AU759010B2 - Braking system for a hand operated vehicle - Google Patents

Description

4 P00011 Regulation 3.2 Revised 2/98

AUSTRALIA

Patents Act, 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT 4* TO BE COMPLETED BY THE APPLICANT a NAME OF APPLICANTS: ACTUAL INVENTORS: ADDRESS FOR SERVICE: INVENTION TITLE: DETAILS OF ASSOCIATED PROVISIONAL APPLICATION NO(S): GORDON BUTLER and NEIL STEPHENS GORDON BUTLER NEIL STEPHENS Peter Maxwell Associates Level 6 Pitt Street SYDNEY NSW 2000 BRAKING SYSTEM FOR A HAND OPERATED VEHICLE PP 2750 3 April 1998 Australia The following statement is a full description of this invention including the best method of performing it known to me:- 2 The present invention relates to a braking system for a hand operated vehicle and, in particular, to a retro-fittable cam brake for hand operated pallet trucks. The invention can be applied to a wide range of hand operated vehicles, particularly to those which are regularly moved over sloping terrain, such as lawn mowers, wheel chairs and the like, where a simple, but dependable brake is required. The braking system of the invention exerts a braking force on the circumferential surface of the wheels of the hand operated vehicle, which may be either fixed wheels or •swivelable castor wheels.

10 In many industrial workplaces, materials handling equipment play an important, if not essential, role in providing an efficient and safe working environment. In the warehousing and distribution industry, for instance, materials handling equipment, such as hand operated pallet trucks, are coming under close scrutiny by both Government and industry regulatory 15 bodies who are attempting to address the many manual handling based -problems and related injuries caused by the conventional design and customary use of the equipment. A range of problems has been identified *as stemming from the design and use of hand operated pallet trucks.

These pallet trucks are, in the main, not manufactured with an inbuilt braking system (to keep purchase costs low), and nor can they be retrofitted with any disc brake or shoe brake type systems that are being used for other applications, without major expense or complex and time consuming structural changes.

A new pallet truck with an inbuilt brake is about A$500.00 more expensive than a conventional unbraked pallet truck. Given that there are tens of thousands of unbraked pallet trucks already in use in Australia, it is 3 unlikely that thousands of owners will be swayed by safety concerns to replace their functioning unbraked pallet trucks with braked models.

One such braked pallet truck, manufactured under the "Crown" banner, employs a brake shoe and contact drum assembly against the inner side wall of the wheel. However, the assembly has many components, all of which gather dust and can break down in like manner to many other shoe and drum type braking systems.

In view of the continued widespread use of unbraked pallet trucks, S" several stopping methods have evolved to brake such pallet trucks, 10 especially when carrying a load or when being pushed over a sloping surface. One method is to exert considerable muscular force to slow the pallet truck, an approach that is limited to those operators with the necessary strength and control. Another method is to suddenly drop the forks of the pallet truck to the ground whereby the weight of the truck and any load carried thereon is utilised to bring the truck to a stop. However, *the jolting stop often causes the load to dislodge from the pallet being transported by the truck, and the load risks falling over the loading dock edge. Another method is to rapidly turn the rear steering wheels at right angles to the direction of movement of the truck, whereby the side of the wheels dig in to the surface and the resultant frictional force brings the truck to a stop. This method also carries with it a significant risk that the load will topple from the pallet on the truck, given the tendency of the load and indeed the pallet on which the load is carried to conserve its momentum when the truck is brought to a sudden stop. Rapidly turning the steering wheels perpendicularly whilst in motion also places large mechanical stresses on the wheels, shaft and bearings, causing damage to parts and wearing flat spots on the wheels. All of these methods are dependent on the skill of the pallet truck operator who must correctly time the stopping manoeuvre to ensure that, when approaching the edge of a loading dock, the pallet truck stops at the desired location rather than overshoot the edge or stop at a location too near the edge where the load subsequently tumbles to the floor of the loading bay. There is also a risk of injury to the operator in carrying out all of the aforementioned customary stopping methods.

It is an object of the present invention to overcome or at least S" substantially ameliorate the disadvantages and shortcomings of the prior oooo S. 10 art.

