PLATE LOCKING MECHANISM

Abstract

A plate locking mechanism for a surface preparation device comprising a connecting plate having a receiving aperture, a base plate and a floating plate capable of being substantially aligned with the base plate. A fastener extends through a floating plate aperture and engages with a base plate aperture and a resilient member is operatively associated with the fastener to maintain the floating plate in contact with the base plate and wherein, when the base plate is located within the receiving aperture, the floating plate is rotatable to retain the connecting plate in position.

Description

FIELD OF THE INVENTION

The present invention relates to the field of mechanical locking mechanisms. More particularly, this invention relates to a plate and associated plate locking mechanism for a surface preparation device.

BACKGROUND OF THE INVENTION

Surface preparation techniques are commonly used to give a desired finish to a surface in both home and work environments. Common examples are the fine sanding of wooden floors and the grinding and perhaps subsequent polishing of concrete floors to give a smooth and aesthetically appealing finish.

Typically, mechanised surface preparation devices are used for such tasks since large surface areas need to be prepared. Such devices are well known and generally take the form of either hand held devices with single grinding discs, such as an orbital sander, or larger devices which are controlled by an operator pushing them along and which may have a number of grinding discs or like preparation tools allowing a larger surface area of floor or other surface to be appropriately finished in a shorter time period.

These larger devices generally have a rotatable plate which is rotated by a drive shaft and onto which are attached one or more surface preparation discs. The surface preparation discs may rotate relative to the rotatable plate and contact and add the desired finish to the surface to be prepared. The rotatable plate must be held in place by some form of holder or locking mechanism.

One example of such a large surface preparation device is a concrete grinder/polisher. These are typically very heavy machines which are further weighed down by the inclusion of weights, either on the housing or built into the machine itself, to increase the grinding/polishing force. This makes it difficult to transport the device and also requires a certain amount of physical strength from the operator to force the device to move in the desired manner from side to side in a sweeping motion during operation. Control of the device during grinding/polishing is crucial as the high operating speeds of the grinding discs mean that any unwanted movements can result in gouging of the surface being prepared and fine control of the machine when encountering irregularities on the surface being prepared is necessary to prevent a similar result.

There is a need for a surface preparation device which can more easily be controlled during operation and which effectively and efficiently prepares surfaces such as concrete and wooden floors.

Accordingly, it is an aim of the present invention to overcome or alleviate at least some of the disadvantages of current surface preparation devices and otherwise to provide consumers with a more convenient choice.

SUMMARY OF THE INVENTION

The present invention provides for a plate locking mechanism and reciprocating plate for use in releasably attaching a rotatable plate, the rotatable plate having one or more surface preparation tools attached, to a surface preparation device.

In one form, although it need not be the only or indeed the broadest form, the invention resides in a plate locking mechanism for a surface preparation device comprising:

• • (a) a base plate having a base plate aperture;
  • (b) a floating plate capable of being substantially aligned with the base plate, the floating plate having a first surface, an actuator and a floating plate aperture, the first surface in contact with the base plate;
  • (c) a fastener extending through the floating plate aperture and engaging with the base plate aperture; and
  • (d) a resilient member operatively associated with the fastener and in contact with a second surface of the floating plate, the resilient member capable of generating a force on the second surface of the floating plate to maintain the first surface of the floating plate in contact with the base plate;

wherein, rotation of the actuator results in relative movement of the floating plate and the base plate to enable locking of a plate.

Preferably, the base plate is adapted to attach to an underside of the surface preparation device.

In a further form the invention resides in a plate locking mechanism for a surface preparation device comprising:

• • (a) a connecting plate having a receiving aperture and at least one blocking member;
  • (b) a base plate having a base plate aperture, the base plate having a shape complimentary to that of the receiving aperture;
  • (c) a floating plate capable of being substantially aligned with the base plate, the floating plate having a first surface, at least one floating plate projection and a floating plate aperture, the first surface, in use, in contact with the base plate;
  • (d) a fastener extending through the floating plate aperture and engaging with the base plate aperture; and
  • (e) a resilient member operatively associated with the fastener and in contact with a second surface of the floating plate to maintain the first surface of the floating plate in contact with the base plate;

wherein, when the base plate is located within the receiving aperture, the floating plate is rotatable to align the at least one floating plate projection with the at least one blocking member to thereby lock the connecting plate in position.

