HYDRAULIC ACTUATOR FOR A TRIP PLOW

Abstract

A hydraulic actuator that can be used on trip plows to hold the trip blade in its operative downward position and to control the return of the trip blade after tripping. The actuator has a body with first and second ends. A piston rod reciprocates within the tube. A plate with a channel is positioned within the tube a spaced distance from the tube ends. The plate creates an oil reservoir between the plate and the piston rod. A reciprocating piston is positioned within the tube between the second end and the plate. A spring is mounted between the second end and the reciprocating piston and normally biases the reciprocating piston into engagement with the channel normally closing the channel. The piston rod moves in the direction of the plate when the trip blade hits an obstruction, forcing the oil through the channel moving the reciprocating piston and opening the channel allowing oil to flow into an oil chamber created between the reciprocating piston and the plate. The spring biases the reciprocating piston back to the normally closed position and forces the oil into the oil reservoir after the trip blade has cleared the obstruction.

Description

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

NONE.

TECHNICAL FIELD

This invention relates generally to hydraulic springs and more particularly to hydraulic springs used on trip plows.

BACKGROUND OF THE INVENTION

Trip plows are well known. One example is their use on snowplows for plowing a roadway surface with snow and/or ice. Trip plows have a main blade and a trip blade connected to the main blade. A linkage system connects the trip blade to the main blade and a spring forces the hip blade to the lowered operational position. When an obstrudion is encountered the trip blade trips to a raised inoperative position which compresses the spring. Tripping the trip blade prevents damage to the plow, the plow vehicle, and the driver. When tripped, the spring is compressed. When the obstruction is cleared, the spring forces the trip blade back to its operative lowered position.

The problem with spring type trip blades is the size of the springs or spring rate needed to keep the trip blade in its operative position. The spring rate must be high enough to keep the trip blade down against the road surface to clear the road surface. With high spring rates, the stored energy of the spring when compressed is extremely high. When the Obstruction is cleared, the stored energy is violently released which is loud and jarring to the plow, vehicle, and driver.

What is needed is a trip blade that requires a smaller spring and which has a controlled return of the trip blade to its operative position after tripping.

SUMMARY OF THE INVENTION

The present invention discloses a hydraulic actuator that can be used on trip plows to allow a smaller spring to be used to hold the trip blade in its operative downward position and control the return of the trip blade after tripping. The hydraulic actuator has a body, shown as a tube, with first and second ends. A piston rod reciprocates within the tube. A plate with a channel is positioned within the tube a spaced distance from the tube ends. The plate creates an oil reservoir between the plate and the piston rod.

A reciprocating piston is positioned within the tube between the second end and the plate. A spring is mounted between the second end and the reciprocating piston and normally biases the reciprocating piston into engagement with the channel normally closing the channel.

The piston rod moves in the direction of the plate when the trip blade hits an obstruction, forcing the oil through the channel moving the reciprocating piston and opening the channel allowing oil to flow into an oil chamber created between the reciprocating piston and the plate. The spring biases the reciprocating piston back to the normally closed position and forces the oil into the oil reservoir after the trip blade has cleared the obstruction.

The spring can be much smaller than would be required if only a compression spring were used. The spring only needs to hold the reciprocating piston in its normally closed position. This force is a fraction of the force required to hold the trip blade in its downward operating position because of the areas of the channel, nose, and the piston head. If the diameter of nose is 1/25 the diameter of piston head, the spring would only need a spring rating of 1/25 of the normal spring rate required to force and hold the trip blade in its downward operative position. Also, the channel controls the retain of the oil to the oil reservoir and returns the trip blade to its operating position without the crashing that would result from a coil spring.

In this way, the trip blade is held at the desired trip force to ensure that it engages the surface for snow and ice clearing. When tripped, the trip blade can trip to rapidly clear an obstruction. When the obstruction is cleared, the trip blade can return to the working position under a slower controlled return without the jarring impact of typical trip plows.

These and other features and advantages of this invention will become more apparent to those skilled in the art from the detailed description of a preferred embodiment. The drawings that accompany the detailed description are described below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the actuator of the present invention.

FIG. 2 is a cutaway view of the actuator of the present invention.

FIG. 3 is a detail view of B in FIG. 3.

FIG. 3A is a second embodiment view of B in FIG. 3.

FIG. 4 is a perspective view of a trip plow with the actuators attached.

FIG. 5 is a partial perspective view of a trip plow with an actuator attached.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

The actuator of the present invention is shown generally at 10 in FIGS. 1 through 3. Actuator 10 has a tube assembly 12 with a piston rod 14 extending from a first end 15. The piston rod 14 has a connector 11 at the distal end and a piston head 13 at the proximal end.

A head cap 16 closes the first end 15. An end cap 18 closes the opposite or second end 19 of tube assembly 12. The head cap 16 includes seals 20 to seal against the rod 14. The seals 20 seal the opening 21 in the head cap 16 against the rod 14 to contain oil in the oil reservoir 23.

