Ratchet mechanism

Abstract

To provide a brake device that can inhibit reverse rotation of a ratchet wheel even if a switching knob is erroneously operated in a winding-down direction during hoisting, and a lever hoist and a ratchet mechanism.SOLUTION: A ratchet mechanism comprises a ratchet wheel 80 with a plurality of ratchet teeth 83 formed on an external periphery, and at least two claw members 90 which engage with the ratchet teeth 83. The ratchet mechanism thus allows rotation of the ratchet wheel 80 in only one direction. The ratchet teeth 83 include high teeth 831 and low teeth 832, and high teeth 831 and low teeth 832 are alternately arranged on the ratchet wheel 80. When one claw member 90 is engaged with a trough part 833 located between neighboring ratchet teeth 83, at least another claw member 90 is simultaneously engaged with another trough part 833 which is located between the neighboring ratchet teeth 83.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a ratchet mechanism. [Background technology]

[0002] Lever hoists are widely used for tasks such as lifting and pulling loads, and securing loads with slings or the like (tie-down). These lever hoists allow the chain to be wound up (reeled in) and lowered (reeled out) by manually operating the control lever. An example of such a lever hoist is shown in Patent Document 1. In the lever hoist shown in Patent Document 1, operating the control lever drives a drive member, which in turn rotates a drive shaft, thereby rotating a load sheave. This allows the load to be lifted or lowered. This lever hoist is equipped with a switch knob, which can be used to switch the transmission of drive force from the control lever between the hoisting direction and the lowering direction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-102182 Summary of the Invention [Problem to be solved by the invention]

[0004] However, if the switch knob is accidentally switched to the lowering direction when the lever hoist is hoisting up, the brake mechanism may not function. Specifically, if the switch knob is accidentally switched to the lowering direction while the tip of the pawl member is in contact with the tip of the ratchet tooth of the ratchet wheel, the ratchet wheel may start to rotate forcefully due to the load weight.

[0005] If the tip of the pawl member can fit into the gap between the ratchet teeth when the ratchet wheel starts to rotate, the ratchet wheel can be stopped. However, if the switch knob is switched and the ratchet wheel starts to rotate vigorously while the tip of the pawl member is in contact with the tip of a ratchet tooth, the next ratchet tooth (next tooth) may arrive faster than it takes for the pawl member to fit into the gap, causing the pawl member to collide with the tip of that tooth and be repelled. A similar situation may occur thereafter, preventing the tip of the pawl member from fitting into the gap and making it impossible to stop the ratchet wheel from rotating. The configuration disclosed in Patent Document 1 cannot prevent such ratchet wheel rotation.

[0006] SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a brake device, a lever hoist, and a ratchet mechanism that are capable of preventing a ratchet wheel from rotating in the reverse direction. [Means for solving the problem]

[0007] In order to solve the above problems, according to a first aspect of the present invention, there is provided a brake device that prevents reverse rotation of a load sheave by stopping the reverse rotation of a drive shaft that transmits rotation to a load sheave around which a chain is wound, the brake device comprising: a brake receiver that is non-rotatably supported on the drive shaft and has a flange portion and a boss portion; a female thread member that is rotatably supported on the drive shaft and screws into a male thread portion provided on the outer periphery of the drive shaft; a ratchet wheel that is sandwiched between the opposing flange portion and female thread member and has ratchet teeth on the outer periphery for restricting the direction of rotation to one direction; at least one of the flange portion and the female thread member; a brake plate that is arranged between the ratchet wheels; and at least one pawl member that engages at its tip side with a valley portion located between adjacent ratchet teeth and meshes with the ratchet teeth, and the ratchet wheel is provided with high teeth and low teeth that protrude lower from the center of rotation of the ratchet wheel than the high teeth.

[0008] In another aspect of the present invention, in the above-described invention, it is preferable that a pair of claw members are provided, and the pair of claw members are arranged at symmetrical positions with the drive shaft as the center.

[0009] In another aspect of the present invention, in the above-mentioned invention, it is preferable that the ratchet wheel is provided with high teeth and low teeth alternately.