In yet a further form the invention resides in a plate locking mechanism for a surface preparation device comprising:

• • (a) a floating plate having an actuator, at least one floating plate projection and a floating plate aperture;
  • (b) a fastener extending through the floating plate aperture, the fastener having a head and a shank and being adapted to engage a base plate;
  • (c) a resilient member at least partially surrounding the shank and extending between the head of the fastener and a receiving surface of the floating plate;

wherein, moving the head of the fastener towards the receiving surface of the floating plate compresses the resilient member.

In still a further form the invention resides in a method of retaining a connecting plate on a surface preparation machine including the steps of:

• • (a) connecting a floating plate to a base plate using a fastener, the base plate being attached to an underside of the surface preparation machine, the floating plate and base plate being capable of being substantially aligned, the floating plate having at least one floating plate projection and the fastener being operatively associated with a resilient member which is maintained in a partially compressed state by the fastener;
  • (b) locating a connecting plate to surround the base plate, the connecting plate having a receiving aperture and at least one blocking member, the receiving aperture being complimentary in shape to the aligned floating plate and base plate;
  • (c) rotating the floating plate to align the at least one floating plate projection with the at least one blocking member to thereby retain the connecting plate.

In yet still a further form the invention may reside in a rotatable plate for a surface preparation device comprising a plate collar defining a hollow passage, the plate collar extending generally perpendicularly from the plane of the rotatable plate and ending in a connecting plate, the connecting plate in a plane parallel to that of the rotatable plate and having a receiving aperture continuous with the hollow passage

Further features of the present invention will become apparent from the following detailed description.

Throughout this specification, unless the context requires otherwise, the words “comprise”, “comprises” and “comprising” will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

BRIEF DESCRIPTION OF THE FIGURES

In order that the invention may be readily understood and put into practical effect, preferred embodiments will now be described by way of example with reference to the accompanying figures wherein like reference numerals refer to like parts and wherein:

FIG. 1 is a perspective view of the underside of a surface preparation device employing a plate locking mechanism according to an embodiment of the invention;

FIG. 2 is an exploded view of the components of a plate locking mechanism, according to an embodiment of the invention, with associated rotatable plate and accessories;

FIG. 3 is a perspective view of a plate locking mechanism according to an embodiment of the invention;

FIG. 4A is a perspective view of a plate locking mechanism, according to an embodiment of the invention, when in the unlocked/removal configuration;

FIG. 4B is a perspective view of a plate locking mechanism, according to an embodiment of the invention, when in the locked/operational configuration;

FIG. 5 is a perspective view of a plate locking mechanism according to a further embodiment of the invention;

FIG. 6 is a perspective view of a plate locking mechanism according to yet a further embodiment of the invention; and

FIGS. 7A to 7D are plan views of a number of alternative designs for use in forming a plate locking mechanism according to various embodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The plate locking mechanism embodiments which are discussed herein are described in relation to their use in a concrete grinder/polisher surface preparation device. It should be understood, however, that they can be equally applied to a number of other surface preparation devices such as sanders or road surface preparation machines.

The term “surface preparation” as used herein may refer to levelling, polishing, grinding, cleaning, removing resins/lacquers/paint or the like, slicing, shredding and scraping. The term “grinding” will be commonly used to refer to any type of surface preparation employing an abrasive/frictional treatment step.

FIG. 1 is a perspective view of the underside of a surface preparation device 10 employing a plate locking mechanism 50 according to an embodiment of the invention. The surface preparation device 10 may be any concrete grinder, floor polisher, sander etc of a type commonly used in the industry. Non-limiting examples of such surface preparation devices 10 are those commercially available from Polivac International Pty Ltd (such as a Polivac PV 25 floor polisher with a brush speed of 420 rpm, a Polivac SV 30 with a brush speed of 350 rpm or a Polivac SV25 sander with a brush speed of 192 rpm) or Rotavac. The housing, body and inner workings of the surface preparation device 10, per se, are not the subject of the present invention and will generally be of a standard type well known to those skilled in the art of surface preparation.

Surface preparation device 10 has a housing 11 and travels along on grinding discs 21 when driven by an operator pushing on handle 12. The underside of surface preparation device 10 reveals a rotatable plate 20 onto which are attached surface preparation tools in the form of the grinding discs 21. Rotatable plate 20 has a cylindrical through hole or aperture in its centre formed by a plate collar 22 of which the interior wall can be viewed in FIG. 1. At the internal upper extent of plate collar 22 is located plate locking mechanism 50 which operates to hold rotatable plate 20 in position during use. FIG. 2 provides further detail.

