SITEMA Locking Unit / Data sheet - SITEMA - #3

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Locking by Spring Force / Hydraulic Releasing SITEMA - Locking Unit KFH Technical Data Sheet TI-F50-EN-06/2010 SITEMA GmbH & Co.KG . Im Mittelfeld 10 . D-76135 Karlsruhe . Phone: +49(0)721/98661-0 . Fax: -11 . www.sitema.com 3/4 Operational purpose The Locking Device KFH clamps a shaft in any position. It is commonly used on a cylinder rod or an other round shaft and holds axial forces in both axial directions. Load direction A force in load dircetion 1 is always held without backlash If the force acts in load direction 2 a backlash also does not occur, provided the force is not exceeding approx. 80% of the nominal holding force F. Otherwise the possible axial displacement is 0.1 - 0.3 mm. Choosing the right size The table (Page 1 and Page 2) shows the nominal holding force F of the various items. The value F must be higher than the static load in the particular application. In case a vertically moved mass is to be secured, a reasonable safety factor must be applied by the designer. This factor depends on the kind of machinery, but shoudn't be less than 1.5. If people have to be secured against dangers of lifted static loads at the necessary regular testing must be performed with at least 1.5 times the load. To guarantee the holding force during service even under unfavourable conditions, the actual holding force when new has to be higher than the nominal holding force. It will not, however, exceed twice the value. The fixing elements that absorb the force (e.g. articulations for the holding rod) must therefore be dimensioned for 2 x F. T- port The tapped hole marked T (tank, oil leakage) is used for pressure compensation (breathing). It is plugged with a filter element when supplied from the factory. In case the Locking Unit KFH is to work in corrosive environment, e.g. coolant spray, port T must be connected to clean atmosphere or hydraulic tank by a pipe or hose Rod material The Locking Unit KFH will operate correctly only if the rod has the correct surface: • ISO tolerance field f7 or h6 • Surface roughness: Rz = 1 to 4 ìm. • Rod surface hardened (min HRC 52). If only static load is applied, hardening not necessary. • Hardchrome plated surface recommended • Lead-in chamfer 3x20°, rounded. As the actual holding force can be as high as two times the nominal holding force F (for F see data sheets or dimensional drawing), care must be taken to ensure that the strength of rod material is adequate. In the case of compression-loaded rods, sufficient buckling resistance must be assured. In practice, suitable and commercially available rods are: 1. Piston rods, hard chrome plated (ISO tolerance f7) Basic material: Yield strength, min. 580 N/mm² Induction hardened HRC 52 - 64 / min. 1 mm deep Hard chrome plating: 800-1100 HV min. 13 ìm deep Surface finish: RA 0,15 - 0,25 2. Shafts for linear ball bearings (ISO tolerance h6) Induction hardened HRC > 60 Surface finish: RA 0,15 - 0,25 Pressure fluid Hydraulic oil (HLP) in accordance with DIN 51524-2 must be used as pressure medium. Please consult us before using any other media. Control In most applications the actuation suggested in Abb.3 is used. During every operational cycle the 3/2-way valve is actuated electrically and releases the locking unit. In all other operational conditions, as well as in cases of power failure, emergency stop, etc. the locking unit becomes effective secures the rod and stops the load. In case the pressure should fail, the load is secured in the same way. To avoid possible problems, the shaft should not be driven unless the proximity switch 2 indicates "unclamped". Fig. 3: Schematic diagramm of hydraulic circuit * If impact noises are audible when pressuring the Locking Unit KFH due to excess pressure, they can be suppressed by means of a flow control valve in the p-line. ** If the pressure (p) is not suficiently constant (e.g. pressure drop at the beginning of a downward stroke) we recommend a check valve in the p-connection of the valve. Under no circumstances may the hydraulic flow between connection L and the tank be impaired by any additional components. If a particular quick response of the Locking Unit KFH is required, the following preconditions must be met: • Short piping distances • large valve and pipe cross-sections • fast valve response times * ) * * ) p