Patent Grant
7128640
Powered disk and drum sanders are commonly known and used for sanding floors and other surface areas. Floor sanders designed specifically for floor surface applications are of the motorized drum sander type. Traditionally, the leading and trailing edges of a sheet of sand paper are secured within a slot on the drum by a paper edge gripping mechanism in order to hold the sand paper on the drum. There are other methods of doing it; such having three screws securing a bar that captures the butting edges of the sheet. The screws are known to come loose and scrap the floor. All of these methods rely on the butt joint as the point of security, the point where the sheet is attached to the drum. The remaining surface area of the sheet is wrapped around the drum but is not secured to the drum body or surface.
There are other methods of mounting disposable sanding material to sanders. One method employs a loop or belt of sand paper that must be slid over one end of the drum, where the drum is supported on the sander at its other end by a heavy bearing. The belts may be used in combination with drums of retractable diameters which are then expanded to hold the belt in place. The drum designs are complex, and often don't perform well due to the expansion mechanisms, causing excessive “chatter” in use and leaving undesirable marks on the sanded floor surface.
Other types of sanders such as hand held or bench mounted rotating disk sanders (as opposed to drum sanders) have been known to try to use hook and loop fastener materials such as Velcro® brand material to secure the sand paper to the flexible sanding pad. However, the load and load distribution are markedly different for a disk sander than for a drum. There is not the continuous weight of a floor sander bearing on the contact interface causing increased pressure and temperature at the sandpaper to pad attachment interface, there is no centrifugal force normal to the attachment interface attempting to dislodge the sandpaper from the pad, and there is no paper joint on the sanding disk exposed to the leading edge lip peeling action of the passage of sandpaper over the surface or floor being sanded. The contact area or pressure print of a rotating sanding disk to the floor is typically constrained to less than one side of the disk area, and so excludes the region of the point of attachment, at the center of the disk.
For all drum type floor sanders, the weight of the machine combined with the rotating drum works to remove material from the floor surface. In finishing or re-finishing operations, some skill is required to achieve a satisfactory result. As is well known, the sanding sheets are consumed by use and must be replaced frequently. There is some user resistance to the effort and attention to detail required to install new sanding blanks with the necessary precision on the drum, so better and easier mounting methods are sought.
It is unknown to this Applicant for portable drum type floor sanders used with sand paper sheets to achieve commercial success using a hook and loop fastener system such as a Velcro® brand material to secure a sand paper blank to a fixed diameter drum surface where a joint in the sheet must be exposed on the drum surface. The reasons why can be readily deduced by one skilled in the art: rotational speed, machine weight, inherent resistant in the abrading motion, exposed leading edge of the sandpaper blank at a joint the drum, effects of the resulting high heat, peeling and shear pressure on the fastening materials, and cost. It has been tried without success by others.
What is disclosed is a unique drum and sanding sheet configuration for attaching and using sand paper sheets or blanks to a fixed diameter drum by use of a hook and loop fastening system. The invention, in its simplest form, is a fixed diameter drum for a powered floor sander that has a somewhat compliant layer of dense material firmly attached by adhesive to a rigid drum core, and which is further uniquely modified by having its cylindrical surface being completed covered by a sheet of the hook component of a hook and loop fastener system, the backside of which is firmed attached to the compliant layer by a high temperature adhesive. The corresponding sanding sheets are backed or laminated with a loop component sheet or layer of fabric, using a high temperature adhesive, so that a sheet may be wrapped and attached by surface contact via the hook and loop interface over the full surface of the drum, with its sheet ends abutting in a joint line extending across the width of the drum, with the sanding surface exposed for sanding of a floor surface by weight of the sander and motor-driven rotation of the drum.
The invention is deceptively simple on its face, but not at all easily arrived at in practice. It was through extensive inventive efforts and experimentation that a practical solution to the problem posed by the prior art was developed and reduced to practice as elsewhere described herein and expressed in the appended claims.
Other objects and advantages of the invention will be apparent to those skilled in the art from the description and figures provided.
The invention is susceptible of various embodiments. What follows are descriptions of preferred embodiments and should not be construed as limiting of the scope of the invention.
The Applicant, a manufacturer and supplier of industrial quality, drum-type, floor sanders for many years, recognized the long standing need to simplify the attachment of sanding sheets to the drum, to promote ease of use and greater productivity.
