United States Patent 5,760,485: Scope, Claim Architecture, and Patent Landscape
United States Patent 5,760,485 claims a vehicle starter architecture that couples an electric starter motor to an engine ring gear through a planetary reduction gear mechanism built into a single-unit reduction gear. The core claim tightens scope around (i) a 6:1 to 10:1 speed reduction range, (ii) a specific planetary geometry (sun gear on the armature shaft end; planetary gear on the drive shaft end; internal gear forming a stationary side), and (iii) transmission direction defined as planetary rotation carrying torque between armature shaft and drive shaft. Dependent claims add electrical commutation coil structure, brush insulation and placement, and motor cooling using a fan or groove-induced airflow. Additional dependent claims push into parameterized gear ratios using teeth-count math and physical diameter constraints for packaging minimization.
What is the claimed invention, in scope terms?
Independent claim 1 (starter with planetary reduction gear)
Claim 1 defines a starter comprising:
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Starter motor
- Armature core with an armature coil wound thereon
- Armature shaft rotatably holding the armature core
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Kinematic link to engine ring gear
- Drive shaft with a pinion meshing with the ring gear of an engine
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Reduction gear mechanism between drive shaft and armature shaft
- Reduction gear mechanism is interposed to reduce relative rotation and transmit reduced rotation to the drive shaft
- Speed reduction ratio: 6:1 to 10:1
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Reduction gear is planetary; single-unit type; stationary side defined
- Planetary reduction gear mechanism including:
- Sun gear formed at one end of the armature shaft
- Planetary gear mounted on one end of the drive shaft and meshing with the sun gear
- Internal gear meshing with the planetary gear to form a stationary side
- The reduction gear is single unit type
- The planetary gear transmits rotation of the armature shaft to the drive shaft
Claim 1 is the primary scope anchor: it is a structural combination claim for a starter system with a planetary reduction gear located between motor armature and drive pinion, with a narrow ratio band and a defined tooth-kinematic topology.
What do the dependent claims add to scope and enforceability?
Claim 2 (armature coil conductor layout)
Claim 2 narrows the starter of claim 1 by specifying an armature coil structure:
- Armature coil includes upper-layer and lower-layer coil members fitted in slots of the armature core
- First connection portions
- connected to one end of the lower-layer coil member
- extend generally in parallel with an axial end face of the armature core and in the shaft direction
- Second connection portions
- connected to one end of the upper-layer coil member and the other end of the first connection portions
- extend generally in parallel with the first connection portions
This creates a specific winding lead routing and end-turn connection geometry tied to slot layers.
Claim 3 (insulators and brush arrangement)
Claim 3 further requires:
- Insulators between:
- first connection portions and the armature core
- first connection portions and second connection portions
- Brushes arranged slidably on the second connection portions
This ties electrical isolation and brush contact positioning to the coil lead geometry.
Claim 4 (cooling fan for brush sliding faces)
Claim 4 adds:
- A cooling fan that cools sliding faces of the starter motor with the brushes
Claim 5 (grooves producing cooling wind)
Claim 5 adds a more specific cooling approach:
- Grooves formed between the second connection portions
- Grooves protrude relative to rotating direction of the armature shaft
- The grooves act as the cooling fan to produce cooling wind when the armature coil rotates
This is a specific mechanical airflow generator linked to conductor lead orientation and rotor motion.
Claim 6 (limit means for power supply within time)
Claim 6 adds:
- Limit means that limits power supply to the starter motor within a predetermined time period
This is a functional timing limitation, but still claimable as a component “means” requirement.
How tight is the gear ratio scope?
Claim 7 (specific ratio)
Claim 7 specifies the reduction gear ratio:
This narrows to a target ratio within the claim 1 band (6:1 to 10:1).
