The present invention provides a melamine resin foam comprising a foam body obtained by foaming a resin composition composed mainly of a melamine-formaldehyde condensate and a blowing agent, and hydrophobic component coated on said foam body. This melamine resin foam is improved in fragility and water absorbability and in which the drawbacks of the prior art have been alleviated.

A retractable pusher dog for an overhead power and free conveyor system is provided. The retractable pusher dog comprises a body portion formed from a rectangular cylinder with a spring and pusher member disposed within the cylinder. When a force greater than the static spring force is applied to the pusher member, the pusher member retracts into the body portion thus reducing the overall height of the pusher dog. Due to its self-actuating retraction, the retractable pusher dog of the subject invention requires no modifications to the powered and free rails or to the load trolleys. The retractable pusher dog will prevent jamming of load trolleys by allowing the pusher dog to bypass an off-timed load carrier, introduced from a different powered rail, until it is properly aligned on the main rail. Also, the body plates of the pusher dog facilitates coupling the pusher dog to the drive chain without disassembling the drive chain thus reducing downtime of the conveyor system and labor costs.

A powered pushing unit transfers ads no greater than a predetermined magnitude in one direction along the length of a load transfer system. The pushing unit includes a frame and a source of power for moving the pushing unit back and forth along the length of the load transfer system. A dog for engaging a load is pivotally mounted with respect to the frame. A restricting mechanism applies a load engaging force to hold the dog at a load transfer range of positions until the load is greater than the predetermined magnitude. A toggle joint is mounted between the dog and the frame. The toggle joint forms an angle in a first angular direction to lock the dog in a load engaging position during engagement of a load under the predetermined magnitude. The toggle joint further shifts to form an angle in a second angular direction upon engagement of a load in excess of the predetermined magnitude, thereby allowing the dog to pivot away from the load which is in excess of the predetermined magnitude. When pivoting away from and passing beneath the toad, the dog exerts a force against the load that is substantially less than the predetermined magnitude. A toggle force mechanism returns the toggle joint to a first angular direction after the dog passes the load.

A power and free conveying system includes a track assembly having a power track and a free track spaced vertically from the power track, a power trolley supported on the power track for movement therealong and a free trolley supported on the free track for movement therealong. The free trolley includes a moveable holdback dog engageable and disengageable with the power trolley. The free trolley includes a retractable dog having a first position engageable with the power trolley and a second position disengageable with the power trolley and engageable with the holdback dog to completely disengage the free trolley from the power trolley upon engaging another one of the free trolley. The track assembly includes a C-shaped first side support member having an upper transverse end connected to the power track and a lower transverse end connected to the free track and a C-shaped second side support member opposite and spaced from the first side support member having an upper transverse end connected to the power track and a lower transverse end connected to the free track.