Patent Publication Number: US-2023136146-A1

Title: Linear-Actuated Press Machine Having Multiple Motors And Clutch System For Multi-Speed Drive Functionality

Description:
RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Application Ser. No. 63/261,453, filed Sep. 21, 2021, and U.S. Provisional Application Ser. No. 63/263,603, filed Nov. 5, 2021, each of which is herein incorporated by reference in its entirety. 
    
    
     COPYRIGHT 
     A portion of the disclosure of this patent document may contain material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent disclosure, as it appears in the Patent and Trademark Office patent files or records, but otherwise reserves all copyright rights whatsoever 
     FIELD OF THE INVENTION 
     The present invention relates to press machines for forming parts. More particularly, this invention relates to press machine that includes motors that are coupled to an actuator for driving the actuator in a linear direction at various speeds and with various torques. 
     BACKGROUND OF THE INVENTION 
     In a typical linear-actuated press, there are a pair of tools that are used to form a part. (e.g., a die used to bend a part). One tool in the pair of tools is typically stationary. The other tool moves in a linear fashion toward the stationary tool. The to-be-formed part is located between the pair of tools and is formed by the pressing force created by the moving tool. The linear motion of the moving tool is typically created by a motor that rotates a male-and-female screw mechanism that directly or indirectly couples the moving tool to the output shaft of the motor. 
     The moving tool in a linear-actuated press engages in linear movement in two directions. In the downward stroke, the moving tool is moved downwardly with no resistive force to the point in Which it engages the to-be-formed part. The tool then continues the downward movement as it engages the part to form it. In the upward stroke, the tool moves away from the now-formed part. The productivity of these machines (e.g., parts formed per unit time) is dependent on the speed at which the tool can be moved downwardly to engage the to-be-formed part and upwardly to move away from the formed part. This type of operation can be effectuated in smaller presses with fair productivity (e.g., 50 ton-presses or less) in that the same motor can deliver enough vertical speed to the moving tool and also enough torque to create the force necessary on the moving tool for forming the part. 
     However, in large presses (e.g., greater than 50-ton presses, such as a 100-ton press or more), the problem is that a motor cannot be commercially selected that delivers both the high-speed condition to advance the tool to the to-be-formed part and the high-torque condition necessary for forming the part. If the motor is chosen that is capable of delivering the high torque (i.e., to produce high force on the moving tool), its rotational speed and, hence, the vertical speed of the moving tool is limited. Thus, the machine&#39;s productivity is compromised because it takes too much time to advance the moving tool to the part and retract the tool from the formed part. 
     Consequently, large presses commonly utilize hydraulic actuators that can deliver the high forces for forming the part and do so with acceptable speed so as to have adequate productivity. However, there are several problems associated with hydraulic actuators, such as the temperature dependency of the working fluid and the messiness of hydraulic fluid that flows through various pumps, valves, and filters, often resulting in leaks of the fluid within the manufacturing facility. Furthermore, many large presses are driven by crankshafts that are critical components requiring significant bearings with tight tolerances and lubrications systems for preventive maintenance. Crankshafts for these high-force presses also require the use of a flywheels and counterbalance systems for creation of bearing journal clearances for lubrication, which that can also be problematic. Further, large presses using a crankshafts and flywheels often require to two or more connecting rods that attach to the ram slide and are subject to timing issues if they become twisted or bent. These crankshafts are subject to deformation when the mechanical press is under certain conditions, such as when they are overloaded or become stuck at bottom dead center. 
     The present disclosure provides for a linear-actuated press machine that delivers high forces (such as attainable in a hydraulic press) with the controllability and high speeds that increase productivity and without the problems associated with hydraulic presses. The linear-actuated press system also avoids the problems associated with high-force presses that use crankshafts for driving the press ram. 
     All these and other objects of the present invention will be understood through the detailed description of the invention below. 
     SUMMARY OF THE INVENTION 
     In one aspect, the present invention is directed to a press machine for forming a part, comprising a moveable press ram, an actuator, a first motor, and a second motor. The moveable press ram is for holding a tool that forms the part. The actuator moves the moveable press ram. The actuator includes a first male-female thread mechanism for producing a first linear movement of the moveable press ram and a second male-female thread mechanism for producing a second linear movement of the movable press ram. The first linear movement is a high-force linear movement condition and the second linear movement is a high-speed linear movement condition. The first motor drives the first male-female thread mechanism to produce the first linear movement. The second motor drives the second male-female thread mechanism to produce the second linear movement. 
     In another aspect, the present invention is a press machine for forming a part comprising a moveable press ram, an actuator, a first motor, and a second motor. The moveable press ram is for holding a tool that forms the part. The actuator moves the moveable press ram by use of at least one male-female thread mechanism for producing a linear movement of the press ram. The first motor drives the actuator to produce a high-force linear movement condition to the moveable press ram. The second motor drives the actuator to produce a high-speed linear movement condition to the moveable press ram. The first motor and second motor linearly move away from each other when the first motor is operational driving pressing ram. One way this is accomplished is by optionally mounting the second motor to the press ram such that it moves with the moveable press ram. 
     In a further aspect, a press machine for forming a part comprises a moveable press ram, an actuator, a first motor, and a second motor. The moveable press ram holds a tool that forms the part. The actuator moves the moveable press ram. The actuator includes a first male-female thread mechanism for producing a first linear movement of the moveable tool and a second male-female thread mechanism for producing a second linear movement of the movable press ram. The first linear movement is a high-force linear movement condition and the second linear movement is a high-speed linear movement condition. The first motor drives the first male-female thread mechanism to produce the first linear movement. The second motor for driving the second male-female thread mechanism to produce the second linear movement. 
     In another aspect, the invention is a method of operating a linear-actuated press machine for forming a part. The press machine comprises a first motor, a second motor, a linear actuator having a first male-female thread mechanism and a second male-female thread mechanism, and a tool coupled to the linear actuator. The method comprises (i) by use of the second motor and the second male-female thread mechanism, advancing the tool toward the part in a low-force and high-linear-speed condition, (ii) by use of the first motor and the first male-female thread mechanism, forming the part with the tool in a high-force and low-linear-speed condition, and (iii) after the part has been formed by the tool, retracting the tool from the part by use of at least one of the first motor and the second motor. 
