Wheel locking mechanism

Abstract: A lawn mower comprising a deck (2) mounted on at least one castor wheel assembly (4) characterised in that there is provided a locking mechanism (29, 34) capable of holding the or at least one castor wheel assembly (4) in the direction it is travelling when the locking mechanism (29, 34) is operated. The locking mechanism (29, 34) comprises a braking surface (29) and a brake band which is movable between a first position where the braking surface (29) is rotatable relative to the braking element (34) to allow the castor wheel assembly to swivel about a substantially vertical axis and a second position where the brake band engages and holds the braking surface (29). The locking mechanism is manually operable by an operator standing behind the lawn mower and holding the handle thereof.

Description: The present invention relates to lawn mowers and in particular to lawn mowers mounted on castor wheels. A conventional lawn mower comprises a cutting deck mounted on four wheels. A motor, which can be either an electric motor or an internal combustion engine, is mounted on the cutting deck and which rotatingly drives a cutting blade mounted below the cutting deck about a substantially vertical axis of rotation. A handle is attached to the rear of the cutting deck to enable an operator to manoeuvre the mower. Often a grass collection box is also attached to the rear of the cutting deck to collect the grass cuttings generated by the mower when in use. In common mower designs the wheels have a direction of travel which is fixed in a forward and rearward direction. Thus the mower is able to be pushed or pulled in a forward or rearward direction. This is particularly desirable when an operator wishes to operate the mower in straight lines, for instance to generate stripes on a lawn. However, such a design of mower is unable to change direction easily. In order for the direction of travel to be altered, the operator must raise either the front or rear wheels above the ground and rotate the mower to the new direction of travel before then lowering the wheels in order to re-engage the ground. This requires a substantial effort on the part of the operator. Furthermore, the direction of travel of the mower whilst cutting the grass still remains in a forward/rearward direction which may not be desirable in certain circumstances. One known method of overcoming these problems is to mount the mower on castor wheels which are capable of swivelling freely through 360°. This enables the lawn mower to be manoeuvred in any direction, in a forward/rearward direction, sideways, diagonally, rotationally etc. This makes the lawn mower highly manoeuvrable. Furthermore, it obviates the need for the operator to raise the wheels off the ground when he wishes to change direction. However, such manoeuvrability may not be desirable in certain circumstances. For instance, if an operator is using the mower on an inclined surface such as the side of a hill or bank and the operator wishes to traverse along the side of the hill or bank in a straight line with the mower, the operator would have to use considerable effort to maintain the direction of travel of the mower in a straight line and to prevent the mower from sliding sideways down the hill or bank. It is therefore desirable to have a lawn mower which is able to be changed between two modes of operation, a first mode where the mower is able to move in any direction both linearly and rotationally (i.e. the wheels can freely swivel to any direction of travel), and a second mode where the mower is only able to move in one fixed direction of travel. US 5 653 096 discloses such a mower. The cutting deck of the mower is mounted on three castor wheels. In its first mode of operation, the castor wheels are able to swivel freely, thereby enabling the mower to be manoeuvred in any direction. In its second mode of operation, the direction of travel of the two rear castor wheels of the mower can be locked in a forward/reverse direction or sideways direction. When the direction of travel of the two rear wheels is fixed, the mower is only able to travel in either a forward/reverse direction or a sideways direction. The locking mechanism disclosed in US 5 653 096 for each rear castor wheel comprises a locking pin mounted on the cutting deck close to the castor wheel. Corresponding holes, which are capable of receiving the locking pin, are formed in the castor wheel. In the first mode of operation the pin is held away from the holes. The castor wheel is able to freely swivel through 360°. However, when one of the holes in the castor wheel is aligned with the locking pin and the locking pin is moved such that it engages with the hole, the castor wheel is prevented from swivelling, its direction of travel being fixed. The direction of travel of the castor wheel is determined by the position of the