Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16H—GEARING
  • F16H25/00—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms
  • F16H25/18—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms for conveying or interconverting oscillating or reciprocating motions
  • F16H25/20—Screw mechanisms
  • F16H25/2003—Screw mechanisms with arrangements for taking up backlash
  • F16H25/2006—Screw mechanisms with arrangements for taking up backlash with more than one nut or with nuts consisting of more than one bearing part

Definitions

• the present invention relates to anti-backlash nuts generally and, more particularly, to a novel spiral compression anti-backlash nut.
• the ratcheting device nut has two nut halves on a screw locking into each other by compression. A ratcheting type mechanism integrated into the two parts prevent them from spinning free from each other. This device has axial stiffness but doesn't compensate for wear. Once the threads wear, the device has to be manually tightened to take up the wear.
• split anti-backlash device design There is a split anti-backlash device design.
• the device is notched in four equal sections perpendicular to the direction of the internal threads. These notches produce four lever arms with internal threads. The four lever arms are then threaded onto the screw and a compressive member is wrapped around them, closing the threads around the shaft. This will resolve any axial slop in the lead screw and lead screw nut. However, it doesn't have much axial stiffness.
• Another anti-backlash device design pushes two nuts apart while on a screw, with a force great enough to overcome any clearance between the two nuts.
• This force can be produced by any type of compressive object (rubber, springs, etc.)
• This device can compensate for wear because of the constant force being applied by the compressive object.
• This device has little axial stiffness in that any load greater than the spring force will cause backlash.
• This anti-backlash device has a torsional spring which turns a nut threaded to the outside of a first threaded acme nut. A second acme nut is captivated by the first acme nut. As the torsional spring winds up, the nut spins up the first acme nut and applies a force against the second acme nut.
• the coil spring allows the device to compensate for wear.
• Anti-backlash devices aren't self contained. They have working parts on the outside. This can allow for tampering (tightening/loosing preload and torque) which can affect the way the anti-backlash device performs.
• an apparatus comprising: a body; a right hand nut half fixedly disposed in said body; a left hand nut half disposed in said body and moveable toward said right hand nut half; a pusher pressing against a distal end of said left hand nut half; and said pusher causing said left hand nut half to move toward said right hand nut half.
• Figure 1 is a fragmentary is an isometric view showing how an anti-backlash nut eliminates axial play.
• Figure 2 is a side elevational view, in cross-section, showing in more detail the embodiment of Figure 1.
• Figure 3 is an exploded isometric view of one embodiment of the present invention.
• Figure 4 is an isometric view of a portion of the embodiment of Figure 3 in assembled relationship.
• Figure 5 is an isometric view of the ratcheting cap of the embodiment of Figure 3.
• Figure 6 is an exploded isometric view of a further embodiment of the present invention.
• Figure 7 is a side elevational view, in cross-section, of the embodiment of Figure 6 in assembled relationship.
• FIGS 1-5 illustrate the anti-backlash device of one embodiment of the present design, generally indicated by the reference numeral 40.
• FIGS. 1 and 2 those figures illustrate how first and second nut halves 10 and 12 screwed onto a lead screw 14 and having opposing forces may be used to take up any backlash that may exist.
• nut halves 10 and 12 are forced together by biasing means (not shown) such that nut half 10 contacts the left sides of the flanks of lead screw, as at 20 ( Figure 2), and nut half 12 contacts the right sides of the flanks of the lead screw, as at 22.
• biasing means not shown
• anti-backlash device 40 overcomes all of the defects of conventional anti-backlash devices.
• Anti-backlash device 40 is self contained in one complete unit. It is able to be screwed on and off of a lead screw without falling apart.
• Anti-backlash device 40 is adjusted once it is screwed onto the lead screw, is able to compensate for backlash for a particular range of force.
• First and second nut halves 52 and 54, respectively, will be pushed toward each other in a manner that will prevent them from naturally wanting to pop apart from each other.
• the housing 50 has a hexagonal shape (or any type of captivated feature such as a spline, etc.) on the inside, that the first and second nut halves 52 and 54, respectively, fit into.
• First nut 52 is fixed to housing 50.
• Second nut 54 is free to move in the axial direction toward first nut 52. There should be a distance of two thread lengths between first and second nuts 52 and 54 to compensate for wear on the thread face.
• first and second nut halves 52 and 54 separate from housing 50:
• First and second nut halves 52 and 54 are made from a form of high quality engineering plastic.
