TECHNICAL FIELD

The present invention relates to the design and fabrication of a push-button shaft coupler for connecting shaft segments to each other

BACKGROUND

Couplers are devices that may be used for connecting shaft segments that rotate a brush or other device when the interior of a fireplace chimneys or a duct is cleaned. Newth U.S. Pat. 10,288,123 describes good-performing two-button and single-button couplers for joining two rotatable shaft segments.

An exemplary coupler of the above ‘123 patent comprises two mating coupler halves that are secured to each other by a radially- moving pushbutton. A portion of the male coupler half which has a spring loaded button is received within a concavity of the female coupler half. When the coupler halves are mated, the button projects through a radial opening in the wall of the concavity of the female coupler half, thereby enabling transmission of lengthwise and torsional forces between the mated coupler halves. To disengage the coupler halves from each other, a user manually depresses the button.

Heretofore, exemplary coupler halves have been fabricated from metal bar stock, such as steel or aluminum alloy barstock. To form the interior of the body of a male coupler half, fabrication involves metal removal by lathe-turning, drilling, and milling.

To reduce manufacturing cost, it would be desirable to use injection molding to make coupler halves of plastic material, such as glass fiber filled Nylon 66. However, if the interior configuration of a machined male coupler body were to be replicated in an injection molded part, that would likely require complicated and movable mold parts and secondary operations, which lessen the economic benefit that is sought. Thus there is a need for changes in design of coupler parts, particularly the male half coupler so a coupler can be made for low cost while maintaining functionality compared to a metal coupler. There is also a continuing further need to make easier the assembly of male coupler halves which have small interiors, within which it is difficult to insert a pushbutton and associated spring.

SUMMARY

An object of the invention is to provide an improved configuration of pushbutton coupler, in particular an improved male half coupler that is adapted to economical manufacture, while maintaining the functionality of the prior coupler configuration.

An embodiment of coupler of the present invention comprises a female half coupler having a concavity which receives and engages a portion of a male half coupler that has a spring actuated push button. The body of the male half coupler has a central lengthwise axis and a blind bore running lengthwise from an opening at the proximal end to a wall at the distal end. The bore has an outer section running from the proximal end to an inner section which runs to the wall. The outer bore section is shaped for attachment to a round cross section shaft. The push button and the spring are positioned within the inner bore section. The push button sets within a radial opening that connects the inner bore section to the exterior of the male coupler half. The push button is urged radially outwardly through the opening by the spring extends from a recess in the button to the floor of the inner bore section. Preferably, the inner bore section has a substantially flat floor and a roof which may be curved or flat. In one embodiment, the flat floor starts at the proximal end opening of the bore and runs the whole length of the bore. In another embodiment the flat floor is only present within the inner bore section. In another embodiment the flat floor has a slope of 2 to 4 degrees to the lengthwise axis.

A method of assembly of a male coupler half comprises first pushing the button along the bore of the body and into the button opening. Then, the spring is compressed and slid lengthwise on the flat floor of the inner bore section to the location of the push button. The spring is released so one end sets within the recess of the button and the other end sets on the flat floor. Another method of assembly comprising setting a first end of the spring within the recess of the button, compressing the spring and sliding the spring and button along the length of the bore with the second end of the spring in contact with the flat floor until the button springs into the radial button opening running from the bore.

In embodiments of the invention, the male half coupler comprises a buttress on or close to the end wall. The buttress limits the lengthwise movement of the lower end of the spring during male coupler half assembly, to help locate the spring with respect to the recess of the button. A buttress may comprise one or two pedestals on the floor, or a member projecting from the wall.

The configuration of the interior of the male half coupler makes economical manufacture by injection molding feasible, and makes easier the process of assembly, while still maintaining the functionality associated with prior art machined metal half couplers, and couplers as a whole.

The foregoing and other objects, features and advantages of the present invention will become more apparent from the following description of preferred embodiments and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a partial cutaway perspective view of a prior art coupler half body.

Fig. 2 is a transverse cross section of the body of Fig. 1.

