A snow plow includes a primary moldboard and auxiliary plow positioned behind the primary moldboard. The snow plow may be a one-way or reversible snow plow. In the later case, the primary moldboard and auxiliary plow are attached to a drive frame that is rotatable about a frame. The frame is secured to the front of a vehicle by a frame and bracket, and controlled by hydraulic mechanisms. The auxiliary plow is operated independently of the moldboard by a pair of hydraulic cylinders and includes tines or a resilient blade for clearing snow and ice that is not taken up by the primary moldboard. The device also includes a mechanism whereby the scraping edge of the secondary plow follows the same path as the scraping edge of moldboard by sliding movement of the secondary plow relative to the drive frame, and the blade of the auxiliary plow may be formed by tines or a resilient blade.

FIELD OF THE INVENTION

The present invention relates to plows and more particularly relates to plowing arrangements for clearing snow from pavement such as a road, a highway or a runway as well as to methods of clearing snow from pavement.

BACKGROUND OF THE INVENTION

An accumulation of snow is usually removed from pavement by a truck that is provided with a snowplow having a moldboard mounted on the front end of the truck. Typically, the plowing operation leaves some amount of snow or ice or slush on the pavement being cleared. When the snow or ice is packed down on the pavement surface, the ability of the moldboard to remove all or substantially all of the snow and ice is significantly reduced.

During a plowing operation, it is conventional to raise and lower the moldboard of the snow plow as desired and to change the angle that the moldboard of the snow plow makes with the longitudinal center axis of the truck, and therefore with respect to the longitudinal axis of the lane of pavement being cleared.

The moldboard of the snow plow may be selectively raised and lowered so that the plow truck may be driven with the lowermost edge of the moldboard either in contact (for conducting a plowing operation) or out of contact with the road, such as when the truck is being driven over pavement which has already been cleared of snow. Also, the snow plow is typically arranged to enable the angle of the plow with respect to the truck to be changed so that the snow plow can be used to divert snow to the left or to the right of the truck or used to push snow directly in front of the truck such as when clearing a driveway or parking lot.

A wing plow or another attachment may be provided to effectively extend the width of the lane that can be plowed by a single truck in a single pass. Such wing plows are typically mounted at one side of the truck.

Snow plow vehicles at airfields may sometimes have a front plow blade and a broom which is towed by the vehicle.

The need remains for a snowplow arrangement in which some or essentially all of the snow, ice and slush which has been left by the moldboard may be removed from the pavement being plowed in a single pass of a snowplow vehicle.

SUMMARY OF THE INVENTION

These and other needs are met by the invention. In one embodiment, a snow plow for mounting to a vehicle includes a first frame, a second frame coupled to the first frame for rotation about the first frame, a main plow having a scraping edge and mounted to the second frame, a secondary plow, and a member that couples the secondary plow to the second frame and configured to allow translation of the secondary plow relative to the second frame and in a direction that is parallel to the main plow scraping edge. One example of the member for coupling is sleeves provided on the second frame. These sleeves have bearing surfaces upon which the secondary plow slides as it translates in the parallel direction. A linkage may also be provided which, when combined with the member, allows the secondary plow to translate. The linkage is connected at one end to the secondary plow and at the other end to the first frame. In another embodiment, the member may be formed by a gear train where portions of the gear train are located on the drive frame and the secondary plow.

In another embodiment, a snow plow for mounting to a vehicle includes a drive frame, a main plow coupled to the drive frame, and a secondary plow coupled to the drive frame and positioned behind the main plow, wherein the secondary plow includes a plurality of fingers, each having a straight portion and a curved portion wherein the curved portion is adapted for collecting snow. Each of the tines may be a one piece tine, or a two piece tine. For a two piece tine, the straight portion may be formed by spring steel while a scraping tip may be formed of carbide.

In another embodiment, a snow plow for mounting to a vehicle includes a drive frame, a main plow coupled to the drive frame, a secondary plow coupled to the drive frame and positioned behind the main plow, and a remotely controlled actuator, mounted to the drive frame and configured for selectively placing the secondary plow into a plowing position. The actuator may be a hydraulic cylinder.

In another embodiment, a method for deploying a snow plow mounted to the front of a vehicle includes the steps of lowering a main plow so as to bring it into a plowing position, and lowering a secondary plow, located between the vehicle and the main plow, so as to bring the secondary plow into the plowing position. In this method, the secondary plow may be placed in a plowing position after the main plow has begun plowing. The plows may be raised/lowered by hydraulic cylinders. Further, both plows may have separate hydraulic cylinders and the pressure applied to the secondary plow by its hydraulic cylinder may be remotely controlled by an operator-enabled valve so that as tines of the secondary plow blade begin to erode, the operator can increase the pressure applied to the tines.