[0010] In another aspect of the present invention, in the above-mentioned invention, it is preferable that the number of ratchet teeth provided is twice an odd number.

[0011] In another aspect of the present invention, in the above-mentioned invention, it is preferable that a low tooth tip portion on the tip side of the low tooth forms a part of a circular arc.

[0012] Furthermore, in order to solve the above-mentioned problems, according to a second aspect of the present invention, there is provided a lever hoist comprising: an operating lever equipped with the brake device according to the above-mentioned invention and rotating relative to a female thread member; a hoisting switching claw attached to the operating lever and meshing in the hoisting direction with a switching gear integral with the female thread member; a lowering switching claw attached to the operating lever and meshing in the lowering direction with the switching gear; and a switching knob provided integrally with the hoisting switching claw and the lowering switching claw, for switching whether the switching gear meshes with the hoisting switching claw or the lowering switching claw.

[0013] Furthermore, in order to solve the above-mentioned problems, according to a third aspect of the present invention, there is provided a ratchet mechanism that allows rotation of the ratchet wheel in only one direction by comprising a ratchet wheel having a plurality of ratchet teeth formed on its outer periphery and at least one pawl member that meshes with the ratchet teeth, wherein the ratchet teeth include high teeth and low teeth that protrude lower from the center of rotation of the ratchet wheel than the high teeth. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a brake device, a lever hoist, and a ratchet mechanism that can prevent the ratchet wheel from rotating in the reverse direction even if the switch knob is mistakenly operated toward the lowering direction during hoisting. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a front view showing an example of the configuration of a lever hoist to which the lever hoist power transmission device of the present invention is attached. [Figure 2] FIG. 2 is a cross-sectional view showing the configuration of the lever hoist shown in FIG. [Figure 3] 2 is an enlarged partial cross-sectional view showing the vicinity of a brake device of the lever hoist shown in FIG. 1. FIG. [Figure 4] 2 is a plan view showing a ratchet wheel and a pawl member of the lever hoist shown in FIG. 1, showing a state in which the number of ratchet teeth is twice an odd number. FIG. [Figure 5] 5 is an enlarged view showing the ratchet teeth of the ratchet wheel and its surroundings shown in FIG. 4. [Figure 6] 2 is a plan view showing a ratchet wheel and a pawl member of the lever hoist shown in FIG. 1, showing a state in which the number of ratchet teeth is twice an even number. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0016] A lever hoist 10 according to an embodiment of the present invention will now be described with reference to the drawings.

[0017] <Overall configuration of the lever hoist> In the following description, the X direction is the axial direction of the drive shaft 25 arranged between the gear box (reference numeral omitted) in which the reduction gear 30 is arranged and the fast-turning grip 60 (hereinafter referred to as the "free-rotating grip"), the X1 side is the side where the free-rotating grip 60 is attached, and the X2 side is the opposite side, the gear box side. Also, the Z direction is the vertical direction (hanging direction; hoisting and lowering direction) in the suspended state of the lever hoist 10, the Z1 side is the upper side in the suspended state, and the Z2 side is the lower side in the suspended state.

[0018] Fig. 1 is a front view showing an example of the configuration of a lever hoist 10. Fig. 2 is a cross-sectional view showing the configuration of the lever hoist 10 shown in Fig. 1.

[0019] As shown in FIG. 2, the lever hoist 10 includes a pair of frames 11 and 12, and an upper hook 22 is supported on the upper side (Z1 side) of the pair of frames 11 and 12. A load sheave 20, around which a chain C1 is wound, is rotatably supported between the pair of frames 11 and 12. A load gear 21 that meshes with a small-diameter gear portion 32 of a reduction gear 30 (described later) is integrally molded with the load sheave 20. An insertion hole 20a that penetrates the load sheave 20 in the axial direction (X direction) is formed, and a drive shaft 25 is inserted through the insertion hole 20a. A male thread portion 26 that meshes with a female thread member 35 (described later) is provided on the outer periphery of the drive shaft 25 midway, and a pinion gear 27 that meshes with a large-diameter gear portion 31 of the reduction gear 30 is provided on the other end (X2 side) of the drive shaft 25. The reduction gear 30 is also integrally provided with a small diameter gear portion 32 that meshes with the load gear 21 described above.