Claim 8 (volume minimization parameter)
Claim 8 introduces a packaging-driven optimization:
- Total volume VT = V1 + V2
- V1 = volume of starter motor
- V2 = volume of planetary gear mechanism
- VT is substantially at a minimum
This claim is a structural selection constraint tied to design optimization.
Claims 9 and 10 (tooth-count ratio formula)
Claim 9 sets ratio computation:
- I = Zi / Zs + 1
- Zi = number of teeth of the internal gear
- Zs = number of teeth of the sun gear
- I = reduction ratio
Claim 10 fixes numerical values:
So:
- I = 58/8 + 1 = 7.25 + 1 = 8.25, which matches claim 7’s about 8.25:1.
Claim 11 (diameter constraints for packaging)
Claim 11 fixes specific external diameters:
- Motor external diameter: 68 mm
- Internal gear external diameter: 58 mm
This is a further physical constraint consistent with the volume-minimization approach in claim 8.
What is the enforceable “center of gravity” for infringement risk?
For business and R&D screening, the highest leverage limitations are in claim 1:
- Planetary reduction gear mechanism with:
- sun gear at armature shaft end
- planetary gear at drive shaft end
- internal gear as stationary side
- Single-unit planetary gear
- Speed reduction ratio 6:1 to 10:1
- Drive train definition: pinion on drive shaft meshing ring gear
Dependent claims add secondary constraints that may or may not be present in a target product:
- Coil lead arrangement and insulation/brush contact structure
- Cooling fan and groove-driven airflow
- Timing limit on power supply
- Specific ratio embodiments (8.25:1) and tooth counts (Zi=58, Zs=8)
- Motor and internal gear outside diameters (68 mm and 58 mm)
Practically, a competing starter that uses a planetary reduction gear but with a materially different ratio band, topology (e.g., different stationary element), or gearbox architecture may avoid the core claim even if it shares general “starter with reduction.” Conversely, a product built around an 8.25:1 planetary with the specific tooth-count relationship and stationary internal gear configuration is at the intersection of claims 1, 7, 9, and 10.
Where does this claim sit in the broader patent landscape for starter reduction gears?
This patent is directed to a starter with a planetary reduction gear and defined ratio/packaging constraints. In the landscape, the major axes of differentiation typically include:
- Gear topology
- Planetary vs epicyclic vs spur reduction
- Location of sun/planet/ring and which element is stationary
- Ratio band and target ratio
- Ranges such as 6:1 to 10:1 versus other ratios used for engine cranking torque and motor speed selection
- Integration style
- Single-unit gearbox packaging versus multi-stage modular units
- Electrical commutation and thermal management
- Coil winding geometry and brush cooling mechanisms
- Control features
- Time-limited energization and protective cutoff behavior
Claim 1 ties together the first three axes through an integrated planetary topology and ratio band. Claims 2 to 6 then add commutation and cooling details and a timing cutoff.
