Abstract:
A press with a press lock includes a press frame, a press ram slidably connected with the press frame, a rack fixedly connected with the frame, a pinion block connected with the ram, a pinion actuator operatively interconnected between the ram and the pinion block, and a control operatively connected with the pinion actuator. The press frame defines a stroke length and the press ram slides along the stroke length. The rack also extends along the stroke length, and the pinion block slides generally perpendicular to the stroke length, between open and closed positions of the press lock. The pinion block is also substantially fixed with the ram, relative to movement in a direction along the stroke length. The pinion block further engages the rack in the closed position, fixing the ram at a predetermined location along the stroke length, and disengages the rack in the open position, not inhibiting sliding of the ram along the stroke length. Finally, the pinion actuator slides the pinion block between the open and closed positions.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS  
       [0001]    This is a continuing application of co-pending U.S. Non-provisional Patent Application Ser. No. 60/178,439, entitled Press Lock and filed on Jan. 27, 2000, by Charles J. Finkler, now co-pending, the disclosure of which is incorporated here by reference. 
     
    
     
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
         [0002]    Not Applicable.  
         BACKGROUND OF THE INVENTION  
         [0003]    The invention relates to powered presses. More specifically, the invention is a lock that is useful to improve safe operation and maintenance of powered presses, such as pneumatic and hydraulic presses, which are commonly used in manufacturing stamped parts and the like.  
           [0004]    Many components or parts of assembled products are stamped in a press die from stock material. Corresponding die halves are mounted in the press and used to cut or shape or otherwise form components. One die half is mounted on a bed of the press while a mating die half is mounted on a traveling ram. The ram strokes back and forth, opening and closing the die. The ram stroke is commonly, though not always, oriented generally vertically.  
           [0005]    The one die half remains stationary on the press bed and the mating die half travels with the ram. The mating die half is pulled away from the one die half when the ram strokes back to the open position. A selected piece of material is positioned over the one die half and the mating die half is pressed to the one die half when the ram strokes forth to the closed position, conforming the material to the die.  
           [0006]    From time to time, the press is opened for access to the die halves. This may be for any number of reasons, including maintenance, repair, or changing of the die halves, for example. It is inherent in the design of a press that it is constructed to close the die halves together with great force. Thus, some auxiliary or accessory device is required to hold the die halves open. Perhaps the simplest and most common method of holding a press open is merely blocking the ram open by interposing an obstruction, such as a jack or blocking, for example, between the press bed and ram. This is neither efficient or certain to be used, however. One having even a passing knowledge of presses will understand the danger to an operator if the operator reaches between the die halves when the press is not positively locked in the open position.  
         BRIEF SUMMARY OF THE INVENTION  
         [0007]    Accordingly, a press with a press lock of the invention includes a press frame, a press ram slidably connected with the press frame, a rack fixedly connected with the frame, a pinion block connected with the ram, a pinion actuator operatively interconnected between the ram and the pinion block, and a control operatively connected with the pinion actuator. The press frame defines a stroke length and the press ram slides along the stroke length. The rack also extends along the stroke length, and the pinion block slides generally perpendicular to the stroke length, between open and closed positions of the press lock. The pinion block is also substantially fixed with the ram, relative to movement in a direction along the stroke length. The pinion block further engages the rack in the closed position, fixing the ram at a predetermined location along the stroke length, and disengages the rack in the open position, not inhibiting sliding of the ram along the stroke length. Finally, the pinion actuator slides the pinion block between the open and closed positions.  
           [0008]    These and other features, objects, and benefits of the invention will be recognized by one having ordinary skill in the art and by those who practice the invention, from the specification, the claims, and the drawing figures. 
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0009]    [0009]FIG. 1 is a fragmentary lower perspective view of a press, showing a press lock according to the invention;  
         [0010]    [0010]FIG. 2 is a fragmentary enlarged detail of a left lock assembly of FIG. 1;  
         [0011]    [0011]FIG. 3 is a fragmentary partial cross-sectional view along line III-III of FIG. 2, showing the lock assembly closed;  
         [0012]    [0012]FIG. 4 is the view of FIG. 3, showing the lock assembly open;  
         [0013]    [0013]FIG. 5 is a fragmentary partial cross-sectional front elevational view of the left lock assembly, showing the lock assembly closed;  
         [0014]    [0014]FIG. 6 is the view of FIG. 5, showing the lock assembly open;  
         [0015]    [0015]FIG. 7 is a fragmentary elevational view of the pinion block engaging the rack;  
         [0016]    [0016]FIG. 8 is a fragmentary enlarged cross-sectional detail of the teeth of the pinion block and the rack engaging;  
         [0017]    [0017]FIG. 9 is a fragmentary enlarged cross-sectional detail of a pinion block float pin; and  
         [0018]    [0018]FIG. 10 is a schematic representation of an electrical control circuit of the invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]    A press lock of the invention is most preferably used with a press that has a press frame  20  and a press ram  22 . The frame  20  defines a stroke length and the ram  22  cycles back and forth along the stroke length. The press lock has a lock rack  30 , a pinion block  32 , a pinion actuator  34 , and a lock control.  
