Patent Description:
The present invention relates to a method and apparatus for adjusting the stroke on a random orbital machine, such as, but not limited to, polishing machines, sanding machines, and massaging machines. This adjustment ability allows a user to define the stroke of the random orbital machine and adjust it between a maximum definitive stroke setting and minimum zero orbital or rotary setting.

Polishing machines and sanding machines are routinely used in the automotive detailing industry and home building industry to correct imperfections in the paint or drywall and to apply polishes and waxes. There are three primary machines used, including rotary buffers, random orbital machines, and dual action machines. Each tool has its place, as the manner in which the pad spins on each machine is unique and used for different purposes.

Rotary buffers are the fastest and most effective machine for removing paint defects in a controlled manner with good results. The drive unit used in a rotary buffer is directly connected to the pad and each one is in axial alignment with each other. In order to correct paint scratches, the rotary buffer is commonly used to remove enough paint surrounding the scratches to make the surface level. Removing scratches, however, requires more skill and control of the machine than a typical hobbyist possesses. For this reason, rotary buffers are commonly avoided by average users as it is very easy to remove too much paint and damage the finish by causing swirl marks or by burning the paint.

Random orbital machines were introduced in order to meet the needs of an average user, as they require less experience and control to operate. A random orbital machine uses a gear case that employs two unique mechanisms that move a pad attached to a backing plate. Unlike a rotary buffer, random orbital machines place the central rotational axis of the pad and the backing plate offset from the driveshaft of the machine. This offset is commonly referred to as the "stroke". As a result, the backing plate and pad orbit the driveshaft in a circular motion. At the same time, the pad randomly spins, as it is mounted on an idle bearing. This random spinning varies with pressure applied on the pad and is not directly powered. The result is a polishing action that will not burn or cut through the paint as it will not produce the heat from a powered spinning action. Random orbital machines are, therefore, much safer and dramatically less likely to cause swirls or burn through the paint.

Similar to random orbital machines, dual action machines place the central rotational axis of the pad and the backing plate offset from the driveshaft. As a result of this stroke, the backing plate and pad orbit the driveshaft in a circular motion. However, with a dual action machine the spinning of the pad is directly powered.

At the heart of a random orbital machine is the machine's stroke. The stroke is determined by the offset between the driveshaft axis and the backing axis. A longer offset or stroke places the backing plate rotational axis farther away from the driveshaft axis. Multiplying the offset by two produces the stroke diameter. The "stroke" is, therefore, a term that identifies the diameter of the path the backing plate travels as it orbits around the driveshaft.

A majority of random orbital machines are small stroke machines, which mean they use a stroke length that measures somewhere between approximately <NUM> - <NUM>. A small stroke machine limits the movement of the pad to a smaller and tighter orbit. This results in a smoother action. A small stroke machine is also easier to control because the backing plate orbits around the driveshaft rotational axis in a tighter path. There are less vibrations and movement making the machine easier to hold due to the smoother action.

A large stroke machine delivers increased orbits per minute (OPM) of backing plate motion using the same rotations per minute (RPM), as the orbit of the backing plate and the pad around the drive shaft is increased. A large stroke also increases movement of the pad which helps spread out polishing compounds and treats a larger surface area. It also accomplishes more cutting action into the paint which allows for scratches and paint defects to be corrected. Small stroke machines typically only polish the paint and do not cut into it, and, therefore, are not able to remove surface defects.

One method of addressing the deficiencies of a small stroke has been to increase the RPM of the machine. While this increases the rotation of the motor, the machine stroke stays the same. There are also longevity issues associated with increased RPM for the motor and increased OPM for the pad. Increasing the RPM puts more strain on the motor, while increased OPM burns out a pad faster.

In sum, both long stroke and short stroke machines have their place in the industry. Therefore, what is needed is a machine that can be adjusted by the user without special tools or disassembly of the machine. Finally, what is needed is a compact, simple, and effective method to adjust the stroke of a machine based on the needs of the user. A random orbital machine according to the state of the art, which reflects the preamble of claim <NUM>, can be found in document <CIT>. In addition, a random orbital machine according to the state of the art can be found in document <CIT>.