Fig. 3 is a perspective view of a button that may be positioned within the body of Fig. 1.

Fig. 4 is a lengthwise cross section of a male coupler half comprising the body of Fig. 1. Fig. 5 is a partial cutaway perspective view of an embodiment of a coupler half body of the present invention.

Fig. 6 is a transverse cross section of the body of Fig. 5.

Fig. 6A is a transverse cross section of a body like that of Fig. 6, except for the body now having a flat inner bore roof, compared to a curved inner bore roof.

Fig. 7 is a lengthwise cross section of the body of Fig. 5 showing a phantom button and spring in place.

Fig. 8 is a lengthwise vertical cross section of a body having a floor with buttresses adjacent the end wall.

Fig. 9 is a lengthwise horizontal cross section of the Fig. 8 body, showing the two spaced apart buttress adjacent the end wall.

Fig. 9A is a partial lengthwise cross section of a body, like Fig. 8, showing an alternative buttress configuration.

Fig. 10 is a lengthwise cross section of a body having a stepped floor and one or more buttresses at the end wall.

Fig 11 is a lengthwise cross section of a body of Fig 8 showing how the spring and button are inserted during assembly of a coupler half.

Fig. 12 is a perspective view showing a male coupler half and a female coupler half as they are situated for mating to form a coupler.

Fig. 13 is a lengthwise cross section of a coupler comprising a male half coupler and a female half coupler that are engaged with each other. DESCRIPTION

The present invention includes a coupler which is comprised of a first half coupler and a second half coupler that during use are held together by a spring-actuated push button. (Reference herein and in the claims to a “button” is a reference to a push button.) The second half coupler has a concavity within which is releasably received a portion of the first half coupler that contains the spring loaded button. The first half coupler is often referred to as the male half coupler and the second half coupler is often referred to as the female half coupler. A single-button male half coupler that is taught by the prior art, along with its features, are first described here to provide context for the present invention.

The disclosure of U.S. Pat. No. 10, 288,123 is hereby incorporated by reference. Fig. 1 through Fig. 3 of the ‘123 patent show components of a prior art male coupler half. Fig. 4 shows in cross section the assembled coupler half 122 (also called first fitting 122). Fig. 4 shows how the innermost end of spring 150 sets in a recess 188 in the floor of the coupler half and the outermost end of the spring sets within a recess 158 on the underside of button 130.

Fig. 12 shows a single-button male half coupler 100 and a female half coupler 200 of the present invention, as they are situated for mating with each other (as indicated by the arrows) to connect shaft segment 98A to shaft segment 968. As described in the ‘123 patent, there are opposing planar surfaces 142 on the exterior of the body 221 of male half coupler 100 which mate with planar surfaces within the bore of the female half coupler 200, to lessen the torque load on button 130 during use of a coupler. Fig. 12 also shows a rib 143 that runs lengthwise along only one of the planar surfaces 142 of male half coupler 100, along with a lengthwise groove 145 shaped to receive rib 143 within the bore of female half coupler 200, when the parts are mated. Those are features not taught by the ‘123 patent. Rib 143 and groove 145 are rotationally polarizing features that permit engagement of the half couplers 100, 200 only when button 130 is aligned with opening 246, thus avoiding avoid engagement of the halves when the button is 180 degrees out of position. Other male-female features that reduce torque load on a button and that polarize the coupler halves may be used in the present invention. Embodiments of the present invention shown in the other figures herein may include the foregoing exterior planar surface features and polarizing features. But, to avoid drawing clutter, those features are not pictured in the other figures.

Fig. 1 is a perspective partial cutaway view of the machined body 121 of a prior art male coupler half that is ready for receiving a button and a spring. Fig. 2 is an end view of body 121. Body 121 has a bore comprised of a circular outer bore portion 156 and an oblong cross section inner bore portion 123. Body 121 has a proximal end 136 and a distal end 134.

Bore section 156 runs from the proximal end 136 of the body. Bore section 156 is shaped to fit the end of a circular shaft to which the body is attached during use of a half coupler. The inner bore section 123 runs from bore section 156 to the wall 168 at the distal end of the body.

