Flat belt durability tester

The apparatus is a multi-speed flat belt durability tester that can simultaneously test several belts of different lengths. The tester can apply different tensions to each belt with a tension pulley powered by a hydraulic cylinder, and it monitors the tracking of the belts with photocell sensors. At least two belt test positions located at the outer edges of the apparatus include cantilevered pulley ends that greatly facilitate installation and removal of the belts being tested.

BACKGROUND OF THE INVENTION

This invention deals generally with an apparatus for testing power transmission belts and more specifically for a machine for life testing of flat belts of substantially different lengths.

Numerous power transmission belts are used on farm machinery, and there can even be six to eight belts on a single machine. Although such belts are usually thin flat belts, they can be either true “endless” belts or so called “laced” belts, those that have a spliced junction forming the loop. Field test evaluation of the performance of such belts under normal operation in crop conditions can take years. Furthermore, because of the width of such belts, which are up to a foot wide, the pulleys they ride upon are typically supported at both ends, making installation and removal of such belts very cumbersome and time consuming.

Several belt testing machines are patented, but all such devices have some shortcomings. For one thing most are designed for the common narrow “V” belt, or at least a belt in which the width is comparable to its thickness. This makes installation and removal of the belt relatively simple and reduces the problem of those belts drifting sideways on pulleys. Another aspect of the available testers is that they test one belt at a time.

For life testing wide flat belts it would be very advantageous to have available a machine which facilitates installation and removal of the belts, tests both endless and laced belts, and simultaneously tests several belts of different length.

SUMMARY OF THE INVENTION

The present invention durability tests wide, thin, flat belts, and it can simultaneously test up to three belts that need not be of identical length. The preferred embodiment of the invention tests belts from 343 inch to 420 inches in loop length, and can be adjusted for intermediate lengths. Although one of the three belt test positions is limited to a laced belt, the other two positions can test belts of either endless or laced design. The limitation on the one belt exists because the three belts are positioned side by side. Thus, while the outer two belts are essentially supported by cantilevered pulleys that permit easy belt installation and removal, the center belt is trapped between vertical support structures that can not be easily disassembled. This therefore requires that the center belt be a laced belt that itself can be disassembled for installation.

Several variable parameters are available to change test conditions to accelerate belt wear. One such parameter is speed variation. Although a fixed speed electric motor is used to drive the belts, two different sets of pulleys are available to change the belt speed to speeds greater than those experienced under field conditions. The test time is also reduced by increasing belt tensions. This is accomplished with an idler pulley forced against each belt by a hydraulic cylinder, with a linear variable displacement transducer monitoring the belt stretch, and with a pressure transducer monitoring the belt tension.

The preferred embodiment of the invention also includes adjustable guide pulleys installed on each side of each belt at both ends of the machine. These adjustable guide pulleys gently hold the belt on track without generating heat or belt edge degradation. However, if a belt travels too far sideways on a guide pulley, the movement is sensed by a photocell sensor, and the test machine is shutdown.

An additional feature of the machine is that it includes both “inside-wrap” pulleys that contact the belt surface that usually contacts pulleys and “outside-wrap” pulleys that can be placed in contact with the outside of the belts to add wear and shear stress to that side of the belts and better simulate field conditions.

The present invention can thereby simulate and even accelerate the wear conditions on flat belts used in various applications, and it provides significant information to predict belt performance under field conditions.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1is a schematic side view of flat belt tester10of the preferred embodiment of the invention, andFIG. 2is a schematic top view of belt tester10of the preferred embodiment of the invention. Only a limited part of the support structure of tester10is shown inFIGS. 1 and 2in order to more clearly show the locations and orientations of the various pulleys and the belts being tested. Furthermore, sinceFIG. 1is a side view only a single belt12would normally be seen in that view.FIG. 2, which is a schematic top view of tester10, shows the location of all three belts that can be tested simultaneously. As is also more clearly shown inFIG. 2, most of the pulleys whose ends are shown inFIG. 1extend for the entire width of tester10and can, but most need not always, be used for all the belts being tested.

FIG. 1also shows the manner in which belts of two different sizes can be tested. Belt12, indicated as a dark solid line, shows the path of a420inch belt installed on the near outer location of tester10. Belt13shown inFIG. 2as installed in the center position of tester10, is indicated as a dark dashed line and shows the path for a 343 inch belt. Paths of various other lengths are also possible with the depicted selection of adjustable pulley locations. Belts12,13and15are shown inFIG. 2to more clearly show the positions of three belts when they are being tested simultaneously on tester10.

Drive pulley14is one pulley that all the test belts must contact, because drive pulley14powers the movement of all the belts. Drive pulley14is powered from speed change apparatus16by belt18, and speed change apparatus16is driven by electric motor20through belt22. Drive pulley14has a second speed change apparatus17to permit even greater variation in the speeds for testing belts. Drive pulley14also includes conventional smaller diameter “crown” sections upon which each test belt is located. This “crown” structure aids in maintaining the belts in their positions on belt tester10.

