connecting plate 2041. The first connecting plate 2041 is fixedly connected to the end of the connecting shaft 202. The mushroom-shaped pins 206 are positioned on the inner end face of the first connecting plate 2041 (facing the end face of the connecting shaft 202) by mounting nuts. The second connecting plate 2042 has cylindrical holes (through holes) corresponding to the mushroom-shaped pins 206. The tips of the mushroom-shaped pins 206 face the cylindrical holes, and the inner end face of the cylindrical holes (near the first connecting plate 2041) is provided with rounded chamfers to facilitate the mating connection of each mushroom-shaped pin 206 with its corresponding cylindrical hole. A rubber ring 2061 is provided at the joint between the mushroom-shaped pins 206 and the second connecting plate 2042 to mitigate the impact when the first connecting plate 2041 and the second connecting plate 2042 are connected, ensuring a smooth connection. When connector 204 is in the connected state, mushroom-shaped pin 206 ensures the reliability of the first connecting plate 2041 and the second connecting plate 2042, allowing the second connecting plate 2042 to rotate synchronously with the first connecting plate 2041. Furthermore, the internal spline in the center hole of the second connecting plate 2042 drives the spline shaft 205 to rotate synchronously. When the second connecting plate 2042 of connector 204 is folded upwards with the spline shaft 205, it automatically disengages from the mushroom-shaped pin 206.

[0057] Connector 204 adopts a dual-disc connection method, which can effectively improve the stable connection between the transmission mechanism and the auxiliary gearbox, ensure its power transmission effect, and facilitate disconnection when folded.

[0058] In this embodiment, the folding mechanism of the rotary tiller is as follows: Figure 8 and 9 As shown, the support shaft 111 is arranged longitudinally along the rotary tiller (crossbeam), and a sleeve 112 is provided on its outside. The sleeve 112 can rotate around the support shaft 111. The two ends of the sleeve 112 are supported by a pair of first support frames 113 fixed on the front and rear sides of the crossbeam 105 and a pair of second support frames 114 fixed on the front and rear sides of the cantilever beam 105a, respectively, through bearings. The two pairs of first support frames 113 and second support frames 114 can rotate around the sleeve 112. The two ends of the support shaft 111 extend a certain length relative to the sleeve 112. The front end (closer to the tractor end) is used to install the connecting rod 115. The first sleeve 115a at the lower end of the connecting rod 115 is assembled to the front end of the support shaft 111 through a needle roller bearing and can swing freely around it. The second sleeve 115b at the upper end of the connecting rod 115 is mounted on the connecting rod pin 116 via a needle roller bearing and can swing freely around it. Meanwhile, the first piston rod 117a of the first hydraulic cylinder 117 and the second piston rod 118a of the second hydraulic cylinder 118, which are mounted on the connecting rod pin 116, are spaced apart. The upper ends of the first piston rod 117a and the second piston rod 118a are hinged to the connecting rod pin 116 via a circular support ring and can swing freely around it.

[0059] A first support seat is fixedly mounted on the front side of the crossbeam 105. The lower end of the cylinder of the first hydraulic cylinder 117 is connected to the first support seat via a first support pin 117b, allowing the first hydraulic cylinder 117 to rotate around the first support pin 117b. The first support pin 117b is parallel to the support shaft 111. A second support seat 105aa is fixedly mounted on the front side of the cantilever beam 105aa. The lower end of the cylinder of the second hydraulic cylinder 118 is connected to the second support seat 105aa via a second support pin 118b, allowing the second hydraulic cylinder 118 to rotate around the second support pin 118b. The second support pin 118b is parallel to the support shaft 111. The first support seat and the second support seat 105aa have the same structure.

[0060] When the tractor is traveling on the road, the suspension beams 105a at both ends of the rotary tiller are folded via the folding structure 110. The oil reservoir in the hydraulic system is connected via oil pipes to the first upper oil port 1171 and the first lower oil port 1172 of the first hydraulic cylinder 117, and the second upper oil port 1181 and the second lower oil port 1182 of the second hydraulic cylinder 118. For example... Figure 10As shown, when the hydraulic system is activated to fold the rotary tiller, hydraulic oil in the oil tank flows through the oil pipe into the first upper oil port 1171 of the first hydraulic cylinder 117 and the second upper oil port 1181 of the second hydraulic cylinder 118. As the oil flows in, the oil pressure in the upper chamber of the first hydraulic cylinder 117 and the second hydraulic cylinder 118 continuously increases, causing the first piston rod 117a and the second piston rod 118a to compress into the hydraulic cylinder. At the same time, the oil in the lower chamber of the first hydraulic cylinder 117 and the second hydraulic cylinder 118 flows back to the oil tank through the oil pipe from the first lower oil port 1172 and the second lower oil port 1182, respectively. Under the action of the pressure difference in the upper and lower chambers of the hydraulic cylinder, the piston rod is compressed relative to the hydraulic cylinder. The suspension beams 105a at both ends rotate upward around the support shaft 111 by a certain angle along with the connecting rod 115 as the compression of the first hydraulic cylinder 117 relative to the first piston rod 117a and the second hydraulic cylinder 118 relative to the second piston rod 118a changes. The structural parameters of the first hydraulic cylinder 117, the second hydraulic cylinder 118, the first piston rod 117a, and the second piston rod 118a are matched to allow the suspension beam 105a to fold upwards by 180 degrees until the second cutter shaft bracket 109a at the outer end of the suspension beam 105a rests on the bracket assembly 101a at the top of the suspension lifting system 101. Figure 11 As shown. During this process, the first connecting plate 2041 and the second connecting plate 2042 of connector 204 automatically disengage.

