Clamp lock apparatus and method for a paint mixer

An improved paint mixer of the type rotating a paint container about a tumbling axis and a perpendicular spin axis, the improvements of a clamp assembly and lock, splash guards protecting a range-of-travel of upright clamp portions, low friction guide plates, an adjustable height strike plate and roller, a rigid gear assembly, an offset in the clamp to return the paint container to an upright position after mixing, and a relief in a raised portion on a lower plate of the clamp for assisting loading and unloading of the paint container.

BACKGROUND OF THE INVENTION

The present invention relates to the field of paint mixers of the type for mixing paint and related liquid coatings in conventional containers in the range of about 5 gallons or about 20 liters. More particularly, the present invention relates to such mixers which utilize gyroscopic mixing motion while the coating container is clamped between a pair of opposed plates. It is to be understood that such mixers are suitable for mixing coatings in the range of about 1 gallon to about 5 gallons (or the metric equivalent), and may be utilized to mix coatings in other than cylindrical containers, including, but not limited to so-called “square” containers, particularly when adapters or special shaped container holders are used.

In the past, one such mixer clamped the coating container by advancing one plate towards the other using a lead screw rotated by a hand wheel. While such an approach was generally satisfactory, the lead screw was prone to unscrewing during mixing, resulting in unintended partial or full release of the coating container, with consequent damage to the coating container and possibly the mixer. If the coating container was breached during such release, the coating would typically spill, contaminating the mixer and possibly the environment of the mixer. Such a result is naturally undesirable.

The present invention overcomes the shortcoming of the above described prior art mixer by providing a locking clamp for a gyroscopic type paint mixer which prevents the unintended release of the opposed plate clamp.

In another aspect, the above described prior art machine had a single traveling clamping screw attached to a handle and threaded through a stationary nut. Rotating the handle turned the screw and resulted in an axial displacement of the screw. In this prior art machine, the top clamping plate was attached to the screw and thus traveled up and down to clamp and unclamp the paint container.

The present invention also uses a single lead screw. However, in the present invention, the screw can rotate but is axially fixed. In the present invention, the screw is threaded through a nut which is free to travel axially but is fixed against rotation by rigidly mounting it to a cross member or bridge portion captured between two upright members or portions. By fixing the nut against rotation in the present invention (i.e. not allowing the nut to turn with the lead screw), the nut travels up and down when the screw is rotated, thus moving the top clamp plate to clamp and unclamp the paint container.

Another prior art gyroscopic type mixer used twin lead screws and two or more upright supports. In that prior art machine, turning the crank handle engaged a series of gears which rotated the twin lead screws. The lead screws were free to rotate but were fixed axially. The clamp plates were attached to cross-members that had threaded nuts fixed against rotation. In that prior art machine, turning the lead screws caused both the top and bottom clamp plates to move towards or away from each other to clamp or unclamp a paint container, in contrast to the present invention which moves only the top plate. The prior art machine which moves both plates simultaneously tended to keep the center of mass close to the tumble axis. In contrast, one aspect of the present invention permanently positions the center of mass below the tumble axis, allowing gravity to urge the rotating frame and paint container to stop in an upright position. Furthermore, the present invention greatly simplifies the design by requiring fewer parts in series in the clamping mechanism, with consequent reduction in cost and friction between operating parts.

