Abstract:
A valve tip and its associated recess are provided along each line from the center of the cylinder through the center, or axis, of a suction port.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    A typical reciprocating compressor will have a valve plate with one, or more, suction ports and discharge ports formed therein. Normally the suction and discharge valves will be of the same general type. Each valve would be normally closed and would open due to a pressure differential across the valve in the direction of opening. Since suction valves open into the compression chamber/cylinder they generally do not have valve backers in order to minimize the clearance volume and thus deflection of the valve is not physically limited. When a suction valve opens, the valve tip(s) engage recess(es) in the crankcase after a small amount of opening movement with further opening being due to flexure of the valve away from the valve seat and into the cylinder.  
           [0002]    The resilience of the suction valves and adherence of the valve to the valve seat due to an oil film (“stiction”) resists the opening of the suction valve. The opening movement of the suction valve before the tip(s) engage the recess(es) would only permit a restricted flow into the cylinder. So, the valve tip slams into the recess and flexes into the cylinder for every cycle. The greatest degree of flexure occurs, nominally, at the mid-point of the valve between the tip support and the pin support. Because the valve tips are located near the suction ports and because the valve tips are in a nominal line contact with the crankcase, the valve tips tend to be stressed which can result in valve failure by permitting the valve to be drawn into the cylinder.  
         SUMMARY OF THE INVENTION  
         [0003]    For multi-port suction valves, each valve tip and the associated tip recess are located along lines extending from the axis of the cylinder through the axis of the associated suction port. This arrangement minimizes the distance between the axis of each suction port and the tip recess and places the load due to flow through the suction ports as close as possible to the cylinder wall tip support thereby minimizing the effects of transverse bending while shortening the span from the pins to the tips. This combination yields the valve with the lowest maximum stress.  
           [0004]    It is an object of this invention to reduce maximum operating stress on suction valves.  
           [0005]    It is another object of this invention to optimize valve tip and valve tip recess locations. These objects, and others as will become apparent hereinafter, are accomplished by the present invention.  
           [0006]    Basically, a valve tip and its associated recess are provided along each line from the center of the cylinder through the center, or axis, of a suction port. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    For a fuller understanding of the present invention, reference should now be made to the following detailed description thereof taken in conjunction with the accompanying drawings wherein:  
         [0008]    [0008]FIG. 1 is a cylinder side view of a valve plate showing one of two suction valves in place;  
         [0009]    [0009]FIG. 2 is a sectional view taken along line  2 - 2  of FIG. 1; and  
         [0010]    [0010]FIG. 3 is a view taken along line  3 - 3  of FIG. 2 and with the second suction valve in place. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0011]    In FIGS. 1 and 2, the numeral  30  generally designates a valve plate associated with two cylinders of a reciprocating compressor. Two, or more, suction passages  30 - 1  and  30 - 2  having axes A and B, respectively, and at least one discharge passage  30 - 3  having an axis C are associated with each cylinder. The point D corresponds to the axis of a cylinder. The point E corresponds to the axis of the bore  30 - 4  and pin/bolt  60  holding valve plate  30 , and discharge valve  50  in place when a single bolt  60  is used. If more than one bolt  60  is used, axis E would be at a mid-point of a line going through their centers. Pins  22  are received in bores  30 - 5  and secure suction valve  20  in place. Axis F is the mid-point between the axes of pins  22  and their bores  30 - 5  for each suction valve  20 . The axes A, B, C, D, E and F are illustrated as points or lines, even in the absence of the related structure, because of their relationships relative to the present invention. Referring specifically to FIG. 1, suction passages  30 - 1  and  30 - 2  are symmetrically located relative to a plane defined by axes C, D, E and F. It will be noted that the plane defined by axes C, D, E and F divides suction valve  20  into two symmetrical portions but that only two of the axes are necessary to define the plane. If there were two discharge passages associated with a cylinder, the plane of symmetry would be defined by axis D and E together with a mid-point of the axes of the two discharge passages. It will be noted that suction passages  30 - 1  and  30 - 2  are also symmetrically located as to suction valve  20  when it is in place. Discharge valve  50  is only visible through discharge passage  30 - 3 . Suction valve  20  has two arms or projections,  20 - 1  and  20 - 2 , respectively, which, as noted, are symmetrical with respect to suction valve  20 . The first arm  20 - 1  extends in the direction of a plane defined by axes A and D and terminates in a tip  20 - 1   a  which is symmetrical relative to the plane defined by axes A and D. The second arm  20 - 2  extends in the direction of a plane defined by axes B and D and terminates in a tip  20 - 2   a  which is symmetrical relative to the plane defined by axes B and D.  