It is another object to provide a hand operated braking system which can be readily retrofitted to any existing unbraked pallet truck without major expense and structural modifications.

According to the present invention, there is provided a braking 15 system for a hand operated vehicle, comprising:a brake assembly for a wheel of the vehicle, a brake handle means for an operator of the system, and a cable operatively connecting the brake assembly to the brake handle means, the brake assembly including removable mounting means for mounting the brake assembly to a fixed reference location with respect to the wheel of the vehicle, pivotal arm means adapted to pivot between first and second positions in response to operation of the brake handle means, and cam means rotatably mounted to the pivotal arm means and including a cam surface which, when the arm means is in the first position, frictionally engages the circumferential surface of the wheel and, when the arm means is in the second position, is spaced apart from the circumferential surface of the wheel so as not to engage same, the cam surface having an initial engagement position defined by a first cam surface radius which initially engages the wheel circumferential surface, and at least one final engagement position defined between the first radius and a second cam surface radius being larger than the first radius, to which at least one final engagement position the cam means rotates under further frictional engagement with the wheel circumferential surface so as to cause the rotation of the wheel to be stopped by the cam means, whereby further rotation of the wheel is prevented.

In order that the invention may be readily understood and put into practical effect, reference will now be made to the accompanying drawings, in which:- Fig. 1 is an isometric view of a brake handle means and cable connection for a braking system according to a preferred 15 embodiment of the present invention, the brake handle means o being mounted to the steering column of a hand operated pallet truck, *Fig. 2 is an isometric view of an in situ brake assembly and cable connection for a braking system according to a preferred embodiment of the present invention, the brake assembly being mounted to the steering wheels support mast of a hand operated pallet truck (shown in part) having two steerable rear wheels, Fig. 3 is a side elevational view of the brake assembly and cable connection shown in Fig. 2 mounted to the pallet truck steering wheels support mast, and illustrating the relationship of the brake assembly and cable connection to a single wheel (shown in incomplete outline) not engaged by the brake assembly, Fig. 4 is a view similar to that of Fig. 3, except that the wheel is engaged by the brake assembly, and Fig. 5 is a side elevational view of a brake assembly and cable connection for a braking system according to another preferred embodiment of the present invention, and illustrating the relationship of the brake assembly and cable connection to a single wheel (shown in outline) not engaged by the brake S 10 assembly and which is operated specifically as a "deadman" type brake, S•The brake handle means shown in Fig. 1 is removably mounted to a S:conventional steering column of a hand operated pallet truck by a housing 12 and bolts 14. The housing 12 fits over a cross-piece 16 and upper portion of a shaft 18 of the steering column. There is a gap between the 0 housing panel 20 and the portion of the shaft 18 over which it fits of sufficient width to locate therewithin the brake handle means.

The brake handle means consists of a hand brake lever 22 pivotally mounted to the panel 20. A flexible cable 24 housed in a sheath 26 is connected at its uppermost end to the hand brake lever 22 so that an operator pivoting the lever 22 upwardly will cause the cable 24 to be pulled upwardly through the sheath 26. The upper end of sheath 26 is captured tightly in the bore of a cable adaptor 28 that is screwably secured through an aperture formed in the underside of the housing 12. The brake handle means may operate either as a normal manually applied stopping brake or as a "deadman" type brake that operates only after release of the lever 22.

The steering column also supports a conventional fork height adjusting lever 30 operating a cable (not shown) passing through the shaft 18 for lifting and lowering the forks of the pallet truck in the usual manner.

The brake assembly shown in situ in Fig. 2 and in side elevation against a single wheel and support mast therefor in Figs. 3 and 4 consists of a mounting bracket 32 removably mounted to the lower end of the steering wheels support mast 34 of the pallet truck, a "bell crank" type arm 36 pivotally connected to the mounting bracket 32 and rotatably supporting a cam wheel 38, the pivotal motion of the arm 36 being .o 10 controlled by the cable 24 so that the axial position of the cam wheel 38 is able to reciprocate between being, say when the lever 22 is not pivoted upwardly, spaced apart from the wheel 40 (as shown in Fig. 3) and being, say when the lever 22 is fully pivoted upwardly, engaged with the wheel 40 (as shown in Fig. 4).

