US3124909A

US3124909A - Combination drum and belt sanding surfacing machines

Info

Publication number: US3124909A
Authority: US
Publication date: 1964-03-17
Anticipated expiration: 1981-03-17

Description

March 17, 1964 J NYLUND ETAL 3,124,909

COMBINATION DRUM AND BELT'SANDING SURFACING MACHINES Filed April 24, 1961 John AZNyJund Frank clMiehe INVENTORS United States Patent 3,124,909 COMBENATION DRUM AND BELT SANDING SURFACING MAC John A. Nylund, Portland, and Frank J. Miehe, Lake Grove, 0reg., assignors to Tidland Machine Company, a corporation of Washington Filed Apr. 24, 1961, Ser. No. 105,184 18 Claims. (Cl. 51-141) This invention relates to sanding machines or sanders. The particular embodiment of the invention disclosed herein has utility in sanding the faces of panels or lumber. The sanding machine may be used to smooth a panel in a limited cutting type of operation, and also may be used in sizing or dimensioning a panel so that when it leaves the sander it has uniform thickness.

A general object of the invention is to provide improved sanding mechanism that may be used with equal facility in either a limited cutting or a dimensioning type of sanding operation, or in sanding operations somewhere between these types.

Another object is to provide a sander that can perform both limited cutting and dimensioning type of sanding operations, and is quickly and easily converted from one type of operation to the other.

A still further object is to provide an improved sander capable of first sanding and then polishing an article, which utilizes a sanding belt and resilient pressure-producing mechanism acting on the belt for performing the polishing action.

Another object of the invention is to provide an improved construction for such a resilient pressure-producing mechanism in a sander that is operable to produce regular and uniform pressures in those portions of a sanding belt performing a polishing action, without excessive unequal distortions occurring in the resilient part of the mechanism. The mechanism also features means whereby heat as the result of friction in the mechanism is quickly dissipated. The pressure-producing mechanism in the sander can be operated over long periods without replacement needed in the parts thereof.

Other objects and advantages of the invention will become more fully apparent upon reading the following description. In the description of the invention that follows, reference is made to the accompanying drawings, wherein:

FIG. 1 is a side elevation of a sanding machine as contemplated according to one embodiment of this invention;

PEG. 2 is an end view, on a somewhat enlarged scale, of portions of resilient pressure-producing mechanism present in the sander used in pressing a sanding belt against an article such as a panel during the final polishing and smoothing of the article;

FIG. 3 is a perspective view of table structure present in the sander provided for supporting the underside of an article as its top side is sanded;

FIG. 4 is a perspective View illustrating a removable insert used to provide rigidity in the table structure of FIG. 3; and

FIG. 5 illustrates another removable insert in the sander.

Common types of sanding operations performed on articles such as plywood panels, for instance, are size or dimension sanding of a panel, where a panel of uniform thickness is produced regardless of irregularities in thickness prior to sanding, and limited cutting where smoothness primarily is desired without regard to irregularities in thickness. The former type of sanding might be used with plywood having relatively thick outer veneer layers, whereas the latter type might be carried out on a panel which has a very thin specialty wood veneer over 3,124,909 Patented Mar. 17, 1964 its faces, where excessive sanding would destroy the veneer layers. Some panels, of course, require sanding treatments somewhere between the two types of sanding just discussed. An important advantage and feature of the invention is that the sander may readily be set up for either type of sanding, or for any kind of sanding between the two extremes just outlined. Adjustment is made with a minimum amount of shut-down time, and by means readily understood by an ordinary mill worker.

In the sanding of a panel, whether limited cutting or dimensioning is being done, it is desirable that a sander be provided with means for fast cutting (to remove most of the wood), and also with means for smoothing and finally polishing the panel. A simple construction providing for both fast cutting and smoothing comprises a sanding drum or pulley that trains a sanding belt, with means for supporting a panel against the belt where it extends over the sanding drum so that these portions of the belt can perform fast cutting, and to the off-bearing side of this sanding drum resilient pressure-producing means acting on a run of the belt extending from the drum. Such pressure-producing means urges the belt run against an article with lighter pressure than the drum, so that a polishing action results. Important in obtaining good polishing is that the pressure-producing means impart even pressures to the belt run across its entire width, so that a panel passing against the belt run have even polishing pressure applied thereto. Pressures should also stay fairly uniform irrespective of thickness variations in the panel. This invention features a pressure shoe for the pressure-producing means which takes care of the above outlined requirements in a highly satisfactory manner.

