US 3319686 A
Description (OCR text may contain errors)
May 16, 1967 M. H. PREVETTE PROTECTIVE COVER FOR SANDING MACHINES Filed Sept. 15, 1965 2 Sheets-Sheet 1 INVENTQR MELVIN H. PREVETTE ATTORNEY May 16, 1967 M. H. PREVETTE PROTECTIVE COVER FOR SANDING MACHINES 2 Sheets-Sheet 2 Filed Sept. 13, 1965 FIG. 3
INVENTOR MELVIN H. PREVETTE ATTORNEY United States Fatent G 3,319,636 HRGTEJTTVE CGVER FUR SANIBih-lt IyiACI-HNES lVIeivin I i. Prevette, Lexington, N.., assignor to Lexington Abrasive Belts, incorporated, Lexington, N.C., a corporation of North Carolina Filed Sept. 13, 1965, Ser. No. 436,679 Claims. (Cl. 150-52) This invention relates to protective covers for sanding machines, and more particularly to that type of cover adapted to be positioned between an ex-pansible pneumatic tube of a sanding machine and the abrasive sleeve which contacts the work.
Covers of this type have been use-d for many years to protect the pneumatic tube and prolong its useful life. For the most part, such prior art covers are formed from lengths of canvas which are formed into sleeves corresponding in diameter to the mean diameter of the pneumatic tube with which each such sleeve is to be used. These canvas sleeves are formed by overlapping the end edges of a rectangular length of canvas and stitching the overlapped portions with several rows of stitches.
The completed sleeve is pulled axially over a deflated pneumatic tube and tied in place by drawstrings at each end of the canvas cover. After the canvas cover is in place, an abrasive belt is drawn axially over the tube and the canvas cover, after which the tube is inflated. The abrasive sleeve is held in place on the sanding machine by friction exerted through the radial expansion of the pneumatic tube. Toward this end, the canvas cover must have sufficient capacity to stretch to bear firmly against the non-stretchable abrasive sleeve and hold it in place and against slipping.
The canvas cover of the prior art which are overlapped at their end portion have proven objectionable in that the overlapped portions create bumps which adversely interfere with the sanding operation, in that it makes it difficult to obtain a smooth surface on the work piece. Moreover, the bump creates a high spot on the abrasive sleeve which is more susceptible to wear than the rest of the abrasive belt and which thereby shortens the useful life of the abrasive sleeve.
Another difficulty which has been found with the prior art canvas covers stitched along overlapped end edge portions is that care must be taken to form puckers of an optimum size in the fabric between rows of stitches in order to protect the stitches from abrasion in use. The puckering of material between rows of stitches is also useful in that the puckers permit uniform stretching of the bias-cut cover by enabling stretching of that portion of the fabric between the rows of stitches under pressure of the inflated pneumatic tube. The positioning of puckers between the rows of stitches is a time-consuming and rather expensive operation requiring a certain amount of skill, thereby contributing to the cost of the cover.
Recently, an attempt has been made to overcome the diiliculties experienced with the prior art canvas cover with overlapped stitched end portions through the use of a stretchable nylon cover made from one-piece tubular fabric. While the nylon cover has the advantage of being made in tubular form without bumps and has the advantage of stretchability, it has proven objectionable in that difiiculty is encountered in drawing it axially on the pneumatic tube. Much more time is required in placing a stretchable nylon cover on a pneumatic tube than is the case with the canvas cover whose diameter more nearly coincides with the diameter of the deflated tube. Another objection found in using the stretchable nylon cover is the tendency of the nylon cover to twist on the pneumatic tube and the tendency of the abrasive sleeve to slip in use when positioned about a nylon cover.
It is the primary object of this invention to overcome the foregoing objections to the prior art covers known to applicant and to provide a cover which combines the advantages of a smooth surface contour eliminating objectionable bumps and suflicient stretchability and roughness to firmly engage the abrasive sleeve and hold it against slipping in use.
It is another object of the invention to provide a cover for pneumatic sanders which is free of objectionable bumps and which may be installed on a pneumatic tube of a sander with a minimum amount of down time.
One of the major objections to the prior art cover is the ninety degree straight splice. This makes it necessary for the work piece that is being sanded to meet the splice in a direct manner, causing wear on both abrasive sleeve and canvas cover at this point. The new type covers have thirty-five degree to forty-five degree angle splices which allows the work piece to slide over easily, thus eliminating bump, longer life on both cover and abrasive and gives a more desirable finish.
