BACKGROUND ART There are in existence many different kinds of honing devices and honing heads including many which are expandable and contractable and are used to hone cylindrical surfaces

, _n such as the cylindrical surfaces of bores and the like. Some of the known devices use rack and pinion gear arrangements for radially moving the work engaging parts in order to change the operating diameter and to apply honing pressure during operation. Typical of known honing heads of

-, m this general type are the honing heads disclosed in Sunnen U.S. Patent Nos. Re 18,763; 1,929,613; 1,946,041; 1,982,836; 2,002,649; 2,020,589; 2,040,281 and 3,378,962. The patented constructions employ various devices wherein the honing assemblies or stone assemblies, each of which has one stone 0 on it, as well as guide shoe assemblies in some, cases each of which has one work engaging guide member thereon, are moved radially by means of rack and pinion gear arrangements. There are also known constructions that have stone assemblies with circumferentially spaced stones thereon but wherein the rack gears are located more closely 5 behind the leading stone members than behind the trailing stone members to somewhat unbalance the assemblies, see for example the constructions shown in copending U.S. patent ^' application Serial No. 314,856, filed October 26, 1981, and 0 assigned to applicant's assignee. However, the known devices use a single, centrally located, pinion gear and rack gear members that are mounted substantially off center or off axis of the device to engage opposite side of the common pinion gear. As a result the stone and guide 5 assemblies supported by the rack gears in the known devices are supported by means located away from or offset from the

center or axis of rotation. This is done in the known devices because by so doing it is possible to use the same pinion gear to move or drive and maintain pressure on more than one stone or shoe assembly at the same time. There are, however, disadvantages with the known constructions including the fact that by having the rack gears located off center as described it substantially limits the possible range of radial movement available for the radially adjustable assemblies, and therefore the range of possible bore diameters that can be honed by any given honing head. It has been discovered that mounting the stone and shoe assemblies on rack gears located on or closely adjacent to the center or axis of rotation makes it possible to have a substantially increased range in a more balanced construction but it may also introduce other problems which need to be addressed,. These include problems caused by constructions where the stone assemblies each have two or more circumferentially spaced stones mounted thereon. With such constructions it is found that the leading or forward work engaging member on each assembly, especially if it is a vitrified stone member, has a tendency to dig or bite into the work surface causing undesirable chatter and vibration and also potential damage to the stones and especially to the forward stones on such assemblies. Also, such digging in may cause stone chipping and breaking and almost always makes the operation very noisy. This can adversely affect the honing operation.

DISCLOSURE OF INVENTION The present invention teaches the construction of a novel honing head and novel honing assemblies for use thereon which overcome these and other undesirable conditions. To accomplish this the present construction includes a dual pinion head construction having two spaced pinion gears and with the work engaging assemblies supported for movement by rack gears mounted on or closely adjacent to the axis of rotation thereof and in the space between the

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pinion gears for engagement with the respective pinion gears. The present device also includes means for simultaneously rotating the pinion gears. Each of the honing assemblies, one being engaged with each of the pinion gears, has a forward and a trailing work engaging member or stone mounted thereon. The forward work engaging member on each assembly is modified to prevent it from digging into the work surface, to reduce mandrel chatter, vibration and noise, and to improve the honing operation. In the balanced construction, the two work engaging portions on each honing assembly, which may or may not both include stones such as vitrified stones, come into contact with the work surface at the same time. In the unbalanced more conventional construction the rear working engaging members, or stones, tend to be deflected inwardly as they are being used so that on re-entry into another bore they will be higher than the leading stone until they deflect inwardly to resume their normal cutting position, and in doing so they will produce noise and vibration until they re-establish their normal cutting positions. However, a negative feature of the present more balanced construction results from the leading work engaging members on each assembly being located on the respective stone assemblies further ahead of the rack pins that support and drive the assemblies than is true of the unbalanced constructions. In the more forward locations any deflection of the rack pins will create a condition wherein the leading more forward work engaging members can self-energize into the bore causing undesirable noise, vibration, and damage to the parts. To prevent these conditions the leading member on each assembly must not be allowed to bite into the bore excessively. This can be accomplished either by making the leading work engaging member at least in part of a material such as zinc which will slide on the work surface rather than bite in, or by utilizing a vitrified abrasive as the leading work engaging member and placing some zinc or other like material ahead of

the abrasive to limit the ability of the forward abrasive members to bite into the bore surface. This allows for some cutting action by the forward work engaging member, unlike the condition previously mentioned where only a zinc member is used for the forward member, but yet limits the ability of the leading abrasive to bite in, thereby preventing the undesirable self-energizing action previously mentioned. To be able to use the same honing assembly to hone different diameter bores, especially to hone larger diameter bores, it may also be desirable to also place some zinc behind the vitrified abrasive members in the forward positions so that the zinc will engage and slide on the bore before the abrasive comes in contact therewith. This occurs where the rear edges of the forward work engaging members come in contact with the work surface before the abrasive, and this to some extent limits the cutting action under these conditions. This occurs especially where the hone was previously used for honing in relatively small diameter bores and is expanded to engage and hone a larger diameter bore, thereby causing the rear edges of the forward work engaging members to at least initially engage the work surface.

