阅读说明：本技术 轮式机器的传动装置 (Transmission device of wheeled machine ) 是由 克里斯多夫·W·沃恩 纳撒尼尔·伦弗特 于 2018-12-14 设计创作，主要内容包括：本发明公开了一种用于手动操作的轮式机器的传动装置,该传动装置包括具有封闭端轴向通道的输出轴。安装在输出轴上的驱动齿轮包括接合沟槽。棘轮被接纳在通道中并且与接合沟槽接合。安装在输出轴上的保持器包括接纳棘轮的凹陷部。摩擦构件向保持器施加径向摩擦,以在机器的驱动状态下暂时防止保持器跟随输出轴一起旋转,从而将棘轮移动成与接合沟槽接合,并且在驱动状态下,驱动齿轮和保持器与输出轴一起旋转。在机器的惯性滑行状况下,输出轴是静止的,并且驱动齿轮的过驱动使棘轮与接合沟槽脱离,从而允许驱动齿轮围绕静止的输出轴自由旋转。(A transmission for a manually operated wheeled machine includes an output shaft having a closed end axial passage. A drive gear mounted on the output shaft includes an engagement groove. The ratchet is received in the channel and engages the engagement groove. A retainer mounted on the output shaft includes a recess that receives the ratchet. The friction member applies radial friction to the holder to temporarily prevent the holder from rotating with the output shaft in a driving state of the machine to move the ratchet into engagement with the engagement groove, and the drive gear and the holder rotate with the output shaft in the driving state. Under freewheeling conditions of the machine, the output shaft is stationary and overdriving of the drive gear disengages the ratchet wheel from the engagement groove, allowing the drive gear to rotate freely about the stationary output shaft.)

1. A transmission for a manually operated wheeled machine having a drive state and a freewheeling state, said transmission comprising:

an output shaft having a closed end passage formed in an end portion thereof, the passage extending in an axial longitudinal direction of the output shaft and being axially spaced from an end face of the output shaft;

a drive gear rotatably mounted on the end portion of the output shaft, the drive gear including an engagement groove formed in an inner circumferential surface thereof, the drive gear in meshing engagement with a driven gear carried within a drive wheel of the wheeled machine;

a ratchet having a key and a leg extending from the key in a radial direction of the output shaft, the key being received in the channel and selectively engaged with the engagement groove;

a retainer rotatably mounted on the end portion of the output shaft, the retainer including an end face facing the drive gear, a recess formed in the end face receiving the leg of the ratchet; and

a friction member fixed to the holder and adapted to apply radial friction to the holder to temporarily prevent the holder from rotating along with the output shaft in the driving state of the wheeled machine in which the output shaft rotates in a first rotational direction together with the drive gear and the holder, and thus, the key portion of the ratchet wheel moves into engagement with the engagement groove of the drive gear,

wherein in the freewheeling state the output shaft is stationary and overdriving the drive gear in the first rotational direction causes the key portion of the ratchet wheel to disengage from the engagement groove, thereby allowing the drive gear to rotate freely about the stationary output shaft.

2. The transmission of claim 1, wherein to prevent dust intrusion into the channel, the drive gear and the retainer are arranged on the end portion of the output shaft to cover the channel in both the driving condition and the freewheeling condition of the wheeled machine.

3. The transmission of claim 2, wherein an inner wheel cover of the drive wheel includes a shroud covering each of the drive gear and the retainer.

4. The transmission of claim 1, wherein the friction member is a spring member wrapped at least partially around an outer circumferential surface of the retainer.

5. The transmission of claim 4, wherein the free end portion of the spring member is secured to an inner wheel cover of the drive wheel.

6. The transmission of claim 4, wherein the outer circumferential surface of the retainer includes a circumferential groove sized to receive the spring member.

7. The transmission of claim 1, wherein the channel is rectangular in cross section taken perpendicular to the axial longitudinal direction of the output shaft, the channel being defined by first and second sides and a base, and

wherein the key of the ratchet wheel includes a first end and a second end having a first ramped surface, wherein in the drive state, the first ramped surface engages the first side of the channel and the base, and the second end engages the engagement groove of the drive gear.