Other aspects of the present invention include at least one splash guard for each range-of-travel portion for the movable part or parts of the clamping mechanism to prevent contamination with consequent increase in friction. A flange on the splash guard also acts as a stop to limit motion of the movable parts of the clamping mechanism at an end of the range-of-travel. In addition, the present invention includes at least one corresponding guide member to maintain the relationship between the fixed and moving parts of the rotatable clamp apparatus, with the guide member(s) formed of a polymer to reduce friction. Another aspect of the present invention is a strike plate located below a guide roller at a lower edge of a front opening of the mixer. The strike plate prevents the roller from denting the paint container as it is removed from the mixer, particularly when the container is metal. A still further aspect of the present invention is a relief formed in a raised lip on the lower clamp plate to aid in the transfer of the paint container into and out of the clamping apparatus. Yet another aspect of the present invention is to have a common base on which both a stationary sun gear and a planet gear (on the rotating clamp) are rigidly mounted, eliminating the play present with one prior art mixer design in which vibration mounts allowed the planet gear to “float” with respect to the sun gear, causing excessive misalignment and wear.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the Figures, and most particularly toFIGS. 1 and 2, an improved paint mixer20may be seen. Mixer20is of the type having a clamping mechanism21which includes a rotatable frame23and a pair of opposed plates22and24sized and spaced to receive and clamp a conventional 5 gallon container of paint or similar coating material. In operation, mixer20will rotate the container about a pair of axes26and28as indicated by arrows30and32. Mixer20has an enclosure34with a door36, shown in an OPEN position inFIGS. 1 and 2. Suitable controls38may be mounted on a control panel40to start, stop and control the operation (e.g., timing) of the mixer20.

As may be seen most clearly inFIG. 2, mixer20may have a single pivot point system42on each side (only one of which is shown) which improves alignment and durability of the door36. System42includes a mounting pad44secured to the enclosure34, and a boss46for pivotably receiving and supporting a door mounting arm48for pivoting movement thereabout. Arm48is pivotably secured to boss46via a bushing50and cap screw52. Referring now again toFIG. 1, arm48is preferably secured to door36via one or more gussets54.

Referring now toFIGS. 3 and 4, certain details of the clamping mechanism21may be seen. The clamping mechanism21has a channel56supporting the lower plate24through intermediate structure to be described infra. A pair of shaft weldments58support channel56. A tumble arm weldment60has a pair of projecting channels62securing shaft weldments58to a back plate64of the tumble arm weldment60. In the embodiment ofFIG. 3, frame23is made up of a number of pieces secured together, as described above.

Referring now toFIG. 3A, a first alternative embodiment of a unitary frame23′ including backplate and upright portions of the clamping mechanism21may be seen. In this embodiment, a backplate64′ is formed from the same piece of material as upright portions58.′ Upright portions58′ may have flanges57to maintain alignment of the movable portion66of the clamping mechanism21. As a further alternative embodiment, an extension56′ of the backplate64′ may extend under lower plate24in place of channel56. Either channel56or extension56′ may be secured to upright portions58′ by any conventional means, such as welds59. Similarly, as a still further alternative embodiment, the bridge78may be formed as an extension78′ shown in phantom inFIG. 3Aas a folded top extending from and formed of the same piece of material as backplate64′ and secured by conventional means to upright portions58.′

An upper clamp mechanism or yoke assembly66includes a movable cross member68, top plate22, a pair of paint splash guards70, a pair of polymer guide plates72, a lead screw nut76and a bearing assembly88(shown inFIGS. 5 and 5A). Mechanism66is free to travel up and down along portions73of shafts58, as controlled by a lead screw74turning in the nut76mounted in cross member68. Upper clamp mechanism66is carried by an upper portion69of the frame23of the clamping mechanism21. Lead screw74is rotatably mounted in a bridge78spanning the two shaft weldments58. Lead screw74is secured to and rotatable by a wing plate80having a rotatable handle82and a fixed handle84. A sprocket86is secured to wing plate80for rotation therewith. Wing plate80, together with its associated handles82and84, sprocket86, and a pawl assembly95together form a lock105. Lock105and bridge78, together with associated parts, such as fasteners, form the upper portion69of rotatable frame23.

