Hydraulic or pneumatic actuation SITEMA - Safety Catchers Technical Information TI-A10-EN-09/2011 1/4 SITEMA GmbH & Co.KG . Im Mittelfeld 10 . D-76135 Karlsruhe . Phone: +49(0)721/98661-0 . Fax: -11 . www.sitema.com Technical Information TI-A10 Safety Catchers High holding force by self-intensifying clamping Hydraulic respectively pneumatic actuation Approved for use in presses and lifting gear (DIN EN 693) Contents 1 Purpose ....................................................................... 1 2 Function........................................................................ 1 3 Design types ................................................................ 2 4 Control .......................................................................... 2 5 Choosing the right size ............................................... 2 6 Rod requirements ........................................................ 2 7 Service life.................................................................... 2 8 Acceptance by Safety Authorities.............................. 3 9 Required risk assessment ......................................... 3 10 Operating conditions.................................................. 3 11 Overall documentaion and CE label .......................... 3 12 Regular functional checks .......................................... 3 13 Maintenance ................................................................. 3 14 How to attach ............................................................... 4 A detailed description of the control, assembly and operational test of the SITEMA Safety Catchers can be found in the „Operating Manuals BA-A11 to BA-A14“ . 1 Purpose Safety Catchers are used where protection of personnel and accident prevention must be achieved in connection with raised loads or tools in case of failure of load-bearing machine parts. This may be a leakage or breakdown, for example, of a hydrau- lic or pneumatic pressure system. Safety Catchers catch falling masses infinitely variable at any position of the stroke, in a me- chanically secure and absolutely reliable manner. The design principle of the self-reinforcing clamping ensures an extremely high safety level. 2 Function Fig. 1: Design principle The piston shaft (1) is surrounded by the housing (2) in which several wedged clamping jaws (3), each with one slide lining (4) and one brake lining (5), are assembled. When pressure (p) is applied to the plungers (8), the clamping jaws are held in a raised position so that the shaft can move freely. The springs (6) are compressed in this position. The Safety Catcher becomes effective as soon as pressure is released from the plungers (8). The action of the springs cau- ses the clamping jaws (3) to then clamp the shaft (1) firmly, thus securing the load. The clamping force, however, is not built up until the shaft has been moved by the load. Due to the self-intensifying static fric- tion at the shaft, the clamping jaws (3) are drawn into the clam- ping position at their stops (7) after having moved the distance "e" (approx. 5 to 15 mm, depending on the design). This move- ment is illustrated as phase A in the force-path diagram. If the load is increased further (phase B), the shaft remains in its position, independent of the load, until the static holding force F* is reached. As soon as this limit is exceeded, the clam- ping device (phase C) generates a mean dynamic braking force F -- the holding force -- and thus dissipates the kinetic energy of the falling mass. The clamping is released by an upward movement of the shaft through path "e", by applying pressure corresponding to the load being lifted. Thus the release operation is only possible if the pressure system is intact. Excess pressure (e.g. for brea- king loose) is normally not required. e 6 5 4 3 2 7 p 1 released clamped C F B A structure force-parth diagram 8 F F* English translation of German original
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Safety Catchers High holding force by self-intensifying clamping
Hydraulic respectively pneumatic actuation
Approved for use in presses and lifting gear (DIN EN 693)
Contents
1 Purpose ....................................................................... 12 Function........................................................................ 13 Design types ................................................................ 24 Control .......................................................................... 25 Choosing the right size ............................................... 26 Rod requirements ........................................................ 27 Service life.................................................................... 28 Acceptance by Safety Authorities.............................. 39 Required risk assessment ......................................... 310 Operating conditions.................................................. 311 Overall documentaion and CE label .......................... 312 Regular functional checks.......................................... 313 Maintenance................................................................. 314 How to attach ............................................................... 4
A detailed description of the control, assembly and operationaltest of the SITEMA Safety Catchers can be found in the„Operating Manuals BA-A11 to BA-A14“ .
1 PurposeSafety Catchers are used where protection of personnel andaccident prevention must be achieved in connection with raisedloads or tools in case of failure of load-bearing machine parts.This may be a leakage or breakdown, for example, of a hydrau-lic or pneumatic pressure system. Safety Catchers catch fallingmasses infinitely variable at any position of the stroke, in a me-chanically secure and absolutely reliable manner. The designprinciple of the self-reinforcing clamping ensures an extremelyhigh safety level.
