Abstract:
A slotted spool valve for a speed control apparatus offering rapid response to prevent speed searching and cogging at low speed settings. Round port spool valve arrangements are replaced with a valve arrangement having rectangular-shaped ports. Response of the rectangular-shaped ports provides for rapid and sufficient fluid flow or bypass with less movement of a control shaft than that required for use with round port spool valve arrangements.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     This patent application is an improvement over the invention by the same inventors entitled “Speed Control Apparatus” which forms the subject matter of U.S. Pat. No. 3,703,810 issued Nov. 28, 1972. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is for a slotted spool valve for use in a speed control apparatus. 
     2. Description of the Prior Art 
     The prior art speed control apparatus disclosed in U.S. Pat. No. 3,703,810 includes an arrangement of gears and other components which operates a rotary spool valve  22  in a manifold  17  in which the rotary spool valve  22  resides. Variation from the desired controlled speed as sensed or determined by an input shaft  14 , such as caused by imposing a load on the hydraulic motor  10  referred to in said patent 3,703,810, for example, would cause rotation of the rotary spool valve  22  to decrease the amount of pressurized hydraulic fluid bypassed in the manifold  17 , thereby allowing increased porting of pressurized hydraulic fluid to the motor  10  and thereby compensating for the speed of the motor, such compensation being of lasting duration or being only momentarily. Upon regaining and coming up to speed, or even when slightly overspeeding, such rotation speed is yet sensed by the input shaft  14 , and the rotary spool valve  22  is rotatingly positioned in the opposite direction to establish or limit the revolutions per minute of the motor  10  by increasing the amount of pressurized hydraulic fluid bypassed, thereby decreasing the amount of ported pressurized hydraulic fluid to the motor  10 . Such controlling or governing of motor speed at higher RPMs of the motor  10  virtually goes unnoticed to an observer as the compensations occur over fractions of a second. However, during desired lower RPM operation of the motor  10 , undesirable speed variations become noticeable to an observer where speed variations, being sometimes referred to as cogging, are manifested when pressurized hydraulic fluid is delivered to the motor in a lagging or sluggish fashion. The relationship of the rotary spool valve  22  angular rotation to the amount of fluid at the motor  10  is such that the amount of fluid bypassed or not bypassed in a condition requiring compensation is not suitable to prevent noticeable cogging. The ports  24  which determine the amount of bypassing are circular in shape and as such do not provide for sufficiently decreased bypassing to allow for increased amounts of pressurized hydraulic fluid to be bypassed or delivered in a timely fashion to the motor  10  during low speed operation. Insufficiently pressurized hydraulic control fluid bypass or delivery allows the motor to laggingly slow and then to laggingly come up to speed (or approach overspeed) to cause cogging. Clearly, what is needed is a restructuring of the ports or orifices of a rotary spool valve to allow for bypass control to deliver and control sufficient quantities and pressure of pressurized hydraulic fluid in a timely fashion to prevent hydraulic motor speed variations and to stabilize rotation at low motor speeds. 
     SUMMARY OF THE INVENTION 
     The general purpose of the present invention is to provide a slotted spool valve for use in a speed control apparatus. 
