Interconnection mechanism

Abstract: A lawn mower comprising a cutting deck (2), which is mounted on at least two wheel assemblies (4), each wheel assembly having a height adjustment mechanism comprising a pivoting mechanism (22) and which is configured so that the height of the cutting deck (2) above the wheel assembly (4) is dependent on the angular position of the pivoting mechanism (22), the axes of pivot of the pivoting mechanisms (22) being substantially parallel, characterised in that the pivoting mechanisms (22) are interconnected by an interconnecting bar (38) so that pivotal movement of one pivoting mechanism (22) in one direction about its axis of pivot results in a pivotal movement of another pivoting mechanism (22) about its axis of pivot in the opposite direction. Each of the pivoting mechanisms raise the height of the deck (2) by substantially equal mounts when pivoted through any part of their full range of pivotal movement.

Description: The present invention relates to lawn mowers. 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. The cutting blade cuts the grass beneath the deck as it rotates. The cutting deck is commonly mounted on wheels or rollers. The wheels can either have a fixed direction of travel so that the lawn mower moves over the lawn in a forward and reverse direction, or can be castor wheels which are able to freely swivel so that the mower can travel over the lawn in any direction of travel. It is desirable to have the height of the cutting blade adjustable in relation to the surface of the lawn. This 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 levers pivot in unison so that the height adjustment of the wheels is uniform. In one type of mower, the forward and rear axles are mounted on the end levers which are pivotally mounted on the cutting deck which are parallel and are interconnected by a bar so that they pivot in unison. However, the forward rear axles pivot about their axes in the same direction. US 4,835,952 shows a mower having a typical design of height adjusting mechanism. In US 4,835,952 the front axle is mounted on to arms of two bell cams which are pivotally mounted onto the body of the mower at their apexes. The second arm of the bell cams project in a generally upward direction. The rear axle is mounted in a similar fashion. Two interconnecting bars interconnect between the second arms of the front and rear bell cams. As the front bell cams pivot, the rear bell cams also pivot in the same direction thus lowering or highering the body of the mower uniformly. However, such designs are bulky taking up valuable space on the mower because it is necessary for the interconnecting bars to project beyond the wheels. In addition, the length of the interconnecting bars has to be approximately the same as the distance between the front and rear wheels if the rate which the height of the deck rises above each wheel is to be constant. US 3269100 discloses a lawn mower having two wheel assemblies with height adjustment mechanisms and which comprises the features of the pre-characterising part of claim 1. The height adjustment mechanism in US 3269100 comprises an interconnecting bar which interconnects between the front and rear wheel assemblies so that the height of mower above both wheel assemblies can be adjusted simultaneously. However, the length of the interconnecting bar is at least equal to the length of the distance between the axes of pivot of the two pivoting mechanisms. Accordingly, there is provided a lawn mower comprising cutting deck which is mounted on at least two wheel assemblies, each wheel assembly having a height adjustment mechanism comprising a pivoting mechanism and which is configured so that the height of the cutting deck above the wheel assembly is dependent on the angular position of the pivoting mechanism, the axis of pivot of the two pivoting mechanisms being substantially parallel wherein the pivoting mechanisms are interconnected by an interconnecting bar, one pivoting mechanism being pivotally connected at a point away from its axis of pivot to an end of the interconnecting bar, the other pivoting mechanism being pivotally connected at a point away from its axis of pivot to the other end of the interconnecting bar so that the pivotal movement of one pivoting mechanism in one direction about its axis of pivot results in a pivotal movement of the other pivoting mechanism about its axis of pivot in the opposite direction characterised in that the length of the interconnecting bar is less than the distance between the axes of pivot of the pivoting mechanisms. By constructing the height adjustment mechanisms in this fashion, it can provide a compact construction. It can also enable the height adjustment mechanism to be located between the wheel assemblies thus reducing the amount of mechanical linkage required. Furthermore, this provides the advantage that the points of articulation at the ends of any interconnecting bar joining the pivoting mechanisms can lie between the pivoting mechanisms while allowing substantially equal vertical movement of the different height adjustment mechanisms. Preferably, each of the pivoting mechanisms raise the height of the deck by substantially equal amounts when pivoted through any part of their full range of pivotal movement. In a direction parallel to the plane which passes through both axes of pivot of the pivoting mechanisms the point at which the interconnecting bar pivotally connects to one