Abstract:
A lawn mower having a deck height adjustment mechanism for simultaneously adjusting a height of a deck of a lawn mower at all four wheels of the lawn mower by the use of a single hand of the operator. The mechanism includes an index plate having a plurality of teeth thereon defining a plurality of deck height positions, and therefore a plurality of height positions of a cutting blade supported by the deck. The index plate is fixedly secured to an offset rear axle. An engaging plate having a pawl is coupled to an actuating member which is slidably, vertically moveable relative to the deck when the operator grips the actuating member and pulls upwardly away from the deck, while resting a palm of the same hand on a palm rest portion of the mechanism. A linkage member couples the index plate to a bracket of an offset front axle positioned at a front end of the deck. The operator adjusts the height of the deck relative to a ground surface by pulling upwardly with the fingers of one hand on the actuating member, while resting the palm of the same hand on the palm rest. This causes the engaging plate, and thus the pawl thereon, to be drawn out of engagement with the teeth of the index plate. The operator, while holding the actuating member engaged, may either pull upwardly with the same hand, thus raising the entire deck of the mower, or may urge the deck into a lower position. Movement of the index plate causes a simultaneous rotational movement of the offset front axle. Thus, all four corners of the deck are caused to be raised or lowered simultaneously as the operator either lifts or lowers the deck while engaging the actuation member.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The subject matter of the present application is related to U.S. patent application Ser. No. 29/027,102, filed Aug. 12, 1994, and entitled &#34;Design: Lawn Mower&#34;, assigned to the assignee of the present application; and 
     U.S. patent application Ser. No. 08/289,453, filed Aug. 12, 1994, and entitled &#34;Lawn Mower Having Improved Handle To Deck Coupling Arrangement&#34;, assigned to the assignee of the present application. 
     U.S. patent application Ser. No. 08/383,755, filed Feb. 2, 1995, and entitled &#34;Mulching Lawnmower Having Volute Deck&#34;, assigned to the assignee of the present application. 
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     This invention relates to lawn mowers, and more particularly to a lawn mower having a height adjustment mechanism for enabling an operator to adjust the height of a deck of a lawn mower relative to a ground surface at all the wheels of the lawn mower simultaneously by temporarily, manually engaging a single actuating member. 
     2. Discussion 
     Some form of deck height adjustment is common with virtually all lawn mowers. Typically, such deck height adjustment mechanisms incorporate an independent adjusting plate at each one of the four wheels of the mower. Some manually engageable release member is typically associated independently with each one of the adjusting plates and releasably engageable with its associated adjusting plate. Each adjustment plate, in turn, is usually fixedly secured to a portion of an offset axle supporting the wheel associated with the particular adjusting plate. When the release member is engaged, the offset portion of the axle is allowed to rotate which allows the vertical height of the wheel to be adjusted relative to the deck. Releasing the release member causes it to engage the adjusting plate, thus maintaining the adjusting plate stationary, and thereby maintaining the wheel at the desired position relative to the deck. By thus controlling the relative position of the wheel of the deck, the cutting height of the lawn mower blade can be adjusted relative to the ground. 
     While the above arrangement has proved to be satisfactory for allowing the deck height of the mower to be adjusted relative to the ground surface at all four corners (i.e., wheels) of the lawn mower deck, this arrangement does provide for some inconvenience to the operator. To adjust the deck height, the operator must manually adjust the position of each adjustment plate, and thus each wheel, relative to the deck. Since four wheels are typically employed with most lawn mowers, the operator must typically make four independent deck height adjustments, one at each wheel of the mower, when the deck height is to be raised or lowered. 
     More recently, improvements have been made to simplify the matter in which the deck of a lawn mower is adjusted to provide a greater degree of convenience to the operator. The assignee of the present application has utilized a form of deck height adjustment mechanism in which the operator is able to adjust the deck height of a mower relative to a ground surface by engaging a single deck height adjustment control. This system is embodied in a lawn mower manufactured by the assignee of the present application, and is disclosed in U.S. Pat. No. 5,230,208. The disclosure of this patent is hereby incorporated by reference into the present application. While the deck height adjustment mechanism disclosed in this patent has proved effective for increasing the ease with which the operator may adjust the deck height, it would be desirable to provide a mechanism which is even simpler and even less costly to manufacture, and which requires a fewer number of independent component parts to accomplish simultaneous adjustment of the deck height at all four wheels of the mower. 