[0061] When the tractor tills the land, the suspension beams 105a at both ends of the rotary tiller unfold via a folding mechanism. The oil reservoir in the hydraulic system is connected via oil pipes to the first upper oil port 1171 and the first lower oil port 1172 of the first hydraulic cylinder 117, and the second upper oil port 1181 and the second lower oil port 1182 of the second hydraulic cylinder 118. For example... Figure 10 As shown, when the hydraulic system is activated to enable the rotary tiller to unfold, hydraulic oil in the oil tank flows through the oil pipe into the first lower oil port 1172 of the first hydraulic cylinder 117 and the second lower oil port 1182 of the second hydraulic cylinder 118. As the oil flows in, the oil pressure in the lower chamber of the first hydraulic cylinder 117 and the second hydraulic cylinder 118 continuously increases, causing the first piston rod 117a and the second piston rod 118a to extend outward. At the same time, the oil in the upper chamber of the first hydraulic cylinder 117 and the second hydraulic cylinder 118 flows back to the oil tank through the oil pipe from the first upper oil port 1171 and the second upper oil port 1181, respectively. Under the action of the pressure difference in the upper and lower chambers of the hydraulic cylinder, the piston rod is stretched outward relative to the hydraulic cylinder. The two end suspension beams 105a, together with the connecting rod 115, extend and rotate downward 180 degrees around the support shaft 111 as the first hydraulic cylinder 117 and the second hydraulic cylinder 118 extend and change, until they return to the initial unfolded position of the rotary tiller. During this process, the cylindrical hole on the second connecting plate 2042 of the connector 204 automatically engages with the mushroom pin 206 of the first connecting plate 2041, thereby achieving synchronous rotation of the connecting shaft 202 and the spline shaft 205.

[0062] The folding mechanism provided by this utility model has a simple structure, occupies little space, and can maintain the stability of the rotary tiller shaft in both the unfolded and folded states.

[0063] The folding mechanism provided by this utility model is not limited to the folding rotary tiller of this embodiment; it can be applied to other rotary tillers that require folding.

[0064] Although the embodiments of this utility model have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for this utility model. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, this utility model is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A folding mechanism for a folding rotary tiller, characterized in that, include: A pair of first support frames, the bottoms of which are fixedly installed on the front and rear sides of the rotary tiller's crossbeam, respectively; A pair of second support frames, the bottoms of which are fixedly installed on the front and rear sides of the rotary tiller's suspension beam, respectively; The sleeve has one end rotatably supported on the top of the first support frame behind the crossbeam and the top of the second support frame behind the cantilever beam, and the other end rotatably supported on the top of the first support frame in front of the crossbeam and the top of the second support frame in front of the cantilever beam. A support shaft, which is rotatably inserted through the sleeve, with both ends of the support shaft extending to the outside of the sleeve; A connecting rod, one end of which is rotatably sleeved on the support shaft; A connecting rod pin, which rotatably passes through the other end of the connecting rod, is arranged parallel to the support shaft; The first hydraulic cylinder has its cylinder barrel hinged to the crossbeam; the piston rod is hinged to the connecting rod pin and can rotate around the connecting rod pin. The second hydraulic cylinder has its cylinder barrel hinged to the suspension beam; the piston rod is hinged to the connecting rod pin and can rotate around the connecting rod pin.

2. The folding mechanism of the folding rotary tiller according to claim 1, characterized in that, A first support seat is fixedly provided on the front side of the crossbeam, and the end of the cylinder of the first hydraulic cylinder is connected to the first support seat through a first support pin. The first support pin is arranged parallel to the support shaft.

3. The folding mechanism of the folding rotary tiller according to claim 2, characterized in that, A second support seat is fixedly installed on the front side of the suspension beam, and the end of the cylinder of the second hydraulic cylinder is connected to the second support seat through a second support pin. The second support pin is arranged parallel to the support shaft.

4. The folding mechanism of the folding rotary tiller according to claim 3, characterized in that, The two ends of the sleeve are respectively supported by bearings in the first support frame and the second support frame.

5. The folding mechanism of the folding rotary tiller according to any one of claims 1-4, characterized in that, The link includes: Two plate-shaped connecting rods are arranged in parallel and opposite directions; The first sleeve is fixedly installed at one end of both plate-shaped connecting rods, and the first sleeve is rotatably sleeved on the support shaft. Two second sleeves are fixedly installed at the other end of the two plate-shaped connecting rods, one to one. The two second sleeves are coaxially arranged and parallel to the first sleeve. The two second sleeves are rotatably mounted on the connecting rod pin.

6. The folding mechanism of the folding rotary tiller according to claim 5, characterized in that, The first sleeve is mounted on the support shaft via a needle roller bearing; the second sleeve is mounted on the connecting rod pin via a needle roller bearing.

7. The folding mechanism of the folding rotary tiller according to claim 6, characterized in that, The piston rods of the first hydraulic cylinder and the second hydraulic cylinder are respectively connected to circular support rings at their tops, and are rotatably sleeved on the connecting rod pins through the circular support rings.

8. The folding mechanism of the folding rotary tiller according to claim 7, characterized in that, The circular support ring of the first hydraulic cylinder is disposed between the two second sleeves, and the circular support ring of the second hydraulic cylinder is disposed near the rear end of the connecting rod pin.

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