Fig 3 shows exemplary button 130 that has a flat top 35 with a bevel. The opposing end flanges 92, 94 of button 130 have curved upper surfaces 54 that mate with the curved contours of bore section 156 of body 121 that are adjacent button opening 133. When the button moves during use, the opposing planar sides 78 (only one is visible) fit the opposing planar sides 144 of section 123 of the body, to guide the radial movement of the button. Button 130 and variations may be used within bodies of the present invention that are part of a male half coupler. Useful buttons may have alternative surface finishes on the top 35 which the user typically contacts with a finger to disengage a coupler. For instance, the surface may be flat with no bevel, may be curved, and may have ribbing or other texturing.

In the prior art, body 121 is typically machined from a piece of metal barstock by plunging a drill along lengthwise axis CL, followed by use of one or more end mills to create opposing side walls 144 that are parallel to each other. The button opening 133 is formed by another end-milling operation. A small end mill is then plunged through opening 133 to form recess 188 which enables the innermost end of spring 150 to sit stably on the otherwise curved surface of the floor of the inner bore section. Referring to body 121 as it is oriented in Fig. 1, 2, and 4, the machining method that is used leads to a curved “roof’ and a curved “floor” 125 of the inner bore section 123. Because of the length of the bore comprising sections 156, 123, it is practically disadvantageous to produce by ordinary machining a bore with other than curved roof and floor when planar sides 144 for button guidance during use are required.

If the internal configuration of body 121 were replicated by injection molding of a plastic resin, it is likely that cavities 156, 123 would be defined by the core part of the mold, and a slide in the cavity part of the mold would be used to form the button opening 188. A secondary machining operation would likely be needed to form spring recess 188.

The present invention includes an improved design of coupler body that avoids the foregoing complications and costs. Fig. 5, 6, 6A and 7 show an exemplary coupler body 221 of the present invention. Fig. 5 is a perspective partial cutaway view, like that of Fig. 1. Fig. 6 is an end view of body 221. Fig. 6A, a variant, body 221A, and is discussed below. Fig. 7 is a lengthwise cross section of body 221.

The blind bore of body 221 comprises outer section 256 and inner section 223. Outer section 256 extends from body end 236 (the proximal end of the body) to a point where it meets inner bore section 223. Inner bore section 223 extends to integral wall 268 that is at the distal end 234 of the body. During use, the outer bore section 256 is secured to the end of a shaft segment and the inner bore section 223 holds the button and spring. Button opening 233 extends radially form the inner bore section 223 to the exterior of body 121. Flat floor 225 extends lengthwise within the bore of the body, from the proximal end 236 to the wall 268.

For perspective, an exemplary body 221 may have a diameter of about 0.67 inch (17 mm) and the outer section bore might have a diameter of about 0.44 inch (11.2 mm). The floor may be about 0.25 inch (6.4 mm) wide.

In a plane which is perpendicular to the lengthwise axis CL, floor 225 has negligible width-wise curvature, as illustrated in Fig. 6. In a lengthwise direction, floor 225 is substantially flat. See Fig. 7. Floor 225 may rise so it become closer to the lengthwise axis CL with distance from end 236. For example, flat floor 225 may have an angle of about 1 to about 4 degrees. Such angle range could be reflective of angles associated with plastic molding cores and dies.

Floor 225 facilitates sliding placement and functioning of the spring, as described below. Floor 225 provides good support for the bottom of the spring. Opposing side walls 244 of the inner bore section 223 are planar and parallel, thus providing opposing sliding surfaces that guide button movement through opening 233.