2 Function
Fig. 1: Design principle
The piston shaft (1) is surrounded by the housing (2) in whichseveral wedged clamping jaws (3), each with one slide lining(4) and one brake lining (5), are assembled. When pressure (p)is applied to the plungers (8), the clamping jaws are held in araised position so that the shaft can move freely. The springs(6) are compressed in this position.
The Safety Catcher becomes effective as soon as pressure isreleased from the plungers (8). The action of the springs cau-ses the clamping jaws (3) to then clamp the shaft (1) firmly, thussecuring the load.
The clamping force, however, is not built up until the shaft hasbeen moved by the load. Due to the self-intensifying static fric-tion at the shaft, the clamping jaws (3) are drawn into the clam-ping position at their stops (7) after having moved the distance"e" (approx. 5 to 15 mm, depending on the design). This move-ment is illustrated as phase A in the force-path diagram.
If the load is increased further (phase B), the shaft remains inits position, independent of the load, until the static holdingforce F* is reached. As soon as this limit is exceeded, the clam-ping device (phase C) generates a mean dynamic braking forceF -- the holding force -- and thus dissipates the kinetic energyof the falling mass.
The clamping is released by an upward movement of the shaftthrough path "e", by applying pressure corresponding to theload being lifted. Thus the release operation is only possible ifthe pressure system is intact. Excess pressure (e.g. for brea-king loose) is normally not required.
3 Design typesDepending on size there are different types of SITEMA SafetyCatchers. K-, KR- and KRP-type Safety Catchers are identicalas far as function and application are concerned.
Type KThis type has a number of small plungers to lift the clampingjaws. They are pressurised simultaneously by a common, an-nular groove.
Type KRIn this case the lifting function is ensured by an annular pistoninstead of the individual plungers used in type K. For reasonsof design and cost, this solution is preferred to type K if used onshaft diameters of less than approximately 80 mm.
Type KRPThe KRP-type is the pneumatic option within the familiy of Sa-fety Catchers. Although the forces of pneumatic actuators area lot less than of comparable hydraulic ones, the KRP-typesand KR-types of same rod size have same outer dimensionsand same holding capacity. This is why - thanks to the self-in-tensifying friction - the holding force does not depend on the ac-ting spring force or actuator force.
4 Control
Fig. 2: Schematic circuit diagramm
* If impact noises are audible when pressuring the Safety Catcherdue to excess pressure, they can be suppressed by means of a flowcontrol valve in the p-line.
** If the pressure (p) is not suficiently constant (e.g. pressure drop atthe beginning of a downward stroke) we recommend a check valvein the p-connection of the valve.
Under no circumstances may the hydraulic flow between connec-tion L and the tank be impaired by any additional components.
If a particular quick response of the Safety Catcher is required,the following preconditions must be met:
• Short piping distances
• large valve and pipe cross-sections
• fast valve response times
JAll connection lines must be laid out without kinks. If the-re is any danger of kinking, particulary in case of pneu-matic units, appropriate precautions must be taken (protective tube, thicker hose etc.)
Pressure fluidsSITEMA Safety Catchers mostly are hydraulically actuated. Forsmaller units, also pneumatic versions are available.
Hydraulic actuation:
Hydraulic oil (HLP) in accordance with DIN 51524-2 must beused as pressure medium. Please consult us before using anyother media.
* )* * )
p
Pneumatic actuation:
The compressed air must be dried and filtered.
Actuation with a 3/2-way valveIn most applications the actuation suggested in fig.2 is used.During every operational cycle, the 3/2-way valve is actuatedelectrically and releases the clamping device.
In all other operational conditions, as well as in cases of powerfailure, emergency stop, etc. the clamping device becomes ef-fective, secures the shaft and/or stops the load. In case thepressure line should fail, the load is secured in the same way.
If required e.g. in hydraulic lifts, the valve can also be controlledby a speed governor. In this case the safety catcher acts as asafety gear (braking mechanism).
Monitoring by proximity switchesThe proximity switch 1 „Load secured“ signals the secure stateand is used to authorise entrance to the danger area. Switch 2„released“ is used to activate the downward movement of thedrive.
For automatic detection of failures both signals are compared.In case both switches indicate the same state - apart from minoroverlapping periods - there is a defect present.
5 Choosing the right sizeThe admissible load M is stated for all types in the „TechnicalData Sheets TI-A11 to TI-A14“. During usual conditions (verti-cal movement), the criteria as below is to be maintained..
The holding (braking) force for dry running or mineral-oil wettedshafts is not less than 2 x M, but will not exceed 3,5 x M. Thefixing elements which accept the load (e.g. linking the rod to thetravelling tool etc.) must therefore be dimensioned for a 3.5 xM force. This maximum force can occur with emergency braking and also if, in case of control errors , the fuill driving forceis exerted against the Safety Catcher. However, circumstancesof this kind should remain accidental exceptions, as otherwisepossible damage could occur to the Safety Catcher.
