Snowplow provided with a protection device against collision with fixed obstacles

Abstract

 A snowplow, provided with a protection device against collision with fixed obstacles, comprises a blade (2) carried by a frame that can be fastened to the front part of a vehicle and that is provided with means (10) for varying the distance of the blade (2) from the ground; the blade is coupled with a frame element that can slide parallel to the direction of advance of the snowplow, against the action of contrasting springs (8) and that is equipped with a detecting system comprising a pressure sensor (18), a control unit (20) and an electric valve (22) and arranged to detect displacements of the blade (2) exceeding a given intervention threshold and to lift the blade (2) from the ground thereby overcoming the obstacle.

Description

[0001] The present invention concerns a snowplow provided with a protection device against collision with fixed obstacles.

[0002] More particularly, the invention concerns a snowplow of which the blades are mounted so as to allow overcoming fixed obstacles of limited height, projecting from the ground.

[0003] One of the biggest problems when using devices intended for road cleaning, such as snowplows, is that collision against fixed obstacles projecting from the ground blocks the advance of and causes important stresses on the blade or other operating tool as well as on the members connecting such tool to a tractor. Consequently, deformation or breaking of the tool, of the supports and possibly even of the tractor is possible. Mounting the tool so that it can be lifted from the ground is not sufficient to solve this problem, since very often the obstacles are hidden and the operator cannot timely lift the blade.

[0004] Single-blade snowplows are already known in which the blade is hinged on a horizontal axis parallel to its scraping edge and is associated with protection means allowing at least the blade overturning about said axis upon a collision, bringing then the blade back to the operating position. Clearly, such means are not effective in case of snowplows of which the blade cannot be overturned, such as spade snowplows.

[0005] Italian patent application No. TO93A000411 in the name of the same Applicant discloses a hydraulic system allowing automatically lifting the snowplow blade when the latter finds an obstacle. The blade, which can be a single blade or a spade, is mounted on a frame which can slide parallel to the direction'of advance of the snowplow and is arranged to cause the frame to slide when the blade meets a resistance to the advance exceeding a predetermined value. The frame is connected to a hydraulic jack that is part of the blade lifting system and reacts to the frame sliding by making the blade to be lifted.

[0006] Italian patent application No. TO94A000313 in the name of the same Applicant discloses instead a spade snowplow in which the blades can be opened or closed by means of respective rotation jacks. Such jacks are connected, through branching valves, with a jack that is part of the blade lifting system. A collision on one of the two blades results in fluid passing from one rotation jack to the lifting jack, thus causing the operation of the latter and lifting the blades.

[0007] In the construction of such snowplows great difficulties have been encountered both for achieving fast response times of the protection devices, since these devices are completely passive, and for determining a proper intervention threshold, possibly variable at will, such as to prevent a blade shift merely due to an increased resistance of the snow mass to be removed.

[0008] The aim of the invention is to provide a snowplow provided with an active protection device against collision with fixed obstacles, suitable for being mounted on any kind of blade.

[0009] This aim is achieved by a snowplow provided with a protection device against collision with fixed obstacles comprising an electrical/electronic system for detecting and controlling the movements to the blade carrying means.

[0010] The above and other aims are achieved by the snowplow according to the invention, as claimed in the appended claims.

[0011] The system for protection against collision with fixed obstacles, made in accordance with the invention, can advantageously be employed in conjunction with any device intended for road cleaning, such as for instance a snowplow, mounted in the front part of a tractor or similar vehicle. The system is capable of intervening quickly, in precise and selective manner, since it has an intervention threshold which is programmable and readily modifiable.

[0012] The above and other aims of the invention will become more apparent from the description of a preferred embodiment, with reference to the accompanying drawing, which shows an electrical/hydraulic diagram of a snowplow provided with a protection device against collision with fixed obstacles and made in accordance with the invention.

[0013] A snowplow, of the single-blade or spade type, is mounted on the front part of a vehicle or tractor by means of a frame equipped with an articulated quadrilateral structure allowing the distance of the scraping blades 2 from the ground to be varied by means of a lifting cylinder or jack 10. Double-cylinder jack 10, besides being operable by an operator, in conventional manner, can also cause the lifting of the structure in case of a collision against an obstacle, as will be disclosed hereinafter. Blade 2 is secured to a sliding frame element, joined to the movable part of the articulated quadrilateral and associated with a hydraulic cylinder 4 having a first chamber 4b connected, through a hydraulic connection 28, with a pressure sensor or transducer 18. In accordance with the teachings of the prior art, chamber 4b of hydraulic cylinder 4 can be directly connected with a chamber 14 of jack 10, through hydraulic connection 30, thereby allowing combining the lifting system according to the present invention with the conventional safety systems.

[0014] Piston rod 6 of pump hydraulic cylinder 4 is secured to blade 2, whereas the body of pump cylinder 4 is secured to the fixed part of the frame. Thus, the movements of blade 2 upon a collision with a fixed obstacle, which are hindered by the action of contrasting springs 8, cause a pressure increase in hydraulic connection 28 with sensor 18, and a consequent liquid inflow into chamber 14 of hydraulic jack 10, if hydraulic connection 30 is provided.