hole on the castor wheel. However, the locking mechanism disclosed in US 5 653 096 suffers from a number of problems. Firstly, and most importantly, the direction of travel of the mower when in the second mode of operation is fixed to two pre-determined directions, namely sideways and forward/reverse. In certain situations this is undesirable. The user may wish to push the lawn mower diagonally or at an angle and therefore would like to fix the direction of travel of the wheels in these particular directions. Furthermore, the operator may wish to fix the wheels in an orientation which enables the mower to move in an arc, so that it cuts the grass in a uniform manner around an object. This is not possible with the wheel alignment mechanism disclosed in US 5 653 096. Secondly, the operator has to bend down in order to grasp the pin in order to either lock or unlock each of the castor wheels individually, which may cause discomforture for an operator who suffers from back problems. Furthermore, the operator is required to place his hands close to the cutting blade whilst locking or unlocking the castor wheel, thus putting the operator at unnecessary risk. Thirdly, as the direction of travel of the castor wheel must be fixed with some reasonable accuracy, the diameter of the hole must be similar to that of the pin. However, the castor wheels and hence the holes are located close to the zone swept out by the cutting blade when in use and, as such, would encounter grass cuttings and other debris generated by the cutting action of the mower. When the pins are held away from the holes to allow the wheels to freely swivel, that the holes are filled up with grass cuttings and/or debris, thus preventing the pins from being inserted into the holes. In such circumstances an operator may be likely to try and force the pin into the hole, which could be dangerous, particularly in view of the close proximity of the cutting blade to the castor wheel. Australian Patent Publication No. 2,487,497 discloses a lawn mower according to the characterising portion of claim 1. According to the present invention there is provided a lawn mower comprising a deck mounted on at least one castor wheel assembly wherein there is provided a locking mechanism capable of holding the or at least one castor wheel assembly in the direction it was travelling when the braking mechanism is operated; the locking mechanism comprising two parts, a first part mounted on the castor wheel assembly, a second part mounted on the deck, a braking surface formed on one part and a braking element mounted on the other part, the braking element being movable between a first position where the braking surface is rotatable relative to the braking element to allow the castor wheel assembly to swivel about a substantially vertical axis and a second position where the braking element engages and holds the braking surface, characterised in that the braking element can comprise a band that extends around at least part of the braking surface. By constructing the lawn mower in such a manner, the lawn mower has the benefits that firstly it is able to operate in two different modes, namely a first mode where it is highly manoeuvrable and a second mode where the direction of travel of castor wheels is fixed, secondly, the mower can easily be changed between the two modes of operation and thirdly, when the mower is used in the second mode of operation, the direction of travel of the castor wheels can be locked in any desired angular position. The locking mechanism holds each castor wheel assembly and prevent it from swivelling about a substantially vertical axis. The cutting deck can be mounted on four castor wheel assemblies at least two of which are provided with a locking mechanism. Ideally the castor wheel assembly comprises a sleeve which is rotatably mounted on a rod attached to the deck, the braking surface being formed around the sleeve. The band can be attached at one end to the deck and which wraps around the sleeve in a corresponding manner to the braking surface This provides a simple construction of castor wheel assembly which is capable of interacting with the brake band in a reliable manner. The locking mechanism may be manually operable by an operator standing behind the lawn mower and holding the handle thereof. The brake band can be moved between its first and second position by a mechanical link between the handle and the locking mechanism. Such a link could comprise a bowden cable. Where a bowden cable is used, preferably, the deck is mounted on at least two castor wheel assemblies, both castor wheel assemblies having a locking mechanism wherein the cable of the bowden cable is attached to one braking mechanism, the sleeve of the bowden cable is attached to the other locking mechanism, the two locking mechanisms being configured so that operation of the bowden cable operates the