Damper assembly for shift lever mechanism

Abstract: A compound shift lever mechanism employs a noise and vibration damper assembly for isolating an upper shift lever 12 from a lower shift lever 14 of a transmission. In a preferred form, the levers 12,14 are held in spaced, coaxial alignment for unitary movement in a plurality of planes by a damper 20 which comprises two parts. The first part is a cylindrical elastomeric sleeve 22 defining axially spaced female end portions comprising bores 32 which frictionally overlie and snugly encase the two lever end portions 16,18 which extend thereinto. The second part is a cylindrical metallic shell 24 which circumferentially encapsulates the elastomeric sleeve 22 which contains the respective ends 16,18, of the upper and lower levers 12,14. The shell 24 thus radially encapsulates both of the end portions 16,18, as well as the sleeve 22, which incorporates a midportion containing a radial internal barrier 36 to prevent direct physical contact between the extremities of the levers 12,14. Finally, spaced female ends 26,28 of the shell 24 are crimped radially inwardly against the female end portions of the sleeve and, in turn, against both lever end portions 16,18, to frictionally retain the end portions 16,18 in spaced, coaxial alignment.

Description: Background of the Invention This invention relates to a shift lever mechanism as specified in the preamble of claim 1, for example as disclosed in EP-A-0 345 001. Numerous damper assemblies for absorbing noise and vibrations have been designed for compound shift lever assemblies, particularly for use in heavy trucks. It is well known to provide rubber or elastomeric materials in joints or connections between upper and lower levers of compound shift levers. A great number of such damper assemblies, however, employ such elastomeric materials between selective portions of relatively complex apparatus. For example, in one compound shift lever device a metallic female extension is attached to a lower portion of an upper male lever to co-axially fix the upper lever to a lower male lever. The metallic extension is threaded, and contains a bore lined with elastomer into which a lower extremity of the upper portion extends. Enshrouded about the coupled levers is an elastomeric boot to enhance vibration absorption capability. Such conventional devices are typical; yet they have been unsatisfactory for lack of simplicity. As a result, such damper systems are often prone to early failures; perhaps such failures have often been statistically introduced into their manufacture via mere complexity. It would be desireable to provide a shift lever assembly with a vibration and noise damper to isolate noise from the cabin of a truck or other vehicle without the use of complex parts. It would be particularly desirable to completely isolate upper and lower shift levers from vibrations and noise inherent in metal to metal contact via employment of a simple two-piece damper assembly. To this end, a shift lever mechanism in accordance to the present invention is characterized by the features specified in the characterising portion of claim 1. Summary of the Invention The invention disclosed herein provides a simple two-part damper assembly for isolating noise and vibration from a lower to an upper shift lever of compound shift lever mechanism. The shift mechanism includes a pair of co-axially aligned shift levers axially spaced in a male-to-male relationship with each other. The levers are fixed together along a longitudinal axis by a noise and vibration damper assembly, which holds the levers in fixed position for unitary movement in a plurality of planes. The first of the two-part damper assembly is a cylindrical elastomeric sleeve, which circumferentially encapsulates each of the male end portions of the levers. The sleeve thus radially overlies and surrounds each of the male end portions of the levers, the sleeve having axially spaced female end portions defining axially opposed bores which terminate in a midportion therebetween. The second part of the damper assembly is a separate cylindrical metallic shell which makes no physical contact with the levers. The shell engages and circumferentially encapsulates the sleeve, the shell having a midportion axially coincident with the midportion of the sleeve. The midportion of the sleeve comprises a radially extending elastomeric barrier adapted to prevent physical contact between the extremities of the male end portions. In the preferred form, female end portions of the shell, although radially spaced from any contact with the levers, are radially inwardly crimped against the sleeve to frictionally retain the male end portions in a fixed co-axial relationship. Description of the Drawings Figure 1 is a cross sectional view of a compound shift lever mechanism which incorporates the damper assembly of the present invention. Figure 2 is a cross sectional view of a cylindrical elastomeric sleeve which forms one part of the two-part damper assembly of Figure 1. Detailed Description of A Preferred