     Accordingly, it is an object of the present invention to provide a deck height adjustment mechanism for a lawn mower which allows an operator of the lawn mower to easily and conveniently adjust the height of the deck at all four wheels of the lawn mower simultaneously. More specifically, it is an object of the present invention to provide a deck height adjustment mechanism by which all four wheels of a lawn mower may be simultaneously adjusted for height relative to the deck of the mower by simply, temporarily engaging a single actuating member and subsequentially using the actuating member to lift or lower the deck to a desired position before releasing the actuating member, whereafter the height of the deck is maintained at the desired position relative to the ground. Such an arrangement would obviate the need to independently adjust the deck height at each one of the four wheels of the mower one at a time. 
     It is yet another object of the present invention to provide a deck height adjustment mechanism for a lawn mower which allows the deck height to be adjusted at all four wheels of the lawn mower simultaneously with a single hand, and which is even simpler in construction and lower in cost to manufacture than previously existing deck height adjustment mechanisms. 
     It is yet another object of the present invention to provide a deck height adjustment mechanism for a lawn mower having a manually, grippable actuating member which allows the height of the deck to be adjusted simultaneously at all four wheels of the lawn mower when the operator grippingly engages the actuating member while simultaneously lifting up on or lowering the deck to the desired height with the same hand. When the deck is positioned at the desired height, releasing the actuating member locks the position of the deck, and thus the height of the cutting blade, at the desired position simultaneously at all four wheels of the mower. 
     SUMMARY OF THE INVENTION 
     The above and other objects are accomplished by a lawn mower having an improved deck height adjustment mechanism in accordance with a preferred embodiment of the present invention. In the preferred embodiment, the present invention includes an index plate which is fixedly secured to one of an offset rear axle or an offset front axle. Merely as an example, in the preferred embodiment the index plate is fixedly secured to the rear axle. An actuating assembly having means for engaging the index plate and holding it stationary relative to the deck of the lawn mower is provided and positioned above the deck to even further increase the convenience of access to the user. The operator can quickly and easily uncouple (i.e., release) the actuating assembly from engagement with the index plate by gripping the actuating assembly and easily and quickly re-engage the index plate by releasing the actuating assembly. 
     The index plate is mechanically coupled with the other one of the front or rear offset axles by a linkage member such that rotational movement of the index plate causes a corresponding rotational movement at the other one of the front or rear axles. In the preferred embodiment, the linkage member is coupled intermediate the index plate and the offset front axle of the lawn mower. Each of the front and rear offset axles further extend width-wise across the deck to support a pair of the wheels of the mower. In the preferred embodiment, the rear offset axle supports the rear wheels of the lawn mower for rotational movement relative to the deck, while the front offset axle supports the front wheels of the lawn mower for rotational movement relative to the deck. 
     When the operator grippingly engages the actuating assembly, the actuating assembly is drawn out of engagement with the index plate, thus allowing it to rotate in accordance with the offset rear axle, and thus allowing the vertical position of the two rear wheels to be adjusted relative to the deck. Simultaneously, the linkage member couples the rotational movement of the index plate to the offset front axle, thus causing a corresponding rotational movement of the offset front axle. The simultaneous rotational movement of the front and rear offset axles thus adjusts the height of the entire deck at all four wheels relative to a ground surface supporting the four wheels. 
     When the operator achieves the desired deck height, the operator releases the actuating assembly which causes it to reengage with the index plate. This maintains the index plate stationary relative to the deck and prevents further vertical movement of the four wheels. In this manner, the height of the deck, and thus the height of the cutting blade relative to the ground surface, can be quickly, easily and conveniently controlled by the use of a single hand which simultaneously engages the actuating assembly and either lifts or lowers the deck while the actuating assembly is held in its engaged position. 
     In a preferred embodiment, the index plate further includes a pair of shoulder portions spaced vertically apart from one another to define first and second mounting positions for the offset rear axle. In the first mounting position, the offset rear axle is positioned to accept a first diameter wheel, for example, a wheel having a diameter of 7 inches. When the offset rear axle is fixedly secured to the second shoulder portion, and therefore in the second position, the offset rear axle is held in a position closer to a bottom-most edge of the deck to provide for a greater minimum ground clearance when a smaller diameter wheel is used, such as a six inch diameter wheel. Thus, the first and second shoulder portions enable the offset rear axle to be secured in two positions without any additional component parts being secured to the index plate. Thus, a single index plate can be used for mowers having different rear wheel diameters. It will be appreciated that this represents an important manufacturing advantage in that multiple index plates need not be manufactured to accommodate wheels of differing diameters. 