Referring now to the drawings, the sanding machine or sander is indicated in FIG. 1 generally at 10. The sander comprises a frame 12 supporting the operating parts of the sander off the ground. Mounted on frame 12 is a conveyer mechanism generally indicated at 14 for transporting articles such as panels in a path through the sander, and sanding mechanism 16 for removing wood from the panel as the same is transported by mechanism 14.

Conveyer mechanism 14 comprises, at the feed end of the sander (or the right end in FIG. 1), a pair of

opposed pinch rolls

18, 20. One of these (in the drawings, the upper roll 18) has a rubber covering 19, which increases the grab of the pinch rolls, and accommodates variations in thickness in a panel passed between the rolls. The pinch rolls are suitably journaled in bearings such as bearings 22 secured to the frame.

At the off-bearing or discharge end of the sander are another pair of

pinch rolls

24, 26, similar to rolls 13, 20, and these are journaled in bearings 28. Roll 24 is provided with a rubber covering 25.

A panel, illustrated by panel 30, is transported by

pinch rolls

18, 20 and 24, 26 in a substantially horizontal path through the sander, with movement of the panel being from right to left. The pinch rolls are driven in any suitable manner, as by motor 32 connected to the upper pinch roll of each set by drive belt 34, 36.

Panel 30 while traveling through the sander has its bottom face slidably supported on a flat table or guide 40 extending beneath sanding mechanism 16. Sliding against the top face of the panel, i.e., the face that is subjected to sanding, is a guide 4-2 on the feed side of sanding mechanism 16, and a guide 44 on the off-bearing side of mechanism 16.

Describing now sanding mechanism 16, this comprises a sanding belt 50 trained over pulleys or drums indicated at 52, 54, 56. Drum 52 constitutes a driving drum, and

3

druilns

54, 56 constitute sanding and idler drums, respective y.

Driving drum 52 is supported on the top of frame 10 in bearings such as bearing 64). The driving drum is rotated under power. Thus, connected to the drum to drive it is a motor 62. In operation of the sander, the drum is rotated by motor 62 in a counterclockwise direction in FIG. 1, and sanding belt 50 travels in the direction indicated by the arrow in FIG. 1.

Sanding drum 54 is journaled on the frame in bearings such as bearing 64. The drum is positioned in the embodiment illustrated approximately directly below the driving drum, and opposite and a short distance above the top of table or guide 40. Belt 50 on traveling about the sanding drum produces the principal cutting of a panel during operation of the sander. The spacing between the top of table or guide 40 and the outer surface of the belt at the base of the sanding drum determines the thickness of a sanded panel.

Idler drum 56 is journaled on frame 10 in bearings such as hearing 66. A run 5001 of sanding belt 50 extends from the sanding drum toward the idler drum. Training this belt run and slidably pressing against the inner surface of the belt run is pressure-producing mechanism 68. Pressure-producing mechanism 68 by forcing portions of run 50a resiliently downwardly against the top of a panel after cutting of the panel by the sanding drum polishes the panel and thus finishes it off. In the embodiment of the invention illustrated, mechanism 68 comprises a support 70 fixed to the frame, and secured to support 70 a bracket 72. Bracket 72 is provided at the base thereof with a removable shoe construction 74 extending across the frame the width of belt 51), and it is the removable shoe construction that contacts the inner surface of the sanding belt as it travels past mechanism 68.

With reference now more particularly to FIG. 2, shoe construction '74 comprises a metal mounting plate 76 as long as the belt 50 is wide, with

opposed edges

77, 78 turned toward each other on one side of the plate to define grip flanges for the plate. On the other side of the plate between

opposed edges

77, 78 are an expansive heel portion 80, and a recessed portion 82 next to heel portion 80. Within recessed portion 82, and with an outer surface substantially flush with and forming a smooth continuation of the outer surface of heel portion 8%) is a resilient pad 84. This may be made of rubber, a synthetic, and the like.

