referring to fig1 - 3 , a bag opening apparatus 10 constructed according to the principles of the present invention includes a frame or plate 12 and a movable carriage 14 . the carriage 14 is mounted on a pair of support rods 16 slidably mounted in linear bearings 18 . the linear bearings are mounted on the bottom ( as illustrated in fig1 - 3 ) of the frame 12 . the carriage moves between a retracted position ( as illustrated in fig1 and 2 ) and an extended position ( as illustrated in fig5 a ) by a first piston and cylinder assembly 22 ( fig2 ). rod 24 of the piston and cylinder assembly 22 is secured to the back ( to the left in fig2 ) of the carriage 14 so that the carriage may be extended forward or retracted backward by means of the piston and cylinder assembly . as illustrated , the first piston and cylinder assembly 22 is fixably secured to the bottom of frame 12 , although it would be possible to provide for axial adjustment of the assembly so that the extent of travel could be modified . alternatively , the extent of travel of the rod 24 could be internally adjusted with the piston and cylinder assembly by well - known means . a second piston and cylinder assembly 26 is mounted in a sliding block 28 on top of frame 12 . the sliding block 28 is secured in a slot 30 and frame 12 by a pair of screws 32 . in this way , the extent of travel of rod 34 of the piston and cylinder assembly 26 may be adjusted by moving the block 28 axially within the slot 32 . a resilient bumper 36 is mounted on the distal end of rod 34 so that it will engage a cavity or receptacle 38 formed in the rear of carriage 14 . although the bumper 36 is not secured to the carriage 14 in any way , the extension of rod 34 forward , as illustrated in broken line in fig5 a , will prevent the full rearward retraction of the carriage 14 by the first piston and cylinder assembly 22 . a pair of pins 42 are mounted in collars 44 on top of the carriage 14 . each collar 44 , in turn , is mounted on a post 46 which is rotatably mounted in a vertical shaft 48 formed in the body of the carriage . the collars 44 are fixedly mounted on the posts 46 so that rotation of the posts results in pivoting of the collars 46 and pins 42 . a third piston and cylinder assembly 50 is mounted by a bracket 52 on the carriage 14 . rod 54 of the piston and cylinder assembly 50 is connected to a linkage assembly 56 comprising a clevis 58 and a pair of arms 60 and 62 . each arm 60 and 62 is mounted to pivot at the bottom of one of the vertical posts 46 . referring now to fig6 details of the linkage assembly 56 will be described . each arm 60 and 62 includes a slot ( 64 and 66 , respectively ) which receives a pin 68 carried by the clevis 58 . thus , as the rod 54 is moved forward and backward by the piston and cylinder assembly 50 , the clevis 58 rotates each of the linkage arms 60 and 62 in the opposite direction around the respective vertical post 46 . as the rod 54 is moved forward , post 46a carried by arm 60 is rotated in the counter clockwise direction ( as viewed in fig1 ) while the post 46b carried by the second linkage arm 62 is rotated in the clockwise direction . referring also to fig1 it can be seen that the forward movement of rod 54 causes the pins 42 to move apart from each other , while the retraction of rod 54 causes the pins to move toward each other . referring now to fig4 the utilization of the bag opening apparatus 10 of the present invention will be illustrated and described in connection with a conventional automatic bag filling system 70 . the bag filling system 70 is illustrated schematically , with only the essential aspects of the equipment being shown . such bag filling systems , however , are well - known in the art and need not be described in detail herein . the bag filling system 70 includes a wicket assembly 72 including a pair of wicket pins 74 ( only one of which is illustrated in fig4 ) for receiving the mesh bags thereon . a single mesh bag b is illustrated as hanging vertically from the wicket pins at the forwardmost end ( to the right in fig4 ) of the wicket assembly 72 . one face 76 of the bag includes an upper extension 78 , which is received on the wicket pins 74 , while the opposed face 80 is free from the wicket pins 74 . in this way , the opposed face 80 may be drawn away from the suspended face 76 by the bag opening apparatus 10 , as will be described in detail hereinafter . the wicket pins 74 are mounted on wicket brackets 48 which are spaced apart and adjustable so that the wicket pins 74 may be adjusted to accomodate the wickets of premade bags . the wicket assembly 72 further includes a knife block 82 reciprocatably mounted on a knife cylinder 84 . the knife block 82 carries a knife blade 86 which is located to sever the extension 78 of the bag to release the bag from the wicket assembly 72 . the bag filling system 70 also includes a bag suspension assembly 90 which supports and holds open the bag during the filling operation . the suspension assembly 90 includes four hanging fingers 92 ( only two of which are illustrated ) which are inserted into the open bag while it is held open by the bag opening apparatus 10 . the four fingers 92 are initially collapsed so that they may enter the bag b without interference , and thereafter expanded to open the periphery of the open end of the bag to its full extent . after the bag b has been hung , the knife cylinder 84 is actuated to reciprocate knife blade 86 and sever the wicket extension 78 of the bag . at least some of the hanging fingers 92 include detection heads 94 which are capable of sensing when the bag b is firmly secured by the suspension assembly 90 . conveniently , the detection head may work by bleeding a small air stream which is shut off as pressure is exerted laterally on the detection head 94 . this results in a pressure increase which may be detected automatically . failure to detect pressure increase will prevent product from being inserted into the bag and may also trip an alarm or the like . referring now to fig5 a - 5c , the operation of the bag filling assembly 70 and the bag opening apparatus 10 of the present invention will be described . as illustrated in fig5 a , the bag opening operation begins by extension of the first piston and cylinder assembly 22 so that pins 42 penetrate at least the first bag . as they penetrate , the pins 42 are held parallel to each other by the linkage assembly 56 . as the first piston assembly 22 is extended , the second piston and cylinder assembly 26 is also extended so that the bumper 36 is in its extended position as shown in broken line in fig5 a . after the pins 42 have penetrated the bags b , the pins 42 are pivoted away from each other , as illustrated in fig6 . the first piston and cylinder assembly 22 is then retracted , and the pins 42 will draw the opposed face 80 of the first bag b on the wicket to the right as illustrated in fig5 a - 5c . as the face is drawn to the right , the bag will open as illustrated at b &# 39 ; in fig5 b . the extent of the opening is controlled by the position of the bumper 36 which stops the travel of carriage 14 at a desired location . as illustrated in fig5 b , the bag b &# 39 ; is supported on one side by the wicket extension 78 on the bag and on the other face by the pins 42 of the bag opening assembly 10 . once the bag b has been opened , the hanging fingers 92 of the bag suspension assembly 90 are lowered into the bag and expanded outward to secure the bag b &# 39 ; about its peripheral opening . once the bag b &# 39 ; is firmly suspended by the suspension asemmbly 90 , the wicket 78 is severed by knife blade 86 and the stop bumper 36 of the second piston and cylinder assembly 26 is retracted . the pins 42 are then returned to their parallel position , and the carriage 14 is retracted . the bag filling operation is accomplished simultaneously with the retraction of the bag opening apparatus 10 , and once completed , the bag filling cycle is ready to be repeated . although the foregoing invention has been described in some detail by way of illustration and example for purposes of clarity of understanding , it will be obvious that certain changes and modifications may be practiced within the scope of the appended claims .