Abstract
A speed reduction mechanism reversible for use with electric hand tools comprises a pair of juxtaposed epicyclic gear train mounted on a common carrier, to independently engage a pair of cage or ring gears. The cages can be alternately locked or released from an outer casing to perform bidirectional transmission of rotational power. The complete reversal mechanism is in a generally cylindrical body suitable for mounting between a conventional unidirectional motor and gear head or powered device. Output rotation forward or reverse is selected by moving a control button located on the periphery of the reverse. Reduced velocity in the range of 3 to 5 to 1 can be achieved through this mechanism.
DescriptionBackground of the InventionThe invention relates to a speed reduction mechanism for reversible use with hand-held power tools and more particularly to a reversing mechanism for use with tools energy production line having a motor and gear head separable it also provides a reduction in speed three to 1:00 to 12:55 and a proportional increase in output torque concomitant.The increasing reliance of the method of the production line of manufacturing has created a dependency of equality in lightweight portable power tools for use by assembly personnel in the manufacturing process. The vast majority of these tools are powered by compressed air or electricity. Various devices, such as gear trains, and ratchet mechanisms pulse devices can be attached to relatively simple high rpm motors to provide energy in the form required by an assembly operation indicated.One of the most common requirements of these power tools is the ability to reverse the direction of the unit in order to facilitate removal of a threaded fastener that may have been improperly inserted or which must be removed in order to remove other components.The electrically powered tools, directional control is a tricky problem. It is well known that by simply reversing the polarity of the electricity to the motor windings is some directional control effect and this can be accomplished by conventional switching means. However, seldom appreciated that the rotational speeds of these motors may be as high as 15,000 RPM, and that the sudden change of the motor driven elements undergoes a tool to severe shock which considerably shortens its lifetime. Second, the current increase associated with investment EMF motor reversing switch requires a heavy duty too. Unfortunately, a circuit which exhibits the necessary durability is generally bulky and often fatiguing to the operator of the tool due to its high activation force.In the case of pneumatic engines, the most commonly invoked to provide bidirectional rotation is a vane motor that has two input ports, arranged symmetrically on opposite halves of the vane motor chamber and an exhaust port common positioned midway between the ports. Air that enters a port of entry and exits through the common exhaust port engine causes the air to rotate in one direction while the air entering the other port of entry and exit of the exhaust port common causes motor rotation in the opposite direction. This type of air motor reverse has a drawback. Since the air has to enter and exit the vane motor to compensate less than 180 degrees, the expansive force and thus the power produced by the air motor is less than that which can occur in an engine in the conventional way that the radial separation of the input and output ports from the effective use of the expansive force air over approximately 240 degrees. Therefore, if the output of an air motor must be bidirectional, a certain amount of output power must be compromised to achieve this.The alternative to using a bidirectional air or electric motor in a hand tool is the incorporation of an independent reversing mechanism into a tool that has a unidirectional motor. In general, these devices have the power output lower than a unidirectional tool. In this case, the power loss is due to additional gear in the reverse. Reversing Such mechanisms also generally add substantially to the weight of the hand power tool. In the work of the production line, where an operator can lift and move the tool continuously for several hours, any additional weight greatly increases operator fatigue. Moreover, the tool size is also an important consideration, as it often is necessary to operate the tool in the structure being assembled, such as an automobile. A bulky tool that includes the ability of investment required in an application may, however, be unusuable because it can not participate or can not be easily manipulated to engage the closure or other device that is intended to mount due to limited space in which to function.If a production process requires slow rotation, the mechanism can be even more complex. Preparing addition needed to produce bedirectional output rotation may be necessary and the size and weight of the rollback mechanism then may increase to a point where the tool is unsurpassed for production line use.SUMMARY OF THE INVENTIONThe invention comprises a speed reduction mechanism for use with reversible electric hand tools which have a pair of epicyclic gear trains juxtaposed mounted in a vehicle independently engage a pair of cage or ring gear. The cages can be locked to or released selectively to an outer housing for effecting bidirectional output tool supply air stream. A reduction ratio in the range of 3 to 5 to 1 that can be different in the forward and reverse directions slows the rotational speed of the drive motor while effecting an increase in torque. The reversal mechanism is contained in a generally