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How to Prevent the Sliding Block of Hydraulic Press From Falling Off?

With the vigorous development of aviation, aerospace, energy, automobile, household appliances and other industries, more and more hydraulic presses are produced and put into use in factories.

The development of social humanization has higher and higher requirements for the safety system of the hydraulic press.

It not only requires humanization, but also requires its performance to be safe, stable and reliable. The safety protection measures in the use of hydraulic press are particularly important.

This post briefly discusses several safety protection measures to prevent the sliding block of hydraulic press from falling off.

Slider hydraulic locking device

The slider hydraulic locking device is generally installed on the upper plane of the slider and the lower plane of the upper cross beam, or on the side of the column, as shown in Fig. 1.

Schematic diagram of slider locking device

  • 1 – upper bracket
  • 2 – lower bracket
  • 3-locking pin
  • 4-impact block
  • 5 – hydraulic cylinder
  • 6 – loosen the limit in place
  • 7 – locking in place limit

Fig. 1 Schematic diagram of slider locking device

The slider locking device is mainly composed of upper support, lower support, locking bolt, impact block, hydraulic oil cylinder, limit switch, screw, washer, etc.

The lower support is installed and fixed on the upper plane of the sliding block by screws and washers, the hydraulic oil cylinder is connected with the upper support, the locking bolt and striker are connected with the piston rod of the oil cylinder, and the upper support is installed and fixed on the lower plane of the upper cross beam by screws and washers.

When the impact block touches the limit switch, the limit switch sends a message, indicating that it is locked in place or loosened in place. Fig. 2 is a physical photo of the slider locking device.

Physical drawing of slider locking device

Fig. 2 Physical drawing of slider locking device

Locking action: when the main slider is at the upper limit position, press the locking button, and the locking device will automatically lock the main slider.

However, when the main slider is not at the upper limit position, press the locking button, the slider will rise to the upper limit position first, and then lock automatically.

Release action: when the slider is at the upper limit position and the locking device is locked, press the release button to unlock and release immediately.

If the locking device is locked, but the slider is out of the upper limit position, press the release button, the slider will return to the upper limit position slowly, and then perform the unlocking and releasing action.

Hydraulic support safety circuit

In order to prevent the sliding block from falling out of control, a double support safety circuit is set in the lower chamber of the piston main oil cylinder to ensure safety.

Fig. 3 is the schematic diagram of hydraulic double support safety circuit.

The double support safety circuit is mainly composed of support valve, solenoid ball valve, solenoid valve, overflow valve and pipeline system.

When the solenoid ball valve (2) and solenoid valve (3) are not energized, the support valve (1) and support valve (4) are firmly closed, and the oil in the lower chamber of the oil cylinder cannot flow back to the oil tank to ensure that the sliding block does not go down.

Schematic diagram of the hydraulic double support safety circuit

  • 1 – support valve
  • 2 – electromagnetic ball valve
  • 3 – solenoid valve
  • 4 – support valve
  • 5 – overflow valve

Fig. 3 Schematic diagram of the hydraulic double support safety circuit

Safety bolt device

Figure 4 is the structural diagram of the rotary safety bolt device.

The fixing ring (2) is fixed on the pillar (1) through the set screw, the support (6) is fixed on the front of the pillar through the screw and washer, the rotating arm (4) is installed together with the support (6) through the pin shaft (5), the pillar (1) is installed into the circular hole at the outer end of the rotating arm (4), and the weight of the fixing ring (2) is supported by the spring (3).

The limit switch (7) is installed at the corresponding position on the front of the column.

The rotating arm (4) can rotate with the pin shaft (5) as the center, screw the column (1) into the worktable or to the outside of the column, send a signal by the limit switch (7) and interlock with the action of the host.

Structural diagram of rotary safety bolt

  • 1-strut
  • 2-retaining ring
  • 3-spring
  • 4-swivel arm
  • 5-pin shaft
  • 6-bracket
  • 7-limit switch

Fig. 4 Structural diagram of rotary safety bolt

Rotate the column (1) to the outside of the column through the rotating arm (4) and fix it firmly. The limit switch (7) sends a message, and the press can enter the working mode normally;

When repairing the mold or the press, screw the strut (1) into the working table area, press the strut (1) onto the working table by the weight of the slider and the mold, and the strut (1) supports the weight of the sliding block, the mold, piston rod, plunger rod and other moving parts.

