Note: Descriptions are shown in the official language in which they were submitted.
1015202530CA 02265078 2002-11-14COUNTERWEIGHT FOR HERMETIC COMPRESSORSFIELD OF THE INVENTIONThe present invention relates to hermetic pumps or compressors, particularlyreciprocating piston type pumps or compressors.BACKGROUND OF THE INVENTIONHermetic compressors typically include a crankshaft having an eccentricportion coupled to a compression mechanism which is driven when the crankshaftrotates. For example, the compression mechanism may comprise a piston slidablydisposed in a cylinder, the piston operatively coupled to the eccentric of the rotatingcrankshaft by a connecting rod, whereby the orbiting motion of the eccentric about theaxis of rotation of the crankshaft imparts reciprocating motion to the piston. Due tothe dynamic imbalance of the operating compression mechanism, counterweights areoï¬en attached to the crankshaft, in some cases directly attached to the eccentric of thecrankshaft, to offset the inertial loads generated by the moving members of thecompression mechanism and by the eccentric itself.Previous counterweights for hermetic compressors have been formed directlyinto the crankshaft or comprise a separate piece assembled thereto, the separate piecebeing, for example, formed of powdered metal or of stamped sheet metal. Previousstamped sheet metal counterweights, however, have been formed by stampingoperations which are unique to the size and weight requirements of a particularcounterweight designed to balance only a particular compressor assembly. Forexample, a product line of several reciprocating piston compressor assemblies, eachsubstantially similar except for the displacement of the compression mechanism, mayrequire unique counterweight tooling to manufacture each of the variety of severalcounterweights necessary to accommodate all of the compressor assemblies in theproduct line. A method of providing a variety of stamped sheet metal counterweights,each having different weights but substantially similar in size, whereby a variety ofdifferent compressor assembly designs may be balanced, is desirable.SUMMARY OF THE INVENTIONAccording to an aspect of the present invention, there is provided a method formanufacturing compressors having installed therein counterweights of differentweights and having substantially identical axial projection proï¬les, comprising thesteps of:1015202530CA 02265078 2002-11-14providing a progressive stamping die, and planar metal stock material havingone of a plurality of different widths between ï¬rst and second opposite side edges;feeding the stock material through the progressive stamping die in a directionsubstantially parallel with the ï¬rst side edge;progressively forming from the stock material a counterweight having a freeedge defined by the ï¬rst stock material edge;separating from the stock material a counterweight having a weight whichvariably corresponds to different stock material widths; andconnecting the counterweight to a rotatable compressor shaft.According to another aspect of the present invention, there is provided amethod of manufacturing a compressor having installed therein a counterweight,comprising the steps of:feeding planar stock having side edges and an axial dimension to one or morestamping dies;stamping a segment of the stock into a desired shape;folding the stamped segment in a direction substantially perpendicular to theaxial dimension of the stock such that the segment folds back on itself and one of theside edges forms a free end in overlapping arrangement to the segment;detaching the segment from the stock to yield a counterweight; andconnecting the yielded counterweight to a rotatable compressor shaft.According to another aspect of the present invention, there is provided amethod of manufacturing a plurality of sets of compressors having installed thereinrespective sets of counterweights, each counterweight of one set having a differentweight than each counterweight of another set, comprising the steps of:providing a ï¬rst substantially planar stock material having one of a plurality ofwidths between side edges into a die;fonning a ï¬rst counterweight having an edge which is deï¬ned by one of theside edges of the ï¬rst stock material;separating the ï¬rst counterweight from the ï¬rst stock material, the separatedï¬rst counterweight being one of a ï¬rst set of counterweights;providing a second substantially planar stock material having a different oneof a plurality of widths between side edges into the same die;forming a second counterweight having an edge which is deï¬ned by one of theside edges of the second stock material;1015202530CA 02265078 2002-11-14separating the second counterweight from the second stock material, theseparated second counterweight being one of a second set of counterweights;connecting the separated ï¬rst counterweight to a rotatable shaft of acompressor of one of the plurality of compressor sets; andconnecting the separated second counterweight to a rotatable shaft of acompressor of a different one of the plurality of compressor sets.According to yet another aspect of the present invention, there is provided acompressor assembly comprising:a housing;a compression mechanism disposed in said housing;a crankshaft having an eccentric portion, said eccentric portion operativelyengaged with said compression mechanism;an electric motor disposed in said housing, said motor drivingly engaged withsaid crankshaft, whereby said compression mechanism is driven by said motorthrough said