Pad 84 is held in position within the recessed portion by an antifriction covering 86 (that may be, for instance, a graphite coated canvas sheet, or similar low coeflicient of friction material). Covering 86 has

edges

87, 88 that extend over

edges

77, 78 of the mounting plate. Between covering 86 and the outer surface of heel portion and the outer surface of resilient pad 84 is a thin, metallic (and therefore conducting) sheet 90. The sheet extends over the heel portion and thence over shoulder 78 beneath edge 38, and is in intimate contact with the heel portion.

Covering 86 and metal sheet 90 along edge 78 of the plate are secured in place on the mounting plate by an elongated clip 96. A similar clip 98 secures edge 87 of the covering to edge 77 of the plate. The clips have a length coextensive with the length of the metal mounting plate. With the shoe construction 74 mounted on bracket 72, plate edge '78 and clip 96 about it fit within groove 99 along one side of bracket 72. Plate edge 77 and clip 98 fit over the end of the bracket, as illustrated in FIG. 2.

Directly behind heel portion 80 of the mounting plate is a pipe or conduit 102 lying within an elongated groove 104 provided bracket 72. The conduit extends the length of the shoe construction, and means (not shown) is provided for circulating a coolant through the conduit. The conduit has a surface that contacts the metal mounting plate. During operation of the sander, a coolant such as water and the like is circulated through the conduit, with such coolant carrying heat away from the heel portion. Belt 50 slides on the shoe construction, and heat of friction so developed is conducted through metal sheet and the metal heel portion to conduit 102.

It will be noted with reference to FIG. 1 that run 50a of the sanding belt between

drums

54, 56 bows outwardly with respect to a plane tangent to the two drums or pulleys. Such a tangent plane is indicated by the dashed line 107. This is because the shoe construction is positioned below such a tangent plane, and belt 50 that slides over the shoe construction, in doing so, travels below the plane. Bowing of the belt tensions the belt, so that it slides tightly over the shoe construction with friction between the shoe construction and belt tending to produce heat.

A feature of the invention is the provision of a heel portion 80 which is conductive (plate 76 is metallic), and which performs substantially all tensioning of the belt between

drums

52, 56. Note that it is the heel portion that protrudes the greatest distance from tangent plane 107. The heel portion thus constitutes a deflecting portion in the shoe construction, such deflecting portion in addition to being heat conductive being nonyieldable. Pad 84 adjacent the deflecting portion primarily functions as a resilient backing for belt run Sila between drum 54 and the heel portion, the belt run progressing in substantially a straight line along this portion thereof. As a consequence, while pad 84 is effective yieldably to press the sanding belt against a panel to produce a polishing action, excessive distortions in the pad tend to be minimized, and heat build up therein also is minimized. The construction makes for a longer pad life, and also produces a more even polishing action.

Considering now the construction of table or guide 40, this comprises a plate 109 substantially rectangular in plan, supported at each of its four corners by a threaded stud 110 that is aflixed to the plate and that extends through a platform 112 which is integral with the frame. Threaded adjusting sprockets 114 screwed onto studs 110 are journaled in platform 112. Turning of the adjusting sprockets functions to raise or lower the threaded studs relative to platform 112. The adjusting sprockets are turned in unison by means of a crank handle 116 having a sprocket 118' secured thereto that engages a chain 121), such chain being trained over adjusting sprockets 114. The studs, adjusting sprockets, handle 116 and associated mechanism are used to position properly the top of table 40 relative to the base of drum 54.

Plate 109 has

upstanding shoulders

126, 128 extending along its front and rear edges. Fitted between these shoulders is an envelope structure, indicated generally at 130 and shown separated from the sander in FIG. 3.

Envelope structure 130 comprises a flat, bottom piece 134 that is rectangular in shape. Extending along the forward and rear edges of the piece and affixed to the piece are

strips

136, 138, respectively. These, for instance, may be made of rubber, or suitable flexible and resilient synthetic material. Over the top sides of the

strips

136, 138 there is aflixed a rectangular, flexible top piece 140. This has an upper surface that is smooth, selected so that a low coefflcient of friction exists between the top of the piece and a panel when the panel slides thereover. Suitable smoothness and flexibility are found in plastic sheets, although relatively thin, smoothed metal sheets may also be used.