Embodiment Referring to Figures 1 and 2, a compound shift lever mechanism 10 includes an upper lever 12 and a lower lever 14 fixed together coaxially along a longitudinal axis "a-a". The levers 12 and 14 define respective male end portions 16 and 18 which are adapted to be resiliently secured together via a two-part lever damper assembly 20. For this purpose, the male end portion 16, which comprises the lower portion of the upper lever 12, and the male end portion 18, which comprises the upper end of the lower lever 14, are adapted to fit snugly in upper and lower sleeve bores 32 (Figure 2) of the sleeve 22, which forms a first part of the damper 20. The sleeve 22 includes a mid portion 34 which includes a radially extending elastomeric barrier 36. The barrier, preferably a disc integrally molded into the sleeve, is adapted to prevent direct physical contact between radially extending axial extremities 38 and 40 of the upper and lower male end portions 16 and 18, respectively. An exterior cylindrical metallic shell 24 forms the second part of the damper assembly 20. The shell is a structural support member for frictionally securing the levers 12 and 14 together under compressive forces against the sleeve and, in turn, against both male end portions 16 and 18, for frictional retention of the levers in substantially fixed, spaced, coaxial alignment. Thus, an upper female end portion 26 of the shell 24 is crimped about the upper male end portion 16, while an axially spaced lower female end portion 28 of the shell 24 is crimped about the lower male end portion 18. A midportion 30 of the shell 24 remains uncrimped and has a larger diameter than the shell end portions 26 and 28. As such, the midportion 30 is able to accommodate elastomeric flow of the sleeve 22 upon crimping of the end portions 26 and 28. In the preferred embodiment disclosed, knurled surfaces 44 extend circumferentially about the male end portions 16 and 18 to enhance frictional engagement of the levers 12 and 14 within the bores 32 of the sleeve 22. Those skilled in the art will appreciate that the circumferential exterior surface 50 of the sleeve 22 will be compressed radially inwardly by the compressive forces imparted by the upper and lower crimped shell end portions 26 and 28. The barrier 36 in the preferred form of the present invention is an integral disc effective to prevent direct physical contact between upper and lower levers 12 and 14. Although the disc is preferably molded as an integral part of the sleeve 22, the disc may optionally be a separate elastomeric part or member, installed within the sleeve during manufacture. As such however, it must function to maintain spacing between and to prevent contact between extremities 38 and 40 of the levers. In the finished assembly 10, the barrier 36 defines the axial spacing between the noted lever end extremities. In one preferred embodiment the barrier had an axial thickness of one-half inch in a sleeve 22 which was five inches in length. Alternatively, of course, an air gap may be employed in lieu of an actual physical barrier 36. Use of the physical barrier 36 will, however, always assure requisite axial spacing. In the preferred form, the crimped upper female end portion 26 and lower female end portion 28 of the shell 24 define segments which each comprise approximately 20 to 35% of the overall axial length of the shell which in the as described preferred embodiment has a length equal to that of the shell 22. As depicted in Figure 1, each segment ideally surrounds the one knurled surface 44 of each respective one of the male end portions. Thus both knurled portions of the levers are encapsulated. In a preferred form, the sleeve 22 has a cross-section in the form of an "H", with upper and lower ends of the "H" defining the bores 32 while the cross-bar "midsection" 34 of the "H" defines the barrier 36. The levers 12 and 14 are assembled together by inserting upper and lower male end portions 16 and 18 into respective bores of the sleeve, and then installing the metallic shell 24 about the sleeve to circumferentially encapsulate the sleeve within the shell. The final step is to crimp the ends of the shell about the sleeve to form permanent radially inwardly directed compressive forces against the sleeve within the damper assembly. As noted, the midportion of the shell remains uncrimped, and hence provides a relief area for the elastomer of the sleeve to flow into upon crimping of the respective ends 26 and 28 of the shell. Finally, in the preferred form, the extremities 60 of the metallic shell 24 are beveled angularly inwardly toward the axis "a-a" by an angle "A" (see Figure 1). The angle "A" preferably ranges between 15 to 20 degrees. The inwardly turned extremities 60 will more readily accommodate a rubber or plastic cover or boot which may be optionally added to the shift lever mechanism 10. A radial clearance "B" between the extremities 60 and surfaces of levers 14,16 is preferably in a range of 50 to 75 thousandths of an inch to absolutely assure avoidance of metal-to-metal contact.