FIG. 2 is an exploded view of the components of the plate locking mechanism 50, according to an embodiment of the invention, with associated rotatable plate 20 and accessories. Rotatable plate 20 has, in the embodiment described, three grinding discs 21 attached to its grinding surface which will, during operation, contact and grind the surface being prepared. Grinding discs 21 may be metal structures with abrasive material such as sand paper, stones, silicon carbide or diamond tips. On the opposite surface to the grinding surface, rotatable plate 20 has a plate collar 22 projecting generally upwards from the plane of the rotatable plate 20 to define a hollow interior forming a cylinder which is continuous with an aperture in the grinding surface of rotatable plate 20 of equal diameter.

Rotatable plate 20 is also provided with a disc attachment aperture 23 for each grinding disc 21 which, in use, is in alignment with a grinding disc aperture 24 formed in each grinding disc 21. These aligned apertures, 23 and 24, receive a grinding disc fastener 25 to hold the grinding disc 21 firmly in place but may, if required, allow for rotation of grinding disc 21. In the embodiment shown, the grinding disc fasteners 25 take the form of a mandrel and, advantageously, mandrels 25 may be magnetic mandrels. Mandrel head 26 can be seen abutting the upper surface of rotatable plate 20 to prevent the associated grinding disc 21 from inadvertently detaching. The use of magnetic mandrels 25 enables the grinding discs 21 to be attached and removed quickly and easily which can save considerable time when abrasives of progressively finer material need to be used to achieve a sufficiently smooth finish.

Rotatable plate 20 is further provided with a number of ballast attachment apertures 27 to enable the placement and attachment of weights as ballast 28 onto rotatable plate 20 to provide for an increased grinding force. Ballast fastener 29, which may be a simple bolt or the like, is used to pass through an aperture formed in the ballast 28 (not shown) and the ballast attachment aperture 27 to fasten the ballast 28 to the rotatable plate 20. It is a distinct advantage of the present invention that ballast 28 is able to be carried on the rotatable plate 20 rather than placed on the housing 11 of the surface preparation device 10 or built into the device 10 itself. The plate collar 22 provides sufficient clearance between the rotatable plate 20 and the underside of the surface preparation device 10 to allow the ballast 28 to be placed there between and the plate locking mechanism of the present invention allows rotatable plate 20 to effectively float (as will be described in detail herein) which means the ballast 28 can be better supported and much more effectively put to use.

Although, for the sake of clarity, connecting plate 30 is shown in the figures as being separate to the plate collar 22 it will preferably be integrally formed with or may be in some manner permanently attached onto the rim of plate collar 22 nearest the surface of rotatable plate 20 having no grinding discs 21, to form a partial cover over the hollow cylindrical interior formed inside plate collar 22. Connecting plate 30 may be welded, bolted or otherwise fixed onto the upper rim of plate collar 22 and is provided with a receiving aperture 31 which is shaped so as to form blocking members 32 which, in the embodiment shown, take the form of projecting wedges, this results in a pattern whereby a blocking member 32 is adjacent cut away portions on either side thereof. Connecting plate 30 forms a component of the plate locking mechanism 50 of the invention.

Plate locking mechanism 50 further comprises a locking base plate 51 which is shaped so as to compliment the shape of receiving aperture 31 and is capable of being located therein. The locking base plate 51 has a central aperture 52 formed in its body 55 and radial apertures 53 formed in projecting members 54 which radiate from the body 55 of locking base plate 51. The alternating pattern of projecting members 54, in the form of wedges, and cut away portions mirrors that of connecting plate 30 so the two can fit together to form one solid plate, ignoring the relatively small apertures in the locking base plate 51. The thicknesses of locking base plate 51 and connecting plate 30 are substantially the same so that, when one is fitted inside the other, the surfaces of the two seen by a viewer looking at the underside of the surface preparation device 10, sit flush. The locking base plate 51 can be connected to the underside of the surface preparation device 10 by means of locking base fasteners 56, which may take the form of screws, bolts or the like, passing through radial apertures 53 and connecting to any suitably strong and rotatable component of the surface preparation device 10. In alternative embodiments, locking base plate 51 may simply be a rotatable plate or surface already present on the underside of the surface preparation device 10 to which a floating plate 60 can be attached. The present invention can thus not only be incorporated into new surface preparation devices 10 but is capable of being retrofitted to existing devices with a minimum of modification.