Compared to a curved floor, the flat floor of the present invention enables good, stable sliding of a spring lengthwise during assembly and provides a surface for the base of the spring that is desirably nearly perpendicular to the spring length and the button travel direction through opening 233. This will be appreciated from discussion below relating to Fig. 11. In body 221, floor 225 runs from the proximal end 236 of the body to vicinity of wall 268, as shown in Fig. 5 and Fig. 7. The floor interrupts the circularity of outer bore section 256. In the Fig. 6 embodiment, about 60 degrees of the circumference is missing. As a corollary, 83 percent of the circumference is still present, and that is more than adequate to run around the exterior of a round shaft and hold it. Thus, outer bore section 256 is characterized here as being “substantially circular” in terms of its function of receiving and being secured to a round shaft end. A shaft may be secured to the body by means of such as adhesive, a pin, screw or crimping, none shown. In an alternative embodiment of the invention, it may be sufficient to have a flat floor in the inner bore section 223 and not in the outer bore section 256. Reference may be made to Fig. 10, discussed below.

Fig. 7 shows button 130 and spring 150 in phantom working position within body 221. The spring and button used with body 221 are preferably like those described in connection with the prior art coupler half shown in Fig. 1 to Fig. 4. The roof 227 of bore section 223 of exemplary body 221 is curved. Thus, the roof portions on either lengthwise side of button hole 233 mate well with the curved upper surfaces of the button flanges 54 of button 130. See Fig. 3.

Fig. 6A is an end view like Fig. 6, showing alternative embodiment body 221 A, which is much like body 221. Body 221A has an outer bore section 256A running from proximal end 236A and an inner bore section 223A running to wall 268A. Button opening 233A runs radially from the bore section 223A to the exterior of the body. Inner bore section 223A has both a flat floor 225A that extends from end wall 268 A to the proximal end of body 221, and it has flat roof 227A that is only present in the inner bore section 223 A. The top surfaces of the flanges of a button which is configured to fit body 221 A will have flat flange top surfaces, compared to the curved flange top surfaces 54 of button 130 that is used with body 221. As with body 221, the opposing side walls 244A of the inner bore section 223 A of body 221 A are planar, for guiding in-out button movement during use a coupler half.

Fig. 8, a vertical lengthwise cross section, and Fig. 9, a horizontal lengthwise cross section that show coupler body 321 which is also largely like body 221. Body 321 has an outer bore section 356, an inner bore section 323, and a flat floor 325. Within the inner bore section 323, there are two spaced apart buttresses 380 at the distal end of flat floor 325, adjacent end wall 368. The buttresses extend lengthwise from end wall 368 in the direction of proximal end 336. Phantom spring 150 is shown in both Fig. 8 and Fig. 9. (A button within opening 333, at the outer end of the spring may be inferred from the prior figures.) When spring 150 is pushed lengthwise along the bore to place is below the button opening during assembly as described below, the lengthwise movement of the spring bottom along floor 325 is stopped when the lower end of the spring contacts the buttresses 380. Preferably the buttresses are configured so that the spring will then be centered on button opening 333. The buttresses extend upwardly from the floor a short distance, for example 2 mm, sufficient to provide a barrier for continued lengthwise motion of a spring.

In an alternative buttress embodiment, the lateral space between the two buttresses 380 may be filled in, to provide a single buttress that extends across the width of the inner bore section at the bottom of wall 368. See buttress 480 in Fig. 10. In a further variation, not pictured, the vertical face(s) of the buttress(es) that the spring contacts when pushed lengthwise into the inner bore section 323 may be curved in the horizontal plane to nominally fit the spring outside diameter.

Fig. 9A shows body 521 that is largely like body 221. Buttress 580 that is a web-like or shelf-like member that cantilevers lengthwise from the end wall 568. Buttress 580e web extends partially or wholly across the width of the end wall and is spaced apart vertically from floor 525. Buttress 580 will contact spring 150, shown in phantom, a short distance above the floor.

Fig. 10 shows body 421, an embodiment in which the floor has a small step 423. A floor portion 425A at a first elevation runs through the outer bore section 456 and partially through an adjacent first portion of the inner bore section 423. At a step 423, inner floor portion 425B runs to buttress 480, or to the wall 368 when there is no buttress on the floor, at a second elevation that is slightly higher than the first portion. In an alternative embodiment, when the flat floor has a slope, the inner floor portion 425B may have a slope that is less (even zero) than the slight slope of the flat floor of the outer portion 425 A, which was described above. Spring 150, shown in phantom, sets on the second floor portion 425B next to the buttress. The small step may be of the order of 1 mm. In such instance, the whole of the floor of body 421 would still be characterized here as being “substantially flat”.

