Abstract:
A pressure intensifier for generating a relatively large force includes a plurality of pistons driven in advancing and retracting directions. The pressure intensifier includes a body having a cavity used as an internal fluid reservoir. Furthermore, a damping mechanism limits the relative acceleration between pressure intensifier components during operation.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
   The present invention relates generally to a force producing apparatus and, more particularly, to an air-to-oil pressure intensifier for providing relatively large forces to machines such as clamps, grippers, presses and punches. 
   Many systems utilize the basic principle of inserting a rod into an enclosed oil-filled chamber to produce force. Several of the oil systems use multiple steel cylinder sections interconnected with threaded tie rods and nuts. An oil reservoir is either contained internally within one of the steel cylinder sections or mounted externally. The external reservoir is piped to the intensifying cylinder. Difficulties may arise when attempting to package the cylindrically shaped assemblies as well as provide space and structure to mount the external oil reservoirs. To provide various stroke lengths and power strokes, many slightly different components must be constructed and maintained in an inventory. 
   Accordingly, it would be beneficial to provide a compact air-to-oil intensifier having a one-piece rectangular body. It would also be beneficial to provide a device eliminating the need for an external oil reservoir. 
   The present invention provides a pressure intensifier for providing relatively large output forces using an air over hydraulic force amplification system. According to one aspect of the present invention, a rod is driven into a sealed chamber of substantially incompressible fluid to generate an output force. 
   According to another aspect of the present invention, a compact, lightweight pressure intensifier is provided. 
   According to another aspect of the present invention, a bore is machined into the body and is utilized as an internal fluid reservoir. 
   Yet another aspect of the present invention relates to a body having internal porting to minimize the need for external fluid lines. 
   Another aspect of the present invention includes a damping mechanism to limit the accelerations of pressure intensified components relative to one another. 
   Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
       FIG. 1  is a perspective view of a pressure intensifier according to the principles of the present invention; 
       FIG. 2  is a partial exploded perspective view of the pressure intensifier shown in  FIG. 1 ; 
       FIG. 3  is another partial exploded perspective view of the pressure intensifier shown in  FIG. 1 ; 
       FIG. 4  is a cross-sectional side view of a body of the pressure intensifier of the present invention; 
       FIG. 5  is a partial, fragmentary cross-sectional side view of a ram of the pressure intensifier; 
       FIG. 6  is an exploded perspective view of an anti-shock assembly constructed in accordance with the teachings of the present invention; 
       FIG. 7  is a cross-sectional side view of the anti-shock assembly; 
       FIG. 8  is a cross-sectional end view of the body taken along line B—B as shown in  FIG. 4 ; 
       FIG. 9  is a cross-sectional end view of the body of the pressure intensifier of the present invention taken along line C—C of  FIG. 4 ; 
       FIG. 10  is a cross-sectional end view of the body of the pressure intensifier taken along line F—F as shown in  FIG. 4 ; and 
       FIGS. 11–14  are cross-sectional side views of the pressure intensifier of the present invention depicting the position of various components at different stages during operation. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   With reference to  FIGS. 1–3 , an air-to-oil pressure intensifier constructed in accordance with the teachings of the present invention is identified at reference numeral  10 . Pressure intensifier  10  functions to provide a relatively large output force at a driven end using only compressed air at relatively low pressure (80 to 120 psi) as the power source. Typically, the driven end of the pressure intensifier is coupled to tooling such as a clamp half, a rivet hammer or a punch, collectively identified as a tool  12 . 
   Pressure intensifier  10  operates by advancing and retracting a ram assembly  14  to place tool  12  into engagement with a work piece  16 . As will be described in greater detail hereinafter, pressure intensifier  10  operates to rapidly translate tool  12  toward work piece  16  using relatively low force. Once tool  12  contacts work piece  16 , pressure intensifier  10  generates a greatly multiplied force between tool  12  and work piece  16 . On the return stroke, pistons with relatively large working areas within pressure intensifier  10  are pressurized to retract the ram in preparation for the next work cycle. 
