ELASTIC DRIVE BELT ASSEMBLY

Abstract

The elastic drive belt system connects the belt directly to a drive shaft and driven pulley. The elastic drive belt has a plurality of longitudinal ribs on the traction side of the belt. The drive shaft has a plurality of grooves sized and arranged to receive and engage the longitudinal ribs on the belt to facility torque transfer and alignment. This system facilitates delivery of relatively high amounts of torque to the driven pulley using relatively low horsepower motors. In many applications, such as a sander, the elastic drive belt system eliminates the need to readjust the tension on the belt as it wears.

Description

BACKGROUND OF INVENTION

The present invention uses an elastic drive belt assembly containing tensile cord members with elastic properties that does not require retensioning as the belt wears. This elastic drive belt assembly can be used in many different applications, such as wooden floor sanders, floor cleaning machines, metal cutting and grinding equipment, compressors, pumps, wood working equipment, etc.

Belt driven sanders for wooden floors have traditionally been produced for decades with conventional non-elastic drive belts with tensile cords passing around a drive and driven pulley. Since the tensile cords are inelastic they permanently elongate as they wear. This permanent elongation reduces the tension in the belt which often ultimately causes the belt to slip and not properly drive the sanding pad. Therefore, conventional belts have to be retensioned as the belt wears and stretches. Other prior art belt driven sanders use synchronous “timing” type belts with a drive pulley and a driven pulley. Pulleys for synchronous drives are more expensive than conventional pulleys since teeth are machined into them. Manufacturing variability in the pulleys also increase the probability (due to additional manufacturing variability) of machine induced vibration. In addition, to possibly increasing operator fatigue and component failures, vibration can also cause “chatter” which appears as undesirable marks on the wooden floor being sanded.

Clarke® American Sanders has been producing sanders for wooden floors for decades. Some of these sanders are used to sand the wooden floor where it abuts a wall and are thus called “edgers” in the trade. One such sander is the Clarke American Super E Edger described in the Operators Manual and Parts and Service Manual included in the Information Disclosure Statement. The body of this Super E Edger is produced separately from the kick-toe extension so that the tension on the conventional drive belt can be adjusted as the belt stretches. This is an added expense in the manufacture of the sander. Specifically, there are elongate channels in the kick-toe extension that can be adjusted relative to the body with wing nuts or conventional nuts and bolts. Adjustment of a worn belt can be time consuming and often requires tools. There is a need to reduce/eliminate this time consuming adjustment procedure and reduce the cost of production for this type of sander and other belt driven products.

Further, the Clarke Super E sander can produce noise in excess of about 95 dB(A). Since the noise scale is logarithmic, slight numeric reductions in the dB(A) value can significantly reduce the amount of emitted noise in the environment.

Some vacuum cleaners, like the venerable Kirby® vacuum have used elastomeric drive belts wrapped around a drive shaft that has a slight taper to keep the drive belt in place. These Kirby drive belts do not have longitudinal ribs, nor does the drive shaft have grooves. The typical motor in a vacuum cleaner is thought to have a nominal rating of about 0.5 hp or less and the drive shaft is thought to have speeds of about 16-20,000 rpm. This results in a low transfer of torque of about 1.5 to about 3 inch pounds. There is still a need for a drive belt system that can transfer higher amounts of torque such as those needed in the sander industry and other high load applications.

SUMMARY OF THE INVENTION

The present invention is an elastic drive belt assembly that includes a) a elastic drive belt possessing longitudinal ribs on the traction side of the elastic drive belt, b) a drive shaft with grooves sized and arranged to receive and engage the ribs on the elastic drive belt and c) a driven pulley. Since the elastic drive belt assembly does not permanently elongate, the belt does not need to be re-tensioned as it wears. Conventional non-elastic drive belts require adjustment as the belt wears and stretches. Costs for assembly and manufacture of products that utilize this elastic drive belt assembly should be less than some prior art designs that use non-elastic drive belts. Products that use this invention should require less maintenance because the elastic drive belt will not require readjustment as the belt wears and stretches. One specific application of this elastic drive belt assembly is a sander for wooden floors commonly referred to as an edger. In addition, the edger of the present invention should be quieter than some prior art edgers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the sander for wooden floors viewed from the right front of the apparatus.