In another embodiment, a method for positioning a snow plow at the commencement of snow plowing includes the steps of rotating a main plow relative to a vehicle carrying the main plow and translating a secondary plow, positioned between the main plow and the vehicle, in a direction parallel to a scraping edge of the main plow. In this embodiment, the secondary plow may be translated by allowing it to freely slide along bearing surfaces which may be formed on a drive frame. Additionally, the steps may include lowering the main and secondary plows after the rotating and translating steps.

In another embodiment, a method for snow plowing using a vehicle having a snow plow attached at a front end of the vehicle includes the steps of providing a first plow in a stowed position, providing a second plow that is located between the first plow and the vehicle, and lowering the second plow so as to place it into a plowing position while maintaining the first plow in the stowed position.

In another embodiment, a method for adding a secondary plow to an existing plowing apparatus, the plowing apparatus having a frame, a main plow supported by the frame, and a bracket for securing the frame to a front end of a vehicle, includes the steps of providing a secondary plow blade, an actuator having a first end and a second end, and an actuator mount, securing the actuator mount to the frame, coupling the secondary plow to the frame for pivotal motion relative to the frame and attaching the actuator first end to the actuator mount and a second end to the secondary plow blade. In this method, the conventional frame for the main plow may provide adequate clearance for operating the secondary plow, or it may require a modification to the frame.

Additional features and advantages of the invention will be set forth or be apparent from the description that follows. The features and advantages of the invention will be realized and attained by the structures and methods particularly pointed out in the written description and claims hereof as well as the appended drawings. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation without limiting the scope of the invention as claimed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference toFIG. 1, a snow plow according to the prior art is shown with a moldboard100of conventional design which is carried by a truss102. The truss102is arranged to be removably mounted on the front of a truck or other suitable vehicle (not shown) through a bracket104in a suitable and conventional manner well known in the art. A back brace106is provided to support an upper portion of the moldboard100.

An arrangement108including a plow shoe108and vertical member112is provided behind the moldboard100. The vertical member112has a plurality of holes114which correspond to holes in a bracket116so that the plow shoe may be adjusted vertically to provide a support for the moldboard on the pavement.

The truss102has a mounting member118which is formed from steel square tubing and which comprises a box beam, i.e., a member having a square cross-section, which is hollow along the length of the box beam. The moldboard100is pivotally attached to the mounting member118by a bracket120. Typically, the back brace106is formed by a pair of hydraulic cylinders which are provided to selectively orient the moldboard100with respect to the truss102. In this way, the angle that the moldboard makes with respect to the pavement may be varied as desired. In addition, the truss102includes an arrangement (not shown) such as one or more hydraulic cylinders to lift the moldboard100when desired.

If desired, the scraping edge122of the moldboard100may be made of a flexible or resilient material in order to minimize damage to the moldboard in the event that the cutting edge122should strike an obstruction during plowing. The cutting edge122may also be provided with a trip mechanism such as is described in U.S. Pat. No. 5,079,866, which is incorporated herein by reference.

With reference toFIG. 2, a trip mechanism124is provided for the moldboard100with the trip mechanism having a compression spring125which urges the lower portion of the moldboard against the pavement being plowed. The trip mechanism124includes a slot126through which a member128may slide to allow the moldboard to lift above the pavement upon striking an object. With reference toFIG. 2, the movement of the member128along the slot126moves a member130to compress the spring125. After the moldboard has passed over the object, the moldboard is urged back against the pavement by the spring125which urges the member128downwardly along the slot126.

With reference now toFIG. 3, vehicle which carries the moldboard is illustrated schematically by the tires130. The moldboard may be angled with respect to a center line132of the vehicle in order to divert snow and ice to one side of the vehicle. If desired, the moldboard (not shown) may be oriented perpendicular to the center line132or angled to the left or to the right of the centerline132of the vehicle. If desired, a wing plow134may be provided on one side of the vehicle to extend the width of the pavement being cleared by the vehicle in a single pass over the pavement.

With reference toFIG. 4, a two stage snow plow200of a preferred embodiment of the invention has a primary moldboard202and a secondary plow204which is mounted to a drive frame212for pushing the moldboard202. Plow200is shown attached to the front of a vehicle130, secured to a bracket266. A lifting mechanism10is mounted to the vehicle front end to lift and lower drive frame212and moldboard202. Mechanism10includes a pivot arm13and lifting arm12that are controlled by a double action hydraulic cylinder11. Moldboard202is of suitable conventional form and may be rigid or flexible, made from metal or from a non-metal material such as plastic, and it may also have a predetermined cross section or a cross section that can be changed to alter the ability of the moldboard202to divert snow and ice to one side of the vehicle. Moldboard202is coupled to drive frame212at a lower end to a trip mechanism218and at an upper end to a brace206. Two vertically adjustable shoes15(only one shown inFIG. 4) are located on opposed sides of drive frame212. Shoes15are connected to a bracket16that is mounted (by way of removable bolts) to an L-frame17which is connected at ends of a stiff, square tube220(FIG. 5) of drive frame212. Shoes15are used to support drive212when moldboard202is raised off the pavement by the trip mechanism218. Shoes15also protect secondary plow204so that the much heavier moldboard202does not cause damage to secondary plow204as moldboard202skips over obstacles encountered on a road surface.