   As shown in  FIGS. 1–4 , pressure intensifier  10  includes a substantially rectangular one-piece body  18  coupled to an end cap  20 . Ram assembly  14  is positioned within a first cavity  24  of body  18 . An intensifier assembly  26  is positioned within a second cavity  28  of body  18 . First cavity  24  and second cavity  28  are interconnected by a first passageway  30 . An oil piston  32  is positioned within a third cavity  34  of body  18 . Third cavity  34  is plumbed in fluid communication with passageway  30 . An oil filling port  36  extends from an outer surface of body  18  and terminates at third cavity  34  to allow a user to add fluid to the reservoir defined by third cavity  34  without disassembling pressure intensifier  10 . 
   Ram assembly  14  is positioned within first cavity  24  and is free to axially move therein. A key  38  is positioned within a slot  40  formed at a first end  42  of body  18 . A fastener  44  couples key  38  to body  18 . Key  38  engages ram assembly  14  and functions to prevent rotation of ram assembly  14  relative to body  18 . 
   With reference to  FIGS. 2 and 5 , ram assembly  14  includes a ram guide  46 , a ram  48  and an anti-shock assembly  50 . Ram guide  46  is a substantially cylindrical hollow member preferably constructed from bronze. Ram guide  46  includes an externally threaded first section  52  and a second section  54  having a reduced outer diameter. A seal  56  is positioned within a groove  58  formed in second section  54 . Seal  56  engages a smooth bore portion  60  of first cavity  24 . First cavity  24  includes an enlarged threaded portion  62  proximate to first end  42  of body  18 . Externally threaded section  52  of ram guide  46  is coupled to body  18  at threaded portion  62 . Ram guide  46  includes a slot  64  aligned with key  38  and slot  40  of body  18 . 
   Ram  48  is an elongated member having a substantially cylindrical body  66  and an enlarged head  68 . Body  66  includes a threaded nose portion  70  positioned at an end opposite head  68 . A pocket  72  extends axially through head  68  and into body  66 . A bleeder assembly  74  is positioned in fluid communication with pocket  72 . Bleeder assembly  74  is operable to allow air which may have been inadvertently trapped within pocket  72  to escape to atmosphere. An inner diameter seal  76  is positioned within a groove of ram guide  46  to sealingly engage body  66  of ram  48 . 
   Ram  48  functions as a piston slidable positioned within first cavity  24 . To form a sealing piston, a seal  78  and back up ring  80  are positioned within a forward groove  82  of head  68 . A high pressure seal  84  is positioned within a rearward groove  86  positioned on head  68 . 
   As shown in  FIGS. 5 ,  6  and  7 , anti-shock assembly  50  includes a seal retainer  88 , a seal  90  and a washer  92 . Seal retainer  88  is a substantially cylindrical member having a threaded outer portion  94  and an adjacent pilot portion  96  having a diameter less than threaded portion  94 . A bore  98  extends through seal retainer  88 . Seal  90  is seated within a counter bore  100  coaxially positioned with bore  98 . 
   Washer  92  is a substantially disk shaped member having a first aperture  102  axially aligned with bore  98  of seal retainer  88 . A second aperture  103  extends substantially parallel to first aperture  102 . Second aperture  103  functions as an orifice for damping undesirable shock produced during piercing type operations as will be described in greater detail hereinafter. 
   Anti-shock assembly  50  is threadingly engaged with a threaded portion of a counter bore  104  formed in the head end of ram  48 . Seal  90  and washer  92  are trapped within an unthreaded portion of counter bore  104  adjacent the threaded portion. 
   As shown in  FIGS. 8–11 , a seal retainer  106  is threadingly fitted within a stepped recess  110  formed at the rearward end of first cavity  24 . A counter bore  112  extends through seal retainer  106 . A seal  114  is positioned within counter bore  112  and captured within recess  110  upon installation of seal retainer  106 . Preferably, seal  114  and seal retainer  106  are assembled separately and coupled to body  18  as one unit. Seal retainer  106  includes a pair of blind bores  116  for receipt of a tool (not shown) for installing the seal retainer and seal assembly to body  18  without the use of snap rings and snap ring pliers. A seal  117  seals the outer diameter of seal retainer  106  and body  18 . 