FIG. 2 is a left side elevation view of the sander of FIG. 1 and also illustrates an attached vac hose.

FIG. 3 is a top view of the sander of FIG. 1

FIG. 4 is a bottom perspective view of the sander of FIG. 1 with the bottom dust plate in place.

FIG. 5 is identical to FIG. 4 except the bottom dust plate has been removed.

FIG. 6 is a left side section view of the sander, similar to FIG. 2.

FIG. 7 is a section view of the sander taken along the line 7-7 of FIG. 6.

FIG. 8 is a section view of the sander taken along the line 8-8 of FIG. 6.

FIG. 9 is a section view of the drive assembly including the drive shaft, drive belt and the driven pulley.

FIG. 10 is an enlarged section view of the grooves in the drive shaft and a ion of the elastic drive belt.

FIG. 11 is a left side elevation view of the sander of FIG. 2, except a dust collection bag has been substituted for the vac hose.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIGS. 1-3, a sander for wooden floors is generally identified by the numeral 20 and is often referred to as an “edger”. The sander 20 includes a lower body 22 connected to a motor housing 90. The lower body 22 is supported by a left caster assembly 24 and a right caster assembly 26. The motor housing defines a left handle 28 and a right handle 30. In the right handle is an on/off switch 32 and in the left handle is an optional motor speed switch 34. A light assembly 36 is positioned in the upper part of the body so the light shines down on the floor in front of the sander.

The sander is driven by an electric motor 38, better seen in FIG. 6. An electric cord, 40 provides electricity to the electric motor and the light assembly. In normal sanding operation, the dust emitted during the sanding process passes through a vac hose 42 to a dust collection receptacle, not shown such as an industrial vacuum cleaner. Operators generally move from the left to the right while sanding a floor, so it is convenient to have the electric cord 40 and the vac hose 42 positioned on the left of the sander 20 to allow unencumbered movement to the right. In an alternative embodiment, better seen in FIG. 11, a removable dust collection bag is used in lieu of the vac hose and dust collection receptacle. The dust collection bag may also be referred to as a dust collection receptacle. A bumper 44 is positioned at the front of the sander to prevent damage to walls. A sanding disk 46, better seen in subsequent figures rotates clockwise immediately below the bumper. Sanding paper 48 is attached to the sanding disk 46 by a bolt 54 and washer 55.

Referring now to FIGS. 4-8, the internal components of the sander are shown in various views. The sanding disk 46 is attached to the sanding disk driver 50 by a plurality of screws 52. The sanding disk driver 50 threads onto the shaft 104 of the driven pulley 102. Rotation of the drive shaft 56 imparts rotational motion via the elastic drive belt 100 to the sanding disk driver 50, the sanding disk 46 and the sanding paper 48 which is in contact with the wooden floor.

In FIG. 4 the bottom dust plate 58 is attached to the body by screws 60. In FIG. 5, the bottom dust plate has been removed to better show the flow of dust through the sander. An external dust containment wall 62 surrounds most of the perimeter of the rotating sanding paper 48. The bottom dust plate 58 and the external dust containment wall 62 define a dust containment chamber 63. A dust fan shroud 64 partially surrounds the dust fan blade element 66 and defines the inlet 68 for the dust fan assembly 70. The dust fan blade element 66 mounts on the bottom of the motor drive shaft 56 and is secured in place by a retaining key 72 and ring 73.

The flow of dust through the sander 20 is best seen in FIGS. 5 and 6. Rotation of the dust fan blade element 66 inside the dust fan shroud 64 creates negative pressure at the inlet 68 of the dust fan assembly 70. This negative pressure draws the dust from the dust containment chamber 63 through the inlet 68 as indicated by the flow arrows in FIG. 6. The dust then exits the dust fan assembly 70 through the outlet 74, best seen in FIGS. 6 and 8 and passes through the dust exhaust duct 76, as shown by the flow arrows, through the vac hose to a dust collection receptacle, not shown or a dust collection bag, best seen in FIG. 11.