     According to one embodiment of the present invention, there is provided a slotted spool valve the major components of which are a liner and a spool which is accommodated by the liner. The slotted spool valve can be incorporated into existing manifolds or can be incorporated into newly manufactured manifolds. The cylindrical liner is fabricated to be accommodated by a bore extending into or through a manifold and is sealingly fitted therein with a plurality of O-ring seals. Pressurized hydraulic fluid is delivered through the manifold to provide pressurized hydraulic fluid to a motor and to the slotted spool valve which can control motor speed by varyingly bypassing pressurized hydraulic fluid around the motor. A plurality of liner supply ports around and about the liner of the slotted spool valve communicate with and supply pressurized hydraulic fluid to one or more spool supply ports positioned on the spool of the slotted spool valve. The pressurized hydraulic fluid passes through the spool supply ports and through the interior of the spool to exit the spool at a plurality of rectangular-shaped spool bypass ports located around and about one end of the spool which communicate with a plurality of rectangular-shaped liner bypass ports located around and about the encompassing liner. Full communication of pressurized hydraulic fluid between the fully aligned rectangular-shaped spool bypass ports and the rectangular-shaped liner bypass ports results in bypassing the pressurized hydraulic fluid around the motor to cease or slow motor operation. Rotation of the spool toward lesser alignment of the rectangular-shaped spool bypass ports and the rectangular-shaped liner bypass ports results in reducing the bypassing, whereby the motor receives an increased share of pressurized hydraulic fluid to increase the motor speed. The relationship of the rectangular-shaped spool bypass ports and the rectangular-shaped liner bypass ports when compared to the relationship of round-shaped spool bypass ports and round-shaped liner bypass ports is such that only a small angular rotation of the spool in the slotted spool valve as rotationally positioned by an actuation shaft is required to produce the same degree of bypassing (or fluid delivery) as that produced by a valve having round bypassing ports and requiring a comparatively larger angular rotation by an actuation shaft of the spool having round liner or spool bypass ports. Or, for the same amount of actuation shaft rotation, a more rapid response is provided by the slotted spool valve where a proportionately larger passageway is provided due to the cross-section of the geometry provided therein. As such, response time of the motor is improved as pressurized hydraulic fluid is either bypassed about the motor or delivered to the motor in a more rapid fashion due to the increased sensitivity and shortened response time of the slotted spool valve incorporating rectangular-shaped spool bypass ports and rectangular-shaped liner bypass ports. 
     One significant aspect and feature of the present invention is the use of a slotted spool valve to control bypassing, metering or supply of hydraulic fluid to a hydraulic motor. 
     Another significant aspect and feature of the present invention is a slotted spool valve having a spool with rectangular ports and a liner with rectangular ports which are positioned with respect to each other to rapidly control the bypassing, metering of and supply of pressurized hydraulic fluid to a hydraulic motor. 
     Still another significant aspect and feature of the present invention is the use of a slotted spool valve incorporating rectangular ports to significantly increase responsiveness and sensitivity of a spool valve to increase the responsiveness of a hydraulic motor at low speeds. 
     Yet another significant aspect and feature of the present invention is the increased responsiveness and sensitivity of spool valves having rectangular-shaped spool and liner bypass ports over spool valves having round-shaped spool and liner bypass ports. 
     Another significant aspect and feature of the present invention is a slotted spool valve having a spool which can be rotatably positioned. 
     Having thus briefly described an embodiment of the present invention, it is the principal object of the present invention to provide a slotted spool valve having increased response and sensitivity for use in a speed control apparatus. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects of the present invention and many of the attendant advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, in which like reference numerals designate like parts throughout the figures thereof and wherein: 
     FIG. 1 is an isometric view of a slotted spool valve for a speed control apparatus, the present invention, aligned to a representative manifold; 
     FIG. 2 is an exploded view of the slotted spool valve; 
     FIG. 3 is a cross sectional view of the assembled spool aligned with the assembled liner; 
     FIG. 4 is a cross sectional view of the slotted spool valve consisting of the liner and the contained the spool both residing in the bore of the manifold; 
     FIG. 5 is a hydraulic schematic showing the incorporation of the slotted spool valve within the manifold; 
     FIG. 6 is an isometric view of the slotted spool valve in the partially open position where the spool is at a position which allows a sufficient amount of hydraulic fluid to pass therethrough to maintain a desired hydraulic motor speed; and, 
     FIGS. 7 a - 7   d  are views comparing a prior art spool valve (round ports) with the inventive slotted spool valve (rectangular ports). 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 illustrates an isometric view of a spool valve for a speed control apparatus, herein called a slotted spool valve  60 , an improved spool valve, which can be incorporated into the speed control apparatus described in U.S. Pat. No. 3,703,810 by the applicants. The slotted spool valve  60  is shown prior to alignment with a bore  62  extending through a representative manifold  64 , different from but serving the same purpose as the manifold  17  of U.S. Pat. No. 3,703,810, which is detached from or which could be geometrically configured, if desired, to mount on or about or be connected to the motor  10  of U.S. Pat. No. 3,703,810. The manifold  64  includes at least an inlet attachment port  66  and a motor supply attachment port  68 , which are in common, and an outlet attachment port  70 , each port being appropriately connected and in communication with the slotted spool valve  60 , as later described in detail. 
