Lifting device including telescoping mast

Abstract

A lifting device for elevating a load includes a telescoping mast having an inner mast section telescopically received within an outer mast section and configured to extend in an upward direction and retract in a downward direction relative to the outer mast section. An emergency brake is secured to the inner mast section and includes first and second eccentrics configured to rotate relative to the inner mast section between an unlocked position, in which the first and second eccentrics are free from locking engagement with the outer mast section to allow retraction of the inner mast section, and a locked position, in which the first and second eccentrics are in locking engagement with the outer mast section to inhibit retraction of the inner mast section. A base of the lifting device may include a holder having a tapering interior for receiving the telescoping mast.

What is claimed is: 
     
         1 . A lifting device for elevating a load, the lifting device comprising:
 a telescoping mast having opposite upper and lower ends, the telescoping mast including an outer mast section and an inner mast section telescopically received within the outer mast section and configured to extend in an upward direction and retract in a downward direction relative to the outer mast section; and   an emergency brake secured to the inner mast section, the emergency brake including first and second eccentrics configured to rotate relative to the inner mast section between an unlocked position, in which the first and second eccentrics are free from locking engagement with the outer mast section to allow retraction of the inner mast section within the outer mast section, and a locked position, in which the first and second eccentrics are in locking engagement with the outer mast section to inhibit retraction of the inner mast section within the outer mast section.   
     
     
         2 . The lifting device of  claim 1 , wherein the first and second eccentrics are configured to rotate to the locked position when the inner mast section accelerates relative to the outer mast section in the downward direction at a magnitude that is greater than a threshold magnitude. 
     
     
         3 . The lifting device of  claim 2 , wherein the eccentrics are configured to be free from engagement with the outer mast section to allow retraction of the telescoping mast when the when the inner mast section accelerates relative to the outer mast section in the downward direction at a magnitude that is less than a threshold magnitude. 
     
     
         4 . The lifting device of  claim 1 , wherein the emergency brake further includes a shaft attached to the inner mast section, the first and second eccentrics rotatably mounted on the shaft. 
     
     
         5 . The lifting device of  claim 4 , wherein the emergency shaft is attached inside the inner mast section. 
     
     
         6 . The lifting device of  claim 5 , wherein the inner mast section defines first and second openings, wherein the first eccentric is configured to extend through the first opening in the locked position, and the second eccentric is configured to extend through the second opening in the locked position. 
     
     
         7 . The lifting device of  claim 1 , wherein the emergency brake further includes a spring applying a spring force to the first and second eccentrics when the first and second eccentrics are in the unlocked position to facilitate rotation of the first and second eccentrics toward the locked position. 
     
     
         8 . The lifting device of  claim 7 , wherein the first and second eccentrics compress the spring when the first and second eccentrics are at rest relative to the inner mast section and in the unlocked position. 
     
     
         9 . The lifting device of  claim 8 , wherein the emergency brake further comprises a mechanical linkage interconnecting the first and second eccentrics, the linkage facilitating compression of the spring by the first and second eccentrics. 
     
     
         10 . The lifting device of  claim 1 , wherein the first and second eccentrics are configured to rotate in opposite directions from the unlocked position to the locked position. 
     
     
         11 . The lift of  claim 1 , wherein each of the first and second eccentrics includes a friction-enhancing structure configured to engage the outer mast section in the locked position. 
     
     
         12 . The lifting device of  claim 1 , wherein the telescoping mast further comprises:
 a second inner mast section telescopically received within the inner mast section and configured to extend in an upward direction and retract in a downward direction relative to the inner mast section; and   a second emergency brake secured to the second inner mast section, the second emergency brake including first and second eccentrics configured to rotate relative to the second inner mast section between an unlocked position, in which the first and second eccentrics of the second emergency brake are free from locking engagement with the inner mast section to allow retraction of the second inner mast section within the inner mast section, and a locked position, in which the first and second eccentrics of the second emergency brake are in locking engagement with the inner mast section to inhibit retraction of the second inner mast section within the inner mast section.   
     
     
         13 . The lifting device of  claim 11 , wherein the inner mast section includes a stop positioned above the brake and configured to engage a lower end of the second inner mast section to inhibit the second inner mast section from contacting the emergency brake. 
     
     
         14 . The lifting device of  claim 1 , further comprising a prime mover operatively connected to the inner mast section and configured to extend the inner mast section in an upward direction and retract the inner mast section in a downward direction, wherein the emergency brake operates independent of the prime mover. 
     
     
         15 . The lifting device of  claim 1 , further comprising a base configured to support the telescoping mast in an upright position. 
     
     
         16 . The lifting device of  claim 16 , wherein the base includes a mast holder sized and shaped to receive a lower end of the telescoping mast therein, the mast holder defining an opening at an upper end thereof and through which the lower end of the telescoping mast enters the mast holder, wherein the mast holder includes opposing interior holder surfaces configured to engage the lower end of the telescoping mast when the telescoping mast is received in the mast holder, the opposing interior holder surfaces defining a transverse distance therebetween that tapers in a downward direction away from the opening. 
     
     
         17 . The lifting device of  claim 1 , further comprising a head piece secured to the telescoping mast and configured to support the load thereon. 
     
     
         18 . A lifting device for elevating a load, the lifting device comprising:
 a telescoping mast configured to extend and retract in a heightwise direction, the telescoping mast having opposite upper and lower ends;   a head piece secured to the telescoping mast at the upper end thereof and configured to support the load thereon; and   a base configured to support the telescoping mast in an upright position, the base including a mast holder sized and shaped to receive a lower end of the telescoping mast therein, the mast holder defining an opening at an upper end thereof and through which the lower end of the telescoping mast enters the mast holder, wherein the mast holder includes opposing interior mast holder surfaces configured to engage the lower end of the telescoping mast when the telescoping mast is received in the mast holder, the opposing interior holder surfaces defining a transverse distance therebetween that tapers in a downward direction away from the opening.   
     
     
         19 . The lifting device of  claim 18 , wherein the mast holder further includes second opposing interior holder surfaces configured to engage the lower end of the telescoping mast when the telescoping mast is received in the mast holder, the second opposing interior holder surfaces defining a transverse distance therebetween that tapers in the downward direction away from the opening. 
     
     
         20 . The lifting device of  claim 18 , wherein the telescoping mast is removably receivable in the mast holder.