         [0020]    The lock rack  30  is preferably a generally linear array of teeth  36 , and is fixed relative to the press frame  20  in an orientation that is generally parallel with the stroke length (FIGS. 1, 2, and  7 ). While the rack  30  may be directly attached to the frame  20 , the rack is more preferably mounted to a rack base  38  that may be directly attached to the frame (FIGS. 3 and 4). In this way, the rack  30  may be removably mounted to the rack base  38 , which may facilitate initial installation and subsequent maintenance and repair. One having ordinary skill in the art will understand that the rack base  38  is not subject to wear like the rack  30 , which will be engaged by the pinion block  32 , which may cause wear or other damage over time. Thus, the rack  30  is preferably made of a hardened material, such as AISI 1215 carbon steel, while the rack base  38  may be made of a more standard mild steel. The rack base  38  then provides strength and support to the rack  30 , especially when mounted to the press frame  20 , with a less expensive material that is more easily formed than a harder material, which is preferred for the rack.  
         [0021]    More particularly the rack  30  may be a length of about 1.5 inch (38 mm) square stock with the teeth  36  formed with a #8 pitch into one side, as is available from Browning Manufacturing Division of Emerson Electric Co., Maysville, Ky., as part 4YSR8X. The length of the rack  30  that is required will vary from installation to installation, depending upon the actual length of the press stroke. A formula for the length of the rack  30  would then be at least the stroke length plus the length of the pinion block  32 . This length of rack will allow full length engagement of the pinion  32  with the rack  30  along the length of the press ram stroke.  
         [0022]    The pinion  32  is substantially a corresponding short length of the rack material. A ten inch (254 mm) length of the pinion block  32  can provide a press lock holding strength of about twenty-two tons, for example, with only one lock assembly  40 , which comprises one each of the rack  30 , pinion block  32 , and pinion actuator  34 . The lock assemblies  40  are most preferably mounted in opposing pairs, however, as shown at the left and right sides in FIG. 1.  
         [0023]    The pinion  32  is mounted on the ram  22 , and so travels with the ram along the stroke path, and along the lock rack  30 . The pinion  32  is oriented generally parallel with the rack  30  and slides generally perpendicular to the length of the rack and the stroke path. More specifically, the pinion  32  slides into engagement with the lock rack  30  in the lock closed position (FIGS. 3 and 5). The corresponding teeth  36  of the pinion  32  and the rack  30  register and mesh in the closed position, thereby preventing sliding of the pinion along the rack and in turn holding the ram  22  fixed relative to the press frame  20 .  
         [0024]    As with the rack  30 , the pinion  32  is preferably mounted indirectly on the ram  22 . A pinion block assembly includes the pinion actuator  34 , a pinion guide  42 , a pinion base  44 , and the pinion  32  (FIGS. 3 and 4). The pinion guide  42  is a generally U-shaped open sided frame or housing member that defines a channel through which the pinion  32  slides (FIGS. 1 and 2). The pinion guide  42  fixes the pinion  32  from moving in a direction along the stroke path relative to the ram  22 . Yet, the pinion guide  42  allows sliding of the pinion  32  into and out of engagement with the lock rack  30 , in a direction generally perpendicular to the stroke path.  
         [0025]    The pinion  32  does not slide through the guide by itself. Rather, the pinion  32  is supported and strengthened by mounting the pinion to the pinion base  44 , like the rack  30 , which is discussed in greater detail above. Thus, the pinion base  44  is easily formed from a standard, mild steel, while the pinion  32  is formed of a hardened carbon steel. The pinion  32  and the rack  30  are aligned with and oriented relative to one another for full engagement of their respective teeth  36  along the width of the teeth, in the closed lock position. During operation of the press, it is probable that the press will be stopped and the ram  22  will coast to a stop at a location along the stroke path where the respective teeth  36  of the pinion  32  and the lock rack  30  are not aligned where they will register and mesh one with the other.  
         [0026]    Thus, some degree of float should be provided for one of the pinion  32  and the rack  30 , preferably the pinion. The pinion  32  is, therefore, provided with extra clearance with the pinion guide  42  to float about half a tooth pitch along the length of the pinion and lock rack  30 . A float pin and bias spring assembly  46  as is known to one having ordinary skill in the art, is also provided between the pinion  32  and the pinion base  44  for this purpose (FIGS. 5, 6, and  9 ).  
         [0027]    One having ordinary skill in the art will know that a load ‘L’ applied to the engaged pinion  32  and rack  30  in a direction along the lengths of the pinion and rack (FIG. 8), will create a force ‘R’ that is generally perpendicular to the toothed interface of the pinion and rack and that will act to disengage the pinion and the rack. Thus, the toothed interface of the pinion  32  and rack  30  is most preferably not generally perpendicular to the direction of the pinion sliding motion. Rather, the pinion  32  and rack  30  are rotated so the direction of the pinion sliding motion intersects the toothed interface of the pinion and rack at an angle of about ten to twenty degrees (FIGS. 3 and 4). This angle range minimizes the force required of the pinion actuator  34  to retain the pinion  32  in locked or closed engagement with the rack  30 , without excessive required travel of the pinion between closed and open positions of the lock. Of course the angle may be increased with associated increase of the required retention force. The required retention force is reduced by about two thirds when the direction of the pinion sliding motion intersects the toothed interface of the pinion  32  and rack  30  at an angle of about ten to twenty degrees, however.  