FIG. 5illustrates plow200shown inFIG. 4, but with lifting mechanism10and shoes15removed for purposes of illustration, andFIG. 6illustrates a top partial schematic view of plow200. Referring toFIGS. 5-6, secondary plow204is mounted to drive frame212, located directly behind moldboard202, and operated independently of moldboard202. Plow204is pivotally mounted to each of two supporting plates236of the plow's two trip mechanisms218and pivotally controllable by a pair of hydraulic cylinders224which pivot secondary plow204about an axis corresponding to the polar axis of a pivot tube230inFIG. 5, or axis B inFIG. 6. Plow204may also slide lengthwise over pivot tube230, for purposes of repositioning plow204relative to moldboard202(as discussed in greater detail, below). A plurality of individual tines208are secured to and removable from a U-channel210of secondary plow204using, e.g., removable bolts (an angle iron, an I-beam, or round tube or other similarly suited supporting structure may be used in place of U-channel210), extend along the length of U-channel member210, and have substantially the same length as moldboard202. Tines208form a scraping edge of the secondary plow204for purposes of removing residual snow left behind by moldboard202. Tines208are discussed in greater detail, below.

Referring toFIG. 6, secondary plow204has four hinge points (shown schematically inFIG. 6as214a,214b,214cand214d) that are located on the side of the U-channel member210that faces moldboard202. These hinge points pivotally mount secondary plow204to drive frame212. As indicated earlier, the rotation axis for secondary plow204is illustrated schematically inFIG. 6by broken line B which corresponds to the polar axis of pivot tube230inFIG. 5, a tube which has a longitudinal extent approximately equal to the length of square tube220. Two of the secondary plow204hinge mounts, namely,214aand214dare formed by sleeved holes in support plates236of trip mechanisms218, one of which is illustrated inFIG. 7as hole236a, while the other hinge mounts214b,214care formed on U-channel210.

To position the outermost ends of secondary plow204within the path of moldboard202during snow plowing, pivot tube230, which is mounted and secured with two lock nuts and bolts to U-channel210, is arranged to slide either to the right or to the left over bearing surfaces provided by the holes formed in support plates236as moldboard202is angled to discharge snow to the right or to the left, respectively, of the plowing vehicle. Separate bearing sleeves are preferably installed in holes236ato facilitate sliding motion of secondary plow204. The sliding feature of secondary plow204is described in greater detail, below and illustrated inFIG. 11.

Drive frame212is coupled to bracket266by an A-frame268. A pair of hydraulic cylinders270,272(not shown inFIG. 5) are used to rotate drive frame212about a rotation axis A so that moldboard202may be angled to divert snow left or right of the vehicle path, as illustrated inFIG. 11. Drive frame212includes an arcuate member260and truss members261a,261b, which provide structural support for drive frame212and mount flanges263a,263b, respectively, which are used with braces206to pivotally support moldboard202at an upper end thereof. Hydraulic cylinders may also be used in place of braces206. A-frame268is pivotally coupled to drive frame212at hinge264located centrally on square tube220, while actuating ends of hydraulic cylinders270,272respectively are pivotally connected at locations262a,262brespectively. Synchronous actuation of hydraulic cylinders270,272effect rotation of drive frame and thus plow204and moldboard202about rotation axis A.

FIG. 7illustrates structure mounted on drive frame212and associated with moldboard202and secondary plow204. This structure is also shown inFIG. 5with secondary plow204and moldboard202. Square tube220supports a pair of trip mechanism support plates236having lower slots252that receive a pins (not shown) coupling moldboard202to drive frame212, as discussed below, and flanges263for braces206. A hole236ais formed in plate236to allow tube230to pass through and be supported by support plate236. As indicated earlier, tube230may also slide within hole236a. Drive frame212also includes a pair of flanges226for mounting hydraulic cylinders224for secondary plow204, as discussed in greater detail below.

With reference toFIG. 9, which shows a partially exploded view of plow200, the attachment of moldboard202to drive frame212, by way of trip mechanism218, will now be described. As mentioned earlier, drive frame212mounts a trip mechanism support plate236at square tube220(recess238is mated with tube220). A rod242is fixed at its lowermost end242ato an upper portion236bof support plate236. A sleeve259is placed over rod242. A flange259of sleeve abuts a washer256and rod242is secured to nut256. A trip helper plate248is provided with lower and upper pins250a,250bwhich are arranged to slide within corresponding slots252of support plate236. Lower pin250ais also pivotally connected to a lower portion of moldboard202by pin250abeing simultaneously received in a hole202aof moldboard202and slot252of support plate236. The upper end of helper plate248has a flange258that engages the lower end of spring240, so that spring240is compressed between flanges258and259awhen helper plate248is pushed upwards by moldboard202. Accordingly, the trip support plate236, fixed to drive frame212, is arranged to allow upwards and rearwards movement of support plate248along slots252against the force of compression spring240, which lifts the scraping edge of moldboard202off of the ground. When the moldboard202encounters an obstacle, helper plate248and therefore moldboard202are urged upward and over the obstacle. After the moldboard202has passed over the obstacle, the compression spring urges the trip helper plate248and therefore the moldboard202downwardly until the moldboard again encounters the pavement. Shoes215(FIG. 4) are used to stabilize plow200and protect secondary plow204when moldboard202is pushed off the ground by an obstacle.

