Tire Shredding Machine

Abstract

A shredding machine for tires or the like including a head having generally parralel, rotatable shafts each bearing feeding and cutting elements thereon for coaction with the feeding and cutting elements on the other shaft. Bidirectional, hydraulic motors are operable to rotate the shafts in opposite directions and are included in a closed loop hydraulic circuit with a hydraulic pump. The circuit is also provided with a device for reversing the direction of fluid flow in the line to reverse the direction of the motors in response to an increase in pressure in the line in excess of a predetermined amount. The circuit also includes a flow control valve for limiting volumetric flow of hydraulic fluid to one of the motors so that the same will, when in a no-load condition, rotate at a lesser rate than the other. The circuit also includes a bidirectional pressure relief valve.

Description

BACKGROUND OF THE INVENTION

This invention relates to shredding machines and, more specifically, to shredding machines designed to shred, for disposal purposes, difficult material, such as used tires.

Published prior art known to the applicant includes Bowman U.S. Pat. No. 2,368,102; Stanton U.S. Pat. No. 3,627,212; Nelson U.S. Pat. No. 3,565,697; Schweigert et al. U.S. Pat. No. 3,664,592; and Rossler U.S. Pat. No. 3,662,964.

In present-day society, waste disposal problems of all kinds are on the upsurge. One particular facet of the problem is posed by the increasing number of vehicles on the road. It is the disposal of worn-out vehicle tires.

There have been a variety of prior proposals for tire cutting, shredding or subdividing apparatus, some of which are exemplified by the foregoing patents. In general, prior proposals have not proved satisfactory for any one of a variety of reasons. Frequently, the apparatus is extremely expensive and, therefore, out of the reach of the owner of a relatively small tire servicing facility with the result that such an owner is forced to have whole tires removed from his premises.

Where attempts have been made to overcome the foregoing problem, other difficulties have resulted. Frequently, tire shredders designed for use by individual owners of tire servicing facilities are underpowered due to the nature of the shredding apparatus itself and a desire to adapt the same for hookup to a conventional source of electrical power without the need for special wiring. This has produced apparatus having a special motor reversing circuit.

Specifically, in one such apparatus, an electrical motor is mechanically coupled to the shredding head and a current monitoring device monitors the flow of electrical current to the motor. When the current flow increases beyond a predetermined point, indicative of an increased load on the motor due to jammed tire carcasses in the cutting head, a reversing circuit is energized to reverse the motor for a short period of time to expel the tire. This approach, while theoretically practical, has proved less than satisfactory in practice due to the expense of the circuits, the possibility of reversing circuit failure resulting in motor burn-out; and difficulties encountered in rapidly reversing relatively large motors.

SUMMARY OF THE INVENTION

It is the principal object of the invention to provide a new and improved shredding apparatus that is especially adapted for use in tire shredding or cutting operations for disposal purposes. More specifically, it is an object of the invention to provide such an apparatus which is economical in cost so as to enable its use by individual owners of tire servicing facilities and which is not prone to damage due to electrical malfunction or difficulties encountered in the operation of large electrical motors.

The exemplary embodiment of the invention achieves the foregoing objects in a structure including a cutting head having a pair of parallel shafts, each of which bears cutting and feeding devices which coact with the cutting and feeding devices on the other shaft to shred a tire. The shafts are intended to be rotated in opposite directions and to this end, a pair of bidirectional, hydraulic motors are provided, one for each shaft. The hydraulic motors are included in parallel in a closed hydraulic circuit with a hydraulic pump. The pump may be driven by any suitable means such as an electric motor and the hydraulic circuit includes means whereby the direction of fluid flow may be changed so as to reverse the direction of rotation of both motors simultaneously.

A pressure sensing device is associated with the hydraulic circuit and, when pressure in the same rises to exceed a predetermined value, the same is operative to cause reversal of the direction of flow of hydraulic fluid to reverse the bidirectional hydraulic motors for a short period of time sufficient to partially expel a tire.

In a highly preferred embodiment, a unidirectional volumetric flow rate control valve is located in the hydraulic circuit between the two motors so that, when the motors are operating in a relatively unloaded condition, one of the motors will rotate at a different rate than the other to thereby cause the associated shaft to rotate at a different rate than the other to promote self-cleaning of accumulated rubber strips between the cutting devices on the two shafts.

The invention also contemplates a bidirectional pressure relief valve across the pump so that, should the reversing operation fail for any reason, a bypass circuit is immediately established to preclude damage to the components.

Other objects and advantages will become apparent from the following specification taken in connection with the accompanying drawings.

DESCRIPTION OF THE DRAWING

The FIGURE is a schematic illustration of a tire shredding apparatus made according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

An exemplary embodiment of a tire shredding machine made according to the invention is illustrated in the FIGURE and is seen to include two main components, including a power pack, generally designated 10, and a cutting apparatus, generally designated 12, which may be, in practice, disposed some distance from each other.