     In another aspect, the invention is a press machine for forming a part comprises a moveable press ram, an actuator, a first motor system, a second motor system, and a belt system. The moveable press ram is for holding a tool that forms the part. The actuator moves the moveable press ram by use of a male-female thread mechanism for producing a linear movement of the moveable press ram. The actuator includes an actuator sprocket coupled to the male-female thread mechanism. The first motor system produces a high-force linear movement condition to the moveable press ram. The first motor system includes a clutch coupled to a first motor and a first motor sprocket coupled to the clutch. The second motor system produces a high-speed linear movement condition to the moveable press ram. The second motor system includes a second motor coupled to a second motor sprocket. The belt system couples the actuator sprocket, the first motor sprocket, and the second motor sprocket such that (i) operation of the first motor rotates the actuator sprocket, the first motor sprocket, and the second motor sprocket, and (ii) operation of the second motor rotates the actuator sprocket, the first motor sprocket, and the second motor sprocket. The clutch allows the first motor to partially or fully disengage from rotational movement of the first sprocket when the belt is being driven by the second motor. 
     In a further aspect, the invention is a method of operating a linear-actuated press machine for forming a part. The press machine comprises a first motor, a second motor, a linear actuator having a male-female thread mechanism, a tool coupled to the linear actuator, and a belt system coupling the first motor, the second motor, and the male-female thread mechanism. The method comprises (i) by use of the second motor and the belt system, advancing the tool toward the part in a low-force and high-linear-speed condition, (ii) while advancing the tool in the low-force and high-linear-speed condition, partially or fully disengaging the first motor from rotational movement caused by the belt system, (iii) by use of the first motor and the belt system, forming the part with the tool in a high-force and low-linear-speed condition, and (iv) after the part has been formed by the tool, retracting the tool from the part by use of the second motor. 
     In another aspect, the present disclosure is a method of operating a linear-actuated press machine for forming a part. The press machine comprises a first motor, a second motor, a linear actuator having a male-female thread mechanism, a press ram coupled to linear actuator and holding a tool, and a clutch coupled to the first motor. The method comprises (i) driving the linear actuator with the second motor to advance the press ram toward the part in a low-force and high-linear-speed condition, (ii) while advancing the press ram toward the part in the low-force and high-linear-speed condition, partially or fully disengaging the clutch so as to reduce the rotational movement on the first motor, (iii) driving the linear actuator with the first motor to form the part with the tool in a high-force and low-linear-speed condition, (iv) after the part has been formed by the tool, retracting the tool from the part by use of at least the second motor, and (v) while retracting the press ram from the part in a second low-force and high-linear-speed condition, partially or fully disengaging the clutch so as to reduce the rotational movement on the first motor. 
     In a further embodiment, a linear-actuated press machine for forming a part comprises a moveable press ram, an actuator, a first motor system, a second motor system, and a belt system. The moveable press ram holds a tool that forms the part. The actuator moves the moveable press ram by use of a male-female thread mechanism for producing a linear movement of the moveable press ram. The actuator includes at least one sprocket for driving the actuator. The at least one sprocket is coupled to the male-female thread mechanism for rotating the male-female thread mechanism. The first motor system produces a low-speed high-force linear movement to the moveable press ram via the actuator. The first motor system includes a first motor, a clutch operationally coupled to the first motor, and a first motor sprocket operationally coupled to the clutch. The second motor system produces a high-speed low-force linear movement to the moveable press ram via the actuator. The second motor system includes a second motor and a second motor sprocket operationally coupled to the second motor. The belt system couples the at least one actuator sprocket, the first motor sprocket, and the second motor sprocket. During the high-speed low-force linear movement of the second motor system to advance or retract the press ram relative to the part, the clutch is at least partially disengaged from the first motor to maintain a rotational speed of the first motor below a limit to reduce possible damage to the first motor. During the low-speed high-force linear movement of the first motor system to form the part, the clutch is operationally engaged to transfer high torque from the first motor to the linear actuator via the belt system. 
     In another embodiment, a press system for forming a part comprises a first linear actuator, a second linear actuator, a press ram, a high-speed motor, a first high-torque motor, a second high-torque motor, a first clutch, and a second clutch. The first linear actuator has a first male-female screw arrangement and a first actuator rod that is coupled to the first male-female screw arrangement. The first actuator rod undergoes linear movement in response to rotational movement of the first male-female screw arrangement. The second linear actuator has a second male-female screw arrangement and a second actuator rod that is coupled to the second male-female screw arrangement. The second actuator rod undergoes linear movement in response to rotational movement of the second male-female screw arrangement. The press ram is coupled to the first actuator rod and the second actuator rod. The press ram receives a tool for engaging and forming the part. The press ram undergoes movement toward or away from the part in response to the corresponding linear movement of the first and second actuator rods. The high-speed motor is coupled to the first male-female screw arrangement of the first linear actuator for providing a high-speed and low-force condition on the press ram. The high-speed motor is for advancing the press ram toward the part and retracting the press ram from the part. The first high-torque motor is coupled to the first male-female screw arrangement of the first linear actuator. The second high-torque motor is coupled to the second male-female screw arrangement of the second linear actuator. The first and second high-torque motors provide a low-speed and high-force condition on the press ram for forming the part. The first clutch that is operatively coupled to the first high-torque motor. The second clutch that is operatively coupled to the second high-torque motor. While the high-speed motor is providing a high-speed and low-force condition on the press ram, the first and second clutches are partially or fully disengaging so as to reduce the rotational movement on the first and second high-torque motors. 
     In another aspect, the invention is a press machine for forming a part comprising a moveable press ram, an actuator, a first motor system, and a belt. The moveable press ram is for holding a tool that assists in forming the part. The actuator moves the moveable press ram by use of a male-female thread mechanism for producing a linear movement of the moveable press ram. The actuator includes an actuator sprocket coupled to the male-female thread mechanism. The first motor system produces a linear movement to the moveable press ram via the actuator. The first motor system includes a first motor, a multi-speed gearbox coupled the first motor, and a motor sprocket coupled to the multi-speed gearbox. The belt couples the actuator sprocket and the motor sprocket. The multiple-speed gearbox allows the first motor to provide the linear movement (i) in a low-force and high-linear-speed condition to advance and retract the press ram and (ii) in a high-force and low-linear-speed condition when the press ram is forming the part with the tool. 
     In all of the aspects of the present invention defined above, the press machine produces at least 100 tons of force on the press ram for forming the part. 
     Additional aspects of the invention will be apparent to those of ordinary skill in the art in view of the detailed description of various embodiments, which is made with reference to the drawings, a brief description of which is provided below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be described with greater specificity and clarity with reference to the following drawings, in which: 
         FIG.  1    illustrates a side view of one embodiment of a press machine that uses a linear actuator with two motors and two male-female threaded mechanisms for controlling the linear velocity and force of the press ram; 
         FIG.  2    illustrates a perspective view of the linear actuator for the press machine of  FIG.  1   . 
         FIG.  3 A  illustrates a side view of the actuator for the linear-actuated press in a fully retracted position. 
         FIG.  3 B  illustrates a side view of the actuator for the linear-actuated press in which the high-speed section is fully extended. 