pivoting mechanism can be located in the opposite direction from the axis of pivot of that pivoting mechanism to the other point where the bar pivotally connects to the other pivoting mechanism from the axis of pivot of the second pivoting mechanism. As such, the interconnecting bar does not have to project pass any of the wheel assemblies when moved through its full range of positions and thus avoids taking up valuable space. Each pivoting mechanism can be pivotally connected to the interconnecting bar via a rod which is rigidly attached to the pivoting mechanism and which preferably projects perpendicularly away from the axis of pivot of the pivoting mechanism. In a direction perpendicular to the plane which passes through both axes of pivot of the pivoting mechanisms, the two rods ideally project in opposite directions to each other and preferably in a direction parallel to a plane which passes through both axes of pivot, towards each other. The pivoting mechanism can comprise at least one lever pivotally mounted on the cutting deck and which interacts with the wheel assembly and ideally the levers are configured to move as a mirror image of each other in the plane located equidistantly between the two axes of pivot of the levers. The levers can project from their axis of pivot in a direction parallel to a plane which passes through both axes of pivot away from each other. This can result in a very compact yet simple height adjustment mechanism, the whole of the interconnecting mechanism being located between the wheel assemblies throughout its full range of movement. A lawn mower according to the present invention will now be described by way of example with reference to the following drawings of which:- Figure 1 shows the cutting deck of a lawn mower mounted on four castor wheels; Figure 2 shows the central mount of a castor wheel; Figure 3A and 3B show the pivotal lever from above and in perspective respectively; Figure 4 shows a vertical section of the height adjustment mechanism, the cutting deck and the caster wheel when the height of the deck is at its maximum; Figure 5 shows a vertical cross section of the height adjustment mechanism, the cutting deck and the castor wheel when the height of the deck is at its minimum; Figure 6 shows a perspective view of the front pair of castor wheels together with corresponding pivotal levers to the ends of an interconnecting rod; and Figures 7A and 7B show the deck of the mower in its lowered and raised positions respectively. Referring to Figure 1, the cutting deck (2) (or frame) of the lawn mower is mounted on four castor wheels (4) located near to the four comers of the deck (2), upon which is mounted an electric motor (not shown) and a hood (not shown) which encloses the motor. The motor rotatingly drives a cutting blade (not shown) mounted below the deck on the output drive spindle of the motor about a substantially vertical axis in known fashion. A grass chute (6) is mounted on top of the cutting deck (2) which directs the grass cuttings from the cutting blade to a grass box (not shown) which attaches to the rear of the cutting deck (2). A height adjustment mechanism is attached to the mower which raises or lowers the height of the cutting deck (2) in relation to the castor wheels (4), hence lifting or lowering the height of the cutting blade in relation to the ground below the mower. Each of the four castor wheels (4) of the mower and its corresponding height adjustment mechanism are constructed and operate in the same manner. As can be seen in Figure 1, each castor wheel (4) comprises two wheels (8) of equal dimensions which are mounted on a central mount (10) adjacent to each other and which have the same axis of rotation. Figure 2 shows the central mount (10) which comprises a vertical sleeve (12), a vertical triangular flange (14) attached to the side of the base of the sleeve (12) and two shafts (16) of circular cross section which project perpendicularly from the sides of the triangular flange (14) in opposite directions. The sleeve (12) forms a bore (18) of circular cross section which is sealed at the base end. The two horizontal shafts (16) form axles upon which the two wheels (8) are mounted. The wheels (8) are retained upon the axles (16) by means of a clip (not shown) and are able to freely rotate about the axles (16). The central mount (10) is formed from a low friction plastic in a one piece construction. Each castor wheel (4) is mounted on a metal rod (20) which is rigidly attached to and projects vertically downwards from the underside of the cutting deck (2) as best shown in the cross sectional drawings shown at Figures 4 and 5. The metal rod (20) has a circular cross section having a diameter which is slightly less than that of the bore (18) of the central mount (10). The metal rod (20) is located within the bore (18) of the central mount (10), the central mount (10) being able to freely slide along and rotate about the metal rod (20). The height adjustment mechanism for each castor wheel (4) comprises a lever (22) which is pivotally mounted on the cutting deck (2) about an axis of pivot (24). Figures 3A and 3B show the pivotal lever (22). The lever is slidably attached to the sleeve (12) of the castor wheel (4) and acts as a cam, sliding the central mount (10) back and forth along the rod (20) as the lever (22) pivots in either direction, as shown in Figures 4 and 5. A collar (26) is formed around the top of the sleeve (12) of each castor