     In a preferred embodiment, the linkage member further includes an indicator which moves in accordance with the movement of the linkage member to provide a visual indication to the operator as to the current deck height position. A preferred embodiment of the lawn mower includes a shroud having a portion adjacent the indicator which includes suitable indicia for enabling the current deck height setting of the lawn mower to be read. 
     It is a principle advantage of the deck height adjustment mechanism of the present invention that an even simpler, less costly height adjustment mechanism having fewer component parts over prior developed mechanisms is provided. The deck height adjustment mechanism of the present invention provides a further advantage of not adding appreciably to the overall cost, size or weight of the lawn mower while significantly increasing the ease and convenience with which the deck height may be adjusted by an operator. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The various advantages of the present invention will become apparent to one skilled in the art by reading the following specification and subjoined claims and by referencing the following drawings in which: 
     FIG. 1 is a perspective view of a lawn mower incorporating a deck height adjustment mechanism in accordance with the present invention; 
     FIG. 2 is a perspective, fragmentary view of a portion of the lawn mower shown in FIG. 1 illustrating the index plate and actuating member in greater detail; 
     FIG. 3 is a perspective view of a rear portion of the deck of the lawn mower in FIG. 2 showing more clearly the shape of the offset rear axle; 
     FIG. 4 is an exploded perspective view of the component parts of the deck height adjustment mechanism; 
     FIG. 5 is a rear perspective view of the actuating member, engaging member and palm rest; 
     FIG. 6 is a cross-sectional view in accordance with section line 6--6 of FIG. 5 showing the coupling and capturing of the palm rest between a tubular handle member of the lawn mower and the handle support area of the deck; 
     FIG. 7 is a front view of a portion of the engaging member lockingly intergaging the arm portion of the actuating member; 
     FIG. 8 is a side view of the deck of the lawn mower shown in FIG. 1 illustrating in broken-away fashion the orientation of the index plate and linkage member when the deck is adjusted to its maximum height position relative to the ground surface; and 
     FIG. 9 is a side view of the lawn mower of FIG. 8 showing the orientation of the index plate and linkage member when the deck is adjusted to its minimum height position. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1, a vegetation cutter in the form of a lawn mower 10 is shown which incorporates a deck height adjustment mechanism 12 in accordance with a preferred embodiment of the present invention. The lawn mower generally includes a removable shroud 14 secured to a deck 16. The deck is supported above a ground surface 18 by a pair of rear wheels 20a and 20b and a pair of front wheels 22a and 22b. The lawn mower 10 is traversed over the ground surface 18 by the operator gripping a handle member 24 near a top portion thereof (not shown) and pushing the lawn mower, if the lawn mower is not of the self-propelled variety, or simply steering the lawn mower as needed if the lawn mower is of the self-propelled variety. It will be appreciated that while the mechanism of the present invention has been described in connection with a lawn mower, that the mechanism 12 could easily be adapted with little or no modification for use with a wide variety of vegetation cutters having at least two wheels. The mechanism 12 can provide quick and easy height adjustment on virtually any form of vegetation cutter where it is important to have corresponding height adjustments made at the front and rear wheels of the cutter. Still further, the adjustment mechanism 12 of the present invention can be used with little or no modification with cordless (i.e., battery powered) mowers, &#34;corded&#34; mowers driven by an AC power source, bagging mowers, discharge mowers, mulching mowers and self-propelled mowers, or a combination thereof. 
     With further reference to FIGS. 1 and 2, the shroud 14 includes an opening 26 through which an actuating member 28 of the deck height adjustment mechanism 12 protrudes. As will be described more fully in connection with FIGS. 2-9, the deck height adjustment mechanism 12 allows the operator to adjust the height of the deck 16 relative to the ground surface 18 by merely grippingly urging a gripping portion 28a of the actuating member 28 upwardly in a generally linear path of movement, relative to the ground surface 18, and holding the member 28 engaged while lifting or lowering the deck 16 with the same hand. Thus, there is no need to make separate deck height adjustments at all four wheels of the mower 10 as would be required with most prior deck height adjustment systems. By using a single hand, the operator is able to simultaneously adjust the deck height at all four wheels 20a, 20b and 22a, 22b of the lawn mower 10. The actuating member 28 is further positioned well above the rear wheel 20a so that the operator is not required to bend over to a significant degree to make a deck height adjustment. The positioning of the actuating member 28 therefore adds significantly to the comfort and convenience of making height adjustments of the deck 16. 