Referring now also toFIGS. 5,5A and6, the bearing assembly88supports lead screw74on bridge78. A retaining ring83is received on a retaining ring groove85located just below a square shaped end87on lead screw74. A mating square shaped hole81for receiving end87is located in wing plate80. Referring most particularly toFIG. 5A, the bearing assembly88includes a sealed double row anti-friction ball bearing89for radial loads, a bearing bracket91, and an anti-friction roller bearing93and associated thrust washers97for axial thrust loads imposed on the lead screw or centrally-located threaded rod74. Referring now most particularly toFIG. 6, a pawl assembly95includes a pawl shaft96, a spring102, a bracket104and a pair of set screws98, along with a manually releasable pawl90having a tooth92. Referring now again also toFIGS. 4 and 5, tooth92has an involute-like profile and is biased into engagement with sprocket86(which also has involute-like teeth) but allows wing plate80to rotate in the direction of advancing the lead screw74, tightening the clamping mechanism21. When it is desired to retract the lead screw74to loosen the clamping mechanism21, a pawl handle94of the pawl assembly95is grasped and used to rotate pawl90until the tooth92is out of engagement with sprocket86, allowing reverse rotation of the wing plate80, preferably via handle82. Pawl90is secured to the rotatable pawl shaft96by the pair of set screws98(seeFIG. 6) and pawl90is biased in the direction opposite arrow100(seeFIG. 7) by the spring102carried on pawl shaft96and acting against the bracket104also carried on pawl shaft96. Spring102reacts against a threaded fastener103secured to bridge78. A second threaded fastener107acts as a stop to limit the degree of rotation of pawl assembly95.

Referring now also toFIGS. 7 and 8, the parts of a selectively releasable lock105(including pawl assembly95and wing plate80) for the clamping mechanism21may be seen in plan view in two operating positions. Lock105has a first state shown inFIG. 7preventing retracting movement of the second plate22with respect to the first plate24and permitting advancing movement of the second plate22with respect to the first plate24. InFIG. 7, wing plate80is cutaway to show the engagement of tooth92with sprocket86. As wing plate80is rotated in the direction of arrow106, sprocket86drives the pawl90to rotate in the direction of arrow100until the tooth92is clear of the sprocket86, permitting clamping force to be applied to a paint container (with or without an adapter) located between plates22and24. It is to be understood that pawl90will ratchet against sprocket86as rotation of wing plate80continues. Initially, rotatable handle82may be used in a single-handed fashion, if desired, to rapidly rotate wing plate80to advance plate22towards a top of a paint container resting on plate24. Once plate22comes into contact with the top of the paint container, fixed handle84may be used along with movable handle82in a two-handed fashion to snugly seat plate22against the top of the paint container to securely clamp the paint container using the clamping mechanism21.

If wing plate80is urged in the direction opposite that of arrow106without releasing the pawl90, the lock105will prevent release of the clamping force previously applied to the paint container located between plates22and24. Once the paint container is securely clamped, the mixer is preferably operated to mix the contents of the paint container with a spinning and tumbling motion.

When it is desired to remove the paint container from the clamping mechanism21, the lock105is released, and the wing plate rotated to retract plate22from the top of the paint container. Lock105is released by manually moving the pawl90to at least the position shown inFIG. 8, where pawl90is shown with tooth92clearing the sprocket86.FIG. 8illustrates a second state for lock105permitting retracting movement of the second plate22with respect to the first plate24. To maintain lock105in the second state it is to be understood that pawl handle94must be manually grasped and pawl90moved in the direction of arrow100to at least the position shown inFIG. 8, where the tooth92is clear of the sprocket86, permitting wing plate80to be rotated in the direction of arrow108, releasing the clamping mechanism21. It is to be understood that if pawl90is moved further than as shown inFIG. 8such that there is clearance between tooth92and sprocket86, lock105will still be in the second state, i.e., the state permitting release of the clamping mechanism21.

It may thus be seen that when lock105is in the first state, pawl90is biased into engagement with sprocket86, permitting clamping motion and preventing releasing motion. When lock105is in the second state, pawl90is manually urged out of engagement with sprocket86, permitting releasing motion of the clamping mechanism21.