8. The transmission of claim 7, wherein the second end of the ratchet includes a curved surface that allows the second end to slide along the second side of the channel when the wheeled machine transitions from the driving state to the freewheeling state.

9. The transmission of claim 7, wherein the second end includes a second inclined surface, wherein the second inclined surface engages the inner circumferential surface of the drive gear in the freewheeling state.

10. The transmission of claim 1, wherein the recess of the retainer is defined by a front surface and a rear surface relative to the first rotational direction of the output shaft, wherein in the drive state the leg of the ratchet contacts the front surface and is spaced apart from the rear surface.

11. The transmission of claim 10, wherein a front surface of the leg of the ratchet includes a first portion and a second portion that is inclined relative to the first portion, wherein in the drive state the first portion is in contact with the front surface, the leg pivots on the front surface when the wheeled machine transitions from the drive state to the freewheeling state, and wherein in the freewheeling state the second portion is in contact with the front surface.

12. The transmission of claim 1, wherein the inner circumferential surface of the drive gear is a polygonal shape.

13. A manually operated wheeled machine having a drive condition and a freewheeling condition, the wheeled machine comprising:

a motor;

an output shaft operably coupled to the motor, the output shaft having a closed end channel formed in an end portion thereof, the channel extending in an axial longitudinal direction of the output shaft and being axially spaced from an end face of the output shaft;

a drive wheel connected to the end portion of the output shaft, the drive wheel including an inner wheel cover having an opening for the output shaft; and

a transmission housed within the drive wheel, wherein the transmission comprises:

a drive gear rotatably mounted on the end portion of the output shaft, the drive gear including an engagement groove formed in an inner circumferential surface of the drive gear,

a ratchet having a key and a leg, the key being received in the channel, the ratchet being selectively engaged with the engagement groove,

a retainer rotatably mounted on the end portion of the output shaft immediately adjacent the drive gear, the retainer including an end face having a recess formed therein that receives the leg of the ratchet gear,

a driven gear carried within the drive wheel and in meshing engagement with the drive gear,

wherein the drive gear and the retainer are arranged on the end portion of the output shaft to cover the passage in order to prevent dust from invading the passage,

and the inner wheel cover includes a shroud covering each of the drive gear and the retainer.

14. A wheeled machine according to claim 13 wherein a friction member is fixed to the holder and adapted to apply radial friction to the holder to temporarily prevent the holder from rotating with the output shaft in the driving condition of the wheeled machine.

15. The wheeled machine of claim 14, wherein in the drive condition, the key portion of the ratchet wheel engages the engagement groove of the drive gear and the output shaft rotates with the drive gear and the holder in a first rotational direction, and

wherein in the freewheeling state the output shaft is stationary and overdriving the drive gear in the first rotational direction causes the key portion of the ratchet wheel to disengage from the engagement groove, thereby allowing the drive gear to rotate freely about the stationary output shaft.

16. The wheeled machine of claim 14, wherein the friction member wraps at least partially around an outer circumferential surface of the retainer, and a free end portion of the friction member is secured to the inner wheel cover of the drive wheel.

17. The wheeled machine of claim 13, wherein the channel is rectangular in cross section taken perpendicular to an axial longitudinal direction of the output shaft.

18. A transmission for a manually operated wheeled machine having a drive state and a freewheeling state, said transmission comprising:

an output shaft having a closed end passage formed in an end portion thereof, the passage extending in an axial longitudinal direction of the output shaft and being axially spaced from an end face of the output shaft;

a drive gear rotatably mounted on the end portion of the output shaft, the drive gear including an engagement groove formed in an inner circumferential surface of the drive gear;

a ratchet received in the channel and selectively engaged with the engagement groove;

a retainer rotatably mounted on the end portion of the output shaft, the retainer including an end face facing the drive gear, a recess formed in the end face receiving the ratchet;

a friction member wrapped at least partially around an outer circumferential surface of the retainer and adapted to apply radial friction to the retainer to temporarily prevent the retainer from rotating with the output shaft in the driving condition of the wheeled machine; and

a driven gear in meshing engagement with the drive gear and carried within a drive wheel of the wheeled machine.