wheel (4) (as best shown in Figure 2). A groove (28) is formed around the outer periphery of the collar (26). The pivotal lever (22) is trough shaped as best shown in Figure 3B. An elongate slot (30) is formed along the length of the lever (22) in the base of the trough. At one end of the elongate slot (30), towards the axis of pivot (24) of the lever (22), a large aperture (32) has been formed resulting in an overall key shaped slot. The diameter of the large aperture (32) in the lever (22) is greater than that of the outer circumference of the collar (26). The width of the elongate slot (30) is less than the diameter of the outer circumference of the collar (26) but less than the diameter of the circumference of the groove (28). The sleeve (12) of the central mount (10) of the castor wheel (4) is attached to the lever (22) by passing the top end of the sleeve (12), having the entrance to the bore (18), through the large aperture (32) until the groove (28) formed around the collar (26) becomes aligned with the elongate slot (30) in the lever (22). The thickness of the lever (22) around the edge (34) of the elongate slot (30) is less than the width of the groove (28). The collar (26) is moved along the length of the lever (22), the edge (34) of the elongate slot (30) entering into and sliding through the groove (28). The sleeve (12) is, therefore, able to slide back and forth along the lever (22) within the elongate slot (30). The groove (28) acts as a cam follower, sliding along the edge (34) of the elongate slot (30) as the lever (22) pivots. However, the collar (26) is prevented from being moved perpendicularly to (apart from the slight movement due to the thickness of the edge (34) of the elongate slot (30) being less than the width of the groove (28)) or withdrawn from, and hence detached from the lever (22) whilst the collar (26) is located within the elongate slot (30). When the lawn mower is fully assembled the metal rod (20) is located within the bore (18) formed by the sleeve (12) and the collar (26) is located within the elongate slot (30) in the lever (22), such that the edge (34) of the elongate slot (30) are located within the groove (28) around the collar (26) as best shown in Figures 4 and 5. The height of deck (2) above the castor wheel (4) is at its maximum when the lever (22) is pivoted in downward position, (as best shown in Figure 4). In this position the collar (26) is located at the end of the elongate slot (30) furthest away from the large aperture (32) and the axis of pivot (24) of the lever (22). The rod (20) is of sufficient length that part of the rod (20) still remains within the bore (18) of the central mount (10) when the deck (2) is at its maximum height. Sufficient overlap is provided between the rod (22) and the bore (18) (i.e. the amount of rod (20) still located within the sleeve (12)) when the central mount (10) is extended away from the cutting deck (2) by its maximum amount to provide a strong and sturdy interconnection between the sleeve (12) and the metal rod (20), particularly when the forces are applied to the castor wheel perpendicularly to the vertical axis of swivel. When the height of the cutting deck (2) above the castor (4) is to be reduced, the lever (22) is pivoted in an upward direction, (as best shown in Figure 5). This moves the sleeve (12) and hence the central mount (10) along the rod (20), a greater proportion of the length of the rod (20) being located within the bore (18) of the sleeve (12). As the central mount (10) moves along the rod (20), the groove (28) slides along the sides (34) of the elongate slot (30) in the lever (22). When the height of the cutting deck (2) above the castor is at its minimum (as best shown in Figure 5), the whole of the metal rod (20) is located within the bore (18) of the central mount (10). In this position the collar (26) of the central mount (10) is located towards the end of the elongate slot (30) closest to the large aperture (32). The large aperture (32) is located in such a position that the collar (26) is unable to slide far enough along the elongate slot (30) in order to enter into the large aperture (34) from the elongate slot (30) while the castor wheel (4) is adjusted through its full range of height positions. The height of deck (2) above the castor wheel (4) is fixed by locking the angular position of the lever (22). Because the groove (28) is formed around the full circumference of the collar (26), the central mount (10) and hence the castor wheel (4) is able to freely rotate about the rod (20) whilst the collar (26) is located within the elongate slot (30) within the lever (22). The two levers (22) which are connected to the front two castors (4) on the mower are rigidly attached in parallel to the two ends of a rod (36) perpendicularly to longitudinal axis of the rod (36) as best shown in Figure 6. The rod (36) is mounted onto the underside of the cutting deck (2) by means of resilient clips (not shown) which wrap around and hold the rod (36). The clips are configured to allow the rod (36) to rotate about its longitudinal axis, thus enabling the two levers (22), attached to its ends, to pivot in unison about the longitudinal axis of the interconnecting rod (36). The two levers (22) attached to the two rear castors (4) on the mower are similarly attached to the ends of a second rod (37) which is mounted in parallel to the first rod on the underside of the cutting deck (2) by resilient clips. Thus, the