crankshaï¬; anda counterweight attached to said crankshaft, said counterweight having ï¬rstand second planar sections joined by a portion integral with and extending from saidï¬rst and second planar sections, said ï¬rst and second planar sections lying in differentplanes.According to yet another aspect of the present invention, there is provided acompressor assembly comprising:a housing;a compression mechanism disposed within said housing;a crankshaft having an eccentric portion operatively engaged with saidcompression mechanism;an electric motor disposed in said housing and having a stator and a rotor, saidrotor rotatably ï¬xed to said crankshaft; anda counterweight attached to said crankshaft, said counterweight comprising aunitary piece of sheet metal having formed therein ï¬rst and second planar sections,said second planar section overlying said first planar section.According to yet another aspect of the present invention, there is provided acompressor assembly comprising:a housing;a compression mechanism disposed in said housing;1015202530CA 02265078 2002-11-143aa crankshaft having an eccentric portion, said eccentric portion operativelyengaged with said compression mechanism;an electric motor disposed in said housing, said motor drivingly engaged withsaid crankshaft, whereby said compression mechanism is driven by said motorthrough said crankshaï¬; anda counterweight attached to said crankshaft, said counterweight being formedby a process which includes feeding planar stock having side edges and an axialdimension to one or more stamping dies, stamping a segment of the stock into adesired shape, folding the stamped segment in a direction substantially perpendicularto the axial dimension of the stock such that the segment folds back on itself and oneof the stock side edges forms a free end in overlapping arrangement to the segment,and detaching the segment from the stock.BRIEF DESCRIPTION OF THE DRAWINGSThe above-mentioned and other features and advantages of this invention, andthe manner of attaining them, will become more apparent and the invention will bebetter understood by reference to the following description of embodiments of theinvention taken in conjunction with the accompanying drawings, wherein:Fig. 1 is a cross-sectional side view of one type of hermetic compressorassembly which includes a first embodiment of a counterweight according to thepresent invention;Fig. 2 is an enlarged fragmentary side sectional view of a portion of thecompressor shown in Fig. 1;Fig. 3 is an axial view of the counterweight shown in the compressor of Figs.1 and 2;Fig. 4 is a partial section side view of the counterweight of Fig. 3;Fig. 5 is the counterweight of Fig. 3 unfolded, and further shows the locationsof the free edges of further embodiments of counterweights according to the presentinvention;Fig. 6 is a side view of a second embodiment of a counterweight according tothe present invention;Fig. 7 is a side View of a third embodiment of a counterweight according tothe present invention;Fig. 8A is a schematic plan View of a progressive die apparatus, also showingsheet metal stock of width âaâ therein and counterweights according to the ï¬rstCA 02265078 2002-11-143bembodiment being fonned therefrom;Fig. 8B is a section side View of a pair of ï¬nished counterweights according tothe first embodiment along line 8B-8B of Fig. 8A;Fig. 9A is a schematic plan View of the same progressive die apparatus asshown in Fig. 8A, also showing sheet metal stock of width âbâ therein andcounterweights according to1015202530CA 02265078 1999-03-094the second embodiment being formed therefrom;Fig. 9B is a section side view of a pair of ï¬nished counterweights according to thesecond embodiment along line 9B-9B of Fig. 9A;Fig. 10A is a schematic plan view of the same progressive die apparatus as shown inFigs. 8A and 9A, also showing sheet metal stock of width "c" therein and counterweightsaccording to the third embodiment being formed therefrom; andFig. 10B is a section side view of a pair of ï¬nished counterweights according to thethird embodiment along line 10Bâ10B of Fig. 10A.Corresponding reference characters indicate corresponding parts throughout theseveral views. Although the drawings represent embodiments of the present invention, thedrawings are not necessarily to scale and certain features may be exaggerated in order tobetter illustrate and explain the present invention. The exempliï¬cations set out hereinillustrate embodiments of the invention in alternative forms, and such exempliï¬cations arenot to be construed as limiting the scope of the invention in any manner.DETAILED DES; §RIPTI§ 2N QF THE INVENTIONReferring ï¬rst to Fig. 1, there is shown compressor assembly 20 which compriseshousing 22 having lower portion 24 and upper portion 26 which are sealably attached to oneanother as by welding or brazing. Suspended within housing 22 is electric motor andcompression mechanism subassembly 28 comprising electric motor 30 and compressionmechanism 32. Electric motor 30 comprises stator 34 which surrounds rotor 36. Electricalpower is provided to the windings of stator 34 through terminal cluster 38, thereby impartingrotating motion to rotor 36 in the well-known manner. Crankshaft 40 is press-ï¬tted withincentral aperture 42 of rotor 36 and extends therethrough.Stator 34 is attached to frame 44 of subassembly 28, which is provided with journalportion 46 which radially supports shaft 40 which extends therethrough. Shaft 40 is alsoprovided with thrust portion 48 which slidably abuts thrust