6 Rod requirementsThe Safety Catcher will operate correctly only if the rod has thecorrect surface:
• ISO tolerance field f7 or h6
• Surface roughness: Rz = 1 to 4 µm
• Hardchrome plated surface recommended
• Lead-in chamfer 3x20°, rounded.
As the maximum load can be as high as 3,5 times the nominalforce M (for M see data sheets or dimensional drawing), caremust be taken to ensure that the strength of the rod material isadequate. In the case of compression-loaded rods, sufficientbuckling resistance must be assured.
In practice, suitable and commercially available rods are:
Piston rods with,
Rod diameter toleranz: ISO f7Basic material: 42CrMo4VHard chrome plating: 800-1100 HV min. 13 µm deepSurface finish: RA 0,15 - 0,25
MMoving weight
Number of safety catchers----------------------------------------------------------------------
7 Service lifeWhen discussing the service life of SITEMA Safety Catchers, adistinction must be made between two different types of use. Inhe normal case of securing a stationary load (e.g. the slideetc.), the clamping jaws (3) will only cover a very small distance,until the radial play is eliminated and an equilibrium betweenthe spring forces and the forces generated on the slide and bra-ke linings is achieved. The stress caused by this operations isextremely low and can certainly be cycled millions of times. Forthis reason, securing of a stationary slide, for example at eachstroke of the press, will certainly not cause any wear or fatigueof safety-relevant parts, even after years of service. The radialforces and material stresses for which the unit is initially desig-ned will occur only if unoperational lowering of the shaft occursin clamped "load secured" condition, due to leakage, pipe breaketc. In this case the clamping jaws are drawn into the clampingposition after moving the full distance "e". Lowering throughsuch a distance as a result of leakage is very rare, however,and only occurs when the machine is stopped for an extendedperiod of time. Pipe breaks are even less frequent. Such eventswill certainly not occur more than several times a day or a fewhundred times per year.
Based on the results of fatigue tests it can be guaranteed thatfor several years in normal use, the holding force will not dropbelow the nominal value, and that even after lots of clampingcycles, no relevant changes in the diameter or surface qualitywill be observed on the clamping shaft. The service life ofSITEMA Safety Catchers will therefore not be less than theusual service life of production machinery.
There will be no relevant reduction of service life even in theoccasional case of slippage when catching the load or due tooverloads resulting from incorrect operation of the press cylin-der with the clamp engaged, or the lifting of load without apply-ing pressure simultaneously. However, abnormal situations likethis should be avoided.
On the other hand it should be mentioned, that from our expe-rience certain undesired operational conditions could diminishthe service life considerably.
Most of all following operating conditions must be avoided:
• Radial forces or side loads due to misalignmet
• Finish of the rod too rough
• Penetration of corrosive substances into the housing (in-cluding humid compressed air)
• Lowering of the load in "load secured" position with everystroke due to control.
8 Acceptance by Safety AuthoriesSITEMA Safety Catchers have been tested and approved assafety devices for a number of different applications by
• TÜV Technischer Überwachungsverein
• Berufsgenossenschaften (Workers Insurance)
• Lloyd's Register of Shipping
Particularly SITEMA Safety Catchers are certified with respectto the European Standard DIN EN 693 (Machine tools - Safety- Hydraulic presses) and DIN EN 692 (- Mechanical presses)as mechanical restraint device to prevent gravity fall.
A copy of respective certification and additional informationcan be found in „Technical Information TI-A40“
9 Required risk assessmentIt must be ensured that the dimensions and arrangement ofSITEMA - Safety Brakes in safety-relevant applications meetthe requirements of the risk evaluation DIN EN ISO 14121-1and also comply with any further standards and regulations ap-plying to the intended use. This is the duty of the system man-ufacturer and the user.
10 Operating conditionsThe Safety Catcher is designed to operate in usual clean anddry shop atmosphere. In case of other environments at leastthe port T for breathing purposes is to be connected to a clenand dry volume (tank).
Should heavy soiling conditions (grinding dust, chips, other li-quids, etc.) exist, please contact SITEMA. Grease on the rodmay reduce the holding force.
The permissible surface temperature is 0 - 60°C.
11 Overall documentation and CE label
The Safety Catcher is designed as a component to be integra-ted into a machine or system and as such can never be CE-certified itself. The seller of the machine or system must provideinformation on the Safety Catcher with the overall documenta-tion and if applicable ensure that the machine or system is CE-certified.