     Referring now to FIGS. 2-4, the component parts of the deck height adjustment mechanism. 12 can be seen even more clearly. The mechanism 12 generally includes an index plate 30, a linkage member 32 pivotally secured to a pivotal mounting portion 31 of the index plate 30 at an aperture 32d of a first end 32a of the linkage member 32, an actuating assembly comprising an engaging member 34 and the actuating member 28, and a palm rest 36. The index plate 30 is physically coupled to an offset portion 38 of an offset rear axle 40 of the lawn mower 10, as shown in FIG. 3. The index plate 30 is preferably fixedly secured, such as by welding, to the offset portion 38 and includes a notched portion 42 for receiving a portion of the offset rear axle 40. By this arrangement, rotational movement of the offset portion 38 of the rear axle 40 causes a corresponding rotational movement of the index plate 30. With further reference to FIG. 2, a second end 32b of the linkage member 32 extends through an opening 14a in the shroud 14 and through an opening 16c in the deck 16, as shown in FIG. 3. The linkage member 32 has fixedly secured thereto a height indicator 33. The height indicator is shown disposed closely adjacent where the front wheel 22a would be mounted, but it will be appreciated that its placement could just as well be at almost any point along the length of the linkage member 32. It will also be appreciated that the height indicator 33 could just as well be placed on any other moving component part of the adjustment mechanism 12, such as the index plate 30 or a bracket 48 (to be discussed) associated with a front axle 44 (also to be discussed). In these instances, any indicia also used to help visually indicate the present deck 16 height will preferably be located closely adjacent the height indicator 33 on a stationary component of the lawn mower 10. 
     With further reference to FIG. 2, the shroud 14 also preferably includes some form of indicia 35, such as a label, disposed on a portion thereof for cooperating with the indicator 33 to provide an immediate visual indication as to the height that a cutting blade (not shown) housed underneath the deck 16 is presently set at for any given deck height. As will be appreciated, the indicia 35 could be in the form of inches, millimeters, etc. 
     With specific reference to FIG. 3, the entire construction of the rear axle 40 can be seen. Since the rear axle 40 is a single-piece component which extends across the entire width of the deck 16 and supports both of the rear wheels 20a and 20b, rotational movement of the offset portion 38 allows the vertical height of both rear wheels 20a and 20b to be simultaneously varied relative to the deck 16, in addition to varying the position of the index plate 30 relative to the deck 16. 
     With further brief reference to FIG. 2, it will be appreciated that an offset front axle 44 is provided for supporting the two front wheels 22a and 22b. Fixedly secured (as by welding) to an offset portion 46 of the front axle 44 is a bracket 48 similar in shape to the index plate 30. The second end 32b of the linkage member 32 is pivotally coupled via an aperture 32e to a pivotal mounting portion 48a of the bracket 48 such that rotational movement of the index plate 30 causes a corresponding rotational movement of the offset portion 46 of the offset front axle 44. This, in turn, causes the vertical position of both front wheels 22a and 22b, relative to the deck 16, to be changed in accordance with the degree of vertical adjustment provided at the rear wheels 20a and 20b. As shown in FIG. 3, it will be appreciated that the construction of the offset front axle 44 is similar to the offset rear axle 38 in order to provide relatively consistent height adjustment from front to back of the mower 10 throughout the adjustment range. 
     With brief reference to FIGS. 8 and 9, to aid in lifting the deck 16 during an adjustment, an elongated coil spring 49 is preferably included. The spring 49 is secured to the linkage member 32 through an aperture 32c, and, via an aperture 24b, to a tab portion 24a (FIG. 3) of one handle bar of the handle member 24. The biasing force of the spring 49, which is under constant tension, assists in urging the linkage member 32 to the left in the drawings of FIGS. 3, 8 and 9, and therefore rotating the index plate 30 counter-clockwise to thus help lift the deck 16 when the actuating member 28 is lifted to its disengaged position. This operation will be described in greater detail in connection with FIG. 8 and the operation of the mechanism 12. 