Referring to the cutting apparatus 12, the same includes a cutting head, generally designated 14, which may be configured as disclosed in the commonly assigned Cunningham et al. application, Ser. No. 396,185, filed Sept. 11, 1973, the details of which are herein included by reference; or which may take on other configurations as known in the art.

Briefly, the cutting head 14 includes a cutter box 16 through which a pair of parallel shafts 18 extend. The shafts 18 are rotatable and each mounts cutting and feeding means shown schematically at 20 which coact to feed, cut and shred tires in a manner such as that disclosed in the above identified Cunningham et al. application.

A pair of bidirectional hydraulic motors 22 and 24 are respectively associated with the shafts 18, the arrangement being such that the shafts 18 will be rotated in opposite directions. The hydraulic motors 22 and 24 are connected in parallel between hydraulic lines 26 and 28. In normal operation, the line 26 will be the high pressure line, while the line 28 will be the low pressure line. However, this will not always be the case, as will be seen. In addition, each motor 22 and 24 includes a connection to a drain line 30 which extends to a hydraulic fluid reservoir 32 located within the power pack 10.

The line 26 includes, at a location between the motors 22 and 24, a unidirectional, volumetric flow rate control valve system, generally designated 34. The same includes a flow control valve 36 which may be in the form of a needle valve, and a check valve 38 connected in parallel. The flow control valve 36 is connected in the line so as to limit the volume of hydraulic fluid flowing to the motor 24 while not restricting the volume of hydraulic fluid flowing to the motor 22, when the line 26 is the high pressure line. When, however, the line 26 is the low pressure line and normal flow is reversed from the direction shown by the arrows of the FIGURE, the flow control valve 36 becomes ineffective by reason of the parallel circuit including the check valve 38 which will open at that time.

As illustrated, the cutting apparatus also includes a bidirectional, pressure relief valve 39 across the lines 26 and 28. While the valve 39 is shown as being located within the cutting apparatus, it is to be expressly understood that the same could be located in the power pack 10 so long as the same is connected across lines 26 and 28.

Finally, the cutting apparatus 12 may include a stop-start switch 40 which is connected to the power pack 10 by an electrical line schematically illustrated at 42 for controlling the energization of the cutting head 14 as will be seen.

Turning now to the power pack 10, the same includes the hydraulic reservoir 32, as mentioned previously. The reservoir 32 receives oil from the line 30 and includes an outlet line 44 including a filter 46 to a charge pump 48 for a bidirectional hydraulic pump 50 of the swash plate type. The pumps 48 and 50 are conventional and the latter is connected to the lines 26 and 28 to define a closed loop hydraulic circuit. The pump 50 may be driven by a conventional electric motor 54 having an electrical motor starting circuit 56 of conventional design. The starter circuit 56 is connected to the line 42 as well as to a further stop-start switch 58. Thus, the motor 54 can be energized or de-energized either at the location of the power pack or at the location of the cutting apparatus 12.

Returning to the pump 50, the same includes a swash plate control linkage 60 which is connected to the armature of a solenoid 62. When the linkage 60 is in the dotted line position shown in the FIGURE, the line 26 will be the high pressure line. However, when the solenoid is energized to move the linkage to the solid line position shown in the FIGURE, the line 28 will become the high pressure line by reason of the change in position of the internal swash plate of the pump 50 reversing the direction of fluid flow.

The solenoid 62 is connected electrically to be energized by a conventional time delay relay 64 which is powered by a low voltage power supply 66 connected to the electrical motor starter circuit 56. Control of the relay 64 is obtained from a pressure switch 68 which is connected to sense the pressure in the line 26.

Preferably, the pressure switch 68 is adjustable and is arranged so that when the pressure in the line 26 exceeds a predetermined value, it will energize the relay 64 to in turn energize the solenoid 62 to shift the swash plate linkage 60 to the reverse position. The relay 64, being a time delay relay, will maintain the solenoid 62 energized for a predetermined time period notwithstanding a drop in pressure in the line 26 which will occur upon reversal of the pump 50. Normally, the arrangement is such that the solenoid 62 will be energized for several seconds.

The operation of the appparatus is as follows. Operation of either of the stop-start switches 40 or 58 will cause energization of the electrical motor to in turn drive the pump 50. Initially, fluid will flow in the direction of the arrows through the lines 26 and 28 to energize both the motors 22 and 24. Due to the presence of the flow control valve 36, under no-load conditions, the motor 24 will rotate its associated shaft 18 at a lesser rate than the rate of rotation of the shaft 18 associated with the motor 22. For example, in one embodiment, under no-load conditions, the motor 22 will rotate its shaft at approximately 42 rpm, while the motor 24 will rotate its shaft at approximately 22 rpm.

Reference to the previously identified Cunningham et al. application will illustrate that the difference in rates of rotation will cause the feeding means on each of the shafts to tend to clear out accumulated rubber strips caught between the cutting elements. Thus, the flow control valve 36 provides for the elimination of refuse between the cutting elements when the device is operating under a no-load condition.

