Concrete block molding machine having continuously driven vibrating shaft mechanism which can be programmably vibrated and method of programmably vibrating such machines

In a concrete block molding machine having a vibratible frame with a mold box incorporating molding cavities therein for a concrete mix which is to be densified in said cavities;

• the combination comprising:
• a. at least one vibration causing shaft assembly supported on said frame to impart vibrating motion thereto;
• b. bearings on said frame for journaling the ends of said shaft assembly;
• c. drive means connected with said shaft assembly for driving said shaft assembly in continuous rotation;
• d. said shaft assembly comprising opposite end stubs having circumferential portions eccentric to the axis of rotation of said shaft assembly and a circumferentially movable balancing mass mounted for rotation on said stubs for movement between circumferential positions in which said mass substantially balances the centrifugal force imparted eccentrically by said eccentric portions of said stubs to produce a null level of vibration and a second position in which densifying vibration is produced, said mass in the first position being substantially 180.degree. opposite said eccentric portions on said stubs;
• e. one of said stubs being recessed to provide a piston cylinder with a piston therein;
• f. means interconnecting said piston and mass to produce rotary motion of said mass relative to said stubs with axial movement of said piston in said cylinder, to move said mass from a balancing position in relation to said eccentric portions toward a radially offset position;
• g. spring means of predetermined rate opposing axial movement of said piston and operative to move said piston in an opposite direction to restore said piston and mass when pressure on said piston is released;
• h. fluid pressure supply means for supplying fluid under a predetermined pressure to one end of said piston in opposition to said spring means to control the axial position of said piston and consequentially the circumferential position of said mass relative to said eccentric portions of said stubs via said spring;
• i. said spring means including a coil spring, and said piston and said opposite stub being recessed to provide opposing spring seats for the opposite ends of said coil spring;
• and
• j. said shaft assembly including a radially inner shaft portion, and said stubs and piston being bored to receive said shaft portion;
• said piston and coil spring being in a surrounding position relative to said shaft portion, and said drive means being connected to said inner shaft portion to impart rotative driving force thereto.

A method of molding concrete blocks by programmably vibrating a concrete block molding machine having a vibratible frame with a mold box incorporating at least one molding cavity for a concrete mixture which is to be densified in said cavity;

• at least one vibration-causing shaft assembly supported on said frame to impart vibrating motion thereto;
• bearings on said frame for journaling the ends of said shaft assembly;
• a drive connected with said shaft assembly for driving said shaft assembly in continuous rotation;
• said shaft assembly mounting a first portion eccentric to the axis of said shaft assembly and a circumferentially movable balancing mass mounted for relative rotation with said first eccentric portion on said shaft assembly between circumferential positions in a first of which said mass substantially balances the centrifigal force imparted eccentrically by said first eccentric portion to produce a null level of vibration and a second position in which densifying vibration is produced, said mass in said first position being substantially 180.degree. opposite said first eccentric portion;
• said shaft assembly having a cylinder with a piston thereon, one of which is axially movable relative to the other;
• means interconnecting said axially movable one of said cylinder and piston with said mass to produce rotary motion of said mass in one circumferential direction relative to said first eccentric portion to move said mass from a balancing position relative to said first eccentric portion toward a radially offset position;
• spring means of predetermined rate opposing axial movement of said movable one of said piston and cylinder and operative to move it in an opposite direction to restore said mass;
• and fluid pressure supply means for supplying fluid under a predetermined pressure to said cylinder in opposition to said spring means to control the axial position of said movable one of said piston and cylinder and consequentially the circumferential position of said mass relative to said first eccentric portion via said spring means, said method comprising the steps
• a. supplying said concrete mixture to said molding cavity for densification during a predetermined time period of a cycle;
• b. continuously driving said shaft assembly at a predetermined speed;
• c. cyclically over said predetermined time period successively introducing fluid under a predetermined variable pressure to said cylinder and piston in opposition to the force exerted by said spring means to relatively move said mass and said first eccentric portion from substantially a position of 180.degree. circumferential opposition in which the vibration produced is substantially null to a substantial vibration producing position out of substantial centrifugal balance to produce densifying vibration having an intensity during a predetermined first portion of said time period in which said mold cavity is supplied with said concrete mixture to be molded;
• d. thereafter introducing additional fluid under pressure to said cylinder and piston in opposition to said force exerted by said spring to relatively move said mass and said first eccentric portion to a position further removed from said position of 180.degree. circumferential opposition in which said densifying vibration produced is of greater intensity during a second portion of said time period than during said first portion of said time period, and in which said second portion of said time period a final densifying of said concrete mixture supplied to said mold cavity occurs to produce a molded product;
• and;
• e. then removing said fluid introduced to said cylinder and piston to restore said mass to a position of 180.degree. circumferential opposition such that said vibration produced is substantially null and stripping said molded product from said mold box during a third portion of said predetermined time period of said cycle.