   Intensifier assembly  26  includes an intensify rod  118  coupled to an intensify piston  120  and a damping washer  122 . A fastener  124  couples intensify rod  118  and damping washer  122  to intensify piston  120 . 
   Intensify piston  120  includes a body  126  having an annular groove  128 . A seal  130  is positioned within groove  128  and sealingly engages the wall of second cavity  28 . A second seal retainer  132  is substantially identical to seal retainer  106 . Second seal retainer  132  is threadingly coupled to body  18  within a stepped recess  134  positioned at a forwardmost end of second cavity  28 . A seal  136  is positioned within a counter bore of second seal retainer  132 . A seal  138  is positioned within an external groove formed on second seal retainer  132  and engages body  18 . Intensify piston  120  includes a cylindrically shaped protrusion  140  which cooperates with end cap  20  to reduce impact of the intensify piston with the end cap during the return stroke as will be described in greater detail hereinafter. 
   Intensify piston  120  is slidably positioned within second cavity  28 . Intensify rod  118  extends from second cavity  28  through passageway  30  into first cavity  24 . During operation, intensify rod  118  selectively enters pocket  72  of ram  48 . 
   Oil piston  32  is a substantially cylindrical member having a first pair of external annular grooves  142  for receipt of a pair of seals  144 . A second pair of annular grooves  146  are formed at each of end of oil piston  32 . Bearing sleeves  148  are coupled to oil piston  32  at second grooves  146 . Bearing sleeves  148  are preferably constructed from a bearing material such as a RULON® (a reinforced PTFE compound) to ensure that oil piston  32  slides within third cavity  34 . 
   End cap  20  is coupled to body  18  via threaded fasteners  150 . End cap  20  includes a first port  152 , a second port  154  and a third port  156 . First port  152  is in fluid communication with third cavity  34 . Second port  154  extends through end cap  20  and is in fluid communication with second cavity  28 . A boss  158  of end up  20  extends into second cavity  28 . A first passageway  160  extends through boss  158  in communication with second port  154 . First passageway  160  is sized for receipt of protrusion  140  of intensify piston  120 . A seal  162  is positioned within first passageway  160  to selectively engage protrusion  140  during a retracting motion of intensifier assembly  26 . An orifice  164  is also formed in boss  158 . Orifice  164  provides a parallel path for fluid to escape second cavity  28  during retraction of intensifier assembly  26 . Impact of intensify piston  120  on boss  158  is alleviated because protrusion  140  engages seal  162  to block first passageway  160 . At this time, air trapped between end cap  20  and intensify piston  120  is forced to travel through orifice  164  in order to escape. The restricted flow retards the rate of retraction of intensify piston  120 . 
   With reference to  FIG. 4 , body  18  includes a return passageway  166  in fluid communication with third port  156 . Return passageway  166  provides a path for pressurized air to act on a forward face  167  of intensify piston  120  and a forward face  168  of ram  48 . Specifically, return passageway  166  communicates with first cavity  24  as depicted in  FIG. 8 . Furthermore, return passageway  166  communicates with second cavity  28  as shown in  FIG. 9 . 
   With reference to  FIGS. 11–14 , operation of pressure intensifier  10  will now be described.  FIG. 11  depicts ram assembly  14 , intensifier assembly  26  and oil piston  32  in their fully retracted positions. At this time, it should be appreciated that intensify rod  118  is sealingly engaged with inner diameter seal  114  of second seal retainer  132  but is spaced apart from the seal of seal retainer  106 . Accordingly, fluid may flow from third cavity  34  into first cavity  24  and pocket  72 . 
   To initiate movement of ram assembly  14  in an advanced direction, pressurized air is supplied to first port  152  while second port  154  and third port  156  are opened to atmosphere. Pressurized fluid acts on oil piston  32  causing it to advance from right to left as shown in  FIG. 12 . A substantially incompressible fluid is positioned within a portion of third cavity  34  and a portion of first cavity  24  between oil piston  32  and head  68  of ram  48 . The pressurized incompressible fluid acts on ram  48  causing the ram to advance. During the first phase of actuation, ram  48  is extended rapidly using relatively low force to cause tool  12  to contact workpiece  16 . 
