Patent Publication Number: US-2005121843-A1

Title: Pneumatic clamping device

Description:
FIELD OF THE INVENTION  
      The present invention concerns a pneumatic clamping device for the controlled blocking and releasing of items.  
     STATE OF THE TECHNIQUE  
      There are already well known clamping devices of the type here considered, which include a clamping arm turning with a shaft between an inactive rest, position, and an active, operating position, controlled by a pneumatic cylinder through a toggle joint.  
      Normally, the clamping arm is sustained by a body associated with the pneumatic cylinder. More precisely, on one side, the body is fundamentally made up of at least two elements or complementary shells, joined together and which support the shaft of the clamping arm and enclose the toggle joint. On the other side, the pneumatic cylinder houses a piston with a stem that extends into the body, where it connects to the toggle joint so that the rotations of the clamping arm correspond to the alternating movements of the piston between the rest and operating positions.  
      In other words, the pneumatic cylinder represents a structurally autonomous, linear actuator, complete with head flange, both on the side of the piston stem and on the opposite side, as a standard cylinder, whereas the body that supports the turning, clamping arm is in addition made of steel and it is connected and fixed to the cylinder. Furthermore, to maintain its linearity, even under force when the clamping arm is in the operating position, the stem of the piston is fitted with two rollers on opposite sides which rest against and slide, following the stem, on surfaces shaped inside the body.  
      It is however evident how the realisation and assembly of a pneumatic clamping device according to the known techniques are rather complex and costly, because the components have to be fitted separately in the body holding the turning clamping arm and the toggle joint and then such body must be fitted with a pneumatic cylinder, which is, in itself, not built for this type of fitting and therefore must be adapted.  
     OBJECTS AND SUMMARY OF THE INVENTION  
      Starting from this premise, one of the objects of this invention is to provide a pneumatic clamping device in which one component forms both the chamber, that is the cylinder, housing of the control piston, and the body supporting the toggle joint and controlled clamping arm.  
      Another object of the invention therefore is to provide a pneumatic clamping device wherein the cylinder for the piston and the body supporting the toggle joint and clamping arm are integrated, namely made out of a single component that, in addition, can be advantageously made starting from an extruded aluminium element or one of its alloys.  
      In this way, compared to the known technique, the clamping device of the present invention does not require a flange on a level with the cylinder on the side of the piston stem, but simply a closing flange on the opposite side; the piston stem is positively guided in the integral body for most of its length; the body requires a member for completion only as regards to the toggle joint, which, in actual fact can be provided by the extruded element forming the body; the group becomes must simpler to make, more economic and compact even with the use of a cylindrical piston.  
      Said objects are achieved, according to the invention, with a pneumatic clamping device in accordance with claim  1 . 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      This invention will however be described more in detail in the continuation of this description made in reference to the enclosed indicative and not limiting drawings, in which:  
       FIG. 1  is an exploded view in perspective of the components of the device;  
       FIG. 2  is a perspective view of only the piston connected to the clamping arm by means of the toggle joint;  
       FIG. 3  is a perspective view of the device as assembled;  
       FIG. 4  is a perspective view again of the assembled device, but in a longitudinal cross-section to illustrate the components;  
       FIG. 5  is a side view of the device with the clamping arm seen in different angles;  
       FIGS. 6 and 7  are partial cross-section view from front and rear of the device in  FIG. 5 ;  
       FIG. 8  is a vertical cross-section of the device in the plane of the toggle joint;  
       FIGS. 9 and 10  are views from above and from below of the device; and  
       FIGS. 11 and 12  are cross sections of the device respectively on a level with a lateral support roller of the stem and of rotation shaft of the clamping arm. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      As shown, the clamping device is indicated globally by  10  and comprises a body  11 , a piston  12  with relative piston stem  13 , best cylindrical but not necessarily, a clamping arm  14  and a toggle joint  15 .  
      The body  11  is substantially one piece only, made from an extruded profile in aluminium or one of its alloys, therefore with uniform cross-section and having a proximal end or base  11 ′ and a distal end  11 ″, the latter possibly rounded off according to needs.  
      In the body  11  there are provided, in an axial direction from the proximal to the distal ends, a chamber  16  which houses the piston  12  and a hole  17  which houses and guides the piston stem  13  with interposition of seals both on the piston and the stem. At the proximal end of the body, the chamber  16  is closed by a base flange  18  inside which there is a seal plug  18 ′. Holes can be envisaged on the sides of the body for holding the device in place and for the application of further accessories, including grooves for fitting sensors.  
      The piston stem  13  extends into the guide hole  17  towards the distal end of the body. Here a portion of the body has been removed to leave room for an integral flange  19 , equal to about half the width of the body itself, and the guide hole  17  for the stem  13  open on one side for a part of its length— FIG. 1   
      An added flange  20  is formed, also made from the extruded profile of said body, and fitted to and facing the flange  19  integral with the body. The added flange  20  is shaped so as to fit complementary to flange  19  so as to integrate the body and completely re-establish the guide hole  17  of stem  13 . At the distal end  11 ″ of the body  11 , between the two associated flanges  19 ,  20  is fitted a cap  21  closing the guide hole  17  for the stem  13 .  
      Together, the two integral and shaped flanges  19 , 20 , support a shaft  22  which turns on bearings or bushings  23 , and the ends of which extend from the opposite sides of said flanges.  
      The clamping arm  14  is shaped like a fork and fixed to the ends of said shaft  22  and turning with the latter through an angle of usually about 90°-120° between an inactive rest position  1  and an active operating position  2 — FIG. 5 .  
      The toggle joint  15  is placed between the two associated flanges  19 ,  20 , located between the piston stem  13  and the shaft  22  of the clamping arm  14 . More precisely, the toggle joint  15  includes a forked element  24  adapted to and fixed to the free end of the stem  13 , a lever  25 , also forked, fixed and turning with said shaft  22  and a rigid connecting element  26  which is pivoted on one side, in  27 , to the element  24  fixed to the stem  13  and on the other, in  28 , to the lever  25  fixed to the shaft  22 — FIGS. 2, 4 .  
      On one side of the forked element  24  at the end of the piston stem  13 , on the opposite side of the latter to the one adjacent to the shaft  22  of the clamping arm  14 , there is a flat area  29  which rests against a locator roller  30 , stationary compared to the stem, but rotating on an axis  31  supported between the flanges  19 ,  20 , parallel to said shaft.  
      The piston  12  is usually double effect and from one side of the chamber  16  that houses it are cut two passages  32 ,  33  at different levels for the alternative input and output of a fluid under pressure conveniently fed for the movements of the piston in opposite directions.  
      The rotation of the clamping arm  14  from the inactive position to the active operating position, and the stop of the arm itself in this work position by means of the toggle joint, corresponds to the forward movement of the piston  12 , that is towards the distal end of the body  11 . To be noted that the locator roller  30 , stationary in the body even if it can turn, resting against the lateral slat side  29  of the stem  13 , helps to maintain the latter on an axis even when in the block and unblock phases of the toggle joint it finds itself subjected to the maximum crosswise thrust, and the cover  21  at the distal end of the body holds a thrust pin  21 ′ in case an emergency release of the toggle joint is required if there is a lack of fluid.