The present honing mandrel includes an elongated body rotatable about an axis of rotation and having spaced longitudinal bores extending therethrough for rotatably accommodating respective pinion gears, and first drive means including drive means for rotating the mandrel and other drive means engageable with the pinion gears for simultaneously rotating the same to radially expand or contract the honing diameter and to maintain honing pressure on the work engaging members. The body also has spaced transverse bores therethrough in the space between the pinion gears for receiving rack gear portions of respective opposed work engaging assemblies such as honing or bearing shoe assemblies. The rack gear portions of one stone or bearing shoe assembly cooperate with one of the pinion

gears, and the rack gear"portions of the other assembly cooperatively engage the ^" other pinion gear.

It is a principal object of the present invention to teach the construction of a honing mandrel using rack and pinion drive means for radially moving the work engaging members, which mandrel is capable of honing over a greater range of bore diameters for a given mandrel size.

Another object is to reduce noise and vibration associated with honing mandrels. Another object is to minimize the possibility for damage to the work engaging portions of a honing mandrel and to work surfaces engagable thereby.

Another object is to provide improved means for supporting radially movable work engaging assemblies on a honing mandrel or like device.

Another object is to provide a honing mandrel with spaced pinion gears for simultaneously oppositely radially advancing or retracting the work engaging members.

Another object is to teach the construction of a honing mandrel having opposed work engaging assemblies with support means therefor that are able to pass through one another during adjustment to increase the range of possible radial movement thereof.

Another object is to teach a relatively simple and inexpensive mandrel construction, and one which is relatively easy to assemble and operate even by persons having relatively little skill and training.

Another object is to reduce the number of honing mandrels required to cover the honing of a range of bore diameters.

BRIEF DESCRIPTION OF DRAWINGS These and other objects and advantages of the present invention will become apparent after considering the following detailed specification which discloses several embodiments thereof in conjunction with the accompanying drawings wherein;

Fig. 1 is a side elevational view partly in section showing a honing mandrel and the drive connections therefor constructed according to one embodiment of the present invention; Fig. 2 is a cross-sectional view taken on line 2-2 of Fig. 1;

Fig. 3 is a cross-sectional view taken on line 3-3 of Fig. l;

Figs. 4, 5 and 6 are cross-sectional views similar to Fig. 3 but taken at line 4-4 of Fig. 1 showing alternative forms of honing assemblies for use on the subject device;

Fig. 7 is a cross-sectional view similar to Fig. 3 but showing the mandrel in a substantially fully retracted condition; and, Fig. 8 is a perspective showing another embodiment of the subject device wherein the rack gear support members for supporting the opposite work engaging assemblies are located more precisely on the axis of rotation of the device. BEST MODE FOR CARRYING OUT THE INVENTION Referring to the drawings more particularly by reference numbers, number 10 in Fig. 1 refers to a honing mandrel assembly constructed according to the present invention. The mandrel assembly 10 has a body portion 12 which includes a drive end portion 14 for coupling to drive means shown as including universal drive connection means 16. The drive connection means 16 may be a known constructions such as those employed on known honing machines, see, for example, the construction shown in Sunnen U.S. Patent Nos. Re 18,763; 1,929,613; 1,946,041; 1,982,836; 2,002,469; 2,020,589; 2,040,281; and 3,378,962. The universal drive means 16 include means for rotating the mandrel and other means extending therethrough for radially moving the work engaging portions as will be explained. The means 16 include spaced arms 18 and 20 which are pivotally connected to a ring member 22 by oppositely located pivot members or pins 24. The ring 22 is also pivotally connected by other pivot

members 26 located at right angles to the pins 24 to the member 14 which houses an optional assembly 28 which is operatively connected to the mandrel body 12. The mandrel end portion 14 has a connection to the assembly 28, or more directly to means in the honing machine, where mandrel size and space will not accommodate an assembly such as the assembly 28. In the construction of Fig. 1 a rotatable adjustment member 30 is connected to the assembly 28 and has a transverse slot 32 formed in the free end thereof, which slot is used for coupling to means in the honing machine that are used for expanding and contracting the work engaging portions of the mandrel, as will be explained.

