Harvesters – Motorized harvester – Having motor on ground-supported carrier
Reexamination Certificate
1999-06-16
2001-04-10
Will, Thomas B. (Department: 3671)
Harvesters
Motorized harvester
Having motor on ground-supported carrier
C056S016700
Reexamination Certificate
active
06212863
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to lawn mowers and, in particular, to lawn mowers mounted on castor wheels.
Household lawn mowers comprise a cutting deck upon which is mounted a motor. The motor can be either an electric motor powered by either a mains electricity supply or a battery or an internal combustion engine. The motor rotatingly drives a cutting blade mounted below the cutting deck about a substantially vertical axis, which cuts the grass beneath the deck as it rotates. The cutting deck is commonly mounted on wheels or rollers, having a fixed direction of travel so that the lawn mower moves over the lawn in a forward and reverse direction.
It is desirable to have the height of the cutting blade adjustable in relation to the surface of the lawn which allows the grass to be cut to differing heights. One common way of achieving this is by having the cutting deck of the lawn mower mounted on the wheels or rollers in such a manner that the height of the deck, and hence the height of the cutting blade, is adjustable relative to the wheels.
Such mechanisms include mounting the axles of the wheels or rollers on the ends of levers which are pivotally mounted onto the deck and which are capable of being releasably locked into a plurality of angular positions. The height of the cutting deck in relation to the wheels or rollers is dependent upon the angle of pivot of the levers. Interconnecting bars can be added between the levers to ensure that the height adjustment of interconnected wheels is uniform.
In order to increase the maneuverability of the mower, it is known to mount the cutting deck of a lawn mower on castor wheels which can freely swivel through 360° instead of wheels or rollers which have a predetermined fixed direction of travel. This allows the cutting deck of the mower to travel in any direction, both linearly and rotationally.
It is desirable to mount the cutting deck on the castor wheels in such a manner that the height of the cutting deck in relation to the surface of the lawn is adjustable in a similar fashion to that of mower having the cutting deck mounted on wheels which have a fixed direction of travel. However, the mechanisms which are commonly used to mount standard wheels so that they are adjustable in height cannot be utilized to mount castor wheels in a similar manner. This is due to the requirement of having to maintain the axes of swivel of the castor wheels vertical regardless of the height setting of the castor wheels in relation to the cutting deck.
AU 24874/97 discloses a lawn mower having a cutting deck mounted on castor wheels. The height of the deck is adjustable relative the castor wheels. The height adjustment mechanism comprises two parallel levers which are both pivotally attached to the deck at one end and which are also both pivotally attached to the stem of the castor wheel at the other end. The two levers form a parallelogram with the stem of the castor wheel and the deck such that the stem and thus the axis of swivel of the castor wheel remains vertical regardless of the angular position of the two levers. A rotatable threaded shaft is provided for adjusting and maintaining the angular position of the two levers.
However, the design of the height adjustment mechanism disclosed in AU 24874/97 is complicated and requires a substantial amount of space to provide a sufficiently large region through which the castor wheel can sweep to allow it to travel through its full range of pivot.
SUMMARY OF THE INVENTION
According to the first aspect of the present invention there is provided a lawn mower comprising a cutting deck mounted on a castor wheel assembly via a height adjustment mechanism. The height adjustment mechanism comprises a two part system having a first part mounted on the cutting deck and a second part that is mounted on the castor wheel assembly and that is slidably disposed on the first part. The height adjustment mechanism further includes a locking mechanism for releasably locking the first part and the second parts of the height adjustment in any of a plurality of positions.
The second part can be slidably disposed on the first part by means mounted on one part which sliding engages corresponding means mounted on the other part. Such sliding mechanisms can include rails or grooves or tracks, either on the cutting deck or castor wheel assembly and along which the castor wheel or cutting deck respectively slides. Such a design can provide a very simple and robust construction of sliding mechanism which requires little space.
The relative sliding movement between the first and second part can be vertical. This is able to produce the most compact design.
The height adjustment can comprise a sleeve mounted on one part and which mounted upon and axially slidable along a rod mounted on the other part.
When the height adjustment mechanism comprises a rod and sleeve the locking mechanism ideally is capable of releasably locking the sleeve in a plurality of axial positions along the rod whilst allowing the sleeve to freely rotate about the rod.
This can provide a simple design of sliding mechanism. Furthermore, when the rod is vertical, as the sleeve is capable of rotating about the rod in addition to sliding along the rod, the rod and sleeve can provide the mechanism by which the castor wheel is able to swivel, in addition to providing a sliding mechanism. This can simplify the design as it obviates the need for the castor wheel to have separate means which enable it to swivel.
When a single rod is used in conjunction with a sleeve, it is desirable that there is a substantial overlap between the vertical rod and the sleeve throughout the full range of axial positions of the sleeve along the rod. When the lawn mower is moved across the ground, substantial forces can be exerted on the castor wheel due to the inconsistent terrain. As such, substantial forces can be transmitted between the sleeve and the rod particularly in a direction perpendicular to the longitudinal axis of the rod. Therefore, sufficient overlap can ensure that the sleeve or rod do not break or bend.
The locking mechanism can comprise an arrangement for converting rotational motion to translational motion. One such arrangement comprises a rotatable cam mounted on one part which interacts with a cam follower mounted on the other part and which is configured so that the relative positions of the two parts is dependent on the angular position of the cam.
The use of a cam mechanism within the height adjustment mechanism can produce a simple yet compact design of locking mechanism which is cheap and simple to manufacture, yet is easy to operate.
The use of a cam can provide a mechanism by which both the axial position of the sleeve is locked and by which the sleeve is moved along the rod.
Preferably, the cam is releasably lockable in a plurality of angular positions. By making the cam releasably lockable, the cam can be used to maintain the height of the cutting deck above the castor wheel, thus avoiding the need for additional mechanisms to maintain the height of the cutting deck.
The cam can either be a lever or a snail cam.
One particular design of height adjustment mechanism comprises a cam having an elongate slot and a cam follower having at least one groove which engages with and is capable of sliding along the edge of the elongate slot and which is configured so that rotational movement of the cam results in a sliding movement of the cam follower along the elongate slot. This provides a simple method of attaching the cam to the cam follower whilst allowing the cam follower to freely slide along the cam. Ideally, the cam follower comprises a single 360° groove which allows the cam follower to freely rotate within the elongate slot.
An alternative design of locking mechanism comprises a rotatable crank mounted on one part which interacts with the other part and which is configured so that the relative positions of the two parts is dependent on the angular position of the crank.
The use of a crank instead of a cam provides an alternative wa
Black & Decker Inc.
Harness & Dickey & Pierce P.L.C.
Mammen Nathan
Will Thomas B.
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