12 Regular functional checksThe Safety Catcher must be functionally checked at regular in-tervals. Regular checking is the only way to ensure that the unitwill operate safely in the long run.
Please see the respective operating manual for further details.For standard versions „Operating Manuals BA-A11 to BA-A14“are valid.
13 MaintenanceThe maintenance of the SITEMA Safety Catchers is limited tothe prescribed regular functional check.
Should the Safety Catchers cease to comply with the requiredcharacteristics, the aforementioned safety of working with themachine or system is no longer given. In this case the SafetyCatchers must be removed immediately and professionally re-paired by SITEMA.
Any repair or refurbishing must be carried out by SITEMA.SITEMA cannot take any responsibility for repairs by anotherparty.
There are various ways to attach theSafety Catchers type K and KR/KRP.
In any case it must be ensured, that noside load can be induced due to toleran-ces in dimensions or angular alignmentrelative to other guiding means.
If the Safety Catcher is directly mountedto a cylinder end cap, it usually is pro-perly centered to the rod. In all other se-tups either the rod or the body of thecatcher must not be rigidly fixed butmounted floating with enough radialclearance.
The 4 basic options are illustrated below,using hydraulic presses as an exampleof application.
They can be applied in other cases aswell if the expression slide is replaced bythe more general term load carrying de-vice.
Suitable attachment flanges are offeredin „Technical Data Sheet TI- A30“.
If the clamping device is firmlyboled to the machine frame, the re-taining rod must have sufficientclearance at its attachment, so thatthe transverse or tilting move-ments of the slide will not createtransverse forces to the rod.
1. Safety Catcher fixed to machine frame -
- rod floating on slide
clearance
2. Alternative:coupling flange(KR/KRP only)
1. Alternative:bolting frombelow
The collar flange as shown aboveis one of the common solutions fora mounting with radial play. Alter-natively a spring-base can be re-commended, which on top isproviding other advantages as de-scibed in "Technical InformationTI-A20".
Both mounting versions make surethat the safety catcher can movefreely in order to compensate fortransverse movements of the tra-velling rod.
2. Safety Catcher floating on machine frame -
Safety Catcherwith shoulder(KR/KRP only)
- rod fixed to slide
clearance
If the moving Safety Catcher isfirmly mounted on the slide, thestationary rod must be loosely at-tached, similar to the option 1.
This is another application using acoupling flange. In addition an axi-al clearance of h = approx. 5 to 10mm is used, so that this design willperform the function of the spring-base as well.
3. Safety Catcher fixed to slide - rod floating on machine frame
4. Safety Catcher floating on slide - rod fixed to machine frame
Fig. 1: Dimensions Safety Catcher KR (CAD-Files download at www.sitema.com)
bold types = recommended standard, on stock Subject to modification without prior notice
1 M is the admissible force the mass to be secured exerts on theclamping device. The holding (braking) force for dry running or mineral-oil wetted shafts is not less than 2 x M, but will not exceed 3,5 x M.2 Minimum operating pressure is 40 bar. In case a spring base is in-stalled, for releasing without lifting the required pressure is 60 bar, conf."Technical Information TI-A20“. Admissible working pressure is 250bar.3 As supplied port LL is plugged by a plug screw. It may be used al-ternatively to port L and is usefull for air-bleeding. It is generally recom-mended to install the Auto-Bleeder as descibed in the "TechnicalInformation TI-Z10“ at port LL (or L respectively).
4 Hydraulic operating volume.5 Proximity switch holders are provided for standard proximity swit-ches M12x1 shielded and with a nominal switching distance of 2 mm,except KR 25 and KR 28: M8x1 with nominal distance 1,5 mm.For easier service, the proximity switch holders have a positive stopand are presetted when deliverd from the factory.6 Port T is used for pressure compensation (breathing). It is pluggedwith an air filter element.If, however, moisture or aggressive media are present, a hose insteadof the filter must be installed to connect the device with a clean atmos-phere (e.g. hydraulic tank).
1 4
Type Ident.-No. d M D D1 H Y Z X L1 G1 T1 L2 G2 T2 V HL H1 H2 w Weight
mm kN mm mm mm mm mm mm mm mm mm mm cm3 mm mm mm mm kg
Due to tolerancesthe ports 1 and 2may be misali-gned up to +/-4°relative to port L.
Load direction
Technical Data Sheet TI-A11Safety Catcher KR Load direction compressive (to mounting surface)
General information, particularly regarding purpose, function, choosing right type and control is provided in "Technical Information TI-A10“. Furthermore important practical advices are given in the "Operating Manual BA-A11“.
