IES58108B2

IES58108B2 - A scraper drive

Info

Publication number: IES58108B2
Authority: IE
Inventors: Edmond Patrick Harty; Edmond Patrick Harty Junior
Original assignee: Aratech Ltd
Priority date: 1992-12-21
Filing date: 1992-12-21
Publication date: 1993-07-14
Also published as: GB9325222D0; IES922929A2; GB2273581A

Abstract

A scraper drive 1 for driving a scraper blade 2 comprises a ram 14 for driving the blade 2 through a drive member 3. Pressure sensors 45 and 46 monitor fluid pressure in the lines 36 and 37 to the ram 14 and operate a solenoid valve 48 for inhibiting delivery of fluid to the ram 14 in the event of the scraper blade 2 encountering an obstruction, except when proximity switches 52 and 53 detect the piston rod 19 reaching either end of its stroke. In this event the sensors 45 and 46 are isolated from the valve 48 by a relay 50 to prevent the valve 48 being closed on a build up pressure, thereby permitting hydraulic pressure to build up to a level for reversing an auto-reversing valve 34 to reverse the direction of the piston rod 19.

Description

A scraper drive The present invention relates to a scraper drive for operating a yard scraper blade.

In general, scraper drives comprise a housing in which a double acting hydraulically powered ram is housed. A piston rod of the ram extends from the housing and is connected to an elongated drive member which is engagable with a yard scraper blade. Generally, the yard scraper blade is driven by the ram through the drive member along a longitudinally extending path, the distance of which is considerably longer than the stroke of the piston. The drive member slidably engages the scraper blade and drives the scraper blade forwardly away from the scraper drive through incremental distances corresponding to the stroke length of the piston rod through a ratchet and pawl mechanism mounted in the scraper blade. Accordingly, as the drive member is driven outwardly of the housing by the piston rod the scraper blade is urged forwardly an incremental distance. On the piston rod returning the drive member the drive member slides trough the scraper blade, thereby leaving the scraper blade stationary. Thus, the yard scraper blade is moved along the path through incremental distances corresponding to the length of the piston rod stroke. ιιο α. » A high pressure hydraulic fluid source is connected to the double acting ram for operating the ram.

Such scraper drives for yard scraper blades, in general, are adequate for scrapping muck and other material from a yard. However, should an obstruction, such as, an animal be in the path of the scraper blade, one of two problems, in general, arises. In cases where the scraper drive is fitted with an autoreversing valve responsive to pressure build up when the scraper blade reaches the animal, the back pressure build up in the hydraulic fluid caused by the obstruction to the passage of the scraper blade causes the ram to reverse. In other words, the piston rod is reversed. This, in general, occurs prior to the piston rod having reached the end of its stroke. Should the animal continue to obstruct the passage of the scraper blade, the ram is reversed each time a pressure build up occurs in the hydraulic fluid. Eventually, when the obstruction is removed the scraper blade commences to move from a position in the path which does not correspond with the beginning of a stroke of the piston rod. This creates considerable problems when the scraper blade is approaching the end of the path to be scraped. Alternatively, where a scraper drive is not fitted with an auto-reversing valve of a safety cut out, the ram continues to operate and push the scraper blades against the obstruction, which may either cause injury to the animal, or damage to the drive member or scraper blade.

This is undesirable, and accordingly, there is a need for a scraper drive which overcomes these problems.

The present invention is directed towards providing such a scraper drive.

According to the invention there is provided a scraper drive for operating a yard scraper blade, the scraper drive comprising a double acting ram having a piston rod for operably connecting to a drive member of the scraper blade for urging the scraper blade along a path to be scraped, a pair of fluid lines for communicating respective ports of the ram with a reversing valve for controlling the supply of fluid to the ram from a high pressure fluid source, a pressure sensing means in at least one fluid line for monitoring the fluid pressure in that fluid line, a valve means in one of the fluid lines for selectively inhabiting fluid flow through the line, the valve means being responsive to the pressure sensing means for inhibiting fluid flow on the pressure sensing means sensing a fluid pressure above a predetermined level, position sensing means for monitoring the position of the piston rod of the ram, and isolating means for isolating the valve means from the pressure sensing means for preventing inhibiting of flow, the isolating means being responsive to the position sensing means for isolating the valve means from the pressure sensing means on the position sensing means sensing the piston rod having reached an end of a stroke.