Floating plate 60 has a contact surface which sits in contact with locking base plate 51 and this surface has a shape which substantially conforms to that of plate 51. The surface of floating plate 60 opposite to that in contact with locking base plate 51 is provided with an actuator in the form of a handle 61 in which there may be provided a handle aperture 62 (as shown more clearly in FIG. 3). Located beneath the handle 61 is a fastening member 63 in the form of a bolt having an at least partially threaded shank 64 around which is placed a resilient or dampening member 65 which, in the embodiment shown, takes the form of a spring such as a compression spring. The resilient member 65 may take a range of other forms which would be known to a skilled addressee such as various designs of spring or solid rubber and/or polymeric compressible bodies so long as the material used can withstand the relatively abrasive environment of use. The threaded portion of shank 64 passes through a floating plate central aperture 66 and ends in the threaded central aperture 52 of locking base plate 51 to engage therewith. The threaded portion of shank 64 does not actually threadedly engage with the floating plate central aperture 66 but rather merely passes through said aperture. The components of the plate locking mechanism 50 can be seen in more detail in FIG. 3.

FIG. 3 is a perspective view of a plate locking mechanism 50 according to an embodiment of the invention. Once again, connecting plate 30 is shown separate to the rest of the rotatable plate 20 simply for the sake of clarity. It is clear from FIG. 3 that the shapes of floating plate 60 and locking base plate 51, when in alignment, will fit closely into the complimentary shape of receiving aperture 31 of connecting plate 30.

As discussed previously, locking base plate 51 will be fastened to the underside of the surface preparation machine 10 at a suitable location by locking base fasteners 56 and so it will not be free to move in any manner. The component to which locking base plate 51 is attached (or locking base plate 51 itself) will be the normal component of the device which is rotatable by the motor of the surface preparation device 10 to thereby ultimately effect rotation of rotatable plate 20. The contact surface of floating plate 60 will be maintained in direct contact with locking base plate 51 unless a pulling force is exerted on handle 61 and so, once floating plate 60 and locking base plate 51 are in place and aligned, the connecting plate 30, and attached rotatable plate 20, will be appropriately located by lifting the rotatable plate 20 such that handle 61 enters first through receiving aperture 31 until locking base plate 51 is located within receiving aperture 31 and the visible surfaces of connecting plate 30 and locking base plate 51 are substantially flush with one another. The rotatable plate 20 is then in place and ready to be locked.

The floating plate central aperture 66 is not threaded and does not engage, as such, with the threaded shank 64 of bolt 63 but rather the floating plate 60 is maintained in forced contact with the surface of locking base plate 51 by the compression force created by resilient member 65. This force is generated as bolt 63 will be screwed into and therefore engaged with locking base plate 51 to a sufficient extent to have the head or associated washer thereof compress the resilient member 65 which transmits this force to the surface of floating plate 60 which it contacts thereby forcing floating plate 60 into contact with locking base plate 51. The extent to which bolt 63 is tightened will determine the force transmitted to floating plate 60 and hence will determine the extent of the dampening effect created when forces from rotatable plate 20 try to work against this effect.

In one embodiment the invention resides in a plate locking mechanism for a surface preparation device comprising:

• • (a) a connecting plate having a receiving aperture and at least one blocking member;
  • (b) a base plate having a base plate aperture, the base plate accommodated within the receiving aperture;
  • (c) a floating plate in contact with and capable of being substantially aligned with the base plate, the floating plate having at least one floating plate projection and a floating plate aperture;
  • (d) a fastener extending through the floating plate aperture and engaging with the base plate aperture; and
  • (e) a resilient member adapted to exert a force on a surface of the floating plate;

wherein, rotation of the floating plate to align the at least one floating plate projection with the at least one blocking member causes the connecting plate to be retained.

Preferably, the resilient member is operatively associated with the fastener.

Suitably, the resilient member is a spring through which the fastener passes.

The fastener being located further into the base plate aperture causes the resilient member to be compressed to a greater degree. Compression of the resilient member to a greater degree increases the force exerted on the surface of the floating plate. The force exerted by the resilient member on the surface of the floating plate works against the force exerted by the weight of the connecting plate on the floating plate.

