Patent Application
20120071083
Not applicable.
The present invention relates to a damper for controlling the flow of fluid in a duct and, more specifically, to an apparatus for controlling the position of the blade of a damper.
A damper is a valve or plate that stops or regulates the flow of fluid inside a duct, chimney, air handler, or other fluid handling equipment. The fluid is commonly a gas, such as air, but may be a liquid or vapor and the duct may be under positive or negative pressure. Referring to
The frame 22 typically comprises a length of duct similar in cross-section to the ducting 28 in which the damper is to be installed. The frame 22 may be round or rectangular and may have one or two flanges 30 for connecting the damper to the contiguous sections of ducting 28. On the other hand, particularly in lower pressure systems, the cross-section of one end of the frame may be expanded and the cross-section of other end of the frame may be reduced to enable the ends of the frame to, respectively, slip over and into the ends of the contiguous sections of ductwork.
The substantially planar blade 24 of the damper is rotatable to a position normal to the flow of fluid, substantially blocking flow of fluid in the duct. Dampers may include seals that engage the blade when it is oriented normal to the fluid flow to minimize the flow of fluid between the periphery of the blade and the interior surface 32 of the frame. When the blade is rotated to an orientation substantially parallel to the flow of fluid, the planar blade produces a minimal pressure drop and the flow through the damper is substantially unrestricted. Blade orientations between the two extreme orientations produce pressure drops of varying magnitude and restrict flow to varying degrees.
The position of the blades(s) of a damper may be mechanically or manually controlled. Electric motors, hydraulic cylinders and pneumatic cylinders are commonly used to position the blades of dampers, particularly in automated systems. However, many dampers are used in applications where the damper is only rarely adjusted after the initial balancing of the system's flows. In these applications, mechanical operation of the damper may not be economically justifiable and dampers are commonly equipped for manual operation. A manually operated butterfly damper typically includes a handle 34 affixed to the axle that rotatably supports the blade 24. By moving the handle a user can rotate the blade to adjust the fluid flow through the damper. While manual adjustment of the damper is typically less expensive than mechanical actuation, dampers are often located in areas with limited or difficult manual access to the damper's handle.
Typically, a damper is adjusted to balance the flows in the ductwork or to limit the flow in a particular duct. Once the adjustment is completed, the position of the damper's blade is secured against further movement. Manual adjustment handles commonly utilize a friction lock, such as a screw 36 and wing nut 38 that can be tightened to increase the friction between the handle 34 and the handle's mounting 40 on the frame. Friction locks provide infinite adjustment of the blade's position but the position of the blade can be altered if the handle is bumped by a person or equipment. Referring to
Maintaining control of the damper's blade during adjustment is also important, particularly in industrial applications. Typically, a damper is adjusted while fluid is flowing in the ductwork. When either a friction lock or a sector lock of a manually operated damper is released, the user must maintain a grip on the handle to prevent movement of the blade often while trying to measure the pressure drop across the damper. If the user releases or inadvertently moves the handle, the flow of fluid in the damper and in other parts of the system can change significantly. A change in the flow rate in the ductwork can disrupt manufacturing processes, damage products and, in some cases, present a safety hazard.
What is desired, therefore, is an apparatus for controlling the position of the blade of a damper which is economical to manufacture, suitable for retrofitting an existing damper or for use with a new damper, enables manual adjustment in areas with limited access, provides fine levels of adjustment, secures the blade in the adjusted position and prevents uncontrolled movement of the blade during adjustment.
A damper is a valve enabling regulation of the flow of fluid inside a duct, chimney, air handler, or other fluid handling equipment. The fluid is commonly a gas, such as air, but may be a liquid or vapor. Referring in detail to the drawings where similar parts are identified by like reference numerals, and, more particularly to
The exemplary damper 60 is a butterfly valve or damper and includes a rotatable blade 24 supported by an axle 26 which is journaled for rotation in the wall on opposing sides of the frame. The axle may be supported in the frame by bearings or bushings (not shown) and the frame may be equipped with seals (not shown) to prevent leakage where the axle passes through the wall of the frame. To control the flow of fluid in the duct, the blade can be rotated between a position where the plane of the blade is normal to the flow of fluid and a position where the plane of the blade parallel to the fluid flow. When the blade is oriented normal to the fluid flow, the flow of fluid is blocked or, at least, restricted to leakage between the periphery of the blade and the internal surface(s) 32 of the frame. Some dampers also include seals on the inner surface 32 of the frame to seal any gap between the periphery of the blade and the periphery of the frame's aperture. When the blade is oriented parallel to the flow of fluid, the planar blade produces a minimal pressure drop and the flow through the damper is maximized. Blade orientations between the two extreme orientations produce varying magnitudes of pressure drop and flow restriction.
Referring also to
The lead screw is rotatably journaled in a second anchor 70 proximate the second end of the lead screw. The second anchor is pivotally attached 72 to a mounting plate 74 which is, in turn, secured to the exterior of the frame 22 by screws 76. The lead screw is rotatable in the anchor but is restrained against translation by one or more snap rings 71, collars and/or shoulders bearing on the anchor. As illustrated in
Referring also to
Dampers are commonly located in areas where there is limited access making engagement with a tool difficult. The tapered portion 84 of the head is preferably frustoconical and aids in guiding the tool into engagement with the non-circular portion of the head.
The damper positioner includes a lead screw lock 90 that shields the head 82 of the screw from inadvertent contact and locks the screw against unintentional rotation. The lead screw lock comprises a body 92, 106 including portions defining a socket 94, 108. The socket has a cross-section complementary to the cross-section of the non-circular portion of the head and a depth enabling engagement of the socket with a first length 95A of the non-circular portion 84 of the head of the lead screw. Engagement of the facets 85 or lobes 105 of the lead screw head by the surfaces of the complementarily shaped socket in the body prevents independent rotation of the lead screw and the body 92, 102 of the screw lock.
Preferably, a second length 95B of the non-circular portion of the head protrudes beyond the body 92 enabling a tool to engage the non-circular portion of the head while the body is engaged with head.
A spring 96 or other resilient member urges the body 92 which is slidable on the lead screw toward the head end of the screw, urging engagement of the socket with the non-circular portion of the head of the lead screw. Interaction of the complementary shapes of the non-circular portion of the screw's head and the socket prevents the screw from rotating independent of the socket. When a user wishes to rotate the lead screw, the body 92 of the screw lock is displaced toward the anchor, for example by the tool engaging the head of the screw, until the non-circular portion of the head is disengaged from the socket in the body of the screw lock enabling rotation of the head of the screw and adjustment of the damper's blade.
The body 92 of the screw lock 90 is prevented from rotating relative to the anchor and, therefore, the frame of the damper. Referring to
The detailed description, above, sets forth numerous specific details to provide a thorough understanding of the present invention. However, those skilled in the art will appreciate that the present invention may be practiced without these specific details. In other instances, well known methods, procedures, components, and circuitry have not been described in detail to avoid obscuring the present invention.
All the references cited herein are incorporated by reference.
The terms and expressions that have been employed in the foregoing specification are used as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding equivalents of the features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only by the claims that follow.