cylindrical housing having a diameter approximately equal to the engine to which it is mounted and which includes a control button that can be moved to the front or rear of the cylindrical housing by the operator to select the rotational direction of the output.The only speed reduction mode or forward operation, the first cage is locked to the outer casing and the second cage is free to rotate. The first epicyclic gear train is driven from the input shaft and rotates inside the first cage. The carrier on which is mounted the first epicyclic gear train is connected directly to the output shaft that transfers rotational power out of the mechanism. Operating in the back, how to accelerate the reduction, the second cage is locked to the first cage housng and is free to rotate. The second epicyclic gear train comprising two pairs of meshing gears one of each pair is indirectly driven by the input shaft, the second gear of each pair engaging the cage closed. The second epicyclic gear train thus rotates in the reverse direction of the input shaft and causes a reverse rotation as the carrier and the output shaft.It is therefore an object of this invention to provide a speed reduction mechanism for use with reversible electric hand tools.It is a further object of this invention to provide a speed reduction mechanism reversible, so it can be retrofit to existing electrical hand tools separable between the motor and the drive head.It is yet a further object of this invention to provide a mechanism of this type in a compact, light weight that does not add substantially to the weight and dimensions of the power tool.It is yet a further object of this invention to provide a speed reduction mechanism reversible, so that has a structure that is easy to control and positively operable.It is yet a further object of this invention to provide a reversible speed reduction mechanism, which incorporates both equal and unequal forward gear ratios and the reverse.BRIEF DESCRIPTION OF THE DRAWINGS. Figure 1 is a top plan view of a speed reduction mechanism according to the present invention in place on a power hand tool;. Figure 2 is a side elevational view in full section of a speed reduction mechanism reversible according to the present invention, taken along line 2 - 2 of FIG. 1;. Figure 3 is an end elevational view in full section of a speed reduction mechanism reversible according to the present invention taken along line 3 - 3 of FIG. 2;. Figure 4 is a full sectional elevation of a mechanism reversible speed reduction according to the present invention taken along line 4 - 4 in Fig. 2, and. Figure 5 is a perspective exploded view in partial section of the components of a speed reduction mechanism reversible according to the present invention.DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to FIG. 1, a speed reduction mechanism reversible according to the present invention is generally designated by reference numeral 10. The mechanism 10 is adapted to be positioned between a motor housing 11 and an outlet head 12 in a conventional power tool. The mechanism 10 is entirely contained within a cylindrical housing 13.Referring now to FIG. 2, the assembly between the motor housing 11 and the outlet header 12 is facilitated by female threads 14 and male threads 16 on housing investment mechanism 13 which engage matching male thread 15 and the female thread 17 in the housing 11 and head 12 respectively. An input shaft 18 transfers power from the motor mechanism 10. The input shaft 18 includes gear teeth 19 along a portion of its length and tapers near its terminus to a reduced diameter portion 20. The reduced diameter portion 20 seats within an axial bearing aperture 22 is formed within a gear holder 23. The gear holder 23 is disposed concentrically about the input shaft 18 and also includes a recessed portion 24 which is engageable by an engagement surface toothing (not shown) on an output shaft 25 is illustrated in Fig. 1. The input shaft 18 and carrier gear 23 are rotatably positioned within the housing 13 and are maintained in coaxial alignment by two anti-friction bearings 26. Antifriction bearings 26 may be ball bearings or other suitable means. The input shaft 18, the gear carrier 23 and antifriction bearings 26 are kept in proper relative longitudinal alignment within the housing 13 by spacers 27 and retaining rings 28. The rings 28 are seated in the circumferential grooves 29 in the input shaft 18 and the gear carrier 23.Referring now to FIGS. 2 and 3, the investment mechanism 10 is seen to include a first planetary gear set or idler 31. Each intermediate gear 31 is fixed to an axis structure 32 which is mounted on pairs of apertures 33 in the carrier 23 about axes parallel to the drive shaft 18. As seen in Fig. 3, idler gears 31 engage the teeth of gear 19 in the input shaft 18 and the gear teeth 35 on the inner surface of a circumferential planetary gear cage 36. The gearbox 36 is positioned concentrically within the housing 13 and bears axially against an annular thrust bearing assembly 37. The cage 36 also includes a plurality of teeth 38 radially arranged on a surface protruding outward adjacent to the thrust bearing assembly 37. The profile of the teeth 38 can be any one of a series of conventional gear profiles subject to common connection engagement softer compared to the minimization of the axial forces that tend to disengage resolved said teeth.Referring again to FIG. 2, the mechanism 10 can also be seen to include a brake for inhibiting rotation of ring 41 concentrically disposed within the housing 13. The brake ring 14 contains a plurality of