[0015] The signal generated by sensor 18, which can be a transducer or a pressure switch, is fed to an electronic control unit 20, which controls the operation of a double electric valve 22. Control unit 20 is equipped with a console 42 for the management of the threshold of intervention of the blade lifting system, which console allows the operator to vary at will such threshold depending on the operating conditions, such as for instance the amount of snow to be removed, the snow density or the presence of ice slabs on the road. A second console 44 allows instead varying, by means of a programmable timer, the time by which the blade remains lifted after having met an obstacle.

[0016] A function of control unit 20 is therefore comparing the signal coming from sensor 18 with a threshold value set by means of console 42, and operating a first section 22a of electric valve 22 when said threshold value is exceeded. Thereafter, when the time set by means of timing console 44 is over, the control unit commands the closure of the first section 22a of electric valve 22 and at the same time the opening of the second section 22b, thereby causing the blade lowering.

[0017] Actually, the first section 22a of electric valve 22 allows, through a hydraulic connection 38, the inflow of pressure liquid, fed from a oil-pressure pump 24 equipped with a tank, into a second chamber 16 of lifting jack 10, thereby causing the immediate lifting of blade 2.

[0018] According to a variant embodiment, the first section 22a of electric valve 22 can also be connected, through a hydraulic connection 40, to a second chamber 4a of pump cylinder 4, so as to cause the closure thereof. Such a closure makes blade 2 move back and, through hydraulic connection 30, assists in the blade lifting by means of cylinder 10, thereby contributing to the shock absorbing action upon a collision.

[0019] The second section 22b of electric valve 22 on the contrary allows discharging the pressure liquid present in duct 30 or in duct 40 into a tank 26, thereby causing the lowering of blade 2.

[0020] The provision of the sliding frame element, required in a snowplow with wedge or spade blade, might be not indispensable in a single-blade snowplow, since that blade is already equipped with an overturning system for protection against collision. In the latter case, the blade overturning itself could exert a pressure on the piston of pump cylinder 4 or, in the alternative, could directly activate a sensor connected with control unit 20.

[0021] Also the provision of pump cylinder 4 is not indispensable since sensor 18, e.g. in the form of an electric contact, a slide-wire potentiometer, a magnetic sensor or an opto-electronic device, can directly detect the displacements of blade 2 and transmit a corresponding signal to control unit 20 which will control electric valve 22 according to the principles described above.

[0022] In the alternative, pressure sensor 18 could be connected with the hydraulic circuits of the oil-pressure cylinders used in spade snowplows to open and close the two blades. In effect, the collision with an obstacle would cause a pressure increase, which could be readily detected by the proper sensor.

Claims

1. Snowplow provided with a protection device against collision with fixed obstacles, comprising at least one blade (2) carried by a frame that can be fastened to the front part of a vehicle and that is provided with means (10) for causing a vertical displacement of the blade (2) to vary its distance from the ground, said blade being arranged to perform a translation movement in the direction of advance of the snowplow or a rotation movement about an own axis, characterised in that the snowplow comprises a detection system (4, 18) arranged to detect said movement of the blade (2), and an active operating system (20, 22) arranged to lift said blade (2) from the ground, by operating said means (10) for causing a vertical displacement of the blade (2) if said movement of the blade (2) exceeds a predetermined intervention threshold.

2. Snowplow according to claim 1, comprising a pump cylinder (4), arranged between said blade (2) and said frame so as to be compressed when said blade (2) is pushed towards said vehicle upon a collision with an obstacle, said pump cylinder (4) having a first chamber (4b) connected with a pressure sensor (18) through a hydraulic circuit (28).

3. Snowplow according to claim 1 or 2, wherein said sensor (18) is a transducer connected with a control unit (20) which acts upon a lifting cylinder (10) arranged to cause the vertical displacement of said blade (2).

4. Snowplow according to claim 3, wherein said sensor (18) is a pressure switch.

5. Snowplow according to claim 3 when referred to claim 2, wherein said first chamber (4b) of the pump cylinder (4) is connected, through a hydraulic circuit (30), also with said lifting cylinder (10).

6. Snowplow according to claim 3, wherein the control unit (20) is an electronic control unit.

7. Snowplow according to claim 3, wherein said control unit (20) is provided with a programmable timer (44) which allows keeping said blade (2) in lifted position for a predetermined time.

8. Snowplow according to claim 3, wherein said control unit (20) allows modifying said intervention threshold by means of an external console (42).

9. Snowplow according to claim 3, wherein said control unit (20) controls the opening and closing of a first electric valve (22a) which enables the inflow of a pressure liquid into said lifting cylinder (10), thereby causing the lifting of the blade (2) from the ground.

10. Snowplow according to claim 9, wherein said control unit (20) controls the opening and closing of a second electric valve (22b) which enables the outflow of said pressure liquid from said lifting cylinder (10), thereby causing the lowering of the blade (2).

11. Snowplow according to claim 5, wherein said control unit (20) controls the opening and closing of a first electric valve (22a) which enables the inflow of a pressure liquid into a second chamber (4a) of said pump cylinder (4), thereby causing the closure thereof and the consequent compression of said first chamber (4b), with a consequent lifting of the blade (2) from the ground.

12. Snowplow according to claim 11, wherein said control unit (20) controls the opening and closing of a second electric valve (22b) which enables the outflow of said pressure liquid from the second chamber (4a) of said pump cylinder (4), thereby causing a pressure decrease in the lifting cylinder (10) and the consequent lowering of the blade (2).

Drawing