         [0012]    In FIGS. 2 and 3, the numeral  10  generally designates a reciprocating compressor with two cylinders being illustrated. As is conventional, each cylinder of compressor  10  has a suction valve  20  and a discharge valve  50 , which are illustrated as reed valves, as well as a piston  42  which is located in bore a  40 - 3  of crankcase  40 . Valves  20  and  50  coact with valve plate  30  in their valving action. Discharge valve  50  has a backer  51  which limits the movement of valve  50  and is normally configured to dissipate the opening force applied to valve  50  via discharge passage  30 - 3  over its entire opening movement. When the valve  20  is in the open position which is shown in phantom in FIG. 2, tips  20 - 1   a  and  20 - 2   a  engage ledges  40 - 1   a  and  40 - 2   a  in recesses  40 - 1  and  40 - 2 , respectively, in crankcase  40  which act as valve stops. Ledges  40 - 1   a  and  40 - 2   a  are engaged after an opening movement of suction valve  20  on the order of 0.1 inches, in order to minimize the clearance volume, with further opening movement occurring by flexure of valve  20  as shown in phantom. Specifically, movement of valve  20  is as a cantilevered beam until tips  20 - 1   a  and  20 - 2   a  engage ledges  40 - 1   a  and  40 - 2   a , respectively. At this point there are three locations of support. The first is at the secured end of valve  20  and is in the nature of a line or thin band contact with crankcase  40  symmetrically located with respect to a plane defined by axes C, D, E and F and tending to produce the flexure shown in phantom in FIG. 2. This flexure is essentially about an axis perpendicular to the plane defined by axes C, D, E and F. At one level tips  20 - 1   a  and  20 - 2   a  effectively support the free end of the valve  20  to produce the flexure illustrated in phantom. This, however, is the result of the individual coaction of tips  20 - 1   a  and  20 - 2   a  with ledges  40 - 1   a  and  40 - 2   a , respectively. As best shown in FIG. 3, the portions of tips  20 - 1   a  and  20 - 2   a  overlying ledges  40 - 1   a  and  40 - 2   a , respectively, are the narrowest portions of valve  20  and are symmetrical about the planes defined by axes A and D and axes B and D, respectively. Being narrow, tips  20 - 1   a  and  20 - 2   a  are prone to being flexed. Due to the symmetry, tips  20 - 1   a  tends to flex about an axis transverse to the plane defined by axes A and D and tips  20 - 2   a  tends to flex about an axis transverse to the plane defined by axes B and D.  
         [0013]    Because flexure relative to tips  20 - 1   a  and  20 - 2   a  is about axes transverse to planes defined by axis A and D and axes B and D, respectively, the greatest amount of movement of tips  20 - 1   a  and  20 - 2   a  due to flexure is required to draw valve  20  into bore  40 - 3 . Because of the symmetry of tips  20 - 1   a  and  20 - 2   a  relative to the planes defined by axis A and D and axes B and D, the forces due to the gas flow through the suction ports  30 - 1  and  30 - 2  also act symmetrically. Stress is minimized by minimizing the effects of transverse bending by minimizing the distance between the applied load on the valve due to gas flow and the valve tip support by ledges  40 - 1   a  and  40 - 2   a.    
         [0014]    In operation, suction valves  20  are unseated during the suction stroke when the pressure differential across valves  20  is sufficient to overcome the inherent spring force of the valve  20 , adhesion forces, etc. Upon the unseating of a valve  20 , impingement by the suction flow through suction passages  30 - 1  and  30 - 2  flexes valve  20  relative to the fixed end of valve  20  until tips  20 - 1   a  and  20 - 2   a  engage ledges  40 - 1   a  and  40 - 2   a  of recesses  40 - 1  and  40 - 2 , respectively. At this point there is no longer flexure solely relative to a single fixed end. The major flexure is at a, nominal, mid-point between the fixed end and the tips  20 - 1   a  and  20 - 2   a  which engage ledges  40 - 1   a  and  40 - 2   a  about an axis transverse to a plane defined by axes C and D. Additionally, there is flexure by each of the tips  20 - 1   a  and  20 - 2   a  and/or by their respective arms and  20 - 1  and  20 - 2 . Tip  20 - 1   a  flexes about an axis transverse to a plane defined by axes A and D and tip  20 - 2   a  flexes about an axis transverse to a plane defined by axes B and D. The flexure of tips  20 - 1   a  and  20 - 2   a  causes their movement relative to ledges  40 - 1   a  and  40 - 2   a , respectively, to be directly towards axes A and B, respectively, which are at a minimum distance such that the maximum stress produced is reduced.  
         [0015]    It will be noted that movement of tips  20 - 1   a  and  20 - 2   a , to permit flexure, is along planes A-D and B-D, respectively, which is also along a radius of bore  40 - 3 . This results in movement along planes which results in the tips  20 - 1   a  and  20 - 2   a  being centered relative to recesses  40 - 1  and  40 - 2 . Accordingly, clearances around the tips  20 - 1   a  and  20 - 2   a  can be minimized thereby reducing the clearance volume and forces are balanced on the tips  20 - 1   a  and  20 - 2   a  in their engagement with recesses  40 - 1   a  and  40 - 2   a , respectively.  
         [0016]    Although a preferred embodiment of the present invention has been described and illustrated, other changes will occur to those skilled in the art. For example, three, or more, suction ports may be used. It is therefore intended that the scope of the present invention is to be limited only by the scope of the appended claims.