two rear levers (22) pivot in unison about the longitudinal axis of the second rod (37). An interconnecting bar (38) is pivotally attached between one of the levers (22) connected to one of the front castors via a rod (21) rigidly attached to it and one of the levers (22) connected to one of the rear castors via a second rod (23) rigidly attached to the rear lever (2) so that all four levers (22) pivot in unison. The levers (22) attached to the front castor wheels (4) project forward in the opposite direction to the levers (22) attached to the rear castor wheels (4) which project rearward. The first rod (21) points in a general upward direction. The second points in a general downward direction. The interconnecting bar (38) pivotally attaches to the ends of the rods (21, 23) and is arranged so that clockwise rotation of the forward levers (22) results in an anti-clockwise rotation of the rear levers (22). This enables the height of the deck above all four castors to be kept constant, and that the height of the deck is adjusted in uniform manner above the four castor wheels. Figure 7A shows the mower with the cutting deck (2) in its lowest position, Figure 7B shows it in its highest position. A handle (40) extends perpendicularly from one of the interconnecting rods. Pivotal movement of the handle by an operator pivots all four levers and this adjusts the height of the cutting deck and hence the cutting blade above the ground. The height of the mower is maintained at the desired height by locking angular positions of the levers (22) by locking the angular position of the handle (40) in well known manner. It is clear from the description that design of interconnecting bar (38) used in conjunction with the two rods (21, 23) can be utilised on a mower mounted on wheels having their axles attached to the ends of pivotal levers in a similar manner to that described in US 4,835,952 and arranged so that the levers attached to the front axle of the front wheels pivot in the opposite direction to the levers on which the rear axle for the rear wheels is attached.

Claims: A lawn mower comprising cutting deck (2) which is mounted on at least two wheel assemblies (4), each wheel assembly having a height adjustment mechanism comprising a pivoting mechanism (22) and which is configured so that the height of the cutting deck (2) above the wheel assembly (4) is dependent on the angular position of the pivoting mechanism (22), the axes of pivot of the pivoting mechanisms (22) being substantially parallel, wherein the pivoting mechanisms (22) are interconnected by an interconnecting bar (38), one pivoting mechanism (22) being pivotally connected at a point away from its axis of pivot to an end of the interconnecting bar (38) the other pivoting mechanism (22) being pivotally connected at a point away from its axis of pivot to the other end of the interconnecting bar (38) so that pivotal movement of one pivoting mechanism (22) in one direction about its axis of pivot results in a pivotal movement of another pivoting mechanism (22) about its axis of pivot in the opposite direction, characterised in that the length of the interconnecting bar (38) is less than the distance between the axes of pivot of the pivoting mechanisms (22). A lawn mower as claimed in Claim 1 wherein each of the pivoting mechanisms raise the height of the deck (2) by substantially equal mounts when pivoted through any part of their full range of pivotal movement. A lawn mower as claimed in either of Claims 1 or 2 wherein, in a direction parallel to the plane which passes through both axes of pivot of the pivoting mechanisms (22) the point at which the interconnecting bar (38) pivotally connects to one pivoting mechanism (22) is located in the opposite direction from the axis of pivot of that pivoting mechanism to the other point where the bar (38) pivotally connects to the other pivoting mechanism (22) from the axis of pivot of the second pivoting mechanism (22). A lawn mower as claimed in any one of Claims 1 to 3 wherein each pivoting mechanism is pivotally connected to the interconnecting bar (38) via a rod (21; 23) which is rigidly attached to the pivoting mechanism (22). A lawn mower as claimed in Claim 4 wherein the rod projects perpendicularly away from the axis of pivot of the pivoting mechanism (22). A lawn mower as claimed in either of Claims 4 or 5 wherein, in a direction perpendicular to the plane which passes through both axes of pivot of the pivoting mechanisms (22), the two rods (21; 23) project in opposite directions to each other. A lawn mower as claimed in any one of Claims 4 to 6 wherein in a direction parallel to a plane which passes through both axes of pivot the rods (21; 23) project towards each other. A lawn mower as claimed in any one of the previous claims where the pivoting mechanism (22) comprises at least one lever pivotally mounted on the cutting deck and which interacts with the wheel assembly A lawn mower as claimed in Claim 8 wherein the levers (22) are configured to move as a mirror image of each other in the plane located equidistantly between the two axes of pivot of the levers (22). A lawn mower as claimed in Claim 8 wherein in a direction parallel to a plane which passes through both axes of pivot the levers (22) project from their axis of pivot away from each other.

Inventors: ROGER THOMAS, ROGER, THOMAS
Applicants: BLACK & DECKER INC, BLACK & DECKER INC.
Application year: 1999
Main classification: A01D34
IPC codes: A01D34