Refer to Figure 1 / Face View of the Gear Box and Figure 2 / Power Flow Diagram
This gear box is composed of an input set of spiral bevel gears (#1 & #2), two spur gears (#3 & #4), a herringbone· shaft containing herringbone gears ( #5 & #6) . The definition of herringbone is two helical gears on the same shaft with an identical helical angle but of opposite direction, for example, one is left hand then the other has to be right hand. The herringbone gears mate with two helical gears (#7 & #8).
There are two planetaries: one on centerline “E” composed of one ring gear, one carrier, one sun gear (#9), three planet gears (#10), and one ring gear (#11) and; one on centerline “D”. ( The two planetaries have identical components, they are noted by the same numbers with the addition of the letter “A”.)
There are also two gears ( #12 and #12A) that are in mesh with the ring gears (#11 and #llA) respectively. These two gears power two output pinions (#13 and #13C) which are parallel with output pinions (#13A and #13B). Output pinions (#13A & #13B) are each driven by a planetary carrier.
The main advantage of the arrangement of this gear box is the fact that it is possible to have a large output gear mounted on a shaft and four pinions can power the output gear with an equal power distribution. In Figure 1 / Face View the pinion Fl, D, E, and Fare all parallel and rotate the output gear from a single input gear (#1).
The first equal di vision of torque ( or power) takes place at the herringbone shaft “C” with the herringbone gears (#5 & #6). It may be seen that herringbone gear (#6) powers helical gear (#7) which in turn powers the sun (#9) of the planetary on centerline “E”. At the same time, the second herringbone gear (#5) powers helical gear (#8) which in turn powers sun pinion (#9A) on centerline “D”. To this point we have equal power division at the herringbone, therefore, the two sun pinions are independently powering two separate planetaries at equal power and equal speed.
To provide equal load division from the herringbone pinion into the two helical gears, the herringbone pinion must be allowed to float axially a small amount of distance to make up for wear, case deflection, etc.
A planetary is composed of three principle members: a sun pinion (in this case the input power member), a planetary carrier (the output torque member which powers an output pinion), and a ring gear (#11 and #llA). This ring gear has two sets of teeth; an internal set of teeth which is used in a planetary in a normal way and an external set of teeth which is used as an output power planetary member to power gear #12 and #12A respectively, which in turn power
output pinion #13 and #13C respectively.
The three principle planetary members are conveniently used to again divide the power into two paths, one being the output carrier and the second one being the external ring gear. It can be seen that the carrier powers one output pinion and the ring gear at the same time powers a second output pinion. Since there are two planetaries in this gear box it is possible for each planetary to power two output pinions for a total of four output pinions.
Simply summarizing the arrangement; there is one input source of power which happens to be a bevel gear in this case. There is a power and speed division at the herringbone shaft centerline “C” to provide two paths of power flow. There is an additional power division at each identical planetary at centerlines “E” and “D” to power two output pinions. This allows the one input source of power to be divided into four sources of power, which are the four output pinions that drive the single output gear. This method obtains the power multiplication that is desired.
May 1993