Again referring also toFIGS. 3 and 4, the paint guards70respectively shield each of a reduced diameter portion73of the shaft weldments58that provide a range of travel for the movable part66of the clamping mechanism21. If paint were allowed to accumulate on these portions of the shaft weldments58, it would subject the movable upper clamp mechanism66to the possibility of uneven loading, due to one side or the other binding between the mechanism66(more particularly, the guide plate72) and a reduced diameter portion73of the shaft weldments58. In other words, the paint guards70keep the reduced diameter portions73(which correspond to the range-of-travel for the upper clamp mechanism66) clean and free of paint that may escape from a lid or bung of a coating container when the mixer20is operated. Each paint guard70may have a flange71with an aperture79having a diameter slightly larger than a diameter of portion73and smaller than a diameter of portion58below a step77. Contact between flange71and step77on shaft weldment or upright member or portion58prevents further downward travel of the clamping mechanism21to provide a stop or limit to motion of the movable part66at the end of the range-of-travel when flange71contacts step77.

The guide plates72provide a low-friction interface between the upper clamp mechanism66and each of the range-of-travel portions73of shaft weldments58. It is to be understood that each of the guide plates72have a U-shaped cutout75that closely interfits with the reduced diameter portion73of shaft weldments58. Guide plates72are formed of a polymer, preferably acetal or UHMW polyethylene. Referring toFIGS. 3 and 4, it can thus be seen that the pair of polymer guide members72are secured to cross member68, with each of the guide members72in contact with a respective one of the upright members or portions58for reducing noise and friction that could otherwise result from contact with at least one of the upright members or portions.

Another aspect of the mixer20may be seen with respect toFIGS. 9,10and11. In this aspect, the paint mixer includes a main drive110having an output112connected to the rotatable frame23to rotate the frame about the first axis28with the main drive rigidly mounted on a common base114to which a stationary gear116is rigidly mounted. The mixer20also includes a gear box or gear train118mounted on the rotatable frame23with an output120connected to the first plate24to rotate the first plate about the second axis26. The gear train has a gear ratio between the rotations of the frame23about the first axis28and the rotations of the first plate24about the second axis26in a fixed ratio. The gear train also has an input122connected to a planet gear124engaged with the stationary gear116such that the rigid mounting of the main drive110and stationary gear116to the common base114maintains a desired engagement between the stationary gear116and the planet gear124. Suitable vibration dampers126may be located between the common base114and a main base assembly128of the mixer20. Main base assembly may include a generally pan-shaped lower portion129and a bridge-shaped upper portion131, with the lower and upper portions secured together, such as by welding. The main drive110thus provides a means for rotating the frame23about the first axis28within the enclosure or housing34; and the gear box118provides means for spinning a paint container about the second axis26, which is perpendicular to the first axis28.

The main drive110may have an electric motor130and a right angle gear reducer132to drive output112connected to the frame23. The output112may have a shaft134supported by a flanged bearing136and by gear reducer132. It is to be understood that shaft134extends into gear reducer to be driven therefrom and is secured thereto by a threaded fastener133and washers135. Shaft134carries a drive plate138for attachment to the back plate64of the clamping mechanism21. Bearing136is mounted on common base114. Common base114has a vertical portion140and a horizontal portion142, and may have gussets144welded to portions140and142to stiffen the common base114. Motor130and gear reducer132are mounted on the common base114. Bearing136is preferably secured to shaft134by a conventional squeeze clamp type attachment.

Referring now most particularly toFIGS. 12 and 13, another aspect of the present invention may be seen. InFIGS. 12 and 13a cross150indicates the center of rotation for the tumble axis28. InFIG. 13, a cross152indicates the center of gravity of the rotatable clamping mechanism21(including frame23) and one type of conventional paint container such as a conventional five gallon cylindrical container156. It is to be understood that in the practice of the present invention the location of the assembly and container center of gravity indicated by cross152is desirably located below cross150by an offset distance154. The offset distance154will vary, depending upon the size, shape and type of container and the mass of the coating material contents of the container156. For example mixer20is suitable for mixing paint in polymer or metal containers, which are known to have different aspect ratios, i.e., height to diameter ratios. Nevertheless, requiring the location of the center of gravity152of the combination of the clamping mechanism21and container clamped in the frame23to be below the center of rotation150for the tumble axis28(when the container and frame are in an upright position) will, as a result, allow the rotatable clamping mechanism21(including frame23) to come to rest with the paint container156in a generally upright position after mixing, as shown inFIG. 13, when the container156is clamped between plates22and24regardless of the size, type, shape or material of the container or the mass of the coating contents, and whether or not an adapter is used (for example, to hold a special shaped or sized container).