The present invention resides primarily in the construction of the honing mandrel assembly 10, the drive means therefor, and in the construction of the radially movable work engaging assemblies mounted thereon. The construction of the members 16, 22 and 28 may be known as stated above and are not part of the present invention as such. The slot 32 in the member 30 cooperates with drive means in the honing machine, not shown, which drive means includes a member that extends through the tubular drive portion 33 of the member 16 for connection with drive means in the honing machine. The drive connecton provided by the means 16, operating through the connection means or pins 24 and 26 and the ring 22, produces the main drive force for rotating the mandrel assembly 10, and the drive force applied directly through the universal joint 16 to the member 30 and through the associated assembly 28, if used, produces the force for expanding or_contracting the work engaging members and for controlling the force produced by the work engaging members against the work surface. When the member 30 is rotated it rotates a gear member 34 (Fig. 2) which is located in the enlarged mandrel body end portion 14. The gear 34 is positioned between and is engaged with two elongated spaced pinion gears 36 and 38 which extend through respective elongated bores 40 and 42 in the body 12

to adjacent to the opposite end thereof. When the gear 34 is rotated by the rotation of the member 30 it will simultaneously rotate the pinion gears 36 and 38 and their adjacent surfaces will move in opposite directions as can be seen from Fig. 2. This produces the motion and force to radially move the work engaging assemblies in opposite directions.

The mandrel assembly 10 includes two spaced honing assemblies 46 and 48, one being located on each opposite side of the body 12. The assembly 46 includes an elongated support member or backing 50 (Fig. 3) which is attached to an elongated master stone holder 52 by means which may be similar to the means disclosed in pending Sunnen U.S. Patent Application Serial No. 314,856, filed October 26, 1981. The backing 50 has spaced angularly related lands 54 and 56 on which work engaging members 58 and 60 are attached. The details of the various forms of work engaging members 58 and 60 will be described later. The master stone holder 52 is shown fixedly attached to two spaced rack gear members 62 and 64 which extend through respective bores 66 and 68 in the body 12, see Fig. 1. The rack gears 62 and 64 have respective rack gears teeth 70 and 72 which mesh at spaced locations along the teeth of the pinion gear 36 as clearly seen in Figs. 1 and 3. The work engaging assembly 48 is similar in construction to the work engaging assembly 46 including having a backing member 74 such as a die-cast member with two spaced and angularly related lands 76 and 78 on which respective work engaging members 80 and 82 are mounted. The assembly 48 also includes a master holder 84 to which is attached two spaced rack gears 86 and 88. The rack gears 86 and* 88 are located closer together than the rack gears 62 and 64 as shown in Fig. 1 and extend through other respective transverse body bores 90 and 92 at the locations shown. The rack gears 86 and 88 have respective teeth 94 and 96 which cooperate with the teeth on the pinion gear 38. It can be

seen that when the input gear 34 is rotated the pinion gears 36 and 38 will have their adjacent or facing teeth move in opposite directions as shown in Fig. 2, and this will cause their respective work engaging assemblies 46 and 48 to move radially either inwardly or outwardly relative to the mandrel body 12. This is done to increase or decrease the honing diameter of the mandrel assembly 10 and also to apply the desired honing pressure by the work engaging members against a work surface. It is also contemplated to have the positions of the rack gears on the respective honing assemblies staggered so that one of the rack gears on each assembly is between the rack gears on the other assembly, and it is contemplated to have a third centrally located rack gear on the assembly that has the two more widely spaced rack gears without changing the nature of the invention.

Referring again to Figs. 1 and 3 it can be seen that the backing member 50 and the master holder 52 therefor have spaced radially extending bores 98 and 100 therethrough. These bores are in positions to be in alignment respectively with the rack gear members 86 and 88 on the assembly 48. This is so that when the assemblies 46 and 48 are moved to their retracted positions as shown in Fig. 7 the rack gears 86 and 88 can move through the bores 98 and 100 so that the assembly 48 can move against the body 12. In like manner, the assembly 48 has spaced bores 102 and 104 formed through the- ortions 74 and 84 thereof in positions to be in alignment with the respective rack gears 62 and 64 so that the assembly 46 can also move into engagement with the body 12 simultaneously with the assembly ^" 48. This provision in an expandable honing mandrel construction is an important provision since it substantially expands the range of possible bore diameters that can be honed using the same mandrel. It is important in this regard that the mandrel be constructed so that the rack gears do not extend too far through and beyond the respective bores in the opposite

assemblies to assure that they are not able to come in contact with the work surface.

The ability of the rack gears on the respective work engaging assemblies to be located on or closely adjacent to the axis of rotation of the mandrel is made possible largely because of the use of the two spaced pinion gears 36 and 38. This also enables the rack gears on the respective assemblies to be located so as to extend from positions between the work engaging members or stones 58, 60, 80, and 82 on the respective assemblies. This means further that the holes through the assemblies for accommodating the rack gears can be located in the assemblies at locations entirely between the stones which is not possible in a construction having a single centrally located pinion gear as in the known constructions.