Claim chart style mapping (to support landscape scoring)
Core mandatory elements to screen in products
| Element |
Where in claims |
Practical screen |
| Starter motor with armature core and armature coil |
Claim 1 |
Exists in essentially all electric starters |
| Drive shaft pinion meshes ring gear |
Claim 1 |
Standard starter mechanical link |
| Reduction gear interposed between drive shaft and armature shaft |
Claim 1 |
Must be integrated into drivetrain |
| Planetary reduction gear with sun on armature shaft |
Claim 1 |
Packaging and shaft arrangement |
| Planetary gear mounted on drive shaft |
Claim 1 |
Planet carrier/planet location |
| Internal gear defines stationary side |
Claim 1 |
Which gear is fixed in housing |
| Single-unit planetary reduction gear |
Claim 1 |
Packaging architecture |
| Reduction ratio 6:1 to 10:1 |
Claim 1 |
Must fall within band |
| Planetary gear transmits rotation armature to drive |
Claim 1 |
Direction/kinematic relationship |
Secondary elements that narrow to specific embodiments
| Element |
Where in claims |
Risk signal |
| Ratio about 8.25:1 |
Claim 7 |
Near-unique target |
| Total volume VT minimized by V1 + V2 |
Claim 8 |
Requires design intent/packaging matching |
| Ratio formula I = Zi/Zs + 1 |
Claim 9 |
Validates specific internal/sun tooth pairing |
| Zi=58 and Zs=8 |
Claim 10 |
Highly specific |
| External diameter motor 68 mm |
Claim 11 |
Specific packaging dimension |
| External diameter internal gear 58 mm |
Claim 11 |
Specific packaging dimension |
| Two-layer coil members in slots + specific connection portions |
Claim 2 |
Mechanical winding lead layout |
| Insulators and brush sliding on second connection portions |
Claim 3 |
Brush/lead geometry |
| Cooling fan for brush sliding faces |
Claim 4 |
Thermal structure |
| Grooves between second connection portions generate cooling wind |
Claim 5 |
Distinct airflow mechanism |
| Limit means for power supply within time period |
Claim 6 |
Control/protection strategy |
Business and R&D implications
High-confidence claim hit conditions
A starter is likely to fall within claim 1 and related dependent claims if it uses:
- A single-unit planetary reduction integrated between armature shaft and pinion drive shaft
- A ratio in the 6:1 to 10:1 band
- A topology where:
- sun gear is on the armature shaft end
- planetary gear is on the drive shaft end
- internal gear is stationary
- And especially if it targets:
- 8.25:1, with internal gear teeth 58 and sun gear teeth 8
- matching external diameter packaging (68 mm motor OD; 58 mm internal gear OD)
Claim 1 avoidance levers
Design changes that commonly move outside claim 1’s tight structural and ratio band include:
- A planetary system where the stationary side is not the internal gear as defined
- A topology where the sun gear is not formed at the armature shaft end or the planetary is not mounted on the drive shaft end
- A ratio outside the 6:1 to 10:1 band
- A gearbox that is not a single unit type as required by claim language
Dependent claim targeting
If a competitor copies the drivetrain topology and ratio but not coil lead/brush cooling geometry, that may still avoid claims 2 to 6. If they also match the cooling grooves or specific insulation and brush placement, they move into higher claim coverage.
Key Takeaways
- Claim 1 is a tight starter drivetrain claim focused on a single-unit planetary reduction gear with sun gear on the armature shaft, planetary gear on the drive shaft, and an internal gear that is stationary, with a 6:1 to 10:1 ratio.
- Claims 7, 9, and 10 converge on a specific embodiment: about 8.25:1, derived from Zi=58 teeth and Zs=8 teeth using I = Zi/Zs + 1.
- Claims 11 locks packaging geometry: 68 mm motor OD and 58 mm internal gear OD, supporting the VT minimization constraint in claim 8.
- Claims 2 to 6 expand coverage into winding lead geometry, insulation, brush sliding arrangement, and brush cooling via fan or groove-driven airflow, plus time-limited power supply.
FAQs
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Which claim most directly defines the mechanical drivetrain?
Claim 1, through its planetary topology, stationary internal gear definition, single-unit requirement, and 6:1 to 10:1 ratio band.
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Does the patent cover only a single gear ratio?
No. Claim 1 covers 6:1 to 10:1; dependent claims add specific embodiments including about 8.25:1.
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What makes the 8.25:1 embodiment unusually specific?
Claims 7, 9, and 10 tie the ratio to a tooth-count relationship with fixed values Zi=58 and Zs=8.
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Are coil winding and brush cooling required for infringement of claim 1?
No. Winding and brush cooling limitations appear in dependent claims (2 to 5). Claim 1 does not require those features.
-
What is the most likely “design-around” approach?
Change the planetary configuration such that the stationary element and gear mounting relationships do not match claim 1’s defined topology, or select a reduction ratio outside 6:1 to 10:1, or both.
References
[1] U.S. Patent No. 5,760,485.