Referring to FIG. 8, a motor cooling fan assembly 82 includes a cooling fan blade element 84, motor cooling air inlets 86, fan intake baffle 87, a first motor cooling air outlet 88 and a second motor cooling air outlet 89, better seen in FIGS. 5 and 6. The motor cooling air inlets 86 are located under the left and right handles 28 and 30 and are best seen in FIGS. 4 and 5. The electric motor 38 is positioned in the motor housing 90, as best seen in FIG. 6. The cooling fan blade element 84 is mounted on the motor drive shaft 56. Rotation of the motor drive shaft causes the cooling fan blade element to rotate which creates negative pressure at the motor cooling air inlets 86. The negative pressure draws ambient air through the motor cooling air inlets 86 and between the motor 38 and the motor housing 90 as shown by the flow arrows in FIG. 6. The ambient air flowing past the motor components provides convective cooling and draws away heat, thus cooling the motor. The heated air then exits the body through the first motor cooling air outlet 88 and a second motor cooling air outlet 89 as shown by the air flow arrows in FIG. 6. The second motor cooling air outlet 89, also seen in FIG. 5 directs some of the motor cooling air towards the floor. Therefore, rotation of the motor drive shaft imparts rotational motion to both the cooling fan blade element 84 and the dust fan blade element 66. Rotation of the cooling fan blade element 84 cools the electric motor 38 and rotation of the dust fan blade element 66 helps to control unwanted dust caused by the sander 20.

Further, applicants believe that the present invention will reduce the noise level during operation when compared with a prior art sander like the Clarke Super E Edger. This anticipated noise reduction should occur due to several reasons. First, the present invention uses a smaller diameter cooling fan blade element 84 and smaller diameter dust fan blade element 66 than some prior art devices. The smaller diameter means that the tip speed is less which in turn decreases the noise level. In one embodiment, the diameter of the cooling fan blade element 84 of the present invention is about 3.75 inches and the diameter of the cooling fan blade in the Super E Edger is about 4.35 inches. Second, the flow path of the cooling air is more tortuous in the present invention than some prior art devices. For every 90 degree change in direction that the cooling air takes, there is an approximate 3 dB(A) reduction in noise. The motor cooling air inlet 86 of the present invention is located under the handles of the sander, which is directed away from the operators ear, unlike some prior art devices. Furthermore, some of the motor cooling air discharge is directed towards the floor through second motor cooling air outlet 89, best seen in FIG. 5, and some is directed out the side of the motor housing 90 through the first motor cooling air outlet 88, best seen in FIG. 6. The diameter of the dust fan blade element 66 is about 3.75 inches and is less than the 5 inch diameter of the dust fan blade element in the Super E sander. Reduction in fan diameter reduces fan tip speed and noise.

Referring now to FIGS. 6-10, an elastic drive belt 100 wraps around the motor drive shaft 56 and imparts rotational motion to the driven pulley 102. The outside circumference 103 of the driven pulley 102 may be smooth as shown in these drawings to further reduce production costs. However, if more torque needs to be transferred, the outside circumference of the driven pulley may also have grooves sized and arranged to receive and engage the longitudinal ribs in the elongate belt. The shaft 104 of the driven pulley 102 extends through one or more bearing assemblies 106 into the dust containment chamber 63. The driven pulley 102 and the pulley shaft 104 can be formed from separate components or formed as one component. Applicants form the driven pulley 102 and the pulley shaft 104 as one component. The elastic drive belt assembly generally identified by the numeral 108 as best seen in FIGS. 9 and 10 includes the elastic drive belt 100, the motor drive shaft 56, and the driven pulley 103. The elastic drive belt assembly 108 may be positioned outside the dust containment chamber 63, the dust exhaust duct 76 and the dust flow path to reduce fouling and contamination by dust and other particles. Likewise, the elastic drive belt assembly 108 may be positioned outside the motor cooling air flow path to reduce fouling and other contamination.