19. The transmission of claim 18, wherein the friction member is a spring member and a free end portion of the spring member is secured to an inner wheel cover of the drive wheel.

20. The transmission of claim 18, wherein to prevent dust intrusion into the channel, the drive gear and the retainer are disposed on the end portion of the output shaft to cover the channel, and the inner wheel cover of the drive wheel includes a shroud covering each of the drive gear and the retainer.

Background

Currently, the drive system of a wheeled machine (e.g., a lawn mower) includes a transmission and wheels driven by a pinion on an output shaft of the transmission. To minimize the friction when the user pushes the mower forward, a simple ratchet mechanism has been used inside the pinion mounted on the transmission output shaft. This allows one-way driving of the wheels by the transmission and less friction in the forward direction. However, if the user wishes to pull the mower rearwardly, the ratchet does not disengage from the transmission output shaft. This results in the user having to overcome the high back roll friction to move the mower backwards. In many cases, the pullback load is high enough to cause customer dissatisfaction with it.

It is known to use a combination of mechanisms to allow freewheeling when the transmission is not driving the system, and many of these designs are incorporated into the transmission itself. The internal-to-transmission type solves the freewheeling problem by separating the output shaft from the input shaft from the transmission, thus reducing the total friction that the user must overcome to move the mower. However, in this configuration, the output shafts of the transmission are independent of each other. This separation requires additional support for the shaft in the transmission housing. The shafts must be supported because they have joints between the left and right output shafts. It is also known to use a freewheeling ratchet system mounted within the wheel pinion on the output shaft of the transmission. However, such designs are susceptible to dust intrusion due to the tight tolerances of the mating parts.

Disclosure of Invention

According to one aspect, a transmission for a manually operated wheeled machine having a drive state and a freewheeling state is provided. The transmission includes an output shaft having a closed end passage formed in an end portion thereof. The channel extends in an axial longitudinal direction of the output shaft and is axially spaced from an end face of the output shaft. A drive gear is rotatably mounted on an end portion of the output shaft. The drive gear includes an engagement groove formed in an inner circumferential surface of the drive gear. The drive gear is in meshing engagement with a driven gear carried within a drive wheel of the wheeled machine. The ratchet has a key portion and a leg portion extending from the key portion in a radial direction of the output shaft. The key is received in the channel and selectively engages the engagement groove. The retainer is rotatably mounted on an end portion of the output shaft. The retainer includes an end surface facing the drive gear. A recess formed in the end face receives the leg of the ratchet. The friction member is fixed to the holder and is adapted to apply radial friction to the holder to temporarily prevent the holder from rotating with the output shaft in a driving state of the wheeled machine. Thus, the key portion of the ratchet wheel moves into engagement with the engagement groove of the drive gear, and in the driving state, the output shaft rotates in the first rotational direction together with the drive gear and the holder. In the freewheeling state, the output shaft is stationary and overdriving of the drive gear in the first rotational direction causes the key portion of the ratchet wheel to disengage from the engagement groove, thereby allowing the drive gear to rotate freely about the stationary output shaft.

According to another aspect, a manually operated wheeled machine has a drive state and a freewheeling state. The wheeled machine includes a motor and an output shaft operably coupled to the motor. The output shaft has a closed end passage formed in an end portion thereof. The channel extends in an axial longitudinal direction of the output shaft and is axially spaced from an end face of the output shaft. The drive wheel is connected to an end portion of the output shaft. The drive wheel includes an inner wheel cover having an opening for the output shaft. The transmission is housed within the drive wheel. The transmission includes a drive gear rotatably mounted on an end portion of the output shaft. The drive gear includes an engagement groove formed in an inner circumferential surface of the drive gear. The ratchet has a key and a leg. The key is received in the channel. The ratchet gear is selectively engaged with the engagement groove of the drive gear. The retainer is rotatably mounted on an end portion of the output shaft proximate the drive gear. The retainer includes an end face having a recess formed therein that receives the leg of the ratchet. A driven gear carried within the drive wheel is in meshing engagement with the drive gear. To prevent dust from invading into the passage, a drive gear and a retainer are arranged on an end portion of the output shaft to cover the passage, and the inner wheel cover includes a hood covering each of the drive gear and the retainer.

