Blade holder for a snow-clearing device

The invention relates to a holder for connecting a blade (7) to the lower edge (6) of a snow-clearing device, such that the blade is given an acute, cutting angle to the base and can be folded backwards, thereby avoiding damage when running into an obstacle, and automatically resume its cutting angle after passing the obstacle. The holder comprises a trilateral hollow beam (1), the three sides of the beam forming respectively: a first fixing element (3) which is adapted to be fixed to the lower edge (6) of the snow-clearing device; a second fixing element (4) which is adapted to engage the back of the blade (7), and a support element (5) connecting the other two elements (3, 4). At least the second fixing element (4) and the support element (5) are made of an elastic polymer material. The hollow beam is adapted to fix the blade along a line along the lower part of the second fixing element (4) close to a corner of the beam, and the elastic elements (4, 5) are adapted, on overloading, to be buckled, the support element (5) being buckled towards the cavity (2) of the beam, and the second fixing element (4) being buckled forwards/upwards.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The invention relates to a holder for connecting a blade to the lower edge
 of a snow-clearing device, such that the blade is given a cutting (acute)
 angle to the base and can be folded backwards, thereby avoiding damage
 when running into an obstacle, and automatically resume its cutting angle
 after passing the obstacle.
 2. Description of the Related Art
 In the first place, the invention is intended for use on a snow-clearing
 device comprising a plough wing, snow scraper or snow blade which is
 supported by a vehicle or device carrier of some type and which in its
 lower part has at least one blade serving to engage the ground with its
 cutting edge and ensure a snow-cutting and snow-raising action. Use is
 normally made of a plurality of relatively short blades which are mounted
 side by side along the lower edge of the snow-clearing device.
 It is desirable that the device can remove substantially all loose snow
 lying on a roadway, i.e. as far as possible also snow lying in cavities in
 the form of e.g. ruts in the roadway, to provide a safe base. This means
 that the blades of the snow-clearing device must be able to operate in
 close engagement with the roadway, which can be achieved if they are
 flexibly fixed to the lower part of the plough and thus can be
 individually inclined in the lateral direction relative to the lower part
 of the plough. It is also desirable that the device can cut or scrape away
 snow or ice adhering to the roadway. Moreover, it should be possible to
 carry out the above-mentioned snow-clearing work at high speed. It goes
 without saying that snow-clearing under these conditions subjects both the
 snow-clearing device and the device carrier to heavy stress, and they can
 be damaged if the blade strikes against a stationary obstacle, for
 instance, protruding gutters, kerbs, and railway tracks.
 To protect the device and the device carrier against damage arising in case
 of running into an obstacle, it is previously known to mount the blade to
 be pivotable backwards, against the action of a spring, about a hinge
 located above the blade. In this case, the blade must be essentially
 vertically oriented to the roadway, thereby making it possible for the
 lower edge of the blade to move backwards/upwards without causing a
 lifting motion of the device. It is not possible to position the blade at
 an evidently positive angle relative to the vertical plane, i.e. with the
 lower edge of the blade extended forwards in the travelling direction.
 With this design, the blade therefore operates with a scraping effect
 against the roadway, thereby making it necessary to press the blade
 against the roadway relatively firmly to ensure good snow-clearing
 results. The construction also results in the snow-throwing ability being
 limited.
 A prior-art arrangement for protecting devices and device carriers when the
 blade is oriented at an acute, cutting angle to the roadway is disclosed
 in International Patent Application WO 95/23894. The blade is hingedly
 attached to the front end of a forwardly extended pivot arm. When running
 into an obstacle, the blade can, against the action of a spring, be folded
 backwards while at the same time the pivot arm is raised against the
 action of another spring. In this construction, the blade has a positive
 angle relative to the vertical plane and also vertical flexibility
 relative to the roadway. However, a drawback is the fact that the blades
 cannot be inclined in the lateral direction and, thus, do not achieve the
 flexibility that is required to obtain a good snow-clearing effect on a
 rutted roadway. Besides, the mechanical construction requires much repair
 and maintenance since it is subjected to heavy wear and is easily damaged
 in this environment.