The mounting bracket 32 is held firmly against the support mast 34 by a U-bolt 35 with nuts 37 and accompanying washer piece 39 and by an anchor bolt 42 with nut 43. The U-bolt 35 passes through one of two ~mounting holes 41 in the bracket 32, the holes 41 being so positioned as to enable height adjustment of the bracket 32, and so as to suit the model of the pallet truck to which the braking system is fitted. The anchor bolt 42 passes through a tubular portion 44 of the bracket 32 and through the axle locking hole formed perpendicularly across both the support mast lower portion 34a and axle 46 (shown sectionally) for the pair of steerable wheels 40a and 40b (shown in Fig. The axle locking hole of conventional unbraked pallet trucks is normally used for receiving therethrough a locking bolt, and this locking bolt must be removed in order that the anchor bolt 42, which is of greater length than a locking bolt to accommodate also the mounting bracket 32, may be passed therethrough and so lock the axle 46 to the support mast 34 and securely retain the relative locations of the mounting bracket 32, arm 36, cam wheel 38, cable 24 and wheel The "bell crank" type arm 36 is pivotally connected to the mounting bracket 32 by a pivot bolt 48 with nut 49 that passes through one of two pivot holes 50 in the bracket 32, the holes 50 being so positioned as to suit the particular diameter of the wheels 40a and 40b of the pallet truck to which the braking system is fitted. Ideally, the positioning of the arm 36 with respect to the wheel 40 should be such as to allow about a 1 mm gap (as shown by arrows A in Fig. 3) between the cam wheel 38 (when in the S"position as shown in Fig. 3) and the circumferential surface of the wheel 40. The arm 36 is subject to the force of a spring 51 that retains it in the position as shown in Fig. 3. A first end 52 of the spring 51 is secured to an anchoring site on the mounting bracket 32, a looped intermediate portion 54 of the spring 51 is arranged about pivot bolt 48, and a second end 56 of the spring 51 urges against a casing 57 for a cam shaft 58 0 which rotatably supports the cam wheel 38, applying a spring force against the shaft 58 in a direction away from the circumferential surface of wheel 40. Upwardly pulling the cable 24 by squeezing the lever 22 towards cross-piece 16 causes the arm 36 to pivot towards the wheel 40 against pressure exerted by spring 51.

The lower end of the cable 24 is secured around a casing 70 for a bolt 72 with nut 74, such as with a screwed locking clamp. The cable adjuster 76 is adjustably screwed into a tubular portion 78 of the mounting bracket 32 and retains the spatial relationship between the cable 24 and the arm 36 during their movement relative to the mounting bracket 32.

9 The cam shaft 58 passes through a cylindrical passageway formed axially through the cam wheel 38 and through a cam shaft locating hole formed through the arm 36, and is secured thereto with nut The cam wheel 38, which may be made of steel, has a cam surface 62 of variable radius and an axially centred surface 64 of uniform radius about the rotational axis of the cam wheel 38. The rotational axis of the cam wheel 38 thus serves as an eccentric axis for the cam surface 62.

The cam surface 62 has both a minimum radius point 66 from the ooooo= rotational axis and a pair of maximum radius points 68 from the rotational axis at respective opposed locations about the minimum radius point 66, the maximum radius points 68 having the same radius as the axially S"centred surface 64.

It is the minimum radius point 66 of the cam surface 62 which initially frictionally engages against the circumferential surface of the wheel 40 when, for a normal manually applied stopping brake, the lever 22 is pivoted fully upwardly to cause, by the upward pulling of cable 24, the arm 36 to pivot to a first position for enabling said frictional engagement.