[0020] A casing 13 is attached to the frame 11, protecting drive components such as the reduction gear 30 and load gear 21. The male thread portion 26 is engaged with a female thread portion 36 of a female thread member 35. In addition to the female thread portion 36, a switching gear 37 is also provided on the periphery of the female thread member 35, which can engage with a switching pawl 40 at a lower position (Z2 side). The switching pawl 40 is, for example, a ratchet pawl provided on one side and the other side of an operating lever 50 (described later). When the operating lever 50 (described later) is rotated with the switching pawl 40 engaged with the switching gear 37, a driving force is transmitted to the female thread member 35.

[0021] In addition, a switch knob 45 is attached coaxially with the switch pawl 40, and by operating the switch knob 45, it is possible to switch between the winding direction and the lowering direction of the driving force transmitted to the female thread member 35. For example, when the lower side (Z2 side) of the switch knob 45 is tilted to the left in FIG. 1, the winding switch pawl 40 engages with the switch gear 37. As a result, when the operation lever 50 is repeatedly turned, the switch gear 37 rotates in the winding direction but does not rotate in the lowering direction. This corresponds to the winding state of the chain C1.

[0022] 1, a pair of engaging protrusions 46 are provided on the upper side (Z1 side) of the switching knob 45. When one of the pair of engaging protrusions 46 engages with the flange portion 65 of the idling grip 60, the idling grip 60 is prevented from being pulled out to one side (X1 side) in the axial direction (X direction). Therefore, the biasing spring (not shown) can maintain a state in which it presses the brake mechanism.

[0023] On the other hand, for example, when the lower side (Z2 side) of the switch knob 45 is tilted to the right in FIG. 1, the lowering switch pawl 40 engages with the switch gear 37. As a result, when the operation lever 50 is repeatedly turned, the switch gear 37 rotates in the lowering direction but not in the winding direction. This corresponds to the lowering state of the chain C1. In addition, the other engaging protrusion 46 engages with the flange portion 65 of the idling grip 60, preventing the idling grip 60 from being pulled out to one side (X1 side) in the axial direction (X direction). This allows the biasing spring (not shown) to maintain its state of pressing the brake mechanism.

[0024] Furthermore, when the lower side (Z2 side) of the switch knob 45 is positioned in the neutral position, which is between the winding direction and the lowering direction (in this case, the switch knob 45 is positioned along the longitudinal direction of the operation lever 50), neither the winding switch pawl 40 nor the lowering switch pawl 40 meshes with the switch gear 37. As a result, even if the operation lever 50 is rotated, neither the winding nor lowering operation of the chain C1 is performed, and the chain C1 enters a free (idle) state. At this time, neither of the pair of engaging protrusions 46 engages with the flange portion 65 of the idler grip 60. Therefore, the idler grip 60 can be pulled out to one side (X1 side) in the axial direction (X direction), and the state in which the biasing spring (not shown) presses against the brake mechanism can be released.

[0025] In addition, a cam member 55 is attached to the drive shaft 25 in a state where it cannot rotate relative to the drive shaft 25, and a member called a free-rotating grip 60 is also attached to one end side (X1 side) of the cam member 55 in the axial direction (X direction) in a state where it cannot rotate relative to the drive shaft 25.

[0026] The idling grip 60 is a generally circular handle-shaped portion that can rotate together with the drive shaft. A flange portion 65 is provided on the other side (X2 side) of the idling grip 60 in the axial direction (X direction). When either of the pair of engaging protrusions 46 described above engages with this flange portion 65, the idling grip 60 cannot be pulled out to one side (X1 side) in the axial direction (X direction). This allows the biasing spring (not shown) to maintain a state in which it presses the brake mechanism.