According to another aspect, a transmission for a manually operated wheeled machine having a drive state and a freewheeling state is provided. The transmission includes an output shaft having a closed end passage formed in an end portion thereof. The channel extends in an axial longitudinal direction of the output shaft and is axially spaced from an end face of the output shaft. A drive gear is rotatably mounted on an end portion of the output shaft. The drive gear includes an engagement groove formed in an inner circumferential surface of the drive gear. A ratchet received in the passage selectively engages the engagement groove. The retainer is rotatably mounted on an end portion of the output shaft. The retainer includes an end surface facing the drive gear. A recess formed in the end face receives the ratchet. A friction member wrapped at least partially around an outer circumferential surface of the retainer is adapted to apply radial friction to the retainer to temporarily prevent the retainer from rotating with the output shaft in a driving condition of the wheeled machine. A driven gear in meshing engagement with the drive gear is carried within a drive wheel of the wheeled machine.

Drawings

Fig. 1 is a schematic perspective view of a manually operated wheeled machine in the form of a walk-behind self-propelled lawn mower.

Fig. 2 is a partial cross-sectional view of a drive wheel of the mower.

Fig. 3 is an enlarged view of fig. 2.

FIG. 4 is an exploded perspective view of an exemplary transmission housed in a drive wheel.

Fig. 5 is a perspective view of a drive gear of the transmission.

Fig. 6 is a front view of the drive gear of fig. 5.

Fig. 7 and 8 are perspective views of a holder of the transmission.

Fig. 9 and 10 are perspective views of the ratchet wheel of the transmission.

FIG. 11 is a front view of the ratchet of FIG. 10.

Fig. 12 and 13 are perspective views depicting partial assembly of a transmission within a drive wheel of a lawn mower.

Fig. 14 and 15 are partial views of the inner cover of the drive wheel.

Fig. 16(a) -16 (H) illustrate various operating states of an exemplary transmission.

Detailed Description

It should be understood, of course, that the description and drawings herein are merely exemplary and that various modifications and changes can be made in the structures disclosed without departing from the disclosure. Referring now to the drawings, in which like numerals indicate like parts throughout the several views, the present disclosure is directed to a transmission 100 for a manually operated wheeled machine 102 having a drive state and a freewheeling state. As used herein, a driving state refers to a state of a wheeled machine in which the transmission 100 is in an engaged state and torque is transmitted to at least one drive wheel 104 of the wheeled machine 102, and a freewheeling state refers to a state of a wheeled machine in which the transmission 100 is in a disengaged state and the at least one drive wheel 104 is free to rotate in both a forward direction and a rearward direction. Fig. 1 shows the application of a transmission 100 to a self-propelled walk-behind mower (i.e., a wheeled machine 102) that an operator uses to mow. It should be noted, however, that the transmission 100 may be used with a variety of manually operated wheeled power tools, including various types of lawn mowers, power carriers (i.e., wheeled carts), snow plows, and the like. The lawn mower 102 is merely an example of the present disclosure.