Some of the objects of the invention having been stated, other objects will appear to those skilled in the art as the description proceeds when taken in conjunction with the accompanying drawings, in which:
FIGURE 1 is a fragmentary view of one embodiment of the invention with parts broken away;
FIGURE 2 is a fragmentary longitudinal sectional view of the cover and abrasive belt assembled on an inflated pneumatic tube of a sanding machine;
FIGURE 3 is an enlarged fragmentary transverse sectional view taken substantially along the line 3-3 in FIGURE 2;
FIGURE 4 is a view similar to FIGURE 1 but illustrating a modified form of the invention;
FIGURE 5 is an enlarged transverse sectional view taken substantially along the line 5-5 in FIGURE 4.
Referring more specifically to the drawings, a cover made in accordance with the invention is indicated at 10 in FIGURES 1 through 3. The cover ll) is made from a piece of canvas which has been cut on the bias into rectangular configuration. Opposite end edges of the canvas are cut at an angle and are parallel to each other as shown at 11 and 12 in FIGURE 1 when brought together to form a tubular sleeve. v
The cover is hemmed as at 25 adjacent its side edges to define channels 26 through which drawstrings or wires 27 are passed for securing the cover to an inflated tube of a pneumatic sanding drum. Although only one is shown, it will be understood that drawstrings or wires 27 are provided at each side edge of the cover.
According to the preferred form of the invention, the end edges ill and 12 are brought together in a butt joint as most clearly seen at 13 in FIGURES l and 3. The end edges 11 and 12 are held in abutting relation by a strip of relatively thin tape 14 adhered to the inner surface of the cover lltl and extending coextensively with the butt joint 13 between the sides of the cover.
The tape 14 is preferably a composite fabric made from fifty percent cotton and fifty percent nylon with the cotton extending lengthwise of the tape and with the tape'cut on the bias to impart a modulus of elasticity to the tape at least equal to that of the cover. The nylon extends widthwise of the tape for added strength. As most clearly seen in FIGURE 3, the gauge or thickness of the tape is only a fraction of the gauge or thickness of the canvas cover. The relatively thin tape 14 is compressed within the body of the relatively thick canvas cover 16, and as shown in FIGURE 3, the thickness of the tape 14 is insufficient to adversely affect the uniformly smooth upper surface of the canvas cover 10 in use.
In FIGURE 2 the cover is shown installed on a pneumatic sanding drum. The sanding drum comprises an inflatable tube secured to end plates 16, only one of which is shown and held in place by a mounting ring 17. The end plates 16 are journalled on a rotatable shaft 18 which may be driven by a suitable mechanism, not shown. An air valve 19 provides communication between the atmosphere and the interior of the tube 15 whereby compressed air may be selectively introduced into and removed from the interior of the tube 15 to inflate it after the cover 10 and abrasive sleeve 20 have been mounted as shown in FIGURE 2.
Mounted as shown in FIGURE 2, the abrasive sleeve 20 is frictionally held against movement relative to the tube 15 even under pressure of a work piece, not shown, by the canvas cover 10 which has stretched under pressure of the inflated tube 15. The cover It), being cut on the bias, has an inherent modulus of elasticity and consequent capacity to stretch in a direction between the end edges 11 and 12. Although limited, this inherent elasticity is to permit the canvas cover to conform to the shape of the inflated tube 15 as shown in FIGURE 2 and thereby bear against the inner surface of the relatively non-stretchable abrasive sleeve 20.
The tape 14 may be adhered to the inner surface of the cover 10 along the butt joint 13 with any suitable adhesive. Adhesives which have been found satisfactory for this purpose must have the inherent ability to stretch to the extent required by inflation of the tube 15 and to retract without losing its adherence when the tube 15 is deflated. The adhesive must also be capable of withstanding the pressures exerted by the work piece which further stretch the cover 10, the tape 14 and the adhesive, not shown. One adhesive which has been found suitable for use with the invention is sold by United Shoe Machinery Corporation under the designation Bostic 7070. It has been found preferable to combine five parts of Bostic 7070 with one part of Boscoater No. 2, also sold by United Shoe Machinery Corporation.