With reference again toFIG. 6, rotation of secondary plow204about drive frame212(axis B inFIG. 6, bar230inFIG. 5) is controlled by a pair of hydraulic cylinders224. Each hydraulic cylinder224is identical to that illustrated inFIG. 5. The line of action for both these hydraulic cylinders is illustrated schematically inFIG. 6by C. Hydraulic cylinders224are coupled to U-channel210by way of a box215formed by two opposed plates (FIG. 5shows one of these plates) that mount a rod attaching actuating end224aof hydraulic cylinder224to secondary plow204, specifically, U-channel210. Flange226mounts the housing end224bof hydraulic cylinder224. The box215for actuating end224aof hydraulic cylinder224has two half-round grooves that receive two rods210awhich are welded to the inner surfaces of U-channel210. When secondary plow204translates as illustrated inFIG. 11, the box215slides along rods210a. At the same time, secondary plow204is supported by way of the coupling between box215and U-channel210when secondary plow204is raised and lowered by hydraulic cylinder224.

Referring toFIGS. 6 and 8, hydraulic cylinder224raises and lowers secondary plow204by applying a force at position C, which causes secondary plow204to rotate about bar230(rotation axis B). Hydraulic cylinder224may be used to raise tines208from (position I) or lower tines208to (position II) the plowing surface. Additionally, hydraulic cylinder224may be operated to rotate tines208to a position III, which would be needed to bring tines208into contact with the ground after the lower portion of tines208(indicated by D) has eroded. Thus, even when the tines208have undergone a significant amount of erosion, tines208may still be used by further extending hydraulic cylinder224so that an appropriate pressure may be applied to tines204.

Hydraulic cylinders224provide an appropriate and steady pressure for tines208to scrape the residual snow/ice from the road. Further, hydraulic cylinders224provide the steady pressure regardless of and compensating for, the wear that takes place at a scraping edge of the tines208or fingers while they are plowing. The appropriate pressure provided by the hydraulic cylinders to urge the tines208against the pavement is dependent on the condition of snow (i.e., lightly packed to highly packed snow) on the road. The pressure can be set as well as monitored accurately at a gauge installed in a cab of the vehicle, throughout the plowing operation. SeeFIG. 20and related discussion, infra.

If the pressure urging the tines208downwardly is unnecessarily high, the tines208may be subjected to undue wear at a scraping edge. Unnecessarily high pressure may also cause damage to the pavement. However, inadequate pressure at the tine tips may be ineffective for removing packed snow and ice from the pavement. Because the drive frame212is supported by plow shoes15,FIG. 4, the amount of downward pressure provided by the two hydraulic cylinders is independent of the weight of moldboard202.

In the preferred embodiment, tines208are urged downward by hydraulic cylinders. Springs may be used, however, it is preferred to use controllable hydraulic cylinders because it may be difficult for one or more springs to provide a relatively constant amount of downward pressure on the tines208, especially by one or more coil springs. Further, the coil springs may not deliver a relatively constant pressure at the tips of the tines or fingers because of the shortening of the tines at the ends or tips as the tines start to wear during a plowing operation.

If the tines208were urged downwardly by coil springs, the downwardly directed pressure exerted by the coil springs may not be easily compensated for as the fingers208wear. Therefore, the downwardly directed pressure exerted by the coil spring will tend to decrease as the tines erode and get shorter and shorter. In order to scrape the snow and ice from the road efficiently, in the preferred embodiments an appropriate and steady downwardly directed pressure is applied by the tips of the fingers or tines against the pavement during the entire plowing operation. Of course, an arrangement, not shown, could readily be provided for adjusting (either automatically or manually) the downward force applied by one or more coil springs to the tips of the tines against the pavement.