As best seen in FIGS. 9 and 10, the elastic drive belt 100 receives torque direct from the motor drive shaft 56. The Poly V® 6 PJ 450 Flexonic, elastic drive belt may be suitable to use in this invention and is available off-the-shelf from Hutchinson located at 1835 Technology Drive, Troy, Mich. 48083. This belt from Hutchinson has six PJ section longitudinal ribs 110 on the traction side of the belt, an overall nominal length of about 450 mm, and elastic cords that when installed are stretched (elongated) approximately 3½% over its nominal length. The cross section of the six ribbed belt is about 0.55 inch wide (14 mm) and about 0.157 inch tall.

The electric motor 38 in this sander has a nominal horsepower rating of about 1.8 hp. The nominal speed for the motor drive shaft 56 is in the range of about 12,000 rpm to about 14,000 rpm, having an optimal speed of about 13,500 rpm. The nominal speed for the sanding disk is in the range of from about 2,800 rpm to about 3,200 rpm with an optimal working speed of about 3,000 rpm for a 7 inch sanding disk. In other words, there is a speed reduction of about 4.63:1. A motor speed of 13,500 rpm allows for good dust fan performance for a 3.75 inch OD fan.

The sanding disk 46 is driven by the elastic drive belt 100 that extends from the motor drive shaft 56 to a driven pulley 102. Speed is reduced by using a driven pulley 102 that is 4.63 times larger than the OD of the motor drive shaft 56. The nominal diameter of the motor drive shaft is 1 inch, but it is turned down to an effective diameter of about 0.787 inches (20 mm) where the belt is installed. The minimum diameter of a drive shaft that is suitable for the PJ section belt is about 0.8 inches (20 mm). However, Hutchinson makes other elastic drive belts with a plurality of longitudinal ribs that may also be suitable in this or other applications. For example, the PH cross-section belt from Hutchison may be able to take torque from a drive shaft having a diameter as small as 0.25 inches (about 7 mm).

The motor drive shaft 100 is machined with six grooves 112 that complement the six ribs 110 in the PJ elastic drive belt from Hutchinson. The grooves 112 contact the sides of each rib 110 and when coupled with the angle of belt wrap defines the total area of contact needed to impart the torque required to drive the sanding pad. Applicant believes that the dimensions for the grooves 112 as suggested for V-Ribbed Belts, cross sections PJ and PH, in the Rubber Manufacturers Association draft Standard RMA IP-26 are suitable for use in this invention. The present invention produces about 8 inch-pounds of torque using a nominal 1.8 hp electric motor with a drive shaft speed of about 13,500 rpm. Other cross section type V-Ribbed elastic belts such as PK, PL, and PM may also be suitable for use in this invention.

The OD of the driven pulley is 3.854 inches (97.9 mm) and is smooth. There are no sidewalls on the pulley. Grooves are not needed in the driven pulley because there is sufficient contact area (pulley OD and amount of belt wrap) with the bottom of the six belt ribs to transfer the torque from the belt to the pulley. However, grooves may be added to the driven pulley to transfer more torque.

The elastic drive belt has a plurality of ribs 110 on the traction side of the elastic drive belt and a flat surface on the opposite side of the drive belt. A plurality of grooves 112 are formed in the motor drive shaft 56 and are sized and arranged to receive and engage with the ribs 110 on the traction side of the elastic drive belt. In most prior art applications, a separate pulley is placed on the motor drive shaft and the drive belt is driven by this pulley. The present invention eliminates the need for this drive pulley and therefore is more economical to produce than some prior art devices. Eliminating the drive pulley also decreases the probability of machine induced vibration which can increase component failures, operator fatigue, and the presence of undesirable marks emitted to the floor being sanded. Furthermore, the elastic drive belt eliminates the need to readjust the tension on the belt as it wears, thus saving further on production costs of the sander and operational maintenance. Productivity increases as maintenance and service time are decreased.