     FIG. 2 illustrates an exploded view of the slotted spool valve  60 , the present invention. The major components of the slotted spool valve  60  include a spool  72 , which can be rotationally positioned, and a liner  74  into which the spool  72  and into which a snap ring  76  and a plug assembly  78  are aligningly accommodated. The liner  74  is shaped generally as a cylinder and includes an exterior surface  80  which is interrupted by an O-ring groove  82 , an annular channel  84  having a plurality of rectangular liner bypass ports  86   a - 86   n  extending therethrough to a liner interior  88 , an annular channel  90  having a plurality of liner supply ports  92   a - 92   n  extending therethrough to the liner interior  88 , and an interior groove  93  for accommodation of the snap ring  76  which secures the plug assembly  78  in one end of the liner  74 . The spool  72  is formed, in general, in cylindrical fashion being interrupted by an annular channel  94  through which one or more spool supply ports  98  extend therethrough to communicate with the spool interior  100 . A plurality of rectangular spool bypass ports  102   a - 102   n  are located around and about one end of the spool  72  and extend therethrough to communicate with the spool interior  100 . The spool  72  is closed on one end and sealed at the opposite end by a plug  96 . The plug  96  includes a coupling receptor  97  for accommodation of a coupling  99  such as attached to the end of shaft  36  shown in U.S. Pat. No. 3,703,810. Grooves  104  and  106  encompass one end of the spool  72 . 
     FIG. 3 illustrates an assembled view of the spool  72  and of the liner  74  in cross section. 
     FIG. 4 illustrates the slotted spool valve  60  consisting of the liner  74  and the contained the spool  72  residing in the bore  62  of the manifold  64 . The manifold  64  includes annular channels interrupting the bore  62  including an inlet channel  112  which is annular and which communicates through the inlet attachment port  66  and an outlet channel  114  which is also annular and which communicates through the outlet attachment port  70 . The inlet channel  112  also communicates directly to the motor supply attachment port  68 . The preceding mentioned ports  66 ,  68  and  70  are shown in simple form for the purposes of brevity and clarity. 
     The inlet channel  112  aligns closely to the annular channel  90  surrounding the liner  74  and as such communicates through the liner supply ports  92   a - 92   n  to the spool interior  100  via the annular channel  94  and the spool supply port  98  extending through the annular channel  94 . Such communication, as described, is continuous regardless of the rotational position of the spool  72 . 
     The outlet channel  114  aligns closely to the annular channel  84  surrounding the liner  74  and as such is in a position to variably communicate through the rectangular liner bypass ports  86   a - 86   n  of the liner  74  through the rectangular spool bypass ports  102   a - 102   n  of the spool  72  with the interior  100  of the spool  72 . Such communication, as described, is variable depending on the angular rotational position of the spool  72 . The spool  72  can be positioned to allow no communication therethrough or can be positioned to allow partial communication therethrough or can be positioned to allow full communication therethrough. 
     The exterior surface  80  of the liner  74  is in close juxtaposition with the bore  62  of the manifold  64 , and the liner  74  is sealed by O-rings to seal the slotted spool valve  60  to and within the bore  62 . A plurality of O-rings  108   a - 108   n  residing in O-ring grooves in the bore  62  of the manifold  64  seal against the exterior surface  80  of the slotted spool valve  60  at one end of the slotted spool valve  60 , and another O-ring  110  residing in the O-ring groove  82  of the liner  74  seals the bore  62  of the manifold  64  at the opposing end of the slotted spool valve  60 . An intermediate O-ring  111  residing in an O-ring groove in the bore  62  of the manifold  64  seals against the exterior surface  80  of the liner  74 . An oil groove  109  in the bore  62  of the manifold  64  is connected to a passage  113  in the manifold  64 . Passage  113  also connects to the rectangular liner bypass ports  86   a - 86   n  of the liner  74  through the outlet channel  114 . A check valve  115  is located in the manifold  64  and sealed thereto by O-rings  116  and  128 . The check valve  115  allows passage from the motor return port  117  to the outlet channel  114  with a restriction at the ball  126  to stabilize the motor  10 . The check valve  115  will also ensure that the motor  10  will not run backwards. Also shown in FIG. 4 is a liner nut  119  threadingly engaged in one end of the liner  74  in close proximity to the plug  96  and sealed therein by an O-ring  121 . The shaft  36  previously shown and described in U.S. Pat. No. 3,703,810 is accommodated by the liner nut  119  and extends therethrough to attach in a suitable manner to the coupling  99  which is accommodated by and attached in a suitable manner to the coupling receptor  97  at the one end of the spool  72 . 
