GB2299923A - Lawn mower blade mount - Google Patents

Abstract

A blade mounting apparatus for a lawn mower includes a rotatable support member (1) for supporting a cutter member (5) for rotation therewith. The support member (1) has an external peripheral wall and at least one access chamber (3) disposed inwardly of the peripheral wall. A passage (4) extends from the access chamber (3) to open into the peripheral wall. The cutter member (5) includes a retaining head (7) and a blade portion (6) which is adapted to be inserted via the access chamber (3) and the passage (4) to project outwardly from the opening. The head (7) serves to locate the cutter member (5) within the access chamber (3).

Description

BLADE MOUNTING APPARATUS This invention relates to blade mounting apparatus for mounting one or more cutter members for rotary motion.

Rotatable blading is commonplace in many kinds of machinery, for example fans, propellers and rotary lawnmowers. One conventional arrangement used in lawn mowers includes a support hub attached to a drive line having a single bar-type metal blade bolted thereto so that the bar-type blade rotates with the hub.

In another conventional arrangement lawnmowers, a circular disc-like hub has a plurality of plastic blades attached around its periphery. In use, the plastic blades extend radially outwardly from the hub to cut grass very effectively and, generally speaking, more safely than metal blades since they bend or break upon impact with a hard object in the path of the blade.

In all bladed machinery, the blades may require removal for replacement or sharpening and it is an object of the present invention to produce an apparatus which permits blades to be mounted and removed with ease and without requiring special tools.

According to a first aspect of the invention, a blade mounting apparatus includes a rotatable support member having an external peripheral wall, at least one opening in the peripheral wall, an access chamber disposed in the support member inwardly of the peripheral wall and a passage extending inwardly from the opening to the access chamber, a cutter member including a retaining head and a blade portion, the blade portion adapted to be inserted via the access chamber to project outwardly from the opening and the head serving to locate the cutter member within the access chamber of the support member.

The apparatus may include a locking member for retaining the cutter member within the access chamber and this locking member may form part of the support member.

According to one embodiment, the locking member is a tongue extending into the access chamber so that, where the head of the cutter member includes a projection, the projection is engageable with the tongue. According to another embodiment, the tongue is displaceable so as to permit insertion and removal of the cutter member.

The inwardly extending passage may be a slot which terminates in the access chamber. The support member may be flexible, at least in the region of the access chamber, so as to permit temporary deformation of the slot. Such flexibility facilitates insertion and removal of the cutter member. In other embodiments insertion and removal of the cutter member is facilitated by making the tongue flexible or by making the cutter member itself flexible.

The apparatus of the present invention is particularly applicable for mounting replaceable plastic or metal cutting blades in a rotary lawn mower, and especially when the support member is an impeller or a part of an impeller.

Embodiments of the invention are now described by way of example, with reference to the drawings in which: Figure 1 shows the blade mounting apparatus according to the present invention as applied to a lawn mower and with one cutter member in position and another removed; Figure 2 is a sectional view taken on line A-A in figure 1; Figures 3 and 3A show in partial plan and sectional view similar to Figure 2 another embodiment of the present invention including a spring catch to retain a cutter member in position; Figure 4 shows a sectional view of a further embodiment of the present invention in which the access chamber and the cutter member are respectively tongued and grooved; Figures 5 and 6 show plan and end views of a cutter member of a further embodiment; Figure 7 shows a plan view of a support for use with the cutter shown in Figures 5 and 6; and Figure 8 shows a partial sectional view taken on line B-B in Figure 7.

The present invention will be described in relation to a rotary lawnmower but is also applicable to other rotary bladed machinery such as fans.

Referring to Figures 1 and 2, a support member 1 in the form of a disc is rotatable about an axis 2 which corresponds to the axis of rotation of a drive line which drives the support member 1. The support member 1 is mounted on the drive line by a bolt (not shown). The support member includes two diametrically opposed blade mounting points disposed in the region of the periphery of the support member 1. It is possible to have just one cutter member 5 mounted on the support member 1 but for reasons of balance it is preferable to have two or more cutter members 5 equally angularly spaced from each other thereby reducing the amount of vibration of the machine during use.

The points for mounting the cutter members 5 on the support member 1 include a passage (4) in the form of a mortice slot which extends radially inwardly from an opening (8) in the peripheral edge of the support member 1 and terminates in an access chamber 3.

Each cutter member 5 includes an enlarged head 7 and a blade portion 6 extending from the head 7. When mounted on the support member 1, the head 7 is retained in the access chamber 3 with the blade portion 6 passing through the passage 4 to extend outwardly from the opening 8. When the support member 1 rotates, the cutter member 5 rotates with the support member 1 and is rigid radially outwardly under centrifugal force whilst the head 7 is retained in the access chamber 3 since it is too large to pass through the passage 4. The enlarged head 7 abuts the wall of the access chamber 3 against which it is firmly seated by centrifugal force. If during use, the cutter member (5) hits an obstacle it is angularly displaced into a segmental slot (1A) (see right hand side of Figure 1) which also constitutes a part of the passage 4.

One of the major advantages of the present invention is that the cutter member 5 may be easily inserted into and removed from the support member 1. Figures 1 and 2 show one passage 4 and access chamber 3 which are empty, and one passage 4 and access chamber 3 which has a cutter member 5 mounted in its engaged position. To insert a cutter member 5 into the passage 4 and access chamber 3, the blade portion 6 of the cutter member 5 is passed into the access chamber 3 and through the passage 4 until the head 7 of the cutter member 5 sits within the access chamber 3. The head 7 is slid into the access chamber 3 until it abuts the outer wall of the access chamber adjacent the passage 4.