FIG. 11 is a side elevation view of the sander 20 similar to the sander in FIG. 2, except a dust collection bag 114 has been substituted for the vac hose 42. In FIG. 11, the sander 20 is running and the dust collection bag 114 is shown in the fully expanded position since it is pressurized from the exhaust air from the dust exhaust duct 76. The dust collection bag 114 may sometimes also be referred to as a dust collection receptacle.

Claims

1. A sander for a wooden floor with an elastic drive belt having a plurality of longitudinal ribs comprising: a drive system,the drive system consisting of:a drive shaft protruding from an electric motor, the shaft having a plurality of grooves formed therein to engage the ribs in the elastic drive belt;a driven pulley operatively connected to a sanding disk for sanding the wooden floor, the driven pulley aligned with the grooves in the drive shaft;the drive shaft and the driven pulley being fixed in relation to each other; andthe elastic drive belt being positioned around the drive shaft and the driven pulley to transfer torque from the electric motor to the driven pulley and the sanding disk.the sander further comprising:a dust fan blade element mounted on the drive shaft and driven by the electric motor; the dust fan blade element positioned between the sanding disk and a dust collection receptacle to facilitate dust control.

2. The apparatus of claim 1 wherein the speed of the drive shaft and the fan is in the range of about 12,000 rpm to about 14,000 rpm and the speed of the sanding disk is in the range of about 2,800 rpm to about 3,200 rpm.

3. A sander for a wooden floor with an elastic drive belt having a plurality of longitudinal ribs comprising: a generally cylindrical drive shaft protruding from a motor, the drive shaft characterized by an absence of a pulley on the drive shaft;a driven pulley remotely located from the drive shaft, each fixed in location to each other;the elastic drive belt contacting the drive shaft and the driven pulley to transfer torque from the drive shaft to the remotely located driven pulley;a dust fan blade element mounted on the drive shaft;a plurality of grooves formed in the drive shaft between the fan and the motor, the grooves sized to engage the ribs in the elastic drive belt;the driven pulley operatively connected to a sanding disk for sanding wooden floors; anda shroud surrounding the fan and proximate the sanding disk to direct dust from the wooden floor, past the fan to a dust receptacle.

4. The apparatus of claim 3 wherein the speed of the drive shaft and the fan is in the range of about 11,000 rpm to about 13,000 rpm and the speed of the driven pulley is in the range of about 2,000 rpm to about 4,000 rpm.

5. The apparatus of claim 3 wherein the fan rotates at about 12,000 rpm and the sanding disk rotates about 3,000 rpm.

6. A sander for wooden floors with an elastic drive belt having a plurality of longitudinal ribs comprising: a generally cylindrical drive shaft protruding from a motor;a driven pulley remotely located from the drive shaft;the elastic drive belt wrapping around and engaging a portion of the drive shaft and also wrapping around and engaging at least a portion the remotely located driven pulley to transfer torque from the drive shaft to the driven pulley, the drive shaft characterized by an absence of a pulley on the drive shaft;the drive shaft and the driven pulley being fixed in relation to each other;a plurality of grooves formed in the drive shaft and sized to engage the ribs in the elastic drive belt; andthe driven pulley operatively connected to a sanding disk for sanding wooden floors.

7. The apparatus of claim 6 wherein an outside surface of the driven pulley is substantially smooth.

8. The apparatus of claim 6 wherein an outside surface of the driven pulley is formed with a plurality of grooves having a size and shape to engage the longitudinal ribs on the elastic drive belt.

9. The apparatus of claim 6 further including: a fan mounted on the drive shaft, anda shroud surrounding the dust fan blade element and having an inlet proximate the sanding disk and an outlet connected to a receptacle, the dust fan blade element creating negative pressure in the inlet to draw a sanding dust through the duct and deposit the sanding dust in the dust collection bag.

10. The apparatus of claim 9 wherein the speed of the drive shaft and the fan is in the range of about 12,000 rpm to about 14,000 rpm and the speed of the driven pulley is in the range of about 2,800 rpm to about 3,200 rpm.