Overload protection apparatus for hoisting machine

• US 4,103,873 A
• Filed: 03/18/1977
• Issued: 08/01/1978
• Est. Priority Date: 04/02/1976
• Status: Expired due to Term

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Sato, Isao, Furuichi, Mitsuyuki, Gomi, Shigenori
• Primary Examiner(s): Hoffman, Drayton E.
• Assistant Examiner(s): Underwood, Donald W.
• Application Number:
  US05/778,934
• Time in Patent Office: 501 Days
• Field of Search: 192/150, 188/181 T, 254/168, 254/167, 254/173 R, 254/174, 254/187.1, 254/187.3, 254/187.4, 254/187.8
• US Class Current: 254/275
• CPC Class Codes: B66D 1/58 responsive to excess of load

Abstract

The disclosure relates to an overload protection apparatus for hoisting machines such as rope hoists or chain blocks. One gear incorporated in the reduction gear train of the hoisting machine is composed of an outer and an inner gear units between which torque is transmitted through resilient means acting therebetween. The resilient means are adapted to be compressed, upon receipt of an excessively large torque, i.e. in case of an overload, to allow a relative movement in the direction of rotation between the outer and the inner gear units. The relative movements of the gear units in the direction of rotation is then converted into a movement in the direction of thrust. Detecting switch is provided for opening an electric circuit for lifting, upon detecting the movement in the direction of thrust, thereby to stop the lifting operation.

Claims

1. In an overload protection apparatus for hoisting machines having a driving section including an electric motor, an output, and a reduction section interconnecting said driving section and said output, with said reduction section having parallelly disposed input and output shafts, the improvement comprising:

a gear drivingly mounted and connected between said input and output shafts, said gear including an outer gear unit having peripheral gear for engagement with a pinion and an inner gear unit constituted by first and second gear support means facing to each other and housed by said outer gear unit, said first and second gear supporting means have respective projecting members, said first and second gear supporting means abutting each other at their projecting members to provide a power transmission path to raise the load, spring means disposed between said first and second gear support means and in contact with said outer gear unit, said spring means being adapted to allow a relative movement of said inner and outer gear units when the load torque actually applied exceeds a predetermined torque in the direction of rotation applied to raise the load, means for converting the relative movement in the direction of rotation into a movement in the direction of thrust, and means for detecting the movement caused by said converting means and wherein said means for detecting the movement of said converting means effects a stopping of the lifting operation upon the movement of said converting means in the direction of thrust.

2. An improvement as claimed in claim 1, wherein said spring means are constituted by compression springs.

3. An improvement as claimed in claim 1, wherein said projecting member of said first gear supporting means has projections and the inner peripheral surface of said outer gear unit has projections, said spring means being disposed to act between said projections on said first gear support means and said projections formed on the inner peripheral surface of said outer gear unit.

4. An improvement as claimed in claim 3, wherein said means for converting the relative movement in the direction of rotation into a movement in the direction of thrust includes an interacting member which is mounted between the first and the second gear support means on said projecting member of said second gear support unit.

5. An improvement as claimed in claim 4, wherein said means for converting the relative movement in the direction of rotation into a movement in the direction of thrust further includes spherical balls which are retained between corresponding openings formed in said second gear support means and said interacting member, said improvement further including a provision of a striker member adapted to resiliently press said second gear support means, said strike member being further adapted to allow the movement of said balls through said openings of said second gear support means, said balls are retained between said interacting member and said striker member.

6. An improvement as claimed in claim 5, wherein said striker member is pressed against said second gear support means by means of a spring.