Energy-absorbing and force-limiting friction coupling

Abstract

A device having kinetic energy-absorbing properties is connectable between selected points within a structure, for example a building within a seismic area. When one connectable part moves against another during an earthquake, friction is ensured by tension implanted internally at the time of manufacture, when one part of the device had been yieldingly forced into place in relation to another part. When in use the device provides a damping force should a force applied b etween its parts be greater than or equal to a predetermined force at which sliding friction begins.

1 - 15 . (canceled) 
   
   
       16 . An energy-absorbing and force-limiting friction coupling device for reducing damage arising from movements induced within artificial structures including buildings by, events such as earthquakes, characterized in that the device includes a first member extending outwards from the device and terminating with a first attachment means at a first end for fastening to a first structural element, and a second member extending outwards from the device and terminating with a second attachment means at a second end for fastening to a second structural element; the first and second members being held in contact at an intermediate frictional region occupied by a slidable portion of the first member and by a slidable portion of the second member by a force forcing the first and second members into factional contact; the force originating within a clamping member exhibiting elastic (Hookean) and ductile (plastic) properties capable of holding the slidable portions in tight contact after having been plastically deformed during manufacture by a process of forcing together the slidable portion of the first member and the slidable portion of the second member despite misfitting dimensions; the clamping member being capable of continuing to apply a substantial portion of the force across the factional region between the friction-capable portion of the first member and the friction-capable portion of the second member for an extended period; so that, when in use, a force having more than a predictable magnitude applied between the first and the second attachment means will cause frictional, sliding movement over a distance and conversion of kinetic energy into heat within the device at the frictional region. 
   
   
       17 . An energy-absorbing and force-limiting friction coupling device as claimed in  claim 16 , characterized in that the friction-capable-portion of the first member and the friction-capable portion of tine second member are forced into contact with each other by a manufacturing process causing elastic and then plastic distortion of one member so that after the force of the manufacturing process has ceased, the respective members remain strongly forced together by substantially all of the force that had been required to cause elastic distortion so mat, when in use, a force having at least a predictable magnitude applied between the first and the second attachment means will cause frictional, sliding movement over a distance and conversion of kinetic energy into heat within the device at the frictional region. 
   
   
       18 . An energy-absorbing and force-limiting friction coupling device as claimed in  claim 17 , characterized in that the frictional region includes a friction-enhancing material attached to one member and capable of sliding along a portion of the other member. 
   
   
       19 . An energy-absorbing and force-limiting friction coupling device as claimed in  claim 18 , characterized in that the friction-enhancing material attached to one member is in the form of a hollow cylinder and exists in a state of radial tension while forcibly stretched around and and in frictional contact with a parallel-sided shaft forming the friction-capable portion of the other member,. 
   
   
       20 . An energy-absorbing and force-limiting friction coupling device as claimed in  claim 18 , characterized in that the friction-enhancing material attached to one member is forcibly enclosed within and exists in a state of radial compression and in frictional contact with the other member; the friction-capable portion of the other member comprising an elongated parallel-sided cavity enclosing the friction-enhancing material. 
   
   
       21 . An energy-absorbing and force-limiting friction coupling device as claimed in  claim 19 , characterized in that the friction-enhancing material is the same component as the clamping means. 
   
   
       22 . An energy-absorbing and force-limiting friction coupling device as claimed in  claim 20 , characterized in that the friction-enhancing material is the same component as the clamping means. 
   
   
       23 . An energy-absorbing and force-limiting friction coupling device as claimed in  claim 19 , characterized in that the frictional region includes apposed frictional surfaces each comprised of a metal. 
   
   
       24 . An energy-absorbing and force-limiting friction coupling device as claimed in  claim 20 , characterized in that the frictional region includes apposed frictional surfaces each comprised of a metal. 
   
   
       25 . An energy-absorbing and force-limiting friction coupling device as claimed in  claim 23 , characterized in that a first frictional surface is comprised of a metal selected from the range including copper and alloys of copper. 
   