[0027] During winding up and lowering, this idling grip 60 is pushed in toward the other side (X2 side) in the axial direction (X direction), as shown in Figure 2. However, when the switch knob 45 is in the neutral position (neutral state), the idling grip 60 can be pulled out to one side (X1 side) in the axial direction (X direction). When the idling grip 60 is pulled out to one side (X1 side) in the axial direction (X direction), the pressing force of the biasing spring that biases the brake mechanism weakens, resulting in the brake being released, and the chain C1 can be freely pulled out in either the winding up side or the lowering side while holding it with a hand or the like.

[0028] <Regarding the Brake Device 70> Fig. 3 is an enlarged partial cross-sectional view of the brake device 70 and its vicinity in the lever hoist shown in Fig. 1. As shown in Figs. 2 and 3, the brake device 70 is disposed between the operating lever 50 and the drive shaft 25. The brake device 70 mainly includes a brake receiver 71, brake plates 72a and 72b, a ratchet wheel 80, a ratchet member 90, a ratchet shaft 91, a bushing 92, etc.

[0029] The brake receiver 71 has a flange portion 71a and a hollow boss portion 71b (corresponding to the boss portion). The flange portion 71a has a larger diameter than the hollow boss portion 71b and is capable of receiving the brake plate 72a.

[0030] The hollow boss portion 71b is located closer to the female thread member 35 (X1 side) than the flange portion 71a, and supports the ratchet wheel 80 via a bushing 92. The inner periphery of the hollow boss portion 71b is engaged with the drive shaft 25 by means of a key connection, a spline connection, or the like, so that the drive shaft 25 and the brake receiver 71 rotate integrally.

[0031] Brake plates 72a and 72b are journaled on the hollow boss portion 71b between the flange portion 71a and the ratchet wheel 80, and between the female thread member 35 and the ratchet wheel 80. The brake plates 72a and 72b are friction materials formed, for example, by sintering a predetermined material.

[0032] Here, when a load acts on the drive shaft 25 in the winding-down direction, the female thread member 35 presses against the brake plates 72a, 72b due to the screw tightening action between the female thread member 35 and the brake receiver 71 (flange portion 71a). As a result, the brake plates 72a, 72b are strongly pressed, and the ratchet wheel 80 is strongly pressed by the brake plates 72a, 72b. Here, the ratchet wheel 80 is prevented from rotating in the winding-down direction by the claw member 90 being engaged with the ratchet wheel 80, so the rotation of the drive shaft 25 in the winding-down direction is braked by the strong pressure.

[0033] When the selector knob 45 is switched to the winding direction and the operating lever 50 is operated, the ratchet wheel 80 can rotate in the winding direction, and so this rotation in the winding direction is not blocked by the ratchet wheel 80. Therefore, by operating the operating lever 50, the female thread member 35, brake plates 72a, 72b, ratchet wheel 80, and brake receiver 71 rotate the drive shaft 25 as a unit, and the resulting drive force is transmitted to the load sheave 20 via the reduction gear 30, thereby winding up the chain C1.

[0034] On the other hand, when the switch knob 45 is switched to the lowering direction and the operating lever 50 is operated, the female thread member 35 rotates by the amount of operation, and the screw tightening action of the brake receiver 71 is alleviated. As a result, the braking force of the ratchet wheel 80 is released in accordance with the amount of operation of the operating lever 50 (i.e., the amount of rotation of the female thread member 35), and the brake receiver 71 and drive shaft 25 rotate in the lowering direction. The driving force in the lowering direction is transmitted to the load sheave 20 via the reduction gear 30, thereby lowering the chain C1.

[0035] Additionally, ratchet teeth 83 (described later) provided on ratchet wheel 80 mesh with tip end 90a of pawl member 90. This meshing forms a ratchet mechanism that prevents ratchet wheel 80 from rotating in the lowering direction but allows it to rotate in the winding direction, except when switching knob 45 to the lowering direction and operating lever 50.

[0036] As shown in FIG. 3, a bushing 92 is provided on the outer periphery of the hollow boss portion 71b of the brake receiver 71, and a ratchet wheel 80 is provided on the outer periphery of the bushing 92.