         [0028]    With the pinion  32  and rack  30  so rotated, the majority of the disengaging force ‘R’ is directed generally perpendicular to both of the direction of the pinion sliding motion and the direction of the press stroke. Thus, the pinion guide  42  is adapted to overlay not only the pinion  32  and the pinion base  44 , but also the lock rack  30  and the rack base  38  (FIGS. 3 and 4). So constructed and securely fastened to the ram  22 , the pinion guide  42  further holds the pinion  32  engaged with the lock rack  30  in the lock closed position.  
         [0029]    The pinion actuator  34  is most preferably a double acting pneumatic cylinder, such as an about two inch (51 mm) diameter cylinder with an about three inch (76 mm) stroke, as is commonly available from Nogren (FIGS.  1 - 6 ). For complete actuation control, the cylinder  34  should be equipped with a pair of magnetic switches  50  and  52  or the like. The switch  50  at the front of the cylinder  34  indicates when the cylinder piston and rod  54  are extended. The switch  52  at the back of the cylinder  34  indicates when the cylinder piston and rod  54  are retracted. The pinion actuator cylinder  34  is pivotally connected between the ram  22  and the pinion  32  with a pivot mount  56  to the ram and a pivotable connection with the pinion base  44 . With the flexibility of pivotally connecting the cylinder  34  between the ram  22  and the pinion  32 , the pinion can be allowed to float a small distance to accommodate a situation when the pinion and the lock rack teeth  36  are aligned crown to crown and one, preferably the pinion, must move a distance of about half a tooth pitch in order to mesh the teeth together and engage the pinion with the rack  30 .  
         [0030]    The lock control includes the magnetic switches  50  and  52  on the cylinder  34 , that indicate the extended or retracted condition of the cylinder piston and rod  54 . Redundant micro switches  60  and  62  are also provided. While the micro switch  60  indicates when the pinion  32  is extended or engaged with the rack  30  in the lock closed position, the micro switch  62  indicates when the pinion  32  is withdrawn or disengaged from the rack  30  in the lock open position. Thus, not only is the cylinder position accounted for, but the pinion position is also accounted for. Further, a pneumatic pressure sensing switch is provided to assure adequate operating air pressure.  
         [0031]    In operation, an operator will manipulate the standard press controls to start the press. The press lock control is operatively interconnected in sequence with the press control, so the press lock takes priority over the press operation. In the start sequence, the press is presumed stopped and the press lock closed. Thus, the pinion  32  is engaged with the lock rack  30 , so the micro switch  60  is closed. Also, pinion actuator cylinder piston and rod  54  are in the locked or extended position, so the magnetic switch  50  is closed. The pneumatic pressure sensing switch will open or be open if air pressure is insufficient for operating the press lock and will generally preclude press start up. When air pressure is adequate, above eighty pounds per square inch, for example, then the pinion actuator cylinder  34  is activated to retract the piston and rod  54 , withdrawing the pinion  32  from the lock rack  30 . As the pinion  32  is pulled back from the rack  30 , the micro switch  60  and the magnetic switch  50  open. The micro switch  62  and the magnetic switch  52  close when the lock opens with the pinion  32  and piston retracted, completing the standard press control circuit and allowing the press control circuit to proceed with start up in its normal course.  
         [0032]    The lock control is also preferably provided with a motion sensor at the press fly wheel. In shut down, then, the press control circuit proceeds to stop the press in its normal course until the fly wheel stops and the motion sensor activates the lock control. The micro switch  62  and the magnetic switch  52  are still closed with the lock open and the pinion  32  and piston retracted. The pinion actuator cylinder  34  is activated to extend the piston and rod  54 , extending the pinion  32  into engagement with the lock rack  30 . As the pinion  32  is pressed into the rack  30 , the micro switch  62  and the magnetic switch open  52  open, opening the standard press control circuit. The micro switch  60  and the magnetic switch  50  close when the lock closes with the piston and rod  54  extended and the pinion  32  engaging the lock rack  30 . The standard press control circuit is interrupted by the lock control with the micro switch  62  and the magnetic switch  52  open, so the press should not start unintentionally.  
         [0033]    It will be understood by one having ordinary skill in the art and by those who practice the invention, that various modifications and improvements may be made without departing from the spirit of the disclosed concept. Various indicators, including status lights may be provided at an operator&#39;s control panel, for example. Also, various relational terms, including left, right, front, back, top, and bottom, for example, may be used in the detailed description of the invention or in the claims only to convey relative positioning of various elements of the claimed invention. The scope of protection afforded is to be determined by the claims and by the breadth of interpretation allowed by law.