pad 50 of frame 44, therebyaxially supporting shaft 44 and rotor 36 within the subassembly. Adjacent shaft thrustportion 48 is shaft eccentric 52 about which is rotatably disposed connecting rod 54.Connecting rod 54 is attached to piston 56 and, as crankshaft 40 rotates, causes piston 56 toreciprocate within cylinder 58 in the well-known manner for compressing refrigerant gaswithin compressor assembly 20. Counterweight 60 is attached to the axial end of eccentric1015202530CA 02265078 1999-03-095shaft portion 52 by bolt 62 as will be discussed further hereinbelow. Fig. 2 is an enlargedfragmentary portion of Fig. 1 showing the inventive counterweight 60.Although compressor assembly 20 is of a reciprocating piston type, the presentinvention should not be construed as being so limited, for it is to be understood that thepresent invention may also be applied to other types of compressor or pumps whereincounterweights would ordinarily be prescribed for offsetting dynamic imbalances.Referring now to Fig. 3 there is shown an axial end view of a first embodiment ofcounterweight 60. Counterweight 60a represents a ï¬rst embodiment of counterweight 60which is of a maximum weight and, as will be discussed further hereinbelow, is formed fromsheet or strip metal stock material which has a maximum width between opposite first andsecond side edges. Counterweight 60a comprises first and second portions 64 and 66,respectively. First counterweight portion 64 is provided with aperture 68 through which bolt62 extends, bolt 62 threadedly received in a hole (not shown) provided in the axial end ofeccentric 52. To prevent rotation of the counterweight relative to eccentric 52, ï¬rstcounterweight portion 64 is also provided with axially-extending protuberance 70 which isreceived in a recess (not shown) provided in the axial end of eccentric 52 adjacent thethreaded hole therein, thereby preventing the counterweight from rotating about bolt 62.As best shown in Fig. 4, each of first and second counterweight portions 64, 66 areattached at junction 72 and are each substantially planar. Further, it can be seen that first andsecond counterweight portions 64, 66 are oriented at an obtuse angle 8 relative to oneanother, thereby providing clearance for counterweight 60 to rotate with shaft 40 withoutinterfering with connecting rod 54 or piston 56. Second counterweight portion 66 comprisesfirst and second planar sections 74, 76, respectively. Planar sections 74, 76 are attached byportion 78 of the strip stock material which extends therebetween. As shown, stock materialportion 78 is formed into a U-shape, having a bend of approximately 180°. Therefore, it willbe understood that planar sections 74 and 76 overlie one another and the thickness of planarsecond counterweight portion 66 is thus at least twice the thickness of the stock material. Fig.5 shows counterweight 60a in an unfolded state. The dashed lines therein identifying thelocations of free edges associated with further embodiments of the inventive counterweightdescribed below.Referring now to Fig. 6, there is shown a second embodiment of the inventive1015202530CA 02265078 2002-11-14counterweight. Counterweight 60b is identical in structure to counterweight 60a except thatsecond planar section 76b of its second counterweight portion 66 is shorter than secondplanar section 76a of counterweight 60a, and thus has less mass. Counterweight 60b is)manufactured using the same apparatus andmethod which produces counterweight 60a, but isformed from stock" material which has a smaller width between opposite ï¬rst and second sideedges.That is to say, each of the embodiments of the inventive counterweight are providedon the same tooling. The differences between the shown embodiments are generated only byprocessing stock material having different widths between their first and second side edgesthrough the progressive die apparatus.Referring now to Fig. 7, there is shown a third embodiment of the inventivecounterweight which is identical in structure to counterweights 60a and 60b, except that itssecond portion 66 does not include second planar section 76, and thus has even less mass.That is to say, counterweight 60c does not include U-shaped stock material portion 78 oroverlying second planar section 76. Counterweight 60c is manufactured using the sameapparatus and method which produces counterweights 60a and 60b, but is formed from-stockmaterial which has an even smaller width between opposite first and second side edges thanthe material ï¬om which the first and second counterweight embodiments are made. Notably,the truncated or free edge at the end of first planar section 74' of counterweight 60c is mostremote from ï¬rst counterweight portion 64.Referring againcto Fig. 3, it is seen that an axial projection of counterweight 60apresents a proï¬le or outline which is generally deï¬ned by the outer periphery of the shownï¬gure. It will be understood that in their ï¬nished forms, each of the three depictedcounterweight embodiments, when so axially projected, will have substantially identicalproï¬les.Referring again to Fig. 5, which shows ï¬rst embodiment of the counterweight 60a inits unfolded state, the relationship between the three depicted embodiments is readily seen.As noted above, the three counterweight embodiments are structurally identical except fortheir second portions 66, which includes free edge 80a, 80b or 80c which is deï¬ned by theedge of the respective stock material from which a counterweight is made. As shown,counterweight 60a has free edge 