When a tire is introduced into the cutting box 16, the shafts 18 will continue to rotate to feed, cut and shred the tire in the manner described by Cunningham et al. However, due to the coupling between the shafts 18 established by the presence of the tire, and the fact that the valve 36 restricts flow but not operating pressure, during load conditions, the motors 22 and 24 will tend to drive their shafts at the same rate of rotation.

If the tire tends to become jammed in the cutting head, this will be reflected in an increase in pressure in the line 26. When the pressure builds up to the point where the motor 54 and pump 50 could be stalled, and thereby cause damage to the system, the pressure switch 68 will sense such an occurrence and throw the system into reverse by shifting the swash plate linkage 60. This will cause the motors 22 and 24 to rotate their respective shafts in directions opposite that of the arrows shown in the FIGURE with the result that the tire will be moved backwardly and out of the cutting nip in the cutting head. Such action will continue to occur for the period established by the time delay relay 64. Once the relay 64 has timed out, the solenoid 62 will be de-energized with the result that the swash plate linkage 60 will be returned to its forward position thereby causing the line 26 to again become the high pressure line to reinitiate cutting of the tire. It is to be noted that the presence of the check valve 38 insures that during such reverse energization of the system, both motors 22 and 24 will be driven at approximately the same rate, there being no restriction on the volumetric flow to the motor 24. The purpose of this function is to insure rapid clearing of the cutting nip.

It will also be observed that in the event the pressure switch 68 or the appurtenances thereto for reversing the direction of flow of hydraulic fluid in the lines 26 and 28 fail, the pressure relief valve 39, which may be set to open at a slightly higher pressure than the setting on the pressure switch 68, will open to effectively shunt the flow of fluid to the motors 22 and 24 before the system can stall thereby precluding damage to the system.

It should be recognized that while electrical components are illustrated in the reversing system, the same action could be obtained through a hydromechanical linkage. It will also be observed that while a bidirectional hydraulic pump of the swash plate type is employed to achieve reversing action, a unidirectional pump could be employed in lieu thereof along with a four-way valve, if desired.

From the foregoing, it will be appreciated that a shredding machine made according to the invention possesses substantial advantages over the prior art apparatus. For example, the same is constructed so that damage to an electrical drive motor such as the motor 54, due to overloading cannot occur even when load sensing and reversing equipment including the pressure switch 68 may fail. It will also be observed that the system accomplishes, through the use of a flow control valve 36, a self-cleaning action without the need for special mechanical components to achieve this action. Moreover, the use of independent drives for the shafts 18 and the cutting head, eliminate the need for expensive, heavy duty gearing that would be subjected to substantial probability of failure due to the high loading conditions encountered in tire shredding operations.

Claims

We claim:

1. A shredding machine comprising: a cutting head including a pair of generally parallel, rotatable shafts each having cutting and feeding means thereon; a pair of bidirectional, rotational output, hydraulic motors, one for each shaft, for rotating the shafts in opposite directions; a hydraulic pump; means for driving said pump; conduit means connecting said pump to said motors in parallel and defining a closed loop; means associated with one of said pump and said conduit means operable to reverse the direction of flow of hydraulic fluid in said conduit means to thereby reverse the direction of rotation of said hydraulic motors; and pressure responsive means associated with said conduit means for sensing when the pressure therein exceeds a predetermined value for operating said reversing means for a predetermined period of time.

2. A shredding machine comprising: a cutting head including a pair of generally parallel, rotatable shafts each having cutting and feeding means thereon; a pair of bidirectional, rotational output, hydraulic motors, one for each shaft, for rotating the shafts in opposite directions; a hydraulic pump; means for driving said pump; conduit means connecting said pump to said motors in parallel and defining a closed loop; means associated with one of said pump and said conduit means operable to reverse the direction of flow of hydraulic fluid in said conduit means to thereby reverse the direction of rotation of said hydraulic motors; pressure responsive means associated with said conduit means for sensing when the pressure therein exceeds a predetermined value for operating said reversing means for a predetermined period of time; and flow control means in said conduit means between said motors for limiting the volumetric flow rate to one of said hydraulic motors for one direction of fluid flow in said conduit means.

3. A shredding machine comprising: a cutting head including a pair of generally parallel, rotatable shafts each having cutting and feeding means thereon; a pair of bidirectional, rotational output, hydraulic motors, one for each shaft, for rotating the shafts in opposite directions; a hydraulic pump; means for driving said pump; conduit means connecting said pump to said motors in parallel and defining a closed loop; means associated with one of said pump and said conduit means operable to reverse the direction of flow of hydraulic fluid in said conduit means to thereby reverse the direction of rotation of said hydraulic motors; pressure responsive means associated with said conduit means for sensing when the pressure therein exceeds a predetermined value for operating said reversing means for a predetermined period of time; and a bidirectional pressure relief valve connected to said conduit means across said pump and operable to establish a bypass for fluid flow when a predetermined pressure develops across said pump.

4. A shredding apparatus according to claim 3 further including a unidirectional volumetric fluid flow control valve in said conduit means between said motors for limiting the volumetric flow rate of hydraulic fluid to one of said motors for one direction of rotation thereof.