Claims: A shift lever mechanism comprising a first lever member (12) and a second lever member (14) which are secured together in alignment with each other by means of a damper assembly (10) which comprises: a cylindrical elastomeric sleeve (22) which encloses the ends (16,18) of the respective lever members (12,14), the sleeve (22) having a mid-portion (36) comprising means for providing spacing between, and preventing direct physical contact between, the said ends (16,18); and a hollow housing (24) having first and second open ems (60), the housing (24) encapsulating the sleeve (22), characterized in that the housing (24) is crimped against the sleeve (22) to compress the sleeve (22) radially inwardly against the ends (16,18) of the lever members (12,14) thereby to retain frictionally the lever members (12,14) in spaced coaxial alignment. A shift lever mechanism as claimed in claim 1 in which the means for spacing between, and preventing direct physical contact between, the end portions (16,18) comprises a radially extending elastomeric barrier situated within said mid-portion (36) of said sleeve. A shift lever mechanism as claimed in claim 2 in which said barrier defines an axial spacing between the end portion (16,18) of the lever members (12,14). A shift lever mechanism as claimed in claim 3 in which the elastomeric barrier is moulded into said sleeve and defines an integral part of said sleeve. A shift lever mechanism as claimed in any preceding claim in which the ends (16,18) of the lever members (12,14) comprise circumferentially extending knurled surfaces to enhance frictional retention of said lever members (12,14) in said sleeve (15). A shift lever mechanism as claimed in any preceding claim in which the hollow housing (24) comprises spaced female end portions which define crimped segments of said housing (24) and a housing mid-portion situated between said segments, in which said segments directly engage the exterior circumferential surface of the sleeve (22), and in which each one of said segments surrounds a knurled surface of one of said ends (16,18) of the lever members (12,14). A shift lever mechanism as claimed in claim 6 in which said crimped segments each comprise approximately 20 to 35% of the axial length of the housing (24). A shift lever mechanism as claimed in claim 6 or 7 in which the housing mid-portion comprises a larger diameter portion of said housing (24) than either of the crimped segments. A shift lever mechanism as claimed in any one of claims 6 to 8 in which said female end portions of the housing (24) define extremities which are bevelled angularly inwardly towards the axis of the lever members (12,14). A method of forming a damper assembly for a shift lever mechanism having a pair of levers coaxially fixed together in end-to-end relationship to define a longitudinal axis comprising the steps of: (i) providing a cylindrical elastomeric sleeve containing a pair of coaxially aligned, axially spaced bores, and a mid-portion of said sleeve containing an internal radially extending barrier integral to the sleeve, (ii) inserting one end of each lever into one of each of said bores, (iii) installing a cylindrical metal housing circumferentially about the exterior of the circumferential surface of said sleeve, such that said sleeve is radially encapsulated within the housing, and (iv) radially crimping axially spaced end portions of said housing to form an un-crimped mid-portion therebetween, said mid-portion having a diameter greater than that of either of said crimped ends.

Inventors: DEUTSCHMAN ERNEST F, JESTER TERRY L, WATSON RICK D, DEUTSCHMAN, ERNEST F., JESTER, TERRY L., WATSON, RICK D.
Applicants: DANA CORP, DANA CORPORATION
Application year: 1992
Main classification: F16H59
IPC codes: F16H59, F16H61, F16F15