FIG. 4A is a perspective view of a plate locking mechanism 50, according to an embodiment of the invention, when in the unlocked/removal configuration. The floating plate 60 and locking base plate 51 are in alignment and they, together, have been inserted into the receiving aperture 31 of connecting plate 30, as described in relation to FIG. 3. The view shown in FIG. 4 makes it clear that when floating plate 60 and locking base plate 51 are in alignment then the heads of locking base fasteners 56 are accommodated within floating plate apertures 68, formed in floating plate projections 67, which thereby prevents any rotational movement of floating plate 60.

This position shown in FIG. 4A represents the situation whereby locking base plate 51 has been fastened to the underside of the surface preparation device 10 and the connecting plate 30 with attached rotatable plate 20 (not shown for the sake of clarity) has been slipped over handle 61 and locking base plate 51 sits flush within receiving aperture 31. It can be seen that, since locking base plate 51 and connecting plate 30 are of the same thickness, floating plate 60 sits above the surface of connecting plate 30. From the position shown the user is ready to lock rotatable plate 20 and connecting plate 30 in place.

FIG. 4B is a perspective view of the plate locking mechanism 50, according to an embodiment of the invention, when in the locked/operational configuration. In moving from the position shown in FIG. 4A to that in FIG. 4B the user is required to lift handle 61 which, since it is integrally formed or attached to floating plate 60, results in floating plate 60 moving away from the surface of locking base plate 51 in which it was in contact with and in resilient member 65 being compressed. The user needs to raise floating plate 60 in this manner to a point whereby floating plate projections 67 are above the level of the heads of locking base fasteners 56 and then apply a twisting or rotating motion to handle 61 to rotate floating plate 60 with respect to both shank 64 of bolt 63 and locking base plate 51. This results in floating plate projections 67 being located between the heads of locking base fasteners 56 at which point the user can release handle 61. The locking base fasteners 56 prevent rotation of the floating plate 60 from reaching the point where floating plate projections 67 would be in alignment with projecting members 54 and so the rotatable plate 20 would be released. The locking base fasteners 56 thereby act not only to affix locking base plate 51 to the surface preparation device 10 but also to maintain the plate locking mechanism in the locked/operational position.

It will be appreciated that, at this point, the blocking members 32 of connecting plate 30 are now trapped behind and are at least partially in contact with the face of floating plate projections 67 which was previously in contact with the projecting members 54 of locking base plate 51. This is the operational configuration as rotatable plate 20 (which is integral with or attached to connecting plate 30) is now held in place on the underside of surface preparation device 10 and locked in that position by the configuration of the floating plate 60. The locking base plate 51 and floating plate 60 are, in this operational configuration, located within the hollow cylindrical aperture defined by the walls of plate collar 22. This can be seen in FIG. 1. Grinding discs 21 can then be placed in position on rotatable plate 20 and the user is ready to commence the surface preparation treatment, such as grinding of a cement floor.

When the treatment is complete and the user wishes to remove rotatable plate 20 or wants to add or remove ballast 28 there from then, starting from the position shown in FIG. 4B, handle 61 is lifted and rotated until the heads of locking base fasteners 56 are aligned with floating plate apertures 68 at which point the handle 61 is released and the unlocked or removal position shown in FIG. 4A has been achieved. The rotatable plate 20 is then easily removed for adjustment and re-attachment or storage.

The system described above presents a number of advantages over the prior art. Firstly, once locking base plate 51 has been permanently attached to the underside of the surface preparation device 10 then attaching and removing the rotatable plate 20 is a simple matter of pulling and twisting handle 61 to switch between the locked and release configurations. This results in major time savings during jobs such as concrete polishing where, to grind the surface to a fine finish, a range of different grade grinding discs 21 and ballast 28 may need to be added or removed from rotatable plate 20 or indeed different size or weight rotatable plates 20 employed. This regular changing necessitates frequent removal of rotatable plate 20 and so any mechanism whereby the changeover can be speeded up can result in time and cost savings for the operator.

Secondly, and importantly, the design shown provides a dampening effect to bumps and vibrations caused by an uneven surface during surface preparation. The manner or angle in which grinding discs 21 are held or presented to the surface to be prepared by rotatable plate 20 is critical during surface preparation. Changes in this angle due to an uneven surface can result in a more aggressive cutting or grinding action than is desirable and may permanently damage the surface. The present invention provides a system whereby the rotatable plate 20 is not held in an absolute fixed position but rather, due to the resilient member 65 and the manner in which it is suspended from the underside of the device 10 by locking mechanism 50, it can flex and re-orient itself in response to the particular contours of the surface being treated. This effect will be described in more detail below.