[0037] A pawl shaft 91 is attached to the frame 12, and a pawl member 90 is rotatably supported on the pawl shaft 91. A coil portion 93a of a torsion spring 93 is attached to the pawl shaft 91, and the torsion spring 93 applies a biasing force in a direction that presses the pawl member 90 against ratchet teeth 83 (described later) of the ratchet wheel 80. A pair of pawl members 90 are provided, and are arranged point-symmetrically with respect to each other in the circumferential direction of the ratchet wheel 80 with respect to the central axis of the drive shaft 25.

[0038] <About the ratchet wheel 80> Next, the configuration of the ratchet wheel 80 will be described. Fig. 4 is a plan view showing the ratchet wheel 80 and the pawl member 90, illustrating an example of a configuration in which the number of ratchet teeth 83 is twice an odd number, and also illustrating the arrangement of the pawl member 90. As shown in Fig. 4, the ratchet wheel 80 is provided with a ring-shaped portion 81, and the front and back surfaces of the ring-shaped portion 81 are portions that press against the brake plates 72a, 72b described above. Note that the bushing 92 described above is positioned in the center hole 82 located at the center of the ring-shaped portion 81, thereby supporting the ratchet wheel 80 so that it can rotate freely.

[0039] Ratchet teeth 83 protrude from the ring-shaped portion 81 toward the outer periphery. FIG. 5 is an enlarged view of the ratchet teeth 83 and the vicinity thereof of the ratchet wheel 80. As shown in FIG. 5, the ratchet teeth 83 include high teeth 831 and low teeth 832. Of these, the high teeth 831 have their tips (high tooth tip portions 831a) that protrude radially outward beyond the tips (low tooth tip portions 832a) of the low teeth 832. Therefore, due to the biasing force of the torsion spring 93, the tip portions 90a of the pawl member 90 are located radially closer to the center (inner diameter side) than the position where the tip portions 90a contact the low tooth tip portions 832a.

[0040] In this embodiment, the high teeth 831 and the low teeth 832 are alternately adjacent to each other and have the same circumferential length (pitch). If a valley 833 is defined between the high teeth 831 and the low teeth 832, the inclination angle of a tapered portion 831b extending from the valley 833 toward the high-tooth tip 831a at the tip of the high tooth 831 is equal to the inclination angle of a tapered portion 832b extending from the valley 833 toward the low-tooth tip 832a at the tip of the low tooth 832. Therefore, in this embodiment, the low teeth 832 are formed in a shape such that the tip of the high tooth 831 is cut off. The low-tooth tip 832a of the low tooth 832 may be part of an arc concentric with the ratchet wheel 80. However, the low-tooth tip 832a may have a shape other than part of an arc (for example, a straight line), or may be part of an arc that is not concentric with the ratchet wheel 80.

[0041] The total number of ratchet teeth 83, including the high teeth 831 and the low teeth 832, is an even number. If the number of ratchet teeth 83 is twice an odd number, as shown in FIG. 4 , when the tip 90a of one pawl member 90 is pressed against the high teeth 831, the other pawl member 90 is pressed against the low teeth 832. Since either one pawl member 90 or the other pawl member 90 is always pressed against the low teeth 832, when reverse rotation occurs, at least the tip 90a of the pawl member 90 pressed against the low teeth 832 will always collide with the back of the adjacent high tooth 831. This ensures that reverse rotation of the ratchet wheel 80 is prevented. In the configuration shown in FIG. 4 , the ratchet teeth 83 have a total of 22 teeth. However, the number of ratchet teeth 83 may be any number as long as it is twice an odd number.