• Housing 50 can be made from a cheap structural plastic. This design utilizes using minimal amounts of expensive engineering plastic. Most other anti-backlash devices have the threads as part of the housing. Therefore, the whole housing would have to be made from an expensive high-grade engineering plastic.
• Housing 50 can be made as one part and different threaded first and second nut halves 52 and 54 can be used in the same housing. Therefore, the need to have a different housing for each different thread type is not necessary.
• a pusher 60 is threaded into housing 50, with the torsional member 62 attached to it and to a ratcheting cap 64.
• Ratcheting cap 64 can be integrated into the end of housing 50 in any manner (molded, threaded, glue, etc.). The inside of ratcheting cap 64 is free to rotate and lock in any angular position. The rotating portion of ratcheting cap 64 is attached to torsional member 62 by means of an end 66 of the torsional member ( Figure 4) being inserted into a hole 68 ( Figure 5) defined in ratcheting cap 64 and is attached to pusher 60 by means of an opposite end 72 of the torsional member being inserted in a hole 74 ( Figure 3) defined in the pusher.
• Pusher 60 spins on the housing threads 70 and provides a force on second nut half 54 inside housing 50.
• Torsional member 62 apples a constant torque to pusher 60 when the former is wound up.
• Torsional member 62 can be any product that produces a torsional force (spiral spring, torsion spring, etc.). This constant torque on pusher 62 leaves a constant force on first nut half 52. When first nut half 52 wears, pusher 62 compensates for the extra clearance between the first nut half and screw 20 ( Figure 1).
• anti-backlash device 40 The force on anti-backlash device 40 is the result of rotational forward movement. As long as torsional member 62 is wound enough, there will be no backlash in anti- backlash device 40. Anti-backlash device 40 can push and pull any force that the threads will physically hold without pusher 60 unscrewing, which would delete the anti-backlash effect.
• Anti-backlash device 40 also has a mounting flange 80 that can be integrated into housing 50.
• Mounting flange 80 can also be made as a separate part, so many different types of mounting flanges could be used without requiring the need for different housings.
• Mounting flange 80 can be attached with threads, glue, etc.
• Anti-backlash device 40 allows users to easily adjust the device while on the lead screw consistently. Anti-backlash device 40 prevents errors as well.
• FIGS 6 and 7 show another embodiment of the present invention, generally indicated by the reference numeral 100.
• Anti-backlash device 100 includes a main body 110 that has a captive feature 112 on the inside that first and second nut halves 114 and 116 mate into. Captive feature 112 allows first and second nut halves 114 and 116 to move only in the axial direction.
• First and second nut halves 114 and 116 are made as separate pieces as a cost saving and can be made from a form of high quality engineering plastic. Main body 110 can then be made of any other cheaper plastic or metallic material.
• a pusher nut 120 threads into main body 110.
• a torsion spring 130 is attached to pusher nut 120 and a body cover/torque adjuster 132, with end 134 captured between the pusher nut and the body cover/torque adjuster and with end 136 inserted in the end of the body/torque adjuster.
• Body cover/torque adjuster 132 has an anti-rotation feature 140 on a proximal end which can be manually engaged and disengaged from main body 110 at a series of detents 142 encircling and fixedly attached to the main body at a proximal end thereof.
• Body cover/torque adjuster 132 anti-rotation feature 140 is disengaged from series of detents 142 and can be turned to increase or decrease how much torsion spring 130 is wound up.
• torsion spring 130 When torsion spring 130 is wound up, it causes pusher nut 120 to rotate and apply a linear pressure to first and second nut halves 114 and 116. This pressure resolves the backlash in both nut halves 114 and 116.
• torsion spring 130 allows pusher nut 120 to move toward the nut halves, keeping up the pressure. As long as torsion spring 130 is wound up enough, there will be no backlash in anti- backlash device 100. Anti-backlash device 100 can push and pull any force that the feature 112 will allow without the pusher nut unscrewing.
• Anti-backlash device 100 also integrates a mounting flange 150 at its proximal end and the mounting flange can be made separately or as part of main body 110. Manufacturing mounting flange 150 as a separate piece allows main body 110 to be used with many different mounting flanges with vising a different main body. Separate mounting flange 150 can be attached in any manner.
• Anti-backlash device 100 allows users to easily adjust torque and backlash force while on the lead screw.
• Anti-backlash device 100 eliminates user error and provides a cover to keep the device contaminant free.

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Transmission Devices (AREA)
• Devices For Conveying Motion By Means Of Endless Flexible Members (AREA)

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Publications (1)

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• 2005
  • 2005-10-13 EP EP05811984A patent/EP1819946A2/de not_active Withdrawn
  • 2005-10-13 CA CA002583905A patent/CA2583905A1/en not_active Abandoned
  • 2005-10-13 WO PCT/US2005/037081 patent/WO2006044698A2/en not_active Ceased

Non-Patent Citations (1)

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