In one embodiment of the invention pressure sensing means are provided in the respective fluid lines, and the position sensing means comprises a pair of proximity switches for detecting a predetermined portion of the piston rod of the ram, the proximity switches being located at spaced apart locations corresponding to the respective positions occupied by the predetermined portion of the piston rod at each end of a stroke.

In another embodiment of the invention each pressure sensing means comprise a pressure sensor located in the corresponding fluid line adjacent corresponding ports of the ram, each pressure sensor comprising means for delivering a signal on the fluid pressure exceeding a predetermined level, and the isolating means comprises a switch means for preventing passage of the signals generated by either of the respective pressure sensors passing to the valve means.

In a further embodiment of the invention the scraper drive comprises the reversing valve and the reversing valve is provided by an auto-reversing valve responsive to back pressure in the fluid flowing to the ram for reversing the flow of fluid, the predetermined pressure to which the pressure sensing means is responsive being less than the back pressure for reversing the auto-reversing valve, and the isolating means is connected to the high pressure fluid source for deactivating the high pressure fluid source when the valve means is closed.

The invention will be more clearly understood from the following description of a preferred embodiment thereof given by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a perspective view of a yard scraper according to the invention which comprises a scraper drive also according to the invention, Fig. 2 is a plan view of the yard scraper of Fig. Ir Fig. 3 is a plan view of the scraper drive of Fig. 1, and Fig. 4 is a circuit diagram of the scraper drive of Fig. 1.

Referring to the drawings there is illustrated a scraper drive according to the invention indicated generally by the reference numeral 1 for driving a scraper blade 2 through a drive member 3 for scraping an elongated path 4 through a yard. The path 4 is illustrated in chain lines in Fig. 2. The scraper drive 1 comprises a housing 5 of heavy gage sheet metal which comprises a base 7 and side walls 8 extending upwardly from the base 7 joined by end walls 9 extending upwardly from the base 7. A double acting hydraulic ram 14 is mounted in the housing 5 and secured to the base 7 for driving the scraper blade 2 along the path 4 from one end 16 adjacent the housing 5 illustrated in Fig. 2 with the scraper blade 2 in full lines to another end 17 illustrated with the scraper blade 2 in broken lines. A piston rod 19 of the ram 14 is connected to the drive member 3 by a connecting bracket 20 for driving the drive member 3.

An opening 21 in one of the end walls 9 of the housing 7 accommodates the connecting bracket 20 through the housing 5. The scraper blade 2 slidably engages the drive member 3 and is operably connected to the drive member 3 by a ratchet and pawl drive mechanism (not shown) so that on each outward stroke of the piston rod 19 in the direction of the arrow A the drive member 3 is also moved in the direction of the arrow A and moves the scraper blade 2 in the direction of the arrow A an incremental distance along the path 4 corresponding to the length of the stroke of the piston rod 19. On the return stroke of the piston rod 19 in the direction of the arrow B the drive member 3 slides relative to the scraper blade 2 thereby leaving the scraper blade 2 stationary. Such arrangements of ratchet and pawl mechanisms for connecting a scraper blade to a drive member will be well known to those skilled in the art. The connecting bracket 20 is of L-shaped construction comprising an elongated leg 23 to which the drive member 3 is secured by screws 24, and a leg 26 which is secured to a threaded end 27 of the piston rod 19 by a nut 28.

Hydraulic fluid is supplied to the ram 14 from a high pressure hydraulic source which comprises a reservoir 30 for the hydraulic fluid and a high pressure pump 33 connected to the reservoir 30 for delivering high pressure hydraulic fluid to the ram 14, see Fig. 4. Hydraulic fluid is delivered by the pump 33 to the ram 14 through an auto-reversing valve 34 for controlling the operation of the ram 14. A pair of hydraulic fluid lines 36 and 37 connect the auto-reversing valve 34 to ports 38 and 39, respectively, of the ram 14. Hydraulic fluid lines 40 and 41 connect the pump 33 to the reservoir 30 and to the auto-reversing valve 34, respectively. An hydraulic fluid line 42 from the auto-reversing valve 34 returns fluid to the reservoir 30. The auto-reversing valve 34 is of the type which on sensing back pressure in the hydraulic fluid flowing to the ram 14 reaching a predetermined level reverses the direction of flow of fluid through the lines 36 and 37 for reversing the direction of the movement of the piston rod 19. Such auto-reversing valves 34 will be known to those skilled in the art.