Sliding Feature

FIGS. 10-11are top view illustrations of plow200without tines208of secondary plow204or moldboard202shown. Instead, secondary plow204and moldboard202are represented by their respective scrapping edges TSand MS, i.e., edges that come into contact with the ground. Plow200is located at the front of a vehicle (the vehicle orientation is indicated by the tire silhouettes10) with the vehicle path being left to right and the drive frame212rotated approximately 30 degrees so as to divert snow right of the vehicle.FIG. 10illustrates the position of tine edge TSrelative to moldboard edge MSif secondary plow204were fixed relative to drive frame212. As shown, an upper portion of edge TSencounters a section of snow SSthat is not first met by a corresponding upper portion of edge MSwhile a lower portion of edge TSdoes not cover a section of snow S2that is encountered by a corresponding lower portion of edge MS.FIG. 11illustrates the positioning of edge TSrelative to edge MSif secondary plow204is free to slide relative to drive frame212and coupled to linkages267a,267b. By comparison withFIG. 9, it is seen that edge TScovers the same path of snow first encountered by edge MS. Thus, by repositioning secondary plow204behind moldboard202along its entire edge, all areas of the roadway encountered by edge MSare also covered by edge TS. Edge TSis repositioned relative to edge MSinFIG. 11by a force F applied to secondary plow204by linkage267a, which is under tension. The force applied by linkage267apulls upon secondary plow204, causing it to slide along its track, toward the lower end of square tube220. If drive frame212were rotated counterclockwise, then linkage267bwould come under tension and pull secondary plow204towards the upper end of square tube220. This behavior is evident when considering that linkages267a,267bhave a fixed length and thus, when drive frame212rotates, one end of drive frame212is brought closer to the location where both linkages267are fixed, while the other end is further away, causing the connecting linkage to go under tension (thereby pulling secondary plow towards it). Accordingly, in an embodiment of the invention, when the plow is positioned to plow snow, the moldboard202is rotated and the secondary plow204is rotated and translated along a direction parallel to a scraping edge of the moldboard202. Additionally, as discussed above and below, secondary plow204may also be operated independently of moldboard202.

A variety of mechanisms may be employed as alternatives to the first embodiment for translating secondary plow204when drive frame212rotates into a plowing position. For a example, three interlocking gears (two rotary and one linear) may be used. One rotary gear would mount to the drive frame212, e.g., at axis A, and would engage a second rotary gear, which could be mounted to the A-frame268. This pair of gears would have a greater than 1:1 gear ratio. The second gear would then engage with a linear gear on secondary plow204, e.g., a rear surface of U-channel210would have gear teeth adapted for engaging the second rotary gear. When drive frame is rotated, the second gear rotation would cause the U-channel210, and therefore tines208, to translate parallel to the moldboard202scrapping edge.

In preferred embodiments, two sections of steel chain are used to pull secondary plow204over the bearing surfaces defined by holes236aand towards one or the other end of square tube220of drive frame212. One end of each chain is attached to two lugs, each of which is welded to two ends of a rear flange of U-channel220(not shown inFIG. 6but illustrated schematically inFIG. 11). The rear flange faces rearwardly toward the truck. The other end of each chain is attached to a common sleeve266awith lugs that swivel within a vertical short shaft that is welded to a bottom face of a stiffener plate of the swivel hitch.

As mentioned earlier, tines208form a scraping edge of the secondary plow204for purposes of removing residual snow left behind by the primary moldboard202while it is plowing. Referring toFIGS. 15-16, each have a first portion that is curved, preferably substantially semi-circular in shape, and a second portion that is generally straight. They are made from flat spring steel, preferably one-piece, and are readily available for replacement as suitable tines are often used for agricultural applications. When plow204is mounted to drive frame212, tines208will extend in a concave manner towards the main moldboard202. Tines208may be one-piece. However, upon conducting a series of road tests, it was found that tines208, when formed from spring steel, can erode at an undesirable rate. A two piece tine was therefore employed. In this design, tines208have a first part made of spring steel and a tip made of carbide that is bolted to the first part. The carbide tip may form a portion of the curved section of tine208illustrated inFIGS. 15-16or a straight part secured at the distal end of a tine.FIG. 17illustrates one example of a secondary plow with tines that include a carbide tip. Tine209ahas an end in which a carbide scraping tip209bis secured thereto by a releasable fastener209c.

In the preferred embodiments, the spacing between adjacent tines is preferably about 0.016 inch. In the preferred embodiments, the tines do not overlap one another because overlapped tines or fingers are unduly rigid because each tine or finger effectively becomes an integral part of effectively a single blade extending along the length of the U-channel member. Accordingly, overlapped tines or fingers are effectively prevented from individually following the contour of the road or pavement and the scraping ability of the tines is relatively poor and inefficient. On the contrary, when the fingers or tines are not overlapped, the fingers are flexible and able to oscillate especially when they are made of spring steel.

Oscillating fingers are considered to be especially desirable for scraping bonded snow and ice because the oscillating fingers provides an impact force against the packed snow and ice when they oscillate (move back and then forth) during the plowing operation.