A plate 24 is housed within the tube assembly 12, a spaced distance from the first end 15 of the tube assembly 12. Plate 24 includes channel 26. The channel communicates fluid between the oil reservoir 23 and an oil chamber 25. Oil flows from oil reservoir 23 to oil chamber 25 as the piston head 13 moves toward plate 24.

Channel 26 is normally closed by a reciprocating piston 28. The reciprocating piston 28 is biased to the closed position by a spring 30. The reciprocating piston 28 includes seals 29 which seal against the interior wall of the tube assembly 12. The seals 29 prevent oil in the oil reservoir 23 from flowing past the reciprocating piston 28 in the tube assembly area housing the spring 30.

In the disclosed embodiment, the plate 24 includes a check valve 32, see FIGS. 2 and 3. The check valve 32 allows oil to flow from the oil chamber 25 to the oil reservoir 23 but not to flow from reservoir 23 to chamber 25. The check valve 32 empties any remaining oil from the oil chamber 25 into the oil reservoir 23 when the reciprocating piston 28 nears the closed position. It should be understood that the majority of oil in chamber 25 empties into reservoir 23 through channel 26. It should be appreciated that an additional seal, such as a rubber gasket or o-rings, can be added to the nose 34 and/or recess to enhance sealing.

A sealing nose 34 protrudes from the face 35 of reciprocating piston 28 and partially enters channel 26 when the reciprocating piston 28 is closed. In the disclosed embodiment, nose 34 has a truncated cone-shaped end which mates with the recessed opening 33 in channel 26.

A moveable plate 36 abuts against the end of spring 30. A bolt and jam nut 38 engage the moveable plate 36. The bolt and jam nut 38 can be rotated to move the plate 36 within the tube assembly 12 to compress the spring 30 to change its tension against the reciprocating piston 28.

A capped opening 40 is provided for the addition of oil to the oil reservoir 23. In the disclosed embodiment, oil is added to reservoir 23 when actuator 10 is assembled and then the opening 40 is closed. In normal operation, additional oil is not required to be added. In other words, actuator 10 is a sealed system with a single charge of oil, and no additional oil is required. It will be appreciated that other ways of charging the actuator 10 are known and could be used.

A mounting ear 42 is provided on the exterior of the tube assembly 12 for mounting the actuator 12.

With reference to FIG. 3A, a second check valve 50 is provided in the channel 26. This is an alternative embodiment. In this embodiment, the check valve 50 facilitates the holding of the oil in the reservoir 23 when the trip blade is in the operative position. The check valve 50 works in the opposite direction to check valve 32. Check valve 50 only trips when the force exceeds the trip force.

In operation, the actuator is mounted to for example a trip plow 44, see FIGS. 4 and 5. The mounting ear 42 would be mounted to the plow body 46 and the connector 11 is mounted to the trip blade 48 as shown in FIG. 4, a number of actuators 10 could be used. As will be appreciated, a trip plow is a type of plow that has a trip blade 48 that pivots or moves upwardly when an obstruction is hit. This tripping feature prevents the plow or the vehicle from being damaged when obstructions are hit by the plow.

When trip blade 48 hits an obstruction, it is forced upward. This force moves the rod 14 into the tube assembly 12. The piston head 13 moves within the oil reservoir 23 forcing the oil through channel 26 against the sealing nose 34, moving the reciprocating piston 28 towards end 18 and introducing oil into the oil chamber 25. Due to the impact force acting on the trip blade 48 and the oil being forced through channel 26, the reciprocating piston 28 moves rapidly against the bias of the spring 30 allowing the trip blade to clear the obstruction. The spring bias of spring 30 is low compared to the force of the trip blade 48. The spring bias of spring 30 is only enough to hold the reciprocating piston 28 against the plate 24, when the trip blade 48 is in the operative position.

When the obstruction is cleared, spring 30 biases the reciprocating piston 28 back to its normally closed position against plate 24. The oil in the oil chamber 25 is forced back through channel 26 at a much slower rate to refill the oil reservoir 23. A slower rate when compared to a compression spring releasing its stored energy. The nose 34 reseats into channel 26. Residual oil in oil reservoir 23 is forced through the check valve 32 to ensure that the nose 34 can properly reseat. This is important to ensure that a proper trip force is required to trip the trip blade 48.

The trip force, the initial force required to trip the trip blade 48 can be set by adjusting the bolt and jam nut 38. The adjusting bolt and jam nut 38 are optional. The spring force can be pre-set at the factory obviating the need for the adjusting bolt and jam nut 38.

It will be understood that the spring 30 can be much smaller than what would be required if only a compression spring were used. The spring 30 only needs to hold the reciprocating piston 28 in its normally closed position. This force is a fraction of the force required to hold the trip blade 48 in its downward operating position because of the areas of the channel 26, nose 34, and the piston head 13. If the diameter of nose 34 is 1/25 the diameter of piston head 13, the spring 30 would only need a spring rating of 1/25 of the normal spring rate required to force and hold the trip blade 48 in its downward operative position.