As shown schematically in fig. 1, the mower 102 has a blade housing 110 carried by a rear drive wheel 104 (the right rear drive wheel is not shown, as fig. 1 is a view of the mower 102 taken from one side) and a front wheel 112. Mounted atop the housing 110 is a "prime mover" 116, which in the embodiment shown in FIG. 1 is a gasoline engine, but may alternatively be an electric motor. As is well known, the cutting blade (not shown) is connected to an output shaft (not shown) of the engine 116, the drive unit 118 is operatively coupled to the output shaft, and the drive wheel 104 is operatively connected to the drive unit 118 (fig. 2 and 3) via an output shaft or drive shaft 120 of the drive unit 118 (fig. 1). An operating handle 122 extends obliquely in a rearward and upward direction from the rear of the housing 110 and includes an operator control 124, the operator control 124 being configured to selectively engage and disengage the drive unit 118. Referring to fig. 2 and 3, the drive wheel 104 includes an outer cover 130 and an inner cover 132, each of the outer cover 130 and the inner cover 132 being coupled to a hub 134. The shaft 136 of the drive wheel 104 is fixed to a support 138 of the housing 110 and extends through the inner cover 132. The shaft 136 fits within the tubular portion 142 of the hub 134. The inner cover 132, together with the outer cover 130, defines an enclosure 144, and the example actuator 100 is received in the enclosure. Drive shaft 120 is received in bearings 146 mounted in bearing housing 148, which is secured to housing 110. Support 138 is connected to bearing housing 148.

In accordance with the present disclosure, the transmission 100 includes a first or drive gear 150 rotatably mounted on an end portion of the drive shaft 120, a retainer 152 rotatably mounted on the end portion of the drive shaft 120 proximate the drive gear 150, a ratchet gear 154 selectively engaged with the drive gear 150 and the retainer 152, and a friction member 156 (see fig. 4) secured to the retainer 152. A second or driven gear 158 is fixedly mounted on the hub 134, coaxial with the axis of rotation of the drive wheel 104, and in meshing engagement with the drive gear 150. The transmission 100 is used to transmit power from the drive shaft 120 to the drive wheel 104 through the driven gear 158. The transmission 100 is configured to allow the drive wheel 104 to freely rotate bi-directionally when the drive shaft 120 is stationary (i.e., the drive shaft is not rotated by the drive unit 118).

Fig. 5 and 6 illustrate an exemplary drive gear 150. Drive gear 150 includes a first facing surface 170, a second facing surface 172, a through-hole 174 extending between first and second facing surfaces 170, 172 (sized to receive an end portion of drive shaft 120), and teeth 176 formed on an outer circumferential surface of drive gear 150. The through bore 174 is defined by an inner circumferential surface 180, and at least one engagement groove 186 is formed in the inner surface 180 for engagement with the ratchet 154. In the illustrated aspect of the drive gear 150, the inner surface 180 is polygonal in shape, wherein vertices of the polygonal shaped inner surface 180 form the engagement grooves 186 of the drive gear 150. For example, as shown, the inner surface 180 is pentagonal; however, this is not essential. Further, the edge portion 188 of the inner surface 180 may be concave and curved for maintaining the positional relationship of the ratchet 154 within the selected engagement groove 186.

Fig. 7 and 8 illustrate an exemplary retainer 152. The retainer 152 may be annular and includes a first facing surface or end surface 190, a second facing surface or end surface 192, and an inner surface 194 defining a through bore 198. The first end surface 190 has at least one recess 200 formed therein that receives the ratchet 154. As shown, the first end face 190 is provided with diametrically spaced recesses 200, 200' that allow the respective transmissions 100 of the left and right drive wheels 104 to share a single retainer. In the driven state of the mower 102, the recess 200 of the retainer 152 (which is for use with the transmission 100 received in the left drive wheel 104) is defined by a front surface 202 and a rear surface 204 relative to a first rotational direction RD (see fig. 4) of the drive shaft 120. The front surface 202 includes a first portion 210 contiguous with the inner surface 194, a second portion 212 extending from the first portion, and a third portion 214 extending from the second portion. Each of the first portion 210 and the third portion 214 may project substantially radially with respect to an axial longitudinal direction of the drive shaft 120, wherein the first portion 210 is circumferentially spaced from the third portion 214 in the first rotational direction. Second portion 212 extends angularly between first portion 210 and third portion 214. The rear surface 204 includes a first portion 220 adjacent the inner surface 194 and a second portion 222 extending from the first portion. The first portion 220 may be inclined rearwardly with respect to the first rotational direction RD, and the second surface may extend substantially radially with respect to the longitudinal direction of the drive shaft 120. The recess 200' of the retainer 152 (which is intended for use with the transmission 100 received in the right drive wheel 104) is similarly formed with a front surface 202' and a rear surface 204 '.