         FIG.  3 C  illustrates a side view of the actuator of the linear-actuated press in which the high-speed section is fully extended and the high-force section is fully extended. 
         FIG.  4 A  illustrates a first side view the linear-actuated press in an open state. 
         FIG.  4 B  illustrates a second side view the linear-actuated press in an open state. 
         FIG.  4 C  illustrates the linear-actuated press in a closed state. 
         FIG.  5    illustrates the side view of an alternative embodiment of a linear-actuated press in which the press ram is moved by two motors linked to a single male-female threaded mechanism within the actuator. 
         FIG.  6    illustrates the side view of another alternative embodiment of a linear-actuated press in which the press ram is moved by a single motor linked to a single male-female threaded mechanism within the actuator. 
         FIG.  7 A  is a perspective view of an alternative linear actuator having two motors and a clutch system; 
         FIG.  7 B  is a side view of the alternative linear actuator of  FIG.  7 A . 
         FIG.  7 C  is an end view of the alternative linear actuator of  FIG.  7 A . 
         FIG.  7 D  is a top view of the alternative linear actuator of  FIG.  7 A . 
         FIG.  7 E  is a bottom view of the alternative linear actuator of  FIG.  7 A . 
         FIG.  8    is a perspective view of a four-post press machine that is driven by the linear actuator of  FIG.  7   . 
         FIG.  9 A  is a perspective view of a gib-style press machine that is driven by multiple linear actuators illustrated in  FIG.  7   . 
         FIG.  9 B  is a side view of the gib-style press machine of  FIG.  9 A . 
         FIG.  10    is a perspective view of a press machine that is driven by the single linear actuator illustrated in  FIG.  7    and multiple high-force, low speed linear actuators. 
         FIG.  11 A  is a perspective view of a further alternative linear actuator having two motors and a clutch system; 
         FIG.  11 B  is a side view of the alternative linear actuator of  FIG.  11 A . 
         FIG.  11 C  is a top view of the alternative linear actuator of  FIG.  11 A . 
         FIG.  11 D  is a bottom view of the alternative linear actuator of  FIG.  11 A . 
         FIG.  12    is a perspective view of a four-post press machine that is driven by the linear actuator of  FIG.  11   . 
     
    
    
     While the invention is susceptible to various modifications and alternative forms, specific embodiments will be shown by way of example in the drawings and will be described in detail herein. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. 
     DETAILED DESCRIPTION OF THE DRAWINGS 
     The drawings will herein be described in detail with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the broad aspect of the invention to the embodiments illustrated. For purposes of the present detailed description, the singular includes the plural and vice versa (unless specifically disclaimed); the words “and” and “or” shall be both conjunctive and disjunctive; the word “all” means “any and all”; the word “any” means “any and all”; and the word “including” means “including without limitation.” 
     As shown in  FIGS.  1  and  2   , a linear-actuated press machine  10  includes a first motor  12  and a second motor  14  (discussed further below) that are used to drive the press machine  10 . A gearbox  16  is coupled to the output shaft of the first motor  12  and the output of the gearbox  16  is used to drive a pulley and belt system  18 . The gearbox  16  allows for on-the-fly adjustments to the output of the first motor  12  before it is transferred to the pulley and belt system  18 . The output shaft of the gearbox  16  spins slower than the input shaft from the first motor  12  at a fixed ratio. (e.g., when there is a 12:1 ratio, the input shaft RPM divided by 12 is the output shaft RPM). The gearbox  16  also increases the torque output of the first motor  12  by a factor corresponding to the fixed ratio. Therefore, the output shaft speed (and torque) of the gearbox  16  is a variable that depends on the variable input shaft from the first motor  12 . 
     The pulley and belt system  18  is also coupled the linear actuator  20  by connection to the upper screw  21  of the actuator  20 . Consequently, when the first motor  12  is operational, the upper screw  21  of the actuator  20  rotates as well. The upper screw  21  is permitted to rotate, without moving vertically, and is supported by at least one thrust bearing  22 . The linear actuator  20  further includes a planetary roller nut  23  (or other threaded structure) that is threadably connected to the upper screw  21 . The planetary roller nut  23  is externally shaped to non-rotationally lock within the structure of the actuator  20 , such that rotation of the upper screw  21  causes vertical movement of the roller nut  23 . The roller nut  23  is integrated with or connected to an upper tube  24  of the actuator. Consequently, when the first motor  12  is operational, the upper screw  21  is rotating at a known speed and with a known torque, which causes the roller nut  23  and upper tube  24  to linearly move at a known linear velocity and with a known force. 
     At its lower end, the upper tube  24  is also rigidly connected to a lower screw  25 , such that any vertical movement of the upper tube  24  also causes corresponding vertical movement of the lower screw  25 . The upper tube  24  is also telescopically fitted within a lower tube  26  that is coupled to a lower planetary nut  27  (or other threaded structure). As the second motor  14  operates, it turns a second pulley and belt system  28  that then rotates the lower planetary roller nut  27 . As the lower planetary roller nut  27  rotates, it moves vertically along the fixed lower screw  25 . The second motor  14 , the second pulley and belt system  28 , the lower planetary roller nut  27 , and the lower tube  26  are all fixedly mounted on a platform  29 . This platform  29 , which is at the lower end of the actuator  20 , is mounted to the press ram  32 , which shown in more details in  FIGS.  4 A- 4 C , such that movement of the platform  29  leads to the movement of the press ram  32  (and any type of tool attached to the press ram  32 ), as discussed below. 
       FIGS.  3 A- 3 C  illustrate the operation of the actuator  20 , which causes the platform  29  to move and drive the press ram  32  that is shown in  FIGS.  4 A- 4 C .  FIG.  3 A  illustrates the actuator  20  in the fully retracted position, which would lead to the press machine  10  being in an opened position, as shown in  FIGS.  4 A and  4 B .  FIG.  3 B  illustrates the actuator  20  after the second motor  14  has been activated to cause high-speed rotation to the roller nut  27 , causing it to rotate around the lower screw  25  and linearly move downwardly in a high speed condition along with the lower tube  26  and the platform  29  (and hence the press ram  32  of  FIGS.  4 A- 4 C ). Because the press machine  10  is not forming the part in this phase of movement, the amount of torque required by the second motor  14  is low, allowing it to be designed for a high-speed movement to quickly advance the press ram  32  and attached tool to a point where the tool can begin forming the part. 