two locking mechanisms in unison. This enables the locking mechanisms for two castor wheel assemblies to be locked simultaneously. As an alternative to a mechanical link, a hydraulic mechanism can be used. A specific embodiment of the invention will now be described with reference to the accompanying drawing of which:- Figure 1 shows a side view of a lawn mower according to the present invention; Figure 2 shows a perspective view of the central mounts of the castor wheel according to the first embodiment of the present invention; Figure 3A and 3B show the band brake mechanism from above in the "OFF" and "ON" position respectively; and Referring to Figure 1, the lawn mower comprises a cutting deck (2) mounted on four castor wheels (4) located near to the four corners of the deck (2), an electric motor (not shown) mounted on the deck (2) and a hood (4) which encloses the motor. The motor rotatingly drives a cutting blade (not shown) mounted below the deck (2) on the output drive spindle of the motor about a substantially vertical axis in known fashion (8). A handle is attached to the rear of the deck (2). Located on the handle (8) is a lever (10) which projects from a lever box (12) attached to the handle (8) and which encloses an electric switch (not shown). An electric cable (14) runs between the lever box (12) and the motor. A second cable (18) runs from the lever box (12) to a plug (16) for attachment to a mains electricity power supply. Depression of the lever (10) activates the motor when the plug (16) is attached to a power supply. Each castor wheel (4) comprises two wheels (20) of equal dimensions which are mounted on a central mount (22) (as shown in Figure 2) adjacent to each other and which have the same axis of rotation. The central mount (22) comprises a vertical sleeve (24), a vertical triangular flange (26) attached to the side of the base of the sleeve (24) and two rods (28) of circular cross section which project perpendicularly from the sides of the triangular flange (26) in opposite directions. The sleeve (24) forms a bore (30) of circular cross section which is sealed at the base end. The two horizontal rods (28) form axles upon which the two wheels (20) are mounted. Each of the wheels (20) are retained upon the axles (28) by means of a clip (not shown) and are able to freely rotate about the axles (28). A collar (29) is formed around the top end of the sleeve (24). The central mount (22) is formed from a low friction plastic in a one piece construction. In the first embodiment of the present invention, each castor wheel (4) is mounted on a metal rod (32) which is rigidly attached to and projects vertically downwards from the underside of the cutting deck (2) (the central mount (22) is best seen in Figure 1). Referring to Figure 2 the metal rod (32) has a circular cross section having a diameter which is slightly less than that of the bore (30) of the central mounts (22), the central mount (22) being able to freely rotate about the metal rod (32). A clip (not shown) holds the castor wheel (4) onto the metal rod (32) and prevents it from sliding off the rod (32), whilst allowing the central mount (22) to freely rotate about the metal rod (32). Band brake mechanisms are attached to the cutting deck (2) in close proximity to each of the rear castor wheels (4). The band (34) of each brake encircles the outer circumference of the collar (29) (as best shown in Figures 3A and 3B). One end (36, 38) is rigidly attached to the cutting deck (2). The other end (40, 42) is attached to part of a bowden cable (44). The brakes operate as a pair. The free end (40) of a band (34) of one of the brakes is attached to the cable (46) which runs within the bowden cable (44). The free end (42) of the band (35) of the other brake is attached to the sleeve (48) of the bowden cable (44). The sleeve (58) of the bowden cable (44) is attached to the underside of the deck (2) by clips (not shown) in such a manner that it is able to axially slide in relation to the underside of the deck (2). The other end of the bowden cable (44) (as best shown in Figure 1) is attached to a lever (50) mounted on the handle (8) of the lawn mower. Pivotal movement of the lever (50) draws the cable (46) into the sleeve (48). Figure 3A shows the bands (34, 35) of the band brakes when no force is being applied to the bands (34, 35) by the bowden cable (44). Figure 3B shows the bands (34, 35) of the band brakes wrapped tightly around the collars (29) of the central mounts (22), frictionally holding the central mounts thus preventing them from rotating. The free end (40, 42) of the two bands (34, 35) in each pair face towards each other so that, when the cable (46) is drawn into the sleeve (48) of the bowden cable (44) by the pivotal movement of the lever (50), the two free ends (40, 42) are pulled towards each other causing them to tighten around the collars (29) of