Top piece 140 and bottom piece 134 together with the

flexible strips

136, 138 together define a cavity 141 within the envelope structure. The cavity receives an insert, such as that illustrated in perspective in FIG. 4 and indicated at 142. The insert is used to provide support for the flexible top piece and the resilient strips underlying it along its edges, whereby a panel passed over the envelope structure will be pushed upwardly with suitable pressure against the base of the sanding drum and pressure-producing mechanism 68.

Insert 142 is shaped snugly to be received within cavity 141. In some sanding operations, the insert may be made of stiff, nonyieldable material, such as a solid piece of plastic or wood. In such an event, the top surface of piece 140 is rigid and unyielding, and table 40 supports a panel at a fixed distance from the sanding drum. In other sanding operations, a resilient pad may be used, made of rubber or synthetic. With such an insert, top piece 140 is permitted to give, and the function of the table 40 is more to press a panel with a uniform pressure against the sanding drum. Inserts between these extremes may also be used.

Guide 44 to the off-bearing side of the sanding drum comprises an expansive plate 150, made of steel or other rigid material, extending across the path of travel for panels. The plate is aflixed to a support 152 joined in a fixed position on frame 12.

Considering now guide 42, this is somewhat similar to table or guide 40 in construction. The guide comprises a heavy plate 156 extending across the path of a panel through the sander and secured to frame 12 of the sander in a suitable manner. Fastened to the underside of plate 156 are spaced-apart flexible strips 158, 160 similar to

strips

136, 138. Joined to the bottom sides of the strips is a flexible bottom piece 164. Bottom piece 164, like piece 146 of table 40, is smooth-surfaced, and made of a material having a low coefiicient of friction when a panel slides thereacross. A plastic sheet is also preferable for this bottom piece.

Plate 156, bottom piece 164, and strips 158, 160 constitute envelope structure defining a cavity 166 within the envelope structure. This cavity receives a removable insert, such as the insert 168 illustrated in FIG. 5. The insert fits snugly within the cavity and provides support for flexible piece 164. For some purposes, an insert which is flexible and resilient may be used, whereas in other sanding operations a rigid, stiff insert is preferred. With a stiff insert, the position of the bottom of piece 164 is fixed, whereas with a flexible insert, the bottom may yield with variations in panel thickness.

Explaining now how the sander of the invention may be used, first of all it will be assumed it is desired to size or dimension a panel, so that the finished panel has uniform thickness regardless of nonuniformity prior to sanding. For such sizing or dimensioning, the operator places within cavity 141 of'table 40 a rigid noncompressible insert. This backs up top piece 140 so that the upper surface thereof occupies a fixed plane, which is located a predetermined distance from the bottom of the sanding belt as it passes over the sanding drum. For cavity 166 of guide 42, an insert of resilient, yieldable material is selected. When a panel is then passed through the sander, guide 42 functions to hold the panel in place, but gives to take care of variations in thickness. Since the relative positions of the top of table 40 and the sanding drum are fixed, the panel passes beyond the drum only on reaching desired thickness.

In a limited cutting type of sanding operation, where smoothness is desired over true thickness, cavity 166 of guide 42 is filled with a rigid insert, whereby the top of a panel is guided to the sanding drum while supported at a fixed elevation relative to the drum. On the other hand, cavity 141 of table 40 is filled with a yieldable, compressible insert, that enables top piece 140 to give with respect to the sanding drum. When a panel now is fed the sander, the resilient nature of the insert for table 40 functions to enable thick and thin areas of the panel to be pressed against the sanding drum with approximately uniform pressure.

Using the sanding machine, panels that have patches and localized areas of unevenness are handled efficiently and effectively. Where a resilient insert is used, resiliency extends both transversely of and in a direciton parallel to the path of travel for a panel.

Particularly important, a Workman may change the type of sanding operation with a minimum of shut down 6 time. The two extreme types of sanding may be performed, as well as sanding operations lying somewhat in between. Once the type of sanding has been determined, it is an easy matter to insert proper inserts into suitable cavities.