     Once the upper tool engages the part, the second motor  14  stops operation and the first motor  12  begins to operate, as shown in  FIG.  3 C . The first motor  12  causes the upper screw  21  to rotate at a lower speed, but with high-torque, which provides enough linear force on the upper tube  24  and the attached lower screw  25  that is fixedly attached to the upper tube  24 . The telescopic movement of the upper tube  24  within the lower tube  26  helps to stabilize the actuator  20  while high downward force is transferred by the platform  29  to the press ram  32  ( FIG.  4   ) and the attached upper tool. Thus,  FIG.  3 C  illustrates the actuator  20  in a fully extended position that was brought about by the first male-female thread mechanism associated with the first motor  12 , the second male-female thread mechanism associated with the second motor  14 , and the telescoping upper and lower tubes  24 ,  26 . 
       FIGS.  4 A- 4 C  illustrate the overall movement for the press  10  for forming a part in the press  10  based on the movements of the linear actuator  20  in  FIGS.  3 A- 3 C .  FIGS.  4 A and  4 B  are two side views of the press machine  10  in the opened position. The main body of the actuator  20  is mounted on the press crown  30 , which remains in a fixed position. The vertical movement of the platform  29  caused by the actuator  20  creates corresponding vertical movement of the press ram  32  to which it is attached. The press ram  32  holds an upper tool  42  and a press bed  34  may hold a lower tool  44 . The to-be-formed part (e.g., a piece of sheet metal) is placed between the upper tool  42  and the lower tool  44 . The press ram  32 , which is a four-post press, includes ram guide bushings  38  that slide along the ram guideposts  36  as the press ram  32  moves relative to the press bed  34 . 
     As shown in  FIG.  4 C , the upper tool  42  and the lower tool  44  are in close proximity with the now-formed part located between them when the press machine  10  is in the closed position. To transition to that closed position, the second motor  14  creates the high-speed linear movement of the press ram  32  and the upper tool  42  until the upper tool  42  is in an operational or engagement position immediately adjacent to or on the to-be-formed part, which is typically resting on the lower tool  44 . Then, the first motor  12  creates the high-torque linear movement (with slower linear speed) for the press ram  32  and the upper tool  42  to form the part with high force. After the part is formed, the second motor  14  operates in the reverse fashion to retract the upper tool  42  from the now-formed part with high linear speed, such that the formed part can be removed from the press machine  10  and a new unformed part can be inserted between the tools  42 ,  44  for forming in the next cycle. 
     Consequently, the linear force and linear speed of the press ram  32  is controlled by the operation of the first motor  12  and the second motor  14 . During the downward advancement stroke when the press ram  32  and upper tool  42  are moving toward the to-be formed part, the linear motion of the press ram  28  is preferably at a high speed since no force is yet needed for forming at this point. This is accomplished by operating the second motor  14  that drives the lower roller nut  27 , causing it to quickly rotate around the lower screw  25  ( FIG.  1   ). When the upper tool  42  begins to engage the part, more force is needed. In this working stroke, the second motor  14  stops movement and the first motor  12  begins to drive the upper screw  21  with lower rotational speed, but with high torque, to advance the upper nut  23  downwardly along the upper screw  21  with high force. To aid in the high-torque condition, the rotation of the lower roller nut  27  is held by a brake  48  to prevent the lower roller nut  27  from inadvertently advancing upwardly along the lower screw  25  when the large force is placed on the press ram  32 . In other words, the brake  48  ensures that the downward force on the press ram  32  does not result in any back-driving on the actuator  20  (i.e., unintended rotation of the lower roller nut  27  along the stationary lower screw  25  while higher force is being transferring to the press ram  32 ). 
     By using the two separate threaded screw mechanisms controlled by two separate motors  12  and  14 , different types of outputs to the press ram  32  can be supplied. The overall productivity of the press machine  10  can be increased because the moving upper tool  42  can be quickly advanced to the to-be-formed part and quickly retracted from the formed part by use of the second motor  14 , yet the high-force conditions (e.g., 100 tons, 125, ton, 150 tons, 200 tons, 300 tons, 400 tons) required to form the part can still be accomplished by the first motor  12 . In one embodiment for a 100-ton press, the second motor  14  can operate at about 1500 RPMs with a gear reduction of 3:1 to produce an output of about 500 RPMs. The first motor  12  also operates at about 1500 RPMs with a gear reduction of 25:1 to produce an output of about 60 RPMs. The actuator screws  21 ,  25  may have a lead in the range of about 12 mm per revolution to about 30 mm per revolution (such as about 25 mm (about 1 inch) per revolution), which dictates the linear velocity of the two male-female thread mechanisms of the actuator  20 . In one embodiment, the press ram  32  and upper tool  42  move at about 500 inches per minute when the second motor  14  is in operation and at about 60 inches per minute when the first motor  12  is in operation. In some embodiments, the second motor  14  includes a gear reduction in the range of 2:1 to 5:1. In some embodiments, the first motor  12  has a gear reduction in the range of 15:1 to 35:1. 
     Because the first and second motors  12  and  14  independently drive the two male-female threaded mechanisms of the linear actuator  20 , they can be different motors for producing the desired result on the actuator  20  (i.e., high-linear speed and low-force conditions, or low-linear speed and high-force conditions). And because the press machine  10  allows one motor to be decoupled from the other motor (i.e., one motor rotates while the other motor is still), the possibility of one motor producing an undesirable condition on the other motor (e.g., RPM outside the other motor&#39;s limits) or on other parts associated with the other motor (e.g., the pulley systems) is eliminated. One novel aspect of this press machine  10  is that the second motor  14  moves with the platform  29  (i.e., the second motor  14  moves vertically relative to the first motor  12 , as it rides along the platform  29 ) such that the second motor  14  remains in close proximity to the lower tube  26  and the lower nut  27  that it is controlling during operation, thereby limiting the size and weight of the various linkages (e.g., shafts, gears, pulleys, etc.) to these components that it drives. 
     Though the press machine  10  has been described by operation relative to a single actuator  20  that is driven by two motors  12  and  14 , the present invention contemplates a linear press with multiple actuators  20  driving a single press ram  32  and upper tool  42 , in which each of the multiple actuators  20  is associated with a pair of motors and the telescopic upper and lower tubes  24 ,  26 . In such a design for a linear press, more force can be transferred to the upper tool  42  by multiple actuators  20 , leading to more force for forming the part by use of the multiple actuators  20  acting in parallel. The present invention also contemplates a linear press in which the high-linear speed condition is produced by a single motor (in the position of the second motor  14 ) that drives the platform  29  downwardly with a high speed by providing power to multiple lower roller nuts  27  on the platform  29 , but has multiple upper motors that produce the high-force conditions in parallel, driving multiple actuators  20  acting on the press ram  32 . Further, the present invention contemplates multiple actuators  20  in which one actuator  20  includes a first motor for operation in the low-speed/high-force mode and a second motor for operation in the high-speed/low-force mode, and one or more additional actuators  20  having a motor for operation in the low-speed/high-force mode to deliver additional force as the part is being formed by the tool on the press ram  32 . In such a system, the one actuator  20  may include a clutch that limits the rotational speed of the low-speed/high-force motors when advancing and retracting the press ram  32  in the high-speed/low-force mode so as to ensure the low-speed/high-force motors are not damaged by the high speeds. 