     With continued reference to FIGS. 3, 4, 5 and 7, the engaging member 34 is disposed for sliding movement within a channel 50 (FIG. 3), integrally formed in a sidewall portion 52 of the deck 16. The engaging member 34 includes a &#34;pawl&#34; 54 formed from a punched out section 56 thereof. The pawl 54 further includes a tooth 54a protruding laterally therefrom, as best seen in FIG. 4. The pawl 54 is positioned such that it is disposed closely adjacent a plurality of teeth 30a of the index plate 30 so that when the engaging member 34 is urged slidably into its lowermost position, the tooth 54a is in interlocking engagement between an adjacent pair of teeth 30a to thus maintain the index plate 30 stationary. The teeth 30a define a plurality of predetermined cutting blade height positions. A slot 54b is also provided to allow a lower end portion 54c to fit over a portion of the offset rear axle 40, to thus provide horizontal stability of the engaging member 34, while allowing vertical sliding movement. 
     With specific reference to FIG. 5, the coupling of the engaging member 34 and the actuating member 28 can be seen, together with the construction of the palm rest 36 relative to the deck 16. The palm rest 36 includes an upper surface portion 36a against which a palm of a hand is placed when the actuating member 28 is to be engaged. The palm rest 36 includes a generally hollow bottom portion 58 from which a pair of integrally formed outward locating posts 60 and a centrally disposed boss portion 62 project. A mounting portion 64 projects generally laterally of the locating posts 60 and includes a semicircular cut-out 66 and a pair of somewhat flexible arm members 67. The palm rest 36 is integrally formed as a single-piece component, and preferably from a high-strength plastic. 
     With continued reference to FIG. 5, the actuating member 28 includes a pair of tubular locating posts 68 positioned to slidably accept the locating posts 60, and a central mounting post 70 positioned between the tubular locating posts 68. A biasing member in the form of a coil spring 72 is positioned between the palm rest 36 and the actuating member 28 such that an upper end 72a is held within the central boss portion 62, and a lower end portion 72b fits over an upper portion 70a of the central mounting post 70. In this manner, the spring 72 is held captively under compression between the palm rest 36 and the actuating member 28 when the height adjustment mechanism 12 is assembled, and provides a biasing force against the actuating member 28 to hold the pawl 54 in a normally downwardly biased position in engagement with the index plate 30. 
     With further reference to FIGS. 4, 5 and 7, the engaging member 34 includes a cut-out portion 74 at an upper end portion 76 thereof. When assembling the actuating member 28 and the engaging member 34, the upper end portion 76 is slidably inserted into a main body portion 78 of the actuating member 28. With specific reference to FIG. 7, the actuating member 28 includes a tapered rib portion 80 projecting from a locking arm member 82 which is integrally formed with the main body portion 78 of the actuating member 28. The tapered rib portion 80 is shaped so as to lockably engage the cut-out portion 74 as the upper end portion 76 of the engaging member 34 is slidably inserted into the main body portion 78 of the actuating member 28. 
     With specific reference to FIG. 5, to further help maintain the coupling of the engaging member 34 with the actuating member 28, a pair of lip members 84 are also preferably integrally formed with the main body portion 78 so as to form a channel 86 into which the upper end portion 76 of the engaging member 34 is inserted. Optionally, an aperture 88 is provided in the upper portion 76 of the engaging member 34 together with a slot 90 (FIG. 4) in the main body portion 78 of the actuating member 28. A threaded fastener may be inserted through the slot 90 and the aperture 88 to even more securely hold these two component parts together. 
     With specific reference to FIG. 6, the mounting portion 64 of the palm rest 36 is coupled to a portion 92 of the tubular handle member 24 via a conventional threaded fastener 94 (or other form of fastener), shown in phantom, which extends through apertures (not shown) in the tubular handle member, through an aperture 96 in the mounting portion 64, and through an aperture 97 in a handle support portion 99 of the deck 16. A conventional threaded nut 98 or other fastener may be used together with the threaded fastener 94 to securely hold the palm rest 36 to the portion 92 of the handle member 24. The arm portions 67 may be used to help engage one or more electrical cables running parallel to the length of the tubular handle member 24. 