teeth 42 on its face adjacent teeth 38 which are of similar profile and mate therewith. Similarly, the opposite face of the brake ring 41 includes a plurality of teeth 43. The brake ring 41 further includes a radially extending protrusion 44 that passes through an aperture 45 in the housing 13 and is equipped with a control knob or button 46 which is manually positionable at a position forward or backward by the tool operator.Referring now to FIGS. 2 and 4, shaft 32 structures which are mounted on the first pair of intermediate gears 31 extend axially forward inside the housing 13 and mounting a second pair of idler gears 50. The intermediate gears 50 represent an average of the second epicyclic gear train also containing a third pair of idler gears 51. Each intermediate gear 51 is placed in a short axis 52 and an anti-friction bearing 53 between the intermediate gears 51 and the axle stub 52 minimizes friction between those components. The stub shafts 52 are mounted on pairs of aligned apertures 54 in the carrier 23. The intermediate gears 51 engage the intermediate gear 50 and the gear teeth 55 on a second gearbox 56. The gear cage 56 is positioned concentrically within the housing 13 and is coaxial with the input shaft 18. An anti-friction assembly 57 is disposed between an axial end of the cage 56 and the shoulder section of the housing 13. Cage 56 further includes a plurality of teeth 58 radially arranged on a surface that protrudes outwardly from the cage 56. Teeth 58 are engageable with teeth 43 disposed on the adjacent radial surface of the brake ring 41.Referring now to FIG. 5, the spatial positioning of the reverse elements can be seen clearly. Note that the shaft 18 including the gear teeth 19 and the reduced diameter portion 20 is mounted from the left end of the carrier 23 and the seats at the inlet opening 22. Similarly, the rollers 31 on the shaft structure 32 are seated on the carrier 23 between the gear teeth of the input shaft 19 and the gear teeth 35 on the inner surface of the gearbox 36. The second epicyclic gear assembly 50 includes the intermediate gears and the idler gears 51 which are located within the carrier 23. The rollers 51 are positioned at the heel of the shafts 52 and mesh with the rollers 50 and the gear teeth 55 on the inner surface of the cage 56. Teeth 42 and 43 on the brake ring 41 to selectively engage and disengage the engagement teeth 38 and 58 in the boxes 36 and 56, respectively.The operating mechanism 10 may be better understood by reference to FIGS. 2 and 5. The only speed reduction mode or running forward, the brake ring 41 moves to the left as shown in FIGS. 2 and 5. The cage 36 is therefore locked in the housing 13 while the second cage 56 is free to rotate. The gear teeth 19 on input shaft 18 driving the intermediate gear 31 rotating in the opposite direction. Rollers 31, however, must rotate against the gear teeth 35 on the inner surface of the closed cage 36 and thus force the carrier 23 to rotate in the same direction as the input shaft 18, but at a reduced speed .Operation mode reverse speed reduction is similar. The brake ring 41 moves to the right as illustrated in Fig. 2, the unlocking of the locking cage 36 and the cage 56 to the housing 13. The rotary motion is imparted to the shaft structure 32 through the intermediate gears 31, the gear teeth 19 on the input shaft 18. Intermediate rollers 50 power transmission to the second rollers 51 which are in engagement with the gear teeth 55 on the inner surface of the cage 56. Since the rollers 51 are engaged with the cage 56 in a manner similar to the engagement of the rollers 31 in the cage 36, but are rotating in the opposite direction to roller 31, the support 23 is forced to rotate in the opposite direction to the drive mode (a reduced speed) of the operation. Again, since the output of the mechanism 10 is derived from the carrier 23, it is evident that a reduction in the rotation speed and a change of direction is achieved.Regarding the range of reduction rates, various combinations of gear teeth can be incorporated into the reverse gear ratios to produce in the range of approximately 3 to 5 to 1. For example, the cages 36 and 56 can include gear teeth 42 on its inner surface, the gear teeth 19 on the input shaft 18 can be 12 in number, 31 May rollers have 15 teeth, the rollers 50 may have 9 tooth, and the rollers 51 may have 12 teeth. In the forward mode of operation of this combination results in a reduction gear of the speed of 4.5 to 1. In the inverse mode of operation is effected a reduction in speed from 4.833 to 1. Therefore, it is clear that the reduction ratios for forward drive and reverse need not be equal.As a second example, the number of gear teeth on the intermediate gears 31 can be increased to 14, while using the same number of gear teeth in all other elements. This results in reduction of the same feed rate of 4.5 to 1, while reducing the speed in the reverse mode will be from 4.444 to 1. As noted above, various combinations of gear teeth and various gear ratios produced pulleys in the range from 3 to 1 to 5 to 1.The above description is the best mode devised by the inventor for practicing this invention. However, the invention should not be construed as limited by the foregoing description. It is evident that various other embodiments incorporating modifications and variations will be obvious to one skilled in the art to which the invention pertains. Such obvious variations are included and the invention limited only by the spirit and scope of the following claims.
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