When in the locked configuration shown in FIG. 4B the rotatable plate 20 is effectively hanging from the underside of the surface preparation device, suspended by the overlapping engagement of blocking members 32 of connecting plate 30 with the floating plate projections 67 of floating plate 60. The floating plate 60 would be forced towards the preparation surface by its own weight if it were not for the resistive force it receives from compression spring 65 which is held in place by the head and associated washer of bolt 63 which is engaged at its threaded shank 64 portion with locking base plate 51. When bumps or dips are encountered during operation on the surface being treated then the rotatable plate 20 will be caused to tip to one side or another. The force caused by this shift is transmitted to the floating plate projections 67 which are caused to push against compression spring 65 and further compress it. The compression spring 65 will allow this slight movement but will dampen the shock of the force and then return to its normal state once the additional force felt by rotatable plate 20 ends. This action provides for uneven surfaces to be accommodated by enabling rotatable plate 20, and hence attached grinding discs 21, to move to the necessary extent while dampening the jerking or sharp motion caused by uneven surfaces which can result in overly aggressive grinding and surface damage.

A further advantage of the flexibility achieved by the use of floating plate 60 and resilient member 65 is that the surface preparation device 10 is easier for the operator to manoeuvre. A relatively slight pressure will result in a movement of floating plate 60, as described above, and the device 10 will follow that movement while it is maintained. Less effort is asked of the operator to move the device 10 from side to side and it is easier to control thereby enabling a better finish to be achieved with less physical exertion. This is a great improvement over prior art machines which could not always be operated by those of a slight build and were more prone to unexpected or undesired movements providing a less than ideal finish.

Further, the easy attachment and removal of the rotatable plate 20 coupled with the design of rotatable plate 20 itself allows the ballast 28 to be connected directly to rotatable plate 20 rather than to the housing 11 of the surface preparation device 10. This makes it easier to separate out the weight of the machine from the weight of the ballast allowing them to be separated for easier and safer lifting and transport. Importantly, this also reduces wear and tear on the surface preparation device itself as the rotatable plate 20 is made to bear the weight of ballast 28 and thereby takes on much of the actual work of the device 10 in grinding the surface to be prepared. The provision of a system which enables the grinding plate in contact with the preparation surface via the grinding tools, i.e. rotatable plate 20 and grinding discs 21, to hang and float more or less free of the body of the surface preparation device 10 is a significant advantage as all of the adjusting to the surface being prepared, the jolts from bumps etc and the resistance encountered at the preparation surface are all passed onto rotatable plate 20 and hence to resilient member 65 thereby reducing the work required from and wear and tear caused to the surface preparation device 10 as well as making it considerably easier for the user to control the device 10 during these events. Due to the advantages provided by the floating effect described it is preferred that the present invention is used with surface preparation devices 10 which do not have wheels or have wheels which are removable. This is because the permanent raised support provided by a set of wheels reduces the effectiveness of the floating support system due to a reduced contact with the surface being prepared.

In one embodiment the invention lies in a rotatable plate for a surface preparation machine comprising a plate collar defining a hollow passage, the collar extending generally upwards from the plane of the rotatable plate and ending in a connecting plate having a receiving aperture continuous with the hollow passage.

Preferably, the collar extends a sufficient distance above a surface of the rotatable plate to accommodate a locking mechanism within the hollow passage thereby formed.

Suitably, the receiving aperture is of a complimentary shape to a locking base plate which can be accommodated therein. The rotatable plate will be provided with disc attachment apertures and/or ballast attachment apertures for the attachment of grinding tools and weights, respectively. The grinding tools may be attached to the rotatable plate by means of fasteners such as magnetic mandrels. The use of magnetic mandrels means the grinding tools can be removed and replaced with great efficiency.

It will be appreciated that the plate locking mechanism 50 may be considered to include connecting plate 30 of rotatable plate 20 since the receiving aperture 31 of connecting plate 30 must accommodate the shape of locking base plate 51 for the locking mechanism to successfully work but it is the combination of locking base plate 51, to attach to the surface preparation device 10, and floating plate 60, with resilient member 65, which effects the actual locking action. The connecting plate 30 will generally be integrally formed with or permanently attached to the rotatable plate 20 and so the inventive solution offered is shared by the rotatable plates and the other locking mechanism components due to their interworking relationship defined by their complimentary shapes and working engagement.

