SCREWJACKS BEVELGEARS SHAFTS AND COUPLINGS TECHNICAL CATALOGUE MecVel - Edizione 2023 MecVel - Edition 2023

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MecVel - Edizione 2023 MecVel - Edition 2023

MecVel - Edizione 2023 MecVel - Edition 2023

SCREWJACKS - TECHNICAL CATALOGUE max load 5000 N max speed 58 mm/s AC motor max load 10000 N max speed 58 mm/s AC motor max load 25000 N max speed 96 mm/s AC motor max load 50000 N max speed 96 mm/s AC motor max load 200000 N max speed 98 mm/s AC motor MecVel - Edizione 2023 MecVel - Edition 2023

SCREWJACKS SELECTION GUIDELINES WARNINGS Screwjacks are devices usually integrated into compelex machineries, therefore can’t be considered as safety devices (Art. 1 of EC89/392-91-368.93/44.93/689). Mecvel Screwjacks shall not be used as safety elements because, any failure they should provide, could harm the security and health of people. DESCRIPTION Screwjack is a mechanical device providing an output linear movement by means of a spinning input movement. It can be uused as a single unit, or more screwjacks can be connected via shafts transmissions and angular drives. Input rotational movement...

LOADS ACTING ON SCREWJACKS Type and Size of loads are extremely important for screwjack selection. We can split these loads as follows: static loads dynamic loads These two categories can be furtherly divided into: pull loads compression loads side-loads off-center loads shock loads loads due to vibrations STATIC LOAD Load that screwjack shall bear when standing still, that is when all its components are not moving. DYNAMIC LOAD Load that screwjack shall handle, when all its components are in movement (no matter which movement is, extension, retraction, pulling, pushing...). PULL LOADS Pull load...

SHOCK LOADS Generated by shocks/bumps along stroke, whose force is rather difficult to foresee or rate. OFF-CENTER LOADS Load is applied on a point not straightly in line with leadscrew axis. Static off-center load: see paragraph about side-loads. Dynamic off-center load: frame where screwjack is installed shall absorb all the side-forces/off-center forces, therefore frame shall be carefully guidad and Size d to do so. VIBRATIONS Generated by oscillations of kinematic sequence (of screwjack) happening after an impact. This is the main difference towards the bumping loads, i.e. the frequence....

Pull load Compression load Side load Off-center load MecVel - Edizione 2023 MecVel - Edition 2023

BACKLASH BACKLASH BETWEEN WORMSCREW AND WORMWHEEL Accurate interface between these two components allows for a low angular backlash. Output movement, i.e. the linear translation ofleadscrew, results then 0.1 or lower. HT SERIES - RADIAL BACKLASH Connection between leadscrew profile and inner wormwheel features a certain radial backlash, necessary for a correct workout of screwjack. See drawing A Integration of a 2’ guide bushing (optional), allows for lowering such backlash, because it provides more radial stiffness. Traction loads are usually lowering this radial backlash, while compression...

INPUT DRIVING MANUAL DRIVE Screwjacks can be manually driven via a handwheel, the easiest form of input movement. Dimensions of handwheels in the section Input Options (see page 49). Considering a force of 50N on a 250 mm-radius handwheel, max loads (in N) are available according to reduction ratio. Higher loads can be scored by raising handwheel radius or integrating a further reduction stage. Manual drive max loads [daN] Size MOTOR INTEGRATION Size HT200-HR200 features only “bell + coupling”. So, except for Size HT200/HR200, motor gets directly connected to gearbox via a motorflange/hollowshaft...

EMERGECY DRIVING In case of power failure, screwjacks can be moved manually via some handwheel: to do this, one inputshaft shall be available on the screwjack (or one of the screwjacks if there are more than one connected together) for connection of this handwheel. If a brakemotor is used, the brake shall be un-clamped firstly, so to allow for movement. Also, a safety switch should be installed in the control panel, so that no power is suppled to motor while operator is using handwheel. LUBRICATION GEARSTAGE INTERNAL LUBRICATION Gearstage, as standard, is lubricated with synthetic long-life grease....

INSTALLATION It is extremely important that screwjack gets only axial loads, and no radial ones: so, this shall be considered at earlier design stage. When installing, user shall make sure of perfect perpendicularity between leadscrew and surface where screwjack exerts its force. Also, load to be moved shall be perfectly axial to leadscrew. All this will avoid incorrect working and lubricant leakage. In case of pulling load, screwjack shall be mounted so that tightening bolts to gearbox are not the ones handling the load. Mechanical stroke-ends damage screwjack and its components. Off-center...

MAINTEINACE Screwjacks shall be periodically checked: time-schedule is according use and environment where screwjacks are working. Gearstage for all screwjacks is filled with long-life grease that does not require refills. Make sure there are no grease leakages from gearbox: if so, search and eliminate its cause, and re-fill lubricant which escaped. Regarding leadscrew, recurrent control of its cleaniness and correct lubricant layer is necessary. Safety components of installation shall be Size d according to the laws in force. NUT WEAR CHECK-UP ACME nut shall be recurrently checked. Following...

SELECTION PARAMETERS FOR SCREWJACK SELECTION The main parameters for a correct selection of a screwjack are: load cycle (trend of the load along the stroke), travelling speed (trend of the speed along the stroke), duty cycle environmental conditions working stroke of the jack supply voltage bucking load type of constrains radial load if any LOAD AND TRAVELLING SPEED Besides their own intrinsic characteristics, load and speed must be evaluated considering the influences generated by the trend of both of them during the working cycle, expecially if heavy inerti a’s phenoma and/or vibrations are...