       FIG.  5    illustrates the side view of an alternative embodiment of an actuator  120  for a linear-actuated press machine  10  in which the press ram  32  and the upper tool  42  are moved by a first motor  112  producing high-force conditions and a second motor  114  for producing high-speed conditions. Like the previous embodiments, each of the motors  112 ,  114  is capable of delivering a variable speed to actuator  120  and the actuator  120  is a screw-driven linear actuator, which includes either a rotating screw and a non-rotating nut that vertically moves, or a fixed screw and a rotating nut that vertically moves (e.g., as described above in the embodiment of  FIGS.  1 - 4   ). The actuator  120  includes an actuator rod  122  that moves due to this male-female threaded connection and is coupled to the press ram  32 . 
     The first motor  112  is coupled to a clutch  126 , which is coupled to a high-torque synchronous sprocket  128 . On the other hand, the second motor  114  is directly coupled to a high-speed synchronous sprocket  129 . The rotating portion of the male-female threaded connection of the actuator  120  is coupled to a synchronous drive sprocket  130 . A synchronous belt  135  is coupled to all three sprockets  128 ,  129 ,  130 , such that all three sprockets  128 ,  129 ,  130  are rotating in the same direction together. The three sprockets  128 ,  129 ,  130  may have different sizes, depending on the gear reduction desired among them. 
     In the embodiment of  FIG.  5   , the linear force and linear speed of the press ram  32  is controlled by the operation of the first motor  112  and the second motor  114 . During the downward advancement stroke when the press ram  32  and the attached upper tool  42  are moving toward the to-be formed part, the linear motion of the press ram  32  is preferably high speed since no force is yet needed for forming at this point. This is accomplished by operating the second motor  114  that drives the high-speed sprocket  129 , which thereby provides the driving force for the drive sprocket  130  and the screw-driven mechanism of the actuator  120  via the belt  135 , causing a high-speed movement of the actuator rod  122 . However, the high rotational speeds created by the second motor  114  would be too fast for the high-force motor  112 . Thus, the corresponding movement in the high-torque sprocket  128  in the high-linear speed condition from the second motor  114  in the actuator  120  is received by the clutch  126 , which spins without transferring the high rotational speeds to the shaft of the first motor  112 . In other words, the clutch  126  at least partially or fully disengages the shaft of the first motor  112  when the second motor  114  is operational. 
     When the upper tool  42  begins to engage the part that must be formed in the press  10 , more force is needed. In this working stroke, the second motor  114  stops operational as the first motor  112  becomes operational. When this occurs, the clutch  126  is fully engaged to the first motor  112 , causing the high drive torque from the first motor  112  to be transferred to the high-torque sprocket  128 , which is then transferred to the drive sprocket  130  of the actuator  120 . Thus, the actuator rod  122  advances downwardly at a lower speed, but with high force, to form the part. In the high-torque condition, the rotation of the high-speed sprocket  129  still occurs via the belt  135 , but it is less rotational speed than when the second motor  114  is in operation. Thus, the second motor  114  is being driven by the first motor  112  at the speed chosen for the first motor  112 . Of course, it is also possible to add more torque by powering the second motor  114  at the same speed dictated by the first motor  112  when forming the part. 
     In one embodiment for the press machine  110  of  FIG.  5   , the second motor  114  operates at about 1500 RPMs with a sprocket reduction of 3:1 to produce an input of 500 RPMs at the threaded-screw mechanism of the actuator  120 . The first motor  112  also operates at about 1500 RPMs with a gear reduction of 25:1 to produce an input of 60 RPMs at the threaded-screw mechanism of the actuator  120 . In some embodiments, the second motor  114  includes a sprocket gear reduction in the range of 2:1 to 5:1. In some embodiments, the first motor  112  has a sprocket gear reduction in the range of 15:1 to 35:1. Though each motor  112 ,  114  can spin at 1500 RPMs, due to the gear reduction ratios, rotating the second motor  114  at high levels (e.g., 1500 RPM) would cause the first motor  120  to rotate at much higher RPM levels (e.g., at 12,500 RPM) if the clutch  126  were not present, which would cause damage to the first motor  120 . 
     The actuator screw (not shown) in the actuator  120  of  FIG.  5    may have a lead in the range of about 12 mm per revolution to about 30 mm per revolution (such as about 25 mm (about 1 inch) per revolution), which dictates the linear velocity of the male-female thread mechanisms of the actuator  120 . In one embodiment, the moving upper tool  42  moves at about 500 inches per minute when the second motor  114  is in operation and at about 60 inches per minute when the first motor  112  is in operation. The clutch  126  may be, for example, an air clutch although other type of clutches may be suitable. Because the first and second motors  112  and  114  separately drive the male-female threaded mechanism of the linear actuator  120 , they can be different motors for producing the desired result on the actuator  120  (i.e., high-linear speed and low-force conditions, or low-linear speed and high-force conditions). 
       FIG.  6    illustrates the side view of another alternative actuator  220  of a press machine  10  in which the press ram  32  is moved by a single motor  212  linked to a single male-female threaded mechanism within the screw-driven linear actuator  220 . The motor  212  has a shaft that is linked to a multi-speed gearbox  230  that has an output shaft that drives a synchronous sprocket  232 . The synchronous sprocket  232  is coupled to another synchronous drive sprocket  234  for the actuator  220  via a synchronous belt  236 . The rotating portion of the male-female threaded connection of the actuator  220  is coupled to a synchronous drive sprocket  234 . 
     In the embodiment of  FIG.  6   , the linear force and linear speed of the press ram  32  is controlled by the operation of only the first motor  212 . During the downward advancement stroke when the press ram  32  and the upper tool  42  are moving toward the to-be formed part, the linear motion of the press ram  32  is preferably high since no force is yet needed for forming at this point. This is accomplished by operating the first motor  212  at a gear ratio, as dictated by the gearbox  230 , that drives the sprocket  232  at a high speed, thereby causing a high linear-speed movement of the actuator rod  222  via the drive sprocket  234  of the actuator  220  and the belt  236 . When the upper tool  42  begins to engage the part that must be formed, more force is needed. In this working stroke, the first motor  212  switches to a lower speed and the multi-speed gearbox  230  switches to a different gear needed to provide higher drive torque at the sprocket  232 , which is then transferred to the drive sprocket  234  of the actuator  220 . The multi-speed gearbox  230  includes an internal clutch to help switch between the gears. Thus, the actuator rod  222  advances downwardly at a lower speed, but with high torque, to form the part. When the part is fully formed, the motor  212  operates in the reverse direction and with a higher speed to retract the press ram  32  and the upper tool  42  from the formed part. In this retraction part of the cycle, the multi-speed gearbox  230  again shifts gears to help provide a high linear speed retraction. 