With reference toFIGS. 15-16, in one configuration for the individual tines208, the concave portion of the tines or fingers are substantially semi-circular with two substantially tangential straight top and bottom end portions. The bottom straight end portion of the tines together essentially functions as the blade of a plow even though the individual tines are spaced apart from one another. The top straight portion, made of spring steel, is fastened to U-channel210. The bottom straight portion, i.e., the portion in contact with pavement, is made from carbide or another sufficiently hard material. The inside surface of the arrangement of tines or fingers formed by the lower relatively flat lower portion and the curved semi-circular portion may be made relatively smooth to essentially provide a continuous surface for facilitating efficient snow and ice flow along the plurality of tines or fingers.

The inside surface and contour of the arrangement of tines or fingers corresponds closely to the inside surface and contour of a conventional plow or moldboard. In this way, secondary plow204may be used as a small-scale reversible plow. The tines or fingers208face toward the front of the vehicle (i.e., in the plowing direction) as does the moldboard202. In the preferred embodiment, a space adequate to accommodate at least about 80% of the residual snow left behind by the main plow, is provided between the rear of the moldboard202and the front of the secondary plow204beneath the drive frame212so that the snow and ice left by the moldboard202and scraped by the secondary plow204can flow without interruption along the inside curvature of the secondary plow204and be discharged from one end of the secondary plow204, substantially as in a curved moldboard of a typical snow plow.

An obstacle or shield provided in front of secondary plow204would narrow down the space needed between plow204and moldboard202and tend to prevent scraped snow and ice from flowing. As a result, secondary plow204may clog. In a preferred embodiment, secondary plow204, the uppermost portion of the individual tines or fingers are not inclined with respect to the plowing direction because such an incline would tend to pack the snow and thereby clog the flow of snow and ice along the inside surface of plow204.

Because secondary plow204operates independently of moldboard202, it is not necessary that plow204be used every time moldboard202is used for snow removal. Instead, the operator may decide based on conditions. For example, plow204may not be needed if the snow is not packed to the ground and plowing with moldboard202is deemed sufficient to keep the road open and safe. Additionally, it may not be necessary to use secondary plow204when residual unpacked snow is left behind by moldboard202if the road that has been treated with anti-icing treatment before a snowstorm and warm weather is expected. In this situation, most or all of the residual snow will be melted by the anti-icing treatment and the warming weather. By selective use of secondary plow204, the life of the individual tines or fingers can be extended.

When cold weather is forecasted to continue or worsen after plowing, when another snowstorm is expected, or when anti-icing treatment would need to be reapplied, it is desirable to remove most or all of the residual snow (whether packed, unpacked or slushy). Removing this residual snow and ice prevents an excessive dilution of the anti-icing chemicals which makes the chemicals ineffective to prevent the packed snow or ice from developing a bond with the pavement. In a situation such as this, use of secondary plow204, either with tines or a resilient blade (discussed infra) would be helpful.

Anti-icing chemicals are applied to pavement, typically before a winter storm to prevent bonding between snow or ice and the pavement. The anti-icing chemicals depress the freezing point of water. If the snow or ice is not bonded to the pavement, plowing of the un-bonded snow and ice is relatively effortless. Accordingly, the use of anti-icing chemicals is well suited to roads that have a relatively high level of traffic and is considered to be relatively cost effective.

De-icing of pavement is considered to be a highway snow and ice control operation. The typical, traditional procedure of snow and ice control practice is to wait until an inch or more of snow accumulates on the pavement before beginning to plow and to treat (de-ice) the highway with chemical abrasives and then plow away the slushy snow. The amount of residual packed or unpacked snow and ice that typically remains on the road (after the application of the conventional anti-icing chemicals) is generally considered to be high. Therefore to keep the road open and safe, the amount of de-icing material needed to penetrate the pavement is relatively high and considered to be expensive.

Secondary plow204, when used in conjunction with moldboard202, reduces the amount of residual snow and ice left on the pavement after plowing. Therefore, the amount of de-icing chemicals can be reduced and the time taken for chemicals to reach the pavement (by melting through the ice and snow) is reduced. A reduction in the use of anti-icing chemicals is usually considered beneficial to the environment.

Secondary plow204facilitates the reduction of anti-icing chemicals, such as sodium chloride, calcium chloride, magnesium chloride and salt etc., required by anti-icing and de-icing treatments of roads in order to keep them open and safe in the winter storm. Tines208remove a layer of snow from the pavement that is left behind by the moldboard202. In addition, tines208help break apart frozen snow on the pavement being plowed into tiny pieces so that chemicals may more quickly penetrate through the snow. In this way, the amount of time needed to melt any remaining snow on the pavement is shortened and the amount of chemicals that are needed to treat the road is reduced.

With reference to FIGS.8and15-16, preferably, the angle that tines208make with the pavement, almost vertical (about 75 to 90 degrees), is desirable with 85 to 90 degrees preferred, and close to 90 degrees is most preferred. Close to vertical is more effective and good for scraping. Tines208are preferably inclined more than 45 or 50 degrees (like a plow blade) because a more shallow angle typically cannot take hard pack off. Instead, the tines tend to slide over hard packed snow. Tines208may be formed from one-piece metal with slots up to four inches from the securing bolts but it is preferred to have industrial tines which better follow the contour of the road. The tips of tines may be square (commercially available ones have a notch) and of the type used for cultivators, as are available from John Deere (a support spring from a tooth cultivator). Preferably, tines are two-piece, with tips made of carbide.

