Flexible gear coupling inspection port
BACKGROUND OF THE INVENTION 
     This invention relates to flexible gear couplings used to connect rotating shafts in machinery. It relates particularly to a means of inspecting the gears used in such couplings. 
     Flexible couplings are commonly used for connecting rotary shafts in machinery such as the shafts connecting an electric motor to a pump. Such couplings are very useful in prolonging the life of the machinery since the repeated flexing of rigidly coupled rotary shafts, regardless of how slightly they are misaligned, can produce severe stresses in the shafts, the bearings and the machinery. Also excessive stresses can be incurred when the normal axial movement of rigidly coupled rotary shafts is constrained. A flexible coupling on the shafts permits such excessive stresses by compensating for any misalignment of the shafts or axial shaft movement, while at the same time transmitting the torque from one shaft to the other. 
     Gear type flexible couplings are manufactured by many manufacturers of mechanical power transmission equipment and are widely used in industry. The gear-type coupling consists of two similar hubs with external gear teeth and a floating sleeve assembly with internal gear teeth. The hubs are fitted to the ends of the driving and driven shafts, and as the driving shaft rotates, the driving hub gear teeth engage the internal gear teeth of the floating sleeve assembly so that the entire coupling rotates as a unit. 
     Flexible gear couplings, like any other piece of rotating machinery, are subject to excessive wear if not properly lubricated and maintained. In addition, flexible gear couplings are frequently subjected to starting and stopping impact loads that can damage the gears, if excessive. As a result flexible gear couplings need to be regularly inspected and repaired or replaced if necessary. Regular inspections are often required by OSHA regulations. The sealed sleeve over the hubs prevents a visual inspection of the conditions of the gears on the hubs and the gears in the sleeve. An inspection requires the removal of the motor or prime mover and a complete disassembly of the flexible gear coupling, which is time-consuming and expensive. 
     SUMMARY OF THE INVENTION 
     It is an object of this invention to provide a means for quickly and easily inspecting the condition of the gears in a flexible gear coupling. 
     It is a further object of this invention to provide a means for inspecting the condition of the gears in a flexible gear coupling that can be easily applied to all types of gear couplings and to couplings now in service. 
     It is a further object of this invention to provide a flexible gear coupling that will provide longer trouble-free service. 
     It has been discovered that the foregoing objectives can be attained by a flexible gear coupling having an inspection aperture in the sleeve assembly which extends through the sleeve assembly and through the central section of at least one tooth of the internal gear teeth of the sleeve assembly of the coupling. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an isometric view, partially in section, of a flexible gear coupling of this invention. 
     FIG. 2 is an enlarged view of the gears viewed through the inspection port of the flexible gear coupling of this invention. 
     FIG. 3 is the closure member used to seal the inspection port of the flexible gear coupling of this invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION 
     FIG. 1 illustrates a flexible gear coupling of the type for which this invention is useful. 
     As shown in FIG. 1, flexible gear coupling 1 comprises a pair of hubs 2 and 2&#39; and a pair of sleeve members 6 and 6&#39; which are bolted together to form a sleeve assembly 5. The hubs 2 and 2&#39; each have a keyway 3 to secure a cylindrical shaft (not shown). A ring of gear teeth 4 is formed on the external surface of each of hubs 2 and 2&#39;. The hubs 2 and 2&#39; are usually of the same diameter. 
     Surrounding the hubs 2 and 2&#39; is a sleeve assembly 5 consisting of mating flanged sleeve members 6 and 6&#39; which are connected together at their flanges 7 and 7&#39; by bolts 8. The sleeve members 6 and 6&#39; are each provided with an internal ring of gear teeth 9 positioned to engage the external gear teeth 4 of hubs 2 and 2&#39; when the coupling 1 is assembled. 
     As the driving shaft (not shown) rotates hub 2, the external gear teeth 4 of hub 2 engage the internal gear teeth 9 of the sleeve member 6 causing the entire sleeve assembly 5 to rotate and in turn rotate hub 2&#39; and the driven shaft (not shown) connected thereto. 
     The sleeve members 6 and 6&#39; are provided at their outer ends with O-rings 10 or similar seals which engage the hubs 2 and 2&#39; to prevent dirt and water from entering the coupling 1 and to retain a lubricant within the coupling 1. Some couplings have a mechanical configuration designed in the sleeve end that maintains the required lubricant level without the need for a resilient seal. Most couplings of this type require an internal lubricant which injected into the coupling 1 through a lubrication passage 11 formed in the flanges 7 and 7&#39; of the sleeve members 6 and 6&#39;. 
     In accordance with this invention, each sleeve member 6 and 6&#39; is provided with an inspection port or aperture 15 extending through the sleeve 6 and 6&#39; and through the central section of at least one tooth 16 of the internal gear teeth 9 of the sleeve members 6 and 6&#39;. Since the hubs and sleeves never disengage, the wear seen on one tooth is indicative of the wear on all the teeth. 
     As best shown in FIG. 2, which is an enlarged view of what one would see in looking through the inspection aperture 15 of this invention, the central section of at least one tooth 16 is removed leaving the side sections 17 and 17&#39; of that tooth in place. The removal of the central section of tooth 16 exposes the profile of the side sections 17 and 17&#39; and the tooth thickness and also the face flanks of teeth 4 on the hubs 2 and 2&#39; to a visual inspection through the inspection aperture 15. Preferably, the aperture 15 is in a circular hole whose center is aligned with the midpoint of the width of the internal gear teeth 9 of the sleeve members 6 and 6&#39;. The diameter of the aperture 15 should be greater than two times but less than three times the pitch of the external gear teeth 4 on the hubs 2 and 2&#39; to permit an inspection of two hub teeth thickness conditions at a time. The bottom of the aperture 15 is formed by the tops of gear teeth 9 adjacent to gear tooth 16. 
     FIG. 3 is a sectional view of the inspection aperture showing the means to seal said aperture 15 between inspections. The seal is a resilient elastomer plug 20 having a head 21 and shank 22 and a circumferential shoulder 23 between the head 21 and the leading end 24 of the shank. When inserted in aperture 15, the shoulder 23 of plug 20 fits into a circumferential groove 25 in the sleeve assembly around the aperture 15 to retain the plug 20 in place. 
     The exact dimensions of the aperture 15 and plug 20 will vary according to the size of the coupling 1. The inspection aperture 15 can be easily machined in the sleeve members 6 and 6&#39; of all flexible gear couplings on the market although the exact location and size may vary according to the specific brand of coupling used. 
     While the present invention has been described and illustrated with our preferred embodiment, it will be appreciated by those skilled in this art, after understanding this invention, that various changes and modifications may be made without departing from the spirit and scope of this invention. It is therefore intended that all such changes and modifications will be included in the following claims.