An essential element of this invention is that the abutting edges 11 and 12 be secured together in a manner that does not adversely affect the uniformly smooth upper surface of the cover 10 and at the same time preserving the inherent stretchability of the fabric from which the cover 10 is made adjacent the butt joint 13.
The form of invention shown in FIGURES 4 and 5 is generally .similar to that shown in FIGURES 13, and differs from that just described only in that the end edges of the cover are adhesively secured together without a tape. Instead, the overlapping end portions 11 and 12 are secured directly together by a suitable adhesive which may be the same as that described in connection with the first form of the invention and indicated at 21 in FIG- URE 5.
While the overlapped joint 22 does result in the end edge 12 being slightly above the plane of the upper surface of the cover 10, it has been found in practice that this does not create an objectionable bump or adversely interfere with the uniformly smooth upper surface of the cover 10. This surprising result is believed to be attributable to the reduced thickness obtained by elimination of the need for puckering the upper layer of the overlapped end portions in the fabric as had previously been the practice in the prior art cover in which the overlapped end portions were sewn together by thread. According to the present invention sufficient stretchability is imparted to the overlapped joint 22 by the stretchable and retractable adhesive 21 without need for unduly thickening the overlapped joint by puckering the fabric as has previously been required in order to achieve the desired stretchability at the joint in the prior art covers. In practicing both forms of the invention care is to be taken that the area immediately adjacent the joint is not undesirably stiffened. It is a characteristic of this invention that the inherent capacity of the cover to stretch in a direction between its end edges 11 and 12 is not impaired by the adhesive used to form the joint. This is the reason for selecting an adhesive characterized by its capacity to stretch. Otherwise, the area adjacent the joint would be undesirably stiffened and thereby offer greater resistance than the remaining portions of the cover to the application of inward pressure by the work piece against the abrasive sleeve during a sanding operation. Such a stiffened area would be undesirable because it would be, in effect, a bump in use which would hasten the deterioration of the abrasive sleeve and also adversely affect the smoothness of the sanding operation.
It will be appreciated by those skilled in the art that the cover according to either form of the invention may be made in any desired size and shape to snugly conform to the configuration of the pneumatic tube in connection with which the cover is intended to be used.
There is thus provided an improved cover with characteristics of optimum stretchability and smoothness for efficient protection of a pneumatic tube and retention of the abrasive sleeve on the tube in use.
In the drawings and specification there have been set forth preferred embodiments of the invention and although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being defined in the claims.
I claim: 7
1. A cover for pneumatic tube sanding machines com prising a rectangular piece of canvas cut on the bias and having opposite end edges cut at an angle in parallel relation to each other, and an elastic adhesive adhering the said end edges in adjoining relation, the joint defined by the adjoining end edges being of substantially the same modulus of elasticity as the remainder of said cover.
2. A protective covering for pneumatic sanding drums of the type having an inflatable tube adapted to support an abrasive sleeve, said cover comprising a rectangular piece of canvas cut on the bias and having end edges and side edges, means adjacent said side edges for retaining the cover on the tube, said cover having a substantially uniform modulus elasticity between its end edges, and means adhesively securing said end edges together without adversely increasing the thickness of the cover at the joint and while preserving the same modulus of elasticity adjacent the end edges as exists throughout the remainder of the cover.
3. A cover according to claim 2 wherein said end edges abut one another to form a butt joint, and wherein said means for adhesively securing together the end edges comprises a length of tape adhesively secured to the end edges and overlying the butt joint, and a layer of adhesive between the tape and the cover, said adhesive being characterized by its capacity to stretch and retract to the same degree as said cover.
4. A cover according to claim 3 wherein said tape is stretchable in the same direction as said cover and to at least the same degree as said cover.
5. A cover according to claim 3 wherein said tape is formed from nylon yarns in one direction and from cotton yarns in the other direction and is cut on the bias to impart a measure of stretchability to the tape corresponding to the stretchability in said cover between its end edges.
References Cited by the Examiner UNITED STATES PATENTS 206,976 8/1878 Sands -52 767,767 8/1904 Ruegg 15052 2,225,073 12/1940 Miller 51-373 2,796,700 6/1957 Katz 4731 FOREIGN PATENTS 649,558 1/1951 Great Britain. 978,459 12/1964 Great Britain.
FRANKLIN T. GARRETT, Primary Examiner.