Abstract:
An assembly tool for insertion of engine piston/rod assemblies into an engine cylinder includes a frame, a support arm pivotally carried on the frame, an insertion cylinder carried by the support arm and including an extendable insertion rod having an end adapted to engage a piston in position for insertion; a positioner for positioning the support arm in an insertion position with the rod end engaging a piston; and a control for actuating the insertion rod to insert a piston/rod assembly into the cylinder. Various additional features of an exemplary embodiment are also disclosed.

Description:
TECHNICAL FIELD 
     This invention relates to assembly tools for installing piston and connecting rod assemblies in an engine. 
     BACKGROUND OF THE INVENTION 
     A common method of installing a piston/connecting rod assembly in an engine cylinder involves sliding a piston ring compressor sleeve (ring compressor) over the skirt and piston rings of the piston and manually inserting the connecting rod end of the assembly into the outer end of the engine cylinder. The piston/rod assembly is slid into the cylinder until the ring compressor engages the outer end of the engine cylinder. A guide finger may be utilized on the crank end of the connecting rod to guide the connecting rod in the cylinder and align the bearing recess with the crankpin of the engine crankshaft. The assembly is then forced into the engine cylinder so that the piston rings compressed by the ring compressor are guided into the cylinder and the piston is forced inward until the connecting rod bearing recess or bearing insert engages the engine crankpin. This “stuffing” step may be accomplished manually, such as by applying force against a stuffing block engaging the piston head. Automatic piston installing machinery has also been developed but it is very expensive to make as well as to maintain. 
     A form of manually-operated tool which is in common use in many engine assembly plants utilizes a manually-operated lever arm that is pivotable by the operator and has a roller that is moved into engagement with the piston head. The lever arm has a handle which is grasped by the operator and provides a mechanical advantage to assist the operator in pivoting the arm to force the piston through the ring compressor and into the cylinder until the connecting rod engages the associated crankpin. As the piston is forced into the cylinder, the ring compressor slides off and is caught by a hook on the lever arm as the arm is retracted by the operator. A biasing spring assists the retraction and holds the arm out of the way for insertion of the next piston/rod assembly. 
     Over a number of years, piston compression ring tension has been increasing in order to reduce the amount of piston ring blowby to better control exhaust emissions. The increased ring tension has tended to increase the force the operator must apply to overcome the ring tension acting against the cylinder as the piston is inserted into the cylinder bore. In order to reduce the effort required for this process, an assembly tool has been desired which could significantly reduce operator effort while being capable of construction at a reasonable cost and application to current and future assembly lines without requiring the significant outlays of capital required for a fully automatic machine. 
     SUMMARY OF THE INVENTION 
     The present invention provides a semi-automatic engine piston assembly tool which can be applied in place of the manual tool currently used in many assembly lines. The new tool utilizes a pivoting support arm which is controlled and moved into position by the operator grasping a handle in a manner similar to the prior manually actuated tool. However, the tool is provided with an air insertion cylinder, mounted on the end of the arm, that is moved into a position so that the piston head is engaged by the end of an insertion rod actuatable by the cylinder. A ring compressor retractor is carried on the end of the insertion rod. 
     The pivoting support arm is biased upwardly into a loading position by a balancing cylinder which utilizes low pressure air to retract the arm to the loading position. A piston/rod assembly is then loaded through the outer end of the engine cylinder with a ring compressor on the piston and engaging the engine cylinder outer end. 
     The operator manually moves the support arm into the insertion position with the end of the insertion rod against the piston head. The operator actuates and holds a trigger switch, which applies high pressure to lock the support arm in position and applies controlled air pressure to the insertion cylinder. This causes the insertion rod to advance through the ring compressor and force the piston/rod assembly into the engine cylinder until a bearing recess or bearing insert of the connecting rod engages the associated crankpin. 
