Patent Publication Number: US-6698113-B1

Title: Decelerating fluid actuator for snowplows and other heavy machinery

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority under 35 USC §119(e) to U.S. Provisional Patent Application No. 60/346,533 filed Jan. 8, 2002, the entirety of which is incorporated by reference herein. 
    
    
     FIELD OF THE INVENTION 
     This disclosure concerns an invention relating generally to actuators for heavy machinery, and more specifically to fluid actuators (i.e., hydraulic and/or pneumatic actuators) used in snowplows to reposition plow moldboards with respect to the plowing vehicle. 
     BACKGROUND OF THE INVENTION 
     In machinery wherein heavy components are repositioned with respect to the remainders of the machines—for example, in plows where plow moldboards are repositioned with respect to the plowing vehicle—it is often useful to have some form of means for decelerating the heavy component as it approaches the remainder of the machine to reduce the chance of collision between components. As an example, consider FIG. 1, which illustrates an exemplary snowplowing vehicle at  100 . The snowplowing vehicle  100  has a front moldboard  102 , and a side moldboard  104  (commonly referred to as a wing plow because it is unfoldable from the plowing vehicle  100  like a wing). The wing plow  104  is hingedly affixed to the plowing vehicle  100  at an inner end  106 , and a fluid actuator  108  (generally a hydraulic actuator) extends between the plowing vehicle  100  and the midsection of the wing plow  104  to move the wing plow  104  between the folded and unfolded positions. When standard hydraulic actuators are used at  108 , problems sometimes arise when the actuator  108  is retracted. The wing plow  104  is pulled towards the plowing vehicle  100 , and depending on the fastening arrangement between the wing plow  104  and the plowing vehicle  100 , its retraction speed may increase as the wing plow  104  approaches the plowing vehicle  100 . This may lead to collision between the wing plow  104  and the plowing vehicle  100 , particularly when the wing plow  104  is more flexible and/or when the retraction speed is high. Even where the wing plow  104  is withdrawn at constant or diminishing speed, the inertia of the heavy wing plow  104  generally causes it to overshoot its standard at-rest folded position during retraction, and thereby causes it to collide with a plowing vehicle  100 . 
     Because of the size and weight of the wing plow  104 , it is capable of inflicting thousands of dollars of damage on the plowing vehicle  100  if the impact is significant. Such damage often occurs owing to the speed of plowing operations. Cities and counties necessarily try to limit their fleets of plowing vehicles  100  to no more than the minimum number of plows necessary because each plowing vehicle  100  involves a significant capital investment which is only used during a small portion of the year. However, during periods of heavy snow, public safety demands that the roads be cleared as soon as possible. Thus, the operator of each plowing vehicle  100  is concerned with clearing as much snow as possible, as soon as possible. The plowing vehicles  100  are therefore operated at slow driving speeds, generally 20-30 mph in residential areas, though faster speeds may be used on highways and on highly-traveled thoroughfares where fast clearance is needed for safety. During operation, the plow moldboards must often be rapidly repositioned for effective road clearance and/or to avoid obstacles, and the need for rapid repositioning may increase where there are driving conditions of low visibility. As an example, the wing plow  104  may need to be rapidly folded adjacent the plowing vehicle  100  when the operator of the vehicle  100  suddenly sees a mailbox or other object within the path of the wing plow  104 . The wing plow  104  may then be retracted at such a speed that it strikes the cab of the vehicle  100 , which may cause significant damage. The problem cannot be avoided by driving more slowly owing to the aforementioned need for rapid plowing; additionally, the operator cannot simply allow the wing plow  104  to strike objects in its path, since this will rapidly destroy the wing plow  104  (as well as the vehicle hydraulics owing to the shock to actuator  108 ). 