The limit switch (7) does not send a signal, and the press cannot enter any working mode to ensure the safety of the operator.

The safety bolt device is generally set at the diagonal front of the column, which is convenient for rotation operation.

It is also set at the inner side of the column, and the structural forms are relatively diverse.

The structural form of the safety bolt can be reasonably selected according to the specific situation.

Safety claw device

Fig. 5 is a schematic diagram of the safety claw device.

Schematic diagram of safety claw device

  • 1-rack
  • 2-flat key
  • 3-limit switch
  • 4-jaw
  • 5-bracket
  • 6-cylinder
  • 7 – connecting rod
  • 8-spring

Fig. 5 Schematic diagram of safety claw device

The rack (1) is positioned by the flat key (2), and is installed and fixed on the side of the sliding block by screws and washers;

The claw (4) is assembled on the support (5) through the pin shaft, the oil cylinder (6) is installed and fixed on the support (5) through screws and washers, and the claw (4) is connected with the piston rod of the oil cylinder (6) through connecting rod (7), spring (8), etc.

The bracket (5) is installed and fixed on the inner side of the column by screws and washers.

The oil cylinder (6) has a rod cavity to feed oil, which drives the claw (4) to release, the limit switch (3) sends a signal, and the slider can move downward;

The oil cylinder (6) has a rod cavity for oil discharge, the spring (8) resets the claw (4), locks the rack (1), and firmly locks the slider.

The limit switch (3) does not send a signal, and the slider cannot move downward to ensure the safety of the operator.

Sitema unit

A sitema safety locking device can be effectively used to prevent the sliding block from falling off, as shown in Fig 6. Sitema (3) is installed and fixed on the upper plane of the upper beam through the connecting plate (4), screws, washers, etc., the pull rod (1) passes through sitema (3) and the upper beam and is connected with the sliding block through nuts (6) and flanges (5), and the protective cover (1) is installed on the upper surface of sitema (3).

Sitema safety locking device

  • 1 – protective cover
  • 2-tie rod
  • 3-setma
  • 4-connecting plate
  • 5-flange
  • 6-nut

Fig. 6 Sitema safety locking device

Sitema safety clamping device is used for personnel protection and accident protection in case of load-bearing machine failure when improving the connection between load and tool, such as accident protection in case of leakage or failure of the hydraulic or pneumatic pressure system.

The safety clamping device can keep the slider in any position within the stroke in a mechanically stable and absolutely reliable manner.

The design principle of self reinforcing clamping device ensures a very high level of safety.

As shown in Fig. 7, the pull rod (1) is surrounded by several wedge-shaped clamping jaws (3), and each wedge-shaped clamping jaw is surrounded by a frame (2) assembled with a guide rail lining (4) and a drive lining (5).

Structural principle diagram of Sitema

  • 1-tie rod
  • 2-rack
  • 3-wedge claw
  • 4 – guide rail lining
  • 5 – drive lining
  • 6-spring
  • 7 – holding position
  • 8 – piston

Fig. 7 Structural principle diagram of Sitema

When the pressure (P) acts on the piston (8), the spring (6) is compressed and the wedge claw is held in a rising position so that the pull rod (1) can move freely.

When the pressure is unloaded from the piston (8), the safety clamping device takes effect immediately, the spring acts on the wedge clamping claw (3), and then locks the pull rod (1), so as to fix the load device.

However, the clamping force is not generated until the pull rod (1) is moved by the load force.

Due to the self-reinforcement of the static friction force on the pull rod (1), the wedge-shaped clamping claw (3) moves to the clamping position and stops at the clamping position (7) after moving the distance “e” (about 5 ~ 15mm, depending on the design diameter).

This motion is called phase A on the force/path.

Conclusion

The above briefly discusses several common safety measures to prevent the sliding block of the hydraulic press from falling off.

Of course, there are many other safety protection measures for the hydraulic press, such as setting a safety light curtain at the front and rear of the fuselage, setting two hand operation buttons, emergency stop buttons, interlocking function of the hydraulic and electrical system, etc., which will not be described in detail here.

At present, the safety protection measures of the hydraulic press are basically perfect, which meets the safety requirements of social humanization development for hydraulic press.

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