While a modification of the invention has been described, it is apparent that other embodiments and variations are possible without departing from inventive concepts present in the invention. It is desired not to be limited to the specific embodiment of the invention disclosed, but to cover all modifications and variations that would be apparent to one skilled in the art, and that come within the scope of the appended claims.

It is claimed and desired to secure by Letters Patent:

1. In a sanding machine having a pair of spaced pulleys and a sanding belt traveling over the pulleys with a run of the belt extending between the pulleys, pressure means intermediate the pulleys training said run of the belt, said pressure means comprising a deflecting portion deflecting said run of the belt outwardly from a plane tangent to the two pulleys and tensioning the belt, said deflecting portion being of nonyieldable material that is heat conductive, means for cooling said deflecting portion including conduit means for circulating a coolant, and a backing portion of resilient material yieldably backing a portion of said belt between said deflecting portion and one of said pulleys.

2. In a sanding machine having a pair of spaced pulleys and a sanding belt traveling over the pulleys with a run of the belt extending between the pulleys, pressure means intermediate the pulleys training said run of the belt, said pressure means comprising a deflecting portion deflecting said run of the belt outwardly from a plane tangent to the two pulleys and tensioning the belt, said deflecting portion being of nonyieldable material that is heat conductive, a backing portion of resilient material yieldably backing a portion of said run of the belt between said deflecting portion and one of said pulleys, a low coeflicient of friction cover extending over said deflecting and backing portions having an outer surface contacting said belt with said run sliding thereagainst, and a heatconducting sheet between said cover and said backing and deflecting portions and in contact with said deflecting portion whereby heat may be conducted from the sheet to said deflecting portion.

3. In a sanding machine having a pair of spaced pulleys and a sanding belt traveling over the pulleys with a run of the belt extending between the pulleys, pressure means intermediate the pulleys training said run of the belt, said pressure means comprising an expansive and smooth-surfaced deflecting portion over which the belt slides, said deflecting portion deflecting the belt outwardly from a plane tangent to the two pulleys and tensioning the belt and being made of nonyieldable material that is heat conductive, means for cooling said deflecting portion including conduit means for circulating a coolant, and a backing portion adjacent said deflecting portion of resilient material and yieldably backing a portion of the belt between said deflecting portion and one of said pulleys, said run of the belt extending in substantially a straight line from said deflecting portion over said backing portion to said one pulley.

4. In a sanding machine having a pair of spaced pulleys and a sanding belt traveling over the pulleys with a run of the belt extending between the pulleys, pressure means intermediate the pulleys training said run of the belt, said pressure means comprising an expansive and smooth-surfaced deflecting portion over which the belt slides, said deflecting portion deflecting the belt outwardly from a plane tangent to the two pulleys and tensioning the belt and being made of nonyieldable material that is heat conductive, a backing portion adjacent said deflecting portion of resilient material and yieldably backing a portion of the belt between said deflecting portion and one of the pulleys, said run of the belt extending in substantially a straight line from said deflecting portion over said backing portion to said one pulley, a low coeflicient of friction cover extending over said deflecting and backing portions having an outer surface contacting said belt with said run sliding thereagainst, and a heat-conducting sheet between said cover and said backing and deflecting portions and in contact with said deflecting portion whereby heat may be conducted from the sheet to said deflecting portion.

5. In a sanding machine having a pulley and a sanding belt trained over said pulley and means for guiding material against said belt where it extends about said pulley, pressure-producing mechanism on the offbearing side of said pulley constructed slidably to support the belt and hold it against material being sanded, said pressureproducing mechanism comprising a metal mounting plate having opposed edges turned toward each other on one side of the plate to define grip flanges therefor, said mounting plate between said opposed edges presenting on the other side of said plate an expansive heel portion extending the width of the belt and adjacent said heel portion and toward said pulley from said heel portion a recessed portion also extending the width of the belt, a resilient cushion disposed within said recessed portion and bounded by an outer surface that forms a smooth continuation of the surface of said heel portion, and a low coefiicient of friction cover extending over the surface of said heel portion and said outer surface of said cushion.