     A number of modifications have been made to plow actuators (such as actuator  108 ) to attempt to allow more rapid actuation without impact on the plowing vehicle  100 . A first approach is illustrated in FIG. 2, wherein a cross-sectional view of a modified wing plow fluid actuator  200  is shown. The fluid actuator  200  includes an actuator arm  202  which is driven by a piston  204  moving within a cylinder casing  206 . One of the piston  204  and the cylinder casing  206  is affixed to the plowing vehicle  100  or associated structure, while the other is affixed to the plow moldboard or associated structure, so that extension and retraction of the piston  204  within the cylinder casing  206  actuates the plow moldboard with respect to the plowing vehicle  100 . Within the cylinder casing  206 , the piston  204  is driven by fluid pumped into (or from) a face port  208  situated in front of the face of the piston  204 , and a tail port  210  situated on the opposite side of the piston  204 . Hydraulic lines  212  are shown connected to each of the face port  208  and tail port  210 . A restrictor  214  containing an orifice with reduced flow area is situated between the face port  208  and its hydraulic line  212 . Thus, when the actuator arm  202  is retracted within the cylinder casing  206  by pumping hydraulic fluid into the tail port  210  and/or out of the face port  208 , the restrictor  214  causes the piston  204  to travel more slowly owing to the decreased flow area it presents for withdrawal of hydraulic fluid. While this works well in helping to deter harsh impact of the wing plow  104  on the plowing vehicle  100 , it is disadvantageous in that folding and unfolding of the wing plow  104  is slowed throughout the entire range of motion of the actuator arm  202 . Therefore, this modification is disadvantageous where the wing plow  104  needs to be rapidly deployed or withdrawn. 
     Owing to this problem, the fluid actuator  300  shown in FIGS. 3-4 was developed. Such a fluid actuator  300  is commonly referred to in the industry as a “cushion cylinder” or “decel” (deceleration) cylinder because retraction is initially fast, but it slows in the latter part of retraction to avoid the shock of moldboard impact. Fluid actuator  300  is similar to the fluid actuator  200  in that it has an actuator arm  302  driven by a piston  304  within a cylinder casing  306  by fluid being pumped into or out of a face port  308  and a tail port  310  via hydraulic lines  312 . However, the piston  304  is modified so that it will decelerate during retraction. This is done by providing a cavity  316  in the sides of the piston  304  adjacent the cylinder casing  306 , and an aperture  318  in the face of the piston  304  which opens onto the cavity  316 . Thus, as the piston  304  is retracted, it will initially block the face port  308  (as shown in FIG.  3 ). Once the piston  304  is sufficiently retracted that the face port  308  opens onto the cavity  316  (as shown in FIG.  4 ), hydraulic fluid in front of the face of the piston  304  will flow through the aperture  318 , into the cavity  316 , and then through the face port  308 . The aperture  318  is formed with smaller flow area than the face port  308 . Therefore, once the piston  304  moves rearwardly of the face port  308 , the effective flow area for escape of hydraulic fluid from in front of the face of the piston  304  is reduced, causing the piston to retract at slower speed. The piston  304  therefore has a higher retraction speed over a first portion of its retraction, and a slower retraction speed over the latter portion of its retraction. An optional restrictor  314  having a function similar to that of restrictor  214  is also shown, and may be omitted if desired. 
     This arrangement works very well to avoid collision between the wing plow  104  and the plowing vehicle  100 , but is subject to certain disadvantages. The fluid actuator  300  is not well suited for mass manufacture because different plowing vehicles  100  have hydraulic pumps of different capacities, differently-sized moldboards  102 , etc., which leads to the problem that an aperture  318  which is appropriately sized for a desired retraction speed in one plowing vehicle  100  might not be appropriately sized for another plowing vehicle  100 . Thus, an approach as in FIGS. 3 and 4 was taken wherein the aperture  318  is defined within a restrictor  320  threadedly inserted in the piston  304 . Thus, the piston  304  and cylinder casing  306  could be mass-manufactured, and different restrictors  320  of different sizes could be installed within the pistons  304  to attain the desired retraction speed. 
     However, this approach is not entirely problem-free because the restrictors  320  cannot be removed and replaced without disassembly of the cylinder casing  306  to remove the piston  304 . The cylinder casing  306  is opened at its seams (not shown in the drawings) and the piston is withdrawn, generally after the fluid actuator  300  has been left to drain for a while to avoid excessive spillage of hydraulic fluid. This is messy and time-consuming work, and the time needed to modify the fluid actuator  300  is particularly troublesome. Plowing shops may have a number of different plowing vehicles but may keep only one spare fluid actuator  300  on hand in case of breakage in one of the vehicles. When such breakage occurs, there is generally a need to replace the broken actuator with a new fluid actuator  300  as soon as possible to get the plowing vehicle  100  back on the road. This is difficult to do when one must disassemble the fluid actuator  300  in order to install and properly tune its restrictor  320 . Thus, it would be desirable to have a fluid actuator which decelerates in the latter part of its retraction, and which allows a user to tailor such deceleration as desired without having to disassemble the cylinder casing. 