     FIG. 5 is a hydraulic schematic showing the incorporation of the slotted spool valve  60  within the manifold  64  and the relationship thereof to a motor such as motor  10  shown in U.S. Pat. No. 3,703,810. 
     FIG. 6 illustrates the slotted spool valve  60  in the partially open position where the spool  72  is at a position which allows a sufficient amount of hydraulic fluid to bypass therethrough to maintain a desired hydraulic motor speed as controlled by the mechanisms described in U.S. Pat. No. 3,703,810. 
     FIGS. 7 a - 7   d  illustrate a comparison of prior art spool valves incorporating round ports  24 , such as incorporated in U.S. Pat. No. 3,703,810, with the rectangular ports of the slotted spool valve  60 . 
     FIG. 7 a  shows the normal operating position of the prior art rotatable round port(s)  24  with respect to the bypass passage  20  and FIG. 7 b  shows the normal operating position of the rotatable rectangular spool bypass port(s)  102   a - 102   n  with respect to the rectangular liner bypass port(s)  86   a - 86   n . The cross sections of bypass for FIGS. 7 a  and  7   b , as shown by cross hatches  118  and  120 , respectively, are identical in cross sectional area where each bypasses the same amount of hydraulic fluid to maintain a motor speed. 
     FIGS. 7 c  and  7   d  show the situation where a load is placed upon the motor whereby increased bypassing is invoked to allow a greater hydraulic delivery to the motor to allow the motor to handle the newly imposed load. FIG. 7 c  shows the components of FIG. 7 a  where a newly desired bypass cross hatch  122  of required size is produced by rotation of the port  24 . Such rotation of the port  24  could be clockwise, and, for example of illustration and demonstration, could be 10°. FIG. 7 d  shows the components of FIG. 7 b  where a newly desired bypass cross hatch  124  of required size is produced by rotation of the ports  102   a - 102   n . The area of the cross hatch  124  is equal to that of the cross hatch  122  (FIG. 7 c ) Such rotation of the ports  102   a - 102   n  could be clockwise, the same as for FIG. 7 c , but the amount of rotation of the rectangular spool bypass ports  102   a - 102   n  to achieve the same cross section  122  is less than 10° such as described for rotation of the round port  24 , and, for purposes of example and demonstration could be 5° of rotation. Because the rectangular spool bypass ports  102   a - 102   n  require less rotation to achieve an identical result, speed compensation response is increased significantly at a greater and faster rate than that provided for using the round port(s)  24 . It follows that reduction of the load on the motor calls for a response to offer more bypassing calls for actuation of the ports in an opposite direction. Of course, less movement is required by the rectangular spool bypass ports  102   a - 102   n , thus enhancing reduced response time. Such reduced response time in both directions is improved to a degree that speed hunting and searching is so quick and rapid that it is not discernible. 
     Various modifications can be made to the present invention without departing from the apparent scope hereof. 
     Slotted Spool Valve Parts List 
       20  bypass passage 
       24  round port 
       60  slotted spool valve 
       62  bore 
       64  manifold 
       66  inlet attachment port 
       68  motor supply attachment port 
       70  outlet attachment port 
       72  spool 
       74  liner 
       76  snap ring 
       78  plug assembly 
       80  exterior surface 
       82  O-ring groove 
       84  annular channel 
       86   a-n  rectangular liner bypass ports 
       88  liner interior 
       90  annular channel 
       92   a-n  liner supply ports 
       93  interior groove 
       94  annular channel 
       96  plug 
       97  coupling receptor 
       98  spool supply port 
       99  coupling 
       100  spool interior 
       102   a-n  rectangular spool bypass ports 
       104  groove 
       106  groove 
       108   a-n  O-rings 
       109  oil groove 
       110  O-ring 
       111  O-ring 
       112  inlet channel 
       113  passage 
       114  outlet channel 
       115  check valve 
       116  O-ring 
       117  motor return 
       118  cross hatch 
       119  liner nut 
       120  cross hatch 
       121  O-ring 
       122  cross hatch 
       124  cross hatch 
       126  ball 
       128  O-ring