Referring to
To the rubber sole or compliant layer there is adhered a sheet of high temperature tolerant, high strength hook material such as or equivalent to Velcro brand, Nylon, non-adhesive backed, style HTH 22 Hook, hook component material, adhered with a high performance adhesive such as or equivalent to 3M brand Scotch-Grip brand High Performance Contact Adhesive 1357. The sheet of thermoplastic hook material is positioned such that the trailing edge of the sheet is aligned with the leading edge side of the alignment bar, the hook material sheet wrapped around the rubber sole, and the leading edge terminating within the edge recess adjacent the alignment bar. The adhesive bond between the rubber sole and the sheet of fastener material is adequate to hold the hook component material in place, but is also manually peelable, facilitated by the use of a solvent such as acetone or other solvent suitable for the adhesive, for occasional replacement of the hook component material when wear or damage requires it. The adhesive provides a uniform grip over the full surface area of the hook component, holding it to the compliant layer of the drum, and tolerates the high heat and pressure of sanding, but remains peelable with the use of acetone for replacement when required.
The preferred embodiment sand paper sheet is a paper or fabric or composite paper/fabric-backed sanding sheet. Paper backed sanding sheets are normally provided for the floor sander rental market in grit numbers from #100 to #36; as are nylon reinforced paper backed sheets in grit numbers #20 to #12. Commercial grade sheets may have a resin over resin construction for greater durability under higher temperature and pressure and can be paper/fabric composites used in all grit sizes from smaller than #100 to as coarse or low as #16–4 or lower.
To the back side of the sanding sheet is laminated or adhered a 100% Nylon, low profile loop material fabric, of a weight of 3.0 oz. per square yard or 101.4 grams/meter2. It is laminated using a hot melt polyurethane adhesive capable of withstanding temperatures in excess of 300 F. The hook component and the loop fabric material of the fastener system each have a yet a higher temperature rating.
The drum and sheet combination is sized so that there is normally an intentional small gap between the trailing edge and the leading edge of the sanding sheet when wrapped on a new drum; which permits the rubber sole and drum assembly to be resurfaced to a slightly smaller diameter once or twice over the life of the drum and still accommodate the same size sanding paper blanks.
The placement of the sanding blank on the drum is important to assure a smooth wrap with fully functionally hook and loop engagement over the entire surface; especially at the leading and trailing edge or butt joint.
The size and speed of the drum rotation is preferably limited, such as to not more than 2800 rpm (rotations per minute), although speeds of not more than 2400 rpm are preferred, for 5½ and 7 inch diameter drums has been demonstrated to be effective without failure due to the centrifugal peeling force on the leading and trailing edge of the sandpaper sheet. Drum lengths of 8 to 12 inches have been demonstrated, although shorter and longer drum lengths are considered to be within the scope of the invention, up to the limit of drum core rigidity. The soft rubber sole or compliant layer in combination with the leading edge recess provides a smooth, chatter-free, trailing edge to leading edge transition for the sanding sheet during each rotation of the drum so that normal sanding operations are not affected by the joint line, and there is no visible affect in the results of the workpiece or floor being sanded.
Referring still to
The first working iterations of the invention used the existing slot 5 in the existing drum core design (a legacy of the former slot-grip mechanism) for installation of the base plate 6 so that it protruded radially from the drum core. Later embodiments oriented the base plate flatwise in a slot or recess 4A on the rubber substrate 4, providing more cushioning for the base plate. Accordingly, the base plate may be oriented radially or tangentially with reference to the drum, or simply be of square cross section and oriented tangentially. It may have a taper of between about 5 to 10 degrees, preferably 5½ degrees off square which will coincide with the slightly angular end cut on the abutting sheet ends as they wrap around the drum. At the right side of the baseplate 6 as viewed in
A conforming sheet 8 of high strength hook component material of a hook and loop fastener system, the “hook” component, is aligned with the baseplate 6 and glued, using for uniform adhesive layer 7 the contact adhesive cited previously, to the rubber substrate 4 so as to be removable by careful peeling without significant damage to the rubber substrate, yet be securely enough attached to the rubber layer so as to provide a full surface gripping system for holding a loop fabric backed sandpaper sheet 20 to the drum for extended periods of floor sanding use. The baseplate 6 serves as the edge guide for initial alignment of the trailing edge of the sandpaper blank. The drum is run at preferably not more than about 2400 rpm, but it may be up to 2800 rpm, which limits the centrifugal force on the sandpaper sheet and still provides good rotary inertia and sanding action. Professional models may have larger drum diameters, up to 7 inches and more, and be operated at even lower speeds, for example as low as 1600 rpm or as high as 2800 rpm. Actual floor weight per surface area of the sanders thus equipped and operated may be as much as 145 psi (pounds per square inch), but is preferably closer to 50 psi. Floor weight per surface area is measured as the width times drum length of a contact line of a floor sander and revolving drum bearing on a steel plate coated with a layer of markover paint.