     SUMMARY OF THE INVENTION 
     The invention involves a plowing vehicle which incorporates a decelerating fluid actuator, and which is intended to at least partially solve the aforementioned problems. To give the reader a basic understanding of some of the advantageous features of the invention, following is a brief summary of preferred versions of the decelerating fluid actuator. As this is merely a summary, it should be understood that more details regarding the preferred versions may be found in the Detailed Description set forth elsewhere in this document. The claims set forth at the end of this document then define the various versions of the invention in which exclusive rights are secured. 
     In particularly preferred versions of the invention, a plow including a plowing vehicle and a moldboard has a decelerating fluid actuator. The fluid actuator includes a piston which travels within a cylinder, with an actuator arm extending from the piston so that connection of the actuator arm to one of the plowing vehicle or moldboard, and connection of the cylinder&#39;s casing to the other of the plowing vehicle or moldboard, allows adjustable positioning of the moldboard with respect to the plowing vehicle during operation of the fluid actuator. The cylinder has first and second ports which are successively blocked as the piston is retracted within the cylinder, with the second port being blocked after the first port during retraction. An enclosure having an enclosure interior and an enclosure exterior is provided outside the cylinder, with the enclosure interior defining a passage between the ports and connecting the ports to a fluid supply. The flow area of the passage between the ports is adjustable from the enclosure exterior without removal of the enclosure from the cylinder casing. As a result, when the piston begins retraction, fluid in front of the face of the piston may flow through both of the first port and through the enclosure interior to the fluid supply, and also through the second port and through the passage within the enclosure interior to the fluid supply. The flow areas of both the first port and the second port (and passage) are therefore effective to convey fluid to the fluid supply. However, when the piston retracts to a sufficient degree that the first port is blocked, fluid may flow solely through the second port, and in turn through the passage in the enclosure interior to the fluid supply. If the flow area of the passage is smaller than the flow area presented when the first port is unobstructed by the piston, the retraction speed of the piston is reduced once the first port is obstructed (i.e., during the latter portion of retraction), thereby reducing the speed at which the moldboard approaches the plowing vehicle. 
     To allow adjustment of the retraction speed during the latter portion of retraction, the flow area presented by the passage is preferably made adjustable from the enclosure exterior without the need to remove the enclosure from the cylinder casing. This is preferably done by providing a restrictor within the enclosure between the first and second ports, wherein the restrictor defines the flow area of the passage. In one version of the invention (illustrated in FIGS.  5  and  6 ), this arrangement may be provided by an aperture extending from the enclosure exterior to the enclosure interior, and a removably insertable member can be received in the aperture to define a door allowing access to the enclosure interior. A removable restrictor having the passage defined therein may then be situated between the first and second ports, and the door may be used to access the restrictor (and remove it and replace it with other restrictors having different aperture sizes) when desired. In another version of the invention (illustrated in FIG.  7 ), an aperture extends from the enclosure exterior to the enclosure interior, and a removably insertable member can be received in the aperture to rest at least partially within the enclosure interior, and thereby define a restrictor which varies the flow area of the passage in accordance with its degree of removal from the enclosure interior. Other versions of the invention are possible in accordance with the foregoing concepts. 
    
    
     Further advantages, features, and objects of the invention will be apparent from the following detailed description of the invention in conjunction with the associated drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side perspective view of a plow, wherein a plowing vehicle  100  has plow moldboards  102  and  104  affixed thereon, and fluid actuators  108  which drive the plow moldboards with respect to the plowing vehicle. 
     FIG. 2 is a schematic view of a fluid actuator  200  suitable for use in a plow such as that of FIG. 1 (shown in cross-section). 
     FIGS. 3 and 4 are schematic views of a modified version of the fluid actuator of FIG. 2 (shown in cross-section), with FIGS. 3 and 4 illustrating the piston  304  of the fluid actuator  300  in different stages of retraction. 