     At this point, the ring compressor slides downward and is captured on the face of the ring retractor. A magnet on the retractor retains the steel ring compressor on the angled face of the retractor and allows the flange of the ring compressor to fall into a hook-like groove at the bottom of the retractor member. The operator then releases the trigger switch, which retracts the insertion rod into the insertion cylinder carrying the ring compressor with it. The support arm is then allowed to be raised by the balancing cylinder, carrying with it the ring compressor mounted to the face of the ring retractor at the end of the insertion rod. The tool is then moved on a carriage longitudinally along the side of the engine to the next cylinder position and a piston/rod assembly with the ring compressor attached is installed into the next cylinder for repetition of the assembly operation. 
     The semi-automatic assembly tool significantly reduces operator required effort since the force required for stuffing the piston into the cylinder is applied by the insertion air cylinder. At the same time, the improved operation with the automatic insertion and retraction steps is accomplished with a relatively simple but effective mechanism which can be applied to current assembly lines with a minimum of disturbance to the established features of the line. In addition, the tool is applicable to new assembly lines which can be fitted and installed at a relatively reasonable cost as compared to automatic machines which are both expensive and costly to maintain. 
    
    
     These and other features and advantages of the invention will be more fully understood from the following description of certain specific embodiments of the invention taken together with the accompanying drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an end view of an assembly station for an engine including a mounting fixture shown in phantom carrying a V-type engine inverted for insertion of piston/connecting rod assemblies, with an assembly tool in accordance with the invention shown in the loading position. 
     FIG. 2 is a view similar to FIG. 1 with the assembly tool shown in the insertion position. 
     FIG. 3 is a similar view with the assembly tool shown in the actuated position and the piston/rod assembly fully installed. 
     FIG. 4 is a similar view showing the tool retracted to the initial loading position and carrying the ring compressor ready for removal and installation on the next piston/connecting rod for assembly. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the drawings in detail, numeral  10  generally indicates an engine assembly station that includes a fixture base  12  carried on conveyor rails  14  and supporting a mounting fixture  16  on which an engine block  18  is mounted inverted for assembly of a piston/rod assembly, generally indicated by numeral  20 . Assembly  20  includes a piston  22  connected by a piston pin to a connecting rod  24 . The piston has a skirt  26  which is partially inserted into an engine cylinder  28 . The head portion  29  of the piston including the piston rings, not shown, is received in a ring compressor  30 . The ring compressor is held in place on the piston by the friction of the piston rings, not shown, the friction of the skirt engaging the walls of the cylinder  28  and a guide finger  32  retaining the assembly  20  in position. 
     The guide finger  32  is mounted on the inner end of the connecting rod  24  and extends through the inner end of the engine cylinder  28  into engagement with a crankpin  34  of an associated engine crankshaft, not otherwise shown. The guide finger  32  supports the connecting rod in alignment with the crankpin and maintains the connecting rod out of contact with the cylinder bore so as to avoid scratching the bore during the assembly process. 
     The assembly station  10  is provided with an assembly tool  40  in accordance with the invention. Tool  40  includes a mounting frame  42  supported by a carriage  44  for longitudinal motion along a support rail  45 . The frame  42  pivotably carries a support arm  46  having at its distal end an insertion cylinder  48 . The cylinder  48  includes an insertion rod  50  having an end  52  which carries a ring retractor  54 . The insertion cylinder  48  is connected with a source of air pressure, not shown, which actuates a piston internally to extend the insertion rod  50 . The ring retractor  54  includes a support face  56  having a hook-like arcuate recess  58  along its lower end and a magnet  60  along its upper edge. 
     A manual handle  62  is mounted intermediate the ends of the support arm  46  and includes a trigger  64  engaging a trigger switch  66  which can be actuated by the operator to operate the insertion cylinder  48 . The support arm  46  is biased into the loading position shown in FIG. 1 by a balancing and locking air cylinder  68  which is supported at one end by an extension of the frame  42  and connects at the other end with the support arm  46  between the handle  62  and a pivot pin  70  on which the arm  46  is pivoted. 