the castor wheels (4) (as shown in Figure 3B). When the band (34, 35) are tightly wrapped around the collars (29), the collars (29) and thus the castor wheels are prevented from rotating about the metal rods (32), hence locking the direction of travel of the castor wheels. The bands (34, 35) are held in a locked position by the operator holding the lever (50) in a pivotal position. The brakes are released by the operator releasing the lever (50) allowing the cable (46) to slide out of the sleeve (48) due to the biasing force of the two bands (34, 36) of the brakes. The fixed direction of travel of the castor wheels is locked in the angular orientation that the wheel (4) was travelling when the brakes were applied. In use the band brakes are biased towards the first position by the bands (34, 35) (as shown in Figure 3A). The rear wheels are, therefore, able to freely rotate about the rods (32). An operator can manoeuvre the lawn mower in any direction. However, when the operator wishes to fix the direction of travel of the mower, he pulls the lever (50) which, in turn, pulls the cable (46) into the sleeve (48) of the bowden cable (42). The relative movement of the cable (46) and sleeve (48) of the bowden cable (44) pulls the two free ends (40, 42) of the bands (34, 35) towards each other moving the two bands (34, 35) from their first outer positions (as shown in Figure 3A) towards their second inner positions (as shown in Figure 3B), tightly gripping the collar (29) of the castor wheels (4). The collars (29) and thus the castor wheels (4) are prevented from swivelling. The operator ensures that the fixed direction of travel is that desired by moving the orientation of the castor wheels (4) whilst they are able to freely swivel, to the desired angle and then locks the wheels (4). The operator can achieve this by moving the mower in the desired direction of travel with the wheels able to freely swivel and then locking the direction of travel of wheels (4). Once the wheels (4) are locked, the operator would continue to hold the lever (50) maintaining the fixed direction of travel of the wheels (4). When the operator wishes the wheels to rotate freely, he releases the lever, allows the bands (34, 35) to release the collars (29) under the biasing force of the bands (34, 35) of the brakes.

Claims: A lawn mower comprising a deck (2) mounted on at least one castor wheel assembly (4) wherein there is provided a locking mechanism (29, 34) capable of holding the or at least one castor wheel assembly (4) in the direction it is travelling when the locking mechanism (29, 34) is operated; the locking mechanism (29, 34) comprising two parts, a first part mounted on the castor wheel assembly (4), a second part mounted on the deck (2), a braking surface (29) formed on one part and a braking element (34) mounted on the other part, the braking element (34) being movable between a first position where the braking surface (29) is rotatable relative to the braking element (34) to allow the castor wheel assembly to swivel about a substantially vertical axis and a second position where the braking element (34) engages and holds the braking surface (29), characterised in that the braking element (34) comprises a band that extends around at least one part of the braking surface (29). A lawn mower as claimed in Claim 1 wherein the cutting deck is mounted on four castor wheel assemblies at least two of which are provided with a locking mechanism. A lawn mower as claimed in either of Claims 1 or 2 wherein the castor wheel assembly comprises a sleeve (24) which is rotatably mounted on a rod (32) attached to the deck (2), the braking surface (29) being formed around the sleeve. A lawn mower as claimed in any one of the previous claims wherein the locking mechanism is manually operable by an operator standing behind the lawn mower and holding the handle thereof. A lawn mower as claimed in any one of the previous claims wherein the brake band is moved between the first and second position by a mechanical link (44) between the locking mechanism and the handle (8). A lawn mower as claimed in Claim 5 wherein the mechanical link comprises a bowden cable (44). A lawn mower as claimed in Claim 6 wherein the deck (2) is mounted on at least a pair of castor wheel assemblies (4), both castor wheel assemblies of the pair (4) each having a locking mechanism (29, 34) wherein the cable (46) of the bowden cable (44) is attached to one of the locking mechanisms, the sleeve of the bowden cable is attached to the other locking mechanism (29, 35), the two locking mechanisms (29, 34; 29, 35) being configured so that operation of the bowden cable (44) operates the two locking mechanisms (29, 34; 29, 35) in unison.

Inventors: THOMAS ROGER, THOMAS, ROGER
Applicants: BLACK & DECKER INC, BLACK & DECKER INC.
Application year: 1999
Main classification: A01D75
IPC codes: A01D75, B60B33