1.  Field of the Invention
The present invention relates to a double bedded warp knitting machine, and in particular to a double bedded warp knitting machine that utilizes an adjustment mechanism to separate the needle bars and associated trick plates to provide pile ware with different pile lengths. 
2.  Discussion of the Relevant Art
U.S. Pat.  No.  3,221,520 issued to R. G. Bassist on Dec. 7, 1965 discloses a double-needlebed warp knitting machine that makes provision for adjusting the pile height of the ware manufactured by individually moving the knockover points and needle bar by means of adjustment screws.  As disclosed, this was accomplished by utilizing two or more guide bars which cooperate with a needle and trick plate mounted and driven in one housing and a separate guidebar cooperating with a needle bar and trick plate mounted in another housing.  Both housing are capable of being moved apart so that the knockover points of both needle bars may be spaced apart as desired.  A third independent guidebar is used to swing from one needle bar to the other needle bar thereby providing the pile threads.  This causes the guide bar that swings from one needle bar to the other to be adjusted each time the distance between the two needle bars are varied.  This resetting requires a substantial amount of time and sufficient skill to have each piece aligned in the proper manner. 
The present invention overcomes this shortcoming by providing an adjustment mechanism that simultaneously moves the support members that carry the needle bar and trick plate close together or further apart while maintaining a constant distance between the needles on one needle bar with respect to the needles on the second needle bar at their uppermost dead point of travel so that a guide bar swinging around the pair of needle bars always swings the same distance regardless of the setting of pile height. 
Therefore, it is an object of the present invention to provide a needle bar adjustment mechanism to alter the separation between knockover points on a warp knitting machine that may be easily adjusted by a person having minimum skills. 
It is another object of the present invention to provide a needle bar adjustment mechanism to alter the separation between knockover points without deteriorating the speed of the machine. 
It is a further object of the present invention to provide a needle bar adjustment mechanism which simultaneously moves both needle bars and their associated trick plates with a single control knob. 
A needle bar adjustment mechanism to alter the separation between knockover points on a warp knitting machine, according to the principles of the present invention, having a frame, a pair of needle bars with a plurality of needles affixed thereon, a trick plate cooperating with each of the needle bars, a plurality of guide bars having a plurality of guides affixed thereon and a driving power source operatively coupled to the needle bars and the guide bars comprises in combination, a pair of support members having a guiding device for one of the needle bars and its associated trick plate affixed thereon.  An adjustment control is provided for simultaneously moving the support members apart to increase the separation between the trick plates while maintaining essentially constant the distance between the needles on one of the pair of needle bars with respect to the needles on the other needle bar at their uppermost dead point of travel. 
The foregoing and other objects and advantages will appear from the description to follow.  In the description, reference is made to the accompanying drawing which forms a part hereof, and in which is shown by way of illustration a specific embodiment in which the invention may be practiced.  This embodiment will be described in sufficient detail to enable those skilled in the art to practice the invention, and that it is to be understood that other embodiments may be utilized and that structural changes may be made without departing from the scope of the invention.  The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is best defined by the appended claims.