6. In a sanding machine having a sanding belt, pressure-producing mechanism constructed slidably to support the belt and hold it against material being sanded, said pressure-producing mechanism comprising a metal mounting plate having opposed edges turned toward each other on one side of the plate to define grip flanges therefor, said mounting plate between said opposed edges presenting on the other side of said plate an expansive heel portion extending the width of the belt and adjacent the heel portion along the length of the belt a recessed portion also extending the width of the belt, a resilient cushion disposed within said recessed portion and bounded by an outer surface that forms a smooth continuation of the surface of said heel portion, a low coefficient of friction cover extending over the surface of said heel portion and said outer surface of said cushion, and a heat-conducting sheet between said cover and said outer surface of said cushion and said surface of said heel portion contacting said heel portion whereby heat may be conducted from the sheet to the heel portion.

7. In a sanding machine having a sanding belt, pressure-producing mechanism constructed slidably to support the belt and hold it against material being sanded, said pressure-producing mechanism comprising a metal mounting plate having opposed edges turned toward each other on one side of the plate to define grip flanges therefor, a bracket mounting said mounting plate with said grip flanges detachably holding the plate on said bracket, coolant conduit means for circulating a coolant mounted on the bracket and in contact with said metal mounting plate, said mounting plate between said opposed edges presenting on the side opposite said one side an expansive heel portion extending the width of the belt and adjacent the heel portion along the length of the belt a recessed portion also extending the width of the belt, a resilient cushion disposed within said recessed portion and bounded by an outer surface that forms a smooth continuation of the surface of said heel portion, a low coefiicient of friction cover extending over the surface of said heel portion and said outer surface of said cushion, and a heatconducting sheet between said cover and said outer surface of said cushion and said surface of said heel portion contacting said heel portion whereby heat may be conducted from the sheet to the heel portion.

8. In a sanding machine, a frame, a pair of spaced pulleys mounted on the frame, a sanding belt traveling over the pulleys, means for transporting work in a path adjacent one of said pulleys, guide means to the feed side of said one pulley constructed to guide work while it travels toward said one pulley by sliding against the side of the work that is to be sanded, guide means disposed opposite said one pulley constructed to guide work during the actual sanding thereof by sliding against the other side of the work, each of said guide means comprising envelope structure with a yieldable surface facing said path that slides against the work, and a removable insert Within each envelope structure providing support for said surface.

9. in a sanding machine for panels having a frame and sanding mechanism for sanding a side of a panel as it travels through the sander, a first guide means disposed to the feed side of said sanding mechanism constructed to guide a panel while it travels toward said sanding mechanism by sliding against the side of the panel that is to be sanded, a second guide means disposed opposite said sanding mechanism constructed to guide a panel during the actual sanding thereof by sliding against the other side of the panel, at least one of said guide means providing yieldable support for a panel to be sanded, said one of said guide means having a removable insert determining the yieldability of said one of said guide means and the yieldability of the support that the guide means provides a panel as the panel slides thereagainst.

10. In a sanding machine for panels, a table with an expansive and smooth surface for slidably supporting one side of a panel as the side opposite is sanded and defining a path of travel for the panel, said surface being yieldable in a direction normal to said path, a pair of guides spaced along said path of travel disposed opposite said table, each of said guides being constructed to slide against said opposite side of said panel, sanding mechanism intermediate the guides and opposite said table for sanding said opposite sides, the guide means to the feed side of said sanding mechanism including a yieldable surface that supports said opposite side of said panel, said table and said guide to the feed side of said sanding mechanism each having a removable insert that determines the yieldability of its said surface and the amount it may yield as a panel slides thercagainst.

11. in a sanding machine for panels, a frame, a table mounted on the frame with an expansive and smooth surface for slidably supporting one side of a panel as the side opposite is sanded and defining a path of travel for the panel, a pair of guides mounted on the frame spaced along said path of travel and disposed opposite said table, each of said guides being constructed to slide against said opposite side of the panel, a sanding belt and a pair of pulleys mounted on the frame with the pulleys training the belt and with the belt where it extends about one pulley adjacent said path and in position to contact said opposite side of the panel at a location disposed between said guides, and pressure mechanism bearing on the inside of a run of said sanding belt as it extends between the pulleys, said pressure mechanism being to the offbearing side of said one pulley and producing contact of said belt with a panel, said pressure mechanism comprising a deflecting portion deflecting said run of the belt between the pulleys outwardly from a plane tangent to the two pulleys whereby tension is produced in the belt, said deflecting portion being of nonyieldable material that is heat conductive, said pressure mechanism also having a backing portion of resilient material yieldably backing a portion of said run of the belt between said deflecting portion and said one pulley, said run of the belt extending in substantially a straight line from said deflecting portion to said one pulley, the guide to the feed side of said one pulley and said table each having a removable insert determining its resiliency and the amount that it may yield as a panel slides thereagainst.