Figs. 4, 5, and 6 show cross-sectional views of the subject mandrel construction, all of which show the device in a position for rotating in a clockwise direction. This means, that work engaging portions 60A and 80A in Fig. 4, 60B and 80B in Fig. 5 and 60C and 80C in Fig. 6 will be the more forward work engaging member on each of the assemblies. It has been found that if the forward assemblies 60A-80C are entirely formed of a vitrified abrasive material such as of honing stone similar to the stones 58A, 82A, 58B, 82B, 58C, and 82C, that there is a tendency for the forward stones 60 and 80 to dig into the work surface being honed and to cause vibration, chatter, noise and in some cases chipping or breakage of the stone members. In order to overcome these undesirable possibilities, the forward stone assemblies 60A-80C are formed to include at least some of a non-abrasive material that is more likely to make sliding engagement with the work than to abrade thereby reducing or eliminating undesirable energizing or biting in action of the forward member which otherwise might occur if the forward member were of stone only. Several different constructions having these

characteristics are disclosed.

In Fig. 4 the work engaging assemblies 60A and 80A are formed having the forward work engaging members include stone members positioned between opposed wall portions 108 and 110 formed on opposite sides thereof. The wall portions 108 and 110 are formed of a material such as die-cast zinc which is the same material that is used to form the backing member 50 on which the stones are mounted. This means that the walls 108 and 110 can be cast at the same time as the member 50 (or 74) and thereafter the stones can be adhesively or otherwise attached thereto in the positions shown. With this construction, when the assemblies 46 and 48 are moved into engagement with a surface to be honed, the wall portions 108 and 110, which provide some support for the stones therebetween, will engage the work, and even though they may be made of material somewhat more prone to wear than the stones they will be worn down at approximately the same rate as the stones because of the balanced construction. In this regard, it is discovered that by including the portion 108 and 110 the noise and vibration that occurs when two stones are used is almost completely eliminated, and there is noticeable improvement in performance. Hence a mandrel so constructed will produce relatively little vibration, noise or chatter and will minimize the chance for stone damage.

In Fig. 5 the forward stone assemblies 60B and 80B are shown having a forward wall 112 only formed of die-cast zinc or other like material, and this construction has also worked satisfacto ily under relatively high honing pressures with the same advantages. This is because the forward edge of the work engaging portions 60B and 80B are the portions of this construction that are most likely to engage the work surface and cause undesirable noise, chatter, vibration and damage. In this case the forward walls 112 can also be formed as by die-casting during formation of the respective backing members.

In Fig. 6 the forward work engaging members 60C and 80C are shown formed entirely of some material such as zinc. These members can be formed integrally with the backing members to which they are attached which may be of die-cast zinc or they can be formed of some other suitable material including materials such as aluminum, brass, bronze, certain plastics, and even wood. The principles and features described above in connection with Figs. 4 and 5 also apply with respect to the construction shown in Fig. 6. Fig. 8 shows a modified embodiment 120 of the subject mandrel wherein the body portion 122 is shown transparent to illustrate the locations and construction of the modified pinion gears 124 and 126 and the associated rack gears 128, 130, 132 and 134. The rack gears 128 and 130 are attached to the master stone holder 136 for one of the two work engaging assemblies, and the rack gears 132 and 134 are attached to the master stone holder 138 for the other work engaging assembly 140. In the construction of Fig. 8 the pinion gears 124 and 126 are shown having annular round bottom grooves 142, 144, 146 and 148 located at the locations of the respective adjacent rack gears. This is done so that the rack gears 128, 130, 132 and 134 can be located on or very close to the axis of rotation of the mandrel. While the construction shown in Fig. 8 may require some additional machining in order to form the round grooves in the pinion gears, it has the advantage that the rack gears can be even more centrally located relative to their respective honing assemblies, and therefore the construction of Fig. 8 may be an even somewhat more balanced construction. The construction shown in Fig. 8 also has holes through the respective honing assemblies through which the rack gears on the opposite assemblies can move to enable the mandrel to hone over a wide range of bore diameters as in the case of the mandrel discussed above. INDUSTRIAL APPLICABILITY

The present invention substantially increases the range

of diameter that can be accommodated by a work engaging assembly such as by an expandable honing mandrel which hones cylindrical bores.

Thus there has been shown and described a novel honing mandrel construction and novel honing assemblies for use therewith which fulfill all of the objects and advantages sought therefor. It will be apparent to those skilled in the art, however, that many changes, modifications, alterations, and other uses and applications for the subject devices are possible and all such changes, modifications, alterations and other uses and applications which do not depart from the spirit and scope of the invention are deemed to be covered by the invention which is limited only by the claims which follow.