The main drive110provides a first means for rotating the frame23of clamping mechanism21about the first axis28within the enclosure or housing34; and the gear box or gear train118provides a second means for spinning the paint container156about the second axis26, which is perpendicular to the first axis28. As described above, the frame23is offset by the distance154with respect to the first axis28such that the frame23will come to rest with the paint container156in a generally upright position after mixing.

Referring now toFIGS. 14 through 20a still further aspect of the improved paint mixer20of the present invention may be seen. A strike plate assembly160is located at a lower edge162of an opening164in the enclosure34for loading and unloading the paint container156with respect to the mixer20. The strike plate assembly160includes a strike plate166located generally at or below the lower edge162of the opening164and facing an inside165of the mixer20for receiving the impact of the paint container156as it is unloaded from the paint mixer20, as shown inFIG. 14. Without the strike plate166, it is to be understood that a side168of the paint container156may easily be dented (when the container is made of metal) upon impact with a roller170located above the strike plate166for transferring the paint container156into and out of the mixer20. As may be seen most clearly inFIGS. 14 and 20, the strike plate166contacts the bottom edge172of the paint container156, and prevents the side168from becoming dented when the paint container156is tilted as shown inFIG. 14while being removed from mixer20. The strike plate166forms a part of a roller bracket174carrying the roller170and adjustably secured to a lower front plate176of the housing34for adjusting the height of the roller170and strike plate166forming the strike plate assembly160. Bracket174is secured to front plate176by a first pair of screws178extending forward through front plate176and a second pair of screws179extending rearward through an interrupted flange181, which is preferably formed from the same material as front plate176. A cross section view of the relationship of the strike plate assembly160(including roller bracket174) and the flanged front plate176is shown inFIG. 20. Height adjustment of the roller170may be achieved by loosening both sets of attachment screws178,179and sliding the assembly160vertically with respect to slots180,182and then tightening screws178,179. InFIGS. 15 and 16, slots182may be seen. These slots receive screws (not shown) similar to screws178. The slots180align with pressed in nuts184in front flanges186and slots182align with pressed in nuts188in rear flanges200. The strike plate166may have a stiffener angle plate202for reinforcement, it being understood that strike plate166and stiffener angle plate202together make up an “L” shaped cross-section204as shown most clearly inFIG. 20.

Referring back to FIGS.3and10–13, in another aspect of the present invention a relief210is formed in lower plate24to assist in loading and unloading paint containers on to and off of plate24. The lower plate24includes a raised portion or lip212surrounding a portion of a periphery of the plate and the relief210in the raised portion212is sufficiently wide to enable or assist in loading and unloading the paint container on to and off of the first or lower plate24by permitting sliding the container through or across the relief210instead of having to lift the container over the lip212. The relief210is oriented towards a front of the mixer when the mixer is stopped. This is accomplished by providing an integer gear ratio and synchronizing the timing of rotation about spin axis26with the tumble axis28such that the relief210is forward facing each time the rotatable frame23of clamping mechanism21reaches an upright position, as shown inFIGS. 12 and 13. The number of teeth in the stationary gear116and in the planet or spur gear124and the ratio of gear train118set the ratio of the spin and tumble revolutions and the positioning of the spur gear124with respect to the stationary gear116(once the ratio of gear train118is fixed) may be used to synchronize the timing of the spin and tumble rotational movements.

The invention is not to be taken as limited to all of the details thereof as modifications and variations thereof may be made without departing from the spirit or scope of the invention.