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Q: Can I reduce the screw backlash? Q: How much backlash is in a Joyce machine screw jack? A: In machine screw jacks there are two types of backlash. Worm to worm gear backlash (typically 8-15 degrees worm rotation) and lifting screw to lifting nut backlash, sometimes called endplay (up to .020 inches on new standard jacks). Note: Due to the high ratios in worm gearing, worm to worm gear backlash is not a significant factor in most jack applica- tions since it normally corresponds to less than .002” backlash of the lifting screw.

Joyce Jacks, Actuators & Systems - 9253 E

Q: Can I buy a screw jack with a clevis on both ends? A: Yes, when freedom of movement in two axes is required, a double clevis jack may be specified. This design incorporates a

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FAQ

Q: What is the calculated life for a screw jack? A: Because of the variables involved, it is impossible to accurately predict the life of a machine screw jack. Bevel Ball Actuators shown on page 104 should be specified if life pre- dictability is required since they are the only screw jacks avail- able with a completely mathematically predictable life. See Bevel BallActuator life expectancy charts on page 109. clevis machined or pinned on the screw end and a clevis welded Q: Can I order a mechanical stop to limit jack screw travel? A: Yes, screw backlash (endplay) can be adjusted via any of threefollowing optional anti-backlash devices: Standard split-nut design; A90 external nut adjustment; and our patent pending A95 design. Please consult page 113 for the features and benefits of each design. to the protection tube. Double clevis units are useful in applica- tions that require actuating a hinged platform or door. Q: What are the standard end conditions for the liftingscrews on a screw jack? Q: What do I need to consider when ordering a bellows bootto protect the jack lifting screw? A: When a bellows boot is ordered for a jack, the closed height dimensions may change from those listed on the jacks without boots. Refer to the chart on pages 110-112 for jack closed height dimensions. When ordering a bellows boot for an inverted jack, the collar diameter for the end of the boot that fastens to the mounting structure must be customer specified. A: Our standard lubrication and seals are rated for a tempera- ture range of 0-250 Q: What is a screw jack's normal operating temperature? A: Joyce Machine Screw and Bevel Gear
® Jacks are available withany of the following four standard end conditions: Type 1 is a plain,
o F. For operation outside of this range,special lubricant and/or seals can be provided. Please contact Joyce for recommendations. turned-down end; Type 2 is a circular load pad with mounting holes; Type 3 is a threaded end; and Type 4 is a male clevis. Please refer to the jack drawings for dimensional information. Note: Ball Screw Jacks and Bevel Ball Actuators have a Type 3 screw end standard. Optional ends are available. Please refer to the jack drawings for dimensional information. Q: Are Joyce screw jacks lubricated prior to shipment? A: All Joyce Machine Screw, Ball Screw Jacks and Bevel Ball Actuators are lubricated for normal operation before leaving the factory and are ready for use. The standard lubricant provided is an extreme pressure NLGI grade #1 (EP1). Specific information and commercial brand names can be found in our O&M manual. Q: What is screw lead error? The Bevel Gear
® A: The deviation from the mathematical lead expressed in inches per foot cumulative. Jack utilizes both grease and oil. The upperbearing and jackscrew are both grease lubricated while the remaining internal components are oil lubricated. These jacks are grease lubricated prior to shipment; however oil must be added to the unit prior to operation. A: Yes, an optional stop can be ordered on either or both ends ofthe screw. However, mechanical stops are not intended to be used as operating limits. Engaging the stop may prevent damage to your Q: What is the amount of lead error in a standard lifting screw? Q: How much side load can I place on a screw jack? A: Thread Milled Acme Screws up to .003"/ft. cumulative; Ball Screws up to .007"/ft. cumulative; Rolled Acme Screws up to .010"/ft. cumulative. structure but will most likely damage the jack. To control jack A: Standard jacks are not designed to accommodate side travel, please refer to the limit switches shown on pages 120 & 121. A: The worm shaft rotating as shown (looking down on the jack) raises the load. Note: Mechanical stops are standard on all Joyce ComDRIVE
® jacks. Q: How can I determine wormshaft rotation for raising and lowering the jack? loadsin a dynamic condition. We recommend the use of external guides when dynamic side loads are expected. Jacks can however accommodate some side loading in a static condition. The screw column length generally becomes the limiting factor in these applications. Please contact Joyce Application Engi- neering direct at 1-800-523-5204 for additional assistance.
Screw Center Line LeftSideRightSide 1-800-523-5204 Visit our website now for 2D and Interactive 3D models of all our Jacks and Actuators. www.joycedayton.com 15