According to the disclosure, an adjustable stroke mechanism for a random orbital machine comprises a housing having a central axis and a wall enclosing a cavity. At least one counterweight is movably disposed within the cavity. A mounting assembly is disposed within the cavity. The mounting assembly includes a workpiece attachment mechanism. A stroke adjustor couples the at least one counterweight with the mounting assembly. The stroke adjustor enables the counterweight and mounting assembly to move with respect to one another such that a distance between the counterweight and the mounting assembly is variable adjusted. This also provides both a static and dynamic balancing of the stroke adjustor. Accordingly, this variable adjustable the stroke radius of the workpiece attachment mechanism with respect to the central axis of the housing. The stroke adjustor includes an adjusting ring and a cam mechanism. The adjustor ring surrounds the wall of the housing. The adjustor ring is axially movable along the central axis. Additionally, the adjustor ring is rotatable around the central axis. The counterweight engages the cam mechanism to move the counterweight in response to adjustor ring movement. The mounting assembly, including a bearing carriage, engages the cam mechanism to move the mounting assembly in response to adjustor ring movement. The workpiece attachment mechanism further comprises a bearing axle. The bearing axle extends through the housing through a bearing carriage and into the counterweight. At least one bearing surrounds the bearing axle and the at least one bearing is disposed within the orifice of the bearing carriage. A locking plate mechanism is associated with the cam mechanism. The locking mechanism locks the workpiece attachment mechanism in position. The cam mechanism further comprises at least one tab. The at least one tab engages a slot in a hub for locking the stroke adjustor in position.

According to a second embodiment, a method of adjusting a stroke of a random orbital machine comprises coupling an adjustable stroke mechanism. It includes, according to the disclosure, an adjustable stroke mechanism for a random orbital machine comprises a housing having a central axis and a wall enclosing a cavity. At least one counterweight is movably disposed within the cavity. A mounting assembly is disposed within the cavity. The mounting assembly includes a workpiece attachment mechanism. A stroke adjustor couples the at least one counterweight with the mounting assembly. The stroke adjustor enables the counterweight and mounting assembly to move with respect to one another such that a distance between the counterweight and the mounting assembly is variable adjusted. This also provides both static and dynamic balancing of the stroke adjustor. Accordingly, this variably adjusts the stroke radius of the workpiece attachment mechanism with respect to the central axis of the housing. The stroke adjustor is axially moved with respect to the central axis of the housing. The stroke adjustor rotates about the central axis of the axis. The counterweight and mounting assembly move with respect to one another. A distance between the counterweight and the mounting assembly is variably adjusted. A stroke radius of the workpiece attachment mechanism is variably adjusted with respect to the central axis.

Turning to the figures, a tool is illustrated with an adjustable stroke device and is designated with the reference numeral <NUM>. The tool <NUM> includes a motor <NUM>, a power source <NUM> and a switch <NUM> for activating and deactivating the power source. The power source is shown as a cord but could be a rechargeable battery. The motor includes a pinion <NUM> that is positioned inside of a head housing <NUM> of the tool. The head housing <NUM> includes a cavity to house a drivetrain <NUM>. The drivetrain <NUM> includes a gear <NUM> meshing with the pinion <NUM> and a rotatable spindle <NUM>. The head housing has a spindle housing <NUM> and cover <NUM>. The cover <NUM> includes a push button <NUM>. A pin <NUM> is attached to the push button <NUM>. The pin <NUM> engages bores <NUM> in the gear <NUM> to lock the rotation of the drive train <NUM>. The stroke adjustor <NUM> is rotatably coupled with the spindle <NUM> and is mounted with the bottom of the head housing <NUM>.