A preferred way of assembling a small male half coupler which comprises a body of the present invention is as follows: An exemplary coupler for use with a shaft/rod segments that are about 5/16 inch (8 mm) diameter may have an about 7/16 inch (11 mm) outside diameter. It should be appreciated that the small size of the coupler makes assembly trickier than may appear from the drawings here.

With reference to Fig 11 and exemplary body 321, an assembler (which may be a worker or automated piece of equipment) first slides the button 330 lengthwise and into the opening 333, as indicated by the curved arrow. Spring 150 is then compressed as shown in the Figure 11 and slid in that condition lengthwise within outer bore section 356 and inner bore section 323. A compression fixture, not shown, may be used for the spring. The spring is moved to a point in the bore which is beneath the recess 358 of button 330, when the bottom end of the spring hits buttress 380. Then spring compression is released, allowing one spring end to set within recess 358 of the button and allowing the other spring end to rest of flat floor 325.

Another way to assemble a male half coupler having a body along the lines of body 321 would be to set a first end of the spring within the button recess, and then slide the spring and button assembly lengthwise along the bore while keeping the spring compressed due to contact of the spring second spring end with the floor of the bore, or with a fixture. With sufficient lengthwise movement the button will “pop into” the button opening 333, perhaps sometimes with jiggling- help of an assembler.

Coupler halves of the present invention may be made of injection molded Nylon 66 that is 30 percent glass fiber filler. Other plastic materials may be used. The button may be made of plastic or metal. The spring is preferably a steel coil spring. Other kinds of springs may be used. An exemplary spring used with the 7/16 in (11 mm) outside diameter coupler mentioned above is made of 0.030 inch (0.76 mm) diameter wire, has an about 0.234 inch (6 mm) diameter, a free length of about 0.49 inch (12 mm). A button used with the spring may have a pocket 358 that has a depth of about 0.08 inch (2 mm). When the button is depressed sufficient to enable disengagement of a coupler, the exemplary spring will be compressed about 25-30 percent compared to the spring length when the button is at its home (maximally outward) position. A buttress 380 of the 7/16 inch (11 mm) half coupler may be about 0.095 inch to 0.115 inch (2.4 mm to 2.9 mm) high relative to floor 325.

Fig. 13 shows in lengthwise cross section coupler 90 comprising male half coupler 500 that is mated with female half coupler 600, to connect shaft segments 98 A, 98B, shown in phantom. Each shaft segment may be secured within the proximal end-cavity of a coupler half by adhesive, crimping, or pinning (not shown). The exterior of coupler half 600 and the bore of coupler half 500 are respectively is shaped like male coupler half 100 and female coupler half 200 in Fig. 12; that is there are opposing flats and a polarizing lengthwise rib and groove.

Coupler half 500 has a body 521 that is much like body 321 in Fig. 11. Spring 550 sets within the recess of button 530 and rests on the flat floor 525, adjacent buttress 580. When the two coupler halves were being mated, the distal end 534 of coupler half 500 entered the bore 620 of half coupler 600. During that process, the distal end 605 of coupler half 600 hit button 530 causing the button to move inwardly against the spring. With further mating motion, the spring caused button 530 to move outwardly into the radial opening 646 of coupler half 600, thereby holding the two coupler halves to each other, as pictured. The objects of the invention are achieved. The invention accommodates injection molding. The need for machining a recess for the spring within the inner bore is eliminated. There is improved ease of positioning of the spring and button.

The invention, with explicit and implicit variations and advantages, has been described and illustrated with respect to several embodiments. Those embodiments should be considered illustrative and not restrictive. Any use of words such as “preferred” and variations suggest a feature or combination which is desirable but which is not necessarily mandatory. Thus embodiments lacking any such preferred feature or combination may be within the scope of the claims which follow. Persons skilled in the art may make various changes in form and detail of the invention embodiments which are described, without departing from the spirit and scope of the claimed invention.