In this way, the trip blade 48 is held at the desired trip force to ensure that it engages the surface for snow and ice clearing. When tripped, the trip blade 48 can trip to rapidly clear an obstruction. When the obstruction is cleared, the trip blade 48 can return to the working position under a slower controlled return without the jarring impact of typical trip plows.

The foregoing invention has been described in accordance with the relevant legal standards, thus the description is exemplary rather than limiting in nature. Variations and modifications to the disclosed embodiment may become apparent to those skilled in the art and do come within the scope of the invention. Accordingly, the scope of legal protection afforded this invention can only be determined by studying the following claims.

Claims

1. A trip snowplow comprising: a plow and body:a trip blade mounted to said plow body,a hydraulic actuator connected between said plow body and said trip blade, said hydraulic actuator having a tube with first and second ends, a piston rod extending from said first end, said piston rod having a piston head adapted to reciprocate within said tube;a plate having a first surface and a second surface, said first surface spaced from said first end and said second surface spaced from said second end, said plate positioned within said tube a space different distance from said first end creating an oil reservoir containing oil between said plate and said piston head;a channel extending through said first and second surfaces of said plate,a reciprocating piston position within said tube between said second end and said second surface of said plate;a spring mounted between said second end and said reciprocating piston said spring normally biasing said reciprocating piston into engagement with said channel normally closing said channel;said piston rod and said piston head moving in the direction of said plate when said trip blade hits an obstruction, said oil in said oil reservoir being partially forced through said channel against said reciprocating piston moving said reciprocating piston in the direction of said second end and opening said channel allowing said oil to flow into an oil chamber created between said reciprocating piston and the second face of said plate when said reciprocating piston moves in the direction of said second end, said spring biasing said reciprocating piston back to said normally closed position and forcing said oil from the oil chamber into said oil reservoir after said trip blade has cleared said obstruction whereby said trip blade trips upon hitting an obstruction and is returned under controlled force to its normal position period.

2. The trip snowplow of claim 1, further including an oil passage extending through said reciprocating piston and a check valve located in said oil passage; said check valve allowing oil to flow through said passage from said second side to said first side.

3. The trip snowplow of claim 1, further including a second check valve located in said channel; said second check valve allowing oil to flow through said channel from said first side to said second side.

4. The trip snowplow of claim 1, further including a nose extending from said reciprocating piston in the direction of said channel, said nose normally closing said channel.

5. The trip snowplow of claim 4, wherein said nose has a truncated cone shaped free end.

6. The trip snowplow of claim 1, wherein said channel has a first opening adjacent said first surface and a second opening adjacent said second surface.

7. The trip snowplow of claim 6, wherein said channel second opening is recessed.

8. The trip snowplow of claim 7, further including a nose extending from said reciprocating piston in the direction of said second opening, said nose normally closing said channel, said nose having a truncated cone shaped free end that is received within said second opening to normally seal said channel.

9. A hydraulic actuator comprising: a tube with first and second ends, a piston rod extending from said first end, said piston rod having a piston head adapted to reciprocate within said tube;a plate having a first surface and a second surface, said first surface spaced from said first end and said second surface spaced from said second end, said plate positioned within said tube a space different distance from said first end creating an oil reservoir containing oil between said plate and said piston head;a channel extending through said first and second surfaces of said plate,a reciprocating piston position within said tube between said second end and said second surface of said plate;a spring mounted between said second end and said reciprocating piston said spring normally biasing said reciprocating piston into engagement with said channel normally closing said channel;said piston rod and said piston head moving in the direction of said plate when said trip blade hits an obstruction, said oil in said oil reservoir being partially forced through said channel against said reciprocating piston moving said reciprocating piston in the direction of said second end and opening said channel allowing said oil to flow into an oil chamber created between said reciprocating piston and the second face of said plate when said reciprocating piston moves in the direction of said second end, said spring biasing said reciprocating piston back to said normally closed position and forcing said oil from the oil chamber into said oil reservoir after said trip blade has cleared said obstruction whereby said trip blade trips upon hitting an obstruction and is returned under controlled force to its normal position period.

10. The trip snowplow of claim 9, further including an oil passage extending through said reciprocating piston and a check valve located in said oil passage; said check valve allowing oil to flow through said passage from said second side to said first side.

11. The trip snowplow of claim 9, further including a second check valve located in said channel; said second check valve allowing oil to flow through said channel from said first side to said second side.

12. The trip snowplow of claim 9, further including a nose extending from said reciprocating piston in the direction of said channel, said nose normally closing said channel.

13. The trip snowplow of claim 12, wherein said nose has a truncated cone shaped free end.

14. The trip snowplow of claim 9, wherein said channel has a first opening adjacent said first surface and a second opening adjacent said second surface.

15. The trip snowplow of claim 14, wherein said channel second opening is recessed.

16. The trip snowplow of claim 15, further including a nose extending from said reciprocating piston in the direction of said second opening, said nose normally closing said channel, said nose having a truncated cone shaped free end that is received within said second opening to normally seal said channel.