Pressure sensing means comprising a pair of pressure sensors 45 and 46 are provided adjacent the ports 38 and 39, respectively, for monitoring the pressure of hydraulic fluid in the lines 36 and 37. The pressure sensors 45 and 46 are of the type which comprise a bistate electrical switch (not shown) which is operable from one state, namely, an open state to a second state, namely, a closed state on pressure in the respective lines 36 or 37 reaching a predetermined level. A valve means comprising a solenoid operated valve 48 which is operable in two states, namely, an open and a closed state is provided in the line 36 for selectively inhibiting fluid flow through the line 36 for stopping operation of the ram 14. The solenoid valve 48 is connected to the pressure sensors 45 or 46 and is responsive to the sensors 45 and 46, so that on either of the pressure sensors 45 or 46 sensing the pressure in the lines 36 or 37 exceeding the predetermined level which is less than the predetermined pressure at which the auto-reversing valve 34 reverses, the valve 48 is operated into the closed state for preventing further operation of the ram 14. The sensors 45 and 46 are connected to the hydraulic pump 33 for switching off the pump 33 while the solenoid valve 48 is closed to prevent a further build up in hydraulic pressure which could reverse the auto-reversing valve 34. Isolating means for isolating the solenoid valve 48 from the pressure sensors 45 and 46 comprises a relay 50 through which the pressure sensors 45 and 46 are connected to the solenoid valve 48. Position sensing means comprising a pair of proximity switches 52 and 53 are located in the housing 5 at positions which correspond to the respective positions of the leg 26 of the connecting bracket 20 when the piston rod 19 is in its respective extreme inner and outer positions, respectively, for monitoring when the piston rod 19 is in either of its extreme positions, in other words, at the end of a stroke in either direction. The relay 50 is connected to the proximity switches 52 and 53, and is responsive to the proximity switches 52 or 53 sensing the piston rod 19 at the end of a stroke for isolating the solenoid valve 48 from the pressure sensors 45 and 46 to prevent the build up in back pressure in either of the lines 36 or 37 closing the solenoid valve 48, and thereby permitting the hydraulic fluid pressure to build up to the level for reversing the auto-reversing valve 34. Thus, should the scraper blade 2 encounter an obstruction when moving in the direction of the arrow A and the piston rod 19 is intermediate its extreme positions, the build up of hydraulic pressure in the line 36- causes the pressure sensor 45 to close the solenoid valve 48 thereby preventing further movement of the piston rod 19. The solenoid valve 48 is retained closed by the sensor 45 until the pressure in the line 36 drops, at which stage the solenoid valve 48 is opened thereby permitting the piston rod 19 to continue its outward stroke in the direction of the arrow A.

A timer and other suitable control circuitry (not illustrated or described but which will be well known to those skilled in the art) is provided in a control box with the high pressure hydraulic fluid source permits selection of the times at which the scraper drive 1 is to operate for driving the scraper blade 2 to scrape the path 4.

