Reconditioning of internal combustion engines, particularly those of an automotive vehicle type, is a significant business founded upon the economic savings achieved through reconditioning of an engine as contrasted to purchase of a complete new engine. Engine reconditioning is labor intensive and thus to be economically feasible, procedures must be employed to minimize labor costs. One aspect of engine reconditioning that has heretofore involved a substantial amount of labor and time and thus accounting for a significant portion of the cost of reconditioning has been the cleaning of the major engine components such as the cylinder heads, blocks, crankshafts, piston rods and oilpans. The cylinder heads, engine blocks and other components of internal combustion engines accumulate not only a heavy external coating of oil and dirt, but the internal surfaces become covered with a scale formed from combustion products in the case of the surfaces associated with the combustion chamber, but other cavities in the head such as those formed for a flow of fluid through the head also become coated with a scale formed from mineral products contained debris materials as a consequence of the elevated temperatures at which internal combustion engines operate, tend to tenaciously adhere to those surfaces and become very difficult to remove. Exterior coatings of oil and dirt can generally be removed to a satisfactory degree through use of cleaning solvents to soften the material and utilization of hand scraping. This is a time consuming process and usually cannot be accomplished to effect the desired degree of cleaning. Similarly, the combustion product scales and the mineral scales that develop on the interior surfaces of the cylinder head can also be removed to an extent by manual means using hammers and chipping tools. However, such techniques are less than desirable not only from the standpoint of general ineffectivity in removing all of the scale, but subject the cylinder head surfaces to mechanical damage from impact with the various types of cleaning tools that are employed.
To enhance cleaning operations, various alternative procedures have been employed not only to enhance the economics through reduction of labor costs, but to improve the effectivity of the cleaning operations. One such procedural technique that has been used is the subjecting of the cylinder head to a heating operation. One of the objectives of the heating operation is to, in effect, burn off the oil or hydrocarbons coating the exterior surfaces. This procedure has been found less effective than desired since the burning procedure results in other combustion products which still combine with other debris that is not combustible and still remains adhered to the exterior surfaces requiring scraping or other removal techniques. A second objective is to attempt loosening of the scales and conditioning them at the elevated temperatures to be more readily removed through employment of scraping and chipping tools. This procedure of heating, but still relying upon the use of manual scraping for removal of the materials, has failed to provide the desired results since considerable labor time is still required and the results are less than desirable since these cylinder heads are of a complex geometrical shape with various configured cavities that are difficult to work with and in many instances are essentially inaccessible through the use of conventional manual tools.
While cleaning of articles that may be caked with oil and dirt coatings or scale formations can be more readily and effectively accomplished by shot blasting operations, the use of shot blast cleaning has not heretofore been deemed suitable for use in connection with cylinder heads because of the difficulty in removing the shot particles from the various internal cavities. This removal of the shot is of particular significance with respect to cylinder heads. The shot, while generally small in size, is fabricated from hardened steel and is highly destructive if retained within the engine cylinders. In shot cleaning techniques, the shot enters the numerous irregularly shaped cavities of the head and may be retained in areas that are not subject to visual inspection. Although the shot may be retained even though various mechanical vibrating and shaking techniques are employed to dislodge the shot, it nevertheless is frequently possible for retained shot to ultimately become dislodged such as during the time that the cylinder head is remounted on an engine block and the shot, even though contained within a coolant cavity, may fall into a cylinder and not be detected. Subsequent operation of the engine will result in effectively destroying the engine through the shot becoming wedged between the circumference of the top of the piston and adjacent cylinder wall and result in scoring of the cylinder wall.
In attempting to more effectively and efficiently remove the shot, techniques such as use of compressed air for blowing out the shot have also been employed, although the results have been less than satisfactory. There have been attempts to devise apparatus to effectively perform this shot removal function by mechanical manipulation of the cylinder heads so as to enable the shot to fall out of the cavities. One such apparatus included several large sized truck tires supported in vertical planes adjacent to each other in axial alignment. The tires are supported on a pair of drive rollers that are rotated and through frictional engagement with the outer face of the tires cause the tires to revolve. A cylinder head or other component that has been shot blasted is placed in the center of the tires with the objective being to roll the cylinder heads about their longitudinal axis to effect removal of the shot. However, this apparatus has not been found satisfactory as it not only fails to effectively manipulate the heads so as to remove all of the shot, but it is inherently limited to processing only one cylinder head at a time thereby failing to achieve a significant monetary saving. As a consequence of the difficulty in removing the shot and inability of these prior techniques to effect removal to a one hundred percent degree, shot cleaning has not been generally accepted or utilized in the cleaning operations for these engine components.
While a heating operation employed in cleaning of cylinder heads assists in the previously employed manual cleaning operations, that heating has not reduced the labor costs to any significant degree. One reason the heating operation, while perhaps enhancing the effectivity of the cleaning, has failed to enable realization of cost reduction is that the cylinder heads, after they are heated to the necessary elevated temperatures of the order of five hundred degrees Fahrenheit must be permitted to cool to a temperature where the workers can again safely handle the heads in performance of the various manual cleaning operations.