 SUMMARY OF THE INVENTION
 An object of the present invention is to provide an improved blade holder
 of the type mentioned by way of introduction, i.e. which is adapted to
 orient the blade at an acute, cutting angle to the roadway and which has
 an automatic folding back effect when running into an obstacle. A further
 object is to provide a blade holder which under all snow-clearing
 conditions gives the blades good flexibility and close engagement with the
 roadway, i.e. also on roadways with ruts and ridges. One more object is to
 provide a simple, robust and light construction which has no mechanical
 hinges. It should be possible to use the same type of blade holder for all
 types of snow-clearing devices which are provided with blades, e.g. front
 mounted ploughs, side wing ploughs, rear mounted ploughs, snow scrapers
 and blades mounted underneath, which makes it possible for the user of the
 device to simplify and standardise his stock-keeping of wearing parts and
 spare parts.
 These and other objects and advantages, which will appear from the
 following specification, are achieved by a holder as defined in the
 claims.
 The inventive holder comprises a trilateral hollow beam, the three sides of
 the beam forming respectively: a first fixing element (3) which is adapted
 to be fixed to the lower edge (6) of the snow-clearing device; a second
 fixing element (4) which is adapted to engage the back of the blade (7),
 and a support element (5) connecting the other two elements (3, 4) to a
 triangular cross-section of the hollow beam (1), at least the second
 fixing element (4) and the support element (5) being made of an elastic
 polymer material ensuring that each element, i.e. each side of the hollow
 beam, is resilient in the transverse direction and bendable about its
 longitudinal direction; and means for attaching the blade to the hollow
 beam (1). The holder is characterised in that the hollow beam (1) has such
 a shape that, when mounted against the lower edge (6) of the device, the
 second fixing element (4) and the support element (5) are directed
 obliquely downwards/forwards and meet in a corner in front of the lower
 edge (6) of the device; that the hollow beam is adapted to fix the blade
 along a line along the lower part of the second fixing element (4) close
 to said corner of the beam, the second fixing element (4) and the support
 element (5), in operation of the device, exerting on the blade a pressure
 spring action directed obliquely downwards/forwards, and that said
 elements (4, 5) are adapted, on overloading, to buckle, the support
 element (5) being adapted to buckle towards the cavity (2) of the beam,
 and the second fixing element (4) being adapted to buckle
 forwards/upwards.
 Preferably, the trilateral hollow beam has the same length as the blade
 that has been chosen. Normally, each blade consists of a section of
 600-1800 mm, and a plurality of such sections are arranged side by side
 along the lower edge of the plough.
 The invention is based on the idea of forming of a flexible material a
 blade holder which operates as pressure springs over the length of the
 blade and presses the blade in its direction of engagement against the
 roadway, thereby making it possible for the blade to follow the roadway in
 the vertical direction and to be automatically inclined in the lateral
 direction for close engagement in ruts and on ridges in the roadway.
 The blade holder orients the blade at an acute, cutting angle relative to
 the roadway, which results in good clearing and snow-throwing ability. The
 blade is folded backwards when striking against stationary obstacles such
 as gutters, kerbs etc. and automatically resumes its operating position
 after passing the obstacle. This is achieved by the second fixing element
 and the support element being adapted to be folded (buckled) when
 subjected to an overloading pressure, such that the blade is temporarily
 folded backwards and then is moved back to its operating position by the
 elasticity of the elements.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 Further scope of applicability of the present invention will become
 apparent from the detailed description given hereinafter. However, it
 should be understood that the detailed description and specific examples,
 while indicating preferred embodiments of the invention, are given by way
 of illustration only, since various changes and modifications within the
 spirit and scope of the invention will become apparent to those skilled in
 the art from this detailed description.
 FIG. 1 thus shows a holder according to the invention, comprising a
 trilateral hollow beam 1 with an inner cavity 2, the three sides of the
 beam forming: a first fixing element 3, a second fixing element 4 and a
 support element 5, respectively.
 The first fixing element 3 is fixed to the lower edge 6 of the
 snow-clearing device. This edge is adjusted to the hollow beam to give a
 surface of attachment which is suitable in respect of size and angle, for
 instance, by a bent edge on the lowermost part of a plough blade.
 At least the second fixing element 4 and the support element 5 are made of
 an elastic polymer material which ensures that each element, i.e. hollow
 beam side, is resilient in the transverse direction and bendable about its
 longitudinal direction. Many different types of elastomers which are
 resistant to loads are conceivable as polymer materials, e.g. urethane
 rubber or some other type of rubber material. Polyurethane is a preferred
 type of material.
