Abstract: A centrifugal fan is formed from an impeller installed within a casing. The impeller is formed from two plates that are interconnected by a plurality of blades. A duct extends through each blade. At each of its ends, the duct opens at one of the plates. Air enters the fan from through a central opening formed in one of the plates, moves to a medial zone between the plates, and exits the fan at the medial zone's unwalled periphery. Air also crosses the fan by way of the ducts formed within each blade.

Abstract: A centrifugal fan is formed from an impeller installed within a casing. The impeller is formed from two plates that are interconnected by a plurality of blades. A duct extends through each blade. At each of its ends, the duct opens at one of the plates. Air enters the fan from through a central opening formed in one of the plates, moves to a medial zone between the plates, and exits the fan at the medial zone's unwalled periphery. Air also crosses the fan by way of the ducts formed within each blade.

Abstract: A centrifugal fan is formed from an impeller installed within a casing. The impeller is formed from two plates that are interconnected by a plurality of blades. A duct extends through each blade. At each of its ends, the duct opens at one of the plates. Air enters the fan from through a central opening formed in one of the plates, moves to a medial zone between the plates, and exits the fan at the medial zone's unwalled periphery. Air also crosses the fan by way of the ducts formed within each blade.

Abstract: A centrifugal fan is formed from an impeller installed within a casing. The impeller is formed from two plates that are interconnected by a plurality of blades. A duct extends through each blade. At each of its ends, the duct opens at one of the plates. Air enters the fan from through a central opening formed in one of the plates, moves to a medial zone between the plates, and exits the fan at the medial zone's unwalled periphery. Air also crosses the fan by way of the ducts formed within each blade.

Abstract: A centrifugal fan is formed from an impeller installed within a casing. The impeller is formed from two plates that are interconnected by a plurality of blades. A duct extends through each blade. At each of its ends, the duct opens at one of the plates. Air enters the fan from through a central opening formed in one of the plates, moves to a medial zone between the plates, and exits the fan at the medial zone's unwalled periphery. Air also crosses the fan by way of the ducts formed within each blade.

Abstract: A beadlock to secure a tire to a wheel. The beadlock comprises a first grip element and a second grip element. The first grip element is welded to the outer rim of a wheel. A bead of the tire is positioned over the first grip element. The second grip element has a plurality of rib elements angularly spaced around its periphery. The second grip element is secured to the first grip element such that the ribs grip the bead to hold it in place and secure the tire to the wheel.

Abstract: A centrifugal fan is formed from an impeller installed within a casing. The impeller is formed from two plates that are interconnected by a plurality of blades. A duct extends through each blade. At each of its ends, the duct opens at one of the plates. Air enters the fan from through a central opening formed in one of the plates, moves to a medial zone between the plates, and exits the fan at the medial zone's unwalled periphery. Air also crosses the fan by way of the ducts formed within each blade.

Abstract: A beadlock to secure a tire to a wheel. The beadlock comprises a first grip element and a second grip element. The first grip element is welded to the outer rim of a wheel. A bead of the tire is positioned over the first grip element. The second grip element has a plurality of rib elements angularly spaced around its periphery. The second grip element is secured to the first grip element such that the ribs grip the bead to hold it in place and secure the tire to the wheel.

Abstract: A trencher boom sprocket having a hub body rotatable at an engagement point by the shaft, a plurality of teeth supported on the hub body, an excluder ring supported within the hub body on the first side, at least one O-ring provided between the hub body and the excluder ring and applying a spring-load to the excluder ring, a cap supported within the hub at the second side to substantially seal the second side of the hub, a bearing disposed between the shaft and the hub between the engagement point and the second side, and a spacer disposed between the bearing and the cap.

Abstract: An apparatus used to excavate trenches. In a preferred embodiment the trenching machine has a cutting disc supported on a frame and adapted to operate with the center point of the cutting disc below ground. A spoils handler supported above the cutting disc and forward of the center point is used to move spoils away from the cutting disc. The ratio of cutting depth to weight of the trenching assembly and the cutting depth to wheel diameter is improved through the use of a cutting disc that is concave. The outer rim of the concave disc may support a plurality of replaceable cutting member. The cutting disc is rotated using a drive assembly that is contained within the cutting width of the cutting disc.