The stroke adjustor <NUM> includes a drive hub <NUM>, a workpiece mounting assembly <NUM> and a counterbalance mechanism <NUM> and a stroke adjustment mechanism <NUM>. The drive hub <NUM> includes a drive hub body <NUM> with a nipple <NUM> as well as extending legs <NUM>. The nipple <NUM> extends from one side of the drive hub body <NUM> while the legs <NUM> extend from the other. The nipple <NUM> is threaded to receive the spindle <NUM>. A hub plate <NUM> is attached to the legs <NUM> by threaded fasteners. The drive hub body <NUM> includes a plurality of slots <NUM> that couple with the counterweight mechanism <NUM> and workpiece mounting assembly <NUM> as will be explained later. Additionally, the hub plate <NUM> includes a plurality of slots <NUM> that couple with the counterweight mechanism <NUM>. Also, the hub plate <NUM> includes an aperture <NUM>, with an elliptical shape, that receives a portion of the workpiece mounting assembly <NUM>. Thus, rotation of the spindle <NUM> is applied to the drive hub <NUM> to drive the stroke adjustor <NUM>.

The workpiece mounting assembly <NUM> includes a carriage <NUM>. The carriage includes a first carriage block <NUM> and a second carriage block <NUM>. The carriage blocks <NUM>, <NUM> include bores to receive bearings <NUM>. A spindle <NUM> is passed through the bearings <NUM> and held by the carriage <NUM>. The spindle <NUM> is rotatable in the bearings <NUM>. Also, the spindle <NUM> includes a threaded tip <NUM> that enables a workpiece, such as a pad or the like, to be attached to the spindle <NUM>. The spindle <NUM> passes through the aperture <NUM> in the hub plate <NUM>. The first carriage block <NUM> includes a post <NUM> that passes through the slot <NUM> in the drive hub body <NUM>. The post <NUM> is coupled with the stroke adjustment mechanism <NUM> as will be explained later.

The counterweight mechanism <NUM> includes a frame <NUM> and a counterweight ring <NUM>. The counterweight ring <NUM> is secured to the frame <NUM> via fasteners <NUM>. Both the frame <NUM> and counterweight ring <NUM> have an overall U-shape. The frame <NUM> includes a plurality of posts <NUM> that pass through the channels <NUM> in the hub plate <NUM>. Thus, the counterweight ring <NUM> is attached to the underside of the hub plate <NUM>. Also, the counterweight ring <NUM> includes a slot or channel <NUM> that enables the spindle <NUM> to pass through the channel <NUM>. The counterweight frame <NUM> also includes a post <NUM>. The post <NUM> passes through the slot <NUM> in the drive hub body <NUM>.

The stroke adjustment mechanism <NUM> includes a cam <NUM> and housing <NUM> surrounding the drive hub <NUM>, workpiece mounting assembly <NUM> and counterweight mechanism <NUM>. The housing <NUM> includes a sleeve <NUM>, ring <NUM> and grip <NUM>. The grip <NUM> is connected with the ring <NUM> which, in turn, is coupled with the sleeve <NUM>, all of which are cylindrical and enable the stroke adjustment mechanism <NUM> to be moved axially along the spindle axis <NUM> as well as rotatable about the axis of the spindle <NUM>.

The sleeve <NUM> includes a plurality of slots <NUM> that receive tabs <NUM>. The tabs <NUM> contact the cam <NUM>. The tabs <NUM> have a stepped shape body <NUM>. The tread <NUM> is positioned underneath the cam <NUM>. This enables the tabs <NUM> to push the cam <NUM> away from the hub plate <NUM> into engagement with the spindle housing <NUM>. Underneath the tread <NUM> is a channel <NUM>. The channel <NUM> receives a coil of the spring <NUM> to position the spring <NUM> and the tabs <NUM> with respect to the sleeve <NUM>. The sleeve <NUM> includes a reduced circumferential portion <NUM> that receives the spring <NUM>. The tread <NUM> of tab <NUM> includes a ledge <NUM> that is received within the ring <NUM>. Also, the tab <NUM> includes a projection portion <NUM> that slides in a slot in the head housing <NUM>. A C ring <NUM> is attached with the head housing <NUM> covering the tab projections <NUM> to retain the adjustable stroke mechanism onto the head housing <NUM>.

The <NUM> includes a pair of arcuate slots <NUM>, <NUM>. Slot <NUM> receives the workpiece mounting assembly post <NUM> and the arcuate slot <NUM> receives the counterweight frame post <NUM>. As the drive hub <NUM> is rotated by the stroke adjustment mechanism <NUM>, the post <NUM>, <NUM> move the counterweight <NUM> and workpiece mounting assembly <NUM> with respect to one another. This movement moves the axis <NUM> of the spindle <NUM> toward or away from the central axis <NUM> of spindle <NUM>. This movement also provides both static and dynamic balancing of the stroke adjustor.