Fig. 2: Dimensions Safety Catcher K (CAD-Files download at www.sitema.com)
bold types = recommended standard, on stock Subject to modification without prior notice
1 M is the admissible force the mass to be secured exerts on theclamping device. The holding (braking) force for dry running or mineral-oil wetted shafts is not less than 2 x M, but will not exceed 3,5 x M.2 Minimum operating pressure is 40 bar. In case a spring base is in-stalled, for releasing without lifting the required pressure is 60 bar, conf."Technical Information TI-A20“. Admissible working pressure is 250bar.3 As supplied, port LL is plugged by a plug screw. It may be used asan alternative to port L and is useful for air-bleeding.4 Hydraulic operating volume.
5 Proximity switch holders are provided for standard proximity swit-ches M12x1 shielded and with a nominal switching distance of 2 mm. 6 Port T is used for pressure compensation (breathing). It is pluggedwith an air filter element.If, however, moisture or aggressive media are present, a hose insteadof the filter must be installed to connect the device with a clean atmos-phere (e.g. hydraulic tank).7 For air-bleeding, an automatic air-bleeder is integrated.Due to the permanent bleeding, a small quantity of oil-air mix will es-cape from port E. Therefore, a connection to the tank is necessary. (For further information see "Technical Information TI-Z10“)
1 4
Type Ident.-No. d M D H Z X L1 n G1 T1 L2 G2 T2 V HL H1 H2 H3 Weight
Technical Data Sheet TI-A11Safety Catcher K Load direction compressive (to mounting surface)General information, particularly regarding purpose, function, choosing right type and control is provided in"Technical Information TI-A10“. Furthermore important practical advices are given in the "Operating Manual BA-A11“.
Fig. 1: Dimensions Safety Catcher KRP (CAD-Files download at www.sitema.com)
bold types = recommended standard, on stock Subject to modification without prior notice
1 M is the admissible force the mass to be secured exerts on theclamping device. The holding (braking) force for dry running or mineral-oil wetted shafts is not less than 2 x M, but will not exceed 3,5 x M.2 Minimum operating pressure is 4 bar. In case a spring base is ins-talled, for releasing without lifting the required pressure is 6 bar, conf."Technical Information TI-A20“. Admissible working pressure is 10 bar.3 Pneumatic operating volume.
4 Proximity switch holders are provided for standard proximity swit-ches M12x1shielded and with a nominal switching distance of 2 mm,except KRP 25 and KRP 28: M8x1 with nominal distance 1,5 mm.For easier service, the proximity switch holders have a positive stopand are presetted when deliverd from the factory.5 Port T is used for pressure compensation (breathing). It is pluggedwith an air filter element. If, however, moisture or aggressive media arepresent, a hose instead of the filter must be installed to connect the de-vice with a clean atmosphere (e.g. hydraulic tank).
1 3
Typ Ident.-Nr. d M D D1 H Y Z X L1 G1 T1 L2 G2 T2 V AG HL H1 H2 w Weight
mm kN mm mm mm mm mm mm mm mm mm mm cm3 mm mm mm kg
Due to tolerancesthe ports 1 and 2may be misalignedup to +/-4° relativeto port L.
Technical Data Sheet TI-A12Safety Catcher KRP Load direction compressive (to mounting surface)
General information, particularly regarding purpose, function, choosing right type and control is provided in"Technical Information TI-A10“. Furthermore important practical advices are given in the „Operating Manual BA-A12“.
To hold the tensile forces these KR/T types have a strong shoul-der near the upper end, which is designed to transmit the forceto a collar flange.
Therefore it is possible to attach the safety catcher to the ma-chine frame in a fixed or floating manor according to the ex-planation given in „Technical Information TI-A10“, §14 „How toattach“.
Standard versions of those flanges are listed „Technical Infor-mation TI-A30“. Such flange is not part of the Safety CatcherKR/T and K/TA, but available as an option.
bold types = preferential sizes, available from stock Subject to modification without prior notice
1 M is the admissible force the mass to be secured exerts on theclamping device. The holding (braking) force for dry running or mineral-oil wetted shafts is not less than 2 x M, but will not exceed 3,5 x M.2 Minimum operating pressure is 40 bar. Admissible working pressu-re is 250 bar.3 As supplied port LL is plugged by a plug screw. It may be used al-ternatively to port L and is usefull for air-bleeding. It is generally recom-mended to install the Auto-Bleeder as descibed in the „TechnicalInformation TI-Z10“ at port LL (or L respectively.4 Hydraulic operating volume.