The skilled addressee will appreciate that the present invention is not limited to the particular shapes of connecting plate 30, receiving aperture 31, locking base plate 51 and floating plate 60 shown in FIGS. 1 to 4B. Other shapes may also be suitable and, indeed, may provide particular advantages of their own, as is discussed below.

FIG. 5 is a perspective view of a plate locking mechanism 100 according to a further embodiment of the invention. This plate locking mechanism 100 works in essentially the same manner as described above but the shapes of the components have been altered from the wedge-shaped blocking members 32, projecting members 54 and floating plate projections 67 to take on a clover-shaped design whereby each individual projection is circular at its border.

Connecting plate 101 has a receiving aperture 102 and blocking members 103 which resemble rounded peak-like projections. Locking base plate 110 has three projecting members 111, a central aperture 112 and a number of radial apertures 113 to receive fasteners which will attach the locking base plate 110 to the underside of the surface preparation device 10. Floating plate 120 has floating plate projections 121, floating plate apertures 122 and floating plate central aperture 123 which is threaded and engages with the complimentary threaded portion of bolt 125. Handle 126 is integrally formed on a surface of floating plate 120 which does not contact locking base plate 110 and resilient member 127, in the form of a compression spring, is located around bolt 125.

As in the embodiment discussed previously, the contacting surfaces of floating plate 120 and locking base plate 110 are substantially similar in shape and dimension and so can be aligned with one another without any substantial overlap. Their shape is complimentary to that of receiving aperture 102 and so locking base plate 110 can be located therein and the rotatable plate (not shown but integral with connecting plate 101) attached and removed as already described.

The main difference achieved by the alteration in shape from the wedge design to the clover leaf design is the differing manner in which the floating plate moves in response to movement transmitted from the rotatable plate. The clover-leaf design shown in FIG. 5 allows for a slightly more pronounced circular movement of the rotatable plate which will advantageously suit certain users and certain surface types.

FIG. 6 is a perspective view of a plate locking mechanism 200 according to yet a further embodiment of the invention. This plate locking mechanism 200 works in essentially the same manner as described above but this time the shapes of the components have been altered from the wedge-shaped or clover-leaf design to take on an X-shaped or cross-shaped design whereby each individual projection is reminiscent of the upper and side faces of a pentagon.

Connecting plate 201 has a receiving aperture 202 and blocking members 203 which are triangular in shape. Locking base plate 210 has four projecting members 211, a central aperture 212 and a number of radial apertures 213 to receive fasteners which will attach the locking base plate 210 to the underside of the surface preparation device 10. Floating plate 220 has floating plate projections 221, floating plate apertures 222 and floating plate central aperture 223 which is threaded and engages with the complimentary threaded portion of bolt 225. Handle 226 is integrally formed on a surface of floating plate 220 which does not contact locking base plate 210 and resilient member 227, in the form of a compression spring, is located around bolt 225.

As in the embodiments discussed previously, the contacting surfaces of floating plate 220 and locking base plate 210 are substantially similar in shape and dimension and so can be aligned with one another without substantial overlap. Their shape is complimentary to that of receiving aperture 202 and so locking base plate 210 can be located therein and the rotatable plate (not shown but integral with connecting plate 201) attached and removed as already described.

As with the embodiment shown in FIG. 5, the main difference achieved by the alteration in shape of the various projections, blocking members and receiving aperture is the differing manner in which the floating plate moves in response to movement transmitted from the rotatable plate. The design shown in FIG. 6 may serve to provide additional stability to the rotatable plate when operating at higher rpm's.

FIGS. 7A to 7D are plan views of a number of alternative designs 310, 320, 330 and 340 for use in forming a plate locking mechanism according to various embodiment of the invention. Each embodiment is a view of a locking base plate accommodated within a connecting plate and so for each design the floating plate would be underneath (obscured in this view) the locking base plate and would have a substantially similar shape to that plate, as with the embodiments described above. These alternative designs each provide their own advantage in terms of the dampening effect they provide and the experience the operator feels when driving the device 10. 310 represents a locking base plate and floating plate structure whereby their projections are squared off in shape on extending from the central portion, 320 represents a three-pronged pentagon shape of projections, 330 represents a simple triangle with cut off points and 340 represents a similar situation to 310 but with each of the faces of the square projections having been curved (outwards i.e. convex at the outermost and inwards i.e. concave at the sides).

