To provide an attachment for falling weight type crushing preventing damage to a hydraulic cylinder by an excessive reaction acting thereto when locking the hook of a chuck device to the locking part of a ram by extension of the hydraulic cylinder.

The ram 16 is vertically movably contained in a casing 10 attached to the working arm of a self-propelled working machine. The hydraulic cylinder 20 drawing up the ram 16 is mounted to an upper part of the casing 10. A chuck releasing rod 44 releasing chuck by the hook 34 of the chuck device 21 is provided at an upper part of the casing 10. The chuck device 21 is vertically movably attached at the lower end of a piston rod 20b of the hydraulic cylinder 20. A press spring 53 is provided between the piston rod 20b and chuck device 21.

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