The head 7 of the cutter member 5 will not pass through the passage 4 since it is either too large or differently shaped.

To remove the cutter member 5 from the passage 4 and access chamber 3 the cutter member must be retracted from is engaged position by sliding the head 7 to the inner end of the access chamber 3 whereupon the head 7 of the cutter member 5 may be lifted from the access chamber 3 and the remainder of the blade 6 pulled from the passage 4 and out of the access chamber 3. In order to facilitate the easy insertion and removal of the cutter member 5 into and from the passage 4 and access chamber 3, the cutter 6 may be manufactured from a flexible plastics material. When the support member 1 is not rotating, the cutter member 5 may only slide inwardly towards the axis of rotation until it meets the inner wall of the access chamber 3.The cutter can thus only be removed from the access chamber 3 if the head 7 of the cutter member 5 is lifted out of the access chamber 3 by flexing the cutter member so that the head 7 is no longer restricted to movement within the access chamber 3.

In Figure 1 the cutter member 5 is held in the engaged position by two resilient lugs 10 shaped to receive the head 7 and formed integrally with the support member 1. In an alternative arrangement a spring catch 9 (see Figure 3) is formed integrally with the support member 1 shaped as shown to form a step over which the cutter member 5 must pass if it is removed from the support member 1. To insert the cutter member the spring catch 9 is automatically pushed down by the head 7 of the cutter member 5 as it is inserted into the access chamber.

Figure 4 shows another embodiment of the present invention in which the head 7 of the cutter member 5 has a generally circumferential groove 11 which engages with a corresponding projection 110 around the inner wall of the access chamber 3. If desire, the groove 11 and projection 110 may be reversed.

As indicated above, the passage may be a hole, but may, as shown in Figures 1 and 2, be an open faced channel.

Alternatively an open and dovetailed sectioned channel may be used.

A further embodiment of the invention is shown in Figures 5 to 8. Figures 5 and 6 show a cutter member 5 including a blade portion 6 and a modified head 7. The head 7 includes an enlarged arcuate rim 21 which is adapted to retain the head 7 within the access chamber 3 without slipping through the passage 4, and a projection 22 extending from the rim 21 away from the blade portion 6.

Figures 7 and 8 show the support member 1 rotatable about an axis 2 and a pair of diametrically opposed blade mounting points. Each blade mounting point includes a segmental slot 1A which extends inwardly from an opening 8 in the peripheral edge of the support member and terminates in an access chamber 3. A tongue 23 extends into the access chamber 3 from the inner wall of the chamber 3. The slot 1A is formed between two flanges 24.

The cutter member 5 is inserted blade portion 6 first through the access chamber and into the slot 1A until the rim 21 of the cutter abuts the outermost wall of the access chamber. Insertion is facilitated by one or more of the following: the flexibility of the support member 1 whereby the flanges 24 flex apart as the cutter member is pushed in; by the flexibility of the cutter member 5; or by the flexibility of the tongue 23. When engaged, the head 7 is held against the outer wall of the chamber 3 by the tongue 23 which prevents the projection 22 from moving radially inwardly.

To remove the cutter member 5, the flanges 24 must be temporarily deformed so that the cutter member 5 may pass the tongue 23.

Claims (19)

1. A blade mounting apparatus including: a rotatable support member for supporting at least one cutter member for rotation with the support, the support member, having an external peripheral wall and at least one access chamber disposed inwardly of the peripheral wall, and a passage extending from each access chamber to open into the peripheral wall a cutter member including a retaining head and a blade portion which is adapted to be inserted via the access chamber and the passage to project outwardly from the opening, the head serving to locate the cutter member within the access chamber.

2. The apparatus according to claim 1 further including a locking member for retaining the cutter member within the access chamber.

3. The apparatus according to claim 2 wherein the support member includes the locking member.

4. The apparatus according to claim 3 wherein the locking member is a tongue extending into the access chamber.

5. The apparatus according to any preceding claim wherein the passage is a mortice slot which terminates in the access chamber.

6. The apparatus according to claim 5 wherein the support member is flexible so as to permit temporary deformation of that part of the support in the region of the slot.

7. The apparatus according to any of claims 3 to 6 wherein the head of the cutter member includes a projection engageable with the locking member.

8. The apparatus according to any preceding claim wherein the blade portion is removable from the support member via the access chamber.

9. The apparatus according to claims 1 to 4 wherein the passage extending inwardly from the opening is an open channel which terminates in the access chamber.

10. The apparatus according to claim 9 wherein the channel includes radially extending sides shaped to retain the blade portion of the cutter member.

11. The apparatus according to any of claims 1 to 10 wherein the retaining head of the cutter member is shaped to be retained in the access chamber.

12. The apparatus according to any of claims 4 to 11 wherein the tongue is displaceable permitting insertion and removal of the cutter member.

13. The apparatus according to any preceding claim wherein the blade portion of the cutter member is made from flexible material to assist in the insertion and removal of the cutter blade.

14. The apparatus according to any preceding claim wherein interlocking projections and grooves are disposed around the head of the cutter member and within the access chamber.

15. The apparatus according to any preceding claim wherein the cutter member is replaceable.

16. The apparatus according to any preceding claim adapted for use in a rotary lawnmower.

17. The apparatus according to claim 17 wherein at least a part of the support member constitutes an impeller.

18. A blade member for use in the apparatus according to any preceding claim and as shown in the accompanying drawings.

19. A rotary lawnmower including a cutter mounting apparatus according to any of claims 1 to 17.