Fig. 9-11 illustrate an exemplary ratchet 154 of the transmission 100. The ratchet 154 has a key portion 228 and a leg portion 230 extending from the key portion in the radial direction of the drive shaft 120. In the depicted aspect, the key 228 of the ratchet 154 is generally wedge-shaped and includes a first end 234, a second end 236 opposite the first end, a first side 238, and a second side 240 opposite the first side. The first end 234 may have first angled surfaces 244, 246 that extend to the first and second sides 238, 240, respectively. The second end 236 may include a curved surface 248 and a second surface 250. As shown, the second surface 250 extends to the first side 238 and slopes toward the first end 234. In accordance with one aspect of the ratchet 154, the leg 230 includes a front surface 256 and a rear surface 258 relative to the first rotational direction RD of the drive shaft 120. The front surface 256 may include a first portion 260 and a second portion 262 that is angled with respect to the first portion. The first and second portions 260, 262 substantially conform to the second and third portions 212, 214 of the front surface 202 of the holder recess 200. The rear surface 258 may include a first portion 266 and a second portion 268 that is angled relative to the first portion. The first and second portions 266, 268 substantially conform to the first and second portions 220, 222 of the rear surface 204 of the retainer recess 200.

The transmission 100 also includes a friction member 156 configured to wrap at least partially around the outer circumferential surface 270 of the retainer 152. In the embodiment shown in fig. 4, the friction member 156 may be comprised of a spring member. To accommodate the spring member, the outer circumferential surface 270 of the retainer 152 includes a circumferential groove 272 (see fig. 7) sized to receive the spring member. The free end portion 276 of the spring member is secured to the inner wheel cover 132 of the drive wheel 104 as described below.

Fig. 12 and 13 depict the components of the transmission 100 on the drive shaft 120. The retainer 152 is positioned on the drive shaft with the friction members 156 received in the circumferential groove 272 of the retainer 152. The key 228 of the ratchet 154 is received in a closed end channel 280 formed in the end portion of the drive shaft 120. The channel 280 extends in the axial longitudinal direction of the drive shaft 120 and is axially spaced from the end face 282 of the drive shaft. According to one aspect, the channel 280 is substantially rectangular in cross-section taken perpendicular to the longitudinal direction of the drive shaft 120. The leg 230 of the ratchet 154 is received in the recess 200 formed in the retainer 152. The drive gear 150 is then positioned onto the drive shaft 120. With additional reference to fig. 3, the washer 288 is received in a recessed portion 290 formed in the second end face 192 of the retainer 152, and the washer 292 is received in a recessed portion 294 formed in the second facing surface 172 of the drive gear 150. Snap rings 296,298 fitted into circumferential grooves on the drive shaft 120 secure the transmission 100 to the drive shaft 120. Additionally, referring to fig. 3, 14 and 15, to secure the free end portion 276 of the friction member 156 to the inner wheel cover 132, the inner cover 132 includes a recess 310 having an opening 312 on an outer surface 314 of the inner cover 132. The recess 310 receives the free end portion 276 and the teeth 316 protruding into the recess 310 engage the free end portion 276, thereby securing the friction member 156 to the inner cover 132.

It should be appreciated that the closed end passage 280 for the ratchet wheel 154 is advantageous over prior art designs in which the passage for the ratchet wheel has an open end formed on the end face of the drive shaft. With the channel 280 axially spaced from the end face 282, dust intrusion into the channel 280, which can affect the operational movement of the ratchet 154, can be prevented. To further prevent intrusion of dust into the channel 280, the drive gear 150 and the retainer 152 are disposed on an end portion of the drive shaft 120 to cover the channel 280 (see also fig. 3). Further, the inner wheel cover 132 includes a shroud 320 extending from an inner surface 322 of the inner cover 132. A shroud 320, which may be arcuate in shape, covers each of the drive gear 150 and the retainer 152.