In use, the scraper drive 1 is connected to the high pressure hydraulic source comprising the reservoir 30, the pump 33 through the auto-reversing valve 34. The scraper blade 2 is connected to the drive member 3 which is in turn connected to the connecting bracket 20 of the scraper drive 1. On the timer activating the high pressure hydraulic source, hydraulic fluid is delivered to the scraper drive 1, the flowing fluid being delivered through the hydraulic line 36 for driving the piston rod 19 in its outward stroke in the direction of the arrow A and for moving the scraper blade 2 its first incremental distance along the path 4. The piston rod 19 continues its outward stroke until pressure begins to build up in the line 36 thereby indicating an obstruction having been encountered by the scraper blade 2 or the piston drive 19 having reached the end of its outward stroke. In the event of an obstruction and the proximity switch 53 does not detect the leg 26 of the connecting bracket 20, the relay 50 remains closed and the hydraulic pressure sensor 45 on the pressure in the line 36 reachiny its predetermined level closes the solenoid valve 48. The scraper drive 1 remains in this mode until the hydraulic pressure sensed by the pressure sensor 45 drops below its predetermined level at which stage the solenoid valve 48 is again opened and fluid is delivered to the ram 14 to move the piston rod 19 along the rest of its outward stroke in the direction of the arrow A. On the proximity switch 53 detecting the leg 26 of the connecting bracket 20, the relay 50 isolates the pressure sensors 45 and 46 from the solenoid valve 48, thereby permitting pressure to continue to build up in the line 36 until the auto-reversing valve 34 reverses the flow of fluid to the ram 14, for in turn, reversing the direction of the stroke of the piston rod 19. Needless to say, each time pressure in the line 36 or 37 exceeds the predetermined level to which the pressure sensors 45 and 46 are sensitive and the proximity switches 52 or 53 fail to detect the leg 26 to the connecting bracket 20 the solenoid valve 48 closes thereby preventing further flow of fluid to the ram 14 until the pressure in the respective lines 36 or 37 drop below the predetermined level of the sensors 45 and 46.

Accordingly, should an obstruction be encountered by the scraper blade 2 the piston rod 19 and scraper 2 are stopped in the position at which the obstruction is encountered. The piston rod does not return, and remains in an intermediate position between its two extreme positions until the obstruction is removed, at which stage the piston rod 19 continues its stroke. Accordingly, the incremental distances which the scraper blade 2 is moved by each outward stroke of the piston rod 19 are constant, irrespective of whether an obstruction is encountered or otherwise. Thus, the last outward stroke of the piston rod 19 always parks the scraper blade 2 at its end position 17 when the piston rod 19 is at the extreme end of its last outward stroke 19.

While particular pressure sensing means and position sensing means have been described, other suitable pressure sensing means and position sensing means could be used. Further, while particular valve means and isolating means have been described, other suitable valve means and isolating means may be used.

The invention is not limited to the embodiment hereinbefore described which may be varied in construction and detail.

Claims

CLAIMS:

1. A scraper drive for operating a yard scraper blade, the scraper drive comprising a double acting ram having a piston rod for operably connecting to a drive member of the scraper blade for urging the scraper blade along a path to be scraped, a pair of fluid lines for communicating respective ports of the ram with a reversing valve for controlling the supply of fluid to the ram from a high pressure fluid source, a pressure sensing means in at least one fluid line for monitoring the fluid pressure in that fluid line, a valve means in one of the fluid lines for selectively inhabiting fluid flow through the line, the valve means being responsive to the pressure sensing means for inhibiting fluid flow on the pressure sensing means sensing a fluid pressure above a predetermined level, position sensing means for monitoring the position of the piston rod of the ram, and isolating means for isolating the valve means from the pressure sensing means for preventing inhibiting of flow, the isolating means being responsive to the position sensing means for isolating the valve means from the pressure sensing means on the position sensing means sensing the piston rod having reached an end of a stroke.

2. A scraper device as claimed in Claim 1 in which pressure sensing means are provided in the respective fluid lines, and the position sensing means comprises a pair of proximity switches for detecting a predetermined portion of the piston rod of the ram, the proximity switches being located at spaced apart locations corresponding to the respective positions occupied by the predetermined portion of the piston rod at each end of a stroke.

3. A scraper drive as claimed in Claim 1 or 2 in which each pressure sensing means comprise a pressure sensor located in the corresponding fluid line adjacent corresponding ports of the ram, each pressure sensor comprising means for delivering a signal on the fluid pressure exceeding a predetermined level, and the isolating means comprises a switch means for preventing passage of the signals generated by either of the respective pressure sensors passing to the valve means.

4. A scraper drive as claimed in any preceding claim in which the scraper drive comprises the reversing valve and the reversing valve is provided by an autoreversing valve responsive to back pressure in the fluid flowing to the ram for reversing the flow of fluid, the predetermined pressure to which the pressure sensing means is responsive being less than the back pressure for reversing the auto-reversing valve, and the isolating means is connected to the high pressure fluid source for deactivating the high pressure fluid source when the valve means is closed.

5. 5. A scraper drive substantially as described herein with reference to and as illustrated in the accompanying drawings.