 The first fixing element 3 may consist of, for example, a steel sectional
 element, the other two elements being fixed to the steel sectional element
 so as to form a hollow beam. However, it is preferred to form the entire
 hollow beam in one piece of the same elastic polymer material, as shown in
 the Figures. It is particularly preferred to cast the hollow beam in e.g.
 urethane rubber. The urethane rubber should then have a hardness of at
 least 50.degree. Shore A and, in many applications, preferably at least
 70.degree. Shore A.
 The second fixing element 4 acts as a mounting for a blade 7. This side of
 the hollow beam thus engages the back of the blade and is in its lower
 part formed with holes 8 for detachable fixing of the blade. The
 attachment line of the blade thus is relatively close to a corner of the
 hollow beam. The material between the attachment line of the blade and the
 lower edge 6 of the device serves as pressure springs which are
 distributed over the entire length of the blade and press the blade in its
 direction of engagement against the roadway. The attachment of the blade
 can be effected in a conventional manner by means of, for instance, a key
 and a key bolt, and the blade may be of a reversible type with pairs of
 fixing holes 9 and 10.
 To avoid cracking around the holes 8, the second fixing element 4 is
 provided with a reinforcing steel bar 11, which is embedded in the elastic
 polymer material and extends along the element 4 in the area of attachment
 of the blade in the hollow beam.
 The third side of the hollow beam, the support element 5, connects the
 other two elements to a triangular cross-section of the hollow beam and
 acts as a spring holding the blade in place when affected by the friction
 against the roadway, and also when the blade is inclined in the lateral
 direction, as described in connection with FIGS. 4 and 4a.
 The blade holder 1 can be fixed to the lower edge of the snow-clearing
 device by means e.g. bolt joints. When the first fixing element 3 is made
 of a polymer material, a reinforcing steel bar 12 is arranged on the back
 of the fixing element in the cavity 2 of the beam. In the embodiment shown
 in the Figures, the steel bar 12 has a downwardly bent portion 13 along
 its one long side. The portion 13 extends a distance along the back of the
 adjoining second fixing element 4 and serves to stabilise this element and
 control the direction of buckling, as described in connection with FIG. 3.
 FIG. 2 shows the behaviour of the blade holder during operation of the
 snow-clearing device. When clearing snow, friction develops between the
 blade and the roadway and the blade is pressed slightly backwards. The
 support element 5 acts as a spring and is compressed, and the motion makes
 it slightly curved upwards towards the cavity 2 of the beam. This
 curvature controls the direction of the buckling that is to happen when
 the blade strikes against an obstacle which may cause damage to the device
 and the device holder.
 FIG. 3 shows the situation in which the blade strikes against an obstacle.
 The support element 5 will then be buckled upwards while at the same time
 the fixing element 4 is buckled forwards/upwards owing to the upwardly
 directed force generated by the blade when being raised vertically. The
 motion is reinforced by a turning moment forming around the attachment
 line of the blade at the steel bar 11. The blade achieves a dragging
 angle. After passing the obstacle, the blade holder springs back to its
 operating position.
 FIG. 4 is a schematic view of a plough blade 14, to the lower edge of which
 a number of blades 7 are mounted side by side. Each blade can be mounted
 with a blade holder which has a length corresponding to the length of the
 blade. In the operating position, the blades should have a pressure of
 engagement against the roadway to allow efficient clearing of snow. This
 means that the second fixing element 4 is compressed while at the same
 time the support element 5 is compressed owing to the friction when
 advancing the device. The force which thus is built up in the elements 4
 and 5 will incline the blade in the lateral direction as shown in FIG. 4a
 if the roadway has ruts or ridges.
 The good flexibility of the blades against the roadway increases the
 clearing effect and means that the blades require but a small pressure
 against the roadway to achieve satisfactory engagement, which in turn
 reduces blade wear and power consumption in the snow-clearing work. The
 simple and robust construction minimises repairs and maintenance, and the
 low weight reduces the weight of the device, which is of special
 importance to front mounted ploughs which are to be transported in an
 uplifted position and thus load the front axle of the device carrier. The
 flexible fixing of the blades also reduces noise and vibrations, which,
 inter alia, creates a better working environment for the driver and
 reduces damage to the device and the device holder owing to vibrations.
 The invention being thus described, it will be obvious that the same may be
 varied in many ways. Such variations are not to be regarded as a departure
 from the spirit and scope of the invention, and all such modifications as
 would be recognized by one skilled in the art are intended to be included
 within the scope of the following claims.