Other embodiments, examples and variations of the floor sander and drum component of the invention will be evident to those skilled in the art. For example, there is a drum for a drum sander consisting of a drum core attachable to a drum sander for rotatingly contacting a work surface such as a floor, to which is attached a compliant sole such as a rubber layer or substrate. There is an alignment bar embedded in the compliant sole not higher than flush with the surface of the compliant sole. There is a leading edge sloping recess in the compliant sole terminating at the alignment bar. There is a sheet of hook component fastener material aligned by one edge with the alignment bar and adhered around the drum to the compliant sole so as to conform the opposing edge of the base fastener to and within the sloping recess. There is a sanding material sheet, to the backside of which is laminated a nylon loop fabric with a high temperature adhesive, the sheet sized to abut the backside of the alignment bar and wrap fully around the drum so as to firmly and fully engage the hook and loop components over the full surface area of the drum.
Not satisfied with the above embodiments, Applicant conducted additional testing and experimentation attempting to further simplify the drum and the changing of sanding materials. Referring now to
The
Applicant's further improvements and testing have demonstrated that there is no need for a ramp or indentation in this embodiment for the leading edge or trailing edge of the sanding blank, so substrate 14 is of uniform diameter including the area of its butt joint. A conforming sheet 18 of the same hook component of a high strength hook and loop fastener system as described in the above embodiment is adhered to the rubber substrate 14, using the same adhesive layer 7 of
Referring now to
Referring back to
Referring to
It will be readily understood that the drum, under the weight and power of the floor sander, is driven in rotation and puts the sanding sheet and underlying layers of the drum in the area of contact of the drum to the floor under compression, while pulling the sanding sheet around by all of its hook and loop fastening interface against the resistance of the floor, so as to abrade the floor, removing material from the surface. A myriad of forces are at play at the nip and in the contact area between the drum and the floor, where the compression and drag are applied to the sanding sheet first, including its joint, and translated through the hook and loop interface to the compliant layer of the drum and hence to the drum core.
The thermoplastic hooks of these embodiments hook component 8 are molded in uniform rows and columns on a backing layer yielding a density of 900 hooks per square inch, rows defined as running with the roll or web of material as produced and columns as running across the roll as produced. The hook direction is oriented with the rows, 50% facing in one direction and 50% in the other direction, with hooks of either direction uniformly distributed within the array. The hook component sheets, sized for their respective drums, are cut from the supplied roll of hook component material so as to maintain or repeat the same orientation on the drum as was present in the roll; that is, the rows of hooks are wrapped and running around the drum, and the columns run across the face or length of the drum.
Maintaining the same orientation of the hook material from roll to drum has two benefits. First; the bending bias of the hook component backing layer resulting from the manufacturing and rolled packaging process is repeated on the drum, minimizing the introduction of any new bending stress in the hook component backing layer. Second, the hook component material is oriented with the plane of the hooks aligned with the direction of rotation, 50% facing in one direction and 50% facing in the other direction. Hence the hook material can be applied to the drum without regard to the intended direction of rotation. Consequently, drum 10, with respect to its hook component material, can be rotated in either direction with the same effective hook holding power.
Which ever way rotated, the resistance to rotation caused by the drag of the sanding paper tends to draw or pull the loop fabric component into further engagement with at least the forward facing hooks of the hook component material.