     Referring now to FIGS. 2, 3 and 8, to adjust the deck height of the lawn mower 10 to a higher position of height relative to the ground surface 18, the operator places his/her palm on the palm rest 36, places the fingers of the same hand over the gripping portion 28a of the actuating member 28 and lifts up on the actuating member 28 against the biasing force of the spring 72, thus causing the pawl 54 to be slidably released from engagement with the teeth 30a of the index plate 30. While the engaging member 34 and the pawl 54 are held in an upper, released position by the operator, the operator may lift upwardly on the deck 16 via the actuating member 28 with the same hand. The biasing force provided by the spring 49 provides an assist to the operator in lifting the weight of the deck 16. As the operator lifts upwardly, the index plate 30 is urged rotatably in a counter-clockwise direction, as viewed in FIG. 8, by the rotation of the offset portion 38 of the offset rear axle 40. Simultaneously, the linkage member 32 urges the bracket 48 counter-clockwise a corresponding degree which, in turn, causes the offset portion 46 of the offset front axle 44 to be rotated by a corresponding degree. In this manner, the axis of rotation of the rear wheels 20a and 20b and the axis of rotation of the front wheels 22a and 22b are lowered relative to a lower edge surface 16b of the deck 16. Put differently, the lower edge surface 16b of the deck 16, and thus a cutting blade 17 housed within the deck 16, are raised relative to the axis of rotation of all four wheels 20a, 20b and 22a, 22b of the lawn mower 10. The orientation of the wheels 20a, 20b and 22a, 22b, the index plate 30, the engaging member 34, the actuating member 28 and the linkage member 32 are shown in FIG. 8 when the deck 16 is in its maximum height position relative to the ground surface 18. 
     To maintain the deck 16 at the position shown in FIG. 8, the operator merely releases the actuating member 28 once the deck is positioned at the desired height relative to the ground surface 18. Releasing the actuating member 28 causes the actuating member 28, and thus the pawl 54, to be urged downwardly by the spring 72 to engage between the right-most pair of teeth 30a of the index plate 30, as viewed in FIG. 8. The index plate 30, and thus the axis of rotation of all four wheels 20a, 20b and 22a, 22b will be maintained at this desired position until the operator readjusts the height of the deck 16. 
     With brief reference to FIG. 9, the orientation of the above mentioned components and the position of the deck 16 relative to the ground surface 18 is shown with the deck 16 height adjusted to its lower most position relative to the ground surface 18. This is achieved by gently urging the palm of the hand positioned on palm rest 36 downwardly, while holding the actuating member 28 engaged with the fingers of the same hand. In the lower most position, the index plate 30 is held in its clockwise-most position by engagement of the pawl 54 between the left-most pair of teeth 30a of the index plate 30, after the operator releases the actuating member 28. 
     With brief reference again to FIGS. 3, 4 and 8, the index plate 30, in the preferred embodiment, includes an upper shoulder portion 100 defining a first axle position and a lower shoulder portion 102 defining a second axle position. In the figures, the offset portion 38 of the offset rear axle 40 is shown fixedly secured to the lower shoulder portion 102, which places the rear wheels 20a, 20b in the second position relative to the deck 16, and thus positions the deck 16 in a second position relative to the ground surface 18. When the offset portion 38 is secured fixedly to the first shoulder portion 100, the rear wheels 20a,20b are supported in the first position relative to the deck 16 which positions the deck 16 in a first position relative to the ground surface 18 which is closer to the ground surface for any given position of the index plate 30 than it would be when the offset portion 38 is secured to the second shoulder portion 102. Accordingly, a single index plate 30 may be used with wheels of differing diameters provided it is known in advance of assembly of the lawn mower 10 the diameter of the rear wheels 20a, 20b to be employed. As an example, when seven inch diameter rear wheels 20a, 20b are used, the offset rear axle 38 may be fixedly secured to the upper shoulder portion 100. When a six inch diameter wheel is to be used, the offset rear axle 38 may be fixedly secured to the lower shoulder portion 102, thus allowing a similar degree of minimum ground clearance to be provided as when the larger diameter rear wheels 20a, 20b are used. It will be appreciated by those of ordinary skill in the art that this feature represents a significant manufacturing advantage in that only a single index plate 30 need be used for the lawn mower 10, regardless if the lawn mower 10 is to be assembled with rear wheels 20a, 20b having diameters which may vary from between two predetermined, desirable wheel diameters. This further obviates the need to modify the linkage member 32 and the deck height indicator 33 to ensure consistent deck height indications when rear wheels 20a, 20b having differing diameters are employed. 
     From the above, it will be appreciated that the height adjustment mechanism 12 of the lawn mower 10 represents a significant improvement over prior designs by requiring fewer component parts, generally less complicated construction and generally greater ease of operation. The deck height adjustment mechanism 12 of the present invention further does not add appreciably to the overall cost of the lawn mower 10, nor does it tangibly increase the overall outer dimensions of the lawn mower 10 or its overall weight. Because of the simplified construction of the mechanism 12, reliability of operation is also improved. 
     Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present invention can be implemented in a variety of forms. Therefore, while this invention has been described in connection with particular examples thereof, the true scope of the invention should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, specification and following claims.