       FIGS.  7 A- 7 E  illustrate an alternative linear actuator  320  that is similar to the linear actuator  120  of  FIG.  5    that included the clutch  126 . The linear actuator  320  includes a first motor  312  and a second motor  314  that drive a ram for a press machine (exemplary press machines  400 ,  500 , and  600  are shown in more detail in  FIGS.  8 - 10    below), and a clutch  326  to protect the high-torque first motor  312  from the high rotational speeds that could otherwise damage the first motor  312  when the second motor  314  is advancing and retracting the press ram from the part. 
     Like the previous embodiments, the linear actuator  320  is preferably a screw-driven linear actuator that includes either a rotating screw and a non-rotating nut that vertically moves an actuator rod  322 , or a fixed screw and a rotating nut that vertically moves the actuator rod  322  (e.g., as described above in the embodiment of  FIGS.  1 - 4   ). The actuator  320  moves the actuator rod  322  due to the first motor  312  and the second motor  314  driving this male-female threaded connection via an actuator input shaft  350  that is coupled to the male-female threaded connection of the actuator  320 . The first motor  312  causes the actuator rod  322  to linearly move at a lower speed, but with a high force for forming the part in the press machine. The second motor  314  causes the actuator rod  322  to linearly move at a high speed, but with a lower force for advancing and retracting the press ram relative to the part when little force is needed (other than to move the weight of the press ram). In the illustrated embodiment, a platform  339  is used to mount various parts of the actuator  320 , the first motor  312 , the second motor  314 , and the belt system, which is described in more detail below. 
     The actuator input shaft  350  is driven by a belt system that includes a first belt system coupling the actuator input shaft  350  and a first motor drive shaft  352 , and a second belt system coupling the actuator input shaft  350  and a second motor drive shaft  354 . The first and second belt systems can include belts and various pulleys and/or sprockets that drive or are driven by the belts. As used in this patent application, the term “sprocket” includes both traditional sprockets with teeth that engage a chain or belt, pulley sprockets that resemble pulleys but have smaller radially extending projections (e.g., small teeth) for engaging grooves within a belt, and also pulleys with a smooth surface for engaging a smooth belt. The skilled artisan will understand that these various types of pulleys and sprockets are circular driving mechanisms that can be interchanged in many arrangements. 
     In one illustrated embodiment, the first belt system includes a first belt  361  coupling the first motor drive shaft  352  and a first intermediate shaft  363 , and a second belt  365  ( FIGS.  7 B and  7 E ) coupling the first intermediate shaft  363  and a second intermediate shaft  367 . A third belt  369  couples the second intermediate shaft  367  to the actuator input shaft  350 . Each of the shafts  352 ,  363 ,  367 ,  350  is associated with a circular driving mechanism to receive and rotate with the first belt  361 , the second belt  365 , and the third belt  369 . 
     In the illustrated embodiment of  FIGS.  7 A- 7 E , the first motor shaft  352  is associated a first motor sprocket  371 . The first intermediate shaft  363  is associated with a first intermediate top sprocket  372  for engaging the first belt  361 , and a first intermediate bottom sprocket  373  ( FIGS.  7 B and  7 E ) for engaging the second belt  365 . The terms “top” and “bottom” are used to indicate the location relative to the platform  339 . The second intermediate shaft  367  is associated with a second intermediate top sprocket  375  for engaging the third belt  369 , and a second intermediate bottom sprocket  376  ( FIG.  7 E ) for engaging the second belt  365 . 
     Lastly, the actuator input shaft  350  is associated with a circular driving mechanism, which is a first actuator sprocket  377  that is driven by the third belt  369 . The ratio of the diameters of the pulleys and/or sprockets in the first belt system dictate the transfer of speed and torque from the first motor shaft  352  to the actuator input shaft  350 . In one embodiment, the first motor shaft  352  rotates at a speed of about 250 RPM and delivers about 1050 Nm of torque, causing the actuator input shaft  350  to rotate at a speed of about 50 RPM and delivers about 5200 Nm of torque. As such, in this embodiment, the torque output from the first motor shaft  352  is increased by the first belt system by about a factor of 5 relative to the torque at the actuator input shaft  350  that ultimately drives the actuator rod  322 . The present invention contemplates the first belt system increasing the torque output from the first motor shaft  352  to the actuator input shaft  350  in the range of 3 to 7. Although the first belt system of the illustrated embodiment includes three belts  361 ,  365 ,  369  and two intermediate shafts  363 ,  367 , other configurations for the first belt system are available as well. 
     By use of the first intermediate shaft  363  and the second intermediate shaft  367  in the first belt system, the drive system associated with the first motor  312  can include additional components for enhancing performance of and protecting the first motor  312 . Specifically, the clutch  326  is mounted on the first intermediate shaft  363  below the platform  339  and limits the rotational speed of the first intermediate top sprocket  372 , which, in turn, limits the rotational speed of the first motor  312  via the first belt  361 . The clutch  326  is preferably a bi-directional clutch such that it can limit the rotational speed of the first motor  312  when necessary. During the high-speed low-force linear movement of the second motor  314  to advance or retract the press ram relative to the part, the clutch  326  is at least partially disengaged from the first motor  312  to maintain a rotational speed of the first motor shaft  352  and, hence, the first motor  312  below a limit to reduce possible damage to the first motor  312 . However, when the part is being formed during the low-speed high-force linear movement of the press ram caused by the first motor  312 , the clutch  326  is fully engaged to the first motor  312  to transfer high torque from the first motor  312  to the linear actuator  320  via the first belt system. 
     The first belt system may optionally include a torque limiter  390  that is also associated with the first intermediate shaft  363 . The purpose of the torque limiter  390  is to mechanically limit the maximum torque transferred into the male-female threaded mechanism to protect the screw, the nut, the bearings, and associated power transmission components from unanticipated events. Errors in tooling set up or product loading can result in the press ram and tool making contact with the work piece before the programmable controller begins ramping down the speed from the second motor  314 , resulting in undesirable forces being experienced throughout the system. 
     The second belt system in  FIGS.  7 A- 7 E  includes a second-motor belt  381  that directly couples the second motor drive shaft  354  and the actuator input shaft  350 . Unlike the first belt system, there are no intermediate shafts that rotate when the second motor  314  is driving the actuator  320 . As shown, the second-motor belt  381  engages a second-motor pulley  383  associated with the second motor drive shaft  354  and an actuator pulley  385  associated with the actuator input shaft  350 . As the second motor  314  is used for the high-speed, low-force movement of the actuator rod  322  and press ram coupled thereto, the ratio of the diameters of second-motor pulley  383  and the actuator pulley  385  dictates the speed of the actuator input shaft  350  relative to the second motor drive shaft  354 . In one embodiment, the ratio of the diameter of second-motor pulley  383  to the diameter of the actuator pulley  385  is in the range from about 2:1 to about 3:1. 