The thermoplastic hook material sheet 18 of this embodiment is as described in the embodiments above, but the scope of the invention includes variations from the specified hook engagement depth of 0.008 and hook height of 0.028 in., and 900 hook psi density that will provide an equivalent fastening power between the sanding sheet and the drum. Applicant's testing has demonstrated a peel line strength failure limit of 7–9 pounds per lineal inch of peel line for the described hook and loop attachment system of the invention, as measured by peeling a one square inch sample sanding sheet off a 5½ inch drum, staring along one of the one inch long edges. Preferred embodiments have a peel line attachment strength of at least 5 pound per lineal inch. The shear strength limit of the attachment system, analogous to the effect of floor resistance to drum rotation tending to pull the sandpaper along or over the drum surface, measured using a one square inch sample, was 24–26 psi. Preferred embodiments have a shear strength of at least 20 pounds per square inch. Centrifugal strength, pulling resistance normal to the attachment interface, using one square inch samples of sanding sheets attached to a drum in accordance with the invention, and superglued to a one square inch surface area pulling block, measured 22–23 psi at the point of failure, nearly the same as shear strength. Preferred embodiments have a centrifugal attachment strength of not less than 20 pounds per square inch.
Hook component sheet 8 or 18 is applied to respective substrate 4 or 14 with a uniform coating layer 7 of the previously specified adhesive. The adhesive is applied to the surface of the substrate, and the hook component sheet is then tightly wrapped on it and retained until the adhesive sets properly. The use of this type adhesive permits the hook material sheet to be manually removed for replacement by careful peeling from the corner of the joint edge, without damage to the compliant substrate. Yet the hook component is securely enough attached by the cured adhesive layer 7 to the substrate so as to hold a sandpaper sheet 20 to the drum for extended periods of floor sanding use.
As in earlier embodiments, the drum 10 style of drum is operated in the range of 1600 to 2800 rpm, which keeps the centrifugal force on the sandpaper sheets at acceptable levels and still provides good rotary inertia and sanding action. Professional models may have larger drum diameters, and be operated at lower speeds, preferably about 1600 rpm. Again, actual floor weight per surface area of the sanders thus equipped and operated may be as much as 145 psi (pounds per square inch), but is preferably closer to 50 psi.
Other embodiments are within the scope of the invention. For example, there is a powered floor sanding system consisting of a motorized floor sanding machine adapted to accept and rotate a sanding drum that consists of a drum core with a cylindrical surface to which is adhered by a first adhesive layer a compliant sole, to which is adhered by a second adhesive layer a hook component of a hook and loop fastener system so as to substantially encompass the drum with an outwardly exposed layer of the hook component cushioned by the compliant sole. There is a sanding sheet comprising a sand paper blank with a loop fabric component of the hook and loop fastener system laminated to the backside thereof using a loop fabric adhesive of high temperature tolerance. The sanding sheet is wrappable (may be manually wrapped around the drum) as previously described around the sanding drum such that the loop fabric component is fully engaged with the hook component, and the leading and trailing edges of the sanding sheet form a joint without overlap.
The hook component may consist of Velcro brand, Nylon, non-adhesive backed, style HTH 22 Hook material or other equivalent hook material. The floor sander may be operable within a range of 1600–2800 rpm. The drum may be configured with an alignment bar for mounting the sanding sheet. The drum may have a recess for the leading edge of the sanding sheet. The high temperature tolerance may be at least about a 300 F tolerance. The first adhesive layer may be 3M brand Scotch-Grip brand 1300-L Rubber and Gasket Adhesive or other equivalent adhesive. The second adhesive layer may be 3M brand Scotch-Grip brand High Performance Contact Adhesive 1357 or other equivalent adhesive. The loop fabric component may be 100% Nylon, low profile loop material fabric. The loop material fabric may have a weight of about 3.0 oz. per square yard. The loop fabric adhesive may consist of a hot melt polyurethane adhesive capable of withstanding temperatures up to at least 300 F.
The powered floor sanding system may have a weight of floor sander on drum and sanding sheet of within the range of 50 to 145 psi. The sanding sheet when fully engaged with the drum may be inseparable from the drum by a shear force of less than 20 psi.
This application relates and claims priority to pending U.S. application Ser. No. 60/588,913 filed Jul. 16, 2004.
| Number | Name | Date | Kind |
|---|---|---|---|
| 1395468 | Beal | Nov 1921 | A |
| 1640933 | Gries | Aug 1927 | A |
| 2375102 | Harris | May 1945 | A |
| 6645054 | Raffo, Sr. | Nov 2003 | B1 |
| Number | Date | Country |
|---|---|---|
| 219709 | Sep 1957 | AU |
| 400754 | Nov 1933 | GB |
| Number | Date | Country | |
|---|---|---|---|
| 20060014481 A1 | Jan 2006 | US |
| Number | Date | Country | |
|---|---|---|---|
| 60588913 | Jul 2004 | US |