[0042] However, if the total number of ratchet teeth 83, which is the total number of high teeth 831 and low teeth 832, is twice an even number (a number that is a multiple of four), as shown in Figure 6, when tip portion 90a of one pawl member 90 is pressed against high tooth 831, the other pawl member 90 is also pressed against high tooth 831. Also, when tip portion 90a of one pawl member 90 is pressed against low tooth 832, the other pawl member 90 is also pressed against low tooth 832. In this case as well, when reverse rotation occurs, tip portion 90a of pawl member 90 that has been pressed against low tooth 832 will inevitably collide with (the back of) the adjacent high tooth 831, or tip portion 90a of pawl member 90 that has been pressed against high tooth 831 will be able to sufficiently prevent reverse rotation of ratchet wheel 80 because the spacing between adjacent high teeth 831 is wider than the spacing between ratchet teeth of the same height that a current ratchet wheel has. In the configuration shown in FIG. 6, there are a total of 20 ratchet teeth 83, but the number of ratchet teeth 83 may be any number as long as it is an even number multiplied by two.

[0043] <About the effects> The brake device 70 and the lever hoist 10 configured as described above include a brake receiver 71 that is non-rotatably supported on the drive shaft 25 and has a flange portion 71a and a hollow boss portion 71b (boss portion), a female screw member 35 that is rotatably supported on the drive shaft 25 and that screws into the male screw portion 26 provided on the outer periphery of the drive shaft 25, and ratchet teeth 8 that are sandwiched between the flange portion 71a and the female screw member 35 that face each other and that restrict the rotation direction to one direction on the outer periphery. 3, at least one of a flange portion 71a and a female thread member 35, brake plates 72a, 72b arranged between the ratchet wheels 80, and at least one pawl member 90 that meshes with the ratchet teeth 83 and has a tip portion 90a (tip side) that engages with a valley portion 833 located between adjacent ratchet teeth 83, and the ratchet wheel 80 is provided with a high tooth 831 and a low tooth 832 that protrudes lower from the center of rotation of the ratchet wheel 80 than the high tooth 831.

[0044] Now consider a case where the switch knob 45 is mistakenly switched to the lowering direction while the tip 90a of the pawl member 90 is in contact with the high tooth tip 831a on the tip side of the high tooth 831. In this case, the load causes the ratchet wheel 80 to begin to rotate (reverse rotation) with force. However, as described above, the ratchet wheel 80 has high teeth 831 and low teeth 832. Therefore, after passing the low tooth tip 832a of the low tooth 832, the tip 90a of the pawl member 90 collides with the back of the adjacent high tooth 831. This prevents the ratchet wheel 80 from rotating reversely.

[0045] Furthermore, in this embodiment, it is preferable that high teeth 831 and low teeth 832 are provided alternately on the ratchet wheel 80. In this configuration, if the tip 90a of at least one ratchet member 90 is in contact with the low-tooth tip 832a of the low tooth 832, when the ratchet wheel 80 starts to rotate (reverse rotation), it will immediately collide with the back of the next tooth, the high tooth 831. Also, if the tip 90a of at least one ratchet member 90 is in contact with the high-tooth tip 831a of the high tooth 831, even if the ratchet wheel 80 starts to rotate (reverse rotation) and passes over the low-tooth tip 832a, it will immediately collide with the back of the high tooth 831. This makes it possible to prevent the ratchet wheel 80 from rotating reversely at an early stage.

[0046] Furthermore, in this embodiment, it is preferable to provide twice the number of ratchet teeth 83 as an odd number. With this configuration, when the tip 90a of one pawl member 90 is pressed against the high teeth 831, the other pawl member 90 is pressed against the low teeth 832. By ensuring that either one pawl member 90 or the other pawl member 90 is pressed against the low teeth 832, even if the ratchet wheel 80 rotates in reverse at a speed faster than expected, the tip 90a of either pawl member 90 can be pressed against the low tooth tip 832a of the ratchet wheel 80, which is located radially inward of the high tooth tip 831a, thereby reliably preventing the ratchet wheel 80 from rotating in reverse.

[0047] In this embodiment, the low tooth tip portion 832a at the tip side of the low tooth 832 can be formed to form a part of a circular arc. In this configuration, the circumferential length of the low tooth tip portion 832a is longer than the circumferential length of the high tooth tip portion 831a. This allows the tip portion 90a of the pawl member 90 to contact the low tooth tip portion 832a for a longer period of time compared to the high tooth tip portion 831a, thereby more reliably preventing reverse rotation of the ratchet wheel 80. Furthermore, the low tooth tip portion 832a can be easily machined using, for example, a machine tool, thereby improving productivity.