When the secondary plow uses tines208, about 70% or more of the residual snow and ice left on the pavement by the primary moldboard202is reduced and therefore the amount of the chemical needed to clean the road from a snowstorm is reduced. Additionally, secondary plow204reduces the time required for chemicals to penetrate through to the pavement and melt the remaining snow left by secondary plow204(typically less than about 30% of the residual snow of the primary moldboard). Thus, delays caused by snowstorms are significantly reduced.

In one embodiment of secondary plow204, ninety-six tines are arranged vertically, with a 1/16 inch gap provided between adjacent tines. Tines are composed of a flat spring bar which is 1 inch× 5/16 inch thick and shaped to an overall height of 13 inches with a depth of 16 inches. The top horizontal arm is 7 inches long and the bottom vertical arm is 6 inches long with the curved section having a radius of 6 inches. In another embodiment, the bottom vertical arm may be made of carbide or another relatively hard material.

In one embodiment, tines were set at an angle of 37 degrees with respect to the forward direction of the vehicle and the hydraulic cylinders224provided a downward force of about 3500 lbs. to about 4000 lbs. on the tines208to scrape the packed snow from the road. This arrangement produced satisfactory results.

A second embodiment of a secondary plow, plow304, is illustrated inFIGS. 12-14and described below. Drive frame, moldboard and other structure associated with the use of plow304, was sufficiently described in connection with the first embodiment above in order to fully appreciate much of the attributes and construction of a plow incorporating plow304. Reference will therefore be limited in discussing secondary plow304. Plow300engages the ground with a resilient blade308, preferably rubber that is impregnated with vertical steel cable. The mounting arrangement is essentially the same as in secondary plow204. Plow304may be employed with or without the primary moldboard202as it is especially suitable for snow removal in large cities where snow usually does not accumulate excessively or develop a bond to the pavement.

Resilient blade308may be used when the pavement has been treated with solid chemicals and/or with liquid chemicals (typically after one inch or more of snow has accumulated on the pavement). Plow300is used to plow away the slushy snow and reduce or minimize the ability of the slushy snow from re-freezing into ice. Plow300is also beneficial, especially in relatively congested areas and heavily traveled streets and roads such as in the center of cities, where snow typically does not bond to the pavement road but instead remains slushy due to dense traffic. Plow300is also especially useful to prevent an excessive dilution of anti-icing chemicals by residual slushy snow remaining on the pavement before an anti-icing treatment of the road is to be provided (such as before a snowstorm is expected).

As illustrated in the drawings, blade308is mounted to a series of supporting plates310which are connected to drive train212. Hydraulic cylinders224may be used to raise or lower blade308and may selectively apply pressure to blade308when it engages the road surface. Plow300may be mounted with or without secondary plow204. Additionally, as both of these secondary plows may have a common mounting device, either may be interchangeably mounted with moldboard202. In other embodiments, conventional plows may be modified to mount a secondary plow controlled by a hydraulic cylinders, where the secondary plow may use one or both of tines and a resilient blade. As in the previously described embodiments, the blade types may be used separately or together, and the plow may be configured to readily to switch one for the other as needed.

To mount the secondary plow204on an existing, conventional plow, the frame between the swivel plate at the back and the square tube, e.g., tube120inFIG. 1, for mounting the plow at the front may require modification to accommodate a secondary plow204behind moldboard202. The space that is available under the drive frame to accommodate secondary plow204may be limited and may not permit the discharge end of secondary plow204to be extended without having tines interfere with a front post of a wing plow (at the rear) and without having the mounting channel of the tines interfere with the forward trip springs of the primary moldboard202. To have the snow discharged beyond the trail of the tire of the vehicle and beyond the intake end of the wing plow, the secondary plow204is preferably installed relatively close to the primary moldboard202. Thus, the discharged snow from secondary plow202can be removed from the road and thrown away into the ditch by a wing plow for safer driving in winter months. Secondary plow204may be more effectively integrated into an existing plow (e.g., by bringing it closer to the primary moldboard by about 10 inches) without jeopardizing the efficient operation of both the primary moldboard and the secondary plow204, as well as the tripping device of the primary moldboard202, by modifying the drive frame. These modifications may include relocating the primary moldboard trip mechanism including replacing the inclined plow lift trip and compression spring with a modified inclined plow lift trip and compression spring arrangement. In addition, a parallel lift for the push frame may be provided and the push frame may be replaced with a push frame having a high bow configuration.