5 Proximity switch holders are provided for standard proximity swit-ches M12x1 shielded and with a nominal switching distance of 2 mm, except KR/T 25: M8x1 with nominal distance 1,5 mm.For easier service, the proximity switch holders have a positive stopand are presetted when deliverd from the factory.6 Port T is used for pressure compensation (breathing). It is pluggedwith an air filter element.If, however, moisture or aggressive media are present, a hose insteadof the filter must be installed to connect the device with a clean atmos-phere (e.g. hydraulic tank).
1 4
Type Ident.-No. d M H D1 D2 D X Y V HL H1 H2 w Weight
Due to tolerances the ports 1 and 2may be misaligned up to +/-4° relati-ve to port L.
Technical Data Sheet TI-A13Safety Catcher KR/T Load direction tensile (to mounting surface)General information, particularly regarding purpose, function, choosing right type and control is provided in„Technical Information TI-A10“. Furthermore important practical advices are given in the „Operating Manual BA-A11“.
The attachment flange of type K/TA is supplied with boreholesto fix the device with bolts firmly to the frame.
As explained in „Technical Information TI-A10“, it must be en-sured that the retaining rod has sufficient clearance at its at-tachment so that no transverse forces can be induced to theclamping device due to tolerances in dimensions or angularalignment..
bold types = preferential sizes, available from stock Subject to modification without prior notice
1 M is the admissible force the mass to be secured exerts on theclamping device. The holding (braking) force for dry running or mineral-oil wetted shafts is not less than 2 x M, but will not exceed 3,5 x M.2 Minimum operating pressure is 40 bar. Admissible working pressu-re is 250 bar.3 As supplied port LL is plugged by a plug screw. It may be used al-ternatively to port L and is usefull for air-bleeding.4 Hydraulic operating volume.5 Proximity switch holders are provided for standard proximity swit-ches M12x1 shielded and with a nominal switching distance of 2 mm. 6 Port T is used for pressure compensation (breathing). It is pluggedwith an air filter element.
If, however, moisture or aggressive media are present, a hose insteadof the filter must be installed to connect the device with a clean atmos-phere (e.g. hydraulic tank).7 An automatic bleeder is integrated in the unit.Due to the permanent bleeding, small quantities of an air-oil-mixturewill escape from the port. Therefore, a connection line to the tank is in-dispensable.( For further information see „Technical Information TI-Z10“ )8 Optionally, the unit can be equipped with an oil sensor. This sensorindicates at an early stage beginning leakage due to worn or damagedseals.
1 4
Type Ident.-No.
d M HG H D1 D2 D X Z S n B L1 V w HL H1 H2 H3 Weight
mm kN mm mm mm mm mm mm mm mm mm mm cm3 mm mm mm mm kg
Technical Data Sheet TI-A13Safety Catcher K/TA Load direction tensile (to mounting surface)General information, particularly regarding purpose, function, choosing right type and control is provided in„Technical Information TI-A10“. Furthermore important practical advices are given in the „Operating Manual BA-A11“
To hold the tensile forces these KRP/T types have a strongshoulder near the upper end, which is designed to transmit theforce to a collar flange.
Therefore it is possible to attach the safety catcher to the ma-chine frame in a fixed or floating manor according to the ex-planation given in „Technical Information TI-A10“, § 14 „How toattach“ .
Standard versions of those flanges are listed „Technical Infor-mation TI-A30“. Such flange is not part of the Safety CatcherKRP/T, but available as an option.
Fig. 1: Dimensions Safety Catcher KRP/T (CAD-Files download at www.sitema.com)
Subject to modification without prior notice
1 M is the admissible force the mass to be secured exerts on theclamping device. The holding (braking) force for dry running or mineral-oil wetted shafts is not less than 2 x M, but will not exceed 3,5 x M.2 Minimum operating pressure is 4 bar. In case a spring base is ins-talled, for releasing without lifting the required pressure is 6 bar, conf.„Technical Information TI-A20“. Admissible working pressure is 10 bar.3 Pneumatic operating volume.
4 Proximity switch holders are provided for standard proximity swit-ches M12x1 shielded and with a nominal switching distance of 2 mm,except KRP/T 25: M8x1 with nominal distance 1,5 mm.For easier service, the proximity switch holders have a positive stopand are presetted when deliverd from the factory.5 Port T is used for pressure compensation (breathing). It is pluggedwith an air filter element. If, however, moisture or aggressive media arepresent, a hose instead of the filter must be installed to connect the de-vice with a clean atmosphere (e.g. hydraulic tank).