The underside of the cam <NUM> includes a plurality of tabs <NUM>. The tabs <NUM> position into slots <NUM> on the drive hub body <NUM>. Thus, depending upon the position of the spindle <NUM> with respect to the central axis <NUM>, the tabs <NUM> will be in different hub slots <NUM> to enable variable positioning of the spindle <NUM> with respect to the central axis <NUM>.

An axle lock bridge <NUM> is positioned adjacent to the drive hub <NUM>. The axle lock bridge <NUM> includes legs <NUM> that slide in slots between the drive hub legs <NUM>. Thus, the axle lock bridge <NUM> is positioned between the legs <NUM>. A ring <NUM> encircles the hub <NUM>. The ring <NUM> includes apertures that enable fasteners to pass through the ring to position the axle lock bridge on the drive hub <NUM>. The axle lock bridge <NUM> includes an aperture <NUM> to receive the top <NUM> of the spindle <NUM>. When the workpiece mounting assembly spindle <NUM> is aligned coaxially with the drive spindle <NUM>, the axle lock bridge aperture <NUM> receives the top <NUM> of the spindle <NUM> to lock the spindle <NUM> in a coaxial position. This provides a zero orbital or rotary position for the stroke adjustor <NUM>. Also, the axle lock bridge <NUM> is biased to rest in channels <NUM> in the counterweight frame <NUM>.

The above adjustable stroke adjustor <NUM> functions as follows. The push button pin <NUM> engages a gear bore <NUM>. The grip <NUM> is pushed towards the drive head housing <NUM>. As this occurs, the spring <NUM> is compressed by the tabs <NUM>. The tab treads <NUM> lift the cam <NUM> so that the cam tabs <NUM> disengage from the hub slots <NUM>. The projections <NUM>, on top of the cam <NUM>, engage the slots <NUM> in the spindle housing <NUM>. This secures the cam <NUM> in place.

The grip <NUM>, connects with the ring <NUM> which, in turn, contacts with the drive hub <NUM>. The ring projections <NUM> engage the slots <NUM> of the hub plate <NUM>. As the grip <NUM> is rotated, the drive hub <NUM> is rotated. As this occurs, the posts <NUM>, <NUM> in the cam arcuate slots <NUM>, <NUM> are moved with respect to one another. As the posts <NUM>, <NUM> move with respect to one another, the counterweight mechanism <NUM> as well as the workpiece mounting assembly <NUM> are moved with respect to one another so that the spindle <NUM> is moved with respect to the central axis <NUM> of the spindle <NUM>. This variably adjust the stroke of the adjustable stroke adjustor <NUM>. The stroke is adjusted between a true rotary position to a maximum orbital position.

Claim 1:
An adjustable stroke mechanism (<NUM>) for a random orbital machine comprising:
a housing (<NUM>) having a central axis (<NUM>) and a wall enclosing a cavity;
at least one counterweight (<NUM>) movably disposed within the cavity;
a mounting assembly (<NUM>) disposed within the cavity, the mounting assembly (<NUM>) including a workpiece attachment mechanism;
characterized in that
a stroke adjustor (<NUM>) including a rotatable cam mechanism comprising a cam (<NUM>), the cam mechanism coupling the at least one counterweight (<NUM>) with the mounting assembly (<NUM>), the stroke adjustor (<NUM>) including an adjustor ring (<NUM>) surrounding the wall of the housing, wherein the adjustor ring (<NUM>) is axially moveable and is rotatable around the central axis (<NUM>), the stroke adjustor cam mechanism, upon rotation of the cam mechanism, enabling the counterweight (<NUM>) and mounting assembly (<NUM>) to move in response to adjustor ring (<NUM>) movement and with respect to one another such that a distance between the counterweight (<NUM>) and the mounting assembly (<NUM>) is variably adjusted which, in turn, variably adjusts a stroke radius of the workpiece attachment mechanism with respect to the central axis (<NUM>) of the housing (<NUM>).