     FIGS. 5 and 6 are schematic views of a first preferred version of a decelerating fluid actuator  500  for use in the invention (shown in cross-section), with the piston  504  of the fluid actuator shown in different stages of retraction. 
     FIG. 7 is a schematic view of a second preferred version of a decelerating fluid actuator  700  for use in the invention (shown in cross-section). 
    
    
     DETAILED DESCRIPTION OF PREFERRED VERSIONS OF THE INVENTION 
     Turning to FIGS. 5 and 6, a first preferred version of a decelerating fluid actuator  500  suitable for use with a plowing vehicle (such as the plowing vehicle  100  of FIG. 1) is schematically illustrated in cross-section. The fluid actuator  500  includes an actuator arm  502  connected to a piston  504 , with the piston  504  being movable within a cylinder defined by a cylinder casing  506 . The piston  504  is actuated within the cylinder casing  506  by the pressure of fluid coming to or from a first face port  508   a  and/or a second face port  508   b  adjacent the face of the piston  504 , and also by the pressure of fluid coming to or from a tail port  510  adjacent the tail of the piston  504 . The face ports  508   a / 508   b  are connected by a hydraulic line  512  to a fluid supply (not shown), as is the tail port  510 . As the piston  504  travels within the cylinder casing  506  to retract the actuator arm within the cylinder casing  506 , the first face port  508   a  and second face port  508   b  are successively blocked by the piston  504 , with the second face port  508   b  being blocked after the first face port  508   a.    
     An enclosure  522  is provided on the cylinder casing  506  outside the cylinder (i.e., outside the path of travel of the piston  504 ), with the enclosure  522  having an enclosure exterior  524  which is preferably contiguous with the cylinder casing  506 , and an opposing enclosure interior  526 . The enclosure interior  526  defines a passage  528  between the first face port  508   a  and second face port  508   b . At the side of the passage  528  adjacent the second face port  508   b , a door  530  leads from the enclosure exterior  524  to the enclosure interior  526 . While such a door may take a variety of forms, here the door  530  is depicted as a member which is threaded into an aperture  532  which extends between the enclosure exterior  524  and enclosure interior  526 . At the side of the passage  528  adjacent the first face port  508   a , the passage  528  opens on to an exterior enclosure port  534 , which in turn opens onto hydraulic line  512 . A restrictor  514  is illustrated between the exterior enclosure port  534  and the hydraulic line  512 , but this restrictor  514 —which serves essentially the same purpose as the restrictor  214  of FIG.  2 —is optional and need not be included. 
     A restrictor  536  is then provided within the enclosure interior  526  between the first face port  508   a  and second face port  508   b , with the interior of the restrictor  536  defining a portion of the passage  528  with diminished flow area. Thus, as can be seen by comparison between FIG.  5  and FIG. 6, when the piston  504  is retracted, fluid in front of the face of the piston  504  exits the cylinder casing  506  through both the first face port  508   a  and second face port  508   b  and then through the exterior enclosure port  534 , with lesser fluid flowing through the second face port  508   b  owing to the presence of restrictor  536  between the second face port  508   b  and the exterior enclosure port  534 . Stated succinctly, greater flow may occur out the first face port  508   a  than second face port  508   b . Turning then to FIG. 6, when the piston  504  is retracted sufficiently to obstruct the first face port  508   a , the fluid may only exit through second face port  508   b  (and thus must pass through restrictor  536 ). Since flow is restricted, the piston  504  experiences greater resistance to retraction once the first face port  508   a  is blocked, and thus the piston  504  slows once it is retracted sufficiently that the first face port  508   a  is blocked. 