[0048] <Modification> Although the embodiments of the present invention have been described above, the present invention can be modified in various other ways, which will be described below.

[0049] In the above embodiment, the free-spinning device is described, which switches between free-spinning and non-free-spinning by operating the free-spinning grip 60, but the lever hoist may also be equipped with a free-spinning device of another type, such as an automatic free-spinning type.

[0050] In the above-described embodiment, the brake device 70 is described as being applied to the lever hoist 10. However, the brake device may be applied to a hoisting machine other than a lever hoist, such as a chain block.

[0051] Furthermore, in the above-described embodiment, a pair of pawl members 90 is provided. However, only one pawl member 90 may be provided, or three or more pawl members 90 may be provided. When three or more pawl members 90 are provided, it is preferable that the pawl members 90 are evenly spaced around the outer periphery of the ratchet wheel 80, and that when one pawl member 90 engages with a valley portion located between a ratchet tooth adjacent to a high tooth, at least one other pawl member engages with a valley portion located between a ratchet tooth adjacent to a low tooth.

[0052] However, it is also possible to displace the multiple pawl members 90 unevenly around the outer periphery of the ratchet wheel 80. In this case, it is preferable to dispose them so that the radial force acting on the ratchet shaft 21 of each pawl member 90 is equal. For example, four pawl members 90 may be disposed two by two, symmetrically with respect to a line perpendicular to the drive shaft 25. By disposing the multiple pawl members 90 so that the radial force acting on their respective pawl shafts 21 is equal, the force acting from the pawl members 90 on the ratchet wheel 80 is dispersed, thereby increasing the durability of the ratchet wheel 80. Furthermore, disposing the pawl members 90 in this manner reduces the imbalance in the force acting from the ratchet wheel 80 on the drive shaft 25, thereby increasing the durability of the drive shaft 25 and its surrounding components.

[0053] Furthermore, a pair of pawl members 90 are provided, and it is most preferable that the pair of pawl members 90, 90 have the same shape and are positioned in positions that are point-symmetrical with respect to the drive shaft 25. However, the pawl members 90 may have different shapes as long as the tip ends 90a of the respective pawl members 90 simultaneously engage with the valleys 833 with which they engage. For example, by evenly arranging two or more pawl members 90 on the outer periphery of the ratchet wheel 80, the force acting on each pawl member 90 can be dispersed and the radial force acting on the ratchet shaft 91 on which the ratchet wheel 80 is mounted can be reduced. However, in practice, it is most preferable that the engagement positions of the tip ends 90a be positioned in positions that are point-symmetrical, and they may be positioned offset by an even number of teeth. However, since a larger offset increases the load on the drive shaft 25, it is not preferable to offset the engagement positions more than necessary.

[0054] Furthermore, in the above embodiment, the brake plate 72 is disposed as a separate member from the ratchet wheel 80, but friction members may be baked onto both sides of the ratchet wheel 80, for example.

[0055] Furthermore, in the above-described embodiment, the female thread member 35 that presses the ratchet wheel 80 with the load torque acting on the drive shaft 25 is configured so that the male thread portion 26 of the drive shaft 25 and the female thread portion 36 of the female thread member 35 are threadedly engaged with each other. However, the female thread member 35 may be provided separately from the drive shaft 25 (for example, a male thread provided on the outer periphery of a hollow shaft that is an extension of the hollow boss portion 71b of the brake receiver 71), and furthermore, a mechanism that converts the load torque into a thrust force using a cam may also be used.

[0056] Furthermore, in the above embodiment, the brake device 70 of the lever hoist 10 has been described as an example, but in a broader sense, the present invention can be said to relate to a ratchet mechanism. That is, the present invention is a ratchet mechanism that allows rotation of the ratchet wheel in only one direction by including a ratchet wheel with many ratchet teeth formed on its outer periphery and at least one pawl member that meshes with the ratchet teeth, and the ratchet teeth include high teeth that protrude high from the center of the ratchet wheel and low teeth that protrude low from the center of the ratchet wheel.