     Because the actuator input shaft  350  has the actuator pulley/sprocket  385  that is driven by the second motor  314  and the first actuator sprocket  377  that is driven by the first motor  312 , the drive function of either motor  312 ,  314  results in rotation of the motor input shaft of the other motor. Hence, the clutch  326  limits the rotational speed of the first motor  312  when the second motor  314  is driving the actuator  320  at a high rotational speed. On the other hand, when the actuator  320  is driven by the first motor  312 , the actuator pulley/sprocket  385  is still rotating the second-motor belt  381 , which causes the second motor  314  to also rotate. Thus, the second motor  314  is preferably operational to deliver some smaller amount of additive torque when the first motor  312  is powered in the working stroke of the cycle when the part is being formed. 
       FIG.  8    illustrates the actuator  320  of  FIG.  7    within a four-post press  400 . The actuator  320  is mounted to the stationary press crown  430  and the actuator rod  322  is mounted to the press ram  432 . The press ram  432  moves under the power of the actuator rod  322  to and from the press base  434  based on the outputs of the first motor  312  and second motor  314 , as described above relative to  FIG.  7   . The press ram  432  holds an upper tool  442  and the press base  434  holds a lower tool  444 . A part is formed by the four-post press  400  between the upper tool  442  and lower tool  444 . As shown, the upper tool  442  and lower tool  444  are for forming a curved sheet-metal part, but a variety of different forming, cutting, and punching tools can be applied to the press  400 . The press machine  400  may include a brake to hold the position of the press ram  432  when the press machine  400  is powered down or at a steady state. 
     When the part is being formed during the low-speed, high-force stroke of the cycle, both of the first motor  312  and the second motor  314  are rotating as the low-speed, high-force first motor  312  provides power to the actuator  320  because there is no clutch or mechanism to disconnect the second motor  314  from the actuator  320 . In other words, while the actuator  320  is being powered by the first motor  312 , the second-motor belt  381  is still turning due to the rotation of the actuator sprocket or sprocket  385  (see  FIGS.  7 A and  7 D ), which causes the second motor  314  to rotate. As such, during the low-speed, high-force stroke of the cycle, the second motor  314  is preferably operational to provide torque (albeit a smaller amount of torque relative to the torque provided by the first motor  312 ) such that the torque of the high-speed, low-force second motor  314  is additive to the torque of the low-speed, high-force first motor  312 . 
       FIGS.  9 A and  9 B  illustrate the use of two linear actuators  320  in a gib-style press machine  500 . Instead of sliding on posts, the press ram  532  moves along gibs (e.g., wedge-shaped gibs) located within the frame of the press machine  500 . The gibs precisely guide the reciprocating motion of the press ram  532  toward and away from the base  534 . The linear actuators  320  are mounted to the frame so as to remain stationary while the actuator rods  322  are mounted to and move the press ram  532 . An upper tool  542  and a lower tool  544  are mounted, respectively, to the press ram  532  and the press base  534 . By using two actuators  320  in parallel, the amount of force on the press ram  532  produced by the first motors  312  can be doubled so as to provide extra force that is necessary to form the parts by the tools  542 ,  544 . Further, the high-speed movement of the press ram  532  in the advancement stroke and the retraction stroke is brought about by the synchronous operation of the second motors  314  on both of the linear actuators  320 . 
       FIG.  10    illustrates alternative post-style press machine  600  using multiple linear actuators  320 ,  620   a ,  620   b . The middle linear actuator  320  (described in detail relative to  FIG.  7   ) includes the first motor  312  for delivering high force to the press ram  632  when forming a part, and the second motor  314  for delivering high speed to the press ram  632  in the advancement and retraction strokes. The other two linear actuators  620   a ,  620   b  in the press machine  600  include only a first motor  612   a ,  612   b  that delivers high force to the press ram  632  when the part is being formed. Consequently, the press ram  632  moves at a high speed relative to the base  634  in the advancement and retraction strokes under the power of only the second motor  314  of the middle linear actuator  320 . When that high-speed condition occurs, the first motors  612   a ,  612   b  of the other two linear actuators  620   a ,  620   b  are protected from high speed conditions by use of clutches  626   a ,  626   b , which operate in the same manner as the clutch  326  described relative to the actuator  320  in  FIG.  7   . The clutches  626   a ,  626   b  are coupled to the output shaft of the first motors  612   a ,  612   b  either directly or indirectly, such as through an intermediate shaft that is driven by the first motors  612   a ,  612   b  via a belt. When the part is being formed by the tools  642 ,  644  and higher force is needed, the first motors  612   a ,  612   b  are operational and the clutches  626   a ,  626   b  engage to permit the torque to be transferred to the first male-female thread mechanism of the linear actuators  620   a ,  620   b . The high torque from the first motors  612   a ,  612   b  is converted to a high force by the first male-female thread mechanism and transferred to the actuators rods  622   a ,  622   b , which drive the press ram  632 . At the same time, the first motor  312  of the middle linear actuator is also delivering high force to the press ram  632 . The embodiment of the press machine  600  of  FIG.  10    may allow for forces in excess of 300 tons (e.g., more than 100 tons delivered per actuator  320 ,  620   a ,  620   b ) when needed, but lesser force amounts can be delivered by powering the three first motors  312 .  612   a ,  612   b  at lower levels to produce less torque. 
       FIGS.  11 A- 11 D  illustrate an alternative linear actuator  720  that is similar to the linear actuator  120  of  FIG.  5    and the linear actuator  321  of  FIG.  7   . The linear actuator  720  includes a first motor  712  and a second motor  714  that drive a ram for a press machine in the same manner and configurations described in the exemplary press machines  400 ,  500 , and  600  of  FIGS.  8 - 10   . The linear actuator  720  includes a clutch  726  ( FIGS.  11 B and  11 D ) to protect the high-torque first motor  712  from the high rotational speeds that could otherwise damage the first motor  712  when the second motor  714  is advancing and retracting the press ram from the part. 