1 3
Type Ident.-No. d M H D1 D2 D X Y V AG HL H1 H2 w Weight
Due to tolerances the ports 1 and 2 maybe misaligned up to +/-4° relative toport L.
Load direction
Technical Data Sheet TI-A14Safety Catcher KRP/T Load direction tensile (to mounting surface)General information, particularly regarding purpose, function, choosing right type and control is provided in„Technical Information TI-A10“. Furthermore important practical advices are given in the „Operating Manual BA-A12“.
General InformationPurposeSITEMA Safety Catchers can only be unlocked if their clampingsystem is not under load. This is a matter of principle and com-plies with the relevant safety regulations. If, however, the slideor any other load carrying device overshoots after reaching itstop cut-off position, or moves slightly downward for any particu-lar reason, the Absturzsicherung K und KR is subjected to apartial load. In practice this means that the slide must first beraised before a closing movement of the press is possible. Thiseffect oft can be avoided by not bolting the safety catcher di-rectly to the machine frame, but rather on a spring-base.
SolutionThe housing (1) is securely fixed to the machine frame. Insidethis housing the flange plate (2) which bears the safety catcher,is free to move vertically (stroke "h") as well as transversely (bythe permitted eccentricity of "x"), and is allowed to tilt. The safe-ty catcher when released (i.e. not under load) is pressed up-ward by the spring (3), against the stop. If the slide should settleslightly (due to leakage, for example) while the safety catcheris engaged, only the spring force — which is very low in com-parison to the holding force — is exerted on the safety catcher.In this case, the safety catcher can be released without an up-ward movement. Only when the lowering movement exceedsstroke length “h”, the full weight of the slide will be borne by thesafety catcher. Now it is possible to release the safety catcherafter only a short upward movement.Note:The overall lowering path, after which the slide will be securedmechanically, is increased by the distance h (for h see pictureat page 2). This amount is to be taken into consideration whenmaking safety analyses for engineering purposes. Special notemust be made of this in the operating instructions for the press.
AdvantagesRaising the slide before the lowering movement is no longerrequired, even if a leakage should occur at the cylinder seals.The crucial safety criteria, “safety catcher can only be re-leased when the weight of the slide is supported entirelyby the hydraulic pressure”, is satisfied without restriction. En-larging the maximum lowering distance by the stroke "h" is notrelevant to safety in this case.The spring-base also compensates for certain misalign-ment between the slide guide and the clamping rod. Other me-thods („Technical Information TI-A10“ § 14 „How to attach“) arenot necessary in this case. There are two alternatives for attaching the Safety Catcher tothe machine frame. Either using threaded holes arrangedidentical to the ones on the clamping device or the externallyattached shoulder which engages with the coupling flange FL/FS („Technical Data Sheet TI-A30“)
MountingAs usually ordered the the spring-base is factory-mounted un-der the Absturzsicherung K und KR, ready for use. Specialmounting instructions are supplied for retrofitting.The electric control of the Safety Catcher unit is described in„Technical Information TI-A10“. The required release pressureis 60 bar for standard hydraulic versions and 6 bar for pneu-matic ones. Pressure must be supplied via a flexible line.
Technical Data Sheet TI-A20Spring-base for SITEMA - Safety Catchers K and KR
DimensionsFor KR 25/FS 25 to KR 80/FS 80In these sizes a centrally located spring carries the weight ofthe clamping device. The housing has no protection against tor-sion and is therefore self-aligning to the forces applied by theconnecting hose.
For KRP 25/FS 25 to KRP 80/FS 80For these pneumatic version the connecting hoses often rathersmall and flexible. In order to prevent kinking or squeezing, thesuiting spring bases are equipped with a twist protection.
Fig. 1: Spring base for KR 25 to KR 80 and KRP 25 to KRP 80
For KRP 100/FS 100, K 100/FS 100 to K 140/FS 140By contrast, these sizes are fitted with a set of borehole guidedcompression spring, which by the way prevents the body frombeing rotated.
Fig. 2: Spring Base for KRP 100 and K 100 to K 140
Subject to modification without prior notice
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H1
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H1
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Safety Catcher Spring-base H H1 D D1 D2 Y L G T h XIdent.-No. mm mm mm mm mm mm mm mm mm mm
General InformationenThe standard SITEMA Safety Catcher K and KR are suppliedwith a set of threaded boreholes to bolt the unit to the machineframe.But often a mounting flange is required, because bolting frombelow is impossible or a floating attachment is necessary (seealso „Technical Information TI-A10“, §14 „How to attach“).