FIGS. 18-19illustrate an example of a secondary plow404fitted to a conventional snow plow, such as the plow illustrated inFIGS. 1-3(shoes110and the associated shoe mounting bracket are not shown). Referring toFIG. 18, the fitting of secondary plow404begins with removing a section402from truss102and replacing it with a modified support structure including support member406having end plates408,410and a square tube section bridging plates408and410. Support member406effectively provides a raised area in the truss102extending over the length of the moldboard's scrapping edge so that the secondary plow404may be raised and lowered without interference from truss102and independently of moldboard100. Support member406may be welded to truss102at plates408and410. Referring toFIG. 19, the mounting and operation of secondary plow404is similar to that described for secondary plows204and304. Secondary plow404, which includes a pair of hydraulic cylinders424, is configured to rotate tines408(or a resilient blade308) about a rotation bar430by operation of hydraulic cylinders424. Hinge mounts, which retain bar430(not shown), may be located on plate408and a channel holding tines or a resilient blade. Hydraulic cylinders424are attached at a housing end to flanges426, which are mounted to a square tube120, and at an actuating end to mounts415. Flanges may, of course, be mounted to any suitable hard point on the truss. These mounts hold pins for receiving the actuating ends. For reversible plows, e.g.,FIG. 9, secondary plow404may be configured to slide relative to the truss and may also be fitted with linkages in a similar manner as described above to reposition secondary plow404behind moldboard100. Of course a one-way plow, e.g.,FIG. 1may already have sufficient clearance for operation of secondary plow and thus only relatively minor modification may be needed. In these embodiments, secondary plow204may be mounted to a square tube and positioned at an effective distance behind moldboard202, and fitted with hydraulic cylinders to raise and lower secondary plow.

Hydraulic Circuit for a Plow

A hydraulic circuit for a snowplow configured to operate in the manner previously described for the first embodiment, plow200, will now be described with reference to theFIG. 20. The circuit is used to extend and retract a first double action hydraulic cylinder11(seeFIG. 4) and a pair of second double action hydraulic cylinders224(FIG. 5) which are used to raise and lower moldboard202and secondary plow204, respectively.

When moldboard202and secondary plow204are in their fully retracted positions, i.e., raised off the ground, the arm of cylinder224is fully retracted whereas the arm of cylinder11is fully extended. To lower the plows, an operator opens a four-way, three positional directional control valve508, permitting liquid, e.g., oil, to flow from a reservoir or tank501via pump502, through fluid line520and towards cylinders11and224. A pressure relief valve502ais used to limit the fluid pressure generated by pump502.

As the moldboard202is more massive than secondary plow204, it is preferred to lower moldboard202first, followed by secondary plow204, to avoid damaging secondary plow204when moldboard202is lowered. This may be accomplished by incorporating a reversible valve516which prevents flow towards cylinders224until cylinder11is filled with fluid, i.e., moldboard202is on or near the ground. As cylinder11fills with fluid, the pressure above valve516increases to a level that causes valve516to open. When valve516opens, fluid begins to flow into cylinders224. This delay in the fluid flow into cylinders224results in moldboard202being lowered first, followed by secondary plow204. Moldboard202and secondary plow204may be raised in any order or simultaneously. Thus, the fluid may be emptied from both cylinders11and224at the same time, pass through a common node532and drain into tank. A check valve510is opened to allow fluid flow back to the tank (“T” inFIG. 20) from cylinders11and224.

The circuit allows an operator to vary the pressure applied to tines208. It also gives the operator the option of deploying both moldboard202and secondary plow202, or only moldboard202for snow plowing, by monitoring the fluid pressure at input line522using a pressure gauge512. If only moldboard202is used for snow plowing, valve508is placed into a neutral position when fluid begins to pass through input line522. If both moldboard202and secondary plow204are used, the operator allows fluid to enter cylinders224, thereby deploying secondary plow204, until an acceptable pressure level is reached that is not too great as to cause damage to the tines204and/or roadway but sufficient to lower the tines204and adjust the applied pressure as needed.

In another embodiment of a hydraulic circuit, an operator may also have the option of lowering only the secondary plow204(e.g., as when a resilient blade is used to remove slush). For example, an additional, one-way valve may be placed in parallel with and upstream of valve516with only one of these two valves being in fluid communication with the tank at a given time. If an operator wants to use both the moldboard and secondary plow204(or only moldboard202), valve assembly516is used. If an operator only wants to use secondary plow204, then the additional one-way valve is opened and valve516is closed. In the later case, the additional one-valve is both opened and fluid is prevented from entering cylinder11, thereby causing only secondary plow204to lower when valve508is opened.

The principles, preferred embodiments and mode of operation of the present invention have been described in the foregoing specification. However, the invention which is intended to be protected is not to be construed as limited to the particular embodiments disclosed. The embodiments are therefore to be regarded as illustrative rather than as restrictive. Variations and changes may be made without departing from the spirit of the present invention. Accordingly, it is expressly intended that all such equivalents, variations and changes which fall within the spirit and scope of the present invention as defined in the claims be embraced thereby.