     The first motor  712  and the second motor  714  cause the rotation of an actuator input shaft  730  via a first actuator sprocket  731  and a second actuator sprocket  732 , respectively. A first belt system couples the first motor  712  and the first actuator sprocket  720  and includes a first belt  741  and a second belt  743 . The first belt  741  engages a first motor sprocket  733  and a bottom intermediate sprocket  735  ( FIG.  11 D ) below a mounting platform  739  of the actuator  720 . The second belt  743  engages a top intermediate sprocket  737  and the first actuator sprocket  731 . The bottom intermediate sprocket  735  ( FIG.  11 D ) and the top intermediate sprocket  737  are located on and rotate around an intermediate shaft  738 . The clutch  726  is also coupled to the intermediate shaft  738  below the platform  739 . In one embodiment, the first motor  714  rotates at a speed of about 250 RPM and delivers about 1050 Nm of torque, causing the actuator input shaft to rotate at a speed of 50 RPM and delivers about 5200 nm of torque. As such, in this embodiment, the torque output from the first motor shaft is increased by the first belt system by about a factor of 5 relative to the torque at the actuator input shaft that ultimately drives the actuator rod  722 . The present invention contemplates the first belt system increasing the torque output from the first motor to the actuator input shaft in the range of 3 to 7. 
     The second motor  714  is directly coupled to the second actuator sprocket  732  by a single belt  745 . The single belt  745  engages a second-motor sprocket (not shown) on the output shaft of the second motor  714 . As the second motor  714  is used for the high-speed, low-force movement of the actuator rod  722  and the press ram that coupled to the rod  722 , the ratio of the diameters of the second-motor sprocket and the second actuator sprocket  732  dictates the speed of the actuator input shaft relative to the second motor drive shaft. In one embodiment, the ratio of the diameter of second actuator sprocket  732  to the diameter of the second motor sprocket (mounted to the second motor  714 , but not shown) is in the range from about 2:1 to about 3:1. 
     Because the actuator input shaft has the second actuator sprocket  732  that is driven by the second motor  714  and the first actuator sprocket  731  that is driven by the first motor  712 , the drive function of either motor  712 ,  714  results in rotation of the motor input shaft of the other motor. Hence, the clutch  726  limits the rotational speed of the first motor  712  when the second motor  714  is driving the actuator  720  at a high rotational speed. 
     In an alternative arrangement, the actuator  720  can be configured such that both the first motor  712  and the second motor  714  are coupled to intermediate sprockets on the same intermediate shaft via first and second belts. The intermediate shaft would include a drive sprocket that is directly coupled to a sprocket on the actuator  720 . Thus, only a single belt is coupled to and drives the actuator  720 . 
       FIG.  12    illustrates the actuator  720  of  FIG.  11    within a four-post press  800 . The actuator  720  is mounted to the stationary press crown  830  and the actuator rod  722  is mounted to the press ram  832 . The press ram  832  moves under the power of the actuator rod  722  to and from the press base  834  based on the outputs of the first motor  712  and second motor  714 , as described above relative to  FIG.  11   . The press ram  832  holds an upper tool  842  and the press base  834  holds a lower tool  844 . A part is formed by the four-post press  800  between the upper tool  842  and lower tool  844 . As shown, the upper tool  842  and lower tool  844  are for forming a curved sheet-metal part, but a variety of different forming, cutting, and punching tools can be applied to the press machine  800 . The press machine  800  may include a brake to hold the position of the press ram  832  when the press machine  800  is powered down or at a steady state. 
     When the part is being formed during the low-speed, high-force stroke of the cycle, both of the first motor  712  and the second motor  714  are rotating as the low-speed, high-force first motor  714  provides power to the actuator  720  because there is no clutch or mechanism to disconnect the second motor  714  from the actuator  720 . In other words, while the actuator  720  is being powered by the first motor  712 , the second-motor belt  745  is still turning due to the rotation of the second actuator sprocket  732  (see  FIGS.  11 A and  11 C ), which causes the second motor  714  to rotate. As such, during the low-speed, high-force stroke of the cycle, the second motor  714  is preferably operational to provide torque (albeit a smaller amount of torque relative to the torque provided by the first motor  712 ) such that the torque of the high-speed, low-force second motor  714  is additive to the torque of the low-speed, high-force first motor  712 . 
     Like the actuator  320  from  FIG.  7   , the actuator  720  can be used in various types of press machines (e.g., gib-style presses) and other metal bending machines, such as press brake machines and metal bending machines, in which a high-forces (e.g. +100 tons) are required. Furthermore, like the actuator  320  from  FIG.  7   , the actuator  720  can be used in multiple actuator arrangements, such as those shown in  FIGS.  9 - 10   . 
     In the press machines with the multi-speed linear actuators in accordance to the previous embodiments of  FIGS.  1 - 12   , the downward force can result in 75 tons, 100 tons, 125 tons, 150 tons, 175 tons, 200 tons or more than 200 tons of force on the part in the working stroke driven by the first motor(s). In one embodiment, the force provided by the linear actuators of the press machine is at least 50 tons, but preferably more than 100 tons. Press machine systems using multiple actuators (e.g.,  FIGS.  9  and  10   ) can deliver in excess 200 tons, 300 tons, 400 tons, or 500 tons by adding additional actuators with high-torque, low-speed motor systems. Further, the linear press machines will provide a linear velocity of the press ram (and upper tool) via the actuator typically in the range of 300 to 700 inches per minute in the advancement and retraction strokes driven by the second motor(s). In one embodiment, the velocity of the actuator is at least 250 inches per minute, is preferably greater than 500 inches per minute, and is most preferably greater than 750 inches per minute (such as 800 or 900 inches per minute) in the advancement and retraction strokes. In these embodiments, the linear velocity of the linear actuator and, hence, the press ram in the advancement stroke is: greater than about 4 times the linear velocity in the working stroke when the part is being formed, greater than about 5 times the linear velocity in the working stroke when the part is being formed, greater than about 6 times the linear velocity in the working stroke when the part is being formed, greater than about 7 times the linear velocity in the working stroke when the part is being formed, greater than about 8 times the linear velocity in the working stroke when the part is being formed, greater than about 9 times the linear velocity in the working stroke when the part is being formed, or greater than about 10 times the linear velocity in the working stroke when the part is being formed. 
     In the previous embodiments, the pulleys and belts can be interchanged with gears or other drive systems. Similarly, the sprockets and belts can be interchanged with gears or other drive systems. 
     As shown in the figures, the multi-speed linear actuators of the present invention are contemplated for use on the press machines in which the press ram slides along posts, such as a four-post press (all four posts can be seen, for example, in  FIG.  8   ) or a two-post press. Furthermore, the present invention is also contemplated for use on the press machines in which the press ram moves along gibs (e.g., wedge-shaped gibs) in the frame that guide the reciprocating motion of the press ram. 
     These embodiments and obvious variations thereof is contemplated as falling within the spirit and scope of the claimed invention, which is set forth in the following claims. Moreover, the present concepts expressly include any and all combinations and subcombinations of the preceding elements and aspects.