Operation of the exemplary transmission 100 will now be described with reference to various operating states of the transmission shown in fig. 16(a) -16 (H), with the drive shaft 120, drive gear 150 (partially cut away), holder 152 and ratchet gear 154 being shown by different types of lines. It should also be noted that the identifying features of the components of the transmission 100 in the following description refer to fig. 1-15 of the present disclosure. First, in the freewheeling state (i.e., the free position state — fig. 16(a) and 16(B)) of the mower 102, the transmission 100 does not transmit the driving force from the drive unit 118 to the driven gear 158. Specifically, the key 228 of the ratchet wheel 154 does not engage any of the engagement grooves 186 of the drive gear 150. Fig. 16(B) shows the leg 230 of the ratchet 154 in contact with the rear surface 204 of the recess 200 of the retainer 152.

When the engine 116 of the mower 102 is started and the drive shaft 120 starts to rotate in the direction indicated by the arrow in fig. 16(C) (i.e., the shaft driving (1) state), the friction member 156 fixed to the holder 152 applies radial friction to the holder 152 to temporarily prevent the holder from rotating along with the drive shaft 120 in the driving state of the mower 102. This frictional retention of the retainer 152 causes the ratchet 154 to rotate with the drive shaft 120 to engage the front surface 202 of the recess 200 of the retainer 152. In particular, the second portion 262 of the front surface 256 of the ratchet leg 230 contacts the third portion 214 of the recess front surface 202. This contact causes the ratchet wheel 154 to at least partially rotate in a direction opposite the direction of rotation of the drive shaft 120. In fig. 16(D) (shaft driving (2) state), the ratchet key portion 228 abuts the inner circumferential surface 180 of the drive gear 150.

Next, in the driven state of the mower 102 (i.e., the driving position state-fig. 16(E) and 16(F)), the leg 230 of the ratchet 154 pivots on the front surface 202 of the recess 200 such that the first portion 260 of the leg front surface 256 is now in contact with the second portion 212 of the recess front surface 202 and the leg 230 is spaced apart from the recess rear surface 204. In the driven state, the first inclined surfaces 244, 246 of the first end 234 of the ratchet key 228 engage the first side 330 of the channel 280 and the base 332 (see fig. 12), and the second end 236 of the ratchet key 228 engages the engagement groove 186 of the drive gear 150. This engagement of the keys 228 with the engagement grooves 186 of the drive gear 150 causes the drive gear 150 and the retainer 152 to rotate with the drive shaft 120.

In an overdrive starting state (fig. 16G) of the transmission 100, in which the drive shaft 120 is stationary, overdrive of the first gear 150 in the direction of rotation (which naturally occurs due to the inertia of the wheeled machine 102, which tends to cause complementary propulsion of the wheeled machine) causes the ratchet wheel 154 to pivot in the direction of rotation. Thus, in the overdrive state (fig. 16H) of the transmission 100, the ratchet leg 230 pivots on the recess front surface 202 and the curved surface 248 of the second end 236 of the ratchet key 228 allows the second end 236 to slide along the second side 334 of the channel (fig. 12) as the mower 102 transitions from the drive state to the freewheeling state. Also, in the freewheeling state, the key portion 228 of the ratchet wheel 154 disengages from the engagement groove 186 of the drive gear 150, allowing the drive gear to rotate freely about the stationary drive shaft 120. Additionally, it should be appreciated that the second end 236 of the key 228 includes a second ramped surface 250, wherein in the freewheeling condition, the second ramped surface 250 engages the inner circumferential surface 180 of the drive gear 150 (fig. 16(B) to prevent unwanted movement of the ratchet gear 154 in the freewheeling condition that may result in re-engagement of the drive gear 150.

It will be appreciated that the above-disclosed and other features and functions, or alternatives or variations thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.