This invention relates to vehicle support equipment. More particularly this invention relates to improved support structure for the tracks of vehicles which are supported by tracks e.g. asphalt paving machines, cranes, bulldozers and the like.
One of the more vexing problems facing those who operate tracked vehicles, e.g. asphalt paving machines, is the rapid wear occurring to the track pads on such machines. In this regard a track pad is a structure which is secured removably to the drive track of a track supported vehicle and which provides the contact surface between the tracked vehicle and its supporting surface, e.g. a road, the earth, the rock bed of a quarry or the like. Typically such vehicles utilize a plurality of track pads, e.g. as many as two hundred and fifty such pads utilized on equipment such as asphalt paving machines.
A typical tracked vehicle, such as the asphalt paving machine with respect to which the invention is described, weighs several thousand pounds and is required to transmit both supporting and propelling forces between the equipment and the support surface. For example, in normal operation, a typical asphalt paving machine is positioned behind a truck which contains the asphalt. The paving machine not only transports itself during paving but also provides the power to push the truck thus insuring the paving machine of a continuous and uninterrupted engagement with the truck. Thus, in addition to supporting and propelling its own weight, the paving machine propels the truck and its load of asphalt, a weight of several tons. This type of operation produces extreme-load and frictional forces upon the track pads.
Known track pads presently in use comprise rubber pads secured to metal support elements. The rubber pad material is secured only to one side of the support element viz. the side on which the pad makes surface-to-surface- contact with the supporting medium e.g. the ground or road. Further, known support elements comprise planar plates and have no means of effectively gripping the pad material. As is recognized in the art, such pads have been incapable of withstanding the loads attendant to supporting and propelling of heavy tracked equipment and have failed, often within days of installation. The failure ordinarily takes the form of complete separation of the pad material from the structural support element because of the inability of the track pad to withstand the frictional (propelling) forces to which it is subjected. When this occurs there is loss of frictional engagement between the supporting surface and the track pad and the asphalt paving machine is no longer capable of being propelled without damage to the vehicle tracks or damage to the supporting surface.
This rapid wear, deterioration and ultimate failure of the pads is expensive not only by way of replacement costs but also because of costly down time for the equipment during replacement of the worn track pads. The present invention relates to track pad for use with vehicles of the type described above, which pad solves the above related problems. Summary
It is the object of the present invention therefore to provide a track pad for tracked vehicles that is more durable and longer lasting.
It is a further object of this invention to provide a track pad for tracked vehicles wherein the pad portion of the device is secured to the structural portion so as to effectively preclude a separation during normal operation.
A still further object of this invention is to provide a method of manufacturing a track pad for tracked vehicles so as to achieve a more durable and longer lasting pad.
These objects and others not enumerated are achieved by a track pad structured in accordance with the present invention, one embodiment of which may include a generally rectangular base plate having a plurality of openings therein, securing means mounted on the base plate, the securing means extending through at least one of the plurality of openings, the securing means for removably attaching the track pad to a track of a tracked vehicle, and pad means comprising a molded thermoplastic urethane elastomer resin member which substantially encapsulates the base plate, the pad means including at least one opening to permit the extension therethrough of at least a portion of the securing means.
Manufacture of such a track pad in accordance with the teachings of the invention may include the steps of inserting the securing member through the opening in the support plate so as to form a sub-assembly, positioning the sub-assembly in a die so that the securing member extends outwardly from the die cavity, securing sub-assembly within the die cavity, injecting preheated thermoplastic urethane elastomer resin into the die cavity such as to substantially encapsulate the base plate, but not the securing member, cooling the assembly for a sufficient period of time to permit the thermoplastic urethane elastomer resin to set, and removing the track pad.