The other vital pulleys for all belts are the tension pulleys. There is an independent tension pulley for each belt being tested, and each tension pulley applies suitable tension for testing its own belt. As shown inFIG. 1tension pulley24A is located between idler pulleys34and36on belt12, and positioned to contact the opposite surface of belt12from the surface contacted by the idler pulleys34and36. The tension is thereby adjusted by moving hydraulic cylinder26to place the tension pulley in an appropriate position, three of which are shown inFIG. 1and labeled24A,24B, and24C. These positions are monitored by linear variable displacement transducers28attached to each hydraulic cylinder26, and they permit data to be acquired and recorded continuously for each belt. The reading from each linear variable displacement transducer28along with concurrent hydraulic pressure reading from each pressure transducer27in hydraulic line29permits calculation of the belt tension.

Additional idler pulleys30,32,38,40,42, and44are located throughout the tester10to provide possible belt length variations and to contact the outside surfaces of test belts. As shown inFIG. 1for belt12idler pulleys14,30,32,34, and36are “inside-wrap” pulleys that contact the surface of belt12that usually contacts drive pulleys, and idler pulleys24A,38, and44are “outside-wrap” pulleys for belt12that are in contact with the outside of the belt to add wear and shear stress to that side of the belt.

FIG. 1also shows the vertical locations, but not the support structure, of guide pulley sets46and48. These pulley sets, the horizontal orientation of which is shown inFIG. 2, are shown in greater detail inFIG. 3. Guide pulley sets46and48are actually each a pair of pulleys installed at the ends of tester10and located along opposite edges of each belt. Thus, there are actually six sets of guide pulleys totaling twelve pulleys. Guide pulleys46and48are supported by ball bearings and gently hold the belt on track without generating heat or degradation of the edges of the belts. The guide pulleys are constructed with low end flanges separated by a wide flat section that permits a belt to move sideways on the guide pulley and buckle along the edge if the misalignment is too great. Under such circumstances, belt safety control50takes over.

Belt safety control50supplements the guide pulleys in that it stops belt tester10when any test belt moves off track by a prescribed distance. Belt safety control50includes two light sources and photocell alignment sensors52and light reflectors54for each belt. This arrangement is best viewed inFIG. 2. There is one light source and alignment sensor52at one end of belt tester10and one light reflector54at the other end of belt tester10located on each side of each belt being tested. All the alignment sensors52are interconnected to safety control50, and each alignment sensor52is aligned with a light reflector54along a light sight line56that parallels the belt path. Thus, if any belt moves more than a prescribed distance off track to cross a light sight line56, the light signal to the appropriate photocell alignment sensor52is broken and belt safety control50stops belt tester10. Of course, a similar arrangement can be constructed with the light source located where reflector54is shown. In that case light sight line56originates at the opposite end of belt tester10rather than adjacent to the photocell alignment sensor.

It should be appreciated that lower support beam58, vertical support beams65, and upper support beams60are shown inFIGS. 1 and 2to emphasize a very important structural feature of tester10. Almost all of the pulleys contacting belts12and13are constructed as cantilevered out from support beams58,60, and65. This permits very simple installation of test belts in these outer locations, because they can simply be slipped over the exposed pulleys.

FIG. 3is a schematic side view of a pair guide pulleys46(and48) that limit the sideways drift of the belts being tested. Unlike the other pulleys on tester10, guide pulleys46and48are located in the same vertical planes as the test belts and aligned with the belt edges. Therefore, they only contact the edges, not the flat surfaces, of belt12, or any of the other belts for which they serve as guides. However, even that edge contact is not actually required. Pulleys14,32, and24A are constructed with “crown” structures, the smaller diameter sections upon which the belts usually run, so that the belts will stay quite well centered on the pulleys. Nevertheless, the guide pulleys are installed to limit sideways drift of the belts, and, ideally, guide pulleys46and48would never actually exert any significant force on the belt. Thus, guide pulleys46and48gently hold the belt on track without generating heat or belt edge degradation for normal belt tracking. All the guide pulleys are installed on supports similar to support62and within slots64that permit adjustment for the running position and the width of the belt being tested. As previously described in regard toFIG. 2, if any test belt drifts too far sideways, belt safety control50stops tester10before any damage occurs.

The belt tester of the invention thereby furnishes a valuable durability test for flat belts that simulate and even accelerate field conditions. Furthermore, it permits changing endless belts by one operator in less than 30 minutes as opposed to field test belt changes that can take hours and require several operators. The invention can also be safely operated unattended on a continuous 24 hour a day schedule, and, by virtue of its linear variable displacement and hydraulic pressure transducers can offer continuous data acquisition. It has, in fact, tested belts that failed in as few as 30 hours, and operated others for 700 hours without failure.

It is to be understood that the form of this invention as shown is merely a preferred embodiment. Various changes may be made in the function and arrangement of parts; equivalent means may be substituted for those illustrated and described; and certain features may be used independently from others without departing from the spirit and scope of the invention as defined in the following claims. For example, belt tester10could be constructed to test only a single belt at a time, but can also include additional internal test positions for laced belts. Furthermore, belt tester10can have additional or fewer idler pulleys to permit testing larger or smaller belts.