80a; should images of counterweights 60b and 60c, in theirunfolded states, be1015202530CA 02265078 1999-03-097superimposed on Fig. 5, their respective free edges 80b and 80c would be located as indicatedby the dashed lines. Each counterweight 60a, 60b, 60c has a length L from their commonjunction 72 to their respective edges 80a, 80b, 80c. Length L varies with the width of thestock material used to produce the counterweight; this is shown with reference to lengths La,Lb and Lc, respectively associated with counter weights 60a, 60b and 60c. Thus, length La ofsecond counterweight portion 66 in counterweight 60a extends from junction 72 along ï¬rstplanar section 74 through stock material portion 78 and along second planar section 76a toedge 80a. Similarly, length Lb of second counterweight portion 66 in counterweight 60bextends from junction 72 along ï¬rst planar section 74 and through stock material portion 78and through second planar section 76b to counterweight edge 80b. In counterweight 60c,length Lc of second counterweight portion 66 extends from junction 72 to edge 80c at thedistal end of second counterweight portion 66 and ï¬rst and only planar section 74. Becausesecond planar sections 76 of counterweights 60a and 60b are folded over their ï¬rst planarsections 74 (see Figs. 4 and 6) and counterweight 600 has no second planar section 76 (seeFig. 7), it can be understood that the distance from counterweight edge 80 to the axial end ofcrankshaft extension 52 is inversely proportional to the length of second counterweightportion 66.Each of edges 80a, 80b and 80c are defined by, and are, a side edge of the stockmaterial which is progressively stamped. Therefore, by forming stock material of differentwidths between its ï¬rst and second side edges through a common progressive stamping dieapparatus, counterweights of different weights but with substantially identical shape and sizemay be easily manufactured. Referring now to Figs. 8A, 9A and 10A, there is shownprogressive stamping die apparatus 82 into which stock material 84 of various widths is fed.As seen by comparing Figs. 8A, 9A and 10A, stock material 84 has varying widths Wa, Wb,Wc, which respectively produce counterweights 60a, 60b and 60c. As discussed above, Wais greater than Wb, and Wb is greater than Wc. Each of stock material members 84a, 84b and84c has ï¬rst and second side edges 86 and 88. Apparatus 82 has central axis 83 about whichthe dies of apparatus 82 are symmetrical. Axis 83 also coincides with the longitudinalcenterline of the stock material equidistant between its respective ï¬rst and second side edges86, 88. Stock material 84 is longitudinally fed through apparatus 82, in a direction along axis83.1015202530CA 02265078 1999-03-098Apparatus 82 is the only die apparatus necessary to produce the variety ofcounterweights 60 above described. Apparatus 82 has a plurality of die stations labeled Ithrough VI, the upper dies of which may be respectively ganged together and cycledsimultaneously to interact with their corresponding lower dies, with stock material 84advancing through the apparatus by one die station along axis 83 between each cycle. Oncepunch 90 of apparatus 82 cycles, at station I of the apparatus, a pair of blanks 92 appears inthe stock material. Each of the pair of blank forms 92 includes edge 80 which is deï¬ned bystock material edges 86 and 88.As blank 92 proceeds through apparatus 82, to the left in Figs. 8-10, the upper andlower die sets at each of stations 11 through V interact to shape the blank into a further-ï¬nished form. Notably, however, the blank associated with counterweight 60c (Fig. 10A), isnot formed at die stations II-IV, which act to fold section 76 over section 74, because thisblank has no second planar section 76; width Wc of stock member 84c is so narrow that thematerial does not extend between the upper and lower dies at these three stations. At stationV, ï¬rst and second counterweight portions 64 and 66 are bent relative to one another to formangle 0 in the counterweight.At station VI, a pair of counterweights are separated from the stock material onopposite sides of axis 83. Separating punch 94 also forms outside edge 96 which partlydeï¬nes first counterweight portion 64. The resulting counterweights are shown in cross-section in Figs. 8B, 9B and 10B. Although the pair of counterweights formed on oppositesides of axis 83 are preferably identical, the method of the present invention may be modiï¬edto feed stock material of an alternative width (not shown) through apparatus 82 such that thelongitudinal centerline of the stock material, which lies equidistantly between edges 86 and88, is offset from axis 83, thereby producing one embodiment of a counterweight (e.g., 60a)on one side of axis 83, and a different embodiment (e.g., 60c) on the other side of axis 83.While this invention has been described as having preferred designs, the presentinvention can be further modiï¬ed within the spirit and scope of this disclosure. For example,counterweights of varying weights may be produced according to the present inventionhaving shapes which deviate from those of the embodiments above described. Therefore, thisapplication is intended to cover any variations, uses or adaptations of the invention using itsgeneral principles. Further, this application is intended to cover such departures from theCA 02265078 1999-03-099present disclosure as come within known or customary practice in the art to which thisinvention pertains and which fall within the limits of the appended claims.