   Once ram  48  contacts the workpiece, pressure continues to build within third cavity  34 . Once a predetermined pressure is met, first port  152  is closed and pressurized air is supplied to second port  154 . Pressurized air acts on a rearward face  169  of intensify piston  120  causing intensifier assembly  26  to advance as depicted in  FIG. 13 . During advancement, intensifier rod  118  engages the inner diameter seal of seal retainer  106 . Pressure intensification begins at this time because the incompressible fluid is trapped within first cavity  24  and pocket  72 . Pressure intensification continues to occur while intensify rod  118  enters anti-shock assembly  50  at  FIGS. 13 and 14 . 
   Anti-shock assembly  50  functions to minimize undesirable acceleration of ram  48  which may occur at the end of certain processes such as stamping or punching. For example, during a punching operation, resistance to pressure applied by ram  48  is great during the initial stages of material deformation. However, it is common for the last two-thirds of the thickness of material to rapidly break away offering little to no resistance to the force from ram  48 . During this last portion of the punching operation, ram  48  has a tendency to accelerate relative to intensify rod  118  possibly causing internal cavitation of hydraulic fluid, premature cylinder wear and/or premature seal wear. To limit these possibly negative effects, anti-shock assembly  50  sealingly engages intensify rod  118  to define a first trapped volume in pocket  72  and a second trapped volume in the rearmost portion of first cavity  24 . Intensify rod  118  may enter pocket  72  but only at the rate defined by the orifice extending through anti-shock assembly  50 . Similarly, the speed at which intensify rod  118  may exit pocket  72  is limited by the flow rate of incompressible fluid through the orifice of anti-shock assembly  50 . 
     FIG. 14  depicts ram  48  and intensifier assembly  26  at their fully advanced positions where the work has been completed. Pressurized air is supplied to third port  156  while first port  152  and second port  154  are exhausted. As mentioned earlier, supply of pressurized air to port  3  travels through return passageway  166  to act on forward face  167  of intensify piston  120  and forward face  168  of ram  48 . Hydraulic fluid is transferred from first cavity  24  to third cavity  34  once intensify rod  118  clears seal retainer  106 . At this time, each of ram assembly  14 , intensifier assembly  26  and oil piston  32  will be returned to their fully retracted positions shown in  FIG. 11 . 
   An oil level indicator  170  is positioned near a forward end of third cavity  34 . Oil level indicator  170  functions to signal an operator that it is time to add fluid to the reservoir. A magnet  172  is coupled to oil piston  32 . As oil is depleted from the system during use, oil piston  32  is allowed to advance further within third cavity  34 . When oil piston  32  advances to a position where magnet  172  is proximate oil level indicator  170 , a lamp is illuminated to signal the operator. In one embodiment, the lamp pulsates on and off to attract the operator&#39;s attention. 
   An optional proximity sensing assembly  174  includes a longitudinal rod  176  and a transverse rod  178 . Longitudinal rod  176  is slidably positioned within a bore  180  ( FIG. 10 ) extending substantially parallel to first cavity  24 . One end of transverse rod  178  is coupled to a necked-down portion  182  of longitudinal rod  176 . An opposite end of transverse rod  178  is positioned within an aperture  184  transversely extending through ram  48 . As ram  48  axially translates, transverse rod  178  and longitudinal rod  176  also translate. Proximity switch  186  is coupled to body  18  to bore  180 . Longitudinal rod  176  includes a relieved portion  188  axially extending along a substantial portion of longitudinal rod  176 . Relieved portion  188  effectively defines a step  190  at the free end of longitudinal rod  176 . As step  190  is positioned proximate one of sensor heads  192 , a signal is generated. The position of transverse rod  178  may be adjusted relative to longitudinal rod  176  to allow a user to correlate the position of ram  48  to the signal produced by proximity switch  186 . 
   Furthermore, the foregoing discussion discloses and describes merely exemplary embodiments of the present invention. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims, that various changes, modifications and variations may be made therein without department from the spirit and scope of the invention as defined in the following claims.