   
       26 . An energy-absorbing and force-limiting friction coupling device as claimed in  claim 23 , characterized in that a second frictional surface is comprised of a steel. 
   
   
       27 . An energy-absorbing and force-limiting friction coupling device as claimed in  claim 23 , characterized in that a lubricant, selected from a range including graphite and plated lead, is included at the time of manufacture. 
   
   
       28 . A method of making an energy-absorbing and force-Limiting friction coupling device as claimed in  claim 16 , characterized in that the residual tensile force is implanted within at least the elastic portion of the clamping means of the device during a process of assembly;
 during which process a selected shaft comprising the friction-capable part of the first member is forced past the friction-capable part of the second member through an under sized space or aperture; the shaft dimension being selected so that a force applied to the clamping means during the assembly process is sufficient to exceed the yield strength of the clamping means such that at least a portion of the clamping means of the device is caused to enter the ductile range, so that a maximised tensile force present within the clamping means shall be consistently applied to the frictional area over time,   
   
   
       29 . A method of making an energy-absorbing and force-Limiting friction coupling device as claimed in  claim 27 , characterized in that the amount of force applied to the clamping means during manufacture is recorded as a descriptive property applicable to that device during use. 
   
   
       30 . A method of making an energy-absorbing and force-Limiting friction coupling device adapted mainly for linear motion as claimed in  claim 28 , characterized in that the method includes at least one step that pre-selects parts having specified force characteristics and comprises the steps of:
 (a) applying the following formula when selecting parts to be assembled:
   Sliding Force ( N )=2·μ ·L·π·t·F   y   
   where: L=the length in mm of the friction-enhancing material (assumed to be an annulus); P 1  μ=the coefficient of friction of the friction-enhancing material against the friction-capable portion of the other member;   t=the thickness of the annulus (mm);   F y =the yield stress of the annulus (in MPa).   r f =the radius of the friction surface of the annulus (mm)   (b) placing the parts so selected within a press, and   (c) forcing the parts together.   
   
   
       31 . A method of making an energy-absorbing and force-Limiting friction coupling device adapted mainly for linear motion as claimed in  claim 29 , characterized in that the method includes at least one step that pre-selects parts having specified force characteristics and comprises the steps of:
 (a) applying the following formula when selecting parts to be assembled:
   Sliding Force ( N )=2·μ· L·π·t·F   y   
   where: L=the length in mm of the friction-enhancing material (assumed to be an annulus);   μ=the coefficient of friction of the friction-enhancing material against the friction- capable portion of the other member;   t=the thickness of the annulus (mm);   F y =the yield stress of the annulus (in MPa).   r f =the radius of the friction surface of the annulus (mm)   (b) placing the parts so selected within a press, and   (c) forcing the parts together.   
   
   
       32 . A method of making an energy-absorbing and force-limiting friction coupling device as claimed in  claim 30  though adapted mainly for rotational motion, characterized in that the method includes pre-selection of parts having specified force characteristics and comprises the steps of:
 (a) applying the following formula when selecting parts to be assembled: having specified torque characteristics:
   Rotational Torque=2 ·πr   f    μ·L·t·F   y   
   where: L=the length of the friction-enhancing material (assumed to be in the shape of an annulus);   μ=the coefficient of friction of the friction-enhancing material against the friction- capable portion of the other member;   t=the thickness of the annulus;   F y =the yield stress of the annulus.   r f =the radius of the friction surface of the annulus.   (b) placing the parts so selected within a press, and   (c) forcing the parts together.   
   
   
       33 . An energy-absorbing and force-limiting friction coupling device manufactured according to  claim 32  and adapted mainly for rotational motion, characterised in that the coupling device is provided with one co-axial coupling means at each end of the device and that the coupling device will faithfully couple axial rotation from one end to the other unless the relative torque applied between one co-axial coupling means and the other exceeds a predetermined limit.