Die casting machine with piston positioning control

• US 3,956,973 A
• Filed: 01/02/1974
• Issued: 05/18/1976
• Est. Priority Date: 07/11/1972
• Status: Expired due to Term

• Current Assignee: The Basic Aluminum Castings Co.
• Original Assignee: The Basic Aluminum Castings Co.
• Inventors: Pomplas, Leonard J.
• Primary Examiner(s): Schwadron, Martin P.
• Assistant Examiner(s): Hershkovitz, Abraham
• Application Number:
  US05/429,485
• Time in Patent Office: 867 Days
• Field of Search: 91/1, 91/363 R, 340/195, 340/196, 340/199, 92/5 R, 92/5 L, 92/223, 92/248, 74/DIG. 4, 74/DIG. 7, 116/124 A, 116/124 D
• US Class Current: 92/5.00R
• CPC Class Codes: B22D 17/32 Controlling equipment
• CPC Class Codes: B29C 45/76 Measuring, controlling or regulating measuring in general G01; controlling or regulating in general G05
• CPC Class Codes: B30B 15/18 controlling the reciprocating motion of the ram
• CPC Class Codes: F01B 31/12 Arrangements of measuring or indicating devices warning apparatus F01B25/26; measuring instruments or the like per se G01
• CPC Class Codes: F15B 15/2846 using detection of markings, e.g. markings on the piston rod
• CPC Class Codes: F15B 15/2861 using magnetic means
• CPC Class Codes: G01D 5/2013 by a movable ferromagnetic element, e.g. a core G01D5/2033 takes precedence
• CPC Class Codes: G01P 15/16 by evaluating the time-derivative of a measured speed signal
• CPC Class Codes: G01P 3/50 for measuring linear speed G01P3/56 takes precedence

Abstract

A die casting machine has a piston rod connected to its main ram for positioning the ram as the piston rod extends and retracts from a cylinder. A control system is provided which directly senses the position, velocity and acceleration of the piston rod. A smooth continguous outer surface is formed on the piston rod. Magnetic and non-magnetic materials spaced alternately axially along the rod provide a series of magnetic discontinuity fields along the piston rod. Transducers are provided to sense the magnetic discontinuities as the piston rod moves to provide signals indicative of the position, velocity and acceleration of the piston rod. An electrohydraulic servo valve is electrically connected to the transducers and to a control console for moving the piston rod and for recording its position, velocity, and acceleration.

Claims

1. A cylinder and reciprocating piston combination, comprising:

a. a cylinder body defining a chamber and having an open end;

b. a piston movable in said chamber in response to a supply of pressurized fluid to said chamber;

c. a piston rod connected to said piston for movement therewith relative to said body and extending through said open end;

d. said piston rod being formed from a first magnetic material having a peripheral surface including a plurality of axially spaced groove portions said peripheral surface and said groove portions being covered by a second non-magnetic material which provides a smooth outer wear surface for said piston rod;

e. packing means carried by said body and forming a seal circumferential of said wear surface to inhibit the escape of pressurized fluid through said open end; and

f. transducer means positioned near said wear surface, said first and second materials cooperating to define a magnetic discontinuity means for cooperating with said transducer means to produce electrical pulse signals for indicating the passage past said transducer means of one of the groove portions in said peripheral surface.

2. The apparatus of claim 1 wherein said second material fills the groove portions in said peripheral surface.

3. The apparatus of claim 1 wherein said first material is a ferrous metal and said second material is a substantially non-ferrous metal.

4. The apparatus of claim 3 wherein said second material is a chrome coating.

5. The apparatus of claim 1 wherein threads form said groove portions.

6. The apparatus of claim 1 wherein said second material extends at least partially into the groove portions.

7. The apparatus of claim 1 wherein said transducer means includes at least two transducer units mounted at axially spaced positions along the path of movement of said piston rod to provide successive variations in electrical signals when said piston rod moves relative to said transducer units.

8. A cylinder and reciprocating piston combination, comprising:

a. a cylinder body defining a chamber and having an open end;

b. a piston movable in said chamber in response to a supply of pressurized fluid to said chamber;

c. a piston rod connected to said piston for movement therewith relative to said body and extending through said open end;

d. said piston rod having a substantially cylindrical core formed from a ferrous metal having a circumferentially grooved peripheral surface, said peripheral surface being covered by a substantially non-ferrous metal coating which extends at least part way into the grooves of said peripheral surface and which extends across peripheral core portions between such grooves to define a smooth, substantially cylindrical outer wear surface extending coaxially of said core;

e. packing means carried by said body and forming a seal circumferential of said wear surface to inhibit the escape of pressurized fluid through said open end; and

f. transducer means positioned near said wear surface, said ferrous metal core and said non-ferrous metal coating cooperating to define a magnetic discontinuity means for cooperating with said transducer means for providing a variation in an electrical signal indicative of the passage past said transducer means of one of the grooves in said peripheral surface.

9. The apparatus of claim 8 wherein said non-ferrous metal is chrome.

10. The apparatus of claim 8 wherein threads form said grooved peripheral surface.