12. The apparatus of claim 11, wherein the table and the guide to the feed side of said one pulley each comprises envelope structure with a flexible and substantially flat side facing the path of travel for a panel, the removable insert being positioned within the envelope structure and providing support for the side.

13. In a sanding machine, a frame, a rotatable sanding drum mounted on said frame, a sanding belt trained over said drum, guide means disposed opposite said beit where it is trained over said drum constructed to guide work against said belt where it is trained over said drum during the actual sanding of the work, said guide means comprising envelope structure with a yieldable surface facing said drum, and a removable insert within said envelope structure providing support for said surface.

14. In a sanding machine, a continuous movable sanding belt, means training the sanding belt including a drum mounted with the sanding belt extending about a portion of the periphery of said drum, resilient means mounted opposite said belt where it extends about a portion of the periphery of said drum yieldable away from said belt, and means providing a surface for supporting work as it is sanded extending over said resilient means and interposed between said resilient means and said belt where it extends about a portion of the periphery of said drum.

15. In a sanding machine, a continuous movable sanding belt, means training the sanding belt including a drum mounted with the sanding belt extending about a portion of the periphery of said drum, resilient means mounted opposite said belt where it extends about a portion of the periphery of said drum yieldable away from said belt, and means providing a surface for supporting work as it is sanded extending over said resilient means and interposed between said resilient means and said belt where it extends about a portion of the periphery of said drum, said means providing a surface for supporting work having a predetermined minimum spacing from said belt where it is trained over said drum and being yieldable away from said belt and drum together with said resilient means on the passage of work of greater thickness than said minimum spacing thereover and against said belt.

16. The sanding machine of claim 15, wherein the means providing a surface for supporting work and said resilient means comprises envelope structure with a surface facing the drum for supporting work, and a removable insert within said envelope structure.

17. In a sanding machine, a continuous movable sanding belt, means training the sanding belt including a drum mounted with the sanding belt extending about a portion of the periphery of said drum, means defining a path of travel for work positioned opposite said belt where it extends about a portion of said drum and spaced from said drum a predetermined distance, and resilient means supporting said means defining a path of travel for work, said last-mentioned means and the means defining the path for travel for work being yieldable away from said belt where it passes over said portion of said drum.

18. In a sanding machine, a pair of spaced pulleys mounted for rotation about parallel axes, a sanding belt trained over the pulleys with a run of the belt extending between the pulleys, pressure means intermediate the axes of said pulleys and to one side of the plane defined by said axes over which said belt run travels, said pressure means being operable to deflect said belt run outwardly from a plane tangent to the two pulleys and to support said belt run in a position where the belt run, starting at each pulley and progressing toward the other pulley, defines an acute angle relative to said plane tangent to the two pulleys, said pressure means comprising a deflecting portion that engages said run of the belt at that point where the belt run is spaced its greatest distance from said plane tangent to the two pulleys, said deflecting portion being of non-yieldable material and heat conductive, said pressure further comprising a backing portion of resilient material yieldably backing a portion of said run of the belt between said deflecting portion and one of said pulleys, and means for guiding work in a path first adjacent said belt where it travels over said one pulley and then over said belt where it travels over said backing portion.

References Cited in the file of this patent UNITED STATES PATENTS 1,921,513 Emmons Aug. 8, 1933 2,761,256 OConnor Sept. 4, 1956 2,762,173 Bottcher Sept. 11, 1956 2,791,070 Schaller May 7, 1957 2,895,262 Nylund et al. July 21, 1959 2,934,863 Pendergast May 3, 1960