     In operation, the engine assembly station may be temporarily stationary or continuously moving depending upon the particular operation mode of the assembly line in which the station is located. The operator first provides or obtains a piston rod assembly  20  having a ring compressor  30  slid over the piston rings and inserts this assembly into the cylinder  28  until the piston skirt engages the cylinder  28  and the finger  32  rides on the surface of the crankpin  34 . The assembled components are retained in place by friction of the piston skirt in the cylinder and the finger on the crankpin, also the friction of the piston rings against the ring compressor which is positioned in engagement with the outer end of the cylinder  28 . 
     The operator then uses the handle  62  to manually pivot the support arm  46  down against the bias of the balancing cylinder  68  and forward toward the insertion position shown in FIG.  2 . There the ring retractor  54  engages a lip on the ring compressor  30  and the end  52  of the insertion rod  50  engages or closely approaches the head  29  of the piston  22 . 
     When the support arm and associated insertion cylinder  48  reach the insertion position, the operator pulls the trigger  64  actuating the trigger switch  66 . This causes high pressure air to be applied to the other side of the balancing cylinder  68  to lock the insertion cylinder in position with the ring retractor  54  against the ring compressor  30 . At the same time, controlled air pressure is fed to the insertion cylinder  48 . The air pressure urges the insertion rod end  52  against the piston and forces the piston/rod assembly fully into the bore  20  until the connecting rod recess with an associated bearing insert, not numbered, engages the crankpin  34  as shown in FIG.  3 . 
     When the assembly tool reaches the fully inserted position, the operator releases the trigger switch  66 , which cuts off the air pressure and actuates the insertion cylinder  48  to retract the insertion rod  50 , leaving the piston/rod assembly in place and withdrawing the rod into the cylinder. At this point or before, the ring compressor  30  falls away from the engine cylinder block against the support face  56  of the ring retractor  54 . The magnet  60  holds the steel ring compressor against the face  56  and allows it to slide downward so that the rim is received into the arcuate recess  58  and the magnet  50  holds the ring compressor rim against the support face  56 . 
     As the insertion rod  50  is retracted, the lock pressure on the balancing cylinder  58  is also released and the biasing pressure is again applied so that the operator is easily able to control return of the support arm to the loading position shown in FIG.  1 . During the return motion, the ring compressor  30  is carried by the ring retractor  54  and is retained in place by the magnet  60 , as shown in FIG.  4 . Thus, the ring compressor is immediately available by the operator to be removed from the ring retractor and placed together with another piston/rod assembly for manual insertion into another engine cylinder. Alternatively, of course, piston/rod assemblies with ring compressors installed could be provided in advance for installation on the engine and the ring compressors could be placed aside as they are removed for assembly by a third person into assemblies for installation in the next engine. 
     Upon manual insertion of the next piston/rod and ring compressor assembly into an adjacent cylinder, the assembly tool  40  is again aligned by the operator with the adjacent cylinder and the assembly process is again repeated. If desired, guide means could be utilized to align or assist the operator in aligning the assembly tool frame along its supporting guide rail into the proper position of alignment with the cylinder in which the piston/rod assembly is to be installed. Any form of alignment means may be utilized, such as, for example, an aiming device or an indicator, such as a laser beam  72  (FIG. 1) projected on the associated guide finger, in order to provide a proper alignment reference. 
     The assembly tool of the invention is easily substituted for the manual assembly tool previously utilized in many engine assembly lines in current use. The tool is relatively economical to manufacture and easy to utilize by the operator while relieving the operator from the effort needed for manual “stuffing” of the piston/rod assemblies. 
     While the invention has been described by reference to certain preferred embodiments, it should be understood that numerous changes could be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the disclosed embodiments, but that it have the full scope permitted by the language of the following claims.