Family of electric drills and two-speed gear box therefor

A handheld electric tool, comprising:

• a housing including a motor compartment and a gear box compartment;
• an electric motor in said motor compartment and having a motor drive shaft extending into said gear box compartment;
• a two speed gear transmission in said gear box compartment connected to said motor shaft to be driven thereby;
• a tool holder connected to said gear transmission to be driven thereby;
• said gear transmission comprising a lay shaft carrying first, second, and third lay shaft gears, and an output shaft carrying first and second output gears;
• said third lay shaft gear being freely rotatable on said lay shaft and driven by said motor shaft;
• said second lay shaft gear being freely rotatable on said lay shaft, and said first lay shaft gear being secured to said lay shaft for rotation therewith;
• said first and second output gears being arranged for drivingly rotating said output shaft with said first lay shaft gear meshing with said first output gear and said second lay shaft gear meshing with said second output gear;
• a pair of dogs slidably mounted in holes through said third lay shaft gear, said dogs being disposed radially outwardly of said lay shaft;
• a first dog clutch member secured to said lay shaft for rotation thereof;
• a second dog clutch member secured to said second lay shaft gear for rotation thereof;
• a shift arm extending transversely to said lay shaft and having a ring portion encircling said lay shaft and engaging through slots in said dogs;
• said shift arm being mounted in said gear box compartment for manual displacement to a limited extent in a direction parallel to said lay shaft between two end positions;
• means for releasably latching said shift arm in either of said two end positions;
• displacement of said shift arm to one of said end positions moving said dogs to drivingly engage said first dog clutch member to cause driving rotation of said lay shaft and said first lay shaft gear therewith;
• displacement of said shift arm to the other of said end positions causing said dogs to disengage from said first dog clutch member and drivingly engage said second dog clutch member to cause driving rotation of said second lay shaft gear;
• and
• said shift arm being flexible and flexing if said dogs are not in register for engagement with and do not drivingly engage the respective dog clutch member when said shift arm is moved to a respective end position, the shift arm when so flexed urging said dogs to move into driving engagement with the respective dog clutch member when said dogs and the respective dog clutch member are in register for engagement.

A family of handheld electric tools, members of the family being adapted to perform different functions, wherein each member of the family has the following items identically in common:

• a motor compartment;
• an electric motor mounted in said motor compartment and having a forwardly extending armature shaft with a pinion at a forward end;
• a handle depending from said motor compartment and having means for supplying electric power to said motor;
• a mounting plate closing a forward end of said motor compartment, a forward bearing of said armature shaft being mounted in said mounting plate and said armature shaft extending forwardly through said mounting plate;
• a two speed gear train disposed forwardly of said mounting plate and having a lay shaft journalled in a bearing in said mounting plate;
• said mounting plate having a bearing support for an output shaft;
• a plurality of lay shaft gears on said lay shaft, one of these gears meshing with said pinion;
• a plurality of output gears meshing with at least some of said lay shaft gears;
• and
• means for changing the gear ratio of said gear train between low and high speed ratios, said changing means including a manually operable member and means for selectively placing different gears on said lay shaft in driving relationship between said lay shaft gear meshing with said pinion and said output gears;
• and further wherein:
• different family members have differently formed output shafts upon which said output gears are mounted, a rear end of each output shaft being journalled in a bearing mounted in said bearing support;
• said output shafts together with other parts directly associated therewith determine different functions performable by different members of the family;
• outside said gear box compartment all items of each member of the family are identical to the same items of the other members of the family;
• said two speed gear train of each family member comprises three lay shaft gears on said lay shaft, and two integrally connected output gears on said output shaft, all these gears being interchangeable between all family members;
• each of said family members has interchangeably the following parts in said gear box compartment;
• a pair of dogs slidably mounted in holes through one of said lay shaft gears which meshes with said pinion, said dogs being disposed radially outwardly of said lay shaft;
• a first dog clutch member secured to said lay shaft for rotation therewith;
• a second dog clutch member secured to another of said lay shaft gears for rotation therewith, said second dog clutch member and said another lay shaft gear being freely rotatable relative to said lay shaft;
• and wherein
• said gear ratio changing means in each of said family members identically comprises an eccentric on said manually operable member engaged in a base member slidably mounted on a pair of guide rods, a shift arm extending from said guide member transversely to said lay shaft, said shift arm having a ring which encircles said lay shaft and passes through slots in said dogs for shifting the position of said dogs, said shift arm being formed from sheet steel and being flexible;
• and wherein
• said means for supplying electric power to said motor comprises identically in each family member a trigger switch mounted in said handle and a rechargeable battery pack housed in said handle.