     The door  530  is then beneficial because it allows a user to access the restrictor  536  from the enclosure exterior  524  for adjustment without the need to disassemble the cylinder casing  506  or otherwise remove the piston  504 , and the user additionally need not remove the enclosure  522  from the cylinder casing  506 . In the fluid actuator  500  shown in FIGS. 5 and 6, the restrictor  536  is provided in the form of a plug which has a portion of the passage  528  defined therein, and which is threadedly inserted within the enclosure interior  526  between the first face port  508   a  and the second face port  508   b . Close inspection of the restrictor  536  illustrated in FIGS. 5 and 6 with restrictors previously described (e.g., restrictor  514 ) shows that restrictor  536  is differently shaped: the portion of the passage  528  within the restrictor  536  has a converging orifice portion  538  providing an orifice with reduced flow area, and an engagement portion  540  configured so that an allen wrench, screwdriver, or other common tool can be inserted into the restrictor engagement portion  540  of the passage  528  to engage the restrictor  536 . After such a tool is inserted in the engagement portion  540 , the restrictor  536  may be adjusted within the enclosure interior  526  by moving it along its threads  542 . Thus, if the user needs to rapidly replace a restrictor  536  with a different restrictor having a differently-sized converging orifice portion  538 , the user need merely remove the door  530 , insert an appropriate fastener within the engagement portion  540  of the restrictor  536 , and unscrew it until it may be removed from the door  530 . The user may then insert an appropriately-sized restrictor  536 , replace the door, and the modified fluid actuator  500  is ready for use. 
     Turning to FIG. 7, a second preferred version of a decelerating fluid actuator for use in the invention is generally depicted by the reference numeral  700 . Similarly to the foregoing fluid actuators, an actuator arm  702  is moved by a piston  704  situated within a cylinder casing  706 , with the piston  704  being moved within the cylinder by hydraulic fluid coming to/from a first face port  708   a , a second face port  708   b , and a tail port  710 . Hydraulic lines  712  communicate fluid to these ports, and an optional restrictor  714  (which may be omitted if desired) is also depicted. An enclosure  722  is provided outside the cylinder on the cylinder casing  706 , and has an enclosure exterior  724  and an opposing enclosure interior  726  wherein a passage  728  leads between the first and second face ports  708   a  and  708   b . The size of the passage  728  is regulated by a restrictor  730  which is threadedly inserted into an aperture  732  extending between the enclosure exterior  724  and the enclosure interior  726 . Thus, as the piston  704  is retracted within the cylinder casing  706  along the path defined by the cylinder, hydraulic fluid in front of the face of the piston  704  will initially travel through both of the first and second face ports  708   a  and  708   b , with flow in the second face port  708   b  being lesser (provided the passage  728  defined the restrictor  730  provides less flow area than the first face port  708   a ). When the piston  704  retracts to a sufficient degree that the first face port  708   a  is blocked, fluid will flow solely through the second face port  708   b , through the passage  728 , and in turn through the exterior enclosure port  734 . Since the effective flow area for hydraulic fluid is reduced once the first face port  708   a  is blocked, retraction of the piston  704  is slowed during the latter portion of retraction of the piston  704 . 
     The various preferred versions of the invention are shown and described above to illustrate different possible features of the invention and the varying ways in which these features may be combined. Apart from combining the different features of the above versions in varying ways, other modifications are also considered to be within the scope of the invention. Following is an exemplary list of such modifications. 
     A wide variety of other restrictor arrangements are possible apart from those described here. For example, the restrictor  536  of FIG. 5 could be integrally formed within enclosure  522 , and might be provided to a user with a minimally-sized converging orifice portion  538 . If the user then requires a larger converging orifice portion  538 , a user may insert a drill bit into door  530 , bore out the converging orifice portion  538  to adjust its size as desired, and then close the door  530  to prepare the fluid actuator  500  for use. Naturally, this only allows only upward adjustment in the size of the converging orifice portion  538  rather than downward sizing, though a user might insert a separate restrictor (similar to restrictor  536 ) within the bored-out converging orifice portion  538  if downward sizing is desired. 
     As another example, the restrictor  536  in the fluid actuator  500  need not include a converging orifice portion  538  at all, and the restrictor engagement portion  540  may simply be extended through the restrictor  536  to provide the passage  528 . The flow area between the first face port  508   a  and the exterior enclosure port  534  may then be adjusted by moving the end of the restrictor  536  sufficiently close to the door  530  that the space between that end of the restrictor  536  and the door  530  effectively becomes the restrictor&#39;s converging orifice portion. Alternatively, the door  530  might itself include a protruding portion which extends partway into the passage  528  to reduce its effective flow area (in which case the door  530  effectively becomes a restrictor similar to the restrictor  730  of FIG.  7 ). 
     The invention is not intended to be limited to the preferred versions described above, but rather is intended to be limited only by the claims set out below. Thus, the invention encompasses all alternate versions that fall literally or equivalently within the scope of these claims.