Different mounting flanges for typical applications are listed be-low.Additionally page 3 shows coupling flanges for Spring Bases.Page 4 shows mounting flanges for tensile versions of SafetyCatchers.
Flange FL/SL (standing / floating)For attachment of Safety Catchers K, KR and KRP on the machine frameTo avoid possible transverse forces it is often helpful to attachthe safety catcher FL/SL floating on the machine frame.Floating coupling flanges for Safety Catcher K and KR are lis-ted below.Pressure must be supplied via a flexible line, in order to allowthe desired three-dimensional motions of the housing. Pleasenote, that there is no stop in torsional direction, so that the hou-sing will be self-aligning to the forces applied by the connectinghose.For type KR
For type KR
The mounting flanges for the two types K and KR are identicalas far as function and application are concerned, but for designreasons (no shoulder at K-type flanges) the flange for type Ksafety catchers consists of two parts. One part is at first bolted to the safety catcher from below, whilethe other one is then bolted to the machine frame.
For type K ( 2 parts )
For type K ( 2 parts )
Subject to modification without prior notice
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1m
mAx
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Radial playLoad 3 m m
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1m
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T ( m i n . )
Axia
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Radial play
Load
Type for Safety Catcher D C A G E n T Smm mm mm mm mm mm mm
Flange FL/SF (standing / fixed)For attachment of Safety Catchers KR and KRP on the machine frame or travelling overhead with the slideAlternatively to the fixation by bolting from below, the mountingflange FL/FS can be used to fix the safety catcher to the ma-chine frame.In this case it has to be ensured, that the retaining rod has suf-ficient clearance at its attachment so that no transverse forcescan be induced to the clamping device.This standard flange is only available for KR and KRP-typesafety catchers. Nevertheless, fixed flange attachments for Kty-pe units are available on request. Pease ask for details.
For type KR and KRP
For type KR and KRP
Subject to modification without prior notice
øAøCøD
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n x øE
G
Load
Type for Safety Catcher D C A G E n Smm mm mm mm mm mm
Flange FL/HL ( hanging / floating )For attachment of Safety Catchers KR and KRP travelling with the slideThe floating flange FL/HL should be used, if the safety catcheris arranged attached to the slide from below and travelling withit, while the rod is fixed stationary to the machine frame (nor-mally hanging).Due to the axial play of 8 mm this flange additionally fulfils thefunction of the Spring-base „Technical Information TI-A10“, §13„Attachment“.Pressure must be supplied via a flexible line, in order to allowthe desired three-dimensional motions of the housing. Pleasenote, that there is no stop in torsional direction, so that the hou-sing will be self-aligning to the forces applied by the connectinghose.Due to the design, this flange is only available for KR and KRP-type safety catchers.
For type KR and KRP
Für Bauart KR und KRP
Subject to modification without prior notice
øAøCøD
n x øE
G
8mm
3mmS(min)
Radial play
Axi
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rod stationary
slide travellingLoad
Type for Safety Catcher D C A G E n Smm mm mm mm mm mm
Flange FL/FS ( spring-base )For attachment of spring-bases FS on the machine frameAlternatively to the bolting of the springbase from below, thisflange can be used.
Mounting Flanges for type KR/T or KRP/TMounting flange fix - type FL/TFIf the retaining rod has sufficient clearance on the slide or loadcarrying device to move freely, the safety catcher can be cen-tered and bolted on the machine frame.The flange FL/TF offers the possibility to turn the ports in a desi-red direction before the housing is fixed by fastening the bolts.
For type KR/T and KRP/T
For type KR/T and KRP/T
Subject to modification without prior noticen
( ø D 1 )ø Cø D
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n x ø E
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Safety catcher
Type for safety Catcher AF C D G E nmm mm mm mm mm
Mounting flange floating - type FL/TLTo avoid possible transverse forces it is often helpful to attachthe safety catcher floating on the machine frame, using flangeFL/TL. It allows the housing to move radial (3mm) and axial(1mm) as well as to tilt (approx. 0.25°).Pressure must be supplied via a flexible line, in order to allowthe desired three-dimensional motions of the housing. Pleasenote, that there is no stop in torsional direction, so that the hou-sing will be self-aligning to the forces applied by the connectinghose.
For type KR/T and KRP/T
For type KR/T and KRP/T
Subject to modification without prior noticen
ø Cø D
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n x ø E
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1m
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3 m mSafety catcherRadial play
Axi
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Type for Safety Catcher AL C D G E nmm mm mm mm mm