:Under further frictional engagement or interaction between the cam surface 62 and the circumferential surface of wheel 40, the cam wheel 38 rotates (as shown in Fig. 4) towards one of the two maximum radius points 68 depending on the direction of rotation of the wheel 40, until a final engagement position of the cam wheel 38 is reached where the cam wheel 38 jams against the circumferential surface of wheel 40 sufficiently to prevent any further rotation of the wheel The rotation of the cam wheel 38 is against force exerted by a coil spring 80 looped around the cam shaft 58 and anchored at one end 82 through a selected one of a plurality of spring adjustment holes 84 located through the pivotal arm 36 and at the other end 86 through a dead end hole formed into the inner side wall of the cam wheel 38. When the cam wheel 38 is released from its engagement against the circumferential surface of wheel 40, the cam wheel 38 springedly rotates back to a position corresponding to its initial engagement position as shown in Fig. 3.

The cam wheel 38 is shown in Fig. 4 nearing one of its two possible final engagement positions to which it is being rotated against the force of coil spring 80 under frictional interaction with the rolling wheel 40. The i arrows C, D and E in Fig. 4 identify the relative directions of movement of 10 the cable 24, arm 36 and cam wheel 38 respectively during upward rotation of the lever 22 and during the time of engagement of the cam S•surface 62 with the circumferential surface of wheel 40 rotating in the direction of arrow B in Fig. 3.

The use of coil spring 80 also allows the braking force to be feathered, whereby only that amount of squeezing pressure on lever 22 is •ill required to be maintained that is needed for stopping the pallet truck.

It is apparent from the above description that the braking force **required to stop the pallet truck is not only dependent upon the squeezing pressure applied on lever 22 but on the action of the cam wheel 38 itself, which is caused, under frictional interaction of the cam surface 62 with the circumferential surface of wheel 40, to rotate and progressively apply a greater moment of force against the wheel 40 by a jamming or wedging effect. In this way, the momentum of the pallet truck is utilised to apply the additional braking force required to bring the pallet truck to a stop.

The brake assembly and cable connection shown in Fig. 5 is adapted for operation as a "deadman" type brake that operates only after the release of a hand operated lever or the like. Those features in Fig. 5 which 11 are identical or functionally similar to features in Figs. 2, 3 and 4 are numbered identically. The cable 90 is shown transmitting a force that moves a link member 92 secured to the cable towards the left as seen in Fig. 5. The link member 92 has a lower portion 93 that is securely fixed to a drive shaft 94 and the leftward movement is against the force of a coil spring 96 located between the lower portion 93 and the stationary mounting bracket 32. Leftward movement causes the shaft 94, which is connected to the bolt 72 or casing 70 of pivoting arm 36, to pivot the arm S• 36 upwardly so that the cam wheel 38 does not engage the circumferential •O l S 10 surface of the wheel 40 (as shown in Fig. The lower end of cable 90 is fixed to the mounting bracket 32 so that the leftward movement of cable results in the cable bending slightly between its fixed point on the bracket 32 and the link member 92 which is secured to it. In this way, a braking force is applied by the cam wheel 38 against the circumferential surface of the wheel 40 when there is no force being transmitted through cable 90 by the operator. A pallet truck having such a "deadman" type brake can be moved only when the operator causes a force to be **transmitted through the cable 90, otherwise the braking force is applied, say, when the pallet truck is left on a sloping surface.

The braking system of the present invention is equally effective when the pallet truck wheels against which the brake assembly is applied rotate in either a clockwise or anticlockwise direction.

The braking system described above also has the advantage that a braking force may be applied by the foot of the operator pressing the arm 36 towards the wheel 40 so that it pivots sufficiently about its pivotal axis for the cam wheel 38 to frictionally engage the circumferential surface of 12 wheel 40. The position of the arm 36 also serves to create a bump brake should the arm 36 of the pallet truck collide with an obstacle.

Other advantages of the braking system of the present invention are that it can be retrofitted onto conventional unbraked pallet trucks by persons with average mechanical ability in about 20 minutes, and can later, if required, be refitted onto other pallet trucks quickly and easily. Faults occurring in the braking system will not lead to the removal from operation of the entire pallet truck, as the braking system (or that part thereof that is faulty) may be readily removed from the pallet truck for service and the 10 pallet truck, now unbraked, may be used as is or refitted with an operational braking system or part thereof.

Various other modifications may be made in details of design and construction without departing from the scope and ambit of the invention.

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