Throughout the specification the aim has been to describe the preferred embodiments of the invention without limiting the invention to any one embodiment or specific collection of features. It will therefore be appreciated by those of skill in the art that, in light of the instant disclosure, various modifications and changes can be made in the particular embodiments exemplified without departing from the scope of the present invention.

Claims

1. A plate locking mechanism for a surface preparation device comprising:

(a) a connecting plate having a receiving aperture and at least one blocking member;

(b) a base plate having a base plate aperture, the base plate having a shape complimentary to that of the receiving aperture;

(c) a floating plate capable of being substantially aligned with the base plate, the floating plate having a first surface, at least one floating plate projection and a floating plate aperture, the first surface in contact with the base plate;

(d) a fastener extending through the floating plate aperture and engaging with the base plate aperture; and

(e) a resilient member operatively associated with the fastener and in compressing contact with a second surface of the floating plate;

wherein, location of the base plate within the receiving aperture enables the floating plate to be rotated to align the at least one floating plate projection with the at least one blocking member to thereby lock the connecting plate in position.

2. The plate locking mechanism of claim 1 wherein the connecting plate is connected to a rotatable plate comprising a grinding tool.

3. (canceled)

4. The plate locking mechanism of claim 1 wherein the connecting plate is integral with the rotatable plate.

5. The plate locking mechanism of claim 1 wherein the floating plate further comprises an actuator.

6. The plate locking mechanism of claim 1 wherein the base plate comprises at least one projecting member extending from a body thereof.

7. The plate locking mechanism of claim 6 wherein the at least one floating plate projection can be aligned with the base plate at least one projecting member.

8. The plate locking mechanism of claim 6 wherein the base plate at least one projecting member is adapted to be accommodated within a complimentary portion of the receiving aperture.

9. The plate locking mechanism of claim 1 wherein the fastener threadedly engages with the base plate aperture.

10. (canceled)

11. The plate locking mechanism of claim 1 wherein the resilient member is a compression spring through which the fastener passes.

12. The plate locking mechanism of claim 11 wherein movement of the fastener further into the base plate aperture causes compression of the compression spring and increases the force maintaining the first surface of the floating plate in contact with the base plate.

13. The plate locking mechanism of claim 6 wherein the base plate at least one projecting member comprises a radial aperture to receive a locating fastener.

14. The plate locking mechanism of claim 13 wherein a head of the locating fastener can be accommodated within a floating plate aperture formed within the at least one floating plate projection.

15. The plate locking mechanism of claim 14 wherein the actuator is moved in a direction away from the base plate to place the floating plate above the level of the head of the locating fastener prior to rotation of the actuator.

16-27. (canceled)

28. A plate locking mechanism for a surface preparation device comprising:

(a) a floating plate having an actuator, at least one floating plate projection and a floating plate aperture;

(b) a fastener extending through the floating plate aperture, the fastener having a head and a shank and being adapted to engage a base plate; and

(c) a resilient member at least partially surrounding the shank and extending between the head of the fastener and a receiving surface of the floating plate;

wherein, moving the head of the fastener towards the receiving surface of the floating plate compresses the resilient member.

29. The plate locking mechanism of claim 28 wherein the floating plate has a plurality of floating plate projections extending from a central body.

30. (canceled)

31. The plate locking mechanism of claim 28 wherein the resilient member is a compression spring through which the fastener passes.

32. (canceled)

33. (canceled)

34. A rotatable plate for a surface preparation device comprising a plate collar defining a hollow passage, the plate collar extending generally perpendicularly from the plane of the rotatable plate and ending in a connecting plate, the connecting plate in a plane parallel to that of the rotatable plate and having a receiving aperture continuous with the hollow passage.

35. The rotatable plate of claim 34 wherein the plate collar extends above a surface of the rotatable plate to accommodate a plate locking mechanism within the hollow passage.

36. The rotatable plate of claim 34 wherein the receiving aperture is adapted to accommodate a base plate having a shape complimentary to the receiving aperture.

37. The rotatable plate of claim 34 further comprising disc attachment apertures and/or ballast attachment apertures for the attachment of grinding discs and weights, respectively.

38. (canceled)