Heald frame driving method in negative dobby machines or cam machines
BACKGROUND OF THE INVENTION 
     This invention relates to a driving method for moving a healed frame up and down in negative dobby machines or negative cam machines installed to looms. 
     In the prior art, when a resilient transmission member such as a rope connected to a shedding lever of a negative dobby machine or cam machine is disposed above a heald frame, the heald frame driving method is performed by raising the heald frame using tension of the rope and depressing it using spring restoring force. In this driving method, however, for example, when spun yarn fabric is woven in refined clothing fashion, if the tension of the downward warp is made larger than that of the upward warp, spring tension must be increased. Since the heald frame is raised against the above mentioned spring tension, a large force acts on the rope and on the negative dobby machine body or the negative cam machine body, thereby abrasion is increased in such part and power is lost. Moreover, since the spring and related members are disposed below the heald frame, maintenance is inconvenient and operability is not favorable. 
     SUMMARY OF THE INVENTION 
     This invention involves a heald frame driving method when a resilient transmission member such as a rope connected to a shedding lever of a negative dobby machine or cam machine is disposed above a heald frame, wherein the resilient transmission member is engaged with the heald frame through a working lever, a connecting rod or the like, and driving is effected so that the heald frame is moved downwards by tension of the resilient transmission member and upwards by restoring force of a spring, and the operating lever, connecting rod, spring and the like are arranged at the side or top of the heald frame. 
     An object of this invention is to provide a heald frame driving method apparatus wherein spring tension acting on a heald frame is small when tension of the downward warp is less than that of the upward warp, and abrasion is small on the resilient transmission member at the working member such as the negative dobby machine body or cam machine body. 
     Another object of this invention is to provide a heald frame driving method, wherein the working lever, connecting rod and spring to engage the resilient transmission member with the heald frame are arranged at the side or top of the heald frame, and maintenance and adjustment are easy. 
     Still another object of this invention is to provide a heald frame driving method wherein power loss is small. 
     The above mentioned and other objects and features of this invention will be apparent from the following description referring to the accompanying drawing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a schematic front view of an embodiment of this invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows an embodiment of this invention. In the figure, a negative dobby machine body 2 is mounted on the right end of the upper surface of a top beam 1 of a loom, and a plurality of heald frames 11, which correspond to a plurality of shedding levers (not shown) of the negative dobby machine body 2 and have the same number as that of the shedding levers, are arranged in the longitudinal direction. One shedding lever is connected to two ropes 3a, 3b for one heald frame 11 corresponding thereto. The top beam 1 of the loom is provided with pins projecting at positions left and right of the center of the beam, and a plurality of guide pulleys 15a, 15b corresponding to the heald frames 11 are rotatably supported by respective pins. Shafts 10 project respectively on both side frames 9a, 9b of the loom at the sides of the heald frames 11, and a plurality of working levers 4a and 4b are pivotally supported respectively by the shafts 10 corresponding to each heald frame 11. The working levers 4a and 4b are formed in lateral symmetry and are provided with sector portions 5a, 5b on the upper side, connecting portions 6a, 6b on the inner side, and arms 7a, 7b on the outer side. The rope 3a guided by the guide pulley 15a is connected to the sector portion 5a; the rope 3b guided by the guide pulley 15b is connected to the sector portion 5b.  Connecting rods 8, 8 are joined with pins respectively to the connecting portions 6a, 6b, and each of the connecting rods 8, 8 stands upright and the bottom end thereof is pivotally connected to the heald frame 11. Hooks 12, 12 are joined with pins respectively to outer ends of the arms 7a, 7b, and brackets 14a, 14b are installed below the arms 7a, 7b in opposing relation thereto. The brackets 14a, 14b are attached to the side frames 9a, 9b, and two tension coil springs 13 are stretched between the hooks 12, 12 and the brackets 14a, 14b respectively. 
     In the negative dobby machine as above constituted, when the shedding lever (not shown) of the negative dobby machine body 2 oscillates and the ropes 3a, 3b are pulled, the left working lever 4a rotates in the clockwise direction against torque of the coil spring 13 and the right working lever 4b rotates in the counterclockwise direction, thereby the heald frame 11 is moved downwards through the connecting rods 8, 8. When the shedding lever is restored, both working levers 4a, 4b are also restored by means of the restoring force of the coil spring 13, thereby the heald frame is moved upwards. Since the longitudinal position on the upper side of the heald frame 11 is defined by the connecting rods 8, the heald frame 11 is provided with a guide member (not shown) only at the lower side thereof. In order to refine clothing fashion in spun yarn fabric, the distance from the shedding neutral position (i.e. the position where the warp is displaced neither upwards nor downwards by means of the heald) to the downward warp position is set larger than that to the upward warp position. Accordingly, tension in the downward warp is larger than that in the upward warp tension coil spring 13 with less tension may be used. As a result, the force applied to the rope or the negative dobby machine body 2 in order to drive the heald frame 11 against the spring tension becomes small. 
     Although the above mentioned embodiment is described regarding a negative dobby machine, similar function is obtained when the negative dobby machine body 2 is replaced by a negative cam machine body in the above mentioned embodiment. 
     Moreover, the tension coil spring 13 in the above mentioned embodiment may be replaced by another tension coil spring connecting the heald frame 11 with the top beam 1.