[0057] By configuring the ratchet mechanism in this way, even if the tip of the pawl member is positioned on the tip of a high or low tooth and reverse rotation occurs, the tip of the pawl member will collide with the back of at least the next high tooth (the slope that forms the high tooth) and enter the valley between the ratchet teeth, thereby immediately and reliably preventing the ratchet wheel from rotating reversely.

[0058] As shown in Figure 4, it is preferable that two pawl members are provided at symmetrical positions, and that high teeth and low teeth are provided alternately. It is also preferable that the number of ratchet teeth is double the odd number.

[0059] In addition, by arranging the two pawl members in symmetrical positions, it is possible to eliminate uneven stress on the ratchet wheel. Furthermore, by arranging the high and low teeth alternately, the tip of the pawl member can be caused to collide with the back of the nearest high tooth when a reverse rotation occurs. Furthermore, by providing twice the number of ratchet teeth as an odd number, when the tip of one symmetrically positioned pawl member is at the tip of a high tooth, the tip of the other pawl member will be at the tip of a low tooth. Therefore, when a reverse rotation occurs, the tip of at least the pawl member that was at the tip of a low tooth will always collide with the back of the adjacent high tooth, thereby immediately and reliably preventing the ratchet wheel from rotating reversely.

[0060] Such a ratchet mechanism is applied to a brake device of a lever hoist that resists input torque in one direction, as described in the above embodiment, and is particularly effective for preventing the ratchet wheel that constitutes the brake device from rotating in the reverse direction. [Explanation of symbols]

[0061] 10...lever hoist, 11...frame, 12...frame, 13...casing, 20...load sheave, 20a...insertion hole, 21...load gear, 22...upper hook, 25...drive shaft, 26...male thread portion, 27...pinion gear, 30...reduction gear, 31...large diameter gear portion, 32...small diameter gear portion, 35...female thread member, 36...female thread portion, 37...switching gear, 40...switching claw, 45...switching knob, 46...engaging protrusion, 50...operating lever, 55...cam member, 60...idling grip, 65...flange portion, 70...bleed Brake device, 71...brake receiver, 71a...flange portion, 71b...hollow boss portion (corresponding to boss portion), 72a...brake plate, 72b...brake plate, 80...ratchet wheel, 81...ring-shaped portion, 82...center hole, 83...ratchet teeth, 90...pawl member, 90a...tip portion, 91...pawl shaft, 92...bush, 93...torsion spring, 93a...coil portion, 831...high teeth, 831a...high tooth tip portion, 831b...tapered portion, 832...low teeth, 832a...low tooth tip portion, 832b...tapered portion, 833...valley portion, C1...chain

Claims

1. A ratchet mechanism that allows rotation of the ratchet wheel in only one direction by including a ratchet wheel having a plurality of ratchet teeth formed on its outer periphery and at least two pawl members that mesh with the ratchet teeth, The ratchet teeth include high teeth and low teeth that protrude lower from the center of rotation of the ratchet wheel than the high teeth, The ratchet wheel is provided with the high teeth and the low teeth alternately, the high teeth and the low teeth are alternately adjacent to each other, and are provided at equal circumferential pitches, When one of the pawl members is engaged with a valley portion located between adjacent ratchet teeth, at least one other of the pawl members simultaneously engages with another valley portion located between adjacent ratchet teeth. A ratchet mechanism characterized by:

2. When one of the claw members is engaged with the valley portion located on the back side of the high tooth, at least another of the claw members is engaged with another of the valley portions located on the back side of the low tooth.

2. The ratchet mechanism of claim 1.

3. The two pawl members are arranged at symmetrical positions around the axis of rotation.

3. A ratchet mechanism according to claim 1 or 2.

4. The number of ratchet teeth is twice an odd number.

4. The ratchet mechanism of claim 3.

5. A low tooth tip portion on the tip side of the low tooth forms a part of a circular arc.

5. A ratchet mechanism according to claim 1, wherein the ratchet mechanism comprises a first end and a second end.

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